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Biomedical subjects

D C Herbert

Publications and source records attributed to D C Herbert.

At least 73 records · Page 4Linked to original sources
PubMed1987

Response of pituitary thyrotrophs to thyrotrophin-releasing hormone in Snell dwarf mice.

The effect of thyrotrophin-releasing hormone (TRH) on pituitary thyrotrophs was investigated in Snell dwarf mice (dw/dw) that are genetically deficient in thyrotrophin (TSH) and in normal animals of the same strain. The normal animals were treated with either saline or 10 micrograms TRH per day for 2 weeks, while the dwarf mice were given daily injections of saline, 10 micrograms TRH for 2 weeks or 10 micrograms for 6 weeks. At the end of each experimental period, the pituitary glands were removed and fixed for light-microscopic analysis using immunocytochemistry, or for transmission electron-microscopic study. Compared to thyrotrophs observed in the pituitary glands of untreated normal mice, thyrotrophs in TRH-treated normal mice appeared to be more numerous by immunocytochemistry and showed signs of stimulation by electron microscopy. In contrast, immunostainable thyrotrophs could not be identified in the pituitary glands of untreated or TRH-treated dwarfs. However, a few cells exhibiting ultrastructural features of stimulated thyrotrophs, were noticeable in the dwarfs following TRH administration. Thus, while failing to induce the synthesis of immunoreactive TSH under the applied experimental conditions, exogenous TRH appeared to elicit differentiation of thyrotroph precursors into ultrastructurally recognizable thyrotrophs. The discrepancy between the immunocytochemical and ultrastructural findings remains unresolved; more work is required to clarify the question as to why ultrastructural maturation of thyrotrophs was unaccompanied by the production of immunoreactive TSH.

Animals↗
PubMed1987

Uptake and retention of 3H-estradiol by gonadotrophs and lactotrophs in the pituitary glands of the guinea pig, hamster and gerbil.

Nuclear uptake and retention of 3H-estradiol by luteinizing hormone (LH) and prolactin (PRL) cells was examined in three species of rodents (guinea pigs, hamsters and gerbils) using the combined techniques of immunocytochemistry and autoradiography. Castrated animals were injected with 3H-estradiol and decapitated 1.5 h later. The pituitary glands were processed for thaw-mount autoradiography followed by conventional immunocytochemical staining for LH and PRL. 3H-estradiol accumulated in more than 80% of the anterior pituitary cells in the gerbils, while only 33 and 22% of the cells accumulated 3H-estradiol in the hamsters and guinea pigs, respectively. A varying percentage of immunoreactive LH and PRL cells in all three species were found also to contain binding sites for estradiol. Some LH and PRL cells in hamsters and guinea pigs and only some in PRL cells of gerbils were found to be devoid of grains. Quantitative analysis revealed that the number of grains per nucleus differed considerably from cell to cell. LH cells of guinea pigs accumulated much larger amounts of 3H-estradiol than did the PRL cells, while the LH cells in the hamsters and gerbils accumulated only slightly more 3H-estradiol than the PRL cells. These results confirm the previous observations in rats and baboons that demonstrated tremendous species differences in percentage of cells in the anterior pituitary gland that accumulated 3H-estradiol. Also, these data suggest that there are functionally heterogeneous cell types among the LH and PRL cells in hamsters, guinea pigs and gerbils as has been previously demonstrated in rats and baboons.

Animals↗
PubMed1986

Target cells for dihydrotestosterone in the guinea pig pituitary gland.

Adult male guinea pigs were castrated and 24 h later injected with [3H]dihydrotestosterone. Their pituitary glands were then processed for autoradiographic and immunocytochemical analyses. Three percent of the parenchymal cells in the pars distalis were radiolabelled. These cells were primarily gonadotrophs; a small population of thyrotrophs were also found to retain the [3H]androgen. Labelling occurred in cells of the pars intermedia (3.2%) as well as in 9.6% of the pituicytes. These data indicate that in addition to gonadotrophs, the pars nervosa is a major target for dihydrotestosterone in the guinea pig pituitary gland.

Animals↗
PubMed1986

Do C cells of the thyroid gland of the baboon contain estrogen receptors?

The uptake and retention of radiolabelled estradiol was studied in the thyroid gland of the female baboon. Four baboons were injected intravenously with 1 micron/kg body weight of 3H-estradiol. One animal, which served as a control, received an additional injection of 100 micrograms/kg body weight of unlabelled hormone. One hour after the injections, the animals were killed and the thyroid glands removed and processed for either autoradiography or autoradiography in combination with immunocytochemical staining for C cells. Localization of estradiol was observed in the nuclei of interstitial cells, but not in those of the follicular cells. Nuclei of immunostained calcitonin-containing cells in both the walls of the follicles and the interfollicular compartment were not radiolabelled. This study suggests that estrogen does not regulate calcitonin secretion by the C cells of the thyroid via a classical receptor system.

