ViPAR: a software platform for the Virtual Pooling and Analysis of Research Data

Background: Research studies exploring the determinants of disease require sufficient statistical power to detect meaningful effects. Sample size is often increased through centralized pooling of disparately located datasets, though ethical, privacy and data ownership issues can often hamper this process. Methods that facilitate the sharing of research data that are sympathetic with these issues and which allow flexible and detailed statistical analyses are therefore in critical need. We have created a software platform for the Virtual Pooling and Analysis of Research data (ViPAR), which employs free and open source methods to provide researchers with a web-based platform to analyse datasets housed in disparate locations.

Methods: Database federation permits controlled access to remotely located datasets from a central location. The Secure Shell protocol allows data to be securely exchanged between devices over an insecure network. ViPAR combines these free technologies into a solution that facilitates ‘virtual pooling’ where data can be temporarily pooled into computer memory and made available for analysis without the need for permanent central storage.

Results: Within the ViPAR infrastructure, remote sites manage their own harmonized research dataset in a database hosted at their site, while a central server hosts the data federation component and a secure analysis portal. When an analysis is initiated, requested data are retrieved from each remote site and virtually pooled at the central site. The data are then analysed by statistical software and, on completion, results of the analysis are returned to the user and the virtually pooled data are removed from memory.

Conclusions: ViPAR is a secure, flexible and powerful analysis platform built on open source technology that is currently in use by large international consortia, and is made publicly available at [ http://bioinformatics.childhealthresearch.org.au/software/vipar/ ].

Origins of epidemiology

In this paper we trace the history of epidemiology from 1800 to the present time. The history is highly selective because our purpose is to illuminate the evolving relationship of epidemiology with demography. We first describe the common "prehistory" of these two disciplines in the early nineteenth century, and then describe their divergence during three successive eras of epidemiology up to the end of the twentieth century. In the final section, we draw attention to exceptional individuals who bridged the two disciplines despite the historical trend in the other direction, and express our hope that recent signs of convergence in the face of globalization and the AIDS pandemic will be borne out during the coming decades.

Influence of variation in birth weight within normal range and within sibships on IQ at age 7 years: cohort study

OBJECTIVE

To examine the relation between birth weight and measured intelligence at age 7 years in children within the normal range of birth weight and in siblings.

DESIGN

Cohort study of siblings of the same sex.

SETTING

12 cities in the United States.

SUBJECTS

3484 children of 1683 mothers in a birth cohort study during the years 1959 through 1966. The sample was restricted to children born at >/=37 weeks gestation and with birth weights of 1500-3999 g.

MAIN OUTCOME MEASURE

Full scale IQ at age 7 years.

RESULTS

Mean IQ increased monotonically with birth weight in both sexes across the range of birth weight in a linear regression analysis of one randomly selected sibling per family (n= 1683) with adjustment for maternal age, race, education, socioeconomic status, and birth order. Within same sex sibling pairs, differences in birth weight were directly associated with differences in IQ in boys (812 pairs, predicted IQ difference per 100 g change in birth weight =0.50, 95% confidence interval 0.28 to 0.71) but not girls (871 pairs, 0.10, -0.09 to 0.30). The effect in boys remained after differences in birth order, maternal smoking, and head circumference were adjusted for and in an analysis restricted to children with birth weight >/= 2500 g.

CONCLUSION

The increase in childhood IQ with birth weight continues well into the normal birth weight range. For boys this relation holds within same sex sibships and therefore cannot be explained by confounding from family social environment.

Vasoactive potential of the b(1) bradykinin receptor in normotension and hypertension

