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Biomedical subjects

G Rojas

Publications and source records attributed to G Rojas.

At least 73 records · Page 4Linked to original sources
PubMed1991

Quantitation by enzyme-immunoassay of antibodies against Bothrops myotoxins in four commercially-available antivenoms.

An enzyme-immunoassay (EIA) for the quantitation of antibodies against myotoxins present in the venoms of Bothrops asper (Costa Rica), B. atrox (Colombia) and B. moojeni (Brazil), was developed. This EIA was utilized for the evaluation of four antivenoms produced in Mexico (Laboratorios Myn; MYN), Costa Rica (Instituto Clodomiro Picado; ICP), Colombia (Instituto Nacional de Salud; INS) and Brazil (Instituto Butantan; IB). Antivenoms ICP, IB and INS showed a higher titer of antibodies against the three myotoxins tested, with only slight differences between them, depending on the antigen utilized. In contrast, MYN antivenom had very low levels of antibodies to the three myotoxins. Seventeen batches of ICP antivenom were analyzed by EIA, using B. asper myotoxin II as antigen. Although all batches had high anti-myotoxin titers, these varied significantly. Batches produced after 1988 had, in general, higher titers than older (1986-1987) ones. Antivenom stored for one year at 37 degrees C had a slight, but significant (P less than 0.002) decrease of anti-myotoxin activity, compared to antivenom stored at 4 degrees C or 23 degrees C. No correlation was found between anti-myotoxin concentration and lethality-neutralizing ability of the ICP antivenom.

Animals↗
PubMed1991

Biochemical and pharmacological similarities between the venoms of newborn Crotalus durissus durissus and adult Crotalus durissus terrificus rattlesnakes.

A comparative study was performed with the venoms of newborn Crotalus durissus durissus, adult Crotalus durissus terrificus and adult Crotalus durissus durissus snakes. Venom of newborn specimens of C.d. durissus is very similar to that of adult specimens of C.d. terrificus, since they have strong lethal and myotoxic activities, and weak proteolytic, hemorrhagic and edema-forming effects, in contrast to venom of adult specimens of C.d. durissus. In addition, the two former venoms have high amounts of the neurotoxic complex crotoxin, whereas venom from adult C.d. durissus has a low concentration of crotoxin. Electrophoretic analysis corroborates the strong similarities between the former two venoms. It is concluded that venom of newborn C.d. durissus contains high concentrations of crotoxin and low amounts of hemorrhagic and proteolytic components, and that a drastic ontogenetic change takes place in the venom composition of this subspecies.

Animals↗
PubMed1991

Idiopathic membranous nephropathy, associated with HLA-DRw3 and not related to monocyte-phagocyte system Fc receptor dysfunction, in father and son.

Familial idiopathic membranous nephropathy, an immune-complex-associated glomerulopathy, has not been previously reported in father and son, despite its striking immunogenetic correlation, especially with HLA-DR3. As a dysfunction of the monocyte-phagocyte system (MPS), it has been observed linked to DR3 antigen, so we studied the MPS Fc receptor function in a father and his son with a histologically proven membranous nephropathy, associated with the haplotype A9-B35-DR3-DQw2. The Fc receptor function of the MPS was examined by measuring the clearance of IgG-sensitized, 51Cr-labeled erythrocytes and by measuring the ability of isolated monocytes to ingest autologous red blood cells coated with IgG anti-Rh (D) antibody. Immune clearance and in vitro phagocytosis was normal in both patients and not related to their levels of immune complexes (as measured by ELISA C1q and Conglutinin solid-phase binding assay). This report suggest that genetic factors may play an important role in the development of membranous nephropathy, and it seems not to be related to a dysfunction of MPS as measured by these tests.

Adolescent↗
PubMed1991

Neutralization of coral snake Micrurus nigrocinctus venom by a monovalent antivenom.

