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Biomedical subjects

R G Knodell

Publications and source records attributed to R G Knodell.

At least 19 recordsLinked to original sources
PubMed2001

Long-term mortality and morbidity of transfusion-associated non-A, non-B, and type C hepatitis: A National Heart, Lung, and Blood Institute collaborative study.

Persons with non-A, non-B hepatitis (cases) identified in 5 transfusion studies in the early 1970s have been followed ever since and compared for outcome with matched, transfused, non-hepatitis controls from the same studies. Previously, we reported no difference in all-cause mortality but slightly increased liver-related mortality between these cohorts after 18 years follow-up. We now present mortality and morbidity data after approximately 25 years of follow-up, restricted to the 3 studies with archived original sera. All-cause mortality was 67% among 222 hepatitis C-related cases and 65% among 377 controls (P = NS). Liver-related mortality was 4.1% and 1.3%, respectively (P =.05). Of 129 living persons with previously diagnosed transfusion-associated hepatitis (TAH), 90 (70%) had proven TAH-C, and 39 (30%), non-A-G hepatitis. Follow-up of the 90 TAH-C cases revealed viremia with chronic hepatitis in 38%, viremia without chronic hepatitis in 39%, anti-HCV without viremia in 17%, and no residual HCV markers in 7%. Thirty-five percent of 20 TAH-C patients biopsied for biochemically defined chronic hepatitis displayed cirrhosis, representing 17% of all those originally HCV-infected. Clinically evident liver disease was observed in 86% with cirrhosis but in only 23% with chronic hepatitis alone. Thirty percent of non-A, non-B hepatitis cases were unrelated to hepatitis viruses A,B,C, and G, suggesting another unidentified agent. In conclusion, all-cause mortality approximately 25 years after acute TAH-C is high but is no different between cases and controls. Liver-related mortality attributable to chronic hepatitis C, though low (<3%), is significantly higher among the cases. Among living patients originally HCV-infected, 23% have spontaneously lost HCV RNA.

Aged↗
PubMed1992

Long-term mortality after transfusion-associated non-A, non-B hepatitis. The National Heart, Lung, and Blood Institute Study Group.

BACKGROUND: Acute non-A, non-B hepatitis after blood transfusion often progresses to chronic hepatitis and sometimes culminates in cirrhosis or even hepatocellular carcinoma. However, the frequency of these sequelae and their effects on mortality are not known. METHODS: We traced patients with transfusion-related non-A, non-B hepatitis who had been identified in five major prospective studies conducted in the United States between 1967 and 1980. We matched each patient with two control subjects (identified as the first and second controls) who received transfusions but who did not have hepatitis. The mortality rates in the three groups were determined with use of data from the National Death Index and Social Security Death Tapes. Cause-specific mortality was determined by reviewing death certificates. RESULTS: Vital status was established for over 94 percent of the 568 patients who had had non-A, non-B hepatitis and the two control groups (526 first controls and 458 second controls). After an average follow-up of 18 years, the estimate by life-table analysis of mortality from all causes was 51 percent for those with transfusion-associated non-A, non-B hepatitis, as compared with 52 percent for the first controls and 50 percent for the second controls. The survival curves for the three groups were virtually the same. Mortality related to liver disease was 3.3, 1.1, and 2.0 percent, respectively, among the three groups (P = 0.033 for the comparison of the group with non-A, non-B hepatitis with the combined control group). Seventy-one percent of the deaths related to liver disease occurred among patients with chronic alcoholism. CONCLUSIONS: In this long-term follow-up study, there was no increase in mortality from all causes after transfusion-associated non-A, non-B hepatitis, although there was a small but statistically significant increase in the number of deaths related to liver disease.

Alcoholism↗
PubMed1991

Differential inhibition of individual human liver cytochromes P-450 by cimetidine.

