Infectious disease and the Unesco basic education initiative

As part of a Basic Education for All campaign, Unesco is exploring ways to improve health and nutrition in school-age children in order to help them take advantage of the only schooling they may ever receive. At the first international Unesco working meeting on health, nutrition and school performance, intestinal helminths were identified as more appropriate immediate targets than malaria and other infectious diseases. Prevalence and intensity of infection in school-age children, the schools as vehicles of intervention, and the availability of interventions contributed to this choice. However, there are still many gaps in our knowledge of the effects of infectious diseases in schoolchildren. Through the improvement of understanding in this area, the parasitology community may be able to contribute to the Unesco project.     

Schools for health: Focus on health, education and the school-age child

Mortality in children under five years old has been dramatically reduced through successful programmes of immunization and control of diarrhoeal diseases. UNICEF estimates that some 90% of children in developing regions now survive to reach school age. These survivors face new and continuing threats to their health, which can affect their physical development and may also prevent them taking full advantage of their only opportunity for formal education. The physical and mental growth of the 1000 million school-age children today will influence how the world is shaped for coming generations. Yet the health problems of this age group have received little attention. Recognizing the importance of this age group, a workshop funded by the Edna McConnell Clark Foundation was held 10-13 November 1994 in Fort Mitchell, Kentucky, USA, to review what is known about the health of school-age children, what is or can be done to improve their health, and what steps must be taken to find ways to improve the health and educational achievement of this important segment of the world's population. Don Bundy and Helen Guyatt here report on the workshop, which had three major conclusions: (1) the school-age children of developing countries face health problems that remain neglected and poorly understood; (2) an important research need is to develop simpler means of monitoring the health status of school-age children and evaluating the impact of public health interventions in this age group; and (3) two strategies are available to address this public health problem. The first is to develop further and test programmes that appear, from available evidence and pilot studies, to offer effective means of improving the health of this age group at reasonable cost, and to be sustainable; and the second is, over a longer term, to develop the capacity within countries to assess the health problems of school-age children and devise cost-effective strategies to address these problems. This report attempts, in brief form, to survey what is known about the health status of school-age children, to discuss the possible benefits to health and learning that accrue from health interventions, and to suggest some avenues currently available for both research and application.     

Localization of sequences regulating ancestral and acquired sites of esterase6 activity in Drosophila melanogaster

We have broadly defined the DNA regions regulating esterase6 activity in several life stages and tissue types of D. melanogaster using P- element-mediated transformation of constructs that contain the esterase6 coding region and deletions or substitutions in 5' or 3' flanking DNA. Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and the primary sequences regulating its activity lie between -171 and -25 bp relative to the translation initiation site: deletion of these sequences decrease activity approximately 20-fold. Hemolymph activity is also modulated by four other DNA regions, three of which lie 5' and one of which lies 3' of the coding region. Of these, two have positive and two have negative effects, each of approximately twofold. Esterase6 activity is present also in two male reproductive tract tissues; the ejaculatory bulb, which is another ancestral activity site, and the ejaculatory duct, which is a recently acquired site within the melanogaster species subgroup. Activities in these tissues are at least in part independently regulated: activity in the ejaculatory bulb is conferred by sequences between -273 and -172 bp (threefold decrease when deleted), while activity in the ejaculatory duct is conferred by more distal sequences between -844 and -614 bp (fourfold decrease when deleted). The reproductive tract activity is further modulated by two additional DNA regions, one in 5' DNA (-613 to -284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to +2731 bp; threefold decrease when deleted) that probably overlaps the adjacent esteraseP gene. Collating these data with previous studies suggests that expression of EST6 in the ancestral sites is mainly regulated by conserved proximal sequences while more variable distal sequences regulate expression in the acquired ejaculatory duct site.      

Microjet impingement followed by scanning electron microscopy as a qualitative technique to compare cellular adhesion to various biomaterials

Adhesion of cells to biomaterial surfaces is one of the major factors which mediates their biocompatibility. Quantitative or qualitative cell adhesion measurements would be useful for screening new implant materials. Microjet impingement has been evaluated by scanning electron microscopy, to determine to what extent it measures cell adhesion. The shear forces of the impingement, on the materials tested here, are seen to be greater than the cohesive strength of the cells in the impinged area, causing their rupture. The cell bodies are removed during impingement, leaving the sites of adhesion and other cellular material behind. Thus the method is shown not to provide quantification of cell adhesion forces for the metals and culture plastic tested. It is suggested that with highly adherent biomaterials, the distribution and patterns of these adhesion sites could be used for qualitative comparisons for screening of implant surfaces.     

