Genetic polymorphisms and heart failure.

Heart failure is a complex clinical syndrome. There is evidence for a genetic contribution to the pathophysiology of heart failure. Considering the fundamental role of neurohormonal factors in the pathophysiology and progression of cardiac dysfunction and hypertrophy, variants of genes involved in this system are logical candidate genes in heart failure. In this report, genetic polymorphisms of the major neurohormonal systems in heart failure will be discussed. Studies on polymorphisms of the renin-angiotensin-aldosterone system (RAAS), adrenergic receptor polymorphisms, endothelin (receptor) polymorphisms, and a group of miscellaneous polymorphisms that may be involved in the development or phenotypic expression of heart failure will be reviewed. Research on left ventricular hypertrophy is also included. The majority of genetic association studies focused on the ACE I/D polymorphism. Initial genetic associations have often been difficult to replicate, mainly due to problems in study design and lack of power. Promising results have been obtained with genetic polymorphisms of the RAAS and sympathetic system. Considering the evidence so far, a modifying role for these polymorphisms seems more likely than a role of these variants as susceptibility genes. Besides the need for larger studies to examine the effects of single nucleotide polymorphisms and haplotypes, future studies also need to focus on the complexity of these systems and study gene-gene interactions and gene-environment interactions.     

Formation of DNA adducts of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in male Fischer-344 rats.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP) is known to induce colon tumors in male Fischer-344 rats. Using 32P-postlabeling assays, we have examined PhIP-DNA adduct formation in various organs and white blood cells (WBCs) of the male Fischer-344 rat 24 h after a single oral dose of 0, 0.5, 5 or 50 mg PhIP/kg. Three PhIP-DNA adducts were detected in WBCs and in all organs, except in the liver and stomach which had only two adducts. The extent of adduct formation was dose-related, but at 0.5 mg/kg no adducts could be detected in any of the organs. At 50 mg/kg, adduct levels, expressed as relative adduct labeling values (RAL x 10(7), or adducts per 10(7) nucleotides assuming complete labeling) were highest in the large intestine (5.66), followed by WBCs (5.04), stomach (1.44), small intestine (1.32), kidney (1.16), liver (0.67) and lungs (0.52). It is concluded that orally administered PhIP forms high levels of specific DNA adducts in the large intestine, the target organ in PhIP carcinogenesis in the male Fischer-344 rat, and that the high level of adducts in WBCs indicates that significant amounts of the ultimate carcinogenic form of PhIP are present in the circulation.     

Striatal monoamine neurotransmitters and metabolites in dominantly inherited olivopontocerebellar atrophy.

We measured the levels of the monoamine neurotransmitters and metabolites in striatum of 14 patients with end-stage dominantly inherited olivopontocerebellar atrophy (OPCA). On average, dopamine levels were reduced in putamen (-53%), caudate (-35%), and nucleus accumbens (-31%). However, individual patient values showed a wide variation, indicating that mild to moderate striatal dopamine loss is a common but not constant feature of OPCA. Seven patients had marked putamen dopamine loss (-62% to -81%) but without evidence of correspondingly severe substantia nigra cell damage; this suggests the possibility of a "dying-back" phenomenon in which nerve terminal loss precedes cell body degeneration. Severe substantia nigra cell loss with almost total (-95% to -99%) putamen and caudate dopamine depletion was present in two patients; however, none of the 14 patients had had a clinical diagnosis of parkinsonism or was receiving antiparkinsonian medication. Mean striatal serotonin levels were normal, whereas concentrations of the serotonin metabolite 5-hydroxyindoleacetic acid were elevated by 47% to 63%; this suggests increased activity of raphe dorsalis serotonin neurons innervating the striatum, which might aggravate the functional consequences of the dopamine deficit.     

Effects of local nerve cooling on conduction in vagal fibres shed light upon respiratory reflexes in the rabbit

In ten vagus nerves the effect of local cooling on the compound action potential was studied in the temperature range of 34 to 0 °C in spontaneously breathing, anaesthetized rabbits. The mean temperature at which the myelinated (A) fibres were completely blocked, was 10.2±2.4 °C (mean ± S.D.). In nine nerves, local vagus cooling to 0 °C failed to block all non-myelinated (C) fibres. In one nerve, total blocking occurred at 2.0 °C. We conclude that in the rabbit, the earlier found increase in tonic activity of the diaphragm following lung inflation or deflation during bilateral local vagus cooling to a temperature between 8 and 0 °C is due to afferent impulses in vagal C fibres.     

