Biomedical subjects

M T Moslen

Publications and source records attributed to M T Moslen.

At least 37 records · Page 2Linked to original sources

PubMed1992

Hepatic function during short-term total parenteral nutrition: effect of exposure of parenteral nutrients to light.

Total parenteral nutrition (TPN) solutions either exposed to light (+L) or protected from light (-L) were infused for 5 days through jugular cannulas in freely moving rats placed in metabolic cages. At the end of the 5 day period, bile flow, biliary inorganic phosphate and biliary gamma-glutamyl transferase activity, as well as biliary concentrations of several essential and branch chain amino acids were significantly lower in the -L animals compared to +L animals. In addition, biliary glutathione was significantly lower in the +L animals. In both groups of animals, plasma tyrosine decreased significantly from pre-TPN values despite a doubling of plasma phenylalanine concentrations suggesting that tyrosine may become a conditionally essential amino acid in rats provided TPN. Our findings indicate that short-term parenteral infusion of light exposed TPN solutions alters hepatobiliary function as well as amino acid homeostasis and that the changes are minimized by light protection of the infusates. The exact mechanisms of the contribution of light exposure in the induction of hepatic dysfunction remain to elucidated.

Amino Acids↗

PubMed1991

1,1-Dichloroethylene hepatotoxicity: hypothyroidism decreases metabolism and covalent binding but not injury in the rat.

Our objective was to determine if the previously reported protective effect of hypothyroidism against 1,1-dichloroethylene hepatotoxicity was associated with a change in distribution and covalent binding. Sprague-Dawley male rats were made hypothyroid (HypoT) by surgical thyroidectomy 2 weeks prior to studies and compared to euthyroid (EuT) rats. Hypothyroidism decreased body weights and liver to body weight ratios while mitochondrial non-protein sulfhydryl groups and cytosolic alcohol dehydrogenase activities were increased by 50%. Rats received a single oral dose of 100 mg [14C]1,1-dichloroethylene (DCE)/kg in mineral oil and were killed at 2, 4, 12 or 24 h; controls received mineral oil only. More rapid liver injury, as measured by serum alanine aminotransferase activity and histology, was present at 2 and 4 h after DCE in HypoT than EuT rats, but a similar magnitude of injury was evident at 12 and 24 h. DCE decreased liver non-protein sulfhydryl groups to a comparable extent in HypoT and EuT rats. Cytosolic glutathione S-transferase and alcohol dehydrogenase activities were decreased only in HypoT rats after DCE. HypoT rats excreted approximately 30% less total [14C]DCE-derived label in urine and their livers, kidneys and lungs consistently contained slightly less covalently bound [14C]DCE-derived label. In contrast, between 1 and 4 h after DCE, greater amounts of acid-soluble and acid-precipitable [14C]DCE-derived label were recovered in red blood cells of HypoT rats. Our results indicate that hypothyroidism did not protect against oral DCE hepatotoxicity but was associated with a more rapid injury at early times. Concurrently, hypothyroidism was found to change the fate of [14C]DCE with higher amounts of 14C-label recovered at early times in red blood cells while less 14C-label was excreted in urine and bound to liver.

Administration, Oral↗

PubMed1989

A combined testing protocol for assessing genotoxicity in individual animals: application to environmental toxicology.

