Phylogeny and historical biogeography of neotropical catfishes Trichomycterus (Siluriformes: Trichomycteridae) from eastern Brazil

The catfish subfamily Trichomycterinae is widely distributed in South America inhabiting several habitats, but specially mountain streams. Trichomycterus is the most speciose trichomycterid genus and recently due to his paraphyletic condition has been restricted to a clade from eastern Brazil called Trichomycterus sensu stricto comprising around 80 valid species distributed in seven areas of endemism of eastern Brazil. This paper aims to analyse the biogeographical events responsible for the distribution of Trichomycterus s.s., by reconstructing the ancestral data based on a time-calibrated multigene phylogeny. A multi-gene phylogeny was generated using 61 species of Trichomycterus s.s. and 30 outgroups, with divergence events calculated based on the estimated origin of Trichomycteridae. Two event-based analyses were applied to investigate the biogeographical events responsible the present distribution of Trichomycterus s.s. and suggest that the modern distribution of the group is a result of different vicariance and dispersal events. The diversification of Trichomycterus s.s. subgenera occurred in the Miocene, except for Megacambeva, with different biogeographical events shaping its distribution in eastern Brazil. An initial vicariant event split up the Fluminense ecoregion from the Northeastern Mata Atlantica + Paraíba do Sul + Fluminense + Ribeira do Iguape + Upper Paraná ecoregions. Dispersal events occurred mainly between Paraíba do Sul and neighboring river basins, with additional dispersal events from Northeastern Mata Atlantica to Paraíba do Sul, from São Francisco to Northeastern Mata Atlântica, and from Upper Paraná to São Francisco.

Detecting Common Eye Diseases Using the First Teleophthalmology GlobeChek Kiosk in the United States: A Pilot Study

PURPOSE

The aim of this study was to assess the benefit and feasibility of the teleophthalmology GlobeChek kiosk in a community-based program.

DESIGN

Single-site, nonrandomized, cross-sectional, teleophthalmologic study.

METHODS

Participants underwent comprehensive evaluation that consists of a questionnaire form, brief systemic evaluation, screening visual field (VF), and GlobeChek kiosk screening, which included but not limited to intraocular pressure, pachymetry, anterior segment optical coherence tomography, posterior segment optical coherence tomography, and nonmydriatic fundus photography. The results were evaluated by a store-and-forward mechanism and follow-up questionnaires were obtained through phone calls.

RESULTS

A total of 326 participatents were screened over 4 months. One hundred thirty-three (40.79%) participants had 1 condition in either eye, and 47 (14.41%) had >1 disease. Seventy (21.47%) had glaucoma, 37 (11.34%) narrow-angles, 6 (1.84%) diabetic retinopathy, 4 (1.22%) macular degeneration, and 43 (13.10%) had other eye disease findings. Age >65, history of high blood pressure, diabetes mellitus, not having a dental examination >5 years, hemoglobn A1c measurement of ≥5.6, predibates risk score of ≥9, stage 2 hypertension, and low blood pressure were found to be significant risk factors. As for the ocular parameters, all but central corneal thickness, including an intraocular pressure >21 mm Hg, vertical cup to disc ratio >0.7, visual field abnormalities, and retinal nerve fiber layer thinning were found to be significant.

CONCLUSIONS

GlobeChek kiosk is both workable and effective in increasing access to care and identifying the most common causes of blindness and their risk factors.

Quantitative trait loci for interhemispheric commissure development and social behaviors in the BTBR T⁺ tf/J mouse model of autism

Background

Autism and Agenesis of the Corpus Callosum (AgCC) are interrelated behavioral and anatomic phenotypes whose genetic etiologies are incompletely understood. We used the BTBR T⁺tf/J (BTBR) strain, exhibiting fully penetrant AgCC, a diminished hippocampal commissure, and abnormal behaviors that may have face validity to autism, to study the genetic basis of these disorders.

Methods

We generated 410 progeny from an F2 intercross between the BTBR and C57BL/6J strains. The progeny were phenotyped for social behaviors (as juveniles and adults) and commisural morphology, and genotyped using 458 markers. Quantitative trait loci (QTL) were identified using genome scans; significant loci were fine-mapped, and the BTBR genome was sequenced and analyzed to identify candidate genes.

Results

Six QTL meeting genome-wide significance for three autism-relevant behaviors in BTBR were identified on chromosomes 1, 3, 9, 10, 12, and X. Four novel QTL for commissural morphology on chromosomes 4, 6, and 12 were also identified. We identified a highly significant QTL (LOD score = 20.2) for callosal morphology on the distal end of chromosome 4.

Conclusions

We identified several QTL and candidate genes for both autism-relevant traits and commissural morphology in the BTBR mouse. Twenty-nine candidate genes were associated with synaptic activity, axon guidance, and neural development. This is consistent with a role for these processes in modulating white matter tract development and aspects of autism-relevant behaviors in the BTBR mouse. Our findings reveal candidate genes in a mouse model that will inform future human and preclinical studies of autism and AgCC.

