Search PubMed⌕ Search

Biomedical subjects

G León

Publications and source records attributed to G León.

At least 19 recordsLinked to original sources
PubMed2006

Composting anaerobic and aerobic sewage sludges using two proportions of sawdust.

Sawdust has been proven to be a good bulking agent for sludge composting; however, studies on the most suitable ratio of sludge:sawdust for sludge composting and on the influence of the sludge nature (aerobic or anaerobic) on the composting reaction rate are scarce. In this study two different sewage sludges (aerobic, AS, and anaerobic, ANS) were composted with wood sawdust (WS) as bulking agent at two different ratios (1:1 and 1:3 sludge:sawdust, v:v). Aerobic sludge piles showed significantly higher microbial activity than those of anaerobic sludge, organic matter mineralization rates being higher in the AS mixtures. The lowest thermophilic temperatures during composting were registered when the anaerobic sludge was mixed with sawdust at 1:1 ratio, suggesting the presence of substances toxic to microorganisms. This mixture also showed the lowest decreases of ammonium during composting. All this matched with the inhibitory effect on the germination of Lepidium sativum seeds of this mixture at the first stages of composting, and with its low values of microbial basal respiration. However, the ANS+WS 1:3 compost developed in a suitable way; the higher proportion of bulking agent in this mixture appeared to have a diluting effect on these toxic compounds. Both the proportions assayed allowed composting to develop adequately in the case of the aerobic sludge mixture, yielding suitable composts for agricultural use. However, the ratio 1:1 seems more suitable because it is more economical than the 1:3 ratio and has a lower dilution effect on the nutritional components of the composts. In the case of the anaerobic sludge with its high electrical conductivity and ammonium content, and likely presence of other toxic and phytotoxic substances, the 1:3 ratio is to be recommended because of the dilution effect.

Aerobiosis↗
PubMed2005

Pan-African polyspecific antivenom produced by caprylic acid purification of horse IgG: an alternative to the antivenom crisis in Africa.

A polyspecific Pan-African antivenom has been produced from the plasma of horses immunized with a mixture of the venoms of Echis ocellatus, Bitis arietans and Naja nigricollis, the three most medically important snakes in sub-Saharan Africa. The antivenom is a whole IgG preparation, obtained by caprylic acid precipitation of non-IgG plasma proteins. The antivenom effectively neutralizes the most important toxic activities of the three venoms used in the immunization in standard assays involving preincubation of venom and antivenom before testing. This antivenom compares favourably with other antivenoms designed for use in Africa with respect to neutralization of the toxins present in the venom of E. ocellatus. Caprylic acid fractionation of horse hyperimmune plasma is a simple, convenient and cheap protocol for the manufacture of high quality whole IgG antivenoms. It constitutes a potentially valuable technology for the alleviation of the critical shortage of antivenom in Africa.

Animals↗
PubMed2002

Prenatal diagnosis of Cantrell's pentalogy with conventional and three-dimensional sonography.

Omphaloceles and gastroschisis are the most common defects of the fetal anterior abdominal wall. The association of an omphalocele with an anterior thoracic wall defect could result from a variety of congenital syndromes of which Cantrell's pentalogy is the most common. For proper surgical scheduling of the neonate, early diagnosis of each of the components of this syndrome is important. The presence of a congenital intracardiac anomaly is the best predictor of neonatal mortality. We present a case of Cantrell's pentalogy diagnosed prenatally with conventional and three-dimensional sonographic imaging, and confirmed at birth. We discuss this case and the reports in the world literature.

Abdominal Wall↗
PubMed2001

Modulation of the susceptibility of human erythrocytes to snake venom myotoxic phospholipases A(2): role of negatively charged phospholipids as potential membrane binding sites.

