Synthesis and pharmacological evaluation of triflate-substituted analogues of clozapine: identification of a novel atypical neuroleptic

The trifluoromethanesulfonyloxy (TfO) analogues 3 and 4 of 8-chloro-11-(4-methyl-1-piperazinyl)-5H-dibenzo[b,e][1,4]diazepine (clozapine, 1) and its 2-chloro isomer (iso-clozapine, 2), respectively, were synthesized via their OMe and OH analogues with the conventional synthetic method of the tricyclic dibenzodiazepines and evaluated pharmacologically along with their parent drugs. The binding profile of the 2-OTf analogue (4) is comparable to the binding profile of 1, although the affinity for the dopamine (DA) D2 receptors is higher (IC50 values are 31 nM and 330 nM for compounds 4 and 1, respectively). Interestingly, no notable affinity for muscarinic receptors could be detected in compound 4. On the contrary, the 8-OTf analogue 3 only displayed affinity for muscarinic M1 receptors (IC50 value 35 nM) and no affinity (IC50 value > 500 nM) for the other receptors tested. The 10 mumol/kg sc dose, but not the 10 mumol/kg po dose, of compound 4 stimulated the output of DA. Increases of 80% and 35% in DOPAC output from the dorsal striatum were seen after sc and po administrations of 10 mumol/kg of compound 4, respectively. Doses up to 100 mumol/kg of compound 3 had no effect on either parameter. Doses up to 100 mumol/kg of compound 4 were not cataleptogenic, but significantly decreased apomorphine-induced locomotor activity. In conclusion, compound 4 (GMC1-169) is a new clozapine-like neuroleptic candidate, which is lacking anticholinergic properties and displays a higher potency, as compared to clozapine (1) itself.

[Analysis of the pyridinoline and deoxypyridinoline in urine by reversed-phase high performance liquid chromatography (RP-HPLC)]

A method for the simultaneous and rapid determination of pyridinoline and deoxypyridinoline in urine using RP-HPLC has been established. After hydrolysis for 18 hours at 107 degrees C in 6 mol/L HCl, the urine sample was prefractionated by partition chromatography using a column packed with cellulose CF1. The appropriate fractions were freeze-dried. The samples were analyzed by HPLC with a 5 microm Spherisorb C18 column, a mobile phase of MeOH/H2O containing 0.1% heptafluorobutyric acid at a rate of 1.2 mL/min and fluorescence detector monitoring at lambda(ex) 290 nm and lambda(em) 400 nm. The limit of a detection for PYD was 10 nmol/L and DPD 7 nmol/L. The recovery of PYD was 91.5% and that of DPD was 106.1%. Within day CV for the two compounds were 1.39% and 0.16% respectively and day-to-day CV 3.71% and 1.32% respectively.

Mortality from coronary heart disease and cardiovascular disease among adult U.S. Hispanics: findings from the National Health Interview Survey (1986 to 1994)

OBJECTIVES

We sought to estimate the coronary heart disease (CHD) and cardiovascular disease (CVD) mortality experience of U.S. Hispanics.

BACKGROUND

Limited information is available concerning the mortality from CHD among U.S. Hispanics, the nation's second largest minority group.

METHODS

The study used data from the National Health Interview Survey (1986 to 1994), including representative national samples of 246,239 non-Hispanic whites, 38,042 blacks and 14,965 Hispanics who were > or = 45 years old at baseline. Mean follow-up of mortality was 5 years (range 1 to 10).