A multiple end-point approach to assessing genetic toxicity (the combined testing protocol, CTP) was evaluated in male and female CD-1 mice exposed subacutely (3 and 6 weeks) to low levels of a custom-blended gas mixture (epichlorohydrin, benzene, chloroprene and xylene, at 50, 100, 100, and 100 ppb, respectively, as the low dose, with concentration levels 10-fold and 100-fold higher as the intermediate and high doses, or 0.1, 1 and 10 ppm of benzene). Urine mutagenicity was tested in the Salmonella/microsome assay, chromosome aberrations were examined in bone marrow and spleen lymphocytes, micronuclei were measured in bone marrow and peripheral erythrocytes, and cytochrome P450 and glutathione S-transferases were measured in the liver. Structural aberrations in alveolar macrophages and spermatocytes, and thioguanine resistance in spleen lymphocytes were examined for their suitability for incorporation into the overall protocol. Spleen lymphocytes were the most sensitive indicator cells, and showed a dose-related increase (P less than 0.01) in structural chromosome aberrations and in cytotoxicity after 6 weeks of exposure. Analysis of micronucleus formation and metaphase aberrations in the bone marrow, and micronuclei in peripheral erythrocytes showed an overall statistically non-significant but positive trend at the high dose. No mutagenicity was detected in pooled urine samples. Liver microsomal cytochrome P450 was not increased, but cytosolic glutathione S-transferases were significantly increased in a dose-related manner. Since the probability of detecting a genotoxic effect increases with the number of endpoints and tissues examined, this approach should be applicable to many situations without having to perform separate experiments for each tissue examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants, Occupational↗

PubMed1989

The use of a silastic shield to protect an externalized biliary cannula.

A simple shield made of a folded silastic sheet is described for the protection of the externalized portion of a permanent biliary cannula in rats. Advantages of this shield are its light weight, flexibility, transparency, and ease of resealing for repeated interruption of hepatobiliary circulation. Since the shield is positioned around rather than being a segment of the cannula, a single length of tubing can be used.

Animals↗

PubMed1989

Histochemical and immunocytochemical evidence of early, selective bile canaliculi injury after 1,1-dichloroethylene in rats.

Canalicular and mitochondrial membranes were investigated as early foci of hepatocyte injury in fed and fasted male Sprague-Dawley rats given 50 mg of 1,1-dichloroethylene (DCE)/kg. Staining of the bile canaliculi localized enzymes, leucine aminopeptidase (LAP), and Mg++-dependent ATPase (Mg++-ATPase), was examined by histochemistry in frozen sections. Mitochondrial membrane enzymes, including succinate dehydrogenase, also were examined by histochemistry. Staining of two monoclonal antibodies, C-1 and 9-B1, whose binding is localized in the bile canalicular region, was examined by immunofluorescence in frozen sections. Fasted rats treated with DCE developed moderate liver damage by 4 hours as evidenced by increases in serum transaminase and bilirubin, whereas fed rats developed only slight cell damage. Centrolobular loss of immunocytochemical and histochemical canalicular staining, especially for C-1 and Mg++-ATPase, was evident as early as 1 hour after DCE and was striking by 2 hours in both fed and fasted rats. Decreases in mitochondrial enzymes were not evident histochemically in fed animals at any time after DCE and were found only at the later times in fasted animals given the toxin. Thus, DCE administration to fed rats provides a new model system of selective bile canaliculi injury.

Alkaline Phosphatase↗

PubMed1989

Protection by L-2-oxothiazolidine-4-carboxylate, a cysteine prodrug, against 1,1-dichloroethylene hepatotoxicity in rats is associated with decreases in toxin metabolism and cytochrome P-450.

Our objective was to determine if the intracellular cysteine precursor, L-2-oxothiazolidine-4-carboxylate (OTZ), would protect rats against the hepatotoxicity of 1,1-dichloroethylene (DCE) by altering the toxin's biologic fate. Fasted male rats were pretreated with 10 mmol of OTZ per kg s.c. in saline or with saline only 1 hr before administration of 14C-labeled DCE (50 mg/kg) p.o. in mineral oil. Serial blood samples were taken from permanent jugular cannulas between 1 and 24 hr to monitor the time course of injury and circulating levels of 14C-derived label. DCE caused less liver injury in the OTZ-pretreated group. This protection was associated with about 50% less total, acid soluble and acid precipitable 14C-label in serum; 30% less label in urine; and at 24 hr, 30 to 68% less covalently bound label in liver, kidney and lung. Extent of peak liver injury in individual animals correlated well with the amount of 14C-label in serum at early times and with the amount covalently bound to liver at 24 hr, but correlated poorly with label excreted into urine. An explanation for the apparent decrease in DCE metabolism by OTZ-pretreated animals was investigated by examining effects of OTZ on liver constituents known to have a role in DCE metabolism. Fasted rats given 10 mmol of OTZ per kg showed a persistent loss of hepatic cytochrome P-450 at 3 and 6 hr whereas their hepatic and renal reduced glutathione contents were transiently diminished at 3 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

A stable colorimetric assay to measure toxin elevation of inorganic phosphate in bile.

