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Biomedical subjects

A H Brady

Publications and source records attributed to A H Brady.

15 recordsLinked to original sources
PubMed1978

Solubilization and partial characterization of a phosphoprotein phosphatase from human myelin.

The phosphoprotein phosphatase (phosphoprotein phosphohydrolase, EC 3.1.3.16) solubilized from human central nervous system myelin has been shown to possess a comparatively high degree of specificity towards myelin basic protein, a constituent of the membrane and most likely its natural substrate, rather than the mixed histones. The enzyme has a pH optimum of 7.5. Hydrolysis of both the substrates is stimulated by dithiothreitol and is almost completely dependent upon the presence of divalent metal ions. The maximum rate of dephosphorylation of basic protein is attained in the presence of 125 micrometer Mn2+ whereas a much higher concentration of Mg2+ (50--100 mM) is required for the optimal dephosphorylation of histones. The dephosphorylation of basic protein was also stimulated by Triton X-100 (0.15%, v/v) and was shown to result from a 3-fold increase in the V of the reaction catalyzed by the phosphatase. The apparent Km values for basic protein and histones were unaffected by the presence of Triton X-100 and were found to be approx. 1 and approx. 160 micrometer, respectively. Under optimal conditions of assay, the phosphatase cleaved approx. 32 and approx. 0.7 nmol of orthophosphate.min-1.mg-1 of protein from basic protein and histones, respectively.

Corpus Callosum↗
PubMed1975

Collagenase in scleroderma.

Collagenase activity was measured by direct assay in skins from 12 patients afflicted with systemic sclerosis. In seven of those cases where extensive involvement of the forearm and trunk skin existed, collagenase activity of the involved skin was minimal or absent. Moreover, in the same patient, regions of marked skin involvement (e.g., forearm) showed no collagenase activity, when clinically uninvolved areas (thigh) exhibited normal or nearly normal levels of enzyme activity. In other patients where clinical symptoms were systemic and not associated significantly with the skin, collagenase activity approximated normal levels. Measurements of collagenase activity and tensile strength in another condition (basal cell carcinoma) that includes changes in mechanical properties of skin that any be regarded as the opposite end of the spectrum from those of sclerodermatous skin support a general correlation between collagenase activity and tensile strength. These studies indicate that the major defect responsible for the hidebound skin lesions of scleroderma may be decreased collagenase activity.

Adult↗
PubMed1971

Circular dischroism of bradykinin and related peptides.

1. The circular dichroism of bradykinin and a number of its analogues and homologues was measured over the spectral range 200-300nm. All of the biologically active peptides showed maxima at 220nm and minima at 235nm. The spectra were independent of solvent and temperature. The vibronic transitions of phenylalanyl residues in the 250-280nm range showed no evidence of intra- or inter-molecular interactions. We take this as evidence that bradykinin and its biologically active analogues and homologues exist in solution as disordered chains. 2. None of the analogues with spectra unlike bradykinin possessed biological activity. However, peptides such as retro-bradykinin, des-6-serine-bradykinin, des-1-arginine-bradykinin and des-9-arginine-bradykinin produced spectra like that of bradykinin but were devoid of biological activity. Although we could not identify spectral features that were clearly correlated with biological activity, it appears unlikely that highly ordered peptides of the same amino acid composition as bradykinin would possess bradykinin-like effects.

Amino Acids↗