Evaluation of platelet reactivity during combined antiplatelet therapy in patients with stable coronary artery disease in relation to diabetes type 2 and the GPIIB/IIIA receptor gene polymorphism.

Antiplatelet therapy resistance against acetylsalicylic acid (ASA) and/or clopidogrel in coronary heart disease (CHD) is common with diabetes mellitus. One factor might involve platelet receptor ITGB3 gene polymorphism. We aimed to assess resistance together with platelet reactivity parameters, the polymorphism, plus diabetes type 2 coexistence. The study included 185 patients with CHD, including 58 diabetics, aged 62.3 ± 8.2 years. Patients were treated long-term with ASA, plus clopidogrel, both 75 mg/d. Platelet aggregation was measured with arachidonic acid (ASPI test; ASA-response assessment) or ADP (ADP test; clopidogrel-response assessment). Thromboxane B2 (TXB2) and fibrinogen concentrations were measured and ITGB3 PIA1>A2 variants identified. Increases in PLT, glucose and SBP were demonstrated with dual resistance or to clopidogrel. Regardless of response, diabetics (versus non-diabetics) had elevated platelet aggregation with the ADP test (P = 0.0198), higher TXB2 (P = 0.0501), BMI (P = 0.0003) and SBP (P = 0.0627). ITGB3 PIA1/A1 homozygotes had higher platelet aggregation with the ASPI test (P = 0.0513), and fibrinogen concentrations (P = 0.0133), relative to A2 allele carriers. Significant associations of diabetes with clopidogrel resistance (P = 0.0011) and PIA1/A1 homozygotes with ASA resistance (P = 0.0518) were found. Higher concentrations of TXB2 (P = 0.0223) and higher SBP (P = 0.0063) were found with diabetes (versus non-diabetic) in PIA1/A1 homozygotes. We concluded that diabetes with CHD weakens response to antiplatelet drugs, especially to clopidogrel; and hyperglycaemia, hypertension and obesity might also play an important role. Diabetics' resistance to ASA is associated with increased platelet reactivity, perhaps related to the more frequent ITGB3 PIA1 allele and increased TXB2 generation. The PIA1 allele may be a potential factor for aspirin resistance with elevated fibrinogen concentration.

Variable gender-dependent platelet responses to combined antiplatelet therapy in patients with stable coronary-artery disease.

Antiplatelet therapy is considered as a standard procedure against atherosclerotic cardiovscular disease but this therapy has limited effect if resistance to acetylsalicylic acid or clopidogrel is present. Important factors associated with resistance are gender; or inflammation possibly associated with membrane microparticles (MP). It was decided to challenge the hypothesis that differential responses to dual antiplatelet therapy are conditioned by gender and/or proinflammatory status. The study involved 160 patients with stable coronary heart disease (118 men, 42 women) aged 65.2 ± 7.8 years. Patients were treated long-term with acetylsalicylic acid (ASA); plus clopidogrel starting 6 days before percutaneous coronary intervention (both 75 mg/day). Response was evaluated using platelet aggregation with either arachidonic acid (the ASPI test; predominantly for ASA response) or adenosine diphosphate (the ADP test; predominantly for clopidogrel response). MP levels were measured as follows: total (MP-total); with TF expression (MP-TF); or platelet-derived microparticles (PDMP), as well as proinflammatory parameters: C-reactive protein (CRP), leukocytes (WBC) and platelet numbers (PLT). Analysis of platelet-aggregation levels with regard to gender revealed higher aggregation in women: with resistance to ASA (ASPI test: P = 0.0383, ADP test: P = 0.0027); resistance to clopidogrel (ASPI test: P = 0.0003; ADP test: P = 0.0566) and with sensitivity to both drugs with the ADP test (P = 0.0190). In women relative to men, regardless of response, significantly higher CRP (P = 0.0012), WBC (P = 0.0244) and PLT numbers (P = 0.0001) were found. In contrast, in men significantly higher concentrations of MP-TF (P = 0.0286) and triglycerides (P = 0.0296) were found in the clopidogrel-resistant group. We conclude that women have an inferior response to dual antiplatelet therapy relative to men, possibly associated with higher platelet reactivity (especially when measured with the ADP test), with a more accentuated proinflammatory status. In contrast, among the factors supporting the resistance in men can be an elevated concentration of MP-TF which, together with the coexistence of hypertriglyceridemia, may constitute an important mechanism of resistance to clopidogrel.

