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PubMed1997

Classification of the southern African sanga and east African shorthorned zebu.

Humped African cattle, which are differentiated into zebu and sanga types, have traditionally been classified as Bos indicus. This paper discusses existing evidence and presents new evidence supporting the classification of southern African sangas as Bos taurus and East African zebus as 'taurindicus'. Classification is based on karyotype, frequencies of DNA markers and protein polymorphisms. The Boran, an East African zebu, has an acrocentric Y chromosome typical of Bos indicus. The southern African sanga breeds have a submetacentric Y chromosome typical of Bos taurus. Frequencies of four DNA markers support the hypothesis that the Tuli, a southern African sanga, had taurine ancestors and the Boran had both taurine and indicine ancestors. Frequencies for several protein polymorphisms strongly suggest that southern African sangas have more in common with taurine than with indicine breeds, while East African zebus are an admixture of African taurine and Asian indicine breeds.

Africa, Eastern↗

PubMed2005

African sequence variation accounts for most of the sequence polymorphism in non-African Drosophila melanogaster.

We compared the sequence polymorphism of 12 genomic fragments in six geographically dispersed African populations to one European Drosophila melanogaster population. On the basis of one African and one European population half of these fragments have strongly reduced levels of variability outside of Africa. Despite this striking difference in European variation, we detected no significant difference in African variation between the two fragment classes. The joint analysis of all African populations indicated that all high-frequency European alleles are of African origin. We observed a negative Tajima's D in all African populations, with three populations deviating significantly from neutral equilibrium. Low, but statistically significant, population differentiation was observed among the African populations. Our results imply that the population structure and demographic past of African D. melanogaster populations need to be considered for the inference of footprints of selection in non-African populations.

Africa↗

PubMed1995

Metabolic characteristics of African descendants: a comparative study of African-Americans and Ghanaian immigrants using minimal model analysis.

We have previously demonstrated that glucose-tolerant American blacks manifest significantly higher insulin concentrations and a lower insulin sensitivity than native African blacks who reside in their respective countries. It is, however, unknown whether the serum glucose, beta-cell function and insulin sensitivity are different in native Africans and African-Americans who reside in the same environments. We have studied 68 healthy American blacks and age- and weight-matched 30 African blacks recently immigrated from Ghana residing in Franklin County, Ohio, USA. Each subject underwent a standard oral glucose tolerance test to determine glucose tolerance status. Insulin sensitivity index (Si) and glucose effectiveness (Sg) were measured by the insulin-modified, frequently-sampled intravenous glucose tolerance test. The body composition variables were measured by the bioelectrical impedance analyser and body fat distribution pattern by the waist-hip ratio. The clinical characteristics were identical in the African-American and the African blacks; the mean fasting serum glucose, insulin and C-peptide levels were not different. Following the oral and intravenous glucose administration, the mean peak and incremental areas of serum glucose, insulin and C-peptide were not different in the two groups. The mean Si (3.1 +/- 0.7 vs 2.4 +/- 0.3 x 10(-4).(min/microU.1-1)-1 and Sg (2.5 +/- 0.3 vs 2.7 +/- 0.2 x 10(-2).min-1) were not significantly different in the American and African blacks, respectively. In summary, the metabolic parameters measured in the American blacks and recent African immigrants were identical.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1997

Five complete genomes of JC virus type 3 from Africans and African Americans.

