Further studies on the neurohypophysis of the hedgehog (Erinaceus europaeus)

Summary Further studies of the neurohypophysis of the hedgehog have confirmed the presence of two distinct types of neurosecretory fibre in the infundibular process. A third type of fibre, possibly containing catecholamines, is found in the upper infundibular stem.Lesions of the paraventricular nuclei result in vacuolation of type I nerve fibres, which contain crystal-like and aggregate bodies. Type II fibres, containing membranous inclusions, with or without osmiophilic material, apparently do not degenerate. The evidence suggests that type I fibres arise in both the paraventricular and supraoptic nuclei.Dedicated to Professor Berta Scharrer on the occasion of her 60th birthday.     

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.     

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.     

The structure of the hypothalamic neurosecretory cells of Zoarces viviparus L. under the conditions of constant dark and light during the reproductive cycle

Summary The Structure of the hypothalamic neurosecretory cells during their activity in continuous light and dark conditions and depending on the seasonal alteration has been investigated in Zoarces viviparus L. in the level of light and electron microscopy.The depletion of AF- or AT-stainable material, of the elementary neurosecretory granules and the disappearance of smooth-surfaced vesicles occur during April and June. The accumulation of the stanable material as well as the elementary neurosecretory granules and the smooth-surfaced vesicles has been observed in the cell body in late September.An excess increase in number of the smooth-surfaced vesicles of dark-induced animals and light-induced animals kept in a black stained tank is apparent. On the other hand, the disappearance of the elementary granules and the smooth-surfaced vesicles and an enlargement in the reletive nuclear surface of the neurosecretory cells of light-induced animals which were kept in a gray stained tank in April is also evident.Taking into consideration the responsiveness of both the elementary neurosecretory granules and the smooth-surfaced vesicles in relation to the external environment as well as their topographical arrangement in the cell body the possible differences in their origin and function are discussed.Numerous studies indicate that the physical environment is in part responsible for the functional properties of the hypothalamic neurosecretory centers of various vertebrates. In the level of light microscope, it has been repeatedly shown that the neurosecretory cells are activated in the animals subjected to continuous illumination, and in those subjected to long daily photo period (Oksche et al., 1958; Fiske and Greep, 1959; Öztan and Gorbman, 1960; Satyanesan, 1965). The enlargement of the nuclei and the amount of Gomori — or aldehyde fuchsin — stainable material, as well as the enzymatic activity, were used as the criteria of cellular activity in the histological preparation. In the level of electronmicroscope it has been shown that Gomori positive material (Bargmann, 1949) is represented as aggregated elementary neurosecretory granules in the ultrathin sections of neurohypophysis (Bargmann et al,. 1957). Although the fine structure of the hypothalamic neurosecretory cells of various fishes and higher vertebrates have been studied in normal and experimental conditions (Palay, 1960; Lederis, 1962, 1964; Follenius et Porte, 1962; Follenius, 1963; Murakami, 1961–1964; Gansler, 1965; Holmes, 1965) the type of granules and their function still remains as an open question (see Bargmann, 1963; Knowles, 1965).This work was aided by a grant from Nato and the Deutsche Forschungsgemeinschaft.This paper was written as a tribute in honor of the 60th birthday of Prof. Dr. Berta Scharrer.     

The effect of castration upon the ultrastructure of the rat hypothalamus

Summary The neurosecretory hypothalamic nuclei and the inner zone of the median eminence of castrated rats were studied under the electron microscope. After one month of castration all the neurosecretory neurons of both nuclei show signs of hyperactivity characterized by dilated cisternae of the endoplasmic reticulum containing a macromolecular filamentous material and an increase in the number of ribosomes. After six months of castration, some neurosecretory neurons show an increased number of neurotubules and larger lysosomes than in the controls. Other neurons show a very significant hypertrophy of the endoplasmic reticulum, with large amounts of intracisternal filamentous material. These cells have few neurosecretory granules and in the adjacent synapses the number of granulated vesicles is increased. In the supraoptic nucleus there are two kinds of neurosecretory axons: the clear ones, which are similar to those that appear in control animals and the dark ones, which have smaller elementary granules. In the inner zone of the median eminence the axons show an increase in the number of neurosecretory granules with respect to the controls. After supplementary administration of sexual hormones, all the modifications produced by castration disappear. The ultrastructural changes observed in the neurosecretory nuclei after castration are discussed in relation to those previously described in the neurohypophysis under the same experimental conditions. A feedback regulatory action of sex hormones on hypothalamic neurosecretory neurons is postulated.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).We are deeply indebted to Mrs. Defilippi-Novoa and Mr. Alberto Saenz for their skillful assistence.     