RESULTS

During the follow-up period, 27,702 whites (11%), 4,976 blacks (13%) and 1,061 Hispanics (7%) died. Among men, the age-adjusted total mortality per 100,000 person-years was 3,089 in whites and 2,466 in Hispanics, and among women, it was 1,897 and 1,581 in whites and Hispanics, respectively. The Hispanic/white mortality rate ratio for CHD was 0.77 (95% confidence interval [CI] 0.64 to 0.93) and 0.82 (95% CI 0.66 to 1.01) for men and women, respectively. The rate ratio was 0.79 (95% CI 0.68 to 0.91) and 0.80 (95% CI 0.69 to 0.94), respectively, for mortality from cardiovascular diseases. Given the lower all-cause mortality in Hispanics, the proportion of total deaths due to CHD and CVD was similar between the two populations for the same gender and were, respectively, 29.7% and 44.7% in white men, 28.1% and 44.3% in Hispanic men, 24.9% and 43.2% in white women and 24.1% and 41% in Hispanic women.

CONCLUSIONS

These data from a cohort of a large national sample are consistent with vital statistics that show that all-cause, CHD and CVD mortality is approximately 20% lower among adult Hispanics than among whites in the United States.

Polarization characteristics of a Nd:YAG laser side pumped by diode laser bars

A detailed experimental investigation of the polarization characteristics of a diode laser side-pumped Nd:YAG laser has been performed. A Brewster plate inserted into the cavity resulted in a decrease of 50% of the output power that is due to depolarization. A thin-film polarizer (TFP) was introduced into the cavity and the depolarization loss served as the output coupling. By introduction of a quarter-wave plate (QWP) the output coupling rate and the beam shape were improved. An analytical expression for the output coupling rate of a cavity containing a TFP and a QWP has been derived. The experimental results are in good agreement with the simplified theoretical analysis.

Highly efficient diode-stack, end-pumped Nd:YAG slab laser with symmetrized beam quality

An efficient high-power cw Nd:YAG slab laser, partially end pumped by diode-laser stacks, and a novel beam-shaping technique are reported. The optical efficiency amounted to 44 %, and the slope efficiency amounted to 55 %. Introducing an intracavity Brewster plate to polarize the laser beam, we obtained an optical efficiency of 35 % and a slope efficiency of 41 %. The output beam was rectangular and the beam quality asymmetric in two orthogonal directions. To equalize the beam quality, we introduced a step-mirror beam-shaping technique. The beam-shaping technique and the results obtained are discussed.

[The preliminary study on WCMM machinable glass-ceramics]

The aim of this work was to investigate machinable glass-ceramics used as oral restoration material in K2O-MgO-Al2O3-SiO2-F glass system. By using of DTA, XRD and SEM investigation, the crystalline structure and characteristics were tested. The chemical composition of WCMM machinable glass-ceramics was defined by the following general formula: (K,Na)Mg3-3x Al2x (AlSi3) O10F2(0.5 < or = x < 0.7). The experimental results show that WCMM is an excellent oral restoration materials in the fabrication of crowns, inlayers and veneers.

Relative weight and mortality in U.S. blacks and whites: findings from representative national population samples

PURPOSE

To examine the impact of relative weight on mortality in black and white men and women.

METHODS

Two representative national populations samples were used: the NHANES-I Epidemiologic Follow-up Study (NHEFS), and the National Health Interview Survey (NHIS). The principal analysis focused on 13,242 participants in the NHEFS and 114,954 in the NHIS. Minimum mortality was estimated from both categorical analysis and a logistic model.

RESULTS

Minimum mortality ranged from a body mass index (BMI) of 25 to 32 kg/m2. The model-estimated BMI of minimum mortality for NHEFS was 27.1 (24.8-29.4, 95% CI), 26.8 (24.7-28.9, 95% CI), 24.8 (23.8-25.9, 95% CI) and 24.3 (23.2-25.4, 95% CI); for black men, black women, white men and white women, respectively, whereas for NHIS the corresponding values were 30.2 (24.8-35.6, 95% CI) 26.4 (24.2-28.7, 95% CI), 27.1 (25.5-28.7, 95% CI), and 25.6 (24.2-27.0, 95% CI). In all groups the shape of the relative risk curve was virtually identical and a broad range of BMI values in the middle of the distribution was associated with low relative mortality risk. Averaging the results from both surveys, the observed BMI of minimum risk was 3.1 kg/m2 higher in black men and 1.5 kg/m2 higher in black women than in their white counterparts; when adjusted for covariates these differences were only of borderline statistical significance, however.

