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Biomedical subjects

C A Blake

Publications and source records attributed to C A Blake.

At least 55 records · Page 3Linked to original sources
PubMed1984

Administration of monosodium glutamate to neonatal male rats: alterations in the gonadotrophs and in gonadotrophin secretion.

We have studied the effect of administration of L-monosodium glutamate (MSG) to neonatal rats on gonadotroph morphology and gonadotrophin secretion in the prepubertal male rat. Rats were injected with MSG (4 mg/g body weight) or with 0.1 ml saline/10 g body weight on days 1, 3, 5, 7 and 9 of life (day of birth = day 0) and were used for experiment on day 40. Trunk blood was collected from 8 saline- and 9 MSG-injected rats for assay of serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations. One-half of the anterior pituitary gland was assayed for LH and FSH concentrations and the other half was placed in culture medium for a 30-min preincubation and then placed in fresh medium for a 2-hour incubation (basal LH and FSH release). An additional 4 rats in each group were killed and the pituitary glands were prepared for histological examination and immunocytochemical staining of LH and FSH cells and morphometric examination of these cells at the light microscopic level. The morphometric analyses were compared with those performed previously by us on adult male rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

The localization of gonadotrophs in normal adult male and female rats.

We investigated the localization of LH and FSH cells within the pituitary glands of normal adult rats. Groups of four female rats were decapitated at one of five different times during the estrous cycle. Four male rats were also decapitated. Paired horizontal flip-flopped serial paraplast sections from the dorsal, middle, and ventral portions of each pituitary gland were stained. For each pair, one section was stained with antirat LH-S4 and the other section with antirat FSH-S7, by the unlabeled antibody peroxidase-antiperoxidase method. All immunoreactive cells were counted, and the area of pars distalis in each section was determined. We studied the spatial distribution of gonadotrophs within the sections and determined if a polarization along the antero-posterior axis existed. In the "sex zone" of the pars distalis, the cross-sectional area of LH cells and the percentages of LH cells that also contained FSH and vice versa were determined and compared with those obtained from the entire pars distalis. Additional sections were stained for TSH, ACTH, GH, or PRL, and the distribution of stained cells was compared with that of those that stained for LH or LH/FSH, particularly in the sex zone and in the pars intermedia. The results indicate that 1) gonadotrophs are more evenly distributed dorsoventrally within the pars distalis of male rats than in that of female rats; 2) an antero-posterior polarity in gonadotropic distribution is more pronounced in male rats than in female rats; 3) gonadotrophs containing only LH are less numerous in male than female rats, and in the female tend to be centrally located within the pars distalis; 4) the sex zone contains PRL cells and gonadotrophs, and the percentages of gonadotrophs that contain LH or LH and FSH are not different from those of the entire pars distalis; 5) LH, and occasionally LH/FSH cells, are present between lobules of immunoreactive ACTH cells in the pars intermedia; and 6) LH cells in the pars intermedia are smaller than those in the sex zone or entire pars distalis.

Adrenocorticotropic Hormone↗
PubMed1984

Effects of neonatal administration of monosodium glutamate on somatotrophs and growth hormone secretion in prepubertal male and female rats.

Female and male rats were injected with monosodium L-glutamate (MSG; 4 mg/g BW) or 0.9% saline as neonates and then decapitated on days 35 and 40 of life, respectively. Trunk blood was collected for RIA of serum GH. Anterior pituitary glands (APGs) were bisected. One half was assayed for GH. The other half was placed in culture medium to study the basal GH release rate. Pituitary sections from additional rats were stained for GH, and morphometric analyses were performed on the GH cells. Treatment with MSG lowered serum GH levels and gland GH content in female but not in male rats. MSG did not alter the gland GH concentration or the basal GH release rate whether expressed per mg APG or per entire gland in either sex. The mean cross-sectional area of GH cells was reduced in either sex of MSG-treated rats. The numerical density of GH cells and the percentage of GH cells in APGs were similar in saline- and MSG-treated rats of either sex. The volume density of GH cells was lower in MSG-treated male rats only. The results suggest that in prepubertal rats which had been given MSG as neonates there is a sex difference in mean serum GH concentration and APG GH content, GH cell size is reduced in both sexes, and the individual GH cells contain normal amounts of GH in spite of their smaller size.

Animals↗
PubMed1984

Pars distalis cell quantification in normal adult male and female rats.

