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Biomedical subjects

M T Moslen

Publications and source records attributed to M T Moslen.

At least 55 records · Page 3Linked to original sources
PubMed1984

Increased incidence of hepatic foci and nodules in rats given one or two doses of 1,2-dibromoethane.

Livers of male Sprague-Dawley rats were evaluated for foci and nodules 90 days and 16 months after one or two oral doses of 1,2-dibromoethane (DBE). Rats (190 g) were given the following oral treatments. Controls received corn oil (2.5 ml/kg) at 0 and 24 hr. DBE X 1 received corn oil at 0 hr and 75 mg DBE/kg at 24 hr. DBE X 2 received 75 mg DBE/kg at 0 and 24 hr. All rats underwent a two-thirds partial hepatectomy at 28-29 hr, a one-third partial hepatectomy at 90 days, and were given 0.05% phenobarbital in drinking water for 4 months beginning at 1 yr. DBE was given to the DBE X 2 group twice within 24 hr because the compound is a hepatocyte mitogen. At 90 days, no appreciable changes were evident in any group. At 16 months, the incidence of nodules in the DBE X 2 group (25 of 41) was double that of the DBE X 1 group (12 of 38) (p less than 0.01) and triple that of the control group (6 of 34) (p less than 0.0001). Both the DBE X 1 and the DBE X 2 groups had higher incidences of eosinophilic foci, and also higher numbers, larger sizes, and larger areas of gamma-glutamyltranspeptidase-positive foci than the control group. These results demonstrate for the first time that hepatocyte foci and nodules are initiated by limited exposure of animals to DBE.

Animals↗
PubMed1984

1,1-Dichloroethylene: an apoptotic hepatotoxin?

Within 2 hr after 1,1-dichloroethylene administration, the following phenomena occur in livers of fasted rats: dilation and disruption of bile canaliculi, plasma membrane invagination and loss of microvilli, cytoplasmic vacuolation, and loss of density in mitochondrial matrices. Early, selective loss of enzyme activities was localized by histochemical staining to bile canalicular, and inner and outer mitochondrial membranes. Biliary permeability to inulin increased, a change suggestive of the breakdown of junctions between hepatocytes. Endoplasmic reticulum and lysosomes appeared spared. In addition, scattered, individual hepatocytes exhibited changes characteristic of apoptosis by 2 hr: chromatin aggregation and margination, nucleolar coarse granulation and enlargement, rounded blebs and proturberances on cell surfaces, and the separation of these cells from surrounding parenchyma. In contrast, evidence of plasma membrane leakiness to K+, Ca2+ and soluble cytoplasmic enzymes was not detected until after 2 hr. Based on these observations, we propose that 1,1-dichloroethylene may initiate apoptosis-like cell degradation in selected parenchymal cells prior to or coincident with centrolobular necrosis.

Animals↗
PubMed1982

Isopropanol enhancement of carbon tetrachloride metabolism in vivo.

We examined the effects of isopropanol (ISOP) pretreatment on the metabolism of 14CCl4 to 14CO2 and CHCl3 exhaled in the breath, to 14C metabolite excreted in 24 hr urine and feces from 0 to 24 hr, and to 14C metabolite bound to liver at 24 hr. Fasted male rats were given 0.1 or 2.0 mmoles 14CCl4/kg. ISOP pretreatment, which markedly enhanced the hepatotoxicity of CCl4, selectively enhanced the rate and total extent of 14CO2 and CHCl3 metabolite exhalation. The pathways of CCl4 metabolism leading to CO2 and CHCl3 metabolite formation may be more relevant to the hepatotoxicity of CCl4 than the pathways leading to urinary, fecal or covalently bound metabolites.

1-Propanol↗
PubMed1982

Transient decrease of liver cytosolic glutathione S-transferase activities in rats given 1,2-dibromoethane or CCl4.

