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Biomedical subjects

K Brendel

Publications and source records attributed to K Brendel.

At least 91 records · Page 5Linked to original sources
PubMed1987

In vitro cytotoxicity of allyl alcohol and bromobenzene in a novel organ culture system.

Two well-known hepatotoxicants, allyl alcohol (AA) and bromobenzene (BB), were studied using an in vitro system of cultured liver slices from control and phenobarbital-treated rats, respectively. Dose- and time-dependent increases in media lactate dehydrogenase (LDH), and decreases in slice K+ content and in protein synthesis were observed in rat liver slices incubated with either compound at concentrations between 0.1 and 1 mM over a period of 6 hr. The histopathological changes which occurred in the intoxicated slices appeared to parallel these biochemical changes. Additionally, the toxicity of either BB or AA, evaluated at 4 hr, was inhibited when slices were preincubated for 30 min with beta-ethyl-2,2-diphenylvalerate hydrochloride (SKF 525-A) (0.1 mM) or pyrazole (1.0 mM), respectively. In this in vitro incubation system the cytotoxicity of xenobiotics can be studied under conditions where the multicellular hepatic lobular architecture is partially maintained, and alterations in biochemical and functional processes may be correlated to pathological changes.

1-Propanol↗
PubMed1987

Preparation of positional renal slices for study of cell-specific toxicity.

To reduce structural complexity, rabbit kidneys were sliced perpendicular to their cortical-papillary axis to isolate four distinct cell groupings. This positional orientation allows identification of each renal cell type based on its location within the slice. A mechanical slicer was used to make several precision-cut slices rapidly from an oriented cylindrical core of renal tissue, with minimal tissue trauma. Slices were then submerged under a gently circulating oxygenated media in a fritted glass support system that maintains viability (intracellular K+/DNA ratio) and structural integrity (histology) for at least 30 h. A high dose of mercuric chloride (10(-3) M) was used to demonstrate the structural and biochemical changes of intoxicated slices. This method provides a controlled subchronic in vitro system for the study of the individual cell types involved in cell-specific renal toxicities and may also be a useful tool for addressing other pharmacological and physiological research questions.

Animals↗
PubMed1986

Metabolism-related spectral characterization and subcellular distribution of polychlorinated biphenyl congeners in isolated rat hepatocytes.

The disposition and biotransformation of 4,4'-dichlorobiphenyl (4-DCB), 2,2',3,3',6,6'-hexachlorobiphenyl (236-HCB), and 2,2',4,4',5,5'-hexachlorobiphenyl (245-HCB) were studied in isolated rat hepatocyte suspensions. The polychlorinated biphenyls (PCBs) were taken up rapidly by the cells but incompletely metabolized. Metabolism followed first-order Michaelis-Menten kinetics for 20 min and plateaued by 60 min, at which point only 32% of 4-DCB (0.005 to 100 microM) and 60% of 236-HCB (0.001 to 100 microM) were metabolized, while metabolism of 245-HCB was not detected (0.1 to 200 microM). Kinetic studies revealed that both 4-DCB and 236-HCB were metabolized by two Michaelis-Menten processes, displaying high- and low-affinity binding. Readdition of congener once metabolism plateaued resulted in a reinitiation of metabolism with the same proportion of metabolites produced. The termination of metabolism was not due to destruction of the mixed-function oxidases or to depletion of cofactors. The metabolism of PCB congeners is influenced by the affinity of the congener for cytochrome P-450 and partitioning of the congener within the hepatocyte. Analysis of absorbance differences (delta absorbance 390-240 nm) of equimolar concentrations of congener (100 microM) revealed that 236-HCB displayed the greatest affinity of binding to cytochrome P-450 followed by 4-DCB, while 245-HCB showed virtually no binding. Microsomal preparations demonstrated equivalent but greater absorbance values. Subcellular distribution of 14C-labeled congener and its metabolites showed that the majority of radioactivity appeared in the cytosolic fraction, representing 70% of the dose added for each congener. Cytosolic binding of congener and metabolites may influence both the availability of congener to cytochrome P-450 and the excretion rate of metabolites from the cell.

Animals↗
PubMed1986

Maintenance of adult rat liver slices in dynamic organ culture.

Adult rat liver slices were maintained for 20 h in a novel organ culture system with minimal loss of viability and function. Potassium and adenosine triphosphate levels were maintained at in vivo levels, following an initial recovery period (2 to 4 h), for up to 20 h. Protein synthesis and secretion were linear for 20 and 16 h, respectively. In addition, the liver slices synthesized glycogen between 4 and 12 h in culture. Finally, the liver slices were hormonally responsive during the 20 h culture period as exemplified by glucagon-stimulated glucose production. This system provides a simple and effective method for the culture and biochemical maintenance of adult rat liver for 20 h with minimal loss of biochemical function.

Adenosine Triphosphate↗
PubMed1986

Adaptation of a gamma-glutamyl transpeptidase assay to microtiter plates.

