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Biomedical subjects

A Jones

Publications and source records attributed to A Jones.

At least 631 records · Page 35Linked to original sources
PubMed1978

Egg-laying and hatching rhythms in the monogenean Diplozoon homoion gracile from the southern barbel (Barbus meridionalis).

Diplozoon homoion gracile from the southern barbel (Barbus meridionalis) displays an egg-laying and an egg hatching rhythm, the latter being more clearly defined. Egg laying continues both day and night but significantly more eggs are laid at night. The oncomiracidia hatch at dusk. If parasite eggs are eaten by the host they pass through the gut undamaged and hatch normally.

Animals↗
PubMed1978

The relationship between circadian variations in circulating thyrotrophin, thyroid hormones and prolactin.

Half-hourly blood samples were taken from six clinically euthyroid men over a continuous period of 24 h. Their concentrations of total thyroxine (T4), total triiodothyronine (T3), thyrotrophin (TSH) and prolactin (PRL) were assessed together with the degree of unsaturation of thyroid hormone binding proteins as determined by the thyroid hormone uptake test (THUT). Both T3 and T4 were also measured in urine samples collected serially during the same 24 h period. Significant circadian changes in serum TSH, THUT, serum and urine T4 and serum PRL were demonstrated in all subjects. TSH showed a reciprocal pattern to serum T4, with higher levels during the evening and at night than the daytime. This TSH pattern did not coincide with PRL secretion. Further studies on the same subjects did not show any significant effect of posture, corticosteroid or T4 administration upon circadian changes in TSH. There appeared to be no consistent circadian changes in serum or urinary T3. It seems likely that the TSH circadian rhythm is centrally determined and that free T3 levels are maintained more or less constant by variation in peripheral conversion from T4.

Adult↗
PubMed1978

Biosynthesis of chloramphenicol in Streptomyces sp. 3022a. Properties of an aminotransferase accepting p-aminophenylalanine as a substrate.

In the presence of alpha-ketoglutarate, cell-free extracts of Streptomyces species 3022a catalysed transfer of the amino group from p-aminophenylalanine, yielding an unstable product similar to that obtained by the action of D- and L-amino acid oxidases on the amino acid. The enzyme, purified 16-fold from cell homogenates by chromatography on ion-exchange celluloses, hydroxyapatite, and cross-linked dextran gel, has a molecular weight of 90 000 and a broad pH optimum at 8.0. It is active with L-phenylalanine and L-tyrosine as well as p-amino-DL-phenylalanine as amino donors, and its relative activity towards these substrates did not change during purification. Polyacrylamide disc-gel electrophoresis of the partially purified enzyme gave single zones with identical mobility when the gels were assayed for activity with p-aminophenylalanine and tyrosine as amino donors. The results indicate that synthesis of p-aminophenylalanine en route to chloramphenicol uses a multispecific aminotransferase for aromatic amino acids. With L-phenylalanine as substrate, the preferred amino-accepting co-substrate was alpha-ketoglutarate. Some kinetic constants for the enzyme were determined, and its requirement for pyridoxal phosphate was demonstrated.

Amino Acids, Diamino↗
PubMed1978

Effect of the dopamine agonist, lergotrile mesylate, on circulating anterior pituitary hormones in man.

The effects of the ergoline derivative, lergotrile mesylate, on the serum levels of PRL, GH, TSH, LH, FSH, cortisol, and blood sugar were studied in six normal males. The effects of lergotrile mesylate on the serum levels of GH and PRL were also studied in eight patients with acromegaly and in two with idiopathic hyperprolactinemia. In the normal subjects, 2 mg oral lergotrile lowered basal PRL levels after 90 min and markedly impaired the PRL response to TRH (200 micrograms iv); the mean peak value +/- SE was 8.3 +/- 1.1 micrograms/liter, compared to the control value of 66.6 /+- 11.3 micrograms/liter. Lergotrile raised serum GH levels in five of the six subjects to peaks of 8-49 micrograms/liter, compared to 2-8 micrograms/liter after placebo. In three subjects, the GH response to lergotrile was attenuated by the prior administration of the dopamine antagonist, metoclopramide (10 mg orally). Lergotrile had no effect on FSH and LH levels under basal conditions or after the gonadotrophin-releasing hormone (GnRH; 100 micrograms iv). Circulating TSH levels were unaltered basally but impaired after TRH. Blood sugar levels were unaltered; serum cortisol was elevated in five of six subjects; there was a brief depression of diastolic blood pressure, but no change in pulse rate. The side effects after lergotrile were variable, with drowsiness as a consistent feature. These actions are similar to those of bromocriptine (an ergot derivative treatment of hyperprolactinemia and acromegaly, to suppress PRL and GH secretion, and in parkinsonism. Therefore, it may be expected that lergotrile could fulfill these clinical uses; however, in the studies comparing the effects of single oral doses of lergotrile (2 mg) and bromocriptine (2.5 mg) on GH and PRL secretion in patients with acromegaly and hyperprolactinemia, lergotrile in the dose used has been found to have an earlier onset and shorter duration of action.

