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Biomedical subjects

K Brendel

Publications and source records attributed to K Brendel.

At least 127 records · Page 7Linked to original sources
PubMed1982

In vitro degradation of L-phenylalanine mustard (L-PAM).

L-Phenylalanine mustard (L-PAM), a bis-choroethylamine, is an important drug in the treatment of multiple myeloma and ovarian cancer. It undergoes rapid hydrolysis in vitro and in vivo, forming the mono-and dihydroxy degradation products. L-PAM's first-order disappearance rate in a phosphate-buffered solution did not differ statistically according to the presence or absence of activated rat liver microsomal enzymes. Furthermore, L-PAM's disappearance rate in a rat whole liver perfusion system was not greater than its hydrolysis rate in water. In vitro plasma recovery studies showed that up to 85% of the 14C L-PAM drug equivalents could be recovered as the parent compound and the mono- and dihydroxy degradation products. Thus, L-PAM in in vitro degradation was similar qualitatively and quantitatively to its reported in vivo degradation in animals and man. It is concluded that L-PAM does not undergo important, active in vivo metabolism.

Animals↗
PubMed1982

Effects of ethanol diets on cholesterol content and phospholipid acyl composition of rat hepatocytes.

Chronic treatment of adult male rats with ethanol liquid diets resulted in alterations in phospholipid and cholesterol contents as well as the acyl composition of phosphatidylethanolamine (PE), phosphatidylinositol (PI)-phosphatidylserine (PS) mixture, and phosphatidylcholine (PC) of isolated hepatocytes. The influence of ethanol on these lipids was largely dependent on the proportion of dietary fat. Phospholipid and total cholesterol contents were elevated 23 and 27%, respectively, by ethanol when offered in a low-fat diet (5% corn oil). Only the percentage of arachidonic acid from PI-PS was significantly reduced in the low-fat ethanol group. Exposure to a high-fat (34% corn oil) diet in the presence of ethanol for 4-5 weeks resulted in a significant decrease in arachidonate/linoleate ratios of hepatic PE, PS-PI and PC, while total phospholipid content remained constant. In the high-fat, ethanol-treated group, hepatic cholesterol content was increased 2-fold. These results suggest that the level of dietary fat plays an important role in determining the effects of chronic ethanol consumption on hepatic cholesterol content and phospholipid acyl composition.

Animals↗
PubMed1982

Chromatographic resolution of amino acid adducts of aliphatic halides.

Numerous xenobiotics are known to be bioactivated and to covalently and to proteins, but the resulting amino acid adducts (AAAs) are unknown. In this study the AAAs of twelve 14C-labeled aliphatic halides were examined after formation in an in vitro microsomal system. After exhaustive solvent extraction of the precipitated microsomal protein, the AAAs were isolated by Pronase digestion, followed by filtration through a 500 mol. wt. exclusion membrane. The liberated AAAs were applied to a constant flow DC-4A cation exchange column, resolved by stepwise buffer elution, collected and counted for radioactivity. Column recovery for applied radioactivity was 100 +/- 4%. Generally, 1-4 different AAAs (defined by eluting radioactivity) were resolved, with each organohalogen displaying a characteristic elution profile. Methyl iodide, trichloroethylene and 1,2-dichloroethylene had a single major AAA while bromotrichloromethane, 1,2-dibromoethane, 1,1,1-trichloroethane, 1,2-dichloroethane, 1,1,2-trichloroethane, 2-bromo-2-chloro-1,1,1-trifluoroethane, chloroform and carbon tetrachloride had up to 4 AAAs or more, indicating combinations of binding site(s) and reactive intermediate(s). The single AAA formed following incubation of methyl iodide with the microsomes was identified as S-methylcysteine. Thus, this method appears capable of resolving binding sites and is the initial isolation step for identifying specific adducts to proteins.

Amino Acids↗
PubMed1982

The bioactivation of 1,2-dibromoethane in rat hepatocytes: covalent binding to nucleic acids.

