Exome sequencing identifies breast cancer susceptibility genes and defines the contribution of coding variants to breast cancer risk

Linkage and candidate gene studies have identified several breast cancer susceptibility genes, but the overall contribution of coding variation to breast cancer is unclear. To evaluate the role of rare coding variants more comprehensively, we performed a meta-analysis across three large whole-exome sequencing datasets, containing 26,368 female cases and 217,673 female controls. Burden tests were performed for protein-truncating and rare missense variants in 15,616 and 18,601 genes, respectively. Associations between protein-truncating variants and breast cancer were identified for the following six genes at exome-wide significance (P < 2.5 × 10-6): the five known susceptibility genes ATM, BRCA1, BRCA2, CHEK2 and PALB2, together with MAP3K1. Associations were also observed for LZTR1, ATR and BARD1 with P < 1 × 10-4. Associations between predicted deleterious rare missense or protein-truncating variants and breast cancer were additionally identified for CDKN2A at exome-wide significance. The overall contribution of coding variants in genes beyond the previously known genes is estimated to be small.

DNA repair gene polymorphisms, tumor control, and treatment toxicity in prostate cancer patients treated with permanent implant prostate brachytherapy

BACKGROUND

Radiotherapy and brachytherapy are common treatments for localized prostate cancer (PCa). However, very few studies evaluated the association of variations in DNA damage response genes and treatment outcomes and toxicity in brachytherapy-treated patients.

PURPOSE

To evaluate the association of inherited germline variations in DNA repair-associated genes with tumor control and treatment toxicity in patients treated with low-dose-rate prostate brachytherapy (LDRB).

MATERIAL AND METHODS

The cohort consists of 475 I-125 LDRB patients with a median follow-up of 51 months after seed implantation. Patients were genotyped for 215 haplotype tagging single nucleotide variations (htSNPs) in 29 candidate genes of DNA damage response and repair pathways. Their association with biochemical recurrence (BCR) was assessed using Cox regression models and Kaplan-Meier survival curves. Linear regressions and analysis of covariance (ANCOVA) between early and late International Prostate Symptom Score (IPSS) with htSNPs were used to evaluate the association with urinary toxicity.

RESULTS

After adjustment for the established risk factors, six htSNPs in five genes were found to be significantly associated with an altered risk of BCR, with adjusted hazard ratios (HR_adj. ) ranging between 3.6 and 11.1 (P < .05). Compared to carriers of the ERCC3 rs4150499C allele, patients homozygous for the T allele (n = 22) had a significant higher risk of BCR with a HR of 11.13 (IC₉₅  = 3.9-32.0; P < .0001; q < 0.001). The Kaplan-Meier survival curve revealed a mean BCR-free survival time reduced from 213 ± 7 to 99 ± 12 months (log-rank P < .0001) for homozygous T carriers compare to noncarriers. For late IPSS (>6 months after treatment), htSNP rs6544990 from MSH2 showed a statistically significant b-coefficient of 1.85 ± 0.52 (P < .001; q < 0.1). Homozygous carriers of the MSH2 rs6544990C allele (n = 62) had a mean late IPSS 3.6 points higher than patients homozygous for the A allele (n = 132). This difference was significant when tested by ANCOVA using pretreatment IPSS as a covariate (P < .01).

CONCLUSIONS

This study suggests an association of the intronic variants of the DNA nucleotide excision repair ERCC3 and DNA mismatch repair MSH2 genes with elevated risk of BCR and late urinary toxicity respectively after LDRB. Further validation is required before translational clinical advances.

The fundamentals of cross-sector collaboration for social change to promote population health

Cross-sector collaboration is increasingly relied upon to tackle society's pressing and intractable problems. Chief among societal problems are unfavorable structural and social determinants of health. The ability to positively change these health determinants rests on the collaborative processes and structures of governance across diverse sectors in society. The purpose of this article is to present a conceptual framework that sheds light on the basic requirements of cross-sector collaboration for social change to promote the health of populations. A search for theoretical articles on cross-sector collaboration in the fields of public administration and public health was conducted within the journal databases ABI/INFORM Complete and MEDLINE. This search strategy was supplemented by an internet search of the grey literature for high-profile models of cross-sector collaboration. The conceptual framework builds on previous scholarly work by placing emphasis on five essential conditions for collective impact, and on the pivotal role of collective learning. Collective learning, at the basis of planning and taking action, is at the core of effective cross-sector initiatives, specifically because of its critical role in constantly adapting strategies to changing circumstances and unanticipated situations within complex socio-ecological systems.

