The fine structure of the hypothalamic secretory neurons of the White-crowned Sparrow,Zonotrichia leucophrys gambelii (Passeriformes: Fringillidae)

Summary The fine structures of the neurons and neuropils of the magnocellular supraoptic nucleus and the parvocellular nuclei of the rostral hypothalamus, including the suprachiasmatic and medial, lateral and periventricular preoptic nuclei, and the neuronal apparatus of the organum vasculosum laminae terminalis, have been examined in the male White-crowned Sparrow, Zonotrichia leucophrys gambelii, by correlated light and electron microscopy.The magnocellular supraoptic nucleus is characterized by large neurosecretory perikarya which contain a well developed Golgi complex and densecored granules 1,500–2,200 Å in diameter. The neuropil displays axons, dendrites and glial fibers. Some axonal profiles contain dense-cored vesicles 800–1,000 Å in diameter and clear vesicles 500 Å in diameter. Axo-somatic and axo-dendritic synapses are conspicuous in this nuclear region.The suprachiasmatic nucleus is characterized by an accumulation of small neurons with moderately developed cellular organelles and some dense-cored granules, approximately 1,000 Å in diameter. The profiles of axons within the neuropil contain dense-cored granules 800–1,000 Å in diameter and clear vesicles 500 Å in diameter.The neurons of the medial preoptic nucleus are relatively large and exhibit well developed cellular organelles and dense-cored granules 1,300 to 1,500 Å in diameter. Granular materials are formed within the Golgi complex. The medial preoptic nucleus is rich in secretory perikarya.Occasionally, neurons with granules 1,500–2,200 Å in diameter are encountered in the lateral preoptic and periventricular preoptic nuclei. They may be considered as scattered elements of the magnocellular (supraoptic and paraventricular) system.The organum vasculosum laminae terminalis consists of three layers, i.e., ependymal, internal and external zones, and exhibits a vascular arrangement similar to that of the median eminence. The perikarya of the parvocellular neurons and their axons in the internal zone contain numerous secretory granules ranging from 1,300 to 1,500 Å in diameter.This investigation was supported by Grant No. 5R040 Japan-U.S. Cooperative Science Program of the Japan Society for the Promotion of Science to Professor H. Kobayashi and Professor S.-I. Mikami, by a Scientific Research Grant No. 56019 from the Ministry of Education of Japan to S.-I. Mikami, by support from the Deutsche Forschungsgemeinschaft (Schwerpunktprogramm Biologie der Zeitmessung) to Prof. A. Oksche and by Grant No. GF 33334, U.S.-Japan Cooperative Science Program of the National Science Foundation to Prof. D.S. Farner.Herrn Professor Dr. Dres h.c. Wolfgang Bargmann zu seinem 70. Geburtstag am 27. Januar 1976 gewidmet.     

Ultrastructure of the median eminence of the rat

Summary The ependymal cells bordering the median eminence to the third ventricle are characterised by many microvillus-like projections and bulbous cell processes of the luminal plasma membrane. The latter contain many vesicles 500–1,000 Å in diameter. Cilia with 9+2 fibrillar pattern are seen occasionally. Adhesive devices in the from of zonula adhaerens and zonula occludens are found in the apical part of the intercellular junction. Unmyelinated nerve fibres with a mean diameter of 1 and containing many electron dense granules of 830–1,330 Å are often seen between the ependymal cells.Two types of glial cells are found in the median eminence. One is characterised by a nucleus with dense blods of chromatin and dense cytoplasm, and it is associated chiefly with the nerve fibres in the region of the hypothalamo-hypophysial tract. The other type of glial cell is characterised by fine, uniformly distributed chromatin in the nucleus and a relatively pale cytoplasm and branched processes which terminate perivascularly in the base of the median eminence.Myelinated nerve fibres are seen only in the region of the hypothalamo-hypophysial tract. Only a part of them contain electron dense granules 1,330–2,330 Å in diameter.Three types of unmyelinated nerve fibres can be distinguished in the median eminence according to the size of the electron dense granules they contain: 1. Nerve fibres containing granules 1,330–2,330 Å in diameter. They are seen primarily in the hypothalamo-hypophysial tract, but also in the zona externa; 2. those containing granules with a mean diameter of 1,330 Å; and 3. those containing granules with a mean diameter of 1,000 Å. The last two types are both encountered in the hypothalamo-hypophysial tract, the zona externa and the perivascular region of the base of the median eminence. Under high magnification, the membrane of the granules show evidence of a trilaminar structure and the content of the granules with a low electron density appeares to consist of small microvesicles or globular components. Besides granules, these nerve fibres contain vesicles mostly 420 Å in diameter whose relative number increases towards the perivascular nerve endings. 53 per cent of the inclusions in the hypothalamo-hypophysial tract are granules and 47 per cent vesicles, while the corresponding percentages for the zona externa are 40 and 60 and for the perivascular nerve endings 20 and 80.The mean width of the pericapillary space is 1 , but it varies greatly. It containes many collagen fibrils and fibroblasts. The capillary endothelium is frequently fenestrated and contains many vesicles of various sizes.Two types of granules-containing cells are found in the pars tuberalis depending on the size of the electron dense granules: 1. cells containing granules with a mean diameter of 1,330 Å: and 2. cells containing granules with a mean diameter of 2,000 Å. In addition, there are occasional follicular cavities filled with amorphous material, microvilli and cilia of 9+2 fibrillar pattern.Aided by a grant from the Sigrid Jusélius Stifteise.     