CONCLUSIONS

Because of the wide range of BMI values associated with low risk, and the consistency of the point of the up-turn in risk, group specific definitions of optimal values do not appear to be warranted.

Rapid detection of Mycoplasma pneumoniae by an assay based on PCR and probe hybridization in a nonradioactive microwell plate format

A new molecular assay, based on a rapid DNA extraction protocol, PCR, and hybridization to a specific probe in a nonradioactive microwell plate format was used to detect Mycoplasma pneumoniae in bronchoalveolar fluid specimens. The sensitivity of the assay was determined to be 10 to 100 organisms with M. pneumoniae reference strains. Specificity testing with different bacteria capable of producing pneumonia showed no cross-reactivity. In a prospective study, bronchoalveolar lavage fluids obtained from patients with pneumonia were investigated with the PCR assay and compared to culture. Twelve positive samples were detected with the PCR assay. Seven of them were subsequently confirmed by culture. All patients with positive PCR results seroconverted. Application of the PCR assay described may lead to safe and early diagnosis of M. pneumoniae in patients with pneumonia.

[The crystallization feature of a castable apatite glass-ceramics]

The crystallization feature of a castable apatite glass-ceramics was studied by the means of DTA, XRD and SEM. The effect of chemical composition on the microsturcture of the glass-ceramics was discussed. The introduction of MgO and Al2O3 into the system has a substantial influence on the crystallization feature.

Dynamics and stability of a laser system with second-order nonlinearity

We use a multimode rate-equation model to investigate the stability of a laser system with second-order nonlinearity and compare the results with the literature on intracavity frequency-doubled lasers. The emphasis is on the Hopf bifurcation between the asymptotically stable state and the stable oscillation that occurs with variation of the conversion efficiency from the fundamental frequencies to their sum. This bifurcation results in two simple expressions that describe the stability curve, depending on material and cavity parameters. We also report on an experimental confirmation of the predicted temporal behavior of sum-frequency generation.

[The study on apatite castable glass-ceramics in composition and physicochemical properties]

The authors reported the result of the study of the glass formation range and physicochemical characteristics of apatite (APA) castable ceramics in the CaO-MgO-Al2O3-SiO2-P2O5 system. The relationship between its component and casting properties, the mechanical property and chemical stability was mainly discussed. The result showed that homogeneous glass could be formed in the experimental scope. This glass crystallized enamel-analogous apatite phase. It has improved mechanical property of parent glass, the bending strength was up to 165 MPa and possessed a fine chemical stability. This investigation could provide a new castable ceramics material for dental restoration.

Prediction of mortality risk by different methods of indexation for left ventricular mass

OBJECTIVES

We sought to compare the predictive value of echocardiographically determined left ventricular hypertrophy on death from all causes and cardiac mortality using various methods of indexation for left ventricular mass.

BACKGROUND

Considerable controversy exists regarding the optimal method for indexing left ventricular mass to body size in the clinical setting.

METHODS

The study included 988 consecutive patients who had both coronary angiograms and echocardiographic examinations in an inner-city public hospital in Chicago, Illinois. Patients were followed up for a mean of 7 years (range 2 to 11).

RESULTS

Various left ventricular mass indexes (e.g., mass indexed for height, height2, height2.13, height2.7, body surface area and body surface area1.5 were highly correlated (r = 0.90 to 0.99). Used as a continuous measure, an increase in any left ventricular mass index was associated with similar risk of death from all causes and cardiac diseases. Although left ventricular hypertrophy assessed by mass indexed for body surface area using the published conventional partition values provided somewhat better prediction, the adjusted relative risk was in general not significantly different from hypertrophy based on other indexes. Patients with left ventricular hypertrophy defined concordantly by indexes based on both body surface area and height (or height2.7) had, by definition, the highest average mass indexes among all groups and experienced as much as a threefold greater risk of death than those without hypertrophy. A small proportion of patients (12%) who were classified into the hypertrophy group by height-based indexes alone, but not by body surface area, had a moderate increase in mass and showed no increase in risk, even though being overweight was extremely prevalent in this group.

