Showing papers in "Cell and Tissue Research in 1975"

Identification of the vasopressin producing and of the oxytocin producing neurons in the hypothalamic magnocellular neurosecretroy system of the rat.

Abstract: Immuno-enzyme histochemical investigations showed that, in the magnocellular hypothalamo-hypophysial neurosecretory system of the rat, vasopressin and oxytocin are synthetized in separate neurons. Both the vasopressin neurons and the oxytocin neurons are present in both the supraoptic and the paraventricular nuclei in about the same number. Preferential location of the two kinds of rat neurosecretory neurons is not as obvious as in the bovine hypothalamus. Their perikarya do not show distinct morphological differences. The two kinds of neurosecretory perikarya are the origin of separate vasopressin-containing and oxytocin-containing axons respectively. In the neural lobe, the distribution of the two different types of axons is described.

Oogenesis in Xenopus laevis (Daudin)

Abstract: This study was designed to explore the relationship of estrogen, human chorionic gonadotropin (HCG), and food availability to endocytosis in developing oocytes. When estrogen alone is administered to an animal, large amounts of vitellogenin are synthesized by the liver and secreted into the circulatory system, where it accumulates. Under these conditions there is no evidence of endocytosis at the surface of the oocytes. Other studies have shown that following HCG injection into estrogen-treated animals, vitellogenin is removed from the circulation and the oocyte surface is highly contoured and displays endocytotic activity. Food deprivation has much the same effect on oocyte endocytosis as does estrogen. When animals are given HCG and subsequently starved for 20 days, developing oocytes show little endocytotic activity. We conclude that HCG acts to promote or stimulate endocytosis in developing oocytes while estrogen and/or starvation inhibits this process.

Identification of the vasopressin-neurophysin producing neurons of the rat suprachiasmatic nuclei.

Abstract: Immuno-enzyme histochemical investigations on the hypothalamus of the normal rat showed (1) that the Suprachiasmatic nuclei produce vasopressin; (2) that it is highly probable that these nuclei do not produce oxytocin.

White pulp compartments in the spleen of rats and mice. A light and electron microscopic study of lymphoid and non-lymphoid celltypes in T- and B-areas.

Abstract: The spleen of rats and mice was studied with the light and electron microscope. Special attention was paid to the delineation and composition of the white pulp compartments: periarteriolar lymphatic sheath (PALS), follicles and marginal zone. These three compartments each have their specific lymphoid and non-lymphoid cells. Reticulum cells and reticulin fibres, although occurring in all three compartments, from a characteristic pattern in each compartment. In the PALS two areas can be distinguished: a central area, largely devoid of reticulum cells, and a peripheral area where reticulum cells are arranged in cylindrical shells. The central PALS FORMS THE THYMUS DEPENDENT AREA OF THE SPLEEN, THE PERIPHERAL PALS contains both T- and B-lymphocytes. T-B-interactions requiring cell contact could take place in the latter area. Lymph vessels originate from the shells of reticulum cells around the smaller arterioles; these vessels follow the central arteriole to the hilus of the spleen. Circumstantial evidence suggests that the lymph vessels form a recirculation pathway for T-cells and possibly also for B-cells. In two areas of the splenic white pulp characteristic non-lymphoid cells are present. The central PALS contains interdigitating cells (IDC), which show a close contact with surrounding T-lymphocytes. The light zone of the follicle centre exhibits dendritic cells (DC). B-cells are found between the ramifications of the DC. It is conceivable that these cells play a role in the homing of T-cells and B-cells respectively. In addition they might create a microenvironment supporting differentiation and proliferation of T- and B-cells. The marginal zone does not contain a characteristic non-lymphoid cell type. However, in this compartment B-cells are directly exposed to the circulating blood. It is suggested that this factor constitutes one of the essentials of the microenvironment in the marginal zone.

Immunohistochemical localization of human pancreatic polypeptide (HPP) to a population of islet cells

Abstract: HPP is the human counterpart of APP--a polypeptide that has been isolated from avian pancreas and shown to exert pronounced biological effects. The availability of anti-HPP serum enabled us to use immunohistochemical procedures for the localization of HPP in human pancreas. A small population of pancreatic islet cells showed strong immunofluorescence after staining with anti-HPP serum. The HPP cells were mainly localized at the periphery of the islets. Sometimes they were also seen scattered in the exocrine parenchyma as well as within the epithelium of small to medium-sized ducts. While rare in the pancreas of adult man, HPP cells were abundant in certain parts of the pancreas of foetuses (18-20 weeks gestational age). Their staining properties showed them to be distinct from the A, Band D cells of the pancreatic islets.

