Showing papers by "University of Nairobi published in 1980"
TL;DR: Bird distribution can be explained largely by slow dispersal outwards from refugia as climatic conditions allowed forest to spread, combined with a relaxing of the distinction between “montane” and “lowland” species under conditions of reduced interspecific competition.
Abstract: A cluster analysis of the distribution patterns of forest passerine birds in tropical Africa showed that they could be divided into three main distribution types: those of restricted distribution (144 species), those of disjunct distributions across West, Central and rarely to East Africa (65 species) and those of very wide distribution (81 species). Centres of species richness, endemism and disjunction coincide spatially, and are identified as forest refugia, where forest persisted throughout Quaternary climatic vicissitudes. These distribution patterns agree with modern interpretations of Quaternary palaeoclimatic changes, which show that glacial periods were arid and interglacials humid. Glacial periods were therefore too dry for montane forest to have spread into areas at present occupied by lowland forest, as advocated by Moreau and other supporters of ihe “pluvial” theory; montane forest is probably as extensive now as at any time during the Quaternary and there is no evidence of past connections between currently isolated montane forests. Bird distribution can be explained largely by slow dispersal outwards from refugia as climatic conditions allowed forest to spread, combined with a relaxing of the distinction between “montane” and “lowland” species under conditions of reduced interspecific competition.
157 citations
TL;DR: Regressions of relative abundance of photosynthetic types on climatic variables showed that both mean annual temperature and annual precipitation were equally reliable as predictors of C3−C4 biomass, although it is felt that temperature is of primary importance in explaining the observations.
Abstract: Based on the physiological characteristics and responses of C3, C4, and CAM plants to environmental factors, it is generally predicted that C4 and CAM plants will become more abundant with increasing temperature and decreasing precipitation. To test this prediction, the relative contribution of each photosynthetic type to total plant community biomass was examined at seven study areas along an altitudinal transect in southeastern Wyoming grassland. In going from high (2,652 m) to low (1,405 m) elevation along this transect, mean annual temperature increased and annual precipitation decreased.
127 citations
TL;DR: In this paper, photosynthetic rates of coffee plants grown under the full sun and shade were compared and it was concluded that coffee is more suited to high density plantings where mutual shading, resulting in low light intensities and lower leaf temperatures, are likely to produce a favourable environment for efficient photosynthesis and growth.
Abstract: Photosynthetic rates of coffee plants grown under the full sun and shade were compared. The saturating irradiance of 300 μE−1 m s−1 of shade plants shifted to near 600 μE in sungrown plants, but shade plants possessed substantially higher photosynthetic rates. Photosynthetic rates decreased above 25°C, which was apparently due to a decline in the mesophyll conductance, as stomatal conductance remained more or less unchanged between 25° and 35°C. Most of these measurements were made on seedlings in plastic bags. It is concluded that coffee is more suited to high density plantings where mutual shading, resulting in low light intensities and lower leaf temperatures, are likely to produce a favourable environment for efficient photosynthesis and growth.
106 citations
TL;DR: Studies on winter water relations show a significant decline in the actual moisture content and osmotic potentials of twigs, especially in the kampfzone and at treeline, which indicates the importance of high winter winds and plant temperatures as causes of winter desiccation damage at the alpine treeline.
Abstract: The importance of high winter winds and plant temperatures as causes of winter desiccation damage at the alpine treeline were studied in the Austrian Alps. Samples of 1- and 2-year twigs of Picea abies and Pinus cembra were collected from the valley bottom (1,000 m a.s.l.), forestline (1,940 m a.s.l.), kampfzone (2.090 m a.s.l.), wind-protected treeline (2,140 m a.s.l.), and wind-exposed treeline (2,140 m a.s.l.). Cuticular transpiration was measured at three different levels of wind speed (4, 10, and 15 ms-1) and temperature (15°, 20°, and 25° C). At elevated wind speeds slight increases in water loss were observed, whereas at higher temperatures much greater increases occurred. Studies on winter water relations show a significant decline in the actual moisture content and osmotic potentials of twigs, especially in the kampfzone and at treeline. The roles of high winds and temperatures in depleting the winter water economy and causing desiccation damage in the alpine treeline environment are discussed.
