Showing papers by "University of Nairobi published in 1974"

Antibody-dependent cell-mediated damage to schistosomula in vitro.

Abstract: ANTIBODY-DEPENDENT cell-mediated cytotoxic effects have been described in many in vitro models involving single-cell suspensions of mammalian or avian target cells, and could be important in the rejection of tumours and allografts1–6. Similar responses could also be involved in protective immunity against metazoan parasites, and evidence for cell-mediated effector mechanisms of various types has emerged from work on Nippostrongylus braziliensis7 and Litomosoides carinii8 in rats. Here we present two new aspects of cell-mediated responses to metazoan parasites. First, we have adapted the 51Cr-release technique to assay damage to schistosomula of Schistosoma mansoni in vitro. Second, we provide evidence that normal human peripheral blood leukocytes, in the presence of sera from patients infected with S. mansoni, can damage labelled schistosomula in the absence of added complement.

Paleomagnetic Stratigraphy and Chronology of Hominid-bearing Sediments East of Lake Rudolf Kenya

Abstract: Palaeomagnetic measurements of the polarity of sediments from the Koobi Fora Formation east of Lake Rudolf provide a valuable check on other dating methods and allow a polarity stratigraphy to be suggested for the Formation.

Observations on the ecology and breeding biology of the genus Chiromantis (Amphibia: Rhacophoridae)

Abstract: The construction of foam nests by the Anura seems to be a habit that has evolved separately in all the main zoogeographical regions. Chiromantis is a large tree frog weighing up to 5.5 g which is restricted to the Ethiopian region. This genus comprises three species which are found in the three main African biomes from rain forest (C. rufescens), through woodland (C. xerampelina) to semi-arid savannah (C. petersii). The female of C. rufescens is shown in this study to construct her nest with the assistance of three males, and like the other two species, the nests are always fastened to objects over temporary water sources. Although the rain forest and savannah species are the same size the latter lays twice as many eggs as the former. Additionally it is shown that the eggs of C. petersii are only half the size of C. rufescens. These facts can be correlated with the degree of permanence of the water source over which the nest is constructed. Features of the water economy and ecology are also described.

Structure and fine structure of the hypophyseal pars distalis in endigenous African species of the genus Tilapia

Abstract: The structure and fine structure of the pars distalis hypophyseos was examined in five species of Tilapia fishes (T. alcalica, T. grahami, T. leucosticta, T. zillii, T. nigra) which were collected from lakes of a wide range of salinities. The pars distalis in all the species is composed of 5 granulated (“secretory”) and 1 chromophobic cell types. The rostral pars distalis prolactin cells appear most numerous and active in the fresh water species and smaller and least active in the “soda” lake fish. The evidence from nuclear measurements suggests that the species adapted to hyposmotic media have compensated for the freshwater environment (and the subsequent need for greater prolactin secretion) by increasing the number of prolactin cells rather than by increasing the synthetic activity of individual cells. In “soda” lake species which were acclimated to fresh water the prolactin cells are markedly hyperactive and degranulated when compared with any other group. The ACTH cells appear more active in the “soda” lake species than in the fresh water groups, however, these cells are maximally active in “soda” lake fish acclimated to fresh water. The rostral pars distalis stellate cells are described and discussed in relation to their possible involvement in the release of hormone from the pars distalis “secretory” cells. The proximal pars distalis somatotrophs appear active in all the species investigated although they were maximally active in fresh water acclimated “soda” lake species. The structure of the proximal pars distalis gonadotrophs and thyrotrophs is variable both within the same animal and between the species but the variation is not consistent with environmental salinity parameters. The means by which granules are released from the different cell types is discussed. The work was supported by grants in aid of research from SRC (J.F.L), University of Nairobi (J. F. L. and M. H), NRC (J.F.L.), USPMS (AM 13795, J. N. B.), Munitarp Foundation (M. H.) and by a travel scholarship from the Royal Society (J.F.L.). The paper is number 091 in the physiology of migration series.

pH, Salinity and Temperature Tolerance of Lake Magadi Tilapia

Abstract: THERE are several species of Tilapia isolated in the alkaline lakes of the Great Rift Valley of Africa, living in extreme conditions of temperature, salinity and pH. One of these fish, the Lake Magadi Tilapia (Tilapia grahami), lives in the lagoons and alkaline volcanic springs around the margin of Lake Magadi in Kenya1. The main salts of the springs, and the lake, are carbonate and bicarbonate of sodium.