We analysed cell types in the pars distalis of normal young adult male and female rats with respect to their percentages and the relative volumes they occupy. In male rats the percentages of the cell types were: prolactin 49.80, GH 22.67, LH 5.04, FSH 4.22, ACTH 2.93 and TSH 2.09. The volume densities were: prolactin 20.48, GH 20.95, LH 7.34, FSH 6.73, ACTH 3.75 and TSH 3.19. In female rats the percentages of the cell types were: prolactin 52.40, GH 20.30, LH 5.89, FSH 4.06, ACTH 2.53, TSH 2.40 and the volume densities were: prolactin 28.09, GH 20.86, LH 8.11, FSH 5.46, ACTH 3.49 and TSH 2.91. The percentages of pars distalis cells which did not stain with the antisera to the six classical hormones were 17.47 in male and 16.48 in female rats. The results suggest that (1) in both sexes the number (N) of prolactin cells greater than N of GH cells greater than N of gonadotrophs greater than N of TSH or ACTH cells, (2) the percentage of each cell type was similar in both sexes, (3) the volume density (Vv) of prolactin cells was greater than the Vv of GH cells in female but not in male rats and in both sexes the Vv of GH cells greater than the Vv of gonadotrophs greater than the Vv of TSH or ACTH cells, (4) in both sexes the volume (V) of prolactin cells less than the V of GH cells less than the V of gonadotrophs, the V of TSH cells or the V of ACTH cells, (5) the V of prolactin cells was greater in female than in male rats and (6) approximately 17% of the cells in the pars distalis of both sexes did not contain 'immunoreactive' prolactin, GH, LH, FSH, TSH or ACTH.

Adrenocorticotropic Hormone↗
PubMed1983

Dissociation between increased growth hormone and prolactin secretion during the morning hours of early pregnancy in the rat.

We investigated whether serum growth hormone (GH) concentration changes in association with the rise in serum prolactin (PRL) concentration known to occur during the early morning hours in the pregnant rat. Animals were kept in a room with the lights on from 0500 to 1900 hours (hr) daily and decapitated for the collection of trunk blood at 2200 or 2400 hr on Day 6 of pregnancy or at 0200, 0400, 0800 or 1000 hr on Day 7 of pregnancy. Serum GH concentration rose more than 4-fold from low levels at 2200 and 2400 hr to higher levels at 0400 and 0800 hr and then declined by 1000 hr. Serum prolactin (PRL) concentration followed a similar pattern except that it returned to low levels earlier, by 0800 hr. Serum luteinizing hormone, follicle-stimulating hormone and thyroid-stimulating hormone concentrations showed no significant changes. Serum GH levels at 0800 hr in pregnant rats were higher than those observed in cyclic rats (13 time periods sampled). The results demonstrate that serum GH concentration is elevated during a circumscribed period in the 6- to 7-day pregnant rat. The time of onset of the rise is similar to that for serum PRL but the elevation in GH levels persists longer than that for PRL.

Animals↗
PubMed1983

Effects of acute ovariectomy on anterior pituitary gland follicle-stimulating hormone and luteinizing hormone secretion in the metestrous rat.

Changes at the anterior pituitary gland level which result in follicle-stimulating hormone (FSH) release after ovariectomy in metestrous rats were investigated. Experimental rats were ovariectomized at 0900 h of metestrus and decapitated at 1000, 1100, 1300, 1500, 1700 or 1900 h of metestrus. Controls consisted of untreated rats killed at 0900 or 1700 h and rats sham ovariectomized at 0900 h and killed at 1700 h. Trunk blood was collected and the serum assayed for FSH and luteinizing hormone (LH) concentrations. The anterior pituitary gland was bisected. One-half was used to assay for FSH concentration. The other half was placed in culture medium for a 30-min preincubation and then placed in fresh medium for a 2-h incubation (basal FSH and LH release rates). The basal FSH release rate and the serum FSH concentration rose significantly by 4 h postovariectomy and remained high for an additional 6 h. The basal FSH release rate and the serum FSH concentration correlated positively (r=0.71 with 72 degrees of freedom) and did not change between 0900 and 1700 h in untreated or sham-ovariectomized rats. In contrast, the serum LH concentration and the basal LH release rate did not increase after ovariectomy. Ovariectomy had no significant effect on anterior pituitary gland FSH concentration. The results suggest that the postovariectomy rise in serum FSH concentration is the result, at least in part, of changes which cause an increase in the basal FSH secretion rate (secretion independent of the immediate presence of any hormones of nonanterior pituitary gland origin). The similarities between the selective rises in the basal FSH release rate and the serum FSH concentration in the ovariectomized metestrous rat and in the cyclic rat during late proestrus and estrus raise the possibility that an increase in the basal FSH release rate may be involved in many or all situations in which serum FSH concentration rises independently of LH.

Animals↗
PubMed1983

A quantitative immunocytochemical study of the luteinizing hormone and follicle-stimulating hormone cells in the adenohypophysis of adult male rats and adult female rats throughout the estrous cycle.

