Showing papers by "University of Aberdeen published in 1978"

Sequence of chicken ovalbumin mRNA

Abstract: The complete sequence of chicken ovalbumin mRNA is presented; it is 1,859 residues long, excluding its terminal 'cap' and poly(A). The region coding for ovalbumin lies close to the 'cap' but is separated from the poly(A) by an extensive 3' noncoding region of 637 nucleotides which may have no function that is precisely dependent on its sequence.

Glacial Erosion by the Laurentide Ice Sheet

Abstract: The aim of the paper is to analyse landscapes of glacial erosion associated with the Laurentide ice sheet at its maximum and to relate them lo the three main variables affecting glacial erosion, namely former basal thermal regime of the ice sheet, the topography of the bed, and the geology of the bed. The key to the analysis is the comparison of the distribution of landscape types with the simulated pattern of the basal thermal regime of the former ice sheet. Landscapes of areal scouring are found to be associated with zones of basal melting and occur beneath much of the former ice-sheet centre and in those places where the topography favoured converging ice flow. The landscape type may also have formed beneath cold-based ice when it was carrying debris inherited from an up-stream zone of regelation. Areas with little or no sign of glacial erosion occur primarily in the north in the Queen Elizabeth Islands but they also occur on uplands associated with diverging ice flow; they coincide with areas calculated to have been covered by cold-based ice devoid of debris. Landscapes of selective linear erosion are common on uplands near the eastern periphery of the ice sheet. In these situations, pre-existing valleys channelled ice flow and created a situation where there was warm-based ice over the valleys and cold-based protective ice over the intervening plateaux. Variations in the permeability of the bedrock base have modified the landscape pattern, mainly in those areas where there was a change from one basal thermal regime to another. In general, permeable rocks tend to have experienced less erosion than impermeable rocks. Using lake-basin density as an indication of the intensity of glacial erosion, a zone of maximum erosion is identified and this forms a ring between the centre of the former ice sheet and its periphery. This ring coincides with a zone where melt water from the ice-sheet centre is calculated to have frozen on to the bottom of the ice sheet. This regelation incorporated basal debris into the ice, forming a basal layer 20-50 m thick and afforded an efficient means of debris evacuation. A conceptual model is developed and hangs round the following postulates: (1) Landscapes of glacial erosion are related primarily to the basal thermal regime of the ice sheet. (2) Landscapes of glacial erosion are equilibrium forms related to maximum glacial conditions. This implies that at some stage in the Pleistocene the Laurentide ice sheet was in a stable maximum condition for a long period of time. (3) Mechanisms allowing evacuation of debris rather than those of abrasion or fracture may be the most important in influencing the amount of erosion achieved by an ice sheet. (4) Cold-based ice may accomplish erosion if it contains debris.

The size ramsey number

Abstract: Let denote the class of all graphsG which satisfyG→(G 1,G 2). As a way of measuring minimality for members of , we define thesize Ramsey number ř(G 1,G 2) by . We then investigate various questions concerned with the asymptotic behaviour ofř.

Resources, Environment, and Economics: Applications of the Materials/Energy Balance Principle

Abstract: Presents the basic economic and physical theory underlying modern resource/environmental economics, its application to the construction of analytical models, and the corresponding requirements for statistical data. Places particular emphasis on realistic'' models. Maps past, present and future flow of materials and energy through processing, consumption, and environmental wastes. Discusses available data sources and the organization of data into appropriate statistical subsystems. Jointly treats economic and technological considerations.

The Measurement of Optical Radiation Pressure in Dispersive Media

Abstract: The paper describes the details of a repetition of the Jones-Richards experiment (1954) to compare the recoil of a mirror due to the radiation pressure of light striking it in an optically dense medium with the recoil of the same mirror from the same light in air. A more than tenfold improvement in precision has been possible through the development of the laser and of multilayer reflectors of high reflectivity and low absorption. The new experiment confirms, to a precision of about 0.05%, that the momentum associated with electromagnetic radiation increases directly with the refractive index of the medium into which it passes, discriminating substantially in favour of the phase velocity ratio and against the group velocity ratio. The experiment also shows that the magnitude of recoil of a mirror in oblique incidence does not vary, within the foregoing precision, when the plane of polarization is changed from perpendicular to parallel to the plane of incidence.