A kinetic assay for measuring gamma-glutamyl transpeptidase (GGT) activity has been adapted to microtiter plates and an automated microtiter plate reader. This method permits the simultaneous analysis of enzyme activity in a large number of samples incubated with the chromogenic GGT substrate gamma-glutamyl-p-nitroanilide. A major advantage of this assay over previously reported methods is the substantial reduction in the time needed for measuring sample enzyme activity. In addition, reduction of the total assay volume to 0.28 ml conserves both sample and reagents. This method has been calibrated at 23 degrees C using purified GGT, and used to analyze GGT activity in human sera. The assay is sensitive over a range of 3-200 U/liter.

Humans↗
PubMed1986

Effect of volatile anesthetics on protein synthesis and secretion by rat hepatocyte suspensions.

The effect of volatile anesthetics on protein synthesis and secretion by isolated rat hepatocytes in suspension was investigated. Halothane and enflurane inhibited protein synthesis in a dose-dependent manner. Diethyl ether had little effect on protein synthesis while isoflurane caused a mild inhibition. This effect was more pronounced in hepatocytes from phenobarbital treated male rats when compared to hepatocytes from control rats. Protein synthesis in hepatocytes from phenobarbital treated female rats was inhibited similar to that seen with control male rat hepatocytes. Isoflurane, enflurane, and halothane also caused a dose-dependent inhibition of protein secretion, while diethyl ether was only mildly inhibitory. From these studies it appears that inhibition of protein synthesis and secretion might be an early and sensitive indicator of cellular injury by volatile anesthetics.

Anesthetics↗
PubMed1986

Early biological indicators of S-(1,2-dichlorovinyl)-L-cysteine nephrotoxicity in the rabbit.

The progression of changes in rabbit kidney function following dosing with the nephrotoxin S-(1,2-dichlorovinyl)-L-cysteine (DCVC, 20-50 mg/kg) was determined. Proteinuria was observed 0.5-1 hr after administration of DCVC at doses of 20-50 mg/kg. Blood urea nitrogen levels, glomerular filtration rates, urinary glucose excretion, and urine volume were also altered following DCVC dosing; however, these parameters were less sensitive than proteinuria as markers of early renal dysfunction. None of these latter four indicators were affected by low DCVC doses, nor were they altered by high DCVC doses until 1.5-2.5 hr after dosing. Dose-dependent morphological changes to kidney structure were also observed 5 hr after DCVC administration. Low doses caused damage restricted to brush border membranes in the pars recta, while higher doses produced a necrotic lesion encompassing all regions of the proximal tubule. This study indicates that DCVC can cause rapid renal dysfunctional changes which are first detected by elevated urinary protein excretion.

Animals↗
PubMed1985

Dynamic organ culture of precision liver slices for in vitro toxicology.

The lack of a reproducible method for the production of thin tissue slices has hindered the use of liver slices as an in vitro tool for hepatotoxicity studies. Fresh human, rat, and rabbit liver was processed using a mechanical slicer. With this instrument, precision (5% of thickness) liver slices in the submillimeter range could be produced at a rapid rate. Slices were prepared from fresh livers in chilled, oxygenated buffer to minimize trauma. Following incubation for up to 20 h in a dynamic organ culture system, histology of incubated slices suggested that 250 m precision-cut slices were optimum in regard to morphology relative to liver slices incubated under conventional organ culture conditions. Addition of bromobenzene to the culture showed time-dependent hepatotoxicity based on two classic parameters of cell degeneration. Histological evidence is presented which suggests the usefulness of this system for hepatotoxicity studies and the production of focal necrosis in vitro.

Animals↗
PubMed1985

Homogeneous populations of Artemia nauplii and their potential use for in vitro testing in developmental toxicology.

Efforts have begun to establish test subjects other than the intact pregnant mammal to serve as models for rapid teratology screens. Artemia nauplii transcending instar I to later instars were examined to determine their potential for indicating chemicals as potential developmental hazards and thus prioritizing them for more extensive in vivo testing. Several criteria selected for assessing the system's potential for screening were the ability to: collect homogeneous populations of instar I nauplii; characterize intermediate development by technically simple measurements; and demonstrate development-related differentials in naupliar vulnerability. Homogeneous populations of nauplii were harvested from a flow-through hatching and cold storage system. Nauplii accumulated in the system are stored at 4 degrees C in a quiescent state with little physical (body length, body water volume) and biochemical (DNA and protein levels) change and thus are maintained at instar I. Intermediate development of nauplii transcending instar I to IV was characterized after the onset of 25 degrees C incubation by measuring changes in drinking activity, body length, body water volume, and DNA and protein levels. During the first day of incubation, development was greatest between 6 and 24 hours of incubation. Development-related differentials in naupliar vulnerability were shown by comparing median lethal concentrations (LC50) estimated for cadmium sulfate (CdSO4), mercuric chloride (HgCl2), and sodium azide (NaN3) at various times during incubation. With cadmium and mercury, LC50s decreased as nauplii aged and developed; whereas, with azide, LC50s did not vary. Developing nauplii were differentially vulnerable to cadmium and inorganic mercury. Artemia nauplii transcending instar I to IV appear useful for indicating chemicals that preferentially interact with developmental events.

