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Biomedical subjects

D C Herbert

Publications and source records attributed to D C Herbert.

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

Analysis of colloidal gold methods for labelling proteins.

The relationship between unbound and bound proteins prepared during labelling with colloidal gold (Au) was investigated. For this aim, labelled 125I-bovine serum albumin and 125I-rabbit immunoglobulin were employed. The procedures associated with the washing of the Au labelled proteins (i.e. albumin) had a marked influence on the dissociation of the bound ligand. This was most evident when the concentration of albumin that was used for labelling was too high (0.1 or 1.0 mg/ml Au sol). We suggest that purification of labelled proteins be conducted shortly before use so as to avoid a significant amount of dissociation during the time when the solution is coming to equilibrium.

Animals↗
PubMed1982

The hypophyseal-adrenal axis in the protein-calorie malnourished rat.

Male rats were fed an 8% low protein diet for 30 consecutive days beginning at 20 days of age. On day 50, the effect of the diet was evaluated on the hypophyseal-adrenal axis and the observations compared with those noted in age-matched controls fed a standard laboratory diet. The malnourished animals had significantly larger adrenal gland weights, relative to body size, and higher levels of serum corticosterone. Additionally, the number of ACTH-secreting cells in the pituitary glands of these rats was 63.8% greater than that present in the controls. These results suggest that ACTH secretion and adrenocortical physiology are stimulated under conditions of experimentally induced protein-calorie malnutrition.

Adrenal Glands↗
PubMed1982

Experimental protein malnutrition decreases calcium-binding protein in rat intestinal mucosa.

Calcium-binding activity was measured in duodenal mucosal homogenates of rats 50 days after weaning onto a protein-deficient diet providing 3-4 g of protein per kilogram of body weight per day compared to control animals, who were fed an isocaloric diet providing 9-12 g of protein per kilogram of body weight per day. Calcium-binding activity was decreased (44% of control) further than can be explained by the decrease in intestinal mucosal weight (70% of control) or supernatant protein content (80% of control). The results suggest that the decrease in calcium-binding activity reflects decreased synthesis of the vitamin D-dependent calcium-binding protein (CaBP) as an adaptive response to the stunted growth associated with protein malnutrition.

Animals↗
PubMed1981

Postnatal development of the ventral prostate gland in normal versus protein-calorie malnourished rats.

The ultrastructure of the postnatal development of the secretory cells within the ventral prostate gland was studied in the protein-calorie malnourished rat. Twenty-day-old Sprague-Dawley rats were fed either a low protein diet (LPD) containing 8% protein in the form of vitamin free casein or a standard laboratory diet (SLD) containing 27% protein. Animals maintained on the LPD and SLD were sacrificed every 7 days, beginning on Day 27 and ending on Day 55. The ventral prostate glands were perfused by whole body vascular perfusion via the left ventricle and processed for electron microscopy. The secretory cells of the prostates of the SLD-fed rats demonstrated progressive development of the organelles involved in protein synthesis which included an increase in cisternal profiles of the rough endoplasmic reticulum (RER), an enlargement of the Golgi apparatus, and an increase in the number of mature secretory granules. On the other hand, the growth of the secretory cells of the animals fed the LPD was retarded. The cells had an overall reduction in RER, the elements of the Golgi complex and the size of the nuclei as compared to age-matched controls. Additionally, they were characterized by an increase in various vacuole-like structures along with a concomitant decrease in mature secretory granules. These morphological observations suggest that protein-calorie malnutrition impedes both the development of the ventral prostate gland and the secretory activity of its epithelial cells.

Animals↗
PubMed1981

Localization of 3H-dihydrotestosterone in the pituitary gland of the rhesus monkey.

The uptake and retention of radiolabelled dihydrotestosterone by the pituitary gland was examined in the rhesus monkey. Two animals were given an intravenous injection of 1.0 microgram/kg 3H-dihydrotestosterone (DHT) alone while one monkey received both the labelled androgen and 100 micrograms/kg of unlabelled steroid. One and a half hours later, they were sacrificed. The pituitary glands were removed and processed for autoradiography and immunocytochemistry. Autoradiographic localization of DHT was discernible in the partes nervosa, intermedia and distalis, albeit the highest concentration of radiolabelled cells was noted in the pars distalis. Immunocytochemical staining with antibodies to rat PRL, human TSH beta and ovine LH beta revealed a population of steroid-concentrating cells that contained TSH and a second group that contained LH. None of the cells that reacted with the anti-PRL serum were radiolabelled.

