Search PubMed⌕ Search

Biomedical subjects

E Rubin

Publications and source records attributed to E Rubin.

At least 271 records · Page 15Linked to original sources
PubMed1976

Muscle damage produced by chronic alcohol consumption.

The effects of chronic alcohol consumption on skeletal muscle, independent of nutritional factors, were studied. Chronic alcohol ingestion led to striking ultrastructural changes in skeletal muscle, including intracellular edema, enlarged and distorted mitochondria, dilatation of sarcoplasmic reticulum, and increased amounts of fat and glycogen. Actomyosin was isolated from skeletal muscle of baboons and volunteers fed alcohol. In this preparation, ATPase activity and the calcium sensitivity of ATPase were decreased. The isolated actomyosin displayed reduced contractility in vitro, measured by the association of actin and myosin and the response to adenosine diphosphate (ADP). In 2 of 3 volunteers, isolated membranes of the sarcoplasmic reticulum exhibited decreased calcium uptake. The pressure-rate product was increased in some of the volunteers after submaximal or maximal work. The changes decribed in this study were found after alcohol administration had been discontinued, and they may play a role in the development of alcoholic myopathy and cardiomyopathy.

Actomyosin↗
PubMed1976

Kinetic properties of alcohol dehydrogenase in hepatocellular carcinoma and normal tissues of rat.

It was previously reported that the properties of alcohol dehydrogenase of a rat hepatocellular carcinoma (Becker H-252), a tumor of intermediate growth rate, were different from those of the liver enzyme, suggesting different isozymes. To determine whether the degree of differentiation affected the isozyme of alcohol dehydrogenase, a fast-growing, poorly differentiated tumor and one that is well differentiated and of intermediate growth rate were studied. Alcohol dehydrogenase from Morris hepatoma 7288ctc, a fast-growing, poorly differentiated tumor, had properties similar to those found with the Becker-H-252 tumor, including a high Km for ethanol and acetaldehyde and the absence of substrate inhibition. By contrast, alcohol dehydrogenase from the well-differentiated Morris hepatoma 5123C had properties similar to those of the liver enzyme. Thus, alcohol dehydrogenase is another example of an enzyme the isozyme composition of which changes with neoplastic de-differentiation. Further studies, including gel electrophoresis, substrate specificity patterns, and interaction with antibodies to alcohol dehydrogenase, are required to determine the factors responsible for the biochemical defect that occurs at the molecular level during carcinogenesis and whether the alcohol dehydrogenase isozymes in the Becker H-252 and Morris 7288ctc hepatomas are identical. A survey of several normal rat tissues revealed that only the stomach contains this unique isozyme of alcohol dehydrogenase.

Alcohol Oxidoreductases↗
PubMed1976

Fatty acid oxidation, substrate shuttles, and activity of the citric acid cycle in hepatocellular carcinomas of varying differentiation.

Fatty acid oxidation, reconstituted substrate shuttles, and the activity of the citric acid cycle were studied in mitochondria isolated from Becker transplantable hepatocellular carcinoma H-252 AND Host livers, and the results were compared with those obtained with Morris hepatomas 7288CTC and 5123C. Whereas the activities of the malate-aspartate and the alpha-glycerophosphate shuttles were only slightly lower than those of host livers, the activity of the fatty acid shuttle was much lower in H-252 mitochondria. Oxygen uptake and CO2 production associated with the oxidation of fatty acids was much lower in tumors H-252 and 7288CTC, compared with host livers, whereas tumor 5123C mitochondria show a high capacity to oxidize fatty acids. Ketogenesis and beta-hydroxybutyrate dehydrogenase activity were also lower in tumor H-252 mitochondria. However, neither oxygen uptake associated with the oxidation of other respiratory substrates nor CO2 production from succinate or malate was strikingly elevated in these tumors. These factors suggest that the respiratory phosphorylation chain and activity of the citric acid cycle are fully functional in tumors H-252 and 7288CTC. The defects responsbile for the lower rates of fatty acid oxidation in these tumors probably involves the beta-oxidation pathway, as well as the activation of fatty acids. The impairment of fatty acid oxidation may explain the lower activity of the reconstituted fatty acid shuttle for transporting reducing equivalents into H-252 mitochondria. The different properties with regard to fatty acid oxidation in Morris hepatoma 5123C, compared with those in Becker H-252- AND Morris hepatoma 7288CTC, may reflect the different extent of differentiation in these tumors, the former being a slow-growing, well-differentiated tumor, whereas the latter represent tumors that are less differentiated and of more rapid growth rate.

Animals↗
PubMed1975

Effect of chronic ethanol ingestion on fatty acid oxidation by hepatic mitochondria.

