Genome-wide association study of NMDA receptor coagonists in human cerebrospinal fluid and plasma.

The N-methyl-D-aspartate receptor (NMDAR) coagonists glycine, D-serine and L-proline play crucial roles in NMDAR-dependent neurotransmission and are associated with a range of neuropsychiatric disorders. We conducted the first genome-wide association study of concentrations of these coagonists and their enantiomers in plasma and cerebrospinal fluid (CSF) of human subjects from the general population (N=414). Genetic variants at chromosome 22q11.2, located in and near PRODH (proline dehydrogenase), were associated with L-proline in plasma (ß=0.29; P=6.38 × 10(-10)). The missense variant rs17279437 in the proline transporter SLC6A20 was associated with L-proline in CSF (ß=0.28; P=9.68 × 10(-9)). Suggestive evidence of association was found for the D-serine plasma-CSF ratio at the D-amino-acid oxidase (DAO) gene (ß=-0.28; P=9.08 × 10(-8)), whereas a variant in SRR (that encodes serine racemase and is associated with schizophrenia) constituted the most strongly associated locus for the L-serine to D-serine ratio in CSF. All these genes are highly expressed in rodent meninges and choroid plexus, anatomical regions relevant to CSF physiology. The enzymes and transporters they encode may be targeted to further construe the nature of NMDAR coagonist involvement in NMDAR gating. Furthermore, the highlighted genetic variants may be followed up in clinical populations, for example, schizophrenia and 22q11 deletion syndrome. Overall, this targeted metabolomics approach furthers the understanding of NMDAR coagonist concentration variability and sets the stage for non-targeted CSF metabolomics projects.

Genome-wide association study of monoamine metabolite levels in human cerebrospinal fluid.

Studying genetic determinants of intermediate phenotypes is a powerful tool to increase our understanding of genotype-phenotype correlations. Metabolic traits pertinent to the central nervous system (CNS) constitute a potentially informative target for genetic studies of intermediate phenotypes as their genetic underpinnings may elucidate etiological mechanisms. We therefore conducted a genome-wide association study (GWAS) of monoamine metabolite (MM) levels in cerebrospinal fluid (CSF) of 414 human subjects from the general population. In a linear model correcting for covariates, we identified one locus associated with MMs at a genome-wide significant level (standardized ß=0.32, P=4.92 × 10(-8)), located 20 kb from SSTR1, a gene involved with brain signal transduction and glutamate receptor signaling. By subsequent whole-genome expression quantitative trait locus (eQTL) analysis, we provide evidence that this variant controls expression of PDE9A (ß=0.21; P unadjusted=5.6 × 10(-7); P corrected=0.014), a gene previously implicated in monoaminergic transmission, major depressive disorder and antidepressant response. A post hoc analysis of loci significantly associated with psychiatric disorders suggested that genetic variation at CSMD1, a schizophrenia susceptibility locus, plays a role in the ratio between dopamine and serotonin metabolites in CSF. The presented DNA and mRNA analyses yielded genome-wide and suggestive associations in biologically plausible genes, two of which encode proteins involved with glutamate receptor functionality. These findings will hopefully contribute to an exploration of the functional impact of the highlighted genes on monoaminergic transmission and neuropsychiatric phenotypes.

Prognostic significance of presenting blood pressure in non-ST-segment elevation acute coronary syndrome in relation to prior history of hypertension.

