Cholinesterases in the hypothalamo-hypophysial neurosecretory system of the White-crowned Sparrow,Zonotrichia leucophrys gambelii

Summary The distribution of cholinesterases in hypothalamo-hypophysial neurosecretory system of the White-crowned Sparrow has been examined histochemically. The perikarya of the neurosecretory cells of the paraventricular and supraoptic nuclei have a high acetylcholinesterase activity. Acetylcholinesterase activity also occurs in the cells of the infundibular nucleus. The proximal parts of the axons of the cells of the neurosecretory and infundibular nuclei have strong acetylcholinesterase activity and weak non-specific cholinesterase activity. In the median eminence, the activity of acetylcholinesterase is strongest in the palisade layer. In the pars nervosa, there is definite, although weak, acetylcholinesterase activity.This investigation was supported by grants from the National Institutes of Health to Professor Farner (B-1353) and to Dr. Kobayashi (A-3678).     

The distribution of monoamine oxidase and acetylcholinesterase in the hypothalamus and its relation to the hypothalamo-hypophysial neurosecretory system in the white-crowned sparrow,Zonotrichia leucophrys gambelii

Summary The distribution of monoamine-oxidase and acetylcholinesterase activities in the hypothalamus of the White-crowned Sparrow has been studied in relation to the hypothalamohypophysial neurosecretory system. The enzyme activities, as revealed by the methods employed, are unaffected during photoperiodically induced testicular growth. Monoamine oxidase has a distribution distinctly different from that of the aldehyde-fuchsin positive neurosecretory material in that there is high activity in the peripheral palisade layers of both the anterior and posterior divisions of the median eminence. Intimate contact is made between these areas with the primary vessels of the hypophysial portal system. A second concentration of activity lies in a layer between the ependymal cells and the neurosecretory material of the fiber tract. In general, monoamine oxidase appears to be associated with glial elements and non-neurosecretory axons. The pars nervosa has little or no monoamine-oxidase activity. The distribution of acetylcholinesterase activity in the anterior division of the median eminence is very similar to that of the aldehyde-fuchsin positive neurosecretory neurons; however, acetylcholinesterase also occurs in the posterior division without associated neurosecretory fibers. These distribution of enzyme activities are considered in relation to possible adrenergic and cholinergic mechanisms in the median eminence.Dedicated to Professor Berta Scharrer in honor of her 60th birthday.Supported by grant NB-01353 from the National Institutes of Health to Professor Farner. This investigation was conducted while Doctor Kobayashi was a National Science Foundation Senior Foreign Scientist at Washington State University. We are indebted to Doctor Christian Da Lage, Laboratoire de Histologie, Falculté de Médecine de Paris, for the preliminary development of some of the techniques used in these investigations.     

Fine structure of the median eminence and the pars nervosa of the bullfrog,Rana catesbeiana

Summary The hypothalamic neurosecretory system of the bullfrog, Rana catesbeiana, was studied with light- and electron microscopy. The median eminence is roughly divided into two portions. The upper portion mostly consists of ependymal cells, glial cells and preoptico-hypophysial nerve tract, whereas in the lower portion, neurosecretory axons, glial cells, processes of glial and ependymal cells, and fine blood vessels of the hypothalamic portal vein are located. A part of the neurosecretory axons of the preoptico-hypophysial tract proceeds to the lower portion of the median eminence. These axons are arranged perpendicularly to the capillaries of the hypothalamic portal vein. The glial cells are densely located in the area of the median eminence where neurosecretory material is abundant. The neurosecretory material in the neurosecretory cells, their axons, the median eminence and the pars nervosa of the bullfrog shows a positive reaction to PAS treatment.The neurohemal area of the median eminence is occupied by many neurosecretory and non-neurosecretory axons, containing neurosecretory granules and/or synaptic vesicles. The axonal portions with the synaptic vesicles which are considered to be the nerve endings abut on the capillaries of the portal system. The size of synaptic vesicles in the axon terminals containing few neurosecretory granules is larger than those in the endings with many neurosecretory granules. Infrequently glial and ependymal processes are interposed between the nerve endings and the capillary wall.In the hilar region of the infundibulum, synapses are frequently observed between the thin fibers with or without neurosecretory granules and dendrites of non-neurosecretory neurons. The probable functions of these synapses are briefly discussed on the basis of our findings. Both in the hilar region of the infundibulum and in the pars nervosa, electron-dense neurosecretory granules of two different sizes were observed. The median eminence contains only one type of granules.The fine structure of the pars nervosa shows similar structures to those of the median eminence. Both in the median eminence and the pars nervosa, the fenestrated endothelium of the capillaries was frequently observed. The thick perivascular connective tissue space containing fibroblasts and collagen fibrils was observed both in the median eminence and the pars nervosa. Vesicles in the cytoplasm of the endothelial cells which appear to take a part in the transendothelial transport were observed.This investigation was supported in part by United States Public Health Service Research Grant, No. A-3678, to Hideshi Kobayashi from the National Institute of Arthritis and Metabolic Diseases and partly by a grant for Fundamental Scientific Research from the Ministry of Education of Japan. The authors wish to express their thanks to Prof. K. Takewaki for his kind encouragement.     

