Showing papers in "Philosophical Transactions of the Royal Society B in 1974"
TL;DR: Most of the thirty-three ossicles are found in each of the species, but there are some major differences between species.
Abstract: The stomatogastric nervous system of the reptantian Decapoda Crustacea, particularly the small isolated stomatogastric ganglion containing the 25-30 motor neurons that control the muscles of the gastric mill and the pyloric filter of the stomach, is an important preparation for research in comparative neurophysiology. Unfortunately there are no comprehensive descriptions of the neuromuscular system of the stomach in these animals. Therefore, since the stomatogastric motor neurons are identified by reference to the muscles they innervate, it has been difficult to identify neurons within or between species. The most important features for classifying the muscles of the decapod stomach are the ossicles to which the muscles attach. In the latter part of the last century Mocquard demonstrated that the stomach ossicles of the decapods could be compared in different groups despite the large variations from group to group. A summary of Mocquard’s (1883) classification scheme, with some modifications, is given. The scheme recognizes 33 ossicles in seven categories (cardiac gastric mill, I—VII; lateral supporting cardiac ossicles, VIII-XV ; ossicles of the cardio-pyloric valve, XVI-XVIII; supporting ossicles of the dorsal pyloric stomach, XIX -XXI; supporting ossicles of the ventral pylorus and ampullae, XXII-XXVII; supra-ampullary ossicles, XXVIII-XXX ; supporting ossicles of the lateral pylorus, XXXI-XXXIII). Where necessary, comments are then made on the ossicles of the three divergent species studied, the blue crab, Callinectes sapidus (Brachyura); the lobster, Homarus americanus (Macrura) and the spiny lobster Panulirus argus (Palinura). Most of the thirty-three ossicles are found in each of the species, but there are some major differences between species. Callinectes , for example, has the most complex ossicle system and Panulirus the most reduced.
259 citations
TL;DR: In this article, the results from stratigraphy, radiocarbon dating and pollen analysis of three salt-lake deposits at Sambhar, Lunkaransar and Didwana in western Rajasthan, and one freshwater lake deposit at Pushkar in the Aravalli Hills, are described in conjunction with some archaeological soil samples from the Indus Valley site at Kalibangan in northern India.
Abstract: The results from stratigraphy, radiocarbon dating and pollen analysis of three salt-lake deposits at Sambhar, Lunkaransar and Didwana in western Raj9asthan, and one freshwater lake deposit at Pushkar in the Aravalli Hills, are described in conjunction with pollen analysis of some archaeological soil samples from the Indus Valley site at Kalibangan in northern Rajasthan. The salt-lake deposits studied are stratigraphically divisible into (a) pre-lacustrine, (b) lacustrine and (c) post-lacustrine sections. The pre-lacustrine section is characterized by a thick bed of aeolian sand underlying lacustrine sediments, while the lacustrine and post-lacustrine sections are broadly circumscribed by laminated clay and nonlaminated silt respectively. The pollen record from the four lake profiles studied is divided into local pollen zones. Four regional pollen assemblage zones are delineated for the area west of the Aravalli Range in Rajasthan. The environmental history deduced from the pollen record is divisible into phases I-V, of which phases II-V follow the regional pollen assemblage zones. Phase I is stratigraphically determined, and is representative of severe arid environments under which the sand dunes, now stabilized, are suggested to have been active. The plant microfossils first appear in phase II with the deposition of lacustrine sediments dated to around 10000 b . p . The vegetation comprises an openland steppe which is rich in grasses, Artemisia and sedges and poor in halophytes. Artemisa, Typha angustata, Mimosa rubicaulis and Oldenlandia , which now grow under areas of comparatively higher average annual rainfall (above 50 cm), appear to have flourished in the semi-arid belt, while the first two plant taxa had encroached even as far as the arid belt, both suggesting that a general westward shift of the rainfall belts had taken place. Vegetation destruction through burning by man is suggested to have started together with the first occurrence of Cerealia-type pollen at about 7500 b . c . and continued thereafter throughout phases III and IV. The increase in swamp vegetation and the intensification of vegetation cover inland together with the maxima of all mesophytic elements in phase IV ( ca. 3000 b .c . to ca. 1000 b .c .) indicate an increase in the rainfall, apart from a short relatively drier time about 1800-1500 b . c . at Sambhar which correlates with the decline of the Indus culture in northwest India. Phase IV is immediately followed by aridity for which there is stratigraphic evidence that the salt lakes started drying. At Pushkar, there is evidence that the vegetation showed a marked change in the Aravallis. The onset of this aridity is suggested to have been widespread. The climate did not ameliorate until about phase V (? early centuries a .d . to present) at which time the Rangmahal culture perhaps flourished in Rajasthan, the remains of which imply good water supply. In conclusion it is suggested that the Rajasthan desert is primarily natural, its history punctuated by at least one more vegetated, humid period during the Holocene, the climatic control of which as indicated by the vegetation history is consistent with climatic events elsewhere in the world.
199 citations
TL;DR: Evidence is presented to show that this permeability barrier passively depends on the structure of the unusual, thick, rigid membrane which limits the urinary surface of the epithelial cells.
Abstract: The epithelium of the mammalian urinary bladder is an effective barrier to the free flux of urea, water and small charged ions between urine and tissue fluids In this paper we present evidence to show that this permeability barrier passively depends on the structure of the unusual, thick, rigid membrane which limits the urinary surface of the epithelial cells The normal structure of this membrane is unique Thickened plaques, composed of a hexagonal lattice of dodecameric subunits which extend through the depth of the membrane, are separated by thinner, unstructured, narrow bands The regular structure of the lattice may be disrupted or distorted by treatment with urea, guanidine hydrochloride or sodium dodecyl sulphate Chemically the membrane is also remarkable Its lipid component contains cerebroside, which apparently has an important effect in lowering water permeability This effect is reinforced by cholesterol, which may be important for the maintenance of a condensed lipid layer during the mechanical stresses of bladder contraction and dilation The protein component also is unusual in having a high proline content, and the significance of this is discussed in the context of membrane structure and function At the moment it is not possible to relate the marked subunit structure of the membrane to its protein component although the large particle mass mucoprotein compound, as yet uncharacterized, may be located in the thick, densely staining, negatively charged surface lamina of the membrane This membrane is thus remarkable in both its structure and its function These properties in turn must depend on complex interactions between its lipid and protein components which are themselves unusual
171 citations
TL;DR: Age and body mass showed surprising relationships with energy intake and most of the energy and protein in the diets came from the staple vegetable (taroin Kaul and sweet potato in Lufa), this was less so than in previous studies.