The B(1) type receptor of bradykinin (Bk B(1)R) is believed to be physiologically inert but highly inducible by inflammatory mediators and tissue damage. To explore the potential participation of the Bk B(1)R in blood pressure (BP) regulation, we studied mice with deleted Bk B(2)R gene with induced experimental hypertension, either salt-dependent (subtotal nephrectomy with 0.5% NaCl as drinking water) or renin/angiotensin-dependent (renovascular 2-kidney-1-clip). Compared with the wild-type controls, the B(2)R gene knockout mice had a higher baseline BP (109.7+/-1.1 versus 101.1+/-1.3 mm Hg, P:=0.002), developed salt-induced hypertension faster (in 19.3+/-2.3 versus 27.7+/-2.4 days, P:=0.024), and had a more severe end point BP (148+/-3.7 versus 133+/-3.1 mm Hg, P:<0.05). On the contrary, renovascular hypertension developed to the same extent (149.7+/-4.3 versus 148+/-3.6 mm Hg) and in the same time frame (14+/-2.2 versus 14+/-2.1 days). A bolus infusion of a selective B(1)R antagonist at baseline produced a significant hypertensive response (by 11.4+/-2 mm Hg) in the knockout mice only. Injection of graded doses of a selective B(1)R agonist produced a dose-dependent hypotensive response in the knockout mice only. Assessment of tissue expression of B(1)R and B(2)R genes by reverse transcription-polymerase chain reaction techniques revealed significantly higher B(1)R mRNA levels in the B(2)R knockout mice at all times (normotensive baseline and hypertensive end points). At the hypertensive end points, there was always an increase in B(1)R gene expression over the baseline values. This increase was significant in cardiac and renal tissues in all hypertensive wild-type mice but only in the clipped kidney of the renovascular knockout mice. The B(2)R gene expression in the wild-type mice remained unaffected by experimental manipulations. These results confirm the known vasodilatory and natriuretic function of the Bk B(2)R; they also indicate that in its absence, the B(1)R can become upregulated and assume some of the hemodynamic properties of the B(2)R. Furthermore, they indicate that experimental manipulations to produce hypertension also induce upregulation of the B(1)R, but not the B(2)R, in cardiac and renal tissues.

Public conceptions of mental illness: labels, causes, dangerousness, and social distance

OBJECTIVES

The authors used nationwide survey data to characterize current public conceptions related to recognition of mental illness and perceived causes, dangerousness, and desired social distance.

METHODS

Data were derived from a vignette experiment included in the 1996 General Social Survey. Respondents (n = 1444) were randomly assigned to 1 of 5 vignette conditions. Four vignettes described psychiatric disorders meeting diagnostic criteria, and the fifth depicted a "troubled person" with subclinical problems and worries.

RESULTS

Results indicate that the majority of the public identifies schizophrenia (88%) and major depression (69%) as mental illnesses and that most report multicausal explanations combining stressful circumstances with biologic and genetic factors. Results also show, however, that smaller proportions associate alcohol (49%) or drug (44%) abuse with mental illness and that symptoms of mental illness remain strongly connected with public fears about potential violence and with a desire for limited social interaction.

CONCLUSIONS

While there is reason for optimism in the public's recognition of mental illness and causal attributions, a strong stereotype of dangerousness and desire for social distance persist. These latter conceptions are likely to negatively affect people with mental illness.

Liquid ventilation: a future modality?

Liquid ventilation, an idea currently being trialled in the United States, is increasingly being discussed as a possible future trend in ventilation. A review of the available literature indicates that this treatment provides effective gas exchange and has a number of potential advantages. These include lower airway pressures, decreased alveolar surface tension, alveolar recruitment and removal of pulmonary exudate. While yet to be seen in this country, liquid ventilation may be introduced in the future. If it is, those caring for patients treated in that way will require knowledge of the mechanics and physiological changes involved, as well as the potential hazards of this modality.

Identification of a polymorphic glutamic acid stretch in the alpha2B-adrenergic receptor and lack of linkage with essential hypertension

Essential hypertension, a clinically significant elevation in blood pressure with no recognizable cause, is believed to be attributable to the collective effect of genetic predisposing factors in combination with specific environmental factors, such as diet and stress. Of the genetic causes, genes coding for proteins involved in blood pressure regulation, such as the alpha- and beta-adrenergic receptors, are obvious candidates. The alpha2-adrenergic receptor plays a key role in the sympathetic nervous system by mediating the effects of epinephrine and norepinephrine. To evaluate the potential role between the alpha2B receptor and essential hypertension, we scanned the alpha2B-receptor gene for genetic variation in 108 affected sibling pairs. The screening revealed two major forms of the receptor. They differ by the presence of either 9 or 12 glutamic acid residues in the acidic domain of the third cytoplasmic loop of the protein. Investigation of the pattern of this variation in hypertensive sibling pairs suggests that the alpha2B receptor locus does not contribute substantially to genetic susceptibility for essential hypertension.

Comparison of spirapril, isradipine, or combination in hypertensive patients with left ventricular hypertrophy: effects on LVH regression and arrhythmogenic propensity