We investigated whether 1) the absolute or the relative numbers of LH and FSH cells change during the rat estrous cycle, 2) the percentages of gonadotrophs that contain LH and/or FSH change during the estrous cycle, and 3) gonadotrophs change in size during the rat estrous cycle. Groups of four female rats were decapitated at one of five different times during the estrous cycle. Four male rats were also decapitated. Serum concentrations of LH and FSH were determined by RIA. Paired horizontal flip-flopped or nonflipped paraffin sections were mounted from the dorsal, middle, and ventral portions of each pituitary gland. In each pair of sections, one was stained with a-rat LH-S4 and the other with a-rat FSH-S7 by the unlabeled antibody peroxidase-antiperoxidase method. All immunoreactive cells were counted. Photographs were taken from randomly chosen corresponding areas, and the cells were individually matched to determine the percentage that contained one or both hormones. Correction factors had to be used because in paired flip-flopped or nonflipped sections stained with the same antibody (a-rat LH-S4), not all of the stained cells found in one section were found in the other section. The absolute numbers of LH and FSH cells did not change throughout the estrous cycle. The ratio of LH cells to FSH cells in the pars distalis of female rats was also constant throughout the estrous cycle. In female rats, 75.2% of LH cells also contained FSH, while 99.4% of FSH cells also contained LH. In the male rats, 88.6% of LH cells also contained FSH, while 98.6% of FSH cells also contained LH. Similar results were obtained in paired flip-flopped sections stained with a-rat LH beta and a-rat FSH beta. Sequential staining of additional individual tissue sections with a-rat LH-S4 and then a-rat FHS-S7 or vice versa revealed the following. Staining of LH-stained tissue for FSH revealed less than 1% new cells, but staining of FSH-stained tissue for LH revealed a 8.7% increase in gonadotrophs in males and a 25.4% increase in females. The gonadotrophs in female rats did not change in size during the estrous cycle and were significantly smaller than the gonadotrophs in male rats. The results suggest that in normal adult rats: 1) virtually all FSH-containing cells contain LH, 2) about 25% of the gonadotrophs in females and about 11% of the gonadotrophs in males contain LH but not FSH, 3) the number of cells containing LH or those containing LH and FSH does not change during the estrous cycle, 4) gonadotrophs in female rats do not change in size during the estrous cycle and are smaller than the gonadotrophs in male rats, and 5) FSH release during the early morning of estrus, when the serum FSH concentration is elevated and the serum LH concentration is low, occurs from cells that contain both LH and FSH.

Animals↗
PubMed1982

A decrease of cytosol estrogen receptors in the hypothalamus as a result of treatment of neonatal rats with glutamate.

Experiments were performed to determine whether the neuroendocrine dysfunctions of rats treated neonatally with monosodium glutamate (MSG) could be related to a loss of cytoplasmic estrogen receptors. Female rats treated with MSG as neonates were ovariectomized as adults and killed by decapitation 2 or 3 weeks after ovariectomy. Body, gonadal and anterior pituitary gland weights in MSG-treated rats were depressed when compared to that seen in their littermate controls. Serum prolactin concentration was elevated in the MSG-treated rats. Serum luteinizing hormone (LH) concentration was significantly lower in MSG-treated rats than in controls at 2 weeks, but not at 3 weeks after ovariectomy, suggesting a sluggish postovariectomy rise of serum LH concentration. Serum follicle-stimulating hormone (FSH) concentration was not altered by the MSG treatment. The concentration of cytosol estrogen receptors in the anterior pituitary gland was similar to that of controls, but hypothalamic concentration of estrogen receptors decreased as a result of the MSG treatment. After dissection of different hypothalamic regions, it was found that the greatest depletion of the cytosol estrogen receptors occurred in the arcuate-median eminence region. The results raise the possibility that some reproductive impairments of MSG-treated rats could stem from a decrease in cytosol estrogen receptors in the arcuate-median eminence region.

Animals↗
PubMed1982

Effects of complete hypothalamic deafferentation on the estrous phase of follicle-stimulating hormone release in the cyclic rat.

We investigated whether neural afferents to the medial basal hypothalamus play an acute role in the estrous phase of FSH release in the 4-day cyclic rat. A cannula was inserted into the right atrium of the heart under brief ether anesthesia during the early afternoon of proestrus for subsequent blood collections and injection of LHRH. In some of the rats, the medial basal hypothalamus was surgically isolated from the rest of the brain with a small knife under brief ether anesthesia between 2000 h and 2130 h of proestrus. Control groups consisted of naive rats which were not treated during the night of proestrus and sham-operated animals in which the knife was lowered to the corpus callosum between 2000 h and 2130 h or proestrus. Rats were bled at 2200 h of proestrus and at 0200 h, 0600 h and 1000 h of estrus for radioimmunoassay of plasma FSH and LH. The plasma FSH levels in all 3 groups between 2200 h of proestrus and 1000 h of estrus were elevated above levels observed in other cannulated rats bled to the onset of the proestrous phase of FSH release at 1400 h of proestrus. There were no statistically significant differences in plasma FSH or LH concentrations at any of the time periods between the 3 groups of serially bled rats. The deafferentation procedure did not appear to impair the pituitary gland's ability to secret gonadotrophins as injection of 50 ng of LHRH after the bleeding at 1000 h of estrus caused substantial elevations in plasma FSH and LH concentrations which were not different between the 3 groups. The results suggest that neural afferents to the medial basal hypothalamus play no acute role in the estrous phase of FSH release in the cyclic rat.

