Tropical African Population Research Articles

Carbon and nitrogen isotopic signatures of hair, nail, and breath from tropical African human populations

Stable isotopic analyses are increasingly used to study the diets of past and present human populations. Yet, the carbon and nitrogen isotopic data of modern human diets collected so far are biased towards Europe and North America. Here, we address this gap by reporting on the dietary isotopic signatures of six tropical African communities: El Molo, Turkana (Kerio), Luhya (Webuye), Luhya (Port Victoria), and Luo (Port Victoria) from Kenya, and Baka from Cameroon; representing four subsistence strategies: fishing, pastoralism, agriculturalism, and hunter-gatherer. We used an elemental analyser coupled in continuous-flow mode to an isotope ratio mass spectrometer to measure the carbon and nitrogen isotopic ratios of hair (n= 134) and nail (n= 80) and the carbon isotopic ratios of breath (n= 184) from these communities, as well as the carbon and nitrogen isotopic ratios of some food samples from the Kenyan communities. We expand on the known range of δ13 C values in human hair through the hunter-gatherer Baka, with a diet based on C3 plants, and through the agriculturalist Luhya (Webuye), with a diet based on C4 plants. In addition, we found that the consumption of fish from East African lakes is difficult to detect isotopically due to the combined effects of high nitrogen isotopic ratios of plants and the low nitrogen isotopic ratios of fish. Finally, we found that some of the communities studied are markedly changing their diets through increasing sedentism and urbanisation. Our findings contribute substantially to the understanding of the environmental, demographic, and economic dynamics that affect the dietary landscape of different tropical populations of Africa. These results highlight the importance of studying a broader sample of human populations and their diet, with a focus on their precise context - from both isotopic and more general anthropological perspectives.

Effects of a low dose of ethanol on mating success of Drosophila melanogaster males: implications for the evolution of ethanol resistance?

Ethanol occurs naturally in the decaying fruit in which many species of Drosophila (Diptera: Drosophilidae) breed, potentially generating selection for resistance to its toxic and sedating effects. Studies measuring mortality of flies exposed to a range of ethanol concentrations have shown that within Drosophila melanogaster Meigen, populations from temperate regions are more ethanol resistant than ancestral tropical African populations. The high ethanol resistance of temperate D. melanogaster presents a puzzle, however, because breeding and feeding sites in the wild seldom contain enough ethanol to kill even more ethanol-sensitive Afrotropical genotypes. We hypothesize that the ethanol concentrations encountered by temperate populations, though usually sub-lethal, are nonetheless high enough to reduce fitness in other ways, potentially generating indirect selection for genotypes that can survive exposure to unnaturally high ethanol concentrations. As a first step in testing this hypothesis, we compared the effects of a sub-lethal dose of ethanol, comparable to that obtainable from fermenting fruit, on the mating success of males from one European and one Afrotropical population. Ethanol significantly reduced mating success of males from the Afrotropical population, but had no effect on that of males from the European population. We also show that when flies are placed on medium with a realistic concentration of ethanol, considerably more ethanol is absorbed through vapor than through feeding, suggesting that courting males may be unable to avoid being exposed to ethanol. We hypothesize that the higher resistance of temperate populations to being killed by high, unnatural ethanol concentrations may have evolved in part as a correlated response to selection for behavioral insensitivity to natural concentrations.

Tropically adapted cattle of Africa: perspectives on potential role of copy number variations

Africa is host to diverse and locally adapted cattle breeds that are expected to survive the harsh and extreme tropical environments associated with diseases and parasite infections, heat stress and episodes of feed and water scarcity. Genomic copy number variations (CNVs) are considered to be primary role players in cattle breed formation and adaptation where isolation and genetic drift together with subsequent mutations have created an enormous diversity of local populations. CNVs are modifications in DNA structure comprising deletions, duplications and insertions that are >1kb in size. Despite attracting much attention, the frequency and pattern of bovine CNV events, especially in African cattle breeds, are for the most part largely unknown. Characterization of genetic variation in the indigenous cattle of Africa will be a vital step toward dissecting the molecular mechanisms underlying phenotypic variation and local adaptation. This review therefore aims to describe the current knowledge regarding bovine CNVs and the implications and potentials they encompass for dissecting genetic adaptation and the genotypic skeleton of tropical African cattle populations.