The pattern of lion predation in Nairobi Park

Abstract: Summary The feeding habits of lions in Nairobi National Park have been observed between 1968 and 1972. Nairobi Park is briefly described and the herbivore and predator populations are discussed. The relationship between the changing status of the prey population for the period 1968-72 and the feeding habits of the lions is examined and compared with data from earlier years. Selection ratio (preference ratio) for three of the most important prey species is more closely adjusted to the abundance of these species in the total ungulate population than was the case prior to 1968. Only warthog and eland form an exception. Predation on wildebeest shows the most marked decrease although this species has been increasing during the last 5 years. Wildebeest, kongoni, zebra and warthog have provided 80% of total kills throughout the study on the basis of numbers killed. On this basis, warthog has the highest preference rating. However, the largest contribution to the lions' diet expressed in kg is by kongoni, followed by zebra, wildebeest, eland and warthog, in that order. Kongoni and wildebeest contribute most during the first half of the year and zebra and eland during the last 6 months. Selection for males is significant in zebra and eland and highly significant in kongoni, whilst only in zebra is selection for juveniles evident.

A study of the performance of subjective probability assessors

Abstract: Despite the key role that subjective probabilities play in decisions made under conditions of uncertainty, little is known about the ability of probability assessors in developing these estimates. A literature survey is followed by a review of results from a continuing series of experiments designed to investigate the external accuracy of subjectively assessed probability distributions. Initial findings confirm that probability assessments provided by untrained assessors are of questionable value in predicting the distribution of actual outcomes of uncertain events. Particular difficulty is encountered when subjects attempt to quantify the extremes of their subjective distributions. The impact of extended assessor training and hypotheses regarding the effects of variation in the assessor's information level and the complexity of the assessment task are explored. Implications for applied decision making are drawn, and directions for future investigations are suggested.

Faraday rotation studies in Africa during the solar eclipse of June 30, 1973

Abstract: FOUR stations were set up in southern and eastern Africa (Table 1) to observe variations of total electron content during the eclipse of the Sun on June 30, 1973. Each station was equipped with a conventional Faraday rotation recording system consisting of a receiver and a mechanically rotating aerial. We recorded the amplitude fading of the 137 MHz signals from the geostationary satellite, Intelsat IIF3, located at approximately 14°W. The four stations were operating for a total period of 10 d, including June 30, the day of the eclipse.

The Political Economy of Self-Help: Kenya's 'Harambee' Institutes of Technology

Abstract: RESUMEDepuis le milieu de l'annee 1971, des comites locaux « d'entraide » souscrivent partout au Kenya de grosses sommes d'argent en vue de construire des Instituts « d'entraide » de technologie dits Harambee pour donner des cours d'enseignement secondaires. Dans cet article nous voulons montrer comment ces instituts sont nes grâce a une conjoncture politico-economique afin d'offrir, une base pour la formation des cadres locaux faisant partie de l'elite « non politicisee ».En ce qui concerne l'avenir de ces instituts, il se pose le probleme du personnel enseignant et de celui des frais de fonctionnement. Malgre la lenteur de la collecte de fonds dont l'impact immediat sur la formation peut rejaillir sur l'economie du pays, le risque de former a la longue trop de techniciens reste a ne pas perdre de vue. Le danger est qu'il y aurait un desequilibre dans la repartition des revenus entre les couches sociales et entre les regions: ce qui renforcerait le sentiment de regionalisme. La pression des structures ac...

The distribution, density and biomass density of lizards in a semi–arid environment of northern Kenya*

Abstract: Summary An attempt was made to determine the species composition, density and biomass density of lizards in some of the principal land units in South Turkana. Thirteen species were recorded. Density estimates were determined from quadrat sampling in representative habitats. Because the number of lizards active was found to vary with time of day and temperature, minimum density estimates were obtained by confining counts to peak activity periods. Biomass density was calculated from the product of species density and the mean population weight measured from shot specimens. The biomass density estimate of the lizard fauna was found to be about 4–5% of the large mammal fauna, and appreciably more in the more arid land units. The species composition of South Turkana lizards show affinities to the Somali fauna, though not to the extent of the East Rudolf fauna, suggesting a more recent penetration of arid–adapted species.