The development of the hypophysial portal system in the White-crowned Sparrow,Zonotrichia leucophrys gambelii

Summary The development of the hypophysial portal system has been studied in 35 embryos and 45 nestlings of the White-crowned Sparrow. The primordium of the hypophysis is vascularized by the infundibular (primary) capillary plexus, supplied by the right and left infundibular arteries, which, in the embryo, are constant branches of the right and left internal carotid arteries.The cellular proliferation and differentiation of the pars distalis into rostral and caudal lobes is accompanied by a penetration of portal vessels from the infundibular (primary) capillary plexus into these lobes beginning on the fifth day of incubation. The cellular proliferation of the rostral lobe of the pars distalis and development of the rostral group of the portal vessels precedes that of the caudal lobe of the pars distalis and the development of the caudal group of the portal vessels.The periglandular vessels, which originate in younger embryos from the infundibular (primary) capillary plexus, apparently become a part of the portal vessels.The portal vessels are the sole blood supply to the developing pars distalis of the White-crowned Sparrow; there is no evidence of a direct arterial supply at anytime during embryonic development. The neural-lobe artery appears at the end of incubation as a secondary branch of the right and left infundibular arteries. The rostral and caudal groups of the portal vessels are well-developed at the end of incubation (17–29 mm CRL) when aldehyde-fuchsin positive neurosecretory material first appears in the supraoptic and paraventricular nuclei, in the median eminence and in the neural lobe.The differentiation of the median eminence into rostral and caudal divisions begins at the end of the nestling period although its adult form is not achieved until later. The formation of the portal zone begins at the end of incubation (17–29 mm CRL) and is completed by the time of fledging.Dedicated to Professor Dr. W. Bargmann in honor of his 60th birthday.The investigations reported herein were supported by a research grant (HE 07240 NEUA) from the National Institutes of Health to Professor Vitums, by funds for biological and medical research made available by State of Washington Initiative Measure No 171 to Professor Vitums, by a research grant from the Deutsche Forschungsgemeinschaft to Professor Oksche, by aresearch grant (NB 01353) from the National Institutes of Health to Professor Farner, and by a Research Career Development Award from the National Institute of Arthritis and Metabolic Diseases (5 K 3 AM-18,370) to Professor King. We are grateful to Professor Bargmann for his generosity in making available the facilities of the Anatomisches Institut Kiel for this investigation. We wish to thank Frau Karin Graap and Mrs. Dianne Reno for technical assistance and Miss Janice Austin for the preparation of the drawings.     

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 neurosecretory activity in relation to the reproductive cycle in the common striped skunk (Mephitis mephitis nigra; order carnivora)

Summary The histological appearance of certain cell groups in the anterior hypothalamus was studied during various phases of the reproductive cycle of the common striped skunk (Mephitis mephitis nigra), a carnivore having a very restricted period of sexual activity. Pronounced changes occur in the amount of stainable neurosecretory material in cells of the supraoptic, paraventricular and anterior hypothalamic nuclei. Material staining with aldehyde fuchsin is stored (or inhibited from being released) in these cells during the sexually quiescent period in both the female and male skunk. The time of approaching sexual activity is characterized by the first signs of release of neurosecretory material from these hypothalamic cells and the peak of estrus and rut coincides with a minimal content of the material.Dedicated to Professor Berta V. Scharrer in honor of her 60th birthday.This study was supported by U.S.P.H.S. Training Grant 5 T 1-GM 102 and Research Grant BN-00840, from the National Institutes of Health. This represents a portion of a dissertation, written under the guidance of the late Professor Ernst Scharrer, and submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Yeshiva University, June, 1965. Preliminary reports of this work were presented at the 78th annual session of the American Association of Anatomists, Miami, Florida, and at the VIIIth International Congress of Anatomists, Wiesbaden, Germany, (Hagedoorn, 1965a, b). I thank Dr. H. W. Deane and Dr. J. Osinchak for their critical reading of this manuscipt.     