This study was designed to evaluate in 45 hypertensive patients with left ventricular hypertrophy (LVH) the effects of a 6-month course with one of three different antihypertensive regimens (the calcium channel blocker isradipine, the angiotensin converting enzyme inhibitor spirapril in monotherapy, or a combination of the two drugs, n = 15 per group) on blood pressure, LVH regression, and various functional correlates of LVH. All three treatment modalities decreased significantly LV mass index by an average of 10%, although the combination had the greatest blood pressure-lowering effect and spirapril had the least, as assessed by office resting pressures, ambulatory monitoring, and isometric grip testing. There was no correlation between magnitude of blood pressure lowering and degree of LVH regression. The effects of treatment on pressor hormone profiles differed among groups, as spirapril tended to suppress angiotensin II and norepinephrine, whereas isradipine had opposite effects. Exercise tolerance was prolonged by all three regimens, but significantly more by the combination. All three regimens decreased significantly the double product by 10% to 15%. Indices of electrophysiologic stability calculated from analysis of ambulatory electrocardiogram exhibited significant improvement in several parameters such as QRS duration, presence of late potentials, and measures of heart rate variability, resulting in fewer episodes of simple or complex ventricular arrhythmia. We conclude that all three regimens produce significant LVH regression associated with improved functional capacity and electrical stability. These results reflect the sum of the differential hemodynamic and hormonal effects exerted by each treatment modality.

Hemodynamic and humoral correlates in essential hypertension: relationship between patterns of LVH and myocardial ischemia

While evaluating 45 hypertensive patients with left ventricular hypertrophy (LVH) for enrollment in a clinical research protocol, we had the opportunity to compare anatomic and functional characteristics of those with LVH and ischemia on an exercise tolerance test (ETT), but without coronary artery disease by angiography (group I, n=8), versus those with a normal ETT (group II, n=37). There were no differences in age, sex, severity, and duration of hypertension between the two groups, but group I patients were significantly more overweight and had a worse lipid profile. Blood pressure at peak ETT was higher in group I despite shorter exercise duration, although resting and ambulatory pressures were similar. Group I patients had evidence of more pronounced cardiac enlargement and LVH by both ECG and echo criteria and a characteristic pattern of more pronounced thickening at the apex, but both groups had equally good systolic function and similar degrees of mild diastolic dysfunction. Analysis of 24-hour ambulatory ECG showed a significantly greater propensity to ventricular arrhythmias in group I, as shown by the presence of late potentials in 4 patients, the presence of couplets in 3, runs of ventricular tachycardia in 2 (while none of group II patients had late potentials or complex arrhythmias), and an average frequency of isolated premature ventricular contractions approximately three times higher in group I than group II patients. Our data demonstrate that hypertensives with LVH associated with myocardial ischemia at stress but with normal coronary arteriograms tend to be more overweight, attain a higher systolic blood pressure at ETT despite a shorter duration, have a higher propensity for severe arrhythmias, and have an adverse lipid profile. LVH in these subjects is more pronounced by both ECG and echo criteria and is characterized by predominantly apical hypertrophy with left atrial and ventricular dilatation rather than overall LV wall thickening.

Role of vasopressin in essential hypertension: racial differences

BACKGROUND

Arginine vasopressin (AVP), in addition to being an antidiuretic hormone, might also have pressor effects relevant to the maintenance of hypertension. Results from several experimental and clinical studies suggested that the pressor function of AVP is more important in low-renin hypertension and in the salt-loaded state and that it might be further maximized under sympathetic suppression.

OBJECTIVE

To assess whether selective vasopressin receptor inhibition lowers the blood pressure in a racially diverse group of low-renin hypertensive subjects.

METHODS

Thirty-nine hypertensive subjects (16 Caucasian, 23 African-American) eating a 200 mmol/day sodium diet were administered a single intravenous dose of a selective vasopressin receptor antagonist and their blood pressure was monitored constantly for the ensuing 3 h. The protocol was repeated 3 days later after treatment with a single oral dose of 0.4 mg clonidine.

RESULTS

Of these patients, 54% had their blood sampled for determination of hormone profiles. African-Americans with hypertension had higher baseline plasma AVP levels than did Caucasians (1.13 +/- 0.05 versus 0.37 +/- 0.06 pg/ml, respectively, P < 0.05), and lower plasma renin activity (0.34 +/- 0.07 versus 1.03 +/- 0.08 ng/ml per h, respectively, P < 0.05). Selective vasopressin receptor inhibition lowered the mean arterial pressure in African-Americans but not that in Caucasians (lowering by 28 +/- 4 mmHg in African-Americans versus lowering by 5 +/- 3 mmHg in Caucasians, P < 0.05). Moreover, vasopressin receptor blockade further reduced the arterial pressure in African-Americans but not that in Caucasians after pretreatment with clonidine.

CONCLUSION

AVP seems to play a more important role as a pressor hormone in maintaining the elevation of arterial pressure in African-American hypertensives than it does in Caucasian hypertensives.