In vitro release of Leu- and Met-enkephalin from the corpus striatum.

Abstract: WE have suggested previously that Met-enkephalin and Leu-enkephalin1 may act as neurotransmitters in the central and peripheral nervous systems2,3. Recent studies on the distribution of the enkephalins support this view4–6. An important step in establishing a possible neurotransmitter role of the enkephalins is the demonstration of their release from neuronal sites by potassium ions or veratridine. Indirect evidence for the release of enkephalin or endorphin has been provided by several workers7–10. We now present direct evidence for such release from isolated brain slices and synaptosomal preparations.

Infectious mononucleosis and Hodgkin's disease

Abstract: A cohort of 9,454 patients with infectious mononucleosis, serologically confirmed, was followed up to determine their risk of developing lymphoproliferative diseases. A total of 1,759 patients was identified in Scotland from 1959 to 1971 and 7,695 in Sweden from 1952 to 1970. The cancer cases were identified by matching the list of patients with infectious mononucleosis against a list of patients with lymphoma, nasopharyngeal and colon carcinomas registered through 1972 in Sweden and through 1973 in Scotland. A four-fold increase in risk was found for Hodgkin's disease based on 7 cases observed against 1.8 expected. Most of the excess cases of Hodgkin's disease occurred within three years of the diagnosis of infectious moonucleosis and among females. These results are similar to those of four other cohort studies and it is concluded that a positive association exists between infectious mononucleosis and Hodgkin's disease. Several explanations of this association were evaluated. Firstly, it may be that a very small proportion of persons who are in the course of developing Hodgkin's disease are temporarily misdiagnosed as having infectious mononucleosis. Secondly, infectious mononucleosis may increase the susceptibility to a factor which causes or promotes the development of Hodgkin's disease. Thirdly, infectious mononucleosis and Hodgkin's disease may share a common aetiology. Arguments in favour of, or against, each of these explanations are presented.

Age and origin of the major syenite centers in the Gardar province of south Greenland: Rb-Sr studies

Abstract: Rb-Sr whole-rock isochron data for nine intrusive centers (including the major oversaturated and undersaturated syenite bodies) in the Precambrian Gardar alkalic igneous province of south Greenland complete a systematic isotopic study of the major complexes of the region (15 distinct igneous centers). The new data show that magmatic activity occurred throughout the region over a period in excess of 150 m.y. and that there is a clear distinction between two major magmatic events — an early Gardar (∼1,300 m.y. old) event and a more widespread late Gardar (∼1,160 m.y. old) event, which also involved extensive east-northeast-trending dike emplacement. Two relatively small intrusions in the western part of the province have middle Gardar (∼1,250 m.y. old) ages. There does not appear to be any relationship between emplacement age and geographic location, mode of emplacement, or the recognized petrologic division into saturated or undersaturated types; indeed, some adjacent complexes with strikingly similar petrologic characteristics have originated during different events, and, conversely, adjacent complexes with very different compositions are chronologically indistinguishable with present techniques. Initial 87 Sr/ 86 Sr ratios for the Gardar rocks are broadly divisible into three groups. Low (0.702 to 0.704) ratios are characteristic of most of the intrusions in the province, including most of the syenites (both undersaturated and oversaturated) and gabbros —which indicates a primitive (mantle) origin for the parental Gardar magmas. Intermediate ratios (0.704 to 0.707) are observed in fewer centers, particularly in the Nunarssuit complex (gabbro, oversaturated syenites, and granites). For these centers, the possibility of closed-system enrichment in 87 Sr (by decay of 87 Rb during a complex molten history extending throughout 150 m.y. of Gardar time) is rejected as unlikely, as is a direct origin by partial melting of older crust; field, chemical, and isotopic evidence presented here strongly support a bulk-assimilation hypothesis. Only two complexes have high (>0.707)ratios; both show evidence of introduction of radiogenic 87 Sr into their magmas at a late stage of development through selective leaching of radiogenic 87 Sr from older crust, and both of these complexes are associated with mineralization.