Abstract: Two village populations, Kaul in a coastal region and Lufa in a highland region, were studied each for 9-10 months. Measurements of food intake and total daily energy expenditure were made on individual subjects, 51 men and 69 women in Kaul and 43 men and 41 women in Lufa. Each individual was investigated during a period of 5-7 consecutive days. The way of life for all the people was moderately active - more so in the highlands - since they were subsistence farmers cultivating their own gardens for food. The mean daily energy intakes were 8.12 MJ (1940 kcal) for the Kaul men, 10.55 MJ (2520 kcal) for the Lufa men, 5.95 MJ (1420 kcal) for the Kaul women and 8.81 MJ (2105 kcal) for the Lufa women. There were almost no differences in the energy intakes of the non-pregnant non-lactating, the pregnant, and the lactating women in each village. The intakes of protein were low, providing 6.7, 6.0, 6.5 and 7.2% of the energy value of the diets of the Kaul men and women and the Lufa men and women respectively. Fat provided only about 10% of the energy in the highland diet and 17% in the coastal diet. Age and body mass showed surprising relationships with energy intake. Although most of the energy and protein in the diets came from the staple vegetable (taroin Kaul and sweet potato in Lufa), this was less so than in previous studies. A total of 1160 measurements of energy expenditure were made on various activities of the individual people and mean values are given for these activities. The pattern of daily energy expenditure is also shown. Lying, sitting and standing accounted for about 70% of the total day and 60% of the total energy expenditure. Walking occupied about 10% of the 24 h and between 20 and 27% of the energy output. Some of the results of food intake, particularly on the women in the coastal region, are very difficult to explain on currently accepted grounds.
168 citations
TL;DR: Cell walls from various algae within the Chlamydomonaceae display, when negatively stained and examined in the electron microscope, a crystalline lattice component, and on the basis of the Fourier transforms of micrographs of the cell wall, the algae have been classified into five classes.
Abstract: Cell walls from various algae within the Chlamydomonaceae display, when negatively stained and examined in the electron microscope, a crystalline lattice component. On the basis of the Fourier transforms of micrographs of the cell wall, the algae have been classified into five classes. Most of the algae examined fall into class II. The two-dimensional repeating morphological unit cell of the wall of each class is described and in each case is a parallelogram whose overall dimensions are all of the same order of magnitude. The implications of the classification for classical taxonomy are discussed. More detailed structural information, to a resolution of about 2.5 nm (based on optical filtering and image enhancement techniques), is presented for two of the cell wall classes. From the evidence of polyacrylamide gel electrophoresis, the cell wall of these algae is constructed primarily from a small number of high molecular mass glycoprotein species. In Chlamydomonas reinhardi it has been shown that the hydroxyproline residues in the wall glycoprotein are cross-linked to short oligosaccharides. Some of the conditions necessary for the complete in vitro reassembly of the cell wall of C. reinhardi are presented and include the presence of a discrete nucleating agent and the presence of a physical surface. Dislocations within the crystalline lattice of the cell walls are described and their role as growth points discussed.
160 citations
TL;DR: The optic nerve fibres project on to the optic lobe in a regular manner, being precisely re-assorted after passing through a chiasma, and there is a regular mapping of the visual field throughout much of the system.
Abstract: The optic nerve fibres project on to the optic lobe in a regular manner, being precisely re-assorted after passing through a chiasma. In the outer plexiform zone the optic nerve fibres end in contact with the dendrites of second-order visual cells. These presumably serve to classify the visual input and four types can be recognized anatomically: (1) The smallest have minute circular dendritic fields, in contact with one or few optic nerve fibres. (2) There are also larger circular fields. (3) Many cells have very elongated narrow dendritic fields each running straight in one direction and thus perhaps sensitive to edges. (4) The largest second-order visual cells have enormous oval dendritic fields, several millimetres long, orientated in the long axis of the lobe. Each type of field occupies a different level, producing the characteristic layering of the outer plexiform zone. Numerous amacrine cell processes end in the outer plexiform layer, some are very small with restricted branches, others have wide trees with fibres passing first inwards then outwards several times. There are thus possibilities of establishing uniform conditions of excitation or inhibition over small or large areas of the visual field. The dendrites of the centrifugal cells with axons passing to the retina spread in the various layers of the plexiform zone. They could serve to project information of the areas excited, or inhibited, out to the retina. The axons of the second-order visual cells form radial columns in the outer part of the medulla of the optic lobe. Those with the smaller dendritic fields end more superficially, the largest ones about half-way through the lobe. Each column contains fibres and neuropil at its centre, surrounded by multipolar and bipolar amacrine cells, whose branches enter the neuropil among the endings of the second-order visual cells. Horizontal multipolar cells of various sizes link the columns. Third-order visual cells send dendrites into these columns and axons deeper into the lobe, some directly to the optic tract. The giant cells of the magnocellular lobe can thus be activated by a visual pathway involving only two previous synapses (as well as by a direct static pathway involving none). Central to the zone of radial columns is a zone where many of the connexions are tangential. There is an increasing number of large cells passing centrally, many being presumably fourth-order visual neurons. They send axons either elsewhere within the lobe or to the optic tract. Fibres reaching the lobe from the central brain or opposite lobe are distributed in this region and also reach out into the radial columns. In many of the tracts leaving the optic lobes for other centres the fibres maintain precise topographical relations, as also do those of the optic commissure. This regularity is especially clear in the bundles that pass to the motor centres (peduncle lobes and anterior basal lobes) but may be present in others. There is thus a regular mapping of the visual field throughout much of the system. Other pathways show complex interweaving, for instance those for colour control, where the response pattern is not topographically related to the visual input.
143 citations
TL;DR: The fossil evidence is re-examined to determine the structure of Pteranodon ingens, and it is suggested that extinction could have been due to climatic change, particularly an increase in the average wind speed at the end of the Cretaceous.
