The mutagenic response at the ouabain resistance locus in T cells of mice exposed to N-ethyl-N-nitrosourea parallels the response at the Hprt locus and correlates with mutation target size

The lymphocyte Hprt gene has been used extensively as a reporter locus to monitor the mutational effects of the exposure of animals to genotoxicants. Implicit in this view of the function of a reporter gene is the assumption that its mutagenic response is representative of that of other genes in the organism. As a test of this hypothesis we compared the frequency of 6-thioguanine-resistant (TGr) mutants at the Hprt locus with the mutant frequency (MF) induced at another locus, the ouabain resistance (Oua) locus. The frequency of spontaneous OUA(R) mutants was estimated to be 1.1x10(-7) (MF between <0.3 and 1.1x10(- 7)), which was approximately 30-fold less than the spontaneous TGr MF. Following treatment with N-ethyl-N-nitrosourea (ENU), the induced OUA(R) MF at each of two dose levels (50 and 150 mg/kg ENU) and two time points (3 and 6 weeks post-exposure) was consistently 8- to 9-fold lower than the corresponding TGr MF. Thus the mutagenic response of the Oua locus closely paralleled that of the Hprt locus, indicating a similarity in their response to ENU. In addition, the Oua locus was 3-4 times more sensitive than the Hprt locus to the mutagenic effect of ENU, as measured by the fold increase in MF over the background level. The number of ENU-mutable sites capable of resulting in a TGr or OUA(R) phenotype, otherwise known as the mutation target size, was estimated to differ by an order of magnitude between the two loci. This difference in target size correlates with, and therefore may largely account for, the difference in induced MF between both loci.      

Specificity of mutagenesis by 4-aminobiphenyl: mutations at G residues in bacteriophage M13 DNA and G-->C transversions at a unique dG(8-ABP) lesion in single-stranded DNA

Mutagenesis by the human bladder carcinogen 4-aminobiphenyl (ABP) was studied in single-stranded DNA from a bacteriophage M13 cloning vector. In comparison to ABP lesions in double-stranded DNA, lesions in single- stranded DNA were approximately 70-fold more mutagenic and 50-fold more genotoxic. Sequencing analysis of ABP-induced mutations in the lacZ gene revealed exclusively base-pair substitutions, with over 80% of the mutations occurring at G sites; the G at position 6310 accounted for 25% of the observed mutations. Among the sequence changes at G sites, G- ->T transversions predominated, followed by G-->C transversions and G-- >A transitions. In order to further elucidate the mutagenic mechanism of ABP, an oligonucleotide containing the major DNA adduct, N- (deoxyguanosin-8-yl)-4-aminobiphenyl (dG(8-ABP)), was situated within the PstI site of a single-stranded M13 genome. After in vivo replication of the adduct containing ABP-modified and control (unadducted) genomes, the mutational frequency and mutational specificity of the dG(8-ABP) lesion were determined. The targeted mutational efficiency was approximately 0.01%, and the primary mutation observed was the G-->C transversion. Thus dG(8-ABP), albeit weakly mutagenic at the PstI site, can contribute to the mutational spectrum of ABP lesions.      

Job strain and health behaviors: results of a prospective study

PURPOSE: To assess the association between job demands, job decision latitude, and job strain (defined by Karasek as a combination of high demands and low decision latitude) and cardiovascular disease-related health behaviors such as cigarette smoking, alcohol use, lack of exercise, and overweight. DESIGN: Cross-sectional and prospective. SETTING: Nine New York City public and private sector worksites. SUBJECTS: Two hundred eighty-five male employees, aged 30 to 60, in a wide variety of white-collar and blue-collar job titles. MEASURES: Medical examinations and surveys, which included demographic, health behavior, and job characteristics data. RESULTS: Prospectively, among 189 men, increase in job decision latitude over 3 years was associated with decrease in cigarette smoking, by analysis of covariance, controlling for age, race, education, marital status, and number of children at home (F (8, 180) = 4.37, p = .005). The largest increase in latitude occurred among the 13 men who quit smoking. However, change in job characteristics was not associated with change in overweight or alcohol use. Cross-sectional analyses did not produce consistent associations. CONCLUSIONS: The effectiveness of smoking cessation may be aided by modification of structural features of the work environment, such as job decision latitude. This study is limited by the small number of subjects who were engaged in high risk behaviors.     