Zur Frage der Beziehung der neurosekretorischen Hypothalamuskerne zur Keimdrüsenfunktion

Zusammenfassung Nachdem in einer voraufgegangenen Untersuchung (Smollich, 1968) gezeigt werden konnte, daß das Zellkernvolumen der neurosekretorischen Hypothalamuskerne bei Ratten mit dem ovariellen Zyklus einhergehende Schwankungen aufweist, wird nunmehr nachgewiesen, daß eine Änderung der Konzentration an Geschlechtshormonen im Organismus einen morphokinetischen Effekt der Nuclei supraopticus und paraventricularis zur Folge hat. Er kommt in signifikanten Änderungen des Zellkernvolumens zum Ausdruck und läßt teilweise Geschlechtsunterschiede erkennen. Die Frage nach der Art der Beziehung zwischen den neurosekretorischen Hypothalamuskernen und der Keimdrüsenfunktion muß zunächst unbeantwortet bleiben.

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On neurosecretory hypothalamic nuclei and gonadal functions

Summary In a previous study (Smollich, 1968) it was proved that the cell nuclear size of the neurosecretory hypothalamic nuclei in rats shows differences in coincidence with the ovarial cycle. The present paper makes evident, that changes in the concentrations of gonadal hormones in the organism cause a morphocinetic effect on the supraoptic and paraventricular nuclei. This effect finds its expression in significant changes of the nuclear volumes of the ganglionic cells and exhibits occasionally sex differences at present. The kind of the relationship between the neurosecretory hypothalamic nuclei and the gonadal function is not yet clear.

     

Cytologie du lobe anterieur de l'hypophyse du chien

Summary Detailed histochemical studies have been made on the distribution of various enzymes such as phosphatases, cholinesterases, glycolytic enzymes and respiratory enzymes in various components of the hypothalamus with special reference to the supraoptic and paraventricular nuclei of the Squirrel Monkey. Cytological studies have also been made by the McManus, Einarson, Gomori and Bargmann methods.A few neurons of these nuclei showed scanty Gomori-positive material in the cytoplasm for the Gomori and Bargmann methods. Nissl granules were located in the peripheral cytoplasm of most neurons. No glycogen granules were observed in these neurons. For these reasons, the Squirrel Monkey, like the rat, may not be a suitable species for the study of neurosecretory phenomena.The axons of these neurons were negative for the specific cholinesterase test, though the perikaryon and some parts of the processes gave a moderately positive reaction. These neurons may be non-cholinergic and the cholinergic fibers from an unknown nucleus may end in synapses on their cell bodies. Blood vessels and glial cells in the neurosecretory nuclei showed non-specific cholinesterase activity. This enzyme may hydrolyze the acetylcholine which has escaped splitting by specific cholinesterase. Alkaline phosphatase and acid phosphatase in these neurons may be involved in the metabolism concerned with the production of neurosecretory material. The neurons may be physicochemical receptors and may get enough energy and raw material to synthesize the neurosecretory material from the rich blood supply. Neurons of the supraoptic and paraventricular nuclei as well as other hypothalamic neurons, like neurons of other regions of the brain, are well equipped with the enzymes of the glycolytic pathways and the tricarboxylic acid cycle. Since the glial cells of these nuclei have amylophosphorylase activity and glycolytic pathways, they may work as energy donators to the neurons of the neurosecretory nuclei. T. R. Shanthaveerappa in previous publications.     

