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Biomedical subjects

F D Bertalanffy

Publications and source records attributed to F D Bertalanffy.

13 recordsLinked to original sources
PubMed1987

The effects of melatonin and hypothyroidism on estradiol and gonadotropin levels in female Syrian hamsters.

Since melatonin injections administered near the end of the daily photoperiod influence both gonadal and thyroid hormones in the female hamster, the present study was designed to compare the effects of melatonin and hypothyroidism on the reproductive system and to determine whether thyroid status influenced the action of melatonin on the regulation of the hormones of reproduction. The effects of daily melatonin injections were determined in control hamsters, in hamsters rendered hypothyroid with thiourea, and in hypothyroid hamsters receiving thyroxin (T4) hormone replacement. As previously reported, melatonin injections disrupted estrous cyclicity, disrupted the normal pattern of gonadotropin secretion, and resulted in atrophy of the uterus and vagina. These changes coincided with depressed serum and pituitary prolactin (PRL), and depressed levels of estradiol. The effects of melatonin on uterus, vagina, ovary, and on gonadotropin levels were not prevented by T4 replacement, with the exception of a melatonin-induced increase in serum follicle-stimulating hormone (FSH). This suggested that the cessation of estrous cyclicity was not primarily a result of thyroid deficiency. Hypothyroidism, however, like melatonin, resulted in a reduced number of developing and mature follicles and corpora lutea in the ovaries, and in reduced uterine weight. It also produced follicular atresia, reduced the circulating levels of estradiol, and resulted in reduced incidence of estrus smears. T4 replacement, for 2 weeks, prevented the decline in mature follicles and corpora lutea, reduced the extent of follicular atresia, increased circulating levels of estradiol, and increased uterine weight. PRL and luteinizing hormone (LH) data also provided evidence for antagonistic effects of melatonin and T4 in female hamsters. These data raise the question whether melatonin-induced changes in circulating levels of T4 play a role in the seasonal cycles of reproductive competence in the female hamster.

Animals↗
PubMed1987

Cytostatic action of methylmercuric chloride on mammalian duodenal cells.

Adult male mice of the ICR/Swiss Webster strain received a single intragastric administration of methylmercuric chloride 1,000 ppm, at dose levels of 5,10,15,20,25 and 30 mg/kg of body weight. The animals were killed six hours later. Tissue samples from the duodenum were fixed in 10% neutral buffered formalin for light microscopy. Chromosome clumping was observed in dividing cells at all dose levels, resembling a C-mitotic effect. It would lead to reduced mitotic cell formation on account of the subsequent lysis of the arrested metaphases. The cytostatic effect was brought about by the inactivation of the microtubule spindle fiber polymerization mechanism induced by methylmercuric chloride. There was a direct positive correlation between the varying dose levels of methylmercury and the proportion of cells arrested in metaphase in the crypts of the duodenum.

Administration, Oral↗
PubMed1977

Structure of sinuses in the human lymph node.

A casting technique has been employed to display in three dimensions, the lymphatic microcirculation within the human lymph node. The casting compound filled the marginal sinus, and diffusely permeated the cortical lymphoid parenchyma. However, deep within the lymph node in the medullary region, the medium remained within the limits of the sinus walls. The casts showed well-defined channels appearing similar to vessels. These converged into larger vessels, which drained into efferent lymphatics leaving the node at the hilus. Electron microscopic examination showed that the outer wall of the marginal sinus and the trabecular side of trabecular sinuses had an intact, continuous endothelium with a basement membrane. However, gaps were present in the inner wall of the marginal sinus, as well as in the parenchymal wall of the trabecular sinus. In the medulla, the sinuses were lined by endothelial cells which appeared similar to macrophages. The sinus lining was incomplete and possessed numerous perforations. These observations indicated that sinus walls adjacent to connective tissue served as a barrier to cell movement, but those adjacent to a large lymphoid cell population had gaps, with cells in apparent transit between sinus lumen and parenchyma.

Basement Membrane↗
PubMed1965

Mitotic rates of rat epidermis. During growth, maturity, senility, and regeneration.

Adult epidermal tissues are renewing cell populations. Mitosis continuously provides new cells replacing those that became keratinized and ultimately shed. It seems plausible to assume that in the epidermis of growing individuals mitosis supplies cells both for cell addition (growth) and renewal. During growth, more cells are presumably retained in the tissue than become lost through desquamation. It is feasible by cutaneous incision to temporarily revert adult epidermis into a growing cell population. Presumably also during healing, cell production exceeds cell loss. What is the magnitude of cell production for renewal of adult epidermis, for simultaneous cell addition and renewal during growth, as well as during epidermal regeneration? To elucidate these problems, the mitotic rates of three epidermal cell populations (ear, plantar, and abdominal epidermis) were determined in the growing, adult, and senile rat. Further, the adult ear and back skin epidermis was converted by cutaneous incision into regenerating cell populations, and the mitotic rates were determined during healing at intervals from six hours to nine days.

Aging↗