Mitotic Figures in the Median Eminence of the Hypothalamus

The median eminence of the hypothalamus is part of the avenue by which neurosecreted hormones from the hypothalamic nuclei reach the pars nervosa (neural lobe) of the pituitary and eventually the bloodstream. Lithium treatment and osmotic stress increases the transport of neurosecretory hormones to the pituitary in the adult rat. Specialized astrocytes termed pituicytes in the pars nervosa of the pituitary participate in the secretory process and also develop considerable mitotic activity. The present work reveals similar mitotic figures in cells within the median eminence following 3 days of lithium treatment. The location and appearance of these mitoses add to the evidence that pituicytes are present in the median eminence. Moreover, mitoses occur within the ependymal (tanycyte) layer of the median eminence. Thus, the present results suggest that the tanycyte layer may contain pituicytes, indicating that the hypothalamus possesses specialized cells for modulating neurosecretion in response to osmotic challenges.     

Photoperiodic and osmotic influences on the ultrastructure of the hypothalamic neurosecretory system of the White-crowned sparrow,Zonotrichia leucophrys gambelii

Summary An attempt was made to correlate functional changes in the neurohypophysis of the White-crowned Sparrow, Zonotrichia leucophrys gambelii, with morphologic features on the light- and electron-microscope levels. The aldehyde-fuchsin-staining anterior median eminence possesses essentially the same ultrastructural features as the non-staining posterior median eminence. The axon terminals are characterized by the presence of a large number of small vesicles (approximately 400 Å in diameter) and occasional electron-dense granules. The more-or-less depleted anterior median eminence occasionally evident in the photosensitive bird showing testicular development is indistinguishable ultrastructurally from the more intensely staining median eminence generally characteristic of the photorefractory bird. In the median eminence, stainability and functional state do not seem to be correlated with changes in the type, size or number of vesicles. A slight increase in the number of granules was noted in the photorefractory bird but this was considered insufficient basis to account for differences in stainability.The pars nervosa, on the other hand, responded to osmotic stimuli (saline drinking water) by loss of stainability and decrease in numbers of elementary neurosecretory granules. Small vesicles are also present in the pars nervosa axon terminals, but are intermingled with neurosecretory granules in normal birds. Acute-osmotic birds, however, had axon terminals almost entirely occupied by small vesicles.It is to be emphasized that the pars nervosa and the median eminence are two structurally very different regions of the neurohypophysis. The basis for aldehyde-fuchsin staining in the median eminence appears to differ from that in the pars nervosa. The implications of these findings are considered in regard to hypothalamic control over gonadotropic activity in the White-crowned Sparrow.Dedicated to Professor Dr. W. Bargmann in honor of his 60th birthday.This investigation was supported by grant GB-2484 from the National Science Foundation to Professor Bern, grant GB-2819 from the National Science Foundation to Professor Mewaldt, and grant NB-01353 from the National Institutes of Health to Professor Farner. The authors wish to express their appreciation of the technical assistance of Mrs. Irene Brown, Mr. John Butchart, Sally S. Kibby, Mrs. Carol Nicoll, and Mr. John Striffler. Mrs. Emily Reid kindly prepared the histograms.     