CONCLUSIONS

Because of the high correlation among various body size indexes, left ventricular hypertrophy, defined by different indexes for left ventricular mass, similarly confers increased risk of mortality in patients with or without coronary artery disease.

Performance of the automated COBAS AMPLICOR system for the detection of hepatitis C virus RNA

BACKGROUND

The COBAS AMPLICOR (CA) instrument for the amplification and detection steps of the AMPLICOR molecular diagnostic assays has recently been introduced. The system contains a single thermal cycler with two independently controlled heating/cooling blocks, a pipettor, a magnetic particle washer, a photometer and an incubator.

OBJECTIVE

The performance of the CA instrument was evaluated in a routine diagnostic laboratory for the detection of hepatitis C virus (HCV) RNA. The new system was compared with the corresponding microwell plate assay (AMPLICOR HCV Test).

STUDY DESIGN

Routine clinical sera (350) from hemodialysis patients and patients with chronic HCV infection and interferon therapy were studied. If discrepant results were obtained, both assays were repeated (specimen preparation, amplification and detection); in addition, the HCV copy number was determined with the AMPLICOR HCV MONITOR Test.

RESULTS

There was a correlation between the CA HCV Test and the AMPLICOR HCV Test in 341 of 350 specimens (97%). After resolution of 9 discrepant results, the CA HCV Test gave a sensitivity of 97.8% and a specificity of 99.4%. The most common reason for discrepant results was a low HCV RNA copy number.

CONCLUSION

The CA system was found to be a labor-saving, fast and reliable instrument for the amplification and detection steps of a RT-PCR molecular assay for detection of HCV RNA.

[Mechanism of protective action of Phyllanthus urinaria L. against injuries of liver cells]

It has been found out that the carbon tetrachloride (CCl4)-induced increase of serum glutamic-pyruvic transaminase (ALT) and elevation of MDA in liver of mice are significantly lowered by Phyllanthus urinaria in vivo, and the coincubation of isolated rat hepatocytes with Phyllanthus urinaria in vitro significantly inhibits CCl4-induced decrease of mobility of membrane of liver cells and increase of intracellular free Ca2+ ([Ca2+]i) concentrations of liver cells. These results suggest that the anti-lipid peroxidation effect and protective action of membrane of Phyllanthus urinaria may be related to its protective action against CCl4-induced liver injuries.

Effect of aspirin on prostaglandin E2 and leukotriene B4 production in human colonic mucosa from cancer patients