A modified assay for the measurement of nanomole amounts of Pi in 50 microliters of bile is described. The assay is based on the formation of a complex between malachite green dye and phosphomolybdate under acidic conditions. Only three simple steps are required to produce a colored complex which remains stable for at least 3 h; these steps are precipitation with acid, addition of color reagent containing dye and surfactant, and incubation at 37 degrees C. Analysis of bile samples collected from a rat given the toxin 1,1-dichloroethylene demonstrated that the assay is well suited to routine assays of biliary Pi as an endogenous indicator of aberrant hepatobiliary function.

Animals↗

PubMed1988

Genotoxic effects of a sub-acute low-level inhalation exposure to a mixture of carcinogenic chemicals.

A study was conducted using a combined testing protocol (CTP), to determine whether short-term biological end-points, singly or in combination, are sufficiently sensitive to identify damage induced by exposure to ambient levels of industrial chemicals. A small-scale inhalation set-up which is both economical and easy to assemble was designed. Mice were exposed to 4 concentrations of a custom-blend mixture of benzene, chloroprene, epichlorohydrin and xylene in a ratio of 2:2:1:2, respectively. The concentrations for benzene, chloroprene and xylene were 0, 0.1, 1.0 and 10 ppm each. Concentrations for epichlorohydrin were half those for the other components. Groups of 22 males and 22 female mice were exposed to each concentration of the mixture for 3 and 6 weeks. Selected biological end-points including urine mutagenesis, bone marrow cell aberrations and micronuclei, spleen lymphocyte aberrations and liver enzyme induction were monitored. The spleen lymphocyte aberrations and liver enzyme induction were the most sensitive end-points. The lymphocytes showed a significant induction of chromosome aberrations from exposure for 3 weeks to all 3 concentrations of the mixtures. After 6 weeks of exposure, significant induction of aberrations was observed after exposure to low and medium concentrations but not to the high concentration. This lack of response at the high concentration after 6 weeks exposure, appeared to correlate with a significant induction of glutathione S-transferase in the liver. Since this enzyme is known to detoxify 3 of the 4 chemicals in our mixture, it may indicate a detoxification mechanism after enzyme induction. The present study indicates that the CTP is sufficiently sensitive to identify toxicological effects after exposure to ambient levels of a gas mixture.

Administration, Inhalation↗

PubMed1988

Potentiation of 1,1-dichloroethylene hepatotoxicity: comparative effects of hyperthyroidism and fasting.

The responses of fed, fasted, and hyperthyroid (T4) Sprague-Dawley male rats to 50 mg 1,1-dichloroethylene (1,1-DCE)/kg were compared. Hyperthyroid rats received three sc injections of thyroxine (100 micrograms/100 g) at 48-hr intervals; all other rats were sham-injected. 1,1-DCE was given po in mineral oil 24 hr after the last T4 dose; controls received only mineral oil. Animals were killed at 2, 4, and 8 hr. Liver GSH contents were lowered about 55% by both fasting and T4 while GSH transferase activities were lowered about 20% by fasting and 35% by T4. Only T4 pretreatment lowered alcohol dehydrogenase activities. Liver injury (i.e., serum glutamate pyruvate transaminase, histology) after 1,1-DCE was minimal in fed rats, moderate in fasted rats, and intermediate in T4 rats. Fasted rats showed a more pronounced depletion of liver GSH after 1,1-DCE than T4 rats and only in fasted rats did the toxicant decrease activities of the detoxification enzymes. Hypoglycemia after 1,1-DCE occurred in fed rats, but more rapidly in T4 rats. In contrast, fasted rats unexpectedly became hyperglycemic after the toxicant. Patterns of body temperature change after the toxicant, which might be due to its metabolites, were dissimilar. Hypothermia was not observed in fed rats, was only transiently evident in T4 rats, but occurred rapidly within 1 hr in fasted rats and steadily became more severe. The dissimilar patterns of liver enzyme and body temperature and serum glucose change after the toxicant in the three groups are indicative of different pathways of injury potentiation by fasting and hyperthyroidism.

