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Biomedical subjects

C E Castro

Publications and source records attributed to C E Castro.

At least 19 recordsLinked to original sources
PubMed1999

DNA strand breaks caused by exposure to ozone and nitrogen dioxide.

The present study demonstrates that exposure to ozone (O3) and nitrogen dioxide (NO2) can cause DNA single-strand breaks in alveolar macrophages. Three-month-old male Sprague-Dawley rats, specific pathogen free, were exposed to either 1.2 ppm NO2 or 0.3 ppm O3 alone or a combination of these two oxidants continuously for 3 days. The control group was exposed to filtered room air. The oxidant effects were substantiated by determining total and differential cell counts, lactate dehydrogenase activity, and total soluble protein in bronchoalveolar lavage. DNA damage was measured as single-strand breaks by alkaline elution assay. The results showed that, relative to control, NO2 exposure did not cause any significant change in the parameters studied. Exposure to O3 and combined exposure to NO2 and O3 caused significant changes in all parameters studied except cell viability. The rates of elution (Kc) of single-strand DNA from polycarbonate filter for O3 exposure and combined exposure were 73 and 79% faster than that of the control, respectively. The amounts of DNA single-strand breaks caused by O3 and combined exposure were significantly greater than the amounts detected for the NO2-exposed and control groups.

Animals↗
PubMed1998

Environmental dehalogenation: chemistry and mechanism.

The halogen cycle is one of the great chemical cycles on earth. Haloorganics are both synthesized and destroyed by the chemistry that controls their flux and form. The synthetic leg of the cycle is both biotic and abiotic in nature. The biotic synthesis results primarily from the biochemical activity of marine algae and kelp, although these are by no means the only sources. The abiotic process is vested in large part in volcanic eruption and emission of gases synthesized as a thermal consequence of venting the earth's core.

Biodegradation, Environmental↗
PubMed1997

Ozone-induced DNA strand breaks In guinea pig tracheobronchial epithelial cells.

Ozone (O3), the major oxidant of photochemical smog, is thought to be genotoxic and a potential respiratory carcinogen or promoter of carcinogenic processes. Because of oxidative reactions with the mucus in the upper airway, O3 reaction products are able to penetrate into the tracheobronchial epithelial (TE) cells. The carcinogenic effects of O3 on the TE cells are especially of interest since most previous studies have focused on the morphology or permeability changes of tracheas only. Therefore, the objective of this study was to examine the potential O3 genotoxicity in TE cells after an in vivo exposure, using DNA strand breaks as an index. Two-month-old male Dunkin-Hartley guinea pigs, specific pathogen free, 4 in each group, were exposed to 1.0 ppm O3 for 0, 12, 24, 48, 72, or 96 h. Animals exposed to filtered air without O3 exposure were used as controls. After O3 exposure, the trachea with two main bronchi was removed from each animal, and TE cells were isolated and employed for determination of DNA strand breaks by fluorometric analysis of DNA unwinding (FADU). The statistical significance level was set at alpha = .05. Compared with controls, ozone exposure did not alter the TE cell yield or viability, but caused an increase in protein content in tracheal lavage and an increase in DNA strand breaks. The amount of DNA left in the alkali lysate of TE cells found at 72 h exposure was significantly decreased from controls for 3 different alkali incubation times. An increase of the double-stranded DNA left in the alkali lysate of TE cells was observed at 96 h of exposure and approached the value of 24 h of exposure. The same pattern was seen with all 3 different alkali incubation times at 15 degrees C. One Qd unit was estimated to correspond to 100 strand breaks per cell. The Qd was also used as an indicator for O3 damage. Compared to controls, the Qd increases significantly after 1 ppm O3 exposure for 72 h, regardless of the alkali incubation time at 15 degrees C.

Animals↗
PubMed1996

Reactions of oxymyoglobin with NO, NO2, and NO2- under argon and in air.

