Areas Of Central Africa Research Articles

Considerations relating to the epidemiology of human immunodeficiency virus infection: the impact of bacterial antigens and consequences for treatment.

A treatment for patients with human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) is presented, which is based on an isopathic method that appears to be effective in eliminating bacterial antigens from the body. The concept is based on a new hypothesis concerning the outbreak and spread of AIDS in Africa and worldwide. Laboratory data are presented from five European and seven African patients with HIV. Oral administration of ultra-low doses of a lysate of Staphylococcus aureus Cowan I (12c potency) resulted in a significant increase of CD4 T-cell subsets and CD4/CD8 ratios in patients with HIV infection as well as in advanced stages of HIV disease, concomitant with the improvement of clinical HIV-related symptoms. Based on epidemiologic data, the beginning of the African AIDS epidemic is related-to time, place, and circumstances-to the initial large-scale introduction of antibiotics in areas of Central Africa that would later comprise the AIDS belt. It is concluded that certain antimicrobial agents can enhance the formation of persistent bacterial superantigens, which may indicate a link between asymptomatic HIV carriers and the development of AIDS. According to this view, superantigens and bacterial cell wall components remaining in the body after antibiotic treatment cause a permanent activation of the immune system and would thus favor T-cell infection and viral replication in HIV-infected individuals.

Selenium and thyroid function in infants, children and adolescents.

Selenium is an integral component of the enzymes glutathione peroxidase (GPx) and iodothyronine deiodinases. Although selenium nutrition could conceivably affect thyroid function in infants, children and adolescents, available data suggest that the effect of selenium deficiency on thyroid function is relatively modest. In patients with isolated selenium deficiency (such as patients with phenylketonuria receiving a low-protein diet), peripheral thyroid hormone metabolism is impaired but there are no changes in thyrotropin (TSH) or clinical signs of hypothyroidism, suggesting that these patients are euthyroid. Selenium supplementation may be advisable to optimize tissue GPx activity and prevent potential oxidative stress damage. In areas where combined selenium and iodine deficiencies are present (such as endemic goiter areas in Central Africa), selenium deficiency may be responsible for the destruction of the thyroid gland in myxoedematous cretins but may also play a protective role by mitigating fetal hypothyroidism. In these areas, selenium supplementation should only be advocated at the same time or after iodine supplementation. In patients with absent or decreased production of thyroid hormones and who rely solely on deiodination of exogenous L-thyroxine for generation of the active triiodothyronine (such as patients with congenital hypothyroidism), selenium supplementation may optimize thyroid hormone feedback at the pituitary level and decrease stimulation of the residual thyroid tissue.

Herpetofauna del Parque Nacional de Monte Alén (Río Muni, Guinea Ecuatorial)

In the framework of a broad study of the vertebrate diversity at Monte Alen National Park (Rio Muni, Equatorial Guinea), we identified 16 families, 47 genera, and 65 species of reptiles and seven families, 29 genera, and 56 species of amphibians. 21 species of reptiles and four species of amphibians represent new records for the Rio Muni region. We present the preliminary inventory of the herpetofauna as well as some ecological comments. Monte Alen is considered one of the most diverse protected areas in central Africa from a herpetological standpoint.

Seed dispersal and its implications for silviculture of African mahogany ( Entandrophragma spp.) in undisturbed forest in the Central African Republic

The study of seed dispersal has received considerable attention in tropical ecology with emphasis placed on its role in the maintenance of species diversity. Since seeds of numerous high-value tropical timber trees are nominally or actively wind dispersed, the subject is also of interest to tropical foresters. In central Africa, up to 70% of harvested timber trees are wind dispersed, including African mahoganies of the genus Entandrophragma. The dual goals of managing many remote areas in central Africa for both biodiversity and timber production values has led to the consideration of low impact logging techniques. In the Central African Republic, increasing light downwind of Entandrophragma has been proposed as a way of increasing regeneration and recruitment of these trees. Mean wind direction at the time of dehiscence of Entandrophragma angolense and Entandrophragma cylindricum was compared with compass orientation of seed shadows for five individuals in mature, undisturbed forest. Mean wind direction was found to be toward the northeast for morning, afternoon, and daily winds and was significantly different from the orientation of seed shadows for all trees. Mean branch direction did not vary significantly from a random pattern, but matched the direction of the seed shadow better than wind direction did. It is concluded that harvesting interventions aimed at increasing light downwind of Entandrophragma will not necessarily benefit seedlings of the species at the study site and further silvicultural research is needed to determine appropriate management interventions, particularly in remote areas of Africa where conservation values are important.