Results from epidemiological studies indicate that chronic administration of aspirin reduces the incidence of colon cancer. The mechanism that accounts for this reduction is not known, but it may be related to the decreased production of prostanoids that results from aspirin inhibition of cyclooxygenase. However, it is not known whether aspirin has a local effect on prostanoid production in the colonic mucosa and whether this effect is dose dependent. In this study, we determined the effect of oral administration of aspirin on the production of the prostanoid prostaglandin E2 (PGE2) in the intact human colonic mucosa. Inhibition of cyclooxygenase could result in an increased availability of arachidonic acid and a corresponding increase in production of other eicosanoids. To determine whether such an effect occurs, we also quantitated the concentration of leukotriene B4 (LTB4) in colonic mucosal samples. Mucosal samples were obtained during sigmoidoscopy from the colons of 17 subjects with a history of colonic cancer prior to and following 60 days of self-administration of 325 mg aspirin/day and again 60 days after administration of 650 mg aspirin/day. PGE2 and LTB4 concentrations were determined by enzyme immunoassay for tissue samples that were flash frozen after removal from the biopsy forceps and also in medium that was collected from tissue samples that were incubated for 4 h following removal from the subject. PGE2 concentrations were decreased significantly in samples collected after 60 days of consumption of 325 mg aspirin. An additional 60 days of consuming 650 mg aspirin/day did not result in a further significant decrease relative to that attained after consumption of 325 mg/day. Similar results were obtained using colonic explants, and the addition of aspirin to medium further reduced PGE2 production. LTB4 in tissue and medium was not significantly different in pre-versus post-aspirin samples, with the exception of an increased concentration in medium samples collected after consumption of 650 mg/day relative to pre-aspirin samples. The results indicate that aspirin affects eicosanoid production in the colonic mucosa of humans, but the effect is most likely restricted to products of the cyclooxygenase-dependent pathway. It appears that 325 mg of aspirin is sufficient to affect PGE2 production and that increasing the dosage to 650 mg daily provides an additional decrease in PGE2 synthesis. However, the higher dosage was associated with a considerable increase in complaints of gastric discomfort. Additional study is needed to establish whether doses less than 325 mg also provide a significant decrease in PGE2 production.

Selective reporter expression in mast cells using a chymase promoter

Primate alpha-chymases are mast cell neutral proteases that are involved in regulating several regulatory peptides including angiotensin II. Because of significant substrate specificity differences among the chymase group of enzymes, animal models that overexpress primate chymases are crucial for delineating the in vivo function of these enzymes. Activation of alpha-prochymase requires processing enzymes and proteoglycans found in mast cell secretory granules. Thus, the development of models overexpressing active primate chymase requires a mast cell-specific promoter. We show that the 571-base pair (bp) 5'-upstream sequence of the baboon chymase gene, which encodes an alpha-chymase, coupled to the prokaryotic lacZ gene allows the targeting of beta-galactosidase to mast cells in transgenic mice. Tissue expression of the transgene is similar to the expression of the endogenous mouse alpha-chymase mouse mast cell protease-5. A mouse mast cell line that endogenously expresses mouse mast cell protease-5 (JKras mast cells) also selectively supports the expression of this transgene. In vitro transcription studies in JKras mast cells shows the critical role of a GATA cis-regulatory motif in baboon chymase promoter, located approximately 430-bp upstream of the transcription start site. These results suggest that the 571-bp domain of the baboon chymase promoter contains most, if not all, of the mast cell-specific region of the promoter. We describe here for the first time a promoter that directs expression of transgenes specifically to mouse mast cells. This promoter should be generally applicable for dominant expression of mast cell regulatory proteins.

Apoptosis of human BEL-7402 hepatocellular carcinoma cells released by antisense H-ras DNA--in vitro and in vivo studies

Recent findings suggest that over-expression of activated H-ras inhibited apoptotic cell death by blocking the activity of apoptotic endonuclease(s). This study was designed using antisense H-ras oligodeoxynucleotides (ODN) to evaluate whether alterations of H-ras expression in BEL-7402 human hepatocellular carcinoma cells could influence the induction of apoptosis in vitro and in vivo. We found that, in vitro, continuous suppression of H-ras expression could decrease the proliferation of BEL-7402 cells and inhibit H-ras-induced entry into S phase. In situ end labeling showed that a large number of cells underwent apoptotic cell death after treatment with antisense H-ras ODN (P < 0.01), and gel electrophoresis of DNA extracted from these cells demonstrated a typical DNA ladder, characteristic of apoptosis. In vivo study indicated that pretreatment with antisense H-ras significantly retarded tumor growth in comparison with the untreated controls or tumors treated with non-specific ODN (P < 0.01, P < 0.01). In situ end-labeling revealed that pronounced apoptotic nuclei were also present in the tissue treated with antisense H-ras ODN (P < 0.01). Immunocyto-histochemical study showed that expression of p21H-ras was significantly decreased after treatment with antisense H-ras. These results indicate that suppression of H-ras over-expression by antisense ODN could effectively inhibit tumor growth and revive the apoptotic pathway by releasing the activity of apoptotic endonuclease(s). The data also suggest the need for further studies to elucidate molecular events involved in antisense H-ras-released apoptosis and evaluate its therapeutic implications.