Abstract: The fossil evidence is re-examined to determine the structure of Pteranodon ingens . New measurements include the cross-sections and thickness of the wing bones, the degree and direction of movement of the joints, and the size and position of major tendon and muscle insertions. From this data a reconstruction is made suitable for engineering and aerodynamic analysis. The reconstruction is based largely on Eaton’s type specimen, 1175, and has a wing span of 6.95 m. The mass is estimated as 16.6 kg by calculating the volume of each part, making due allowance for the soft parts and cavities. The engineering design of the wing is considered in some detail. The shape deduced from the angles of the joints agrees well with that required for strength and aerodynamic efficiency. The strength of each part has been compared with the loads on it in gliding flight, showing that the structure is extremely well designed; it is strong enough everywhere, but with little unnecessary weight. Wind-tunnel experiments on model heads show that the sagittal crest was primarily a weight-saving device; by balancing the aerodynamic loads on the beak, it allows the neck muscles to be reduced, saving much more than its own weight. The performance of Pteranodon as a glider has been calculated, and compared with birds and man-made gliders. With a sinking speed of only 0.42 m/s at a flying speed of 8 m/s, Pteranodon is a superb low speed soaring aircraft, able to soar in weak thermals, or hill lift in very light winds. With its low stalling speed, it could also land very gently. Powered flight is considered, and it is shown that Pteranodon is just capable of level flight; but it is clearly primarily a glider. The environment in which Pteranodon lived is determined as far as possible from an analysis of the palaeobotany, palaeozoology and palaeoclimatology of the Cretaceous. The evidence points to a warmer and more uniform climate with lighter winds than today. This agrees well with Pteranodon9s performance, which is ideally suited to light wind conditions. The mode of life is considered, showing that Pteranodon probably lived on sea cliffs facing the prevailing wind. After landing on the top, it would scrabble forwards (it could neither stand up nor walk) and hang from its hind feet over the edge. From here it could easily launch itself. When flying near the cliff it would soar in the hill lift; when far out at sea it would use the weak thermals generated by convection over the warm sea. Dynamic soaring and slope-soaring over the waves are not possible for such a slow-speed glider. Some consideration is given to methods of feeding, social organization and defence against predators. Finally it is suggested that extinction could have been due to climatic change, particularly an increase in the average wind speed at the end of the Cretaceous.
132 citations
TL;DR: Selected examples of the glycocalyx or cell coat on rickettsiae, bacteria, amoebae, sea-urchin eggs and the cat intestinal microvilli are illustrated and their functional roles are discussed.
Abstract: Selected examples of the glycocalyx or cell coat on rickettsiae, bacteria, amoebae, sea-urchin eggs and the cat intestinal microvilli are illustrated and their functional roles are discussed The differences in the form of various surface coats are noted; while many surface components are truely extraneous expend-able coatings, others are so firmly attached that they seem to be a permanent part of the cell The fuzzy surface coat on the cat intestinal microvilli have been considered in some detail and some new observations on the form of the glycocalyx are presented The enteric surface coat is not readily visualized in fractured surface replicas of glycerinated tissue but fixed cells frozen in distilled water when replicated after freeze-etching reveal a flamboyant array of a filamentous meshwork attached to the microvilli This fuzzy coat layer is at least twice as thick in the freeze-etched preparations when compared to thin sectioned material Fresh tissue frozen without fixation or glycerin treatment did not have a thick fuzzy coat In its place a thin amorphous blanket-like layer was found
122 citations
TL;DR: Study of the inputs upon groups of named motoneurons allows identification of the interneurons which act on them, and reveals that posture, elicited responses and spontaneous movements are determined by selection of different combinations of interneURons.
Abstract: 1. Resistance reflexes at each joint of the leg arise from sense organs directionally sensitive to motion. Sensory impulses, acting indirectly through interneuron combinations, excite one set of motoneurons and inhibit their antagonists. 2. These resistance reflexes are not switched off during ‘voluntary’ movements elicited by touch elsewhere on the body, but instead they sum with other responses. 3. Although readily recorded in motoneurons, the resistance reflexes are mechanically so weak compared with voluntary movements that they are not a major item in the control of the leg. This applies also to posture. 4. When a voluntary movement or direct stimulation of a motoneuron causes a muscle to act against a load the reflexes upon motoneurons are quite different from those to motion caused by the same muscle. Therefore the reflex modification of walking patterns, in which legs are loaded by each other’s movements, and by the insect’s weight, cannot be analysed by a study of leg motions , although this has always been the method to date. 5. The positive feedback upon the motoneuron from receptors to loading of the muscle is exemplified in the jump. Between motoneurons to the femur muscles there are other neuronal interactions which accommodate the mechanics of the jump. 6. The angle of the tibial-tarsal joint depends upon sense organs which monitor the angle of the femoral-tibial joint. This inter-joint reflex sums with the local resistance reflex, centrally determined posture and voluntary movements. 7. The study of postsynaptic potentials (p.s.ps) makes possible a number of inferences about the nature of the interneuron pathways antecedent to the motoneurons. 8. Motoneurons to the same muscle usually have a high proportion of p.s.ps in common. Fast motoneurons have phasic properties because they have higher thresholds than the corresponding slow ones, as shown in situations where the p.s.ps are similar. 9. Motoneurons to antagonistic muscles can have synchronous p.s.ps of opposite sign. 10. The intraleg reflex in (6) is controlled by separate interneurons to the motoneurons that are excited together. 11. Study of the inputs upon groups of named motoneurons allows identification of the interneurons which act on them, and reveals that posture, elicited responses and spontaneous movements are determined by selection of different combinations of interneurons. 12. The same method, of recording simultaneously from several known central neurons can progressively reveal the unknown mechanisms by which interneurons integrate sensory input and generate coordinated responses.
118 citations
108 citations
TL;DR: The considerable progress which has been made in the last ten years in elucidating the rules governing the form and composition of cells of Escherichia coli as a function of growth rate and transit time is outlined in the Review.
Abstract: The size, shape and composition of cells in cultures of bacteria maintained in steady states of exponential growth depend on the cultural conditions employed. Important factors influencing these parameters are the growth rate of the culture and the transit time of replication forks from one end of a chromosome to the other. The considerable progress which has been made in the last ten years in elucidating the rules governing the form and composition of cells of Escherichia coli as a function of growth rate and transit time is outlined in the Review.
