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Biomedical subjects

M Hernandez

Publications and source records attributed to M Hernandez.

At least 109 records · Page 6Linked to original sources
PubMed1992

Air pollution and school absenteeism among children in Mexico City.

To determine the acute effects of ozone exposure, the authors conducted a short follow-up study of respiratory illness in a population of 111 preschool children frequently exposed to ozone levels that regularly exceed 0.120 parts per million (ppm). The children attended a private kindergarten in the southwestern part of Mexico City. Parents completed a questionnaire on demographic data, medical history, and potential sources of indoor air pollution. To determine the relation of ozone and respiratory-related school absenteeism, the authors used a logistic regression model for longitudinal data. During the 3-month follow-up, 50% of the children had at least one respiratory-related absenteeism period, and 11.7% had two or more. Children exposed for 2 consecutive days to high ozone levels (> or = 0.13 ppm) had a 20% increment in the risk of respiratory illness. For children exposed for 2 consecutive days to a high ozone level and the previous day to low temperature (< or = 5.1 degrees C), the risk reached 40% (odds ratio = 1.44, 95% confidence interval 1.37-1.52). This study suggests that ozone exposure might be positively associated with the risk of respiratory illness in children and that it may have an interactive effect with low temperature exposure.

Absenteeism↗
PubMed1992

Magnetic resonance diffusion imaging detects structural damage in biological tissues upon hyperthermia.

The use of quantitative nuclear magnetic resonance (MR) imaging to investigate the extent and mechanism of hyperthermic damage in biological tissues has been studied. By using the multiple delay-multiple echo and pulsed-gradient spin echo MR imaging sequences, multiple frame MR images of freshly harvested rabbit tissues (brain, kidney, and muscle) and intact duck embryos in shells were obtained before and after heat treatment (45 degrees C for 30 min) using a clinical 1.5-Tesla whole-body superconducting MR scanner. Based on the relaxation and diffusion models, maps of the proton spin density, relaxation times, and various self-diffusion parameters of tissue water were generated from these multiple frame MR images. Our results indicated that the values of the diffusion barrier size and fractal parameter of the tissues and the self-diffusion coefficient of tissue water increased significantly, i.e., approached that of free water, after the heat treatment. In comparison, only slight changes in the spin density and relaxation times of the tissue water were found after the identical heat treatment. We concluded that the significant changes in the self-diffusive behavior of the tissue water are due to the denaturation of macromolecules (e.g., protein and fiber) within the tissues at elevated temperatures. We further suggested that MR diffusion imaging represents a powerful tool to investigate the extent and mechanism of heat damage of biological tissues in vivo and therefore bears important potential in the clinical assessment of the therapeutic efficacy of hyperthermia in cancer therapy.

Animals↗
PubMed1992

Sexual behavior and status for human immunodeficiency virus type 1 among homosexual and bisexual males in Mexico City.

The authors examined sexual behaviors, the seroprevalence of human immunodeficiency virus type 1 (HIV-1), and condom use among 2,314 homosexual and bisexual men tested during 1988-1989 at the AIDS (acquired immunodeficiency syndrome) National Center in Mexico City. Bisexuals constituted 24% of the sample; the seroprevalence rate was lower for bisexuals than homosexuals (21 vs. 34%). In logistic regressions, HIV-1 seropositivity was independently related to age, education, pattern of insertive/receptive behavior in anal sex, lifetime number of male sex partners, having sex with someone with AIDS, homosexual versus bisexual behavior, and a history of condyloma. The same logistic regressions were found to fit bisexuals and homosexuals. The rate of HIV-1 was reduced in individuals who indicated always requiring their partners to use a condom when practicing receptive anal sex (1% of the total). The most common practice for both homosexuals and bisexuals was "mixed" behavior (i.e., both insertive and receptive anal sex); this was also the practice with the highest risk. Bisexuals practiced both vaginal and anal sex with women and reported little condom use. The substantial seroprevalence among bisexuals, their frequent sexual contact with women, and their low rate of condom use imply a continuing role as a bridge of infection to females. Whether this risk will lead to a sustained heterosexual epidemic remains to be determined.

Adolescent↗
PubMed1992

Cross-cultural perspectives and codependence: the case of poor Hispanics.

Codependence treatment is considered in relation to the cultural narrative embedded in the concept and in light of the values, particularly those of family orientation, characteristic of the poor Hispanic population. Case examples illustrate the need to review the codependence model in sociocultural terms for effective use with poor Hispanic clients.

Adaptation, Psychological↗
PubMed1991

Cadmium and nickel modulation of adherence capacity of murine peritoneal macrophages and lymphocytes. Intersexual comparisons.

