Biomedical subjects

W Dias-da-Silva

Publications and source records attributed to W Dias-da-Silva.

6 recordsLinked to original sources

PubMed1995

Antigenic cross-reactivity among components of Brazilian Elapidae snake venoms.

Snake venoms from M. corallinus (LD50 = 7.1 +/- 0.83 micrograms), M. frontalis (LD50 = 19.3 +/- 3.13 micrograms), M. ibiboboca (LD50 = 19.8 +/- 2.07 micrograms) and M. spiixi (LD50 = 6.7 +/- 1.25 micrograms) (family Elapidae, genus Micrurus) injected into horses alone or in combination (M. corallinus with M. frontalis) elicit antibody production, as indicated in vivo by neutralization of venom lethality and in vitro by enzyme-linked immunosorbent assay (ELISA), immunoelectrophoresis (IE) and Western blotting (WB). Venom lethality was efficiently neutralized by the antisera, with the monovalent antivenoms being more efficient than the bivalent antivenom. Antibodies against venom components were detected by all antisera at different titers by ELISA. Upon IE, antisera against M. spiixi and M. frontalis venoms cross-reacted with the four types of venoms studied and recognized several molecular components, the precipitin lines obtained had distinct intensities and electrophoretic motilities, whereas the antivenom against M. corallinus only recognized components of its venom but not of the others. All antivenoms cross-reacted with all the elapid venoms in WB revealing several bands with distinct MWs in M. corallinus and M. spiixi venoms, two very sharp and separate bands in M. corallinus venom and a very sharp band of high MW together with several other smaller and faint bands in M. frontalis venom. The data indicate that snake venoms of the genus Micrurus are good immunogens that contain many cross-reactive molecules, and that their toxic components are neutralized more effectively by monovalent rather than by bivalent antivenom.

Animals↗

PubMed1992

The complement system of Calomys callosus, Rengger, 1830 (Rodentia, Cricetidae).

The complement system (C) of Calomys callosus, Rengger, 1830 (Rodentia, Cricetidae), a wild reservoir for several infectious agents in Latin America, was characterized. Sera from normal adult animals lysed sheep erythrocytes (Es) previously sensitized with rabbit serum anti-Es (Ar) in the presence of veronal-buffered saline containing 0.15 mM CaCl2 and 0.5 mM MgCl2, pH 7.4, or unsensitized rabbit erythrocytes (Er) in the presence of one-half isotonic strength veronal-buffered-saline containing 2.5% glucose, 2 mM MgCl2 and 10 mM EGTA, pH 7.4. Both hemolytic curves were sigmoidal in shape, with CH50 values of 30-40 for females and 20-30 for males. C5, determined hemolytically using the intermediate cells EsArClm4m2m3m, was approximately 4.5 x 10(8)/ml and 4.0 x 10(8)/ml for females and males, respectively. Immunochemical serum analyses by double immunodiffusion or by immunoblotting using polyclonal antisera against human C1s, C1q, C2, C3, C4, C5, C8 and factors B, I and H indicated that C. callosus C components factor B, C4 and C3 cross-reacted with the corresponding human C components. Thus, C. callosus was found to contain effective classical and alternative pathways (CP, AP) and common pathways, reasonable amounts of C5 and common epitopes in the key C components, factor B, C4 and C3, which were preserved during evolution.

Animals↗

PubMed1989

Immunization of equines with phospholipase A2 protects against the lethal effects of Crotalus durissus terrificus venom.

Equines (2 horses and 2 donkeys) immunized with whole Crotalus durissus terrificus venom or its phospholipase A2 component either presented an increased survival time determined 3 days after challenge or were totally resistant to a challenging lethal dose of 200 mg crude venom 270 days after the initial immunization or 90 days after the last booster injection. The resistance was demonstrable on the basis of a good correlation with antibody titers determined by the ELISA method but not with the flocculation and neutralization assays. Since phospholipase A2 is essentially nontoxic, it can be used as a substitute for whole venom for the production of commercial antisera and as an immunizing agent in prophylactic programs.

Animals↗

PubMed1988

Inherited C3 deficiency of the complement system.

1. We report a patient homozygous for C3 deficiency and several heterozygotes from the same family. Upon follow-up, the homozygote was found to suffer several severe bacterial infections, whereas all the heterozygotes were clinically healthy. 2. C3 was undetectable in the homozygous patient, CH50 was very low and factor I was present. Serum capacity to generate chemoattractant stimuli for peripheral leucocytes was similar to that of normal adults as was also observed for one of the heterozygotes. Serum capacity to opsonize yeast was reduced in the presence of autologous and homologous (normal adult) cells. The CH50 levels of heterozygous patients were within the lower range of normality. 3. The parental consanguinity and the homozygosis state observed here are classical signs of recessive autosomal inheritance. However, the lower or below normal C3 levels detected in parents and relatives point to a co-dominant inheritance of gene S with respect to the "null" gene. 4. C3 polymorphism presented a predominantly "slow" pattern in most family members, which, together with the low C3 levels, indicates the expression of S-allotypes.

Antibodies, Anti-Idiotypic↗

PubMed1986

Effect of Trypanosoma cruzi membrane components on the formation of the classical pathway C3 convertase.

When T. cruzi trypomastigote forms are held at 45 degrees C for 10 min in saline they become susceptible to lysis by the alternative complement pathway. As the result of heating trypomastigotes, but not epimastigotes, substances are released into the fluid phase which inhibit EAC1,4,2,3 by inducing decay. The inhibition was most pronounced at the level of the decay of the C14b2a complex. C3 convertase of the classical pathway was also inhibited by live trypomastigote forms. These data suggest that the trypomastigote but not epimastigote forms of T. cruzi have cell surface modulators of C3 convertase that permit them to evade the lytic action of complement.

Animals↗

PubMed1984

Recovery of schistosomula of Schistosoma mansoni from mouse skin: involvement of mast cells and vasoactive amines.

Normal and S. mansoni-infected mice were exposed to the penetration of 250-350 cercariae through one ear. Two days later, when the ear was removed and chopped, 30 to 50% more schistosomula were recovered from the ears of normal mice than from the ears of infected (immune) mice. Administration of cyproheptadine, a histamine-serotonin antagonist (2 mg/kg), 30 min before challenge infection rendered immune mice indistinguishable from normal mice. Partial depletion of histamine by pretreatment with compound 48-80, a histamine releaser (1 mg/kg) 2 days before challenge infection increased the numbers of schistosomula recovered from the ears of both normal and immune mice. These results are interpreted to mean that vasoactive amines released by skin mast cells play an important role in hindering the viable passage of schistosomula through the skin of normal and immune mice.

Animals↗