BACKGROUND: Hypertension is a well-established risk factor for cardiovascular disease, whereas low systolic blood pressure (SBP) is a powerful adverse prognosticator in acute coronary syndrome. However, it is unclear whether the prognostic significance of low SBP differs in patients with versus without prior history of hypertension. We sought to investigate the relationships between presenting SBP, prior hypertension, antihypertensive medication use, and outcomes in non-ST-segment elevation acute coronary syndrome (NSTEACS). METHODS: Using data from GRACE/GRACE(2) and CANRACE, we stratified 10,337 patients with NSTEACS from 1999 to 2008 into 2 groups: those with and those without prior diagnosis of hypertension. We performed multivariable logistic regression analysis to assess the prognostic significance of prior hypertension on in-hospital mortality and tested for the interactions between prior hypertension, antihypertensive medication use, and presenting SBP. RESULTS: Compared with patients without prior hypertension (n = 3,732), those with prior hypertension (n = 6,605) were older; more likely to be female; and more frequently had diabetes, previous myocardial infarction, heart failure, renal insufficiency, and higher Killip class and GRACE risk scores on presentation. Patients with prior hypertension were more likely to be on antihypertensive medications before admission, to present with higher SBP, and to have heart failure or cardiogenic shock in hospital (6.0% vs 10.1%; P < .001). In-hospital mortality was higher among patients presenting with lower SBP but did not differ between the groups with and without prior hypertension. In multivariable analysis, neither prior hypertension (adjusted odds ratio = 1.15, 95% CI 0.78-1.70, P = .48) nor the number of antihypertensive medications used (P for trend = .84) was independently associated with in-hospital mortality. In contrast, SBP was a strong independent predictor of in-hospital mortality (adjusted odds ratio = 1.21 per 10 mm Hg lower, 1.15-1.27, P < .001). There was no significant interaction between SBP and prior hypertension (P for interaction = .62) or pre-admission antihypertensive medication use (P for interaction = .46) with respect to in-hospital mortality. CONCLUSION: Low SBP on presentation, but not prior hypertension, was independently associated with in-hospital mortality in NSTEACS. The powerful prognostic value of SBP is similar regardless of a history of hypertension or pre-admission antihypertensive medication use.

Screening a large reference sample to identify very low frequency sequence variants: comparisons between two genes.

Most human sequence variation is in the form of single-nucleotide polymorphisms (SNPs). It has been proposed that coding-region SNPs (cSNPs) be used for direct association studies to determine the genetic basis of complex traits. The success of such studies depends on the frequency of disease-associated alleles, and their distribution in different ethnic populations. If disease-associated alleles are frequent in most populations, then direct genotyping of candidate variants could show robust associations in manageable study samples. This approach is less feasible if the genetic risk from a given candidate gene is due to many infrequent alleles. Previous studies of several genes demonstrated that most variants are relatively infrequent (<0.05). These surveys genotyped small samples (n<75) and thus had limited ability to identify rare alleles. Here we evaluate the prevalence and distribution of such rare alleles by genotyping an ethnically diverse reference sample that is more than six times larger than those used in previous studies (n=450). We screened for variants in the complete coding sequence and intron-exon junctions of two candidate genes for neuropsychiatric phenotypes: SLC6A4, encoding the serotonin transporter; and SLC18A2, encoding the vesicular monoamine transporter. Both genes have unique roles in neuronal transmission, and variants in either gene might be associated with neurobehavioral phenotypes.

A gene encoding a P-type ATPase mutated in two forms of hereditary cholestasis.

Cholestasis, or impaired bile flow, is an important but poorly understood manifestation of liver disease. Two clinically distinct forms of inherited cholestasis, benign recurrent intrahepatic cholestasis (BRIC) and progressive familial intrahepatic cholestasis type 1 (PFIC1), were previously mapped to 18q21. Haplotype analysis narrowed the candidate region for both diseases to the same interval of less than 1 cM, in which we identified a gene mutated in BRIC and PFIC1 patients. This gene (called FIC1) is the first identified human member of a recently described subfamily of P-type ATPases; ATP-dependent aminophospholipid transport is the previously described function of members of this subfamily. FIC1 is expressed in several epithelial tissues and, surprisingly, more strongly in small intestine than in liver. Its protein product is likely to play an essential role in enterohepatic circulation of bile acids; further characterization of FIC1 will facilitate understanding of normal bile formation and cholestasis.

Universal DNA methylation age across mammalian tissues.

Aging, often considered a result of random cellular damage, can be accurately estimated using DNA methylation profiles, the foundation of pan-tissue epigenetic clocks. Here, we demonstrate the development of universal pan-mammalian clocks, using 11,754 methylation arrays from our Mammalian Methylation Consortium, which encompass 59 tissue types across 185 mammalian species. These predictive models estimate mammalian tissue age with high accuracy (r > 0.96). Age deviations correlate with human mortality risk, mouse somatotropic axis mutations and caloric restriction. We identified specific cytosines with methylation levels that change with age across numerous species. These sites, highly enriched in polycomb repressive complex 2-binding locations, are near genes implicated in mammalian development, cancer, obesity and longevity. Our findings offer new evidence suggesting that aging is evolutionarily conserved and intertwined with developmental processes across all mammals.