Alcohol Dehydrogenase↗

PubMed1988

Localization of high benzaldehyde dehydrogenase activity in rat upper gastrointestinal tract mucosa: a quantitative histochemical study.

An unusual aldehyde dehydrogenase (AlDH) phenotype, histochemically similar to the "tumor-associated" AlDH appearing during rat hepatocarcinogenesis, was detected in normal rat upper gastrointestinal tract tissues. This phenotype is characterized by high activities with aromatic substrates, i.e., benzaldehyde (Bz) and NADP. Frozen sections of GI tract tissue from normal rats and from liver nodules induced by a Solt-Farber protocol were evaluated for AlDH activity. A sensitive, high-resolution procedure was used in which sections are pre-incubated in nitroblue tetrazolium and then incubated at 20 degrees C in a viscous polyvinyl alcohol medium containing buffer, phenazine methosulfate, sodium azide, substrate, co-enzyme, and nitroblue tetrazolium. Incubation at a suboptimal pH of 7.0 was found to improve retention of the final reaction product and the linearity with time. Activity was quantitated by computer-assisted microscopic photometry. Intense BzDH-NADP activity was localized in the squamous epithelium of the tongue, esophagus, and fore-stomach, and in the glandular pit cells of the glandular stomach; this activity was not evident in the submucosa, muscle walls, and vessels. Little if any BzDH-NADP activity was observed in the small or large intestine, pancreas, and liver. AlDH in upper GI tissues and in liver nodules shared three characteristics: a sharp localization; a preference for Bz and NADP compared to the aliphatic substrate acetaldehyde and NAD; and a high co-enzyme-independent activity in the presence of Bz.

Aldehyde Oxidoreductases↗

PubMed1988

Effects of a cysteine precursor, L-2-oxothiazolidine-carboxylate, nutritional status, and sex on tissue glutathione and hepatic GSH-utilizing enzymes of CD-1 mice.

Objectives of this study were to compare the effects of sex, nutritional status and L-2-oxothiazolidine carboxylate (OTC) treatment on tissue constituents frequently involved in responses to chemical toxins. Four groups of adult CD-1 mice were studied: fed females, fed males, fasted males, and fasted males three hours after treatment with OTC (10 mmoles/kg, sc). Female fed mice were found to differ from male fed mice as follows: lower tissue GSH in liver and kidney but not lung; lower hepatic microsomal cytochrome P-450 content and cytosolic GSH transferase activities, particularly using CDNB as substrate; and higher hepatic GSH peroxidase but similar GSSG reductase activities. Overnight fasting was associated with a decrease in hepatic and renal GSH and hepatic cytochrome P-450. OTC treatment was only found to increase hepatic GSH and decrease renal GSH. Thus in fasted CD-1 male mice, the intracellular cysteine precursor, OTC, has an apparently selective effect on tissue GSH contents without confounding effects on hepatic GSH utilizing or restoring activities.

Animals↗

PubMed1986

Quantitative histochemistry of benzaldehyde dehydrogenase in hepatocellular carcinomas of vinyl chloride-treated rats.

