Metamorphosis Imposes Variable Constraints on Genome Expansion through Effects on Development

Genome size varies ∼100,000-fold across eukaryotes and has long been hypothesized to be influenced by metamorphosis in animals. Transposable element accumulation has been identified as a major driver of increase, but the nature of constraints limiting the size of genomes has remained unclear, even as traits such as cell size and rate of development co-vary strongly with genome size. Salamanders, which possess diverse metamorphic and non-metamorphic life histories, join the lungfish in having the largest vertebrate genomes-3 to 40 times that of humans-as well as the largest range of variation in genome size. We tested 13 biologically-inspired hypotheses exploring how the form of metamorphosis imposes varying constraints on genome expansion in a broadly representative phylogeny containing 118 species of salamanders. We show that metamorphosis during which animals undergo the most extensive and synchronous remodeling imposes the most severe constraint against genome expansion, with the severity of constraint decreasing with reduced extent and synchronicity of remodeling. More generally, our work demonstrates the potential for broader interpretation of phylogenetic comparative analysis in exploring the balance of multiple evolutionary pressures shaping phenotypic evolution.

Reference-free discovery of nuclear SNPs permits accurate, sensitive identification of Carya (hickory) species and hybrids

PREMISE

DNA-based species identification is critical when morphological identification is restricted, but DNA-based identification pipelines typically rely on the ability to compare homologous sequence data across species. Because many clades lack robust genomic resources, we present here a bioinformatics pipeline capable of generating genome-wide single-nucleotide polymorphism (SNP) data while circumventing the need for any reference genome or annotation data.

METHODS

Using the SISRS bioinformatics pipeline, we generated de novo ortholog data for the genus Carya, isolating sites where genetic variation was restricted to a single Carya species (i.e., species-informative SNPs). We leveraged these SNPs to identify both full-species and hybrid Carya specimens, even at very low sequencing depths.

RESULTS

We identified between 46,000 and 476,000 species-identifying SNPs for each of eight diploid Carya species, and all species identifications were concordant with the species of record. For all putative F₁ hybrid specimens, both parental species were correctly identified in all cases, and more punctate patterns of introgression were detectable in more cryptic crosses.

DISCUSSION

Bioinformatics pipelines that use only short-read sequencing data provide vital new tools enabling rapid expansion of DNA identification assays for model and non-model clades alike.

Extensive genome-wide duplications in the eastern oyster (Crassostrea virginica)

Genomic structural variation is an important source of genetic and phenotypic diversity, playing a critical role in evolution. The recent availability of a high-quality reference genome for the eastern oyster, Crassostrea virginica, and whole-genome sequence data of samples from across the species range in the USA, provides an opportunity to explore structural variation across the genome of this species. Our analysis shows significantly greater individual-level duplications of regions across the genome than that of most model vertebrate species. Duplications are widespread across all ten chromosomes with variation in frequency per chromosome. The eastern oyster shows a large interindividual variation in duplications as well as particular chromosomal regions with a higher density of duplications. A high percentage of duplications seen in C. virginica lie completely within genes and exons, suggesting the potential for impacts on gene function. These results support the hypothesis that structural changes may play a significant role in standing genetic variation in C. virginica, and potentially have a role in their adaptive and evolutionary success. Altogether, these results suggest that copy number variation plays an important role in the genomic variation of C. virginica. This article is part of the Theo Murphy meeting issue 'Molluscan genomics: broad insights and future directions for a neglected phylum'.

Functional DSCT assessment of tricuspid regurgitation: AROA reproducibility and comparison with 3D TEE

Funding Acknowledgements

Type of funding sources: None.

onbehalf

Minneapolis Heart Institute Foundation

Background

Tricuspid regurgitation (TR) assessment by echocardiography is often challenging. Functional dual-source CT (DSCT) with third-generation scanners allows accurate evaluation of leaflet anatomy and mobility.

Purpose

Investigate the reproducibility of tricuspid anatomical regurgitant orifice area (AROA) by DSCT, and its correlation with TR quantification by 3D TEE.

Methods

We evaluated patients with symptomatic TR referred for transcatheter tricuspid repair. DSCT (SOMATOM Force [Siemens, Erlangen, Germany]) and 3D TEE was performed on the same day as part of our institutional registry. DSCT scans were retrospective and ECG-gated, with a contrast protocol to enhance the right heart. The reproducibility of tricuspid AROA was assessed in 20 patients. The tricuspid AROA was compared with the TR severity (5-grade classification) and the 3D VCA by TEE (Panel 1).

Results

We included 60 patients (Table). The AROA had excellent intra and interobserver reliability (ICC 0.99 [0.97, 0.99] and 0.99 [0.96, 0.99]). We found a stepwise increase in tricuspid AROA from moderate to torrential TR (Panel 2A). Of 60 patients, 3D VCA was feasible in 39; in those, we found an excellent linear correlation of AROA and 3D VCA (Panel 2B).

Conclusions

Tricuspid AROA by DSCT was reproducible, showed a stepwise increase from moderate to massive TR and correlated with 3D VCA by TEE.

Baseline Patient Characteristics All (n = 60) Age, years 82 ± 7 BSA, m2 1.8 ± 0.2 NYHA III-IV, n(%) 42 (70) Atrial Fibrilation 55 (91) Hypertension 44 (73) Pulmonary Hypertension 34 (56) Chronic Kidney Disease 25 (44) Coronary Artery Disease 17 (28) Chronic Lung Disease 14 (23) Permanent Pacemaker 13 (21) Diabetes Mellitus 10 (17) Mitral Valve Repair (MitraClip) 9 (15) Mitral Valve Replacement 7 (12) Mitral Valve Repair 3 (5) Aortic Valve Replacement 5 (8) Values are mean ± SD and n (%). BSA = body surface area. Abstract Figure. Panels

The why, when, and how of computing in biology classrooms

Many biologists are interested in teaching computing skills or using computing in the classroom, despite not being formally trained in these skills themselves. Thus biologists may find themselves researching how to teach these skills, and therefore many individuals are individually attempting to discover resources and methods to do so. Recent years have seen an expansion of new technologies to assist in delivering course content interactively. Educational research provides insights into how learners absorb and process information during interactive learning. In this review, we discuss the value of teaching foundational computing skills to biologists, and strategies and tools to do so. Additionally, we review the literature on teaching practices to support the development of these skills. We pay special attention to meeting the needs of diverse learners, and consider how different ways of delivering course content can be leveraged to provide a more inclusive classroom experience. Our goal is to enable biologists to teach computational skills and use computing in the classroom successfully.

The why, when, and how of computing in biology classrooms

Many biologists are interested in teaching computing skills or using computing in the classroom, despite not being formally trained in these skills themselves. Thus biologists may find themselves researching how to teach these skills, and therefore many individuals are individually attempting to discover resources and methods to do so. Recent years have seen an expansion of new technologies to assist in delivering course content interactively. Educational research provides insights into how learners absorb and process information during interactive learning. In this review, we discuss the value of teaching foundational computing skills to biologists, and strategies and tools to do so. Additionally, we review the literature on teaching practices to support the development of these skills. We pay special attention to meeting the needs of diverse learners, and consider how different ways of delivering course content can be leveraged to provide a more inclusive classroom experience. Our goal is to enable biologists to teach computational skills and use computing in the classroom successfully.