100 citations
TL;DR: An expression is developed to describe the dependence of mouth angle on speed for the RMT 1+8 when towed horizontally, andoretical estimates of the changes in mouth angle with speed agree well with experimental observations.
Abstract: The behaviour of two rectangular midwater trawls, the RMT 1+8 and the RMT 1+8M, is described. The RMT 1+8 consists of a pair of rectangular nets contained within the same frame-a small mouth area RMT 1 of mesh size 320 μm and a larger RMT 8 of mesh size 4.5 mm. The RMT 1+8M is a multiple version of the RMT 1+8, combining three RMT 1s and three RMT 8s within the same frame. An expression is developed to describe the dependence of mouth angle on speed for the RMT 1+8 when towed horizontally. Theoretical estimates of the changes in mouth angle with speed agree well with experimental observations. Within normal towing speeds the RMT 1+8 is sensitive to changes in speed; this sensitivity is especially marked in the RMT 1. Between speeds of about 2.6 and 8.0 knots the RMT 8 does not alter its mouth angle with changes in speed; this behaviour is not shown by the RMT 1—at least within a practical speed range. The performance of the RMT 1+8M cannot be completely described by the theory developed for the RMT 1+8 and possible explanations for this are discussed. The multiple net is considerably less sensitive to changes in towing speed; all three nets of each type have similar mouth angles at a constant speed. Variations in warp load with speed for both trawls are described.
83 citations
TL;DR: In ‘runted’ populations of Tilapia zilli positive correlations were found between maturation stages and the following: gonadosomatic index, gonad weight, fish weight and fish length.
Abstract: In ‘runted’ populations of Tilapia zilli positive correlations were found between maturation stages and the following: gonadosomatic index, gonad weight, fish weight and fish length. The minimum size at maturity was 9·0 cm in males and 11·0 cm in females. The mean fecundity in the ‘stunted’ females was 2359 eggs and it increased with length (L) weight (HO and depth (D) of the fish. There was, however, no correlation between fecundity and egg size. The results indicated that growth in this ‘stunted’T. zilli population was not isometric. The relative condition factor (Kn) which approached one indicates good condition.
74 citations
TL;DR: The kinetic data of respiration by procyclic trypomastigotes fit a model proposed by Bahr and Bonner to determine the maximum rates of two competing electron transport pathways, and it is concluded that the electron transport chain in T. brucei is branched.
40 citations
TL;DR: In this article, the effects of varying water potential on leaf conductance and photosynthesis in coffee plants were investigated, showing that low water potential reduced photosynthesis through its influence on stomata, but an accompanying rise in temperature could lower the rate by lowering both mesophyll and stomatal conductances.
Abstract: Experiments were carried out to relate soil moisture to leaf water potential (Ψ1), and to determine the effects of varying Ψ1, on leaf conductances and photosynthesis in coffee. Stomatal conductance was maximum at 0900 h, but plants growing in drier soil showed marked mid-day stomatal closure. After 1500 h, stomata began closing although plant water status improved. Photosynthesis in relation to changing Ψ1 appeared to exhibit roughly three different rates. At the fixed experimental temperature (25°C) low Ψ1 reduced photosynthesis throughits influence on stomata, but under field conditions low Ψ1 and an accompanying rise in temperature could lower the rate by lowering both mesophyll and stomatal conductances.
36 citations
TL;DR: The results of this study indicate that digestive functions of the herbivorous Sykes monkey and omnivorous baboon are very similar and the stomach was shown to retain particulate matter longer than fluids and to selectively retain the larger particles for a longer period of time.
34 citations
TL;DR: Findings suggest the occurrence of a local cellular immune response in NPC, possibly directed to EBV‐determined antigens.
