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Biomedical subjects

J Bennett

Publications and source records attributed to J Bennett.

At least 343 records · Page 19Linked to original sources
PubMed1977

The interaction of p-nitrophenyl carbamate with urease.

1. p-Nitrophenyl carbamate and thiourea have been shown to be substrates for urease (urea amidohydrolase, EC 3.5.1.5) 2. Urease has been shown to have a lower Km, 0.67 mM, with p-nitrophenyl carbamate than with urea, 2.0 mM. 3. The V of urease for the hydrolysis of urea, p-nitrophenyl carbamate and thiourea has been shown to be the same, indicating a common rate-limiting step. 4. A mechanism has been proposed for urease where the initial rate-limiting step is the release of a molecule of ammonia from the substrates.

Carbamates↗
PubMed1977

Endocrine studies in the untreated F1 and F2 progeny of rats treated neonatally with thyroxine.

When neonatal rats are made hyperthyroid with large doses of thyroxine during the first 5 days of life, they develop hypothalamopituitary, thyroidal and gonadal abnormalities that persist through life. When female rats, which have been treated neonatally, are subsequently mated to normal males, their offspring show unexpected gonadal and thyroidal defects, such as reduced weaning weight and delayed vaginal opening and first estrus in females; males show a significant increase in relative thyroid weight and a significant decrease in ventral prostate weight. Cross-fostering was done to separate prenatal from postnatal influences. Even more surprising was the finding that when the untreated female F1 progeny were mated with normal males, the untreated F2 progeny showed more defects and to a greater degree than those present in the maternal parent.

Animals↗
PubMed1976

Suppression of sympathetic nervous function in low-renin essential hypertension.

Study of general haemodynamics in 15 patients with low-renin essential hypertension showed haemodynamic and pathophysiological heterogeneity. However, there was suppression of sympathetic nervous system function in all low-renin patients, regardless of haemodynamic pattern. Subnormal sympathetic nervous activity was manifested by a low normal mean plasma-noradrenaline concentration at rest, diminished noradrenaline responsiveness to postural stimulation, and a reduced blood-pressure response to the indirectly acting sympathomimetic amine tyramine. It is proposed that the syndrome of low-renin essential hypertension is of diverse aetiology, but with secondary sympathetic nervous system underactivity as a feature common to the various forms. The low plasma-renin activity is probably an expression of defective sympathetic nervous system stimulation of renin release.

Adult↗
PubMed1976

Comparison of intensive versus moderate chemotherapy of lymphocytic lymphomas: a progress report.

In an Easter Cooperative Oncology Group trial, Cytoxan-prednisone (CP) Induction was compared to BCNU-prednisone (BP) in 273 patients with lymphocytic lymphoma. Response rates were comparable, with 21% achieving complete response and 40%, partial response. Patients with a nodular pattern responded better. Maintenance phase comparing cyclic intensive therapy (BCVP) with intermittent chlorambucil revealed the superiority of BCVP as demonstrated by improvement of the quality of response and somewhat longer remissions. The value of the Rappaport classification in the evaluation of lymphoma chemotherapy results is discussed. It is suggested tha NHL be separated into "favorable" and "unfavorable" groups, based on the presence or absence of nodularity and treatment schedules devised accordingly.

Adult↗
PubMed1976

Behavior and single gene substitution in Drosophila melanogaster. I. Mating and courtship differences with w, cn, and bw loci.

The effect of single allele substitutions into an isogenic background in Oregon-R inbred lines of Drosophila melanogaster on courtship and mating patterns has been studied. A comparison has been made between the white locus w, wco, we, the wild type w+, cn, bw, and cn bw to test the effect of eye pigmentation in influencing courtship and mating patterns. It was found that w, we, wco, cn, and bw females were more successful in mating than were wild-type and cn bw females, cn bw females being less successful than wild-type females. Also, w and cn bw males were equally successful in mating but less successful than wild-type males during the 20-min test period. The mutant males performed as well as the wild-type after courtship was initiated. The behavioral parameters measured were (1) courtship latency, the time from exposure of male to female until orientation; (2) mating speed, the time from beginning of orientation of male to female until successful copulation, and (3) copulation time.

Animals↗
PubMed1976

Observations on the untreated progeny of hypothyroid male rats.

