Liver histology, blood biochemistry and RNA, DNA and subcellular protein composition of various skeletal muscles of rats with experimental cirrhosis: implications for alcoholic muscle disease.

(1) Liver cirrhosis was induced in male rats by treatment with carbon tetrachloride and phenobarbitone for 130-142 days. Detailed histological examination showed all livers from rats treated with carbon tetrachloride had annular fibrosis, necrosis, loss of normal hepatic architecture and other features that were consistent with an established micronodular cirrhosis. (2) Plasma biochemical analysis showed a significant reduction in total protein concentration (13%), which was due entirely to a reduction in plasma albumin (29%). There were also large increases in the plasma activities of alkaline phosphatase (110%) and aspartate aminotransferase (159%), when compared to phenobarbitone-treated controls. Plasma cholesterol was also increased (67%), but other plasma analytes were not significantly altered. (3) The soleus (Type I), plantaris (Type II) and gastrocnemius (Types I and II) muscles were dissected and examined for possible differential effects. There were minor reductions in all three muscle weights, but these changes did not reach statistical significance. The protein, RNA and DNA concentrations, total muscle content and content relative to body weight in cirrhotic rats were also not significantly altered in any of the muscles. Cirrhosis did not cause any perturbations in derived parameters, i.e. amount of synthetic apparatus per cell, RNA/DNA ratio, apparent cell size, protein/DNA ratio and the capacity for protein synthesis or RNA/protein ratio. (4) The gastrocnemius was fractionated into soluble, stromal and myofibrillar proteins. The concentrations and contents of all three proteins were unaltered in cirrhotic animals, compared to controls. (5) It is concluded that in this experimental model of cirrhosis there were no effects on those skeletal muscle variables which are strikingly altered by chronic alcohol feeding.(ABSTRACT TRUNCATED AT 250 WORDS)     

The acute effects of ethanol and acetaldehyde on rates of protein synthesis in type I and type II fibre-rich skeletal muscles of the rat.

Young rats were injected with either ethanol (75 mmol/kg), acetaldehyde (2.8 mmol/kg) or isovolumetric amounts of NaCl (0.15 mol/l, i.e. controls) with or without inhibitors of alcohol dehydrogenase (4-methylpyrazole) or aldehyde dehydrogenase (cyanamide). After 2.5 hr, fractional rates of protein synthesis (i.e. ks) in the soleus (Type I fibre-rich) and plantaris (Type II fibre-rich) muscles were measured. Ethanol alone reduced ks in both soleus and plantaris muscles, by approx. 25%. Pretreatment of ethanol-dosed rats with 4-methylpyrazole raised plasma ethanol levels and reduced ks in the soleus and plantaris by approx. 35%. Pretreatment of ethanol-dosed rats with cyanamide also increased plasma ethanol and further potentiated the effects of ethanol by reducing ks in the soleus and plantaris by approx. 65%. Acetaldehyde alone reduced ks by approx. 15%, and this effect was not significantly altered by 4-methylpyrazole pretreatment. In some instances, the plantaris was slightly more sensitive to ethanol and acetaldehyde than the soleus. Similar conclusions were derived when data were expressed relative to either RNA or DNA. The data thus suggest that the ethanol-induced inhibition of skeletal muscle protein synthesis may possibly be independently mediated by both ethanol and acetaldehyde.     

Effects of chronic ethanol consumption and pair feeding on rates of protein synthesis and nucleic acid composition in rat tibia.