Molecular characterization of a recombinant HIV type 1 isolate (A/G/E/?): unidentified regions may be derived from parental subtype E sequences.

Recombination is one of several factors contributing to the genetic diversity of HIV-1, which is divided into group M (itself comprising 11 subtypes, A-K) and two other groups named O and N. In the present study, the full-length genome of an HIV-1 isolate obtained from a Greek subject (GR17) infected in the Democratic Republic of the Congo (formerly Zaire) was analyzed to reveal a novel mosaic sequence composed of subtypes A, G, and E and regions of indeterminate classification. In particular, most of pol and tat/vpu, as well as the region encoding intracellular domain of gp41, did not cluster with any of the previously characterized HIV-1 subtypes. The clustering of the LTR of GR17 with subtype E was suggestive of a subtype E origin of the unclassified regions. However, the identification of distinct characteristics in the LTR, such as two functional NF-kappaB sites and a distinct TAR element, compared with those of circulating (A/E) recombinants, suggests that the partial subtype E sequences found in GR17 and the mosaic viruses (A/E) have not derived from each other. These results provide evidence that parental subtype E may have existed in the geographic area of Central Africa.

Geochemical balance of lateritization processes and climatic signatures in weathering profiles overlain by ferricretes in Central Africa

A simple geochemical balance of lateritization processes governing the development of several tens of meters of weathering profiles overlain by ferricretes is estimated on the basis of detailed mineralogical and geochemical data. The lateritic weathering mantle of the “Haut–Mbomou” area in Central Africa is composed of different weathering layers described from the base to the top of vertical profiles as a saprolite, a mottled clay layer, a soft nodular layer, a soft ferricrete, and a ferricrete in which kaolinite, gibbsite, goethite, and hematite occur in various quantities. Incongruent dissolution of kaolinite leads to the formation of gibbsite in the upper saprolite, whereas the hematite does not clearly replace the kaolinite according to an epigene process in the upper ferruginous layers of the profiles. Instead, that kaolinite is also transformed into gibbsite according to an incongruent dissolution under hydrated and reducing conditions induced by a relatively humid climatic pattern. The respective relations of the silica, iron, and aluminum balances and the Al substitution rate of the hematite on the one hand, and of RHG [RHG = 100 (hematite/hematite + goethite)] and the kaolinite on the other hand, to the consumption or the release of protons H + permit differentiation of aggrading ferruginization and degradation processes operating in the different lateritic weathering profiles. The Al substitution rate of the Fe–oxyhydroxides varies according to the nature of lateritization processes, e.g., saprolitic weathering and aggrading ferruginization vs. degradation. The observations and results indicate that the ferruginization process of the weathering materials of parent rocks is not a simple ongoing process as often thought. This suggests that the actual lateritic weathering mantle of the Haut–Mbomou area may result from different stages of weathering and erosion during climatic changes.

Extracting ecological and biophysical information from AVHRR optical data: An integrated algorithm based on inverse modeling

Satellite remote sensing provides the only means of directly observing the entire surface of the Earth at regular spatial and temporal intervals. Key Earth system variables can be obtained from satellite data by integrating appropriate processing, interpretation, and modeling. For example, the amount of photosynthetically active radiation absorbed by plants (APAR) and land surface albedo can be inferred from remotely sensed optical measurements. Radiative transfer model inversion exploits the dependence of reflectance on the relative source‐sensor geometry to estimate surface parameters. In contrast, geometrical effects are suppressed in most other approaches. We present an algorithm for the retrieval of fractional APAR (fAPAR), albedo, and other parameters from AVHRR (advanced very high resolution radiometer) reflectance measurements by inverting a modified version of the SAIL (scattering by arbitrarily inclined leaves) canopy radiative transfer model. The model is inverted using an effective bidirectional reflectance factor (BRF) distribution created by aggregating AVHRR data into cells of size comparable to those used in current terrestrial biosphere models (50 × 50 km). Successful inversion results over an area in central Africa are presented and compared with a vegetation index‐based analysis and other satellite data. The procedure also provides unique information on phenology derived from timing of changes in leaf optical properties and canopy structure. Our methods are unique in that they explicitly incorporate a priori ecological knowledge in the choice of model parameters and constraints. This approach can eventually be employed at pixel resolution with the EOS sensors, MODIS (moderate‐resolution imaging spectrometer) and MISR (multiangle imaging spectro‐radiometer).