Regeneration of the supraoptico-hypophyseal and paraventriculo-hypophyseal tracts in the hypophysectomized rat

Summary The effect of hypophysectomy on the nerve fiber pattern in the median eminence and infundibular stem of the rat has been investigated by a slightly modified Bodian technique. Postoperative changes in the distribution of neurosecretory material and connective tissue and changes in vascularity have also been studied.Extensive regeneration of the fibers of the supraoptico-hypophyseal and paraventriculo-hypophyseal tract could be demonstrated. It is most pronounced at the distal extremity of the infundibular stem but occurs also in the rostral part of the infundibular stem and in the median eminence. Regeneration starts in the second postoperative week and is completed about four weeks later. The nervous regeneration observed in the pituitary area after hypophysectomy is more extensive than is usually encountered after lesions elsewhere in the central nervous system.It could be demonstrated moreover that neurosecretory material accumulates at the same sites in which the terminals of the regenerated nerve fibers can be found. Hypophysectomy also causes an increase in capillary density and connective tissue content of the infundibular stem. Accumulations of neurosecretory material are always found in areas showing a high capillary density and a considerable amount of connective tissue.Factors which might be responsible for the extensive nervous regeneration in the pituitary area are discussed as are the factors determining the pattern of outgrowth of the regenerating nerve fibers. Morphological aspects of storage of posterior pituitary hormones are considered in the light of data in the literature and the results of the present work.Partly supported by a U.S. Public Health grant to Dr. E. Scharrer and a travel grant to the author from the Netherlands Organization for pure scientific Research (ZWO).     

The effect of adrenaline and acetylcholine on the hypothalamic-hypophysial neurosecretion in the rat

Summary The present investigation was undertaken to study the effects of adrenaline and acetylcholine on the hypothalamic-hypophysial neurosecretory system in rats.The drugs were injected intraperitoneally and into the lateral brain ventricle. The water diuresis was measured (I group). The animals were killed 45 min after intraperitoneal and 20 min after intraventricular administration of the drugs for the histological observations on the neurosecretory system and the histochemical studies of catecholamines in this area (II group).The antidiuretic effect of adrenaline and acetylcholine was established. The antidiuresis was more remarkable following intraventricular treatment.There was no direct relationship between the amount of neurosecretory substance and ADH activity in the posterior pituitary in the short term experiment after intraperitoneal administration of these drugs.The rapid release of ADH from the posterior pituitary was accompanied with a remarkable output of neurosecretory substance from the neurosecretory cell bodies into the axons and these effects were considerable after intraventricular introduction of the drugs. Some neurosecretory cells in the state of the initial hyperfunction were observed. In the posterior pituitary the initial mobilisation of the neurosecretory material from the neurosecretory terminals following intraventricular introduction of the drugs was observed.The supraoptic nucleus seems to be more sensitive to acetylcholine and the paraventricular nucleus to adrenaline treatment.The significant vasodilatation in the posterior pituitary and in the area of the supraoptic nucleus following intraventricular acetylcholine introduction was established.According to the data described it is possible to expect the existence of control of the hypothalamic neurosecretory activity by means of adrenergic and cholinergic structures.I am very obliged to Prof. W. Bargmann for his stimulating interest in this Study. I am grateful to Dr. G. Leontieva and Dr. V. Govyrin for the possibility to use the fluorescence catecholamine method, to Dr. E. Zeimal and Prof. M. Michelson for using the method for intraventricular injections.     