Mechanism of anti-beta-adrenoceptor antibody mediated myocardial damage in dilated cardiomyopathy

Antibodies against beta(1)-adrenoceptor can be detected in serum of patients with dilated cardiomyopathy (DCM), which have beta-agonist-like activity, and induce a positive chronotropic effect on cardiac myocytes by its persistence at full strength. Effects of the antibodies against beta-adrenoceptor from sera of patients with DCM on myocardial cytotoxicity and cytoplasmic free Ca(2+)-concentration ([Ca2+]i) were observed in the cultured single layer SD rat ventricular cells by using the cytotoxicity assay and fluorescent Ca(2+)-indicator fura-2/AM. The positive sera of the anti-beta-adrenoceptor antibodies from patients with DCM markedly enhanced myocardial [Ca2+]i. Betaloc, a beta(1)-receptor blocker, might inhibit the increase of the antibody-mediated myocardial [Ca2+]i, and the sera from healthy donors had no effect on myocardial [Ca2+]i. Our results suggest that the anti-beta-adrenoceptor antibody might increase myocardial [Ca2+]i and result in myocardial damage. The antibodies might activate receptor-gating Ca(2+)-channel, thereby causing myocardial [Ca2+]i rise and calcium overload. Early use of betaloc is recommended in the treatment of dilated cardiomyopathy.

Patterns of comorbidity and mortality risk in blacks and whites

Comorbidity, the co-existence of multiple chronic conditions in a single individual, has been shown to modify the prognosis of disease states. To estimate disease burdens within and among racial subpopulations of the United States, we examined cross-sectional patterns of comorbidity and their impact on survival using data from the NHANES-1 Epidemiologic Follow-up Study (NHEFS). We considered the occurrence of four cardiovascular conditions: stroke, coronary heart disease, hypertension and diabetes. We summarize the joint occurrence of these four conditions using these different methodologies: the number of conditions occurring in each individual and two summaries that weight the conditions according to their prognostic significance. Using all three methodologies, we found an excess burden of chronic disease in black women as compared with white women. Black men had an excess burden compared to white men for the first two methodologies. However, when we model the relationship of the joint occurrence of the conditions to subsequent mortality, black men and white men are seen to have a similar burden. This similarity of black and white men is due to an interaction between race and prevalent stroke in men that we hypothesize may be due to the small number of black men available for study. Given the apparent conditioning effect of co-existing diseases, it is evident that estimation of disease burdens among groups that differ in terms of health status, in particular among U.S. blacks and whites, requires accounting for the occurrence of multiple chronic diseases. Using either the number of conditions or the prognosis weighted summary, we demonstrated a higher burden of the conditions considered in blacks that in whites in a sample of the U.S. population.

[The effect of antisense H-ras on growth and metastasis of a high metastatic tumor model of human hepatoma in nude mice LCI-D20]

OBJECTIVE

To investigate if treatment with antisense H-ras oligodeoxynucleotides (ODNs) modulates tumor growth, apoptosis and metastasis of a high metastatic tumor model of human hepatocellular carcinoma (HCC) in nude mice LCI-D20, in which over-expression of H-ras has been identified.

METHODS

LCI-D20 cells in primary culture were treated with 10 mumol/L antisense ODNs in vitro. 1.5 x 10(6) LCI-D20 cells with or without pretreatment were inoculated into each elevated subcutaneous (s.c) flap in fourteen nude mice, 6 animals for antisense H-ras ODN treated cells, 4 for H-ras non-specific antisense ODN treated cells, the rest 4 for cells without pretreatment.