Tree water balance drives temperate forest responses to drought.

Intensifying drought is increasingly linked to global forest diebacks. Improved understanding of drought impacts on individual trees has provided limited insight into drought vulnerability in part because tree moisture access and depletion is difficult to quantify. In forests, moisture reservoir depletion occurs through water use by the trees themselves. Here, we show that drought impacts on tree fitness and demographic performance can be predicted by tracking the moisture reservoir available to trees as a mass balance, estimated in a hierarchical state-space framework. We apply this model to multiple seasonal droughts with tree transpiration measurements to demonstrate how species and size differences modulate moisture availability across landscapes. The depletion of individual moisture reservoirs can be tracked over the course of droughts and linked to biomass growth and reproductive output. This mass balance approach can predict individual moisture deficit, tree demographic performance, and drought vulnerability throughout forest stands based on measurements from a sample of trees.

Quantifying global soil carbon losses in response to warming.

The majority of the Earth's terrestrial carbon is stored in the soil. If anthropogenic warming stimulates the loss of this carbon to the atmosphere, it could drive further planetary warming. Despite evidence that warming enhances carbon fluxes to and from the soil, the net global balance between these responses remains uncertain. Here we present a comprehensive analysis of warming-induced changes in soil carbon stocks by assembling data from 49 field experiments located across North America, Europe and Asia. We find that the effects of warming are contingent on the size of the initial soil carbon stock, with considerable losses occurring in high-latitude areas. By extrapolating this empirical relationship to the global scale, we provide estimates of soil carbon sensitivity to warming that may help to constrain Earth system model projections. Our empirical relationship suggests that global soil carbon stocks in the upper soil horizons will fall by 30 ± 30 petagrams of carbon to 203 ± 161 petagrams of carbon under one degree of warming, depending on the rate at which the effects of warming are realized. Under the conservative assumption that the response of soil carbon to warming occurs within a year, a business-as-usual climate scenario would drive the loss of 55 ± 50 petagrams of carbon from the upper soil horizons by 2050. This value is around 12-17 per cent of the expected anthropogenic emissions over this period. Despite the considerable uncertainty in our estimates, the direction of the global soil carbon response is consistent across all scenarios. This provides strong empirical support for the idea that rising temperatures will stimulate the net loss of soil carbon to the atmosphere, driving a positive land carbon-climate feedback that could accelerate climate change.

Spatial differences of matrix metalloproteinase-2 and matrix metalloproteinase-9 within abdominal aortic aneurysm wall and intraluminal thrombus.

Formation of an abdominal aortic aneurysm is a complex process involving aortic wall degradation. The matrix metalloproteinases (MMPs) mainly involved in this process are MMP-2 and MMP-9. Most aneurysms contain an intraluminal thrombus. It is suggested that the thrombus' thickness correlates with the risk of aneurysm rupture and may be a new prognostic factor. The purpose of the present study was to investigate enzyme protein levels in thick (A1) and thin (B1) segments of the thrombus and aneurysm wall sections A (adjacent to A1) and B (adjacent to B1). Aneurysm samples from one aneurism sac were collected from 36 patients that underwent aneurysm repair. MMP-2, MMP-9 and a tissue inhibitor of metalloproteinases (TIMP-1) were measured using enzyme-linked-immunosorbent assay of protein extract. MMP-9 concentrations were significantly higher in B1 samples compared with A1 (113.4 ± 118.0 versus 63.0 ± 61.2, P = 0.004), A(113.4 ± 118.0 versus 31.7 ± 30.0, P < 0.001) or B (113.4 ± 118.0 versus 39.5 ± 41.5, P < 0.001). Likewise MMP-9/TIMP-1 ratio was elevated in B1 compared with A1 (18.9 ± 27.8 versus 9.1 ± 10.6, P = 0.017), A (18.9 ± 27.8 versus 2.5 ± 2.2, P < 0.001) or B (18.9 ± 27.8 versus 3.6 ± 4.5, P < 0.001). MMP-2 and TIMP-1 were higher in A compared with A1 (18.4 ± 8.5 versus 7.2 ± 7.6, P < 0.001; 14.3 ± 5.9 versus 8.5 ± 5.4, P < 0.001, respectively) and B1 (18.4 ± 8.5 versus 5.2 ± 2.9, P < 0.001; 14.3 ± 5.9 versus 8.9 ± 4.9, P < 0.001, respectively) as well as in B compared with A1 (15.9 ± 7.3 versus 7.2 ± 7.6, P < 0.001; 13.0 ± 5.0 versus 8.5 ± 5.4, P < 0.001, respectively) and B1 (15.9 ± 7.3 versus 5.2 ± 2.9, P < 0.001; 13.0 ± 5.0 versus 8.9 ± 4.9, P = 0.003, respectively). There were significant correlations between thin thrombus TIMP-1 and thrombus thickness (ß = -0.24, P = 0.021) and between thin thrombus MMP-9/TIMP-1 ratio and thrombus thickness (ß = 1.75, P = 0.003). Our study has revealed that the presence of thrombi with thin segments in the aneurysm sac, associated with higher proteolytic activity, could possibly be used as a potential indicator of a rupture site.

