Linkage and association analysis of angiotensin I-converting enzyme (ACE)-gene polymorphisms with ACE concentration and blood pressure

Considerable effort has been expended to determine whether the gene for angiotensin I-converting enzyme (ACE) confers susceptibility to cardiovascular disease. In this study, we genotyped 13 polymorphisms in the ACE gene in 1,343 Nigerians from 332 families. To localize the genetic effect, we first performed linkage and association analysis of all the markers with ACE concentration. In multipoint variance-component analysis, this region was strongly linked to ACE concentration (maximum LOD score 7.5). Likewise, most of the polymorphisms in the ACE gene were significantly associated with ACE (P<.0013). The two most highly associated polymorphisms, ACE4 and ACE8, accounted for 6% and 19% of the variance in ACE, respectively. A two-locus additive model with an additive x additive interaction of these polymorphisms explained most of the ACE variation associated with this region. We next analyzed the relationship between these two polymorphisms (ACE4 and ACE8) and blood pressure (BP). Although no evidence of linkage was detected, significant association was found for both systolic and diastolic BP when a two-locus additive model developed for ACE concentration was used. Further analyses demonstrated that an epistasis model provided the best fit to the BP variation. In conclusion, we found that the two polymorphisms explaining the greatest variation in ACE concentration are significantly associated with BP, through interaction, in this African population sample. Our study also demonstrates that greater statistical power can be anticipated with association analysis versus linkage, when markers in strong linkage disequilibrium with a trait locus have been identified. Furthermore, allelic interaction may play an important role in the dissection of complex traits such as BP.

Heritability of angiotensin-converting enzyme and angiotensinogen: A comparison of US blacks and Nigerians

Angiotensinogen (AGT) and angiotensin I-converting enzyme (ACE) are heritable traits, but whether the environmental context influences heritability has not been examined. Known genetic factors explain only a portion of variation in AGT and ACE, and levels of both proteins are influenced by the environment. The African diaspora provides an opportunity to compare these traits in genetically related populations in contrasting environments. As part of a study of the genetics of hypertension, we examined families that included 1449 Nigerians and 1147 African Americans. Body mass index (weight [kg]/height [m](2)) was 21 kg/m(2) in Nigeria and 29 kg/m(2) in the United States, which is consistent with a large environmental contrast. AGT was considerably higher among African Americans (1919 versus 1396, P<0.01), whereas ACE was higher in Nigerians (630 versus 517, P<0.01). A household effect was observed among the Nigerian families (spouse correlations 0.30 for AGT, 0.18 for ACE), and correlations among first-degree relatives were large (0.42 to 0. 51 and 0.36 to 0.38 for AGT and ACE, respectively). Among African Americans, the familial aggregations of AGT and ACE were very limited, and the familial correlation for AGT was not different from zero. Heritability was 77% for AGT and 67% for ACE in Nigeria and 18% for AGT and ACE in the United States. The familial patterns of body mass index and blood pressure were similar among both family sets. In conclusion, less familial aggregation was observed for AGT and ACE in the United States than in Nigeria, most likely reflecting a greater random individual environmental effect on these traits. Variation in heritability of traits could influence the power of epidemiological studies to identify genetic effects.

The distribution and mortality impact of chronic energy deficiency among adult Nigerian men and women

OBJECTIVE

To determine the prevalence of chronic energy deficiency (CED) and associated mortality risk in a cohort of adult Nigerians followed from 1992 to 1997.

RESEARCH METHODS AND PROCEDURES

The data for this investigation were derived from an international collaborative study on chronic diseases in populations of the African diaspora. Body mass index (BMI) was used to define three grades of CED in 4061 men and women aged 25 years and older: Grade I (mild CED) as BMI 17.5-18.4, Grade II (moderate CED) as BMI 16.0-17.4, and Grade III (severe CED) as BMI < 16.0 and BMI > or = 18.5 was considered normal. The odds of mortality associated with differing grades of CED was estimated with logistic regression analysis.

RESULTS

The prevalence of CED (BMI < 18.5) increased from 14.3% in 1992 to 19.6% in 1997, both genders combined. The prevalence of CED was similar for both sexes in 1992 (14%) but increased to 22.4% in men and 17.4% in women by 1997. The prevalence of CED was 8.5%, 7.6 and 3.4 for Grades I, II and III, respectively. Two hundred and seven deaths occurred during the follow-up period. The mortality rate for the 5.5 y of follow-up was 5.1% (207/4061). The odds ratios (95% CIs) for all cause mortality were 1.4 (0.5, 3.8), 2.4 (1.2, 4.9) and 2.5 (1.0, 6.2), respectively, for CED grades I, II and III adjusting for age and sex.

CONCLUSION

Under nutrition is an increasing problem in Nigerian men and women. The economic reforms (structural adjustment program (SAP)) introduced in 1986 in combination with the continued economic woes brought on by political instability, corruption and nepotism have been advanced by several investigators as the main factors in the growing problem of inadequate calorie intake. Intervention strategies both at the government and private sectors are urgently needed to increase food availability.

Staphylococcal pericarditis with pyopericardium

Seven previously well patients with acute staphylococcal pericarditis and purulent pericardial effusion are described. All had a septicaemic illness in which worsening heart failure with signs of cardiac tamponade became the major problems of management. Tropical pyomyositis was probably the predisposing illness in four patients. This number of proven cases within an 18-month period suggests that staphylococcal pyopericardium is in a tropical environment probably commoner than realised.

Simultaneous bilateral carotid endarterectomies

Twelve patients with bilateral symptomatic lesions of internal carotid arteries have had bilateral carotid endarterectomy at single operations without complications. These were patients up to age 80 who had prior mycardial infarction, stroke with recovery, and hemispheric and nonhemispheric episodes. Neurologist's clearance and three- or four-vessel intracranial-extracranial angiography preceded all operations, which were performed with the patient under general anesthesia. Stump pressure measurements were the principal guideline of adequacy of collateral flow and predictor of safe outcome. The safety of this concept of bilateral operations during one anesthesia can eliminate uncertainties of sequence and timing, obviate delay and indecision, and avoid the hazards of a second anesthetic-operative experience.

Aortic insufficiency. A result of intermittent migration of aortic valve prosthesis poppet

A bizarre mechanism of aortic valve incompetence was observed when the occluder of a Braunwald-Cutter aortic valve prosthesis decreased in diameter, volume, and weight, and from time to time fell into the left ventricle. The patient's symptoms were palpitation, coughing, chocking sensations, and fright. An operation disclosed a small, smooth ball with disrupted cloth on all the struts. The residual torn mesh was removed, and the ball was replaced.

Colostomy. Intraperitoneal or extraperitoneal closure?

Forty-three patients who underwent intraperitoneal closure of colostomy are reported on. Complication rates of 4.6 per cent for wound infection and 4.6 per cent for fecal fistulas appear significantly lower than the 10 to 21 per cent complication rates reported for colostomy closure using other technics.