The untreated progeny (F1) of hypothyroid male rats that were either radiothyroidectomized (Tx) or had the neo-T4 syndrome (an endocrine disorder produced by large doses of thyroxine (T4) injected during the neonatal period) were studied. The mother rats were all normal. The fathers never had any contact with their progeny. Unexpectedly, the progeny usually showed delayed eye opening, decreased weaning weights, and increased final body weight. The thyroid glands from F1 offspring of both Tx and neo-T4 fathers were enlarged significantly in all but F1 males of Tx fathers. The F1 of Tx fathers had significantly smaller uteri, both absolutely and relatively. The ovaries were significantly larger, whereas the testes were significantly smaller. Pituitary TSH, stalk-median eminence (SME) TSH, and serum TSH were all normal with the exception of an increase in SME TSH in F1 males born of neo-T4 fathers. The response to thyrotropin releasing hormone (TRH) stimulation of the F1 adult progeny of neo-T4 fathers was significantly blunted in the males, whereas the response was normal in offspring of Tx fathers. The mechanisms by which hypothyroid fathers caused changes in their progeny is not known.

Animals↗
PubMed1976

Lifelong alterations in endocrine function resulting from brief perinatal hypothyroidism in the rat.

The late consequences of a brief period of perinatal hypothyroidism were studied in the rat by giving propylthiouracil (PTU) prenatally to the mothers and/or neonatally for 5 days to the pups. Perinatal hypothyroidism produced a delay in eye opening, a diminution in weaning weight, a delay in puberty and first estrus, and a prolongation of estrus cycles. The neo-PTU rats usually had a persistently enlarged thyroid gland associated with an elevated pituitary, hypothalamic, and serum thyroid-stimulating hormone (TSH) concentration. The metabolic clearance rate of TSH and response to luteinizing hormone-releasing hormone (LH-RH) were normal. The response to thyrotropin-releasing hormone (TRH) stimulation was significantly blunted in adult neo-PUT males, suggesting secondary or tertiary hypothyroidism. As a result of these studies, serious thought should be given to the possible consequences of antithyroid drug therapy of pregnant women, and certainly all pregnant hypothyroid women should receive full replacement therapy.

Animals↗
PubMed1975

Late effects of neonatal undernutrition and overnutrition on pituitary-thyroidal and gonadal function.

Neonatal rats were underfed or overfed and then, at weaning, placed on a normal diet and allowed to mature. Although overfed rats were obese at weaning, they were of normal weight when mature. The underfed rats remained smaller all their lives. The endocrine organs did not share in this retardation, and were actually larger in several instances when expressed per 100 g body weight. Underfed rats also had delayed eye-opening, normal puberty and normal estrous cycles. Pituitary, hypothalamic and serum TSH concentrations were normal, or even increased (in the underfed females). The responses to propylthiouracil and to thyrotropin-releasing hormone (TRH) were both normal. Thus the tertiary hypothyroidism reported in underfed rats 16 days old did not persist into adult life. In all comparisons the males had higher serum TSH concentrations than females and usually had a greater response to TRH stimulation. The various persistent endocrine abnormalities resulting from neonatal thyrotoxicosis differ from those seen after neonatal caloric deprivation in all pertinent regards except that both have reduced body weights.

Animal Nutritional Physiological Phenomena↗
PubMed1975

Altered cardiac responsiveness and regulation in the normal cardiac output type of borderline hypertension.

Of 145 patients with borderline hypertension, 30% had increased resting cardiac index (QI), whereas the remainder had normal values. The specific aim of this study was to investigate cardiac regulation in patients who had normal resting QI. Eighty-five control subjects were used for comparison. At rest, patients with normal QI showed evidence of decreased parasympathetic inhibition; the QI after injection of atropine increased less than in control subjects. After complete cardiac autonomic blockade with propranolol and atropine, QI and stroke volume were significantly lower in patients than in control subjects. The mechanism of this low QI was further analyzed. Central blood volume, which strongly correlates with stroke volume, was used as an estimate of the cardiac venous filling. After blockade, stroke volume was decreased in patients, but central blood volume was normal. Patients also showed a decreased heart rate and QI response to infusion of isoproterenol. It is therefore postulated that two components may be responsible for the low QI in the "denervated" heart: patients exhibit a decreased responsiveness to sympathetic stimulation, and they may also be less responsive to venous filling. Behind the facade of cardiac normality in these borderline hypertensive patients with normal cardiac output, there is evidence of altered autonomic control of the heart (decreased vagal inhibition) and of changed cardiac response to sympathetic stimulation and possibly to venous filling.

Adult↗