Ischial tuberosities and ischial callosities

Abstract: Ischial callosities are specialised regions of skin and subdermal tissue in the form of fibro-fatty cushions with a tough, non-slip surface, firmly bound to the underlying ischial tuberosity. They occur in primates of the families Cercopithecidae and Hylobatidae. Ischial callosity usage helps animals to adopt stable sitting postures on the tops of branches, particularly during feeding, resting and sleeping. Callosity-like areas in pongids are mainly epidermal specialisations and differ in their development and usage from true callosities. They are similar to the para-callosity skin regions in some ground living cercopithecids. The ischial tuberosity in animals with true callosities has a flat surface which flares out from the lower end of the ischial body and which is devoid of muscle attachments. In animals without callosities the ischial tuberosity is not flared, has a curved surface, and acts as a site for muscle attachment. The ischial tuberosity is relatively broader in animals with callosities than in animals without callosities, although the absolute size of the specimens concerned must be taken into account. The combination of qualitative and quantitative features of fossil ischial tuberosities enables the presence or absence of callosities in these forms to be deduced. The recognition of these features in fossil material might be of use in the elucidation of the evolution of one type of primate arboreal adaptation.

Some Observations of Rotational Remanent Magnetization

Abstract: Wilson & Lomax (1972) have recently described experiments which show that a remanence can be induced in rock specimens when they are rotated in a decreasing alternating field. They called this effect rotational remanent magnetization (RRM), and they suggested that other workers might try to duplicate it. We describe here some similar experiments which confirm the existence of the effect but which show that it can occur with either sign. As Wilson and Lomax point out, RRM, if present, can produce apparently erratic behaviour during alternating field demagnetization with a tumbling mechanism. A number of specimens which appeared to show this effect were selected for more detailed investigation. The specimens represent two rock types. One (E25B) is a basalt from a recent lava flow of the volcano Emurangogalok in the Gregory rift valley, 100 km north-north-east of Lake Baringo, Kenya. The others (K3, K4) are lacustrine tuffaceous silts from the Acheulean archaeological site Kilembe near Rongai 30 km west-north-west of Nakuru, Kenya. In one case the remanence is TRM, and in the other probably DRM, but both have the ability to acquire RRM. The specimens were demagnetized in the Nairobi equipment which consists of a two-axis tumbler with the outer axis rotating at 1.8 rotations per second, and the inner axis at 2.7 rotations per second. If RRM is present it would be expected to appear directed along the inner axis. For each maximum value of the demagnetizing field, the specimen is treated twice, with a selected axis parallel, and then anti-parallel to the inner axis of rotation. By vector subtraction any RRM should appear on the relevant specimen axis, the other two axes having near zero components if no other effects are present. Addition will then eliminate the RRM vector, and yield the demagnetized NRM free of RRM. In this way demagnetization curves for the NRM can be obtained at the same time as curves showing the growth of RRM. This follows standard demagnetization procedures, and will yield results of immediate interest to the practising worker. It should be emphasized however, that this RRM is developed on the inner axis of a tumbling mechanism, and is not directly comparable to the RRM of Wilson & Lomax which is developed along an axis perpendicular to the demagnetizing field. In this note we designate the former as RRM2 and the single axis type as RRM1. Experiments on RRMl are described later. The demagnetization’of NRM and the concurrent growth of RRM2 are shown in Fig. 1 (a)-(c). The curves show a variety of shapes, and the relative importance of NRM and RRM2 at a given field varies widely from specimen to specimen. It is this which governs the actual impact of RRM2 in a given case; contrast K3 and E25B. The sense of the RRM2 vector in the sediment samples K3 and K4 was in the direction of -w in agreement with that observed by Wilson & Lomax for RRMl in all their samples. In contrast the RRM2 vector in E25B was in the direction of +w. This was sufficiently surprising for us to make careful repeat measurements and the effect

A note on fully developed turbulent flow down a circular pipe

Abstract: This investigation originated when some difficulties were experienced in establishing good flow conditions in a circular pipe to study the effects of longitudinal cooling on slanted hot-wires. In the past many investigators have presented results on turbulent flow through pipes and it is now generally assumed that this flow field is known in sufficient detail. For example, Schlichting has given a through description of the mean velocity distribution for turbulent flow through pipes based on the experimental results of Nikuradse. On the other hand Townsend describes the structure of the flow based on the results of Laufer. Although the investigation of Nikuradse and Laufer are classical works there appears to be some uncertainty in whether or not their turbulent flows down pipes were really fully developed.

Natural information processing

Abstract: This paper describes a method of analysing information based on theories about the way in which human beings tackle this problem. The method has been realized as a computer program and applied to the analysis of statements in a particular programming language. The application of an “intelligence modelling” approach to statement analysis leads to interesting possibilities particularly in connection with the correction of inaccuracies, and it is suggested that such an “error-tolerant” interface could lead to more effective man-machine communication in the future.