Preference for ethanol in feeding and oviposition in temperate and tropical populations of Drosophila melanogaster.

The natural habitat of Drosophila melanogaster Meigen (Diptera: Drosophilidae) is fermenting fruits, which can be rich in ethanol. For unknown reasons, temperate populations of this cosmopolitan species have higher ethanol resistance than tropical populations. To determine whether this difference is accompanied by a parallel difference in preference for ethanol, we compared two European and two tropical African populations in feeding and oviposition preference for ethanol-supplemented medium. Although females of all populations laid significantly more eggs on medium with ethanol than on control medium, preference of European females for ethanol increased as ethanol concentration increased from 2 to 6%, whereas that of African females decreased. In feeding tests, African females preferred control medium over medium with 4% ethanol, whereas European females showed no preference. Males of all populations strongly preferred control medium. The combination of preference for ethanol in oviposition, and avoidance or neutrality in feeding, gives evidence that adults choose breeding sites with ethanol for the benefit of larvae, rather than for their own benefit. The stronger oviposition preference for ethanol of temperate than tropical females suggests that this benefit may be more important in temperate populations. Two possible benefits of ethanol for which there is some experimental evidence are cryoprotection and protection against natural enemies.

Mechanisms of naturally evolved ethanol resistance in Drosophila melanogaster.

The decaying fruit in which Drosophila melanogaster feed and breed can contain ethanol in concentrations as high as 6-7%. In this cosmopolitan species, populations from temperate regions are consistently more resistant to ethanol poisoning than populations from the tropics, but little is known about the physiological basis of this difference. I show that when exposed to low levels of ethanol vapor, flies from a tropical African population accumulated 2-3 times more internal ethanol than flies from a European population, giving evidence that faster ethanol catabolism by European flies contributes to the resistance difference. Using lines differing only in the origin of their third chromosome, however, I show that faster ethanol elimination cannot fully explain the resistance difference, because relative to African third chromosomes, European third chromosomes confer substantially higher ethanol resistance, while having little effect on internal ethanol concentrations. European third chromosomes also confer higher resistance to acetic acid, a metabolic product of ethanol, than African third chromosomes, suggesting that the higher ethanol resistance conferred by the former might be due to increased resistance to deleterious effects of ethanol-derived acetic acid. In support of this hypothesis, when ethanol catabolism was blocked with an Alcohol dehydrogenase mutant, there was no difference in ethanol resistance between flies with European and African third chromosomes.

Ocular blood flow velocity in primary open angle glaucoma - A tropical african population study

Purpose:To assess blood flow velocity in newly diagnosed indigenous black-skinned Africans with primary open angle glaucoma (POAG).Materials and Methods:Prospective case-control study at Obafemi Awolowo University Teaching Hospital, Ile-Ife, Nigeria on 50 newly diagnosed POAG patients (POAG group) and 50 control patients (control group). Ocular Doppler Color Imaging was performed on subjects in the supine position using 9 MHz linear array transducer of a Fukuda Denshi Ultrasound. The Peak Systolic Velocity (PSV) and End Diastolic Velocity (EDV) values were obtained by finding the average of two readings each for the ophthalmic artery (OA) and central retinal artery (CRA). Resistive Index (RI) was calculated as (PSV − EDV)/PSV. Data were analyzed and statistical significance was defined at P < 0.05.Results:The mean intraocular pressure (IOP) for the POAG group and control group was 28.1 ± 7.4 mmHg and 16.6 ± 2.0 mmHg, respectively (P < 0.001). The mean PSV for OA was 31.35 cm/s in POAG group and 37.61 cm/s for the control group (P < 0.001). The EDV for both OA and CRA were significantly lower in glaucoma patients as compared with the corresponding values in the control group (P < 0.001, both comparisons). The mean RI in the OA was 0.71 ± 0.05 and 0.63 ± 0.03 for the POAG and control group groups, respectively (P < 0.001). The increase in IOP in the POAG group was statistically significantly negatively correlated with PSV and EDV and positively correlated with RI for both OA and CRA.Conclusion:The outcomes of this study indicate that ocular blood flow alterations including reductions in PSV and EDV and increase in RI of the OA and CRA are present in black-skinned Africans with POAG.

