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Biomedical subjects

K Brendel

Publications and source records attributed to K Brendel.

At least 109 records · Page 6Linked to original sources
PubMed1984

The formation and biotransformation of cysteine conjugates of halogenated ethylenes by rabbit renal tubules.

The nephrotoxicity of chlorotrifluoroethylene ( CTFE ) was examined using isolated rabbit renal tubules suspensions. Exposure of the tubules to CTFE resulted in consumption of CTFE , formation of a glutathione conjugate and inhibition of active organic acid transport. Synthetic cysteine, N-acetylcysteine or glutathione conjugates of CTFE inhibited transport indicating S-conjugation as a possible toxic pathway. 1,2-dichlorovinyl glutathione ( DCVG ), a model synthetic glutathione conjugate, was used to examine the degradation and toxicity of these conjugates. DCVG inhibited rabbit renal tubule transport in vivo and in vitro. The DCVG was found to be degraded with the evolution of glutamine and glycine to produce the ultimate nephro-toxicant, dichlorovinyl cysteine. Dichlorovinyl cysteine is then bioactivated with the release of ammonia. This sequential degradation explains the latency of DCVG -induced renal transport inhibition relative to dichlorovinyl cysteine. It is now evident that certain halogenated ethylenes are capable of being biotransformed to glutathione conjugates in the kidney with their subsequent hydrolysis to nephrotoxic cysteine conjugates.

Animals↗
PubMed1984

Detergent-extracted small-diameter vascular prostheses.

The exact mechanism that leads to thrombosis of small-diameter vascular prostheses (less than 4 mm X greater than 6 cm) is unknown. This report presents preliminary patency and healing data on a sequential detergent-extraction technique for the preparation of autogenous small-diameter microvascular grafts. Fifteen carotid interpositional allografts (3 to 4 mm X 4 to 6 cm) were implanted in 15 mixed species adult greyhounds. Ninety days after implantation grafts were perfusion-fixed in situ, harvested, and evaluated by light microscopy and scanning and transmission electron microscopy. Two categories of acellular vascular matrix grafts were evaluated: non-cross-linked and cross-linked (1% carbodiimide). By objective morphologic analysis with blind random view, histologic sections were rated from 0 to 4 in five categories believed to be important for graft healing and patency. Overall graft patency was 80% (12 of 15), and there was no significant difference between cross-linked and non-cross-linked grafts. Non-cross-linked grafts were superior to cross-linked grafts in all areas of histologic evaluation except immunogenicity (p less than 0.01). Most important, non-cross-linked grafts demonstrated complete endothelial coverage (p less than 0.001). There was no significant difference (that is, normal) between control autografts and non-cross-linked grafts; however, there was a significant difference between control autografts and cross-linked grafts in all parameters except immunogenic reaction (p less than 0.01).

Animals↗
PubMed1984

Effect of O2 tension on the bioactivation and metabolism of aliphatic halides by primary rat-hepatocyte cultures.

The covalent binding of CCl4 and CF3CHBrCl to cultured rat hepatocytes was enhanced by anoxic conditions, indicative of enhanced reductive biotransformation. The covalent binding of CHCl3 and CHCl2CH2Cl decreased as the O2 concentration was decreased, indicating a preference for oxidative metabolism. Lower O2 tensions decreased the formation of polar water-soluble metabolites with CHCl3 and CHCl2CH2Cl, while CCl4 and CF3CHBrCl were unaffected. The results indicate that primary cultured hepatocytes can reductively biotransform and bioactivate aliphatic halides under anoxic conditions.

Animals↗
PubMed1983

Influence of chronic ethanol treatment on alpha1-adrenergic and vasopressin receptor-stimulated phosphatidylinositol synthesis in isolated rat hepatocytes.

Adult male rats were given nutritionally balanced high fat (34% corn oil) diets containing either ethanol or isocalorically substituted sucrose for 4-5 weeks. Phosphatidylinositol-phosphatidylserine, phosphatidylethanolamine and phosphatidylcholine contents of whole hepatocytes were not altered in ethanol-treated rats. However, vasopressin and alpha1-adrenergic stimulation of [32P]-incorporation into phosphatidylinositol of isolated hepatocytes from ethanol-treated rats was increased substantially compared to that of controls. Yet, chronic ethanol treatment had no effect on hepatic alpha1 receptor density or affinity as measured by [3H]prazosin specific binding. These results suggest that the supersensitive phosphatidylinositol response to this alpha1 agonist observed in hepatocytes from ethanol-treated rats occurred distal to cell surface receptors and may be similar for vasopressin.