The neurosecretory system of the adult Calliphora erythrocephala

Summary Neurosecretory cells in the brain and suboesophageal ganglion of the adult female Calliphora erythrocephala have been studied in the light microscope. The paraldehydefuchsin stain (PAF) gave by far the clearest pictures.The medial neurosecretory cells of the protocerebrum (m.n.c.) show definite cyclic changes as to the size of the nuclei and the content of secretory material. The cytological changes depend on the age of the fly and the diet given and are correlated with ovarian development.The nuclear size is held to express the metabolic activity of the cells. Cells with large nuclei, as found in young sugar-flies (S1D) and meat-fed flies with developing ovaries (S4D/M2D), contain less secretory material which is released through the axons, while the m.n.c. of old sugar-flies (S6D) have small nuclei and are stuffed with secretory material which is stored in the perikarya.These results confirm those obtained by darkfield microscopy of living m.n.c. by Lea and E.Thomsen (1962 and unpublished).No really convincing evidence for the existence of more than one type of m.n.c. was found.Two small groups of lateral cells were observed. Possibly neurosecretory are further: 1-(2) cells at the base of each optic lobe, two groups of 2–3 cells on the caudal side of the brain, and 2 cells ventrally in the suboesophageal ganglion.Giant neurons of unknown function are situated very near the m.n.c. Their axons join those from the m.n.c., but end in the suboesophageal ganglion.The same region comprises a number of peculiar cells, each containing a large, fluid-filled vacuole (the vacuolated cells). Similar cells are associated with the possibly neurosecretory cells on the caudal side of the brain.My sincere thanks are due to my wife Dr. Ellen Thomsen, who made all the excisions of the brains and the measurements of the nuclei, to T.C.Normann for valuable assistance with the photographic work, and to Mrs. K. Bahnert for technical help with the gallocyanin method. The Carlsberg Foundation has supported the work with grants.     

Ultrastructural changes of the neurohypophysis of the rat after castration

Summary The infundibular processes of the neurohypophysis of male and female rats were studied after different periods of castration. After seven days an increase in neurosecretory granules was observed. Two types of neurosecretory nerve endings were identified: dark ones, with dense neurosecretory elementary granules of 1600 A, and clear ones, with lighter neurosecretory granules of 1800 A. Protoplasmatic pituicytes showed a large increase in lipid granules together with a general hypertrophy. After one week of castration but with hormonal therapy the protoplasmatic pituicytes appeared normal or even showed less lipid granules than in the controls.With one month of castration the changes already mentioned in the nerve endings and pituicytes were more pronounced and after six months even more accentuated. Two types of neurosecretory nerve endings were clearly identified and the protoplasmatic pituicytes were loaded with lipid granules.The probable significance of the two different neurosecretory axons was discussed in relation to recent studies on the isolation of neurosecretory terminals from the neurohypophysis. The changes in the protoplasmatic pituicytes were considered in relation to the possible significance of the lipid granules.Supported by grants from the Consejo Nacional de Investigaciones Cientificas y Técnicas and by the Air Force Office of Scientific Research (AF-AFOSR 963-67).We are deeply indebted to Mrs. Defilippi-Novoa and Mr. Alberto Saenz for their skillful assistence.Associated Investigator, Consejo Nacional de Investigaliones Científicas y Técnicas, Argentina.     

A comparative study of the ultrastructure of the median eminence,infundibular stem and neural lobe of the hypophysis of the rat

Summary The ultrastructure of the infundibulum has been studied and compared with that of neural lobe in normal rats. The neurohemal areas of the median eminence are similar to those of the stem but differ from those of neural lobe. The infundibular axons which end around the primary capillaries of the portal system are of a significantly finer caliber. Secondly they contain a different vesicle population. They lack the large (1500 Å–2100 Å) neurosecretory vesicles so abundant in neural lobe axon terminals but contain a smaller (less than 1000 Å) type of vesicle with an osmiophilic center. These dense-core vesicles are consistently present in the many infundibular levels examined, although they are not as numerous as the neurosecretory ones of neural lobe. They are outnumbered by vesicles of the synaptic type, whereas in neural lobe the neurosecretory ones predominate. Another difference involves the electron lucent, neurosecretory vesicle. These are abundant in neural lobe axons, but comparable aggregations of them have not been seen in infundibular axon endings of the neurohemal areas. In contrast, the internal zone of median eminence and the interior of the stem display, in addition to the fine axons, many large fibers which by size and content match the ones of neural lobe. However, careful study indicates that these are axis cylinders and not axon endings.These observations lead to the conclusion that the small calibered axons which terminate around the infundibular capillaries of the portal system constitute a separate group, and are clearly distinguishable at the ultrastructural level from the large supraoptico-neurohypophyseal axons. The latter normally traverse the infundibulum but terminate in neural lobe.This investigation was supported by U.S.P.H.S. Research Grant 5 RO 1 NB 02321-05, National Institute of Neurological Diseases and Blindness. — The author is particularly indebted to Mrs. Nora Tong for her excellent technical assistance throughout the course of this study.     

