Biomedical subjects

J A Castro

Publications and source records attributed to J A Castro.

At least 55 records · Page 3Linked to original sources

PubMed1998

Brazilian isolates of Trypanosoma cruzi from humans and triatomines classified into two lineages using mini-exon and ribosomal RNA sequences.

Traditional molecular and biochemical methods, such as schizodeme analysis, karyotyping, DNA fingerprinting, and enzyme electrophoretic profiles, have shown a large variability among Trypanosoma cruzi isolates. In contrast to those results, polymerase chain reaction (PCR) amplification of sequences from the 24S alpha ribosomal RNA gene and from the mini-exon gene nontranscribed spacer indicated a dimorphism among T. cruzi isolates, which enabled the definition of two major parasite lineages. In the present study, 86 T. cruzi field stocks (68 isolated from humans with defined presentations of Chagas' disease and 18 from triatomines) derived from four Brazilian geographic areas were typed by the PCR assay based on the DNA sequences of the mini-exon and 24S alpha rRNA genes. These stocks were ordered into the two major T. cruzi lineages. Lineage 1 was associated mainly with human isolates and lineage 2 with the sylvatic cycle of the parasite.

Animals↗

PubMed1998

Mechanisms of the preventive properties of some garlic components in the carbon tetrachloride-promoted oxidative stress. Diallyl sulfide; diallyl disulfide; allyl mercaptan and allyl methyl sulfide.

Previous studies evidenced that garlic extracts and/or garlic components were able to prevent against chemically induced tumors or acute toxic effects of chemicals (e.g. CCl4 induced liver injury). The chemopreventive potential of garlic has been attributed to the presence in it of several bioactive organosulfur compounds. Those components might act as antioxidants able to scavenge free radicals. In the present work we describe initial studies on the antioxidative-stress properties of some garlic components such as: diallyl disulfide (DDS), diallyl sulfide (DAS), allyl mercaptan (AMT) and allyl methyl sulfide (AMS). We found that DAS, DDS and AMT but not AMS were able to trap trichloromethyl and trichloromethylperoxyl free radicals. Further, DDS but not DAS or AMT also inhibited CCl4 promoted liver microsomal lipid peroxidation. DAS, but not DDS, AMT or AMS was able to react with free radicals arised during UVC activation of hydrogen peroxide or terbutyl hydroperoxide but not with those produced during UVC activation of terbutyl peroxide. However, all garlic components tested absorbed energy from UVC and became partially destroyed in the process. AMT, but not DDS, AMS or DAS was able to destroy 4-hydroxynonenal, a key reactive aldehyde produced during lipid peroxidation. AMT and DDS were also able to prevent UVC plus CCl4 promoted oxidation of albumin in vitro, but DAS and AMS failed to do so. Results suggest that the antioxidative stress properties of garlic might result from the contributions of its sulfur component in different steps and not necessarily from the contribution of only one of them.

Allyl Compounds↗

PubMed1998

Mitochondrial DNA: a tool for populational genetics studies.

Mitochondria are cellular organelles that have the function of the oxidative phosphorilation and the formation of ATP. In humans, the mtDNA is a double-stranded, circular, covalent closed molecule of 16.5 kb. The mtDNA is inherited as a haploid from the mother and heteroplasmy has been found rarely. From a populational perspective, it could be considered as a system of small, sexually isolated demes, or clonal lineages, with an evolutionary rate 5 to 10 times faster than the nuclear genome. All these characteristics make this molecule ideal for evolutionary studies. We present two applications of this molecule in genetical studies. One of these is referred to the Balearic Islands populations, Majorca, Minorca, Ibiza, and Chuetas. The other example is the populational dynamics of the different mitochondrial haplotypes in Drosophila subobscura. We also discuss the importance of nuclear markers to complete these studies as well as the study of the Y chromosome to compensate the bias produced by the study of only the mtDNA.

Animals↗

PubMed1998

Effect of trichloromethyl and trichloromethyl peroxyl free radicals on protein sulfhydryl content studies in model and in enzymatic carbon tetrachloride activation systems.