Animals↗
PubMed1986

Fertility onset, spermatogenesis, and pubertal development in male rats: effect of graded underfeeding.

Undernutrition has proven to be a useful model for exploring the relationship between growth and pubertal development in female rats, such as the "critical body weight" hypothesis of pubertal timing, but corresponding studies in the male have been hampered by lack of specific discrete markers of puberty similar to vaginal opening or first estrus in females. In the current study, we explored the effect of five different levels of food intake (as low as one-third of normal) beginning at weaning on pubertal development and timing in male rats, using the date of the initial successful conception with normal females as a discrete marker for puberty in males. In underfed males, there was a weak inverse correlation (r = -0.31, p less than 0.05) between the age at puberty and the growth rate, the latter being used as an index of the degree of underfeeding. In contrast, there was a strong direct correlation (r=0.78, p less than 0.001) between body weight at puberty and growth rate. In the most severely underfed groups, the Lee index of body fat remained subnormal before and after puberty. Initial litter size also tended to be reduced when the males were underfed. At age 51 days (prior to puberty), graded underfeeding led to progressive reductions in serum luteinizing hormone and follicle-stimulating hormone levels as well as in parameters of androgen status (serum and testicular testosterone, prostate, and seminal vesicle weights). Testicular size was also reduced, but daily sperm production rate was not greatly affected by underfeeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1985

Changes in pineal indoleamine metabolism in vitamin A deficient rats.

Weanling, male rats were fed a vitamin A deficient (VAD) diet from 20 to 77 days of age. The circadian rhythms of the precursors and metabolites of pineal melatonin were measured along with the activity of N-acetyltransferase (NAT). Significant decreases in peak melatonin levels (0100 hours) and in nightime NAT activity (0100 and 0300 hours) were found in the pineals of the VAD rats. In contrast, the contents of serotonin, 5-hydroxytryptophan and 5-hydroxyindole acetic acid were only moderately affected by the deficiency. Daily administration of 25 micrograms melatonin from 20 to 74 days of age markedly reduced NAT activity in control and VAD rats. These data suggest that NAT activity is more sensitive to chronic VAD than any other parameters of melatonin metabolism.

5-Hydroxytryptophan↗
PubMed1985

The effect of long-term diethylstilbestrol treatment or hyperprolactinemia on the response of the tuberoinfundibular dopamine neurons to elevated prolactin.

Adult male rats were rendered hyperprolactinemic by two different methods. Some animals received subcutaneous implants of diethylstilbestrol (DES) or empty capsules. After 2 months the capsules were removed. Other rats received 3 anterior pituitary homografts under the kidney capsule or had sham surgery. The DES-treated rats were killed 8 months after capsule removal, while pituitary-grafted rats were killed 4 or 12 months after surgery. The DES-treated rats had hyperplastic anterior pituitaries, and both the DES-treated rats and the rats with anterior pituitary homografts were hyperprolactinemic. The activity of the TIDA neurons, as evidenced by dopamine (DA) synthesis in the median eminence (ME), was markedly and comparably elevated in both of these experimental groups of rats when compared to their respective controls. These data: show that the maintenance of hyperplastic pituitaries 8 months after DES withdrawal is not due to impaired function of the TIDA neurons; and provide no evidence for a neurotoxic effect of prolonged hyperprolactinemia on the response of the TIDA neurons to elevated PRL.

Animals↗
PubMed1985

Changes in the nuclear uptake and retention of 3H-estrogen in gonadotrophs and lactotrophs as a function of age.

A quantitative autoradiographic immunocytochemical study was performed in which the nuclear uptake and retention of 3H-estradiol (3H-E2) by luteinizing hormone (LH) and prolactin (PRL) cells was examined in 19-21-year-old baboons. 3H-E2 concentrating cells were found in all of the three lobes of the pituitary in varying percentages (38.7%, pars distalis; 17.1%, pars intermedia; 6.3%, pars nervosa). Approximately 80% of PRL cells and nearly 100% of LH cells were labeled. A count of the number of silver grains over nuclei revealed a marked variation of the accumulation of 3H-E2 by LH cells and to a lesser extent in PRL cells. These results suggest functional heterogeneity among LH and PRL cells. The present results are discussed in relation to the physiological state of old animals.

Aging↗
PubMed1985

Does neonatal androgen modulate uptake and retention of 3H-estradiol in gonadotrophs and lactotrophs?

