The hypothalamo-hypophysial system in the ground squirrel,Citellus erythrogenys Brandt

Summary Monthly observations of the Gomori-positive hypothalamo-hypophysial neurosecretory system (HHNS) of the ground squirrel, Citellus erythrogenys Brandt, were carried out light microscopically using several quantitative methods. From the beginning of hibernation, formation of neurosecretory material (NSM) in the neurosecretory cells (NSC) progressively decreases and release of neurohormones from the HHNS is almost fully inhibited. A maximal accumulation of NSM in the perikarya of the NSC and in the posterior pituitary (PP) is found in December. By this time the volume of the cell nuclei and nucleoli is at a minimum. Signs of activation of the HHNS appear and become more conspicuous as the time of arousal from torpor approaches. The amount of NSM in the NSC and the PP decreases simultaneously with the increase in volume of the NSC. Hyperemia and activation of glial elements is visible throughout the HHNS. The morphological signs of activation reach their peak in March. After reproduction is completed (April to beginning of May), the NSC and the PP are almost devoid of NSM. Beginning with June and during the summer and autumn months a progressive accumulation of NSM in the NSC and the PP parallels gradual diminution in the volume of the NSC structures and the glial cells. Mechanisms and effector pathways by which the HHNS influences seasonal adaptation of the organism and reproduction are discussed.     

Maturation of the human hypothalamo-hypophyseal neurosecretory system in prenatal ontogeny. A light-optical and electron microscopic study

The hypothalamic-hypophysial neurosecretory system (HHNS) was studied in the human foetuses from the age of 8 weeks till birth. The hypothalamus of 8 weeks old foetuses is weakly differentiated, no individual cell groups, so-called nuclei, are identified. The supraoptic (SON) and paraventricular (PVN) nuclei are identified from the age of 12 weeks on. The size of cell nuclei increases with the age. The Homori-positive granules were first found in some SON and PVN cell and in neurohypophysis in the 18 weeks old foetuses. It was shown under the electron microscope that the neurohypophysis of 8 weeks old foetuses consisted mainly of pituicytes with axons among the cytoplasmic processes of the latter. After the age of 10 weeks, the area of parenchyma of the neurohypophysis occupied by axons increased and typical elementary neurosecretory granules appeared in them. The data obtained are discussed with respect to the participation of HHNS in the regulation of water metabolism in the human foetuses.     

Effect of a lesion of the hypothalamic nuclei on the morphofunctional state of the hypothalamo-hypophyseal system and the development of experimental atherosclerosis]

Injury of individual nuclei of the anterior and the middle portions of the hypothalamus in rabbits by electrocoagulation through the preliminarily implanted electrodes was accompanied by the change in the morpho-functional condition of the hypothalamo-hypophysial neurosecretory system (HHNS). The nearer the focus of injury to the region of the supraoptic nuclei -- the greater the functional activity of the HHNS. In combining the injuries of individual hypothalamic nuclei with the atherogenic diet there occurred marked morpho-functional changes both in the HHNS and in the adrenal glands; as to animals with experimental atherosclerosis, it acquired under these conditions a more severe form than in the animals on the atherogenic diet alone. Results of investigations pointed to the presence of a close association of the genesis of the atherosclerotic process with the neurogenic factors.     

Changes in the activity of the supraoptic nuclei of the hypothalamus and distal portions of the hypothalamo-hypophyseal neurosecretory system of guinea pigs under the influence of high environmental temperature]

The keeping of guinea pigs in a thermochamber at 37 degrees C for 3 days resulted in increased releasing of neurohormones of the posterior lobe of the hypophysis. By the end of the 3d day there was no substantial difference between the average logarhythm of the volume of cell nuclei of the supraoptic nucleus of experimental animals and that of intact animals. Injection of ACTH after a preliminary three-day presence of the animal in the thermochamber caused a pronounced inhibition of the hypothalamo-hypophyseal neurosecretory system (HHNS). The HHNS of animals subjected to 3-day-long continuous exposure to high temperature, in contrast to the HHNS of intact animals is not capable to increase its activity in responses to stress (immobilization).     

The hypothalamo-hypophysial system in the ground squirrels, Citellus erythrogenys Brandt and Citellus undulatus Pallas. I. Microanatomy and cytomorphology of the gomori-positive neurosecretory system with special reference to its state during hibernation.