Identification of the vasopressin-neurophysin II and the oxytocin-neurophysin I producing neurons in the bovine hypothalamus.

Abstract: Immuno-enzyme histochemical investigations on the bovine hypothalamus showed that vasopressin and oxytocin are synthetized in separate neurons. Moreover, it was found that the vasopressin-producing neurons are identical with the neurophysin II-producing neurons, while the oxytocin-producing neurons correspond with the neurophysin I-producing neurons. From this result it is concluded that, in the species studied, neurophysin I is the carrier protein of oxytocin and that neurophysin II is the carrier protein of vasopressin.

Cell number and cell density in the cerebellar cortex of man and some other mammals.

Abstract: The number of cells per unit volume was determined in the cerebellar cortex of man and 19 other mammals. The cell density (i.e. the number of cells per unit volume) decreases from mammals with a low brain weight to those with a higher brain weight. This decrease in the number of cells is found to be proportional for all three layers of the cerebellar cortex. In addition, the ratio of Purkinje cells to granule cells was determined. In contrast to the decrease of all cell types with increasing brain weight, this ratio varies remarkably among the mammals and is not correlated with brain weight. In man, this ratio is 1∶2991, while it is lower in all other mammals investigated. These differences in the ratio of Purkinje cells to granule cells and the decrease in cell density with increasing brain weight are discussed in relation to brain evolution.

Variability of the effects of serum-free medium, dibutyryl-cyclic AMP or theophylline on the morphology of cultured new-born rat astroblasts

Abstract: The effects of serum deprivation, of dibutyryl-cyclic AMP (dBcAMP) and of theophylline on the morphology of cultured new-born rat astroblasts have been studied using Eagle's basal medium (BME) or Eagle's minimum essential medium (MEM) as culture media. Serum deprivation had no effect on cells cultured in BME, while in MEM, deprivation induced a rapid morphological transformation involving the appearance of multiple processes. This phenomenon was rapidly reversible when serum was again added. In serum-supplemented BME, dB-cAMP (1 mM) and theophylline (1 mM) had no effect. In serum-supplement MEM, theophylline (1 mM) had no effect while dB-cAMP (1 mM) induced a slower and poorly reversible morphological alteration. On the other hand cells in serum-free BME showed multiple processes after addition of dB-cAMP (1 mM) or theophylline (1 mM). This rapid alteration was completely reversed either by removal of dB-cAMP and theophylline or by addition of serum.

Quantitative immunocytochemistry of pituitary receptors for luteinizing hormone-releasing hormone.

Abstract: In Araldite sections of male rat pituitaries, stained after embedding by the unlabeled antibody enzyme method with antisera to native luteinizing hormone-releasing hormone (LH-RH) or LH-RH azo-conjugated to bovine serum albumin, localization is confined mainly to the interior of the large, and to a lesser extent to that of the small, secretion granules of the gonadotrophic cells. Plasma membranes are not demonstrated. Except for weak staining in the granules of corticotrophs, no other pituitary cell is stained. Pretreatment of sections with LH-RH (to dilutions of 4 pg/μl) increases staining intensity in the gonadotrophic granules. Other cells are unaffected. The lesser the gonadotroph staining intensity without pretreatment, the greater the increase (more than 23-fold reactivity). Augmented staining is measurable (P<0.001) to antiserum dilutions of 1∶240 000. Pretreatment with des-Glu-1-LH-RH, porcine corticotropin or rat prolactin has no effect. LH-RH-Gly-10(desamide) inhibits. Rat glycoprotein hormones enhance staining with anti-azo-conjugated LH-RH. With antinative LH-RH these hormones enhance weak staining, but inhibit strong staining. Thick vibrotome sections of male rat or rabbit pituitaries stained before embedding reveal specific localization on plasma membrane and gonadotrophic secretion granules, provided the sections have been pretreated with LH-RH (250 pg/μl). The data show that LH-RH after reaction with receptor is not sterically hindered from binding specific antibodies. Receptor may be found in secretion granules, both in the free state or combined with LH-RH. Plasma membrane receptor, on the other hand, was free under the conditions of the experiments. Immunization with LH-RH elicits not only heteroimmune antibodies specific for LH-RH, but also a group of still ill defined autoimmune antibodies, some of which may conceivably be reactive with glycoprotein hormone α-chains.