Combined sympathetic suppression and angiotensin-converting enzyme inhibition in congestive heart failure

Neurohormonal activation is a pathogenic contributor and prognostic marker in congestive heart failure (CHF). While angiotensin-converting enzyme (ACE) inhibition is now first-line therapy, sympathetic inhibition has only lately been proposed to this aim. Recently, we reported improvement of preload parameters by sympathetic suppression with clonidine. In the present paper we studied the effects of a single oral dose of clonidine 0.15 mg+captopril 6.25 mg combination, compared with captopril 6.15+placebo in a single-blind parallel study on 16 patients with Class III or IV CHF (13 males, 3 females, aged 62 +/- 8 years, with an ejection fraction of 33 +/- 8%). Hemodynamic and hormonal measurements were taken at baseline after a diagnostic cardiac catheterization and again 2 hours after treatment. The results indicate that preload parameters such as RAP, PCWP and MPAP decreased significantly with the combination therapy but not with captopril alone. On the contrary, SVR decreased significantly with both treatments and SVI increased significantly with both-but the latter change was significantly greater with the captopril/clonidine combination than with captopril alone. Suppression of plasma norepinephrine occurred with the combination only (evidently attributable to clonidine), whereas plasma renin activity increased with both regimens, due apparently to captopril. Our results indicate that the combination of clonidine with captopril induces significant improvements in both preload and afterload parameters of CHF and correction of activated neurohormones, suggesting additive hemodynamic and hormonal benefits from the two treatment modalities.

Suppressing sympathetic activation in congestive heart failure. A new therapeutic strategy

Neurohormonal activation with increased plasma renin activity and norepinephrine and vasopressin levels is characteristic of congestive heart failure and contributes to further decompensation and poor prognosis. We treated 20 such patients with the centrally acting sympathoinhibitory drug clonidine 0.15 mg BID and obtained hemodynamic measurements by cardiac catheterization and plasma neurohormone levels before and 2 to 3 hours after the first dose; in 7 patients, these measurements were taken again after 1 week of therapy. The initial dose produced significant decreases of 8% in mean arterial pressure, 23% in right atrial pressure, 21% in pulmonary capillary wedge pressure, 19% in mean pulmonary artery pressure, and 12% in heart rate, a 17% increase in stroke volume; and no significant changes in cardiac output and systemic vascular resistance. All changes remained virtually constant after 1 week. Plasma norepinephrine decreased by 28% after the initial dose and 62% after 1 week (P < 0.1), whereas plasma renin activity remained essentially unchanged. Plasma vasopressin tended to increase, its levels being inversely correlated with those of posttreatment norepinephrine (r = -.48 P < .03). Patients with baseline norepinephrine levels > 0.400 ng/mL has significantly poorer baseline hemodynamic parameters and tended to show more improvement with clonidine, although their data remained significantly worse than patients whose baseline norepinephrine was within the normal range. Sympathetic suppression with clonidine in congestive heart failure reduces preload, heart rate, and arterial pressure, all indexes of myocardial energy demand; the lack of significant reduction in systemic vascular resistance and increase in cardiac output might be attributable in part to enhanced release of vasopressin.2+ f2p4

Lifetime and five-year prevalence of homelessness in the United States: new evidence on an old debate

A 1990 household-based telephone survey of 1,507 people was followed up by surveying a subsample of those interviewed for the initial report. Results showed very high prevalence figures for homelessness, quite close to those found in the earlier survey. Moreover, using explicit and stringent definitions of literal homelessness and doubling up, most periods of homelessness were found to last for more than one month and, particularly with regard to literal homelessness, to involve serious deprivations and violent victimization.

A second lineage of mammalian major histocompatibility complex class I genes

Major histocompatibility complex (MHC) class I genes typically encode polymorphic peptide-binding chains which are ubiquitously expressed and mediate the recognition of intracellular antigens by cytotoxic T cells. They constitute diverse gene families in different species and include the numerous so-called nonclassical genes in the mouse H-2 complex, of which some have been adapted to variously modified functions. We have identified a distinct family of five related sequences in the human MHC which are distantly homologous to class I chains. These MIC genes (MHC class I chain-related genes) evolved in parallel with the human class I genes and with those of most if not all mammalian orders. The MICA gene in this family is located near HLA-B and is by far the most divergent mammalian MHC class I gene known. It is further distinguished by its unusual exon-intron organization and preferential expression in fibroblasts and epithelial cells. However, the presence of diagnostic residues in the MICA amino acid sequence translated from cDNA suggests that the putative MICA chain folds similarly to typical class I chains and may have the capacity to bind peptide or other short ligands. These results define a second lineage of evolutionarily conserved MHC class I genes. This implies that MICA and possibly other members in this family have been selected for specialized functions that are either ancient or derived from those of typical MHC class I genes, in analogy to some of the nonclassical mouse H-2 genes.