Microanatomy of the peptidergic hypothalamo-hypophysial neurosecretory system in the ground squirrels, C. erythrogenys and C. undulatus, is similar to that of other rodents, but differs in details. Bundles of neurosecretory fibres with single neurosecretory cells along their course connect the hypothalamic neurosecretory centers into the one system. The dorso-caudal portions of the NPV reach the level of the columna fornix. The NPO is a special indepedent formation and appears to have some specific functions in the HHNS. The infundibular recess penetrates deeply ihto the hypophysial stem, but does not reach the posterior pituitary. The glandular epithelium of the tuberal portions of the adenohypophysis surrounds the median eminence and a considerable part of the lateral surface of the tuber cinereum. Different functional types of neurosecretory cells reflect certain phases of their secretory cycle. Correlations between their size, structure and the content of NSM are found. A low activity of the HHNS is observed in both C. erythrogenys and C. undulatus during December-January. A higher activity of the HHNS in torpid C. undulatus than in C. erythrogenys is established. This correlates with a difference in deepness of torpor in C. erythrogenys and C. undulatus. An important role of the HHNS in hibernation, i.e. in realization of adaption of species in ontogenesis is suggested.     

State of the hypothalamo-hypophyseal neurosecretory system of rabbits in anaphylactic shock]

With the aid of morphometric and histochemical methods a study was made of the hypothalamo-hypophyseal neurosecretory system of rabbits in anaphylactic shock. The following occurred in rabbits which survived the shock: an enlargement of the perikarions and reduction in the size of the nuclei and nucleoli of the neurosecretory cells; the content of the neurosecretory substance was increased in the whole neurosecretory system. In rabbits which perished from shock the nuclei and the nucleoli of the neurosecretory cells diminished to a lesser extent, perikarion measurements remained unchanged and the content of the neurosecretory substance in the posterior lobe of the hypophysis fell. Thus, in the animals which survived the shock the processes of synthesis of the neurohormones by the neurosecretory cells were sharply activated, but the secretion of the neurohormones from the posterior lobe of the hypophysis was inhibited; in animals which perished from shock the activation of the hormone formation in the neurosecretory cells was less pronounced, but the processes of the secretion of the neurohormones from the posterior lobe were apparently intensified.     

Morphofunctional state of hypothalamic and epiphyseal structures in relatively wild and domesticated silver foxes during estrus

Histochemical and cytometric analyses of the hypothalamo-hypophysial neurosecretory system (HHNS), suprachiasmatic and arcuate nuclei, as well as the pineal gland in mature female silver foxes during oestrus revealed activation of peptidergic and monoaminergic neurosecretory units alongside with activation of the glial and vascular components. The increase of the secretory activity of the HHNS and pineal gland was more evident in domesticated animals. The data obtained show more intense production and excretion of neurohormones which are involved in regulation of reproduction, in domesticated foxes. These peculiarities may account for changes in the oestral cycle in domesticated animals.     

The hypothalamo-hypophysial system of the lemming Dicrostonyx torquatus Pallas. IV. Influence of experimental animal cooling on the ultrastructure of the hypothalamo-posthypophysial neurosecretory system

The reaction of the hypothalamo-hypophysial neurosecretory system (HHNS) of lemmings to cold (+4 degrees C) was studied by the method of electron microscopy. The animals were kept in cages with nest, but with no wheel to allow running; in cages with a wheel, but with no nest; in cages with no nest and no wheel. No changes in the HHNS reaction were revealed under cold stimulation, if the animals were not deprived of motor activity (running in a wheel), or could hide in a nest. In case of no nest and restricted motor activity exposition to low temperature led to a progressive activation of neurosecretory cells of the supraoptic and paraventricular nuclei, and finally to their exhaustion and degeneration. The intensity of the HHNS reaction to cold is shown to depend on the initial state of the system which varies according to the stages of population cycle. The present study gives grounds to put forward the hypothesis that the adaptation of the Dicrostonyx torquatus Pallas to cold is made possible due to maximal utilization of ecological conditions and behavioral reactions.     

