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K Brendel

Publications and source records attributed to K Brendel.

At least 19 recordsLinked to original sources
PubMed2000

A simplified isolated perfused rat liver apparatus: characterization and measurement of extraction ratios of selected compounds.

A simplified isolated perfused rat liver (IPRL) preparation has been developed and evaluated. The liver is briefly perfused in situ prior to being placed into a 37 degrees C oven and suspended from a stand. This set-up takes about 5 min. A non-recirculatory or one-pass perfusion approach has been used. The performance of the apparatus was evaluated with use of three model compounds: antipyrine, lidocaine and ethanol. In addition, oxygen extraction was determined. The steady-state extraction ratio (ER) was determined for each compound (and oxygen) as a function of perfusate flow rate (15-35 ml/min) during sequential 45 min perfusion periods. Perfusion experiments lasted for up to 3 hr. The ERs (at 15 ml/min) of ethanol (0.65 +/- 0.15), lidocaine (0.91 +/- 0.01) and oxygen (0.65 +/- 0.10) were dependent upon perfusate flow; whereas, antipyrine ER (0.07 +/- 0.01) was independent of flow. The corresponding values for unbound intrinsic clearances (CLu,int) for antipyrine, ethanol, lidocaine and oxygen were: 1.6, 31.0, 158.0 and 27.5 ml/min, respectively. These findings are consistent with the known hepatic ER values for those compounds reported in the literature.

Animals↗
PubMed1999

Sulindac derivatives inhibit growth and induce apoptosis in human prostate cancer cell lines.

We examined the activity of two metabolites of sulindac (a nonsteroidal anti-inflammatory drug), sulindac sulfide and sulindac sulfone (exisulind, Prevatec), and a novel highly potent analog of exisulind (CP248) on a series of human prostate epithelial cell lines. Marked growth inhibition was seen with the BPH-1, LNCaP, and PC3 cell lines with IC50 values of about 66 microM, 137 microM, and 64 nM for sulindac sulfide, exisulind, and CP248, respectively. DNA flow cytometry and 4',6'-diamido-2-phenylindole (DAPI) staining indicated that these three compounds also induced apoptosis in all of these cell lines. Similar growth inhibition also was seen with the PrEC normal human prostate epithelial cell line, but these cells were resistant to induction of apoptosis at concentrations up to 300 microM, 1 mM, and 750 nM of sulindac sulfide, exisulind, and CP248, respectively. Derivatives of LNCaP cells that stably overexpress bcl-2 remained sensitive to growth inhibition and induction of apoptosis by these compounds. In vitro enzyme assays indicated that despite its high potency in inhibiting growth and inducing apoptosis, CP248, like exisulind, lacked cyclooxygenase (COX-1 and COX-2) inhibitory activity even at concentrations up to 10 mM. Moreover, despite variations of COX-1 and COX-2 expression, the three benign and malignant prostate cell lines showed similar sensitivity to growth inhibition and induction of apoptosis by these three compounds. Therefore, sulindac derivatives can cause growth inhibition and induce apoptosis in human prostate cancer cells by a COX-1 and -2 independent mechanism, and this occurs irrespective of androgen sensitivity or increased expression of bcl-2. These compounds may be useful in the prevention and treatment of human prostate cancer.

Androgens↗
PubMed1998

Benzo(a)pyrene-induced alterations in growth-related gene expression and signaling in precision-cut adult rat liver and kidney slices.

Benzo(a)pyrene (BaP) and related aromatic hydrocarbons are suspected carcinogens; however, the molecular basis underlying tumorigenesis remains unclear. To identify acute molecular targets of BaP within the liver and kidney, precision-cut slices harvested from naive, adult female Sprague-Dawley rats were challenged with BaP (0.3-30 microM) for 0.5 to 24 h. BaP did not elicit cytotoxicity, as assessed by intracellular K+ and ATP content and histological evaluation over the 24-h period. To determine if molecular signaling pathways were maintained in precision-cut slices, induction of the aryl hydrocarbon receptor (AhR) pathway was assessed following BaP challenge. Induction of cytochrome P450IA1 (P450IA1) mRNA and protein expression was observed in both liver and kidney slices. c-fos and c-Ha-ras gene expression was enhanced in liver, but not kidney, slices by BaP. c-jun mRNA levels were decreased in liver and kidney slices, although the effect was earlier (0.5 h) in liver slices compared to kidney slices. BaP increased the DNA binding of nuclear proteins to the AP-1 consensus recognition element in liver, but decreased DNA binding in kidney slices. In contrast, DNA binding of NF-kappa B was not affected by BaP in either liver or kidney slices. These results suggest that acute BaP challenge is associated with altered expression of several growth-related genes and AP-1 signaling and establish precision-cut slices as a useful in vitro system to investigate the molecular basis of BaP-induced tumorigenesis, including organ-specific differences.