Animals↗
PubMed1980

Morphology of the mammotrophs and gonadotrophs in the anterior pituitary gland of rats with protein-calorie malnutrition.

The structure of the anterior pituitary gland of rats with protein-calorie malnutrition was studied at the light and electron microscopic levels. Male Sprague-Dawley rats were fed a low-protein diet from 20 to 50 days of age. The hypophyses from these animals, along with those from age-matched controls, were then removed and fixed for light microscopic immunocytochemical analyses, using anti-rat PRL or anti-ovine LH beta serum, or for routine ultrastructural study. The overall number of mammotrophs and gonadotrophs appeared to be unaffected by the deficiency in dietary protein. However, the nuclei, in both cell types, were significantly smaller in the malnourished rats. Cytoplasmic volume was also apparently less than in control rats, leading to the "crowding" of adjacent cell types. Additionally, in the malnourished rats, the mammotrophs assumed a less polygonal profile, while the gonadotrophs, which were more irregularly shaped in the central zone, rarely displayed the negative image of a Golgi complex. Ultrastructurally, the mammotrophs in the experimental rats had a less extensively developed granular endoplasmic reticulum and Golgi complex. The number of secretary granules was not different; however, their size was markedly less and their shape was round to ovoid, rather than pleomorphic. Two types of gonadotrophs were distinguished, based on the classification of Kurosumi et al. ('76). The type-I cell (former "FSH" cell) had a smaller Golgi complex, less vesicular endoplasmic reticulum and smaller secretory granules. The major alteration in the type-II gonadotroph (former "LH" cell) was the smaller size of the secretory granules. The morphological changes found in this study support our previous physiological observations (Herbert, '80), which demonstrate that prolactin and gonadotrophin secretion are severely impaired in rats suffering from protein-calorie malnutrition.

Animals↗
PubMed1980

Growth patterns and hormonal profile of male rats with protein-calorie malnutrition.

A condition of protein-calorie malnutrition was precipitated in young Sprague-Dawley male rats at 20 days of age using an 8% low protein diet (LPD). At five-day intervals for up to 50 days of age, the rats were studied to determine the effect of an LPD on the reproductive axis of the endocrine system. Daily monitoring of the body weight, as well as the consumption of food, kilocalories, and protein was conducted. The same parameters were followed over the identical time period in a group of animals desigated as controls which were fed a standard laboratory diet (SLD) containing 27% protein. The controls showed a linear growth rate over the 30-day experimental period. In comparison, the malnourished rats grew more slowly so that by 50 days of age, their mean body weight was 68.9 +/- 3.1 g as compared to 248.1 +/- 6.1 g for the controls. The daily food, kilocalorie, and protein intake by the experimental animals were also appreciably less. The pituitary gland, ventral prostate gland, testes and liver were smaller in the animals fed the LPD. This was observed as early as five days after initiating the dietary regimes and remained a consistent observation until the end of the experiment. In general, the absolute weights of these organs in the 50 day-old malnourished rats were similar to those found in 25 to 26-day-old animals fed the SLD. The relative weights of the pituitary gland and liver remained similar between the two animal groups. The testes and ventral prostate gland, however, were relatively smaller in the malnourished animals at nearly every time interval studied. On light microscopic examination of the testes, it was found that normal maturation of the germ cells failed to occur in all but one of the experimental animals, whereas maturation proceeded normally in the rats fed the SLD. Serum luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin (PRL), and testosterone were lower in the malnourished animals at all ages studied. These hormones not exhibit the fluctuations that were seen in the controls and are typical in rats that are becoming sexually mature. The effect of protein deficiency on the concentration of the pituitary gonadotrophins was more varied. FSH concentrations were consistently lower, PRL was moderately affected, and LH remained essentially unchanged. Hypothalamic LH-releasing hormone was measured and found to be significantly less in the rats fed the LPD at most of the time intervals examined. These results indicate that the hypothalamo-hypophyseal-gonadal axis is impaired when the consumption of proteins and calorie is decreased. The possible involvement of extrahypothlamic centers in the control of hormone secretion in the protein-deficient rat is discussed.