Ultrastructure of the peptidergic and monoaminergic neurons in the hypothalamic neurosecretory system of Anuran Batracians

Summary In the toad Bufo arenarum Hensel the following regions of the hypothalamic — neurohypophyseal system were studied under the electronmicroscope: preoptic and paraventricular nuclei, median eminence and infundibular process of the neurohypophysis.Neuronal perikarya of the preoptic nucleus are loaded with typical neurosecretory granules of peptidergic nature having a mean diameter of 1660 Å. While most neurons of the winter toad are in a storage stage a few show signs of a more active synthetic activity. A distinctive feature of preoptic neurons is the presence of large lipid droplets. The paraventricular nucleus contains small neurons containing granulated vesicles with a mean diameter of 800-1000 Å. In the region extending between these two nuclei and the median eminence axons containing either neurosecretory elementary granules or granulated vesicles are observed.The inner zone of the median eminence is occupied by axons of the preoptic neurohypophyseal tract; two types of axons, according to the size and density of the neurosecretory granules, may be recognized. The outer zone of the median eminence contains mainly axons and nerve terminals containing granulated vesicles of probable monoaminergic nature and only a few with granules of peptidergic type.The neurohypophysis contains two kinds of axons: one with more dense granules of 1800 Å and the other with granules of lesser electron density and 2100 Å. At the ending proper small clear vesicles of synaptic type are found.A progressive increase in volume of the peptidergic granules along the axon is demonstrated. This is of the order of 218% from the preoptic perikarya down to the infundibular process. The physiological significance of the two neurosecretory systems — i.e. the monoaminergic and the peptidergic — and the probable nature of the two types of peptidergic axons is discussed.Supported by grants from the Consejo Nacional de Investigaciones Científicas y Técnicas and by the Air Force Office of Scientific Research (AF-AFOSR 963-67).The authors want to express their gratitude to Mrs. Defilippi-Novoa and Mr. Alberto Sáenz for their skillful assistance.     

Ultrastructure and hormonal content of the proximal stump of the transected hypothalamo-hypophysial tract of the frog (Rana pipiens)

Summary Several types of neurosecretory fibers were observed in the normal infundibulum of the frog. After transection of the median eminence, these neurosecretory fibers of the proximal stump reacted asynchronously, but followed approximately the same pattern: a passive accumulation of granules observed early after the transection was followed by an active axonal reaction with the appearance of numerous tubular formations which are thought to be related to the Golgi apparatus. They filled the axon almost completely, and then became dilated and filled with an electron dense material. Subsequently these dilatations pinched off and gave origin to new neurosecretory granules. These locally packed granules plus others which were probably formed in more proximal parts of the axon, and the perikaryon and then transported distally, accumulated in the proximal axonal stumps and started to fill the fibers retrogradely.There was a parallelism between the increase of tubular formations and neurosecretory granules larger then 1,500 Å in diameter, on one side, and the vasopressor activity of the proximal stump, on the other. The latter increased at an approximate rate of 1 mU/stump/day.The regeneration of the fibers of the hypothalamo-median eminence system is suggested by the presence in the proximal stump of fibers filled with granules smaller than 1,000 Å in diameter (normally seen in the median eminence) and the fact that 40% of the vasopressor activity of the extracts was not abolished by the thioglycollate treatment, which could be due to the presence of vasopressor amines other than adrenaline. The appearance towards the end of the observation period of a few nerve endings of several types contacting the perivascular basement membrane of vessels of the proximal stump would indicate that the neural lobe and median eminence functions were being reestablished, at least partially.This investigation was supported by grants 5RO1 NB 06641 NEUA and 5RO1 NB 07492 NEUA from the National Institute of Health and by the Space Sciences Research Center of the University of Missouri. The authors wish to thank Mrs. G. Clark, Mr. G. Ribas and Mr. R. Faup for their valuable technical help.Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina.     