The sensory cilium of retinal rods is analogous to the transitional zone of motile cilia

Abstract: The connecting cilium of rat retinal rods was studied by freeze-fracture and thin-sectioning techniques. Transverse strands of intramembranous particles could be observed on fracture face B of the ciliary plasma membrane. The strands were essentially similar to those found at the transitional zone of motile cilia (“ciliary necklace”). The large number of intramembranous particles obscured the pattern on fracture face A of the membrane. On longitudinal sections of the cilia, beads showing a periodicity similar to the necklace strands were observed. Each bead consisted of two structures apposed to both sides of the plasma membrane. Transverse sections of the cilia revealed radial Y-shaped structures that connected each ciliary doublet with the plasma membrane. Axial tubules, central sheath, radial spokes and dynein arms were missing in the connecting cilium. Comparing the fine structure of the retinal cilia with that of motile cilia it becomes evident that the connecting cilium is analogous in structure with the transitional zone of motile cilia. The present observations suggest that periodic membrane beads along the plasma membrane on thin sections correspond to strands of necklace particles as observed on freeze-fractured membranes. The arrangement of the particles in transverse strands is probably ensured by the radial connecting structures.

Hypertrophy of intestinal smooth muscle.

Abstract: Proximal to an experimental stenosis of the small intestine of rats and guinea-pigs a remarkable hypertrophy of the muscle coat develops 3–5 weeks after the operation. There is no increase in the length of the intestine but an overall increase in volume of the muscularis externa up to 10 times. This increase is accounted for by an increase in size and in number (by mitosis) of smooth muscle cells of both the longitudinal and circular layers. Bundles of newly-formed smooth cells appear in the serosa and are circularly arranged. In the hypertrophic smooth muscle cells of the circular layer the ratio of surface to volume is 0.80 (0.80 μm2 of cell surface for every μm3 of cell volume) as against 1.4 in the control muscle. The hypertrophic muscle cells have a highly developed sarcoplasmic reticulum and show a large number of nexuses. The density of innervation (number of axons per given number of smooth muscle cells) is smaller than in controls. Few collagen fibrils are visible in the extracellular space.

Junctions in the central nervous system of the cat. V. The junctional complex of the pia-arachnoid membrane.

Abstract: The leptomeningeal tissue of the choroid plexuses and of the brain surfaces have been studied by means of the freeze-etching technique. The pia-arachnoid membrane and the subdural neurothel represent the morphological barrier between the extracerebral tissue and the cerebrospinal compartment. The freeze-etch findings indicate that the arachnoid and neurothelial cells are coupled by extensive zonulae occludentes which seem to represent the structural basis of the barrier mechanism provided by these cell layers. Furthermore, it became evident that gap junctions of considerable structural heterogeneity occur on the pial and arachnoid cells of the interstitial choroidal compartment and of the free brain surfaces. The structural heterogeneity of the nexuses is taken as an indication of the plasticity of the leptomeningeal tissue. The different morphological characteristics of the nexal formations are discussed with respect to their probable functional meaning.

The major ganglion in the pelvic plexus of the male rat: a histochemical and ultrastructural study.

Abstract: To further evaluate the role of autonomic ganglia in the regulation of pelvic visceral activity, the neural elements in the major pelvic ganglion of the male rat have been studied with histochemical and electron microscopic techniques. The principal findings are that the ganglion is composed of cholinergic and adrenergic ganglion cells as well as small intensely fluorescent (SIF) cells. Polarity in the ganglion is indicated by clustering of small ganglion cells which stain intensely for acetylcholinesterase (AChE) along the pelvic nerve while larger cells, with weak to moderate AChE activity, collect near small branches of the hypogastric nerve. Some cholinergic ganglion cells are enclosed by a plexus of adrenergic terminals. SIF cells appear to be in contact with both cholinergic and adrenergic cells, although many of the fluorescent beads around adrenergic neurons may be short dendrites of ganglion cells, rather than processes of SIF cells. Two types of SIF cells may be distinguished on the basis of size and morphology of their granulated vesicles. Afferent synapses of the cholinergic type were common on SIF cells of the large granule and small granule type. Portions of SIF cells with large granules occur within the capsule of ganglion cells. Contacts seen here were interpreted as efferent synapses from SIF cells to the dendrites of ganglion cells.

