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Biomedical subjects

J Chayen

Publications and source records attributed to J Chayen.

At least 127 records · Page 7Linked to original sources
PubMed1977

Cold cardioplegia or continuous coronary perfusion? Report on preliminary clinical experience as assessed cytochemically.

Myocardial preservation by continuous coronary perfusion is compared with cold cardioplegia. The 1 L. of St. Thomas' cardioplegic protective solution used for infusion into the coronary arteries was at 4 degrees C. and had a normal electrolyte content except for raised concentrations of magnesium and potassium and the addition of procaine. Myocardial preservation was assessed by cytochemical grading of myocardial biopsy specimens and also by the requirement for significant inotropic support postoperatively. In aortic valve replacements with an aortic occlusion time of 1 1/2 hours, both techniques afforded a similar degree of preservation, except that the inner half of the myocardium was markedly better preserved by cold cardioplegia. After 2 hours in double valve replacements, a single cardioplegic infusion was not as effective as continuous coronary perfusion, but this could be corrected by a second infusion of the cardioplegic solution after an hour.

Aortic Valve↗
PubMed1976

Changes in alkaline phosphatase activity in periosteal cells in healing fractures.

The quantitative changes in alkaline phosphatase activity in the periosteal cells close to the fracture in rat metatarsal bones has been measured during the first 5 days postfracture. This study has been made possible by two technological advances, firstly the development of cryostat microtomy for cutting unfixed, undemineralised bone, and secondly the use of scanning and integrating microdensitometry for quantifying the activity in each periosteal cell. The results showed a loss of alkaline phosphatase activity close to the fracture site, with activity rising to normal values 0.8-1.0 mm from the site. No alkaline phosphatase activity was found in the cells which proliferated from the periosteum. It is suggested that reduced glutathione could cause such inhibition.

Alkaline Phosphatase↗
PubMed1975

The effect of thyrotrophin on oxidative activity in thyroid follicle cells.

Biochemical evidence, based on supra-physiological concentrations of thyrotrophin (TSH), has indicated that this hormone increases the NADP concentration in thyroid follicle cells. The hormone is believed to act both to enhance the reoxidation of the reduced coenzyme and to generate NADP from NAD. The latter effect, mediated by NAD-+-kinase, could be a major control mechanism in thyroid metabolism. In the present study increased sensitivity has been obtained by the use of maintenance culture and of microdensitometry for measuring enzyme activity in the follicle cells. Using low physiological (0.1 muU/ml), and sub-physiological concentrations of the hormone as are used in the cytochemical bioassay systems, it has been shown that the rate of reoxidation of NADPH is enhanced by TSH. Moreover the NAD-+-kinase activity is also greatly increased, and shows a direct relationship to the concentration of the hormone acting on the segments of the gland in vitro. It is possible that this phenomenon could be used to assay TSH. The results indicate that NAD-+-kinase activity may play a significant part in the control of pentose-shunt oxidation in thyroid follicle cells.

Animals↗
PubMed1975

The direct measurement of cytochrome P450 in unfixed tissue sections.

A method for the measurement of cytochrome P-450 in unfixed cryostat sections is described. The sections are incubated for 10 minutes at room temperature in a buffered solution containing polyvinyl alcohol and sodium dithionite. Two incubations are performed on serial sections, one in nitrogen and the other in carbon monoxide. Readings are taken on a Vickers M85 microdensitometer fitted with a high sensitivity photomultiplier amplifier system, the measurements being made on corresponding fields in the serial sections. Subtraction of the nitrogen values from the carbon monoxide values, after allowing for an absorption shift, gives the absolute spectrum of cytochrome P450. The subtraction corrects for the tissue content of other haem-containing proteins. The cytochrome P450 spectrum shows a sharp maximum at 450 nm, and two other minor components absorbing at 444 nm and 458 nm. The content of cytochrome P450 in animals fed with phenobarbitone was 2.4 times greater than in control animals.

Animals↗
PubMed1974

Comparison of effects of long-term corticotrophin and corticosteroid treatment on responses of plasma growth hormone, ACTH, and corticosteroid to hypoglycaemia.

The development of the highly sensitive cytochemical bioassay for ACTH has permitted the measurement of plasma ACTH levels during the insulin hypoglycaemia test (I.H.T.) in patients treated with corticosteroids and corticotrophin. The ACTH, corticosteroid, and growth hormone (GH) responses in the I.H.T. were measured in three groups of 12 rheumatoid arthritis patients. One group was receiving long-term corticotrophin treatment, the second was undergoing long-term corticosteroid treatment, and the third had never received systemic hormone therapy. The increments in plasma ACTH, corticosteroids, and GH were diminished in the corticosteroid-treated group, as were increments in plasma GH and ACTH in the corticotrophin-treated group; but in this group the corticosteroid increment was normal. Examination of the area under the curve of the ACTH response showed that the total amount of ACTH secreted was normal though the rate of secretion was reduced. In the corticosteroid-treated group both rate and total secretion were diminished.

Adrenal Cortex Hormones↗