Pressor hormone profile during stress in hypertension: does vasopressin interfere with left ventricular hypertrophy?

Neurohormonal factors may account for the fact that patients with similar severity and duration of hypertension develop different degrees of left ventricular hypertrophy (LVH). The purpose of this work was to compare the pressor hormone profiles of hypertensive subjects off medication during exercise testing. Nineteen patients, stratified according to echocardiographically diagnosed absence (Group I n = 6) or presence (Group II n = 13) of LVH, underwent testing on the treadmill according to the Bruce protocol. Both groups were comparable in age, severity and duration of hypertension and reached similar double product at peak exercise. Measurements of plasma renin activity (PRA), plasma catecholamines and vasopressin (AVP) at baseline, peak exercise and post exercise revealed significant differences between groups: Group I had suppressed PRA levels throughout and had significantly higher baseline AVP levels, which increased further at peak effort. Group II had significantly higher baseline PRA levels, which tended to increase further at peak effort, and had suppressed AVP levels throughout. There was a significant negative correlation between percent increments in AVP and increments in double product. Norepinephrine increased significantly with effort in both groups, but the levels attained were higher in Group I. In view of the known negative inotropic action of AVP and the trophic effect of angiotensin, we speculate that lower baseline AVP and higher PRA, together with inability of AVP to increase with effort, may be causally related to development of LVH.

Allelic variants of the human putative peptide transporter involved in antigen processing

Antigen processing for presentation of peptide epitopes by major histocompatibility complex (MHC) class I molecules involves genes in the MHC class II region. Among these, PSF1 and PSF2 encode subunits of a transporter, which presumably delivers cytosolic peptides across the endoplasmic reticulum membrane to class I molecules. This close functional relationship of the transporter and class I heavy chain genes and their linkage within the MHC raise the question of whether PSF1 and PSF2, like most class I genes, are polymorphic. By single-strand conformation polymorphism analysis and DNA sequencing, a small number of amino acid sequence variants of both PSF1 and PSF2 was identified in a panel of cell lines. This limited polymorphism may contribute to a higher degree of variability at the level of the functional transporter, in which different alleles of the PSF1 and PSF2 subunits may be combined. A possible involvement of the PSF1 and PSF2 genes in susceptibility to MHC-associated diseases was examined in a preliminary assessment in patients with ankylosing spondylitis, insulin-dependent diabetes mellitus, or celiac disease.

Two putative subunits of a peptide pump encoded in the human major histocompatibility complex class II region

The class II region of the human major histocompatibility complex (MHC) may encode several genes controlling the processing of endogenous antigen and the presentation of peptide epitopes by MHC class I molecules to cytotoxic T lymphocytes. A previously described peptide supply factor (PSF1) is a member of the multidrug-resistance family of transporters and may pump cytosolic peptides into the membrane-bound compartment where class I molecules assemble. A second transporter gene, PSF2, was identified 10 kilobases (kb) from PSF1, near the class II DOB gene. The complete sequences of PSF1 and PSF2 were determined from cDNA clones. The translation products are closely related in sequence and predicted secondary structure. Both contain a highly conserved ATP-binding fold and share 25% homology in a hydrophobic domain with a tentative number of eight membrane-spanning segments. Based on the principle dimeric organization of these two domains in other transporters, PSF1 and PSF2 may function as complementary subunits, independently as homodimers, or both. Taken together with previous genetic evidence, the coregulation of PSF1 and PSF2 by gamma interferon and the to-some-degree coordinate transcription of these genes suggest a common role in peptide-loading of class I molecules, although a distinct function of PSF2 cannot be ruled out.

Effects of bradykinin and prostaglandin inhibition on systemic and regional hemodynamics in conscious normotensive rats

These experiments were designed to study the effects of inhibition of endogenous bradykinin and/or prostaglandins on systemic and regional hemodynamics in conscious normotensive rats, using the radioactive microsphere technique. Administration of either a bradykinin antagonist (50 micrograms/min for 5 min) or indomethacin (10 mg/kg) alone, decreased the cardiac output by an average of 17.58 and 25.94%, respectively (P less than 0.05), without significant change in total peripheral resistance. Regional blood flow decreased and local vascular resistance increased in most organs. Coronary and renal blood flow decreased by an average of 16.45 and 17.26% with bradykinin antagonist and 23.85 and 19.80% with indomethacin, respectively (P less than 0.05). Indomethacin but not bradykinin antagonist also decreased cerebral blood flow by an average of 47.57% (P less than 0.01). Infusion of the bradykinin antagonist following prior prostaglandin inhibition with indomethacin did not induce further changes in either systemic or regional hemodynamics, except in the liver where a significant additional increment in vascular resistance was observed. Our data suggest that most organs have similar patterns of regional vascular sensitivity to bradykinin and prostaglandins (including the heart, kidney, testis, stomach, skin and adrenal). The major differences were in the cerebral vasculature, which was much more sensitive to prostaglandins, and in the liver, spleen and small intestine, which were more sensitive to bradykinin. We conclude that both hormonal systems participate to a varying extent in the maintenance of resting vascular tone in most organs; however, in some cases, their effects may be additive and in others they may work in opposite directions.

