Biomedical subjects

L S DeBruin

Publications and source records attributed to L S DeBruin.

6 recordsLinked to original sources

PubMed2005

Developmental partitioning of myelin basic protein into membrane microdomains.

Specific membrane microdomains (including lipid rafts) exist in myelin but have not been fully characterized. Myelin basic protein (MBP) maintains the compactness of the myelin sheath and is highly posttranslationally modified. Thus, it has been suggested that MBP might also have other functions, e.g., in signal transduction. Here, the distribution of MBP and its modified forms was studied, spatially and temporally, by detailed characterization of membrane microdomains from developing and mature bovine myelin. Myelin membranes were extracted with three different detergents (Brij 96V, CHAPS, or Triton X-100) at 4 degrees C. The detergent-resistant membranes (DRMs), representing coalesced lipid rafts, were isolated as low-buoyant-density fractions on a sucrose density gradient. These myelin rafts were disrupted when cholesterol was depleted with methyl-beta-cyclodextrin. The use of CHAPS detergent led to enrichment of several myelin proteins, including phospho-Thr97-MBP, in the DRMs from mature myelin. Citrullinated and methylated MBP remained in "nonraft" microdomains. In contrast, the DRMs from early myelin were enriched in Golli-MBP, Fyn, Lyn, and CNP. The localization of various proteins in DRMs was further supported by the colocalization of these lipid raft components in cultured mouse oligodendrocytes. Thus, there is a developmental regulation of posttranslationally modified forms of MBP into specific membrane microdomains.

Animals↗

PubMed2001

Detection of PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) in the milk of healthy women.

An increased risk of breast cancer has been observed in women who consume "very well-done" meats. Heterocyclic amines are mutagenic and carcinogenic pyrolysis products formed during high temperature cooking of meats. In the present study, human milk samples were analyzed for PhIP, one of the most abundant dietary heterocyclic amine. A protocol was developed with a mixed-mode cation exchange sorbent for the extraction of heterocyclic amines from milk. Milk samples were acquired from healthy Canadian women. With LC/MS analysis and the method of isotope dilution for quantification, levels of PhIP were determined in human milk samples. PhIP was detected in 9 of the 11 milk samples, at levels as high as 59 pg/mL (ppt). No PhIP was detected in the milk of the vegetarian donor. Detection of PhIP in milk indicates that ductal mammary epithelial cells are directly exposed to this carcinogen, suggesting that heterocyclic amines are possible human mammary carcinogens.

Adult↗

PubMed1999

Detection of monocyclic aromatic amines, possible mammary carcinogens, in human milk.

Environmental chemicals may play a role in the etiology of human breast cancer. Aromatic amines, industrial chemicals found as environmental pollutants, have been identified as rat mammary carcinogens. We have detected the monocyclic aromatic amines, aniline, o-toluidine, and N-methylaniline at parts per billion levels in human milk samples, by applying solid-phase microextraction coupled with gas chromatography/mass spectrometry. Our findings indicate that human breast ductal epithelial cells are directly exposed to aromatic amines, including o-toluidine, which is a mammary carcinogen in female rats.

Adult↗

PubMed1998

Solid-phase microextraction of monocyclic aromatic amines from biological fluids.

A solid-phase microextraction (SPME) protocol was developed for the quantitative analysis of monocyclic aromatic amines from biological fluids. The headspace SPME sampling technique was optimized for extraction and concentration of five target analytes (aniline, o-toluidine, 2-chloroaniline, 2,6-dimethylaniline, 2,4,6-trimethylaniline) from urine, blood, and milk. The temperature, pH, and ionic strength of the matrix sample were modified to allow maximum adsorption of the analytes onto the SPME fiber. This method is rapid yet sensitive and can be completed in 15 min on a 5-mL sample. SPME/GC/MS analysis yielded good reproducibility (RSD > 11%) for each analyte from urine, blood, and milk. Method detection limits for the various biological fluids were determined and ranged from 0.40 ppb for 2,4,6-trimethylaniline in urine to 7.7 ppb for aniline in blood. This SPME sampling protocol can be applied to the biomonitoring of monocyclic aromatic amines from occupational, environmental, and medical exposure.

Calibration↗

PubMed1995

Bioactivation of aromatic amines by recombinant human cytochrome P4501A2 expressed in Ames tester strain bacteria: a substitute for activation by mammalian tissue preparations.

The most widely used bioassay in genetic toxicology is the Ames test, which combines a bacterial mutagenicity assay (reversion of Salmonella typhimurium histidine-auxotrophic tester strains) with an exogenous bioactivation system (hepatic postmitochondrial supernatant or "S9"). The enzymatic activities of S9 prepared from the tissues of experimental animals are difficult to control. We show that the requirement for S9 can be obviated by the engineered expression of enzymes of bioactivation within the bacterial cell. With this strategy, reactive metabolites are produced inside the bacterial cell, proximate to the genetic target. Species boundaries can be crossed, and chimeric or mutant enzymes can be studied. We have constructed an Ames tester strain, expressing both aromatic amine N-acetyltransferase and human cytochrome P4501A2, which detects aromatic amine mutagenicity in the absence of S9.

Acetyltransferases↗

PubMed1989

Dichlorobenzidine-DNA binding catalyzed by peroxidative activation in Salmonella typhimurium.

Peroxidative oxidation of dichlorobenzidine in vitro results in covalent binding to exogenous DNA. In a modified Ames assay, mutagenicity is observed in S. typhimurium strain TA98 following the incubation of dichlorobenzidine, bacteria, and hydrogen peroxide. In this paper, we demonstrate that [14C]dichlorobenzidine becomes covalently bound to S. typhimurium macromolecules, including DNA, when exogenous hydrogen peroxide is supplied. We compared the levels of binding in a pair of otherwise isogenic strains with wild-type (oxyR+) versus constitutive (oxyR1) expression of the hydrogen peroxide stress-induced regulon. Binding was approximately twofold higher in TA4124 (oxyR1) than in TA4123 (oxyR+). Bacterial hydroperoxidases may catalyze the activation of dichlorobenzidine to mutagenic and DNA binding species in this system.

3,3'-Dichlorobenzidine↗