Endogenous Protein Interactome of Human UDP-Glucuronosyltransferases Exposed by Untargeted Proteomics

The conjugative metabolism mediated by UDP-glucuronosyltransferase enzymes (UGTs) significantly influences the bioavailability and biological responses of endogenous molecule substrates and xenobiotics including drugs. UGTs participate in the regulation of cellular homeostasis by limiting stress induced by toxic molecules, and by controlling hormonal signaling networks. Glucuronidation is highly regulated at genomic, transcriptional, post-transcriptional and post-translational levels. However, the UGT protein interaction network, which is likely to influence glucuronidation, has received little attention. We investigated the endogenous protein interactome of human UGT1A enzymes in main drug metabolizing non-malignant tissues where UGT expression is most prevalent, using an unbiased proteomics approach. Mass spectrometry analysis of affinity-purified UGT1A enzymes and associated protein complexes in liver, kidney and intestine tissues revealed an intricate interactome linking UGT1A enzymes to multiple metabolic pathways. Several proteins of pharmacological importance such as transferases (including UGT2 enzymes), transporters and dehydrogenases were identified, upholding a potential coordinated cellular response to small lipophilic molecules and drugs. Furthermore, a significant cluster of functionally related enzymes involved in fatty acid β-oxidation, as well as in the glycolysis and glycogenolysis pathways were enriched in UGT1A enzymes complexes. Several partnerships were confirmed by co-immunoprecipitations and co-localization by confocal microscopy. An enhanced accumulation of lipid droplets in a kidney cell model overexpressing the UGT1A9 enzyme supported the presence of a functional interplay. Our work provides unprecedented evidence for a functional interaction between glucuronidation and bioenergetic metabolism.

ABRAXAS (FAM175A) and Breast Cancer Susceptibility: No Evidence of Association in the Breast Cancer Family Registry

Approximately half of the familial aggregation of breast cancer remains unexplained. This proportion is less for early-onset disease where familial aggregation is greater, suggesting that other susceptibility genes remain to be discovered. The majority of known breast cancer susceptibility genes are involved in the DNA double-strand break repair pathway. ABRAXAS is involved in this pathway and mutations in this gene impair BRCA1 recruitment to DNA damage foci and increase cell sensitivity to ionizing radiation. Moreover, a recurrent germline mutation was reported in Finnish high-risk breast cancer families. To determine if ABRAXAS could be a breast cancer susceptibility gene in other populations, we conducted a population-based case-control mutation screening study of the coding exons and exon/intron boundaries of ABRAXAS in the Breast Cancer Family Registry. In addition to the common variant p.Asp373Asn, sixteen distinct rare variants were identified. Although no significant difference in allele frequencies between cases and controls was observed for the identified variants, two variants, p.Gly39Val and p.Thr141Ile, were shown to diminish phosphorylation of gamma-H2AX in MCF7 human breast adenocarcinoma cells, an important biomarker of DNA double-strand breaks. Overall, likely damaging or neutral variants were evenly represented among cases and controls suggesting that rare variants in ABRAXAS may explain only a small proportion of hereditary breast cancer.

Unitary Transformations in the Quantum Model for Conceptual Conjunctions and Its Application to Data Representation

Quantum models of concept combinations have been successful in representing various experimental situations that cannot be accommodated by traditional models based on classical probability or fuzzy set theory. In many cases, the focus has been on producing a representation that fits experimental results to validate quantum models. However, these representations are not always consistent with the cognitive modeling principles. Moreover, some important issues related to the representation of concepts such as the dimensionality of the realization space, the uniqueness of solutions, and the compatibility of measurements, have been overlooked. In this paper, we provide a dimensional analysis of the realization space for the two-sector Fock space model for conjunction of concepts focusing on the first and second sectors separately. We then introduce various representation of concepts that arise from the use of unitary operators in the realization space. In these concrete representations, a pair of concepts and their combination are modeled by a single conceptual state, and by a collection of exemplar-dependent operators. Therefore, they are consistent with cognitive modeling principles. This framework not only provides a uniform approach to model an entire data set, but, because all measurement operators are expressed in the same basis, allows us to address the question of compatibility of measurements. In particular, we present evidence that it may be possible to predict non-commutative effects from partial measurements of conceptual combinations.

Nurses' evaluations of the CPOT use at 12-month post-implementation in the intensive care unit

BACKGROUND

Performing routine pain assessments with all intensive care unit (ICU) patients is strongly recommended in clinical practice guidelines. As many ICU patients are unable to self-report, the Critical-Care Pain Observation Tool (CPOT) is one of the two behavioural pain scales suggested for clinical use. Still, no study has described the evaluations of its use in ICU daily practice.

OBJECTIVE

To describe the nurses' evaluation of the feasibility, clinical relevance and satisfaction with the CPOT use 12 months after its implementation in the ICU.

METHOD

A descriptive design was used. It was conducted in the medical-surgical ICU of a university affiliated setting at Greenfield Park (Québec, Canada). A self-administered evaluation questionnaire including four sections (i.e. feasibility, clinical relevance, satisfaction and socio-demographic information) was completed by ICU nurses who were all trained to use the CPOT. The questionnaires were completed anonymously.

RESULTS

A total of 38 ICU nurses returned their completed questionnaire (63% participation rate). Regarding its feasibility, the majority rated the CPOT as quick to use, simple to understand and easy to complete (92-100%). According to clinical relevance, close to 70% of ICU nurses acknowledged that the CPOT had influenced their practice, but lower results (<50%) were found for effective communication of pain assessment findings with the physicians and other health professionals. More than 80% of ICU nurses were satisfied with its daily use.

