PubMed Health⌕ Search

Biomedical subjects

C Rios

Publications and source records attributed to C Rios.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1996

Effects of pentoxifylline or dexamethasone in combination with amphotericin B in experimental murine cerebral cryptococcosis: evidence of neuroexcitatory pathogenic mechanisms.

In a murine model of intracerebral infection by Cryptococcus neoformans the therapeutic effects of pentoxifylline or dexamethasone were studied alone and in combination with amphotericin B. Assessed parameters were mean survival time, brain histopathology index, amounts of glutamate and gamma-aminobutyric acid in the brain, and yeast CFU per brain. Survival increased significantly in mice treated with dexamethasone, amphotericin B, amphotericin B plus dexamethasone, and amphotericin B plus pentoxifylline; the latter had significantly longer survival than other treated groups. Indices of histopathological damage were similar in all treated groups. In infected untreated mice, the amounts of glutamate in the brain were decreased, presumably by depletion. In mice treated with amphotericin B plus dexamethasone, glutamate levels returned to the range of control mice. No differences in the amounts of gamma-aminobutyric acid were found between control and treatment groups. Brain fungal counts were significantly lower in mice treated with amphotericin B, amphotericin B plus dexamethasone, and amphotericin B plus pentoxifylline than in untreated animals. In this model, pentoxifylline in combination with amphotericin B improved survival, decreasing the fungal burden, and has potential as adjuvant therapy in cerebral cryptococcosis.

Amphotericin B↗
PubMed1996

Blood lead levels in pregnant women of high and low socioeconomic status in Mexico City.

This study examined the determinants of blood lead (BPb) in 513 pregnant women in Mexico City: 311 from public hospital prenatal clinics, representing primarily women of low socioeconomic status (SES), and 202 from private hospitals, primarily women of high SES. Overall, BPb levels ranged from 1.38 to 29 micrograms/dl, with geometric means of 6.7 and 11.12 micrograms/dl for women from private and public hospitals, respectively. The crude geometric means difference obtained by t-test was 4.42 (p < 0.001). BPb was measured from January 1994 to August 1995 and showed higher levels during fall and winter and lower levels during spring and summer. The main BPb determinants were the use of lead-glazed ceramics in women from public hospitals and season of the year in women from private hospitals. Consumption of tortillas (corn bread rich in calcium) decreased BPb levels in the lower SES group, but the relationship was not statistically significant (p > 0.05). Consumption of milk products significantly (p < 0.05) reduced BPb levels in the higher SES group. In 112 women whose diets were deficient in calcium, taking calcium supplements lowered their blood lead levels about 7 micrograms/dl. A predictive model fitted to these data, using the strongest predictors plus gestational age, showed a difference of 14 micrograms/dl between the best and worst scenarios in women from public hospitals. Avoiding use of lead-glazed ceramics, consuming diets rich in calcium, and, if needed, taking calcium supplements, would be expected to result in substantial lowering of BPb, especially in pregnant women of low socioeconomic status.

Adolescent↗
PubMed1995

Depletion of copper and manganese in brain after MPTP treatment of mice.

The mechanism of action of MPTP, a parkinsonism-inducing drug has been related to trace metals as a result of the observed potentiation of the neurotoxic action of the drug when diethyldithiocarbamate is concurrently administered. Diethyldithiocarbamate is a well-known chelator of trace metals, particularly copper. In the present study we analyzed the concentrations of copper and manganese in four brain regions of mice treated with neurotoxic doses of MPTP, in order to further substantiate the relationship between trace metals of MPTP-induced neurotoxicity. Male Swiss albino mice were administered with MPTP (30 mg/kg) for either three or five days. Seven days after the last MPTP administration, they were sacrificed and the content of manganese and copper in the following regions was determined by graphite furnace atomic absorption spectrophotometry: cortex, cerebellum, midbrain and corpus striatum. Results indicate a significant depletion of manganese in corpus striatum (19.5% versus control) in the mice treated with MPTP for 5 days. Copper was also found to be decreased in corpus striatum (17.3% in mice treated for 3 days and 51.3% in mice treated for 5 days). Midbrain copper was depleted by 42.9% in the group of mice treated for 5 days with MPTP. Results indicate that MPTP induced a diminution of both copper and manganese in corpus striatum, suggesting that this alteration could be related to MPTP mechanism of action.

Animals↗
PubMed1995

Environmental urban lead exposure and blood lead levels in children of Mexico City.

Lead contamination is now a leading public health problem in Mexico. However, there are few data on the lead content of various environmental sources, and little is known about the contribution of these sources to the total lead exposure in the population of children residing in Mexico City. We conducted a cross-sectional study in a random sample of 200 children younger than 5 years of age who lived in one of two areas of Mexico City. Environmental samples of floor, window, and street dust, paint, soil, water, and glazed ceramics were obtained from the participants' households, as well as blood samples and dirt from the hands of the children. Blood lead levels ranged from 1 to 31 micrograms/dl with a mean of 9.9 micrograms/dl (SD 5.8 micrograms/dl). Forty-four percent of the children 18 months of age or older had blood lead levels exceeding 10 micrograms/dl. The lead content of environmental samples was low, except in glazed ceramic. The major predictors of blood lead levels were the lead content of the glazed ceramics used to prepare children's food, exposure to airborne lead due to vehicular emission, and the lead content of the dirt from the children's hands. We conclude that the major sources of lead exposure in Mexico City could be controlled by adequate public health programs to reinforce the use of unleaded gasoline and to encourage production and use of unleaded cookware instead of lead-glazed ceramics.