Apomixis may be widespread among trees of the climax rain forest

Abstract: THE exceptional species diversity of tropical rain forests is well known; of these the lowland forests of the Malay Peninsula are among the richest1. This, and the size of the trees, pose obvious difficulties for the maintenance of pan-mixis, and tempt speculation on the processes by which such diversity has evolved and may now be favoured. Fedorov2 suggested that natural selection is low and self-pollination prevalent, favouring random genetic drift. Prevalence of random drift, or apomixis—agamospermy—would contradict Ashton's3 view that, given a stable environment, evolution proceeds through ecotypic differentiation while diversity accrues through ever increasing niche specialisation; for this view to be correct, maintenance of genetic variability within breeding groups would be essential. Solid evidence has been meagre but there is evidence4 that genetic polymorphism, and hence heterozygosity, is common in the emergent tree Shorea leprosula Miq., and Xerospermum intermedium Radlk., an undeirstorey species. The pattern of spatial variation is consistent with the view that these species are outbreeders in which predominantly short-range pollen and fruit dispersal are accompanied by short-range heterogeneity in gene frequencies. However, both are common trees with minimal spatial isolation. We now report the occurrence of apomixis in some other rain forest trees.

Normal and anomalous tobermorites

Abstract: SUMMARY. Tobermorite minerals vary in some properlies, notably in whether or not unidimensional lattice shrinkage occurs by about 300 ~ to give a 9"3/~ form; specimens that do this are called normal, and ones that do not, anomalous. Data are compared for thirteen natural tobermorites and the extent to which normal or anomalous character is related to other properties is examined. The most definite correlations found are with chemical composition and morphology. The conditions of formation of normal and anomalous tobermorites are discussed in the light of synthetic evidence. TOBERMORITE minerals vary in some properties, most notably in whether loss of molecular water is accompanied by unidimensional lattice shrinkage in the c-direction. Such shrinkage has been observed with specimens from Crestmore, California (Taylor, I953; Farmer et al., 1966), Ballycraigy, Northern Ireland (McConnell, 1954), and Fuka, Japan (Mitsuda et al., I972), but not with those from Loch Eynort, Scotland (Gard and Taylor, 1957) or Heguri, Japan (Mitsuda, 1973). Tobermorites that show this lattice shrinkage have come to be called 'normal' and ones that do not, 'anomalous'. In this paper, data are compared for thirteen natural tobermorites, and the extent to which normal or anomalous character is related to other properties is discussed. Specimens. These are described as 14/~ or I I/~ tobermorite according to the approximate value of the layer thickness. All the specimens mentioned in this paper are I r A tobermorites unless otherwise stated. Of the specimens listed below, all were examined in the present work except numbers 4 and 12. Table I gives analyses for most of them. (l) Crestmore, California: the r4 A tobermorite originally described by M urdoch (196 I) as 'Mineral Z' and further studied by Farmer et al. {I966). (2) Bingham, Utah (USNM 127132): the 14 A tobermorite described by Stephens and Bray (I973).

Incorporation of 6-thioguanosine and 4-thiouridine into RNA. Application to isolation of newly synthesised RNA by affinity chromatography.