Castrated adult male and female and androgenized female rats (AS rats ) were injected i.v. with 3H-estradiol (E2). Nuclear uptake and retention of the 3H-steroid was examined in pituitary luteinizing hormone (LH) and prolactin (PRL) cells by the combined techniques of autoradiography and immunocytochemistry. About 80% of PRL cells were found to concentrate the radioactive steroid compound in all experimental groups, while 89%, 82% and 68% of LH cells were found to be labeled in AS rats, normal female and male rats, respectively. This suggests that there are subpopulations of LH or PRL cells that contain no or, if any, small numbers of E2 receptor. Statistical analysis revealed that PRL cells take up more radioactivity than LH cells in male rats, while there is no significant difference between female and AS rats. Variations in E2 uptake (coefficient of variation) was higher in LH cells than in PRL cells in male rats and in AS rats. In females, on t the contrary, coefficient of variation was larger in PRL cells. Thus the characteristics of nuclear uptake and retention of estradiol in LH and PRL cells appear to be modulated in part by neonatal androgen since the pattern found in AS rats is different than that found in AS rats is different than that found in normal male and female rats.

Animals↗
PubMed1985

Testicular testosterone concentrations in protein-calorie malnourished rats.

The effects of protein-calorie malnutrition on testicular testosterone were studied at 5-day intervals in rats from 20 to 80 days of age. A significant increase in steroid hormone production did not occur in the malnourished rats before 60 days of age, whereas in well-fed controls, a marked rise was recorded between days 35 and 40. These changes correspond to a 5- to 10-day period which preceded the first appearance of mature sperm in both animal groups.

Animals↗
PubMed1984

Progesterone--specific binding sites in the kidney of the female baboon.

The uptake and retention of a radiolabeled synthetic progestin, ORG 2058, was studied in the urinary tract of the female baboon. Four estrogen-primed baboons were injected intravenously with 2.5 micrograms./kg. body weight of 3H-ORG 2058. One animal, which served as a control, received an additional injection of 2.5 mg./kg. body weight of unlabeled progesterone. One hour after the injections, the animals were killed and the kidneys, ureters and urinary bladder were removed and processed for autoradiography. Localization of progestin was observed in the nuclei of the convoluted and straight segments of the distal tubule, the ascending thick limb of the loop of Henle and both cortical and medullary collecting tubules. Connective tissue cells were also labeled in the medulla and cortex of the kidney. An absence of silver grains was noted in the renal corpuscle, all segments of the proximal tubule and the thin loop of Henle. Concentration of the tritiated steroid was not observed in either the ureter or bladder or in any portions of the urinary tract of the control animal. This study suggests that progesterone has a direct effect via a progesterone specific receptor on the various target cells that sequestered the 3H-ORG 2058.

Animals↗
PubMed1984

Identification of the progesterone target cells in the female baboon pituitary gland.

The identification of target cells for progesterone was conducted on pituitary glands obtained from long-term ovariectomized and adrenalectomized female baboons that had been injected with 3H-ORG 2058 (16 alpha-ethyl-21-hydroxy-19-nor-4-pregnene-3,20-dione; Amersham Corp). Binding sites were localized using autoradiography alone or in conjunction with immunocytochemistry. The synthetic progestin was primarily found over nuclei of cells in the pars distalis and pars intermedia, although a small population of pituicytes also bound the 3H-ORG 2058. The majority of steroid-sensitive cells in the pars distalis were gonadotrophs. These observations suggest a role for progesterone in the regulation of not only the gonadotropins but also those hormones secreted by the cells of the pars intermedia.

Animals↗
PubMed1984

Pineal gland morphology in rats with experimentally induced protein-calorie malnutrition.

The morphology of the pineal gland was studied in protein-calorie-malnourished (PCM) rats. Twenty-day-old male Sprague-Dawley rats were placed in a 14:10 photoperiod and fed either an 8% low protein diet (LPD) or a standard laboratory diet (SLD) containing 27% protein for 30 d. At 50 d of age, rats from both animal groups were sacrificed at 0900 h and at 2400 h, and the pineal glands were immersion-fixed for either light or electron microscopic analysis. The cytoplasm and nuclei of the pinealocytes from the SLD-fed rats were consistently larger than those of the animals maintained on the LPD. Additionally, the lipid droplets were larger and more prominent in the controls at both 0900 h and 2400 h. Even though the size of these inclusions did not vary among animals given the same diet as a function of the time of sacrifice, they were more numerous in both the well-fed and malnourished rats during the dark phase of the photoperiod. In contrast neither diet nor sampling time affected the size or number of pinealocyte mitochondria. These morphological observations lend further support to the premise than PCM impairs the cellular activity of the pinealocytes.