A gene in the human major histocompatibility complex class II region controlling the class I antigen presentation pathway

Major histocompatibility complex (MHC) class I molecules export peptides to the cell surface for surveillance by cytotoxic T lymphocytes. Intracellular peptide binding is critical for the proper assembly and transport of class I molecules. This mechanism is impaired as a result of a non-functional peptide supply factor gene (PSF) in several human mutant cell lines with genomic lesions in the MHC. We have now identified PSF in the MHC class II region by deletion mapping in mutants and chromosome-walking. PSF is homologous to mammalian and bacterial ATP-dependent transport proteins, suggesting that it operates in the intracellular transport of peptides.

Effect of aging on vasopressin, catecholamines, and alpha 2-adrenergic receptors

To characterize normal changes with aging, we measured plasma levels of epinephrine, norepinephrine, and vasopressin, as well as alpha 2-adrenergic receptor numbers (Bmax) and the antagonist dissociation constant (Kd) from platelet-derived membranes of white, younger (aged 28 +/- 6 years, n = 30) and older (aged 70 +/- 4 years, n = 41) normotensive, healthy volunteers. There were no differences in resting vasopressin or epinephrine levels at 0.83 +/- 0.83 and 360 +/- 120 pmol/L in the younger versus 1.0 +/- 0.2 and 450 +/- 420 in the older subjects, respectively. However, plasma norepinephrine was significantly higher in the older (2.87 +/- 1.34 nmol/L) versus the younger subjects (1.50 +/- 0.53 nmol/L, P less than .01). Platelet alpha 2-receptor numbers were significantly lower in the older subjects at 289 +/- 79 fmol/mg protein versus 388 +/- 81 fmol/mg protein in the younger subjects (P less than .01), compatible with but not proof of down-regulation by norepinephrine. However, Kd, representing receptor affinity, was similar in both groups. Therefore, studies of hormone and receptor status in various pathologic conditions should always take into account the normal changes attributable to the age of the subject population.

Pressor hormones in elderly hypertensive persons. Racial differences

The purpose of this study was to examine pressor hormones and platelet alpha 2-adrenergic receptors in elderly unmedicated free-living subjects. Eighty-seven subjects, 70 +/- 5 years old (mean +/- SD), hypertensive or normotensive (blood pressure less than 160/90 mm Hg) were recruited for measurement of blood levels of norepinephrine, epinephrine, and vasopressin, as well as density and affinity of alpha 2-adrenergic receptors from platelet membranes, assessed by maximal binding (Bmax) and dissociation constant (Kd) of rauwolscine. They were separated into white hypertensive (n = 22) or normotensive (n = 41), and black hypertensive (n = 11) or normotensive (n = 13) groups, with similar age distribution throughout and similar blood pressure levels in the hypertensive and normotensive groups. Vasopressin was higher in the black hypertensive than white hypertensive group (1.5 +/- 1.0 vs. 0.7 +/- 0.5 pg/ml, respectively, p less than 0.005), whereas epinephrine correlated inversely with diastolic blood pressure (r = -0.7, p less than 0.02, in the black hypertensive group). Kd was higher in the black normotensive group than in the other groups (1.6 +/- 0.6 vs. 1.0 +/- 0.2, 1.1 +/- 0.3, or 1.0 +/- 0.3 nM in the white normotensive, black hypertensive, or white hypertensive group, respectively, p less than 0.002). Bmax was no different among groups but was significantly correlated with vasopressin levels for the whole group (r = 0.4, p less than 0.0004) although no such correlation existed within the black hypertensive group. The data suggest that various vasoconstrictor systems participate to different extents in the mechanisms generating and sustaining hypertension in elderly white and black subjects.

