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Biomedical subjects

J W Bird

Publications and source records attributed to J W Bird.

At least 37 records · Page 2Linked to original sources
PubMed1980

Proteinases in cardiac and skeletal muscle.

Although changes in proteolysis in muscle tissue are now well documented for a variety of physiological and pathological conditions, the mechanism of degradation of cellular protein during normal protein turnover remains to be elucidated. Data from several laboratories have suggested the involvement of alkaline serine proteinases. Recent studies have questioned these results, and demonstrated that the serine proteinases are of mast cell origin and are not present in muscle cells. The only proteinases to date that have been shown to be present in muscle cells and capable of degrading myofibrillar proteins are Ca2+-activated proteinase, cathepsin B, and cathepsin D. Recent interest and developing awareness of endogenous enzyme inhibitors in cells may unmask many new enzymes.

Animals↗
PubMed1977

Degradation of myofibrillar proteins by cathepsins B and D.

1. The procedure of Barrett [(1973) Biochem. J.131, 809-822] for isolating cathepsins B and D from human liver was modified for use with rat liver and skeletal muscle. The purified enzymes appeared to be similar to those reported in other species. 2. Sephadex G-75 chromatography of concentrated muscle extract resolved two peaks of cathepsin B inhibitory activity, corresponding to molecular weights of 12500 and 62000. 3. The degradation of purified myofibrillar proteins by cathepsins B and D was clearly demonstrated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. After incubation with enzyme, the polypeptide bands representing the substrates decreased in intensity and lower molecular weight products appeared. 4. Cathepsins B and D, purified from either rat liver or skeletal muscle, were shown to degrade myosin, purified from either rabbit or rat muscle. Soluble denatured myosin was degraded more extensively than insoluble native myosin. Degradation by cathepsin B was inhibited by lack of reducing agent, or by myoglobin, iodoacetic acid and leupeptin, but not by pepstatin. The same potential modifiers were applied to cathepsin D, and only pepstatin produced inhibition. 5. Rat liver cathepsin B had a pH optimum of 5.2 on native rabbit myosin. The pH optimum of cathepsin D was 4.0, with a shoulder of activity about 1pH unit above the optimum. 6. Rat liver cathepsins B and D were demonstrated to degrade rabbit F-actin at pH5.0, and were inhibited by leupeptin and pepstain, respectively. 7. The degradation of myosin and actin by cathepsin D was more extensive than that by cathepsin B.

Actins↗
PubMed1977

Effect of ovarian hormones on lysosomal acid hydrolase activities in rat myometrium.

The activities of the lysosomal acid hydrolases-cathespin D, acid phosphatase, beta-N-acetylglucosaminidase, and beta-glucuronidase-were measured in rat myometrium under the following hormonal conditions: during the estrus stage of the estrous cycle (NE); at 1,2, and 3 wk after ovariectomy; and in 3-wk postovariectomized females after hormone replacement therapy with 17 beta-estradiol (E2), progesterone (P), or E2 + P. Activities per milligram protein and per milligram DNA of the enzymes were significantly decreased after ovariectomy and were restored to the NE level or above after injecting E2 or E2 + P. Lysosomal enzyme activities did not change with hormonal state in hypophysectomized rats, suggesting that other hormones are required for mediation of enzyme activity. Acid hydrolase activities in other tissues and nonlysosomal enzyme activites in the myometrium did not fluctuate with hormonal state. Studies of lysosomal membrane integrity suggested that one population of lysosomes richer in cathepsin D and acid phosphatase and another rich in beta-N-acetylglucosaminidase and beta-glucuronidase may be present in rat myometrium. Estrogen seemed to labilize the lysosomal membrane of at least the latter of the two proposed populations of myometrial lysosomes.

Acetylglucosaminidase↗
PubMed1977

Degradation of myofibrillar proteins by cathepsins B and D.

Cathepsin B and cathepsin D were purified from rat liver and skeletal muscle. Electrophoretic analyses revealed that the enzymes were highly purified, and isoelectric focusing demonstrated multiple forms of both enzymes. Purified actin and myosin, as well as actin and myosin in myofilaments and myofibrils, were degraded by the purified cathepsins B and D. Degradation of myosin was completely blocked by the cathepsin B and D inhibitors, leupeptin and pepstatin, respectively. Cathepsins B and D were visualized by electron microscopy, using CBZ-Ala- Arg-Arg-4-methoxy-beta-naphthylamine and BZ-Arg-Gly-Phe-Leu-4-methoxy-beta-naphthylamine as substrates.

Animals↗
PubMed1975

Distribution of lysosome populations in rat cardiac tissue.

The post-nuclear fraction of rat heart tissue was fractionated by isopycnic zonal centrifugation in sucrose gradients, followed by differential centrifugation of the zonal fractions (rho-S fractionation). The distribution of 5 lysosomal acid hydrolases, a protease with neutral and alkaline activity and several marker enzymes for cell organelles (catalase, Ca2+-ATPase, cytochrome oxidase, glucose-6-phosphatase and muramidase) were studied. Three major lysosomal populations were described with equilibrium densities of 1.09, 1.17, and 1.23 gms cc-1 (omega2t = 1.54 X 10(11) rad2 sec-1), and a continuum in the size of these particles at the three different densities.

Adenosine Triphosphatases↗
PubMed1970

Lysosomes in skeletal muscle tissue. Zonal centrifugation evidence for multiple cellular sources.

Postnuclear supernates from homogenates of skeletal muscle from rats subjected to starvation, injections of Triton WR-1339, dextran-500, and dextran + corticosterone were fractionated by means of rate and isopycnic zonal centrifugation in sucrose-0.02 M KCl gradients. Zonal fractions were analyzed for protein, RNA, cytochrome oxidase, and up to six acid hydrolases. The results indicate the presence of two groups of lysosome-like particles. One group contributes approximately 95% of the cathepsin D and acid phosphatase activity and 75% of the acid ribonuclease, beta-glucuronidase, and arylsulfatase activity in muscle. It is characterized by a modal equilibrium density of 1.18 that is decreased by starvation, but is not shifted by dextran-500 or Triton WR-1339. The second group has a higher proportion of acid ribonuclease, beta-glucuronidase, and arylsulftase; the equilibrium density can be shifted by dextran-500 and Triton WR-1339. It is suggested that this group of lysosomes is derived from macrophages and other connective tissue cells, whereas the former group represents lysosome-like particles from muscle cells.

Acid Phosphatase↗