Adenosine Triphosphate↗
PubMed1997

Sulindac sulfone inhibits azoxymethane-induced colon carcinogenesis in rats without reducing prostaglandin levels.

Nonsteroidal anti-inflammatory drugs (NSAIDs), such as sulindac, have cancer chemopreventive properties by a mechanism that has been suggested to involve cyclooxygenase inhibition and reduction of prostaglandin (PGE2) levels in the target tissue. To test this hypothesis, we studied the effect of dietary sulindac sulfone (500-2000 ppm), a metabolite of sulindac reported to lack cyclooxygenase inhibitory activity, on tumor formation and PGE2 levels in the azoxymethane model of colon carcinogenesis. Rats treated with sulindac at 400 ppm and piroxicam at 150 ppm were used as positive controls. Rats received two s.c. injections of azoxymethane (15 mg/kg) for 2 weeks and were fed either experimental or control diets until necropsy. After 31 weeks of sulfone treatment, a dose-related increase in sulfone levels in both serum and cecal contents was measured; there was no evidence of metabolic conversion to sulindac or other metabolites. Rats treated with sulfone at 1000 and 2000 ppm, sulindac, and piroxicam had significantly fewer colonic adenomas and carcinomas compared with rats fed control diet as measured by tumor incidence, multiplicity, and tumor burden. Sulfone-treated rats also showed a dose-response relationship for inhibiting all tumor parameters. Colons from rats treated with sulindac or piroxicam contained PGE2 levels that ranged from approximately 16-49% of control levels. PGE2 levels in rats treated with sulfone up to 2000 ppm ranged from 78-118% of control levels. Moreover, the effects of sulindac sulfone on various enzymes responsible for regulating prostaglandin levels were evaluated. No significant inhibitory effects were observed for cyclooxygenase, lipoxygenase, or phospholipase A2. These results suggest that reduction of prostaglandin levels in the target tissue may not be necessary for the chemopreventive properties of sulindac.

Animals↗
PubMed1997

Sampling designs for xerophthalmia prevalence surveys.

BACKGROUND: The purpose of this study was to estimate the bias and design effects associated with the Expanded Program on Immunization's (EPI) sampling design when estimating xerophthalmia prevalence, and to estimate the savings associated with EPI in terms of distance travelled within selected clusters. METHODS: Computer simulation of the EPI sampling strategy was done using maps from a xerophthalmia survey of 40 wards in Sarlahi district, Nepal. Samples of fixed cluster sizes of 7, 10, 15, 20 and 25 were compared. The estimated prevalence using the EPI design was compared with the true prevalence in the 40 wards to estimate the bias. The design effect was estimated by taking the ratio of the variance under EPI sampling to that of stratified random sampling (SRS) with fixed cluster sizes. The EPI was also modified by increasing the distance between selected houses from nearest neighbour to skipping 1-4 houses between selected ones. The difference between the distance travelled within clusters using SRS compared with EPI was weighed against the bias and increased variance. RESULTS: The prevalence of xerophthalmia was 2.8%. The EPI design overestimated xerophthalmia prevalence by between 0.27% and 1.16%. The design effects of EPI cluster sampling within wards varied between 0.73 and 1.35. Neither the bias nor the design effect was related to distance between households or cluster size. Distance travelled within wards was always less for EPI designs with cluster sizes of 7 or 10. There was no saving in terms of distance travelled for designs with cluster sizes from 15 to 25 if there were two or more houses between selected ones. For fixed cluster sizes of 15 or fewer, the EPI sampling design using nearest or next nearest neighbours is a better choice than SRS in terms of minimizing the distance travelled and the mean square error. CONCLUSIONS: The choice of an optimum method would need to account for the density of clusters and difficulty of travel between clusters, as well as the costs of travel within clusters. Based on certain assumptions, EPI with 15 children per cluster would be favoured over examining all children in selected wards unless the travel time between wards was more than 2 days.