Molecular variation and speciation in Antitrichia curtipendula s.l. (Leucodontaceae, Bryophyta)

Molecular variation in Antitrichia curtipendula (Hedw.) Brid. s.l. was studied based on the nuclear internal transcribed spacer (ITS) and the chloroplast markers trnL-trnF and rpl16, and analysed by neighbour joining (for ITS; recombination present), maximum parsimony (chloroplast markers) and TCS (haplotype network). Old World plus E North American populations belong to a different lineage than those of W North America. These are molecularly well differentiated and are treated as A. curtipendula and A. gigantea (Sull. & Lesq.) Kindb. Two distinct groups of Old World haplotypes are separated by one ‘missing’ haplotype and are interpreted as cryptic species. Tropical African populations share one ITS deletion and form a lineage within one of the cryptic species. Molecular variation within A. gigantea, within each of the two cryptic Old World plus E North American (except tropical African) haplotype groups, and among tropical African populations are of similar magnitude, suggesting that analogous mechanisms and similar time spans explain the found variation. Events related to Pleistocene climatic oscillations are suggested as having caused this differentiation within each group, whereas the African lineage was probably split off before this. Identical tRNA-Gly sequences were found in 33 specimens; new primers were designed for rpl16 and ITS 1+2. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 156, 341–354.

A histopathological analysis of cutaneous malignancies in a tropical African population

Aim: To establish the prevalence of cutaneous malignancies in Zaria, Northern Nigeria. Method: This is a histopathological analysis of three hundred and eighty two cases of cutaneous malignancies seen and diagnosed in the department of Pathology, Ahmadu Bello University Teaching Hospital, Zaria from January 1991 to December 2000. The specimens were fixed in formalin, processed in paraffin wax and stained with haematoxylin and eosin. The slides were studied and the lesions were characterized. Results: Three hundred and eighty two cutaneous malignancies were analysed. The M: F ratio of all the tumours was 1.9:1.0. Nonmelanoma skin tumours were the commonest and accounted for 254 (66.8%). They comprised of squamous cell carcinoma 239 (62.9%), basal cell carcinoma 15 (3.9%) and malignant adnexal tumours which were the least common accounting for 2 (0.5%). Sarcomas accounted for 72(18.9%) and kaposi sarcoma 41(10.7%), was the commonest in this group. Malignant melanoma cases were 54 (14.1%). There were two peak age distributions in the 4th and 6th decades (63.6%) for all tumours. The lower limb was the prevalent site of distribution of all the tumours with sixty five percent cases. Conclusion: Cutaneous malignancies are common in our setting and the commonest was squamous cell carcinoma. Prompt and adequate treatment of chronic leg ulcers and burns injury as well as control of HIV infection should help to reduce the burden of these cancers. Keywords: cutaneous malignancy squamous cell carcinoma sarcomas Nigerian Journal of Surgical Research Vol. 7(3&4) 2005: 300-304

