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Biomedical subjects

R Sierra

Publications and source records attributed to R Sierra.

At least 37 records · Page 2Linked to original sources
PubMed1995

Antibodies to Helicobacter pylori in dyspeptic patients, asymptomatic adults, and children from Costa Rica.

An enzyme immunoassay for the detection of serum IgG antibodies to H. pylori whole bacterial sonicate was used in a study of dyspeptic adult patients (n = 165), apparently healthy blood donors (n = 154), and children (n = 66) from Costa Rica, where a very high incidence of gastric carcinoma is observed. The mean antibody levels and frequency distributions were similar in the dyspeptic patients and the blood donors. Meanwhile lower antibody levels to H. pylori were more frequently observed in children than in adults, suggesting an age-dependent increase in seroprevalence, as described in studies from other populations.

Adolescent↗
PubMed1994

Helicobacter pylori in a Costa Rican dyspeptic patient population.

Gastric biopsies from 65 Costa Rican dyspeptic patients were investigated for the presence of Helicobacter pylori DNA by polymerase chain reaction (PCR) amplification of 16S rRNA sequences. Both frozen and paraffin-embedded samples were used, and the results were compared with bacterial culture and histological examination. Helicobacter pylori DNA was detected by PCR in 60 (92%) of the patients, and Helicobacter pylori strains confirmed by PCR could be isolated from 37 of them. Altogether, 59 patients were shown to be infected using the combination of culture and histology as the reference method. The sensitivity of PCR analysis of frozen material was 98% (58/59). The PCR analysis of paraffin-embedded samples seemed less reliable than that of frozen biopsy material.

Adult↗
PubMed1994

Frontier migration as a multi-stage phenomenon reflecting the interplay of macroforces and local conditions: the Ecuador Amazon.

"This paper considers frontier migration to the Ecuador Amazon as a multistage phenomenon, examining the entire migration stream from its origins in highland and coastal locales of Ecuador, to intermediate stops outside and within the Amazon, to final Amazon destinations. The approach is one where models pertaining to regional development, migration, and pioneer activity are treated as complementary to one another and meshed with a qualitative knowledge of place. It is shown that frontier settlement patterns reflect the composite of these models, a maturing space-economy, and the interaction of local characteristics with exogenous circumstances representing national and international contexts."

Americas↗
PubMed1993

Determinants of the geographic variation of invasive cervical cancer in Costa Rica.

The incidence of cervical cancer in Costa Rica is about twice as high in the coastal regions as in the interior. To study these regional variations, we used data from a 1986-1987 case-control study of 192 Costa Rican women with invasive cervical cancer and 372 controls. Risk factors identified included the following: The study participant's (1) number of sexual partners, (2) age at first sexual intercourse, (3) number of live births, (4) presence of type 16/18 human papillomavirus (HPV) DNA, (5) venereal disease (VD) history, (6) Pap smear history, and (7) socioeconomic status. The adjusted relative risks (RR) and 95% confidence intervals (CI) for each of these risk factors were as follows: (1) > or = 4 vs. 1 sexual partner: RR = 2.0, 95% CI = 1.1-3.5; (2) age of initiation < or = 15 vs. > or = 18 years: RR = 1.5, 95% CI = 0.9-2.5; (3) > or = 6 vs. < or = 1 live birth: RR = 1.7, 95% CI = 0.7-3.9; (4) HPV 16/18 DNA in cervix: RR = 2.8, 95% CI = 1.9-4.2; (5) VD history: RR = 2.2, 95% CI = 1.2-4.0; (6) no Pap smear: RR = 2.4, 95% CI = 1.5-3.8; and (7) low socioeconomic status: RR = 2.0, 95% CI = 1.2-3.2. The population-attributable risks related to HPV detection, four or more sexual partners, six or more live births, no prior Pap smear, and low socioeconomic status were 39%, 38%, 29%, 23%, and 22%, respectively. Several of the sexual and reproductive risk factors were relatively more prevalent in the high-risk region, but Pap screening and detection of HPV were equally prevalent in the high-risk and low-risk regions. Though differences in screening quality (laboratory and follow-up) may have been involved, we conclude that the observed regional differences reflect behavioral more than screening differences. This suggests that screening programs should be more aggressive in the high-risk area, given the more frequent occurrence of the disease there. Failure to detect a higher prevalence of HPV in the high-risk region could reflect weaknesses in the in situ hybridization test employed. Alternatively, cofactors may have to be present in order for HPV to exert its role in cervical carcinogenesis.

Adult↗
PubMed1991

Exposure to N-nitrosamines and other risk factors for gastric cancer in Costa Rican children.