SCA8 CTG repeat: en masse contractions in sperm and intergenerational sequence changes may play a role in reduced penetrance

We recently described an untranslated CTG expansion that causes a previously undescribed form of spinocerebellar ataxia (SCA8). The SCA8 CTG repeat is preceded by a polymorphic but stable CTA tract, with the configuration (CTA)(1-21)(CTG)(n). The CTG portion of the repeat is elongated on pathogenic alleles, which nearly always change in size when transmitted from generation to generation. To better understand the reduced penetrance and maternal penetrance bias associated with SCA8 we analyzed the sequence configurations and instability patterns of the CTG repeat in affected and unaffected family members. In contrast to other triplet repeat diseases, expanded alleles found in affected SCA8 individuals can have either a pure uninterrupted CTG repeat tract or an allele with one or more CCG, CTA, CTC, CCA or CTT interruptions. Surprisingly, we found six different sequence configurations of the CTG repeat on expanded alleles in a seven generation family. In two instances duplication of CCG interruptions occurred over a single generation and in other instances duplications that had occurred in different branches of the family could be inferred. We also evaluated SCA8 instability in sperm samples from individuals with expansions ranging in size from 80 to 800 repeats in blood. Surprisingly the SCA8 repeat tract in sperm underwent contractions, with nearly all of the resulting expanded alleles having repeat lengths of <100 CTGs, a size that is not often associated with disease. These en masse repeat contractions in sperm likely underlie the reduced penetrance associated with paternal transmission.     

Does disclosure of emotions facilitate recovery from bereavement? Evidence from two prospective studies

Two longitudinal studies assessed whether disclosure of emotions facilitates recovery from bereavement. Study 1 tested prospectively over a 2-year period whether the extent to which bereaved persons talked about their loss to others and disclosed their emotions was associated with better adjustment to the loss of a marital partner. There was no evidence that disclosure facilitated adjustment. Study 2 randomly assigned recently bereaved individuals either to the Pennebaker writing task (J. W. Pennebaker & S. K. Beall, 1986) or to no-essay control conditions. The writing task did not result in a reduction of distress or of doctors visits either immediately after the bereavement or at a 6-month follow-up. Beneficial effects were not demonstrated for bereaved persons who had suffered an unexpected loss or who at the time of the study still expressed a high need for emotional disclosure.     

Isochromosome 17q in primitive neuroectodermal tumors of the central nervous system

We have prepared karyotypes from 22 primitive neuroectodermal tumors (PNETs) from pediatric patients ranging in age from 10 months to 16 years. Twenty-one cases were newly diagnosed, primary, posterior fossa tumors. One case was a recurrent tumor in a patient previously treated with radiation. Cytogenetic results were obtained from direct preparations and/or short-term (1-10 day) culture. Three tumors had apparently normal karyotypes. Nineteen tumors demonstrated numerical and/or structural abnormalities. The most frequent structural chromosomal changes were deletions and nonreciprocal translocations. Four tumors contained double minutes. Several chromosomes appear to be nonrandomly involved in PNETs. These include chromosomes 5, 6, 11, 16, 17, and a sex chromosome. The most consistent change, however, was an i(17q), present in one-third (8/22) of the cases. Strikingly, in three of these eight tumors, the i(17q) was the only structural abnormality observed. An i(17q) is not specific for pediatric PNETs, as it is also seen in leukemias and other solid tumors. However, in PNETs it may be a primary change related to tumor development and/or progression. Clinically, there was no correlation of the cytogenetic findings with histologic features of the tumors, size of the tumor, extent of metastasis, or surgical resection.     

A study of gene--environment interaction on the gene for angiotensin converting enzyme: a combined functional and population based approach

Introduction: Studies on the role of the insertion/deletion (I/D) polymorphism of the gene coding for angiotensin converting enzyme (ACE) in atherosclerosis have been inconsistent. In a meta-analysis, we recently showed that this relationship is stronger in high risk populations. In this paper, we used a combined functional and population based approach to investigate the gene–environment interaction of the ACE I/D polymorphism in relation to carotid artery wall thickness.

Methods: The study was part of the Rotterdam Study, a prospective population based cohort study. In 5321 subjects, IMT was measured in the carotid arteries by ultrasonography and ACE genotype was determined by size analysis of polymerase chain reaction products.

Results: In multiple regression analysis, I/D polymorphism and smoking were the main determinants for plasma ACE activity (r² = 0.28). There was a positive association between the D allele of the I/D polymorphism and carotid artery thickness among current smokers (p = 0.03). Subjects carrying only one of the risk factors (smoking or the D allele) did not show significant differences in IMT compared with the non-/former smokers group carrying two II alleles, while carriers of both risk factors had significant higher IMT. The association was not present in non-/former smokers.

Discussion: The results provide further evidence that genetic and environmental factors interact in the formation of the arterial lesions. This study shows that large population based studies can be extremely helpful in unravelling the genetic origin of complex diseases such as atherosclerosis.

     

Priority care for employees: a blessing in disguise?

This paper discusses the efficiency and equity effects of priority care for employees. Recent privatization of workers' compensation insurance in the Netherlands caused an increasing tension between public responsibility for health care cost-containment and private responsibility for sick pay. As a result of strict supply side regulation, waiting lists increased, while at the same time employers became fully responsible for sick pay. To reduce sick pay and production losses, employers are prepared to pay for priority care by using available excess capacity. We argue that the criteria of Pareto and Rawls can provide a rationale for the resulting differential treatment of employees and non-employees. However, such a justification crucially depends on weights society assigns to absolute versus relative improvements in access to health care.