Absence of deficits in social behaviors and ultrasonic vocalizations in later generations of mice lacking neuroligin4

Mutations in NLGN4X have been identified in individuals with autism spectrum disorders and other neurodevelopmental disorders. A previous study reported that adult male mice lacking neuroligin4 (Nlgn4) displayed social approach deficits in the three-chambered test, altered aggressive behaviors and reduced ultrasonic vocalizations. To replicate and extend these findings, independent comprehensive analyses of autism-relevant behavioral phenotypes were conducted in later generations of the same line of Nlgn4 mutant mice at the National Institute of Mental Health in Bethesda, MD, USA and at the Institut Pasteur in Paris, France. Adult social approach was normal in all three genotypes of Nlgn4 mice tested at both sites. Reciprocal social interactions in juveniles were similarly normal across genotypes. No genotype differences were detected in ultrasonic vocalizations in pups separated from the nest or in adults during reciprocal social interactions. Anxiety-like behaviors, self-grooming, rotarod and open field exploration did not differ across genotypes, and measures of developmental milestones and general health were normal. Our findings indicate an absence of autism-relevant behavioral phenotypes in subsequent generations of Nlgn4 mice tested at two locations. Testing environment and methods differed from the original study in some aspects, although the presence of normal sociability was seen in all genotypes when methods taken from Jamain et al. (2008) were used. The divergent results obtained from this study indicate that phenotypes may not be replicable across breeding generations, and highlight the significant roles of environmental, generational and/or procedural factors on behavioral phenotypes.

Low sociability in BTBR T+tf/J mice is independent of partner strain

Inbred mouse strains differ greatly in social behaviors, making them a valuable resource to study genetic and non-genetic mechanisms underlying social deficits relevant to autism spectrum disorders. A hallmark symptom of autism is a lack of ability to understand other people's thoughts and intentions, which leads to impairments in adjusting behaviors in response to ever-changing social situations in daily life. We compared the ability of BTBR T+tf/J (BTBR), a strain with low sociability, and C57BL/6J (B6), a strain with high sociability, for their abilities to modulate responses to social cues from different partners in the reciprocal social interaction test. Results indicate that BTBR exhibited low sociability toward different partners and displayed minimal ability to modify behaviors toward different partners. In contrast, B6 showed high sociability toward different partners and was able to modify social behaviors toward different partners. Consistent results were found in two independent cohorts of different ages, and in both sexes. In the three-chambered test, high sociability in B6 and low sociability in BTBR were independent of strain of the novel mouse. Since social deficits in BTBR could potentially be caused by physical disabilities in detecting social olfactory cues, or in cognitive abilities, we tested BTBR and B6 mice on measures of olfaction and cognition. BTBR mice displayed more sniffing of social odors emitted by soiled bedding than of an odorless novel object, but failed to show a preference for a live novel mouse over a novel object. On olfactory habituation/dishabituation to a sequence of odors, BTBR displayed discrimination abilities across three non-social and two social odors. However, as compared to B6, BTBR displayed less sniff time for both non-social and social odors, and no significant dishabituation between cage odors from two different novel mouse strains, findings that will be important to investigate further. BTBR was generally normal in spatial acquisition on the Morris water maze test, but showed deficits in reversal learning. Time spent freezing on contextual and cued fear conditioning was lower in BTBR than in B6. Our findings suggest that BTBR has poor abilities to modulate its responses to different social partners, which may be analogous to social cognition deficits in autism, adding to the value of this strain as a mouse model of autism.

Haploinsufficiency of the autism-associated Shank3 gene leads to deficits in synaptic function, social interaction, and social communication

Background

SHANK3 is a protein in the core of the postsynaptic density (PSD) and has a critical role in recruiting many key functional elements to the PSD and to the synapse, including components of α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid (AMPA), metabotropic glutamate (mGlu) and N-methyl-D-aspartic acid (NMDA) glutamate receptors, as well as cytoskeletal elements. Loss of a functional copy of the SHANK3 gene leads to the neurobehavioral manifestations of 22q13 deletion syndrome and/or to autism spectrum disorders. The goal of this study was to examine the effects of haploinsufficiency of full-length Shank3 in mice, focusing on synaptic development, transmission and plasticity, as well as on social behaviors, as a model for understanding SHANK3 haploinsufficiency in humans.

Methods

We used mice with a targeted disruption of Shank3 in which exons coding for the ankyrin repeat domain were deleted and expression of full-length Shank3 was disrupted. We studied synaptic transmission and plasticity by multiple methods, including patch-clamp whole cell recording, two-photon time-lapse imaging and extracellular recordings of field excitatory postsynaptic potentials. We also studied the density of GluR1-immunoreactive puncta in the CA1 stratum radiatum and carried out assessments of social behaviors.