The effect of trichloromethyl and trichloromethyl peroxyl free radicals on protein sulfhydryl content was studied using both, model and enzymatic activation systems. In the model system activation of CCl4 to both free radicals was by UVC light and the target protein was either delipidated or undelipidated albumin. Under air, the CCl3O2. radicals were able to significantly decrease the protein SH in both albumin preparations. A small but signficant effect of UVC alone was observed with defatted albumin. No significant decreases in protein sulfhydryl were observed by .CCl3 attack on the defatted albumin. Reaction of CCl3O2. on cysteine SH led to chloroform formation indicating that a H abstraction reaction is involved in the process. UVC light has an own effect on SH group content. Similar results were obtained when the interaction was with undelipidated albumin rather than with cysteine. Their formation was significantly prevented by Trolox 1 mM in incubation mixture. When the CCl3O2. were generated by liver microsomal activation of CCl4 under air, a significant decrease in microsomal protein SH content was observed. NADPH also exerted an effect of its own. These decreasing effects were fully prevented by either Trolox or EDTA addition to incubation mixtures but not by alpha-tocopherol free or as a succinate ester. Incubation mixtures containing nuclear suspensions and NADPH led to a decrease in protein SH content. This decrease was not enhanced further by the presence of CCl4. No effect on the protein SH content was observed when either mitochondrial or cytosolic fractions were employed to attempt activation of CCl4 to .CCl3/CCl3O2. free radicals. The ability of CCl4 derived free radicals to decrease protein SH in liver microsomes could be involved in loss of activity of key SH enzymes of relevance such as microsomal calcium pump. This pump is known to be damaged during CCl4 poisoning. This effect was blamed to initiate alterations in calcium homeostasis later leading to CCl4 induced liver cell death.

Animals↗

PubMed1998

Trypanocidal effect of SKF525A, proadifen, on different developmental forms of Trypanosoma cruzi.

SKF525A, an inhibitor and inducer of cytochrome P450, was tested on different developmental stages of Trypanosoma cruzi. Growth, motility and structure of epimastigotes, motility and infectivity of trypomastigotes, and infectivity of trypomastigotes to Vero cells in culture were abolished by the drug at 10-100 microM concentrations. When blood from infected mice was treated with the drug, and used to infect 8 day-old mice, no parasites were observed at 0.6-1 mM, and all animals survived. Blood cell morphology was well preserved, and the sleeping time of pentobarbital-treated mice inoculated with the same amount of drug was not increased. The present results suggest that SKF525A or other related inhibitors of cytochrome P450 coned be tested as an additive for blood sterilization in blood banks.

Animals↗

PubMed1997

[A method of detection psychosocial problems at the family physician's office].

OBJECTIVE: To find the value of the Stressful Vital Events (SVE) scale for detecting patients with psycho-social problems and how these affect family function. DESIGN: A descriptive, crossover study with systematic sampling. SETTING: Almanjayar Health Centre. PATIENTS AND OTHER PARTICIPANTS: 202 patients (138 women and 64 men) who attended for on-demand consultations at two clinics during October and November 1994. They were selected systematically, 1 from every 5, with under-18s eliminated. INTERVENTIONS: The GHQ, SVE and Family APGAR tests were self-administered. The GHQ test was used to detect psycho-social problems, SVE to measure stressful vital events and the APGAR family to find family function. MEASUREMENTS AND MAIN RESULTS: 46% (94) had psycho-social problems; 53% (107), positive scoring in the SVE test; and 21% (42), family dysfunction. The relationship between SVE and GHQ was significant (p < 0.0001), but relationships with the APGAR weren't. CONCLUSIONS: We consider that exploration of SVEs is a good way of detecting psycho-social problems.

Adult↗

PubMed1997

Effect of a commercial disinfectant ('Virkon') on mouse experimental infection by Cryptosporidium parvum.

Cryptosporidium parvum oocysts obtained from naturally-infected calves were exposed to 1-10% 'Virkon' for 10-360 min, then inoculated intragastrically into coccidium-free neonatal mice. Prevalence and intensity of infection were determined seven days later by examination of intestinal homogenates. Although we were unable to abolish infectivity for the mice, the intensity of infection was considerably reduced after long periods of exposure (up to > 90%, depending on disinfectant concentration), indicating that this product may have some value for disinfection when extended exposure is possible (e.g., soaking laboratory glassware).