Abstract: Isolation of newly synthesised RNA can be achieved by treatment of cells in culture with 6-thioguanosine or 4-thiouridine followed by separation of thiol-containing RNA by affinity chromatography on mercurated cellulose columns. After short periods of treatment with 6-thioguanosine the proportion of RNA retained on mercurated cellulose is the same for both poly(A)-containing and poly(A)-free RNA, indicating similar incorporation of the drug into mRNA and rRNA. However, after longer periods of exposure, the cytotoxic effect of 6-thioguanosine results in diminished incorporation of radioactive uridine into RNA and of radioactive leucine into protein; this suggests that synthesis of both RNA and protein are impaired. On the other hand, even after long exposure to high concentrations of 4-thiouridine, the syntheses of RNA and protein are not significantly affected. Proteins synthesised after treatment of cells with 6-thioguanosine are less stable than proteins synthesised after treatment of cells with 4-thiouridine.

The isolation and some properties of a lectin (Haemagglutinin) from Cucurbita phloem exudate.

Abstract: The occurrence of high haemagglutinating (lectin) activity in phloem exudate from three cucurbit species is reported. The protein responsible for this lectin activity in Cucurbita maxima Duch. has been isolated by cation exchange chromatography on Sepharose and identified by gel electrophoresis. The lectin showed agglutinating activity at concentrations as low as 0.1 μg/ml. No sugar, including those transported in the phloem of these species, interacted with agglutination. The lectin could not be extracted from cucurbit seed, but appeared in 5-day old seedlings. The possible role of a lectin in the sieve element is discussed.

A Critical Examination of the Photofit∗ System For Recalling Faces

Abstract: Three experiments are reported which investigate the Photofit System for face recall. In the first experiment it was found that constructions of the videotaped face of a man reading a factual text did not differ among groups of subjects who saw the face for either 15 s or 2-5 min. Further, instructions to attend to face or to the passage resulted in equally good constructions although those who attended specifically to the passage scored significantly higher on a subsequent comprehension test. The second experiment employed an experienced Police Photofit operator as well as our own research operator. Both supervised compositions made while the videotape ran during construction. The results from the two operators' subjects did not differ. Nor were these constructions judged to differ from those made from memory in experiment 1. Finally, the ability of subjects to sketch faces was compared with their ability to construct them under two conditions, working from memory after a 10 s exposure to the fa...

COMPARISON OF THE RECEPTOR BINDING CHARACTERISTICS OF OPIATE AGONISTS INTERACTING WITH μ‐ OR K‐RECEPTORS

Abstract: 1 The receptor binding characteristics of various morphine-like and ketazocine-like opiate agonists were measured by inhibition of [3H]-naloxone binding in homogenates of brain and of ileal myenteric plexus-longitudinal muscle of the guinea-pig. No differences were found for the two tissues. 2 The depressant effect of Na+ on the inhibition of [3H]-naloxone binding by opiate agonists varies widely, giving sodium shifts between 5 and 140. The relationship between Na+ concentration and inhibition of binding is non-linear, the magnitude of the sodium shift varying directly with the slope of the regression of log IC50 on log [NaCl]. 3 The sodium shift of ketazocine-like agonists is lower than that of morphine-like agonists but higher than that of opiates with dual agonist and antagonist action. A working hypothesis is proposed which suggests that the kappa-receptors for the ketazocine-like drugs are less susceptible to the Na+ effect than the mu-receptors for the morphine-like drugs. 4 For most of the morphine-like but not the ketazocine-like agonists, a good correlation has been found for the pharmacological activity in the myenteric plexus-longitudinal muscle preparation and the inhibition of binding of [3H]-naloxone at 12 mM Na+. An exception is fentanyl which has a much greater pharmacological potency than may be expected from its potency in inhibiting [3H]-naloxone binding.

On ramsey numbers for books

Abstract: For n = 1, 2, …, let Bn = K2 + Kn. We pose the problem of determining the Ramsey numbers r(Bm, Bn) and demonstrate that in many cases critical colorings are avialable from known examples of strongly regular graphs.