Cimetidine binds to cytochrome P-450 and inhibits hepatic metabolism of various drugs in humans. However, cytochrome P-450 is a family of enzymes rather than a single protein, and effects of cimetidine on individual human liver cytochromes P-450 have not been previously characterized. Metabolism of selected substrates and cimetidine-binding assays have been performed using human liver microsomes, purified human liver cytochromes P-450, and cytochrome P-450 complementary DNA-expressed yeast proteins to probe interaction of cimetidine with these individual enzymes. Cimetidine (3.0 mmol/L) in incubations reduced bufuralol hydroxylase activity by 80% and strongly inhibited microsomal nifedipine oxidation (23% +/- 13% of control activity). The same concentration of cimetidine produced intermediate inhibition of cytochrome enzymes responsible for ethoxyresorufin deethylation and aniline hydroxylation (77% +/- 6% and 68% +/- 17% of activity in control microsomal incubations, respectively), but little effect on tolbutamide hydroxylation was observed. Concordantly, the calculated binding constant for the binding of cimetidine to a purified cytochrome P-450 with high tolbutamide hydroxylase activity was 4.4 mmol/L, whereas the calculated binding concentration constant for a purified cytochrome P-450-metabolizing nifedipine was 0.7 mmol/L. These studies show a high variability in the effect of cimetidine on drug metabolism by individual human liver cytochromes P-450. In vitro studies using human liver microsomes and genetically engineered human cytochromes P-450 can be very useful in exploring important clinical questions of hepatic drug metabolism.

Adult↗
PubMed1991

Nodular regenerative hyperplasia: a cause of ascites and hepatomegaly after chemotherapy for leukemia.

Tender hepatomegaly and ascites occurred in a young woman receiving cytosine arabinoside and daunorubicin for acute myelogenous leukemia. Whereas veno-occlusive disease was suspected clinically, liver biopsy showed nodular regenerative hyperplasia with no evidence of hepatic vein abnormalities. It is postulated that nodular regenerative hyperplasia can be initiated by hepatotoxicity of chemotherapy agents used to treat leukemia and/or that these agents exacerbate clinical manifestations of this histological abnormality. Nodular regenerative hyperplasia should be added to the list of liver problems occurring in patients with leukemia.

Abdominal Pain↗
PubMed1990

Influence of hyperalimentation on rat hepatic microsomal fluidity and function.

Total parenteral nutrition with an amino acid-glucose solution has previously been shown to decrease rat hepatic drug metabolism compared with drug metabolic activity observed in rats receiving the same solution enterally and chow-fed animals. Because changes in membrane fluidity and lipid composition are reported to influence activity of a number of liver enzymes, effects of parenteral and enteral nutrition on hepatic microsomal membrane fluidity and lipid composition were assessed and compared with hepatic mixed-function oxidase activity. Both parenteral and enteral hyperalimentation produced a significant decrease in microsomal membrane fluidity (fluorescence anisotropy = 0.155 +/- 0.003 in both experimental groups versus 0.129 +/- 0.003 for microsomes from chow-fed animals). However, meperidine demethylase activity was significantly decreased compared with chow-fed experiments only in hepatic microsomes from parenterally hyperalimented animals, whereas ethoxyresorufin deethylase activity was significantly reduced only in the enteral-nutrition group. Inclusion of lipid in the parenterally administered hyperalimentation solution normalized microsomal membrane fluidity and lipid profile to those of chow-fed animals but did not increase hepatic meperidine demethylation. Both parenteral and enteral nutrition produce significant changes in physical state and lipid composition of rat hepatic microsomal membranes, but these changes are not responsible for the altered hepatic drug metabolism observed during hyperalimentation.

Animals↗
PubMed1990

Caseating hepatic granulomas in Hodgkin's lymphoma.

A 68-year-old man presented with recurrent Hodgkin's lymphoma after a 9-year disease-free interval induced by chemotherapy. In addition to histological evidence of recurrent Hodgkin's disease, the liver biopsy specimen showed extensive caseating granulomas. Cultures of bone marrow and liver tissue tested negative for Mycobacterium tuberculosis. No antituberculous treatment was administered, and the patient had an excellent clinical response to additional chemotherapy for lymphoma. Hodgkin's lymphoma should be added to the list of disease entities associated with caseating granulomas in the liver.

Aged↗
PubMed1990

Resolution of inferior vena cava syndrome after embolization of a hepatic adenoma.

A 77-year-old man presented with severe pruritus and massive lower body edema. Computerized axial tomography of the abdomen showed a large hepatic mass compressing the inferior vena cava, and a liver biopsy specimen showed hepatic adenoma. Embolization of vessels feeding the hepatic tumor resulted in complete resolution of pruritus and ascites, and clinical remission has persisted for 1 year following partial obliteration of tumor vasculature. Angiographic ablation of tumor blood supply represents a nonoperative means for inducing clinical remission in patients with symptomatic hepatic adenoma who are at high surgical risk.

Adenoma↗
PubMed1989

Selective alteration of constitutive hepatic cytochrome P-450 enzymes in the rat during parenteral hyperalimentation.

