8 research outputs found
Influence of Age of Mice on the Susceptibility to Murine Schistosomiasis Infection
Intensity of human schistosomiasis infection increases with age, a peak
being attained at early puberty. Hormones could be involved in the
age-related changes in susceptibility to schistosomiasis. Male BALB/c
mice were infected with Schistosoma mansoni either before or after
puberty and worm numbers, cellular immune responses, hormonal levels
and pathology analysed. Pre-puberty infected mice had a significantly
higher number of adult worms (p<0.05), more severe granulomas,
higher mortality rate and higher proliferative responses as compared to
postpuberty infected mice. Levels of the hormones were lower in the
pre-puberty infected mice as compared to the post-puberty group early
in the infection. Plasma levels of testosterone and luteinizing
hormones decreased significantly (p<0.05) in infected mice when
compared to controls. Susceptibility to S. mansoni in male BALB/c mice
seems to be influenced by levels of testosterone and leutenizing
hormone at infection. Albeit, an infection with S. mansoni seems to
lower the hormonal levels
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Coping with a challenging environment: Effects of seasonal variability and reproductive status on glucocorticoid concentrations of female baboons (Papio cynocephalus)
Environmental stressors impact physiology and behavior in many species of animals. These effects
are partly mediated through changing concentrations of glucocorticoids, which also vary with
reproductive state and social conditions. Prior research has focused largely on seasonal breeders, but
the close temporal linkage between season and reproductive state in these species hinders ability to
disentangle environmental effects from those of the animal’s reproductive status. Here we assessed
the effects of environmental challenges on the fecal glucocorticoid (fGC) levels of non-seasonal
breeders, female baboons (Papio cynocephalus) of Amboseli, Kenya. Amboseli is characterized by
a long dry season, during which food and water become scarce, and by extreme temperatures above
40°C in the shade during some months of the year. We found that after accounting for female
reproductive status and individual variability, females exhibited higher fGC levels during the dry
season than during the wet season. Further, during the wet season, fGC levels were higher in months
of high average daily maximum temperatures. During the dry season, fGC levels were elevated both
in hotter months and in months during which the baboons spent a relatively high proportion of time
feeding. In spite of these stressors, female baboons reproduce during all months of the year in
Amboseli, unlike most other mammals in this environment. This may be attributable to their extreme
adaptability, specifically their diversified diet, and their ability to modify their behavior, including
their activity profiles
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Persistence of maternal effects in baboons: Mother's dominance rank at son's conception predicts stress hormone levels in subadult males
Dominance status and reproductive experience are maternal characteristics that affect offspring traits
in diverse taxa, including some cercopithecine primates. Maternal effects of this sort are widespread
and are sources of variability in offspring fitness. We tested the hypothesis that maternal dominance
rank and reproductive experience as well as a male’s own age and dominance rank predicted chronic
fecal glucocorticoid (fGC) concentrations in 17 subadult wild male baboons, Papio cynocephalus
(median age 6.5 years), in the Amboseli basin, Kenya. Among these variables, maternal dominance
rank at a subadult male’s conception was the sole significant predictor of the male’s fGC and
accounted for 42% of fGC variance; sons of lower ranking mothers had higher fGC than did those
of high ranking mothers. This result is striking because subadult male baboons are approximately 4–
6 years past the period of infant dependence on their mothers, and are larger than and dominant to
all adult females. In addition, many males of this age have survived their mothers’ death.
Consequently, the influence of maternal dominance rank persisted well beyond the stage at which
direct maternal influence on sons is likely. Persistence of these major maternal influences from the
perinatal period may signal organizational effects of mothers on sons’ HPA axis. Although shortterm,
acute, elevations in GC are part of adaptive responses to challenges such as predators and other
emergencies, chronically elevated GC are often associated with stress-related pathologies and,
thereby, adverse effects on fitness components
Progesterone, Estradiol and their receptors in leiomyomata and the adjacent normal myometria of black Kenyan women
No abstract available
[Afr. J. Health Sci. 2002; 9: 123-128