Animals↗
PubMed1980

Nuclear uptake and retention of androgen by the pituitary gland of the hamster and the rat.

Castrated adult male hamsters and castrated adult female rats were injected with either 0.2 microgram (hamsters) or 0.5 microgram (rats) of 3H-dihydrotestosterone (107 Ci/mmole)/100 grams body weight and killed 1 1/2 h later. The pituitary glands were removed and processed for both autoradiography and immunocytochemistry (hamster) or only autoradiography (rats). Localization of the androgen was found in 10-15% of the cells of the pars distalis in both species. Only cells that stained for luteinizing hormone (LH) in the hamster's pars distalis concentrated the androgen. Also cells in both the pars intermedia and pars nervosa (1-5%) concentrated the androgen in both species. Although the number of cells that concentrated the androgen in the pars intermedia and pars nervosa was small, this finding may be related to recent physiologic data that suggest that the gonadal steroids may play a role in regulating water retention and natriuresis.

Animals↗
PubMed1980

Early response of the dopaminergic tuberoinfundibular neurons to anterior pituitary homografts.

Two anterior pituitary homografts were inserted under the left kidney capsule of adult male Sprague-Dawley rats (experimental rats). Sham-treated rats were exposed to identical surgical manipulations, but no tissue was inserted under the kidney capsule. The concentrations of dopamine (DA) and noradrenaline (NA) were determined in the median eminence, intermedioposterior pituitary and telencephalon by a radioisotope-enzyme technique. The decline in DA or NA 2 h after treatment with alpha-methyl-p-tyrosine provided a measure of DA and NA turnover, respectively. A marked increase in DA turnover was observed in the median eminence of the experimental compared to the sham-treated rats at 1, 3 and 6 days following surgery. The concentrations of DA and NA were significantly reduced in the median eminence of the experimental rats compared to sham-treated rats at both 3 and 6 days following surgery. No statistically significant increases in DA or NA turnover were observed in either the intermedioposterior lobe of the pituitary or the telencephalon of the experimental animals compared to the sham-treated animals at any time investigated. Serum prolactin (PRL) levels were significantly elevated in the experimental animals compared to the sham-treated animals by 3 days following surgery. The results of these studies clearly show that the turnover of DA in the terminals of the tuberoinfundibular neurons is increased by 1 day following the transplantation of anterior pituitary homografts under the kidney capsule. Future studies will be required to determine if this response is due exclusively to an early increase in serum PRL levels.

Animals↗
PubMed1980

Epididymal androgen binding protein in protein-calorie malnourished rats.

Androgen binding protein (ABP) was measured at five-day intervals from 20 to 50 days of age in the epididymides of rats fed a low protein diet. The results were compared to findings made in age-matched controls fed a standard laboratory diet. ABP was consistently lower in the caputs of the malnourished rats throughout the entire study. Moreover, no significant changes were noted in caput ABP concentrations as these rats aged. In contrast, this protein was observed to increase during the course of the month-long experiment in those animals fed the standard laboratory diet. These findings indicate that dietary protein deficiency has a marked debilitative effect on Sertoli cell function.

Aging↗
PubMed1979

An autoradiographic and immunocytochemical study of the neonatal rat pituitary gland.

Two-day-old female rats were injected with 5 nmole/kg of 6,7-3H-11 beta-methoxy-17-ethylestradiol (R 2858 = moxestrol) and killed one hour later. The animals were decapitated and, the pituitary glands were removed, mounted on tissue holders and frozen in liquified propane. The tissue was then processed for autoradiography according to the thaw-mount technique. At the end of the exposure time, prior to photographic development, some of the tissue was fixed in 10% formalin and then photographically developed for autoradiography. The fixed tissue was subsequently stained immunocytochemically using antibodies to luteinizing hormone or prolactin. Between 10 and 15% of the cells of the pars distalis concentrated the synthetic estrogen or its metabolite. The immunocytochemical procedure revealed that both LH-gonadotrophs and lactotrophs concentrated the steroid. These studies along with earlier studies suggest that the neonatal rat pituitary contains only a small portion of the adult complement of estrogen receptors and that these receptors are dispersed across a number of cell types.

Animals↗