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PubMed1992

Tektite-bearing, deep-water clastic unit at the Cretaceous-Tertiary boundary in northeastern Mexico.

The hypothesis of Cretaceous-Tertiary (K-T) boundary impact on Yucatán, Mexico, predicts that nearby sites should show evidence of proximal impact ejecta and disturbance by giant waves. An outcrop along the Arroyo el Mimbral in northeastern Mexico contains a layered clastic unit up to 3 m thick that interrupts a biostratigraphically complete pelagic-marl sequence deposited at more than 400 m water depth. The marls were found to be unsuitable for determining magnetostratigraphy, but foraminiferal biostratigraphy places the clastic unit precisely at the K-T boundary. We interpret this clastic unit as the deposit of a megawave or tsunami produced by an extraterrestrial impact. The clastic unit comprises three main subunits. (1) The basal "spherule bed" contains glass in the form of tektites and microtektites, glass spherules replaced by chlorite-smectite and calcite, and quartz grains showing probable shock features. This bed is interpreted as a channelized deposit of proximal ejecta. (2) A set of lenticular, massive, graded "laminated beds" contains intraclasts and abundant plant debris, and may be the result of megawave backwash that carried coarse debris from shallow parts of the continental margin into deeper water. (3) At the top, several thin "ripple beds" composed of fine sand are separated by clay drapes; they are interpreted as deposits of oscillating currents, perhaps a seiche. An iridium anomaly (921 +/- 23 pg/g) is observed at the top of the ripple beds. Our observations at the Mimbral locality support the hypothesis of a K-T impact on nearby Yucatán.

Animals↗
PubMed1992

Proximal impact deposits at the Cretaceous-Tertiary boundary in the Gulf of Mexico: a restudy of DSDP Leg 77 Sites 536 and 540.

Restudy of Deep Sea Drilling Project Sites 536 and 540 in the southeast Gulf of Mexico gives evidence for a giant wave at Cretaceous-Tertiary boundary time. Five units are recognized: (1) Cenomanian limestone underlies a hiatus in which the five highest Cretaceous stages are missing, possibly because of catastrophic K-T erosion. (2) Pebbly mudstone, 45 m thick, represents a submarine landslide possibly of K-T age. (3) Current-bedded sandstone, more than 2.5 m thick, contains anomalous iridium, tektite glass, and shocked quartz; it is interpreted as ejecta from a nearby impact crater, reworked on the deep-sea floor by the resulting tsunami. (4) A 50-cm interval of calcareous mudstone containing small Cretaceous planktic foraminifera and the Ir peak is interpreted as the silt-size fraction of the Cretaceous material suspended by the impact-generated wave. (5) Calcareous mudstone with basal Tertiary forams and the uppermost tail of the Ir anomaly overlies the disturbed interval, dating the impact and wave event as K-T boundary age. Like Beloc in Haiti and Mimbral in Mexico, Sites 536 and 540 are consistent with a large K-T age impact at the nearby Chicxulub crater.

Animals↗
PubMed2000

Pica during pregnancy in low-income women born in Mexico.

OBJECTIVE: To describe pica behavior (ingestion of nonfood items) in pregnant low-income Mexican-born women in Mexico and the United States. DESIGN: A convenience sample of informants was interviewed with a questionnaire containing open-ended and closed-ended questions. SETTING: A low-income community on the outskirts of Ensenada, Mexico, and clinics serving low-income people in southern California (Santa Ana, Bakersfield, and Los Angeles). PARTICIPANTS: Of a total of 225 Mexican-born women, 75 (33%) were interviewed in Ensenada, and 150 (67%) were interviewed in southern California. RESULTS: The prevalence of pica during pregnancy was 44% (n = 33) in the Ensenada group and 31% (n = 46) in the southern California group. Those who reported pica behavior more commonly had a relative who also practiced pica. CONCLUSION: The high reported rate of pica in this sample indicates that pregnant Mexican-born women should be screened for pica and educated about the potentially serious effects on the fetus and mother.

Adolescent↗
PubMed2002

Childhood injury prevention practices by parents in Mexico.