The incorporation of 35S-labelled cysteine in the hypothalamic-hypophyseal neurosecretory system of the dehydrated rat

Summary The effect of dehydration upon incorporation of ³⁵S-labelled 1-cysteine in the hypothalamic-hypophyseal neurosecretory system of the rat was studied by autoradiography. Grain counts were made of the supraoptic and paraventricular nuclei, median eminence and neurohypophysis. The results were statistically treated. The effect of dehydration was observed, at first, as an increase of incorporation in all the sites examined. Six hours after administration, the disappearance of the isotope from the nuclei was accelerated, and after 24 hours also that from the distal parts of the neurosecretory system. The results are interpreted, in the first place, in terms of activation of the neurosecretory system caused by dehydration.This work was supported by a grant from the Sigrid Jusélius Foundation, Helsinki.     

Rhythmicity of the activity of the supraoptic and paraventricular nuclei of the hypothalamus of the C57Bl mouse

Rhythmical changes in the activity of the neurosecretory processes have been compared in the supraoptic (SON) and paraventricular (PVN) nuclei in the C57Bl mice hypothalamus during vernal equinox. Parts of the neurosecretory cells, being at stages of synthesis, excretion and accumulation of secrete, volumes of the cell nuclei and nucleoli survey as criteria of their activity. Similar feature for the rhythmic of both nuclei studied is the highest activation of the processes during day time, when mice are resting; this is demonstrated as the maximal amount of actively synthesizing cells, maximal volumes of the cell nuclei and nucleoli. The peculiarities of the rhythmic display in the activity is manifested as a greater ability of the SON cells to accumulate neurosecrete. The accumulation of the secretory material in the SON cells precedes to the period of its maximal activity (1-7 PM) characterized: by making the cells free from the secrete and by a maximal increasing the volume of the nucleoli. In the PVN intensified display of the activity is noted at early hours of the day, and the amount of the cells not containing the secrete--at 6 PM. Lack of the neurosecrete accumulation in the PVN cells speaks in favour of more steady than in the SON cells excretion of the secrete. This demonstrates a more even maintenance of neurohormones concentration in the organism.     

Response of caudal neurosecretory cells of Salvelinus fontinalis to variations in the ionic composition of the environment

Summary The response of caudal neurosecretory cells in Salvelinus fontinalis to exposure to media in which one ion (Na, K, Mg, Ca and Cl) was either selectively enriched or depleted was evaluated by morphometric criteria. Morphological changes indicating stimulation of synthetic activity were observed: exposure to sea water with low potassium concentration was the most efficacious in inducing the increase in the average diameter of caudal cells and the number of nucleoli for both cells with lobed and with nonlobed nuclei. The proportion of cells with lobed nuclei was also increased. To a lesser degree and in decreasing order, experimental milieu with modified magnesium contents, either fresh water enriched in this ion or seawater depleted of the same ion, and fresh water enriched in calcium also resulted in significant increases in cell diameter and the number of nucleoli.The two cytological cell types, viz cells with non-lobed nuclei or cells with lobed nuclei, are interpreted as being linked to different levels of neurosecretory activity.Supported by NSERC (Canada)     

The effect of thermal stress on Ostrini00a nubilalis HBN (Lepidoptera, Pyralidae)—I. The orle of the neurosecretory cells in the survival of diapausing larvae

1. 1.|The effect of short-term exposure (up to 12 h) to upper limiting temperature (45°C) on A-type medial neurosecretory cells (MNSC) of the protocerebrum of Ostrinia nubilalis larvae was studied.

2. 2.|For evaluation of the activity of MNSC, cytological parameters were used: quantity of the neurosecretory material, size of the neurosecretory granules, shape of the nuclei and size of the nucleoli.

3. 3.|After 1 h exposure to 45°C the activity of the MNSC was increased, after 3 h it was decreased, while after 6 h exposure to the same temperature some renewed increase in the activity was observed.

4. 4.|The significance of oscillatory changes in the activity of A-type MNSC in survival of the thermal stress of O. nubilalis diapausing larvae is discussed.