Analysis of Variance↗

PubMed1997

DNA bases attack by reactive metabolites produced during carbon tetrachloride biotransformation and promotion of liver microsomal lipid peroxidation.

Free radicals produced during carbon tetrachloride biotransformation and the promoted lipid peroxidation process of liver microsomal lipids are able to attack the DNA bases guanine, cytosine and thymine to give at least three altered bases. They were identified as 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua); 5-hydroxycytosine (5OHCyt) and 5-hydroxymethyluracil (5OHMeU). No adenine adducts were detected. If these altered bases were formed during carbon tetrachloride poisoning and were not adequately repaired before cell replication, serious permanent consequences for liver cell DNA could be expected and this might be somehow involved in the liver carcinogenic effects of the haloalkane.

Animals↗

PubMed1997

Genetics of the Chuetas (Majorcan Jews): a comparative study.

A study of the Chueta population has been carried out to establish the genetic relationships between the Chuetas and other Jewish and non-Jewish circum-Mediterranean populations and to identify which markers discriminate better between these populations. The analyses used were principal components analysis, factorial analysis of correspondences, and stepwise discriminant analysis. The results indicate that most of the Jewish communities resemble each other and other Middle Eastern populations, because of their common origin, but they also have affinities with their host peoples. The results also agree with those of most researchers in the importance of G6PD, FY, and MN as geographic markers and in the role of HP, GLO1, and Rh as indicators the Middle Eastern origin of the Jews but differ with respect to the geographic pattern of ABO. Moreover, the Jewish origin of the Chuetas remains evident in their genetic pool, although they resemble their neighboring populations more than other Jewish populations. Finally, HP, G6PD, ABO and Rh are the most important variables in determining the position of the Chuetas with respect to other Jewish and non-Jewish populations.

Discriminant Analysis↗

PubMed1997

Study of the populations of the Balearic Islands (Spain) using mtDNA RFLPs.

The Balearic archipelago (Spain) is composed of three major islands, Majorca, Minorca, and Ibiza. Majorca is the largest and most populous island. Minorca is the second largest in area and third in population, and Ibiza is the smallest of the three and has the second largest population. Ibiza also shows differences from the other two islands in its landscape, vegetation, and especially origins of the founding settlements. The three islands also have been settled by people of different cultures. We have carried out a genetic analysis at the level of mtDNA RFLPs in these populations and found that the three populations are genetically structured, with differences in the RFLP haplotype frequencies reflecting the different population substrata of the three islands. In this structure Ibiza is genetically more different from Majorca and Minorca. In addition, we found a new haplotype in Minorca, named haplotype 150, which seems to originate from haplotype 56.

DNA, Mitochondrial↗

PubMed1997

Promotion of the formation of phenylalanine-thymine cross-linked products by free radicals formed during carbon tetrachloride activation with benzoyl peroxide in model systems. A mass spectrometric structural study.

Reaction mixtures containing phenylalanine methyl ester and thymine in pure carbon tetrachloride in the presence of benzoyl peroxide produced trichloromethyl and trichloromethylperoxyl free radicals which via hydrogen abstraction reactions sparked the formation of phenylalanine-thymine adducts, whose structures were elucidated by mass spectrometry. If similar type of reaction occurred under biological conditions, significant deleterious consequences might be anticipated.

Benzoyl Peroxide↗

PubMed1997

Rat liver nuclear nifurtimox nitroreductase activity.

Nifurtimox (Nfx) 4-[(5-nitrofurfurylidine)amino-3-methylthiomorpholine-1-1-di oxide] is a drug that is being used to treat American Trypanosomiasis (Chagas' disease). Nfx has serious toxic effects including mutagenic, reproductive and carcinogenic actions. Its toxicity has been linked to NADPH dependent nitroreductive metabolic biotransformation with production of oxygen reactive species. In this study is reported that rat liver nuclei exhibit Nfx-nitroreductase activity (Nfx-ase). This activity is null under oxygen and partially inhibited under CO. Nfx does not promote a lipid peroxidation process. Results suggest that Nfx is biotransformed partially at a cytochrome P450 level but mostly by NADPH P450 reductase. Formation of reactive metabolites nearby DNA and nuclear proteins might be related to long term deleterious effects of this drug.