Alcoholism↗
PubMed1983

Interaction of capsaicinoids with drug-metabolizing systems. Relationship to toxicity.

The interaction of capsaicin with microsomal drug-metabolizing systems was assessed to determine the role that bioactivation of capsaicin may play in the induction of hepatotoxicity and neurotoxicity. Capsaicin produced a type I spectral change in rat hepatic microsomes in a high affinity (Ks = 8 microM) concentration-dependent manner and was approximately equipotent with SKF-525A in inhibiting ethylmorphine demethylation. Capsaicin (10 mg/kg, s.c.) inhibited biotransformation in vivo as measured by prolongation of pentobarbital sleep time. Reactive metabolites of capsaicin were studied using [3H]dihydrocapsaicin. [3H]Dihydrocapsaicin bound irreversibly to hepatic microsomal protein after in vitro incubation or in vivo administration. No binding was observed in spinal cord or brain. Although the bioactivation and subsequent covalent binding of capsaicin equivalents may initiate events associated with the hepatotoxicity of capsaicin, it appears that capsaicin-induced neuropathy does not involve covalent interactions with neuroproteins in spinal cord or brain.

Animals↗
PubMed1983

Regulation of a S(trans-1,2-dichlorovinyl)-L-cysteine-induced renal tubular toxicity by glutathione.

The nephrotoxin S-(1,2-dichlorovinyl)-L-cysteine (DCVC) is cleaved in the renal tubules to produce a reactive electrophilic intermediate. If this intermediate is responsible for the toxicity, addition of the nucleophilic scavenger glutathione (GSH) should decrease toxicity, and depletion of tubular GSH should enhance toxicity. GSH was added to isolated rabbit renal tubules simultaneously with, 15 min before, and 15 min after the addition of DCVC. The active accumulation of the organic anion para-aminohippuric acid (PAH) and organic cation tetraethylammonium bromide (TEA) was used as an index of renal toxicity. Incubation of renal tubules with 0.01-1 mM DCVC for 15 min decreased active transport, with complete inhibition at 1 mM. This was accompanied by a 50% decrease in non-protein sulfhydryl concentration. The addition of GSH (6 mM) simultaneously with DCVC completely prevented any decrease in active transport. The addition of GSH (6 mM) to tubules in which active transport was inhibited by DCVC reversed the inhibition to 80% of control. Similar enhancement of active transport occurred when tubules isolated 1 h after in vivo exposure to DCVC at 20-100 mg kg-1 were incubated with GSH (6 mM). Preincubation of renal tubules with GSH (5-15 mM) made them more refractory to the DCVC-induced decreased PAH and TEA transport. The inhibition of active transport by DCVC is enhanced if the tubular non-protein sulfhydryl is first lowered by diethyl maleate or glycidol. Thus, the tubular GSH concentration appears to be an integral component in regulating the alterations in active transport caused by DCVC.

Animals↗
PubMed1983

Selective solubilization of two populations of polypeptides from bovine retinal basement membranes.

Basement membranes isolated from the entire neural retinae of normal cows consist of a heterogeneous mixture of polypeptides resolvable as two major populations, one collagenous and the other non-collagenous. The non-collagenous population consists of disulfide-bonded aggregates of which the major fraction is soluble in lithium dodecyl sulfate (LDS) at 4 degrees C without reducing agent, with the remainder requiring reduction for solubilization at 4 degrees C. Only the second 4 degrees C extract is contaminated with small amounts of hydroxylated amino acids. The non-collagenous population consists of up to 25 polypeptides detectable in sodium dodecyl sulfate (SDS) gels, all of which stain blue with Coomassie Blue R-250, are insensitive to bacterial collagenase and migrate on or slightly below the central diagonal in urea-SDS/SDS electrophoresis. The collagenous population is soluble in LDS at 100 degrees C under reducing conditions and has a collagenous amino acid composition, although consisting of only 272 glycine residues/1000. This fraction consists of four major and four minor polypeptides detectable in SDS gels, all of which stain red (metachromatically) with Coomassie Blue R-250, are degraded by bacterial collagenase and migrate below the central diagonal in urea-SDS/SDS electrophoresis. The four major collagenous polypeptides are larger than the alpha-chains of type I collagen. In total, the solubilized proteins account for 60% of the general protein, but only 30% of the sum of hydroxyproline and hydroxylysine. The insoluble residue has a collagenous amino acid composition similar to that of the 100 degrees C extract, but with lower 3-hydroxyproline and hydroxylysine contents.

