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K Brendel

Publications and source records attributed to K Brendel.

At least 37 records · Page 2Linked to original sources
PubMed1995

Use of tissue slices in chemical mixture toxicology and interspecies investigations.

Precision-cut tissue slices have proven to be a useful in vitro system for biotransformation and toxicity studies. Since tissue slices can be readily prepared from a variety of tissues and species, they can easily be used for interspecies investigations and comparisons. Furthermore, slices can be readily prepared from human tissue, thus comparisons (extrapolation) can be made between laboratory animals and humans. Slices can also be used to examine the toxic interactions of chemicals in vitro. It is important to use the correct experimental design to demonstrate toxic interactions and to assure that the tissue slices are properly exposed to the chemicals. Overall, tissue slices offer a valid in vitro system for performing species comparisons and chemical-chemical interaction studies.

Animals↗
PubMed1995

Sodium arsenite and heat shock induce stress proteins in precision-cut rat liver slices.

The present study was undertaken to investigate the usefulness of stress proteins as early, sensitive indicators of hepatotoxicity. Induction of stress protein synthesis in precision-cut rat liver slices was examined following in vitro exposure to sodium arsenite or heat shock. Precision-cut rat liver slices were incubated with 10(-5) or 10(-6) M sodium arsenite for 2, 4 or 8 h in the presence of 35S-methionine or exposed to hyperthermia (42.5 +/- 0.5 degrees C) for 45 min and then incubated with 35S-methionine for 2, 4 or 8 h. Fluorographic analysis indicated an increase in the synthesis of HSP 70 and HSP 90 family of proteins by both treatments. Immunoblot analysis demonstrated that there was a specific induction of HSP 72 and HSP 90. Induction of HSP 70 was greater than that of HSP 90 by both treatments. Stress protein induction occurred at earlier times by concentrations of arsenite which did not alter other viability parameters such as leakage of intracellular K+ or total protein synthesis. The results indicated that induction of stress proteins has the potential usefulness as an early biomarker of arsenite toxicity.

Animals↗
PubMed1995

Antineoplastic drugs sulindac sulfide and sulfone inhibit cell growth by inducing apoptosis.

The nonsteroidal anti-inflammatory drug sulindac is known to inhibit chemical carcinogenesis in rodent models and cause regression of adenomas in patients with adenomatous polyposis coli. Sulindac is a prodrug that is metabolized to a pharmacologically active sulfide derivative that potently inhibits prostaglandin synthesis. Recent studies, however, have shown that a sulfone derivative of sulindac, which essentially lacks prostaglandin synthesis inhibitory activity, also inhibits chemical carcinogenesis, suggesting that reduction of prostaglandin levels is not necessary for the antineoplastic activity of this class of drugs. Both sulindac sulfide and the sulfone inhibit the growth of cultured tumor cells, although the cellular mechanism(s) responsible for the antineoplastic activity of sulindac derivatives is unknown. In this study, we investigated the effects of sulindac sulfide and sulfone on the proliferation, differentiation, and apoptosis of HT-29 human colon carcinoma cells. Sulindac sulfide and sulfone significantly reduced cell number in both preconfluent and confluent cultures of HT-29 cells with the sulfide showing approximately 4-fold greater potency. In addition to HT-29 cells, both drugs inhibited the growth of a variety of tumor cell lines derived from other tissues, as well as normal epithelial cells and fibroblasts. Neither sulindac sulfide nor sulfone inhibited cell proliferation under conditions where the drugs were growth inhibitory. Only under specific conditions involving mitogenic stimulation did sulindac sulfide and sulfone cause cell cycle arrest. Neither sulindac sulfide nor the sulfone induced differentiation of HT-29 cells, but both drugs strongly induced apoptosis. The apoptotic response to sulindac sulfide and sulfone was both time- and dose-dependent and involved a mechanism independent of their inhibitory effect on cell cycle progression. These data suggest that apoptosis is responsible for the cell growth inhibitory activity of sulindac sulfide and sulfone and represents a potential mechanism for the antineoplastic activity of these drugs.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1995

Do NSAIDs exert their colon cancer chemoprevention activities through the inhibition of mucosal prostaglandin synthetase?

