Biomedical subjects

R Sierra

Publications and source records attributed to R Sierra.

40 records · Page 3Linked to original sources

PubMedDate not supplied

Study of the interaction between policosanol and excipients.

Policosanol is an active principle, composed by 8 fatty alcohols: 1tetracosanol, 1-hexacosanol, 1-heptacosanol, 1-octacosanol, 1-nonacosanol, 1-triacontanol, 1-dotriacontanol and 1-tetratriacontanol that shows a very stable, well defined and reproducible composition from batch to batch that is analysed using gas chromatography. Continuing the studies of the compatibility among policosanol and different tablet excipients, it was studied if the mixtures of those excipients with policosanol produce chemical interactions between them, the samples were analysed using gas chromatography and was determined if it was affected the content of policosanol in them. When all the samples were analysed, no changes in the policosanol content of the samples were observed, and it was considered that no interactions are produced in any of the mixtures policosanol/excipients under study.

Anticholesteremic Agents↗

PubMedDate not supplied

Study of the stability of tablets containing 10 mg of policosanol as active principle.

The stability studies of tablets containing 10 mg of policosanol, a new cholesterol lowering drug, were conducted to predict an expiration date and to search the appearance of putative degradation products. All quality specification parameters such as colour, moisture content, hardness, disintegration, policosanol content and microbiological limits of the tablets were done. The effect of drastic treatments such as acid and basic hydrolysis, oxidative and photolytic degradation as well as thermolysis on such parameters was studied. In addition; studies under drastic conditions of storage (40 degrees C and 75% R.H.) and under ambient conditions of storage for climatic zones II and IV were performed. These studies demonstrate that these tablets are a stable pharmaceutical formulation, without significant changes on their quality criteria at the stressed conditions studied. The chromatographic profile of the samples after 9 months of thermal degradation shows chromatographic peaks that corresponds to the octacosanoyl, triacontanoyl and hexacosanoyl esters of palmitate and stearate, being the only degradation products observed on these studies.

Drug Stability↗

PubMedDate not supplied

Antibodies to Helicobacter pylori and pepsinogen levels in children from Costa Rica: comparison of two areas with different risks for stomach cancer.

In children and adolescents from two areas of Costa Rica with contrasting gastric cancer risks, two factors suspected to be linked to the natural history of the disease were tested: serum antibodies to Helicobacter pylori and serum pepsinogen levels. One hundred fifty-five subjects from the high-risk area of Turrubares were compared to 127 from the low-risk area of Hojancha. No significant differences were found in the prevalence of IgG or IgA antibodies to Helicobacter pylori between the two regions. The prevalence of IgG was 65.8% in the high-risk area and 72.4 in the low-risk area, and that of IgA was 43% in both areas. The levels of pepsinogen, especially pepsinogen C, were significantly elevated in subjects with H. pylori antibodies in their serum. The mean levels of pepsinogen C in those negative, positive, and strong positive for H. pylori antibodies were 8.7, 14.3, and 21.1 ng/ml. These findings suggest that H. pylori-associated gastritis, predominantly of antral localization, is very prevalent in Costa Rican children and adolescents. Such gastritis might be associated with a high prevalence of intestinal metaplasia and a high gastric cancer risk in the inland, but not the coastal rural populations. H. pylori may therefore be an insufficient cause whose role in gastric carcinogenesis is contingent upon the presence of other factors.

Adolescent↗

PubMedDate not supplied

In vivo nitrosoproline formation and other risk factors in Costa Rican children from high- and low-risk areas for gastric cancer.

The hypothesis that intragastric synthesis of N-nitroso compounds (NOC) in early life could play a role in gastric carcinogenesis was tested by applying the N-nitrosoproline (NPRO) test to about 50 children living in high- and low-risk areas for stomach cancer in Costa Rica. The median values of excretion of NPRO and the sum of three nitrosamino acids (micrograms/12 h urine) were 10-20% of those in adults from other geographical high-risk areas for stomach cancer. The urinary NPRO level after proline intake was higher in children from the high-risk area (P < 0.04) and markedly reduced after ingestion of ascorbic acid together with proline (P < 0.05). NPRO levels on the day of proline intake were highly correlated with levels of nitrate excretion (P < 0.001). Mean levels of total NOC in an aqueous (pH 2) extract of cooked beans from the high- and low-risk areas were similar. Acid-catalyzed nitrosation of the extract increased the total NOC concentration up to 1000-fold, but there was no difference between samples from the two areas. About 10% of bean extracts from both areas showed weak direct-acting genotoxicity in Escherichia coli; after acid-catalyzed nitrosation, all samples were genotoxic at similar levels. The diet of children in the low-risk area satisfied recommended levels of intake of energy and most nutrients except riboflavin and retinol equivalents. Diets from the high-risk area were deficient in energy intake and all nutrients except protein and vitamin C.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