CONCLUSION

The CPOT use was deemed feasible and relevant in daily practice as per the nurses' evaluations but did not allow an effective communication with other ICU care team members.

RELEVANCE TO CLINICAL PRACTICE

Training should be offered to all members of the ICU care team, and other implementation strategies should be explored as well to ensure optimal uptake of a pain assessment approach which impacts on their decision-making process for pain management.

Exome sequencing identifies mutations in the gene TTC7A in French-Canadian cases with hereditary multiple intestinal atresia

BACKGROUND

Congenital multiple intestinal atresia (MIA) is a severe, fatal neonatal disorder, involving the occurrence of obstructions in the small and large intestines ultimately leading to organ failure. Surgical interventions are palliative but do not provide long-term survival. Severe immunodeficiency may be associated with the phenotype. A genetic basis for MIA is likely. We had previously ascertained a cohort of patients of French-Canadian origin, most of whom were deceased as infants or in utero. The goal of the study was to identify the molecular basis for the disease in the patients of this cohort.

METHODS

We performed whole exome sequencing on samples from five patients of four families. Validation of mutations and familial segregation was performed using standard Sanger sequencing in these and three additional families with deceased cases. Exon skipping was assessed by reverse transcription-PCR and Sanger sequencing.

RESULTS

Five patients from four different families were each homozygous for a four base intronic deletion in the gene TTC7A, immediately adjacent to a consensus GT splice donor site. The deletion was demonstrated to have deleterious effects on splicing causing the skipping of the attendant upstream coding exon, thereby leading to a predicted severe protein truncation. Parents were heterozygous carriers of the deletion in these families and in two additional families segregating affected cases. In a seventh family, an affected case was compound heterozygous for the same 4bp deletion and a second missense mutation p.L823P, also predicted as pathogenic. No other sequenced genes possessed deleterious variants explanatory for all patients in the cohort. Neither mutation was seen in a large set of control chromosomes.

CONCLUSIONS

Based on our genetic results, TTC7A is the likely causal gene for MIA.

Analysis of ZNF350/ZBRK1 promoter variants and breast cancer susceptibility in non-BRCA1/2 French Canadian breast cancer families

ZNF350/ZBRK1 is a transcription factor, which associates with BRCA1 to co-repress GADD45A to regulate DNA damage repair, and the expression of ZNF350 is altered in different human carcinomas. In a previous study, we identified ZNF350 genomic variants potentially involved in breast cancer susceptibility in high-risk non-BRCA1/2 breast cancer individuals, which pointed toward a potential association for variants in the 5'-UTR and promoter regions. Therefore, direct sequencing was undertaken and identified 12 promoter variants, whereas haplotype analyses put in evidence four common haplotypes with a frequency>2%. However, based on their frequency observed in breast cancer and unrelated healthy individuals, these are not statistically associated with breast cancer risk. Luciferase promoter assays in two breast cancer cell lines identified two haplotypes (H11 and H12) stimulating significantly the expression of ZNF350 transcript compared with the common haplotype H8. The high expression of the H11 allele was associated with the variant c.-874A. Using MatInspector and Transcription Element Search softwares, in silico analyses predicted that the variant c.-874A created a binding site for the factors c-Myc and myogenin. This study represents the first characterization step of the ZNF350 promoter. Additional studies in larger cohorts and other populations will be needed to further evaluate whether common and/or rare ZNF350 promoter variants and haplotypes could be associated with a modest risk of breast cancer.

Polymorphic variations in the FANCA gene in high-risk non-BRCA1/2 breast cancer individuals from the French Canadian population

The majority of genes associated with breast cancer susceptibility, including BRCA1 and BRCA2 genes, are involved in DNA repair mechanisms. Moreover, among the genes recently associated with an increased susceptibility to breast cancer, four are Fanconi Anemia (FA) genes: FANCD1/BRCA2, FANCJ/BACH1/BRIP1, FANCN/PALB2 and FANCO/RAD51C. FANCA is implicated in DNA repair and has been shown to interact directly with BRCA1. It has been proposed that the formation of FANCA/G (dependent upon the phosphorylation of FANCA) and FANCB/L sub-complexes altogether with FANCM, represent the initial step for DNA repair activation and subsequent formation of other sub-complexes leading to ubiquitination of FANCD2 and FANCI. As only approximately 25% of inherited breast cancers are attributable to BRCA1/2 mutations, FANCA therefore becomes an attractive candidate for breast cancer susceptibility. We thus analyzed FANCA gene in 97 high-risk French Canadian non-BRCA1/2 breast cancer individuals by direct sequencing as well as in 95 healthy control individuals from the same population. Among a total of 85 sequence variants found in either or both series, 28 are coding variants and 19 of them are missense variations leading to amino acid change. Three of the amino acid changes, namely Thr561Met, Cys625Ser and particularly Ser1088Phe, which has been previously reported to be associated with FA, are predicted to be damaging by the SIFT and PolyPhen softwares. cDNA amplification revealed significant expression of 4 alternative splicing events (insertion of an intronic portion of intron 10, and the skipping of exons 11, 30 and 31). In silico analyzes of relevant genomic variants have been performed in order to identify potential variations involved in the expression of these spliced transcripts. Sequence variants in FANCA could therefore be potential spoilers of the Fanconi-BRCA pathway and as a result, they could in turn have an impact in non-BRCA1/2 breast cancer families.

