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Biomedical subjects

J L Stirling

Publications and source records attributed to J L Stirling.

53 records · Page 3Linked to original sources
PubMed1978

Effects of exercise, altitude, and food on blood hormone and metabolite levels.

Measurements of blood glucose and plasma free fatty acids (FFA), thyroxine (T4), free thyroxine (FT4), triiodothyronine (T3), and thyroid-stimulating hormone (TSH) were made on samples taken from fed and fasted human subjects while at rest and immediately after 20 min moderate exercise. Six subjects were studied on successive weeks before (LA1), during (HA1, HA2, HA3), and after (LA2) a 3-wk sojourn at high altitude (3,650 m). The subjects and location were the same as those used for the energy expenditure measurements described in the preceding paper (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 45:345--349, 1978). The most marked effect of altitude was to potentiate the rise in FFA due to exercise. This effect was most noticeable in fed subjects during HA1 and HA2. Changes in the plasma levels of the thyroid hormones correlated with the FFA changes and, once again, exercise at altitude caused the greatest increase in circulating levels. Possible causes of the parallel changes in FFA and thyroid hormone levels and their relationship to changes in energy metabolism are discussed.

Acclimatization↗
PubMed1977

Glycosidases from the culture medium of Physarum polycephalum.

Eight exo-glycosidase activities were detected in the axenic culture medium of the myxomycete, Physarum polycephalum. The secretion of each enzyme examined followed the growth curve and continued during the stationary phase after the cessation of growth. Two or more forms of each enzyme were detected after electrophoretic separation. The beta-N-acetyl-D-hexosaminidase activity was readily separated into its two electrophoretic forms, X and Y, which were purified 145- and 306-fold respectively. These beta-N-acetyl-D-hexosaminidases had several similar characteristics. Evidence is presented that the major electrophoretic form of alpha-D-galactosidase is heterogeneous. The possible functions of extracellular glycosidases in teir occurrence and properties.

Culture Media↗
PubMed1976

Properties and developmental regulation of an alpha-d-galactosidase from Dictyostelium discoideum.

An alpha-D-galactosidase was detected in cells of the cellular slime mould, Dictyostelium discoideum, at all stages of development. Its specific activity was highest during early development (interphase), and this accumulation of enzyme appears to require protein synthesis de novo. Its subcellular distribution differs from that of other D. discoideum glycosidases, since most activity was recovered in the soluble fraction. No evidence was obtained for more than one isoenzymic form after subjection of extracts to electrophoresis and various chromatographic procedures. It is excreted from the cell during development, but no evidence was found for an extracellular function for the enzyme.

Cycloheximide↗
PubMed1974

NN'-diacetylchitobiase activity in Tay-Sachs disease and Sandhoff's disease.

In Tay-Sachs disease and Sandhoff's disease respectively, one of the N-acetyl-beta-hexosaminidases (form A) or both (forms A and B) are absent, but glycosaminoglycans containing N-acetylhexosamines are not accumulated. The presence of NN'-diacetylchitobiase in livers from patients with these diseases raises the possibility that this new enzyme is involved in the metabolism of glycosaminoglycans rather than the enzymes previously described.

Centrifugation↗
PubMed1968

N-Acetyl-beta-glucosaminidases in human spleen.

1. The N-acetyl-beta-glucosaminidase of human spleen has been separated by gel electrophoresis into two components, an acidic form A and a basic form B. 2. The two forms are readily separated on DEAE-cellulose and have been concentrated 50-fold and sevenfold respectively. 3. They show similar K(m) values towards 4-methylumbelliferyl N-acetyl-beta-d-glucosaminide, and have the same pH optima when compared in citrate, phosphate or acetate buffers. They are inhibited to a similar extent by acetate, heparin, N-acetylgalactosaminolactone, N-acetyl-beta-d-galactosamine and N-acetyl-beta-d-glucosamine. Specificity for C-4 orientation is not absolute and p-nitrophenyl beta-galactosaminide is also hydrolysed but at a rate only 11.6% of that for the corresponding glucosaminide. 4. N-Acetyl-beta-glucosaminidase B is stable over a wider pH range than is N-acetyl-beta-glucosaminidase A, and is less easily denatured by heat. 5. Tissue fractionation indicates that both the A and B forms are present in the lysosomal fraction, whereas the supernatant contains the A form only. 6. Evidence is presented to indicate that the A form contains a number of sialic acid residues.

Acid Phosphatase↗