1. The neutralizing ability of a monovalent anti-Micrurus nigrocinctus (coral snake) antivenom produced in Costa Rica was tested against the lethal, myotoxic and phospholipase A2 activities of homologous venom. In addition, immunodiffusion and Western blot analyses were performed. 2. In experiments where venom and antivenom were incubated prior to the test, antivenom was effective in neutralizing lethal, myotoxic and phospholipase A2 activities, with Effective Doses 50% of 2700 microliters antivenom/mg venom, 1840 microliters antivenom/mg venom, and 3630 microliters antivenom/mg venom, respectively. 3. When coral snake antivenom was administered at different times after coral snake venom injection, neutralization of lethality was achieved when antivenom was injected i.v. immediately and 15 min after venom. In contrast, lethality was not reduced when antivenom was administered by the im route. Only partial neutralization of myotoxicity was observed even when antivenom was injected i.v. immediately after envenomation. 4. Immunodiffusion and immunoblot analyses demonstrated the presence of antibodies in antivenom against several, but not all, venom components.

Animals↗
PubMed1990

Isolation of a galactose-binding lectin from the venom of the snake Bothrops godmani (Godmann's pit viper).

A galactose-binding lectin, isolated from the venom of B. godmani by affinity chromatography, is an acidic protein (pI 4.9) with a subunit mol. wt of about 14,000, occurring mostly as a disulfide-linked dimer of 28,000. A small proportion of lectin appears as a monomer and as a tetramer. The lectin agglutinates erythrocytes from mice, rabbit, cow and human (all ABO types, either Rh positive or negative), but does not agglutinate horse, sheep, goat and snake (Oxybelis aeneus, Colubridae) erythrocytes. The agglutinating activity is inhibited by 1 mM EDTA. The lectin is devoid of lethal, hemorrhagic, myotoxic, proteolytic and phospholipase A2 activities. It is not mitogenic for human peripheral blood mononuclear cells. The only effect observed was a moderate induction of edema in the footpad of mice, with a minimal edema-forming dose of 22 micrograms. This effect developed rapidly, and was significantly inhibited by i.p. administration of cyproheptadine, a histamine and serotonin antagonist, before injection of the lectin. Despite the edema-forming activity observed, the low concentration of lectin in crude venom, together with its relatively low potency, suggest that this lectin is not a key component in the development of edema following envenomations by B. godmani.

Animals↗
PubMed1990

Effect of storage temperature on the stability of the liquid polyvalent antivenom produced in Costa Rica.

The effect of storage temperature on the stability of the liquid polyvalent (crotaline) antivenom produced at the Instituto Clodomiro Picado, Costa Rica, was studied during a twelve-month period. The following parameters were evaluated: neutralizing potency against lethal activity of Bothrops asper venom; protein and phenol concentrations; pH; turbidity; safety; and sterility. Analyses were performed each month on different samples of a batch, stored at 4, 23, 30 and 37 degrees C. No significant (P greater than 0.1) variations occurred in potency, protein and phenol concentrations, pH, sterility or safety, at any of the storage temperatures during the study period. However, visual inspection revealed a moderate increase in turbidity of the samples stored at 23, 30 and 37 degrees C, at nine, four and three months, respectively. Culture of samples excluded the possibility of microbial contamination of the product leading to turbidity. Chromatographic and electrophoretic analyses demonstrated that turbidity was caused by the formation of heterogeneous protein aggregates of high molecular weight. Present results support the conclusion that, although storage temperature (up to 37 degrees C for twelve months) does not alter antivenom potency, it significantly influences the formation of protein aggregates. This phenomenon can be prevented by recommending the storage of antivenom at refrigeration temperature.

Animals↗
PubMed1990

South American snake venom proteins antigenically related to Bothrops asper myotoxins.