Ultrastructural immunocytochemical localization of neurophysin and vasopressin in the median eminence and posterior pituitary of the guinea pig.

Abstract: With the use of tissue prepared by freeze-substitution and the unlabelled antibody enzyme technique, neurophysin and vasopressin were localized at the ultrastructural level in the posterior pituitary and median eminence of the guinea pig. In the posterior pituitary neurophysin was found in the large neurosecretory granules (1300–1500 A) of axons, Herring bodies, and nerve terminals. In some of these axons immunoreactive neurophysin was found outside of granules in the axoplasm. By light microscopy neurophysin was found in both the zona interna and zona externa of the median eminence; this was confirmed by electron microscopy. In the zona interna as in the posterior pituitary, neurophysin was localized both inside and outside the large neurosecretory granules. In the zona externa, immunoreactive deposit was primarily located in granules with a diameter of 900–1100 A in nerve terminals abutting on the primary portal plexus. The distribution of vasopressin paralleled that of neurophysin except that the hormone was rarely extragranular. These results demonstrate for the first time that both neurophysin and vasopressin are present in granules of axons that are in contact with the hypophysial portal vasculature.

The postnatal development of the sexually dimorphic duct system and of amylase activity in the submandibular glands of mice.

Abstract: The submandibular glands of developing and mature Strong A mice were studied by light and electron microscopy. The glands of both sexes show the same cell types during development, but during maturation the glands display a degree of sex-dimorphism. Striated ducts, which differentiate from the larger intralobular ducts present in the neonatal gland, first appear by 5 days of age and reach their mature condition by 20 days of age. Granular convoluted tubule cells, which differentiate from striated duct cells, are first seen at 15 days of age in both sexes. Subsequently, they show a more rapid development in males than in females, and are dimorphically represented by 20 days of age. Intercalated ducts in the neonatal gland contain nongranular and granular cells. With maturation the number of granular cells decreases, apparently due to their conversion into the nongranular type, with their eventual disappearance from the glands of adult males. Their retention in adult females further defines the sexual dimorphism shown by these glands. Amylase activity in gland homogenates is first detectable at 20 days of age in both sexes. During development the male glands show a rapid rise in levels of amylase activity, whereas female glands show a more gradual rise. In mature animals, male glands have higher levels of amylase activity than female glands. The developmental and adult status of amylase activity parallels that of the granular convoluted tubules.

The first optic ganglion of the bee

Abstract: The synaptic relationships between and within receptor-cell axons (RCAs), first-order interneurones (L-fibres) and accessory fibres (acc) in the first optic ganglion (the lamina) of the worker bee were studied in serial sections with Golgi-EM and routine transmission electron microscopy. The ommatidium contains nine retinular (photoreceptor) cells all of which project as RCAs to a single optical cartridge in the lamina. Six of the RCAs end as short visual fibres (svf) in the lamina, while the remaining three, the so-called long visual fibres (lvf), pass the lamina and end in the second optic ganglion, the medulla. In addition to the RCAs and an unknown number of accessory fibres, the cartridge also contains four L-fibres (L 1–4). The spatial arrangement of the RCAs and L-fibres within a cartridge is constant throughout the depth of the lamina. Serial sections reveal a great number of chemical synapses interconnecting RCAs, L-and acc fibres. Double T-shaped presynaptic dense projections are surrounded and in close association with either spherical or flattened synaptic vesicles. The finding of gap junctions between and within identified RCAs and L-fibres suggest that these axons may be electronically coupled. A model for information processing in the lamina of the bee is suggested from observations of synaptic connectivity between and within fibres of one cartridge.

Immunoreactive LH-RH neurons in the hypothalamus identified by light and fluorescent microscopy

