The Na/K-ATPase-rich microsomal fraction and purified Na/K-ATPase membranes of the salt-stressed avian salt gland were studied at defined filipin/cholesterol molar ratios (F/C) using enzyme assay and electron microscopy including negative staining, thin sectioning and freeze fracturing. Comparative examinations of detergent-treated microsomal fractions and the use of electron microscopic tracer...

The purpose of this study was to examine the subcellular distribution and isoenzyme characteristics of carbonic anhydrase from the gills and respiratory air bladder of bowfin Amia calva, a primitive air-breathing fish. Separation of subcellular fractions by differential centrifugation revealed that the vast majority of carbonic anhydrase from the gills of bowfin originated from the cytoplasmic ...

We have investigated the extent to which membrane environment affects the catalytic properties of the malonyl-CoA-sensitive carnitine acyltransferase of liver microsomal membranes. Arrhenius-type plots of activity were linear in the absence and presence of malonyl-CoA (2.5 microM). Sensitivity to malonyl-CoA increased with decreasing assay temperature. Partly purified enzyme displayed an increa...

New methods are required for identifying membranes in subcellular fractions with respect to their origin, if such preparations are to be evaluated morphometrically. One method is freeze-fracturing which reveals intramembrane particles whose size, pattern, and numerical density differ for various membrane types. The question is examined whether the differences in numerical particle density per s...

The properties and subcellular distribution of phosphatidate phosphatase (EC 3.1.3.4) from adipose tissue have been investigated. The enzyme was assayed using both aqueous phosphatidate and membrane-bound phosphatidate as substrates. When measured with aqueous substrate, activity was detected in the mitochondria, the microsomes, and the soluble fraction. Mg(2+) at low concentration stimulated t...

At both 4 and 24 hr after the administration of ethionine, female rats displayed a significant reduction in the RNA:pro tein ratio of liver microsomes. In this respect, ethionine behaved like many other hepatocarcinogens which induce ribosomal separation from the rough endoplasmic reticulum. This separation is usually brought about by the membrane, rather than ribosomal lesions. Using the disul...

The NADPH-dependent reduction of rat hepatic microsomal cytochrome P-450 has been studied as a function of temperature. In the temperature range 4-37’ the reduction reaction was found to be biphasic and composed of two concurrent first order processes. This phenomenon was observed with microsornes from untreated and phenobarbital-induced animals in the presence or absence of exogenous Type I su...

A method has been developed for the separation of the major membrane fractions of Acanthamoeba castellanii after growth at different temperatures. The acyl-lipid compositions of individual membrane fractions, microsomal membranes, plasma membrane and mitochondria were analysed after a shift in culture temperature from 30 degrees C to 15 degrees C. The major change in lipid composition observed ...