Bias↗
PubMed1997

Human and rat lung biotransformation of cyclosporin A and its derivatives using slices and bronchial epithelial cells.

Lung biotransformation of the immunosuppressants, cyclosporin A (CSA), the hydroxyethyl derivative SDZ IMM 125 (IMM), and the methylcarbonate derivative SDZ SCP 764 (SCP), was demonstrated in slices from human and rat. The major biotransformation pathway for CSA and IMM (0.1-10 microM) was hydroxylation at amino acid 1 to form AM1 or IMM1, while for SCP it was an esterase cleavage of the methylcarbonate group to form AM1 in both species. The initial rate (0-1 hr) of human total metabolite formation increased proportionally with substrate concentration. AM1 formation was five times greater from SCP, an esterase pathway, than CSA, an oxidative pathway which was inhibited (50%) by ketoconazole. At 24 hr human lung CSA metabolite formation was greater than IMM (3-fold) or SCP (2-fold), whereas rat lung and liver and human bronchial epithelial cell SCP metabolite formation generally exceeded CSA or IMM metabolism. CSA biotransformation is expected to occur throughout the human lung as demonstrated by the similar metabolite profile and extent of metabolism by slices derived from five different regions. The scaling of slice total metabolism to organ metabolism revealed that initially lung CSA metabolite formation would be equal to liver but with time liver metabolism would exceed lung for human and rat. This study has demonstrated that human and rat lung are metabolically active, exhibiting oxidative and esterase pathways toward cyclosporin derivatives. The lung will play an important role in this metabolism, particularly when administered via inhalation; however, the liver will also be a major organ involved in the total clearance of these compounds.

Adult↗
PubMed1997

Efficiency of EPI cluster sampling for assessing diarrhoea and dysentery prevalence.

This study examines the efficiency of EPI cluster sampling in assessing the prevalence of diarrhoea and dysentery. A computer was used to simulate fieldwork carried out by a survey taker. The bias and variance of prevalence estimates obtained using EPI cluster sampling were compared with those obtained using simple random sampling and cluster (stratified random) sampling. Efficiency ratios, calculated as the mean square error divided by total distance travelled, were used to compare EPI cluster sampling to simple random sampling and standard cluster sampling. EPI cluster sampling may be an appropriate low-cost tool for monitoring trends in the prevalence of diarrhoea and dysentery over time. However, it should be used with caution when estimating the prevalence of diarrhoea at a single point in time because of the bias associated with this cluster sampling method.

Age Factors↗
PubMed1996

Increased resistance to acetaminophen-induced hepatotoxicity in retrovirus-infected mice.

In this research we examined the influence of chronic retrovirus infection on the hepatic metabolism of a model substrate, acetaminophen (APAP), and its induced liver injury in mice inoculated with LP-BM5 murine leukemia viruses. Female C57BL/6 mice at 15-17 wks after LP-BM5 retrovirus inoculation and age-matched control animals were used in the studies. APAP treatment (300 mg kg-1, p.o.) resulted in moderate to severe centrilobular necrosis in control animals, with the necrotic area accounting for 40-60% of the total area. In contrast, the APAP-treated (300 mg kg-1, p.o.) infected animals exhibited mild zonal necrosis with the necrotic area accounting for 1-6% of the total area. In the same study, a statistically significant higher percentage of APAP glucuronide and a lower percentage of unchanged APAP were recovered from the urine of the LP-BM5-inoculated animals than from that of controls. No statistically significant differences between infected and uninfected animals in the urinary recovery of APAP sulfate, APAP cysteine, or APAP mercapturate were observed. The formation of APAP metabolites and APAP-associated biochemical changes were also determined from liver slice preparation to avoid in vivo complicating factors. Consistently more significant depletion of the intracellular glutathione levels and K+ content were observed in slices from the uninfected animals at high concentrations of APAP (1 and 2 mM) than in slices from the retrovirus-infected animals. The differences in APAP-associated biochemical changes were accompanied by a 1.4-1.5-fold increase in the formation of APAP glucuronide, sulfate, and glutathione metabolites in slices prepared from animals inoculated with LP-BM5. We concluded that, based on histological examination and hepatic biochemical measurements, the retrovirus-infected animals were more resistant to APAP-induced liver injury. This could be due, in part, to alterations in the detoxification and activation metabolic pathways of APAP.