Abstract: The sites of luteinizing hormone-releasing hormone (LH-RH) neurons and their axonal pathways in the hypothalami of rats and mice were studied by the immuno-globulin-peroxidase bridge technique and by the immunofluorescent isothiocyanate technique, using rabbit antiserum to synthetic LH-RH. Both of these techniques give similar results concerning LH-RH localization both in rats and mice. The immunoreactive LH-RH positive neurons are about 18–26 μ in diameter, mostly angular, pyriform or spindle shaped and very rarely oval or round. Most of these neurons are generally scattered in the hypothalamus. In the preoptic and medial prechiasmatic areas, ventromedial, arcuate nuclei and ventro-lateral-premammillary body, the neurons are numerous and mostly in groups of 3–6. In other areas of the hypothalamus surrounding the suprachiasmatic area, supraoptic area, paraventricular nuclei and the anterior hypothalamic area, the LH-RH neurons are few and scattered. Very few neurons occur in the median eminence or in the infundibular stem. Major projections of LH-RH neurons apparently originate from preoptic, prechiasmatic and surrounding suprachiasmatic area, and from the anterior hypothalamic area. The fibres run in the fibrillar zone, descend in the external infundibular zone, and finally terminate for the most part around the capillaries of the primary portal plexus of the hypophysis. Other major groups of fibres apparently originate from the arcuate and ventromedial neurons. These fibres bend above the fibrous zone for some distance, ultimately descending in the zona palisadica and zona granulosa of the median eminence, towards the capillaries. The fibres of the ventrolateral-premammillary neurons are seen on the floor of the premammillary recess of 3rd ventricle and apparently terminate close to the capillaries in the infundibular region. Most of the LH-RH nerve fibres terminate near the primary portal plexus of the hypophysis, while some terminate in the pars tuberalis and a few seem to terminate in the 3rd ventricle. The LH-RH antiserum is ineffective after absorption with the antigen, so the staining reaction appears to be specific for LH-RH.

Chicken gonadotrophins: Their effects on the testes of immature and hypophysectomized Japanese quail

Abstract: Five-week old Japanese quail held under short daylengths (8L/16D) were injected daily for two weeks with 20 μg/day of purified chicken luteinizing hormone (LH) or with one of two chicken follicle-stimulating hormone (FSH) fractions. Both intact and hypophysectomized birds were used. After killing, the testes were weighed and fixed for light- and electron-microscopy. Following hypophysectomy testicular weights fell significantly below those of saline-injected controls, indicating that short day conditions are not equivalent to “physiological hypophysectomy”, the pituitary-gonadal axis continuing to function at a low level. Chicken LH stimulated differentiation of the interstitium, producing mature Leydig cells containing the full complement of organelles typical of steroid-secretion. In addition it induced some testicular growth caused by spermatogonial division and partial differentiation of the Sertoli cells. This effect was assumed to be a secondary response to androgen secretion but a direct action of chicken LH on the tubules is not dismissed. LH given to intact quail caused greater testicular growth, presumably due to synergism with endogenous hormones. Both chicken FSH fractions induced testicular growth and development; in intact birds the effects were similar to those observed in intact LH-treated birds. In hypophysectomized quail given FSH the testicular weights were greater than in hypophysectomized LH-treated birds and the seminiferous tubules were larger. Sertoli cells were stimulated and pachytene spermatocytes were numerous. Leydig cell differentiation was minimal in all FSH-treated birds, being less pronounced in hypophysectomized than in intact birds.

Immunofluorescence study of LRF neurons in primates.

Abstract: LRF producing neurons were characterized in the squirrel-monkey (Saimiri sciurus) and Cebus apella monkey, by means of a rabbit antiserum against unconjugated synthetic LRF, previously adsorbed on polyvinylpyrrolidone. These neurons, which vary in number according to the species and physiological or experimental conditions, are mainly concentrated in the mediobasal hypothalamic area (infundibular and premammillary nuclei in particular) and the vascular organ of the lamina terminalis. The neurons of the first group give rise to axons which terminate round the capillaries of the primary portal plexus of the infundibulum. Those of the second group give rise to axons which terminate round the capillaries of the primary and secondary plexuses of the vascular organ of the lamina terminalis and in the ependyma which lines its ventricular side. Some specifically immunoreactive axons apparently run towards the telencephalon (passing in front of and behind the anterior white commissure), the mesencephalon and the epithalamus. Some of the latter give rise to terminal ramifications in the area of the median habenular nucleus.

Changes in parotid acinar cells accompanying salivary secretion in rats on sympathetic or parasympathetic nerve stimulation.