Oxymyoglobin under argon reacts with NO2- and NO2 (N2O4) to produce metmyoglobin in a spectrally clean process with clear isosbestic points. In both cases, the reactant is NO2-. The second-order rate constant for NO2- or N2O4 is the same: d(Mb+)/dt = k(MbO2)(NO2-) where k = 0.21 +/- 0.02 L mol-1 S-1. The reaction of MbO2 with NO under argon is a complex process and entails the generation of Mb+ and OONO- (peroxynitrite) in the first step. The latter (lambda MAX, 302 nm) was poorly resolved from more intense protein absorption in the 300-nm region. However, at pH 9, the change in absorbance corresponded exactly to a quantitative production of the OONO-ion. Hydroxy radicals from it were trapped with ethylene-1, 2-(13) C. The initial step is followed in sequence by the rapid formation of MbNO+. The iron(III)-nitrosyl adduct hydrolyzes slowly to MbII and NO2- (k = 8.0 +/- 0.8 x 10(-5) S-1. MbII then rapidly associates with NO, and MbNO is the final product of this reaction. Oxymyoglobin is inert to NO3-. In contrast to the results under argon, in air the reactions of MbO2 with NO2-, NO, and NO2 (N2O4) all proceed in the same autocatalytic fashion with kAVE (for the autocatalytic rates) approximately equal to 9 +/- 5 L mol-1 s-1. Nitrite is the initial reactant in all cases. Isosbestic points are not observed in the visible spectrum, and additional porphyrin iron-ligated species are intermediates. Based upon work with iron porphyrins.

Air↗
PubMed1991

Primary health services in Ecuador: comparative costs, quality, and equity of care in Ministry of Health and rural social security facilities.

This study of costs, quality and financial equity of primary health services in Ecuador, based on 1985 data, examines three assumptions, common in international health, concerning Ministry of Health (MOH) and Social Security (SS) programs. The assumptions are that MOH services are less costly than SS services, that they are of lower quality than SS services, and that MOH programs are more equitable in terms of the distribution of funds available for PHC among different population groups. Full costs of a range of primary health services were estimated by standard accounting techniques for 15 typical health care establishments, 8 operated by the MOH and 7 by the rural SS program (RSSP), serving rural and peri-urban populations in the two major geographical regions of Ecuador. Consistent with the conventional premise, MOH average costs were much lower than RSSP costs for several important types of services, especially those provided by physicians. Little difference was found for dental care. The lower MOH physician service costs appeared to be attributable primarily to lower personnel compensation (only partially offset by lesser productivity) and to greater economies of scope. Several measures of the quality of care were applied, with varying results. Based on staff differences and patterns of expenditures on resource inputs, notably drugs, RSSP quality appeared higher, as assumed. However, contrary to expectation, a questionnaire assessment of staff knowledge and procedures favored the MOH for quality. Program equity was judged in terms of per capita budgeted expenditures (additional measures, such as the likelihood of receiving necessary care, would have required household survey data beyond the scope of this program-based study). The results support the assumption of greater MOH financial equity, as its program reveals less variation in budgeted expenditures between different population groups covered. Additional evidence of equity, using other indicators, would be helpful in future research. The paper's findings have policy implications not only for Ecuador's health sector but also for policy-makers in other countries at similar levels of socioeconomic development. These implications are spelled out in order to guide officials wrestling with issues of efficiency, quality, and equity as they search for the best use of scarce resources to promote health.

Costs and Cost Analysis↗
PubMed1991

[Primary health care in Ecuador: services provided by the Ministry of Health and Rural Social security Services].

The present study will examine three common premises in the field of international public health: that the primary care services offered by agencies of the Ministries of Health (MH) are less costly than those offered by Social Security institutions, that the former services are inferior to the latter, and that funds are distributed more equitably by the MH centers among their various recipient populations. The 1986 study compared the costs, quality, and equity of the services in 15 primary care centers in Ecuador--eight Ministry of Health centers and seven rural Social Security (RSS) centers--examining budgetary data from 1985 and obtaining information through a questionnaire and interviews with the personnel at those centers. Average costs were calculated by standardized accounting techniques, and it was confirmed that for several important services, especially medical consultations, these costs were much lower in the Ministry centers than in the Social Security centers. However, no differences in the cost of dental care were detected. The evaluation of quality, based on an analysis of the production structure and process, did not yield uniform results. On the one hand, the distribution of personnel and the allocation of funds for drugs and other supplies indicated that the RSS agencies provided better quality services. On the other hand, a questionnaire revealed that the MH health workers' knowledge of various principles of primary care was superior to that of the RSS workers. Upon comparing the per capita budget of the two types of entities, it was confirmed that the Ministry of Health had more equitable per capita coverage than rural Social Security. The implications of these findings for Ecuador and other developing countries are discussed and several recommendations made.

Costs and Cost Analysis↗
PubMed1986

Diet-mediated alteration of chromatin structure.