TL;DR: Six associated rhynchosaur skeletons, recently discovered by the Geological Studies Unit of the Indian Statistical Institute in the Upper Triassic Maleri Formation, allow an almost complete osteological description and restoration of the species Paradapedon huxleyi.
Abstract: Six associated rhynchosaur skeletons, recently discovered by the Geological Studies Unit of the Indian Statistical Institute in the Upper Triassic Maleri Formation, allow an almost complete osteological description and restoration of the species Paradapedon huxleyi. The dentition is highly specialized, ankylothecodont, each tooth firmly fixed with a long root, new teeth added posteriorly in diagonal rows, without tooth replacement. The creatures probably lived in flood-plains or marshy environments, as shell eaters feeding mainly on mussels. Possible evolutionary trends within the family Rhynchosauridae are outlined. The seven genera of rhynchosaurs are grouped on their morphological characters into three well-defined subfamilies which represent three stages in rhynchosaur evolution, occurring in Lower, Middle and Upper Triassic respectively.
TL;DR: It is hypothesized that membrane-attachment of specific regions of the chromosomes are a means to their ordered arrangement during interphase and prophase and underline the relationship to the endoplasmic reticulum.
Abstract: The ultrastructure of the nuclear evelope is described in various cell types with special emphasis on its pore complexes (p.c.). The architecture of the p.c. is defined against the properties of other membranous pore formations. Evidence is presented that the non-membranous p.c. components contain ribonucleo-proteins but do not represent the attachment sites of nuclear chromatin. The possible dynamic nature of the p.c. material is discussed in relation to nucleocytoplasmic translocation processes. DNA of the nuclear genome is firmly attached to interporous sections of the inner nuclear membrane. The stability of this attachment is demonstrated, and chemical and conformational characteristics as well as periods and kinetics of replication are given for both isolated membrane DNA and the corresponding chromatin in situ. The membrane-associated chromatin is dominated by a heterochromatinous character; it does not represent a transitory membrane interaction of replicating DNA. It is hypothesized that membrane-attachment of specific regions of the chromosomes are a means to their ordered arrangement during interphase and prophase. Structure, lipid, protein and enzyme pattern of the nuclear membranes, as well as the incorporation kinetics, underline the relationship to the endoplasmic reticulum.
TL;DR: The general neuroanatomy and details of the nerve roots in the mesothoracic ganglion of adult males of Periplaneta americana are examined and the probable correspondence of some of them with previously identified metathoracics neurons is discussed.
Abstract: Bodian silver-stained sections and Procion Yellow impregnation w ere used to examine the general neuroanatomy and details o f the nerve roots in the mesothoracic ganglion of adult males of Periplaneta americana (L .). General structure of the ganglion is summarized and the basic plan of its tracheation outlined. Fresh details are given of the seven paired longitudinal fibre tracts and ten transverse commissures, and three new oblique tracts of characteristic shape are described : the ring tract, G -tract and I-tract. Regions of the ventral association centre are briefly described. Groups of neuron cell bodies, which lie peripherally in the ganglion, are designated according to position. The fibre bundles that form the roots of each of the six paired peripheral nerves (nerves 2 -7 ) and the single median nerve (nerve 8) are numbered from dorsal to ventral and their courses and fibre com position described. In all, 30 roots are characterized on each side o0f the ganglion, containing over 150 efferent, presumed motor, fibres and over 2000 afferent, presumed sensory, fibres. Function and fibre diameter are not consistently related and almost all sizes of both motor and sensory fibres occur. Nerves 2 and 6 divide into distinct dorsal and ventral roots; the roots of nerves 4 and 8 are dorsal and of nerve 7 solely ventral; roots of nerves 3 and 5 form fairly continuous series from dorsal to ventral. The more dorsal nerve roots tend to be motor in function and the ventral roots sensory. Nearly all motor cell bodies are located ventrally or ventrolaterally and their processes run m ore or less dorsally to give off dendritic branches into dorsal or lateral neuropile before sending axons peripherally in the nerve trunks. Cell bodies of nerves 3 -6 , except for one in the midline, are ipsilateral, those of nerves 3 and 4 lying almost wholly anteriorly and of nerves 5 and 6 both anteriorly and posteriorly. Cell bodies of nerve 2 are contralateral and anterior except for one in the dorsal midline. Nerve 8 receives axons from posterior cell bodies of both sides. An apparently common inhibitorym otoneuron branches to nerves 3 -6 . The topology of some other motoneurons, chiefly of nerves 4 and 5, is outlined and the probable correspondence of some of them with previously identified metathoracic neurons is discussed. Sensory roots, predominantly of very small fibres, of nerves 2, 3 and 5 -7 enter the ventral association centre. Mainly coarser sensory fibres branch into mid-level neuropile or below , though some of those of nerves 2, 3 and 7 ascend more dorsally.
TL;DR: This study shows that the latter two families of the Verticordiidae have been derived from the Anomalodesmacea, and shows that most of the eighteen species have a stomach identical to that of the septibranch families, however, one or two species show limited ciliated surfaces intermediate in extent between the anomalodesmacean, as exemplified by Lyonsia, and the sePTibranch condition.