1. Cadmium and nickel are common environmental toxicants that alter the immune response. 2. Cellular adherence is a crucial immune response, but little is known about it. 3. In the present paper we investigated the effect of CdCl2 and NiCl2 on the early (10 min) and late (45 min) adherence of peritoneal cells from male and female mice. 4. Adherence of macrophages is markedly higher than lymphocytes. Cells from female generally adhere to a greater extent than those from male. 5. The effect of either metal, when noticeable, results in an adherence enhancement which is higher, at 10 min in lymphocytes, in male peritoneal cells and when exerted by Ni.

Animals↗
PubMed1991

Alpha- and beta-adrenoceptors in the sheep urinary bladder.

A study was undertaken to determine the presence and distribution of alpha- and beta-adrenoceptors in the sheep bladder body and base. In the bladder body, noradrenaline and isoproterenol induced relaxation which was significantly inhibited by propranolol, pafenolol and butoxamine. In the presence of propranolol (10(-5) M), noradrenaline induced a small contraction, as well as phenylephrine, but B-HT 920 failed to cause any effect on the bladder body. In the bladder base, noradrenaline caused a contraction that was significantly inhibited by prazosin but not by yohimbine. Phenylephrine also induced a contractile response in this structure which was inhibited by prazosin. Isoproterenol caused a relaxation that was significantly inhibited by propranolol and pafenolol but not by butoxamine. Relaxation was mediated by both beta 1 and beta 2-adrenoceptors in the detrusor muscle and by beta 1-adrenoceptors in the bladder base. Alpha 1-adrenoceptors contributed to maintain the detrusor tone and contract the bladder base.

Adrenergic beta-Antagonists↗
PubMed1991

Maternal ethanol ingestion and somatostatin level and binding in developing rat brain.

The effect of maternal ethanol ingestion on 125I-labeled [Tyr11]somatostatin (SS) binding and somatostatin-like immunoreactivity (SLI) in the rat frontoparietal cortex and hippocampus of developing offspring was explored. Female Sprague-Dawley rats were given ethanol in the drinking water before pregnancy, during gestation, and while nursing, whereas controls received a standard diet and fresh water ad libitum. In the ethanol group, food intake decreased as ethanol consumption augmented, with the ethanol calories comprising greater than 30% of the total energy intake during pregnancy. Total energy intake was similar for the ethanol group and normal controls. Maternal alcohol ingestion is associated with an enhanced SLI level in the frontoparietal cortex and hippocampus on the day of birth. This study provided evidence of a selective decrease in SS receptor binding in frontoparietal cortex but not in hippocampus in the 0- to 10-day-old offspring of the ethanol-fed rats. The SS receptor number increased from day 0 to 10 in both control and ethanol groups. However, the affinity appeared to decrease significantly in the ethanol group during this period. At day 30, no differences were found between offspring of control and ethanol-treated rats in any of the parameters. These results suggest that the development of SS receptors in the rat frontoparietal cortex can be transitorily delayed by maternal ethanol ingestion.

Animals↗
PubMed1990

The Ventura Planning Model: a proposal for mental health reform.

The Ventura Planning Model is a proposal for public mental health reform. It addresses the decline in mental health funding. It offers a rationale for increased support--and funding--for public mental health services. The Planning Model grew out of the experience of implementing and operating the Ventura Children's Demonstration Project. The model has five characteristics, or planning steps: 1) multi-problem target population; 2) systems goals; 3) interagency coalitions; 4) services and standards; and 5) systems monitoring and evaluation. The Ventura Children's Demonstration Project implemented these planning steps, with an infusion of $1.54 million in funds from the state legislature. The project offset at least 66 percent of its cost by reducing other public agency costs and improved a variety of client-oriented outcomes. The success of the project in offsetting its costs has led the legislature to provide additional funds for three more California counties to implement the model for children and youth, and $4 million a year for four years for Ventura County to test the model for adults and seniors. Emphasizing cost offsets in addition to client-oriented outcomes provides a practical rationale for proposing increases in public mental health funds. This rationale also implies substantial changes in the operations of many public mental health agencies.

Adolescent↗
PubMed1990

Morphine inhibition of lymphocyte activity is mediated by an opioid dependent mechanism.