A note on distributed lag models of maize and wheat production response: the kenyan case*

Abstract: In this note the supply responses in maize and wheat production are estimated from distributed lag models. The Nerlove model and the Fisher distributed lag model fit Kenyan data but more complicated models, like the polynomial lag model, do not. The calculated price elasticities suggest that Kenyan large-scale farmers are highly responsive to price changes. Some policy implications are drawn from the analysis.

Ligamentous injuries to the canine hock

Abstract: Ligamentous damage to the canine hock is a relatively uncommon orthopaedic injury. Severe trauma seems to be necessary to produce it. Four cases of tarsal ligamentous damage are reported. Their management is described and discussed along with a brief review of the relevant literature. Resume. Le jarret canin atteint d'un dommage ligamenteux est un accident orthopedique relal ment rare. De severes traumas semblent necessaires pour qu'il se produise. On rapporte quatre de dommage ligamenteux tarsien. On decrit et on discute de la maniere dont on les traite avec breve revue des documents courants. Zusammenfassung. Ligamentoser Schaden an dem Hunde-Fesselgelenk ist eine verhaltnisma ungewohnliche orthopadische Verletzung. Sehr schlimmes Trauma scheint notwendig, um es vorzurufen. Vier Falle von tarsal-ligamentosem Schaden sind berichtigt. Ihre Behandlung won beschrieben und diskutiert, zusammen mit einem kurzen Uberblick von der augenblicklic Literatur hieruber.

Endocardial surfaces in man. I. The tendinous system of the heart.

Abstract: Summary The endocardial surfaces were studied by means of the scanning electron microscope. The subendocardial muscle bundles in the heart were separated by deep and spacious grooves. The division of muscle fibres frequently occurs in an X-figure. The central portion of the figure is always elevated, although its length may vary in different fibres. The striae on the muscular fibres have also been described. Functional significance of the above findings was discussed. Zusammenfassung Endokardiale Oberflachen beim Menschen 2: Die Oberflachen der Muskulatur Rasterelektronenmikroskopische Untersuchungen ergaben, das die subendokardialen Muskelbundel durch tiefe und weite Spalten voneinander getrennt sind. Muskelfasern teilen sich haufig x-formig. Die Kreuzungsstelle dieser x-Form ist stets verdickt, wahrend ihre Lange wechselt. Querfurchen der Muskelfasern werden ebenfalls beschrieben. Die funktionelle Bedeutung der Befunde wird diskutiert. Resume Les surfaces endocardiaques chez l' Homme 2: Les surfaces de la musculature Les recherches de microscopie electronique sur coupes ultrafines montrerent que les faisceaux musculaires sous-endocardiques sont separes les uns des autres par des fentes profondes et larges. Les fibres musculaires se bifurquent frequemment en forme d' Le lieu de croisement de ces formes en X est constamment epaissi, alors que sa longueur varie. Les stries transversales des fibres musculaires sont egalement decrites. La signification fonctionnelle de ces faits est discutee. Resumen Superficies endocardiacas en el hombre 2: La superficie de la musculatura Investigaciones con el microscopio electronico demostraron, que las fibras musculares subendocardiales estan separadas por grietas profundas y anchas. Las fibras musculares frecuentemente se dividen en forma de X, con longitud variable y ensanchamiento en la parte donde se entrecruzan. Tambien se describen surcos transversales en las fibras musculares y se discute la importancia funcional de tales hallazgos.

Sorghum shoot fly species and their control in Uganda

Abstract: Sorghum is an important food crop in Uganda; in some areas it is the staple food grain. Low yields of sorghum are attributed to damage caused by insects, particularly the sorghum shoot fly, and to the weather. Chemical and cultural control measures against sorghum shoot fly in Uganda have given erratic results. It is postulated that these erratic results and unpredictable shoot fly behaviour observed by other workers are due to the presence of at least five species of Atherigona.

Surfaces and cleansing mechanism of the trachea and bronchi.