Histochemical demonstration of monoamine oxidase in the hypothalamo-hypophysial system of the tree sparrow and the rat

Summary Localization of monoamine oxidase (MAO) was investigated essentially according to the method of Glenner et al. (1957) in the hypothalamo-hypophysial system of the tree sparrow and the rat. The hypothalamic neurosecretory cells of both species showed relatively weak MAO activity. A similar localization of MAO activity was observed in the median eminence of both species: (1) slight or no MAO activity was observed in the ependymal layer, (2) relatively strong activity was revealed in the tissue just beneath the ependymal layer, (3) strong activity was revealed in the outer layer, particularly in the tissues surrounding capillary loops of the primary plexus. It is suggested that an adrenergic mechanism functions in the median eminence. In the pars nervosa, strong reaction was observed in the rat, while a weak reaction occurred in the tree sparrow. However, the color and the size of formazan crystals deposited in the rat pars nervosa differed from those in the hypothalamus. As a whole, the distribution of the neurosecretory material differed from the localization of MAO activity in the hypothalamo-hypophysial system. It is discussed that the neurosecretory neuron is not adrenergic but cholinergic.Aided by Grant A-3678 from the United States Public Health Service. The authors are indebted to Dr. S. Kambara, Zoological Institute, and Dr. H. Hirano, Department of Anatomy, University of Tokyo, for their valuable advice, and also to Assoc. Prof. S. Yamamoto, Department of Hygiene, University of Tokyo, for making available some facilities. They also wish to thank Dr. L. M. Barbato, University of Illinois, and Mr. K. Asami, National Institute of Radiological Sciences, Chiba, and Mr. Suzuki, Research Laboratory, Chugai Pharmaceutical Company Ltd., Tokyo, for the kind supply of MAO inhibitors.     

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.     

Light,fluorescence and electron microscopic studies on “neurosecretion” in tritonia diomedia bergh (Mollusca,Nudibranchia)

Summary Membrane-limited electron-dense inclusions designated as elementary neurosecretory granules have a characteristic distribution in cerebropleural ganglia of the nudibranch snail Tritonia diomedia. They occur in the neuropile and also in individual nerve fibres, connectives and commissures. These granules have been found neither in perikarya of nerve cells nor in proximal segments of their processes.Specific fluorescence obtained in Tritonia preparations with Sterba's pseudoisocyanin method for neurosecretory products has the same pattern of location.The distribution of stainable material in preparations prepared with ordinary neurosecretory procedures (chrome haematoxylin-phloxin after Gomori-Bargmann and paraldehydefuchsin after Gomori-Gabe) is similar to that described by different authors in other gastropods, but strongly differs from the locationof elementary neurosecretory granules and of pseudoisocyanin-positive material. The adequacy of different histological methods for studying neurosecretion in gastropods is discussed.     

Occurrence of large hyaline bodies in the preoptic nerve cells of Zoarces Viviparus L.

Summary Specially in stress conditoin, some hyaline droplets occur in the perikarya of the neurosecretory hypothalamic cell of Zoarces viviparus. They first appear as filamentous macromolecular material in the intracisternal space, then tend to accumulate in the form of irregular electron dense rods or reticulum. The neurosecretory cells containing such hyaline bodies have usually few elementary neurosecretory granules and dilated endoplasmic reticulum.Aided by a Grant from NATO and the Deutsche Forschungsgemeinschaft.My thanks are due to Prof. Dr. E. Lindner and Doz. Dr. K. H. Andres for their kind help in the explanation of electronmicrographs.     

Annual changes in the brain neurosecretory profile of the Indian freshwater Leech,Poecilobdella viridis (Blanchard) in relation to reproduction

Annual changes in the brain neurosecretory profile of Poecilobdella viridis in relation to reproductive activity have been investigated. The changes in A cell neurosecretory activities were found to be in strong correlative correspondence with the reproductive programme. Heavy accumulation of neurosecretory material was observed in A cells perikarya during the reproductive period i.e. from March to June, 1975, with enlarged nuclei and during reproductive quiescence i.e. from August, 1974 to January 1975, the neurosecretory activity was low.