Human major histocompatibility complex contains a minimum of 19 genes between the complement cluster and HLA-B

A 600-kilobase (kb) DNA segment from the human major histocompatibility complex (MHC) class III region was isolated by extension of a previous 435-kb chromosome walk. The contiguous series of cloned overlapping cosmids contains the entire 555-kb interval between C2 in the complement gene cluster and HLA-B. This region is known to encode the tumor necrosis factors (TNFs) alpha and beta, B144, and the major heat shock protein HSP70. Moreover, a cluster of genes, BAT1-BAT5 (HLA-B-associated transcripts) has been localized in the vicinity of the genes for TNF alpha and TNF beta. An additional four genes were identified by isolation of corresponding cDNA clones with cosmid DNA probes. These genes for BAT6-BAT9 were mapped near the gene for C2 within a 120-kb region that includes a HSP70 gene pair. These results, together with complementary data from a similar recent study, indicated the presence of a minimum of 19 genes within the C2-HLA-B interval of the MHC class III region. Although the functional properties of most of these genes are yet unknown, they may be involved in some aspects of immunity. This idea is supported by the genetic mapping of the hemopoietic histocompatibility locus-1 (Hh-1) in recombinant mice between TNF alpha and H-2S, which is homologous to the complement gene cluster in humans.

A new cluster of genes within the human major histocompatibility complex

A 435-kilobase (kb) DNA segment, which is centromeric to HLA-B in the human major histocompatibility complex, was isolated by chromosome walking with overlapping cosmids. Within the cloned region, the genes for the tumor necrosis factors (TNFs) alpha and beta and HLA-B were 210 kb apart. The human homolog of a mouse gene, B144, was located next to TNF alpha. Moreover, the presence of additional genes was suggested by a large cluster of CpG islands. With cosmid probes, several distinct transcripts were detected in RNA samples from a variety of cell lines. Altogether, five novel genes were identified by isolation of corresponding complementary DNA clones. These "HLA-B-associated transcripts" (BATs) were mapped to different locations within a 160-kb region that includes the genes for TNF alpha and TNF beta. The presence of the genes for BAT1 and BAT5 in the vicinity of HLA-B again raises the question of which gene in this region determines susceptibility to ankylosing spondylitis.

Central catecholamines and alpha-adrenoceptors in acute hypertension induced by intracerebroventricular hypertonic saline

We measured the tissue content of catecholamines and the numbers and affinities of alpha 1- and alpha 2-adrenergic receptors in specific areas of the hypothalamus and medulla oblongata of rats treated with intracerebroventricular microinjection of hypertonic saline, in comparison to controls treated with an equal volume of iso-osmolar dextrose solution. Rats given 20 microliter of 4% NaCl into the lateral ventricle showed an average rise in blood pressure of 14 +/- 2 mmHg and a decrease in heart rate of 63 +/- 11 beats/min (P less than 0.001 for both), associated with dopamine suppression in the anteroventral area of the third ventricle (AV3V) and increased concentrations of dopamine in the C2 region of the medulla and of epinephrine in the area postrema. Affinities of medullary alpha 2-adrenoceptors were decreased in the saline-treated rats, whereas the number of receptors tended to be higher. It is suggested that sodium may produce its pressor effect by diminishing the affinity of central alpha 2-adrenoceptors for neurotransmitters, resulting in disinhibition of certain sympathoinhibitory neurons and increased sympathetic outflow.

Acute cardiovascular effects of two central phenylethanolamine-N-methyl-transferase inhibitors in unanesthetized desoxycorticosterone-salt hypertensive rats

SKF 64139, an inhibitor of phenylethanolamine-N-methyltransferase (PNMT), has a marked hypotensive effect in models of sodium-dependent hypertension. The mechanism of this effect is obscure, the compound having in addition alpha-adrenoceptor blocking properties. We compared the acute effects of SKF 64139 with those of LY 134046, another PNMT inhibitor with minimal alpha-blocking capacity, in desoxycorticosterone-salt hypertensive rats. The former agent produced profound hypotension whereas the latter caused only bradycardia. Both induced a similar pronounced suppression of PNMT activity in the C1 and C2 region of the medulla oblongata. These results suggest that the alpha-adrenergic effect rather than PNMT inhibition accounts for the acute lowering of blood pressure in this model.