Ultimatum, espaços coloniais e formações políticas africanas

Partindo de uma data paradigmática, 1890, quando a Inglaterra envia um Ultimatum à coroa portuguesa para que se retire de certas áreas da África Central, a autora analisa de forma crítica a geopolítica desenvolvida pela Inglaterra e a geoestratégia não só de Lisboa, mas igualmente dos participantes no comércio de longa distância. Aborda ainda o papel das missões protestantes, uma questão chave para o entendimento das formações políticas do Planalto de Angola

Evaluation of mechanical transmission of HIV by the African soft tick, Ornithodoros moubata

To assess the ability of the African Hut Tampan, Ornithodoros moubata, to mechanically transmit HIV-1 and to re-appraise HIV-1 infectivity in an arthropod cell line at 28 and 35 degrees C. To evaluate HIV-1 transmission by O. moubata, as determined by HIV-1 survival, 'blood-meal' size and interval between feeds, various tick developmental stages were allowed to feed on a heavily infected lymphoblast-rich blood-meal containing HIV-1BRU in an in vitro feeding chamber. Blood-meal regurgitation was evaluated using 51Cr-labelled human erythrocytes, and human lymphoblast survival in ticks using Trypan blue. HIV-1 survival in ticks was evaluated by reverse transcriptase activity in tick homogenates cocultured with CEM lymphoblasts. Polymerase chain reaction and Southern blot analysis were used to detect proviral HIV-1 in arthropod cells in vitro. HIV-1BRU remained viable for up to 10 days with O. moubata adults. This is the longest recorded survival of HIV in an arthropod. In agreement with other studies. O. moubata regurgitated part of its previous blood-meal into the feeding lesion. Human CEM lymphoblasts partially survived for up to 7 days at 28 and 35 degrees C inside O. moubata's digestive tract. The blood-meal of adult female ticks was as high as 240 microliters (approximately 70 times more than a mosquito), while the most likely potential mechanical vectors (fourth- and fifth-stage nymphs) ingested an average of 39 microliters (maximum, 73 microliters), with some ticks re-feeding as early as 14 days postfeed in the absence of a moult. Shortcomings associated with the experimental protocol suggest that HIV survival within O. moubata may reach 14 days following natural infection, or that ticks might re-feed earlier. Although HIV-1BRU and HIV-1NDK were unable to replicate at 28 and 35 degrees C in CD4- Aedes albopictus C6/36 mosquito cells, HIV-1NDK was detected in its proviral form. Our investigations showed that mechanical transmission of HIV-1 by O. moubata is unlikely to occur in the laboratory. This may not be the situation under field conditions.

Comparative Pathogenesis of Animal and Human Retrovirus Infections

ABSTRACT The human immunodeficiency virus (HIV) shares some structural and biological features with other lentiviruses such as maedi, visna, and equine infectious anemia viruses. Both the budding p...

Activated oncogenes in Burkitt's lymphoma.

Burkitt’s lymphoma (BL) was recognized more than 25 years ago as a distinct pathoclinical entitity with peculiar epidemiological characteristics. The tumor, which occurs with a high incidence in certain areas of central Africa, has been suspected of having a viral etiology. This hypothesis was strengthened by the first isolation of the Epstein Barr virus (EBV) from a BL cell culture. More recently, we have learned that the association between the tumor and the EB virus is not as consistent as was initially hoped. The lack of viral association is especially true when tumors which arise in low-incidence areas such as Europe or the United States are considered. However, during the past few years it has become apparent that specific chromosomal rearrangements represent a crucial step in the development of the BL malignant process (Klein 1981, Leder 1983). The chromosomal rearrangement involves translocation of cellular proto-oncogenes, and may lead to their activation. In light of the epidemiological studies which suggest that carcinogenesis is a multistep process, it is interesting to speculate how as yet unidentified viral or cellular functions may contribute to the malignant BL phenotype.KeywordsNIH3T3 CellHematopoietic TumorCellular OncogeneHuman Promyelocytic Leukemia Cell LinePrimary Embryo FibroblastThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Experimental infections of laboratory rodents with recently isolated stocks ofTrypanosoma brucei gambiense

