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Biomedical subjects

C Rios

Publications and source records attributed to C Rios.

At least 19 recordsLinked to original sources
PubMed2002

Personal exposure to benzene, toluene and xylene in different microenvironments at the Mexico City metropolitan zone.

The Mexico City Metropolitan Zone (ZMCM) population's exposure to benzene, toluene and xylene was measured at different microenvironments to establish basic indicators of the presence and effects of these characteristic volatile organic compounds (VOC). In particular, VOC personal exposures were measured in different microenvironments during a 5-day working week, with 12-h daily periods. We have found a good agreement of our results with the registered VOC levels of the Metropolitan Automated Monitor System (RAMA) for the corresponding period. From our results, we expect to generate useful information to evaluate the health effects of these VOCs on exposed people.

Automation↗
PubMed2002

Varicella, ephemeral breastfeeding and eczema as risk factors for multiple sclerosis in Mexicans.

OBJECTIVE: It has been suggested that the incidence of multiple sclerosis (MS) in Mexico and other countries of Latin America has increased steadily for the last two decades. We made a thorough search of antecedents on MS patients that could be potential risk factors. METHODS: A case-control study was conducted using a questionnaire that included demographic, nutritional, infectious and personal antecedents previously identified in other reports as possible risk factors for MS. RESULTS: The frequency of varicella, ephemeral breastfeeding and eczema in the medical history of MS patients were significant when compared with controls; all appeared to be mutually additive. However, they were unrelated with clinical characteristics or disease severity. CONCLUSION: During the last decades, breastfeeding has been abandoned in large segments of society and the incidence of varicella and childhood eczema keeps a north-south gradient similar to that described for MS. These factors may participate in the sharp increase of MS in countries like Mexico traditionally considered as an area of very low incidence.

Animals↗
PubMed2001

Exposure to manganese: health effects on the general population, a pilot study in central Mexico.

To support a risk assessment of manganese exposure in two communities living within a manganese mining district a cross-sectional study was performed on a sample of the adult population of long-term residents. One community was exposed to a point source from an ore primary refining plant. Manganese is an essential mineral for human life. It is also the fourth in importance for industrial metal making. Data were collected on socioeconomic living conditions, emission sources, environmental media concentrations (air, water, soil, dust, food), respiratory symptomatology, and a neuropsychological examination (Mini-Mental Screening test, the Hooper Visual Organization test, the Ardila-Ostroski, and others). We examined 73 subjects (52 women), most of low socioeconomic status. Environmental air concentrations were 2 to 3 times higher than those in other urban concentrations. Manganese blood concentrations ranged from 7.5 to 88 microg/L, with a median concentration of 15, the upper quartile starting at 20 microg/L; the upper 10% was above 25 microg/L. Lead and manganese were highly correlated; there was an inverse relation to hemoglobin. Reduced levels of plasma lipid peroxidation were associated with blood manganese. Using multivariate logistic regression, we identified B-Mn as increasing the risk of deficient cognitive performance 12 times (Mini-Mental score of less than 17).

Adolescent↗
PubMed2001

G protein coupled receptor dimerization: implications in modulating receptor function.

Protein-protein interactions are involved in the regulation of a large number of biological processes. It is well established that a variety of cell surface receptors interact with each other to form dimers, and that this is essential for their activation. Although the existence of G protein coupled receptor dimers was predicted from early pharmacological and biochemical analysis, solid evidence supporting dimerization has come within the past few years following the cloning of G protein coupled receptor cDNAs. Using differential epitope tagging and selective immunoisolation of receptor complexes, dimerization of a number of G protein coupled receptors including members of the rhodopsin, secretin, and metabotropic glutamate receptor families have been reported. More recently fluorescence or bioluminescence resonance energy transfer techniques have been used to examine dimerization of these receptors in live cells. These studies have found that whereas in some cases there is an agonist induced increase in the level of dimers, in others there is a decrease or no change in dimer levels. Several recent studies have also reported the ability of related members of G protein coupled receptors to heterodimerize. These heterodimers exhibit distinct physical and functional properties. Examination of possible sites of interactions between receptors has implicated a role for extracellular, transmembrane and/or C-terminal region in dimerization. The functional consequences of dimerization, explored mainly using mutant receptors, have demonstrated a role in modulating agonist affinity, efficacy, and/or trafficking properties. Thus dimerization appears to be a universal phenomenon that provides an additional mechanism for modulation of receptor function as well as cross-talk between G protein coupled receptors.

