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Relationships between calpains and glutamateor kainate-induced apoptosis in Xenopus laevis tadpoles

100%

Brun C. , Moudilou E. , Bouchot C. , Abrouk-Verot L. , Exbrayat J.-M.

tom 51

nr 4

Effect of 3-hydroxy-3-methylbutyrate [HMB] on muscle cathepsins and calpain activities during the post-dexamethasone recovery period in young rats

100%

Jank M. , Ostaszewski P. , Rosochacki S. , Wilczak J. , Balasinska B.

nr 4

This study was conducted to assess the effect of the leucine metabolite, 3-hydroxy-3-methylbutyrate (HMB) on animal performance, and also cathepsins and calpain II activities in the gastrocnemius muscle in young rats undergoing dexamethasone (DX) treatment and subsequent recovery. Five days of DX administration resulted in an increase in calpain activity. During 5 days of recovery alone, calpain activity was still elevated whereas HMB treatment decreased calpain activity to the values observed in the control group. DX treatment increased the total lysosomal proteolytic activity. HMB administration during the recovery period accelerated return of the proteolytic enzymes activity to the control values. The use of selective inhibitors of thiol and aspartic cathepsins (leupeptin and pepstatin, respectively) allowed us to determine the type of cathepsin responsible for the DX-induced proteolysis observed. Since DX treatment decreased cathepsin D activity (which returned to the control values during recovery) it is assumed that thiol cathepsins are involved in the increase of lysosomal proteolysis observed. We have demonstrated that lysosomal and Ca+2-dependent proteinases involved in myofibryllar protein degradation differ in their activity due to DX treatment. It has been concluded that HMB modifies muscle proteolysis through changes in the activity of the proteolytic enzymes. Practical applications of this phenomenon are discussed.

Myocardial necrosis due to vitamin D3 overdose - scanning electron microscopic observations

100%

Walentynowicz O. , Kubasik-Juraniec J. , Rudzinska-Kisiel T.

nr 4

Our studies were carried out on the hearts of virgin female Wistar rats treated with 100.000 i.u. of vitamin D₃ (calciol) per os for 3 consecutive days. Multifocal cardionecrosis was established macroscopically in 70% of the vitamin D-treated rats on the 7th day of the experiment when the rats were in the acute phase of intoxication. Using a scanning electron microscopy (SEM), we received three-dimensional information about the structural changes to the rat myocardium damaged by high doses of vitamin D₃. The images of necrotic hearts revealed significant disruption of the structural integrity of the myocardium linked to fragmentation of the cardiac muscle bundles and a visible disruption of the extracellular matrix (ECM) components. In healthy hearts, the structural integrity of the myocardium and the dense network of the extracellular matrix were well preserved. In parallel, the effect of an increasing concentration of free Ca²⁺ on the total proteolytic activity of the heart muscle homogenate of the healthy and necrotic rats was investigated at neutral pH. These data showed that following vitamin D₃ intoxication, the proteolytic processes in the rat hearts occurred in Ca²⁺ overload or saturation. On the basis of our morphological and biochemical results we can suggest that calcium-activated neutral proteinases may have contributed to the structural alteration of the extracellular matrix components and were in this way involved in vitamin D-induced cardionecrosis.

Phosphorylation of protein kinase C substrate proteins in rat hippocampal slices-effect of calpain inhibition

80%

Domanska-Janik K. , Zablocka B. , Zalewska T. , Zajac H.

nr 4