Urothelial cell DNA adducts in rubber workers

Workers employed in the rubber industry appear to have a significant excess cancer risk in a variety of sites, including cancer of the urinary bladder. In this cross-sectional study, we investigated the occurrence of DNA adducts in exfoliated bladder cells of currently exposed, nonsmoking rubber workers (n = 52) and their relationship with occupational exposure estimates and acetylation phenotype (NAT2). Four DNA adducts were identified, with the proportion of positive samples (e.g., DNA samples with quantifiable levels of a specific DNA adduct) ranging from 3.8 to 79%. The highest proportion of positive samples and the highest relative adduct labeling levels were in workers involved in the production functions "mixing" and "curing," areas with potential for substantial exposure to a wide range of chemical compounds used in rubber manufacturing (P < 0.05 for adducts 2 and/or 3, compared to all other departments). No statistically significant relationships were found between identified DNA adducts and urinary mutagenicity or personal inhalable and dermal exposure estimates. Interestingly, subjects with a fast NAT2 acetylation phenotype tended to have higher levels of DNA adducts. This study suggests that rubber workers engaged in mixing and curing may be exposed to compounds that can form DNA adducts in urothelial cells. Larger studies among rubber workers should be conducted to study in more detail the potential carcinogenicity of exposures encountered in these work areas.     

Lung preservation solution substrate composition affects rat lung oxidative metabolism during hypothermic storage

Lungs harvested for transplantation utilize oxygen after procurement. We investigated the effects of storage solution substrate composition on pulmonary oxidative metabolism and energetics during the preservation interval. Rat lungs were harvested and stored at 10 degrees C in low-potassium dextran (LPD) solution. Groups of lungs were preserved with preservation solution containing 5mM carbon-13 ((13)C) labeled glucose or increasing concentrations of (13)C labeled pyruvate. Additional groups of rat lungs were studied with dichloroacetate (DCA) added to the pyruvate-modified preservation solutions. Oxidative metabolism (measured by (13)C-enrichment of glutamate) and adenine nucleotide levels were quantified. Increasing preservation solution pyruvate concentration augmented glutamate (13)C-enrichment up to a concentration of 32mM pyruvate. DCA further stimulated oxidative metabolism only at lower concentrations of pyruvate (4 and 8mM). ATP and ADP were not different among groups, but AMP levels were higher in the glucose group. These data suggest that altering the substrate composition of the preservation solution influences lung metabolism during allograft preservation for transplantation.     

Increasing trend of Cesarean deliveries in HIV-infected women in the United States from 1994 to 2000

BACKGROUND: Meta-analysis and randomized clinical trial results reported in June 1998 indicated a significant reduction in perinatal HIV transmission rates among mothers undergoing a cesarean section (C-section). OBJECTIVE: The objective of this study was to examine recent trends in and factors associated with C-section deliveries among HIV-infected women in the United States. DESIGN: A multisite pediatric medical record review of a cohort of HIV-exposed and HIV-infected infants in the Pediatric Spectrum of HIV Disease (PSD) Cohort study (n = 6467) and the national Pediatric HIV/AIDS Reporting System (HARS) (n = 8,306) was conducted. SETTING/PATIENTS: All infants born between 1994 and 2000 to HIV-positive mothers referred to the PSD study or to a Pediatric HARS hospital or clinic site were enrolled. RESULTS: The proportion of deliveries by C-section was steady at about 20% from 1994 through June 1998. From July 1998 through December 2000, this proportion increased to 44% in the PSD study and to nearly 50% in the Pediatric HARS. On analysis by multiple logistic regression, delivery of infants by C-section was associated with the release of study results (OR = 2.83), delivery in four PSD sites in reference to Texas (OR: 2.02-1.43), having private medical care reimbursement (OR = 1.62), and having maternal prenatal care (OR = 1.43). CONCLUSIONS: The PSD and Pediatric HARS data demonstrate a sharp increase in C-section rates mainly among HIV-infected women in the United States after the release of the meta-analysis and randomized clinical trial results in 1998. This finding highlights the rapid impact of study results on obstetric practice. It underscores the critical role of prenatal care in offering perinatal interventions such as scheduled C-section when indicated to reduce the likelihood of HIV transmission.     