Animals↗

PubMed1996

5-Methylcytosine attack by hydroxyl free radicals and during carbon tetrachloride promoted liver microsomal lipid peroxidation: structure of reaction products.

We recently reported that trichloromethyl and trichloromethylperoxyl radicals attack 5-methylcytosine (5MC) to give several products derived from hydroxylation, deamination or halogenation reactions. Hydroxyl radicals and lipid peroxidation (LP) are more frequently involved in deleterious pathological or toxicological processes than those CCl4 derived radicals and thus we considered it of interest to test whether they also alter 5MC. We observed that OH radicals generated by 0.1 mM Fe2+/2.5 mM H202 at 25 degrees C for 1 h led to the production of 5-hydroxymethylcytosine (5MHC). When OH generation was performed with UV light (254 nm, 3400 muWatt/cm2) and 2mM H202 during 4 min at 25 degrees C the following products were observed: 5-hydroxy-5-methylhydantoin, 5-hydroxyhydantoin, 5MHC, thymine glycol (two isomers) and 5-hydroxymethyl-6-hydroxycytosine. When 5MC was exposed to liver microsomal suspensions in the presence of NADPH generating system and carbon tetrachloride during 1 h at 37 degrees C and under air, the formation of only 5HMC was observed. Detection and identification of all reaction products was done by GC/MS analysis of trimethylsilyl derivatives of the bases. If similar reactions occurred in DNA, these results might be of relevance to gene control, differentiation and carcinogenesis.

5-Methylcytosine↗

PubMed1996

Depression of liver microsomal glucose 6-phosphatase activity in carbon tetrachloride-poisoned rats. Potential synergistic effects of lipid peroxidation and of covalent binding of haloalkane-derived free radicals to cellular components in the process.

Depression of liver microsomal glucose-6-phosphatase (G6Pase) activity is a relevant feature of CCl4 poisoning. In vitro studies from several laboratories led to the hypothesis that a CCl4 promoted lipid peroxidation (LP) process is responsible for that effect. In vivo studies from our laboratory with potent antioxidants in dosage regimes inhibiting LP, however, were in contrast with that hypothesis. In this work we studied the potential preventive effects of Pyrazole (Pyr), alpha-tocopherol (alpha T), and 3-amino-1,2,4-triazole (AT) against CCl4-induced depression of G6Pase activity. Pyr decreases the intensity of the covalent binding (CB) of CCl4 reactive metabolites to cellular components but does not inhibit LP in vitro or in vivo. alpha T inhibits LP in vitro and in vivo and AT inhibits both CB and LP. Our present studies give evidence that AT but neither Pyr nor alpha T are able to prevent the CCl4-induced depression of G6Pase activity. Results are compatible with the hypothesis that the cooperation of both factors is critical to explain the observed effects, and suggest that under in vitro experimental conditions used by others the relevance of LP might be artifactually promoted.

Amitrole↗

PubMed1996

Orosomucoid (ORM1) polymorphism in Arabs and Jews of Israel: more evidence for a middle eastern origin of the Jews.

A study of 8 Israeli population groups for the ORM1 polymorphism included 1242 serum samples: 156 samples from Arab Moslems, 139 from Arab Druzes, and 947 from 6 Jewish groups. The two most frequent alleles in Europeans and Asians, ORM1*F1 (ORM1*1) and ORM1*S (ORM1*2) were found in Jews and Arabs at frequencies similar to those in Europe. Unique to Arab and Jewish populations were polymorphic frequencies of two ORM1 slow electrophoretic variants, designated ORM1*S1 and ORM1*S2. These were formerly observed only in Europe, where two individuals with *S1 and two with *S2 have been observed so far. The Chueta community of converted Majorcan Jews is the only previously studied group that, like the other studied Jewish groups, has polymorphic frequencies of both ORM1*S1 and ORM1*S2. In this study we associate the Chuetas with the Israeli groups, as a population of Middle Eastern origin. Published data on ORM1 in Europe and East Asia together with the present data, making a total of 47 populations, were subjected to a discriminant analysis that resulted in a correct classification of 93.6% of the populations. Results of this analysis suggest that ORM1 is a useful polymorphic marker for anthropological studies.