Animals↗
PubMed1984

Effects of estrogen-induced hyperprolactinemia on endocrine and sexual functions in adult male rats.

Chronic estrogen treatment can lead to development of prolactin (PRL) secreting pituitary tumors. We have tested the ability of diethylstilbestrol (DES) to produce persistent hyperprolactinemia (hyperPRL) in adult male rats and examined the effects of this treatment on hypothalamic-pituitary-testicular function, adenohypophyseal structure, copulatory behavior and fertility. Silastic capsules containing approximately 5 mg DES were subcutaneously implanted into adult male CDF (F-344)/CrlBR rats and removed 15 or 20 weeks later. Extreme hyperPRL, as well as suppression of plasma LH and FSH levels, persisted after DES capsules were removed. In contrast, plasma testosterone levels increased rapidly after removal of DES capsules and reached normal levels within 4-6 weeks. Copulatory behavior was assessed on two occasions between 7 and 14 weeks after removal of the DES capsules and was found to be suppressed in DES-treated rats, as evidenced by significant increases in latencies to mount, to intromit and to ejaculate. Moreover, when the animals were placed with normal females, the interval until conception was significantly greater in DES-treated than in control males. In spite of these differences in copulatory behavior, 10 of 11 DES-treated males were fertile. At autopsy, 44 weeks after capsule implantation (i.e. 24 or 29 weeks after capsule removal), DES-treated rats had marked enlargement of the anterior pituitary, increased weights of the lateral prostate and the adrenals, increased levels of testicular hCG-binding sites, reduced concentration of dopamine and norepinephrine in the median eminence and increased concentration of LHRH in the preoptic area.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed1983

Topographical distribution of the gonadotrophs, mammotrophs, somatotrophs and thyrotrophs in the pituitary gland of the baboon (Papio cynocephalus).

The identification and regionalization of four pituitary parenchymal cell types, gonadotrophs, mammotrophs, somatotrophs and thyrotrophs, were studied in the baboon (Papio cynocephalus) hypophysis using immunocytochemistry. The gonadotrophs were homogeneously distributed throughout the entire pars distalis. Both mammotrophs and somatotrophs predominate at the superior and inferior poles of the organ. The medial and anteromedial regions are populated by mammotrophs and thyrotrophs, while the lateral and posterior portions of the pars distalis contain large numbers of somatotrophs.

Animals↗
PubMed1983

Autoradiographic demonstration of binding sites for oestradiol and dihydrotestosterone in the urinary tract of male and female baboons.

By light microscopic autoradiography, the kidneys, ureters and urinary bladder of male and female baboons were examined in an effort to define which cells in these three organs were targets for oestradiol (E2) and dihydrotestosterone (DHT). In the parenchyma of the kidney, there was no specific uptake of either 3H-E2 or 3H-DHT, whereas the cortical and medullary connective tissue cells sequestered only 3H-E2. The latter hormone was also found in cells comprising the tunica intima and tunica media of the renal, interlobar and arcuate arteries. The two radiolabelled steroids were concentrated in connective tissue cells of the lamina propria of the ureter and bladder and in the tissue adjacent to smooth muscle fasciculi. Only 3H-DHT was retained by the smooth muscle in these two organs. These observations indicate that specific steroid binding sites are present in the urinary system of the baboon. Their role in the physiology of the kidney, ureter and urinary bladder remains at this point unclear.

Animals↗
PubMed1983

Uptake and retention of sex steroids by the baboon pituitary gland--evidence of sexual dimorphism with respect to dihydrotestosterone.

The localization and identification of the target cells for estradiol (E2) and dihydrotestosterone (DHT) were studied in the pituitary gland of male and female baboons (Papio cynocephalus) using autoradiography and autoradiography combined with immunocytochemistry. The largest number of cells which sequestered 3H-E2 were located in the pars distalis of both the males and females. Immunocytochemistry revealed that these target cells were predominantly gonadotrophs and mammotrophs, albeit a few somatotrophs and thyrotrophs were also labeled. A distinct sexual dimorphism was not observed with respect to the uptake and retention of the tritiated estrogen but was clearly evident in those animals given 3H-DHT. Significantly more cells in all three lobes of the male baboon, the partes distalis, intermedia and nervosa, concentrated the radiolabeled androgen as compared to that found in the females. Regardless of sex, however, the gonadotrophs were the major cell type in the pars distalis which was labeled. A small population of mammotrophs, somatotrophs and thyrotrophs also retained 3H-DHT. In both males and females, the pars nervosa was the portion of the hypophysis most sensitive to 3H-DHT. These findings indicate that all three lobes of the hypophysis of the male and female baboon contain target cells for E2 and DHT and that the propensity for DHT uptake is greater in males than in females.

Animals↗