Cerrophidion (Bothrops) godmani myotoxins I (CGMT-I) and II (CGMT-II), Asp-49 and Lys-49 phospholipases A(2) (PLA2s), which drastically differ in enzymatic activity, were devoid of direct hemolytic effects on erythrocytes (RBC) from different species despite the fact that enzymatically active CGMT-I was able to hydrolyze RBC membrane phospholipids and disrupt liposomes prepared from RBC lipids. Human RBC did not become susceptible to the toxins after treatment with neuraminidase or after altering membrane fluidity with cholesterol or sublytic concentrations of detergent. Unlike normal RBC, significant hemolysis was induced by CGMT-II and another similar Lys-49 isoform, B. asper MT-II (BAMT-II), in RBC enriched with phosphatidylserine (PS). Hemolysis was greater in RBC preincubated with pyridyldithioethylamine (PDA), a potent inhibitor of aminophospholipid transport. RBC enriched with phosphatidic acid (PA) also became susceptible to the myotoxins but was unaffected by PDA. Cells enriched with phosphatidylcholine (PC) remained resistant to the action of the toxins. BAMT-II also induced damage in black lipid membranes prepared with PS but not PC alone. When RBC binding of BAMT-II was measured by enzyme-linked immunosorbent assay, it was observed that PS- and PA-enriched erythrocytes were always able to capture more toxin than normal and PC-enriched RBC. This effect was significantly improved by PDA (in the case of PS) and it was observed either in the presence or in the absence of calcium in the medium. These data suggest that negatively charged lipids in the outer leaflet of cell membranes constitute myotoxic PLA2 binding sites. The scarcity of anionic phospholipids in the outer leaflet of RBC could explain their resistance to the action of these PLA2s.

Animals↗
PubMed2001

Recognition of carbohydrate epitopes specific for electron-dense granule antigens from Entamoeba histolytica by monoclonal antibodies in the cecal content of infected hamsters.

The pathogenic trophozoites of Entamoeba histolytica produce and secrete electron-dense granules (EDG) containing collagenase, considered a virulence factor. Two monoclonal antibodies (MAbs) (L7.1 and L1.1) anti-EDG antigens were raised. MAb L7.1 has been reported to recognize proteic EDG antigens and MAb L1.1 reacted with a carbohydrate epitope. These epitopes were present in axenic and xenic amoebas. To detect EDG antigens by a enzyme-linked immunosorbent assay (ELISA) in a experimental model of early intestinal amoebiasis, both MAbs were employed. E. histolytica HM1 axenic and monoxenic trophozoites were inoculated into the cecum according to the washed-closed cecal loop technique. The cecal content was recovered at 8, 24, and 48 h post-inoculation. Antigens from EDG in whole trophozoites and cell-free supernatants were detected. Our results indicate that it is possible to detect EDG antigens in the cecal content of hamsters in the early phase of the invasive amoebiasis.

Animals↗
PubMed2001

Comparison between IgG and F(ab')(2) polyvalent antivenoms: neutralization of systemic effects induced by Bothrops asper venom in mice, extravasation to muscle tissue, and potential for induction of adverse reactions.

Whole IgG and F(ab')(2) equine-derived polyvalent (Crotalinae) antivenoms, prepared from the same batch of hyperimmune plasma, were compared in terms of neutralization of the lethal and defibrinating activities induced by Bothrops asper venom, their ability to reach the muscle tissue compartment in envenomated mice, and their potential for the induction of adverse reactions. Both preparations were adjusted to the same potency against the lethal effect of B. asper venom in experiments involving preincubation of venom and antivenom. Then, "rescue" experiments were performed, i.e. antivenom was administered either intravenously or intramuscularly at various times after envenomation. IgG and F(ab')(2) antivenoms were equally effective in the neutralization of lethality, both being more effective when administered i.v. than after i.m. injection. Neutralization decreased as the time lapse between envenomation and treatment increased. No significant differences were observed in the ability of antivenoms to neutralize defibrinating activity of B. asper venom in experiments involving independent injection of venom and antivenoms. There was a much higher accumulation of equine antibodies in muscle tissue that had been injected with B. asper venom than in non-envenomated tissue, indicating that venom-induced microvessel damage probably favors a prominent and similar extravasation of both IgG and F(ab')(2) antibodies. This may explain the similar effectiveness of both types of antivenom in previously reported studies on the neutralization of venom-induced local tissue damage. Both IgG and F(ab')(2) antivenoms activate human complement in vitro and induce an anti-equine immunoglobulin response in mice, indicating that Fc removal per se does not eliminate the potential for inducing adverse reactions. However, IgG antivenom had higher anticomplementary activity and induced a stronger anti-immunoglobulin response than F(ab')(2) antivenom.

Animals↗
PubMed2001

Three different genes encode the iron-sulfur subunit of succinate dehydrogenase in Arabidopsis thaliana.