Animals↗
PubMed2001

Neuroprotective effect of acute and chronic administration of copper (II) sulfate against MPP+ neurotoxicity in mice.

Neurodegenerative effects of MPP+, the main metabolite of MPTP include dopamine (DA) depletion and enhanced lipid peroxidation (LPO) in mice striata, both associated to free radicals overproduction. Since copper is related to several antioxidant enzymes, we tested its neuroprotective effect against MPP+-induced neurotoxicity (20 microg/3 microl). CuSO4 pretreatment was administrated by either acute (2.5 mg/kg, i.p.) or chronic (350 or 700 mg/l doses through drinking water, for 30 days) schemes. Acute administration blocked MPP+-induced striatal LPO only when administered 16 or 24 hours before MPP+, and prevented the DA-depleting effect only at 24 hours. Chronic CuSO4 prevented the LPO increase, and blocked the DA depletion only at the higher dose used (700 mg/l). Neuroprotective effect of CuSO4 was dependent on the dose and the time of pretreatment, which suggest that this lag could be related with mechanisms of activation or synthesis of copper-dependent proteins responsible of cellular defense against MPP+.

1-Methyl-4-phenylpyridinium↗
PubMed2001

EGb761 blocks MPP+-induced lipid peroxidation in mouse corpus striatum.

EGb761 has been suggested to be an antioxidant and free radical scavenger. Excess generation of free radicals, leading to lipid peroxidation (LP), has been proposed to play a role in the damage to striatal neurons induced by 1-methyl-4-phenylpyridinium (MPP+). We investigated the effects of EGb761 pretreatment on MPP+ neurotoxicity. C-57 black mice were pretreated with EGb761 for 17 days at different doses (0.63, 1.25, 2.5, 5 or 10 mg/kg) followed by administration of MPP+, (0.18, 0.36 or 0.72 mg/kg). LP was analyzed in corpus striatum at 30 min, 1 h, 2 h and 24 h after MPP+ administration. Striatal dopamine content was analyzed by HPLC at the highest EGb761 dose at 2 h and 24 h after MPP+ administration. MPP+-induced LP was blocked (100%) by EGb761 (10 mg/kg). Pretreatment with EGb761 partially prevented (32%) the dopamine-depleting effect of MPP+ at 24 h. These results suggest that supplements of EGb761 may be effective at preventing MPP+-induced oxidative stress.

1-Methyl-4-phenylpyridinium↗
PubMed2001

Clomipramine increases the striatal concentrations of dopamine and homovanillic acid in rats chronically consuming alcohol.

OBJECTIVE: There have been many studies on the relationships between the dopaminergic system, alcoholism and antidepressant drugs; the information, however, is controversial. The purpose of this study was to examine the effect of clomipramine (CMI), a tricyclic antidepressant, on the striatal concentration of dopamine (DA) and homovanillic acid (HVA), and their turnover, in a rat model of chronic alcohol ingestion. METHOD: After 10 months of exposure to either water (expW) or alcohol (expA), female Wistar rats (N = 60) were randomly assigned to one of the following six groups: (1) (expW) control group (C), normal diet; (2) (expA) alcohol administration group (A), drinking water was replaced by commercial brandy that was 38% ethanol; (3) (expW) clomipramine group (CMI), received intraperitoneal injections over 4 months; (4) (expA) alcohol administration + clomipramine group (ACMI); (5) (expA) alcohol abstinence group (AA); and (6) (expA) alcohol abstinence + clomipramine group (AACMI). Each group consisted of 10 animals. RESULTS: Chronic alcohol intake decreased striatal dopamine concentration (p < .001), whereas clomipramine administration produced a significant increase (p < .001) when administered in both control rats and rats exposed to long-term alcohol administration. The increase in the ACMI group was significantly different (p < .001) when it was compared with the CMI group. In the AA and AACMI groups, a significant decrease of striatal dopamine was observed (p < .001). During long-term alcohol administration, homovanillic acid decreased (p < .005). HVA/DA ratio increased in AA and AACMI groups (p < .001). CONCLUSIONS: These findings show that clomipramine produces favorable changes in dopaminergic systems altered by chronic alcohol administration. Results also provide evidence to support further prospective studies of potential therapeutic effects of antidepressant drugs in alcoholism.