Decreased drug metabolism and hepatic cytochrome P-450 levels have been shown previously to occur in rats receiving total parenteral nutrition (TPN) compared to animals receiving the same hyperalimentation solution enterally (TEN). In the present studies, animals received a 7-day infusion of a 25% glucose-2.75% crystalline amino acid solution via a catheter in the jugular vein or stomach; hepatic microsomal levels of four major constitutive cytochromes P-450 were determined subsequently by immunoquantitation and correlated with metabolism of selected substrates biotransformed by these enzymes. TPN resulted in a marked decrease in apoprotein of two constitutive cytochromes P-450, P-450UT-A and P-450PCN-E, compared to TEN experiments (for P-450UT-A, 11.0 +/- 1.8 vs 44.7 +/- 6.5% of total cytochrome P-450 measured by CO-difference spectra, P greater than 0.001; for P-450PCN-E, 15.4 +/- 4.4 vs 30.2 +/- 7.6%, P less than 0.01), but apoprotein levels of two other constitutive cytochromes P-450, P-450PB-C and P-450UT-F, showed relatively little change. Concordant reductions in metabolism of benzphetamine, ethylmorphine and erythromycin were seen in TPN animals. While the mechanisms responsible for these selective changes in the synthesis and function of individual cytochromes P-450 remain to be elucidated, altered gene transcription due to differences in portal blood composition elicited by intravenous versus enteral feeding is a possible hypothesis. These studies also provide information which should be valuable in designing studies to probe further the clinical question of whether TPN induces significant alterations in human drug metabolism.

Animals↗
PubMed1988

Primary malignant melanoma of the rectum. Evidence for origination from rectal mucosal melanocytes.

Reports of rectal melanoma often attribute the lesion to tumor extension from anal melanocytes which have undergone malignant transformation while the existence of true primary melanoma of the rectum has been disputed. This dispute primarily relates to past inability to demonstrate normal melanocytes in rectal mucosa. In this case report, two polypoid melanomas clearly located in the rectum were discovered at sigmoidoscopy. Thorough histologic examination failed to demonstrate atypical anal melanocytes, and the presence of normal melanocytes in the rectal mucosa was confirmed by electron microscopy and immunohistochemistry. Although rare, it appears that primary malignant melanoma may arise from melanocytes among columnar rectal epithelium.

Aged↗
PubMed1988

Oxidative metabolism of hexobarbital in human liver: relationship to polymorphic S-mephenytoin 4-hydroxylation.

The major route of hexobarbital metabolism in humans involves hydroxylation at the 3'-position followed by oxidation to a 3'-keto metabolite. Studies were performed to characterize the form of cytochrome P-450 responsible for the initial oxidation. In vitro studies indicated that P-450MP purified from human livers, involved in the 4-hydroxylation of S-mephenytoin, efficiently catalyzed the 3'-hydroxylation of hexobarbital; moreover, polyclonal antibodies raised to this enzyme extensively inhibited such activity in human liver microsomes. S-Mephenytoin 4- and hexobarbital 3'-hydroxylase activities in microsomes from different livers were significantly correlated, and both activities were essentially absent in fetal liver preparations. Hexobarbital was also found to inhibit S-mephenytoin 4-hydroxylation and vice versa, with Ki values similar to the Km values for the measured pathways. These data suggested that in vivo metabolism of hexobarbital would be determined by the same genetic factor(s) responsible for polymorphic 4-hydroxylation of S-mephenytoin. This prediction was confirmed by the finding that, after oral administration of a single dose of hexobarbital (300 mg), the 24-hr urinary excretion of 3'-hydroxy- and 3'-ketohexobarbital in a "poor-metabolizer" was only one third of that in a subject of the "extensive-metabolizer" phenotype. Also, the plasma level of metabolites at 6 hr after administration was reduced, and that of unchanged drug was increased in the poor metabolizer. Finally, a markedly enhanced sedative effect was associated with the impaired metabolism. Accordingly, several lines of in vitro evidence indicate that hexobarbital 3'-hydroxylation is catalyzed by P-450MP.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytochrome P-450 Enzyme System↗
PubMed1987

Newer agents available for treatment of stress-related upper gastrointestinal tract mucosal damage.

Results of animal studies and human clinical trials assessing the efficacy of newer agents in the treatment of stress-related mucosal damage have been reviewed. Currently available data suggest that prostaglandin treatment is as effective in preventing and treating stress-induced mucosal injury as more established therapeutic modalities, but that the proposed efficacy of somatostatin infusion and tranexamic acid administration is highly suspect. Promising agents yet to be evaluated include omeprazole, allopurinol, and epidermal growth factor.