Isolated rat hepatocytes metabolized 1,2-dibromoethane (EDB) to reactive intermediates which covalently bound to cellular nucleic acids. DNA isolated from hepatocytes that had been incubated with [14C]EDB (80 microM) was alkylated with a specific binding of 0.6 nmol/mg DNA. RNA exhibited a greater specific alkylation with 2.1-3.0 nmol bound/mg. High concentrations of EDB (greater than 500 microM) depleted the concentration of hepatocellular glutathione, but binding of [14C]EDB equivalents to nucleic acids occurred at concentrations which had little effect on glutathione levels. Diethylmaleate (750 microM) decreased the binding of [14C]EDB equivalents to nucleic acids by 50%, but SKF-525A (200 microM) did not decrease this binding to nucleic acids. Although both hepatic microsomal and cytosolic fractions catalyzed the covalent binding of [14C]EDB equivalents to calf thymus DNA, the degree of binding was 12 times greater when cytosolic enzymes were used. The results suggest the involvement of glutathione-S-transferases in the bioactivation of EDB to species that covalently bind to DNA.

Alkylation↗
PubMed1982

Thickened cerebral cortical capillary basement membranes in diabetics.

In human diabetes mellitus, thickening of the microvascular endothelial cell basement membrane has been documented by quantitative ultrastructural studies in a variety of vascular beds. We studied the thickness of the cerebral cortical capillary basement membrane in frontal and occipital lobes from 21 diabetics and 16 nondiabetics, and found that those from diabetics were significantly thicker. Skeletal muscle capillary basement membranes have been shown to thicken with increasing age. However, only in the frontal cortex of diabetics was a significant relationship observed between capillary basement membrane thickening and increasing age. We conclude that, along with many of the previously studied microvascular beds, the cerebral cortical microvasculature displays thickening of the endothelial cell basement membrane in diabetes mellitus. No currently known disease is associated with this microvascular change, unlike the closely related retinal vasculature, where the association with diabetic retinopathy is established.

Adult↗
PubMed1981

Glucagon structure-function relationships using isolated rat hepatocytes.

The ability of glucagon and several of its semi-synthetic analogues to stimulate glucose production in isolated rat hepatocytes was measured and compared for relative potencies. The order of decreasing biological activities of glucagon in this assay was as follows: glucagon greater than [HArg12]-glucagon greater than [des-Asn28, Thr29][homoserinehydrazide27]-glucagon approx. equal to [des-His1]-glucagon greater than [des-Asn28, Thr29][homoserinelactone27]-glucagon greater than [des-Asn28, Thr29]-[n-butylhomoserineamide27]-glucagon greater than glucagon1-21. Qualitatively, these results are similar to those obtained previously in the hepatic plasma membrane adenylate cyclase assay. Minor exceptions were noted for the hydrazide derivative and the partial agonist [des-His1]-glucagon, both of which were slightly more potent relative to glucagon in the glycogenolytic assay than in the adenylate cyclase assay. The assay provides important insight into glucagon structure-function relationships.

Amino Acid Sequence↗
PubMed1981

The addition of SDS to the Bradford dye-binding protein assay, a modification with increased sensitivity to collagen.

The standard Bradford protein assay is insensitive to collagen. But if a small, sub-threshold amount of SDS is added to the sample, the response to collagen is increased by at least an order of magnitude, while, on average, the sensitivity for non-collagens is decreased by approximately a factor of 2. As a result, comparable color formation is achieved with both collagen and non-collagens. The addition of protein to a sub-threshold amount of SDS results in the formation of a green color measurable as an increase in absorbance at 700 nm, in contrast to the blue color measured at 595 nm in the standard assay. Depending upon the source, the threshold level for SDS varies from 30 to 50 microgram. The response to protein is linear up to approximately 40 microgram of protein per ml of reagent.

Collagen↗
PubMed1981

A charcoal cartridge for the removal of anionic detergent and electrophoresis stains.