OBJECTIVE: Scientifically based injury prevention efforts have not been widely implemented in Latin America. This study was undertaken to evaluate the baseline knowledge and practices of childhood safety on the part of parents in Monterrey, Mexico and in so doing provide information on which to base subsequent injury prevention efforts. METHODS: Interviews were carried out with parents from three socioeconomic strata (upper, middle, lower). Questionnaires were based on Spanish language materials developed by The Injury Prevention Program (TIPP) of the American Academy of Pediatrics. RESULTS: Data were obtained from parents of 1123 children. Overall safety scores (percent safe responses) increased with increasing socioeconomic status. The differences among the socioeconomic groups were most pronounced for transportation and less pronounced for household and recreational safety. The differences were most notable for activities that required a safety related device such as a car seat, seat belt, helmet, or smoke detector. Appropriate use of such devices declined from 47% (upper socioeconomic group) to 25% (middle) to 15% (lower). CONCLUSIONS: Considerable differences in the knowledge and especially the practice of childhood safety exist among parents in different socioeconomic levels in Mexico. Future injury prevention efforts need to address these and especially the availability, cost, and utilization of specific highly effective safety devices.

Child↗
PubMed1996

Accuracy of mortality data for interstitial lung diseases in New Mexico, USA.

BACKGROUND: The sensitivity and accuracy of death certificates and mortality data as sources of population based data on the occurrence of interstitial lung diseases has received limited attention. To determine the usefulness of these data sources, death certificates and mortality data from patients in New Mexico were examined. METHODS: Patients with an interstitial lung disease were identified from a population based registry. For subjects who had died, diagnostic information from their death certificates and from mortality data was compared with the clinical diagnoses made before death. RESULTS: Of 385 patients with a clinical diagnosis of an interstitial lung disease, 134 died between October 1988 and August 1994. Death certificates were obtained for 96% of these patients. An interstitial lung disease was listed somewhere on the death certificate for only 46% of the patients, and as an immediate cause of death for only 15%. For the patients with an interstitial lung disease listed somewhere on the death certificate the overall concordance between the diagnoses before death and those on the death certificate was 76%. Mortality data for the State of New Mexico showed a diagnosis of interstitial lung disease to be the assigned cause of death for only 22% of the patients. The overall agreement between the diagnoses made before death and those of the state mortality data was only 21%. CONCLUSIONS: These results suggest that death certificates and state mortality data are neither sensitive nor accurate for describing the occurrence of interstitial lung diseases. This finding may partly explain the apparently low mortality rates from idiopathic pulmonary fibrosis in the USA compared with other countries.

Adult↗
PubMed2003

Characterization of a clinical Vibrio cholerae O139 isolate from Mexico.

Pathogenic strains of Vibrio cholerae O139 possess the cholera toxin A subunit (ctxA) gene as well as the gene for toxin co-regulated pili (tcpA). We report the isolation of a ctxA-negative, tcpA-negative V. cholerae O139 strain (INDREI) from a patient in Mexico diagnosed with gastrointestinal illness. Certain phenotypic characteristics of this strain were identical to those of V. cholerae O1 biotype El Tor. Unlike ctxA-positive V. cholerae O139 strains, this strain was sensitive to a wide panel of antibiotics, including ampicillin, chloramphenicol, ciprofloxacin, gentamicin, furazolidone, nalidixic acid, nitrofurantoin, tetracycline, trimethoprim-sulfamethoxazole, and streptomycin, but was resistant to polymyxin B. Ribotype and pulsed-field gel electrophoresis profiles of INDRE1 differed from those of ctxA-positive V. cholerae O139 and other V. cholerae strains. Phenotypic characteristics of the Mexico strain were similar to those reported for V. cholerae O139 isolates from Argentina and Sri Lanka.

Anti-Bacterial Agents↗
PubMedDate not supplied

Changes in dental caries prevalence in 12-year-old students in the State of Mexico after 9 years of salt fluoridation.