Abstract: This study forms part of a larger study on the ecology and functional morphology of deep sea bivalves of the Atlantic. Eighteen living species of the family Verticordiidae are described, of which eight are new species. The descriptions include shell morphology and a detailed analysis of anatomy, particular attention being paid to the mantle, gills and alimentary canal. The Verticordiidae are only taken in deep water and form a small but persistant fraction of the bivalve fauna. They have a morphology that is intermediate between species of the order Anomalodesmacea and the septibranch species of the Poromyidae and Cuspidariidae, and this study shows that the latter two families have been derived from the Anomalodesmacea. The structure of the hinge is very similar to that of species of the latter order as, too, is the gill which, although reduced, is typically eulamellibranch in form. Progressive reduction in the size and the number of lamellae of the gill is evident. With reduction there is an increase in the extent of the gill membranes that are attached by tissue fusion to the mantle, the body and the septum between inhalent and exhalent apertures, i.e. an intermediate stage between the eulamellibranch and septibranch conditions. In contrast, most of the eighteen species have a stomach identical to that of the septibranch families. However, one or two species show limited ciliated surfaces intermediate in extent between the anomalodesmacean, as exemplified by Lyonsia, and the septibranch condition. In addition, the Verticordiidae show features peculiar to themselves. The mantle edge is glandular. The glands take the form of discrete multicellular radial structures. The region of inhalent and exhalent tentacles is richly supplied with papillae that secrete an adhesive fluid. The secretion has two functions; to assist the animal to maintain a position at the surface of the very soft abyssal sediment, and to capture food organisms such as copepods. The sticky tentacles are spread out over the surface of the sediment. On capture the food is 'licked' off the tentacles by an inhalent valve and falls, or is carried, to a posteriorly facing buccal funnel formed by the expanded lips. The palps are extremely reduced in size. Oesophagus and stomach are muscular and the stomach is lined with a scleroprotein and is a crushing organ. It is interesting to note that the rectal region of the hind gut is expanded, probably to assist in further digestion of food remains. This is a further example of hind gut modification in abyssal bivalves, where it is essential that food should be utilized to the full. Other unusual features are the large size of the kidney, often extending along each side of the body as far forward as the mouth. Associated with the kidney is a lacunar system of unknown function. The Verticordiidae are hermaphrodites, producing small numbers of large eggs. Prodissoconch measurements indicate that they have at most a short pelagic life. However, individual species are widespread, many being found on both sides of the Atlantic from arctic to equatorial latitudes.
TL;DR: The Wretton terrace as mentioned in this paper is a low terrace of mainly fluviatile sands and gravels of Devensian age, which contains many organic horizons rich in plant remains, molluscs and bones, and shows well-developed periglacial structures, including involutions and ice-wedge casts.
Abstract: The low terrace at Wretton, Norfolk, is shown to consist of up to 6 m of mainly fluviatile sands and gravels of Devensian age. It contains many organic horizons rich in plant remains, molluscs and bones, and shows well-developed periglacial structures, including involutions and ice-wedge casts. Organic deposits lie in channels beneath, within and above the fluviatile sediments, and also within small depressions, a few metres across, which are interpreted as features formed by the melting of ground-ice mounds. The succession within the terrace is complex, but the detailed sections observed, with petrographical, palaeobotanical and molluscan studies, allow a synthesis of the environmental changes which accompanied terrace formation. The petrography of the sediments in the depressions indicates that certain of the ground-ice mounds formed in lenses of sandy clay derived from weathered interglacial sediments. The sediments redeposited on the melting of the mounds have a characteristic particle-size distribution. Times of coversand formation within the terrace sequence are identified. The palaeobotanical study, by analysis of pollen and macroscopic plant remains, reveals a sequence of pollen assemblage biozones. There are three periods with biozones characterized by herb pollen spectra. These are separated by periods with biozones characterized by pollen spectra indicating the presence of woodland. The earlier sequence of the woodland biozones, named the Wretton interstadial, shows birch-pine woodland and heath. The later sequence shows pine-birch-spruce woodland and heath, and is correlated with the Chelford interstadial. A detailed consideration of the flora and vegetation of the herb biozones is given, with a comparison of the pollen spectra with recent pollen spectra from the Arctic. It is concluded that in these biozones vegetation physiognomically akin to grassland prevailed in the region. Molluscan faunas, found at several horizons, are typical of Early Devensian deposits in other parts of the Fenland drainage basin. The number of species is restricted, but southern forms do survive in small numbers from the Ipswichian interglacial even into the third grassland biozone of the Devensian. On the basis of the periglacial features and plant and animal remains, it seems that the climate was generally continental, with mean annual temperatures at or below 0 $^\circ$ C, probably as low as -8 $^\circ$ C at times of ice-wedge formation, with mean July temperatures as high as 15 to 20 $^\circ$ C. In the pollen-based interstadials the climate was considerably more oceanic. The methods of subdivision of the Devensian are considered, and the sequence then correlated with other Early Devensian sites in England and on the Continent. The Wretton and Chelford pollen-interstadials may be of the same age as the Amersfoort and Brorup interstadials respectively of the Netherlands. The associated herb biozones represent periods before, between and after the pollen-interstadials. The transition from the Ipswichian interglacial to the Devensian in the region of the eastern Fenland margin is considered. Grassland was already present in the late Ipswichian, and the transition to the Devensian was accompanied by a loss of some taxa and a gain of others, with many taxa present in both stages. The coleopteran and moss assemblages from the deposits are described in appendices. There is an unresolved discrepancy between the environmental evidence of the Coleoptera and the pollen in the later woodland biozone, the Coleoptera indicating a barren sandy landscape.
TL;DR: It is suggested that plastic deformation of the intra-membrane protein particles may occur, and that this may be responsible for the lack of small-scale complementarity in freeze-fracture replicas.
Abstract: Basic freeze-etching methods are described. When biological membranes are freeze-fractured the fracture plane is smooth, but interrupted to a greater or lesser extent by numbers of small (8.5 nm) particles. The evidence that the fracture occurs in the interior of the membrane and that the particles represent proteins within the membrane is reviewed. A problem of interpretation of freeze-fracture replicas is that the two 'complementary' faces, produced by the fracture of a single membrane, do not match exactly. In particular, particles on one face are often not matched by corresponding depressions on the other. Work in the author's laboratory using the complementary replica technique is described. One conclusion from this work is that plastic deformation of the intra-membrane protein particles may occur, and that this may be responsible for the lack of small-scale complementarity.
TL;DR: The results indicate that the physique of the Lufa Highlanders has features in common with high-altitude populations, as well as contributing to the variation in anthropometric characteristics with age, although the relative contributions of these phenomena appear to differ in the two populations.
Abstract: Child growth, adult physique and somatic changes in old age are compared in the two populations by means of a cross-sectional survey. The results indicate that the physique of the Lufa Highlanders has features in common with high-altitude populations. Throughout the growth period the Lufa people are heavier, more muscular and skeletally more robust than the Karkar Islanders. Maturity is reached earlier in the coastal population and the close relation between adult height, child growth rate and maturity observed in some parts of New Guinea, including Lufa, does not apply to the island community. The two populations are similar in adult height but differ significantly in body proportions and in dimensions of the head and face. Ageing proceeds rapidly after the third decade and the effects appear with greater uniformity than in Western populations. Decrease in body mass is particularly striking. Physiological and pathological ageing together with secular trends contribute to the variation in anthropometric characteristics with age, although the relative contributions of these phenomena appear to differ in the two populations.