Effect of diet on the neuroendocrine system and egg development in the sheep blowfly, Lucilia sericata

ABSTRACT. A light microscope study of the endocrine and ovarian systems of Lucilia sericata under two diets revealed that in young females fed on sugar and water, medial neurosecretory cells (MNC) synthesized and stored neurosecretory material (NSM) as the flies matured. The MNC remained filled with NSM as long as the diet was maintained. Following a small increase immediately after emergence, the size of the corpora allata (CA) showed little further change, and the nuclei of nurse cells remained small. However, rapid changes occurred in these tissues soon after a meat meal: NSM was discharged from the MNC, and the CA increased in size. These changes were at a maximum 20 h after a meat meal. 4h later, vitellogenesis was well established and the nurse cell nuclei had increased in size 20-fold. Growth of the nurse cell nuclei continued until approximately 6 h before the completion of vitellogenesis when they are resorbed. Oögenesis took about 48 h at 25°C. When 100 μg of each of three different juvenoids were applied topically to different sugar-fed flies, the nuclei of both MNC and nurse cells became enlarged, whereas the CA were somewhat reduced in size. The relationship between protein ingestion and oogenesis is discussed, and the results obtained with L. sericata are compared with those of other species, especially the blowfly Calliphora erythrocephala.     

Hypothalamo-hypophysial Neurosecretory System in Normal and Hypophysectomised Catfish,Clarias Batrachus L

Two neurosecretory centers, nucleus preopticus (NPO) and nucleus lateralis tuberis (NLT), are distinguished in the hypothalamus of Clarias batrachus L. The cell bodies of NPO are grouped into nucleus preopticus magnocellularis (NPM) and nucleus preopticus parvocellularis (NPP). The NLT is recognised into three divisions: pars rostralis, pars medialis and pars ventrolateralis. The neurons of both the NLT and NPO are aldehyde-fuchsin (AF) positive. The axons from NPO run into four or five bundles ventrolaterally and caudally for some distance before all of them from either side join ventromedially into a single thick cord of neurosecretory fibers which finally enters the pars intermedia to form the neurointermediate lobe. The fibers from NLT, which are separate from the neurosecretory fibers of the NPO, anastomose in the region of the pars distalis. The neurosecretory material (NSM) of NPO is transported by axonal route whereas that of NLT is by axonal as well as ependymovascular pathways. Hypophysectomy results in the increase of AF-positive material in the neurons of NPO shortly after the operation, but later on, the material begins to deplete in them. The AF-positive material at the cut end of neurosecretory fibers, however, accumulates. The AF-positive material in the cell bodies of NLT is also depleted, but the nuclei increase in size, after hypophysectomy.     

Changes in nucleus, nucleolus and cell size accompanying somatic embryogenesis of Theobroma cacao L. I. Relationship between DNA and total protein content and size of nucleus, nucleolus and cell

There was a linear relation between an increase in DNA content and size of nuclei, nucleoli and cells in callus and proembryos (Theobroma cacao L.). In callus the increase of DNA content was accompanied by proportional increase in nuclear size whereas in proembryos the increase in nuclear size did not match the increasing amount of DNA. The stimulation of embryogenesis by 10(-2) mg/l 2,4-D was associated with increase in nuclear and nucleolar size and with decrease in cell sizes. Inhibition of embryogenesis by 1.0 mg/l 2,4-D+10% coconut water did not change nuclear size, but increased cell size in relation to the control. The process of embryo formation was accompanied by changes in relationship between nuclear, nucleolar and cell size and the total (DNFB-stained) proteins content. In callus as well as in proembryo the increase in total protein content in nucleus was not equivalent to the increasing sizes of nuclei which leads to the decrease in nuclear protein concentration. Similar situation was observed for nucleoli. Differences were found in the concentration of cytoplasmic proteins between the callus and proembryo cells. The stimulation of embryogenesis by low concentration of 2,4-D resulted in decrease in concentration of total proteins in nuclei and nucleoli and the increase in cytoplasm.     

