Calf thymus Hsc70 protein protects and reactivates prokaryotic and eukaryotic enzymes.

The heat-shock 70 protein (Hsp70) chaperone family is very conserved and its prokaryotic homologue, the DnaK protein, is assumed to form one of the cellular systems for the prevention and restoration of heat-induced protein denaturation. By using anti-DnaK antibodies we purified the DnaK homologue heat-shock cognate protein (Hsc70) from calf thymus to apparent homogeneity. This protein was classified as an eukaryotic Hsc70, since (i) monoclonal antibodies against eukaryotic Hsc70 recognized it, (ii) its amino-terminal sequence showed strong homology to Hsp70s from eukaryotes and, (iii) it had an intrinsic weak ATPase activity that was stimulated by various peptide substrates. We show that this calf thymus Hsc70 protein protected calf thymus DNA polymerases alpha and epsilon as well as Escherichia coli DNA polymerase III and RNA polymerase from heat inactivation and could reactivate these heat-inactivated enzymes in an ATP-hydrolysis dependent manner, likely leading to the dissociation of aggregates formed during heat inactivation. In contrast to this, DnaK protein was exclusively able to protect and to reactivate the enzymes from E.coli but not from eukaryotic cells. Finally, the addition of calf thymus DnaJ co-chaperone homologue reduced the amount of Hsc70 required for reactivation at least 10-fold

Obstructive nephropathy: evaluation with dynamic Gd-DTPA-enhanced MR imaging.

The potential of dynamic gadolinium diethylenetriaminepentaacetic acid (DTPA)-enhanced magnetic resonance (MR) imaging for the examination of obstructive nephropathy was analyzed in 27 subjects (five healthy subjects, seven patients with dilated nonobstructed kidneys, six patients with acute obstruction, and nine patients with chronic obstruction) with use of a 1.5-T magnet. Morphologic findings were compared with quantitative analysis of temporal changes in signal intensity. Dynamic postcontrast images of the normal kidney demonstrated four phases of enhancement; cortical enhancement phase, early tubular phase, ductal phase, and excretory phase. The pattern of enhancement in dilated nonobstructed kidneys was similar to that in normal kidneys. In acutely obstructed kidneys, cortical enhancement was similar to that in normal kidneys (17% increase), but medullary enhancement was higher than normal, resulting in diminished corticomedullary differentiation. The early tubular phase was prolonged (until 2.5 minutes after injection), with delayed appearance of the ductal and excretory phases. In chronically obstructed kidneys, the increase in cortical intensity was less than that in normal kidneys (13% increase). The early tubular phase was prolonged, and the ductal phase was diminished or absent