An investigation was made into the chronic effects of ethanol feeding on bone (represented by the tibia). Treated rats were fed a liquid diet containing ethanol as 36% of total calories, and controls were pair-fed identical amounts of the same diet in which ethanol was substituted by isocaloric glucose. Bone DNA and RNA contents in ethanol-fed rats were not significantly different from glucose-fed controls at days 3, 7, 14, 28 and 42 of treatment. Fractional rates of bone protein synthesis were measured with [43H]-phenylalanine. At 3, 7, 14, 28 and 42 days, ethanol feeding had no effect on free and protein-bound specific radioactivities, nor on fractional or absolute rates of protein synthesis. Synthesis rates relative to RNA (RNA activities) and DNA (cellular efficiencies) were also not significantly altered by ethanol feeding at these time points. Comparisons were made between rats fed a standard solid laboratory diet ad libitum (i.e. normal rats), and those fed restricted amounts of glucose-containing liquid diet (i.e. dietary-restricted rats) for 42 days. In normal rats, there was an increase in tibial mass and accretion of total collagen content, but in dietary-restricted rats, this accretion was markedly impaired. Furthermore, whilst RNA and DNA contents were increased in tibia of normal rats, the contents of these nucleic acids were reduced in bones of dietary restricted rats. Fractional rates of bone protein synthesis in normal rats were unaltered after 42 days, but reduced by feeding the control liquid diet in restricted amounts.(ABSTRACT TRUNCATED AT 250 WORDS)     

In vivo protein synthetic rates of atrial, ventricular, and pulmonary tissue proteins in aortic constriction, goldblatt, and bromoethylamine models of hypertension

Changes in tissue protein synthesis in hypertension have usually been measured in vitro in heart from acutely hypertensive rats without consideration of changes in atrial or pulmonary tissue or changes occurring in long-standing hypertension. The objective of the study was to investigate the in vivo changes in cardiopulmonary protein synthesis in three different rat models of chronic hypertension. Hypertension in aortic constriction, the Goldblatt model, and the bromoethylamine model were induced in rats for 30 days. At the end of the experimental period, in vivo rates of protein synthesis were measured with a flooding dose of [3H]phenylalanine (a method which effectively considers precursor pools). Concomitant measurements included quantification of contractile protein and RNA and DNA contents. Indices of protein breakdown were also assessed by selective measurement of protease activities. At the end of 30 days, aortic constriction induced marked increases in protein contents of the left ventricle, septum, left atria, and lungs. Accompanying changes included concomitant increases in RNA and DNA contents. Left ventricular myofibrillary, sarcoplasmic, and stromal protein contents increased in the aortic constriction model. Less marked changes occurred in the Goldblatt model, though the left atria were not significantly affected. In contrast, the bromoethylamine model had no effect on the protein or RNA contents of any region. In all cardiac regions of all three models, fractional rates of protein synthesis were not significantly affected. However, protein synthesis increased in the lungs of both the Goldblatt and bromoethylamine models at 30 days. Protease activities were decreased in the left ventricles of all three models at 30 days, with lysosomal protease activities declining in the aortic constriction model and cytoplasmic protease activities declining in the other two models. The failure of chronic hypertension to increase ventricular synthesis rates may represent inherent limitations in the time frame for measuring protein synthesis in vivo. However, at earlier time points (i.e., 10 days), the aortic constriction model was characterized by marked increases in left ventricular and atrial protein contents, RNA contents, and fractional rates of protein synthesis. This was consistent with the supposition that, in acute phases of hypertrophy, rates of protein synthesis increase, whereas in established hypertrophy, synthesis rates remain unchanged or decrease. The applicability of the aortic constriction model was investigated by examining the effects of the angiotensin converting enzyme inhibitor lisinopril (5 mg/kg/day). After 30 days treatment, lisinopril impeded the increase in left ventricular mixed and myofibrillar proteins. This effect was accompanied by an apparent increase in protein synthesis. In conclusion, although all three chronic models are able to induce hypertension, varying degrees of hypertrophy develop, which are more pronounced in the aortic constriction model. Accompanying changes include hypertrophy in the atria, reduced rates of ventricular proteolytic activity, and altered rates of protein metabolism in the lungs.     

Lymph node infarction – a rare complication associated with disseminated intra vascular coagulation in a case of dengue fever

Background  

Lymph node infarction is known to occur in association with many non-neoplastic and neoplastic conditions however its occurrence in association with DIC is not reported hitherto in the literature.     