Monoamine oxidase in the hypothalamo-hypophysial region of the teleosts,Anguilla japonica and Oryzias latipes

Summary Distribution of monoamine oxidase (MAO) was histochemically examined in the hypothalamo-hypophysial region of the eel (Anguilla japonica) and the medaka (Oryzias latipes) with a modified Glenner's tryptamine-tetrazolium method. The hypothalamic neurosecretory cells showed very weak MAO activity in their perikarya. MAO-positive fibers were present in close contact with the neurosecretory cells, suggesting that monoaminergic fibers participate in the control of neurosecretory cell activity. The nucleus lateralis tuberis (NLT) contained cells exhibiting strong MAO activity. These cells must be monoaminergic neurons.In the anterior region of the neurohypophysis of both eel and medaka, two bundles of MAO-positive fibers originating from the NLT proceed down along each side of the third ventricle into the pars distalis. This suggests that monoaminergic neurons of the NLT are involved in the release of hormones from the pars distalis. In addition to these tracts, numerous MAO-positive fibers proceed backward from the post-optic area and end around the blood capillaries located between the neurohypophysis and the pars intermedia in both species.I wish to express my gratitude to Prof. H. Kobayashi for his valuable advice during the course of this study. I am indebted to Prof. S. Uchida, Ocean Research Institute, University of Tokyo, for supplying the eels.     

Premigratory Changes in the Hypothalamo-Hypophysial Neurosecretory System in the Red-winged Blackbird (Agelaius phoeniceus)*

Abstract

• 1 The hypothalamo-hypophysial neurosecretory system in the Red-winged Blackbird (Agelaius phoeniceus) has been studied with special reference to changes during the period prior to fall migration.
• 2 In September the supraoptic and paraventricular cells were found to be considerably larger with substantial amounts of aldehyde fuchsin positive neurosecretory material (NSM) accumulating in the perikaryon. Large amounts of the NSM were found also in the anterior median eminence and pars nervosa.
• 3 Towards migration time (November), the cells in the hypothalamic nuclei contained very little NSM. A marked decline in the amount of NSM was also seen in the anterior median eminence and probably in the pars nervosa too.
• 4 The release of NSM toward migration time has been discussed as an important event in the sequence of events that control and regulate migratory activity.

     

Electron microscopic and pharmacological studies on the rat median eminence

Summary The rat median eminence contains at least three kinds of granules or vesicles: 1. large electron-dense granules (perhaps carriers of neurohypophysial hormones), 2. small electron-dense granules with or without haloes (perhaps carriers of catecholamines) and 3. synaptic vesicle-like structures (perhaps carriers of acetylcholine). The former two electrondense granules exist in separate axons but they coexist with the latter vesicles in the same axons.The pars nervosa shows basically a similar structure to the median eminence. However, the axons containing the small electron-dense granules are very few. In the pars tuberalis, there are at least two types of cells: the cells of one type contain much cytoplasm with large round nuclei and those of the other type contain a small amount of cytoplasm with polymorphic nuclei. The cells of the former include multivesicular bodies and secretory granules, but those of the latter do not. Some of capillaries of the primary plexus are surrounded by the cells of the pars tuberalis on one side and by neurosecretory axon endings on the other side.The median eminence contains high concentration of acetylcholine or an acetylcholine-like substance and shows neurohypophysial hormone activity.Aided by Grant A-3678 from the United States National Institute of Arthritis and Metabolic Diseases. The authors are indebted to Dr. Welsh, Harvard University, for the kind gift of Mytolon.     

The distribution of monoamines in the hypothalamus of the Japanese quail Coturnix coturnix japonica

Summary The distribution of monoamines in the hypothalamus of the Japanese quail (Coturnix coturnix japonica) has been studied using a histochemical fluorescence technique. In the posterior hypothalamus catecholamine-containing nerve fibres are localised in the nucleus tuberis and nucleus hypothalamicus posterior medialis and are linked by fluorescent tracts running in the stratum cellulare internum. Further tracts may be traced from the nucleus tuberis around the base of the third ventricle to the sub-ependymal layer of the median eminence, where they then appear to pass through the hypothalamo-hypophysial neurosecretory tract to terminate in the palisade zone on the portal vascular bed. The innervation of the palisade layer by catecholamines is sparse. The fluorescent terminals are spread evenly throughout both the anterior and posterior divisions of the median eminence. There is no monoamine innervation of the pars nervosa. The paraventricular organ has both 5-hydroxytryptamine- and catecholamine-containing cell bodies and axons may be traced into the region of the nucleus hypothalamicus posterior medialis. In the anterior hypothalamus the neurosecretory paraventricular nucleus contains many catecholamine nerve fibres and terminals. These are linked by fibre tracts to the nucleus basalis and to the nucleus hypothalamicus posterior medialis. The supraoptic nucleus is less well innervated although a dense accumulation of fibres lies in the preoptic recess. The latter is thought to give rise to long axons which pass in association with the neurosecretory tract to end in the nucleus tuberis.Supported by a Grant (AG 24/36) from The Agricultural Research Council. We are indebted to Dr. G. A. Clayton, Institute of Animal Genetics, University of Edinburgh, for supplying the birds.     