Animals↗
PubMed1985

An all-glass apparatus for liver perfusion of lipophilic substrates. I. Construction and physical characteristics.

An all-glass apparatus for perfusing isolated rat livers was constructed for use in studies of the metabolism by, or action on, the liver of lipophilic substrates. Other designs, which generally include plastic connections or cannulae, can have unnecessarily complicated kinetics because of adsorption of the agent to the plastic parts. Two versions of an all-glass perfusion apparatus are described in detail. Both instruments operate on the same basic principle, but differ in size, total recirculating volume, pump rate, perfusion head pressures, maximum perfusate flow rate, maximum linear velocity in the perfusion head, and oxygenation efficiency. Although the maximum protein handling capacity differs for the two apparatuses, this capacity is so limited that it disallows the use of albumin in the perfusate.

Animals↗
PubMed1985

Production of DNA single strand breaks in rabbit renal tissue after exposure to 1,2-dichlorovinylcysteine.

S-(trans-1,2-dichlorovinyl)-L-cysteine (DCVC) is a recognized nephrotoxin. To investigate the genotoxic effects of DCVC on the kidney, DNA strand breaks were measured as an indicator of DCVC induced damage. To ascertain if bioactivation of DCVC occurred in the kidney, 3 experimental systems were used: in vivo; isolated perfused kidneys; and isolated proximal tubules of albino male rabbits. A dose-dependent increase in strand breaks in the kidney tubular DNA occurred after in vivo dosing with 5-100 mg/kg DCVC and after in vitro exposure to 10(-5)-10(-2) M DCVC. These results demonstrate the genotoxic effect of this compound on renal tissue.

Animals↗
PubMed1985

Toxicity and biotransformation of volatile halogenated anesthetics in rat hepatocyte suspensions.

This study examines the toxicity (as measured by reduced intracellular K+) and metabolism (defluorination) of halothane and enflurane in rat hepatocytes in suspension (RHS) with regards to O2 tension, time, and concentration. In 95% O2 halothane is more toxic than enflurane when RHS are exposed to 5-20 microliters of these anesthetics. At these levels halothane is not metabolized while enflurane is metabolized. At 21% O2 a similar pattern was seen with regards to toxicity. However, metabolism of halothane rapidly reached an elevated level while that of enflurane is reduced when compared to 95% O2. Thus toxicity of halothane and enflurane at these dose levels appears to be unrelated to metabolism and due solely to a solvent effect.

Anesthesia, Inhalation↗
PubMed1985

Embryotoxic drugs.

Explore the source record for details and available documents.

Abnormalities, Drug-Induced↗
PubMed1984

Differentiation of the cardiac and pulmonary toxicity of monocrotaline, a pyrrolizidine alkaloid.

Monocrotaline, given to rats as a 20 mg/l solution in drinking water for 3 weeks, doubled the mass of the right heart and lung. The rise in lung mass preceded that of the heart. These increases were accompanied by increases in the absolute protein content of the two organs, together with increases in the rates of both protein and RNA syntheses. The increase in lung mass was not accompanied by a change in total collagen content, as measured by two independent methods: 4-hydroxyproline content and detergent fractionation. In contrast, the right ventricle showed more than a 4-fold increase in total collagen content. Total pulmonary lipids increased by 86%, but the lipid: protein ratio was unchanged. Right ventricular lipids were unchanged in amount but the lipid: protein ratio fell by 29%. Lung DNA:RNA ratio decreased 49% and right ventricle DNA:RNA ratio decreased 69%, indicating that both of these organs were responding to monocrotaline with hypertrophy. These results suggest that the processes of hypertrophy differ in the two organs: in the lung, there was no fibrosis despite a marked increase in dry weight, while right ventricular hypertrophy was characterized by increased collagen deposition. There was no alteration in the left ventricle in any of the parameters investigated.

Animals↗
PubMed1984

Factors influencing sulfation in isolated rat hepatocytes.

Sulfation of harmol by isolated hepatocytes was dependent on an exogenous source of sulfate. Inorganic sulfate ion stimulated sulfation by over ten fold. Analysis of the stimulation of harmol sulfation by sulfate indicated a Km of 239 microM and a Vmax of 1.1 mumoles harmol sulfate/min/10(6) cells. Cysteine also stimulated the rate of harmol sulfation but was less effective than sulfate ion. Lithium chloride inhibited harmol sulfation. Sulfation was unaffected by several metabolic alterations which inhibited harmol glucuronidation. Fasting for 24 hours, and incubation with ethanol or linoleic acid, did not influence the rate of sulfation but inhibited glucuronidation by 50 percent.

Animals↗