TL;DR: Sections in the Icenian Crag at Chillesford, Aldeburgh, Thorpe Aldringham, Sizewell, Dunwich, Wangford and Southwold are described in this article.
Abstract: Sections in the Icenian Crag at Chillesford, Aldeburgh, Thorpe Aldringham, Sizewell, Dunwich, Wangford and Southwold are described. Pollen and mollusc assemblages from these sites are tabled. The Icenian Crag is shown to contain a temperate pollen assemblage, resulting from a regional deciduous forest of the time. The assemblage is provisionally correlated with the Pastonian stage of the Middle Pleistocene, as Tsuga is very poorly represented and Abies is absent. The mollusc assemblages are divided into a sublittoral or infralittoral facies, a sheltered estuarine or wadden area facies, an open coast facies and a high-boreal or sub-arctic silty deposit facies, probably infralittoral. The unconformable relation of the Icenian Crag to Red and Coralline Crags at Chillesford and Aldeburgh and to Baventian sediments at Easton Bavents indicates a strong marine transgression over Lower Pleistocene deposits in Pastonian times. The beach plain of the Westleton Beds is included within this transgressive phase. Pollen assemblages from deep boreholes at Sizewell and Southwold show that the transgression deposits overlie Lower Pleistocene sediments correlated with the PreLudhamian, Thurnian and Baventian stages. A correlation is suggested between the Pastonian and the Cromerian III Interglacial of the Netherlands.
TL;DR: For the healthy young adults, analysis of the lung function data in relation to those for exercise point to the differences between the groups being due to the combined effects of an ethnic factor plus differences in the level of physical activity.
Abstract: 1. Information on respiratory symptoms and, in most instances, the ventilatory capacity (forced expiratory volume and forced vital capacity) were obtained on 2026 men, women and children comprising the total population of 12 villages situated at 2000 m in the Eastern Highlands and 1736 coastal people on Karkar Island. On selected healthy adults measurements were made of the total lung capacity and its subdivisions, the transfer factor for the lungs for carbon monoxide (151 subjects aged 20-63 years) and the ventilation and the cardiac frequency during submaximal exercise (132 subjects aged 17-34 years). The transfer factor was standardized to a haemoglobin concentration of 14.6 g/100 ml and alveolar capillary oxygen tension of 14.7 kPa (110 Torr). 2. The ventilatory capacity was reduced by the presence of respiratory symptoms or a loose cough but not by smoking local tobacco (Brus). For subjects with apparently healthy lungs and after allowing for the effects of age and of stature, the ventilatory capacity of the highland men, women and children was similar to that of representative Europeans. The coastal people had lower values including lower partial regression coefficients on age. The total lung capacity, its subdivisions and the transfer factor for the adult highlanders were larger than for the coastal people; the values were similar to or larger than for Europeans. The values for the coastal people resembled those for people of Indian, African and Chinese descent living in the tropics. The partial regression coefficient of transfer factor on age in the New Guineans was more negative than in the Europeans. 3. For the healthy young adults, analysis of the lung function data in relation to those for exercise point to the differences between the groups being due to the combined effects of an ethnic factor plus differences in the level of physical activity. The lung volumes, ventilatory capacity and ventilation during exercise are the resultant of both effects. The exercise tidal volume is a function of the ethnic factor but not the level of activity, while the reverse is true of the lung transfer factor for carbon monoxide.
TL;DR: The mode of implantation is shown to be very different from that in hyrax, which superficially resembles Loxodonta in the morphology of the foetal membranes, and developmental characters are discussed with reference to their functional significance, and compared with the corresponding changes in the Carnivora.
Abstract: The implantation of the blastocyst of Loxodonta, and the early development of the placenta, are described from material collected in Africa by Dr R. M. Laws. Implantation is central, the blastocyst settling in one of three or four deep longitudinal grooves in the uterine lumen. Its growth distends the uterine horn before it becomes attached to the uterine wall. As the bilaminar blastocyst continues to grow the trophoblast erodes the uterine epithelium over a zonary area and is there closely applied to the uterine stroma. It remains unattached over the embryonal and abembryonal poles, where the uterine epithelium is retained. As the yolk-sac approaches its maximum volume it is invested by mesoderm, forming an extensive trilaminar omphalopleur, the outer layer (trophoblast) of which immediately begins to invade the uterine stroma by peg-like proliferations that enter by the uterine glands. The latter undergo little change during these early stages and do not undergo extensive modification at any stage, but their basal portions become moderately distended after the gland openings are blocked by the trophoblast. As the trophoblast of the yolk-sac wall invades the stroma the allantois reaches the chorion and from this time the yolk-sac is rapidly reduced in volume. The allantois soon fills the exocoel and occupies the whole cavity of the conceptus surrounding the embryo and amnion. The allantochorionic placenta develops (over three discrete areas in the specimen described) by the growth of villi which are formed as the earliest trophoblast proliferations acquire a mesenchymal core and become vascularized. There remain areas where the trophoblast does not attach to the uterine wall and in these areas the uterine epithelium proliferates in a characteristic manner and appears to shed cellular material into the residual uterine lumen. As the allantochorionic villi develop, the underlying uterine stroma thickens, and large blood channels appear in it, lined by a shallow endothelium. These blood vessels, which have few branches, penetrate to the face of the placenta. Their investment by the advancing trophoblast leads to the 'vasochorial' condition described in an earlier account. The characteristic marginal haematomata of the elephant apparently form where an extending villous area meets an area of intact (although modified) uterine epithelium. This epithelium is undermined by lateral extension of the invading foetal tissue and some of the adventitious maternal blood vessels that reach the face of the placenta are disrupted and release blood into the uterine lumen where the stromal tissue is exposed between the advancing foetal villi and the surviving uterine epithelium. This blood is trapped in folds of the allantochorion, the trophoblast cells of which often contain maternal erythrocytes. These developmental characters are discussed with reference to their functional significance, and compared with the corresponding changes in the Carnivora, most of which are also characterized by an endotheliochorial placenta of zonary form with haematomata, marginal or otherwise. It is suggested that their occurrence is related to the intermediate position of the endotheliochorial placenta between the epitheliochorial type, in which the uterine glands contribute more importantly to embryonic nourishment, and the haemochorial type, in which transfer from the maternal circulation to the trophoblast is facilitated by the direct contact between them. The mode of implantation is shown to be very different from that in hyrax, which superficially resembles Loxodonta in the morphology of the foetal membranes. Comparison is also made with the aard-vaak and the manatee. The aard-vaak has a zonary endothelial placenta, marginal haematomata and a quadrilocular allantois, but does not resemble Loxodonta closely in detailed placental structure. The mid-term placenta of the manatee, on the other hand, bears a very striking resemblance to that of the elephant in many respects, especially in the manner in which the trophoblast is modified where it invests large maternal blood vessels. The phylogenetic significance of these similarities and differences is briefly discussed.