The central demyelinating disease progressive multifocal leukoencephalopathy (PML) is caused by the human polyomavirus JC virus (JCV). JCV evolved as geographically based genotypes of which Type 3 is an African variant first characterized in HIV-1 positive patients from Tanzania. This study reports the complete sequence of five JCV Type 3 strains. The entire JCV genome was PCR amplified from urine specimens of three African and two African-American individuals. The African consensus sequence was compared to the Type 1 and Type 2 prototype strains, JCV (Mad-1) and JCV(GS/B), respectively. Type 3 differed in 2.2% of its coding region genome from JCV (Mad-1) and in 1.3% from JCV(GS/B). Within the coding region the sequence variation among the three types was higher in the capsid protein VP1 and in the regulatory protein large T antigen than in the agnoprotein or in VP2/3. Notable Type 3-specific changes were located at sites adjacent to the zinc finger motif and near the major donor and acceptor splice junctions of large T antigen. Four of the five urinary Type 3 strains had an unrearranged, archetypal regulatory region. African strain #309 showed a 10-bp deletion at a location similar to that previously described for #307 from Tanzania. The African-American Type 3 strain #312 was closely related to the African consensus sequence. The complete genome of a urinary JCV strain from another African-American male, previously reported as a possible Type 5, showed a sequence difference of only 0.52% from the Tanzanian consensus and has been reclassified as a subtype of Type 3.

Amino Acid Sequence↗

PubMedDate not supplied

Postprostatectomy cancer-free survival of African Americans is similar to non-African Americans after adjustment for baseline cancer severity.

African American men with localized prostate cancer are less likely than White men to receive a radical prostatectomy. This disparity may exist because African American men have prostate cancers that are more biologically aggressive. We investigated if similar stage cancers of African American men and White men show differences in cancer control after radical prostatectomy. Men with localized prostate cancer who underwent radical prostatectomy during a 6-yr period were stratified by race, and time to prostate-specific antigen recurrence was measured. We used Chi-square and t-tests to compare baseline clinical and pathological factors based on race. Cox proportional hazards model was used to determine effects of race on cancer control while controlling for baseline measures of cancer severity. There were 1,228 cases evaluated. At baseline, African American men were treated at a significantly younger age than White men (P = 0.0027) but showed no significant difference in prostate-specific antigen PSA, Gleason score, pathology stage, maximum tumor dimension, and surgical margin status. Multivariable Cox proportional hazards analysis controlling for cancer severity at prostatectomy revealed that cancer-free survival was not worse among African Americans compared to other subjects (P = 0.16). The responsiveness of prostate cancers among African American men to radical prostatectomy was similar to White men of similar stage and grade. Early detection in African American men may facilitate diagnosis of cancer amenable to prostatectomy. Studies are needed to evaluate the possible interaction of prostate cancer stage and grade shift in African American men and the disease free survival in this population.

Black or African American↗

PubMedDate not supplied

Iron overload in Africans and African-Americans and a common mutation in the SCL40A1 (ferroportin 1) gene.

The product of the SLC40A1 gene, ferroportin 1, is a main iron export protein. Pathogenic mutations in ferroportin 1 lead to an autosomal dominant hereditary iron overload syndrome characterized by high serum ferritin concentration, normal transferrin saturation, iron accumulation predominantly in macrophages, and marginal anemia. Iron overload occurs in both the African and the African-American populations, but a possible genetic basis has not been established. We analyzed the ferroportin 1 gene in 19 unrelated patients from southern Africa (N = 15) and the United States (N = 4) presenting with primary iron overload. We found a new c. 744 C-->T (Q248H) mutation in the SLC40A1 gene in 4 of these patients (3 Africans and 1 African-American). Among 22 first degree family members, 10 of whom were Q248H heterozygotes, the mutation was associated with a trend to higher serum ferritin to amino aspartate transferase ratios (means of 14.8 versus 4.3 microg/U; P = 0.1) and lower hemoglobin concentrations (means of 11.8 versus 13.2 g/dL; P = 0.1). The ratio corrects serum ferritin concentration for alcohol-induced hepatocellular damage. We also found heterozygosity for the Q248H mutation in 7 of 51 (14%) southern African community control participants selected because they had a serum ferritin concentration below 400 microg/L and in 5 of 100 (5%) anonymous African-Americans, but we did not find the change in 300 Caucasians with normal iron status and 25 Caucasians with non-HFE iron overload. The hemoglobin concentration was significantly lower in the African community controls with the Q248H mutation than in those without it. We conclude that the Q248H mutation is a common polymorphism in the ferroportin 1 gene in African populations that may be associated with mild anemia and a tendency to iron loading.