Variations in the NBN/NBS1 gene and the risk of breast cancer in non-BRCA1/2 French Canadian families with high risk of breast cancer

BACKGROUND

The Nijmegen Breakage Syndrome is a chromosomal instability disorder characterized by microcephaly, growth retardation, immunodeficiency, and increased frequency of cancers. Familial studies on relatives of these patients indicated that they also appear to be at increased risk of cancer.

METHODS

In a candidate gene study aiming at identifying genetic determinants of breast cancer susceptibility, we undertook the full sequencing of the NBN gene in our cohort of 97 high-risk non-BRCA1 and -BRCA2 breast cancer families, along with 74 healthy unrelated controls, also from the French Canadian population. In silico programs (ESEfinder, NNSplice, Splice Site Finder and MatInspector) were used to assess the putative impact of the variants identified. The effect of the promoter variant was further studied by luciferase gene reporter assay in MCF-7, HEK293, HeLa and LNCaP cell lines.

RESULTS

Twenty-four variants were identified in our case series and their frequency was further evaluated in healthy controls. The potentially deleterious p.Ile171Val variant was observed in one case only. The p.Arg215Trp variant, suggested to impair NBN binding to histone gamma-H2AX, was observed in one breast cancer case and one healthy control. A promoter variant c.-242-110delAGTA displayed a significant variation in frequency between both sample sets. Luciferase reporter gene assay of the promoter construct bearing this variant did not suggest a variation of expression in the MCF-7 breast cancer cell line, but indicated a reduction of luciferase expression in both the HEK293 and LNCaP cell lines.

CONCLUSION

Our analysis of NBN sequence variations indicated that potential NBN alterations are present, albeit at a low frequency, in our cohort of high-risk breast cancer cases. Further analyses will be needed to fully ascertain the exact impact of those variants on breast cancer susceptibility, in particular for variants located in NBN promoter region.

Genetic variants and haplotype analyses of theZBRK1/ZNF350gene in high-risk non BRCA1/2 French Canadian breast and ovarian cancer families

Our current understanding of breast cancer susceptibility involves mutations in the 2 major genes BRCA1 and BRCA2, found in about 25% of high-risk families, as well as few other low penetrance genes such as ATM and CHEK2. Approximately two-thirds of the multiple cases families remain to be explained by mutations in still unknown genes. In a candidate gene approach to identify new genes potentially involved in breast cancer susceptibility, we analyzed genomic variants in the ZBRK1 gene, a co-repressor implicated in BRCA1-mediated repression of GADD45. Direct sequencing of ZBRK1 entire coding region in affected breast cancer individuals from 97 high-risk French Canadian breast/ovarian cancer families and 94 healthy controls led to the identification of 18 genomic variants. Haplotype analyses, using PHASE, COCAPHASE and HaploStats programs, put in evidence 3 specific haplotypes which could potentially modulate breast cancer risk, and among which 2 that are associated with a potential protective effect (p = 0.01135 and p = 0.00268), while another haplotype is over-represented in the case group (p = 0.00143). Further analyses of these haplotypes indicated that a strong component of the observed difference between both groups emerge from the first 5 variants (out of 12 used for haplotype determination). The present study also permitted to determine a set of tagging SNPs that could be useful for subsequent analyses in large scale association studies. Additional studies in large cohorts and other populations will however be needed to further evaluate if common and/or rare ZBRK1 sequence variants and haplotypes could be associated with a modest/intermediate breast cancer risk.

Psychic tonus, body schema and the parietal lobes: a multiple lesion case analysis

The psychic tonus model (Braun and colleagues, 1999, 2002, 2003, 2006) states that the left hemisphere is a “booster” of internal experience and behavior in general, and that the right hemisphere is a “dampener”. Twenty-five patients with a “positive” extreme disturbance of body schema (somatoparaphrenia) and 37 patients with a “negative” disturbance of body schema (autotopagnosia or Gerstmann’s syndrome), all following a unilateral parietal lesion, were found in the literature and were analyzed to test predictions from Braun’s “psychic tonus” model. As expected, patients with a positive syndrome had a right hemisphere lesion significantly more frequently, and those with a negative syndrome had a left hemisphere lesion significantly more frequently. Thus the psychic tonus model of hemispheric specialization, previously supported with regard to psychomotor baseline, libido, talkativeness, memory, auditory and visual perceptual tonus, now incorporates the tonus of representation of the body (body schema) in the parietal lobes.