Results

In Shank3 heterozygous mice, there was reduced amplitude of miniature excitatory postsynaptic currents from hippocampal CA1 pyramidal neurons and the input-output (I/O) relationship at Schaffer collateral-CA1 synapses in acute hippocampal slices was significantly depressed; both of these findings indicate a reduction in basal neurotransmission. Studies with specific inhibitors demonstrated that the decrease in basal transmission reflected reduced AMPA receptor-mediated transmission. This was further supported by the observation of reduced numbers of GluR1-immunoreactive puncta in the stratum radiatum. Long-term potentiation (LTP), induced either with θ-burst pairing (TBP) or high-frequency stimulation, was impaired in Shank3 heterozygous mice, with no significant change in long-term depression (LTD). In concordance with the LTP results, persistent expansion of spines was observed in control mice after TBP-induced LTP; however, only transient spine expansion was observed in Shank3 heterozygous mice. Male Shank3 heterozygotes displayed less social sniffing and emitted fewer ultrasonic vocalizations during interactions with estrus female mice, as compared to wild-type littermate controls.

Conclusions

We documented specific deficits in synaptic function and plasticity, along with reduced reciprocal social interactions in Shank3 heterozygous mice. Our results are consistent with altered synaptic development and function in Shank3 haploinsufficiency, highlighting the importance of Shank3 in synaptic function and supporting a link between deficits in synapse function and neurodevelopmental disorders. The reduced glutamatergic transmission that we observed in the Shank3 heterozygous mice represents an interesting therapeutic target in Shank3-haploinsufficiency syndromes.

Social peers rescue autism-relevant sociability deficits in adolescent mice

Behavioral therapies are currently the most effective interventions for treating the diagnostic symptoms of autism. We employed a mouse model of autism to evaluate components of behavioral interventions that improve sociability in mice. BTBR T+tf/J (BTBR) is an inbred mouse strain that exhibits prominent behavioral phenotypes with face validity to all three diagnostic symptom categories of autism, including robust and well-replicated deficits in social approach and reciprocal social interactions. To investigate the role of peer interactions in the development of sociability, BTBR juvenile mice were reared in the same home cage with juvenile mice of a highly social inbred strain, C57BL/6J (B6). Subject mice were tested as young adults for sociability and repetitive behaviors. B6 controls reared with B6 showed their strain-typical high sociability. BTBR controls reared with BTBR showed their strain-typical lack of sociability. In contrast, BTBR reared with B6 as juveniles showed significant sociability as young adults. A 20-day intervention was as effective as a 40-day intervention for improving social approach behavior. High levels of repetitive self-grooming in BTBR were not rescued by peer-rearing with B6, indicating specificity of the intervention to the social domain. These results from a robust mouse model of autism support the interpretation that social enrichment with juvenile peers is a beneficial intervention for improving adult outcome in the social domain. This novel paradigm may prove useful for discovering factors that are essential for effective behavioral treatments, and biological mechanisms underlying effective behavioral interventions.

Mortality and cancer morbidity in a cohort of Canadian petroleum workers

AIMS

To assess mortality and cancer morbidity in Canadian petroleum workers and explore exposure-response relations for specific petroleum agents.

METHODS

A total of 25 292 employees hired between 1964 and 1994 were linked to the Canadian tumour registry and national mortality database. Exposure-response trends were assessed for hydrocarbon solvents/fuels, hydrocarbon lubricants, petroleum coke/spent catalyst, and hydrogen sulphide (H2S).

RESULTS

External comparison analyses (mortality and incidence) showed deficits for all causes and all malignant neoplasms combined and were consistent with expectation for most malignant and non-malignant sites analysed. Gall bladder cancer mortality was increased among males based on four deaths, but cases had no common job assignments and the increase was focused in workers employed <10 years. Mesothelioma incidence was increased. Most exposure-specific analyses were compromised by small numbers. Statistically significant increases were observed for H2S exposure and a subgroup of accidental deaths as well as for petroleum coke/spent catalyst exposure and lung cancer. While both findings have a degree of biologic plausibility, the H2S association, which exhibited a clearer exposure-response pattern, could be subject to unmeasured confounders. Additionally, interpretation was complicated by the high correlation between hydrocarbon and H2S exposures. With regard to lung cancer, the analysis could not adequately control for smoking, was based on small numbers, and exhibited a tenuous exposure-response pattern.

CONCLUSION

The findings for mesothelioma suggest the need for continued attention to asbestos in the petroleum industry. The relation between accidental deaths and H2S exposure deserves closer scrutiny in similarly exposed populations. Further analyses of lung cancer are underway and will be reported separately.