RESULTS

In in vitro cell culture study, 5-day continuous suppression of H-ras expression by antisense H-ras ODNs resulted in significant inhibition of the proliferation of LCI-D20 cells (t = 31.529, P < 0.01). Cell cycle analysis showed a significant decrease in S phase (36.0 +/- 1.4) and a remarkable increase in G1/G0 fraction (56.7 +/- 1.1) after exposure to antisense H-ras ODNs in comparison with the cells without any treatment (58.5 +/- 0.9, t = 13.519, P < 0.01, 37.4 +/- 0.7, t = 14.802, P < 0.01). In situ end-labeling (ISEL) detection showed that apoptotic cell death was significantly increased in cells with 5-day treatment of antisense H-ras ODNs (34.0% +/- 4.5%) in comparing with cells without treatment (2.5% +/- 1.2%, t = 13. 434, P < 0.01) or treated with non-specific antisense ODNs (4.8% +/- 1.4%, t = 12.453, P < 0.01) at the corresponding time. In in vivo experiment, after six-week observation, tumor growth in antisense H-ras treated animals was significantly retarded in comparison with that of the untreated (t = 3.509, P < 0.01) or nonspecific antisense ODN treated animals (t = 3.452, P < 0.01).

CONCLUSIONS

Specific inhibition of H-ras expression by antisense H-ras ODNs could not only induce apoptotic cell death, inhibit the growth rate of LCI-D20 cells in vitro and in vivo, but also alter in vivo tumorigenesity and metastatic potential of LCI-D20 cells.

[The relationship between human chorionic gonadotrophin and lipoprotein metabolism]

We compared human chorionic gonadotrophin (hCG-beta) with lipids, lipoproteins and apolipoproteins in serum between pre- and postmenopausal women, and observed the changes of levels of hCG-beta in animals suffering from hypertriglyceridemia. The results have shown that the concentration of hCG-beta in postmenopausal women is much higher than that in premenopausal women (P < 0.001). Correspondingly, triglyceride (TG) is elevated (P < 0.05). High density lipoprotein cholesterol (HDL-C) and HDL-C/LDL-C ratio are decreased (P < 0.001, P < 0.01). On the other hand, the tendency of highing hCG-beta level has been found in animal study. The concentration of hCG-beta in male rats suffering form hypertriglyceridemia is higher than that in normal animals (P < 0.05).

Is hypertension more severe among U.S. blacks, or is severe hypertension more common?

It is frequently stated that the risk of sequelae from hypertension at a given level of severity is higher among blacks than whites, although little empirical evidence supports that supposition. In this work we examined the basis for accepting the existence of a black: white differential in hypertension outcomes in a representative biracial sample of the U.S. population followed in the First National Health and Nutrition Examination Survey (NHANES-1) Epidemiologic Follow-up Study. As well recognized, the risk associated with increasing blood pressure is not dichotomous but varies across the entire distribution in a curvilinear fashion. The rightward skew of the blood pressure distribution with increasing mean levels affects comparisons between populations, since the change in shape results in a change in the mix of case severity. These considerations can influence estimates of the relative population-attributable risk from hypertension, considered as a dichotomous classification in blacks and whites. Although the relative risk of death associated with a systolic blood pressure of > or = 140 mmHg in this study was higher for blacks than for whites (1.7 and 1.5, respectively), with all-cause mortality as the outcome, the logistic coefficient for systolic blood pressure was not significantly different among white as compared with black men (beta = 0.016 vs. 0.010; p = 0.320 for race interaction term) and was slightly greater among white vs. black women (beta = 0.013 vs. 0.010; P = 0.05). After strata-specific blood pressure adjustment, the principal determinant of increased population risk for both black men and women was the higher prevalence of hypertension, not differential severity. The population-attributable risk for hypertension was at least two times higher among blacks because of the higher prevalence among them; moreover, the increased prevalence accounted for 10% of the interethnic difference in mortality. Data from this study indicate that hypertension was not more severe among individual blacks, simply more common in the population.