Acetaminophen↗
PubMed1996

Cold- and cryopreservation of dog liver and kidney slices.

The use of tissue slices in culture could decrease the number of animals used in health-related research and decrease experimental variation. This reduction may come about particularly if the methods of cold- and cryopreserving tissue slices are perfected, and one can conduct sequential in vitro experiments into xenobiotic metabolism, organ-specific toxicity, or organ-specific biochemical processes with tissue slices. With this goal in mind, dog liver and kidney slices were placed in cold storage at 0 degrees C using Viaspan (UW), Euro-Collins (EC), Sacks + prostacyclin (SP), and V-7 (V7) cold-preservation solutions for 10 days. Viability was assessed each day by measuring K+ content and protein synthesis after 4 h of incubation in Waymouth + 10% fetal calf serum (FCS). Dog liver slices can be cold-preserved in V7 for up to 7 days using K+ retention as the viability criterion but only up to 4 days using protein synthesis. Dog kidney slices can be cold-preserved in UW, EC, and V7 for up to 10 days using K+ retention, but only V7 could maintain protein synthesis for 10 days. Cryopreserved dog liver and kidney slices retained 63-68% of control viability after 4 h of incubation in FCS. The cryopreservation regimen included using 10% dimethyl sulfoxide in FCS as the cryoprotectant, a freezing rate of 0.5 degrees C/min for liver slices and 12 degrees C/min for kidney slices, and thawing in 37 degrees C FCS. Continued development of cold- and cryopreserving tissue slices could reduce the numbers of animals used and provide accurate and reproducible data.

Animals↗
PubMed1996

Protein arylation precedes acetaminophen toxicity in a dynamic organ slice culture of mouse kidney.

Acetaminophen (APAP) is an analgesic and antipyretic agent which may cause hepatotoxicity and nephrotoxicity with overdose in man and laboratory animals. In vivo studies suggest that in situ activation of APAP contributes to the development of nephrotoxicity. Associated with target organ toxicity is selective arylation of proteins, with a 58-kDa acetaminophen binding protein (58-ABP) being the most prominent cytosolic target. In this study a mouse kidney slice model was developed to further evaluate the contribution of in situ activation of APAP to the development of nephrotoxicity and to determine the selectivity of protein arylation. Precision cut kidney slices from male CD-1 mice were incubated with selected concentrations of APAP (0-25 mM) for 2 to 24 hr. APAP caused a dose- and time-dependent decrease in nonprotein sulfhydryls (NPSH), ATP content, and K+ retention. Preceding toxicity was arylation of cytosolic proteins, the most prominent one being the 58-ABP. The association of 58-ABP arylation with APAP toxicity in this mouse kidney slice model is consistent with earlier, in vivo results and demonstrates the importance of in situ activation of APAP for the development of nephrotoxicity. Precision cut renal slices and dynamic organ culture are a good model for further mechanistic studies of APAP-induced renal toxicity.

Acetaminophen↗
PubMed1996

Determination of aflatoxin B1 biotransformation and binding to hepatic macromolecules in human precision liver slices.