The purpose of this study was to describe the dental caries experience in 12-year-old students in the State of Mexico and to detect changes after 9 years of salt fluoridation (1988-1997). The 1987 WHO dental caries criteria were used in both surveys. The population studied encompassed 2,275 12-year-old students in 1988, and 1,138 in 1997. The proportion of 'caries-free' children was 10. 3% in the first survey and 27.7% in the second one. The mean DMFT index was 4.39 (SD 2.9) in 1988 and 2.47 (SD 2.4) in 1997, the confidence interval of the differences between DMFT means was [95% CI 1.73, 2.11]; the caries reduction detected was 43.7%. The Unmet Restorative Index was 82.3% in 1988 and 72.8% in 1997. The results of the present study indicate that the oral health status of State of Mexico students has improved during the last decade; however, there is still a need for further caries reduction and an increment in access to dental treatment.

Cariostatic Agents↗
PubMed2001

Irritable bowel syndrome in Mexico.

The current review includes all the available original data on irritable bowel syndrome in Mexico. Data were organized in items of interest such as prevalence and gender distribution, health care utilization, psychosocial factors, diagnostic criteria, bowel habit predominance, physiological studies, clinical trials and quality of life assessment. After a systematic review, a total of 18 papers were included, the majority published between 1996 and 2000. We can conclude that irritable bowel syndrome in Mexico is similar to that reported in the international literature with regard to the areas analyzed, and therefore it is suitable to run clinical trials with similar outcomes as has been done in other populations.

Adolescent↗
PubMed2002

Nutritional determinants of epithelial ovarian cancer risk: a case-control study in Mexico.

BACKGROUND: Variations in the incidence of cancer can be influenced by diet and specific lifestyles. In the last years, diet has been evaluated as an important factor in the development of ovarian cancer, even though the results have not been consistent. Dietary factors related to the risk of ovarian cancer in Mexican women were evaluated. METHODS: A case-control study in Mexico City was done during 1995-1997 in a social security hospital, evaluating 84 new cases of ovarian cancer and 629 controls. A validated questionnaire with 116 items about the frequency and type of food intake was used. The analysis of nutrients was done with the residual method adjusted for total energy intake and other predictor variables through logistic regression methods. Also, partition models estimated the total caloric intake for other sources. RESULTS: The nutrients negatively associated with ovarian cancer in the highest versus the lowest tertile were retinol (OR 0.52; p for trend = 0.03) and vitamin D (OR 0.43; 95% CI 0.23-0.80; p = 0.01; residual model). Additionally, carbohydrates were positively associated (partition model: OR 1.08; 95% CI 1.00-1.15), and tortilla intake did not show an association with ovarian cancer (OR 0.96; 95% CI 0.78-1.17). CONCLUSIONS: The diet of the Mexican population is rich in carbohydrates; in Mexico corn intake is the main energy source. On the other hand, vitamins such as retinol and vitamin D were shown to be associated with this neoplasm in a protective way; nevertheless, further studies are necessary to allow us to corroborate our results. This is the first attempt in our country that relates the Mexican diet to ovarian cancer.

Adult↗
PubMed2002

Effects of calcium and phosphorus intake and excretion on bone density in postmenopausal women in Hermosillo, Mexico.

Calcium (Ca) is important in bone formation and as aging progresses, bone loss gradually occurs. With the onset of menopause, reduced estrogen levels and insufficient Ca in the diet often create serious problems with fractures. Since little is known about the diet and other factors related to risk factors in postmenopausal women in northern Mexico, it was the objective of this study to determine the effects of dietary Ca and phosphorus (P) and their excretion, anthropometric measurements, and blood serum estradiol on bone density in women aged 45-63 years. No studies are available on the dietary intake of Ca and P and the effects on bone mineral density (BMD) in postmenopausal women in northern Mexico, so this study reports some of the first data on this population. Women with an average age of 55 years showed a positive relation of Ca intake and Ca excretion, however, dietary intake of Ca and P had no relation to bone density. Age, urinary Ca, Ca/creatinine and years of postmenopause had the highest negative correlation. Weight and body mass index had a positive correlation with BMD in the forearm and heel. Only 15% of the women met the recommendation of 1,500 mg/day of Ca. A high Ca/creatinine ratio has been proposed to indicate excess Ca excretion and subsequent bone density loss. Thirty-five percent of the women exceed the Ca/creatinine indicator of >0.16. In this study, 1% of the subjects were classified as osteoporotic and 37% as osteopenic.

