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At least 19 recordsLinked to original sources
PubMed1999

Genetic evidence of an early exit of Homo sapiens sapiens from Africa through eastern Africa.

The out-of-Africa scenario has hitherto provided little evidence for the precise route by which modern humans left Africa. Two major routes of dispersal have been hypothesized: one through North Africa into the Levant, documented by fossil remains, and one through Ethiopia along South Asia, for which little, if any, evidence exists. Mitochondrial DNA (mtDNA) can be used to trace maternal ancestry. The geographic distribution and variation of mtDNAs can be highly informative in defining potential range expansions and migration routes in the distant past. The mitochondrial haplogroup M, first regarded as an ancient marker of East-Asian origin, has been found at high frequency in India and Ethiopia, raising the question of its origin. (A haplogroup is a group of haplotypes that share some sequence variations.) Its variation and geographical distribution suggest that Asian haplogroup M separated from eastern-African haplogroup M more than 50,000 years ago. Two other variants (489C and 10873C) also support a single origin of haplogroup M in Africa. These findings, together with the virtual absence of haplogroup M in the Levant and its high frequency in the South-Arabian peninsula, render M the first genetic indicator for the hypothesized exit route from Africa through eastern Africa/western India. This was possibly the only successful early dispersal event of modern humans out of Africa.

Africa↗
PubMed1994

Dermatologic diseases of eastern Africa.

The countries of eastern Africa are deprived of the most basic of care for their skin disease. Diagnostic tools and treatment modalities that are commonplace in developed countries are at a bare minimum in these third world nations. In addition, there is a dearth of trained dermatologic specialists, especially in the arid areas of Kenya and Tanzania. The International Foundation for Dermatology was founded in 1987 in an attempt to address this vacuity in medical care. During the last 6 years, they have launched a campaign concentrated on the activation of Regional Training Centers in Africa, where students will enter a 2-year training program and graduate with the title of "Dermatology Officer" possessing those skills required to treat 80% of common skin diseases. It is hoped that this will lead to an increased awareness of skin pathology in general and the specific need for trained specialists in underserved areas. However, a lack of health care specialists is only part of the problem. Better nutrition, clean water, and the education of tribal communities are impending future goals, difficult to attain in a nation burdened with economic and political strife.

Africa, Eastern↗
PubMed1993

Mitochondrial phylogeny of the endemic mouthbrooding lineages of cichlid fishes from Lake Tanganyika in eastern Africa.

Of the three cichlid species flocks in eastern Africa, Lake Tanganyika harbors the oldest species assemblage, which is also the most diverse morphologically and behaviorally. For 12 species (20 individuals) of 12 genera of the tribe Ectodini, 852 bp from two segments (cytochrome b and control region) of the mitochondrial genome were sequenced. In addition, orthologous sequences were obtained from eight species (11 individuals) representing other mouthbrooding lineages from Lake Tanganyika. Comparisons of sequence divergences revealed that the single Tanganyikan tribe Ectodini appears to be approximately five times older than the whole Lake Malawi cichlid species flock, suggesting that the radiation of the Tanganyikan mouthbrooding lineages took place long before the species flocks of Lakes Malawi and Victoria evolved. Seven of nine surveyed tribes of Tanganyikan cichlids appear to be approximately equally divergent, and this seems to corroborate the hypothesis of a rapid simultaneous formation of lineages at an early stage in the history of the Lake Tanganyika species flock. The close genetic relationship between the endemic Tropheus lineage and a nonendemic "Haplochromine," Astatotilapia burtoni, indicates that members of the tribe Tropheini may be the sister group of the cichlid flocks of Lakes Malawi and Victoria. The phylogenetic analyses demonstrate the monophyly of the Ectodini and identify the Cyprichromini as their sister group among the Tanganyikan cichlids. Within the tribe Ectodini the molecular data suggest both a branching pattern different than that previously proposed and a subdivision of the Ectodini into four clades, instead of the two originally described. The previously postulated model of morphological transformations believed to be responsible for the drastically different types of ecological specialization found among the Ectodini might therefore be in need of reinterpretation. Characters immediately related to foraging and nutrition seem to be particularly prone to homoplasy, even among members of a single lineage of cichlid fishes.

Africa, Eastern↗
PubMed1993

Preliminary analysis of the transmission dynamics of Theileria parva in eastern Africa.

Two mathematical models are developed that investigate the transmission dynamics of Theileria parva by the ixodid tick Rhipicephalus appendiculatus to cattle in endemically stable areas. A method of estimating the rate of infection to cattle of T. parva at the endemically stable state is given. Empirical estimates of all the parameters in the model are available. The degree to which animals that have recovered from theileriosis (the 'carrier' state) are able to transmit the infection to tick nymphs or larvae is a crucial determinant of the dynamics of infection in a herd. Two control methods influencing the transmission of infection are considered--infection and treatment immunization and the reduction in tick feeding by acaricide application. The impact of each method on the transmission of infection is evaluated. Future developments and the data required to predict the dynamics of T. parva infections in cattle and ticks are discussed.

Africa, Eastern↗