Use of inhaled steroids by pregnant asthmatic women does not reduce intrauterine growth

BACKGROUND: Inhaled steroids are recommended for the treatment of persistent asthma during pregnancy, but their potential effects on intrauterine growth have been inadequately evaluated. OBJECTIVE: The purpose of this study was to evaluate the association between maternal use of specific inhaled steroids and inhaled steroid dose during pregnancy and the incidence of infants who are small for gestational age (SGA) and mean birth weight. METHODS: Pregnant asthmatic women being treated with inhaled steroids were enrolled in the study before delivery by their managing allergists. Information regarding the specific inhaled steroid and daily dose used, requirement for oral steroids, occurrence of acute asthmatic episodes, maternal race, birth weight, gestational age, and congenital malformations was obtained for each patient. SGA was defined through use of a published normative sample of American births. RESULTS: A total of 474 women were enrolled in the study; of the 451 enrolled participants whose pregnancy ended in a singleton live birth, 396 (88%) completed the study. The incidence of infants with low birth weight, preterm births, and congenital malformations in this cohort was not greater than expected in the general population. The incidence of SGA was 7.1% (95% CI, 5.0% to 10.1%). No significant relationships between specific inhaled steroid or dose of inhaled steroid used and either SGA or mean birth weight were observed. CONCLUSION: These data suggest that the use of inhaled steroids by pregnant asthmatic women does not reduce intrauterine growth and supports the recommendation that inhaled steroids should be used in the management of persistent asthma during pregnancy.     

The patterning of psychological attributes and distress by “job strain” and social support in a sample of working men

As a test of the job strain (job demands-control) model, 297 healthy men aged 30–60 were recruited at eight New York City worksites. The association among job demands and control, social support, and psychological outcomes was tested using both ANCOVA and moderated multiple regression, controlling for demographic variables. The job strain model was supported by various psychological outcome measures, with workers in active jobs reporting the highest level of Type A behavior, job involvement, and positive attributional style, workers in low-strain jobs reporting the lowest job dissatisfaction and trait anxiety, workers in passive jobs reporting the most external locus of control and trait anxiety, and workers in high-strain jobs reporting the highest job dissatisfaction. Low social support was associated with greater symptomatology, and a significant three-way interaction (demands×control×support) for job dissatisfaction was observed. While selection of subjects into jobs may partially explain these findings, the results support the hypothesis that working conditions influence psychological attributes and distress.Supported in part by grants HL 18232 and HL 30605, from the National Heart, Lung and Blood Institute and National Research Service Award HL 08578 to the first author.An earlier version of this paper was presented at the American Psychological Association/National Institute for Occupational Safety and Health Conference Work and Well Being: An Agenda for the 90's, November 17, 1990, Washington, DC.     

The predictive value of the zona-free hamster egg penetration test in relation to in-vitro fertilization at various insemination concentrations

The aim of the study was to evaluate the predictive value of the zona- free hamster egg penetration test (ZHEPT) for success in in-vitro fertilization (IVF) at various insemination concentrations ranging between 0.1 and >0.6 x 10(6)/ml. The ZHEPT was assessed using sperm samples from 87 couples undergoing IVF treatment. A similar test was simultaneously performed on the same semen sample following ionophore induction of the acrosome reaction (ZHEPTii test). Both the tests were poorly correlated with the fertilization rate of IVF at all the insemination concentrations except at >0.6 x 10(6)/ml, when there was good correlation between the ZHEPTii test and the fertilization rate. Following exclusion of two cases with an oocyte problem, further statistical analysis revealed that both the ZHEPT and ZHEPTii tests were poorly correlated with fertilization rate in IVF in this treatment group. This study suggests that the ZHEPT (with and without ionophore induction of the acrosome reaction) has a poor predictive value for the success of fertilization in IVF treatment at any insemination concentration.      

Impact of misclassification in genotype-exposure interaction studies: example of N-acetyltransferase 2 (NAT2), smoking, and bladder cancer.