Ultrastructure of the neurohaemal region of the toad median eminence

Summary According to the internal structure and size of the granules, six types of nerve endings can be distinguished in the toad median eminence: 1. Endings containing mostly dense granules of 600 Å in diameter; 2. Endings containing dense granules of about 800 Å in diameter; 3. Endings which contain dense granules 1,000–2,000 Å in diameter, with the peak at 1,200–1,400 Å; 4. Endings containing granules with a characteristic structure, which differentiate them from the other three types; 5. Scarce endings containing granules 2,000 to 3,800 Å in diameter; and 6. Endings containing only vesicles 400–500 Å in diameter. Types 3 and 4 endings are mainly found in the outer pericapillary zone, and are probably responsible for the strong Gomori-positive reaction observed in this zone. The other four types of endings occur mainly in the inner pericapillary zone, and appear to be Gomori-negative.The probable origins of the different types of endings, and their possible relations with the different releasing factors is discussed.The subendothelial basement membrane has numerous long processes which form a complicated network in contact with all the nerve endings, some nerve fibres and glial cells.Two types of glial cells are described. Pinocytotic vesicles are frequently seen at the points where these cells contact the basement membrane. All the ultrastructural features suggest that these cells are carrying out transport functions.Fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina.The author is very grateful to Professor H. Heller for his continued encouragement and criticism and to Mr. J. Lane and Mr. P. Heap for their valuable help.     

Vesicle and granule content of sympathetic ganglion cells during limb regeneration of the newt Triturus

Summary Fine structural observations were made on the vesicle and granule content of ganglion cells in the posterior subclavian ganglion and peripheral nerve fibers of the upper forelimb of the newt Triturus. The populations of vesicles and granules in normal ganglion cells and nerve fibers were compared with those observed after limb transection. In normal neurons, clear vesicles range in size from 250 to 1000 Å in diameter, but are most frequently 400–500 Å. Vesicles with dense contents (granules) also vary greatly in size, but most are 450–550 Å in diameter and correspond to dense-core vesicles. Large granules that contain acid phosphatase activity are thought to be lysosomes. During limb regeneration, in both the ganglion cells and peripheral nerves, the ratio of dense vesicles to clear vesicles increases. There is a large increase in number of dense granules with a diameter over 800 Å, particularly in the peripheral regenerating fibers. This study shows that regenerating neurons differ from normal in their content of vesicular structures, especially large, membrane-bounded granules.This work was supported by grants from the National Science Foundation (GB 7912) and from the National Cancer Institute (TICA-5055), National Institutes of Health, United States Public Health Service.     