Factors influencing the release of acetylcholine from the myenteric plexus of the ileum of the guinea-pig and rabbit

Abstract: 1 The effects of electrical stimulation, changes in external ion concentrations and various drugs on acetylcholine release from the myenteric plexus were measured by bioassay in the presence of physostigmine and by recording the responses of the longitudinal muscle. In preparations from the guinea-pig, the acetylcholine output per pulse increased with decreasing frequency of stimulation and reached its maximum at a frequency of 0.017 Hz (1/min) and thus ensured that the output per unit of time was constant at frequencies below 0.5 Hz. Spontaneous release was suppressed during stimulation at 0.017 Hz. 2 In the rabbit, the fractional acetylcholine release was lower than in the guinea-pig. The output per pulse increased with decreasing frequency of stimulation but at a lesser rate, with the effect that the output per unit decreased between 0.5 and 0.017 Hz. 3 In the guinea-pig, reduction of the Ca2+ concentration, addition to the bath fluid of Mn2+, ganglion-blocking drugs, morphine and catecholamines reduced output more at low than at high frequencies of stimulation. In the rabbit, acetylcholine output was less sensitive to changes in Ca2+ concentration and insensitive to Mn2+ and morphine. 4 In the guinea-pig, morphine and catecholamines depressed both the contractile response and acetylcholine output whereas Mn2+ in concentrations up to 125 muM, bretylium and ganglion-blocking drugs depressed only acetylcholine output. 5 In preparations from the guinea-pig, drugs blocking noradrenergic neurons or alpha-adrenoceptors, e.g. bretylium, phenoxybenzamine, thymoxamine and phentolamine, increased acetylcholine output during stimulation at high (1.5 to 10 Hz) but not at low frequencies. 6 The implications of these findings for the release of acetylcholine from different pools in the heterogeneous myenteric plexus are considered. The possible errors, introduced by the effects of physostigmine, on the size of the acetylcholine pools and on the transmission of impulses within the myenteric plexus are discussed.

Effects of solution word attributes on anagram difficulty: A regression analysis

Abstract: A sample of 45 student subjects provided solution scores for 80 five-letter anagrams. These scores were analysed as a function of solution word imagery, con-creteness, familiarity, objective frequency, age-of-acquisition and associative meaningfulness using multiple regression techniques. Two bigram measures together with number of vowels, nature of starting letter (vowel or consonant), anagram pronounceability and anagram-solution similarity scores were also entered into the regression equations. The bigram measures, the starting letter and anagram-solution similarity emerged as having significant associations with the solution scores. Previous reports of imagery effects in anagram are discussed in the light of the present results.

Four species of Lophodermium on Pinus sylvestris

Abstract: Four species of Lophodermium Chev. are distinguished on secondary needles of Pinus sylvestris L. by the manner in which their ascocarps are embedded in the host and their ability to produce stromatic lines of different sorts across the needle. The four species, L. pinastri (Schrad. ex Hook.) Chev., L. conigenum Hilitzer, L. pini-excelsae Ahmad and L. seditiosum sp.nov. are keyed out, described and figured.

Further investigations into the location and magnitude of the hydraulic resistances in the soil:plant system

Abstract: SUMMARY In a previous paper (Faiz and Weatherley, 1977), evidence was put forward for the development of steep gradients of water potential in the soil surrounding the individual roots of rapidly transpiring plants (perirhizal gradients). In this paper, similar experiments are described in which additional data on the dimensions of the root system, distribution of soil water potentials within the rooting zone and the water potentials of the roots themselves were obtained. It was found with experiments on soil that the surface area of the root system was × 60 the cross-sectional area of the pararhizal pathway (cross-sectional area of the pot) through which water moved to the root zone from the water table below. Since the volume rate of flow through the peri- and pararhizal zones was the same, the velocity of movement up to the individual root was therefore only 1/60 of that through the soil supplying the root system. Under conditions of rapid transpiration, the gradient of water potential in that part of the pararhizal pathway immediately beneath the root zone was found to be about 1 bar cm−1. Thus it would be expected that the perirhizal gradient would be 1/60 of this, i.e. it would be negligibly small. However, the actual perirhizal drop in water potential was found to be about 8 bars through a distance of 0.1 cm, i.e. the gradient was 80 bars cm−1. Such a steep gradient would require the hydraulic conductivity of the soil in the perirhizal zones to be 4 orders of magnitude lower than that in the pararhizal pathway. An even greater discrepancy was found with fine sand. The soil within the rooting zone had a somewhat lower water content than that in the pararhizal zone, but it is not thought that this, and some other imponderables which are discussed, could account for this enormous discrepancy. It is concluded that in these experiments, measurable perirhizal gradients were unlikely to develop. Nevertheless, a considerable drop in water potential (about 8 bars in these experiments) between the soil and the root surface remains to be explained. The hypothesis is put forward that it is at the soil:root interface that a high resistance barrier can arise.