Animals↗
PubMed1987

Stress-related mucosal damage: critical evaluation of potential new therapeutic agents.

Cell injury produced by hydrochloric acid is the final common denominator for stress-related mucosal damage. Actions of therapeutic agents designed to prevent such damage are directed toward either inhibiting acid secretion or stimulating protective mechanisms. Newer agents that fall into the former category include omeprazole, an inhibitor of the H+-K+-ATPase pump, prostaglandins, and somatostatin. In addition to inhibiting acid, prostaglandins stimulate mucus and bicarbonate secretion and therefore provide a two-pronged protective action. Tranexamic acid is an antifibrinolytic agent that is postulated to promote clotting at bleeding sites in upper gastrointestinal lesions. Analyses of composite data suggest that (1) prostaglandin E preparations appear to be as effective as currently recognized forms of therapy, such as antacid and H2-receptor antagonist administration; (2) little enthusiasm can currently be generated for use of somatostatin or tranexamic acid; and (3) omeprazole is a theoretically attractive agent that remains to be tested in the prophylactic treatment of gastrointestinal ulceration due to severe stress.

Anti-Ulcer Agents↗
PubMed1987

Hepatic bile formation in the rat. Addition of vasoactive intestinal peptide to the equation.

While changes in gastric, pancreatic, and intestinal secretion in response to more recently identified gastrointestinal peptides have been characterized, there has been less investigation into effects of these hormones on hepatic bile production. The isolated perfused rat liver model has been used to examine effects of vasoactive intestinal peptide (VIP), somatostatin, bombesin, and thyrotropin-releasing hormone (TRH) on bile flow and bile acid transport. No changes were seen following bolus administration of bombesin (3 X 10(-8)-1.5 X 10(-6) M) or TRH (3 X 10(-7)-3 X 10(-6) M), while somatostatin (6 X 10(-6) M) produced a small decrease in bile flow without any change in bile acid output. VIP (3 X 10(-7) M) caused a highly significant increase in both volume of bile flow (0.85 +/- 0.8 to 1.11 +/- 0.09 microliter/min/g liver, P less than 0.001) and bile acid output (31.6 +/- 1.5 to 43.2 +/- 1.7 nmol/min/g liver, P less than 0.001). Elimination of Ca2+ from liver perfusate did not prevent VIP-induced increases in bile flow and bile acid output, and no synergistic effect of concomitant theophylline administration was observed. While effects of VIP on bile flow appear to be due to alterations in hepatic transport of bile acids, the exact mechanism(s) producing these changes remains to be elucidated.

Animals↗
PubMed1987

Polymorphism of human cytochrome P-450.

The cytochrome P-450 forms involved in debrisoquine 4-hydroxylation (P-450DB), phenacetin O-deethylation (P-450PA), S-mephenytoin 4-hydroxylation (P-450MP), and nifedipine 1,4-oxidation (P-450NF) have been purified to electrophoretic homogeneity from human liver microsomes. All of these reactions show in vivo polymorphism in humans. Evidence for the roles of the purified proteins in these processes comes from in vitro reconstitution and immunoinhibition studies. The rat orthologs of these enzymes are as follows--P-450DB: P-450UT-H; P-450PA: P-450ISF-G; P-450MP: P-450UT-I; P-450NF: P-450PCN-E. Only in the case of P-450UT-H is the primary rat ortholog the same cytochrome P-450 which catalyses the catalytic reaction under consideration. Reconstitution and immunochemical studies establish that the following reactions are catalysed by the individual P-450s--P-450DB: debrisoquine 4-hydroxylation, sparteine delta 5-oxidation, bufuralol 1'-hydroxylation, encainide O-demethylation, and propanolol 4-hydroxylation; P-450PA: phenacetin O-deethylation; P-450MP: S-mephenytoin 4-hydroxylation and tolbutamide methyl hydroxylation; P-450NF: oxidation of nifedipine and 16 other substituted dihydropyridines, estradiol 2- and 4-hydroxylation, aldrin epoxidation, benzphetamine N-demethylation and 6 beta-hydroxylation of testosterone, androstenedione and cortisol. A cDNA clone has been isolated that corresponds to rat P-450UT-H, as shown by a number of criteria. Studies with this probe establish that the sex and strain variation in debrisoquine 4-hydroxylase and related activities is related to differences in the levels of a 2.0 kb length mRNA present.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Influence of gastrointestinal peptides on bile acid transport by isolated rat hepatocytes.