Nonsteroidal antiinflammatory drugs (NSAIDs) have considerable potential as chemopreventive agents for colorectal cancer. Recent case-control drug surveillance and large cohort studies found that patients with regular aspirin use had a reduced incidence of colorectal cancer and/or decreased death rate from this disease. Several different NSAIDs reduce formation of both colon adenomatous polyps (the precursor lesion of colon cancer) and cancers in experimental animals given known carcinogens. Perhaps most convincing are reports that the NSAID sulindac promotes regression and inhibits recurrence of adenomatous colon polyps in patients with adenomatous polyposis coli. The best characterized pharmacologic effect of the NSAIDs is their reduction of prostaglandin synthesis by inhibiting prostaglandin synthetase PGE2, which catalyzes the formation of prostaglandin precursors from arachidonic acid. Several lines of evidence are contrary to the concept that inhibition of prostaglandin synthesis is central to the NSAIDs' chemopreventive effects. Relatively high levels of prostaglandins have been reported to inhibit tumor cell growth both in vivo and in vitro, and to inhibit differentiation in some tumor cell lines. We evaluated comparative chemopreventive effects on colon tumor formation in an azoxymethane (AOM)-induced colon carcinogenesis rat model using the NSAIDs piroxicam, sulindac, and sulindac sulfone, a metabolite of sulindac which lacks the anti-prostaglandin synthetase activity typically associated with NSAID-induced gastrointestinal toxicities. The results demonstrate that sulindac sulfone, a compound lacking anti-prostaglandin synthetase activity, inhibits AOM-induced colon cancer in rats. Substantial dose-dependent reductions in both tumor burden and tumor multiplicity were observed in the sulindac sulfone-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Precision-cut tissue slices: applications in pharmacology and toxicology.

Almost a decade has passed since the first paper describing the isolation and maintenance of precision-cut liver slices produced using a mechanical tissue slicer was published (1). Although tissue slices of various organs have been employed as an in vitro system for several decades, the lack of reproducibility within the slices and the relatively limited viability of the tissue preparations has prevented a widespread acceptance of the technique. The production of an automated slicer, capable of reproducibly producing relatively thin slices of tissue, as well as the development of a dynamic organ culture system, overcame several of these obstacles. Since that time, significant advances in the methods to produce and culture tissue slices have been made, as well as the application of the technique to several other organs, including kidney, lung and heart. This review will i) summarize the historical use of tissue slices prior to the development of the precision-cut tissue slice system; ii) briefly analyze current methods to produce precision-cut liver, kidney, lung and heart slices; and iii) discuss the applications of this powerful in vitro system to the disciplines of pharmacology and toxicology.

Animals↗
PubMed1995

Comparative metabolism and toxicity of dichlorobenzenes in Sprague-Dawley, Fischer-344 and human liver slices.

1. Precision-cut liver slices, prepared from Sprague-Dawley and Fischer-344 rats and donated human liver tissue, were used to identify differences in 1,2-dichlorobenzene (1,2-DCB), 1,3-dichlorobenzene (1,3-DCB) and 1,4-dichlorobenzene (1,4-DCB) metabolism and how it may relate to toxicity. 2. Rat and human liver slices were incubated with 1 mM of either dichlorobenzene to determine metabolism and toxicity, at 2 and 6 h of organ culture. 3. The human liver slices metabolised the dichlorobenzenes to a greater extent than those from either of the rat strains. Liver slices from the Fischer-344 strain had a higher metabolic rate than the slices from the Sprague-Dawley rat strain. 4. The metabolic rate of dichlorobenzene isomers did not consistently correlate with its toxicity. For example, human slices did not exhibit any hepatoxicity, even though they metabolised these compounds to a greater extent than either rat strain. 5. Cross species covalent binding did not correlate with toxicity endpoints measured in this study. 6. The phase two metabolite profiles for each of the isomers in human and rat slices were similar in that the glutathione-cysteine conjugate was the major metabolite. 7. The use of an in vitro system which utilises human liver slices might provide an important bridge between animal derived data and the human situation.