Abstract: Morphological and secretory effects of stimulating autonomic nerves have been studied in parotid glands of rats Sympathetic stimulation evoked a slow flow of saliva which had a high concentration of amylase After long term sympathetic stimulation secretory granules were heavily depleted from the parotid acinar cells Parasympathetic stimulation evoked a copious flow of saliva with a low concentration of amylase However, at high frequency stimulation the total amount of amylase secreted on parasympathetic stimulation was as great or even greater than on sympathetic stimulation, nevertheless, any loss of secretory granules from the acinar cells was very small

Ultrastructure and fluorescence histochemistry of endocrine (APUD-type) cells in tracheal mucosa of human and various animal species

Abstract: This study describes distinctive cells with ultrastructural and histochemical features of APUD-type endocrine cells within the tracheal epithelium of human fetuses, newborns and children as well as different animal species. These cells referred to as Kultschitzky cells (K cells) were found to be argyrophilic, but not argentaffin, and are considered analogous to the same type of cells in lung and gastro-intestinal tract. Fluorescence histochemistry demonstrated the presence of intracellular amine within tracheal K cells, but only after in-vitro or in-vivo administration of amine precursor (L-DOPA). Ultrastructurally, these cells are characterized by the presence of numerous cytoplasmic granules (dense core vesicles) which show species related morphologic variations. Two different types of K cells were found in trachea of lamb and armadillo, each type possessing morphologically different dense core vesicles. In human and rabbit tracheas, only one type of K cell was identified. K cells in the trachea are distributed as single cells between other epithelial cells; neuroepithelial bodies such as those found in bronchial mucosa were not identified. Well differentiated K cells were found in tracheas of early human fetuses and throughout gestation, infancy, and childhood. Preservation of K cells in human autopsy material and widespread occurrence of these cells in various laboratory animals will permit further studies into the nature and function of tracheobronchial endocrine cells.

An ultrastructural study of the microfilaments in rat brain by means of E-PTA staining and heavy meromyosin labeling. II. The synapses.

Abstract: To identify structures involved in the translocation of the synaptic vesicles towards the presynaptic membrane, an ultrastructural study has been undertaken by means of (1) the E-PTA stain and (2) the HMM-labeling procedure. Using serial sections of E-PTA stained nervous tissue, especially those made in transversal and tangential planes, the geometric order of the presynaptic grid and of its constituents has been described in detail It consisted of dense projections having the shape of small truncated pyramids cut parallel to their hexagonal bases which rested on the electron-lucent presynaptic membrane. The dense projections were arranged at the points of equilateral triangles. Around each dense projection, six asymmetric hexagonal holes were seen to be arrayed in an hexagonal pattern, forming thus the presynaptic sieve. From the spiny tops of the dense projections, which appeared as specialized structures of the dense material coating the inner surface of the plasma membrane at the level of the synaptic cleft, fine filaments, 40–60 A in diameter, radiated and formed a three-dimensional meshwork pervading the presynaptic bag. The dense cytoplasmic coating delineating the plasma membrane served as anchor points for these microfilaments. Upon incubation with rabbit skeletal muscle HMM the microfilaments underwent specific structural changes, consisting of: (1) a striking increase in diameter; (2) the association of periodic and polarized substructures with their surfaces. The synaptic vesicles and mitochondria were seen to be attached to the numerous HMM-decorated filaments or enmeshed in the network formed by these filaments. The actin-like filaments were anchored to the plasma membrane at many points and to the presynaptic dense projections. Following incubation in the buffer alone or in buffered HMM solutions containing Na+ pyrophosphate or ATP, no arrowheaded structures were observed. Thus, a network consisting of actin-like filaments was demonstrated in the presynaptic bag. Of particular interest was the structural relation of the actin-like filaments with the occasional, tapered myosin-like filaments. The role of the presynaptic actin-like network in the transport of synaptic vesicles towards the presynaptic membrane by a mechanism of chemomechanical transduction is discussed. In the postsynaptic dendrite or dendritic spine, a filamentous network was observed to be attached to the subsynaptic web by means of the E-PTA stain and of the HMM-labeling procedure. The occurrence of an actin-like meshwork in the postsynaptic region is suggested to produce changes in the macromolecular configuration of the postsynaptic membrane by a “ mechanoenzyme” system similar to that described in the mitochondrial membrane.

Larval and adult eye of the western rock lobster (Panulirus longipes).

Abstract: A number of differences exists between the compound eyes of larval and adult rock lobsters, Panulirus longipes. The larval eye more closely resembles the apposition type of compound eye, in which retinula cells and rhabdom lie immediately below the cone cells. The adult eye, on the other hand, is a typical clear-zone photoreceptor in which cones and retinula cell layers are separated by a wide transparent region. The rhabdom of the larval eye, if cut longitudinally, exhibits a “banded” structure over its entire length; in the adult the banded part is confined to the distal end, and the rhabdom is tiered. Both eyes have in common an eighth, distally-located retinula cell, which possesses orthogonally-oriented microvilli, and a peculiar lens-shaped “crystal”, which appears to focus light onto the narrow column of the distal rhabdom. Migration of screening pigment on dark-light adaptation is accompanied by changes in sensitivity and resolution of the eye. Retinula cells belonging to one ommatidium do not arrange into one single bundle of axons, but interweave with axons of four neighbouring facets in an extraordinarily regular fashion.