The iron-sulfur protein is an essential component of mitochondrial complex II (succinate dehydrogenase, SDH), which is a functional enzyme of both the citric acid cycle and the respiratory electron transport chain. This protein is encoded by a single-copy nuclear gene in mammals and fungi and by a mitochondrial gene in Rhodophyta and the protist Reclinomonas americana. In Arabidopsis thaliana, the homologous protein is now found to be encoded by three nuclear genes. Two genes (sdh2-1 and sdh2-2) likely arose from a relatively recent duplication event since they have similar structures, encode nearly identical proteins and show similar expression patterns. Both genes are interrupted by a single intron located at a conserved position. Expression was detected in all tissues analysed, with the highest steady-state mRNA levels found in flowers and inflorescences. In contrast, the third gene (sdh2-3) is interrupted by 4 introns, is expressed at a low level, and encodes a SDH2-3 protein which is only 67% similar to SDH2-1 and SDH2-2 and has a different N-terminal presequence. Interestingly, the proteins encoded by these three genes are probably functional because they are highly conserved compared with their homologues in other organisms. These proteins contain the cysteine motifs involved in binding the three iron-sulfur clusters essential for electron transport. Furthermore, the three polypeptides are found to be imported into isolated plant mitochondria.

Amino Acid Sequence↗
PubMed2001

[Low impact of silent hepatitis B virus infection on the incidence of post-transfusion hepatitis in Venezuela].

OBJECTIVE: Silent infection by hepatitis B virus (HBV) occurs in the absence of serological markers for the virus. This type of occult infection is generally chronic, asymptomatic, and associated with low levels of viral replication. This study determined the presence of HBV DNA in the sera of blood donors who were negative for serological markers that were tested during screening, with the goal of evaluating the impact of silent HBV infection in posttransfusion hepatitis B in Venezuela. METHODS: A total of 2,075 sera were tested in 53 serum pools of 25-50 donations (0.5-1.0 mL from each sample). The pools were subjected to ultracentrifugation prior to DNA extraction by the proteinase K, phenol/chloroform method. RESULTS: No HBV DNA was found in any of the pools by nested polymerase chain reaction, using primers for highly conserved regions of the genes that code for the surface antigen and for the viral capsid. Aminotransferase levels were normal in 98% of 200 sera that were tested. CONCLUSIONS: These results suggest that there is a low risk of acquiring posttransfusion hepatitis B in Venezuela.

Adolescent↗
PubMed2000

Cloning, functional expression and partial characterization of the glucose kinase from Renibacterium salmoninarum.

The complete glcK gene from the fish pathogen Renibacterium salmoninarum, encoding a glucose kinase, was analyzed and expressed. The partial characterization of the recombinant enzyme confirmed that it belongs to a group of glucose kinases involved in carbon catabolite repression. Multiple sequence alignments were used to deduce a new consensus sequence for this family of bacterial proteins, characterized by several conserved Cys residues. This sequence was more specific and allowed the detection of the first eukaryotic protein of this family. The recombinant enzyme was inhibited by N-ethylmaleimide and the substrates protected the enzyme from this inhibition, suggesting the presence of Cys residues in or close to the active site.

Amino Acid Sequence↗
PubMed2000

Comparative study on the ability of IgG and Fab sheep antivenoms to neutralize local hemorrhage, edema and myonecrosis induced by Bothrops asper (terciopelo) snake venom.

The ability of sheep antivenoms, consisting of whole IgG molecules or Fab fragments, to neutralize local hemorrhage, edema and myonecrosis induced by Bothrops asper venom was comparatively studied in mice. The two antivenoms were produced from the same batch of hyperimmune plasma and were adjusted to the same neutralizing potency against these effects in assays where venom and antivenoms were incubated prior to injection. Thus, if differences are observed in experiments involving independent injection of venom and antivenoms, they would depend on the pharmacokinetic profiles of the products. Despite the observation that both antivenoms neutralized the three effects if preincubated with venom, neutralization was only partial when antivenoms were administered i.v. at various time intervals after envenomation. No significant differences were observed between IgG and Fab antivenoms concerning neutralization of hemorrhagic and edema-forming activities, whereas IgG antivenom was slightly more effective in neutralizing myotoxic activity in experiments involving independent injection of venom and antivenom. These results do not support the hypothesis that Fab fragments are more effective than whole IgG molecules in the neutralization of locally-acting toxins from B. asper venom.