Absorptiometry, Photon↗
PubMed2004

Genetic services in Mexico City.

In the year 2002, the population of Mexico was approaching 103 million inhabitants. Approximately 74% of them live in the cities with a continuous migration from rural to urban areas. Genetic departments are concentrated in the capital and other big cities. In this paper we review the current status of genetic departments in Mexico City, emphasizing the main areas of genetic services offered to the public and involved in research. We also comment on the deficiencies identified and suggest recommendations to improve the quality of the genetic services offered to the Mexican population.

Congenital Abnormalities↗
PubMed1992

Antimicrobial therapy of bacterial diarrhea in adult residents of Mexico--lack of an effect.

Two clinical trials in adults in Mexico are reported. In the first trial, long-term residents of Mexico with acute fecal leukocyte-positive diarrhea were randomized to receive trimethoprim/sulfamethoxazole (TMP/SMX), clioquinol or a placebo. Neither antimicrobial shortened the illness for all cases or for those with shigellosis or enterotoxigenic Escherichia coli diarrhea. In a second study, US and Mexican students received enoxacin, TMP/SMX or a placebo on a blind random basis. While the placebo-treated subjects with bacterial diarrhea tended to be more ill after treatment than other groups, no statistical differences were seen in treatment groups. These studies cast doubts on the value of antimicrobial drugs for 'invasive' and other forms of bacterial diarrhea in adults living in endemic areas and indicate the importance of a placebo control group when conducting clinical trials in these populations.

Adult↗
PubMed1996

Effects of air pollution on the respiratory health of asthmatic children living in Mexico City.

The relation between air pollution and the exacerbation of childhood asthma was studied in a panel of 71 children (aged 5 to 7 yr) with mild asthma who resided in the northern part of mexico City. During the follow-up, ambient measures of particulate matter less than 10 microns (PM10, 24-h average) and ozone (1-h maximum) frequently exceeded the Mexican standards for these contaminants. The peak expiratory flow rate (PEFR) was strongly associated with PM10 levels and marginally with ozone levels. Respiratory symptoms (coughing, phlegm production, wheezing, and difficulty breathing) were associated with both PM10 and ozone levels. An increase of 20 micrograms/m3 of PM10 was related to an 8% increase in lower respiratory illness (LRI) among children on the same day (95% confidence interval [CI] = 1.04-1.15), and an increase of 10 micrograms/m3 in the weekly mean of particulate matter less than 2.5 microns (PM2.5) was related to a 21% increase in LRI (95% CI = 1.08-1.35). A 50 parts per billion (ppb) increase in ozone was associated with a 9% increase in LRI (95% CI = 1.03-1.15) on the same day. We concluded that children with mild asthma are affected by the high ambient levels of particulate matter and ozone observed in the northern part of Mexico City.

Air Pollutants↗
PubMed1998

Induction of the lung myofibroblast PDGF receptor system by urban ambient particles from Mexico City.

Platelet-derived growth factor (PDGF) and its receptor system regulate mesenchymal cell proliferation. We recently reported that emission-source fly-ash particles and asbestos fibers induce the PDGF alpha-receptor through a macrophage-dependent pathway, and upregulation of this receptor greatly enhances the mitogenic response of lung myofibroblasts to PDGF (Lindroos and colleagues, Am. J. Respir. Cell Mol. Biol. 1997;16:283-292). In the present study we investigated the effect of particulate matter <= 10 micrometers in size (PM10) from the southern, central, and northern regions of Mexico City on PDGF receptor induction and compared these urban, ambient particles with Mt. St. Helen's volcanic ash particles as a negative control. All Mexico City PM10 samples, but not volcanic ash, stimulated rat alveolar macrophages to secrete a soluble, upregulatory factor(s) for the PDGF alpha-receptor on early passage rat lung myofibroblasts. The macrophage-derived upregulatory activity was blocked by the interleukin (IL)-1 receptor antagonist. The ability of PM10 to stimulate IL-1beta release was blocked in part by a recombinant endotoxin neutralizing protein (rENP). Lipopolysaccharide/endotoxin (LPS) and vanadium, both constituents that were present within these PM10 samples, also stimulated macrophages to secrete factor(s) that upregulated PDGF-Ralpha on lung myofibroblasts. Direct exposure of myofibroblasts to PM10 also elicited upregulation of the PDGF alpha-receptor, and this effect was blocked by rENP and mimicked by LPS, but not vanadium. These findings suggest that PM10 particles induce expression of the PDGF receptor system through macrophage-dependent and -independent mechanisms involving endotoxin and metals.