Rates of ingestion and their variability between individual calanoid copepods: direct observations

The goals of this study were to determine rates of ingestionand fecal pellet release, and their variability, for individualplanktonic copepods over extended periods of time (>20 min).Ingestions and rejections of individual cells of the diatomThalassiosira eccentrica by adult females of the calanoid Paracalanusaculeatus were directly quantified by observing individual copepodscontinuously at cell concentrations ranging from 0.1 toli mm³l^–1.Average ingestion rates increased with increasing food concentration,but were not significantly different between 0.3 and 1.0 mm³l^–1(9.8 and 32.7 µg Cl^–1) of T.eccentrica. Rates ofcell rejections were low and similar at 0.1 and 0.3, but weresignificantly higher at 1.0 mm³ l^–1. The coefficientsof variation for average ingestion rates of individual copepodshardly differed between food concentrations, ranging from 17to 22%, and were close to those for average fecal pellet releaseintervals which ranged from 15 to 21%. A comparison betweenindividuals at each food concentration found no significantdifferences at 1.0; at 0.1 and 0.3 mm³l^–1, respectively,ingestion rates of four out of five females did not differ significantlyfrom each other. Average intervals between fecal pellet releaseswere similar at 0.3 and 1.0 mm³l^–1 of T.eccentrica, butsignificantly longer at 0.1 mm³ l^–1. Fecal pellet releaseintervals between individuals were significantly different ateach food concentration; these significant differences wereattributed to rather narrow ranges of pellet release intervalsof each individual female. Potential sources/causes of variabilityin the sizes and rates of copepods in the ocean are evaluated. ³Present address: Great Lakes Environmental Research Laboratory,2205 Commonwealth Boulevard, Ann Arbor, Ml 48105, USA     

Nucleotide variation at the hypervariable esterase 6 isozyme locus of Drosophila simulans

Esterase 6 (Est-6/EST6) is polymorphic in both Drosophila melanogaster and D. simulans for two common allozyme forms, as well as for several other less common variants. Parallel latitudinal clines in the frequencies of the common EST6-F and EST6-S allozymes in these species have previously been interpreted in terms of a shared amino acid polymorphism that distinguishes the two variants and is subject to selection. Here we compare the sequences of four D. simulans Est-6 isolates and show that overall estimates of nucleotide heterozygosity in both coding and 5' flanking regions are more than threefold higher than those obtained previously for this gene in D. melanogaster. Nevertheless, the ratio of replacement to exon silent-site polymorphism in D. simulans is less than the ratio of replacement to silent divergence between D. simulans and D. melanogaster, which could be the result of increased efficiency of selection against replacement polymorphisms in D. simulans or to divergent selection between the two species. We also find that the amino acid polymorphisms separating EST6- F and EST6-S in D. simulans are not the same as those that separate these allozymes in D. melanogaster, implying that the shared clines do not reflect shared molecular targets for selection. All comparisons within and between the two species reveal a remarkable paucity of variation in a stretch of nearly 400 bp immediately 5' of the gene, indicative of strong selective constraint to retain essential aspects of Est-6 promoter function.      

Distribution of alloantigens on human Fc receptor-bearing lymphocytes: the presence of B cell alloantigens on sIg-positive but not sIg-negative lymphocytes.

Human peripheral blood lymphocyte subpopulations were analyzed for the presence of B cell alloantigens with a microcytotoxicity assay. B cell alloantigens were found exclusively on sIg-positive lymphocytes and were not present on sIg-negative, Fc receptor-bearing lymphocytes or sIg-negative, Fc receptor-negative T lymphocytes.     

Carbonic anhydrase.

1. The G + C content of ribosomal RNA of animals seems correlated with the length of periods required for maturation of those organisms. 2. In Protostomes of the animal kingdom, the size of the 28S rRNA molecule does not seem to correlate with the evolutionary stage of the organism. 3. Aphids and water-fleas as well as some protozoa have the 18S rRNA with mol. wt of 0.9 x 10(6) against an overwhelming pressure of evolution to conserve the rRNA molecule of 0.7 x 10(6) daltons. 4. All the Deuterostomes examined were distinguished from Protostomes by having the 28S rRNA's void of the hidden break at the central point. 5. Aphids and nematodes are exceptional Protostomes in that they have the 28S rRNA's without the hidden break. This was discussed in the light of the evolutionary stage of these organisms. 6. Molecular properties of chloroplast rRNA seem to evidence for endosymbiotic origin of this organelle. Mitochondrial rRNA differs considerably from prokaryotic rRNA with respect to molecular size and base composition.     

Experimental investigations on the behaviour of the cercariae of an ectoparasitic digenean Transversotrema patialense: general activity patterns

The activity patterns of the cercariae of Transversotrema patialense have been examined by monitoring the behaviour of individual larvae. Records of three different behavioural modes, namely active, tail-first swimming, passive dropping and resting periods were made separately. The age- and temperature-dependence of the activity patterns during the spontaneously active life of the cercariae were examined and estimates made of the absolute speeds of swimming and dropping. Through the temperature range 25--32 degrees C, the spontaneously active life of cercariae declined from about 18 h to about 6 h. Within this interval, after an initial period of high activity rates, a gradual decline in activity followed. The decline was a result of a decreasing frequency of swimming events rather than any change in the durations of such events. The neural control and energetic significance of the cercarial activity patterns are discussed.