Acromegaly↗
PubMed1977

Contacts between young patients with Hodgkin's disease. A case-control study.

To investigate the possibility that Hodgkin's disease (H.D.) may be transmitted from person to person, a case-control study was conducted among 87 of the 97 H.D. patients diagnosed under the age of 40 years in the period 1962-71, resident at the time of diagnosis in a defined area around Oxford. For each of the 87 H.D. patients a matched control patient was selected with a diagnosis other than that of a chronic or malignant disease. H.D. patients and controls were interviewed to determine their places of schooling and work and attempts were made to link pairs of patients who had attended the same school or work place at the same time. The findings do not support the hypothesis that H.D. patients may pass on the disease to others. Among the H.D. patients, links between 40 pairs were established, compared with 40-75 links expected, based upon the experience of all 174 persons studied. The only finding which was statistically significant (p approximately 0-04) arose when H.D. patients were considered to be "susceptible" from 10 to 5 years before diagnosis and "infective" from diagnosis to 2 years after diagnosis: 7 pairs of links were found against 2-75 expected. However, since 7 postulated periods of susceptibility and 9 postulated periods of infectivity were examined, this one "statistically significant" finding might easily have arisen by chance.

Adolescent↗
PubMed1977

Urinoma.

A urinoma is a mass formed by encapsulated extravasated urine. It may follow closed renal injury, surgical operation or arise spontaneously in the presence of obstruction. The essential factors are continued renal function, rupture of the collecting system and distal obstruction. The extravasating urine is localised within the perirenal fascia and stimulates an intense fibrous reaction which forms a thick wall. Early diagnosis is important for successful treatment. The clinical features include malaise, vague abdominal pain, weight loss and a palpable mass. Plain films usually reveal a mass with loss of the retroperitoneal landmarks. High-dose excretion urography usually shows renal displacement, hydronephrosis and extravasation of contrast medium into the urinoma. Should renal function be inadequate for diagnosis, renal puncture, preceded by ultrasound examination, is the investigation of choice.

Adult↗
PubMed1977

Serum prolactin and oestradiol levels at different stages of puberty.

Serum prolactin and oestradiol levels were measured in 183 children who were staged for pubertal development. Mean serum prolactin levels are higher in girls than in boys at stage 3 of pubertal development. In girls prolactin levels rise at stage 2, and are higher after menarche; in boys there is no change in prolactin levels. In this study serum oestradiol correlates with prolactin in the girls, but not in the boys.

Adolescent↗
PubMed1976

Genomic transcriptional activity and the structure of chromatin.

Nucleic acid hybridisation has shown that micrococcal nuclease-derived chromatin subunits from the cells of Xenopus laevis contain fragments of ribosomal 28S, 18S and 5S RNAS within the population of 200 base-pair pieces of DNA. Subunits from cultured embryonic cells actively transcribing ribosomal RNA contain only 70-74% of the cistrons present in undigested wild-type DNA, while subunits from adult erythrocytes not active in RNA transcription contain close to 90% of the ribosomal cistrons in native chromatin.

Animals↗
PubMed1976

Effects of carotid occlusion and clonidine on renin secretion in anaesthetized dogs.

1. Sympathetic reflexes were activated by carotid occlusion in anaesthetized dogs in which changes in renal perfusion pressure were prevented. This produced a prompt and reversible increase in plasma renin activity. 2. Administration of clonidine decreased plasma renin activity, arterial pressure and heart rate and blocked the renin secretory and blood pressure responses to carotid occlusion. 3. These results support the hypothesis that the suppression of renin secretion by clonidine is a consequence of the decrease in sympathetic activity produced by this drug.

Animals↗
PubMed1976

Incidence of respiratory allergy not increased after anesthesia in infancy.

A 12-year follow-up study of children who had had operations with general anesthesia in infancy and of nonhospitalized children of the same age showed almost identical incidences of respiratory allergy in the test and control groups. General anesthesia in infacy does not predispose to respiratory allergies in childhood.

Adolescent↗