The burden of adult obesity in Canada

Obesity is a major public health problem associated with a wide range of health problems. This study estimates the prevalence of obesity, calculates the proportion (or population-attributable fraction [PAF]) of major chronic diseases which is attributable to obesity, estimates the deaths attributable to it and projects its future prevalence trends. In Canada, the overall age-standardized prevalence proportion of obesity has increased from 10 percent in 1970 to 23% in 2004 (8 percent to 23 percent in men and 13 percent to 22 percent in women). The increasing prevalence of obesity was observed for all five age groups examined: 20-34, 35-44, 45-54, 55-64 and 65+. On average, the PAF of prevalence of selected major chronic diseases which is attributable to obesity from 1970 to 2004 has increased by 138 percent for men and by 60 percent for women. Overall, in 2004, 45 percent of hypertension, 39 percent of type II diabetes, 35 percent of gallbladder disease, 23 percent of coronary artery diseases (CAD), 19 percent of osteoarthritis, 11 percent of stroke, 22 percent of endometrial cancer, 12 percent of postmenopausal breast cancer, and 10 percent of colon cancer could be attributed to obesity. In 2004, 8,414 (95 percent CI: 6,881-9,927) deaths were attributable to obesity. If current obesity prevalence trends remain unchanged, the prevalence proportion of obesity in Canada is projected to reach 27 percent in men and 24 percent in women by the year 2010. These increases will have a profound impact on the treatment needs and prevalence of a wide variety of chronic diseases, and also on the health care system in terms of capacity issues and resource allocation.

Outcomes of an ecological and participatory approach to prevent alcohol and other drug "abuse" among multiethnic adolescents

This study presents outcomes related to adolescents' alcohol use from an evaluation study testing the effectiveness of The Coalition for Youth Quality of Life Project (Le Regroupement pour la qualité de vie des jeunes). This project is an ecological and participatory approach developed to prevent alcohol and other drug use and misuse among multiethnic youth. The intervention was implemented through four channels of program delivery: families, schools, community organizations, and local government. The study involved 411 sixth graders from eight elementary schools and 380 eighth graders from two junior high schools, in two school districts of the Island of Montreal (province of Quebec, Canada). All students were enrolled in regular classes. Follow-up data were collected 18 months and 30 months after pre-test using a school survey. The findings indicated that the program had no significant impact on alcohol use. The program was, however, capable of producing a significant effect on several hypothesized mediating variables. At first follow-up, the sixth graders showed a higher self-esteem, better peer pressure resistance skills, and a more positive relationship with their father than the controls. The eighth graders were also more inclined to get involved in community activities related to substance abuse prevention and to choose more alternatives to "substance abuse" in their leisure time than the controls. The results are discussed by examining attrition effects and also reasons for program failure. Issues are raised about the evaluation of an ecological and participatory approach.

Inhalation toxicology of urban ambient particulate matter: acute cardiovascular effects in rats

Wistar rats were exposed for 4 hours by nose-only inhalation to clean air, resuspended Ottawa ambient particles (EHC-93*, 48 mg/m3), the water-leached particles (EHC-93L, 49 mg/m3), diesel soot (5 mg/m3), or carbon black (5 mg/m3). Continuous data for physiologic endpoints (heart rate, blood pressure, body temperature, animal's activity) were captured by telemetry before and after exposure. Blood was sampled from jugular cannulas 1 to 3 days before exposure and at 2 and 24 hours after exposure, and by heart puncture on termination at 32 hours (histology group) or 48 hours (telemetry group) after exposure. Lung injury was assessed by 3H-thymidine autoradiography after the rats were killed. We measured endothelins (plasma ET-1, big ET-1, ET-2, ET-3) to assess the vasopressor components; nitric oxide (NO)-related metabolites (blood nitrate, nitrite, nitrosyl compounds, and plasma 3-nitrotyrosine) to assess the vasodilator components; and catecholamines (epinephrine, norepinephrine, L-DOPA, dopamine) and oxidative stressors (m- and o-tyrosine) for additional insight into possible stress components. Lung cell labeling was uniformly low in all treatment groups, which indicates an absence of acute lung injury. Inhalation of EHC-93 caused statistically significant elevations (P < 0.05) of blood pressure on day 2 after exposure, plasma ET-1 at 32 hours after exposure, and ET-3 at 2, 32, and 48 hours after exposure. In contrast, the modified EHC-93L particles, from which soluble components had been extracted, did not affect blood pressure. The EHC-93L particles caused early elevation (P < 0.05) of the plasma levels of ET-1, ET-2, and ET-3 at 2 hours after exposure, but the endothelins returned to basal levels 32 hours after exposure. Exposure to diesel soot, but not carbon black, caused an elevation (P < 0.05) of plasma ET-3 at 36 hours after exposure; blood pressure was not affected by diesel soot. Our results indicate that inhalation of the urban particles EHC-93 can affect blood levels of ET-1 and ET-3 and cause a vasopressor response in Wistar rats without causing acute lung injury. Furthermore, the potency of the particles to influence hemodynamic changes appears to be modified by removing polar organic compounds and soluble elements. Because the pathophysiologic significance of elevated endothelins has been clinically established in humans, our observations suggest a novel mechanism by which inhaled particles may cause cardiovascular effects. These findings in rats contribute to the weight of evidence in favor of a biologically plausible epidemiologic association between ambient particulate matter and cardiovascular morbidity and mortality in human populations.