Has the ClOpidogrel and Metoprolol in Myocardial Infarction Trial (COMMIT) of early ß-blocker use in acute coronary syndromes impacted on clinical practice in Canada? Insights from the Global Registry of Acute Coronary Events (GRACE).

BACKGROUND: The COMMIT/CCS-2 trial, published in 2005, demonstrated no net benefit of early ß-blocker (BB) therapy in acute coronary syndromes (ACS). We sought to assess the short-term impact of this landmark trial by comparing the use of early BB therapy in patients with a broad spectrum of ACS before and after 2005. METHODS: Using data from the Global Registry of Acute Coronary Events and Canadian Registry of Acute Coronary Events, we compared the rates of BB use within the first 24 hours of presentation in the periods 1999 to 2005 and 2006 to 2008, after stratifying patients by the type of ACS (ST-segment elevation myocardial infarction [STEMI] and non-ST-segment elevation ACS [NSTEACS]) and clinical presentation. RESULTS: Of the 14,231 patients with ACS, 77.7% received BB therapy within 24 hours of presentation (78.5% and 77.4% in the STEMI and NSTEACS groups, respectively). The early use of BB declined in the STEMI group (80.3% to 76.7%, P = .005) but increased in the NSTEACS group (75.4% to 78.9%, P < .001) after 2005. Long-term BB use, higher systolic blood pressure, and higher heart rate were independent predictors of early BB use. Conversely, patients who were female, older, Killip class >1, and had cardiac arrest at presentation were less likely to receive early BB. Multivariable analysis showed a trend toward lower use of BB among patients with STEMI (adjusted odds ratio 0.76, 95% CI 0.57-1.00, P = .055) and a trend toward more frequent BB use among patients with NSTEACS (adjusted odds ratio 1.22, 95% CI 0.96-1.55, P = .11) after 2005. The temporal trends in the early use of BB differed between patients with STEMI and patients with NSTEACS (P for interaction with period <.001). CONCLUSIONS: Most patients with STEMI or NSTEACS were treated with early BB therapy. In accordance with the COMMMIT/CCS-2 trial, patients with lower systolic blood pressure and higher Killip class in the "real world" less frequently received early BB therapy. Since the publication of COMMIT/CCS-2, there has been no significant change in the use of BB in patients with STEMI or NSTEACS after controlling for their clinical characteristics.

Temporal changes in the management and outcome of Canadian diabetic patients hospitalized for non-ST-elevation acute coronary syndromes.

BACKGROUND: There are limited data on the contemporary management and outcomes of non-ST-elevation acute coronary syndrome (NSTE-ACS) patients with diabetes in the "real world." We sought to evaluate (1) the temporal changes in the medical and invasive management and (2) in-hospital outcome of NSTE-ACS patients with and without diabetes. METHODS: We included Canadian patients hospitalized for NSTE-ACS enrolled in 4 consecutive, prospective, multicenter registries: Canadian ACS-I (n = 3259; 1999-2001), ACS-II (n = 1,956; 2002-2003), Global Registry of Acute Coronary Events (GRACE/GRACE2 [n = 7,561; 2004-2007]) and Canadian Registry of Acute Coronary Events (n = 1,326; 2008). Participants were stratified by the presence or absence of preexisting diabetes on admission. Temporal changes in patient management and outcomes were evaluated across the 4 registries. Multivariable analyses were performed to determine the independent prognostic significance of diabetes. RESULTS: Of the 14,102 NSTE-ACS patients, 4,046 (28.7%) had previously diagnosed diabetes. Patients with diabetes were older; were more likely to have prior cardiac history including myocardial infarction, revascularization, and heart failure; and had worse Killip class and higher GRACE risk score (all P < .001). Over time, there were significant increases in the use of in-hospital coronary angiography and revascularization. However, diabetic patients were less likely to undergo coronary angiography (52.5% vs 57%, P < .001) or revascularization (28.4% vs 33.4%, P < .001). The underuse of invasive procedures in diabetic patients was seen in all registries and was persistent over time. Overall, compared with the group without diabetes, diabetic patients had higher unadjusted rates of in-hospital mortality (3.0% vs 1.6%, P < .001). In multivariable analysis adjusting for components of the GRACE risk score, diabetes remained an independent predictor of in-hospital death (adjusted odds ratio 1.66, 95% CI 1.30-2.11, P < .001). CONCLUSIONS: Over the last decade, NSTE-ACS patients with diabetes continue to be treated more conservatively, despite evidence that they would derive similar or even greater benefits from aggressive treatment. This underutilization of evidence-based therapies among diabetic patients with NSTE-ACS in the "real world" may partly explain their worse outcome.