Central and peripheral indices of sympathetic activity after blood pressure lowering with enalapril (MK-421) or hydralazine in normotensive rats

Various antihypertensive drugs have different effects on vasoactive mechanisms. In normotensive Wistar rats, we investigated the effects on plasma and tissue catecholamines of chronic treatment with two agents: MK-421, an angiotensin converting-enzyme inhibitor (CEI), and hydralazine, a vascular smooth muscle relaxant. Both agents lowered blood pressure via arteriolar dilation, to the same final level. However, hydralazine stimulated the renin-angiotensin system and elevated the plasma norepinephrine (NE) and epinephrine (E) levels, whereas MK-421 did not. In MK-421-treated animals, NE, E, and the ratio of E/NE were decreased in the brain stem, and this ratio was increased in the heart. In hydralazine-treated rats, the catecholamine levels were unchanged in the brain stem and heart. The turnover rate of NE was significantly reduced in the brain stem and heart of MK-421-treated rats, whereas, after hydralazine, the turnover rate in the heart was increased (decreasing the half-life of NE by about 50%), indicating increased sympathetic activity. Thus, elimination of angiotensin II (AII) by CEI is associated with decreased sympathetic activity in both the brain stem and heart, whereas an equipotent antihypertensive action by smooth muscle relaxation leads to stimulation of both the renin-angiotensin and the sympathetic systems. These differences are more readily apparent by measurement of catecholamine turnover rates in tissues than of catecholamine levels, and they may account for the different hemodynamic effects of the two agents, even though both drugs act through arteriolar dilation.

Interaction of the sympathetic nervous system with vasopressin and renin in the maintenance of blood pressure

To evaluate the partial contributions and interaction of three vasopressor systems in blood pressure maintenance, nephrectomized rats and rats with intact kidneys were submitted sequentially to catecholamine depletion, elimination of vasopressin's vasoconstrictor action, and (for those with kidneys in situ) angiotensin blockade. Catecholamine depletion decreased blood pressure and stimulated vasopressin levels in all rats, but significantly more so in the anephric ones. Subsequent injection of an antagonist to the vasopressor effect of vasopressin produced a lasting fall of blood pressure in anephric rats, but only transient fall in those with intact kidneys. Infusion of teprotide--an angiotensin converting enzyme inhibitor--in the latter animals also produced transient blood pressure fall, but if this were followed by injection of the vasopressin antagonist, the pressure remained low for several hours. Blood pressure levels were closely correlated with those of plasma catecholamines throughout these maneuvers. Catecholamine levels were inversely correlated with those of plasma vasopressin, which were far greater in anephric rats through both stimulation and accumulation. Plasma renin activity was increasingly stimulated by falling blood pressure after each maneuver in rats with intact kidneys. Thus, it appears that in the resting state the sympathetic nervous system is more involved in the maintenance of blood pressure, whereas vasopressin and renin are important backup mechanisms.

Effect of pindolol on blood pressure, plasma renin activity, and catecholamines in hypertensive patients

The effects of 45 mg pindolol daily on blood pressure, heart rate, plasma renin activity, and plasma catecholamines were assessed on 11 hospitalized hypertensive patients. Blood pressure decreased significantly after nine days of treatment, but heart rate remained unchanged. Plasma renin activity was in the same average range before and during treatment, with individual values variably increasing, decreasing, or remaining unchanged. Blood pressure changes were independent from the baseline level of plasma renin activity or the change in renin activity observed during treatment. Plasma epinephrine and norepinephrine levels also remained unchanged during treatment. Lack of change in heart rate and hormonal levels may be attributed to the combined effects of the beta-antagonistic and partial agonistic properties of this agent. Thus, pindolol used as monotherapy at this dose significantly lowered blood pressure, but not to normal levels, with only minimal side effects. Because of its combined adrenergic agonistic and antagonistic effects, it may be a preferable alternative to pure antagonists in selected patients.

Studies on the activity of the sympathetic nervous system in essential hypertension

Plasma catecholamine and norepinephrine concentrations have been measured in carefully characterized ambulatory patients with essential hypertension under basal conditions and following experimental procedures known to enhance sympathetic activity. The studies have demonstrated increased levels of plasma catecholamines in patients with mild hypertension as compared with matched controls following 70 degree upright tilt or cold pressor testing. Considerable heterogeneity was apparent in the population of patients with essential hypertension with respect to their plasma norepinephrine concentrations. Significantly greater levels of plasma norepinephrine were present in patients with high plasma renin activity and lesser levels in patients with low renin activity than in normal renin or labile hypertensives. Blood pressure correlated significantly with plasma norepinephrine in male patients with normal renin essential hypertension but not in females. Administration of the diuretic furosemide produced an increase in plasma norepinephrine in almost all hypertensive subjects studied. These studies suggest that peripheral sympathetic activity is abnormal in certain patients with essential hypertension. The results underscore the need to differentiate between subgroups of essential hypertension in studies relating to the role of the adrenergic system in the hypertension. The findings also suggest that the recently developed sensitive techniques for measuring plasma catecholamines of plasma norepinephrine are of value in assessing changes in peripheral sympathetic activity but that enzymatic assays of serum dopamine-beta-hydroxylase activity are probably not useful for this purpose.