An ultrastructural study of the microfilaments in rat brain by means of heavy meromyosin labeling. I. The perikaryon, the dendrites and the axon.

Abstract: Nervous tissue pieces from the caudate nucleus and the substantia nigra of the rat were incubated in cold glycerol solutions of decreasing concentrations and then transferred into standard phosphate buffer (pH 7.0) or into tris-K+-Mg++-Ca++ buffer (pH 7.9) containing HMM, prepared from rabbit skeletal muscle by tryptic digestion. As controls, pieces were immersed for an identical period in the same buffers (1) without HMM or (2) with HMM to which had been added 2.5 mM Na+ pyrophosphate or 5 mM ATP. In control neurons smooth-surfaced microfilaments, about 50 A in diameter, were observed. After reaction with HMM, the microfilaments were increased in number and density and in width to 180-200 A. A meshwork was formed. Arrowheads pointing in the same direction were spaced at regular intervals (300-350 A) among short segments of the surfaces of the microfilaments, depending upon the plane of section. More often, however, typical arrowheads were not observed, and the surfaces of the microfilaments were seen coated with polarized side-arms cross-bridging the spaces between adjacent elements at more or less regular intervals. When cross-sectioned, the microfilaments appeared as dense dots from which a material of lesser electron density radiated. Following incubation in HMM solutions containing Na+ pyrophosphate or ATP, no arrowhead structures were seen. Of particular interest was the structural relation of the actin-like filaments with occasional, tapered myosin-like filaments, and with the plasma membrane, which served as anchor points. Mitochondria and smooth ER membranes were observed to be attached to the actin-like filaments or enmeshed in the network. The microtubules, as well as most of the neurofilaments, were disrupted by the glycerination procedure at 4 degrees, and thus no precision about the structural relationship of the actin-like filaments with the latter elements could be added. The role of the actin-like filaments in the transport of material, by a mechanism of chemomechanical transduction, throughout the neuron from sites of synthesis to functional locations, and between several functional locations, is discussed.

Radioautographic study of the rat brain and pituitary after injection of 3H dexamethasone.

Abstract: The central nervous system and the pituitary of adrenalectomized male rats injected with 3H-dexamethasone were examined by radioautography. At 1 hr after the injection, radioactivity concentration was high in the medial basal hypothalamus, the pituitary and the pineal gland. In the hypothalamus, radioactive material was found to be selectively concentrated in neurons in the ventral part of nucleus arcuatus and in the infundibular region. In the anterior pituitary, a large proportion of cells showed silver grains both in the cytoplasm and over the cell nuclei. However, in a small number of cells, the radioactive material was associated with the cell nuclei. Less radioactivity was present in the intermediate and posterior lobes. The pineal gland contained more silver grains than did other regions of the brain. The results obtained in the present study suggest essentially an action of dexamethasone in the medial basal hypothalamus and at the level of the pituitary.

Histofluorescence characteristics and quantification of small intensely fluorescent (SIF) cells in sympathetic ganglia of several species

Abstract: Small intensily fluorescent (SIF) cells in the superior cervical ganglion of the cow, cat, rabbit, rat, guinea pig and monkey were studied, using the glyoxylic acid monoamine fluorescence method. SIF cell populations per mg ganglion tissue showed great species variation. The greatest numbers of SIF cells per mg were found in the rat (380±30 per mg). Intermediate numbers (76±20 per mg) were found in the guinea pig; and SIF cells in other species were much more sparsely distributed (less than 10 per mg). Two types of SIF cell were identified. Type I cells have long (up to 200 μ) processes which ramify among the principal ganglionic neurons, and this type often occurs singly; whereas type II cells tend to occur in clusters near blood vessels in the interstitial or subcapsular regions of the ganglion. As a general hypothesis we propose that type I SIF cells are interneurons whereas type II SIF cells operate through a neurosecretory mechanism.

Cobalt sulphide staining of optic fibres in the brain of the cricket, Gryllus campestris.