Alcohol Drinking↗
PubMed2000

Lipid peroxidation inhibition in spinal cord injury: cyclosporin-A vs methylprednisolone.

To compare the effectiveness of cyclosporin-A (CsA) with methylprednisolone (MP) or a combination of both upon inhibition of lipid peroxidation (LP) after spinal cord (SC) injury, rats were treated with either CsA, MP, CSA+MP or vehicle starting 1 h after SC contusion at T9 level. LP was assessed 24h after injury by the lipid fluorescent product formation method. The survival rate was also evaluated in other series of rats by the Kaplan-Meier curves. Lipid peroxidation was similarly inhibited in rats treated with CsA, MP, or CSA+MP (p>0.05). Animals receiving MP (alone or combined with CsA) showed the poorest surviving rate. LP was inhibited by CsA to the same extent as by MP but without the lethal effect of the latter.

Animals↗
PubMed2000

Changes of metallothionein I + II proteins in the brain after 1-methyl-4-phenylpyridinium administration in mice.

1-methyl-4-phenylpyridinium (MPP+) is a drug that induces a Parkinson's-like syndrome in several species. Oxidative stress resulting from either excess generation or reduced scavenging of free radicals has been proposed to play a role in its neurotoxicity. It has been suggested that metallothionein (MT) protects against oxidative damage of the central nervous system produced by overproduction of free radicals. This study examined the effect of MPP+ on metallothionein I+II protein content in different brain regions. NIH mice were injected with MPP+ (4.5, 9.0 or 18 microg/3 microl) into their right lateral ventricle. Corpus striatum, cerebellum, midbrain, frontal cortex and hippocampus were dissected out and their metallothionein concentrations were analyzed by radioimmunoassay. MPP+ reduced the concentration of MT I+II proteins (38%) only in the striatum. The results suggest that changes in MT I+II content may be associated with MPP+ neurotoxicity.

1-Methyl-4-phenylpyridinium↗
PubMed1999

Blood lead levels measured prospectively and risk of spontaneous abortion.

Studies of low to moderate level lead exposures have reported mixed findings regarding the risk of spontaneous abortion, despite lead's abortifacient properties at very high doses. To evaluate the risk of spontaneous abortion from low or moderate lead exposures, a nested case-control study was conducted within a cohort of pregnant women in Mexico City, 1994-1996. During their first trimester, 668 women enrolled, were interviewed, and contributed blood specimens. Pregnancies were followed by home visits or telephone calls. Spontaneous abortions before week 21 (n = 35) were matched with pregnancies that survived beyond week 20 (n = 60) on maternal age, hospital, date of enrollment, and gestational age at enrollment. Mean blood lead levels were 12.03 microg/dL for cases and 10.09 microg/dL for controls (p = 0.02). Odds ratios for spontaneous abortion comparing 5-9, 10-14, and > or =15 microg/dL with the referent category of <5 microg/dL of blood lead were 2.3, 5.4, and 12.2, respectively, demonstrating a significant trend (p = 0.03). After multivariate adjustment, the odds ratio for spontaneous abortion was 1.8 (95% confidence interval = 1.1, 3.1) for every 5 microg/dL increase in blood lead. Low to moderate lead exposures may increase the risk for spontaneous abortion at exposures comparable to US general population levels during the 1970s and to many populations worldwide today; these are far lower than exposures encountered in some occupations.

Abortion, Spontaneous↗
PubMed1999

Cyclosporin-A inhibits lipid peroxidation after spinal cord injury in rats.

Besides its immunosuppressive/anti-inflammatory activity, cyclosporin-A (CsA) may protect damaged tissues from lipid peroxidation (LP) by free radicals. To determine the effect of CsA on LP spinal cord (SC) injury, Wistar rats were treated with either vehicle or CsA (2.5 mg/kg per 12 h i.p.) 1, 2, 6 or 12 h after SC trauma by T8-T9 spinal cord contusion, analyzing LP 24 h after injury at the lesion site by the lipid fluorescent products formation method. CsA significantly diminished LP to levels below control values after contusion (P < 0.05). The greater inhibition was observed when CsA was given during the first 6 h after injury, furthermore, animals showed a significant clinical improvement. Results show that CsA may be beneficial to injured tissue by inhibiting the levels of LP.