Amino Acids↗
PubMed1983

The formation of radiolabeled N1- and N8-acetylspermidine in various rat organs following [14C]spermidine administration.

To detect the in vivo formation of acetylspermidine, three female Sprague-Dawley rats were injected intravenously with 20 muCi of [14C]spermidine. Twenty-four hours after the injection of the radiolabel, the kidneys, liver, lungs, pancreas, small intestine, spleen, stomach and thymus were removed under Halothane anesthesia. High performance liquid chromatography (HPLC) of the pooled radiolabeled extracts from each tissue demonstrated the presence of a 14C-labeled material which co-chromatographed with an acetylspermidine standard. Thin layer chromatography (TLC) of the HPLC eluent demonstrated the presence of both radiolabeled N1- and N8-acetylspermidine in the tissues. Concentrations of labeled acetylspermidine ranged from 0.27 to 1.9% of the total tissue radiolabel. The N1-to N8-acetylspermidine ratio in tissues ranged from approx. 5 to 1 in the thymus to 1.5 to 1 in the liver.

Animals↗
PubMed1983

Improved methods for harvesting and counting synchronous populations of Artemia nauplii for use in developmental toxicology.

Artemia nauplii have, within recent years, gained popularity as a test organism for short-term toxicity testing. Because nauplii exhibit rapid development and growth within 48 hr after hatch, their potential as a model organism for teratology screening has been considered. To do this, synchronous populations of nauplii at different developmental intervals must be available. A dual-chamber hatching vessel which enables multiple harvesting of synchronous populations of nauplii from one sample of prepared cysts has been developed. An accumulation period of 2 hr defines the synchronous population and produces around 1000 nauplii among five hatching vessels. The body lengths of nauplii harvested 2 to 9 hr after the initial harvest were equivalent to and lower than that of animals incubated at the hatching temperature (31 +/- 1 degree C); e.g., the body length of freshly harvested nauplii at 9 hr was 473 +/- 6.2 micron (+/- SE) and for nauplii incubated for 8 to 10 hr, the body lengths were 643 +/- 10.7 and 702 +/- 10.9 micron, respectively. A counting method was developed that enabled precise counting up to 400 nauplii in suspension and distinguishing dead from live nauplii. Measurements of body length, body water volume, and whole animal DNA and protein of nauplii harvested sequentially from the same sample of prepared cysts indicated that in addition to temporal differences in hatching, the nauplii may differ both physically and chemically.

Animals↗
PubMed1983

Coomassie Blue R-250 metachromatic staining of histone 5 from goose and chicken erythrocytes.

1. Histone 5 stains metachromatically with Coomassie Blue R-250, a property shared only with collagens and procollagens, histones 1 and 2B, and possibly certain proline-rich salivary gland proteins. 2. Coomassie Blue-stained goose and chicken H5 induce the same degree of metachromasia, which is intermediate between that induced by H1 and H2b. 3. The absorption spectra of all Coomassie Blue-stained gel bands consist of a primary maximum at 555 nm, but the absorption spectra of H5 gel bands also include a prominent shoulder in the vicinity of 525 nm, a region in which H1 gel bands display a secondary maximum. 4. The possible role of proline-rich sequences in the induction of metachromasia is discussed.

Animals↗
PubMed1983

Correlation of the in vivo and in vitro renal toxicity of S-(1,2-dichlorovinyl)-L-cysteine.

The major site at which vinyl cysteine conjugates exert nephrotoxicity is the proximal tubule. Since this is the site of all active anion and cation transport, tubule transport integrity was used to assess nephrotoxicity. Tubules were isolated from young rabbits to study the in vivo and in vitro nephrotoxicity of the conjugate, dichlorovinyl cysteine (DCVC). In vivo exposure to DCVC caused necrosis in the pars recta region of the proximal tubules (20-100 mg/kg ip) and a dose-dependent decrease in tubular active transport. Addition of DCVC to the perfused kidney and tubule suspensions resulted in similar decreases in tubular organic ion transport. At 0.01 mM DCVC, transport was similar to controls while 1 mM DCVC completely inhibited active accumulation of the organic ions. Thus kidney tubule active transport is similarly inhibited in vivo and in vitro by DCVC indicating that bioactivation of DCVC and inhibition of active transport occur directly in the renal tubule.

Animals↗
PubMed1983

Rapid isolation of type II pneumocytes with magnetic removal of macrophages.