Temporal trends and patterns of early clopidogrel use across the spectrum of acute coronary syndromes.

BACKGROUND: Randomized trials have established efficacy of clopidogrel in various types of acute coronary syndromes (ACS). The objective of this study was to examine the temporal trends and patterns of early clopidogrel use (within the first 24 hours of hospitalization) across the spectrum of patients with ACS in Canada. METHODS: Using the multinational, prospective GRACE (Global Registry of Acute Coronary Events) and GRACE(2), we identified 11,177 patients who were admitted for ACS from January 2003 to December 2007 in Canada. Demographic information, clinical features, and treatment were recorded. We examined the early use of clopidogrel over time and in relation to the type of ACS, clinical features on presentation, and the mode of reperfusion therapy. RESULTS: Of the 11,177 patients with ACS, 3,091 (27.7%) had ST-elevation myocardial infarction (STEMI), 5,194 (46.5%) had non-STEMI, and 2,892 (25.9%) had unstable angina; the rates of early clopidogrel administration were 63.0%, 66.6%, and 57.2%, respectively (P < .001). Overall, there was a significant increase in clopidogrel use over the period studied (P for trend < .001). In patients with non-ST-elevation ACS (non-STEMI and unstable angina), clopidogrel use was higher among those with positive cardiac biomarkers compared to those without (67.1% vs 59.8%, P < .001) but similar in the groups with and without ST deviation. There was an inverse relationship between GRACE risk score and rates of early clopidogrel administration. In patients with STEMI receiving fibrinolytic therapy, only 55.7% of patients <65 years old received clopidogrel compared with 47.0% and 42.6% of patients 65 to 74 and >75 years old, respectively (P for trend < .001). CONCLUSIONS: Although early use of clopidogrel therapy has increased over time across the spectrum of ACS, a significant proportion of eligible patients still do not receive this evidence-based therapy. There is a need to optimize the use of proven antiplatelet therapies to improve clinical outcome.

Validation of the Global Registry of Acute Coronary Event (GRACE) risk score for in-hospital mortality in patients with acute coronary syndrome in Canada.

BACKGROUND: The Global Registry of Acute Coronary Event (GRACE) risk score was developed in a large multinational registry to predict in-hospital mortality across the broad spectrum of acute coronary syndromes (ACS). Because of the substantial regional variation and temporal changes in patient characteristics and management patterns, we sought to validate this risk score in a contemporary Canadian population with ACS. METHODS: The main GRACE and GRACE(2) registries are prospective, multicenter, observational studies of patients with ACS (June 1999 to December 2007). For each patient, we calculated the GRACE risk score and evaluated its discrimination and calibration by the c statistic and the Hosmer-Lemeshow goodness-of-fit test, respectively. To assess the impact of temporal changes in management on the GRACE risk score performance, we evaluated its discrimination and calibration after stratifying the study population into prespecified subgroups according to enrollment period, type of ACS, and whether the patient underwent coronary angiography or revascularization during index hospitalization. RESULTS: A total of 12,242 Canadian patients with ACS were included; the median GRACE risk score was 127 (25th and 75th percentiles were 103 and 157, respectively). Overall, the GRACE risk score demonstrated excellent discrimination (c statistic 0.84, 95% CI 0.82-0.86, P < .001) for in-hospital mortality. Similar results were seen in all the subgroups (all c statistics >/=0.8). However, calibration was suboptimal overall (Hosmer-Lemeshow P = .06) and in various subgroups. CONCLUSIONS: GRACE risk score is a valid and powerful predictor of adverse outcomes across the wide range of Canadian patients with ACS. Its excellent discrimination is maintained despite advances in management over time and is evident in all patient subgroups. However, the predicted probability of in-hospital mortality may require recalibration in the specific health care setting and with advancements in treatment.