Black or African American↗

PubMed2005

Lung cancer in Africans in a South African city population in transition.

In South Africa, a study has been carried out on a series of African patients with lung cancer, who were admitted in 1994-1999 to King Edward VIII Hospital (2000 beds), and who lived in Durban (population includes approximately 650 000 resident Africans). In the urban context, Africans have recently experienced numerous changes in environmental, socio-economic and dietary factors and in other respects, thereby undergoing considerable westernization of lifestyle, compared with the past and the situation still prevailing among Africans in rural areas. In the period indicated, the mean annual number of patients admitted with lung cancer included 56 men and 9 women, thereby yielding standardized incidence rates of 15.5 and 3.5, respectively, per 100 000. While such data have their limitations, it is noteworthy that in the South African Cancer Registry for 1993-1995 the corresponding rates (pathology based) for African men and women for the whole country, rural and urban, were 11.7 and 2.6, respectively, per 100 000. In comparison, in the Registry the corresponding rates reported for white South African men and women were 22.3 and 12.3 per 100 000. With the ongoing transitional changes prevailing, most particularly concerning rises in smoking among adolescents, there is little chance of controlling further rises in the occurrence of the disease. It is significant that in the US, African Americans have been reported to have the highest rate for lung cancer in the world.

Adolescent↗

PubMedDate not supplied

Social risks and psychological adjustment: a comparison of African American and South African children.

In the United States, race is highly associated with social risk factors such as poverty and family structure that may account by themselves for developmental outcomes often attributed to race alone. This cross-national study assesses the effects of social risks on adjustment of racially similar groups of 306 African American and 625 South African 6-year-olds. Poverty and gender were confirmed as risk factors but single female headship was not. Moreover, poverty and gender posed less risk for South African than for African American children. Poverty placed children at risk for immaturity, hyperactivity, and difficulty in peer relations. Boys were more likely to have behavior problems than were girls. African Americans exhibited higher rates of emotional symptoms but lower rates of bullying, destructiveness, and social rejection than did South Africans. African Americans, particularly the males, scored higher on the opposition and hyperactivity scales than did South Africans. Distinctive social contexts and cultural resources may account for differences in adjustment.

Adaptation, Psychological↗

PubMed2000

Lower hypertension prevalence in first-generation African immigrants compared to US-born African Americans.

Both genetic and environmental factors have been hypothesized to explain the higher prevalence of hypertension in US African Americans compared to populations still residing in western Africa. Studies of first-generation immigrants can help to identify risk factors for increased chronic disease expression in the developed world. Since we could identify no prior studies of hypertension in African immigrants to the United States, we conducted a cross-sectional survey of African-born and US-born African-American health professionals to compare the two groups for the prevalence of hypertension (blood pressure > or = 140/90 mm Hg or use of antihypertensive medication) and risk factors for hypertension (body mass index, lifestyle factors, and psychosocial variables hypothesized to relate to hypertension). Subjects were registered pharmacists and nurses recruited by mail. For the 182 individuals who completed study measurements (95 US-born and 87 African-born), the unadjusted odds ratio for hypertension associated with birthplace was 2.16 (95% CI = 1.12, 3.98). After adjustment for body mass index and age, the OR for birthplace was 1.92 (95% CI = 0.92, 4.00). No lifestyle or psychosocial variables were associated with hypertension prevalence. We conclude that there is a lower prevalence of hypertension in first-generation African immigrants that cannot be readily explained by the environmental effects measured in this study. Larger scale studies with African immigrants could advance understanding of the causes of the increased hypertension prevalence in US-born African Americans.

Africa↗

PubMed2000

mtDNA variation in the South African Kung and Khwe-and their genetic relationships to other African populations.

