University of Nairobi

About: University of Nairobi is a education organization based out in Nairobi, Nairobi, Kenya. It is known for research contribution in the topics: Population & Health care. The organization has 6702 authors who have published 10777 publications receiving 231294 citations. The organization is also known as: UoN & IAU-020319.

CD8+ lymphocytes respond to different HIV epitopes in seronegative and infected subjects

Abstract: There is substantial variation in susceptibility to HIV-1infection, with some subjects remaining HIV-1 seroneg-ative despite repeated exposure to virus (1–3). HIV-1–specific cytotoxic T-lymphocytes (CTLs) have beendescribed in several HIV-1–exposed, persistentlyseronegative (HEPS) populations, and the generation ofHIV-1–specific CTLs has become a key goal in the devel-opment of a protective HIV-1 vaccine (4). HIV-1–specif-ic CTLs are also found in seropositive donors, wherethey are important in suppressing viremia and prevent-ing disease progression (5–7), but are ultimately unableto prevent eventual immunosuppression and death (8).It remains unclear how HIV-1–specific CTL could playa role in protection against HIV-1 infection in HEPSsubjects, while failing to eliminate the virus in themajority of those who are infected.The epidemiology and immunology of HIV-1 hasbeen studied for over 15 years in an observationalcohort of sex workers based in the Pumwani slum areaof Nairobi, Kenya (9). It is estimated that these womenhave over 60 unprotected sexual exposures to HIV-1 peryear, resulting in intense HIV-1 infection pressure onwomen who are seronegative when joining the cohort.Rates of HIV-1 seroconversion are highest during thefirst year of cohort enrollment and reach a plateau after3 years of seronegative follow-up, although seroconver-sion may occur as late as 10 years after enrollment (10).The subgroup of women who remain both seronegativeand negative as determined by PCR for at least 3 yearswhile continuing sex work are operationally defined asHIV-1 resistant (11). HIV-1–specific CTL have beendescribed previously in both the both the blood andgenital tract of this HIV-1–resistant subgroup, usingIFN-γenzyme-linked immunospot (ELISPOT) respons-es to HIV-1 CTL epitopes (10, 12, 13), lysis of autolo-gous vaccinia HIV-1

Energetic cost of carrying loads: have African women discovered an economic way?

Abstract: When travelling in East Africa one is often surprised at the prodigious loads carried by the women of the area. It is not uncommon to see women of the Luo tribe carrying loads equivalent to 70% of their body mass balanced on the top of their heads (Fig. 1). Women of the Kikuyu tribe carry equally large loads supported by a strap across their foreheads; this frequently results in a permanently grooved skull. Recent experiments on running horses, humans, dogs and rats showed that the energy expended in carrying a load increased in direct proportion to the weight of the load for each animal at each speed, that is, carrying a load equal to 20% of body weight increased the rate of energy consumption by 20% (ref. 1). The purpose of the present study was to determine whether these African women use specialized mechanisms for carrying very large loads cheaply. We found that both the Luo and Kikuyu women could carry loads of up to 20% of their body weight without increasing their rate of energy consumption. For heavier loads there was a proportional increase in energy consumption, that is, a 30% load increased energy consumption by 10%, a 40% load by 20% and so on. We suggest that some element of training and/or anatomical change since childhood may allow these women to carry heavy loads economically.

Global distribution of earthworm diversity

Abstract: Soil organisms, including earthworms, are a key component of terrestrial ecosystems. However, little is known about their diversity, their distribution, and the threats affecting them. We compiled a global dataset of sampled earthworm communities from 6928 sites in 57 countries as a basis for predicting patterns in earthworm diversity, abundance, and biomass. We found that local species richness and abundance typically peaked at higher latitudes, displaying patterns opposite to those observed in aboveground organisms. However, high species dissimilarity across tropical locations may cause diversity across the entirety of the tropics to be higher than elsewhere. Climate variables were found to be more important in shaping earthworm communities than soil properties or habitat cover. These findings suggest that climate change may have serious implications for earthworm communities and for the functions they provide.

Social affiliation matters: both same-sex and opposite-sex relationships predict survival in wild female baboons

Abstract: Social integration and support can have profound effects on human survival. The extent of this phenomenon in non-human animals is largely unknown, but such knowledge is important to understanding the evolution of both lifespan and sociality. Here, we report evidence that levels of affiliative social behaviour (i.e. ‘social connectedness’) with both same-sex and opposite-sex conspecifics predict adult survival in wild female baboons. In the Amboseli ecosystem in Kenya, adult female baboons that were socially connected to either adult males or adult females lived longer than females who were socially isolated from both sexes—females with strong connectedness to individuals of both sexes lived the longest. Female social connectedness to males was predicted by high dominance rank, indicating that males are a limited resource for females, and females compete for access to male social partners. To date, only a handful of animal studies have found that social relationships may affect survival. This study extends those findings by examining relationships to both sexes in by far the largest dataset yet examined for any animal. Our results support the idea that social effects on survival are evolutionarily conserved in social mammals.

Longitudinal Analysis of Human Immunodeficiency Virus Type 1 RNA in Breast Milk and of Its Relationship to Infant Infection and Maternal Disease

Abstract: Transmission of human immunodeficiency virus type 1 (HIV-1) via breast-feeding can occur throughout lactation. Defining both fluctuation in breast-milk virus level over time and how breast-milk virus correlates with mother-to-child transmission is important for establishing effective interventions. We quantified breastmilk HIV-1 RNA levels in serial samples collected from 275 women for up to 2 years after delivery. Higher maternal plasma virus load lower maternal CD4 T cell count and detection of HIV-1 DNA in maternal genital secretions were significantly associated with elevated breast-milk HIV-1 RNA. Within women who breast-fed median virus load in colostrum/early milk was significantly higher than that in mature breast milk collected 14 days after delivery (P = .004 ). Breast-feeding mothers who transmitted HIV-1 to their infants had both significantly higher breast-milk viral RNA throughout lactation and more-consistent viral shedding compared with mothers who did not transmit HIV-1. In breast-feeding women a 2-fold–increased risk of transmission was associated with every 10-fold increase in breast-milk virus load (95% confidence interval 1.3–3.0; P < .001). These results indicate that the risk of infant infection from breast-feeding is influenced by breast-milk virus load which is highest early after delivery. (authors)