Estimating error models for whole genome sequencing using mixtures of Dirichlet-multinomial distributions

MOTIVATION

Accurate identification of genotypes is an essential part of the analysis of genomic data, including in identification of sequence polymorphisms, linking mutations with disease and determining mutation rates. Biological and technical processes that adversely affect genotyping include copy-number-variation, paralogous sequences, library preparation, sequencing error and reference-mapping biases, among others.

RESULTS

We modeled the read depth for all data as a mixture of Dirichlet-multinomial distributions, resulting in significant improvements over previously used models. In most cases the best model was comprised of two distributions. The major-component distribution is similar to a binomial distribution with low error and low reference bias. The minor-component distribution is overdispersed with higher error and reference bias. We also found that sites fitting the minor component are enriched for copy number variants and low complexity regions, which can produce erroneous genotype calls. By removing sites that do not fit the major component, we can improve the accuracy of genotype calls.

AVAILABILITY AND IMPLEMENTATION

Methods and data files are available at https://github.com/CartwrightLab/WuEtAl2017/ (doi:10.5281/zenodo.256858).

CONTACT

cartwright@asu.edu.

SUPPLEMENTARY INFORMATION

Supplementary data is available at Bioinformatics online.

The importance of selection in the evolution of blindness in cavefish

Background

Blindness has evolved repeatedly in cave-dwelling organisms, and many hypotheses have been proposed to explain this observation, including both accumulation of neutral loss-of-function mutations and adaptation to darkness. Investigating the loss of sight in cave dwellers presents an opportunity to understand the operation of fundamental evolutionary processes, including drift, selection, mutation, and migration.

Results

Here we model the evolution of blindness in caves. This model captures the interaction of three forces: (1) selection favoring alleles causing blindness, (2) immigration of sightedness alleles from a surface population, and (3) mutations creating blindness alleles. We investigated the dynamics of this model and determined selection-strength thresholds that result in blindness evolving in caves despite immigration of sightedness alleles from the surface. We estimate that the selection coefficient for blindness would need to be at least 0.005 (and maybe as high as 0.5) for blindness to evolve in the model cave-organism, Astyanax mexicanus.

Conclusions

Our results indicate that strong selection is required for the evolution of blindness in cave-dwelling organisms, which is consistent with recent work suggesting a high metabolic cost of eye development.

Electronic supplementary material

The online version of this article (doi:10.1186/s12862-017-0876-4) contains supplementary material, which is available to authorized users.

Whole Genome Sequencing of Field Isolates Reveals Extensive Genetic Diversity in Plasmodium vivax from Colombia

Plasmodium vivax is the most prevalent malarial species in South America and exerts a substantial burden on the populations it affects. The control and eventual elimination of P. vivax are global health priorities. Genomic research contributes to this objective by improving our understanding of the biology of P. vivax and through the development of new genetic markers that can be used to monitor efforts to reduce malaria transmission. Here we analyze whole-genome data from eight field samples from a region in Cordóba, Colombia where malaria is endemic. We find considerable genetic diversity within this population, a result that contrasts with earlier studies suggesting that P. vivax had limited diversity in the Americas. We also identify a selective sweep around a substitution known to confer resistance to sulphadoxine-pyrimethamine (SP). This is the first observation of a selective sweep for SP resistance in this species. These results indicate that P. vivax has been exposed to SP pressure even when the drug is not in use as a first line treatment for patients afflicted by this parasite. We identify multiple non-synonymous substitutions in three other genes known to be involved with drug resistance in Plasmodium species. Finally, we found extensive microsatellite polymorphisms. Using this information we developed 18 polymorphic and easy to score microsatellite loci that can be used in epidemiological investigations in South America.

Although P. vivax is not as deadly as the more widely studied P. falciparum, it remains a pressing global health problem. Here we report the results of a whole-genome study of P. vivax from Cordóba, Colombia, in South America. This parasite is the most prevalent in this region. We show that the parasite population is genetically diverse, which is contrary to expectations from earlier studies from the Americas. We also find molecular evidence that resistance to an anti-malarial drug has arisen recently in this region. This selective sweep indicates that the parasite has been exposed to a drug that is not used as first-line treatment for this malaria parasite. In addition to extensive single nucleotide and microsatellite polymorphism, we report 18 new genetic loci that might be helpful for fine-scale studies of this species in the Americas.

A composite genome approach to identify phylogenetically informative data from next-generation sequencing

Background

Improvements in sequencing technology now allow easy acquisition of large datasets; however, analyzing these data for phylogenetics can be challenging. We have developed a novel method to rapidly obtain homologous genomic data for phylogenetics directly from next-generation sequencing reads without the use of a reference genome. This software, called SISRS, avoids the time consuming steps of de novo whole genome assembly, multiple genome alignment, and annotation.

Results

For simulations SISRS is able to identify large numbers of loci containing variable sites with phylogenetic signal. For genomic data from apes, SISRS identified thousands of variable sites, from which we produced an accurate phylogeny. Finally, we used SISRS to identify phylogenetic markers that we used to estimate the phylogeny of placental mammals. We recovered eight phylogenies that resolved the basal relationships among mammals using datasets with different levels of missing data. The three alternate resolutions of the basal relationships are consistent with the major hypotheses for the relationships among mammals, all of which have been supported previously by different molecular datasets.

Conclusions

SISRS has the potential to transform phylogenetic research. This method eliminates the need for expensive marker development in many studies by using whole genome shotgun sequence data directly. SISRS is open source and freely available at https://github.com/rachelss/SISRS/releases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12859-015-0632-y) contains supplementary material, which is available to authorized users.

Developing major histocompatibility markers in a species of concern: the Sacramento perch Archoplites interruptus

Primers targeting two non-neutral major histocompatibility complex (mhc) II β genes were developed and assayed across several disjoint Sacramento perch Archoplites interruptus sampling locations. Variability at the two mhc loci among sampling stocks strongly correlated to previous estimates with neutral markers, suggesting that the effect of genetic drift was not limited to neutrally evolving regions of the genome. The novel mhc primers will help develop admixture schemes in A. interruptus captive breeding programmes and will increase the success of future reintroductions of this species of concern.

Improvement in aortic valve area using a new "hour glass" shaped valvuloplasty balloon compared with standard cylindrical balloons in severe aortic stenosis patients

AIM

Balloon aortic valvuloplasty (BAV) has reemerged with transcatheter valve therapy. Cylindrical balloons have been the device of choice despite limitations. An hour glass shaped balloon may permit enhanced fixation and broader leaflet opening without annular compromise.

METHODS

We report our initial BAV experience using the V8 balloon (InterValve Inc.) in 20 consecutive patients compared to 20 patients from a 403-patient BAV database using cylindrical balloons. Patients were propensity matched on a 1:1 basis by age, gender, left ventricular ejection fraction (LVEF), baseline aortic valve area (AVA) and Society of Thoracic Surgery (STS) mortality risk score. End points included change in AVA and aortic insufficiency (AI) by echocardiography. New atrioventricular conduction defects (AVCD), need for post procedure pacemaker were documented. Major adverse events (MAE) included procedure related death, emergency surgery or stroke.

RESULTS

V8 and cylindrical balloon groups were similar across age, gender, LVEF, AVA and STS score. The change in AVA from baseline to post-procedure strongly trended towards being larger in the V8 group than cylindrical balloon group (mean [SD]; 0.30±0.23 cm2 vs. 0.17±0.21 cm2; P=0.063). There were no differences in outcomes for degree of AI, AVCD, need for pacemaker or MAE.