In vivo treatment of fasted male rats with 1,2-dibromoethane (DBE) (0.4 mmol/kg) or carbon tetrachloride (CCl4) (4 mmol/kg) was found to rapidly alter the activities of liver cytosolic and microsomal glutathione S-transferases. Microsomal activities towards chloro-2,4-dinitrobenzene (CDNB) were increased 2 h after either treatment. Cytosolic activities towards CDNB and 3,4-dichloronitrobenzene (DCNB), but not 1,2-epoxy-3-(p-nitrophenoxy)-propane (ENPP), were selectively and transiently decreased after either treatment. Time course studies in DBE animals indicated that the decrease in cytosolic activity was not evident until 2 h although liver glutathione (GSH) concentrations were diminished within 15 min. In contrast, in CCl4 animals the decrease in cytosolic activity was evident within 15 min and was not accompanied by diminished GSH concentrations. By 4 h, cytosolic activities had rebounded to control levels in both DBE and CCl4-treated animals. Kinetic studies of the enzyme in liver cytosol from animals 2 h after treatment with DBE or CCl4 indicated that both treatments decreased the apparent Vmax while neither treatment altered the apparent Km. This pattern of change allows exclusion of a simple competitive mechanism of enzyme inhibition, but cannot distinguish between reversible non-competitive inhibition and irreversible inhibition. It is possible that the observed decreases in the activities of the abundant cytosal enzyme are due to 'sacrificial' covalent linkages between the enzyme and reactive metabolites of DBE or CCl4.

Animals↗
PubMed1982

Histochemical evidence that plasma and mitochondrial membranes are primary foci of hepatocellular injury caused by 1,1-dichloroethylene.

Functional integrity of liver cell organelles in rats given the model abrupt cytotoxin 1,1-dichloroethylene (1,1-DCE) was examined by enzymatic histochemistry. Fasted 200-gm. male Sprague-Dawley rats were sacrificed 1, 2, 4, or 6 hours after an oral dose of 200 mg. of 1,1-DCE per kg. (in mineral oil) and 6 hours after 50, 100, or 150 mg. of 1,1-DCE per kg. Cubes of liver were quick frozen for histochemistry. Stage or degree of liver injury was assessed by histology and by measuring serum transaminase activities and liver ion levels. We found both early injury (2 hours following the 200-mg. per kg. dose) and slight injury (6 hours following the 50-mg. per kg. dose) characterized by: increases in liver sodium levels and striking decreases in the central area staining patterns of bile canaliculi membrane Mg++-ATPase, as well as of outer mitochondrial membrane monoamine oxidase and inner mitochondrial membrane succinate dehydrogenase and cytochrome oxidase. As injury progressed with time or increased in severity with dose, aberrations in the levels of other liver cell ions occurred, serum transaminase activities rose, and decreased staining of plasma membrane and mitochondrial membrane components were evident in progressively wider areas around the central vein. Glutathione depletion was panlobular. In contrast, only at later times (4 and 6 hours) and after the larger doses did alterations to functional components of the mitochondrial matrix, endoplasmic reticulum, lysosomes, and cytosol become evident in a narrow area around the central vein, which became necrotic. We consider these later appearing alterations secondary consequences of the midzonal necrosis and sinusoidal congestion produced by 1,1-DCE, whereas the plasma membranes and mitochondrial membranes appear to be primary foci of injury.

Adenosine Triphosphatases↗
PubMed1980

1,1-Dichloroethylene hepatotoxicity. Time course of GSH changes and biochemical aberrations.

Exposure of fasted rats to 200 ppm 1,1-dichloroethylene (1,1-DCE) for 1-4 hours resulted in striking aberrations in hepatic Na, K, Ca, and GSH levels which preceded and/or accompanied catastrophic histologic alterations of the liver. Na levels began to rise during the first hour, and preceded the morphologically apparent injury. Ca levels increased markedly and K levels declined between the second and fourth hour of exposure, and accompanied the catastrophic morphologic alterations. GSH levels were rapidly depleted but began to recover before the end of the exposure to 1,1-DCE. Functions of components of the mixed-function oxidase system of the liver endoplasmic reticulum were not appreciably affected early in the course of 1,1-DCE exposure; but after injury became massive, cytochrome P-450 and oxidative N-demethylase were deactivated. Thus effects on the functional components of the endoplasmic reticulum mixed-function oxidase system do not appear to be primary events in 1,1-DCE cytotoxicity. In contrast, there were progressive declines in mitochondrial K and marked imbalances in mitochondrial Na, Zn, and Mg preceding the massive influx of Ca into the cell, indicating that mitochondria are involved early in he evolution of injurious molecular events elicited by this potent hepatotoxin.