Animals↗
PubMed1999

Reduced ferroxidase activity in the cerebrospinal fluid from patients with Parkinson's disease.

Recent evidence suggest the implication of transition metals leading to overproduction of free radicals as a possible causal factor in the death of nigral cells associated to Parkinson's disease (PD). Iron depots in the basal ganglia of PD patients have been described; in addition, contents of nigral copper have been found decreased, while its concentration in cerebrospinal fluid (CSF) is raised, particularly the free form of the metal. To search for a possible link between altered copper concentrations and PD, we advanced the hypothesis that ferroxidase activity of ceruloplasmin is decreased in the CSF of PD patients. We studied 35 untreated PD patients, 14 L-3,4-dihydroxyphenylalanine (L-DOPA)-treated PD patients and 26 controls. Both CSF ferroxidase activity and CSF copper content were measured and correlated with the clinical stage of the disease. We found that untreated PD patients had a significant reduction of 40% in CSF ferroxidase while CSF copper was slightly increased as compared with both the values in L-DOPA-treated PD patients and controls. We also found that the fraction of copper linked to ferroxidase in untreated PD is inversely related to the clinical stage of the disease.

Aged↗
PubMed1999

Lead acetate exposure inhibits nitric oxide synthase activity in capillary and synaptosomal fractions of mouse brain.

The toxicity of lead (Pb) is of concern to public health due to its persistence in the environment. Brain is one of the major target organs where severe neurologic alterations may be triggered after exposure. The primary effects of lead on brain functions are thought to be a damage to the nervous system microvasculature. However, the mechanism of this toxicity is poorly understood. Nitric oxide synthase (NOS) may be a target for lead and changes in its function can result in a cascade of pathophysiological effects that may be observed in isolated capillaries and synaptosomes. We have determined the concentration of lead in blood, capillaries and synaptosomes in brain from mice receiving 0, 250, 500, and 1000 ppm of lead for 14 days, through the drinking water. NOS activity was determined in the capillaries and synaptosomes by following the conversion of 3H-L-arginine to 3H-L-citrulline. The results show that blood lead levels were dose-dependent. Brain capillaries showed a preferential accumulation of lead as compared to synaptosomes. With all Pb treatments, synaptosomal constitutive NOS was inhibited (about 50% of control) while the inducible NOS activity in capillaries was enhanced. These data suggest that inhibition of cNOS activity and increase in iNOS may contribute to the Pb effects on the CNS.

Animals↗
PubMed1998

Relationship between peripheral estrogen concentrations at insemination and subsequent fetal loss in cattle.

In a survey on pregnancy rate and embryonic losses in dairy cattle on 6 Israeli farms, cows (n = 78) were divided into 3 groups on the basis of ultrasonography at 21 d post insemination; pregnancy diagnosis at 40 to 50 d post insemination and blood progesterone (P4) levels at 21 d. The groups were either pregnant (P4 level > 1.0 ng/ mL); not pregnant (P4 < 0.5 ng/mL), or showed early embryo loss (P4 > 1.0 ng/mL and the presence of an embryonic vesicle on D 21 but later returned to estrus or were found not pregnant on D 40 to 50). On the day of insemination, peripheral estrogen was significantly higher (P < 0.05) in the early embryo loss group (15.3 +/- 1.1 pg/mL, n = 27) than in pregnant (9.4 +/- 0.6 pg/mL, n = 26) or not pregnant (9.6 +/- 0.7 pg/mL, n = 25) group. The cows on 3 farms which were fed 1 to 2 kg/d of vetch (Vicia sativa), an estrogenic legume, had higher estrogen concentrations on the day of insemination than cows (2 farms) fed other legumes (13.7 +/- 0.64, n = 58 vs 10.7 +/- 0.8 pg/mL, n = 42; P < 0.01). On one of the 3 farms, vetch was replaced with alfalfa after the first year. Following the cessation of vetch feeding the estrogen concentrations in the blood decreased from 32 +/- 5 pg/mL to 14 +/- 2 pg/mL (n = 9). These data suggest that high peripheral estrogen on the day of insemination is associated with early embryonic loss. These data also indicate that estrogen concentrations on the day of insemination can be influenced by diet.