Higher-order chromatin structure and the process of transcription are related. The significance of a nutritional state's altering chromatin structure lies in the potential role of that nutritional state in the regulation of gene expression. In rats short-term feeding of semisynthetic diets varying in the proportion of carbohydrate, protein, or fat alters the configuration of liver chromatin as measured by sensitivity to micrococcal nuclease (EC 3.1.31.1). A carbohydrate-rich, fat-free diet increases the sensitivity of rat liver chromatin to micrococcal nuclease and decreases the nucleosome repeat length. In contrast, a protein-free diet or a diet deficient in magnesium or zinc decreases the sensitivity of liver nuclear chromatin to micrococcal nuclease. Diet-mediated mechanisms that alter chromatin structure are now unknown, but the continued study of nutritional interaction with the genome should identify the responsible features as well as their significance to gene function.

Animals↗
PubMed1985

Biodehalogenation: reactions of cytochrome P-450 with polyhalomethanes.

The products, stoichiometry, and kinetics of the oxidation of the enzyme cytochrome P-450 cam by five polyhalomethanes and chloronitromethane are described. The reactivity of the enzyme is compared with that of deuteroheme and with the enzyme in its native cell, Pseudomonas putida (PpG-786). In all cases, the reaction entails hydrogenolysis of the carbon-halogen bond: 2FeIIP + RCXn----2FeIIIP + RCHXn-1 (P = porphyrin or P-450 cam in vitro and in vivo). Trichloronitromethane was the fastest reacting substrate, and chloroform was the slowest. The results establish that P. putida is a valid whole cell model for the reductase activity of the P-450 complement in these reactions. The reactions of cytochrome P-450 with polyhaloalkanes proceed in a manner quite analogous to other iron(II) proteins in the G conformation. The chemistry observed for the enzyme parallels that of its iron(II) porphyrin active site. Iron-bonded carbenes are not intermediates, and hydrolytically stable iron alkyls are not products of these reactions.

Carbon Monoxide↗
PubMed1985

Nevoid malignant melanoma.

Primary cutaneous malignant melanomas with histological features suggestive of benign nevocytic nevi were studied. From a total of about 3,500 cases, 33 patients with sufficient records, histological slides, and follow-up (at least 5 years for disease-free cases) were found; 15 of them had developed metastases, and 8 had died of disseminated melanoma. Some of the following histological characteristics were always observed: cellular atypia, mitoses, infiltration of adnexa, and in the deeper dermis, infiltrative growth, pigmented tumor cells, sharply demarcated tumor nests, and the absence of maturation. Tumor thickness was the most important prognostic criterion. Clinically, the tumors corresponded to nodular and superficial spreading melanomas. It is concluded that, in rare instances, malignant melanomas strongly resemble benign melanocytic/nevocytic nevi. Such cases do not appear to have a lower degree of malignancy and should be treated as normal malignant melanomas.

Adult↗
PubMed1985

Hepatic level of rat albumin messenger RNA is influenced by factors other than dietary protein.

Dot hybridization of messenger RNA (mRNA) and complementary DNA (cDNA) has been used to measure the relative levels of albumin and alpha-fetoprotein mRNA in liver of rats fed for 5 d a fat-free (carbohydrate-rich) diet, a high fat diet or a basal diet, all three of which were isonitrogenous. The level of albumin mRNA in rats fed the fat-free (carbohydrate-rich) diet was 30 to 45% of the level in animals fed the basal 4% fat diet. The concentration of another mRNA, that for alpha-fetoprotein, remained unchanged. It has been established by others that albumin mRNA levels and albumin synthesis are diminished in response to low levels of dietary protein. We show that albumin mRNA levels are lower than those observed in animals fed the basal 4% fat diet, even when dietary protein is adequate (30% wt/wt), if the nonprotein calories are derived solely from carbohydrate.

Albumins↗
PubMed1984

Frequency and sequence complexity of liver poly(A)+ mRNAs from rats fed fat-free or high fat diets.

We demonstrate by messenger RNA (mRNA) . complementary DNA (cDNA) hybridization that nutrient variation can alter 1) the frequency in which entire classes or families of liver polyadenylated mRNAs [poly(A)+ mRNAs] are present within the cell and 2) the sequence complexity of those transcripts. Feeding a carbohydrate-rich, fat-free diet to rats for 5 days resulted in an increased sequence complexity of rare and moderately abundant liver poly(A)+ mRNAs when compared with poly(A)+ mRNA from rats fed high fat or basal diets. In addition, the frequency of reiteration of abundant sequences increased approximately 10 times compared with the abundant poly(A)+ mRNAs of rats fed high fat or basal diet. The results indicate that the functionality of the template is influenced by nutrient concentrations and may be one means by which complex organisms achieve homeostasis.

Animals↗
PubMed1983

Nucleosomal repeat length in rat liver nuclei is decreased by a high carbohydrate, fat-free diet.