Afferent Pathways↗
PubMed1982

Catecholestrogens and release of anterior pituitary gland hormones. I. Luteinizing hormone.

We investigated the effects of peripheral administration of 17 beta-estradiol (E2), estrone (E1), and the catecholestrogens, 2-hydroxyestradiol (2-OHE2) and 2-hydroxyestrone (2-OHE1), on anterior pituitary gland LH release in the prepuberal rat. Steroids in oil were injected sc into 25-day-old female and 35- to 40-day-old male rats. The injection of E2, E1, or 2-OHE2 caused a surge in serum LH levels in female rats 48 h later, during the after hours. Only E1 induced a LH surge 24 h after injection. The positive effects of 2-OHE2 in the females were only observed if a massive dose was administered, the steroid was injected on 2 consecutive days, or E2 or progesterone was given to 2-OHE2-primed rats. The 2-OHE1 was totally ineffective in causing a serum LH surge under a variety of experimental protocols. In male rats, the injection of any one of the four steroids decreased serum LH levels. Even the injection of E2 or 2-OHE2 for 2 days or the injection of E2 in 2-OHE2-primed rats failed to elevate the serum LH concentration in male rats. The results suggest that 2-OHE2 and E1 could play a role in the preovulatory release of LH in the female; 2-OHE2 and 2-OHE1 could play a role in the negative feedback control of LH release in the male.

Animals↗
PubMed1982

Catecholestrogens and release of anterior pituitary gland hormones. II. Prolactin.

We investigated the effects of the peripheral administration of 17 beta-estradiol (E2), estrone (E1), and the catecholestrogens, 2-hydroxyestradiol (2-OHE2) and 2-hydroxyestrone, (2-OHE1), on anterior pituitary gland PRL release in the prepuberal rat. Steroids in oil were injected sc into 25-day-old female and 35- to 40-day-old male rats. The injection of E2, E1, or 2-OHE2, but not of 2-OHE, caused a surge in serum PRL levels in female rats 48 h later, during the afternoon hours. Only E1 induced a PRL surge 24 h after injection. In male rats, the injection of E1 or 2-OHE2, but not of 2-OHE1, elevated serum PRL levels on a chronic basis. The results suggest that 2-OHE1 plays no discernible role in PRL release in either sex, but that 2-OHE2 might play a role in the tonic release of PRL in the male and in the preovulatory release of PRL in the female.

Animals↗
PubMed1982

Anterior pituitary gland secretion after forebrain ablation: periovulatory gonadotropin release.

We sought to determine whether the estrous phase of FSH release in cyclic female rats is dependent on the immediate presence of the diencephalon. A piece of forebrain, the diencephalon and part of the telencephalon, was surgically removed from female rats between 1130--1300 or 2000-2200 h on proestrus. Blood was withdrawn through indwelling venous cannulae during the afternoon and evening of proestrus and the early morning of estrus for RIA of plasma LH, FSH, and PRL concentrations. In rats sham operated at either time period, plasma LH, FSH, and PRL levels rose from 1345 to 1800 h on proestrus. Whereas the plasma LH and PRL concentrations fell from 1800 h on proestrus to 0300 h on estrus, the plasma FSH concentrations remained elevated during this period. The removal of the piece of forebrain around noon on proestrus blocked the rises in the plasma LH and FSH levels and caused high plasma PRL concentrations from 1345 h on proestrus to 0300 h on estrus. The removal of the piece of forebrain during the evening of proestrus did not interfere with the fall in plasma LH concentrations or the maintenance of elevated plasma FSH concentrations during either late proestrus or the early morning estrus, but did cause high plasma PRL levels during that time interval. Hypophysectomy combined with removal of the forebrain piece during the evening of proestrus resulted in a drop in plasma FSH and PRL concentrations. The results confirm that in the rat, 1) the prosencephalon plays an acute stimulatory role n causing the preovulatory LH surge and the proestrous phase of FSH release, 2) the prosencephalon exerts effects during the afternoon and/or early evening of proestrus that cause the estrous phase of FSH release, and 3) the estrous phase of FSH release occurs in the absence of acute diencephalic stimulation.

Animals↗