Daily variations in photoprotective mechanisms were studied in sun and shade leaves of 40-year-old cork oak (Quercus suber L.) trees during early summer in Portugal. Although trees were not severely water stressed because predawn leaf water potentials remained high, photosynthesis and stomatal conductance decreased at midday. The midday depression in gas exchange was not reversed by short-term exposure to "optimal" conditions of temperature, light and vapor pressure deficit. Chlorophyll a fluorescence, maximum photochemical yield of photosystem II and the quantum yield of noncyclic electron transport showed midday depressions, but recovered by the evening. Both short-term changes in the components of the xanthophyll cycle (reversible de-epoxidation of violaxanthin during the day) as well as long-term changes (higher xanthophyll content in sun compared with shade leaves) were detected and may play a role in the dissipation of excess energy at midday. Because the activities of enzymes of the antioxidant system, superoxide dismutase and ascorbate peroxidase, were high enough to cope with the increase in oxygen reactive species likely to arise under the stressful conditions of midday, we conclude that these enzymes may provide an additional mechanism for energy dissipation.

At the end of the growing season in late July, 20-month-old cork oak (Quercus suber L.) saplings were partially defoliated (63% of leaf area) to evaluate their ability to recover leaf area after defoliation. At 18 and 127 days after defoliation, changes in starch and nitrogen pools were determined in leaves and perennial organs, and variations in photosynthetic carbon uptake were investigated. To determine the role of stored nitrogen in regrowth after defoliation, plant nitrogen was labeled in the previous winter by enriching the nutrient solution with 15N. Plants recovered the lost leaf area in 127 days. Although there was remobilization of starch and nitrogen from leaves and perennial organs, the availability of resources for growth in the following spring was not decreased by defoliation. On the contrary, starch concentration in coarse roots was higher in defoliated saplings than in control saplings, presumably as a result of the higher net CO2 exchange rate in newly developed leaves compared with pre-existing leaves.

No abstract

Over many years Latin American universities have operated 'extension projects' in their surrounding communities. These projects, in health professions schools, frequently involved the establishment of community-based health centres operated by the university. Since the early 1970s, a large number of health professions schools entered into agreements with local or regional health systems for the operation of projects of 'articulation of teaching and services' in well-defined geographic areas. The primary health care strategy emphasized by WHO and actively promoted by national governments since the Alma Ata Declaration of 1978 led to a worldwide movement toward effective 'community participation' in each own local health system. An assessment of these initiatives, involving three types of paired relationships (university-community; university-local health system; local health system-community) provided the idea and the experiential basis for an innovative programme bringing the three partners together in a joint effort. Program UNT was set up and now includes 23 projects which are partially supported by the Kellogg Foundation. They all share a common set of ideas and ideals, emanating from the Alma Ata and Edinburgh Declarations, and are currently being implemented in 11 countries of Latin America.

Resumo: Este ensaio resulta de um esforço de síntese do conhecimento que hoje se possui sobre o caráter multidimensional do setor saúde com os avanços recentes no desenvolvimento de uma teoria, epistemologia ou paradigma da complexidade. O objetivo em vista é o de uma melhor compreensão do processo saúde-doença nas populações. A partir dessa compreensão, sugere-se a construção coletiva de estruturas matriciais que facilitem a criação de parcerias entre múltiplos atores e sistemas sociais na abordagem de problemas do setor saúde.