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 hypothalamo-hypophysial system of the lemming, Dicrostonyx torquatus Pallas. III. Population aspects of neuroendocrine regulation

The structure and ultrastructure of the following regions of the hypothalamo-hypophysial neurosecretory system (HHNS) in the population cycle of lemming were studied: supraoptic (SON), paraventricular (PVN) and arcuate nuclei (AN), the median eminence (ME) and posterior pituitary (PP). Being compared to the state of endocrine glands and gonads, and the level of reproduction stress in the population cycle of the lemming described earlier, the obtained data revealed a certain regularity. First, at the stages of decrease, increase and in the first period of the stage of population peak the activity of the SON-PP complex and AN is gradually increased. This coincides with intensified reproduction, intensified functioning of the thyroid gland and adrenal cortex. Second, while the population is decreasing, all the above functions become depressed, except that of the thyroid gland which, on the contrary, becomes active. In the second period of the stage of population peak, when reproduction stops abruptly, this regularity, however, does not hold, the activity of SON-PP complex and AN is sharply lowered, whereas that of PVN becomes very high. The structure of the thyroid damaged as a result of previous hyperfunction, is restored, and the adrenal cortex shows signs of hypercorticism. The present work is devoted to specificity of the HHNS functioning at the stage of population peak, referred to as crucial, and the pathways and mechanisms by which neurohormones produced by this system can affect the endocrine glands. In addition, the causes likely to lead to the mass death of animals at this stage, and biological significance of this fact are also given attention to.     

Influence of the feeding regimen on the rhythmicity of the processes of secretion of the supraoptic nucleus in C57Bl mice

During the period of vernal equinox in Leningrad 2 groups of C57Bl male mice have been investigated. Ninety-five animals are given food ecologically adequate at 9 p.m. Eighty-four animals are given foot at 9 a.m.--ecologically inverted regimen of feeding (IRF). The mice are decapitated for 4 days with an interval about 1.5 h. Serial paraffin sections are stained with aldehyde-fuchsin after Gomori and an additional staining of the nuclei with azocarmine. Criteria for the neurosecretory activity is the ratio of the cells amount at various stages of synthesis, outflux and accumulation of the secrete, volumes of the nuclei and nucleoli. Spectrum and parameters of the rhythmicity are revealed. IRF produces decrease in the amount of the ultradian component of the rhythmic parameters, characterizing active synthesis and discharge of the secrete. The part of the neurosecretory cells, those actively synthesizing and discharging the secrete, and volume of the cell nucleoli decrease. Range of ultradian component of the cell part rhythm, depositing the secrete, and the cell volume enriches. Thus, IRF produces certain changes in the rhythmicity of the cell secretion at all the stages: synthesis, discharge and accumulation of the secrete. Total intensity of the synthetic processes decreases. A conclusion is made that IRF inhibits the microsecretory process in the supraoptic nucleus (SON) and decreases adaptive possibilities of its cells. Adaptation to IRF is performed at the expense of rhythmic discharge of neurohormones, deposited in the cells, and at the expense of processes, occurring in the neuryoplasm and resulting in increase of the nuclear volume.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relation between the nuclei and the nucleoli during cell differentiation in roots of Vicia faba volumetric and cytochemical analysis

Summary The behaviour of the nuclei and the nucleoli of roots of Vicia faba during cell differentiation was studied quantitatively. The relations between these cell constituents and the polyploidy was analysed. The study was made on isolated nuclei and nucleoli and on plastic sections. A method for the isolation of nuclei and nucleoli of secondary roots fixed in formol was modified and another developed for material fixed in ethanol/acetic acid mixture. The volumetric investigation showed that the nuclear volume increases while the nucleolar decreases during cell differentiation. The mean number of nucleoli decreases. In Vicia faba there is no relation between the ploidy and the volume of nuclei and nucleoli; the protein synthesis rate has an influence on the size of these organelles. Quantitative investigation has shown the proportionality of dry weight, DNA, total protein, histone, protein-bound lysine and arginine content of the nuclei and their ploidy. The same experiments made on nucleoli showed linear relation between their content and volume. The concentration of analysed substances in constant in nucleoli.     

Morphofunctional characteristics of neurosecretory cells of the supraoptic nucleus of rats with parathyroprival hypocalcemia]

Humori-positive neurosecretory cells of the supraoptic nucleus of the hypothalamus have been investigated during various time of parathyroprival hypocalcemia after extirpation of the parathyroid glands. Contents of total and ionized calcium, phosphorus in blood serum have been estimated. Volume of nuclei and nucleoli has been measured. In 5 days functional activity of the supraoptic nucleus increases (lightly stained cells predominate, volume of the nuclei and nucleoli increases). In subsequent 15-30 days its activity decreases (increase in amount of dark-stained cells, nucleolar volume decreases). In 60 days there is a tendency to restoration of neurosecretion.