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Some aspects of calcium (45Ca2+) uptake by isolated washed human and rat platelets in relation to intracellular second messengers, cardiovascular disease and drug action was studied. It was first established that both α - and β- adrenoceptor agonists (activators and inhibitors of platelet function, respectively) elicit the uptake of 45Ca2+. Subsequent studies demonstrated that this uptake of 45Ca2+ may reflect local changes of Ca2+ at the plasma membrane and signal transduction mechanisms (G protein and protein kinase A and C activation). These findings extended to other stimulators (collagen, adenosine diphosphate, Ca2+ ionophore A23187) and inhibitors (dibutyryl cyclic adenosine 3'5'-monophosphate and iloprost [a prostacyclin analogue]) of platelet function. In studies on drug action, it was found that inhibitors of platelet function (angiotensin converting enzyme inhibitors, non-steroidal anti-inflammatory drugs, Ca2+ channel blocking drugs) also inhibit the uptake of 45Ca2+, suggesting that their mode of action also involves the inhibition of Ca2+ mobilisation. 45Ca2+ uptake in platelets from patients in which platelet hyperaggregabi1ity has been reported (anorexia nervosa [AN], peripheral vascular disease [PVD], diabetes mellitus [DM]) was studied. In AN,α- and β-adrenoceptor-stimulated 45Ca2+ uptake was increased and decreased, respectively. In platelets from patients with type I and type II DM, basal 45Ca2+ uptake was significantly enhanced. In contrast, agonist-stimulated 45Ca2+ uptake was significantly diminished in type I DM. In type II diabetics, α- and β-adrenoceptor-stimulated 45Ca2+ uptake was enhanced. In PVD patients, agonist-stimulated 45Ca2+ uptake by platelets was unaltered. Studies on platelets from diabetic rats revealed that α- and β-adrenoceptor-stimulated 45Ca2+ uptake was increased and decreased, respectively. It is concluded that in conditions associated with platelet dysfunction, there are marked alterations in Ca2+ sequestration at the plasma membrane level. The relevance of these findings is discussed in relation to previous reports of altered platelet function in these conditions.

Population pressure in developing countries is believed to be the predominant cause of deforestation, due to the dual needs of food and fuel. This has led to a shortage of firewood (for cooking) and affects especially the rural poor of these countries. One intervention strategy to reduce firewood consumption has been to design, develop and disseminate "improved" (ie fuel efficient) cooking stoves for use in the rural sector. These stove programmes have failed to achieve widespread dissemination of "improved" stoves. One reason is the mismatch between the felt needs and problems of the rural poor and the assumptions of institutions and individuals designing and promoting these stoves. Moreover, traditional stoves and fireplaces are not inherently inefficient for cooking. Not all "improved" stoves have been more efficient than traditional designs in practice. Traditional modes of cooking serve a number of sociocultural and practical functions which have been neglected in stove programmes to date. Stove users in a number of developing countries appear to be more concerned about speedy cooking whilst stove programmes overemphasize fuel savings. Villagers in Zimbabwe appear to have spontaneously transferred to stoves which consume significantly more fuel than their traditional fireplace. However, this lack of fuel economy is offset by the benefits of faster cooking, greater space heat, more stable pots and a modern "image". The higher firewood collection costs are affordable as this takes place in the agriculturally slack season. Deforestation is a complex issue to which there are a number of contributary factors. In Zimbabwe, the processes of land degradation, deforestation, and the ensuing shortage of firewood were set in motion as early as the 1890’s when the African population residing on the fertile highlands was forcibly evicted onto marginal land by European settlers. Strategies to cope with deforestation in Zimbabwe would be aided by user participation in defining needs and problems within the wider framework of land tenure, agroforestry schemes and inputs to increase the productivity of African areas.