Multilocus sequence typing for studying genetic relationships among Yersinia species

The intra- and interspecies genetic relationships of 58 strains representing all currently known species of the genus Yersinia were examined by multilocus sequence typing (MLST), using sequence data from 16S RNA, glnA, gyrB, recA, and Y-HSP60 loci. Yersinia aldovae, Y. bercovieri, Y. intermedia, Y. pestis, Y. pseudotuberculosis, Y. rohdei, and Y. ruckeri were genetically more homogeneous than were Y. enterocolitica, Y. frederiksenii, Y. kristensenii, and Y. mollaretii. The MLST data concerning the genetic relatedness within and among various species of Yersinia support the idea that Y. pestis and Y. pseudotuberculosis are two lineages within the same species rather than two distinct species. Y. ruckeri is the genetically most distant species within the genus. There was evidence of O-antigen switching and genetic recombination within and among various species of Yersinia. The genetic relatedness data obtained by MLST of the four housekeeping genes and 16S RNA agreed in most, but not all, instances. MLST was better suited for determining genetic relatedness among yersiniae than was 16S RNA analysis. Some strains of Y. frederiksenii and Y. kristensenii are genetically less related to other strains within those species, compared to strains of all other species within the genus. The taxonomic standing of these strains should be further examined because they may represent currently unrecognized Yersinia species.     

Polymorphic metabolizing genes and susceptibility to atherosclerosis among cigarette smokers

Atherosclerosis (AR) is the leading cause of morbidity and mortality in the US and cigarette smoking is a major contributing factor to the disease. Like cigarette smoking in lung cancer, genetic susceptibility may be an important factor in determining who is more likely to develop AR. However, the current emphasis has been on susceptibility based on altered cardiovascular homeostasis. In this investigation, we studied 120 AR patients and 90 matched controls to elucidate the association between polymorphisms in some metabolizing genes (GSTM1, GSTT1, CYP2E1, mEH, PON1, and MPO) and susceptibility to AR. We found that the GSTT1 null allele and the fast allele of mEH(*) (exon 4) are associated with risk for AR. Furthermore, the combined genotypes GSTM1 null/ CYP2E1(*)5B, GSTM1 null/mEH YY, and GSTT1 null/mEH YY are significantly associated with susceptibility to AR (OR = 15.42, 95% CI = 1.33-77.93, P = 0.021; OR = 3.48, 95% CI = 1.63-8.04, P = 0.0008; OR = 3.4; 95% CI = 0.99-17.38, P = 0.05; respectively). We have also conducted cytogenetic analysis to elucidate if induction of chromosome aberrations (CAs) is a biomarker of AR susceptibility. We found that among cigarette smokers (AR patients and smoker controls), individuals having the GSTM1 null allele had a significantly higher frequency of CAs compared to those with the normal allele (P < 0.05). This association was not found among nonsmokers. In addition, individuals who had inherited the CYP2E1(*)5B allele exhibited a significantly higher CA frequency (8.0 +/- 0.82) compared to those with the CYP2E1 wild-type genotype (4.31 +/- 0.35). Since the analysis of genetic susceptibility factors is still in its infancy, our study may stimulate additional investigations to understand the roles of genetic susceptibility and cigarette smoking in AR.     

Functional characterization of GABA(A) receptors in neonatal hypothalamic brain slice

The hypothalamus influences a number of autonomic functions. The activity of hypothalamic neurons is modulated in part by release of the inhibitory neurotransmitter GABA onto these neurons. GABA(A) receptors are formed from a number of distinct subunits, designated alpha, beta, gamma, delta, epsilon, and theta, many of which have multiple isoforms. Little data exist, however, on the functional characteristics of the GABA(A) receptors present on hypothalamic neurons. To gain insight into which GABA(A) receptor subunits are functionally expressed in the hypothalamus, we used an array of pharmacologic assessments. Whole cell recordings were made from thin hypothalamic slices obtained from 1- to 14-day-old rats. GABA(A) receptor-mediated currents were detected in all neurons tested and had an average EC(50) of 20 +/- 1.6 microM. Hypothalamic GABA(A) receptors were modulated by diazepam (EC(50) = 0.060 microM), zolpidem (EC(50) = 0.19 microM), loreclezole (EC(50) = 4.4 microM), methyl-6,7-dimethoxy-4-ethyl-beta-carboline (EC(50) = 7.7 microM), and 5alpha-pregnan-3alpha-hydroxy-20-one (3alpha-OH-DHP). Conversely, these receptors were inhibited by Zn(2+) (IC(50) = 70.5 microM), dehydroepiandrosterone sulfate (IC(50) = 16.7 microM), and picrotoxin (IC(50) = 2.6 microM). The alpha4/6-selective antagonist furosemide (10-1,000 microM) was ineffective in all hypothalamic neurons tested. The results of our pharmacological analysis suggest that hypothalamic neurons express functional GABA(A) receptor subtypes that incorporate alpha1 and/or alpha2 subunits, beta2 and/or beta3 subunits, and the gamma2 subunit. Our results suggest receptors expressing alpha3-alpha6, beta1, gamma1, and delta, if present, represent a minor component of functional hypothalamic GABA(A) receptors.     