Hepatocarcinogenesis in rats treated with several chemicals is associated with changes in aldehyde dehydrogenase (AlDH) activity, particularly heterogeneous expression of a "tumor specific" phenotype that is very active with aromatic aldehydes, e.g., benzaldehyde (Bz). Objectives of this study were first, to determine if liver cancers in vinyl chloride-treated rats also expressed this AlDH phenotype, and second, to quantitate the NAD- and NADP-dependent AlDH activity for the substrates Bz and acetaldehyde (Ac) in the cancers and surrounding tissue. Small cubes of tissue containing well-differentiated hepatocellular carcinoma were obtained from five Sprague-Dawley rats exposed to 2500 ppm vinyl chloride for 55 weeks. An optimized procedure was developed for AlDH histochemistry. Frozen sections were preincubated in nitroblue tetrazolium/acetone and then incubated at 20 degrees C in viscous polyvinyl alcohol media containing buffer, phenazine methosulfate, sodium azide, substrate, coenzyme, and nitroblue tetrazolium. Background activity was evaluated by omission of substrate. Activity was quantitated by computer-assisted microscopic photometry. All five carcinomas had heterogeneous staining of NADP- and NAD-dependent BzDH and AcDH activity, with clusters of very high-activity cells. The magnitude of staining in the high-activity neoplastic cells was at least tenfold greater for BzDH-NADP and about twofold greater for BzDH-NAD, AcDH-NADP, and AcDH-NAD than the staining in other liver cells. More neoplastic cells had high BzDH than high AcDH activity. Only BzDH-NADP was localized predominantly to the carcinoma.

Aldehyde Dehydrogenase↗

PubMed1985

Cholestasis and increased biliary excretion of inulin in rats given 1,1-dichloroethylene.

Bile flow and biliary excretion of the inert solute [3H]inulin were monitored in unanesthetized, freely moving male rats for 4 h after oral administration of 1,1-dichloroethylene (1,1-DCE) at a dose of 200 mg/kg. Comparisons were made between 4 groups: fed-controls, fed-1,1-DCE treated, fasted-controls, and fasted-1,1-DCE treated. Biliary inulin excretion was assessed at 30-min intervals as total excretion and as bile/plasma ratio. 1,1-DCE treatment was consistently associated with at least a 2-fold increase in both parameters of inulin excretion within 2 h after toxin administration. In contrast, 1,1-DCE treatment was not associated with changes in plasma inulin values at any time or in liver/plasma inulin ratios at 4 h. Bile flow decreased in all groups: gradually by 30% in the fed and fasted controls, by 40% in the fed-1,1-DCE treated group, and markedly by 65% in the fasted-1,1-DCE treated group. Liver damage at 4 h as reflected by elevated plasma activities of liver-derived enzymes was found only in fasted-1,1-DCE treated rats. Thus the cholestatic effect of 1,1-DCE appears related to the development of liver damage whereas other aspects of the hepatic response to 1,1-DCE may enhanced biliary excretion of inulin.

Animals↗

PubMed1985

1,2-Dibromoethane initiation of hepatic nodules in Sprague-Dawley rats selected with Solt-Farber system.

Initiating effects of the fumigant 1,2-dibromoethane (DBE) for liver were examined using the Solt-Farber selection system. Male Sprague Dawley rats (230-260 g) were given one oral dose of DBE (75 mg/kg), a two-thirds partial hepatectomy 4 h later, five oral doses of 2-acetylamidofluorene (AAF) (25 mg/kg) on days 17-21, CCl4 (2 ml/kg) on day 22, a booster dose of AAF (10 mg/kg) on day 32, and were sacrificed on day 82. Nodules and appreciable gamma-glutamyl transpeptidase foci were found in the livers of four of six animals given DBE, but not in any animals of the control group.

2-Acetylaminofluorene↗

PubMed1985

Rapid, substrate-specific, and dose-dependent deactivation of liver cytosolic glutathione S-transferases in vivo by 1,1-dichloroethylene.

