Schistosoma mansoni and Biomphalaria: past history and future trends.

Schistosoma mansoni is one of the most abundant infectious agents of humankind. Its widespread distribution is permitted by the broad geographic range of susceptible species of the freshwater snail genus Biomphalaria that serve as obligatory hosts for its larval stages. Molecular phylogenetic studies suggest that Schistosoma originated in Asia, and that a pulmonate-transmitted progenitor colonized Africa and gave rise to both terminal-spined and lateral-spined egg species groups, the latter containing S. mansoni. Schistosoma mansoni likely appeared only after the trans-Atlantic dispersal of Biomphalaria from the Neotropics to Africa, an event that, based on the present African fossil record, occurred only 2-5 million years ago. This parasite became abundant in tropical Africa and then entered the New World with the slave trade. It prospered in the Neotropics because a remarkably susceptible and productive host, B. glabrata, was widely distributed there. Indeed, a snail similar to B. glabrata may have given rise to the African species of Biomphalaria. Schistosoma mansoni has since spread into other Neotropical Biomphalaria species and mammalian hosts. The distribution of S. mansoni is in a state of flux. In Egypt, S. mansoni has nearly completely replaced S. haematobium in the Nile Delta, and has spread to other regions of the country. A susceptible host snail, B. straminea, has been introduced into Asia and there is evidence of S. mansoni transmission in Nepal. Dam and barrage construction has lead to an epidemic of S. mansoni in Senegal, and the parasite continues its spread in Brazil. Because of competition with introduced aquatic species and environmental changes, B. glabrata and consequently S. mansoni have become less abundant on the Caribbean islands. Control of S. mansoni using praziquantel and oxamniquine has reduced global prevalence but control is difficult to sustain, and S. mansoni can develop tolerance/resistance to praziquantel, raising concerns about its future efficacy. Because of legitimate environmental concerns, snail control is unlikely to be an option in future control efforts. Global warming will impact the distribution of Biomphalaria and S. mansoni, but the magnitude and nature of the effects are poorly understood.

D-aspartate disposition in neuronal and endocrine tissues: ontogeny, biosynthesis and release.

High levels of D-aspartate occur in the brain and endocrine glands, such as pineal, adrenal and pituitary. In the brain, D-aspartate levels are highest in embryonic and early postnatal stages. Notably high levels occur in the early postnatal cortical plate and subventricular zone of the cerebral cortical cultures, implying a role in development. In embryonic neuronal primary culture cells, we detected high levels of endogenous D-aspartate and demonstrated biosynthesis of [14C]D-aspartate using [14C]L-aspartate as precursor. Synthesis of D-aspartate in cell cultures is inhibited by amino-oxyacetic acid, an inhibitor of pyridoxal phosphate-dependent enzymes. In the rat adrenal medulla, D-aspartate is depleted by treatment of the animals with intraperitoneal nicotine injections. In adrenal slices, D-aspartate is released by depolarization with KCl or acetylcholine, implying physiological release by activation of the cholinergic innervation of the adrenal. Our characterization of D-aspartate ontogeny, biosynthesis and depolarization-induced release implies specific physiological roles for this amino acid.

Challenges and barriers to managing quality in an end-stage renal disease facility.

The End-Stage Renal Disease Program is underfunded and overregulated. Objective parameters of end points of care do not correlate to specific clinical practice patterns. We do not have consensus between payers, providers, and patients as to what the objectives of the End-Stage Renal Disease Program are or should be. This report will address the need for an integrated health care delivery system that would benefit the end-stage renal disease patient and the barriers to designing such a system. The quality improvement program of a five-unit dialysis system will be described. The deficiencies of the quality improvement program and the limitation of the facilities to improve outcome will be discussed, and constructive alternatives to achieve an integrated health care delivery system that promotes improvement in patient outcomes will be suggested.

Coexistence of pulmonary adenomatosis and progressive pneumonia in sheep in the central sierra of Peru.

A survey of sheep with chronic respiratory tract disease was conducted in the central sierra of Peru. Histopathologic examinations coupled with an agar-gel immunodiffusion test for ovine progressive pneumonia (OPP) revealed that sheep pulmonary adenomatosis and OPP were present in these flocks. Of 80 sheep examined, 22 had lesions of sheep pulmonary adenomatosis, and 4 had metastases to regional lymph nodes. Four sheep had lesions consistent with OPP and 9 had lesions indicating the coexistence of both diseases. The agar-gel immunodiffusion test revealed that at least 26% of the sheep had been exposed to the OPP (or an antigenically similar) virus. A variety of other respiratory tract diseases complicated the evaluations of these sheep, including verminous pneumonia, hydatid disease, lung abscesses, and other nonspecific acute and chronic pneumonias.