Heart failure: a hemodynamic disorder complicated by maladaptive proliferative responses

Heart failure has traditionally been viewed as a hemodynamic syndrome characterized by fluid retention, high venous pressure, and low cardiac output. Over the past decade, however, it has become clear that because of deterioration and progressive dilatation (remodeling) of the diseased heart, this is also a rapidly fatal syndrome. The importance of prognosis came to be appreciated when clinical trials showed that therapy which initially improves such functional abnormalities, as high venous pressure and low cardiac output, often fail to improve survival, and that some drugs which improve hemodynamics worsen long-term prognosis. The latter is true for most vasodilators which, in spite of alleviating the adverse short-term consequences of high afterload, shorten survival. Notable exceptions are ACE inhibitors, whose vasodilator effects do not explain their ability to prolong survival; instead, these drugs slow both deterioration and remodeling of the failing heart. Inotropic agents, while providing immediate relief of symptoms, generally shorten long-term survival, whereas beta-blockers slow deterioration and remodeling, and reduce mortality. Aldosterone antagonists exert beneficial effects on prognosis that are not easily explained by their diuretic effects, but instead can be explained by their ability to inhibit signaling pathways that stimulate maladaptive hypertrophy, remodeling, apoptosis and other deleterious responses that cause deterioration of the failing heart. These and other findings demonstrate that heart failure is more than a hemodynamic disorder; these patients suffer from maladaptive proliferative responses that cause cardiac cell death and progressive dilatation that play a key role in determining the poor prognosis in this syndrome.

Circulation Research: origin and early years

Circulation Research, first published in 1953, was created by the American Heart Association as "the authoritative new journal for investigators of the basic sciences as they apply to the heart and circulation." This review of the early years of the journal highlights the contributions of the first four Editors: Carl J. Wiggers, Carl F. Schmidt, Eugene M. Landis, and Julius H. Comroe, Jr. The success of Circulation Research is seen not only in the high quality of the articles published in its pages but also in the remarkable improvements in prevention and treatment of cardiovascular disease that have occurred over the past half century.

Updated mortality among diverse operating segments of a petroleum company

OBJECTIVES

To update mortality for 34 560 employees from diverse operating segments of a Canadian petroleum company; and to investigate potential relations with occupational factors.

METHODS

Employees from 1964-83 were linked to the Canadian mortality data base to provide 11 years additional follow up. There were 6760 deaths and 750 683 person-years of follow up compared with 3909 and 428 190, respectively, in the earlier study. Analyses used standardised mortality ratios (SMRs) to compare worker cause specific mortality with the Canadian general population. Duration of employment and latency analyses were performed for causes previously found to be increased in this and other petroleum cohorts, as well as any findings of interest.

RESULTS

For the period 1964-94, employees experienced significantly low overall mortality (SMR=0.86 men, SMR=0.80 women). Kidney cancer, which has been increased in some studies of petroleum workers, was not increased. Acute non-lymphocytic leukaemia in exposed operating segments was consistent with the expected or only slightly, non-significantly increased. The most notable finding was increased deaths from mesothelioma among refinery and petrochemical workers (SMR 8.68; 95% confidence interval (95% CI) 5.51 to 13.03), most of whom were long term employees in jobs with presumed exposure to asbestos (mechanical and pipefitters). Deaths from multiple myeloma among marketing and distribution workers, which were previously increased, remained increased (SMR 2.08; 95% CI 0.95 to 3.95) in the update period 1984-94; however, there was no clear pattern by duration of employment or latency. Aortic aneurysms, which also were previously significantly increased among marketing and distribution workers approached the expected in the update period (SMR 1.18; 95% CI 0. 65-1.98). Analyses by duration of employment showed suggestive trends for aortic aneurysms, but earlier studies of this cohort have not found a relation between aortic aneurysms and exposure to hydrocarbons.

CONCLUSION

The additional 2851 deaths and 322 493 person-years of follow up strengthened the assessment of mortality patterns relative to occupational factors. With the exception of mesothelioma, no clear work related increases in disease were identified.

A council of elders: creating a multi-voiced dialogue in a community of care

In an era of 'medical care delivery systems', there is an increasing need for the patient's voice to be heard, for it to be invited, listened to, and taken seriously. This challenge is particularly evident in geriatrics education, a domain of clinical training in which educators and clinicians alike must struggle to overcome adverse attitudes towards the elderly ('ageism'). In this paper we introduce a 'Council of Elders' as an educational innovation in which we invited community elders to function as our 'Senior Faculty', to whom medical residents present their challenging and heartfelt dilemmas in caring for elder patients. In the conversations that ensue, the elders come to function not simply as teachers, but collaborators in a process in which doctors, researchers, and elders together create a community of resources, capable of identifying novel ways to overcome health-related difficulties which might not have been apparent to either group separately. Using the first meeting of the Council as an exemplar, we describe and discuss the special nature of such meetings and also the special preparations required to build a dialogic relationship between participants from very different worlds--different generations, different cultures (including the professional culture and the world of lived experience). Meetings with the council have become a required part of the primary care residency program--a very different kind of 'challenging case conference' in which moral dilemmas can be presented, discussed and reflected upon. It is not so much that elders give good advice in their responses--although they often do--as that they provide life world and value orientation as young residents gain a better sense of the elder's experience and what matters most to them. This project has been particularly worthwhile in addressing the problem of ageism--a way to render visible stereotypes and adverse physician values, with implications for decision-making with the patient, not for the patient.