Possible counter effect in newborns of 1936A>G (I646V) polymorphism in the AKAP10 gene encoding A-kinase-anchoring protein 10.

OBJECTIVE: Cyclic adenosine monophosphate/protein kinase A (PKA) is important in embryonic development. The human AKAP10 gene is polymorphic: 1936A>G results in changes to a PKA-binding domain and increased targeting to mitochondria. Previous studies found G1936 as 'deleterious' in adults, and this study investigates whether this holds true in preterm birth. STUDY DESIGN: Study group consisted of 80 preterm newborns (PTNs) born before the 38th gestation week. Control group consisted of 123 full-term healthy newborns born after the 37th gestation week with uncomplicated pregnancies. Genomic DNA was extracted from umbilical blood and AKAP10 genotypes were identified by PCR/restriction enzyme. RESULT: Significant differences in frequencies of 1936A>G genotypes/alleles between both groups were found. PTNs had increased frequency (55%) of AA homozygotes (odds ratio, AA versus AG+GG: 2.63 (95% confidence interval: 1.33 to 5.20), P=0.006) after adjustments: mothers with previous PTNs, smoking, first pregnancy, first delivery and Cesarean section. CONCLUSION: Results suggest G1936 is preventative factor against preterm birth, in contrast with previously asserted negative effects in adults.

Computer based medication error reporting: insights and implications.

BACKGROUND: Despite the growing use of error reporting tools, the healthcare industry is inexperienced in receiving, understanding, and analyzing these reports. OBJECTIVE: To assess the accuracy and define the epidemiology of medication error reports. DESIGN, SETTING, AND PATIENTS: A retrospective cohort study of 581 error reports containing 1010 medication errors reported between July 2001 and January 2003 at a large academic children's institution. MAIN OUTCOME MEASURES: Correct classification and types of medication errors. RESULTS: Of the 1010 medication errors reviewed, 298 (30%) were prescribing errors, 245 (24%) were dispensing errors, 410 (41%) were administration errors, and 57 (6%) involved medication administration records (MAR). Following expert review, 208 errors (21%) were deleted because they had been inappropriately coded as errors and 97 (10%) were added as they were not initially coded despite having occurred. In addition, 352 medication error reports needed to have the subtype of error reclassified; 207 (59%) of these involved the reporter choosing the non-descript "other" category on the reporting tool (such as "Prescribing other") which was able to be reclassified by expert review. The overall distribution of error type categories did not change significantly with expert review, although only MAR errors were underreported by the reporters. The most common medications were anti-infectives (17%), pain/sedative agents (15%), nutritional agents (11%), gastrointestinal agents (8%), and cardiovascular agents (7%). CONCLUSIONS: Despite clear imperfections in the data captured, medication error reporting tools are effective as a means of collecting reliable information on errors rapidly and in real time. Our data suggest that administration errors are at least as common as prescribing errors in children. Further research is needed, not only in the area of computerized physician order entry (CPOE) for children, but also on ways to make the dispensing and administration of medications safer.