1. The presence of proteins antigenically related to Bothrops asper myotoxins in various snake venoms, mainly from South America, was investigated by using polyclonal and monoclonal antibodies. 2. Myotoxin-like components were detected in ten Bothrops venoms from South America, and in the venoms of Crotalus atrox (North America), Trimeresurus flavoviridis (Japan), and Micrurus alleni (Costa Rica). 3. Cross-reactive components detected in several Bothrops venoms show a common subunit of 15-16 kDa by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, although significant charge variations are evident by immunoelectrophoresis. 4. It is concluded that proteins antigenically related to B. asper myotoxins are relatively common in the genus Bothrops and, in the light of findings discussed, are likely to possess myotoxic activity.

Animals↗
PubMed1989

Comparative study on coagulant, defibrinating, fibrinolytic and fibrinogenolytic activities of Costa Rican crotaline snake venoms and their neutralization by a polyvalent antivenom.

The coagulant, defibrinating, fibrino lytic and fibrinogenolytic activities of venoms from ten species of Costa Rican crotaline snakes were studied, together with the neutralization of these effects by a polyvalent antivenom. The venoms of Bothrops asper, B. schlegelii, B. nummifer, B. godmani, Lachesis muta and Crotalus durissus induced a coagulant effect in vitro, and all of them, with the exception of B. nummifer, also induced defibrination in vivo. The four non-coagulant venoms (B. lateralis, B. ophryomegas, B. nasuta and B. picadoi) induced a degradation of the alpha (A) chain of fibrinogen, thereby inhibiting coagulation. However, they did not induce defibrination upon i.v. injection. All of the venoms showed fibrinolytic activity in vitro. Polyvalent antivenom was effective in the neutralization of coagulant, defibrinating, fibrinolytic and fibrinogenolytic activities of these venoms, with the exception of coagulant effect induced by C. durissus venom. Since only three venoms are used in the immunization of horses, these results demonstrate the high degree of immunological cross reactivity between components affecting coagulation in Costa Rican crotaline snake venoms.

Animals↗
PubMed1988

Increased detection of human immunodeficiency virus antigen carriers by simultaneous assay of plasma and extracts from resting and phytohaemagglutinin-stimulated peripheral blood mononuclear cells.

Antigenaemia due to human immunodeficiency virus (HIV) is thought to be significant either before the appearance of a specific antibody response, or after its decline during terminal stages. In order to increase the rate of detection of HIV antigen carriers, regardless of the stage or despite the presence of specific serum antibodies, we assayed, simultaneously, plasma samples and extracts from resting and phytohaemagglutinin-stimulated mononuclear cells from 25 infected, anti-body-positive individuals and 10 healthy, antibody-negative female volunteer blood donors. We detected the presence of HIV antigen in at least one of the three types of specimens obtained from all the 25 infected subjects but in none of the 10 healthy blood donors. This approach might prove most useful for the study of patients with controversial or equivocal antibody test results.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Ability of a polyvalent antivenom to neutralize the venom of Lachesis muta melanocephala, a new Costa Rican subspecies of the bushmaster.

Several toxic and enzymatic activities of the venom of L. m. melanocephala were studied. This venom has many similarities with that of L. m. stenophrys, although there are quantitative differences in venom activities, as well as in the immunodiffusion patterns of these venoms when reacted against polyvalent antivenom. This antivenom was tested for its ability to neutralize a series of toxic and enzymatic effects of L. m. melanocephala venom. A new method to study myonecrosis, based on the quantitation of residual creatine kinase in injected muscle, was used. Antivenom was highly effective in neutralizing lethal, hemorrhagic, myotoxic, edema-forming, defibrinating, caseinolytic and fibrinolytic activities when venom and antivenom were incubated prior to the test or, in the case of edema-forming activity, when antivenom was administered before venom injection. On the other hand, when antivenom was injected i.v. at different time intervals after venom injection neutralization of lethality was good, although neutralization of local effects, i.e. hemorrhage and edema, was poor. These results indicate that polyvalent antivenom contains antibodies capable of neutralizing toxic and enzymatic activities of L. m. melanocephala venom. Moreover, the partial inability of antivenom to neutralize local effects when administered after venom injection is probably due to the rapid development of these effects once venom is injected.