A narrow and highly significant linkage signal for severe bipolar disorder in the chromosome 5q33 region in Latin American pedigrees.

We previously reported linkage of bipolar disorder to 5q33-q34 in families from two closely related population isolates, the Central Valley of Costa Rica (CVCR) and Antioquia, Colombia (CO). Here we present follow up results from fine-scale mapping in large CVCR and CO families segregating severe bipolar disorder, BP-I, and in 343 population trios/duos from CVCR and CO. Employing densely spaced SNPs to fine map the prior linkage peak region increases linkage evidence and clarifies the position of the putative BP-I locus. We performed two-point linkage analysis with 1134 SNPs in an approximately 9 Mb region between markers D5S410 and D5S422. Combining pedigrees from CVCR and CO yields a LOD score of 4.9 at SNP rs10035961. Two other SNPs (rs7721142 and rs1422795) within the same 94 kb region also displayed LOD scores greater than 4. This linkage peak coincides with our prior microsatellite results and suggests a narrowed BP-I susceptibility regions in these families. To investigate if the locus implicated in the familial form of BP-I also contributes to disease risk in the population, we followed up the family results with association analysis in duo and trio samples, obtaining signals within 2 Mb of the peak linkage signal in the pedigrees; rs12523547 and rs267015 (P = 0.00004 and 0.00016, respectively) in the CO sample and rs244960 in the CVCR sample and the combined sample, with P = 0.00032 and 0.00016, respectively. It remains unclear whether these association results reflect the same locus contributing to BP susceptibility within the extended pedigrees.

GRACE risk score: Sex-based validity of in-hospital mortality prediction in Canadian patients with acute coronary syndrome.

BACKGROUND: Although there are sex differences in management and outcome of acute coronary syndromes (ACS), sex is not a component of Global Registry of Acute Coronary Events (GRACE) risk score (RS) for in-hospital mortality prediction. We sought to determine the prognostic utility of GRACE RS in men and women, and whether its predictive accuracy would be augmented through sex-based modification of its components. METHODS: Canadian men and women enrolled in GRACE and Canadian Registry of Acute Coronary Events were stratified as ST-segment elevation myocardial infarction (STEMI) or non-ST-segment elevation ACS (NSTE-ACS). GRACE RS was calculated as per original model. Discrimination and calibration were evaluated using the c-statistic and Hosmer-Lemeshow goodness-of-fit test, respectively. Multivariable logistic regression was undertaken to assess potential interactions of sex with GRACE RS components. RESULTS: For the overall cohort (n=14,422), unadjusted in-hospital mortality rate was higher in women than men (4.5% vs. 3.0%, p<0.001). Overall, GRACE RS c-statistic and goodness-of-fit test p-value were 0.85 (95% CI 0.83-0.87) and 0.11, respectively. While the RS had excellent discrimination for all subgroups (c-statistics >0.80), discrimination was lower for women compared to men with STEMI [0.80 (0.75-0.84) vs. 0.86 (0.82-0.89), respectively, p<0.05]. The goodness-of-fit test showed good calibration for women (p=0.86), but suboptimal for men (p=0.031). No significant interaction was evident between sex and RS components (all p>0.25). CONCLUSIONS: The GRACE RS is a valid predictor of in-hospital mortality for both men and women with ACS. The lack of interaction between sex and RS components suggests that sex-based modification is not required.

In-hospital management and outcomes of acute coronary syndromes in relation to prior history of heart failure.