The mtDNA variation of 74 Khoisan-speaking individuals (Kung and Khwe) from Schmidtsdrift, in the Northern Cape Province of South Africa, was examined by high-resolution RFLP analysis and control region (CR) sequencing. The resulting data were combined with published RFLP haplotype and CR sequence data from sub-Saharan African populations and then were subjected to phylogenetic analysis to deduce the evolutionary relationships among them. More than 77% of the Kung and Khwe mtDNA samples were found to belong to the major mtDNA lineage, macrohaplogroup L* (defined by a HpaI site at nucleotide position 3592), which is prevalent in sub-Saharan African populations. Additional sets of RFLPs subdivided macrohaplogroup L* into two extended haplogroups-L1 and L2-both of which appeared in the Kung and Khwe. Besides revealing the significant substructure of macrohaplogroup L* in African populations, these data showed that the Biaka Pygmies have one of the most ancient RFLP sublineages observed in African mtDNA and, thus, that they could represent one of the oldest human populations. In addition, the Kung exhibited a set of related haplotypes that were positioned closest to the root of the human mtDNA phylogeny, suggesting that they, too, represent one of the most ancient African populations. Comparison of Kung and Khwe CR sequences with those from other African populations confirmed the genetic association of the Kung with other Khoisan-speaking peoples, whereas the Khwe were more closely linked to non-Khoisan-speaking (Bantu) populations. Finally, the overall sequence divergence of 214 African RFLP haplotypes defined in both this and an earlier study was 0.364%, giving an estimated age, for all African mtDNAs, of 125,500-165,500 years before the present, a date that is concordant with all previous estimates derived from mtDNA and other genetic data, for the time of origin of modern humans in Africa.

Black People↗

PubMed2002

Structural analysis of insulin minisatellite alleles reveals unusually large differences in diversity between Africans and non-Africans.

The insulin minisatellite (INS VNTR) associates with susceptibility to a variety of diseases. We have developed a high-resolution system for analyzing variant repeat distributions applicable to all known minisatellite alleles, irrespective of size, which allows lineages of related alleles to be identified. This system has previously revealed extremely low structural diversity in the minisatellite among northern Europeans from the United Kingdom, with all alleles belonging to one of only three highly diverged lineages called "I," "IIIA," and "IIIB." To explore the origins of this remarkably limited lineage diversity, we have characterized an additional 780 alleles from three non-African and three African populations. In total, 22 highly diverged lineages were identified, with structural intermediates absent from extant populations, suggesting a bottleneck within the ancestry of all humans. The difference between levels of diversity in Africans and non-Africans is unusually large, with all 22 lineages identified in Africa compared with only three lineages seen not only in the United Kingdom but also in the other non-African populations. We also find evidence for overrepresentation of lineage I chromosomes in non-Africans. These data are consistent with a common out-of-Africa origin and an unusually tight bottleneck within the ancestry of all non-African populations, possibly combined with differential and positive selection for lineage I alleles in non-Africans. The important implications of these data for future disease-association studies are discussed.

Africa↗

PubMed2002

Larger genetic differences within africans than between Africans and Eurasians.

The worldwide pattern of single nucleotide polymorphism (SNP) variation is of great interest to human geneticists, population geneticists, and evolutionists, but remains incompletely understood. We studied the pattern in noncoding regions, because they are less affected by natural selection than are coding regions. Thus, it can reflect better the history of human evolution and can serve as a baseline for understanding the maintenance of SNPs in human populations. We sequenced 50 noncoding DNA segments each approximately 500 bp long in 10 Africans, 10 Europeans, and 10 Asians. An analysis of the data suggests that the sampling scheme is adequate for our purpose. The average nucleotide diversity (pi) for the 50 segments is only 0.061% +/- 0.010% among Asians and 0.064% +/- 0.011% among Europeans but almost twice as high (0.115% +/- 0.016%) among Africans. The African diversity estimate is even higher than that between Africans and Eurasians (0.096% +/- 0.012%). From available data for noncoding autosomal regions (total length = 47,038 bp) and X-linked regions (47,421 bp), we estimated the pi-values for autosomal regions to be 0.105, 0.070, 0.069, and 0.097% for Africans, Asians, Europeans, and between Africans and Eurasians, and the corresponding values for X-linked regions to be 0.088, 0.042, 0.053, and 0.082%. Thus, Africans differ from one another slightly more than from Eurasians, and the genetic diversity in Eurasians is largely a subset of that in Africans, supporting the out of Africa model of human evolution. Clearly, one must specify the geographic origins of the individuals sampled when studying pi or SNP density.

