PubMed Health⌕ Search

Biomedical subjects

L L Garner

Publications and source records attributed to L L Garner.

14 recordsLinked to original sources
PubMed1990

AF64A depletes hippocampal high-affinity choline uptake but does not alter the density of alpha-bungarotoxin binding sites or modify the effect of exogenous choline.

Sodium-dependent, high-affinity choline uptake (HACU) and the density of alpha-bungarotoxin (BuTX) receptor-binding sites were measured in the hippocampus following the intraventricular infusion of ethylcholine aziridinium ion (AF64A), a neurotoxin that competes with choline at high-affinity choline transport sites and may result in the degeneration of cholinergic axons. Eight days after the infusion of AF64A into the lateral ventricles (2.5 nmol/side), HACU was depleted by 60% in the hippocampus of experimental animals in comparison with controls, but the density of BuTX-binding sites was not altered. The administration of 15 mg/ml of choline chloride in the drinking water increased the density of BuTX-binding sites, as previously reported by this laboratory. The administration of AF64A did not prevent the effect of exogenous choline on the density of binding sites, nor did choline treatment alter the effect of AF64A on HACU. These data indicate that the density of BuTX-binding sites in the hippocampus is not altered following a substantial decrease in HACU and presumed degeneration of cholinergic axons. Since the effect of exogenous choline was not prevented by AF64A treatment, the data are interpreted to support the hypothesis that the increase in the density of BuTX-binding sites following dietary choline supplementation is attributable to a direct effect of choline on receptor sites.

Animals↗
PubMed1990

Light-dark variation in response to chronic nicotine treatment and the density of hypothalamic alpha-bungarotoxin receptors.

Chronic nicotine administration increased locomotor activity during the light, but not the dark, in rats maintained on a 12:12-hr light/dark cycle, but the period and peak of the circadian rhythm (CR) were not affected. In Experiment I, 24 male rats were implanted with battery-operated telemeters and locomotor activity was continuously measured for 10 days before and 10 days after the implantation of osmotic mini-pumps which delivered 0, 0.5, 3.0 or 10 mg/kg/day of (+/-)-nicotine tartrate. Nicotine increased locomotor activity during the light in a dose-dependent manner. Tolerance to the stimulant effects of nicotine during the light occurred in 5-6 days. To determine if the stimulant properties of nicotine were associated with light as opposed to disruption by the environmental stimuli normally present during the day in our animal facility, a second experiment was conducted in which rats were treated with saline or 10 mg/kg/day (+/-)-nicotine di(+)hydrate tartrate and maintained on a reversed light/dark cycle. Again nicotine increased activity during the light (21:00-09:00) but not the dark (09:00-21:00). In a third experiment, the density of alpha-bungarotoxin binding sites was found to be significantly decreased when animals were sacrificed at 06:00 in comparison with animals sacrificed at 10:00 and 14:00.

Animals↗
PubMed1990

Luteinizing hormone (LH)-releasing hormone: chronic effects on LH and follicle-stimulating hormone cells and secretion in adult male rats.

We investigated whether chronic administration of LHRH to normal adult rats could increase the percentages of anterior pituitary gland (APG) cells that contain immunoreactive LH and/or FSH and gonadotropin secretion. Vehicle or 1 microgram LHRH was injected sc twice daily for 6 days, and rats were decapitated 16 h after the last injection. Treatment with LHRH caused nearly a doubling in the numerical density of LH and FSH cells and in the percentage of APG cells that contained LH or FSH. It also caused a shift in the gonadotroph population from LH and LH/FSH cells to LH/FSH cells. It did not change the mean size of gonadotrophs or APG weight. These changes at the light microscopic level were not accompanied by any apparent changes in LH cells at the ultrastructural level. However, they were accompanied by an approximate doubling of the basal serum LH and FSH concentrations, an increase in the APG FSH concentration, and an increase in the basal FSH release rate (measured in vitro). The results indicate that exogenous LHRH can be administered to increase numbers of gonadotrophs in the APG, synthesis of FSH in gonadotrophs, and basal serum LH and FSH concentrations.