TL;DR: Intracellular recordings from tonic and phasic expiratory, inspiratory and spiracular motoneurons and presumed sensory integrating neurons of the metathoracic ganglion in a locust imply that the mechanism of the ventilatory rhythm lies among interneurons.
Abstract: 1. Intracellular recordings have been made from tonic and phasic expiratory, inspiratory and spiracular motoneurons and presumed sensory integrating neurons of the metathoracic ganglion in a locust during rhythmic ventilatory movements of the abdomen. The neurons have somata with diameters of no more than 30 $\mu$ m situated on the ventral surface of the ganglion. 2. No motoneurons showed an intrinsic rhythmicity, all being driven in the ventilatory rhythm by complex patterns of synaptic inputs in one of the following ways: (a) excitation alone during the phase when spikes are produced (spiracle closer and some tonic expiratory motoneurons); (b) excitation during one phase and inhibition during the other (some tonic expiratory motoneurons); (c) excitation and inhibition during both phases (most motoneurons) in which one type of input dominates a particular phase. 3. The burst of spikes by a particular motoneuron may end because of a lack of excitatory input (spiracle closer motoneurons) or be terminated rapidly by inhibition (inspiratory motoneurons). Inhibition may also precede the main burst of spikes (inspiratory motoneurons) so that any spikes during the opposite phase are abolished. The pattern of synaptic input determines the frequency code of spikes within a burst. 4. Phasic expiratory motoneurons receive an underlying pattern of synaptic inputs in phase with ventilation even when they do not spike. Non-specific excitation (for example, a d.c. depolarization of the soma) is able to produce bursts of spikes in the correct phase of ventilation. 5. No direct pathway between any groups of motoneurons was found. Driving by common antecedent interneurons is inferred for those motoneurons which show similar patterns of spikes (inspiratory and spiracle closer motoneurons). 6. Stimulation of descending fibres in the pro-mesothoracic connectives evokes e.p.s.ps in some motoneurons, perhaps monosynaptically. In inspiratory motoneurons these fibres cause e.p.s.ps but will abolish the inspiratory burst of spikes and reset the ventilatory rhythm. All observations imply that the mechanism of the ventilatory rhythm lies among interneurons.
TL;DR: The structure and function of such an array are being examined in a study of the Gram-negative bacterium Acinetobacter strain MJT/F5/199A, and its relevance to the formation of surface layers composed of regular arrays of subunits in intact bacteria discussed.
Abstract: Regular arrays of subunits are observed on the surfaces of many bacteria, and the structure and function of such an array are being examined in a study of the Gram-negative bacterium Acinetobacter strain MJT/F5/199A. The subunits are on the surface of the outer membrane and are visible in electron micrographs of freeze-etched intact cells and of negatively stained preparations of isolated cell walls and outer membranes. The surface subunits can be detached from the membrane by various treatments and will then reassemble spontaneously to form the same regular pattern as that seen on the intact bacterium. The results of studies of the properties of the self-assembly system are described and its relevance to the formation of surface layers composed of regular arrays of subunits in intact bacteria discussed.
TL;DR: A model explaining the role of cellular membranes in protein secretion is proposed, proposing that the intracellular transport is effected through the specific non-random interaction (fusion-fission) and recycling of the various participating membranes.
Abstract: In pancreatic acinar cells the intracellular transport of secretory proteins occurs through the interconnexion of distinct membrane-bounded compartments: in series, the rough surfaced endoplasmic reticulum (r.e.r.), the Golgi complex (g.c.) and the secretory (zymogen) granules (z.g.). The latter organelles are able to fuse their membrane with the plasmalemma (pm.) and discharge their content by exocytosis. In order to investigate the mechanisms by which the intracellular transport occurs we have investigated the composition as well as the rate of synthesis and turnover of the various membranes involved in the process. We found that these membranes have distinct differences in chemical composition and in the distribution of enzyme activities and that their rate of turnover is much slower than that of secretory proteins. Furthermore, SDS polyacrylamide gel electrophoresis of doubly labelled membrane proteins revealed that in each of these membranes there is a marked heterogeneity of turnover rates. These data indicate (a) that the membranes participating in the intracellular transport interact with one another in a non-random fashion, (b) that they are not synthesized concomitantly with the secretion products, (c) that membranes are synthesized independently from one another, and (d) that they are re-utilized in several secretory cycles. Consistent with these results, a model explaining the role of cellular membranes in protein secretion is described. It is proposed that the intracellular transport is effected through the specific non-random interaction (fusion-fission) and recycling of the various participating membranes. The possible relevance of these findings to other secretory systems is discussed.
TL;DR: Clinical evidence of malnutrition was not prominent in either location although occasionally encountered at Lufa, and the normal range of a number of biochemical fractions in the serum has been established for both populations and these can be compared with those in other societies.
Abstract: Assessments of the health standards of the population of two village complexes, selected for investigation in the I.B.P. Human Adaptability Studies in New Guinea, have been made. These investigations have been extended on Karkar to permit a study of epidemiological patterns on the whole island. The observations at Lufa have been made in conjunction with investigations of health in the general area of the Eastern Highlands of New Guinea. Chronic degenerative diseases were uncommon in both locations and particularly noteworthy was the absence of the diseases commonly associated with Western society, such as hypertension, arteriosclerosis, diabetes mellitus and gout. The incidence of chronic infectious diseases in both localities has been influenced by the available health services and the duration of Western contact. The warm, moist climate on Karkar creates an environment which is suitable for the existence of mosquitoes and the presence of endemic malaria contrasts with the infrequent sporadic cases of this disease at Lufa. Differences in the prevalence of certain other infections may also be the result of climatic variations, e.g. the prevalence of certain alimentary parasites, of yaws and of some skin diseases. Tuberculosis is quite prevalent on Karkar and absent at Lufa. Clinical evidence of malnutrition was not prominent in either location although occasionally encountered at Lufa. Anaemia was an almost universal finding on Karkar and, although neither as severe nor as common, was also seen at Lufa. Various investigations have been undertaken to account for the basis of the anaemia, which appears to be principally due to iron deficiency aggravated by chronic malaria and alimentary parasitaemia. The only other evidence of a deficiency disease was the presence of goitre in significant numbers of young women on Karkar. The normal range of a number of biochemical fractions in the serum has been established for both populations and these can be compared with those in other societies.