Albino rats and white mice were infected with populations of Trypanosoma brucei gambiense isolated from patients in four different areas in Central Africa. Differences in virulence as shown by the level of parasitaemia, number of relapses, and length of survival time, were observed amongst the stocks according to their geographical origin and secondarily to the degree of adaptation to the rodents. All the stocks are pathogenic for the laboratory rodents, and the presence of extravascular trypanosomes in the brain was confirmed in all infected animals. Spleen, liver, and kidneys were less constantly found to be positive. The morphology of the extravascular parasites was highly variable, ranging from long slender trypomastigotes to spheromastigotes and even amastigotes.

Distribution and systematic relationship of Tadarida bivittata and Tadarida ansorgei (Chiroptera: Molossidae)

Morphologically similar Tadarida bivittata and T. ansorgei inhabit dry, woodland savannah areas of central Africa, where they are partially sympatric. Specimens of these species were divided into population samples based on geographic proximity. Multivariate analysis of variance indicated that both species are sexually dimorphic. Results of principle components analysis illustrated interspecific differences. In areas of sympatry, specimens were subjected to discriminant analysis to confirm their identity. Based on this analysis, classification functions are provided as a useful aid for identifying the two species.

Religious Movements in Central Africa: A Theoretical Study

A shared sense of discovery and frustration prompts us to write this article. Independently, from our anthropological, historical and sociological research in Zaire over a period of many years, we have been impressed with the pivotal role of religion and magic in that society. The recurrence and development of religious movements in Zaire throughout its known history is an archetypical expression of that predominance. In our view, these movements are an integral dimension of the cultures common to most parts of Zaire and to contiguous areas in Central Africa. A systemic feature of these cultures is that they are conducive to the emergence and evolution of movements with distinctive symbols, rites, beliefs and values. In turn, these movements constantly enrich the underlying cultures from which they emanate.

Loaiasis

Loaiasis has rarely been reported outside its endemic area in central Africa. American dermatologists should remain aware of this characteristic disorder. This nematode infestation, including its treatment and clinical, laboratory, and ecological features is reviewed.

The partial and complete domestication of the oil palm (Elaeis guineensis)

The oil palm (Elaeis guineensis Jacq.) is an important oil crop. Large quantities of mesocarp-oil and kerneloil are consumed in Africa and are exported from there and southeastern Asia to North America and Europe, where they are used mainly for food (margarine), in soap and candle making, and in the tin industry. Furthermore, in most African areas the oil palm is tapped for its wine by cutting the stem of the female or male inflorescence or by making a hole in the palm.'s "cabbage." Disastrous is the felling of palms after which the palm wine is taken. In some areas only raffia palms (Raphia) are tapped, while the oil palm is the source of oil. This takes place, for example, in southeastern Nigeria, where raffia palm seedlings are traded and planted on the compound. From an area in Central Africa, it was reported that, at the end of the 19th Century, the only use made of the oil palm was to fashion old empty inflorescences into brooms (Stuhlmann, 1894). It is probable that at present the usefulness of the palm ha.s been told to the people. But still in Central African Republic two decades ago palm oil was used only as a chrismal oil (Tisserant, 1953). Enormously great numbers of oil palms must occur in the world. For Nigeria alone, 250 millions of stemmed palms have been estimated (Zeven, 1967). To this figure the large number of seedling palms should be added. Fig.

A survey of the fauna of streams on Mount Elgon, East Africa, with special reference to the Simuliidae (Diptera)

SummaryThe stream fauna of Mt Elgon is described from collections taken during a 6‐week visit. Collections were mainly made on the cultivated slopes below the belt of montane forest, and although stations were concentrated on the western sides of the mountain sufficient were worked elsewhere to show that there was little or no geographical variation of the fauna.The streams are physically diverse but faunistically rather uniform, with a few genera dominating the fauna throughout the entire range of altitude investigated. Most of the other taxa showed evidence of altitudinal limitation which may be attri‐buted to the pronounced temperature gradients of the mountain's streams.As the species of Simuliidae and adult Elminthidae could be reliably distinguished their distributions were studied in greater detail. The Simuliidae showed a pronounced zonation of species, the majority being confined to narrow ranges of altitude below the forest margin. Factors considered to influence their distribution were principally altitude (temperature), current speed and, to a lesser extent, stream size. The influence of these factors on the distribution of adult Elminthids was less marked, although all species showed at least an upper or a lower limit of altitude, and more than half the commoner species a preference for a particular stream type.Taxonomic knowledge of African freshwater faunas allows few groups to be identified beyond the genus, and with this limitation the Elgon stream fauna is found to differ in only minor respects from the faunas of other highland areas in Central Africa.