Arabs↗

PubMed1996

Genetic variation in the population of Ibiza (Spain): genetic structure, geography, and language.

A sample of 203 individuals from Ibiza (Balearic Islands, Spain) were tested for blood group and serum protein genetic variation and compared with other circum-Mediterranean populations. Allele frequencies were calculated for the following blood group and serum systems: ABO, Rh, MNSs, P, Lewis, Duffy, Kell, ORM, GC, TF, PI, and HP. The allele frequencies from Ibiza were compared with those from other Balearic Islands (Majorca and Minorca) and with related European and North African groups using an assortment of analytical methods (genetic distances, R matrix analysis, and Mantel tests). R matrix analysis revealed that Ibiza is genetically different from the other Balearic populations and, because of gene flow from Spain, clusters with European groups. The level of genetic microdifferentiation of the Mediterranean populations, measured by RST (average of the R matrix diagonal elements, rii), is 0.028. An examination of the relationship between genetic, geographic, and linguistic distances by Mantel tests revealed that genetic distances are significantly correlated with linguistic distances, whereas the genetic distances are not significantly correlated with geographic distances. The plot of mean per locus heterozygosity versus the genetic distance from the centroid of distribution revealed that all three Balearic Islands have experienced considerable gene flow but that Ibiza has been most affected by the action of stochastic processes.

Blood Group Antigens↗

PubMed1996

Dithiothreitol tetraacetate S-acetyl esterase activity in different liver subcellular fractions and its potential role in the ester-mediated prevention of oxidative stress induced cell damage.

The liver was previously shown to be able to hydrolyze dithiothreitol tetraacetate (DTTAC) to dithiothreitol (DTT) via a DTTAC-S-acetyl esterase (DTTACEST). In the present studies the intracellular distribution of DTTACEST activity and its characteristics are reported. Enzyme specific activity was: microsomes > > mitochondria > > nuclei and was absent in the cytosolic fraction. The Km of the DTTACEST in each fraction was: mitochondria > microsomes > nuclei and the Vmax was microsomes > mitochondria > nuclei. The results were analyzed in relation to the previously established antioxidative stress and free radical trapping properties of DTTAC and DTT and the preventive effects exerted by DTTAC against carbon tetrachloride induced liver necrosis or cancer.

Acetylesterase↗

PubMed1995

Cholesterol interaction with free radicals produced from carbon tetrachloride or bromotrichloromethane by either catalytic decomposition or via liver microsomal activation.

The reaction between cholesterol (Ch) and trichloromethyl or trichloromethyl peroxyl radicals was studied. The latter were generated from CCl4 either by benzoyl peroxide (BP) catalysis or via thermal activation or by liver microsomal NADPH-dependent biotransformation of CBrCl3. The structure of the products formed was elucidated by gas chromatography-mass spectrometry (GC/MS). Under aerobic conditions and using thermal activation of CCl4, the formation of 6 products was observed. Two (I and II) were dehydrated Ch derivatives (one also having a third double bond) (I). Another product was a delta(5)-3 ketone derivative of Ch (III). Two additional reaction products were determined as ketocholesterols (IV and V). One chloro Ch was also formed (VI). At low concentrations of BP, reaction was more extensive than under thermal activation, and the formation of peaks I to IV was also observed. When the reaction was conducted anaerobically and using thermal activation of CCl4 to generate radicals, only products I and II were formed in low yield. Under anaerobic conditions, but using catalyst, compounds I and III were produced plus two new isomeric ketocholesterol derivatives (VIII and IX) and also a compound having an extra hydroxyl group on the Ch structure (X). In order to check whether similar reactions are observable under biological experimental conditions, we used activation of CBrCl3 by liver microsomes. The incubation using only microsomes (without CBrCl3 or NADPH) showed two ketocholesterol peaks (A and B). In the presence of CBrCl3 we could detect peak B and hydroxycholesterol (C) and two others, ketocholesterols (D and E). D was the only peak showing close similarity (spectrum and retention time) to one of those observed in the chemical reaction system (V). The reaction of CBrCl3 in the presence of NADPH showed peaks B, C, D and E, in low abundance and a 7-ketocholesterol (F). If some of the reaction products reported here were formed during the intoxication with these haloalkanes, significant biological consequences might be expected.

Aerobiosis↗