CONCLUSION

Preliminary findings in this small experience suggest an advantage for enhancing AVA when using the V8 compared with cylindrical balloons. Additionally, there was no evidence of increased AI, AVCD or MAE.

Estrogen or raloxifene during postmenopausal weight loss: adiposity and cardiometabolic outcomes

OBJECTIVE

Estrogen-based hormone therapy (HT) attenuates abdominal fat gain after menopause, but whether HT improves abdominal fat loss during weight loss is unknown. It was hypothesized that HT or a selective estrogen receptor modulator (raloxifene) would augment reductions in abdominal visceral fat during weight loss when compared to placebo, potentially increasing improvements in glucose tolerance and lipid profile.

METHODS

Healthy postmenopausal women (n = 119; age 50-70 yr) underwent a 6-month weight-loss (primarily exercise) intervention with randomization to raloxifene (60 mg/d), HT (conjugated estrogens, 0.625 mg/d), or placebo. Outcomes were change in total and abdominal (visceral and subcutaneous) fat mass, lipid profile, and fasting and post-challenge glucose and insulin.

RESULTS

Neither HT nor raloxifene augmented loss of total or abdominal fat mass during exercise-induced weight loss when compared with placebo. Weight loss-induced improvements in risk factors were similar among the three groups, except for a greater reduction in fasted glucose in the HT group (difference in change [95%CI] from placebo; -0.40 [-0.76, -0.05]) and greater reductions in LDL (-0.36 [-0.63, -0.09]) and increases in HDL (0.15 [0.07, 0.24]) in both treatment groups.

CONCLUSIONS

Postmenopausal HT and raloxifene did not increase abdominal fat loss during weight loss, but did improve some cardiometabolic outcomes.

Novel stents for the prevention of restenosis

Since the introduction of Interventional Cardiology in 1976, there has been rapid expansion both in its clinical application and the tools of the trade. This growth was accelerated with the introduction of the intra-coronary stent in 1987. The demonstration that stents may reduce the incidence of restenosis after percutaneous coronary revascularization has further stimulated the search for the perfect endovascular prosthesis. By creating a hybrid stent, incorporating natural coatings and local drug delivery in the design, it is hoped that the complications associated with stent thrombosis and restenosis can be eradicated. (Trends Cardiovasc Med 1997;7:245-249). © 1997, Elsevier Science Inc.

Treating age-related changes in somatotrophic hormones, sleep, and cognition

Many of the body's systems that function to maintain optimal health and well-being decline with advancing age. Aerobic capacity, muscle mass, and strength all progressively decline. Significant sleep disturbances are associated with increases in morbidity and mortality. Cognition declines, impacting an older individual's ability to function independently. Interventions that could at least stabilize or possibly improve functional capacity, sleep quality, and cognitive function have the theoretical potential to prolong an older individual's ability to live independently, and interest in their possible utility is growing rapidly. One such intervention may be stimulation of the “somatotrophic” axis via growth hormone-releasing hormone (GHRH). Here we review the evidence for such somatotrophic interventions. We also report preliminary findings on the effects of chronic GHRH treatment on the somatotrophic hormones, body composition, functional status, sleep, and cognitive function of healthy older men and women from two major GHRH intervention studies, one recently completed and the other ongoing.

Defining vitamin D status by secondary hyperparathyroidism in the U.S. population

BACKGROUND

Vitamin D is associated with a variety of health outcomes, but the exact definition of vitamin D sufficiency remains controversial.

AIM

We sought to define skeletal-related vitamin D sufficiency by estimating maximum PTH suppression in the U.S. population.

METHODS

We performed a cross-sectional analysis of the National Health and Nutrition Examination Survey (NHANES), 2003-2006. We examined the association between serum 25-hydroxyvitamin D (25OHD) level and serum PTH level in 14,681 participants aged ≥6 yr. We also evaluated the 25OHD-PTH association using 2 thresholds of hyperparathyroidism: PTH≥45 pg/ml and ≥75 pg/ml.

RESULTS

The mean 25OHD level was 24 ng/ml and mean PTH was 42 pg/ml. PTH≥45 pg/ml was present in 35% of the population, while PTH≥75 pg/ml was present in 7%. The prevalence of 25OHD levels <40 ng/ml and <30 ng/ml was 95% and 77%, respectively. In both unadjusted and adjusted models, there was a strong inverse relationship between 25OHD and PTH. Compared to 25OHD≥40 ng/ml, the 25OHD-PTH association was 2.36 [95% confidence interval (CI), 2.08-2.67] times greater for 25OHD<5 ng/ml and 1.12 (95%CI, 1.07-1.17) times greater for 25OHD 30-39.9 ng/ml. Compared to 25OHD≥40 ng/ml, 25OHD levels of 20- 29.9 ng/ml [odds ratio (OR) 2.0 (95%CI, 1.4-2.8)] but not 30- 39.9 ng/ml [OR 1.1 (95%CI, 0.8-1.6)] were independently associated with PTH≥45 pg/ml.

CONCLUSIONS

Optimal vitamin D status, defined by estimated maximum PTH suppression, does not occur until at least 25OHD levels ≥40 ng/ml. Using these thresholds, most of the U.S. population needs more vitamin D. Large, prospective studies are needed to determine optimal vitamin D supplementation.

Variation in DNA substitution rates among lineages erroneously inferred from simulated clock-like data

BACKGROUND

The observation of variation in substitution rates among lineages has led to (1) a general rejection of the molecular clock model, and (2) the suggestion that a number of biological characteristics of organisms can cause rate variation. Accurate estimates of rate variation, and thus accurate inferences regarding the causes of rate variation, depend on accurate estimates of substitution rates. However, theory suggests that even when the substitution process is clock-like, variable numbers of substitutions can occur among lineages because the substitution process is stochastic. Furthermore, substitution rates along lineages can be misestimated, particularly when multiple substitutions occur at some sites. Although these potential causes of error in rate estimation are well understood in theory, such error has not been examined in detail; consequently, empirical studies that estimate rate variation among lineages have been unable to determine whether their results could be impacted by estimation error.

METHODOLOGY/PRINCIPAL FINDINGS

To evaluate the extent to which error in rate estimation could erroneously suggest rate variation among lineages, we examined rate variation estimated for datasets simulated under a molecular clock on trees with equal and variable branch lengths. Thus, any apparent rate variation in these datasets reflects error in rate estimation rather than true differences in the underlying substitution process. We observed substantial rate variation among lineages in our simulations; however, we did not observe rate variation when average substitution rates were compared between different clades.

CONCLUSIONS/SIGNIFICANCE

Our results confirm previous theoretical work suggesting that observations of among lineage rate variation in empirical data may be due to the stochastic substitution process and error in the estimation of substitution rates, rather than true differences in the underlying substitution process among lineages. However, conclusions regarding rate variation drawn from rates averaged across multiple branches are likely due to real, systematic variation in rates between groups.

Branch length estimation and divergence dating: estimates of error in Bayesian and maximum likelihood frameworks

BACKGROUND

Estimates of divergence dates between species improve our understanding of processes ranging from nucleotide substitution to speciation. Such estimates are frequently based on molecular genetic differences between species; therefore, they rely on accurate estimates of the number of such differences (i.e. substitutions per site, measured as branch length on phylogenies). We used simulations to determine the effects of dataset size, branch length heterogeneity, branch depth, and analytical framework on branch length estimation across a range of branch lengths. We then reanalyzed an empirical dataset for plethodontid salamanders to determine how inaccurate branch length estimation can affect estimates of divergence dates.