The effects of acutely-administered morphine on mitogen stimulated lymphocyte proliferation and natural killer cell cytolytic activity were investigated. Two hours after a subcutaneous injection of morphine (25 mg/kg), blood lymphocyte proliferation was found to be 70% depressed, compared to saline-injected controls. This effect was partially antagonized in animals pretreated with naltrexone (10 mg/kg) and was present only in blood lymphocytes, since proliferative responses of splenic lymphocytes were not significantly altered. The administration of morphine, however, did result in a 30-40% inhibition of cytolytic activity of natural killer cells, which was completely antagonized in naltrexone-pretreated animals. Naltrexone alone was found to have no effect on either proliferation of blood and splenic lymphocytes or the cytolytic activity of splenic lymphocytes. Although naltrexone had no effect on the activity of lymphocytes, animals treated with either naltrexone or morphine alone, or their combination, had 4- to 8-fold increases in corticosterone in plasma. These results demonstrate that the effect of morphine on immune cells was dependent on the tissue source of lymphocytes. Furthermore, the suppression of blood lymphocyte proliferation and splenic cytolytic activity of natural killer cells by morphine was opiate receptor-mediated, as indicated by the reversibility by naltrexone of the observed effects of morphine. Finally, the accompanying increase in circulating levels of corticosterone most likely did not contribute to these effects.

Animals↗
PubMed1990

Isolation and characterization of a lectin from the seeds of Dioclea lehmanni.

Affinity chromatography of the globulin fraction from the seeds of Dioclea lehmanni on Sephacryl S-200 yielded two lectins, one slightly retarded and another strongly bound. The latter, which was a glucose/mannose specific lectin, was purified and the following properties were determined: pI, Mr of subunits, carbohydrate content, A, aminoacid composition, hemagglutination and inhibition patterns, N-terminal sequence and mitogenic activity. These properties of the lectin were very similar to those of the Con A and Dioclea grandiflora lectins.

Amino Acids↗
PubMed1990

Food predictors of plasma beta-carotene and alpha-tocopherol: validation of a food frequency questionnaire.

Nutrient intakes from a food frequency questionnaire are usually calculated as the product of frequency of intake and nutrient composition of the food, summed over the food items. This involves assumptions about the accuracy of recording, food composition data, stability during storage and preparation, and bioavailability. This usual method of calculation was compared with one using empirical weights derived by multivariate linear regression. Food intakes reported on a food frequency questionnaire by Boston, Massachusetts, area subjects in 1982-1985 were used to predict plasma levels of beta-carotene among 370 male and female nonsmokers and plasma levels of alpha-tocopherol among 339 male and female nonusers of vitamin supplements. Nutrient intake computed using empirical weights yielded a significant correlation with plasma beta-carotene (r = 0.43, p = 0.0001), similar to the correlation using nutrient intake calculated from food composition tables (r = 0.38, p = 0.0001). However, the use of empirical weights significantly improved the correlation of vitamin E intake with plasma alpha-tocopherol levels (r = 0.32, p = 0.0001), compared with the weak correlation obtained using the food composition table method to calculate intake (r = 0.16). The results support the validity of published food composition data used to compute carotenoid intake and illustrate the potential utility of empirically derived weights for foods to predict plasma levels of some nutrients.

Adolescent↗
PubMed1990

Mitochondrial DNA variation and genetic structure in Old-World populations of Drosophila subobscura.

To discover the relation between mitochondrial DNA (mtDNA) polymorphism and the geographic population structure of Drosophila subobscura previously established for other genetic traits, a wide Paleartic survey was carried out. A total of 24 nucleomorphs was observed among 261 isofemale lines assayed by 11 restriction endonucleases with 38 different sites in the mtDNA cleavage map. The differentiation of the Canary Islands populations (delta = 0.0119) compared with the mean among all the other continental and insular populations (delta = 0.0002) is striking. Both the great divergence among Canary Islands nucleomorphs (delta = 0.021) compared with the maximum nucleomorph distance in all other populations (delta = 0.017) and the abundance of endemic nucleomorphs (11) on the Canary Islands (50% of the total number of different nucleomorphs found in the entire distribution area) suggest that this molecular differentiation most probably results from the very old age of the Canary Islands populations rather than from drift and founder effects.

Animals↗
PubMed1990

HLA haplotype segregation in families with allergic asthma.

In order to evaluate genetic linkage between Allergic Asthma (AA) and the HLA system, we studied 20 families having AA affected sib pairs and 8 families with Intrinsic Asthma (IA) affected sib pairs. All AA patients had a strong IgE immune response to the mite D. farinae. Serological HLA typing (A, B, C, DR, and DQ antigens) was performed by the standard microcytotoxicity assay. Genetic analysis was made by means of the "Affected sib pairs" method. Out of the 20 affected sib pairs, 14 shared two HLA haplotypes, five shared one HLA haplotype and one was HLA-non-identical. These results differed significantly from the random ratio 1:2:1 for sharing, 2, 1 or 0 haplotypes (p less than 0.0001), and was very close to that expected for a recessive mode of inheritance. In contrast, among the IA sib pairs there was not an important distortion in the pattern of haplotypes segregation. However, a significant association between any of the HLA alleles and the two types of Asthma studied was not found. The results suggest the existence of an HLA-linked recessive gene controlling the IgE immune responsiveness to mite allergens and conferring susceptibility to AA.

Asthma↗