Lyme disease: summary notes

The intention of the Summary Notes section is to provide the practitioner and trainee with a current, concise reference source to dermatologic diseases and to serve as a form of Continuing Medical Education. Each installment will deal with a specific disease. When included, the pretest questions indicate some of the areas to be covered and will challenge your present knowledge of the material before reading further. The self-assessment post-test questions appear on page 308; the answers are on page 316.

Interval-force relation is unaffected by the presence of cardiomyopathy or coronary artery disease in patients with atrial fibrillation

BACKGROUND

We tested the hypothesis that cycle length-dependent cardiac contractility in atrial fibrillation is primarily governed by the negative interval-force relation in patients with normal and depressed systolic function.

METHODS AND RESULTS

We performed two-dimensional guided M-mode echocardiography in 41 patients (mean age, 69 +/- 4 years; range, 48 to 92 years; 19 men, 11 women). Twelve patients had objective evidence of left ventricular systolic dysfunction (CMP; mean ejection fraction, 37% +/- 7%) in the absence of coronary artery disease (CAD), 13 patients had documented CAD (mean ejection fraction, 43% +/- 6%), and 16 patients had normal resting left ventricular systolic function (mean ejection fraction, 58% +/- 7%). Simultaneous beat-to-beat blood pressure, end-systolic and end-diastolic dimension, circumferential velocity of fiber shortening (Vcf), and end-systolic wall stress (ESWS) were calculated for all patients. All three groups showed a significant linear relation between beat-to-beat Vcf and Vcf corrected for afterload (represented as the Vcf/ESWS ratio) and preceding cycle length. There was, however, no significant difference in the relation between either of these variables and cycle length among the three groups. There was also no difference in the rate of change in either Vcf or Vcf corrected for afterload (Vcf/ESWS ratio) from beat-to-beat among the three groups. Control patients with normal systolic function showed greater Vcf at any given cycle length compared with patients with CMP or CAD.

CONCLUSION

Our data show that, for each beat in atrial fibrillation, Vcf and Vcf/ESWS ratio are decreased after shorter cycle lengths and increased after long cycles, but there is no significant attenuation of this effect in patients with systolic dysfunction with or without coronary disease compared with controls. Thus, the negative interval-force relation, the predominant determinant of beat-to-beat variation in contractility in atrial fibrillation, is preserved in patients with CAD or reduced left ventricular systolic function.

Is the failing heart energy depleted?

This article takes three different approaches to the question of whether the failing heart is in an energy-starved state. A brief historical overview introduces the issue and points out problems in both models and methods. Second, current information regarding the energetic state of the failing heart is examined. Finally, the mechanistic and therapeutic implications of a defect in energy production are described.

Behçet's disease: summary notes

The intention of the Summary Notes section is to provide the practitioner and trainee with a current, concise reference source to dermatologic diseases and to serve as a form of Continuing Medical Education. Each installment will deal with a specific disease. When included, the pretest questions indicate some of the areas to be covered and will challenge your present knowledge of the material before reading further. The self-assessment post-test questions appear on page 89; the answers are on page 101.

Discovery of phospholamban. A personal history

Early efforts to identify mechanisms by which sympathetic stimulation increases myocardial contractility led to studies of effects of beta-adrenergic agonists and cyclic AMP on the cardiac contractile proteins and sarcoplasmic reticulum (SR); initial positive reports, however, could not be confirmed. The discovery that cyclic AMP-dependent protein kinases (PK-A) mediated intracellular actions of cyclic AMP led at least four groups to test the hypothesis that phosphorylation of the cardiac SR played a role in the actions of beta-adrenergic agonists. Three of them (Wollenberger, Wray et al., and LaRaia & Morkin) demonstrated that cardiac SR was a substrate for PK-A phosphorylation; however, the lability of the Ca2+ pump in these membranes made it difficult to demonstrate a functional significance of this finding. Our group, which had extensive experience in measuring SR Ca2+ transport, began by examining the ability of PK-A to activate the SR Ca2+ pump "poised" at half-saturating Ca2+ concentrations. Our initial positive result led to the discovery that a 22,000-dalton protein, named phospholamban by Phyllis B. Katz, mediated effects on Ca2+ transport by the SR that could explain both the inotropic and lusitropic effects of sympathetic stimulation.