Observations on the uptake of 35sulfur by the hypothalamo-hypophysial system of the White-crowned sparrow (Zonotrichia leucophrys gambelii) following intraventricular injection of 35S DL-cysteine

Summary By use of a stereotaxic instrument it has been consistently possible to introduce ³⁵S DL-cysteine into the third ventricle of the White-crowned Sparrow, Zonotrichia leucophrys gambelii. Such injections are followed within six hours by a reproducible pattern of accumulation of the isotope in the hypothalamic nuclei around the third ventricle. The nucleus supraopticus, the nucleus paraventricularis magnocellularis, the lamina terminalis, and the area ependymalis vasculosa consistently showed the greatest accumulation of the isotope. In the supraoptic and paraventricular nuclei, conspicuous accumulation of the isotope was consistently observed in association with cells containing aldehyde-fuchsin positive material. The supraoptico-hypophysial tract, the pars nervosa, and the palisade layer of the zona externa of the median eminence showed pronounced accumulations of the isotope. These accumulations were, to a great extent, associated with aldehyde-fuchsin positive neurosecretory material.Dedicatet to Professor Dr. W. Bargmann in honor of his 60th birthday.This investigation was conducted under Contract No. DA 18-108-AMC-127 (A) US Army Chemical Center Procurement Agency, Edgewood, Maryland, with Professor Farner as principal investigator.     

The effects of adenohypophysectomy on the hypothalamic-hypophysial neurosecretory system and the adrenal gland of the toad Bufo arenarum Hensel

Summary The effects of adenohypophysectomy were studied on the hypothalamichypophysial neurosecretory system and the adrenal glands of Bufo arenarum Hensel. An increase in vascularization of the pars intermedia was found and the neurosecretory material (NSM) in the glandular region of the median eminence disappeared. Its reappearance later was accompanied by hypertrophy of the pars intermedia; differentiated chromophil cells appeared in the pars intermedia around the vessels and, at the same time, the adrenal reverted to normal. These findings are interpreted as hypertrophy and differentiation of the pars intermedia with replacement, at least partly, of the functions of the pars distalis. The probable mechanism of differentiation and the functions of chromophil cells of the pars intermedia are discussed.This paper was presented at the VI Reunión de la Asociación Latinoamericana de Ciencias Fisiológicas (A.L.A.C.F.), Viña del Mar, Chile, 1964. It was carried out under the auspices of the Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina) and the Rockefeller Foundation (School grant RF-58028).Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.The authors wish to thank Prof. M. H. Burgos for his constant interest, Prof. B. A. Houssay, Prof. H. Heller and Dr. J. H. Tramezzani for their criticisms, Miss B. Rodriguez and Mr. L. Castro for their technical assistance.     

The function of the hypophysis without preoptic neurosecretory control

Summary In a large number of adult female and male specimens of Rana temporaria, a total extirpation of the magnocellular neurosecretory preoptic nuclei was performed. Several months after operation, no regeneration of the neurosecretory nuclei had occurred. The results showed 1. that all A.F.-positive neurosecretory nerve fibres of the hypothalamo-hypophysial region originate from nerve cell bodies localized in the magnocellular preoptic nuclei; 2. that the magnocellular preoptic nuclei do not play an important part in the inhibitory control of the activity of the pars intermedia of Rana temporaria; 3. that the possible role of the magnocellular preoptic nuclei in the seasonal development of the gonads and of the secondary sexual characteristics of Rana, could be only of secondary importance; 4. that, in accordance with previous experiments, in Rana, ovulation is dependent on preoptic hypothalamic structures. Some results of the present and of other experiments can be interpreted as supporting the hypothesis of a possible dual higher control over the gonadotropic centre (Dierickx, 1965b, 1966, 1967) of the pars ventralis of the tuber cinereum.A part of these studies has been reported previously in abstract form (Dierickx, 1963a, 1963b, 1965a).     