Animals↗
PubMed1987

Effects of a myotoxic phospholipase A2 isolated from Bothrops asper venom on skeletal muscle sarcoplasmic reticulum.

The myotoxin from B. asper snake venom inhibited Ca-ATPase activity of rabbit sarcoplasmic reticulum after incubation in vitro. Inhibition was non-competitive and albumin enhanced the effect of the toxin. Furthermore, B. asper myotoxin hydrolyzed sarcoplasmic reticulum phospholipids and induced a dose-dependent release of horseradish peroxidase that had been trapped in sarcoplasmic reticulum vesicles. Binding studies indicated that myotoxin does not bind to any particular protein of this membrane, suggesting that the toxin might interact with phospholipids. Inhibition of Ca-ATPase is probably a consequence of an alteration in sarcoplasmic reticulum phospholipids.

Animals↗
PubMed1987

[Neutralization of toxic and enzyme activities of 4 venoms from snakes of Guatemala and Honduras by the polyvalent antivenin produced in Costa Rica].

We studied the ability of the polyvalent antivenom produced in Costa Rica to neutralize lethal, hemorrhagic, edema-forming, proteolytic, hemolytic, hyaluronidase and fibrinolytic activities of the venoms of Bothrops asper and B. nummifer from Honduras, and of Agkistrodon bilineatus and Crotalus durissus durissus from Guatemala. Neutralizing ability of antivenom was expressed as ED50 (effective dose 50%), defined as the antivenom/venom ratio at which the activity of the venom is reduced 50%. Antivenom is highly effective in the neutralization of lethal, hemorrhagic, hemolytic, hyaluronidase, and caseinolytic activities of B. asper, B. nummifer, and C. d. durissus venoms. In the case of B. nummifer venom, neutralization of fibrinolytic effect was only partial, whereas this activity was adequately neutralized when studying the venoms of B. asper and C. d. durissus. The venom of A. bilineatus was adequately neutralized by the antivenom, with the only exception of hemolytic effect that was reduced only partially. However, in quantitative terms, a relatively large volume of antivenom was required to neutralize some effects induced by A. bilineatus venom. Regarding edema-forming activity, antivenom neutralized efficiently the venoms of B. asper and A. bilineatus, whereas that of B. nummifer was neutralized only partially; on the other hand, edema induced by the venom of C. d. durissus was not neutralized at all. Immunochemical results indicate a close immunological relationship between venoms of B. asper, B. nummifer and C. d. durissus collected in Honduras and Guatemala with those of the same species collected in Costa Rica. Interspecies comparison, however, showed variation between venoms obtained from different species.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Comparative study of the edema-forming activity of Costa Rican snake venoms and its neutralization by a polyvalent antivenom.

The edema-forming activity of eight Costa Rican crotaline snake venoms and its neutralization by a polyvalent antivenom were studied using the mouse footpad test. All of the venoms induced edema, the highest activity being present in the venoms of Bothrops lateralis and Bothrops picadoi. When experiments were performed with preincubation of venom and antivenom, neutralization of edema was poor. Moreover, it was observed that, with some venoms, edema increased when large doses of antivenom were used. This effect was also observed when some venoms were incubated with coral snake antivenom, suggesting that venoms may release some pharmacologically active component(s) from antivenom, since the latter contains traces of alpha-2 and beta globulins. Based on these findings, an alternative approach to the study of the neutralization of edema was used; in this new method, antivenom was injected i.v. before venom administration, thereby avoiding preincubation. With this technique, a much better neutralization of edema was observed, although with some venoms it was still poor. Venoms contain low molecular weight factors which induce edema, suggesting that lack of immunogenicity of some components may cause a poor neutralization. However, such components are responsible for only a minor portion of the edema induced by crude venoms. It is suggested that experiments in which venom and antivenom are preincubated preincubated in testing the neutralization of edema should be avoided, and that a more adequate approach may be an independent inoculation of venom and antivenom.

Animals↗