Fire cycles in North American interior grasslands and their relation to prairie drought.

High-resolution analyses of a late Holocene core from Kettle Lake in North Dakota reveal coeval fluctuations in loss-on-ignition carbonate content, percentage of grass pollen, and charcoal flux. These oscillations are indicative of climate-fuel-fire cycles that have prevailed on the Northern Great Plains (NGP) for most of the late Holocene. High charcoal flux occurred during past moist intervals when grass cover was extensive and fuel loads were high, whereas reduced charcoal flux characterized the intervening droughts when grass cover, and hence fuel loads, decreased, illustrating that fire is not a universal feature of the NGP through time but oscillates with climate. Spectral and wavelet analyses reveal that the cycles have a periodicity of approximately = 160 yr, although secular trends in the cycles are difficult to identify for the entire Holocene because the periodicity in the early Holocene ranged between 80 and 160 yr. Although the cycles are evident for most of the last 4,500 yr, their occasional muting adds further to the overall climatic complexity of the plains. These findings clearly show that the continental interior of North America has experienced short-term climatic cycles accompanied by a marked landscape response for several millennia, regularly alternating between dual landscape modes. The documentation of cycles of similar duration at other sites in the NGP, western North America, and Greenland suggests some degree of regional coherence to climatic forcing. Accordingly, the effects of global warming from increasing greenhouse gases will be superimposed on this natural variability of drought.

Use of the Bard Memotherm self-expanding metal stent in the palliation of colonic obstruction.

BACKGROUND: Self-expanding metal stents (SEMS) are a recognized means of palliating large bowel obstruction due to colonic neoplasia. The literature mainly relates to the use of modified esophageal stents (expanded diameter, 18-22 mm) in the colorectum. Stent migration has been a common complication and may be related to expanded stent diameter. This series reports our experience with the Memotherm Colorectal SEMS (expanded diameter, 25-30 mm). METHODS: Prospective data were collected from February 1999 to September 2000. Sixteen patients (age range = 61-99 years) were considered for the Memotherm Colorectal SEMS. Stents were inserted radiologically under fluoroscopic control. Outcome was classified as a technical success (stent in correct position and expanded) and a clinical success (colon decompressed, symptoms relieved, and bowels working). RESULTS: Thirteen cases (81%) underwent successful SEMS placement. These were technically and clinically successful. Two cases required insertion of two overlapping stents to traverse long strictures. Three unsuccessful cases were emergency presentations in which a guidewire could not be passed across the lesion. Two of these were due to benign strictures and the third to extrinsic compression by ovarian carcinoma. CONCLUSION: In our experience, the Memotherm Colorectal SEMS was easy to use, was effective in the palliation of obstructing colorectal carcinoma, and appeared to reduce the risk of stent migration.

Chromosome 2 reciprocal congenic strains to evaluate the effect of the genetic background on blood pressure.

The localisation of quantitative trait loci (QTL) is the first step towards gene identification. This is then verified by the construction of reciprocal congenic strains. The hypertensive SHRSP and normotensive WKY strains were used in a speed congenic approach to confirm the existence of a QTL on rat chromosome 2. Systolic baseline and salt loaded blood pressures were measured by radiotelemetry. Transfer of the chromosome 2 blood pressure QTL region from WKY into an SHRSP background significantly reduced blood pressure, with the increased significance at the salt loaded period, compared to the SHRSP. The reciprocal congenic blood pressure showed a significantly increased baseline systolic pressure compared to the WKY, with no change in significance at the salt loaded period. Thus we have successfully captured a gene(s) which contribute to blood pressure regulation in both congenic strains. This will facilitate further positional cloning of the causative genes first in this model and then in human essential hypertension.

Diels-Alder adducts of medium-ring carbocyclic dienes prepared by rearrangement of catalytically generated cyclic oxonium ylides.

