Biomedical subjects

J Bennett

Publications and source records attributed to J Bennett.

At least 361 records · Page 20Linked to original sources

PubMed1975

Platelet hypersensitivity induced by cholesterol incorporation.

Platelets from individuals with familial hypercholesterolemia show increased sensitivity to the aggregating atents, epinephrine and ADP. Since the mechanism of this abnormal sensitivity is unknown, we examined, in vitro, the influence of the plasma lipid environment on the function of platelets. The composition of plasma lipids was altered by the addition of sonicated cholesterol-dipalmitoyl lecithin liposomes which were "cholesterol normal" (cholesterol-phospholipid mole ratio [C/P] equals 1.0, "cholesterol rich" (C/P eauals 2.2), or "cholesterol poor" (C/P equals 0). Cholesterol-normal liposomes had no influence on platelet lipids or platelet function. In contrast, after incubation for 5 h at 37 degrees C with cholesterol-rich liposomes, normal platelets acquired 39.2% excess cholesterol with no change in phospholipids or protein. The percent increase in platelet membrane cholesterol was three-fold that of the granule fraction. The acquisition of cholesterol by platelets was associated with a 35-fold increase in sensitivity to epinephrine-induced aggregation (P less than 0.001) and 15-fold increase to ADP aggregation (P less than 0.001), as determined both by aggregometry and by [13C]serotonin release. Response to thrombin or collagen was unchanged. Platelets incubated with cholesterol-poor liposomes underwent a selective loss of 21.4% cholesterol and this was associated with an 18-fold reduction in their sensitivity to epinephrine. These studies demonstrate that the cholesterol content of platelets is dependent on the lipid composition of the milier. Cholesterol acquired by platelets may exert its effect on platelet function by a modification of the platelet membrane.

Adenosine Diphosphate↗

PubMed1975

Endocrine studies of the untreated progeny of thyroidectomized rats.

Experiments were conducted to assess late and persistent endocrine changes in the progeny of rats born and/or nursed by thyroidectomized (Tx) dams. Forty-five female rats were radiothyroidectomized several weeks before mating with normal males, and compared with the progeny of 26 control females. In all, 248 progeny were studied when adult. Tx dams had significantly reduced fertility (87% of controls), increased pup (11% versus 0) and maternal mortality (27% versus 0), and smaller litters (6.5 versus 11.8 pups/litter). It was shown that the offspring of thyroidectomized female rats had delayed eye opening (15.3 versus 14.3 days), smaller weaning (40.4 versus 54.4 g) and adult body weight (230 versus 260 g), smaller pituitary glands (12.2 versus 14.0 mg), and enlarged thyroid gland (14.2 versus 12.4 mg). Ovarian and testicular weight were decreased (73.9 versus 83.7 mg and 3.2 versus 3.6 g, respectively). The serum thyroid stimulating hormone (TSH) concentrations were increased from 53.8 to 84.4 muU/ml in the males. The pituitary TSH contents were not significantly altered, and the serum TSH response to thyrotropin releasing hormone (TRH) was normal. These persistent effects differed from the late effects of both fetal and neonatal hypothyroidism and neonatal underfeeding. Cross-fostering experiments showed that the diminished weaning weights were the result of the pups being nursed by the hypothyroid dams. The increased nursing mortality and the pituitary and thyroidal changes were the result of prenatal influences produced by the hypothyroid dams, since being nursed by a normal foster dam did not prevent them. The persistently enlarged thyroid glands and the elevated serum TSH in the male offspring of thyroidectomized dams suggested a permanent alteration in the set point of pituitary-thyroid regulation as the consequence of maternal hypothyroidism.

Adrenal Glands↗

PubMed1975

The late effects of neonatal hyperthyroidism upon the feedback regulation of TSH secretion in rats.

Rats made thyrotoxic with large doses of thyroxine (T4) during the neonatal period (neo-T4) show many abnormalities as adults. These usually include impaired body, pituitary and thyroid growth, diminished pituitary and serum TSH concentrations, a diminished serum T4 and a diminished response to PTU challenge and to thyrotropin-releasing hormone (TRH) stimulation. Experiments are presented which show that these rats are hypersensitive to feedback regulation by T4 in a manner similar to that seen after bilateral anterior hypothalamic lesions. They show a subnormal response to PTU challenge and an excessive suppression of serum TSH and goiter growth after T4. Pituitary TSH was less depleted in neo-T4 rats when a small dose of T4 was given daily with PTU and pituitary TSH was more sensitive to suppression by a larger dose of T4 in the neo-T4 group. There was an impaired rebound increase in pituitary TSH following a single inhibitory dose of T4 injected into the adult hypothyroid rat. Although the hypothalamic TRH content is increased in the neo-T4 rat, the circulating concentration of TRH was found to be significantly decreased, supporting the theory that the defects observed in the neo-T4 rat may be the consequence of an impaired hypothalamic secretion of TRH.

Animals↗

PubMed1975

Human middle ear corpuscles -- A light and electron microscopic study.

The human middle ear corpuscles originally described by von Troeltsch are examined by means of light microscopy in 124 subjects, and electron microscopy in 27 subjects. While the corpuscles are not observed in all 19 individuals under age six, and in all 20 adults who had a history of suppurative otitis media, an average of six corpuscles per temporal bone is found in 98 percent of 83 adult subjects who had no history of middle ear disease. Two-thirds of the corpuscles are located in the mastoid, and the remainder in the middle ear. Often, they become bifurcated or trifurcated. Although light microscopy shows that the corpuscle is formed by lamellar capsules and a central core resembling pacinian corpuscles, electron microscopic study failed to confirm that this structure is a typical pacinian corpuscle. Subsequently, possible physiological significance of this corpuscle is discussed.

Adolescent↗

PubMed1974