Hypothalamic neurosecretion and photoinduced testicular growth in the tree sparrow,Spizella arborea

Summary To assess the role of the hypothalamic neurosecretory system in the mechanism of photoperiodic control of testicular growth in Spizella arborea, we have examined the effect of (1) photostimulation on the density of paraldehyde-fuchsin-stainable (PAF+) material in the neurovascular zone of the median eminence, and (2) interruption of the hypothalamo-hypophysial (neurosecretory) tract on the photoperiodic testicular response. Birds were captured during midwinter and retained on 8-hr daily photoperiods several months prior to the experiment. Interruption of the neurosecretory tract was effected by a small knife fashioned from stainless steel wire; radiography was employed to facilitate stereotaxic placement of the knife assembly.Extending the daily photoperiod from 8 to 20 hrs induced rapid testicular growth in photosensitive Spizella arborea, but had no consistent effect on the density of PAF+ material in the palisade layer of the anterior median eminence. Whereas some terminal controls showed moderate depletion after 21 days' exposure to 20-hr daily photoperiods, others retained as much or more stainable material than initial controls in which testicular growth was not induced. Moreover, testicular growth was induced at essentially identical rates whether the PAF+ innervation of the anterior median eminence was intact or eliminated to varying degrees. The finding that the rate of photoperiodically induced testicular growth is independent of the density or pattern of accumulation of PAF+material in the neurovascular zone of the median eminence, coupled with the inconstant effect of photostimulation on the density of stainable material therein, strongly suggests that the eminential component of the hypothalamic neurosecretory system is not a part of the mechanism that controls photoperiodic testicular growth in S. arborea.Contribution No. 980, Division of Biology, Kansas Agricultural Experiment Station, Manhattan 66502. This investigation was supported in part by the Undergraduate Research Participation Program (GY-771) of the National Science Foundation. We are grateful to French's Pet Bird Laboratory, Rochester, N.Y., for the parakeet foods, to Richard S. Donham, Michael D. Ruff, Thomas G. Shane, and Philip G. Watt for assisting with field operations, to Mr. Gary R. Dierking for preparing the drawing, and to Mr. Don Pihlaja for assisting with the photomicrography.     

The distribution of monoamine oxidase and acetylcholinesterase in the brain of Xenopus laevis tadpoles

Summary The distribution of monoamine oxidase (MAO) in the brain of Xenopus laevis tadpoles (stage 52–56) was studied histochemically with a modified Glenner's tryptamine-tetrazolium method. A moderate activity was observed in fibre regions of the striatum and septum (including the medial and lateral forebrain bundles), in the neuropil of the nucleus amygdalae, in the commissura anterior and commissura hippocampi, in the fibre regions of the diencephalon (including the optic chiasma), in the fibre regions of the tectum opticum and the tegmentum of the mesencephalon and in the white substance of the ventral half of the medulla oblongata. A greater MAO activity was found in the neuropil of the entire nucleus praeopticus. In the partes anterior and magnocellularis of this nucleus, MAO positive fibres are present in close contact with the perikarya, indicating a monoaminergic innervation of these neurons. The perikarya themselves did not show MAO activity. In the neurons of the nucleus praeopticus epichiasmaticus, the paraventricular organ (PVO) and nucleus infundibularis dorsalis (NID), only a slight MAO activity has been demonstrated in the perikarya, whereas a strong MAO positivity was found in the intraventricular protrusions and the neuropil. These data indicate the aminergic character of the neurons of these nuclei. From the postoptic fibre region a MAO positive tract was observed towards the developing median eminence and pars intermedia of the hypophysis. The pars nervosa and some cells of the pars distalis also contained MAO. Along the border of the aquaeduct of Silvius and the fourth ventricle, MAO positive liquor-containing neurons are also present.The distribution of acetylcholinesterase (AChE) was investigated in the hypothalamohypophysial region. AChE activity was found in the neuropil of the nucleus praeopticus magnocellularis, in the fibres of the optic chiasma and in the postoptic fibre region. The neurons of the PVO and NID were AChE negative. An AChE positive tract could be traced from the postoptic fibre region to the developing median eminence and pars nervosa. The pars distalis did not show AChE activity. However, in tadpoles reaching the metamorphic climax, ChE activity appeared in certain cells of the pars distalis; this might be related to degenerative phenomena in the acidophilic cells. The absence of AChE activity in the pars intermedia indicates a regulation of MSH release by peptidergic nerves to be unlikely.The stimulating interest and helpful advice of Prof. Dr. P. G. W. J. van Oordt is gratefully acknowledged. Thanks are also due to Mr. H. van Kooten and his co-workers for making the photographs.     