Animals↗
PubMed1986

Increases in the concentration of brain alpha-bungarotoxin binding sites induced by dietary choline are age-dependent.

We have previously reported that a diet supplemented with choline induces an increase in the concentration of a brain nicotinic-like receptor, as measured by alpha-bungarotoxin (BuTX) binding. Here we report the effects of choline administered in the drinking water on BuTX binding in the cortex, midbrain and brainstem of rats at 3 ages. In comparison with animals fed a choline-free diet, choline supplementation produced increases averaging 50% in 23-day-old rats and increases of approximately 30% in 60-day-old rats. Increases were also found in 6-month-old animals (averaging 16%), but the differences were generally not statistically significant. The mechanism responsible for the increase in the concentration of BuTX binding sites following the administration of dietary choline is not known, but the results are discussed in terms of choline as a precursor for the biosynthesis of acetylcholine and the biosynthesis of phospholipids. These data indicate that the administration of dietary choline is not likely to be effective in reversing cholinergic deficits by increasing the concentration of nicotinic-like receptors in aging rats.

Animals↗
PubMed1985

Monosodium glutamate and pituitary gland luteinizing hormone (LH) release in response to LH-releasing hormone: an in vitro study.

We studied whether an increase in the basal LH release rate and/or the anterior pituitary gland (APG) LH response to LHRH is involved in maintaining normal or near-normal serum LH levels in monosodium L-glutamate (MSG)-treated rats which have small APGs for their body weight. Female rats were injected with MSG (4 mg/g BW) or saline on days 1, 3, 5, 7, and 9 after birth (day of birth = 0). At 8-9 weeks of age, saline-treated and MSG-treated rats were ovariectomized, and 7 days later, they were decapitated. Trunk blood was collected from 18 controls and 19 MSG-treated rats, and serum LH concentrations were measured by RIA. APGs were bisected and each hemi-APG was placed in culture medium for a 30-min preincubation period, followed by two 30-min incubation periods during which water or 10 or 30 ng LHRH were added to the medium. Despite the fact that the APGs of the MSG-treated rats were half the size of those of the saline-treated rats, the serum LH levels in the 2 groups were not different. Basal LH release rates (the response to water) and LHRH-induced LH release per mg APG were increased in MSG-treated rats. Calculation of the basal LH release rates and LHRH-induced LH release on the basis of the entire weights of the APGs showed no differences between the MSG-treated rats and the controls. In 6 additional control and 6 additional MSG-treated rats, the APG LH concentration was measured and was not different between the 2 groups. The results suggest that increases in both the basal LH release rate per mg APG and the amount of LH released per mg APG in response to LHRH are of importance in the maintenance of normal or near-normal serum LH concentrations in MSG-treated rats with small APGs.

Animals↗
PubMed1980

An immunocytochemist's view of gonadotropin storage in the adult male rat: cytochemical and morphological heterogeneity in serially sectioned gonadotropes.

This study was designed to elucidate hormone storage patterns in gonadotropes with the use of ultrastructural immunocytochemistry on serial ultrathin sections. Sets of six serial sections were strained for beta chains of LH, FSH, or the C-Terminal sequence of ACTH, and 430 cells cut in triple or double serial section were collected from a group of seven normal adult male rats. Approximately 50--80% of the cells contained both LH and FSH, and most of these were Type I cells which are distinguished by their round shape and heterogeneous populations of secretion granules. Cells containing only FSH or LH constituted, on average, 19% of the population. These were a mixed group, morphologically, and included Type II cells distinguished by their angular shape and population of secretion granules, 250 nm in average diameter. Also among the FSH cells (and a few LH cells in two of the rats) were Type III cells, which resemble the corticotrope. On average, 10% of the serially sectioned cells contained only ACTH. Our findings show the presence of subpopulations of gonadotropes containing only one of the hormones, in numbers large enough to support the hypothesis that they may be partly responsible for the nonparallel release of gonadotropins. Also, the FSH-LH cells seemed to vary in their staining intensity for the two hormones, suggesting that the gondaotropes are a fluid, heterogeneous population of cells capable of storing both or only one of the hormones.

Adrenocorticotropic Hormone↗