The neurohypophysis of the crested newt

Summary In the median eminence of the newt a medial region and two lateral regions are described.In cross section, the medial region appears to be made up of 1) an outer or glandular zone (Zone I) containing aldehyde-thionine-positive and negative nerve fibres and blood capillaries. Nerve fibres appear aligned in palisade array along the capillaries. 2) An inner zone (Zone II) made up of a) a layer of aldehyde-thionine-positive nerve fibres (fibrous layer) belonging to the preoptic hypophyseal tract and b) a layer of ependymal cells lining the infundibular lumen and reaching the blood vessels with their long processes.The lateral regions display a less pronounced stratification and aldehyde-thionine positive nerve fibres are nearly absent.A slender lamina (ependymal border) containing mainly aldehyde-thionine-positive nerve fibres and ependymal cells connects the median eminence to the pars nervosa.At the ultrastructural level, in the outer zone of the medial region at least 4 types of nerve fibres and nerve endings are identified:Type I nerve fibres containing granular vesicles of 700–1000 Å and clear vesicles (250–400 Å).Type II nerve fibres containing granular vesicles and polymorphous granules of 900–1300 Å and clear vesicles (250–400 Å).Type III nerve fibres containing dense granules of 1200–2000 Å and clear vesicles of 250–400 Å.Type IV nerve fibres containing only clear vesicles of 250–400 Å. In the inner zone too, all these nerve fiber types are found among ependymal cells, while the fibrous layer consists of nerve fibres containing granules of 1200–2000 Å in diameter.In the lateral regions Type I, Type II and Type IV nerve fibres and their respective perivascular terminals are found; axons containing dense granules (1200–2000 Å) are scanty. In these regions typical synapses between Type I nerve fibres and processes rich in microtubules are visible.The classification and functional significance of nerve fibres in the median eminence are still unsolved, but it may be assumed that nerve fibres of the medial region belong to both the preoptic hypophyseal and tubero hypophyseal tract, while the lateral regions are characterized by nerve fibres of the tubero hypophyseal tract. Peculiar specializations of the ependymal cells in the median eminence of the newt are also discussed.Work supported by a grant from the Consiglio Nazionale delle Ricerche.The authors are indebted to Mr. G. Gendusa and P. Balbi for technical assistance.     

On different types of nerve endings in the frog median eminence after fixation with permanganate and glutaraldehyde-osmium

Summary In the frog median eminence, fixed with glutaraldehyde and osmium tetroxide, four types of nerve endings can be generally distinguished. These endings are in contact with the pericapillary spaces of primary portal vessels and can be identified by the internal structure and the size of their granules and vesicles. Type 1 contains large granules (1500–2400 Å in diameter) and small clear vesicles (300–500 Å in diameter), type 2 intermediate granules (about 1100–1700 Å in diameter) and small clear vesicles, type 3 small granules (about 600–1000 Å in diameter) and small clear vesicles, type 4 only numerous small clear vesicles. The mixed types containing the large, intermediate and small dense granules in the same ending are infrequently found.After KMnO₄ or LiMnO₄ fixation the granules and vesicles mentioned above are observed as follows. The large granules in the type 1 nerve ending appear mostly pale or less-dense. The intermediate granules in the type 2 also appear mostly pale or less-dense, but some frequently show granules of high density. The small granules in the type 3 consistently contain the dense substance and these endings can be subdivided into two different types according to the populations of different sizes of dense granules [type 3a (900–1000 Å) and type 3b (500–800 Å)]. Dense-cored and cleared-synaptic vesicles are frequently present with together in the type 3 endings. The small vesicles (300–400 Å), in the type 4, appear generally pale (type 4a), but some nerve endings contain small dense cored-vesicles (type 4b).The author wishes to thank Prof. H. Fujita for his advice and criticism.     

Etude au microscope électronique de la neurohypophyse de Rana esculenta L.

Résumé L'éminence médiane et la pars nervosa de Rana esculenta diffèrent du point de vue de leur structure.L'éminence médiane se compose de 2 zones différentes: la zone externe placée près du lobe distal et la zone interne située sous l'épendyme. Dans la zone externe, on distingue, d'après la taille et la forme des grains de sécrétion, 5 types de terminaisons.1. des terminaisons avec de fins granules sphériques denses de 800 à 1000 Å de diamètre; 2. des terminaisons avec des granules de 1000 à 1200 Å de diamètre; 3. des terminaisons avec des grains de forme irrégulière de diamètre supérieur aux précédents (1200 à 1600 Å); 4. des terminaisons avec de volumineux grains denses sphériques d'environ 1200 à 1800 Å de diamètre; 5. un petit nombre de terminaisons ne contenant que des vésicules. Les terminaisons des catégories 3 et 4 sont probablement du type neurosécrétoire.La zone interne contient de nombreuses fibres neurosécrétrices. Elles sont de 2 types, l'une avec de gros granules (1600–2400 Å), l'autre avec des granules moins volumineux (1300–2000 Å). Des fibres non neurosécrétrices ont également été observées.Dans la pars nervosa, on rencontre deux types principaux de fibres neurosécrétrices, l'une avec des grains denses de 1600 à 2400 Å de diamètre, l'autre avec des grains moins denses d'environ 1300 à 2000 Å de diamètre. Dans la zone externe bordant la pars intermedia des fibres aminergiques avec de fines granulations ont été observées.