Identification of adenohypophysiotropic neurohormone producing neurosecretory cells in Rana temporaria

Summary Electron microscopic investigation of neural isolated and normal pars ventralis of the tuber cinereum showed the presence, in Rana temporaria, of a tubero-hypophysial neurosecretory system. A striking structural resemblance between this parvicellular, aldehydefuchsin negative, tubero-hypophysial neurosecretory system and the magnocellular, aldehydefuchsin positive, hypothalamo-hypophysial neurosecretory system was observed. Six different neurosecretory cell types are described, characterized by different shape and size of their respective secretory granules. The nature of the secretory product of these cells is briefly discussed.Of the results of this investigation, a preliminary note has been published (Dierickx, 1971).The authors wish to thank Prof. Dr. H. Steyaert and Dr. W. Moerdijk of the Laboratory for Mathematical Statistics, Ghent University, for invaluable advice and assistance with their computers. They thank Dr. G. De Waele for his help with the scanning electron microscopy.     

A gradient of activity in the hypophysis of Rana temporaria

Summary In normal pars distalis of Rana temporaria, a gradient of activity of the P.A.S.-positive cells is always present. In animals, with complete and permanent interruption of all nervous pathways to the median eminence and hypophysis and without disturbance of the normal blood supply of the hypophysis, a subtotal disappearance of the gradient of activity occurred and the total activity of the P.A.S.-cells of the pars distalis was lowered. The activity of the P.A.S.-positive cells regressed in a typical way, suggesting a humoral mechanism.In animals with marked regeneration of the interrupted nerve fibres, a normal gradient of activity was present. From these and previous experiments, it is concluded that the gradient of activity of the P.A.S.-positive cells of the pars distalis of Rana temporaria is largely dependent on the A.F.-negative fibres of the median eminence, not originating from the magnocellular neurosecretory preoptic nuclei. It is suggested that these nerve fibres exert their influence on the activity of the P.A.S.-positive cells via substances released in the blood capillaries of the median eminence.The gradient of activity and its variations are mainly related to the gonadotropic function of the pars distalis.I am indebted to miss M. T. Bakeeff and miss C. Everaert who were so kind to check the karyometric results.     

Identification of adenohypophysiotropic neurohormone producing neurosecretory cells in Rana temporaria

Summary By means of electron microscopy, in the median eminence of Rana temporaria, the terminal arborizations of axons of six different types of neurosecretory cells, located in the pars ventralis of the tuber cinereum, were identified. In addition, phenomena connected with the release of neurosecretory material from the axon terminals of these neurosecretory cells into the blood capillaries of the median eminence are described.Preliminary results suggested the existence, in the median eminence, of additional different neurosecretory axon types which could also belong to corresponding neurosecretory cell types probably located in the apical part of the pars ventralis of the tuber cinereum. Moreover, in the external region of the normal median eminence, separate monoaminergic nerve fibres were tentatively identified. Arguments are adduced which plead (1) against the assumption that the ependyma or the pituicytes of the median eminence could produce adenohypophysiotropic hormones; (2) against the inference that the ependymal cells of the median eminence might be involved in the transport of adenohypophysiotropic hormones from the cerebrospinal fluid into the blood capillaries of the median eminence.     

Immunohistochemical demonstration of oxytocin-like, neuropeptide Y-like and gonadotropin-releasing hormone-like substances in the hypothalamo-hypophysial system of ayu,plecoglossus altivelis altivelis, in osmotically different environments