The novel bicyclic and tricyclic systems dimethyl (4aS*,6S*)-6-methoxy-7-oxo-4a,5,6,7,8,9-hexahydro-2H-benzocycloheptene-3,4-dicarboxylate, C(16)H(20)O(6), (I), dimethyl (4aS*,6R*)-6-methoxy-7-oxo-4a,5,6,7,8,9-hexahydro-2H-benzocycloheptene-3,4-dicarboxylate, C(16)H(20)O(6), (II), (3aS*,9R*,10aS*,10bR*)-9-methoxy-2-oxa-1,3a,4,6,7,8,9,10,10a,10b-decahydro-3H-cyclohepta[e]indene-1,3,8-trione, C(14)H(16)O(5), (III), and (1S*,2R*,9S*,10aR*)-9-methoxy-8-oxo-1,2,3,5,6,7,8,9,10,10a-decahydrobenzocyclooctene-1,2-dicarboxylic acid, C(15)H(20)O(6), (IV), have been crystallographically characterized, allowing the determination of the relative configuration of the stereogenic centres. The poor quality of the dicarboxylic acid crystals necessitated the use of synchrotron radiation.

Ecological forecasts: an emerging imperative.

Planning and decision-making can be improved by access to reliable forecasts of ecosystem state, ecosystem services, and natural capital. Availability of new data sets, together with progress in computation and statistics, will increase our ability to forecast ecosystem change. An agenda that would lead toward a capacity to produce, evaluate, and communicate forecasts of critical ecosystem services requires a process that engages scientists and decision-makers. Interdisciplinary linkages are necessary because of the climate and societal controls on ecosystems, the feedbacks involving social change, and the decision-making relevance of forecasts.

Mapping and sequencing rat dishevelled-1: a candidate gene for cerebral ischaemic insult in a rat model of stroke.

A quantitative trait locus on chromosome 5 in the rat is linked to sensitivity to brain ischemia in the stroke-prone spontaneously hypertensive rat (SHRSP). The genes encoding atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) that map to this location have been excluded as candidate genes. We examined dishevelled-1 (DVL-1) as a further candidate gene. DVL-1 had not yet been identified in the rat, but Anp, Bnp, and DVL-1 map to the homologous regions of the rat chromosome 5 quantitative trait locus in both mice and man. Furthermore, DVL-1 is involved in the Notch signalling system, which plays a role in the disorder cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, the symptoms of, which include ischaemic stroke. We show with radiation hybrid mapping that rat DVL-1 indeed maps to chromosome 5, where it is positioned immediately next to microsatellite marker D5Rat49. We sequenced the complete coding sequence and a large part of the intronic genomic sequence for the SHRSP strain and its reference Wistar-Kyoto strain. The DVL-1 sequence in the two strains was identical. Our results essentially exclude the DVL-1 gene as the cause for sensitivity to cerebral ischaemic insult in this rat model of stroke.

Rising CO2 levels and the fecundity of forest trees.

We determined the reproductive response of 19-year-old loblolly pine (Pinus taeda) to 4 years of carbon dioxide (CO2) enrichment (ambient concentration plus 200 microliters per liter) in an intact forest. After 3 years of CO2 fumigation, trees were twice as likely to be reproductively mature and produced three times as many cones and seeds as trees at ambient CO2 concentration. A disproportionate carbon allocation to reproduction under CO2 enrichment results in trees reaching maturity sooner and at a smaller size. This reproductive response to future increases in atmospheric CO2 concentration is expected to change loblolly dispersal and recruitment patterns.

Reciprocal consomic strains to evaluate y chromosome effects.