Abstract: Lymphocytes isolated from the tumors and draining lymph nodes of nasopharyngeal carcinoma (NPC) patients exhibit the following characteristics of immune activation: (1) stable E rosette formation, (2) natural attachment to various human cells, (3) sensitivity in vitro to the lytic effect of glucocorticoids. Although the NPC T cells attach in vitro to various cells they kill only EBV-genome-carrying targets. These findings suggest the occurrence of a local cellular immune response in NPC, possibly directed to EBV-determined antigens.
33 citations
TL;DR: Two out of 288 sick and emaciated dogs from homesteads in the Machakos District of Kenya, where human kala-azar cases existed, were found to be infected with leishmaniasis.
Abstract: Two out of 288 sick and emaciated dogs from homesteads in the Machakos District of Kenya, where human kala-azar cases existed, were found to be infected with leishmaniasis. The leishmanial strain isolated from one of the dogs was characterized enzymologically and serologically and found to be identical with strains isolated from human kala-azar cases and Phlebotomus martini. The significance of these findings is discussed in terms of the general epidemiology of visceral leishmaniasis in Kenya.
TL;DR: In this paper, five types of mulches (black plastic, stone chippings and three types of grass) and a control were used on young clonal tea plants following transplanting.
Abstract: Five types of mulches (black plastic, stone chippings and three types of grass) and a control were used on young clonal tea plants following transplanting. Soil temperature differences were observed in the first two years but disappeared when the tea canopy had developed to cover over 40% or more of the soil surface. Stem diameter, yield (during the first two years) and total dry matter production were positively correlated with soil temperatures over the range 14–21°C. Beneficial effects of raising soil temperature by black plastic mulch were short-lived, but the detrimental effect of reducing temperature by grass mulches was more severe and long lasting. Grass mulches induced shallow rooting, as a result of which the tea was more susceptible to drought.
TL;DR: It is proposed that the diffuseness of the myocardial involvement and its progression with age in a young population without coronary artery disease represents the resolution of the acute inflammatory process of rheumatic fever in diffuse fibrosis of theMyocardium and/or an occlusive vasculitis.
TL;DR: Clinical, parasitological and pathological studies were made on five eland infected with Theileria, finding that the severely affected organs were diffusely infiltrated with parasitised cells both intravascularly and extravascularly.
TL;DR: The Montgenevre ophiolite near Briancon in the French Alps consists of pillow lavas, pegmatitic and flaser gabbros and serpentinite in tectonic contact as discussed by the authors.
TL;DR: In this article, the African cat fish Clarias mossambicus had a total nitrogen output of 0.3 mM N/kg/hr, predominantly ammonia with 13% urea, and when taken out of water and placed in a moist environment ionic losses decreased to less than half the former rate and were divided equally between urine and possibly skin.
TL;DR: With the exception of the potassium flux, the camel, sheep and goat demonstrated similar patterns of colonic electrolyte movement, and Zebu cattle was the least efficient in recovering fluids from colonic contents.
TL;DR: In this article, the authors make proposals for the design of terraces to retain water and a method is given for calculating the depth of storage required, where terraces should be raised periodically to maintain adequate storage capacity which would otherwise be reduced by sedimentation.
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01 Jan 1980TL;DR: An historical analysis of the Kenyan health care system shows that inheritance from Britain has not been lost, it is being strengthened, and the prevailing health system is tailored to suit the growing upper socioeconomic classes.
Abstract: European colonial powers have shaped the philosophies and the social structures in their former colonies. Institutions currently dominating lives in the African states are a reflection of colonial domination. The thrust of colonial activity was to mold political systems, socio-economic activities and cultural patterns which were largely consistent with the prevailing or desired European models. The greatest hindrance to change in the health and other systems in Africa lie in what was inherited. An historical analysis of the Kenyan health care system shows that inheritance from Britain has not been lost, it is being strengthened. The prevailing health system is tailored to suit the growing upper socioeconomic classes.
TL;DR: The kinetics of glutamate influx and efflux on the glutamate-hydroxyl carrier have been measured and compared in rat liver mitochondria and their possible regulatory role in urea synthesis by liver is assessed.