Animals↗
PubMed1999

A randomized blinded clinical trial of two antivenoms, prepared by caprylic acid or ammonium sulphate fractionation of IgG, in Bothrops and Porthidium snake bites in Colombia: correlation between safety and biochemical characteristics of antivenoms.

A randomized blinded clinical trial was performed in 53 patients bitten by Bothrops sp. and Porthidium sp. in Antioquia and Chocó, Colombia, in order to compare the efficacy and safety of two antivenoms made of whole IgG obtained by either ammonium sulphate (monovalent anti-B. atrox) or caprylic acid (polyvalent) fractionation. Additionally, antivenoms were compared by electrophoretic and chromatographic analyses and anticomplementary activity in vitro. With a protocol of 2, 4 and 6 antivenom vials for the treatment of mild, moderate and severe envenomings, respectively, both antivenoms were equally efficient to neutralize the most relevant signs of envenoming and to clear serum venom levels in patients from the first hour and later on. Three patients with severe envenoming and initially treated with less than six vials on admission had persistent or recurrent venom antigenemia within 12-48 h. Monovalent antivenom fractionated by ammonium sulphate precipitation had higher amounts of protein aggregates and nonimmunoglobulin proteins than polyvalent antivenom fractionated by caprylic acid precipitation. Both antivenoms presented anticomplementary activity in vitro, being higher in the monovalent product. In agreement, monovalent antivenom induced a significantly higher incidence of early antivenom reactions (52%) than polyvalent antivenom (25%).

Adolescent↗
PubMed1999

Restricted isotypic antibody reactivity to hepatitis C virus synthetic peptides in immunocompromised patients.

An enzyme immunoassay based on three synthetic peptides from the core, NS4, and NS5 regions of hepatitis C virus allowed the detection of antibodies in 100% of immunocompetent infected patients and in 91% of immunocompromised patients (hemodialysis and hemophiliac patients). Immune impairment seemed to restrict the spectrum of antibody isotypes reacting to the core peptide.

Amino Acid Sequence↗
PubMed1999

Hepatitis B virus DNA in blood samples positive for antibodies to core antigen and negative for surface antigen.

Anti-hepatitis B core antigen (HBcAg)-positive hepatitis B surface antigen (HBsAg)-negative plasma samples from blood donors were tested by nested PCR. DNA positivity was more significantly associated with high levels of anti-HBcAg than with low levels of anti-HBsAg antibodies. Analysis of a dilution of anti-HBcAg antibodies might result in a more rational exclusion of anti-HBcAg-positive HBsAg-negative samples, reducing the number of donations discarded and enabling more countries to incorporate anti-HBcAg testing.

Antibodies, Viral↗
PubMed1999

Comparative study on the ability of IgG and F(ab')2 antivenoms to neutralize lethal and myotoxic effects induced by Micrurus nigrocinctus (coral snake) venom.

A comparative study was performed on the ability of IgG and F(ab')2 antivenoms to neutralize lethal and myotoxic activities of Micrurus nigrocinctus venom. Both antivenoms were adjusted to a similar neutralizing potency in experiments where venom and antivenoms were preincubated prior to injection. No significant differences were observed between IgG and F(ab')2 antivenoms concerning neutralization of lethal effect in rescue experiments, i.e., when antivenom was administered intravenously after envenomation. However, F(ab')2 antivenom was more effective in prolonging the time of death when subneutralizing doses were administered immediately after venom injection. Both products partially reversed the binding of M. nigrocinctus alpha-neurotoxins to acetylcholine receptor in vitro. The IgG and F(ab')2 antivenoms effectively neutralized venom-induced myotoxicity when administered intravenously immediately after envenomation, although neutralization was poor if antivenom injections were delayed. Intramuscular injection of venom promoted diffusion of antivenom antibodies throughout muscle tissue, and F(ab')2 diffused to a higher extent than IgG molecules. Thus, despite the observation that F(ab')2 antivenom was more effective than IgG antivenom in prolonging the time of death when subneutralizing doses were administered immediately after envenomation, no major differences were observed in antivenom neutralization of lethal and myotoxic effects or in their capacity to reverse neurotoxin binding to the acetylcholine receptor.

Animals↗
PubMed1999

[Investigation of HBV-DNA using the polymerase chain reaction (PCR) in HBsAg-negative, anti-HBc-positive Venezuelan donors].