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Electron microscopic study of the neurohypophysis of Rana esculenta L.

Summary The median eminence and the pars nervosa of Rana esculenta have a different structure.The median eminence has 2 different zones: the outer zone situated near the pars distalis and the inner zone under the ependyme. In the outer zone there are, according to the size and the shape of the granules, 5 types of nerve terminals.1. Endings containing spherical fine dense granules of 800 to 1000 Å in diameter; 2. Endings with spherical granules from 1000 to 1200 Å in diameter; 3. Endings with granules of irregular shape which are bigger than the former (1200 to 1600 Å); 4. Endings with spherical dense granules of about 1200 to 1800 Å in diameter; 5. A few endings containing only clear vesicles. Type 3 and type 4 endings are probably neurosecretory.The inner zone contains numerous neurosecretory fibres. They are of two types: one with big granules (1600–2400 Å), the second with smaller granules (1300–2000 Å). Non-neurosecretory fibres have also been observed.The pars nervosa contains two principal types of neurosecretory fibres: one with dense granules of 1600 to 2400 Å in diameter, the other with lighter granules of about 1300 to 2000 Å. In the external zone lining the pars intermedia, aminergic fibres with fine granules have been observed.

Je tiens à exprimer mes vifs remerciements, à Monsieur le Professeur E. Follenius pour l'intérêt constant qu'il prend à ce travail. Je remercie également Madame R. O. Clauss, collaboratrice technique et Madame Schwoerer, photographe, pour leur aide précieuse.     

Observations on the ultrastructure of nerve cells in the brain of the planarian,Dugesia gonocephala

Summary The submicroscopic structure of the nerve cells in the planarian brain was studied. Close similarities with neurons of other invertebrates were noted. In the cytoplasm of the planarian nerve cells there are at least three types of vesicular inclusions: 1) Clear vesicles (200–800 Å in epon embedded tissue) similar in morphological appearance to classical synaptic vesicles. These have generally some content of extremely low density but occasionally a dense core. 2) Dense vesicles (400–1,200 Å in epon embedded tissue) containing highly osmiophilic granules. Between the limiting membrane of the vesicle and the granule there is always a clear rim of variable width. These vesicles closely resemble synaptic vesicles described in vertebrate adrenergic endings. 3) Neurosecretory vesicles (600–1,300 Å in Vestopal embedded tissue) similar to elementary granules observed in neurosecretory systems in vertebrates and invertebrates. All three vesicle types have the same mode of origin from the Golgi membranes. All are present in the nerve cell processes of the neuropil as well as in the perikarya. Any given perikaryon or axon contains only one of the three vesicle types. All of these vesicles are considered to be discharged into the axons from their site of origin within the perikaryon.     

Electron microscopic autoradiography on the localization of serotonin in the frog median eminence

Summary For the identification of the nerve fiber containing serotonin (5-hydroxytryptamine) in the frog median eminence, an electron microscopic autoradiography was performed with 5-hydroxytryptophane-³H which is the precursor of serotonin. At 1 and 24 hours after the intraperitoneal injection, most silver grains were located over the nerve fibers and endings, and a few were also found over the glia cell and the perivascular space. A large number of silver grains were located over the type 3 nerve endings (Nakai, 1971) containing small dense granules about 600–1000 Å in diameter 1 and 24 hours after the injection. Some silver grains were localized over the nerve endings containing intermediate-size dense granules 1100–1700 Å in diameter. Silver grains were also frequently observed over the nerve fibers in the inner layer of frog median eminence. There is no significant difference in the pattern of distribution of silver grains between tissues of 1 hour and 24 hours after the injection.The authors wish to thank Prof. H. Fujita for his advice and criticism.     