Errors in genotype determination can lead to bias in the estimation of genotype effects and gene-environment interactions and increases in the sample size required for molecular epidemiologic studies. We evaluated the effect of genotype misclassification on odds ratio estimates and sample size requirements for a study of NAT2 acetylation status, smoking, and bladder cancer risk. Errors in the assignment of NAT2 acetylation status by a commonly used 3-single nucleotide polymorphism (SNP) genotyping assay, compared with an 11-SNP assay, were relatively small (sensitivity of 94% and specificity of 100%) and resulted in only slight biases of the interaction parameters. However, use of the 11-SNP assay resulted in a substantial decrease in sample size needs to detect a previously reported NAT2-smoking interaction for bladder cancer: 1,121 cases instead of 1,444 cases, assuming a 1:1 case-control ratio. This example illustrates how reducing genotype misclassification can result in substantial decreases in sample size requirements and possibly substantial decreases in the cost of studies to evaluate interactions.     

p14ARF expression in invasive breast cancers and ductal carcinoma in situ – relationships to p53 and Hdm2

Introduction  

p14^ARF stabilises nuclear p53, with a variable expression of p14^ARF mRNA in breast cancers. In vitro, nuclear p14^ARF binds Hdm2 to block Hdm2-dependent nucleocytoplasmic shuttling of p53, which is required before cytoplasmic degradation of p53. p14^ARF is negatively regulated by p53 and through p53-independent pathways. No studies have yet examined levels of p14^ARF protein expression in breast cancer and their relationship to Hdm2/p53 immunoreactivity or subcellular localisation. Previously, immunohistochemical expression of cytoplasmic p14^ARF, p53 and Hdm2 has been described. HER-2 (c-erbB2/neu) predicts prognosis and interacts with the p14^ARF/Hdm2 pathway to inactivate p14^ARF and to influence Hdm2 activity and localisation. This study examined p14^ARF and p53/Hdm2 expression and subcellular localisation by using immunohistochemistry in a series of invasive ductal breast cancers (IDCs) with concomitant ductal carcinoma in situ (DCIS), to evaluate whether findings in vitro were related to clinicopathological parameters such as HER-2 and their effect on patient outcome.     

Differential depression at excitatory and inhibitory synapses in visual cortex

The function of cortical circuits depends critically on the balance between excitation and inhibition. This balance reflects not only the relative numbers of excitatory and inhibitory synapses but also their relative strengths. Recent studies of excitatory synapses in visual and somatosensory cortices have emphasized that synaptic strength is not a fixed quantity but is a dynamic variable that reflects recent presynaptic activity. Here, we compare the dynamics of synaptic transmission at excitatory and inhibitory synapses onto visual cortical pyramidal neurons. We find that inhibitory synapses show less overall depression than excitatory synapses and that the kinetics of recovery from depression also differ between the two classes of synapse. When excitatory and inhibitory synapses are stimulated concurrently, this differential depression produces a time- and frequency-dependent shift in the reversal potential of the composite postsynaptic current. These results indicate that the balance between excitation and inhibition can change dynamically as a function of activity.     

Blockade of clearance of immune complexes by an anti-F(cγ) receptor monoclonal antibody

Clearance of immune complexes by the mononuclear phagocyte system is important for maintaining normal host defenses against bacterial and viral assault (1), but also contributes to the pathogenesis of a variety of immune- mediated diseases . For example, removal from the circulation of IgG-coated erythrocytes and platelets by the MPS is the sine qua non of immune-mediated cytopenias (2, 3). On the other hand, abnormally decreased removal by the MPS of smaller, soluble immune complexes may play a role in the pathogenesis of immune complex-mediated tissue damage found in such autoimmune diseases as SLE (4). Although the physicochemical nature and the size of immune complexes can influence rates of clearance and sites of deposition (reviewed in 5), interactions between immune complexes and the MPS in vivo are poorly understood. The inability to directly measure binding or internalization of immune complexes by cells in the liver and spleen has made the analysis of the molecular basis of immune complex clearance very difficult . Receptors for the Fc portion of IgG (FcγR) and for complement (CR) undoubtedly play a role in the removal of immune complexes, but the relative importance of these receptors is not known.