Search PubMed⌕ Search

Biomedical subjects

M Benjamin

Publications and source records attributed to M Benjamin.

At least 91 records · Page 5Linked to original sources
PubMed1982

The ACTH cells in the pituitary gland of the nine-spined stickleback, Pungitius pungitius L.

The ACTH cells form a layer 1-8 cells thick, dorsal to the prolactin cells in the rostral pars distalis. They react only mildly with a variety of stains including PAS-lead haematoxylin. Their nuclear diameters vary seasonally in a manner that closely parallels that of the prolactin cells. The relative volumes of the ACTH and prolactin cell zones are remarkably constant in animals of different sizes. It is suggested that the two hormones may act synergistically at various body sites and that this accounts for the related morphological features of the ACTH and prolactin cells. There are no changes in the surface density of the ACTH zone with increasing animal size. Consequently, the ACTH/neurohypophysial border is highly convoluted in large animals. The proximity of the neurohypophysis also influences cell ultrastructure, as small processes, packed with secretory granules are more numerous near the basal lamina separating the adeno- and neurohypophyses. A morphometric analysis of ACTH cells provides base-line ultrastructural data for experimental studies and for comparisons with other teleosts. The cells have small, secretory granules, 100-300 nm in diameter, and of variable electron density. There is little rough endoplasmic reticulum and a small Golgi apparatus. There is no evidence of granule release by exocytosis and various explanations for this are suggested.

Adrenocorticotropic Hormone↗
PubMed1982

Morphological studies on the growth hormone cells in the pituitary gland of the nine-spined stickleback, Pungitius pungitius L.

Base-line data is presented on growth hormone cells in adult, nine-spined sticklebacks, Pungitius pungitius L. The cells are smallest in June-August, when adult animals are oldest and many large fish are dying. It may thus be the wrong time for seawater-transfer experiments designed to alter the secretory state of these cells. Starving fish for 3.5-4 weeks in February and in September-October did not markedly affect growth hormone cell numbers, staining properties or size. A detailed morphometric analysis of growth hormone cell ultrastructure is presented. The cells are characterized by their electron dense secretory granules, 150-750 nm in diameter that occupy 33% of the cell volume. Neither the Golgi apparatus nor the rough endoplasmic reticulum are present in large amounts (volume densities 2.9% and 8.1% respectively), but the rough endoplasmic reticulum is conspicuous because of its flocculent cisternal contents. Both 'light' and 'dark' growth hormone cells were found. The dark cells have a densely staining cytoplasmic ground substance and abundant, closely packed secretory granules. The morphometric data is compared with similar information that is available for the related three-spined stickleback, Gasterosteus aculeatus.

Animals↗
PubMed1981

The origin of pituitary cysts in the rostral pars distalis of the nine-spined stickleback, Pungitius pungitius L.

Pituitary cysts in the nine-spined stickleback, Pungitius pungitius L., developed next to blood vessels passing through the prolactin zone of the rostral pars distalis to the connective tissue capsule at its periphery. Cysts were most frequent when pituitaries were large compared with body lengths. However, the incidence of cysts could not be closely related to body length alone. As the rostral pars distalis is more highly vascularised in fish with large pituitaries, and as there was no evidence of accumulating secretion around these blood vessels, it is suggested that cysts develop when vascular demands (or supplies) become excessive. Associated with the greater vascularity of the rostral pars distalis in large pituitaries was a remarkable development of non-granulated cells. Indeed cysts may originate as enlarged intercellular spaces between such cells, as the latter often surround blood vessels. The non-granulated cells are also important in enlarging cyst cavities (by phagocytosing prolactin-cell debris) and perhaps for maintaining their structural integrity. It is suggested that the macrophages within cyst cavities are derived from the non-granulated cells.

Animals↗
PubMed1978

Ultrastructural studies on prolactin and growth hormone cells in Anguilla pituitaries in long term cultures.

Eel hemi-pituitaries were cultured in vitro on high or low sodium media, previously shown to affect differentially prolactin and growth hormone release. After 6 days culture, there were marked differences in the ultrastructure or both prolactin and growth hormone cells from the two groups. Morphometric data on the prolactin cells from SW-adapted eels showed a greater abundance of RER and paucity of secretory granules in cells from the low sodium medium. The size of the Golgi apparatus and the number of exocytosed secretory granules did not differ markedly between experimental groups, in contrast to previous findings on short-term cultures. Differences in the profile diameters of secretory granules are recorded between the experimental groups and the pattern differs markedly from that previously recorded for short-term cultures. The growth hormone cells from low sodium media were characterised by abundant, vesiculated RER, a prominent Golgi apparatus (in SW-adapted animals) and relatively few secretory granules. The activity of these growth hormone cells is in marked contrast to previous findings relating to short-term cultures. The shape and size of the non-granulated (stellate) cells of the RPD was again affected by the osmotic pressure of the medium.

Adaptation, Physiological↗
PubMed1978

Sleep patterns in three acute combat fatigue cases.

A preliminary report is presented on the sleep patterns of three combat fatigued patients with recurrent nightmares, insomnia, low frustration thresholds and impotence. All the patients had undergone acute partial sleep deprivation prior to their breakdown. The results show severe deficiency in REM sleep and absence of stage 4 sleep. EMG was usually high with numerous body movements and bursts of tachycardia throughout the night. Nightmares occurred in stage 2. Total effective sleep time was between 129' and 250'. Most of the sleep was in stage 2, and patients woke up with the feeling that "they had not slept at all." It is hypothesized that acute partial sleep deprivation prior to breakdown was an important predisposing factor, and that chronic partial sleep deprivation was a constant aggravating factor of combat fatigue. Replacement therapy for the specific deficient sleep states is proposed.