The importance of alcohol-induced muscle disease

Alcohol-induced muscle disease (AIMD) is a composite term to describe any muscle pathology (molecular, biochemical, structural or physiological) resulting from either acute or chronic alcohol ingestion or a combination thereof. The chronic form of AIMD is arguably the most prevalent skeletal muscle disorder in the Western Hemisphere affecting more than 2000 subjects per 100,000 population and is thus much more common than hereditary disorders such as Becker or Duchenne muscular dystrophy. Paradoxically, most texts on skeletal myopathies or scientific meetings covering muscle disease have generally ignored chronic alcoholic myopathy. The chronic form of AIMDs affects 40–60% of alcoholics and is more common than other alcohol-induced diseases, for example, cirrhosis (15–20% of chronic alcoholics), peripheral neuropathy (15–20%), intestinal disease (30–50%) or cardiomyopathy (15–35%). In this article, we summarise the pathological features of alcoholic muscle disease, particularly biochemical changes related to protein metabolism and some of the putative underlying mechanisms. However, the intervening steps between the exposure of muscle to ethanol and the initiation of the cascade of responses leading to muscle weakness and loss of muscle bulk remain essentially unknown. We argue that alcoholic myopathy represents: (a) a model system in which both the causal agent and the target organ is known; (b) a myopathy involving free-radical mediated pathology to the whole body which may also target skeletal muscle and (c) a reversible myopathy, unlike many hereditary muscle diseases. A clearer understanding of the mechanisms responsible for alcoholic myopathy is important since some of the underlying pathways may be common to other myopathies. This revised version was published online in July 2006 with corrections to the Cover Date.     

The acute and chronic effects of ethanol on cardiac muscle protein synthesis in the rat in vivo.

An investigation was made into the acute and chronic effects of ethanol on rates of protein synthesis in the hearts of young rats (80-100 g body weight). Acute ethanol administration (75 mmol/kg body weight, IP) significantly reduced the fractional rate of protein synthesis by 20% after 2.5 hr, compared with saline-treated controls. Chronic ethanol feeding (36% of total calories) for 6 weeks significantly reduced cardiac wet weight by 11%, when compared to rats fed isovolumetric amounts of the same diet in which ethanol was substituted by isocaloric glucose. Neither the concentration nor the content of mixed cardiac proteins relative to body weight were overtly altered by chronic ethanol feeding, although, the total content of mixed cardiac proteins were significantly decreased. RNA concentrations and RNA relative to body weight increased slightly, but total cardiac DNA decreased. Indices for the capacity or potential of the heart to synthesis protein (indicated by the RNA/protein and RNA/DNA ratios) and the "DNA-unit" (protein/DNA ratio) were increased in response to chronic ethanol treatment. The fractional and absolute rates of mixed protein synthesis in the heart were (relatively) unaltered by chronic ethanol treatment, as was RNA efficiency and synthesis relative to DNA. It was concluded that the heart displays contrasting responses to acute and chronic ethanol exposure.     

Protein metabolism in alcoholism: effects on specific tissues and the whole body.