Chemical and Drug Induced Liver Injury↗
PubMed1977

Damage to hepatic cellular membranes by chlorinated olefins with emphasis on synergism and antagonism.

The fundamental reactivity or stability of the chloroethylene molecules affects their hepatotoxic potential. Extent and symmetry of the chlorine substitution, which alters electron delocalization, charge polarization, and solubility, affect biologic response. The most nonsymmetrically depolarized chloroethylene, 1,1-dichloroethylene (1,1-DCE) is the most hepatotoxic and causes a unique pattern of hepatocellular injury involving mitochondria, plasma membranes, and chromatin. The injury caused by the other chloroethylenes examined appears to profoundly affect the structural integrity of the endoplasmic reticulum with toxic potential in the order: trichloroethylene (TRI) greater than vinyl chloride (VCM) greater than perchloroethylene (PER). Pretreatments which increased cytochrome P-450 contents, thus presumably augmenting metabolic activation to a reactive intermediate such as an epoxide, enhanced or were synergistic to the hepatotoxic potential of TRI, VCM and PER but were protective or antagonistic to 1,1-DCE hepatotoxicity. Biologic response to 1,1-DCE may be expressed by a different metabolic pathway. Glutathione appears to be involved in the biologic response to all nonsymmetric chloroethylenes and toact as an antagonist against injury. Marked differences in the patterns of injury and the biologic responses suggest that more than one mechanism is involved in the production of injury by chloroethylenes.

Alkenes↗
PubMed1977

Trichloroethylene-induced deactivation of cytochrome P-450 and loss of liver glutathione in vivo.

Liver microsomal enzyme activities and glutathione (GSH) contents of fasted male rats pretreated with phenobarbital (PBT) or vehicle controls were measured during and after exposure to trichloroethylene (TRI) (1% x 2 hr). TRI caused morphologic liver injury only in the pbt animals. Cytochrome P-450 and b5 contents were diminished by the end of the first hr of TRI exposure and NADH-cytochrome c reduction increased three-fold by eight hr in the PBT animals. The only change in vehicle animals exposed to TRI was a decrease in NADPH-cytochrome c reductase activity by eight hr. Hepatic GSH contents of vehicle animals, constant during TRI exposure, rose with time. In contrast, in PBT animals, hepatic GSH contents decreased during TRI exposure and then rebounded. Decreases in GSH were most profound in the microsomal fraction. When fed animals with approximately two-fold higher hepatic GSH levels than fasted animals were exposed to TRI, they had shorter anesthesia recovery times and less liver injury, although excreting similar or slightly more trichlorinated metabolite into their urine in 24 hr than their fasted counterparts. We suggest that the hepatoxic effects of trichloroethylene are caused by inadequate detoxification of its reactive intermediates.

Alanine Transaminase↗
PubMed1976

Neurotoxicity of digitoxin in adult and newborn rats: drug distribution.

Electrocardiographic monitoring of adult and 1 week old (newborn) rats during severe acute digitoxin toxicity demonstrated a lack of acrdiotoxicity despite marked neurotoxicity in both age groups. To examine the possibility that drug disposition is a factor in the unusual digitoxin sensitivity of newborn rats, 3H-digitoxin distribution in liver, heart, brain, kidney, adrenal, blood and fat was compared in 1 and 3 week old (weanling) rats at 2, 12 and 24 hr. H3-label was rapidly sequestered by the liver in weanlings but not in newborn rats. Newborns had significantly higher concentrations of 3H-substance in all other organs, particularly in brain (greater than 25% of the administered dose at 24 hr), indicating a cerebrotoxic basis for the newborn's sensitivity to digitoxin. Only trace amounts of 3H-substance were recovered from adult rat brain during severe neurotoxicity (72 hr) suggesting that digitoxin metabolites may be potent cerebrotoxins. Extremely high adrenal concentrations were noted in all animals.

Aging↗