OBJECTIVE: In our Center the disposal of blood with HBV positive markers is approximately 6%, being 90% AgsHB negative and anti HBc positive. With the purpose of knowing the infected capacities of these donations and to consider the possibility of using them for transfusion, the presence of the viral genoma was investigated by PCR, in a group of samples with these characteristics that were also anti sHB positive. They were correlated with the readings of the anti cHB total, with the anti cHB-IgM and with the titration of the anti sHB. MATERIALS AND METHODS: 87/100 random samples, from February to June 1996, were frozen at -30 degrees C for their later evaluation. In the serological screening were used Auszyme Monoclonal of Abbott and the Heprofile anti cHB, ADI-Diagnostic. The readings of the anti cHB was considered strong, moderate or weak according to its distance to the cut off. For the determination of the anti sHB, Hepanostika anti sHB, Organon Technika was used. They were considered with low titers (< 10 UI/L), high (> or = 10 UI/L) and very high (> or = 100 UI/L). In the determination of the anti cHB-IgM, Heprofile ADI-Diagnostic was used. For the investigation of the viral genoma, it was carried out with double PCR-ADN, using two internal and two external primers for the core-precore region. RESULTS: 70/87 (80.45%) of the samples presented high readings of anti cHB with high titers of anti sHB, being positive for anti cHB-IgM seven of them and one was HBV-ADN positive (1.42%) suggesting the possibility to be cronic carrier. In the remaining 19.55% of the samples we didn't detect positive results in the amplification assays. CONCLUSIONS: 1. The donors showed high levels of immunocompetence. 2. High titer of anti sHB doesn't guarantee the absence of viral genoma and therefore the absence of infectivity can not be sure. This doesn't allow us to come in like donors neither to use their blood in the transfusional therapy.

Blood Donors↗
PubMed1998

Inhibition by CaNa2EDTA of local tissue damage induced by Bothrops asper (terciopelo) venom: application in horse immunization for antivenom production.

The ability of the chelating agent CaNa2EDTA to inhibit local tissue damage induced by Bothrops asper venom was studied in mice and in horses used for polyvalent (Crotalinae) antivenom production. CaNa2EDTA was devoid of toxicity when injected i.m. or s.c. inducing only a mild edema. Preincubation of B. asper venom with CaNa2EDTA inhibited hemorrhagic and dermonecrotic activities, but did not reduce edema-forming and myotoxic effects. A group of horses initially immunized with native venoms developed less severe local tissue reactions when injected with booster doses of venom and CaNa2EDTA than when receiving booster injections of venom alone, although they showed a similar antivenom response. Moreover, antivenoms produced from plasmas of horses that received booster injections of either venom alone or venom plus CaNa2EDTA had similar neutralizing activity against lethal, hemorrhagic and coagulant effects induced by B. asper venom. The similar antibody response was corroborated by Western blotting using crude venom and by an ELISA that estimates anti-myotoxin titer. It is concluded that the chelating agent CaNa2EDTA reduces the extent of local tissue damage induced by B. asper venom, without affecting the immune response of horses against pharmacologically-relevant venom components.

Animals↗
PubMed1998

Pharmacological modulation of edema induced by Lys-49 and Asp-49 myotoxic phospholipases A2 isolated from the venom of the snake Bothrops asper (terciopelo).

The pharmacological modulation of edema-forming activity of Bothrops asper myotoxins II and III, Lys-49 and Asp-49 phospholipases A2, respectively, was studied plethysmographically in the mouse foot pad model. Myotoxin III had phospholipase A2 activity, whereas myotoxin II was devoid of enzymatic activity when tested on egg yolk phosphatidylcholine. Both toxins induced a dose-dependent edema of rapid onset. Chemical modification of myotoxin III with p-bromophenacyl bromide abrogated enzymatic activity and significantly reduced edemat-forming activity, although a residual effect remained. Pre-treatment of animals with diphenhydramine, dexamethasone, indomethacin and prazosin significantly reduced the effect of both myotoxins. It is concluded that (a) these myotoxins are important edema-forming components of B. asper venom, (b) enzymatic activity is not a strict requirement to exert this effect, although in the case of myotoxin III it contributes to its development, and (c) several inflammatory mediators participate in mouse foot pad edema induced by these myotoxins.

Animals↗