Vitamin D-receptor gene polymorphisms and bone density in prepubertal American girls of Mexican descent.

BACKGROUND: Bone mass is under strong genetic control, and recent studies in adults have suggested that allelic differences in the gene for the vitamin D receptor may account for inherited variability in bone mass. We studied the relations of the vitamin D-receptor genotype to skeletal development and variation in the size, volume, and density of bone in children. METHODS: We identified three allelic variants of the vitamin D-receptor gene using the polymerase chain reaction and three restriction enzymes (ApaI, BsmI, and TaqI) in 100 normal prepubertal American girls of Mexican descent. We then determined the relations of the different vitamin D-receptor genotypes (AA, Aa, aa, BB, Bb, bb, TT, Tt, and tt) to the cross-sectional area, cortical area, and cortical bone density of the femoral shaft and the cross-sectional area and density of the lumbar vertebrae. RESULTS: The vitamin D-receptor genotype was associated with femoral and vertebral bone density. Girls with aa and bb genotypes had 2 to 3 percent higher femoral bone density (P=0.008 and P=0.04, respectively) and 8 to 10 percent higher vertebral bone density (P=0.01 and P=0.03, respectively) than girls with AA and BB genotypes. There was no association between the cross-sectional area of the vertebrae or the cross-sectional or cortical area of the femur and the vitamin D-receptor genotype. The chronologic age, bone age, height, weight, body-surface area, and body-mass index did not differ significantly among girls with different vitamin D-receptor genotypes. CONCLUSIONS: Vitamin D-receptor gene alleles predict the density of femoral and vertebral bone in prepubertal American girls of Mexican descent.

Epidemiology of gastric cancer in Chile. III. Diagnostic practices in Santiago, 1976-8.

The purpose of this paper is to estimate the validity of current diagnostic procedures used in Santiago, Chile, in identifying gastric cancer (GC) patients among people with gastric complaints, many of whom suffer possible premalignant conditions. Review of diagnoses on 2296 patients seen at the University Hospital during 1976 and 1977 revealed 103 confirmed cases of adenocarcinoma. This review permitted us to estimate the validity of clinical/radiological and endoscopic methods versus diagnosis made from pathological specimens. A code of diagnostic categories was generated for application in eight hospitals participating in a subsequent case-control study of GC. A high prevalence of chronic atrophic gastritic (CAG) and chronic gastric ulcer (CGU) was found, both conditions together accounting for 50% of diagnoses on 845 clinic controls during the study period 1977-8. The value of gastroscopy and biopsy to separate out GC from other gastric conditions, the importance of studying the epidemiology of premalignant conditions in Chile, and differences between GC in Chile and the United States are discussed.

Epidemiology of gastric cancer in Chile: I - Case-control study.

The results of a case-control study of stomach cancer carried out with the collaboration of 7 participating hospitals in Santiago, Chile are reported. Patients attending gastroscopy clinics were interviewed before or after gastroscopy. The diagnosis was unknown to either the patient or the interviewer at the time of interview. 360 stomach cancer cases were subsequently matched to non-cancer patients selected from the pool interviewed at the same time as the cases. Study findings show: 1) longer-term residence in high-risk areas in early life by cases than controls; 2) an association between stomach cancer and a prior occupation in agriculture. In a subgroup of 98 cases for whom histologic classification was available, the association with residence in early life in a high-risk area was seen only for cases with intestinal-type stomach cancer.

Epidemiology of gastric cancer in Chile: II - Nitrate exposures and stomach cancer frequency.

Nitrate levels in urine and nitrite levels in saliva were determined in school children 11-13 years of age in 2 areas of high stomach cancer mortality located in central Chile and in 2 areas of low stomach cancer mortality located at the extremes of Chile. Levels of both nitrates and nitrites were concurrently determined in selected vegetables obtained in these 4 study areas. Levels of nitrates were significantly higher in the urine of schoolchildren and in vegetables obtained from the northern low-risk area. Levels of nitrites were similar in saliva specimens from all 4 areas, but levels in vegetables were inconsistent. These results are apparently incompatible with the hypothesis of a high nitrate intake in areas of high stomach cancer incidence compared to areas of low incidence. This paradoxical finding suggests that cofactors may be involved in the pathopoiesis of stomach cancer that promote or inhibit the transformation of dietary nitrates to nitrosamines. The soil in the high-risk areas is primarily of volcanic origin, which is reported to be low in levels of selenium. On the other hand, residents of Antofagasta, the northern low-risk area, are known to be exposed to high levels of arsenic. It is possible that the diet of residents of the high incidence area which may be deficient in selenium may enhance promotion of nitrates to nitrosamines as has been reported in the literature, or conversely, that high levels of arsenic or other factors in the diet of individuals in Antofagasta may play a protective role. Other factors may be responsible for the low rate observed in the southern low-risk area.