Abstract: Summary Surfaces of the trachea and bronchi of some Eutheria, Metatheria and Reptiles (including animals under stress) were studied through the light and scanning electron microscope. The epithelial cells could be grouped into 3 classes in accordance with the length of their cilia and 1 class with non-ciliated projections. The interciliary air spaces present between cilia are necessary for the function of the cleansing mechanism in preventing the sinking of mucus between cilia and the agglutination of them. Reduction of interciliary spaces as well as failure to establish them post partum can contribute to pathogenesis of bronchitis. Metatheria have a prominent vascular layer under the epithelium with numerous arterio-venous anastomoses. Zusammenfassung Uberflachen und Reinigungsmechanismus von Trachea und Bronchen Die tracheobronchale Uberfladie sowohl normaler als audi unter Streβ stehender Eutheria, Metatheria und Reptilien wurde lichtmikroskopisch und raster-elektronenmikroskopisch untersucht. Auβer 3 Uberflachenepithelien mit verschieden langen Zilien kommen solche mit nichtzilienartigen Fortsatzen vor. Dem Reinigungsmechanismus dienende interziliare Luftraume verhindern das Eindringen von Schleim zwischen die Zilien und schutzen die Zilien vor dem Zusammenkleben. Die Reduktion der interziliaren Luftraume oder ihre Nichtbildung post partum konnen zur Pathogenese der Bronchitis beitragen. Metatheria haben eine deutliche subepitheliale Gefaβschicht mit zahlreichen arteriovenosen Anastomosen. Resume Surfaces de la trachee et des bronches et mecanisme de leur entretien Les surfaces de la trachee et des bronches des quelques Eutheriens, Metatheriens et Reptiles, y compris des animaux sous contrainte, ont eteetudiees au microscope optique et au microscope a balayage. On a trouve que les cellules epitheliales peuvent etre groupees en trois categories selon la longueur de leurs cils, plus une classe pourvue de projections non ciliees. Les espaces aeriferes presents entre les cils sont necessaires aux mecanismes d'entre-tien en ce qu'ils empechent la descente du mucus entre les cils et Pagglutina-tion de ceux-ci. La reduction de ces espaces peut, tout comme le defaut de leur formation apres la naissance, contribuer a la pathogenie des bronchites. Les Metatheriens possedent une couche vasculaire saillante sous l'epithelium et pourvue de nombreuses anastomoses arterio-veineueses. Resumen Superficies y mecanismos de limpieza en la traquea y en los bronquios La superficie traqueo-bronquial se examino en varios Euterios, Metaterios y Reptiles, mediante el microscopio corriente y electronico, en condiciones normales y durante esfuerzos especiales (stress). Se encontraron 3 tipos de celulas ciliadas, de acuerdo con el tamano de sus pestanas, y un epitelio con prolongaciones de las celulas que no pareces ciliadas. Los espacios interciliares de aire son muy importantes para el mecanismo de limpieza, porque impiden la penetracion del moco y la aglutinacion de las pestanas. Reduccion de los espacios interciliares o la falta de su desarrollo post partum, pueden contribuir a la patogenesis de la bronquitis. Los Metaterios presentan debajo del epitelio una capa vascular bien desarrollada con numerosas anastomosis arterio-venosas.

A bank of frozen peripheral blood lymphocytes for in vitro immunological studies on East African cancer patients.

Abstract: A bank of peripheral blood lymphocytes, frozen in liquid nitrogen, has been established from East African cancer patients and from control donors including healthy individuals and patients with non-malignant disorders. The techniques of collection, lymphocyte separation and cell freezing are simple enough to have been applied successfully in an isolated mission hospital. In the first year of operation samples have been stored from over 400 individuals. On recovery, the cells have high viability, will respond to PHA in culture, are suitable for determination of HL-A phenotype and react with sheep red blood cells in the spontaneous rosette test. It is predicted that lymphocyte banks of this type will have a useful place in the study of immunological factors in cancer, particularly in developing countries.

Formation of acetoacetate from 3-hydroxy-3-methylglutarate by rat liver and isolation of a mitochondrial coenzyme A-transferase activity involved.

Abstract: 1. Formation of acetoacetate from 3-hydroxy-3-methylglutarate was observed in the perfused rat liver. Production of 3.5μmol of acetoacetate/h per g of tissue was obtained. 2. Formation of acetoacetate was catalysed mainly by the mitochondrial fraction of the homogenized liver, at a rate of 62nmol/h per mg of protein. 3. Experiments with hydroxy-[3-14C]methylglutarate demonstrated that the acetoacetate formed was derived mainly from this compound. 4. A mitochondrial transferase activity catalysing the transfer of a CoA molecule from succinyl-CoA (3-carboxypropionyl-CoA) to hydroxymethylglutarate was shown. The Km value for hydroxymethylglutarate was 5×10−3m.