Effects of high pressure on the catalytic and regulatory properties of UDP-glucuronosyltransferase in intact microsomes.

The effects of high pressure on the kinetic properties of microsomal UDP-glucuronosyltransferase (assayed with 1-naphthol as aglycon) were studied in the range of 0.001-2.2 kbar to clarify further the basis for regulating this enzyme in untreated microsomes. Activity changed in a discontinuous manner as a function of pressure. Activation occurred at pressure as low as 0.1 kbar, reaching one of two maxima at 0.2 kbar. As pressure was increased above 0.2 kbar, activity decreased, reaching a minimum at about 1.4 kbar followed by a second activation. The pathway for activation at pressure greater than 1.4 kbar was complex. The immediate effect of 2.2 kbar was nearly complete inhibition of activity. The inhibited state relaxed, however, over about 10 min (at 10 degrees C), to a state that was activated as compared with enzyme at 0.001 kbar or enzyme at pressures between 1.4 and 2.2 kbar, which was the highest pressure we could test. Examination of the detailed kinetic properties of UDP-glucuronosyltransferase indicated that the effects of pressure were due to selective stabilization of unique functional states of the enzyme at 0.2 and 2.2 kbar. Activation at 0.2 kbar was reversible when pressure was released. This was true as well as for activation at pressure greater than 1.4 kbar, but after prolonged treatment at 2.2 kbar, UDP-glucuronosyltransferase became activated irreversibly on release of pressure. The process by which prolonged treatment at 2.2 kbar led to permanent activation of UDP-glucuronosyltransferase after release of pressure was not reflected, however, by time-dependent changes in the functional state of UDP-glucuronosyltransferase at this pressure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Histochemical Demonstration of Enzyme Activities in Plastic and Paraffin Embedded Tissue Sections

Histochemical staining for enzymes is usually performed on frozen sections. This report lists the longer incubation times required to demonstrate esterase, acid phosphatase, β-galactosidase, and cytochrome oxidase in plastic embedded and routine paraffin embedded tissues. The sections embedded in plastic, i.e. water soluble methacrylate (Polyscience's JB-4) and cut at 2 μm, were far superior to frozen Sections and paraffin embedded sections both in tissue detail and in the localization of the histochemical reaction product.     

Characterization,Toxicity, and Optimization for the Growth and Production of Bacteriocin-like Substances by Lactobacillus curvatus

Probiotics and Antimicrobial Proteins - This study aimed to characterize, evaluate toxicity and optimize the conditions for the growth and production of bacteriocin-like substances by Lactobacillus...     

Cutting edge: neutrophil granulocyte serves as a vector for Leishmania entry into macrophages

Macrophages (MF) are the final host cells for multiplication of the intracellular parasite Leishmania major (L. major). However, polymorphonuclear neutrophil granulocytes (PMN), not MF, are the first leukocytes that migrate to the site of infection and encounter the parasites. Our previous studies indicated that PMN phagocytose but do not kill L. major. Upon infection with Leishmania, apoptosis of human PMN is delayed and takes 2 days to occur. Infected PMN were found to secrete high levels of the chemokine MIP-1beta, which attracts MF. In this study, we investigated whether MF can ingest parasite-infected PMN. We observed that MF readily phagocytosed infected apoptotic PMN. Leishmania internalized by this indirect way survived and multiplied in MF. Moreover, ingestion of apoptotic infected PMN resulted in release of the anti-inflammatory cytokine TGF-beta by MF. These data indicate that Leishmania can misuse granulocytes as a "Trojan horse" to enter their final host cells "silently" and unrecognized.