Oesophageal cancer and alcoholic spirits in central Africa.

A geographical pathology survey of a large area in central Africa is described and a contrast is recognized between neighbouring areas with apparently many and apparently few cases of oesophageal cancer. This distribution is compared first with other known areas of high and low incidence in sub-Saharan Africa and then with the drinking of indigenous types of distilled spirits. A significant order of spatial correlation is shown between the geographical pattern of the disease and the drinking of sugar-based alcoholic spirit in central Africa. Samples of spirits from eastern Zambia, central Kenya, and the Transkei, although prepared in apparently dissimilar utensils, were all shown to be contaminated in varying degree with zinc. Nitrosamine-like compounds in native spirits were also reported in all these areas. The need for a geographical survey of indigenous drinking habits in Africa is illustrated. Since legislation against distilling is ineffective, a simple means of excluding carcinogenic compounds from illicit spirits should be ascertained and widely promulgated at village level.

Thyroid Function in a Goitrous Endemic: II. Nonhormonal Iodine Escape from the Goitrous Gland

A comparative kinetic study of the metabolism of inorganic and organic iodine has been carried out by means of radioiodine in 9 goitrous patients of the Uele endemic area in Central Africa. The results of this study were not found in keeping with the classic dynamic model deduced from the assumption that the thyroid gland only releases hormonal iodine. Indeed, at a time when the interference of the administered 131 could be avoided: 1. In most patients the specific activity of iodide in urines was found higher than the specific activity of the plasma PBI. 2. The amounts of endogenous iodide131 appearing in the extrathyroidal space were about 6 times higher than the estimated amounts of organic I131 broken down during the same time. 3. The amounts of I127 and I131 taken up by the glands were 3 times higher than those released as hormonal iodine. To account for these observations, an escape of nonhormonal iodine from the goitrous gland has to be postulated.

Selective Bibliographical Survey for the Study of Politics in the Former Belgian Congo

Recent developments in Belgian Africa have focussed the attention of statesmen and political scientists on one area of Central Africa which has hitherto remained relatively unexplored by English-speaking social scientists. The problems raised by nationalist assertions throughout the continent of Africa are more than a research area of purely academic interest; they also represent a compelling challenge to anyone concerned with sound policy formulation and objective evaluations. With the entrance of the Belgian Congo in the family of independent African states, the policy choices of the United States have involved and will continue to involve additional issues of great urgency and complexity. Other reasons may be invoked for conducting a systematic survey of source material on the social, economic and political aspects of the Congo area. For one thing, the historical experiences and colonial heritage shared by native populations suggest that the intensity of their claims and the choice of their objectives will continue to reflect the impact of a distinctive type of colonial administration. For another, long-range problems of political viability must be viewed against the background of traditional authority systems, whether or not their distribution is coterminous with the geographical boundaries of the area under consideration. Finally, the central position occupied by the Belgian Congo on the map of Africa suggests that the political changes occurring in that area are likely to affect neighbouring territories in a far more decisive manner than those taking place on the periphery of the African continent. As one attempts to judge critically the contributions made by Belgian scholars toward a better understanding of African political phenomena one cannot fail to be impressed by the magnitude of the efforts and the unevenness of the results. This is partly due to the highly legalistic treatment given to various subject matters, and partly to the fact that available studies almost inevitably reflect the official constraints on their authors. Another explanatory factor lies in the absence of focus discernible in the study of traditional societies: frequently the negative and seemingly reprehensible traits of native societies are highlighted while the more positive aspects are deliberately de-emphasized. Finally, the paternalistic assumptions underlying Belgian administrative policies have had definite repercussions on the scope and orientation of official or semi-official research endeavours: by and large the vast field of economic and social development has received a particularly strong emphasis at the expense of other politically relevant research areas.