Evolving concepts of heart failure: cooling furnace, malfunctioning pump, enlarging muscle--Part I

Understanding of the causes of dyspnea and anasarca, the cardinal features of heart failure, has changed dramatically since Greco-Roman times, when sputum and pleural effusions were thought to originate in the brain, and the heart was believed to heat and distribute the vital spirit. It was not until the seventeenth century, when Harvey demonstrated that the heart was a pump and autopsy descriptions revealed valve abnormalities that interfered with the circulation, that it became possible to identify the role of heart disease in causing shortness of breath and edema. Morgagni's recognition, toward the end of the eighteenth century, that overload caused the heart to enlarge was followed less than 50 years later by Corvisart's distinction between hypertrophy and dilation. Differences in the architecture of failing hearts focused attention of nineteenth-century clinical scientists on the myocardial response to overload, and by the end of this century overload-induced hypertrophy was recognized not only to have immediate adaptive effects, but also to cause progressive degeneration of the heart muscle. This focus on the failing myocardium ended in the early years of the twentieth century, when new discoveries in hemodynamic physiology shifted attention to pressure and flow abnormalities caused by the then prevalent rheumatic valvular heart disease. During the past decade, new emphasis on prognosis, along with realization that drugs intended to correct hemodynamic abnormalities often had adverse effects on survival, has led to a reexamination of the biology of the failing heart. As a result, the focus in heart failure research has returned to the myocardium. This article reviews some of the misconceptions and errors of early physicians, who, while often careful and intelligent observers, lacked the means to explain and treat heart failure. It is hoped an appreciation of the evolving concepts of heart failure will help the reader meet today's challenge of incorporating new information from molecular biology that holds the key to further progress in understanding the causes and therapy of this syndrome.

Molecular biology of calcium channels in the cardiovascular system

Calcium ions are key intracellular messengers in the cardiovascular system. Calcium homeostasis is regulated by an extracellular cycle, which controls the entry and removal of calcium between the cytosol and extracellular space, and an intracellular cycle, which controls calcium fluxes between the cytosol and intracellular stores in the sarcoplasmic reticulum. Several protein families mediate these calcium fluxes including those that (1) regulate the entry of calcium into the cytosol; (2) recognize calcium within the cytosol; and (3) remove calcium from the cytosol. Intracellular calcium binding proteins (the "E-F hand" proteins) recognize the appearance of calcium in the cytosol; in the heart and vascular smooth muscle, these proteins initiate excitation-contraction coupling. Calcium efflux occurs via adenosine triphosphate (ATP)-dependent calcium pumps and sodium-calcium exchangers, while two families of channels--intracellular release calcium channels and plasma membrane calcium channels--regulate calcium entry into the cytosol. The plasma membrane calcium channels, which include the L- and T-type channels, are of the greatest clinical interest because they are targets for pharmacologic therapy. T-type calcium channels, which activate contraction in vascular smooth muscle but have little or no role in cardiac excitation-contraction coupling, appear to be involved in signal transduction pathways that promote cell growth and proliferation. Calcium channel blockers that selectively block T-type calcium channels, therefore, offer a novel approach to cardiovascular drug therapy.

The relationship between low-level benzene exposure and leukemia in Canadian petroleum distribution workers

This study was conducted to evaluate the relationship between leukemia occurrence and long-term, low-level benzene exposures in petroleum distribution workers. Fourteen cases were identified among a previously studied cohort [Schnatter et al., Environ Health Perspect 101 (Suppl 6):85-89 (1993)]. Four controls per case were selected from the same cohort, controlling for birth year and time at risk. Industrial hygienists estimated workplace exposures for benzene, without knowledge of case-control status. Average benzene concentrations ranged from 0.01 to 6.2 ppm. Company medical records were used to abstract information on other potential confounders such as cigarette smoking. Odds ratios were calculated for several exposure metrics. Conditional logistic regression modeling was used to control for potential confounders. The risk of leukemia was not associated with increasing cumulative exposure to benzene for these exposure levels. Duration of benzene exposure was more closely associated with leukemia risk than other exposure metrics, although results were not statistically significant. A family history of cancer and cigarette smoking were the two strongest risk factors for leukemia, with cumulative benzene exposure showing no additional risk when considered in the same models. This study is consistent with other data in that it was unable to demonstrate a relationship between leukemia and long-term, low-level benzene exposures. The power of the study was limited. Thus, further study on benzene exposures in this concentration range are warranted.

Protein families that mediate Ca2+ signaling in the cardiovascular system

Five protein families are known to participate in the signaling cascades that enable calcium ions (Ca2+) to regulate functions in the cardiovascular system. Ca2+ signaling is involved in muscle contraction, pacemaking, and perhaps cell growth and differentiation. Recent evidence about the molecular properties of Ca2+ regulatory proteins has suggested possibilities for new therapeutic agents, including T-type Ca2+ channel blockers for patients with cardiovascular disease. This article reviews new information about Ca2+ signaling in the heart, vascular smooth muscle, and other tissues.

