PubMed Health⌕ Search

Biomedical subjects

C Gamboa

Publications and source records attributed to C Gamboa.

16 recordsLinked to original sources
PubMed2003

Solubilization of phenols in surfactant/polyelectrolyte systems.

The properties of the microheterogeneous systems formed by mixtures of cetyltrimethylammonium bromide (CTAB) and an alternating copolymer of maleic acid and styrene, MAS, and their anionic monoesters, MAS-n with n=2, 4, 6, 8, were investigated. The fluorescence of pyrene was used to sense the polarity of the polymer/CTAB aggregates. Measurements of the ratio III/I in pyrene fluorescence spectra indicate that the polymer/CTAB aggregates are more hydrophobic than normal micelles. A series of p-alkyl substituted phenols were employed to probe the solubilization ability of these aggregates. The distribution constant K(S) of phenol, p-methylphenol, p-ethylphenol, and p-propylphenol between water and MAS-n/CTAB aggregates and the corresponding free energy of transfer Deltamicro(0)(t) have been determined using the pseudo-phase model. The results show that the distribution is mainly determined by the phenol structure, and a linear free energy relationship has been found between Deltamicro(0)(t) and the structure of phenols. On the other hand, an increase in the number of methylene groups in the side alkyl chain has no effect on Deltamicro(0)(t). The results are discussed and compared with those obtained for ionic micelles.

Journal Article↗
PubMed2003

Synergism in mixtures of cationic surfactant and anionic copolymers.

Surface tension measurements have been made in aqueous solutions of anionic hemiesters of an alternating copolymer of maleic acid and styrene, MAS-n with n=0-12, in the presence of dodecyltrimethylammonium bromide, DTAB. A synergistic aspect of surface tension reduction efficiency was observed for all systems studied. The pseudo-phase separation approach and regular solution approximation have been applied, and the interaction parameter, beta, and the mole fraction of DTAB in the adsorbed layer (on a surfactant/repetitive unit basis), X, were obtained. Negative values of beta, ranging from -3 to -11, were calculated. On the other hand, the molar fraction of DTAB varies from 0.52 to 0.26. These results are discussed in terms of hydrophobic effects on the distribution of the aggregates between the interface and the bulk of the solution. The conditions predicted by the model to obtain synergism in the tension reduction efficiency are completely satisfied in all cases.

Journal Article↗
PubMed1998

[Comparison of the effects of digoxin or enalapril in the treatment of heart failure due to mitral insufficiency].

BACKGROUND: There is not much evidence about the usefulness of digoxin or enalapril in the treatment of heart failure due to mitral insufficiency. AIM: To compare digoxin and enalapril in the treatment of heart failure due to mitral insufficiency. PATIENTS AND METHODS: Patients with mitral insufficiency, in sinus rhythm, with a heart failure grade II or III and with echocardiographic left ventricular dilatation were eligible for the study. They received sequentially, during 12 weeks each, digoxin 0.25 mg/day or enalapril in doses up to 20 mg/day, with a washout in-between period of 2 weeks. The order of the sequence was determined randomly. At the start and end of treatment, functional class according to NYHA and maximal exercise tolerance in the treadmill were assessed and a color Doppler echocardiogram was done to measure ventricular dimensions, function and degree of mitral insufficiency. RESULTS: Nine patients on enalapril and 12 on digoxin improved their functional capacity. Digoxin improved exercise time in 76 +/- 168 sec (p = 0.022), whereas this change was not significant with enalapril (38 +/- 158 sec; p = 0.2). With enalapril treatment, ventricular diastolic dimension decreased from 59.3 +/- 8.1 to 58 +/- 9.3 mm and the area of mitral insufficiency decreased from 8.1 +/- 3.5 to 6.6 +/- 3.1 cm2. Digoxin did not induce any significant echocardiographic change. CONCLUSIONS: In these patients, digoxin and enalapril improved functional class. Digoxin improved exercise time and enalapril reduced ventricular dimensions and mitral insufficiency.

Adult↗
PubMed1991

[Cryptosporidium: outbreak at a nutrition rehabilitation center, Temuco].

Cryptosporidiosis was observed in 23 undernourished infants of a nutritional center in Temuco. This represents a 34% incidence rate for the period (march to may 1990). Liquid stools (91%), vomiting (39%), resistance to feeding (74%), respiratory symptoms (61%) and weight loss (mean 25 g per day) were the main clinical manifestations. Only 9 patients received specific therapy and all showed clinical improvement and normalization of stool examinations within the study period.

Adult↗
PubMedDate not supplied

[Intestinal infection by parasites and/or hosts in school children of the IX region, Chile].

The prevalence of intestinal infection by parasites and/or commensals in primary school students from Lautaro, IX Region, was studied. The sample included 68 children from rural and 67 from urban areas. A Telemann modified method, Ziehl-Neelsen technique for Cryptosporidium sp. detection and Graham test were used. The results pointed out high rates of infections by protozoa and helminths (85.4%). There are no statistical differences related to origin for sex or scholarship. In the total sample, the more frequent parasite found was G. lamblia (37.8%); among the youngest was 60.7%. The second frequency was for T. trichiura (22.2%) and the third one for A. lumbricoides (12.6%). Among commensals the percentages were: E. coli 45.5% and E. nana 33.3%. It could be concluded that the intestinal infection by parasites and/or commensals in school children is endemic in the IX region, because the environmental conditions are appropriate for its permanence and transmission, specially in lower socioeconomical groups.

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↗