Abstract: The kinetics of glutamate influx and efflux on the glutamate-hydroxyl carrier have been measured and compared in rat liver mitochondria. At pH 7.4 and 25 degrees C, the Michaelis constants and V'max values were in agreement with the Haldane relationship when the alpha pH was accounted for. The Km values for glutamate influx and aspartate efflux on the glutamate-aspartate translocator are also reported. Extrapolation of the maximum velocities to 37 degrees and the intact liver provide values of 5.6 and 2.4 mmol/g dry wt/hr for glutamate influx and efflux, respectively, on the glutamate-aspartate translocator. Both translocators operate by a sequential mechanism with formation of a ternary complex. Their possible regulatory role in urea synthesis by liver is assessed.
TL;DR: In this article, an iterative time-averaging method proposed by Edelmann (1972b) is used for the purpose of suppressing gravitational oscillations and synoptic transient perturbations.
Abstract: Stationary solutions in the presence of bottom topography are computed for a tropical atmospheric belt. A primitive divergent barotropic model is assumed. An iterative time-averaging method proposed by Edelmann (1972b) is used for the purpose of suppressing gravitational oscillations and synoptic transient perturbations. The spatial finite differencing scheme is analogous to the one adopted in the Mintz-Arakawa two-level general circulation model and documented by Gates et al. (1971). Time integration is performed with the leapfrog scheme using a time stop of 10 min. The initial state consists of realistic zonal flow and the initial geopotential height of the free surface is determined from the wind by assuming steady-state conditions. First. we obtain quasi-stationary solutions using an idealized mountain profile over a 36-day integration. The results are used to interpret stationary solutions in the case involving real African orography. When an idealized mountain profile is used, a quasi-stati...
TL;DR: The population dynamics of Pineus pini (Gmel.) was examined in two locations in the Kenya Highlands where the mean annual precipitation ranges from 620 to 1400 mm, and population fluctuations of the most common species of predatory insects, Exochomus spp.
Abstract: The population dynamics of Pineus pini (Gmel.) was examined in two locations in the Kenya Highlands where the mean annual precipitation ranges from 620 to 1400 mm. Variations in population densities were related to rainfall. Generally, there was a marked decrease in population during the three months of heavy rainfall in March to May and a significant increase during dry weather from August to October. This was followed by a slight decrease in the rate of population build-up, until the long rains in April again resulted in another population collapse. Nine species of predatory insects were identified, and population fluctuations of the most common of these, Exochomus spp., was studied. Predators seemed to remove about 12% of the aphid population. Other mortality factors included heat and crawler dispersion. The greatest mortality occurred early in the life-cycle and was mainly due to eggs and crawlers being washed off the host-tree by rain.
01 Mar 1980-Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology
TL;DR: The adaptive significance of the low O2 affinity, the increase ofnH with O2 saturation and the temperature insensitive O2-Hb binding is discussed in relation to the high and fluctuating body temperatures of Chiromantis.
Abstract: Respiratory gas exchange and blood respiratory properties have been studied in the East-African tree frogChiromantis petersi. This frog is unusually xerophilous, occupies dry habitats and prefers body temperatures near 40°C and direct solar exposure. Total O2 uptake was low at 81 μl O2·g−1·h−1±19.0 (SD) at 25°C increasing to 253.5 μl O2·g−1·h−1±94.8 (SD) at 40°C giving aQ10 value of 2.1. Skin O2 uptake at 25°C was 38.5% of total. The gas exchange ratio was 0.71 for whole body gas exchange, 0.61 for the lungs and 1.02 for the skin at 25°C.
TL;DR: Five years after inundation, two varieties of Cyprinus carpio—the common carp and the mirror carp, have appeared in the commercial fishery in Lake Kamburu.
Abstract: Five years after inundation, two varieties of Cyprinus carpio—the common carp and the mirror carp, have appeared in the commercial fishery in Lake Kamburu. Species of Tilapia continue to remain the most abundant fish in the lake and their numbers are on the increase. The second most numerous species is Barbus while Labeo sp. seems to be declining. The numbers of Mormyrus have declined drastically. Species of the genera Tilapia, Barbus and Cyprinus are widely distributed within the lake; Labeo prefers the confluence of the rivers entering into the lake and Mormyrus has moved upriver.
