Biomedical subjects
Publications and source records attributed to M Siqueira.
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Selective breeding has been performed in mice for their high or low antibody responsiveness to Salmonella antigens (Ag). Two noncross-reacting Salmonellae (S. typhimurium and S. oranienburg) have been alternately used to immunize successive generations in order to avoid interference of maternally transmitted antibody. Both Salmonellae carry two independent antigens: flagellar (f) and somatic (s). Two two-way selections were carried out: one for agglutinin response to fAg and the other for agglutinin response to sAg (Selection Ags). The agglutinin response to the other independent Ag was also measured (Associated Ags). The phenotypic character chosen for selection is the maximal agglutinin titer in response to optimal immunization. In both selections, high and low responder lines diverged progressively. There was a 27-fold interline difference in the F13 generation of selection for fAg response and a 38-fold one in the F11 generation of selection for sAg response. This divergence and the continuous distribution of phenotypes in the foundation population indicate that the quantitative character investigated is subject to polygenic regulation. The realized heritability (h2) of the character, measured from the interline divergence, was 0.18 +/- 0.06 in both f and s selections. This means that about 20% of the phenotypic variance of the foundation population is additive. The modification of immune responsiveness to the selection Ag produced by selective breeding was accompanied by a parallel and equivalent effect on immune responsiveness to the noncross-reacting Associated Ag. This effect is therefore entirely nonspecific. A small but definite sex effect in favor of female antibody responsiveness was demonstrated. The results are discussed in comparison with other selection experiments made in mice for quantitative antibody response to other antigens.
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Selection III mice have particular immunological characteristics: they are high (H III) or low (L III) antibody producer animals, yet both lines display similar T cell responses and macrophage activities. We submitted these mice to infection with Schistosoma mansoni to assess in vivo parasite and egg burden, hepatic collagen and cellular composition of granulomas in both lines. Titration of anti-Schistosoma IgG by ELISA showed remarkably higher values in H III line, at both studied periods (8th and 12th weeks post-infection). Nevertheless, the number of adult worms recovered from the portal system was similar in both lines, being not associated with anti-Schistosoma antibody levels. There is an increase in hepatic collagen from the 8th to the 12th weeks post-infection, which is paralleled by an increase in the number of eggs in the liver. This association apparently occurs at the same ratio in H III and L III animals. The most important difference found between the two lines was the outstanding contrast in terms of volume and eosinophil counts in the granulomas, with lesions from H III mice clearly being larger and containing more of these cells than LIII lesions.
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PURPOSE: To study the incidence of cerebellar arteries originating directly from the internal carotid artery, and to discuss the probable embryological origin and clinical implications of this anatomical anomaly. METHODS: We reviewed 5500 angiographic studies done at our institution in the last 4 years, searching for these anomalous vessels as well as for other anatomical variants. RESULTS: Eleven cerebellar arteries originating directly from the internal carotid artery and nine embryonic cerebral arteries were found. CONCLUSION: These arteries are considered persistent trigeminal artery variants and seem to occur as the result of the persistence of a primitive trigeminal artery associated with an incomplete fusion of the longitudinal neural arteries. These anomalous vessels are clinically significant particularly because of their role in endovascular therapeutic and surgical complications and the paradoxical lesions in the cerebellum that occur as a result of carotid disease.
Four two-way genetic selections of outbred mice for the quantitative character "agglutinin production" to heterologous erythrocytes and flagellar or somatic antigens of Salmonella are briefly described. The principal genetic parameters regulating the quantitative antibody response are the following: 1) the character is polygenic; the number of independent loci is estimated between 7 and 16; 2) the heritability of the character (h2) is comprised between 0.17 and 0.21; 3) the maximal interline separation RT (4.8-7.8 log2) is reached after about 15 consecutive generations of selective breeding; (4) the rate of interline separation/generation RG is 0.32-0.48 log2. 5) The phenotypic variance V(P) of the foundation populations is due for 52%-63% to genetic factors V(G) and for 37%-48% to environmental factors V(E); 6) The effect of the selective breeding is essentially non-specific; it modifies the antibody responsiveness to many unrelated complex immunogens.