Light- and electron microscopic investigations on the median eminence of the pigeon after TSH and PTU treatment

Summary 1. The effects of TSH and PTU treatment with thyroid stimulating hormone and propylthiouracil on the structure of median eminence of the pigeon have been studied by light- and electron microscopy.2. By light microscopy it has been found that the aldehydefuchsin positive material of the external layers of the anterior median eminence differs functionally from that of the neural lobe.3. The light- and electron microscopic investigations revealed that the anterior and posterior median eminence differ both structurally and functionally. Specifically after the experimental interventions the considerable reaction can be observed only in the anterior median eminence.4. Electron microscopically it appears possible that the aldehyde-fuchsin positive material of the anterior median eminence may be associated with the 1200–1500 Å—size granules.5. The quantitative changes observed in the granular composition after the treatments show a close correlation with thyroid function, namely after treatment with thyroid stimulating hormone the relative quantity of the 1200–1500 Å—size granules increases markedly, while administration of propylthiouracil has the opposite effect and increases the relative quantity of the 1000 Å—size dense-core vesicles. They presumably may play a role in the control of TSH-secretion.Abbreviations TSH thyroide stimulating hormone - PTU propylthiouracil - ME median eminence - AME anterior median eminence - PME posterior median eminence - AF+ aldehyde-fuchsin positive - AF– aldehyde-fuchsin negative     

LHRH-like system in the brain of Xenopus laevis daud

Summary Rabbit antiserum to synthetic LHRH was used with the immunofluorescence technique to identify the LHRH-secreting neurons and their axonal pathways in the brain of Xenopus laevis. Three groups of immunoreactive neurons were identified: the first, in the telencephalon, is a paired group of cells scattered near the two telencephalic ventricles; the second group lies near the preoptic recess; the third group occurs in the ventral wall of the infundibulum. Two principal neuronal pathways were observed: Fibres originating from the dorsally located telencephalic neurons converge on the cephalic median plane where they form a single bundle behind the telencephalic furrow. This bundle descends towards the anterior border of the preoptic recess where it divides into two nerve bundles which pass on either side of the preoptic recess, run above the optic chiasma then cross the infundibular floor and finally terminate in the median eminence. The second pathway is more direct. The more ventrally located telencephalic LHRH cells give rise to this second pathway. Their axons converge with the other LHRH fibres near the lateral border of the preoptic recess. Most of the LHRH nerve fibres terminate in the median eminence although some terminate near the paired pars tuberalis. No reaction was observed after the use of antiserum absorbed with synthetic antigen.Equipe de Recherche associée C.N.R.S. n 492. This work was financed by the D.G.R.S.T., Contract n 7470046     

Immunofluorescence study of LRH-producing neurons in prosimians (Tupaia and Galago)

Summary Reactive LRH neurons were characterized in prosimians (Tupaia and Galago) by immunofluorescence using rabbit immunesera against unconjugated synthetic LRH, or LRH conjugated with bovine serum albumin. These neurons, which vary individually in number in one species, are mainly concentrated in the rostral hypothalamus (medial preoptic area and anterior hypothalamic area) and in the lamina terminalis. In contrast to the simians and man, immunoreactive perikarya were not routinely found in the mediobasal hypothalamus of the prosimians investigated in the present study. Reactive axons of the hypothalamo-hypophyseal tract are more numerous and conspicuous in the retrochiasmatic area and in the postinfundibular eminence. They give rise to radiating collaterals ending mainly around the capillaries of the primary portal plexus of the median eminence and of the infundibular stem (where they are generally more numerous). Reactive axons of the preopticoterminal tract, originating from the perikarya of the lamina terminalis, end around the capillaries of the vascular organ or below and between the ependymal cells lining its ventricular side.In Galago a small but very distinct tract of reactive axons runs under the optic chiasma, between the lamina terminalis and the ventral labium of the infundibulum. Very fine reactive extrahypothalamic axons were observed in the posterior part of the habenular ganglia, along the preamygdaloid portion of the stria terminalis and along the blood vessels of the parolfactory area.This work was supported by a grant from the Foundation pour la Recherche Médicale Française. The author acknowledges the help of Miss D. Croix for the preparation of LRH-BSA conjugates and the radioimmunological study of the immunosera and A. Pillez (C.N.R.S.) for sectioning and staining the genital tracts     