Adult↗
PubMed1994

Sources of lead exposure in Mexico City.

Many countries, including Mexico, are facing a largely unrecognized epidemic of low-level lead poisoning. Mexico is the sixth largest lead-producing country in the world, and 40% of its production is used locally in different industrial processes that cause lead contamination of the environment. The major sources and pathways of lead exposure among the Mexican population are gasoline emissions, lead-glazed ceramics, leaded paint, and lead in canned foods and beverages. In this paper we present evidence for the presence of lead in different environmental media and its impact on blood lead levels of the Mexican population. Although during the last few years important measures have been implemented to decrease lead exposure, our findings suggest that lead poisoning is still an important problem in Mexico. There is an urgent need for regulatory policies that implement stricter control to protect the Mexican population. There is also a need to develop adequate programs to reduce the lead burden and the associated health effects in the population that has been chronically exposed.

Ceramics↗
PubMed1994

Detrimental effects of malnutrition on the damage induced by alcoholism: a study of animal models that simulate chronic alcoholism and malnutrition of large human groups.

The specific influence of malnutrition on the pathophysiological changes induced by chronic alcoholism is controversial; most studies are inconclusive because they have been made in chronic alcoholics that develop malnutrition as a complication of alcoholism. However, in vast human groups, alcoholism evolves in individuals that belong to a chronically undernourished population. In an attempt to simulate real-life conditions of malnutrition-alcoholism in humans, we studied in rats: (1) the effects of chronic malnutrition with tortilla, a corn bread that constitutes the main diet of large human groups; (2) the effects of chronic alcoholism with commercial brandy; and (3) the effects of chronic alcoholism and malnutrition combined. The damage induced either by alcoholism or that induced by malnutrition alone were of similar degree, whereas the combination of malnutrition and alcoholism led to a worsening of some parameters studied: body weight, leucocyte count and, more remarkably, in the tissue damage of several areas of the central nervous system.

Alcoholism↗
PubMed1993

Increased striatal lipid peroxidation after intracerebroventricular MPP+ administration to mice.

Mice received different doses intracerebroventricularly of MPP+ (1-methyl-4-phenylpyridinium ion), the active metabolite of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), a drug which induces a Parkinson model in rodents. Two indexes of lipid peroxidation were monitored at different times after administration: 1) production of thiobarbituric acid-reactive substances and 2) formation of lipid fluorescence products. A regional-selective overproduction of thiobarbituric acid-reactive substances was observed in corpus striatum and midbrain, but not in frontal cortex, cerebellum nor hippocampus. Enhancement was 70% and 198% at 30 and 60 min. in striatum and 88% at 30 min. in midbrain, when compared with respective controls injected intracerebroventricularly with saline solution. MPP+ also induced lipid fluorescence products formation enhancement in corpus striatum. This increase was dose-dependent in the range of MPP+ doses which induced striatal dopamine depletion. Striatal LFP formation was found increased 24 hr after MPP+ administration (38% vs control), indicating long-lasting lipid peroxidation overproduction. These results suggest that lipid peroxidation might be involved in the neurotoxic effects of MPP+ in vivo.

1-Methyl-4-phenylpyridinium↗
PubMed1992

Ventricular injection of nerve growth factor increases dopamine content in the striata of MPTP-treated mice.

Experimental depletion of dopaminergic striatal neurons was induced in mice with the neurotoxin MPTP. To investigate a possible effect of nerve growth factor on the damaged neurons, we injected 4 micrograms into the right cerebral ventricle of mice three days after the last administration of MPTP. We found a significant increase of dopamine and homovanillic acid in the striatum of MPTP treated mice after NGF administration when compared with dopamine and HVA levels in MPTP-treated control mice (p less than 0.001). The increase of dopamine and homovanillic acid seems to be related to a partial restorative effect of NGF on the damaged dopaminergic cells, since ventricular administration of NGF to normal mice did not increase dopamine or homovanillic acid contents above the levels measured in untreated controls. It appears that administration of nerve growth factor produces a beneficial effect on damaged dopaminergic neurons; this effect could be due to stimulation of neuron sprouting from neurons that survived the toxic effect of MPTP. The increase of dopamine levels was seen 8 days after injection of nerve growth factor and was maintained at least until day 25, showing a lasting persistence of the restorative effect.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1992

Production of heterohybridomas secreting autoreactive and polyreactive human monoclonal antibodies.

Peripheral blood lymphocytes from two polytransfused renal dialysis patients were transformed by Epstein-Barr virus, fused to a heteromyeloma and cloned. Eight human monoclonal antibodies from the resulting clones were tested for their binding to a variety of antigens by ELISA, indirect immunofluorescence and immunoblotting. Antigens tested included B-cell lines, T and B lymphocytes, red blood cells, chronic lymphocytic leukaemic B cells, IgG, ssDNA, dsDNA, histones, nucleoprotamine, sperm nuclei, thymus and spleen extracts, MOLT4 cell lysates, affinity purified autoantigens, tetanus toxoid, bacterial lipopolysaccharide, insulin, and a tissue section screen. These human monoclonal antibodies reacted with more than one antigen to varying degrees and were autoreactive and polyreactive. One of these heterohybridoma cell lines exhibited cytoplasmic staining with an anti-CD5 monoclonal. Our findings support the concept that in adult individuals a subset of B cells produce heterogeneous IgM antibodies which can bind to a variety of different autoantigens and also to foreign antigens. These monoclonals were different from the autoantibodies usually seen in renal dialysis patients in the sense that they were not lymphocytotoxic.

Antibodies↗