RESULTS

The accuracy of branch length estimation varied with branch length, dataset size (both number of taxa and sites), branch length heterogeneity, branch depth, dataset complexity, and analytical framework. For simple phylogenies analyzed in a Bayesian framework, branches were increasingly underestimated as branch length increased; in a maximum likelihood framework, longer branch lengths were somewhat overestimated. Longer datasets improved estimates in both frameworks; however, when the number of taxa was increased, estimation accuracy for deeper branches was less than for tip branches. Increasing the complexity of the dataset produced more misestimated branches in a Bayesian framework; however, in an ML framework, more branches were estimated more accurately. Using ML branch length estimates to re-estimate plethodontid salamander divergence dates generally resulted in an increase in the estimated age of older nodes and a decrease in the estimated age of younger nodes.

CONCLUSIONS

Branch lengths are misestimated in both statistical frameworks for simulations of simple datasets. However, for complex datasets, length estimates are quite accurate in ML (even for short datasets), whereas few branches are estimated accurately in a Bayesian framework. Our reanalysis of empirical data demonstrates the magnitude of effects of Bayesian branch length misestimation on divergence date estimates. Because the length of branches for empirical datasets can be estimated most reliably in an ML framework when branches are <1 substitution/site and datasets are > or =1 kb, we suggest that divergence date estimates using datasets, branch lengths, and/or analytical techniques that fall outside of these parameters should be interpreted with caution.

Limited effects of among-lineage rate variation on the phylogenetic performance of molecular markers

Variation in substitution rates among evolutionary lineages (among-lineage rate variation or ALRV) has been reported to negatively affect the estimation of phylogenies. When the substitution processes underlying ALRV are modeled inadequately, non-sister taxa with similar substitution rates are estimated incorrectly as sister species due to long-branch attraction. Recent advances in modeling site-specific rate variation (heterotachy) have reduced the impacts of ALRV on phylogeny estimation in several empirical and simulated datasets. However, the addition of parameters to the substitution model reduces power to estimate each parameter correctly, which can also lead to incorrect phylogeny estimation. A potential solution to this problem is to identify the levels of ALRV that negatively impact phylogeny estimation such that molecular markers with non-deleterious levels of ALRV can be identified. To this end, we used analyses of empirical and simulated gene datasets to evaluate whether levels of ALRV identified in a mitochondrial genomic dataset for salamanders negatively impacted phylogeny estimation. We simulated data with and without ALRV, holding all other evolutionary parameters constant, and compared the phylogenetic performance of both simulated and empirical datasets. Overall, we found limited, positive effects of ALRV on phylogeny estimation in this dataset, the majority of which resulted from an increase in substitution rate on short branches. We conclude that ALRV does not always negatively impact phylogeny estimation. Therefore, ALRV can likely be disregarded as a criterion for marker selection in comparable phylogenetic studies.

Dehydroepiandrosterone sulfate and cognitive function in the elderly: The InCHIANTI Study

DHEA and its sulfate derivative (DHEAS) decline with age. The decline in DHEAS levels has been associated with many physiological impairments in older persons including cognitive dysfunction. However, data regarding the possible relationship between DHEAS and cognition are scant. We investigated whether DHEAS levels are associated with presence and development of lower cognitive function measured by the Mini Mental State Examination (MMSE) in older men and women. One thousand and thirty-four residents aged > or =65 yr of the InCHIANTI Study with data available on DHEAS and MMSE were randomly selected. MMSE was administered at baseline and 3 yr later. Among these, 841 completed a 3-yr follow-up. Parsimonious models obtained by backward selection from initial fully-adjusted models were used to identify independent factors associated with MMSE and DHEAS. The final analysis was performed in 755 participants (410 men and 345 women) with MMSE score > or =21. A significant age-related decline of both DHEAS levels (p<0.001) and MMSE score (p<0.001) was found over the 3-yr follow-up. At enrolment, DHEAS was significantly and positively associated with MMSE score, independently of age and other potential confounders (beta+/-SE 0.003+/-0.001, p<0.005). Low baseline DHEAS levels were predictive of larger decline of MMSE and this relationship was significant after adjusting for covariates (beta+/-SE -0.004+/-0.002, p<0.03). Our data show a significant and positive association between DHEAS and cognitive function, assessed by MMSE test. Low DHEAS levels predict accelerated decline in MMSE score during the 3-yr follow-up period.

Utility of magnetic resonance imaging in diagnosing ulnarneuropathy at the elbow

OBJECTIVE

Magnetic resonance imaging (MRI) of the ulnar nerve is being increasingly employed in the diagnosis of ulnar neuropathy at the elbow (UNE). Our aims were to: (i) assess the sensitivity of MRI in diagnosing UNE, especially in cases where neurophysiologic studies were non-localizing, (ii) determine the spectrum of MRI abnormalities in patients presenting with symptoms and signs of ulnar neuropathy, (iii) assess whether MRI findings differ between grades of UNE severity, and (iv) to see if MRI findings give an input into the pathological mechanisms of UNE.

METHODS

Clinical, neurophysiologic, and radiologic (MRI) records were reviewed in 52 patients with symptoms and signs of ulnar neuropathy. Ulnar nerve MRI studies were assessed by an unblinded observer.

RESULTS

The sensitivity of MRI at diagnosing UNE was higher than conventional nerve conduction studies, 90 versus 65%, respectively. In patients with non-localizing neurophysiologic studies (n=19), MRI disclosed changes consistent with UNE in 16 (84%) cases. The most frequent MRI findings included a combination of high signal intensity and nerve enlargement (63%), followed by nerve compression (27%) and isolated high signal intensity (23%), and isolated nerve enlargement (2%). There was no significant difference between patients with localizing and non-localizing neurophysiologic testing. Lastly, there were no differences between different grades of UNE, suggesting that UNE may be a neurophysiologically heterogeneous disorder.

CONCLUSIONS

MRI studies proved to be more sensitive than conventional nerve conduction studies at diagnosing UNE. In addition, the MRI studies were highly sensitive in patients with non-localizing UNE.

SIGNIFICANCE

Our study shows that MRI of the ulnar nerve should be used in patients with clinical features of UNE especially in those with non-localizing neurophysiologic testing.

Lower-body adiposity and metabolic protection in postmenopausal women

CONTEXT

It has been suggested that the propensity to store fat in the gluteal-femoral region may be cardioprotective.

OBJECTIVE

The primary aim of this study was to test whether the favorable associations of leg fat with risk factors for cardiovascular disease persist after controlling for the highly unfavorable effects of abdominal (visceral or sc) adiposity in postmenopausal women.

STUDY PARTICIPANTS

The study included 95 postmenopausal women [age, 60 +/- 8 yr (mean +/- SD)].

MAIN OUTCOMES

Whole-body and regional fat distribution was measured using dual-energy x-ray absorptiometry and abdominal computed tomography. Markers of insulin resistance and dyslipidemia were determined from oral glucose tolerance tests and fasted lipid and lipoprotein measurements, respectively. Primary outcomes were: fasting insulin (INS0), area under the insulin curve (INS(AUC)), product of the oral glucose tolerance test insulin and glucose AUC (INS(AUC) - GLU(AUC)), serum triglycerides (TG), and high-density lipoprotein (HDL) cholesterol.

