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Biomedical subjects

M Vargas

Publications and source records attributed to M Vargas.

121 records · Page 7Linked to original sources
PubMedDate not supplied

Displacement of Biomphalaria glabrata by Thiara granifera under natural conditions in the Dominican Republic.

After a study of the population dynamics of Biomphalaria glabrata snails in several breeding places in the Dominican Republic, the snail Thiara granifera was introduced in some B. glabrata habitats. T. granifera became established in one point in one habitat in the town of Quisqueya, in the east of the country. Around this point of establishment 6 points were selected in order to observe the population dynamics of both species of snails and the chemical and biological characteristics at each point. Four of these points already harbored B. glabrata. One control point was selected also harboring B. glabrata. After 14 months of observations, the results showed that T. granifera was competing with and displacing B. glabrata. This competition does not seem to be competition for food or vital space. Rather, B. glabrata avoids the presence of T. granifera and moves away to new areas, and this is possibly due to a chemical substance(s) secreted by T. granifera or by physical contact with the large number of individuals of T. granifera.

Adaptation, Physiological↗
PubMedDate not supplied

Evaluation of the rabbit as a model for Chagas disease-II. Histopathologic studies of the heart, digestive tract and skeletal muscle.

In order to investigate the value of the rabbit as an experimental model for Chagas' disease, seventy one animals were inoculated with different Trypanosoma cruzi strains and routes. The rabbits were submitted to necropsy in acute (earlier than three months of infection), recent chronic (three to six months) and late chronic (later than six months) phases. Myocarditis, generally focal and endomysial, occurred in 94.1%, 66.7% and 70.8% of the infected rabbits respectively in the acute, recent chronic and late chronic phases. The myocardial inflammatory exudate was composed by mononuclear cells, and also polymorphonuclear cells in the acute phase. In most cases of the late chronic phase, the myocarditis was similar to that described in the indeterminate form of human chagasic patients. Initial fibrosis occurred in the three phases but was more severe and frequent in the early chronic. Advanced fibrosis occurred only in the late chronic phase. Tissue parasites occurred only in the acute phase. The digestive tract and skeletal muscles showed mild and occasional lesions. Our data indicate that experimentally infected chagasic rabbits repeat some lesions similar to that of humans chagasic patients, specially that of the indeterminate form. So, it may be a useful, however not an ideal, model.

Animals↗
PubMedDate not supplied

[Fulminant Wilson's disease in Costa Rica. Clinico-pathological study of 7 cases].

In the last eighteen years, from 1972 to 1989, around 150 cases of Wilson's disease have been diagnosed in Costa Rica (6/100.000 inhabitants). In the San Juan de Dios Hospital, 120 cases have been studied during this period, seven of whom died with a picture of acute hepatic insufficiency, hemolytic anemia, encephalopathy, intestinal bleeding and renal insufficiency. In four of the cases, postmortem histopathologic studies were done with high resolution microscopy, which revealed extensive submassive necrosis of the liver, with severe cholestatic, lytic and acidophilic necrosis with nodular, irregular regeneration and specially microvacuolar steatosis, different from that observed in other forms of fulminant hepatitis. With the clinical, laboratory and histopathologic findings, we concluded that fulminant Wilson's disease is a well-defined pathological clinical entity of fatal evolution with no response to therapy, including early treatment with penicillamine and steroids.

Acute Disease↗
PubMedDate not supplied

[Preliminary study of the molluscacide properties of guayacil: a raw extract of Guayacum officinale].

This paper reports the results of a preliminary study of the mollusk-killing properties of guayacil, a raw extract of the plant Guayacum officinalis, on Biomphalaria glabrata. Mollusks are exposed to several concentrations of the substance for periods ranging from 1, 6, and 24 hours and then were allowed to recover, according to the recommendations of the World Health Organization. The results indicate that guayacil has molusk-killing properties with an LC50 of 0.45 ppm and an LC90 of 0.95 ppm at 24 degrees C. Larger concentrations of 1 ppm resulted in 100% death rate, while 0.1 ppm did not prove lethal. All parts of the plant contain the active ingredient. Concentrations lower than 1 ppm are not lethal for flora or fauna.

Animals↗
PubMedDate not supplied

Effect of age and helminthic infection on IgE levels in slum children.

Helminthic infections can cause an IL-4-dependent polyclonal synthesis of IgE, which is the major cause of the elevated serum levels of this immunoglobulin in tropical populations. In the present study, we measured the IgE levels in the serum of children of different ages in slum areas of Caracas, Venezuela, where intestinal helminths are endemic. As would be expected, in children over 5 years of age, the IgE levels were highly elevated, and in addition, the cord blood serum levels were higher than those reported for populations where parasitic infections are uncommon. However, the IgE levels measured in the sera of children under 5 years of age were relatively low, and within the generally accepted normal ranges. This was surprising because the latter children were infected by parasites and had high IgG antibody levels against helminths. We found, however, that whereas older children had detectable IL-4 levels in their sera, the younger children did not. These results suggest that, despite infection of these slum children by common intestinal helminths, a polyclonal stimulation of IgE synthesis did not occur, possibly due to a lack of IL-4 production by an immature immune system.

Adolescent↗
PubMedDate not supplied

Considerations for the aesthetic restoration of endodontically treated anterior teeth following intracoronal bleaching.

The major considerations in restoring the pulp chamber following bleaching of endodontically treated anterior teeth include aesthetics, function, appropriate endodontic access preparation, amount of remaining tooth structure, type of restorative material, prevention of microleakage, and prevention of iatrogenic perforation. The learning objective of this article is to review the considerations that must be made when placing aesthetic restorations in the pulp chamber and access opening of endodontically treated teeth following intracoronal bleaching. The advantages and disadvantages of the proposed techniques and materials are discussed, as are the methods for avoiding excessive removal of the tooth structure. Two case reports are used to demonstrate the clinical procedures. The authors suggest placing white gutta-percha stopping material in the pulp chamber and a composite restoration in the access opening following root canal treatment and/or bleaching procedures in the anterior dentition.

Adolescent↗