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Biomedical subjects

J A Knight

Publications and source records attributed to J A Knight.

At least 91 records · Page 5Linked to original sources
PubMed1979

Neutral protease inhibitors from human intervertebral disc and femoral head articular cartilage.

Assays of several proteases, incorporating guanidinium chloride extracts of human femoral head cartilage and intervertebral disc, demonstrated that both tissues contain inhibitors of certain serine proteases. Trypsin, chymotrypsin and a granule extract of human polymorphonuclear leukocytes containing elastase and cathepsin G activities, were inhibited by low molecular weight fractions prepared by Sephadex G-75 chromatography. Using a radioassay, it was further shown that these fractions inhibit proteolysis of cartilage proteoglycan. The inhibitor in intervertebral disc is concentrated in the nucleus pulposus, with a decreasing gradient to the periphery of the annulus fibrosus. It is proposed that these inhibitors confer at least partial protection against pathological proteolysis of the proteoglycans in human articular cartilage and nucleus pulposus.

Animals↗
PubMed1979

Suppression of mitochondrially-determined resistance to chloramphenicol and paromomycin by nuclear genes in Saccharomyces cerevisiae.

Phenotypic "revertants" of a drug resistant strain of Saccharomyces cerevisiae were induced by mutgenesis with manganese. Several of these drug sensitive mutants have been shown to result from mutations in the nuclear genome that cause phenotypic modification (suppression) of the mitochondrially-determined drug resistant genotype. Four mutants carrying a single recessive nuclear gene capable of modifying mitochondrial chloramphenicol resistance are described; these may be assigned to three complementation groups. Chloramphenicol resistant mutants mapping at five separate mitochondrial loci are described. At least two of the nuclear genes cause modification of mitochondrial chloramphenicol resistance determined by mutations at three of these loci, but the other two loci are apparently non-suppressible by these nuclear alleles. This indicates that these modifiers do not act by causing a general decrease in cellular or mitochondrial permeability to the drug. A single dominant nuclear modifier of mitochondrial paromomycin resistance has been identified. It is non-allelic to and does not interact with the genes modifying mitochondrial chloramphenicol resistance.

Chloramphenicol↗
PubMed1977

Improved colorimetry of urinary 3-methoxy-4-hydroxyphenylacetic acid (homovanillic acid).

Homovanillic acid is an important metabolite of dopamine, and a high proportion of patients with neuroblastoma excrete increased amounts of it in their urine. When this diagnosis is suspected, both homovanillic acid and vanilmandelic acid should be measured, because such a combined measurement reportedly leads to detection of 95% of cases. Although rapid and reliable chemical methods are available for vanilmandelic acid, the same is not true for homovanillic acid. We report here a colorimetric method for homovanillic acid that reasonably fills this void and that can be used in most clinical laboratories. In addition, we present normal values determined for children of various age groups.

Adolescent↗
PubMed1975

Venous serum, capillary serum, and capillary plasma compared for use in determination of lactate dehydrogenase and aspartate aminotransferase activities.

Lactate dehydrogenase and aspartate aminotransferase activities in capillary serum or plasma were significantly greater than in simultaneously assayed venous serum, the greatest differences being between capillary and venous serum. Although some difference is attributable to tissue fluid contributions, platelets seem to account for most of it, with possible small contributions from leukocytes. Capillary tube size and type appear to be important factors. We recommend that when capillary blood is to be used for enzyme assay, it should be processed as plasma.

Aspartate Aminotransferases↗