Effect of aging on the basal expression of c-Fos, c-Jun, and Egr-1 proteins in the hippocampus

In the present study the effect of aging on the basal expression of three different immediate early genes (IEGs) was investigated. The protein products of c-fos, c-jun, and egr-1 genes were visualized immunohistochemically in the rat hippocampus of young adult (4-month-old) and old rats (20-month-old). Astrocytes were quantified by GFAp immunostaining to determine whether changes in the expression of IEGs were correlated with modifications in this marker of degenerative changes. In the young adult rat brain, basal levels of c-Jun and Egr-1 but not c-Fos were detected within the hippocampal formation. Whereas very high basal levels of c-Jun were found in the dentate granule cells and in the pyramidal cells of the ventral hippocampus, Egr-1 was highly expressed in the CA1 pyramidal cells of the dorsal hippocampus. Aging was accompanied by a decrease in Egr-1 expression, by a decrease in total cell density, as well as by a loss of astrocytes in CA1 subfields. In contrast, basal expression of c-Fos and c-Jun as well as astrocyte density within the dentate gyrus were not affected by aging. No difference in these markers was observed in aged rats with or without impairment in spatial learning in a water maze. It was concluded that although these changes may reflect senescence-induced decline of brain function, they do not constitute the defect underlying the age-associated reduction in mnesic capability.

Changes in striatal immediate early gene expression following neonatal dopaminergic lesion and effects of intrastriatal dopaminergic transplants

To evaluate the functional integration of neonatal dopaminergic transplants within host brain we studied the postsynaptic effects induced by their stimulation by following the expression of immediate early genes c-fos, c-jun and egr-1. This study was conducted nine months after the intrastriatal implantation of embryonic mesencephalic neurons to rat pups having sustained a unilateral lesion of the nigrostriatal dopaminergic system. We examined whether, when challenged with d-amphetamine: (1) dopaminergic grafts transplanted into the previously denervated neonatal neostriatum lead to a normal activation of postsynaptic striatal neurons in term of immediate early genes activation; and (2) whether this activation is related to the action of the dopamine released from the grafts using a dopaminergic D1 antagonist. Following a mild stress-injection of saline-c-fos expression was high in the lesioned neostriatum when compared with control animals. This effect was only partially counteracted by a pre-treatment with the D1 antagonist SCH 23390, but was abolished by the graft. Administration of d-amphetamine increased c-fos expression in the neostriatum and the globus pallidus of the control group. This activation was partially blocked by the lesion. The transplant reversed the effect of the lesion and, moreover, led to a c-fos over-expression in the dorsolateral neostriatum and the globus pallidus. These overcompensations positively correlated with the abnormal rotation induced by d-amphetamine in the same animals. Pre-treatment with SCH 23390 blocked the effect of d-amphetamine on c-fos expression in control and grafted animals. Similar results were found for egr-1 but not c-jun expression. It is concluded that the neonatal lesion of the nigrostriatal dopaminergic pathway, in contrast to the adult-stage lesion, modifies the reactivity of c-fos in the neostriatum to stress, presumably in relation with compensatory reorganizations occurring following the neonatal lesion. Grafts made into neonates, when challenged with amphetamine, induce an abnormal c-fos expression which can predict the degree of overshoot observed for rotation activity. This over-expression, which depends upon the stimulation of D1 receptors, indicate an abnormal activation of postsynaptic target cells by the grafts.

Convergence or divergence of male and female physicians' hours of work and income

This article verifies if the increase in the percentage of women in the medical profession led to the convergence of male and female physicians' hours of work as well as income. Active physicians in Quebec in 1978 were compared to the ones in 1988. Data were obtained from the computerized files of the Quebec Corporation of Physicians and the Régie d'assurance-maladie du Quebec. Despite the increasing representation of women in the medical profession, gender differences in hours worked and income remained. However, results also showed a tendency toward a convergence in total hours of work, more behavioral variation among women physicians and some behavioral change among men. The experience of the past should thus not be used as the basis for projections of future physician productivity or for medical manpower planning purposes without a careful analysis of trends in behavioral changes.

Comparative cardiac effects of milrinone and sodium nitroprusside in conscious rats

The rat has been shown to be resistant to the inotropic action of milrinone. We compared in conscious rats, the effects of an i.v. infusion of milrinone (0.3 mg/kg/min), a phosphodiesterase (PDE) inhibitor to those of nitroprusside (50 micrograms/kg/min), a pure vasodilator, on blood pressure and dP/dtmax to determine whether or not an inherent positive inotropic effect of milrinone is offset by its powerful hypotensive action. For the first 10 min of infusion, we found no differences in dP/dtmax, (the first derivative of the left ventricular pressure (LVP), an index of contractility) for equihypotensive doses of milrinone or nitroprusside. A second objective of this study was to determine if milrinone-induced ventricular fibrillation (VF) is due to cardiac ischemia which could be associated with the profound hypotension induced by the drug. Milrinone infusion was accompanied by a significant QTc interval (QT corrected for heart rate) prolongation. VF and death occurred in 5/6 rats at total doses varying from 3.6 to 20.1 mg/kg infused over 12 to 67 min respectively. Premature ventricular contractions (PVCs) were noted in all 6 milrinone infused rats during the first min. of infusion. No arrhythmias were noted during the 2 hour i.v. infusion with nitroprusside. A direct action on the heart is postulated to explain, at least partially, the milrinone-induced VF since nitroprusside had a similar hypotensive action but no effect on the ECG. We conclude that the rat, in analogy to patients with severe cardiac failure, might be resistant to the inotropic action of milrinone but is sensitive to its vasodilatory and arrhythmogenic effects.