To ascertain the role of neuropeptides on the hypothalamo-hypophysial system of a fish in osmotically different environments, an immunohistochemical study of oxytocin (OXT), neuropeptide Y (NPY) and gonadotropin-releasing hormone (GnRH) was carried out on the anadromous salmonoid fish,Plecoglossus altivelis altivelis, commonly known as Ayu. River fish caught were acclimatized in a freshwater aquarium, half of them being subsequently kept as a control group and the remainder being transferred to a sea water aquarium, through 1/3 diluted sea water, as an experimental group. OXT-like immunoreactivity as demonstrated in the neurosecretory pathway, having the same pattern was that shown by aldehyde fuchsin staining. Noticeably, a mass of nucleus preopticus (NPO) and a marginal portion of the pars nervosa in the control group became strongly immunoreactive, whereas a very weak reaction was obtained in the sea water-retained fish, suggesting the release of the labelled substance. In the latter, NPY-like substance was widely distributed in the brain without NPO, with the positive substance being dense in the terminal rami of the pars nervosa bordering the pars distalis. However, no remarkable difference in GnRH-like and NPY-like immunoreactivities in the hypothalamo-hypophysial system was apparent between the two groups. These results suggested that OXT (probably isotocin)-like substance may play a role in osmoregulation.     

Fluoreszenz- und elektronenmikroskopische Untersuchungen am Zwischenhirn-Hypophysensystem von Passer domesticus

Zusammenfassung Fluoreszierende aminerge Nervenfasern bzw. Endigungen und elektronendichte Granula mit einem Durchmesser von 500–1000 Å wurden bei Passer domesticus in den Perikaryen und im Neuropil des Nucleus infundibularis, im Neuropil des Nucleus supraopticus, im rostralen Abschnitt der neurosekretorischen Bahn (Region der Sehnervenkreuzung) und in der retikulären und Palisadenschicht der Eminentia mediana beobachtet. 2000–2500 Å große kontrastreiche Granula finden sich in den Perikaryen des Nucleus supraopticus, im Tractus supraoptico-paraventriculo-hypophyseus und im Hypophysenhinterlappen. Nach Reserpinbehandlung schwanden sowohl die gelbgrüne Fluoreszenz als auch das elektronendichte Material der 1000 Å und z. T. auch der 500–800 Å großen Bläschen. Dieses Ergebnis spricht dafür, daß beide Granulatypen Monoamine enthalten. Der Nucleus infundibularis ist nach unseren Befunden die wichtigste Quelle der etwa 1000 Å großen Granula in der Palisadenschicht der Eminentia mediana.

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Fluorescence- and electronmicroscopic studies on the hypothalamo-hypophysial system of Passer domesticus

Summary In Passer domesticus, fluorescent aminergic fibers and axon terminals and dense-core vesicles of 500 to 1000 Å diameter were found in the perikarya and the neuropile of the infundibular nucleus, in the neuropile of the supraoptic nucleus, in the rostral common neurosecretory pathway (region of the optic chiasma), in the tubero-infundibular tract, and in the reticular and palisade zones of the median eminence. 2000–2500 Å electron-dense vesicles were found in the perikarya of the supraoptic nucleus, in the proximal division of the common neurosecretory pathway and in pars nervosa of the hypophysis. After reserpine treatment, the yellow-green fluorescence as well as the dense material contained in the 1000 Å vesicles and partly also in the 500–800 Å vesicles disappeared. This suggested that the 1000 Å and the 500 Å dense-core vesicles in the hypothalamo-hypophysial system of Passer domesticus contain monoamines and that the infundibular nucleus is an important source of the 1000 Å dense-core vesicles in the palisade layer of the median eminence.

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Herrn Prof. Dr. Dr. E. Horstmann gewidmet.

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Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.

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Stipendiat der Alexander von Humboldt-Stiftung. (On leave from the Department of Veterinary Anatomy, University of Minnesota, St. Paul, Minnesota, U.S.A.).     

Structure of the neurohypophysis and the hypothalamo-hypophysial vascularization in the teleost Channa punctatus Bloch.

In C. punctatus the median eminence includes the subterminal region of the hypothalamus and the anterior neurohypophysis. It is formed of ependymal, fibrous and reticular layers as in the tetrapods. Primary capillary plexus extends from the subterminal region to the extremity of the anterior neurohypophysis. Only few portal vessels from the hypothalamus enter in the pars distalis. All the components of pituitary including the pars intermedia are irrigated by the secondary plexus formed from the portal vessels emerging out of the anterior neurohypophysis. The neurosecretory axons and the ependymal cells are in close morphological contact with the primary plexus. Several axons have perivascular endings at the median eminence. Some axons were found to be only silver or aldehyde fuchsin positive whereas some others take up both. The silver positive axons were abundant in the pars distalis and the AF positive ones were more concentrated in the pars intermedia with greater accumulation of neurosecretory material.