Adolescent↗
PubMed1995

Glutathione effects on toxicity and uptake of mercuric chloride and sodium arsenite in rabbit renal cortical slices.

The mechanism of renal uptake of nephrotoxic heavy metals such as HgCl2 and NaAsO2 is not clear. The metals are known to react with endogenous sulfhydryls such as glutathione (GSH), so metal-GSH conjugates may be delivered to the kidney. To study this possibility, renal cortical slices from male New Zealand white rabbits were incubated with 10(-4) M HgCl2 or 10(-3) M NaAsO2 +/- stoichiometric amounts (1-3x) of GSH; or synthetic metal-GSH conjugates [10(-4) M Hg(SG)2 or 10(-3) M As(SG)3]. Incubations were performed at 37 degrees C in DME-F12 buffer (95/5 O2/CO2) for 8 hr. Hg(SG)2 reduced slice K+/DNA content, as an indicator of viability, significantly less than HgCl2. As(SG)3 exhibited a 2-hr delay in K+/DNA content reduction compared to NaAsO2. This delay in toxicity was not correlated to changes in uptake. Arsenic and mercury accumulation, determined by proton-induced X-ray emission, were also identical between the metal salts and the metal-GSH conjugates. Exogenous GSH decreased HgCl2 cytotoxicity and was correlated to a decrease in Hg accumulation in the slice. Exogenous GSH had limited if any protective effects against cytotoxicity by NaAsO2 and a decrease in As accumulation was not observed. Complex metal-GSH interactions appear to exist and impact on the uptake and toxicity of these metals.

Animals↗
PubMed1995

Biotransformation of sevoflurane by rat neonate liver slices.

Sevoflurane [CF3-CH(OCH2F)-CF3] is biotransformed to inorganic fluoride (F-) and hexafluoroisopropanol, which forms a glucuronide conjugate. Although sevoflurane may be used in newborns without fully developed biotransformation activity, studies were performed using liver slices from rat neonates to determine sevoflurane disposition. Sevoflurane was vaporized in sealed roller culture vials to produce a continuous saturating dose (0.5 mM). After incubation, slices and incubation media were sonicated and centrifuged to remove debris. The supernatant fraction was analyzed for F-, hexafluoroisopropanol, and hexafluoroisopropanol-glucuronide conjugate. The metabolism of sevoflurane by liver slices increased proportionately with time with a stoichiometric production (1:1) of hexafluoroisopropanol and F- in all age groups. Only glucuronide conjugates of hexafluoroisopropanol were found. The rate of sevoflurane biotransformation measured as fluoride production was similar among slices prepared from all neonate age groups. Although no hexafluoroisopropanol-glucuronide was generated by slices from 4-, 6-, and 8-day-old neonates, by day 21, 17% of the total hexafluoroisopropanol is glucuronidated. This contrasts with the lower levels of free hexafluoroisopropanol typically seen in adults liver slices, wherein 51% of the hexafluoroisopropanol was glucuronidated. These studies indicate that sevoflurane is equally metabolized to hexafluoroisopropanol and F-, but a deficiency in glucuronosyltransferase occurs in neonates.

1-Propanol↗
PubMed1995

Sites of biotransformation for the cyclosporin derivative SDZ IMM 125 using human liver and kidney slices and intestine. Comparison with rat liver slices and cyclosporin A metabolism.