RESULTS

Controlling for trunk fat revealed a favorable effect of leg fat on INS0, INS(AUC), INS(AUC) x GLU(AUC), TG, and HDL. However, after controlling for either visceral or sc abdominal adiposity, TG was the only risk factor for which the favorable effect of leg fat persisted.

CONCLUSIONS

The lack of an association between leg fat and most of the risk factors, after adjusting for abdominal visceral or sc fat, suggests an overriding deleterious influence of abdominal adiposity on cardiovascular risk. Nevertheless, our finding that regional adipose tissue depots have apparent independent and opposing effects on serum TG supports the need for further research into the physiological mechanisms governing these effects.

Protection of bone mass by estrogens and raloxifene during exercise-induced weight Loss

The aim of this study was to determine whether estrogen and/or raloxifene help to conserve bone mineral density (BMD) during moderate weight loss. Postmenopausal women (n = 68) participated in a 6-month weight loss program that consisted primarily of supervised exercise training. Another 26 women were studied over 6 months of weight stability. All participants were randomized to three treatment arms: placebo, raloxifene (60 mg/d), or hormone therapy (HT; conjugated estrogens, 0.625 mg/d; trimonthly medroxyprogesterone acetate, 5 mg/d for 13 d, for women with a uterus). Changes in body weight (mean +/- se) averaged 0.8 +/- 0.5 kg in the weight-stable group and -4.1 +/- 0.4 kg in the weight loss group. Across all measured skeletal sites, average changes in BMD in weight stable women were -0.6 +/- 1.1% (n = 7), 0.9 +/- 0.6% (n = 9), and 3.0 +/- 0.7% (n = 10) in the placebo, raloxifene, and HT groups, respectively; comparable BMD changes in the weight loss groups were -1.5 +/- 0.5% (n = 22), -0.5 +/- 0.5% (n = 23), and 1.1 +/- 0.4% (n = 23). There were no significant interactions between weight loss and drug treatment on changes in BMD, but there were significant main effects of weight loss on lumbar spine (P = 0.022), total hip (P = 0.010), and trochanter BMD (P < 0.001). These findings suggest that weight loss, even when modest in magnitude and induced by exercise training, causes a reduction in BMD, particularly in women not taking raloxifene or HT. It is not known whether reductions in BMD of this magnitude increase the risk for osteoporotic fracture.

Intravenous estrogens increase insulin clearance and action in postmenopausal women

To test the hypothesis that estrogens alter insulin action, we evaluated the effects of intravenous conjugated estrogens (CE) on insulin-stimulated steady-state glucose infusion rate (SSGIR) and suppression of plasma glycerol in postmenopausal women (mean +/- SD; 56 +/- 4 yr; n = 12) not using hormone replacement. SSGIR and glycerol were measured during a two-stage (8 and 40 mU. m-2. min-1) hyperinsulinemic euglycemic clamp on 2 days, with or without a 2.5-mg intravenous CE bolus. Serum estradiol concentrations were increased approximately 200% on the estrogen (EST) compared with the control (CON) days. Serum insulin was reduced (P < 0.01) during stage 2 of the clamp for EST (63.3 +/- 12.8 micro U/ml) vs. CON (78.2 +/- 15.8 micro U/ml). Mean SSGIR and plasma glycerol did not differ between CON and EST days. With adjustment for differences in insulin concentration between conditions, stage 2 glucose disposals were significantly higher (8.63 vs. 7.20 mg. kg-1. min-1) and plasma glycerol concentrations were significantly lower (29.4 vs. 35.0 micro mol/l) for EST vs. CON. Our findings suggest that acute CE administration increases insulin clearance and action in postmenopausal women.

Reproductive fitness in maternal homocystinuria due to cystathionine beta-synthase deficiency

Early diagnosis and improved treatment are leading to the potential for increased reproductive capability in homocystinuria due to cystathionine beta-synthase (CbetaS) deficiency, but information about reproductive outcome and risk of thromboembolism in pregnancy is limited. To provide further information, clinical and biochemical information was obtained on women with maternal homocystinuria, on their pregnancies and on the offspring. This information included blood sulphur amino acids and total homocysteine, CbetaS gene mutations and developmental and cognitive scores in the offspring. The study involved 15 pregnancies in 11 women, of whom 5 were pyridoxine-nonresponsive and 6 were pyridoxine-responsive. Complications of pregnancy included pre-eclampsia at term in two pregnancies and superficial venous thrombosis of the leg in a third pregnancy. One pregnancy was terminated and two pregnancies resulted in first-trimester spontaneous abortions. The remaining 12 pregnancies produced live-born infants with normal or above-normal birth measurements. One offspring has multiple congenital anomalies that include colobomas of the iris and choroid, neural tube defect and undescended testes. He is also mentally retarded and autistic. A second offspring has Beckwith-Wiedemann syndrome. The remaining 10 offspring were normal at birth and have remained normal. There was no relationship between the severity of the biochemical abnormalities or the therapies during pregnancy to either the pregnancy complications or the offspring outcomes. The infrequent occurrences of pregnancy complications, offspring abnormalities and maternal thromboembolic events in this series suggest that pregnancy and outcome in maternal homocystinuria are usually normal. Nevertheless, a cautious approach would include careful monitoring of these pregnancies with attention to metabolic therapy and possibly anticoagulation.

Cell proliferation in carcinoid valve disease: a mechanism for serotonin effects

BACKGROUND AND AIM OF THE STUDY

Elevated serum serotonin is associated with carcinoid heart disease, the hallmark of which is valvular thickening. Yet, the mechanistic role of serotonin in carcinoid heart disease is poorly understood. We postulated that serotonin has a direct mitogenic effect on cardiac valvular subendocardial cells, and that this effect is mediated by serotonin receptors.

METHODS

The dose-dependent proliferative effects of serotonin (10(-8) to 10(-4)M) on cultured porcine aortic valve cells via a [3H]thymidine assay were determined in vitro. Serotonin receptor antagonist studies in culture were also performed using methiotepin, a 5HT1b antagonist, and ketanserin, a 5HT2 receptor antagonist, to determine the mechanism of serotonin action. The ex-vivo proliferation level in human carcinoid (n = 26) and normal valves (n = 10) was compared using proliferating cell nuclear antigen (PCNA) staining, a marker for proliferation. Identification and localization of specific 5HT receptor was assessed by immunostaining for serotonin receptors in the valves.

RESULTS

Serotonin increased valvular proliferation in vitro in a dose-dependent manner (10-fold increase) (p <0.001), and this mitogenic effect was inhibited by methiotepin but not ketanserin. In human carcinoid heart valves the level of proliferation was 35-fold higher than in normal human valves (p <0.001). 5HT1b receptors were found only in the carcinoid valves, and not in the normal valves.

CONCLUSION

Serotonin is a powerful mitogen for valvular subendocardial cells. The mitogenic effect is at least partly mediated via 5HT1b receptors. Subendothelial cell proliferation is significantly elevated in human carcinoid valves in vivo. The data suggest a mechanism whereby serotonin may contribute to valvular proliferation in carcinoid heart disease.

Pregnancy-associated plasma protein A as a marker of acute coronary syndromes

BACKGROUND

Circulating markers indicating the instability of atherosclerotic plaques could have diagnostic value in unstable angina or acute myocardial infarction. We evaluated pregnancy-associated plasma protein A (PAPP-A), a potentially proatherosclerotic metalloproteinase, as a marker of acute coronary syndromes.