To study possible factors in the pathogenesis of the ethanol-induced fatty liver, we investigated the effect of chronic ethanol consumption on the metabolism of fatty acids by isolated hepatic mitochondria. Chronic ethanol consumption resulted in decreased fatty acid oxidation, as evidenced by a reduction in oxygen uptake and CO2 production associated with the oxidation of fatty acids. The State 3 rate of oxygen uptake was depressed to a greater extent than the State 4 or the uncoupler-stimulated rate; the respiratory control ratio was also decreased. Therefore, one site of action of chronic ethanol feeding is on oxidative phosphorylation. The reduction in fatty acid oxidation, in general, is not due to an effect on the activation or translocation of fatty acids into the mitochondria. There was no effect by ethanol feeding on the activity of palmitoyl coenzyme A synthetase, whereas carnitine palmitoyltransferase activity was increased. The use of an artificial system (formazan production) to study beta oxidation in the absence of the electron transport chain is described. In the presence of fluorocitrate, which inhibits citric acid cycle activity, ketogenesis and formazan production were increased by chronic ethanol consumption. Thus beta oxidation to the level of acetyl-CoA is not impaired by chronic ethanol consumption. Total oxidation of fatty acids to CO2 is depressed by chronic ethanol intoxication because of effects on oxidative phosphorylation or the citric acid cycle (or both). Neither nutritional deficiency, cofactor depletion, nor the presence of ethanol in vitro explains these effects. Several of the effects of chronic ethanol consumption on fatty acid oxidation are mimicked by acetaldehyde and acetate, products of ethanol oxidation. Chronic ethanol consumption leads to persistent impairment of mitochondrial oxidation of fatty acids to CO2. However, oxidation of fatty acids to acetyl-CoA is not decreased by chronic ethanol consumption.

Alcoholic Intoxication↗
PubMed1975

Adenosine diphosphate effect on contractility of human muscle actomyosin: inhibition by ethanol and acetaldehyde.

Magnesium adenosine triphosphate (Mg-2+-ATP) is known to produce dissociation of muscle actin and myosin in vitro, while its hydrolysis leads to reassociation. The interaction of purified actin and myosin from human muscle, in the presence of Mg-2+-ATP, was stimulated by minute amounts of adenosine diphosphate (ADP), a product of ATP hydrolysis. By contrast, the dissociation of the actomyosin complex was inhibited by ADP. These data suggest that ADP serves to modulate muscle contraction. Ethanol and its primary metabolite, acetaldehyde, inhibited these effects of ADP. The inhibition was reversible when the preparations were freed of these compounds. The effects of ethanol and acetaldehyde on the response of actomyosin to ADP may play a role in the pathogenesis of alcoholic myopathy and cardiomyopathy.

Acetaldehyde↗
PubMed1975

Sequential production of fatty liver, hepatitis, and cirrhosis in sub-human primates fed ethanol with adequate diets.

This study reproduces in experimental animals the sequential development of all the liver lesions seen in the human alcoholic: in 15 baboons fed ethanol, all developed fatty liver, five progressed to hepatitis, and five had cirrhosis. Maintenance of a nutritionally adequate regimen despite the intake of inebriating amounts of ethanol (50% of total calories) was achieved by incorporation of the ethanol in a totally liquid diet. Upon ethanol withdrawal, signs of physical dependence, such as seizures and tremors, developed. Ultrastructural changes of the mitochondria and the endoplasmic reticulum were already present at the fatty liver stage and persisted throughout the hepatitis and cirrhosis. The lesions were similar to those observed in alcoholics (including the inflammation and the central sclerosis) and differed from the alterations produced by choline and protein defiencies. At the fatty liver stage, some "adaptive" increases in activity of microsomal enzymes [aniline hydroxylase (EC 1.14.14.1) and the microsomal ethanol oxidizing system] were observed, but these tended to disappear with the development of hepatitis and cirrhosis. Fat accumulation was also much more pronounced in the animals with the hepatitis as compared with those with simple fatty liver (an 18-fold compared with 3- to 4-fold increase in liver triglycerides). The demonstration that these lesions can develop despite an adequate diet indicates that in addition to correction of the nutritional status, control of alcohol intake is mandatory for the management of patients with alcoholic liver injury.

Animals↗
PubMed1975

The use of cation-bound microsomes for studies of protein synthesis.

Low speed microsomes prepared by centrifuging at 30 times g for 10 minutes after interaction with Ca-2plus or Mg-2plus are comparable to high speed microsomes (105,000 times g) with respect to incorporation of 3-H-leucine in vivo, protein-synthesizing ability in vitro, and the pattern of ribosomal profiles on a linear sucrose density gradient. Low and high speed polyribosomes, i.e., those isolated with and without Ca-2plus or Mg-2plus from a postmitochondrial supernatant, also displayed similar protein-synthesizing capability in vitro and identical profiles on a linear sucrose density gradient. Other divalent cations, such as Ba-2plus, Ni-2plus, Co-2plus, Cu-2plus, Fe-2plus, Hg-2plus, Zn-2plus, and Sr-2plus, inhibited enzyme activities and depressed protein synthesis. Low speed microsomes may now be deemed suitable for all studies of microsomal function.

Animals↗
PubMed1975

Relation of alcoholic liver injury to cirrhosis.

The earliest and most reproduceable lesion associated with chronic alcohol abuse is fatty liver. In some alcoholics this may be superseded by alcoholic hepatitis, which may represent the link between the early lesion and cirrhosis. Alcoholic cirrhosis usually begins as a regular, monolobular variety, but is eventually transformed into an irregular, multilobular type. All stages of alcoholic liver injury have now been produced in the baboon, despite high protein and vitamin supplemented diets. Alcohol may therefore now be regarded as a direct hepatotoxin. Epidemiological studies have indicated that alcoholic liver injury begins with an intake of more than 80 g ethanol a day, and that cirrhosis is generally not seen with an intake of less than 160 g per day. The development of cirrhosis correlates with the total duration and amount of alcohol ingested. Complications of alcoholic cirrhosis include iron overload and primary hepatic carcinoma.

Alcoholism↗