Health problems of mill operators in a tropical African population

The study reports a questionnaire based survey on mill operators in a large market in Ibadan, Southwest Nigeria. One hundred and twenty respondents, 65 males and 55 females aged between 18 and 65 years were interviewed and noise measurements were done at various work stations. Health problems reported by these workers include headaches 73%, backache 53% and respiratory symptoms such as cough 37% rhinitis 63% and wheezing 13%. Thirty four respondents (28%) reported a difficulty in hearing mostly due to tinnitus. Four complained of deafness. Twenty-three (19%) had raised blood pressure of 140/90Hg and above. In spite of the high levels of dust in the work environment only 15 (13%) of workers used a face cloth to cover their noses. Noise levels at the work stations ranged from 88-90dB from smaller machines and 101-105 dB for larger machines. None of the workers used hearing protection in any form. Health education of workers and the provision of low cost protective equipment may alleviate the suffering of these workers.

Abdominal emergencies in a tropical African population.

A decade ago intestinal obstruction was the commonest cause of general surgical abdominal emergency admissions in many tropical African countries. Recently there has been a change in this pattern and acute appendicitis has become the major cause of emergency admissions. Most cases of intestinal obstruction are due to obstructed (strangulated or incarcerated) groin hernia. Intestinal ascariasis is a declining cause of intestinal obstruction while colorectal cancer is now an important differential diagnosis. Trauma due to road traffic accidents is increasing in frequency. Gallbladder disease is not a major problem; symptoms suggestive of acute gallbladder disease are more likely to be due to an amoebic abscess in the West African environment.

Prevalence and causes of blindness in a tropical African population

A population based survey of Egbedore Local Government area (LGA), a tropical African population in Osun State, Nigeria was conducted to determine the prevalence and causes of blindness in the community, Osun State, one of the new states created on 27th August, 1991 is situated in the southwest region of Nigeria. It has a population of about 2, 654,244 using the population growth rate of 3.0 percent per year. Egbedore LGA has a population of 49,555 being the projected estimate of the local census done in 1991. The study was in accordance with World Health Organisation recommendations. 3204 rural dwellers were examined. The survey team was divided into: 1. Registration team 2. Retrieval team 3. Visual acuity team 4. Ocular examination team. The survey candidates, once registered were asked to go to a nearby school or health center where visual acuity and ocular examination teams completed the assignment. The retrieval team consisted of an ophthalmic nurse and a local escort who persuaded and brought to examination site registered individuals who failed to appear voluntarily. Ocular examination team performed the eye examination. Analysis of data was done using personal computer AT model and systat package for analysis. It is found that 1.18% of the population was blind by WHO standard. Cataract alone accounted for 47.4% of the blind, uncorrected aphakia 18.4%, glaucoma 15.8%, phthisis bulbi 5.3%, uveitis, optic atrophy, macular degeneration, retinitis pigmentosa and refractive error all accounted for 2.6% each. More than half of the burden of blindness is potentially curable. About a third is preventable through health education, early diagnosis and prompt treatment. A cataract outreach programme with provision of low cost aphakic glasses will go a long way in reducing blindness in this community and Osun State in general.

Traumatic dislocation of the hip joint--pattern and management in a tropical African population.

Traumatic dislocation of the hip is an orthopaedic emergency for which early reduction is indicated. This article describe our experience of the pattern and choice of management of traumatic dislocation of the hip joint in a tropical African population. Majority of the dislocation (87%) were Thompson and Epstein's grades I and II which were easily managed by closed reduction following the administration of titrated intravenous analgesic and intravenous diazepam. This treatment option is cheap and readily administrable to avoid undue delays in the management of this orthopaedic emergency. All the close reduction were carried out in the accident and emergency room except for one patient with bilateral posterior hip dislocation who had his reduction on the ward. Early diagnosis and treatment of traumatic hip dislocation are essential to reduce the morbidities that are commonly associated with delay in reduction.

Clinical diabetic nephropathy in a tropical African population.