Abstract: Neuronal projections from one optic lobe to other parts of the brain were stained in the cricket Gryllus campestris using the cobalt sulphide technique and Timm's sulphide-silver method. The results are: Four tracts directly connect the medulla with the lobula and medulla of the contralateral optic lobe. Direct medullar projections end mainly in the non-glomerular neuropile of the protocerebrum, but also penetrate the calyx of the mushroom bodies, pons and central body in small numbers. A few somata which send fibres into the medulla lie in the pars intercerebralis, in the protocerebrum ventral to the opposite β-lobe, the outer margin of the medulla of the contralateral optic lobe and between deutoand tritocerebrum. The anatomical and physiological relevance of the stained connections is discussed.

Osteoblasts and collagen orientation.

Abstract: Bone was removed from the calvaria of anaesthetized 70 g rats or freshly killed young monkeys and the fibrous periosteum dissected off the inner, formative surface under 0.15 M cacodylate buffer. The bone and undisturbed osteoblasts were fixed in 3% glutaraldehyde in the same buffer for 24 to 48 hours, critical point dried and coated with evaporated carbon and gold for scanning electron microscopy (SEM). Fields of osteoblasts were photographed and chosen cells dissected off the osteoid using a tungsten needle. The control of the dissection was made possible by the use of a system of real-time stereo tv-speed SEM. The fields were rephotographed and the orientations of the osteoblasts were compared with that of the underlying collagen fibres. 62% of all osteoblasts lay with their long axes within 15 degrees of the collagen fiber orientation below and 80% within 30 degrees. Montages of large areas of osteoblasts were also made, and then compared with ones of the same area after the cells had been stripped off on adhesive tape. In general, the orientation of the collagen tended to be the same as the cell that formed it. Collagen fibers below cells at the periphery of a domain sometimes had the orientation of the cells in the adjacent patch. It is not possible to determine whether the cells controlled the orientation of the collagen, or vice versa, from this experiment, but other SEM evidence suggests that the collagen orientation in hard tissue matrices depends on the freedom of cells to move with respect to matrix surface.

Junctions in the central nervous system of the cat. IV. Interendothelial junctions of cerebral blood vessels from selected areas of the brain.

Abstract: Interendothelial membrane contacts in different segments of brain blood vessels were investigated by the freeze-etching technique. The study demonstrated that the endothelial cells of the pre- and postcapillary segments were coupled by elaborate zonulae occludentes. These tight junction formations encompassed gap junctions of different sizes and distribution. The globules of the pre- and postcapillary tight junctions revealed a great fragility which led to an atypical distribution of the sealing elements. In the "typical" brain capillaries the endothelial cells were connected by continuous tight junctions. In contrast to the structural continuity of these formations the fenestrated segments of capillaries in the choroid plexus and area postrema demonstrated discontinuous fasciae occludentes. They were composed of rows of individual particles which should be regarded primarily as focal in nature.

Ultrastructural studies on the hypothalamic neurosecretory neurons of the rat. III. Paraventricular and supraoptic neurons during lactation and dehydration

Abstract: The ultrastructural features of paraventricular (PVN) and supraoptic (SON) neurons and of their axons were studied in lactating and dehydrated rats. Under both conditions of stimulation, the PVN and SON neurons and their axons enlarge. The protein synthesizing apparatus of the neurons becomes activated, but the number of neurosecretory granules (NSG) is decreased. No differences are seen between the PVN and SON neurons during lactation or dehydration. The similarity and simultaneity of the response of the PVN and SON neurons to these two different stimuli is discussed in the light of the theory of nuclear and neuronal specialization for the production of only one hormone. After prolonged lactation of over 2 1/2 weeks' duration, neurons with extreme vacuolation of the rough endoplasmic reticulum (RER) appear in the PVN and SON; the vacuolated neurons appear earlier and predominantly in the PVN involving a maximum of 10-15% of all PVN neurons. Vacuolated neurons were never seen in either nucleus during dehydration of up to 6 days' duration. The vacuolation is suggested to represent an exhaustion phenomenon due to an intense, long-lasting stimulus for oxytocin synthesis. The predominant location of the vacuolated neurons in the PVN supports the theory that oxytocin is produced predominantly in the PVN. The decrease in the number of NSGs during these states of enhanced hormone secretion is considered to corroborate the proposed existence of an extragranular fast axoplasmic transport mechanism in PVN and SON neurons. The possible existence of a reuptake mechanism into NSGs, similar to that in the vesicles of monoaminergic nerve endings is discussed.