Body temperature daily rhythm adaptations in African savanna elephants (Loxodonta africana)

The savanna elephant is the largest extant mammal and often inhabits hot and and environments. Due to their large size, it might be expected that elephants have particular physiological adaptations, such as adjustments to the rhythms of their core body temperature (T-b) to deal with environmental challenges. This study describes for the first time the T-b daily rhythms in savanna elephants. Our results showed that elephants had lower mean T-b values (36.2 +/- 0.49 degrees C) than smaller ungulates inhabiting similar environments but did not have larger or smaller amplitudes of T-b variation (0.40 +/- 0.12 degrees C), as would be predicted by their exposure to large fluctuations in ambient temperature or their large size. No difference was found between the daily T-b rhythms measured under different conditions of water stress. Peak T-b's occurred late in the evening (22: 10) which is generally later than in other large mammals ranging in similar environmental conditions. (C) 2007 Elsevier Inc. All rights reserved.

Differences in resting metabolic rates of two southern African tortoises: Psammobates oculiferus and Geochelone pardalis

Energy metabolism varies considerably between different groups of endotherms, yet there is little or no reported variation among extant groups of reptiles. We measured lower resting metabolic rates (RMRs) in Kalahari tent tortoises (Psammobate oculiferus) than in sympatric Leopard tortoises (Geochelone pardalis). G pardalis also had RMR values that were higher than the allometric prediction for reptiles whereas P oculiferus had RMR values that were not significantly different from the prediction. Differences in RMR between the two species may have occurred because of the large differences in body mass, differing body temperatures, differences in growth rates, or because there may have been differences in the heat increment of feeding.

Huddling in groups leads to daily energy savings in free-living African Four-Striped Grass Mice, Rhabdomys pumilio

1. Free-living animals make complex decisions associated with optimizing energy and nutrient intake. In environments where ambient temperatures fall below the thermoneutral zone, homeotherms must choose whether or not to forage, how long and what to forage for, and whether or not to perform activities that conserve energy.

Activity against Mycobacterium smegmatis and M. tuberculosis by extract of South African medicinal plants

Seven ethnobotanically selected medicinal plants were screened for their antimycobacterial activity. The mininium inhibitory concentration (MIC) of four plants namely Artemisia afra, Dodonea angustifolia, Drosera capensis and Galenia africana ranged from 0.781 to 6.25 mg/mL against Mycobacterium smegmatis. G. africana showed the best activity exhibiting an MIC of 0.78 mg/mL and a minimum bactericidal concentration (MBC) of 1.56 mg/mL. The MICs of ethanol extracts of A angustifolia and G. africana against M. tuberculosis were found to be 5.0 and 1.2 mg/mL respectively. The mammalian cytotoxicity IC50 value of the most active antimycobacterial extract, from G. africana, was found to be 101.3 mu g/mL against monkey kidney Vero cells. Since the ethanol G. africana displayed the best antimycobacterial activity, it was subjected to fractionation which led to the isolation of a flavone, 5,7,2'-trihydroxyflavone. The MIC of this compound was found to be 0.031 mg/mL against M. smegmatis and 0.10 mg/mL against M. tuberculosis. This study gives some scientific basis to the 14 traditional use of these plants for TB-related symptoms. Copyright (C) 2008 John Wiley & Sons, Ltd.

A family of kassinatuerin-2 related peptides from the skin secretion of the African hyperoliid frog, Kassina maculata.

We describe the isolation and structural characterization of a family of antimicrobial peptides related to kassinatuerin-2, from the skin secretion of the African hyperoliid frog, Kassina maculata. All four peptides, designated kassinatuerin-2Ma through Md, are C-terminally-amidated 20-mers with the consensus sequence – FX1GAIAAALPHVIX2AIKNAL – where X1 = L/F/V/I and X2 = S/N. All four peptides are encoded by precursors of 69 amino acids. Synthetic replicates of all kassinatuerin-2 related peptides displayed a potent inhibitory activity against Staphylococcus aureus with a minimal inhibitory concentration of 16 µM, at which concentration, however, they effected 18% haemolysis of horse erythrocytes after 2 h. Despite obvious membranolytic properties, all peptides were ineffective at inhibiting the growth of Escherichia coli at concentrations up to 200 µM and were relatively ineffective against Candida albicans (MIC 120 µM). The kassinatuerin-2 related peptides of K. maculata skin secretion thus possess a discrete antimicrobial and weak haemolytic activity in contrast to the prototype kassinatuerin-2 from the skin secretion of Kassina senegalensis.

Do benchmark African equity indices exhibit the stylized facts?

This paper investigates if benchmark African equity indices exhibit the stylized facts reported for financial time-series returns. The returns distributions of the Africa All-Share, Large, Medium and Small Company Indices were found to be leptokurtotic, had fat-tails, over time experienced volatility clustering and exhibited long memory in volatility. Both the All-Share and Large Company Indices were found to exhibit leverage effects. In contrast, positive shocks had a greater impact on future volatility for the Small Company Index which implies a reverse leverage effect. This finding could reflect a bull/bubble market for small capitalisation stocks in Africa.

The evolution of authoritarian processes: Fostering cooperation in large-scale groups

Authoritarianism, comprising conventionalism, authoritarian submission, and authoritarian aggression, is an important factor underlying prejudice and social discrimination and therefore is typically perceived as socially problematic. In contrast, our work examines adaptive features of authoritarianism. Evolutionary game theoretical considerations (e.g., biased social learning) point to authoritarian psychological processes that establish and foster group life (e.g., high levels of ingroup cooperation). First, the evolution of social learning (particularly conformist and prestige biases) leads to the establishment of local and distinct cultural groups (conventionalism). Second, local cultural rules solve coordination dilemmas by transforming these rules into normative standards against which others are evaluated (authoritarian submission). Third, the common rules within a particular culture or group are reinforced by a tendency to reward norm compliance and punish norm deviations (authoritarian aggression). Implications regarding the deduction of novel research questions as well as dealing with authoritarianism as a social problem are discussed.