Validation of a human atrial trabecular preparation for evaluation of inotropic substances

Assessment of cardioactive substances is usually performed using animal tissue, with the effects being extrapolated to humans, thereby potentially introducing errors due to species differences. In order to validate the use of human atrial tissue, known positive and negative inotropic agents were tested on trabeculae obtained from patients' atrial appendages at the time of cardiac surgery requiring, cardiopulmonary bypass. Trabeculae were selected according to strict criteria: cross-sectional area less than 1.0 mm2, resting force (RF) less than 0.7 g, and developed force (DF) greater than 0.8 g. Each trabecula received only one drug in a cumulative dose manner. Where necessary, the vehicle used to dissolve or stabilize the drug solution was also tested. In addition, the relative DF of "no-drug," "time-only" controls were measured during the same time period. After adjusting for the effect of time on the preparation, relative DF was increased to 157% by dobutamine (1.5 x 10(-5) M), to 136% by amrinone (5.6 x 10(-4) M), and to 117% by ouabain (2 x 10(-7) M). The relative DF decreased with nifedipine and propranolol, with 50% inhibition for both drugs being 1.5 x 10(-7) M. Although human ventricular muscles might be more appropriate to use in order to determine the effects observed with the whole heart, they are extremely difficult to obtain on a regular basis. The results of this study show that the atrial trabecular preparation offers an acceptable alternative.

Delay in hearing loss following drug administration. A consistent feature of amikacin ototoxicity

The time course of threshold increase in the VIII nerve compound action potential was studied in guinea pigs following amikacin administration at four different constant infusion rates. Despite the wide range of dosing durations required to achieve drug ototoxicity (2-24 days), the full development of both high and low frequency hearing loss was invariably found to be delayed with respect to the time of drug removal. The greatest degree of delayed hearing loss generally occurred within the first 7 days after drug removal, with smaller losses occurring during later time intervals. The delay showed a tendency to decrease as the ototoxic dose was increased. Using the data from the two highest dosing rates, it was estimated that a minimum of 4 days had to elapse before any hearing loss could be detected, once an ototoxic amount of drug had been administered. These data suggest that hearing loss is always substantially delayed with respect to the receipt of an ototoxic dose of amikacin, and that this must be taken into account when conducting animal experiments and when monitoring hearing in patients for the early detection of ototoxicity.

Acute effects of milrinone on the electrocardiogram and the cardiac hemodynamics of rats with pressure overload-induced congestive heart failure

The effects of i.v. bolus injections of milrinone on the electrocardiogram and cardiac hemodynamics were evaluated in old rats with chronic (82-93 weeks) pressure overload induced by aortic constriction. Based on the heart weight/body weight ratio and histopathological findings, the rats with aortic clips were divided into 2 groups: rats with (CHF group) or without (CLIP group) congestive heart failure (CHF). In CHF rats, the cardiac contractility, as measured by the peak of the first derivative of the left ventricular pressure (dP/dt max), was significantly lower than in CLIP rats, confirming the presence of heart failure in these rats. Three groups of anesthetized rats received boluses of milrinone of 0.1, 0.5, 1, 5 and 10 mg/kg: sham-operated rats (SHAM, n = 9), CLIP (n = 22) and CHF (n = 10). A control group of 3 CHF and 5 CLIP rats received only the vehicle. The major effect of milrinone at the 2 highest doses was the induction of ventricular fibrillation and death in approximately 25% of the rats (SHAM 2/9, CHF 1/10 and CLIP 7/22). A significant widening of the QRS complex (which includes ST segment) was also noted 3 min after each dose of milrinone in the SHAM group and at 5 and 10 mg/kg doses in the CHF group. These results were thought to be related to the marked hypotensive effect of milrinone possibly inducing myocardial ischemia. No positive inotropic effect, as indicated by the maximum rise of left ventricular pressure (dP/dt max) could be observed. This might have been because of (1) the marked vasodilating effect of milrinone on venous and arterial beds, negating a possible small positive inotropic effect, or (2) the lack of positive inotropic action of milrinone in rats. Our results thus indicate that, in anesthetized rats, milrinone is a powerful vasodilator but not a positive inotropic agent (or a very weak one).