A method is described for the rapid preparation of lung cell fractions enriched in type II alveolar pneumocytes. Isolated perfused rabbit lungs are exposed to Fe3O4 by tracheal lavage, which permits pulmonary alveolar macrophages to phagocytize the particles. Alveolar epithelial cells are then selectively freed from the basement membrane matrix by critical placement of collagenase and elastase. Detached cells are harvested either by repeated tracheal lavage or by mincing the lobes and filtering freed cells through a series of nylon mesh sieves. Iron oxide-containing macrophages are then removed from the harvested cells by a strong magnetic field. A final sizing of the macrophage-depleted suspension yields a preparation enriched in alveolar type II cells. Eight million viable cells (95% type II) were obtained per rabbit lung when harvested by lavage, while 32 x 10(6) (88% type II) cells were obtained from minced lungs. These values for cell yield and relative purity are comparable to previously described separation methods that depend upon differences in cell density or size. A major advantage of the magnetic separation procedure is the substantially shortened preparation time, typically 2 hr instead of 4. The viability (90-95%), oxygen consumption (88 nmol/10(6) cells/hr), and incorporation of [14C]acetate and [14C]choline (0.44 and 0.115 nmol/10(6) cells/hr, respectively) indicate that these cells will be suitable for pharmacologic and toxicologic investigation.

Animals↗
PubMed1982

Effects of insulin-glucagon interactions on glycogenolysis and protein kinase activity in rat hepatocytes.

The effects of insulin and glucagon on cAMP accumulation, protein kinase activation, and glycogenolysis were investigated in isolated rat hepatocytes. Glucagon (0.01 nM to 10 micro M) increased the activation state of protein kinase and the rate of glucose accumulation. Addition of 1.0 nM insulin to cells preincubated with 0.1 nM glucagon attenuated the rate of glucose accumulation, but did not alter the protein kinase activity ratio. Addition of 0.1 nM glucagon to cells preincubated with 1.0 nM insulin caused a rapid activation of protein kinase; however, glycogenolysis was not immediately affected. These effects were enhanced with pharmacological concentrations of glucagon and insulin. These data indicate that the degree of protein kinase activation does not always correlate temporally or quantitatively with rates of glycogenolysis in liver cells exposed to insulin and glucagon.

Animals↗
PubMed1982

Dihydrocapsaicin-induced hypothermia and substance P depletion.

Administration of dihydrocapsaicin to rats resulted in a dose-dependent (0.5-10 mg/kg s.c.) hypothermia. Dihydrocapsaicin was approximately 65% more effective in producing hypothermia than capsaicin. Desensitization and cross-tolerance occurred to the hypothermic effects of both capsaicin and dihydrocapsaicin. Repeated administration of either dihydrocapsaicin or capsaicin resulted in chemogenic antinociception but not marked thermal antinociception. In addition, repeated administration of dihydrocapsaicin, like capsaicin, resulted in depletion of substance P from dorsal root ganglia and dorsal spinal cord but not from the hypothalamus, corpus striatum or ventral spinal cord. These data indicate that dihydrocapsaicin, or radiolabelled dihydrocapsaicin, may be a useful tool for investigating the mechanisms by which capsaicin alters thermoregulation and primary afferent neuron function.

Animals↗
PubMed1982

Isolation of proline and hydroxyproline from fossil bone.

We describe a simple and rapid procedure for the isolation of proline and hydroxyproline from fossil bone based on the isolation of gelatin, hydrolysis, purification with XAD-2, deamination of primary amino acids with aqua regia, and separation of the imino acids by cation exchange chromatography. This procedure will provide material for accurate bone carbon dating, and stable carbon isotope ratio determinations for the evaluation of paleodiets.

Animals↗
PubMed1982

Preparation of cell-free extracellular matrix from human peripheral nerve.

The extracellular matrix of human peripheral nerve, which is mainly basement membrane and fibrillar collagen, has been prepared by a procedure involving extensive detergent extraction of isolated endoneurium and perineurium obtained from various nerves. The ultrastructure of the isolated nerve extracellular matrix was indistinguishable from that seen in sections of intact nerve, indicating that the extraction procedure preserved the morphological integrity of these connective tissue components. The amino acid and carbohydrate compositions of the nerve extracellular matrix preparations were typically collagenous in nature containing a high content of glycine, proline, 4-hydroxyproline, and alanine and significant amounts of lysine and hydroxylysine. The preparations contained virtually no 3-hydroxyproline and low content of glucose and galactose compared to pure basement membranes, indicating that interstitial rather than basement membrane collagens predominated. This preparation appears well-suited to both the ultrastructural and biochemical study of the extracellular matrix of peripheral nerve.

Cell Fractionation↗