Ethanol is one of the few nutrients that is profoundly toxic. Alcohol causes both whole-body and tissue-specific changes in protein metabolism. Chronic ethanol missuse increases nitrogen excretion with concomitant loss of lean tissue mass. Even acute doses of alcohol elicit increased nitrogen excretion. The loss of skeletal muscle protein (i.e., chronic alcoholic myopathy) is one of several adverse reactions to alcohol and occurs in up to two-thirds of all ethanol misusers. There are a variety of other diseases and tissue abnormalities that are entirely due to ethanol-induced changes in the amounts of individual proteins or groups of tissue proteins; for example, increased hepatic collagen in cirrhosis, reduction in myosin in cardiomyopathy, and loss of skeletal collagen in osteoporosis. Ethanol induces changes in protein metabolism in probably all organ or tissue systems. Clinical studies in alcoholic patients without overt liver disease show reduced rates of skeletal muscle protein synthesis though whole-body protein turnover does not appear to be significantly affected. Protein turnover studies in alcohol misusers are, however, subject to artifactual misinterpretations due to non-abstinence, dual substance misuse (e.g., cocaine or tobacco), specific nutritional deficiencies, or the presence of overt organ dysfunction. As a consequence, the most reliable data examining the effects of alcohol on protein metabolism is derived from animal studies, where nutritional elements of the dosing regimen can be strictly controlled. These studies indicate that, both chronically and acutely, alcohol causes reductions in skeletal muscle protein synthesis, as well as of skin, bone, and the small intestine. Chronically, animal studies also show increased urinary nitrogen excretion and loss of skeletal muscle protein. With respect to skeletal muscle, the reductions in protein synthesis do not appear to be due to the generation of reactive oxygen species, are not prevented with nitric oxide synthase inhibitors, and may be indirectly mediated by the reactive metabolite acetaldehyde. Changes in skeletal muscle protein metabolism have profound implications for whole body physiology, while protein turnover changes in organs such as the heart (exemplified by complex alterations in protein profiles) have important implications for cardiovascular function and morbidity.     

Alcohol increases c-myc mRNA and protein in skeletal and cardiac muscle

The pathogenic mechanisms responsible for alcohol-induced muscle disease are unknown, although it is possible that increased proto-oncogene expression may be the causative process. Therefore, we investigated the responses of skeletal muscle c-myc protein and mRNA to a standard acute ethanol dosage regimen (75 mmol/kg/body weight [BW]) for 2.5 to 24 hours. Comparative studies were made on the heart. Acute ethanol administration in vivo led to an increase in c-myc proto-oncogene mRNA in rat skeletal and cardiac muscle. The changes in c-myc mRNA were mirrored by increases in the c-myc protein as demonstrated by immunohistochemistry. The changes in the c-myc protein were localized to the myonuclei, with no corresponding changes seen in the interstitial cell nuclei. This is the first report of altered proto-oncogene expression in muscle in response to ethanol. Increased c-myc mRNA and protein may reflect adaptive changes, a stress response, or another uncharacterized cellular adaptation.     

Osmotic diarrhoea and skeletal muscle protein synthesis in vivo.

The pathogenic nature of the wasting seen in diarrhoea is unknown. This study measured protein synthesis in an established model of diarrhoea using lactose for seven days. Comparisons were also made with data obtained from rats fed an identical diet in which lactose was replaced by isocaloric glucose ad libitum (that is, the control diet). To account for diarrhoea induced anorexia, a third group of rats were included, which were fed identical amounts of the control diet as the rats with diarrhoea inducing diet. Comparisons of the diarrhoea induced group with rats fed the control diet ad libitum showed that diarrhoea caused a significant reduction in body weights. Type I and type II muscles showed significant reductions in protein, RNA, and DNA contents, as well as a fall in the derived parameters, RNA/DNA, protein/DNA, and RNA/protein. Fractional rates of protein synthesis (ks) were also reduced. However, synthesis rates of type I and II muscles relative to RNA (kRNA) were unchanged in these muscles in diarrhoea induced rats compared with ad libitum fed controls. In the jejunum there was an increase in the RNA/DNA ratio, and reductions in ks and kRNA. Comparisons were also made between rats with diarrhoea and rats pair fed the control diet. There were no changes in total muscle protein, RNA or DNA contents. This suggests that an important feature of body wasting in diarrhoea is the element of anorexia, which induces severe metabolic changes. The comparison between rats with diarrhoea and the pair fed group showed that histological features of the plantaris were not overtly changed, though diarrhoea caused significant reductions in RNA/DNA, protein/DNA, ks, and kRNA. Similar changes were seen for the soleus; though the reduction in ks failed to attain statistical significance. In the jejunum a comparison of diarrhoea induced rats with pair fed controls, showed increases in the ratios of RNA/DNA and protein/DNA.