INTRODUCTION: The prognostic significance of prior heart failure in acute coronary syndromes has not been well studied. Accordingly, we evaluated the baseline characteristics, management patterns and clinical outcomes in patients with acute coronary syndromes who had prior heart failure. METHODS AND RESULTS: The study population consisted of acute coronary syndrome patients in the Global Registry of Acute Coronary Events, expanded Global Registry of Acute Coronary Events and Canadian Registry of Acute Coronary Events between 1999 and 2008. Of the 13,937 eligible patients (mean age 66±13 years, 33% female and 28.3% with ST-elevation myocardial infarction), 1498 (10.7%) patients had a history of heart failure. Those with prior heart failure tended to be older, female and had lower systolic blood pressure, higher Killip class and creatinine on presentation. Prior heart failure was also associated with significantly worse left ventricular systolic function and lower rates of cardiac catheterization and coronary revascularization. The group with previous heart failure had significantly higher rates of acute decompensated heart failure, cardiogenic shock, myocardial (re)infarction and mortality in hospital. In multivariable analysis, prior heart failure remained an independent predictor of in-hospital mortality (odds ratio 1.48, 95% confidence interval 1.08-2.03, p=0.015). CONCLUSIONS: Prior heart failure was associated with high risk features on presentation and adverse outcomes including higher adjusted in-hospital mortality in acute coronary syndrome patients. However, acute coronary syndrome patients with prior heart failure were less likely to receive evidence-based therapies, suggesting potential opportunities to target more intensive treatment to improve their outcome.

Linked and unlinked transposition of a genetically marked Dissociation element in transgenic tomato.

We have introduced a genetically marked Dissociation transposable element (Dsneo) into tomato. In the presence of Ac transposase, Dsneo excised from an integrated T-DNA and reinserted at numerous new sites in the tomato genome. The marker genes of Dsneo (NPTII) and the T-DNA (HPT) facilitated identification of plants bearing transposon excisions and insertions. To explore the feasibility of gene tagging strategies in tomato using Dsneo, we examined the genomic distribution of Dsneo receptor sites, relative to the location of the donor T-DNA locus. Restriction fragment length polymorphism mapping of transposed Dsneo elements was conducted in two tomato families, derived from independent primary transformants each bearing Dsneo within a T-DNA at a unique position in the genome. Transposition of Dsneo generated clusters of insertions that were positioned on several different tomato chromosomes. Dsneo insertions were often located on the same chromosome as the T-DNA donor site. However, no insertion showed tight linkage to the T-DNA. We consider the frequency and distance of Dsneo transposition observed in tomato to be well suited for transposon mutagenesis. Our study made use of a novel, stable allele of Ac (Ac3) that we discovered in transgenic tomato. We determined that the Ac3 element bears a deletion of the outermost 5 base pairs of the 5'-terminal inverted repeat. Though incapable of transposition itself, Ac3 retained the ability to mobilize Dsneo. We conclude that a dual element system, composed of the stable Ac3 trans-activator in combination with Dsneo, is an effective tool for transposon tagging experiments in tomato.

BP as a determinant of cardiac left ventricular muscle mass.

The relationship between casual BPs and measures of cardiac hypertrophy, derived from the ECG, has been described as fairly weak. In this study, ECG and echocardiographic measurements of left ventricular muscle mass were related to various measures of BP obtained during circadian ambulatory BP monitoring in 12 patients with hypertension. Casual BP did not correlate substantially with ECG voltages or with echocardiographic measurements of muscle mass. The correlations between whole-day, daytime, or nighttime BP averages and ECG voltages were not significant. However, echocardiographic left ventricular muscle mass correlated significantly with the averages of whole-day, daytime, and nighttime, and two-hour morning systolic pressures. The correlations between diastolic BP and left ventricular muscle mass were not significant. Therefore, serial BP measurements are required to evaluate the relationship between BP and left ventricular muscle mass as measured by the M-mode echocardiogram. The ECG is of little value in this relationship.

Long-term BP monitoring in the evaluation of antihypertensive therapy.

Noninvasive BP monitoring was performed in hypertensive patients before and during placebo therapy and before and during therapy with the long-acting peripheral alpha-adrenergic receptor antagonist, terazosin hydrochloride. Placebo therapy did not result in significant changes in casual BP or in averages of whole-day, daytime, or nighttime BPs. Short-term therapy with terazosin did not induce significant changes in casual supine or daytime BPs. However, whole-day BP monitoring disclosed that nighttime BPs were lower during shortterm therapy. Moreover, the circadian pattern of BP was shifted downward during terazosin therapy. Long-term therapy with terazosin resulted in significant changes in BP. All BP values were lowered significantly. The differences in the circadian BP pattern between placebo and long-term terazosin therapy show that in these patients BP was lowered throughout the 24 hours of the day. The results of the study emphasize the usefulness of 24-hour BP monitoring in the evaluation of the effectiveness of long-acting antihypertensive agents.

Circadian blood pressure patterns in ambulatory hypertensive patients: effects of age.