Africa↗

PubMed2005

Africanization in the United States: replacement of feral European honeybees (Apis mellifera L.) by an African hybrid swarm.

The expansion of Africanized honeybees from South America to the southwestern United States in <50 years is considered one of the most spectacular biological invasions yet documented. In the American tropics, it has been shown that during their expansion Africanized honeybees have low levels of introgressed alleles from resident European populations. In the United States, it has been speculated, but not shown, that Africanized honeybees would hybridize extensively with European honeybees. Here we report a continuous 11-year study investigating temporal changes in the genetic structure of a feral population from the southern United States undergoing Africanization. Our microsatellite data showed that (1) the process of Africanization involved both maternal and paternal bidirectional gene flow between European and Africanized honeybees and (2) the panmitic European population was replaced by panmitic mixtures of A. m. scutellata and European genes within 5 years after Africanization. The post-Africanization gene pool (1998-2001) was composed of a diverse array of recombinant classes with a substantial European genetic contribution (mean 25-37%). Therefore, the resulting feral honeybee population of south Texas was best viewed as a hybrid swarm.

Africa↗

PubMed2005

Informing cancer prevention strategies for African Americans: the relationship of African American acculturation to fruit, vegetable, and fat intake.

Acculturation has been associated with health-related behaviors in African Americans. We sought to determine if there is a relationship between acculturation and dietary intake in African Americans. African Americans in the PREMIER trial completed the African American Acculturation Scale (AAAS) and 2 nonconsecutive 24-h dietary recalls (n = 238). Analysis of variance (ANOVA) and canonical correlation were used to assess relationships between acculturation and dietary intakes. Canonical correlation (p = 0.05) showed that traditional African Americans had lower intakes of fruits/vegetables and milk/dairy with higher intakes of fats, meat, and nuts. This pattern was supported by differences in the ANOVA. African American acculturation is related to dietary intake. These findings have implications for the design of cancer-related public health messages targeted to African Americans.

Acculturation↗

PubMed2005

Physical activity, cardiorespiratory fitness, and their relationship to cardiovascular risk factors in African Americans and non-African Americans with above-optimal blood pressure.

This report describes cross-sectional associations among physical activity, cardiorespiratory fitness, dietary habits, and cardiovascular disease (CVD) risk factors in a large sample (n = 810) of African Americans (n = 279) and non-African Americans (n = 531) with above-optimal blood pressure. Participants in PREMIER, a clinical trial for blood pressure control through lifestyle approaches, underwent baseline assessments to determine physical activity level, cardiorespiratory fitness category, dietary intake, and CVD risk factors. Mean levels of body mass index (BMI), total cholesterol, LDL cholesterol, HDL cholesterol, daily percent calories from fat and saturated fat, daily servings of fruits and vegetables, and daily fiber intake were examined across three physical activity levels and two fitness categories. Hypertension status was also assessed. Data were stratified by sex and ethnicity. For all participants, those in the low fitness category had higher BMI levels. Total cholesterol was lower in African American women in the high fitness category. Mean values of more than five daily servings of fruits and vegetables were reported by non-African American women and African American men in the high activity category. Higher intake of dietary fiber was found for non-African American women at the high activity level, with a similar trend observed for African American women. Future work examining these associations prospectively should include sufficient minority representation to enhance generalizability to all population groups and determine the beneficial effects from increased physical activity and improved cardiorespiratory fitness.

Adult↗

PubMed1997

The "Bantu Clinic": a genealogy of the African patient as object and effect of South African clinical medicine, 1930-1990.