We have previously demonstrated that the SHRSP Y chromosome contains a locus that contributes to hypertension in SHRSP/WKY F2 hybrids and that SHRSP exhibit an increased vulnerability to focal cerebral ischemia after permanent middle cerebral artery occlusion (MCAO). This increased vulnerability is inherited as a codominant trait, and a putative role for the Y chromosome has been suggested in F1 hybrids. The objective of this study was to investigate further the role of Y chromosome in blood pressure (BP) regulation and in the vulnerability to cerebral ischemia. We have constructed consomic strains by selectively replacing the Y chromosome from WKY rats with that of SHRSP, and vice versa, by using a marker-assisted breeding strategy. Permanent MCAO was carried out by electrocoagulation, with infarct volume expressed as a percentage of the ipsilateral hemisphere. Systolic blood pressure was measured by radiotelemetry during a baseline period of 5 weeks followed by a 3-week period of salt loading. We observed that the transfer of the Y chromosome from WKY onto SHRSP background significantly reduced systolic BP in consomic strains, SP.WKYGlaY(w) (n=6) versus SHRSP (n=6) (209.2+/-10.4 mm Hg versus 241.7+/-7.7 mm Hg, F=5.88, P=0.038) during the salt-loading period. In the reciprocal consomic strain, WKY.SPGlaY(s) (n=5), systolic BP was increased compared with WKY parental strain (n=6) (147.6+/-2.4 mm Hg versus 132.6+/-5.1 mm Hg, F=6.11, P=0.035) during baseline. Infarct volumes in consomic strains were not significantly different from their respective parental strain: WKY.SPGlaY(s) (n=7) versus WKY (n=7), 22.8+/-3.7% versus 22.2+/-8.0%, 95% CI=-12.7, 4.2, P=0.3; SP.WKYGlaY(w) (n=7) versus SHRSP (n=6), 37.7+/-4.4% versus 33.6+/-7.6%, 95% CI=-20.3, 12.1, P=0.5. We conclude that the SHRSP Y chromosome harbors a locus contributing to systolic BP, whereas no contribution to vulnerability to cerebral ischemia can be detected.

Invasion by extremes: population spread with variation in dispersal and reproduction.

For populations having dispersal described by fat-tailed kernels (kernels with tails that are not exponentially bounded), asymptotic population spread rates cannot be estimated by traditional models because these models predict continually accelerating (asymptotically infinite) invasion. The impossible predictions come from the fact that the fat-tailed kernels fitted to dispersal data have a quality (nondiscrete individuals and, thus, no moment-generating function) that never applies to data. Real organisms produce finite (and random) numbers of offspring; thus, an empirical moment-generating function can always be determined. Using an alternative method to estimate spread rates in terms of extreme dispersal events, we show that finite estimates can be derived for fat-tailed kernels, and we demonstrate how variable reproduction modifies these rates. Whereas the traditional models define spread rate as the speed of an advancing front describing the expected density of individuals, our alternative definition for spread rate is the expected velocity for the location of the furthest-forward individual in the population. The asymptotic wave speed for a constant net reproductive rate R0 is approximated as (1/T)(piuR)/2)(1/2) m yr(-1), where T is generation time, and u is a distance parameter (m2) of Clark et al.'s 2Dt model having shape parameter p = 1. From fitted dispersal kernels with fat tails and infinite variance, we derive finite rates of spread and a simple method for numerical estimation. Fitted kernels, with infinite variance, yield distributions of rates of spread that are asymptotically normal and, thus, have finite moments. Variable reproduction can profoundly affect rates of spread. By incorporating the variance in reproduction that results from variable life span, we estimate much lower rates than predicted by the standard approach, which assumes a constant net reproductive rate. Using basic life-history data for trees, we show these estimated rates to be lower than expected from previous analytical models and as interpreted from paleorecords of forest spread at the end of the Pleistocene. Our results suggest reexamination of past rates of spread and the potential for future response to climate change.

DNA synthesis and apoptosis in smooth muscle cells from a model of genetic hypertension.

The present study was designed to assess vascular smooth muscle cell (VSMC) proliferation and apoptosis in primary cultured VSMCs prepared from the aortic tunica media of adult (4 to 5 months old) age- and gender-matched groups of stroke-prone spontaneously hypertensive rats (SHRSP) and the normotensive reference strain, Wistar-Kyoto (WKY) rats. In the present study, VSMC proliferation was assessed with measurement of DNA synthesis in response to stimulation of G(0)/G(1) arrested VSMCs with 10% serum, whereas apoptosis was measured in response to serum deprivation. Apoptosis in aortic VSMCs was assessed in vitro with the technique of Annexin V binding in combination with propidium iodide exclusion with bivariate flow cytometric analysis. The percentage of necrotic VSMCs in the cell populations was assessed simultaneously. The light-scattering properties of the cells were assessed to provide further information on cell shrinkage and chromatin condensation. Results of the present study have shown enhanced DNA synthesis in VSMCs from SHRSP (n=10; 5.2+/-0.9 cpmx10(3)/mg protein) compared with WKY (n=12; 2.4+/-0.7 cpmx10(3) /mg protein; P<0.05, 95% CI, -5271 to -296). In addition, the results of the present study have demonstrated the role of serum in the survival of VSMCs in vitro, because SHRSP VSMCs underwent significantly more apoptosis in response to insult by serum deprivation (n=13; 10.21+/-1.8%) than WKY VSMCs (n=7; 3.44+/-1.4%; P<0.01, 95% CI, -11.5 to -2.0). Thus, it appears that both proliferation and apoptosis are enhanced in synthetic phenotype aortic medial VSMCs from the SHRSP in vitro.