Discrepancies between self-reported years of education and estimated reading level among elderly community-dwelling African-Americans: Analysis of the MOAANS data.

The influence of education on cognition has received a great deal of attention in the literature. Although there is general consensus regarding the importance of education on cognitive functioning, the extent to which self-reported level of education corresponds to true educational attainment remains unclear, especially in ethnic minority populations where equal access to education has not always been available. Several investigators have suggested that reading skill may serve as a quantitative estimate of true education experience. Among African-Americans, however, research has shown that self-reported educational level consistently over predicts estimated reading level. The current study analyzed the discrepancy between self-reported years of education completed and estimated reading level in a sample of community-dwelling, elderly African-Americans participating in Mayo's Older African Americans Normative Studies (MOAANS) (Lucas, J.A., Ivnik, R.J., Willis, F.B., Ferman, T.J., Smith, G.E., Parfitt, F.C., Petersen, R.C., & Graff-Radford, N.R. (2005). Mayo's Older African Americans Normative Studies: Normative data for commonly used clinical neuropsychological measures. The Clinical Neuropsychologist, 19, 162-183). In this sample, 29% of the participants read at a level that was 3 or more years below what would be expected based on self-report of education attained. This study also sought to evaluate the extent to which this discrepancy fluctuated as a function of demographic variables such as location of schooling (urban, suburban, rural; North vs. South), parental education and literacy, and percentage of segregation in schooling. Implications of these results are discussed, as are areas for further inquiry.     

Troponin C regulates the rate constant for the dissociation of force-generating myosin cross-bridges in cardiac muscle

It is well known that cardiac troponin C (cTnC) regulates the association of force-generating myosin cross-bridges. We report here evidence for an additional role for cTnC. This hypothesis states that Car²⁺ binds more strongly to cTnC when force-generating myosin cross-bridges are attached to actin and that removal of this bound Ca²⁺ accelerates the dissociation of force-generating myosin cross-bridges. Intact Fura-2-loaded rat papillary muscles and skinned (permeabilized) ventricular preparations were used. The preparations were mounted in the Guth Muscle Research System which is capable of measuring simultaneously fluorescence and force in response to length perturbations. All mechanical perturbations of muscle length (isotonic shortening, quick stretches and releases, and length vibrations) which cause dissociation of force-generating myosin cross-bridges during a twitch resulted in Ca²⁺ being released from troponin as judged from changes in the Ca²⁺ transients (Fura-2 (340/380) fluorescence ratio). Thus dissociation of force-generating myosin cross-bridges cause Ca²⁺ to be released from cTnC. Conversely, it would be expected that removal of strongly bound Ca²⁺ from cTnC would result in an increase in the rate of dissociation of force-generating myosin cross-bridges. To test this hypothesis actomyosin ATPase (NADH fluorescence change) and isometric force were measured in skinned cardiac preparations. The ratio of the ATPase/Force is proportional to the rate constant (g_app) for the dissociation of force-generating myosin cross-bridges. The data showed that decreasing the amount of Ca²⁺ bound to cTnC in skinned cardiac fibers caused an increase in the ratio of ATPase/Force, the rate of dissociation (g_app) of force-generating myosin cross-bridges.     

Translocation chromosome 7 of A431 cells contains amplification and rearrangement of EGF receptor gene responsible for production of variant mRNA

The epidermal growth factor (EGF) receptor, along with several oncogene protein products, possesses tyrosine-specific protein kinase activity. Furthermore, the EGF receptor has structural similarity to the putitive v-erb-B transforming protein. Because of these closely shared characteristics, it is important to elucidate the possible involvement of the EGF receptor in malignant transformation. The epidermal carcinoma cell line A431 exhibits an abnormally high number of EGF receptors, which is associated with the presence of translocation chromosome M4. Recently, A431 cells have been shown to contain amplified sequences for the EGF receptor gene(s) and also to produce a variant mRNA which diverges from the normal EGF receptor mRNA at the 3 end. Here we report, using the human EGF receptor cDNA probe pE7, that the chromosome M4 has a six-to sevenfold amplification of the EGF receptor gene. Furthermore, the presence of M4 in somatic cell hybrids correlates with the production of the variant 2.9-kb mRNA. This aberrant mRNA is apparently generated by an intrachromosomal rearrangement which was detected using as a probe a fragment of the pE15cDNA encoding the variant mRNA.