Diabetic nephropathy is the single most important disorder leading to renal failure in adults in the Western countries and it is among the first three major causes of end stage renal disease in Nigeria. The aim of this study is to show the features of clinical diabetic nephropathy in the Olabisi Onabanjo University Teaching Hospital, Ogun State, Nigeria. The study group consists of 342 consecutive diabetic patients with persistent proteinuria (positive albustix) and diabetic retinopathy, seen from January 2000 to June 2001 in the Ogun State University Teaching Hospital, Sagamu. Clinical and laboratory parameters were recorded. Students' t-test and Spearman correlation coefficient were used in analysis. The frequency of occurrence of clinical diabetic nephropathy is 28.4% with majority already symptomatic despite normal biochemistry. Mean ages of type 1 and type 2 are 26+/-7.9 years and 53.4+/-6.3 years respectively with a sex ratio of 1.2:1. Mean duration of disease is 6.5+/-3.6 years and 9.4+/-4.1 years respectively. Two hundred and seventy-one (79.2%) patients were hypertensive. Nephrotic syndrome is not a common presentation. Diabetic nephropathy is a significant problem in this environment.

Amylase polymorphism in Drosophila melanogaster: haplotype frequencies in tropical African and American populations

Amylase polymorphism in Drosophila melanogaster: haplotype frequencies in tropical African and American populations

Amylase polymorphism in Drosophila melanogaster: haplotype frequencies in tropical African and American populations

Amylase polymorphism in Drosophila melanogaster: haplotype frequencies in tropical African and American populations

Gastrointestinal malignancies in a young tropical African population.

The records of 695 patients with confirmed gastroenterological malignancies over a 10 year period (January 1976-December 1985) were analysed. Of these, 264 patients (37.98%) were below the age of 40 years. Primary liver cell carcinoma was the commonest malignancy while gallbladder and oropharyngeal cancers were the least common. Most of the patients (66.3%) were in their fourth decade. The prognosis was poor as most of the patients presented late.

Genetic analysis of Drosophila melanogaster in the French West Indies and comparison with populations from other parts of the world

Four natural populations of Drosophila melanogaster, three from Guadeloupe and one from Martinique (French West Indies), were studied with respect to four types of genetically determined traits, namely allozyme frequencies, morphology, ethanol tolerance, and oviposition rhythm. These populations were compared to European (France) and tropical African populations, and, with respect to allozymes alone, to an American population. The four populations from the West Indies were found to be genetically similar; this may reflect a common historical origin, or an adaptive response to similar environmental pressures or possibly some gene flow between the two islands. The comparisons with distant populations led to different conclusions depending upon the trait considered. In the case of allozymes, flies from the West Indies were more similar to tropical African populations than to an American population from Texas, but the main difference observed was in comparison with European populations. The morphology of the West Indies flies resembled a smaller, tropical type, but the size was even smaller than observed in Africa. Both ethanol tolerance and oviposition rhythm were intermediate between flies from tropical Africa and Europe. All these results can be explained in terms of interactions between selection imposed by a tropical environment and the genetic properties of the founder population which first colonized the islands.

Cholecystitis and cholelithiasis in a tropical African population.

Compared with some European and North American countries, inflammatory disease of the gallbladder is not common in tropical Africa. The presentation as seen in our institution is different from reported series because intestinal parasites seem to play a part in the disease, whereas obesity, diabetes, multiparity and socioeconomic class seem to play little or no part. There is also a much higher incidence of gall-bladder stones in our few cases than other reported series. The predominant gallbladder stone seen is the pigment stone. As in other series, the incidence in the females is higher than that in males.

Small bowel neoplasms in a tropical African population

At the University College Hospital, Ibadan, Nigeria, in a 17-year period, 54 cases of small bowel neoplasms were seen. The most common, was lymphosarcoma (29.62%) followed by malignant lymphoma (12.96%). Burkitt's tumour was not seen in anyone above the age of 16 years. Three cases in this series were histopathologically benign. The presentation is usually silent until a complication sets in.