TL;DR: Adzogbo is one of the most complex of the Eve dances, both in the intricacy of its polyrhythmic texture and the precise relationship of the rhythms of the master drum to the vigorous movements of the dancers as mentioned in this paper.
Abstract: The Eve-speaking people of the Guinea Coast of West Africa are rightly renowned for their highly developed drumming and dancing. Among the most exciting of their dances is Adzogbo, originally a warriors’ dance of the Fo-speaking people of the ancient kingdom of Dahomey and now a recreational dance for the Fo and Eve people of southern Benin, Togo and Ghana. Adzogbo is one of the most complex of the Eve dances, both in the intricacy of its polyrhythmic texture and the precise relationship of the rhythms of the master drum to the vigorous movements of the dancers. An outstanding feature of Adzogbo is the key role of drum language in the dance: every sequence of dance movements is introduced by a spoken or sung text which is then almost exactly reproduced in the rhythms of the master drum. Adzogbo thus provides excellent material for an analysis of drum language, especially the relationship between speech tone and drum strokes. In this article we shall sketch the general background of the dance and then look in detail at six examples of spoken texts and their associated drum rhythms.
TL;DR: In this article, the concentrations of Na, K, and Cl and the water content in the large intestine and rectum of an East African ruminant, the Dik-dik antelope, were investigated in hydrated and dehydrated animals.
Abstract: 1.
The concentrations of Na, K, and Cl and the water content in the large intestine and rectum of an East African ruminant, the Dik-dik antelope, was investigated in hydrated and dehydrated animals.
2.
Intestinal contents were removed at six sites along the large intestine and rectum, and the water fraction and the amounts of Na, K, and Cl were measured per g dry matter. An impermeant water marker showed that the dry matter amount was nearly constant along the lower gut. Local electrolyte absorption rates were determined in the terminal colon by a dialysis bag method.
3.
Approximately 4/5 of the absorption of NaCl and H2O took place in the upper large intestine. Throughout the lower gut the Na concentration of the absorbate was close to that of plasma. The Na and Cl concentrations of the digesta decreased aborally while the K concentration rose, but K was still absorbed.
4.
Dehydration resulted in a reduction of 35% of the water lost per gram dry faeces. The water content was reduced from the start of the large intestine (by 13%), but the fractional absorption of salt and water in the large intestine and rectum was not significantly changed. The local electrolyte absorption rates and the electrical potential difference were slightly reduced. The Na and K concentrations of the absorbate remained nearly constant. The water saving during dehydration thus seems to proceed without specific adjustments of the transport parameters of the lower gut. The concentrations of Na and Cl in faeces approach those which in dialysis bag experiments result in zero absorption rates. This explains the constant fractional absorption of NaCl and water in the lower gut at different flow rates of dry matter.
5.
Animals shot in the field were not dehydrated, but more Na-depleted than those studied in captivity. They had a pronounced net K absorption in the lower gut.
TL;DR: It was found that pruning did not increase yields or reduce the usual decline in yield over a three-year period; but light and selective pruning both increased the life of the vine although at very low productivity.
Abstract: SummaryIn an experiment in which one-wire and three-wire trellising as well as severe, selective, light and no pruning were compared, it was found that pruning did not increase yields or reduce the usual decline in yield over a three-year period; but light and selective pruning both increased the life of the vine although at very low productivity. Trellising did not influence yield. Fruiting peaks were in January-February and September-October.
01 Mar 1980
TL;DR: In this paper, the authors investigated the relationship between atmospheric perturbations induced by large scale bottom orography and the intensity of the initial zonal current over a tropical belt centred at the equator.
Abstract: In this study an investigation is carried out regarding the relationship between atmospheric perturbations induced by large scale bottom orography and the intensity of the initial zonal current over a tropical belt centred at the equator. A primitive divergent barotropic model including bottom topography was assumed during the computations. The zonal vertical cross-section of the idealized orography profile which was used is in form of a cosine function. In the meridional direction the orography is flat near the equator and descends exponentially some distance away from the equator.