Instructions are given for the construction of a charcoal-containing cartridge that allows the rapid recirculation through charcoal of any fluid in which the cartridge is submerged; recirculatory flow is achieved by magnetic stirring of the fluid by a stirring bar placed under the cartridge. The device is assembled from nylon mesh and conical sections cut from polypropylene beakers. The device can be used to accelerate the destaining of electrophoresis gels and to remove SDS (sodium lauryl sulfate) from SDS gels. The removal of SDS prior to staining is essential for the staining of SDS gels with Coomassie Brilliant Blue G-250.

Charcoal↗
PubMed1981

Human diabetic perineurial cell basement membrane thickening.

The perineurium of peripheral nerves is a cellular sleeve which surrounds and isolates the endoneurium with its axons and Schwann cells from the epineurium. Basement membrane covers the inner and outer surfaces of perineurial cells. This study concerns ultrastructural thickness measurements of human sural nerve perineurial cell basement membranes. Twenty-four patients with diabetes mellitus had a mean and standard deviation thickness of 174.1 +/- 76.2 nm., which was significantly greater than that found in 19 nondiabetics (67.1 +/- 12.8 nm., pooled variance two-tailed t-test, p less than 0.001). For 13 of the diabetics on insulin, the values were 208.4 +/- 78.1 nm. compared to those not on insulin (133.5 +/- 51.8 nm., p = 0.01). The p values when comparing male versus female sex and source of tissue from autopsy versus biopsy indicated no significant differences. This report documents that in diabetes mellitus, in addition to the well known basement membrane thickening of the microvasculature, there is also thickening of the basement membrane covering a nonvascular cell of nerve, the perineurial cell, and this this thickening is exaggerated in diabetics treated with insulin. We suggest that perineurial cell basement membrane thickness quantitation may be useful in distinguishing diabetic from nondiabetic distal symmetrial neuropathy.

Adult↗
PubMed1980

Metachromatic staining with Coomassie Brilliant Blue R-250 of the proline-rich calf thymus histone, H1.

In this report, we show that calf thymus histone 1 stains metachromatically with Coomassie Brilliant Blue R-250. Histone 1 gel bands appear red instead of the more familiar blue color characteristic of the vast majority of proteins. The red color and the spectral properties of histone 1 bands are qualitatively similar to those of collagen and procollagen bands which, as previously shown by others, also stain metachromatically (Micko, S. and Schlaepfer, W.W. (1978) Anal. Biochem. 88, 566-572 and McCormick, P.J., Chandrasekhar, S. and Millis, A.J.T. (1979) Anal. Biochem. 97, 359-366). In contrast to histone 1, histones 2A, 3 and 4 stain blue; histone 2B also stains predominantly blue, but with a faint red tint. Both red and blue bands display an absorption maximum in the vicinity of 560 nm, but red bands display an additional maximum in the vicinity of 530 nm. There are quantitative differences between the red bands; the 530 nm peak is more prominent in the spectrum of the collagen band than in the spectrum of the histone 1 band. The spectra of the blue bands are all very similar except that the spectrum of the histone 2B band is shifted slightly toward lower wavelengths. To account for the spectral differences between protein bands, we propose a model in which closely-spaced proline residues are responsible for the chromotropic effect. Localized concentrations of proline residues are present in both collagens and histone 1 and a small cluster is also present in histone 2B.

Animals↗
PubMed1980

[Ultrasonics].

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Noise↗
PubMed1980

A symbiotic relationship of energy metabolism between a 'non-glycolytic' mammalian red cell and the liver.

The red cell of newborn pig loses the ability to carry out glycolysis within a month after birth. The metabolic energy source for this 'non-glycolytic' mammalian red cell is unknown. Hepatectomy of an adult pig results in the loss of red cell ATP with a characteristic half-time of 7--8 h which is identical to the rate with which ATP disappears in the pig cells under in vitro substrate-free incubation. Exposure of pig red cells with either normal or depleted levels of ATP to isolated hepatocytes causes a net synthesis of red cell ATP during a 12 h incubation. These findings suggest that a symbiotic relationship of energy metabolism may exist between the red cell and the liver of the pig.

Adenosine Triphosphate↗