This paper is about power, medicine and the identity of the African as a patient of western medicine. From a conventional perspective and as encoded in the current "quest for wholeness" that characterises South African biomedical discourse, the African patient--like any other patient--has always existed as an authentic and subjectified being, whose true attributes and experiences have been denied by the "mechanistic," "reductionistic" and "ethnocentric" practices of clinical medicine. Against this liberal humanist perspective on the body as ontologically independent of power, this paper offers a Foucaultian reading of the African patient as-like any other patient--contingent upon the force relations immanent within and relayed through the clinical practices of biomedicine. A quintessential form of disciplinary micro-power, these fabricate the most intimate recesses of the human body as manageable objects of medical knowledge and social consciousness to make possible the great control strategies of repression, segmentation and liberation that are the usual focus of conventional investigations into the place and function of medicine in society. Since the 1930s when the African body first emerged as a discrete object of a secular clinical knowledge, these have repeatedly transformed the attributes and identity of the African patient, and the paper traces this archaeology of South African clinical perception from then until the 1990s to show how its "quest for wholeness" is not an end point of "discovery" or "liberation," but merely another ephemeral crystallization of socio-medical knowledge in a constantly changing force field of disciplinary power.

Black or African American↗

PubMed2004

Novel 180- and 480-base-pair insertions in African and African-American strains of Helicobacter pylori.

Helicobacter pylori is a genetically diverse bacterial species that chronically infects human stomachs and sometimes causes severe gastroduodenal disease. Studies of polymorphic DNA sequences can suggest geographic origins of individual strains. Here, we describe a 180-bp insertion (ins180), which is just after the translation stop of a gene of unknown function, near the promoter of jhp0152-jhp0151 two-component signal transduction genes in strain J99, and absent from this site in strain 26695. This ins180 insertion was found in 9 of 9 Gambian (West African), 9 of 20 (45%) South African, and 9 of 40 (23%) Spanish strains but in only 2 of 20 (10%) North American strains and none of 20 Lithuanian, 20 Indian, and 20 Japanese strains. Four South African isolates that lacked ins180 and that belonged to an unusual outlier group contained a 480-bp insertion at this site (ins480), whereas none of 181 other strains screened contained ins480. In further tests 56% (10 of 18) of strains from African Americans but only 17% (3 of 18) of strains from Caucasian Americans carried ins180 (P < 0.05). Thus, the H. pylori strains of modern African Americans seem to retain traces of African roots, despite the multiple generations since their ancestors were taken from West Africa. Fragmentary ins180-like sequences were found at numerous sites in H. pylori genomes, always between genes. Such sequences might affect regulation of transcription and could facilitate genome rearrangement by homologous recombination. Apparent differences between African-American and Caucasian-American H. pylori gene pools may bear on our understanding of H. pylori transmission and disease outcome.

Black or African American↗

PubMed2002

Stroke risk factor profiles in African American women: an interim report from the African-American Antiplatelet Stroke Prevention Study.

BACKGROUND AND PURPOSE: If sex differences in stroke risk factor profiles exist among African Americans in the United States, prevention strategies will need to reflect those differences. African Americans and women have been underrepresented in stroke prevention studies. The purpose of this study was to determine whether medical and lifestyle factors differ among women and men who have enrolled in the African-American Antiplatelet Stroke Prevention Study (AAASPS). METHODS: We performed a planned exploratory analysis of differences in baseline characteristics and risk factors between women and men enrolled in AAASPS, a double-blind, randomized, multicenter, controlled trial. Frequencies of vascular risk factors and related conditions, medical therapies, stroke subtypes, and vascular territories were compared between women and men by 1-way ANOVA and Fisher's exact test where appropriate. RESULTS: A total of 1087 African American patients (574 women, 513 men) enrolled between December 1995 and June 1999. Women had higher rates of hypertension, diabetes, family history of stroke, and no reported leisure exercise. Men had higher rates of smoking and heavy alcohol use. Few differences were noted in proportions of stroke subtype or proportions receiving preventive therapy. CONCLUSIONS: AAASPS represents the largest enrollment of African American women in a recurrent stroke prevention study. Our data suggest that African American women in a clinical trial differ from men in the frequency of key vascular risk factors. Although limited, these data provide an important first characterization of sex differences in African Americans with stroke.

Black or African American↗