Lymphohaematopoietic malignancies and quantitative estimates of exposure to benzene in Canadian petroleum distribution workers

OBJECTIVE

To evaluate the relation between mortality from lymphohaematopoietic cancer and long term, low level exposures to benzene among male petroleum distribution workers.

METHODS

This nested case control study identified all fatal cases of lymphohaematopoietic cancer among a previously studied cohort. Of the 29 cases, 14 had leukaemia, seven multiple myeloma, and eight non-Hodgkin's lymphoma. A four to one matching ratio was used to select a stratified sample of controls from the same cohort, controlling for year of birth and time at risk. Industrial hygienists estimated workplace exposures for benzene and total hydrocarbons, without knowledge of case or control status, for combinations of job, location, and era represented in all work histories. Average daily benzene concentrations ranged from 0.01 to 6.2 parts per million (ppm) for all jobs. Company medical records were used to abstract information on other potential confounders such as cigarette smoking, although the data were incomplete. Odds ratios (ORs) were calculated with conditional logistic regression techniques for several exposure variables.

RESULTS

Risks of leukaemia, non-Hodgkin's lymphoma, and multiple myeloma were not associated with increasing cumulative exposure to benzene or total hydrocarbons. For leukaemia, the logistic regression model predicted an OR of 1.002 (P < 0.77) for each ppm-y of exposure to benzene. Duration of exposure to benzene was more closely associated with risk of leukaemia than other exposure variables. It was not possible to completely control for other risk factors, although there was suggestive evidence that smoking and a family history of cancer may have played a part in the risk of leukaemia.

CONCLUSION

This study did not show a relation between lymphohaematopoietic cancer and long term, low level exposures to benzene. The power of the study to detect low-such as twofold-risks was limited. Thus, further study on exposures to benzene in this concentration range are warranted.

Hearing the patient's 'voice': toward a social poetics in diagnostic interviews

In this article we introduce a special practice that we have called the practice of a "social poetics", and explore its nature. The setting is a Primary Care Clinic at a large urban teaching hospital in the northeast of the U.S. As we describe it, the practice is at first conducted by a third person who occupies the position of a "cultural go-between" and who mediates between doctors and their patients in diagnostic interviews. Her task is to be open to being 'arrested', or 'moved' by, certain fleeting, momentary occurrences in what patients do or say. For sometimes in such moments, in our responding to the unfolding motions of their whole body and voice-as they respond to the circumstances in which they find themselves-we can begin to sense that the unique nature of their 'inner world of pain and suffering' is like for them. The practice of a social poetics entails a new relational attitude to the patient's use of words, an attitude that invites a creative, poetic sensibility, as well as a 'boundary crossing' stance that creates comparisons useful in relating what patients say to the rest of their lives. In elucidating the nature of such a practice further, we draw on the work of Wittgenstein, Bachelard, and Bakhtin. Together, these can lead to a new diagnostic practice that enables those involved in it to create, within the practice itself, both ways of talking that draw attention to the new possibilities for interaction the practice itself momentarily makes available, and ways of talking relevant to realizing these possibilities.

Calcium channel diversity in the cardiovascular system

The flux of calcium ions (Ca2+) into the cytosol, where they serve as intracellular messengers, is regulated by two distinct families of Ca2+ channel proteins. These are the intracellular Ca2+ release channels, which allow Ca2+ to enter the cytosol from intracellular stores, and the plasma membrane Ca2+ channels, which control Ca2+ entry from the extracellular space. Each of these two families of channel proteins contains several subgroups. The intracellular channels include the large Ca2+ channels ("ryanodine receptors") that participate in cardiac and skeletal muscle excitation-contraction coupling, and smaller inositol trisphosphate (InsP3)-activated Ca2+ channels. The latter serve several functions, including the pharmacomechanical coupling that activates smooth muscle contraction, and possibly regulation of diastolic tone in the heart. The InsP3-activated Ca2+ channels may also participate in signal transduction systems that regulate cell growth. The family of plasma membrane Ca2+ channels includes L-type channels, which respond to membrane depolarization by generating a signal that opens the intracellular Ca2+ release channels. Calcium ion entry through L-type Ca2+ channels in the sinoatrial (SA) node contributes to pacemaker activity, whereas L-type Ca2+ channels in the atrioventricular (AV) node are essential for AV conduction. The T-type Ca2+ channels, another member of the family of plasma membrane Ca2+ channels, participate in pharmacomechanical coupling in smooth muscle. Opening of these channels in response to membrane depolarization participates in SA node pacemaker currents, but their role in the working cells of the atria and ventricle is less clear. Like the InsP3-activated intracellular Ca2+ release channels, T-type plasma membrane channels may regulate cell growth. Because most of the familiar Ca2+ channel blocking agents currently used in cardiology, such as nifedipine, verapamil and diltiazem, are selective for L-type Ca2+ channels, the recent development of drugs that selectively block T-type Ca2+ channels offers promise of new approaches to cardiovascular therapy.

