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PubMedDate not supplied

[Protein and ribonucleic acid metabolism in the central nervous system of rats during space flight in the "Kosmos-605" satellite].

On the 2nd postflight day the activity of neutral protamine peptide hydrolase of different compartments of the rat brain did not differ from the control level. With respect to the protein and RNA content and concentration motoneurons of anterior horns of the spinal cord and their glial-cells-satellites of rats exposed to the ground-based synchronous experiment did not differ from those of vivarium controls, except cells of the supraoptic nucleus. That was found on the 2nd and 27th postflight days. On the 2nd postflight day the protein and RNA concentration in neurons decreased and the protein concentration and content in gliocytes lowered; the RNA concentration and content in Purkinje cells of the cerebellum became reduced. On the 27th postflight day the RNA concentration in neurons of the supraoptic nucleus remained diminished whereas the protein content increased; in spinal motoneurons the protein concentration decreased and in adjacent gliocytes the protein concentration and content lowered. All the above changes made no more than 15% of the control values.

Animals↗
PubMedDate not supplied

Some biochemical responses of rat skeletal muscle to a single subcutaneous injection of a toxin (notexin) isolated from the venom of the Australian tiger snake Notechis scutatus scutatus.

1. Some biochemical responses of mammalian skeletal muscle to a single subcutaneous injection of a purified toxin from the venom of the Australian tiger snake, Notechis scutatus scutatus, have been investigated to determine the role of changes in peptide hydrolase enzymes in the muscle wasting caused by notexin administration. 2. Within 6 h of injection, serum creatine kinase activity was increased by five- to ten-fold, and remained elevated for at least 24 h. 3. There was an initial inflammatory response in the muscle adjacent to the site of injection; by 12 h after injection, muscle wet weight increased by 60%. 4. After the initial increase, wet weight fell to about 50% of normal at 7 days. Normal wet weight was achieved by 20 days after the injection. Over the period 1-20 days after the injection of the toxin, the changes in wet weight were mirrored by changes in non-collagen protein content. 5. The activities of cathepsin B and acid proteinase were increased following the injection of the toxin. By 2 days after injection, there was a ten-fold increase in the activity of cathepsin B, and a seven-fold increase in the activity of acid proteinase. The activity of both enzymes become normal by 20 days. 6. Experiments utilizing a variety of cytotoxic drugs suggested that the acid proteinase and cathespin B are primarily located within invading phagocytic cells. 7. The results are discussed with reference to the previously described pathology of toxin-damaged skeletal muscle.

Animals↗
PubMed1997

Catalytic properties of 26 S and 20 S proteasomes and radiolabeling of MB1, LMP7, and C7 subunits associated with trypsin-like and chymotrypsin-like activities.

20 and 26 S proteasomes were isolated from rat liver. The procedure developed for the 26 S proteasome resulted in greatly improved yields compared with previously published methods. A comparison of the kinetic properties of 20 and 26 S proteasomes showed significant differences in the kinetic characteristics with certain substrates and differences in the effects of a protein substrate on peptidase activity. Observed differences in the kinetics of peptidylglutamyl peptide hydrolase activity suggest that the 26 S complex cannot undergo the conformational changes of 20 S proteasomes at high concentrations of the substrate benzyloxycarbonyl (Z) -Leu-Leu-Glu-beta-naphthylamide. Various inhibitors that differentially affect the trypsin-like and chymotrypsin-like activities have been identified. Ala-Ala-Phe-chloromethyl (CH2Cl) inhibits chymotrypsin-like activity assayed with succinyl (Suc) -Leu-Leu-Val-Tyr-AMC, but surprisingly not hydrolysis of Ala-Ala-Phe-7-amido4-methylcoumarin (AMC). Tyr-Gly-Arg-CH2Cl inhibits Suc-Leu-Leu-Val-Tyr-AMC hydrolysis as well as trypsin-like activity measured with t-butoxycarbonyl (Boc) -Leu-Ser-Thr-Arg-AMC, while Z-Phe-Gly-Tyr-diazomethyl (CHN2) was found to inhibit only the two chymotrypsin-like activities. Radiolabeled forms of peptidyl chloromethane and peptidyl diazomethane inhibitors, [3H]acetyl-Ala-Ala-Phe-CH2Cl, [3H]acetyl- and radioiodinated Tyr-Gly-Arg-CH2Cl, and Z-Phe-Gly-Tyr-(125I-CHN2), have been used to identify catalytic components associated with each of the three peptidase activities. In each case, incorporation of the label could be blocked by prior treatment of the proteasomes with known active site-directed inhibitors, calpain inhibitor 1 or 3, 4-dichloroisocoumarin. Subunits of labeled proteasomes were separated either by reverse phase-HPLC and SDS-polyacrylamide gel electrophoresis or by two-dimensional polyacrylamide gel electrophoresis followed by autoradiography/fluorography and immunoblotting with subunit-specific antibodies. In each case, label was found to be incorporated into subunits C7, MB1, and LMP7 but in different relative amounts depending on the inhibitor used, consistent with the observed effects on the different peptidase activities. The results strongly suggest a relationship between trypsin-like activity and chymotrypsin-like activity. They also help to relate the different subunits of the complex to the assayed multicatalytic endopeptidase activities.

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