Circadian blood pressure monitoring was performed in 50 untreated ambulatory hypertensive patients to study the effects of age on the pattern and variability of blood pressure and heart rate. Casual blood pressure, measured in the morning, was greater than the average of the blood pressures measured at 7.5 minute intervals for 24 hours (148 +/- 2/95 +/- 2 and 137 +/- 2/88 +/- 2 mm Hg, p less than 0.001). The correlation between casual systolic pressure and the 24 hour average was stronger (p less than 0.05) in younger (less than 55 years of age) patients (r = 0.69, n = 24, p less than 0.001) than in older patients (r = 0.42, n = 26, p less than 0.1). Similarly, diastolic pressures correlated more strongly (p less than 0.05) in younger patients (r = 0.71, p less than 0.001) than in older patients (r = 0.43, p less than 0.05). Variability of systolic pressure, defined as the standard deviation of all readings obtained during 24 hours, was greater than that of diastolic pressure (16.7 and 13.1 mm Hg, respectively, p less than 0.001). Moreover, the variability of systolic pressure was greater in older than in younger patients (18.1 and 15.2 mm Hg, respectively, p less than 0.01). The variability of diastolic pressure was slightly but not significantly greater in older patients (13.7 and 12.5 mm Hg, not significant). The circadian pattern of blood pressure, expressed as averages of readings obtained during consecutive 2 hour intervals, was similar in the two age groups. However, the level of systolic pressure was consistently higher (p less than 0.01) and that of both diastolic pressure and heart rate consistently lower (p less than 0.01) in older patients. Thus, ambulatory circadian blood pressure monitoring reveals significant changes in blood pressure levels and its variability with age; the casual blood pressure does not accurately reflect these changes. Longer periods of blood pressure monitoring are required for accurate assessment of the characteristics of hypertension in the aged.

Whole blood viscosity as a determinant of cardiac hypertrophy in systemic hypertension.

The relationships among blood pressure (BP), blood viscosity and echocardiographic left ventricular (LV) muscle mass were evaluated in 24 patients with essential hypertension and in 13 normotensive control subjects. LV mass was greater in the hypertensive patients than in the control subjects (225 +/- 69 vs 170 +/- 31 g, p less than 0.02) as was blood viscosity at a shear rate of 104 sec-1 (4.7 +/- 0.1 vs 4.3 +/- 0.2 cp, p less than 0.005). Among the hypertensive patients, LV mass was most closely related to viscosity at 104 sec-1 (r = 0.80, p less than 0.001), whereas only weak correlations were found between LV mass and systolic or diastolic BP (r = 0.45, p less than 0.05 for both). The 14 hypertensive patients with normal LV mass had viscosity similar to that in control subjects (4.5 +/- 0.3 vs 4.3 +/- 0.2 cp), whereas viscosity was consistently increased (5.0 +/- 0.4 cp, p less than 0.02) in hypertensive patients with LV hypertrophy. Thus, increased blood viscosity may be a determinant of or a response to hypertensive cardiac hypertrophy.

Characterization of primary cell cultures as potential target cells for analysis of bovine cytotoxic T lymphocytes.

In domestic animal species, assessment of cell-mediated immune responses to virus infection is hampered by the requirement for class I MHC compatibility between target and effector cells. Additional complicating factors can include an inability to infect target cells in vitro, or virus-induced lysis of infected target cells. One way to circumvent these problems is to use virus-mediated gene transfer to deliver individual viral genes to autologous primary target cells. Several primary bovine cell cultures were assessed as potential target cells for cytotoxic T lymphocyte (CTL) assays by measuring their levels of class I MHC expression and susceptibilities to retroviral gene delivery. High levels in both class I MHC expression and susceptibility to gene delivery were seen in adherent cell cultures isolated from peripheral blood (PBAC). PBAC, which arose as an outgrowth of adherent peripheral blood mononuclear cell cultures, had morphology, protein expression patterns, and response to functional assays characteristic of high endothelial cells. Expression of viral vector-delivered genes in PBAC cells was confirmed with a recombinant retrovirus carrying the green fluorescent protein (GFP) gene. The use of vector-mediated delivery of viral genes to bovine high endothelial cells is a promising method for assessment of cell-mediated immunity in cattle.