Adult↗
PubMed1977

The time sequence of response of the prolactin cells of the freshwater teleost, Poecilia reticulata, to an altered environmental salinity.

The time sequence of the ultrastructural changes in the prolactin cells of the adult guppy, Poecilia reticulata, was studied in freshwater fish transferred to 1/3 seawater for 1, 4, 11 and 28 days. The morphological changes were slight and only detectable by quantitative (morphometric) procedures. The secretory granules showed a "biphasic' response to the altered environmental salinity, but the volume density of the Golgi apparatus progressively declined throughout the experiment. After an initial decrease in the volume density of the RER, that organelle regained its original prominence by 11 days in 1/3 seawater. The volume density of the nucleus was markedly higher in fish 28 days after transfer to 1/3 seawater than in any other group. Cell volume estimations showed that a shrinking of the cytoplasm rather than a swelling of the nucleus accounted for the high volume density figure. The changes in the volume density of the mitochondria closely paralleled those of the RER. Profiles of exocytosed granules were rarely found in any of the groups, but were least frequent in fish kept in 1/3 seawater for 28 days, when dense (lysosomal?) bodies were most abundant. The quantitative methods high-lighted some discrepancies in the rate and magnitude of the changes shown by some organelles and have led the authors to suggest that during adaptation of fish to dilute seawater, synthesis and release may not be coupled processes in the prolactin cell of P. reticulata.

Animals↗
PubMed1976

Ultrastructural studies on prolactin and growth hormone cells in Anguilla pituitaries in vitro.

Eel hemi-pituitaries were cultured in vitro on high or low sodium media which are known to affect differentially prolactin and growth hormone release. Ultrastructural examination of the prolactin cells after 24 h culture showed the Golgi bodies were markedly more abundant and widely distributed in hemi-pituitaries from the low sodium medium. Secretory granule release profiles and dense bodies were also more frequent, but the percentage of the cytoplasmic volume occupied by secretory granules was lower than on the high sodium medium. RER was only slightly modified. Significant differences were noted in the shape and processes of the non-granulated (stellate) cells of the RPD, but there were only slight differences in the the ultrastructure of the somatotropes.

Anguilla↗
PubMed1976

Ultrastructure of the endocrine cell types in the adenohypophysis of the teleost, Poecilial latipinna--a morphometric model.

A morphometric model providing detailed quantitative information on the ultrastructure of the adenohypophysial endocrine cells has been developed for Poecilia latipinna. The model consists of various morphological components quantified in terms of volumes, surfaces or numbers. For prolactin and growth hormone cells, appropriate results are expressed relative to the average volume of that cell type. The difficulties of quantifying EM data on pituitary glands, together with the various sources of error to which the data are clearly open, have been discussed. Some practical application of quantitative EM to problems in fish pituitary research are outlined.

Animals↗
PubMed1975

Ultrastructure of the adenohypophysis in the teleost Poecilia latipinna.

In the sailfin molly, Poecilia latipinna, seven morphological endocrine cell-types could be distinguished with the electron microscope. Each of these was identified with one of the seven cell-types distinguished with the light microscope, to most of which endocrine functions have previously been allocated. Corticotrophs and prolactin cells form the rostral pars distalis, and the proximal pars distalis consists of an outer layer of gonadotrophs and an inner zone containing growth hormone cells and thyrotrophs. The pars intermedia contains two cell-types, of uncertain function. Stellate cells (interstitial cells) occur throughout the adenohypophysis, but are most numerous and prominent in the rostral pars distalis. The inner proximal pars distalis contains a cell-type not previously distinguished in this species with the light microscope, the Z-cell, which could be aminergic. The ultrastructural features of each cell-type are described in detail, and discussed in comparisons with the homologous cells described in other teleosts. There is good agreement for different teleosts in the ultrastructural details of each cell type.

Adrenocorticotropic Hormone↗
PubMed1975

The adenohypophysis of the flounder, Pleuronectes flesus, and the minnow, Phoxinus phoxinus.

The pituitary gland of the flounder, Pleuronectes flesus, showed several unusual cytological features. Between the RPD and the PPD was a zone of cells that stained purple with Alcian blue--PAS--orange G. Many of these cells were apparently degenerating. In the PPD the strands and coils of presumptive STH cells showed a tremendous variation in both size and staining properties. In the PI there were two cell types, the PAS-positive one bordering the neurohypophysis. Around the periphery of the PI was a zone of chromophobic cells, and throughout the PI were numerous intracellular and extracellular acidophil spheres. No well defined ACTH cells were found in the RPD of the minnow (Phoxinus phoxinus). The Alcian blue--PAS--orange G technique distinguishes between blue TSH cells and purple GTH cells in the RPD and PPD. GTH cells from animals collected in the winter were vacuolated. The PI contained two cell types whose staining reactions and ultrastructure were extremely variable. Intra- and extra-cellular acidophil spheres were present.

Adrenocorticotropic Hormone↗
PubMed1975

Cardiac anoxia tolerance of carbon monoxide-poisoned, hypoxia-exposed and normal rats.

Under nitrogen anoxia heart rate (HR) persists at a high level for 1 min longer in rats exposed chronically to carbon monoxide and hypoxia than in unexposed control rats. Although declining sharply, HR of exposed animals continues higher than HR of controls during min 1-4 of anoxia. However, during min 5 and 6 of anoxia HR of CO-poisoned rats becomes similar to that of controls, while HR of hypoxia-exposed rats remains above control HR for 3 min longer. The data are discussed in light of cardiovascular changes induced by CO and hypobaric hypoxia.

Animals↗