Liver nuclei of Sprague-Dawley rats fed a high carbohydrate, fat-free diet (diet 1), a low carbohydrate, protein-free diet (diet 2), or a commercial stock diet were purified and mildly incubated with micrococcal nuclease (MN) (EC 3.1.4.7) until 5-6% of the chromatin was acid-soluble. Chromatin fragments generated by MN incubation were deproteinized and sized by electrophoresis. The mobilities of the DNA fragments were used to calculate by two independent methods nucleosomal repeat length. The nucleosome is the fundamental packaging unit of eucaryotic chromatin. When nuclei were incubated with MN for various lengths of time, the nucleosome repeat length for rats fed diet 1 was invariably shorter than that for stock diet-fed rats regardless of method of calculation. After incubation with MN for 10 minutes, the nucleosome repeat length of nuclei from rats fed diet 2 was virtually identical to that for stock diet-fed rats. In addition, after a 30-minute incubation, 32.4% of chromatin from nuclei of rats fed a lipogenic diet was of mononucleosome size, whereas only 9.9% and 20.6% was of the same size in nuclei of rats fed diet 2 or stock diet, respectively. These observations suggest that liver chromatin of rats fed a lipogenic diet may be in a different configuration than that from rats fed diet 2 or stock diet.

Animals↗
PubMed1983

Modification of polycarbonate cages for individual housing of mice.

Polycarbonate cages were modified with clear plastic dividers so that up to four mice could be housed individually in one cage with ad libitum access to feed and water. The method used commercially available components and was applicable for use in any study when it was necessary to keep mice separate for an extended period of time.

Animal Husbandry↗
PubMed1982

Analysis of rat liver chromatin and nuclear proteins after nutritional variation 1,2.

Chemical composition of liver chromatin was determined for rats fed a complete stock diet, or a diet lacking protein or fat. High carbohydrate, fat-free (diet 1) and low carbohydrate, protein-free (diet 2) diets were selected because they elicit structural alteration in chromatin as measured by incubation with micrococcal nuclease (E.C. 3.1.4.7). In the present study, either dietary treatment caused an increase in mass ratios of RNA:DNA and nonhistone:DNA, relative to control ratios. The nonhistone-DNA ratios in liver of rats fed diet 1 or diet 2 were 2.4-fold and 3.5-fold, respectively, larger than control ratios. The histone:DNA ratio remained relatively constant among all three dietary treatments. Liver nuclei were purified from rats fed each dietary treatment and were solubilized in 9 M urea. The nuclear proteins were analyzed by two-dimensional electrophoresis and visualized with a silver treatment that stains proteins in color. The electrophoretograms presented show preferentially proteins with low molecular weights and acidic pIs, two characteristics of nonhistones. The two-dimensional protein patterns are nearly identical for nuclear proteins from all three treatments. Analysis of the electrophoretograms indicates that the diet-induced increased nonhistone:DNA ratios are apparently not attributable to new species of protein, but rather to increased relative abundance of many proteins in the existing populations.

Animals↗
PubMed1980

Alteration of higher order structure of rat liver chromatin by dietary composition.

The higher order structure of rat liver chromatin from nuclei of animals fed stock or semi-synthetic diets for 5 days was investigated by a specific enzymatic probe, micrococcal nuclease (EC 3.1.4.7). Micrococcal nuclease digests 50% of DNA in eukaryotic chromatin into acid-soluble nucleotides while 50% of the DNA is resistant to digestion because of associated nucleoproteins. This selective digestion of DNA reflects higher orders of structure of the universal chromatin subunit, the nucleosome, found in lower eukaryotes, plants and animals. When rats were fed a commercial stock diet, 50.3% of the DNA in liver chromatin was digested by micrococcal nuclease. However, when rats were fed various semi-synthetic diets, the amount of DNA susceptible to micrococcal nuclease digestion varied as a function of diet (P less than 0.0001). Differences in the amount of DNA susceptible to micrococcal nuclease ranged from 71.4% for chromatin of rats fed a high carbohydrate/fat-free diet to 38.8% for chromatin of those fed a low carbohydrate/protein-free diet. DNA fragments generated by brief micrococcal nuclease digestion were analyzed by electrophoresis on 2.5% polyacrylamide--0.5% agarose gels. Chromatin from rats fed the high carbohydrate/fat-free diet was more rapidly digested to the monomer nucleosomin-free diet. To our knowledge, these diet-induced alterations in the higher order structure of chromatin are the first to be reported as occurring by in vivo modulation.

Animals↗