SDZ IMM 125 (IMM), the hydroxyethyl derivative of cyclosporin A (CSA), is metabolized by human liver slices to analogous primary metabolites, hydroxylated IMM1 and IMM9 and N-demethylated IMM4N, as for CSA (M17/AM1, M1/AM9, and M21/AM4N), but the rate and extent of IMM biotransformation is less than for CSA. Initial rates of IMM metabolite formation in the human liver slice cultures are 6.6 +/- 2.8 nmol/hr/g liver at 1 microM IMM and 24.3 +/- 22.9 nmol/hr/g liver at 10 microM IMM, whereas the rate of CSA metabolite formation is 1.8-fold faster at both concentrations. The percentage of unchanged IMM is 73% at 1 microM and 80% at 10 microM after 24 hr, reflecting the lower extent of IMM metabolism, about one-third (1 microM) and one-half (10 microM) that of CSA. In rat liver slices, IMM is metabolized to the same primary metabolites as in human liver slices, but more slowly and remains 90% unchanged at 24 hr. Human jejunum formed the same primary metabolites of IMM and CSA as in liver. Upscaling the slice rate of biotransformation revealed that human jejunum would contribute considerably to the first-pass of IMM and CSA, being approximately 2 to 3-fold slower than the rate in liver. The inhibition of both IMM and CSA biotransformation by triacetyloleandomycin implicates the involvement of cytochrome P4503A proteins. Human kidney cortex slices metabolized IMM to IMM1 and IMM9, accounting for approximately 75% of the total metabolites. Total metabolite formation represented approximately 64% of liver metabolite formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

The interactive toxicity of CHCl3 and BrCCl3 in precision-cut rat liver slices.

The interactive toxicity of two nontoxic concentrations of chloroform (CHCl3) and bromotrichloromethane (BrCCl3) was examined in precision-cut rat liver slices. Liver slices were prepared from male Sprague-Dawley rats (220-250 g) pretreated with phenobarbital for 4 days. Toxicants were administered 1 hr apart. Intracellular K+ levels were similar to untreated controls in slices treated with 0.2 mM CHCl3 or 0.125 microliters (0.25 mg, 1.26 mumol) BrCCl3 alone, indicating that these concentrations were nontoxic. However, addition of both toxicants, irrespective of order, resulted in a time-dependent loss of intracellular K+ which was significant at 9 hr following administration. This was interpreted as evidence of synergistic toxicity. Cytochrome P450 loss was significant as early as 3 hr following exposure to BrCCl3, alone or when added with CHCl3. This loss may be attributed to BrCCl3-induced suicide inactivation of cytochrome P450. Centrilobular hepatocytes may be more susceptible to the interactive toxicity of CHCl3 and BrCCl3. Activity of enzymes found predominantly in this area was significantly decreased in slices exposed to both toxicants relative to controls. Conversely, activity of enzymes found predominantly in the periportal region was similar to that of untreated and treated controls. Interactive toxicity of BrCCl3 and CHCl3 was not a consequence of increased lipid peroxidation or depletion of slice glutathione content. Further studies need to be conducted to elucidate the mechanisms mediating the interactive toxicity of BrCCl3 and CHCl3.

Animals↗
PubMed1994

Cresol isomers: comparison of toxic potency in rat liver slices.

A comparison of the toxicity of cresol isomers (o-, m-, and p-methylphenol) was carried out using precision-cut rat liver slices as a test system. At equimolar concentrations p-cresol was the most toxic isomer. A 5- to 10-fold higher concentration of either the o- or m-isomers was required to observe the same degree of cell killing as p-cresol. The toxicity of p-cresol was inhibited by the thiol precursor N-acetylcysteine and was enhanced by pretreatment of liver slices with diethyl maleate to deplete glutathione. These treatments, however, had little effect on either o- or m-cresol toxicity. p-Cresol rapidly depleted intracellular glutathione levels, while the o- and m-isomers depleted glutathione to a lesser extent. [14C]p-cresol was metabolized to a reactive intermediate which covalently bound to slice protein and was inhibited by N-acetylcysteine. In microsomal incubations covalent binding of [14C]p-cresol metabolites was also observed. This binding was inhibited by glutathione and resulted in the formation of a glutathione conjugate. In the absence of glutathione, p-hydroxybenzyl alcohol was the major microsomal metabolite formed from p-cresol, but this compound was not toxic to liver slices at a concentration of 2 mM. These results demonstrate that p-cresol is the most toxic cresol isomer in rat liver tissue and that its toxicity is dependent on the formation of a reactive intermediate. The results also suggest that the mechanism(s) of toxicity of the o- and m-isomers may differ from that of p-cresol.

Acetylcysteine↗
PubMed1994

Inactivation of cytochromes P450 2B protects against cocaine-mediated toxicity in rat liver slices.