Although epidemiological studies suggest that aflatoxin B1 (AFB1) is a human carcinogen, at least in the presence of hepatitis B virus infection, animal studies have demonstrated large differences in species sensitivity to AFB1, and the sensitivity of humans relative to experimental animals remains unclear. The purpose of this study was to determine the profile of AFB1 metabolism and the extent of AFB1 binding to cell macromolecules in human liver slices under experimental conditions that would allow direct comparison to similar endpoints in the rat, a species sensitive to the carcinogenic actions of AFB1. Liver slices were prepared from three individual human liver samples with a Krumdieck tissue slicer and incubated with 0.5 microM [3H]AFB1 for 2 hr. Significant interindividual variations were observed in the rates of oxidative metabolite formation and in specific binding to cell macromolecules. The rates of oxidative metabolism of AFB1 to AFQ1, AFP1, and AFM1 in the three human liver samples were similar to those previously observed in rat liver slices. AFB1-GSH conjugate formation was not detected in any of the human liver samples, and yet specific binding of AFB1 to cell macromolecules was considerably lower in the human liver slices relative to that in rat liver slices. AFB1-DNA binding levels ranged from 3 to 26% of control rat and AFB1-RNA binding levels ranged from 25 to 49% of control rat. The AFB1-protein binding level in the one human sample measured was 20% of that observed for control rat. While these results suggest that humans do not form as much AFBO as the rat, they are also consistent with the hypothesis that humans do not possess GST isozyme(s) with high specific activity toward AFBO. Significant individual differences in AFB1 metabolism and binding between humans suggest the presence of genetic and/or environmental factors that may confer large variability in susceptibility to AFB1.

Adult↗
PubMed1996

Biotransformation of a somatostatin analogue in precision-cut liver and kidney slices from rat, dog and man.

1. Cleavage of the glucopyranosyl moiety of the somatostatin analogue SDZ CO 611 results in the formation of the major metabolite, SDZ CO 610, in liver and kidney slices of rat, dog and man, as well as in liver S9 and cytosol of rat and man. 2. The rates of SDZ CO 610 formation (nmol/h/mg slice protein) for all three species were determined in liver slices for 24 h and the relative order was: rat (0.12) > dog (0.096) = man (0.095). The rates of SDZ CO 610 formation (nmol/h/mg slice protein) for all three species in kidney were determined, and the relative order was: rat (0.29) > dog (0.16) > man (0.10). 3. SDZ CO 610 was rapidly formed by rat gut contents in the absence of NADPH, possibly by disaccharide-splitting enzymes. 4. Biotransformation of SDZ CO 611 to SDZ CO 610 in human and rat liver S9 and cytosol was similar to that found in liver slices cultures indicating that cleavage of the glucopyranosyl moiety of SDZ CO 611 could occur in the presence and in the absence of cytochrome P450, possibly by glucosidases in liver cytosol. 5. Rat intestinal homogenate also formed SDZ CO 610 but metabolism was dependent upon NADPH, suggestive of a cytochrome P450-dependent reaction.

Adolescent↗
PubMed1996

Vitamin A potentiation of vinylidene chloride hepatotoxicity in rats and precision-cut rat liver slices.

Pretreatment of large doses of vitamin A (VA) is known to potentiate the hepatotoxicity of carbon tetrachloride. Therefore the effects of 1-day VA pretreatment on VDC hepatotoxicity was examined both in vivo and in an in vitro system of precision-cut rat liver slices. Male Sprague-Dawley rats were pretreated with 250,000 IU/kg VA by oral gavage. After 24 hr rats were administered 50, 100, or 200 mg/kg VDC ip. Precision-cut liver slices were prepared from VA pretreated rats 24 hr later and the liver slices were exposed for 2-8 hr to 0.025-1.0 microliter VDC evaporated into the gas phase of the incubation vials. VA pretreatment resulted in an enhancement of VDC toxicity, both in vivo and in vitro. There was a dose-dependent increase in plasma ALT 24 hr after VDC treatment of rats and an increase in K+ leakage from liver slices after VDC exposure. Histological analysis of the liver or the liver slices revealed that VA + VDC treatment resulted in centrilobular necrosis of the liver. When GdCl3 (10 mg/kg iv) was administered just before VA pretreatment of rats, VDC toxicity was partially reversed as observed by a decrease in ALT in vivo and a decrease in the loss of K+ in vitro. These results indicated that Kupffer cells, the resident macrophages of the liver, were partially responsible for the VA-potentiated VDC hepatotoxicity. One-day pretreatment of VA induced cytochrome P450IIE1 protein content as well as its enzymatic activity as measured by pnitrophenol hydroxylation. Because VDC is bioactivated by cytochrome P450IIE1, the increase in VDC hepatotoxicity after VA may be due to an increased bioactivation of VDC in the liver and in precision-cut liver slices. Thus, more than one mechanism may be involved in the VA enhancement of VDC hepatotoxicity.

Animals↗
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↗