METHODS

We examined the level of expression of PAPP-A in eight culprit unstable coronary plaques and four stable plaques from eight patients who had died suddenly of cardiac causes. We also measured circulating levels of PAPP-A, C-reactive protein, and insulin-like growth factor I (IGF-I) in 17 patients with acute myocardial infarction, 20 with unstable angina, 19 with stable angina, and 13 controls without atherosclerosis.

RESULTS

PAPP-A was abundantly expressed in plaque cells and extracellular matrix of ruptured and eroded unstable plaques, but not in stable plaques. Circulating PAPP-A levels were significantly higher in patients with unstable angina or acute myocardial infarction than in patients with stable angina and controls (P<0.001). A PAPP-A threshold value of 10 mlU per liter identified patients who had acute coronary syndromes with a sensitivity of 89.2 percent and a specificity of 81.3 percent. PAPP-A levels correlated with levels of C-reactive protein and free IGF-I, but not with markers of myocardial injury (troponin I and the MB isoform of creatine kinase).

CONCLUSIONS

PAPP-A is present in unstable plaques, and circulating levels are elevated in acute coronary syndromes; these increased levels may reflect the instability of atherosclerotic plaques. PAPP-A is a new candidate marker of unstable angina and acute myocardial infarction.

Comparison of self-expanding and balloon-expandable stents for the reduction of restenosis

To compare the efficacy of self-expanding (SE) and balloon-expandable (BE) stents in native coronary arteries, we randomly assigned 1,096 patients with new and restenotic lesions to receive either device. Baseline demographics and coronary angiographic characteristics were similar in the 2 groups. The incidence of major adverse cardiac events including death, myocardial infarction, bypass surgery, and repeat intervention was similar for both groups at 1 month (2.9% vs 3.1% for SE vs BE, respectively) and at 9 months (19.3% vs 20.1%, SE vs BE respectively). In a subgroup of patients who underwent follow-up angiography (n = 250), the binary restenosis rates (24.2% vs 18.7%, p = 0.30), late loss (0.98 vs 94 mm, p = 0.60), and loss index (0.55 vs 55, p = 0.95) were not significantly different for both groups. In 62 patients who underwent intravascular ultrasound examination (IVUS), there was a trend toward a lower incidence of edge tears in the SE group (6% vs 23%, p = 0.06). Follow-up IVUS analysis showed that the minimum stent area of the SE stent increased by 33% at 6 months, whereas no change occurred in the BE stents; this was accompanied by a greater degree of intimal proliferation in the SE stents compared with BE stents (3.1 +/- 2.0 vs 1.7 +/- 1.7 mm(2)). Thus, the SE stents had similar clinical and angiographic outcomes in patients with lesions in native coronary arteries.

Pressure rinsing of coronary stents immediately before implantation reduces inflammation and neointimal hyperplasia

OBJECTIVES

This study evaluates whether rinsing stents with high pressure immediately before implantation minimizes stent-induced inflammation and neointimal formation.

BACKGROUND

Several reports indicate that manual stent manipulation before implantation results in foreign body contamination and increased neointimal hyperplasia.

METHODS

A stent-cleaning chamber was developed to rinse stents at a sustained hydrodynamic pressure of 4 atm for 10 s. Commercial pre-mounted stents were examined with different levels of manipulation: 1) untouched stents: no stent manipulation before implantation; 2) handled stents: manual stent re-crimping on the balloon; 3) rinsed stents: pressure-rinsed with the stent-cleaning chamber. In vitro surface analysis was evaluated by scanning electron microscopy. Neointimal hyperplasia and inflammation around stent struts were also assessed in the pig in-stent restenosis model.

RESULTS

In vitro analysis revealed fewer contaminants on rinsed stents compared with untouched (p = 0.01) and handled stents (p < 0.001). In vivo, neointimal thickness, neointimal area and vessel percent stenosis were significantly reduced in rinsed, compared with not-rinsed, stents (p = 0.002, p = 0.007, p = 0.008 respectively). In addition, a significant reduction in the inflammatory infiltrate around struts was observed in untouched, compared with handled, stents (p = 0.04) and in rinsed, compared with not-rinsed, stents (p < 0.001). Regression analysis accounting for injury and neointimal thickness showed significant differences in slopes between "handled + not-rinsed" and "handled + rinsed" stents (p = 0.004), and between "untouched + not-rinsed" and "untouched + rinsed stents" (p = 0.037).

CONCLUSIONS

Rinsing stents under high pressure immediately before coronary implantation results in less inflammation around struts and thinner neointima at 28 days in this pig model.

Long-term prognostic value of coronary calcification detected by electron-beam computed tomography in patients undergoing coronary angiography

BACKGROUND

Electron-beam CT (EBCT) quantification of coronary artery calcification (CAC) allows noninvasive assessment of coronary atherosclerosis. We undertook a follow-up study to determine whether CAC extent, measured at the time of angiography by EBCT, predicted future hard cardiac events, comprising cardiac death and nonfatal myocardial infarction (MI). We also assessed the potential of selected coronary artery disease (CAD) risk factors, prior CAD event history (MI or revascularization), and angiographic findings (number of diseased vessels and overall disease burden) to predict subsequent hard events.

METHODS AND RESULTS

Two hundred eighty-eight patients who underwent contemporaneous coronary angiography and EBCT scanning were contacted after a mean of 6.9 years. Vital status and history of MI during follow-up were determined. Cox proportional hazards models were used to compare the predictive ability of CAC extent with selected CAD risk factors, CAD event history, and angiographic findings. Median CAC score was 160 (range 0 to 7633). The 22 patients who experienced hard events during follow-up were older and had more extensive CAC and angiographic disease (P<0.05). Only 1 of 87 patients with CAC score <20 experienced a subsequent hard event during follow-up. Event-free survival was significantly higher for patients with CAC scores <100 than for those with scores >/=100 (relative risk 3.20; 95% CI 1.17 to 8.71). When a stepwise multivariable model was used, only age and CAC extent predicted hard events (risk ratios 1.72 and 1.88, respectively; P<0.05).

CONCLUSIONS

In patients undergoing angiography, CAC extent on EBCT is highly predictive of future hard cardiac events and adds valuable prognostic information.

Evaluation of the percutaneous intramyocardial injection for local myocardial treatment

Therapeutic angiogenesis requires the induction of new blood vessel formation for the treatment of peripheral vascular and coronary artery disease. Efficacious application of this new therapy requires optimizing multiple factors, including the therapeutic agent, dosing, frequency of administration, and delivery modality. In this study, a helical needle drug infusion catheter was applied for optimal application of percutaneous intramyocardial delivery (PIMD). (125)Iodine-labeled albumin was injected by PIMD into the left ventricle myocardium in eight swine. After 1 hr, PIMD resulted in a high concentration of radiolabel at the treatment site; 16.4% +/- 2.1% of delivered and 81.4% +/- 2.6% of the total cardiac activity was concentrated at the site of delivery. The depth of needle penetration correlated with the myocardial retention of delivered protein. The myocardial retention of radiolabel in animals with shallow injections was 10.1% +/- 0.8%, compared to 18.9% +/- 3.3% retention after deep injections. The specific activity at the treatment site (radioactive counts per gram of tissue) was 115 +/- 36, 226 +/- 55, and 47 +/- 10 times higher compared to liver, lung, and kidney, respectively. Continuous coronary sinus and aortic blood sampling indicates that within 15 min following intramyocardial injection, a significant amount of nonretained protein is found within the coronary sinus. This study defines some of the parameters that can affect optimal application of PIMD and demonstrates that PIMD is a safe and efficient method for local drug delivery.