The cardiomyopathy of overload: an unnatural growth response

The poor prognosis in heart failure, which can be reproduced by overloading the normal heart, may reflect molecular abnormalities associated with cardiac hypertrophy. Because terminally differentiated adult cardiac myocytes have little or no capacity to divide, overload-induced hypertrophy represents an unnatural growth response. The mechanism by which this unnatural growth response shortens survival remains speculative, but may involve apoptosis caused when overload reactivates growth factors to which the adult heart cannot respond with normal cell division. The ability of converting enzyme inhibitors and nitrates, which have growth inhibitory as well as vasodilator effects, to improve prognosis in heart failure may reflect the ability of these drugs to modify this unnatural growth response.

Cell death in the failing heart: role of an unnatural growth response to overload

Hypertrophy of the overloaded heart, characterized by an increased number of sarcomeres, provides an adaptive, short-term response. However, when cardiac overload is long-standing, the hypertrophic response appears to cause shortened myocyte survival. The mechanisms responsible for the deleterious effects of chronic myocardial hypertrophy may include a maladaptive growth response of the mature heart. Because terminally differentiated adult cardiac myocytes have little or no capacity to divide, stimuli that promote growth in the overloaded adult heart cannot lead to normal cell division. Instead, overload initiates an unnatural growth response that appears to shorten cardiac myocyte survival, possibly because the same growth factors that mediate the hypertrophic response of the adult heart can also induce programmed cell death (apoptosis). The converting enzyme inhibitors and nitrates, which have growth-inhibitory as well as vasodilator effects, may improve prognosis in heart failure by inhibiting the production of transcription factors. These transcription factors stimulate both the unnatural growth response to overload and stimuli that lead to apoptosis. Since both beta-adrenergic agonists and cytokines, such as tumor necrosis factor-alpha, can stimulate production of similar transcription factors, evidence suggests that beta blockers and vesnarinone improve the prognosis in patients with heart failure possibly because of their ability to inhibit maladaptive growth.

Characterization of Ca(2+)-release channels in fetal and adult rat hearts

The goal of this study was to characterize the Ca(2+)-release channel in whole homogenates of left (LV) and right ventricles (RV) of fetal (22 days in gestation) and adult Sprague-Dawley rat hearts using [3H]ryanodine binding and 45Ca2+ fluxes. Although many features of the Ca(2+)-release channels were similar in fetal and adult hearts, biochemical assays revealed quantitative differences. Similar properties include 1) Ca(2+)-sensitive cooperative ryanodine binding to Ca(2+)-release channel, measured as Ca2+ concentration for half-maximal activation (fetal LV: 0.13 +/- 0.02 microM; adults LV: 0.15 +/- 0.02 microM) and Hill coefficient (fetal LV: 2.5 +/- 0.9; adult LV: 2.7 +/- 0.5), and 2) caffeine-sensitive ryanodine binding, measured as the percent increase in ryanodine binding induced by caffeine (fetal LV: 148.8 +/- 16.9% vs. adult LV: 171.4 +/- 34.9%). The distinguishing property was the lower Ca(2+)-release channel density in the fetal heart (LV: 0.22 +/- 0.03 pmol/mg protein) compared with adult heart (LV: 0.59 +/- 0.04 pmol/mg protein; P < 0.05), as determined by [3H]ryanodine binding. The lower density of Ca(2+)-release channel is supported by the finding that there is very low ryanodine-sensitive oxalate-supported 45Ca2+ uptake in the fetal heart. The tested characteristics of the Ca(2+)-release channel were similar between LV and RV in both fetal and adult rat hearts. Ou results indicate that expression of Ca2+-release channels in sarcoplasmic reticulum increases during postnatal growth in the rat heart. This is consistent with previous physiological reports that Ca2+ available for excitation-contraction coupling in the fetal heart is derived mainly from transsarcolemmal Ca2+ influx.

The cardiomyopathy of overload: an unnatural growth response in the hypertrophied heart

Heart failure is a progressive condition with a 5-year survival of less than 50%. This poor prognosis, which can be reproduced by overloading the hearts of experimental animals, may reflect molecular abnormalities caused when overload stimulates adult cardiac myocytes to undergo hypertrophy. Because these terminally differentiated cells have little or no capacity to divide, hypertrophy represents an unnatural growth response; however, the mechanism by which overload shortens survival remains speculative. Modification of this unnatural growth response by converting enzyme inhibitors and nitrates, which have growth inhibitory as well as vasodilator effects, may contribute to the ability of these drugs to improve prognosis in patients with heart failure.