Mechanism-based inactivators of rat liver cytochrome P450 2B1 and 2B2 were used to evaluate the role of these enzymes in the hepatotoxicity of cocaine. Loss of liver microsomal androstenedione 16 beta-hydroxylation was monitored to determine the extent of P450 2B1/2 inactivation by chloramphenicol (CAP) or its 2B-selective analogue, N-(2-p-nitrophenethyl)chlorofluoroacetamide (pNO2C1FA). The effect of P450 2B1/2 inactivation on cocaine-mediated hepatotoxicity was assessed in rat liver slices. Exposure of slices from phenobarbital-induced Lewis rats to CAP concentrations ranging from 100 to 500 microM resulted in a concentration-dependent decrease in P450 2B activity and a corresponding decrease in cytotoxicity as measured by K+ loss following exposure to 1 mM cocaine. Treating slices from PB-induced rats with 250 microM pNO2C1FA protected slices against cocaine-mediated cytotoxicity after exposure to 500 microM cocaine. In vivo administration of 300 mg/kg CAP or 200 mg/kg pNO2C1FA to phenobarbital-induced Lewis rats decreased androstenedione 16 beta-hydroxylation to 30 or 39% of control, respectively, and blocked cocaine-mediated K+ loss in rat liver slices. Rat liver microsomes from animals treated with either CAP or pNO2C1FA displayed approximately 40% of the control rate of cocaine N-demethylation. Experiments with phenobarbital-treated Munich Wistar (WM) rats, which lack 2B2, revealed similar rates of microsomal N-demethylation and comparable in vitro hepatotoxicity to Lewis rats. The capacity of a specific P450 2B1/2 inactivator to protect against cocaine-mediated hepatotoxicity both in vivo and in vitro and the results with the WM rats support the identification of P450 2B1 as a major cocaine bioactivating form.

Animals↗
PubMed1994

Toxic responses to defined chemical mixtures: mathematical models and experimental designs.

The problem and relevance of assessing biological responses to chemical mixtures is presented with reference to the literature on this problem and its possible solutions. This review is intended for a general audience as an introduction to, and comment on, assessing the interactions of defined mixtures of xenobiotics. The focus is on experimental toxicology, however, the methods are also applicable to pharmacology. Much of the literature on this topic is quite specialized in statistics, theory, or specific applications. This may deter a significant portion of the growing number of investigators in this field from using this literature, and may partially account for the persistent use of methods which have been shown to permit precarious conclusions. References are given for some of the most comprehensive and recent work and reviews on the subject. The reader is given some familiarity with this topic's basic problems and ideas, and the controversy on terminology. One example is presented of a popular experimental design and data analysis method which while applicable in some situations, has been shown to lead to precarious and even erroneous conclusions. Eight other methods of data analysis are briefly presented and some of their advantages, disadvantages, assumptions, and limitations are discussed. These methods were selected to illustrate similarities and differences in the various approaches taken in addressing this problem. Three basic types of experimental design appropriate to these kinds of studies are outlined. General considerations, suggested guidelines, and possible pitfalls in experimental design, and data analysis of biological responses to chemical mixtures are discussed.

Chemical Phenomena↗
PubMed1994

The hepatotoxicities of endotoxin and ethanol comparisons in vitro using the precision-cut rat liver slice model.

Using the precision-cut rat liver slice model, the in vitro toxicities of endotoxin and ethanol, independently and in combination, were evaluated. Hepatotoxicity was assessed by two measures: the leakage of LDH from slice to medium and the ability of slices to reduce a tetrazolium compound, MTT. Ethanol, in concentrations of 1% and greater, exhibited a time and dose dependent hepatotoxicity; MTT reductive capacity was more profoundly affected than LDH leakage. Endotoxin (0.1 to 100 micrograms/ml), however, had only a modest effect on MTT reduction and did not perturb LDH leakage. When combined in vitro, the toxicities of 2% ethanol and various concentrations of endotoxin were additive. Slices prepared from the livers of rats injected ip with endotoxin one day previously sustained considerably more injury (compared to normal rat liver slices) upon subsequent in vitro exposure to either endotoxin or ethanol. Prior in vivo exposure to ethanol, however, did not affect the subsequent in vitro toxicity of endotoxin. Thus, while endotoxin exhibits only subtle toxic effects upon liver slices in vitro, exposure to endotoxin in vivo renders the liver more susceptible to subsequent direct injury by endotoxin or ethanol.