Air Pollutants↗
PubMed1987

Perceptions of mental illness in Mexico: a descriptive study in the city of Chihuahua.

This work is a study of perceptions toward mental illness among respondents from the city of Chihuahua in Mexico. A non-probability sample of forty-seven respondents was taken during a two-week stay in the summer of 1985. To tap respondents' perceptions of mental illness, vignettes characterizing people normally thought to have symptoms of mental illness were employed. The study reveals that men and women perceive mental illness differently. In three out of four vignettes, women perceive mental disorder than men. It is argued that the reason for the disparity in perceptions between the sexes is the result of the sexual differentiation that exists in Mexico. With regard to whom the respondents would refer the person for help, the majority of the respondents recommended that, whether or not the person in the vignette is characterized as mentally ill or simply "sick", the person should seek professional help.

Adult↗
PubMed1990

Comparison of lead levels in human permanent teeth from Strasbourg, Mexico City, and rural zones of Alsace.

A comparative study of the mean lead concentrations in enamel and dentin of human premolars and permanent molars was conducted by means of a systematic sampling procedure with energy-dispersive x-ray fluorescence analysis. In a first series of analyses, no significant statistical differences in mean lead concentrations at various levels of enamel and dentin were noted between young patients of Strasbourg and those of small villages of Alsace, nor between elderly patients living in these two locations, despite the fact that motor traffic was significantly lower in the rural zones. However, in both locations, a significantly higher concentration of lead was observed in enamel and dentin in relation to age. In a second series of analyses, the mean lead concentrations of both dental hard tissues of premolars and permanent molars of young individuals from Strasbourg, rural Alsace, and Mexico City were compared. Significantly higher mean lead concentrations were found in enamel and dentin samples from Mexico City. This was most evident for inner coronal dentin (5.7 and 6.1 times greater than in teeth of Strasbourg and rural zones of Alsace, respectively) and for pulpal root dentin (6.9 and 8.9 times greater than in teeth of Strasbourg and rural zones of Alsace). It is proposed that the higher lead concentrations are related to the higher lead content of motor gasoline and to more intense traffic conditions. The dental hard tissues appear to be of value for the study of environmental lead pollution.

Adolescent↗
PubMed1996

Mycetoma due to Madurella grisea acquired in Mexico.

Mycetomas due to Madurella grisea have been reported from South America, Central America, the Caribbean Islands, Africa and Asia, but only rarely from Mexico. We report a case of mycetoma due to M. grisea acquired in northern Mexico

Adolescent↗
PubMed2004

Transfusion-associated HIV infection in Mexico related to paid blood donors; HIV epidemic.

The objective of the study was to describe the clinical, epidemiological profile and conditional incubation period in a group of transfusion-associated HIV-infected (TAHI) patients seen in five national tertiary care centres in Mexico from 1983 to April 1998. Date of transfusions, AIDS diagnoses, opportunistic infections and malignancies were collected. The incubation period was estimated through a non-parametric conditional analysis. One hundred and fifty-seven TAHI cases were analysed. The frequency of TAHI by year of transfusion was: 0.6% in 1980 and 1981, 4.5% in 1984, 22.4% in 1985, 54.5% in 1986, 10.3% in 1987, 0.6% in 1988, 1.9% in 1989 and 1990, 1.3% in 1993 and 0.6% in 1994 and 1996. The median incubation period was 4.3 years. A well-defined epidemic period of HIV-infection among blood-recipients was identified that coincided with the HIV-epidemic among paid donors. TAHI patients in Mexico developed AIDS in a shorter time than that described for other populations.

AIDS-Related Opportunistic Infections↗