Abortion, Veterinary↗
PubMed1997

Exposure assessment for workers applying DDT to control malaria in Veracruz, Mexico.

DDT has systematically been used in sanitation campaigns against malaria in Mexico. To assess chronic occupational exposure, we studied a group of workers dedicated to spraying houses to control malaria vectors in the state of Veracruz. Exposure was directly estimated for a subgroup of 40 workers by measuring DDT metabolites in adipose tissue samples and indirectly estimated for 331 workers by using a questionnaire to determine their occupational history. Participants ranged in age from 20 to 70 years, and 80% of the workers had been employed in the sanitation campaign for at least 20 years. The mean concentrations of extractable lipids found in adipose tissue samples were as follows: total DDT, 104.48 micrograms/g; p,p'-DDE, 60.98 micrograms/g; p,p'-DDT, 31.0 micrograms/g; o,p'-DDT, 2.10 micrograms/g; and p,p'-DDD, 0.95 microgram/g. The DDT metabolite p,p'-DDE was selected as the indicator of chronic exposure. An index of chronic occupational exposure was constructed according to worker position and based on the historical duration and intensity of DDT application. A linear model including this index, the use of protective gear, and recent weight loss explained 55% of the variation of p,p'-DDE concentrations in adipose tissue. By this model, the predicted values of p,p'-DDE concentration in adipose tissue for the 331 workers are between 9.56 micrograms/g and 298.4 micrograms/g of fat, with a geometric mean of 67.41 micrograms/g. These high levels of DDT in adipose tissue call for exposure prevention programs and the promotion of more secure application measures and hygiene. We also discuss the use of indirect measures of DDT exposure in epidemiological studies of health effects.

Adipose Tissue↗
PubMed1997

Aedes aegypti in Córdoba Province, Argentina.

In 1955, the area infested by Aedes aegypti in Argentina was estimated as 1,500,000 km2; and in 1963, the species was considered to be eradicated from Argentina. In 1995, the Argentine Ministry of Health reported reinfestation by Ae. aegypti. During 1994-95, the Ministry of Health of Córdoba Province, Zoonosis Department, established a surveillance system for Ae. aegypti in Córdoba Province, Argentina. This report is a summary of results obtained thus far. In total, 74 localities in Córdoba Province were sampled during August 1994-April 1996, resulting in 5 positives (6.7%): Villa María city, Villa Nueva, and Córdoba city in 1995, and Juarez Celman and Jesús María in 1996. In Villa María and Villa Nueva, Ae. aegypti was present until June 1995 (autumn) and reappeared in December 1995. In Córdoba city, Ae. aegypti was eliminated from the only positive house in May 1995, but it reappeared in March 1996. Reappearance of Ae. aegypti in this temperate area in early summer may have been due to the survival of individuals during winter and not to reintroduction during summertime. The last previous active surveillance for Ae. aegypti in Córdoba Province was carried out more than 30 years ago.

Aedes↗
PubMed1996

Organization of the origins of replication of the chromosomes of Mycobacterium smegmatis, Mycobacterium leprae and Mycobacterium tuberculosis and isolation of a functional origin from M. smegmatis.

The genus Mycobacterium is composed of species with widely differing growth rates ranging from approximately three hours in Mycobacterium smegmatis to two weeks in Mycobacterium leprae. As DNA replication is coupled to cell duplication, it may be regulated by common mechanisms. The chromosomal regions surrounding the origins of DNA replication from M. smegmatis, M. tuberculosis, and M. leprae have been sequenced, and show very few differences. The gene order, rnpA-rpmH-dnaA-dnaN-recF-orf-gyrB-gyrA, is the same as in other Gram-positive organisms. Although the general organization in M. smegmatis is very similar to that of Streptomyces spp., a closely related genus, M. tuberculosis and M. leprae differ as they lack an open reading frame, between dnaN and recF, which is similar to the gnd gene of Escherichia coli. Within the three mycobacterial species, there is extensive sequence conservation in the intergenic regions flanking dnaA, but more variation from the consensus DnaA box sequence was seen than in other bacteria. By means of subcloning experiments, the putative chromosomal origin of replication of M. smegmatis, containing the dnaA-dnaN region, was shown to promote autonomous replication in M. smegmatis, unlike the corresponding regions from M. tuberculosis or M. leprae.

Bacterial Proteins↗