Les derniers préhumains et les premiers humains

The international expedition to the Omo region of Ethiopia clearly demonstrates for the first time in the 1970s that a discernable change from a probable moist climate regime occurred some 3 millions years ago. This climate change brought about an adaptation process and caused environmental adaptations for all vertebrates. This included ecosystems throughout the central, eastern, and southern regions of tropical Africa that surrounded the equatorial nucleus of dense forest. The Hominids who lived in these ecosystems did not escape these changes, but experienced five, maybe six adjustments to the climatic alteration, e.g., physical sturdiness, feeding habits, locomotion, central nervous system. As always in such circumstances, nature reacts by enabling variations on the same theme by providing answers, which are often comparable, but never the same! Similar to the instance of the vertebrates and Hominids cited above, the Human race, together with all its specific peculiarities, is an example of adaptations made necessary due to climatic and environmental variations.     

Analysis of starch amylolysis using plots for first-order kinetics

Investigators often study product release from starches during prolonged incubations with α-amylase in vitro. The reaction time courses usually fit to a linear form of a first order rate equation, i.e., ln[(C_∞ − C_t)/C_∞] = −kt. This equation calls for an accurate estimate of C_∞, i.e., the concentration of product at the end of the reaction. Estimates of C_∞ from digestibility curves can be unreliable. The Guggenheim method does not require prior knowledge of C_∞ but seems not to have been applied to starch hydrolysis data. An alternative method is also available in which the logarithm of the slope (LOS) of a digestibility curve at various time points is plotted against time. This allows estimations of both k and C_∞ and can also reveal whether changes occur in digestion rate from rapid to slow as digestion proceeds. We describe the Guggenheim and LOS methods and provide examples of their application to starch digestibility data.     

Soldier Tracks in a First World War Fort (Valmorbiawerk,Trento, Italy)

A set of partial or complete boot tracks is described from the floor of a tunnel in a First World War fort in the Trentino Alto Adige region. The tracks belong to the right and left boots of the same person. The deepest imprints have been left by the heels, which were reinforced by rectangular and square-shaped hobnails. From studying all the tracks, it has been possible to reconstruct the complete hobnail set of both boots and compare them with coeval boots used by soldiers. Depending on the nationality and branch of the armed services, the nails had different shapes and arrangements. The layout and the shape of the tracks perfectly match the mountain footwear used by the Austro-Hungarian army. The succession of events during the building of the Valmorbiawerk indicates that the tracks could have been imprinted between spring 1914 and May 1915.     

Adenosine deaminase and immunodeficiency: An in vitro model

We have examined the effect of adenosine and EHNA, a competitive inhibitor of adenosine deaminase (ADA), upon the ability of human peripheral blood lymphocytes to respond to mitogen. Addition of adenosine at concentrations greater than 10 μm (10^?5m) resulted in inhibition of lymphocyte proliferation at 48 hr of culture, provided that the culture medium was relatively free of ADA activity. The actual concentrations of adenosine remaining in inhibited cultures at the time of harvest were considerably lower than those added initially. EHNA alone also inhibited PHA response (and to a lesser extent PWM and Con A responses), but only at high concentrations. Noninhibitory concentrations of EHNA and adenosine together acted synergistically to produce profound inhibition of lymphocyte proliferation. This may provide an in vitro model to explore further the mechanism of the immunodeficiency associated with deficiency of ADA. Adenosine deaminase activity in stimulated cultures did not differ significantly from that found in unstimulated cultures, and the activity per protein or per DNA actually decreased in stimulated versus unstimulated cultures.     

The first optic ganglion of the bee

The nine receptor cells in each ommatidium of the worker bee end as six short visual fibres in the lamina and as three long visual fibres in the medulla. Behavioural and physiological evidence for regional variation in spectral sensitivity prompted observations on the morphology of the visual units. The distribution, branching pattern, diameter and the arrangement of axonal protusions of the characteristic receptor-cell axons were studied in various regions of the lamina. The six short visual fibres and two of the long visual fibres in each laminar cartridge are uniform over the total eye surface. Only the receptor axons of the ninth cell a UV and polarised light-sensitive cell, show obvious regional variation. In view of the regional constancy in morphology of eight of the nine receptor-cell axons, the regional variations in spectral sensitivity demand either functional subdivision of morphologically indistinguishable photoreceptors (e.g., content of different visual pigments) or a highly complex connectivity pattern of their axons in the first optic ganglion.     

Environmentally Contingent Reproductive Strategies in Mayan and Ache Males

This research explores male reproductive parameters, particularly the timing of first reproduction, in two traditional populations. Predictions are drawn from theoretical arguments that have their roots in evolutionary psychology and behavioral ecology, and that interpret variation in reproductive outcomes as environmentally contingent adaptations. In both Ache and Mayan samples, father absence, predicted to act as a stressor that causes precocious sexuality and reproduction as well as unstable pair bonds, did not affect the timing of first reproduction in male offspring in the expected way. Father absence in Mayan men, however, was found to be associated with responses to questionnaire items indicating lack of willingness to pay time and energy costs to maintain existing sexual unions. The results suggest that father absence affects male mating strategy, but that strategic differences did not translate into reproductive outcomes in the sample. In the Mayan population, education was associated with early reproduction, more lifetime sex partners, and higher fertility, which was also contrary to the predicted pattern based on a life-history tradeoff approach. Parental resources were associated with earlier reproduction in the Mayan sample, confirming the prediction that restricted resources should delay reproduction.