Fine structure of the lateral-line organ of the common eel,Anguilla japonica

Summary The sensory epithelium of the lateral line organ of the common eel consists of two types of cells, (sensory and supporting). The sensory cell bears a kinocilium together with about 40 to 60 stereocilia on its surface. The kinocilium is situated either at rostral or at caudal margin of this cilial group. Such polarity of the cilial group of one cell is inverse to that of an adjacent cell.Two types of crystal-like inclusions exist in the sensory cells, consisting of granules 100 Å in diameter. Granules in one type are arranged regularly whereas those in the other rather irregularly.Two types of nerve endings exist at the base of sensory cells: one is predominant in number and contains few vesicles, accompanied by a dense spherical body surrounded by small vesicles in the sensory cell and the other is rare in number and contains many vesicles, accompanied by a small flat sac just beneath the plasma membrane of the sensory cell.The supporting cells contain numerous mitochondria, a well developed Golgi apparatus and rough-surfaced endoplasmic reticulum, and surround a sensory cell completely. Physiologic significance of some of these components is discussed.     

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.     

Mesotocin and vasotocin in the brain of the lizard Gekko gecko

Summary The distribution of mesotocin and vasotocin was studied in the brain of the lizard Gekko gecko with antisera specific for either peptide. Both mesotocinergic and vasotocinergic perikarya are found in the paraventricular and supraoptic nuclei of the hypothalamus, whereas vasotocinergic neurons are exclusively present in the bed nucleus of the stria terminalis and in a cell group of the rhombencephalon. The distributional pattern of the mesotocinergic fibers corresponds closely to that of the vasotocinergic fibers. However, throughout the entire brain the mesotocinergic innervation is less dense than the vasotocinergic innervation. No sex differences are present in the mesotocinergic fiber system.Abbreviations acc nucleus accumbens - bst bed nucleus of the stria terminalis - bv blood vessel - dB diagonal band of Broca - dc dorsal cortex - dth dorsolateral thalamic nucleus - lc lateral cortex - me median eminence - oc optic chiasma - ot optic tract - pag periaqueductal grey - pvn paraventricular nucleus - rc rhombencephalic cell group - sep septum - son supraoptic nucleus - tect mesencephalic tectum - vth ventrolateral thalamus     

Corticotropin-releasing factor (CRF)-immunoreactive neurons in the mammillary body of the rat

Summary The presence and distribution of CRF-immunoreactive cells and nerve fibers were studied in the mammillary body of the rat, 12 days after placing various types of lesions within the hypothalamus. Anterior and anteriolateral cuts, placed in the midhypothalamus immediately behind the paraventricular nuclei resulted in an almost complete disappearance of CRF-immunoreactive fibers from the median eminence and simultaneous appearance of CRF-containing neurons in the mammillary body. Posterior or postero-lateral hypothalamic cuts carried out in front of the mammillary body caused the accumulation of CRF-immunoreactive material in neurons and neural processes located behind the cut-line. This type of intervention had no effect on the quantity of CRF fibers in the median eminence. A cut running through the central part of the mammillary body in the frontal plane resulted in appearance of CRF neurons only in the posterior half of the mammillary region. Placing a cut behind and over the mammillary body, CRF-immunoreactive neurons became detectable below the superior cut-line. No immunoreactive neurons were observed in the mammillary body when the frontal cut reached the base of the brain at the posterior border of the nucleus, leaving intact its anterior and superior connections. In all these cases when the mammillo-thalamic tract was transected, CRF neurons became detectable in the mammillary body.     

The location of LH-RH neurons in the rat hypothalamus and their pathways to the median eminence

Summary The location of the perikarya of LH-RH neurons in the rat hypothalamus and their pathways to the median eminence were studied by immunohistochemistry and radioimmunoassay after placing stereotaxic electrolytic lesions in several parts of the hypothalamus. The principal location of the cell somata was found to be in the ventral part of the medial preoptic area; their pathways were classified into a main baso-lateral pathway and an accessory descending pathway branching off from the former. The main pathway was found to cross in the vicinity of the corresponding neuronal perikarya. The central median eminence and the dorsal and ventral walls of the tubero-infundibular sulcus of the caudal part of the median eminence are innervated mainly by the baso-lateral pathway. On the other hand, the rostral and most caudal portions of the median eminence are innervated principally by the descending pathway and have a subsidiary dual innervation. The projection of LH-RH neurons to the OVLT is believed to originate from perikarya adjacent to this circumventricular organ.This work was supported in part by a grant (No. 248093, 321426) from the Ministry of Education, Science and Culture, Japan     

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.).