Experimental hypercholesterolemia induces apoptosis in the aortic valve

BACKGROUND AND AIM OF THE STUDY

Aortic valve disease is presently the number one indication for valve replacement in the United States, yet its molecular mechanisms remain unknown. As apoptosis (programmed cell death) occurs in degenerative disease states, it was postulated that experimental hypercholesterolemia is associated with apoptosis in rabbit aortic valves.

METHODS

New Zealand White rabbits (n = 8) were fed a 1% cholesterol diet for 12 weeks; control rabbits (n = 8) were fed a normal diet. After sacrifice of the animals, the aortic valves were dissected. Apoptosis was identified in the valvular lesion by TdT-mediated dUTP-biotin nick end-labeling (TUNEL) technique, and confirmed with transmission electron microscopy. The number of apoptotic cells was measured by computed morphometry.

RESULTS

Valves from hypercholesterolemic rabbits showed an increase in apoptosis. TUNEL staining was identified in the atherosclerotic layer of hypercholesterolemic valves (0.1% of cells), but not in the cells of controls (p <0.0001).

CONCLUSION

Apoptosis is increased in rabbit aortic valves during experimental hypercholesterolemia. If fatal cellular degeneration occurs in hypercholesterolemic valve disease, these data suggest that apoptosis may play a role in the mechanism of valvular disease.

Effects of L-749,329, an ET(A)/ET(B) endothelin receptor antagonist, in a porcine coronary artery injury model of vascular restenosis

BACKGROUND

Previous studies in animal models of angioplasty have suggested a role in neointimal hyperplasia for endothelins (ETs), potent vasoconstricting peptides that also exert growth-promoting effects. The present studies were undertaken to test the hypothesis that endothelin receptor blockade can reduce neointimal thickening in injured porcine coronary arteries.

METHODS AND RESULTS

An ET(A)/ET(B) antagonist, L-749,329, was evaluated as an inhibitor of intimal thickening in a porcine balloon/stent model of coronary artery injury. L-749,329 competitively inhibited [(125)I]ET-1 binding to porcine ET(A) (IC(50) approximately 0.3 nmol/L) or ET(B) (IC(50) approximately 20 nmol/L) receptors and inhibited ET-1-stimulated signaling in cell culture. In anesthetized pigs, big ET-1-stimulated increases in systemic blood pressure were totally inhibited after intravenous infusion of L-749,329 (>/=0.2 mg. kg(-1). h(-1)). In vascular injury studies, pigs were treated with vehicle or L-749,329 (1 mg. kg(-1). h(-1)) beginning 2 days before and continuing 28 days after experimental angioplasty. Left anterior descending, left circumflex, and/or right coronary arteries were injured by inflation of an angioplasty balloon wrapped with a coiled metallic stent. After 28 days, mean neointimal thickness in the L-749,329-treated group was reduced by 9.0% compared with vehicle-treated controls, but this effect was not statistically significant (P=0.13).

CONCLUSIONS

Blockade of endothelin receptors for 28 days with only a mixed ET(A)/ET(B) receptor antagonist is insufficient to substantially inhibit intimal hyperplasia after balloon/stent coronary artery injury in the pig, in contrast to results with a selective ET(A) antagonist. The effects of selective or mixed ET(A)/ET(B) antagonists in diseased vessels remain to be determined in this model.

Long-term vessel response to a self-expanding coronary stent: a serial volumetric intravascular ultrasound analysis from the ASSURE Trial.A Stent vs. Stent Ultrasound Remodeling Evaluation

OBJECTIVES

We sought to investigate the in vivo mechanical properties of a new self-expanding coronary stent (RADIUS) and, particularly, the subsequent vessel response over time.

BACKGROUND

Preclinical studies have suggested that self-expanding stents may produce less vessel wall injury at initial deployment, leading to larger follow-up lumens than with balloon-expandable stents. However, the influence of the chronic stimulus from self-expanding stents on the vessel wall remains unknown.

METHODS

Sixty-two patients were randomly assigned to either the RADIUS self-expanding stent group (n = 32) or the Palmaz-Schatz balloon-expandable stent group (n = 30). Intravascular ultrasound was performed after stent deployment and at six-month follow-up.

RESULTS

At follow-up, the RADIUS stents had increased 23.6% in overall volume, while the Palmaz-Schatz stents had remained unchanged. Due to the greater mean neointimal area (3.0 +/- 1.7 mm2 vs. 1.9 +/- 1.2 mm2, p = 0.02) in the RADIUS group, no significant difference in net late lumen loss was observed between the two groups. On the other hand, analysis at the peristent margins demonstrated that mean late loss was significantly smaller in the RADIUS group than it was in the Palmaz-Schatz group (0.1 +/- 2.1 mm2 vs. 1.9 +/- 2.4 mm2, p = 0.02).

CONCLUSIONS

Serial volumetric IVUS revealed that the RADIUS stents continued to enlarge during the follow-up period. In this stent implantation protocol, this expansion was accompanied by a greater amount of neointima than the Palmaz-Schatz stents, resulting in similar late lumen loss in both configurations. In the peristent margins, however, late lumen loss was minimized with the RADIUS stents.

Coronary atherosclerosis in unheralded sudden coronary death under age 50: histo-pathologic comparison with 'healthy' subjects dying out of hospital

AIM

sudden coronary death (SCD) in older individuals is generally associated with extensive coronary atherosclerosis, although it may be the first manifestation of ischaemic heart disease. In younger age-groups, SCD may occur in the presence of less severe disease. We sought to (1) examine the extent of coronary atherosclerosis in young victims of SCD compared with age- and sex-matched controls, (2) analyse the composition of atherosclerotic plaques in these patients, (3) identify the predominant mechanism of SCD, and (4) evaluate the possibility of detecting this mechanism on the basis of morphologic plaque features, in particular presence and amount of lipid accumulation and calcific deposits.

METHODS AND RESULTS

coronary arteries were obtained at autopsy from 28 victims of SCD under age 50 with no prior clinical manifestation of ischaemic heart disease (IHD) and no myocardial scar formation and from 16 age- and sex-matched subjects dying of noncardiac causes out of hospital. Sections of all available major coronary arteries were cut in 5-mm intervals to yield a total of 1357 histologic sections, which were analysed using digitised planimetry. Victims of SCD had significantly more major coronary arteries per subject with luminal area narrowing > or = 75% than controls (on average, 2.1 vs. 0.2). Plaque area per histologic section was 5.1 +/- 2.1 mm(2) in SCD cases and 2.0 +/- 0.9 mm(2) in controls (P < 0.001). The major constituent of all plaques was fibrous tissue. Lipid core area per section was 0.49 +/- 0.59 mm(2) in SCD cases and 0.004 +/- 0.01 mm(2) in controls (P < 0.001), and calcified plaque area was 0.18 +/- 0.19 mm(2) in SCD cases and 0.02 +/- 0.05 mm(2) in controls (P < 0.001), both defining significant differences between SCD cases and controls. Arterial thrombosis, most often with underlying plaque rupture was the mechanism of SCD in > 80% of the cases. Considering histologic sections with > or = 50 and with > or = 75% area stenosis, plaque rupture was independently predicted by lipid core area. Calcific deposits were a frequent feature of plaque rupture but were only associated with it in univariate analysis.

