Biomedical subjects
Publications and source records attributed to M Segovia.
A 16 year old man developed progressive swelling at the left hypochondrium over a 3 month period. Non painful splenomegaly was shown by physical examination and confirmed by ultrasonography and scintigraphy. Successful splenectomy disclosed a primary splenic cyst. The patient recovered uneventfully.
Desferrioxamine was tested in vitro for activity against promastigotes of Leishmania donovani. In addition, the effects of liposome-encapsulated desferrioxamine and free desferrioxamine on macrophages infected with amastigotes of L. donovani were compared. The drug was added to the culture medium for three days, and the results were compared with several controls; the drug solvent, empty liposomes, and desferrioxamine which had been re-ferrated with an equimolar concentration of ferric ammonium sulphate. Desferrioxamine was found to be inactive against growing promastigotes at the highest concentration used, 50 micrograms ml-1. On the other hand, 44% and 60% of amastigotes were eliminated when macrophages infected with L. donovani were exposed to 50 micrograms ml-1 of free or liposome-encapsulated desferrioxamine respectively.
In mice, infection with Leishmania by the subcutaneous route becomes evident after about 2 months. This delay impedes the selection of monoclonal antibodies able to interfere with the infectiousness of the parasite. Using an in vivo culture system--intraperitoneal injection of TG 180 sarcoma cells along with promastigotes or amastigotes--it was possible to define within 15 to 20 days a monoclonal antibody preventing the development of Leishmania. Pretreatment of promastigotes and amastigotes of several Leishmania species with a monoclonal antibody raised against Leishmania infantum prevented infection equally in either system. These cross-reactions may be of importance in designing new approaches of immunotherapy.
The virulence of two isolates of Leishmania donovani (LMU-6 isolated from a human case in Ethiopia and LMU-16 isolated from an asymptomatic dog in the south-east of Spain) in BALB/c and C57Bl/6 mice and in hamsters was observed over a period of 14 weeks. Regular measurements of the liver parasite burdens and observations of external signs of infection were made, and the humoral and delayed type hypersensitivity responses were tested. No major differences were observed in the infection patterns produced by the two isolates in mice, except for a slightly stronger humoral and lower delayed type hypersensitivity response detected in C57Bl/6 mice infected with LMU-16. However, LMU-16 showed a higher virulence in hamsters than did LMU-6.
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Putting aside the very substantial gains made in recent years by health services of the Commonwealth Caribbean, this article reviews the administrative problems faced by those services at the present time. For the most part, these problems appear to have two main sources: weakness of the colonial heritage, and greatly increased popular demands following the attainment of associated or independent status. In general terms, there are a great many current needs. In many cases, for example, it would help to give more attention to identification and delineation of specific health problems, to make more extensive use of planning, to update existing legislation, to establish a better information system, to revise the budget classification system and loosen budgetary controls, to improve supply management, to more thoroughly define areas of official responsibility, to reassert individual responsibility for decision-making, and to streamline administrative channels. All in all, the problems faced by the health services make it imperative to reexamine the possibilities for implementing administrative reforms. It is felt, however, that besides being addressed to current problems, such reforms should be designed to help the health service cope with any new situations that may arise - before such situations can threaten its vital contribution to social and economic well-being.
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INTRODUCTION: One of the different molecules involved in the development of astrocytomas is nitric oxide (NO), a gaseous radical that, depending on the cell type and the experimental paradigm selected in the pathology, can play either a cytotoxic or a cytoprotective role. DEVELOPMENT: During the development of an astrocytoma NO acts as a tumouricidal agent, although it can also alter vascular reactivity and lead to neovascularisation, thereby contributing to the invasive capacity (aggressiveness) of the tumour. One of the mechanisms of tumoural progression consists in the protein inactivation resulting from the NO nitration of tyrosine from proteins coded for by tumour-suppressing genes, such as p53. Furthermore, in malignant astrocytes, nitrosoglutathione, a natural NO-donor, has been seen to play a role in the chemoresistance displayed against nitrosourea derivatives. The NO excreted by irradiated astrocytoma cells also appears to be involved in the resistance to the radiotherapy shown by non-irradiated cells. CONCLUSIONS: The molecular mechanisms behind the complex and paradoxical activity of NO in glioblastoma multiforme have still not been fully explained and its implications in vivo are even further from being completely understood.
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Leishmaniasis is on the increase in Venezuela (ca 30,000 new cases per year) due to deterioration in health management, increased risk groups among inmunosuppressed individuals and increased human penetration into the ecological habitats of sandfly vectors. An STD2-funded project (1989-1992) focused on the Andean state of Táchira, which showed the highest annual index of new cases (ca 200-250). The project aimed at contributing to vector/parasite identification through a combination of molecular and well established field techniques: Newly developed molecular methods distinguished among Lu. spinicrassa, Lu. youngi and Lu. townsendi. These three species of the Verrucarum group are sympatric in the Northeast of the state and could be successfully identified by CHA, DNA probes and RAPD. A Le. braziliensis specific KDNA probe used with squash blots indicated that Lu. spinicrassa is the main vector and that Le. braziliensis is the main parasite species in Táchira state, Venezuela. PCR and the Le. brasiliensis specific DNA probe, schizodemes, isoenzymes and polyclonal antibodies agreed as taxonomic criteria for classification of Leishmania isolated from parasitologically confirmed cases in Tachira. Considerable degree of antigen heterogeneity in Venezuelan Le. braziliensis complex and Le. mexicana complex isolates from Tachira suggests multiple candidate antigens for improving the specificity of immunological diagnosis. The methods developed and tested in Táchira state should be valuable in order to help solving other outstanding epidemiological problems such as following of the epidemiological impact of intervention and vector control measures in highly endemic areas. Future work (STD3 funded, 1993-1996) aims to apply these molecular techniques to a vector control pilot study in Lara state, an area showing the highest incidence of new cases in the country.