Administration of 200 mg 1,1-dichloroethylene (1,1-DCE)/kg to fasted male rats rapidly decreased liver cytosolic glutathione (GSH) S-transferase activities by half within 1 hr. This early decrease was not associated with increased serum activities of this soluble enzyme and is considered due to enzyme deactivation. The early decrease in enzyme activities was concomitant with a three-fourths depletion of cytosolic GSH and preceded changes in cytochrome P-450 and the onset of liver cytotoxicity, both of which occurred abruptly between 2 and 3 hr. Substantial changes in GSH S-transferase activities at 4 hr were produced only by severely hepatotoxic doses of 1,1-DCE. The early decrease in hepatic GSH S-transferase activities was selective for substrates dichloronitrobenzene, chlorodinitrobenzene and 1,2-epoxy-3-(p-nitrophenoxy)-propane with apparent sparing of activity towards ethacrynic acid. The rapid, selective and dose-dependent deactivation of the hepatic GSH S-transferases could be relevant to the catastrophic hepatotoxicity of 1,1-DCE.

Alanine Transaminase↗

PubMed1984

Metabolism of [14C]carbon tetrachloride to exhaled, excreted and bound metabolites. Dose-response, time-course and pharmacokinetics.

Fasted male rats were given six doses of 14CCl4 ranging from non-hepatotoxic (0.1 mmole/kg) to severely hepatotoxic (26 mmoles/kg). Time-course and pharmacokinetics of CCl4, 14CO2 and CHCl3 elimination by exhalation were monitored by measuring amounts recovered in breath during discrete 15-min intervals for 8-12 hr. Amounts of 14C-labeled metabolite recovered bound to liver macromolecules at 24 hr and excreted in urine or feces for 24 hr were also determined. Comparison pharmacokinetic studies were done with 14CHCl3 and Na(2)14CO3. After all doses of 14CCl4, the major metabolite was CO2, twenty to thirty times less metabolite was recovered bound to liver macromolecules, and intermediate amounts of metabolite were excreted in urine and feces. CHCl3 was the least abundant metabolite at low CCl4 doses, but the second most abundant at high doses. Stronger associations were found between the magnitude of liver injury at 24 hr (quantitated as serum glutamate-pyruvate transaminase activity) and the extent or rate of CCl4 metabolism by pathways leading to CO2 and CHCl3 than by pathways leading to 14C-metabolites bound in liver or excreted in urine. Time-course and pharmacokinetic data indicated that a major pathway of CCl4 metabolism leading to CO2 became impaired within 2 hr after administration of hepatotoxic doses of CCl4.

Animals↗

PubMed1984

A single step method for the separation of rat liver cytosolic glutathione S-transferase isozymes.

A simple, single step chromatographic method was developed to separate the liver cytosolic glutathione S-transferase (GSH-S-t) isozymes from each other and from the bulk of the cytosolic protein. Five peaks of GSH-S-t activity, tested with 1-chloro-2,4-dinitrobenzene (CDNB) as a substrate, were eluted. By comparison of the activities with CDNB and the other substrate 3,4-dichloronitrobenzene (DCNB) the five peaks could be identified as GSH-S-t isozymes C, B, A, and AA, being GSH-S-t isozyme C eluted in two different peaks. The method was used to detect a decrease of specific GSH-S-t isozymes in the cytosol of rats intoxicated with carbon tetrachloride, as compared with control rats.

Animals↗

PubMed1984

Relationships between the pharmacokinetics of carbon tetrachloride conversion to carbon dioxide and chloroform and liver injury.

Rate and extent of CCl4 metabolism by pathways leading to CO2 and CHCl3 were evaluated by measuring the amounts of these metabolites exhaled during discrete intervals following six different doses of CCl4. Pulmonary pharmacokinetics of 14CO2 and CHCl3 exhalation after CCl4 administration were compared with those after Na214CO3 and 14CHCl3 administration. Exhalation of 14CO2 metabolite declined more rapidly than expected after hepatotoxic doses of CCl4. This decline could be due to injury associated changes in the metabolism of CCl4.

Animals↗