TL;DR: In this article, body-temperature regulation has been studied in two communities in New Guinea and the results did not reveal any important difference in response between the coastal villagers and the highland people.
Abstract: Body-temperature regulation has been studied in two communities in New Guinea. On Karkar Island in the hotter coastal region, 40 young adult males and the same number of young female villagers, together with 39 plantation workers and 14 Europeans, were examined. At Lufa, near Goroka, in the cooler and drier highlands, 30 male and 25 female adult villagers, together with 36 older people, were investigated. Tem perature regulation was studied using an air-conditioned bed in which the subjects received standardized exposures to cool and warm environments and the sweating response was measured during controlled hyperthermia at 38 °C. The results did not reveal any important difference in response between the coastal villagers and the highland people. The Europeans living on Karkar Island had the high sweating capacity which is characteristic of the acclimatized European, whereas the sweat rates of the New Guinea people were closely comparable to the level for an unacclimatized European. Comparison of the two sexes showed the lower sweat rates and the pattern of deep body and skin temperature changes found in women in previous studies using this technique. The changes in deep body temperature, skin temperature, blood flow and heart rate during the successive periods of exposure to a thermally neutral climate, with cooling and during rewarming, do not indicate that the indigenes of New Guinea utilize the vasomotor control mechanism more efficiently than Europeans.
TL;DR: The membrane system is made up of the nuclear envelopes, rough and smooth endoplasmic reticulum, Golgi apparatus and plasmalemma and it has been shown that the matrix polysaccharides of the wall are formed within the membranes and that the pattern of synthesis of these polymers changes during differentiation of the cells.
Abstract: The membrane system is made up of the nuclear envelopes, rough and smooth endoplasmic reticulum, Golgi apparatus and plasmalemma. Interconnexions between the various parts of the system are shown and these probably represent a flow of membrane from the endoplasmic reticulum through the Golgi apparatus to the plasmalemma. Membrane fractions have been isolated from broken cells and their function in the synthesis of polysaccharides established. It has been shown that the matrix polysaccharides of the wall (pectic substances and hemicelluloses) are formed within the membranes and that the pattern of synthesis of these polymers changes during differentiation of the cells. Cellulose microfibrils are probably synthesized at the plasmalemma which is formed by incorporation of membrane bounded vesicles from the Golgi apparatus. Thus the assembly of the polymers takes place either when the membrane is within the cytoplasm or when it is incorporated as the plasmalemma of the cell.
TL;DR: The effect of this topography on the genetic structure of the populations has been examined using a migration matrix model to predict patterns and levels of genetic heterogeneity from observations on the exchange of individuals between villages.
Abstract: Settlement on Karkar Island is confined to the perimeter, where some 59 villages are arranged more or less in a circle around a central volcanic cone. This cone is essentially impassable and communication links are also forced to follow a circular pattern. The effect of this topography on the genetic structure of the populations has been examined using a migration matrix model to predict patterns and levels of genetic heterogeneity from observations on the exchange of individuals between villages. The information incorporated in the matrix was obtained from the initial demographic survey of the island, in which place of birth and place of residence of the 16 000 inhabitants was recorded. Social organization is patri-local and most of the permanent movement occurs through women moving from their village of birth to that of their husbands. The effects of the enforced circular nature of this movement are clearly apparent but other factors such as tribal affiliations and impassable areas of forest are also important.
TL;DR: Purified fractions of nuclei from rat liver and isolated calf thymocytes are treated with 0.5 M MgCl $_2$ or with an alkaline buffer, pH 8.5 to dissociate nuclear membranes from the chromatin, finding no marker enzymes for the nuclear membrane.
Abstract: Purified fractions of nuclei from rat liver and isolated calf thymocytes are treated with 0.5 M MgCl $_2$ or with an alkaline buffer, pH 8.5. Such procedures dissociate nuclear membranes from the chromatin. The membranes are simply floated in a gradient. The recovery in the membrane band obtained by the Mg $^{2+}$ technique is 55 to 60%. Freeze-etching studies of the membrane pellets provide a good way to check their purity, pores being very conspicuous. A 5'-nucleotidase and an ATPase are detected on the nuclear membranes of thymocytes, as well as a still undescribed 3'-nucleotidase. However, no marker enzymes for the nuclear membrane have been found. The topology of sugar residues on the nuclear membranes is studied by means of lectins. Concanavalin A binds in large amounts to nuclear envelopes, both on the inner and outer leaflets, but not to pores.
TL;DR: The results show that the integrity of the motoneuron is essential for maintenance of its synaptic inputs and the opposite to those expected from simultaneous changes in the time constant.
Abstract: Four interneurons of the ventral cord, the descending movement detectors (DMD) have symmetrical synapses upon the fast extensor tibiae (FETi) motoneurons on each side of the metathoracic ganglion. Each impulse in a DMD interneuron generates an excitatory post-synaptic potential (e.p.s.p.) of constant and similar amplitude in both FETi motoneurons of a normal locust. The symmetry provides inherent controls which makes this a convenient system to study the effect on inputs to a motoneuron caused by peripheral section of its axon. On the operated side the retrograde changes in the FETi motoneuron include, first an increased amplitude of the e.p.s.ps, then a brief period when they are variable, followed by a progressive reduction over a period of days. Other inputs to the FETi motoneurons from head, abdomen and tympanum also decline, but not at equal rates. Changes in e.p.s.p. amplitude are the opposite to those expected from simultaneous changes in the time constant. The observed changes in the e.p.s.ps are attributed to instability and then progressive loss of synapses upon the FETi motoneuron. The results show that the integrity of the motoneuron is essential for maintenance of its synaptic inputs.