Incidence of amikacin ototoxicity: a sigmoid function of total drug exposure independent of plasma levels

A sigmoid curve was found to closely describe the relationship between the incidence of amikacin ototoxicity (greater than or equal to 15 dB hearing loss at a given frequency) and either (1) total dose, or (2) the area under the curve (AUC) describing plasma drug concentration v time over the total period of amikacin administration (total AUC) in continuously infused guinea pigs. Total dose or total AUC estimates of the drug exposure required to produce ototoxicity in 50% of the animals (ED50s) were not significantly different over an eight-fold range of dosing rates or plasma concentrations. A theoretical explanation for this result is that ototoxicity occurs only when a critical amount of drug is accumulated at the ototoxic site by an essentially unidirectional process with a rate that is slow and linearly related to the extracellular drug concentration. The sigmoid relationships for pooled data were parallel in slope for all hearing frequencies from 2 to 32 kHz, and the ED50s showed a strong negative linear relationship to the log of the hearing frequency over this range. The magnitude of ototoxicity expressed as the number of octaves (frequency ratios of 2) for which hearing loss damage was continuous from 32 kHz downward, was correlated to both total dose (r = .605) and total AUC (r = 0.703). No relationship between ototoxicity and plasma level or dosing rate was found. The extreme steepness of the dose-effect curve for the incidence of ototoxicity greatly amplified the variability between individuals and offers an explanation for the unpredictability of aminoglycoside ototoxicity in human patients. The results indicate that either total dose or total AUC (in cases of highly unpredictable blood levels), and not peak or trough serum levels, should be used as an index of ototoxic risk and that the safety limits of drug exposure should be set conservatively.

Effects of milrinone treatment in cardiomyopathic hamsters (CHF 147) with severe congestive heart failure

The effects of oral milrinone treatment in cardiomyopathic hamsters with severe congestive heart failure (CHF) were evaluated. Strict criteria based on increase in body weight were established to define day no 1 of treatment. Survival rate of non-treated hamsters (group 1) ranged between 9 and 16 d, mean 12.9 (SEM 0.8) d, after entering the study. Hamsters treated with milrinone in drinking water (group 2a: 0.3 mg.ml-1, or group 2b: 0.6 mg.ml-1) survived between 6 and 36 d, mean 15.0(2.1) d, NS, for group 2a, and between 6 and 47 d, mean 19.6(4.0) d, NS, for group 2b. There was a significant difference between the number of hamsters that survived longer than 16 d between untreated hamsters (group 1, n = 0/12) and hamsters treated with milrinone (groups 2a, b, n = 7/24). There was no significant correlation between survival duration and milrinone daily dose nor between survival and milrinone plasma concentration at death. Milrinone treatment also significantly decreased pulmonary congestion as measured by the number of pigment containing macrophages per alveolus. No other pathological findings were modified by milrinone. It was concluded that, in addition to exerting a beneficial effect on pulmonary congestion, milrinone improved survival in some CHF hamsters. However, more studies are needed to evaluate the possibility of an arrythmogenic potential that might explain why some treated hamsters died earlier than non-treated hamsters.

A pressure overload model of congestive heart failure in rats

Approximately 32% of the rats used as animal models showed an elevated heart weight/body weight ratio (0.432[SEM 0.022] g.100 g-1 compared to 0.293[0.009] g.100 g-1 for sham-operated rats), a hydrothorax, pulmonary and liver congestion, and specific histological changes 82-93 weeks after surgically induced aortic constriction. The histological changes were comparable to those observed in hearts of people suffering from long term hypertension. Cardiac failure was also confirmed by depressed contractility as measured by maximum and minimum dP/dt (first derivative of left ventricular pressure), which were 4604(346) and 3627(526) mm Hg.sec-1, respectively, compared with 9165(745) and 5835(268) mm Hg.sec-1 respectively in rats that did not develop left ventricular hypertrophy and failure (CLIP rats). Systolic and left ventricular blood pressures measured under anaesthesia were also decreased: 71.6(5.0) and 88.1(6.3) mm Hg respectively in rats with congestive heart failure, compared with 83.6(2.4) and 109.5(3.6) mm Hg in CLIP rats. Except for a prolonged mean PQ interval associated with a lower heart rate and for a slightly shorter QRS interval in the conscious state, the electrocardiograms of rats with congestive heart failure did not show any major abnormalities specific to ventricular hypertrophy and/or failure. This model could be useful for studying the pathology and adaptative mechanisms in compensated pressure overload induced congestive heart failure as well as in studies comparing pathological changes and means of treatment of congestive heart failure with different aetiologies encountered in the human population.

The electrochemical oxidation of silver and tetraethylammonium salts of formamides and imides. N,N-Coupling of formanilidyl radicals

The electrochemical oxidation of [amide-Ag-amide]Ag, [amide-Ag-amide]Et4N, and [amide]Et4N salts of imides and formanilides, in acetonitrile containing tetraethylammonium tetrafluoroborate, at platinum and vitreous carbon electrodes, is a one-electron and irreversible (αn < 1) process leading to an amidyl radicals that preferentially abstracts hydrogen from the medium to give the parent amide. N,N-Coupling (formation of hydrazine derivatives) was observed in the oxidation of the amide-Ag-amide anions of formanilide and p-methoxyformanilide. No coupling was observed in the oxidation of the amide-Ag-amide anion of p-cyanoformanilide and of imides, and in the oxidation of any of the tetraethylammonium salts (amidyl anions) studied. The formanilidyl radical was trapped by N-tert-butyl-α-phenylnitrone. Attempts to trap the succinimidyl radical by addition to olefins were unsuccessful.