The number of connected sparsely edged graphs. II. Smooth graphs and blocks

Abstract: A smooth graph is a connected graph without endpoints; f(n, q) is the number of connected graphs, v(n, q) is the number of smooth graphs, and u(n, q) is the number of blocks on n labeled points and q edges: Wk, Vk, and Uk are the exponential generating functions of f(n, n + k), v(n, n + k), and u(n, n + k), respectively. For any k ⩾ 1, our reduction method shows that Vk can be deduced at once from Wk, which was found for successive k by the computer method described in our previous paper. Again the reduction method shows that Uk must be a sum of powers (mostly negative) of 1 - X and, given this information, we develop a recurrence method well suited to calculate Uk for successive k. Exact formulas for v(n, n + k) and u(n, n + k) for general n follow at once.

Fat and carbohydrate metabolism during low intensity exercise: Effects of the availability of muscle glycogen

Abstract: Four subjects were studied during exercise at 50% of maximum oxygen uptake after a normal diet, after a low carbohydrate (CHO) diet following exercise-induced glycogen depletion, and after a high CHO diet. This regime has previously been shown to cause changes in the amount of glycogen stored in the exercising muscles. Metabolic and respiratory parameters were measured during the exercise. The respiratory exchange ratio, blood lactate, blood pyruvate, blood glucose and plasma triglycerides were lower than normal following the low CHO diet and higher than normal following the high CHO diet. Plasma free fatty acids and plasma glycerol were higher than normal after the low CHO diet and lower than normal after the high CHO diet. The contribution of CHO to metabolism was less than normal after the low CHO diet and greater than normal after the high CHO diet. The altered availability of FFA does not appear to be a result of the variations in the blood lactate content.

A model describing axial flow of liquids through conifer wood

Abstract: A mathematical model has been derived for the prediction of the resistance to viscous liquid flow generated by tracheid lumina and various parts of the bordered pit structure. The model also takes into account changes in pit geometry occurring as the pit membrane deflects when a pressure differential is applied across it. Methods for checking whether flow is truly viscous are presented.

Energy flow in the flora and meiofauna of sandy beaches

Abstract: Investigation of a temperate and tropical beach has shown that, based on chlorophyll a analyses, an epipsammic diatom population present in the temperate beach is absent in the tropical beach. Comparison of community respiration rates for the two beach populations excluding macrofaunal respiration shows that the tropical beach rates (which were constant over the period January-March) were about 9 times the winter rates of the temperate beach and about twice the summer rates. Annual microbial production is estimated at 15 gC/m2 for the temperate beach and 72 gC/m2 for the tropical beach. The greatly increased rate of production in the tropical beach was considered to be a function of increased water flow into that beach. In comparison, meiofauna and macrofauna biomass are less in the tropical beach and their respective production likely to be at most no more than in the temperate beach. It is proposed from experimental studies that the failure of animal populations fully to utilise microbial production in sandy beaches is due to the relative degree of exposure stripping significant quantities of microbial growth from this system. This proposal is discussed as a means of explaining mechanisms of control of animal production in sandy beaches.