The hypothesis that endogenous chemical nitrosation in the normal stomach in early life could play a crucial role in inducing chronic atrophic gastritis/intestinal metaplasia in later life was tested by applying the N-nitrosoproline (NPRO) test to 12-h urine samples from about 50 children (aged 8-14 years) living in high- and low-risk areas for stomach cancer. The median values of NPRO and the sum of four nitrosamino acids analysed were 0.28-0.84 micrograms/12 h and 0.75-1.75 micrograms/12 h, respectively. The NPRO level after proline intake was significantly higher in children from a high-risk area than in those from a low-risk area (p less than 0.04), and markedly reduced after ingestion of ascorbic acid and proline (p less than 0.05). Urinary nitrate level was lower than that of adults. NPRO levels on the day of proline intake, however, correlated well with nitrate levels (p less than 0.001), indicating that children in a high-risk area in Costa Rica have high endogenous nitrosation potential. Blood samples were also collected from about 300 children (aged 7-20 years) and analysed for antibodies against Campylobacter pylori, a suspected gastritis-causing bacteria. About 71% of children in both high- and low-risk areas for stomach cancer had antibodies. In addition, raw and cooked beans, which are consumed very frequently in Costa Rica, were collected from families in both areas and analysed for levels of nitrite/nitrate, total N-nitroso compounds and genotoxicity in the SOS chromotest.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Cancer in Costa Rica.

Data from the national tumor registry of Costa Rica for the years 1979-1983 have been used to calculate incidence rates for the major cancer sites by age, sex, urban-rural residence, and geographic region. Recent trends in mortality rates are also presented. Results are compared with data from elsewhere in Latin America, U.S.A., Europe, and Japan. Stomach cancer is the most frequent neoplasm in Costa Rica; although rates are declining, they are second only to those observed in Japan. There are marked variations in risk by region, suggesting important environmental influences in etiology. The cervix is the major female site; rates are declining in young women, probably due to the introduction of screening programs, although these do not seem to account for the geographic variations in invasive cancer incidence. Breast and prostate cancer show moderate rates, while those for colon and rectum cancer are low; increases in mortality rates for these sites are small, and involve mainly the older age groups. In contrast, rates of lung cancer are increasing dramatically in both sexes. In the childhood age group, very high incidence rates are observed for two neoplasms: Hodgkin's disease and acute lymphocytic leukemia.

Adolescent↗
PubMed1989

Epidemiology of cancer of the uterine cervix in Costa Rica, 1980-1983.

A study was made of all cervical cancer cases that were entered in Costa Rica's National Register of Tumors for the period 1980-1983. The country's average rates of invasive and in situ cervical cancers in these years were 33.6 and 36.3 cases per 100,000 women, respectively. The incidence of invasive cases varied notably in different geographic regions. The approximate cumulative risk of developing invasive cervical cancer by age 74 was 6.3% for women in certain very high risk areas as compared to 1.4% for those in certain low risk areas. Most of the very high risk areas were relatively inaccessible regions located far from the capital city of San José. These findings suggest that the regional differences in the incidence of invasive cervical cancer resulted from better early detection of cervical cancers and precancerous states in the areas of lower risk. More extensive epidemiologic studies will be needed in order to determine the proper weight to assign such factors as race, promiscuity, socioeconomic level, and customs in the incidence and behavior of this cancer in Costa Rica.

Adolescent↗
PubMed1986

Cancer mortality in the Republic of San Marino.

San Marino is a small independent Republic encircled by Italy, with a population of approximately 20,000. It still maintains an ethnic profile favoured by a tendency to genetic segregation due to endogamy. Since 1908 detailed data have been kept on all deaths among residents also for those dying outside the country. In this study the mortality trends based on crude rates are reported for all neoplasms and for selected sites in the years 1908 to 1980, showing increased rates for all neoplasms and the highest rate for stomach cancer. Age-adjusted death rates were calculated for all neoplasms and for selected sites, by sex, in the years 1966 to 1980. Stomach cancer was the commonest cause of cancer death in San Marino and its age-adjusted death rate was the highest in the world. A sharp increase was also observed for respiratory tract and colorectal cancers in recent years.

Female↗
PubMed1983

[Ecological aspects of gastric cancer in Costa Rica].

An analysis of 1315 cases of gastric cancer from the records of the Ministry of Public Health, San José, Costa Rica between 1977 and 1980 showed important geographical differences in the incidence, and especially in relation to the sex ratio, age structure and migratory patterns. Rates of incidence ranged between 12.6 and 153.2 per 100,000 inhabitants in men and 10.6 and 56.6 in women. Variations in the incidence of gastric cancer rates were studied in relation to ecological parameters, including certain soil and drinking water characteristics as well as the presence of vitamins A and C in serum. No significant relation was found between gastric cancer rates and the presence of vitamins and of several components in drinking water. However, a multivariate analysis considering nine soil components and pH showed a statistically significant (p less than 0.01) association with pH, K, Zn and Fe, which account for 22% of the variation in the incidence rates. A dynamic and multifactorial model is proposed to explain regional variations in cancer rates, with a tentative application of this model to the results obtained.

Ascorbic Acid↗