While numerous effects of gut peptides on gastric, pancreatic, and intestinal secretion have been described, there has been little investigation of the influence of these peptides on hepatic function. In the present studies, effects of vasoactive intestinal peptide (VIP), somatostatin, thyrotropin-releasing hormone (TRH), and bombesin on taurocholate transport by isolated rat hepatocytes have been examined. Somatostatin, TRH, and bombesin in incubation media produced no change from control incubations with regard to either uptake of taurocholate by hepatocytes or efflux of bile acid from preloaded cells. However, incubation of hepatocytes with VIP produced a significant decrease in taurocholate uptake (1.34 +/- 0.13 versus 1.73 +/- 0.16 nmole.min-1.10(6) cells-1, P less than 0.001). Studies with verapamil, a calcium-channel blocking agent, and theophylline, an inhibitor of cAMP catabolism, failed to provide evidence for transmembrane Ca2+ flux or alteration in intracellular levels of cAMP, respectively, as mechanisms for the observed inhibition of hepatocyte taurocholate uptake by VIP. These data, coupled with both clinical and other basic observations, suggest that VIP may play a significant role in the regulation of hepatic bile secretion.

Animals↗
PubMed1987

Hepatic metabolism of tolbutamide: characterization of the form of cytochrome P-450 involved in methyl hydroxylation and relationship to in vivo disposition.

In vitro investigations suggest the same human liver cytochrome P-450 that catalyzes S-mephenytoin 4-hydroxylation, P-450MP, is responsible for methyl hydroxylation of the oral hypoglycemic agent tolbutamide. Tolbutamide hydroxylase activity copurified with P-450MP; electrophoretically homogenous P-450MP catalyzed both tolbutamide and S-mephenytoin hydroxylation. Each substrate competitively inhibited hydroxylation of the other, and anti-P-450MP inhibited tolbutamide hydroxylation in human liver microsomes. Significant correlation between tolbutamide and S-mephenytoin hydroxylase activities was seen in a set of human liver samples. These findings suggested that subjects with a genetically determined impairment in ability to hydroxylate mephenytoin might also have deficient tolbutamide metabolism. However, plasma tolbutamide concentration-time profiles and urinary excretion of metabolites formed via the hydroxylation pathway were similar in four phenotypically poor and six extensive metabolizers of mephenytoin. We suggest that alteration of a substrate binding site of P-450MP may reduce its ability to hydroxylate S-mephenytoin but not tolbutamide.

Adult↗
PubMed1984

Separate influences of insulin and hyperglycemia on hepatic drug metabolism in mice with genetic and chemically induced diabetes mellitus.

Numerous investigators have reported abnormalities of hepatic drug metabolism in hypoinsulinemic animal models with chemically induced diabetes mellitus, but there has been little assessment of hepatic drug metabolism in recently described animal models with genetic diabetes mellitus characterized by hyperinsulinemia and insulin resistance rather than insulin deficiency. Hepatic microsomal cytochrome P-450 content and drug metabolizing activity in obese, diabetic C57BL/KsJ mice homozygous for the diabetes gene mutation (db/db) have been compared with levels found in livers of 1) lean, nondiabetic control mice with the same C57BL/KsJ genetic background and 2) lean C57BL/6J animals made diabetic by streptozotocin treatment. No changes in specific enzyme content or activity were seen in young db/db mice, but microsomal protein and total hepatic cytochrome P-450 content and meperidine demethylation and pentobarbital hydroxylation activity were markedly increased compared to controls. In hyperglycemic, hypoinsulinemic mice with streptozotocin-induced diabetes mellitus, the amount of microsomal protein did not change, but hepatic cytochrome P-450 content and enzyme activity were significantly increased whether expressed per milligram of microsomal protein or as totals per liver. In old db/db animals, hyperglycemia persisted but plasma insulin levels fell into the normal range so that the insulin-glucose profile of these animals resembled that seen in the streptozotocin treatment group. In association with these changes, hepatic enzyme specific activities in the old db/db mice approximated values found in the streptozotocin group rather than in the young db/db animals. These differences in hepatic microsomal enzymes between hyperinsulinemic and hypoinsulinemic mice with diabetes mellitus suggest that both hyperglycemia and insulin separately and significantly influence cytochrome P-450 turnover and mixed function oxidase activity.

Animals↗