Genes and hypertension: from gene mapping in experimental models to vascular gene transfer strategies.

Human essential hypertension is a complex, multifactorial, quantitative trait under a polygenic control. Several strategies have been developed over the last decade to dissect genetic determinants of hypertension. Of these, the most successful have been studies that identified rare mendelian syndromes in which a single gene mutation causes high blood pressure. The attempts to identify multiple genes, each with a small contribution to the common polygenic form of hypertension, have been less successful. Several laboratories focused their attention on rat models of genetic hypertension, which can be considered as a reductionist paradigm for human disease. Using numerous crosses between hypertensive and normotensive strains, investigators identified several quantitative trait loci (QTL) for blood pressure subphenotypes and for cardiovascular complications such as left ventricular hypertrophy, kidney failure, stroke, and insulin resistance. Furthermore, congenic strains have been produced to confirm the existence of some of these QTL and to narrow down the chromosomal regions of interest. A number of interesting strategies have been developed, including a "speed" congenic strategy perfected by our group in Glasgow. However, the limit of congenic strategy is estimated at 1 cM, which corresponds to 2x10(6) base pairs of DNA and approximately 50 candidate genes. It is envisaged that gene expression profiling with cDNA microarrays might allow a quick progression toward the gene identification within cardiovascular QTL. In parallel experimental effort, several laboratories have been developing gene transfer/therapy strategies with adenoviral or adeno-associated viral vectors used, for example, to overexpress protective vascular genes such as vascular endothelial growth factor or endothelial nitric oxide synthase. It is anticipated that further developments in positional cloning of susceptibility and severity genes in hypertension and its complications will lead to a direct transfer of these discoveries to essential hypertension in humans and will ultimately produce novel targets for local and systemic gene therapy in cardiovascular disease.

Applicability of a "speed" congenic strategy to dissect blood pressure quantitative trait loci on rat chromosome 2.

The identification of any quantitative trait locus (QTL) via a genome scan is only the first step toward the ultimate goal of gene identification. The next step is the production of congenic strains by which the existence of a QTL may be verified and the implicated chromosomal region be reduced to a size applicable to positional cloning of the causal gene. We used a speed congenic breeding protocol previously verified in mice for 2 blood pressure QTLs on rat chromosome 2. Four congenic strains were produced through introgression of various segments of chromosome 2 from Wistar-Kyoto rats from Glasgow colonies [WKY((Gla)) rats] into the recipient stroke-prone spontaneously hypertensive rats from Glasgow colonies [SHRSP((Gla))], and vice versa. The number of backcross generations required for each strain to achieve complete homozygosity at 83 background genetic markers in a "best" male varied between 3 and 4. Transfer of the region of rat chromosome 2 containing both QTLs from WKY((Gla)) into an SHRSP((Gla)) genetic background lowered both baseline and salt-loaded systolic blood pressure by approximately 20 and approximately 40 mm Hg in male congenic rats compared with the SHRSP parental strain (F=53.4, P<0.005; F=28.0, P< 0.0005, respectively). In contrast, control animals for stowaway heterozygosity presented no deviation from the blood pressure values recorded for the SHRSP((Gla)), indicating that if such heterozygosity exists, its effect on blood pressure is negligible. A reciprocal strategy in which 1 or both QTLs on rat chromosome 2 were transferred from SHRSP((Gla)) into a WKY((Gla)) genetic background resulted in statistically significant but smaller blood pressure increases for 1 of these QTLs. These results confirm the existence of blood pressure QTLs on rat chromosome 2 and demonstrate the applicability of a speed congenic strategy in the rat and emphasize the important role of the genetic background.