CONCLUSIONS

the extent and severity of coronary atherosclerosis in young victims of SCD as the first manifestation of IHD was substantially greater than in age-and sex-matched controls and comparable with that previously reported in SCD cases with a broader age range. Lipid core and calcified plaque areas provided for excellent separation between the two groups, which may have implications for identifying persons at increased risk for SCD by non invasive visualisation and assessment of the coronary arteries.

Relationship of insulin sensitivity and ApoB levels to intra-abdominal fat in subjects with familial combined hyperlipidemia

Familial combined hyperlipidemia (FCHL) is one of the most common familial dyslipidemias associated with premature heart disease. Subjects with FCHL typically have elevated apolipoprotein B (apoB) levels, variable elevations in cholesterol and/or triglycerides, and a predominance of small, dense, low density lipoprotein particles. It is thought that insulin resistance is important in the expression of the combined hyperlipidemia phenotype. To further characterize the relationship between insulin resistance and increased apoB levels, 11 subjects from well-characterized FCHL families and normal control subjects matched for weight and/or age underwent measurement of intra-abdominal fat (IAF) and subcutaneous fat (SQF) by CT scan, insulin sensitivity (Si) by the frequently sampled intravenous glucose tolerance test, and lipoprotein levels. Body mass index and IAF were higher and Si was lower (more insulin resistant) in the FCHL group than in the age-matched group, but the values were similar in the FCHL group and the age- and weight-matched control group. When the relationship between body fat distribution and Si was tested with multiple linear regression, only IAF was significantly correlated with Si after the addition of SQF and body mass index as independent variables. For any level of insulin sensitivity or IAF, however, apoB levels remained higher in the FCHL subjects than in the control groups. In conclusion, in FCHL, visceral obesity is an important determinant of insulin resistance. Visceral obesity and insulin resistance, however, do not fully account for the elevated levels of apoB in this disorder, and this study provides physiological support for separate, but additive, genetic determinants in the etiology of the lipid phenotype.

New approaches to the pharmacological treatment of angina

The treatment of angina is changing, with many new agents being added to those existing agents that have been used for many years. New data regarding the use of glycoprotein IIb/IIIa inhibitors now exist and low molecular weight heparins are used more frequently with greater efficacy than unfractionated heparin. New thrombin inhibitors are also receiving a fresh look. An expert panel has recently published guidelines for the treatment of unstable angina.

Insulin-like growth factor binding protein-4 protease produced by smooth muscle cells increases in the coronary artery after angioplasty

Insulin-like growth factor (IGF)-I stimulates vascular smooth muscle cell (VSMC) migration and proliferation, which are fundamental to neointimal hyperplasia in postangioplasty restenosis. IGF-I action is modulated by several high-affinity IGF binding proteins (IGFBPs). IGFBP-4 is the predominant IGFBP produced by VSMCs and is a potent inhibitor of IGF-I action. However, specific IGFBP-4 proteases can cleave IGFBP-4 and liberate active IGF-I. In this study, we document IGFBP-4 protease produced by human and porcine coronary artery VSMCs in culture as pregnancy-associated plasma protein-A (PAPP-A). This was shown by a distinctive IGFBP-4 cleavage pattern, specific inhibition of IGFBP-4 protease activity with PAPP-A polyclonal antibodies, and immunorecognition of PAPP-A by monoclonal antibodies. Furthermore, we found a 2-fold increase in IGFBP-4 protease activity in injured porcine VSMC cultures in vitro (P<0.05). We also evaluated IGFBP-4 protease/PAPP-A expression in vivo after coronary artery balloon injury. Twenty-five immature female pigs underwent coronary overstretch balloon injury, and vessels were examined at defined time points after the procedure. Abundant PAPP-A expression was observed in the cytoplasm of medial and neointimal cells 7, 14, and 28 days after angioplasty (P<0.01 vs control). The highest PAPP-A labeling indices were located in the neointima (36.1+/-2.1%) and the media (31.7+/-1.2%) 28 days after injury. Western blot analysis confirmed increased PAPP-A in injured vessels. PAPP-A, a regulator of IGF-I bioavailability through proteolysis of IGFBP-4, is thus expressed by VSMCs in vitro and in restenotic lesions in vivo. These results suggest a possible role for PAPP-A in neointimal hyperplasia.

Increased oxidative stress in experimental renovascular hypertension

The pathophysiological mechanisms responsible for maintenance of chronic renovascular hypertension remain undefined. Excess angiotensin II generation may lead to release of reactive oxygen species and increased vasoconstrictor activity. To examine the potential involvement of oxidation-sensitive mechanisms in the pathophysiology of renovascular hypertension, blood samples were collected and renal blood flow measured with electron-beam computed tomography in pigs 5 and 10 weeks after induction of unilateral renal artery stenosis (n=7) or sham operation (n=7). Five weeks after procedure, plasma renin activity and mean arterial pressure were elevated in hypertensive pigs. Levels of prostaglandin F2alpha (PGF(2alpha))-isoprostanes, vasoconstrictors and markers of oxidative stress, also were significantly increased (157+/-21 versus 99+/-16 pg/mL; P<0.05) and correlated with both plasma renin activity (r=0.83) and arterial pressure (r=0.82). By 10 weeks, plasma renin activity returned to baseline but arterial pressure remained elevated (144+/-10 versus 115+/-5 mm Hg; P:<0.05). Isoprostane levels remained high and still correlated directly with the increase in arterial pressure (r=0.7) but not with plasma renin activity. Stenotic kidney blood flow was decreased at both studies. In shock-frozen cortical tissue, ex vivo endogenous intracellular radical scavengers were significantly decreased in both kidneys. The present study demonstrates, for the first time, that in early renovascular hypertension, an increase in plasma renin activity and arterial pressure is associated with increased systemic oxidative stress. When plasma renin activity later declines, PGF(2alpha)-isoprostanes remain elevated, possibly due to local activation or slow responses to angiotensin II, and may participate in sustenance of arterial pressure. Moreover, oxidation-sensitive mechanisms may influence ischemic and hypertensive parenchymal renal injury.

Obesity, body fat distribution, insulin sensitivity and Islet beta-cell function as explanations for metabolic diversity

Studies of metabolic processes have been enhanced by our understanding of the relationships among obesity, body fat distribution, insulin sensitivity and islet beta-cell function. Thus, we have learned that although insulin resistance is usually associated with obesity, even lean subjects can be insulin resistant due to the accumulation of visceral fat. Insulin sensitivity and beta-cell function are also intimately linked. The hyperbolic relationship between these two parameters explains why insulin-resistant individuals have markedly enhanced insulin responses, whereas subjects who are insulin sensitive exhibit very low responses. Failure to take into account this relationship will lead to erroneous conclusions. By accounting for this important interaction, it has been clearly demonstrated that subjects at high risk of developing type 2 diabetes (older individuals, women with a history of gestational diabetes or polycystic ovary syndrome, subjects with impaired glucose tolerance and first-degree relatives of individuals with type 2 diabetes) have impaired beta-cell function. Furthermore, the progression from normal glucose tolerance to impaired glucose tolerance and type 2 diabetes is associated with declining insulin secretion.