Animals↗
PubMed1994

The use of human lung slices in toxicology.

1. Successful use of agar-filled precision-cut rat lung slices in dynamic organ culture prompted the use of this technology with human lung. 2. The larger tissue mass of a human lung required that the trachea be cannulated with a balloon catheter and subsequently inflated with 4 liters of warm agar/medium mixture and then cooled before being precision-cut into 500 microns thick slices. 3. To characterize the human lung slices, viability and the effects of acrolein and nitrofurantoin were assessed over a period of 24 h using protein synthesis and nonprotein sulfhydryl content. 4. Control human lung slices synthesized protein at a linear rate and maintained a stable nonprotein sulfhydryl content for 24 h. 5. Slices incubated with acrolein exhibited no significant decrease in protein synthesis or nonprotein sulfhydryl levels until 24 h. 6. Incubation with nitrofurantoin exhibited a definite time- and dose-dependent inhibition of protein synthesis, and depletion of the cellular thiol pool. 7. These results indicate that this human lung tissue slice system may be used as an in vitro model to identify and screen pneumotoxicants.

Acrolein↗
PubMed1994

Toxicity of cisplatin and mercuric chloride in human kidney cortical slices.

1. Organ specific toxicity such as nephrotoxicity is often investigated with the use of in vivo or in vitro animal models. 2. It would be beneficial if these findings could be verified in a human in vitro system which utilizes non-transplantable human kidneys. 3. Non-transplantable human kidneys were decapsulated, cut in half along the long axis, cores made perpendicular to the hemisphere, and precision-cut renal cortical slices produced. 4. These human kidney slices were incubated for 3, 6, 12, 18 and 24 h, viability assessed using intracellular K+ content, protein synthesis and organic ion transport and the potential nephrotoxicity of cisplatin (0.25, 0.5 and 1.0 mM) and mercuric chloride (10, 50 and 100 microM) on these slices were examined. 5. Control human kidney slices were viable for up to 24 h using all viability parameters while a dose- and time-dependent toxic response was seen using both cisplatin and mercuric chloride. 6. Cisplatin was more nephrotoxic in this human in vitro system than in previously investigated in vitro animal systems whereas mercuric chloride was similar in both systems. 7. These results indicate that human renal cortical slices are useful in predicting and verifying potentially nephrotoxic compounds in man.

Adolescent↗
PubMed1993

Cold- and cryopreservation of human liver and kidney slices.

Tissue slices may provide a rapid and economical way of determining cold ischemic effects on human liver and kidney cell viability and metabolism. In contrast to isolated hepatocyte cultures, tissue slices offer an in vitro system which more closely resembles the in vivo situation because of the differentiation and functional heterogeneity of the slice. In this study, human liver and kidney slices were cold stored for 10 days in Belzers University of Wisconsin (UW), Euro-Collins, and Modified Sacks solutions. Another set of slices was cryopreserved at 1 degree C/min for liver and 12 degrees C/min for kidney using a 10% dimethyl sulfoxide/fetal calf serum (FCS) cryoprotectant solution. The cold- and cryopreserved slices were incubated in roller culture for 4 h using FCS as the media. Liver slice viability was assessed by K+ content, protein synthesis, gluconeogenesis, and urea synthesis. Kidney slice viability was assessed using K+ content, protein synthesis, and organic ion transport (PAH and TEA). Human kidney slices were cold preserved in UW for 4-6 days, while the human liver slices were preserved for 12-24 h depending on the viability parameter. Following cryopreservation, human liver slice viability was retained at between 65 and 90% of control values, while kidney slice viability was maintained between 70 and 90% of control values depending on the viability parameter. These results indicate that this human in vitro tissue slice system can be used to optimize preservation solutions and methods. The ability to cold- and cryopreserve human slices could facilitate the more efficient utilization of human tissue.

Analysis of Variance↗