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Biomedical subjects

E Vargas

Publications and source records attributed to E Vargas.

At least 91 records · Page 5Linked to original sources
PubMed1981

An analysis of impedance cardiography in the elderly.

Non-invasive impedance cardiography has been used to assess cardiac response to postural stress in old people but the results have been conflicting. We have statistically studied the responses of two groups of elderly people (healthy and with postural hypotension) and compared results with those obtained in a young group of controls. We conclude that with suitable precautions this inexpensive method is both reproducible and satisfactory in practice.

Adult↗
PubMed1978

Pulmonary gas exchange, diffusing capacity in natives and newcomers at high altitude.

At high altitude, in resting conditions, no differences have been observed between High Altitude Natives (HAN) and acclimatized Sea Level Natives (SLN) in AaDO2, aADCO2 or venous admixture. In acclimatized SLN, AaDO2 is smaller than at sea level because of: (1) The minor effect on arterial oxygenation of the probably constant venous admixture. (2) The reduction of VA/Q inequality as shown by a smaller aADCO2. In HAN, DLCO is greater than in SLN; the contribution of DM or VC in this difference remains unsettled, mainly because of the difficulties of measurement of DM and VC in HAN suddenly exposed to acute hyperoxia. In SLN, in acute hypoxia, DLCO increased transitorily. Asynchronous mechanisms of adaptation to high altitude are evoked.

Acclimatization↗
PubMed1976

Pressure-flow-volume relationships in pulmonary circulation of normal highlanders.

Pulmonary vascular pressures and blood flow were measured with and without unilateral pulmonary arterial occlusion (UPAO) at rest and during exercise in 10 normal highlanders at La Paz, Bolivia (altitude, 3,750 m). In 6 other highlanders at rest and during exercise, pulmonary pressures, flow, and blood volume were measured during air breathing (PIO2 congruent to 100 Torr) and 29-30% oxygen (PIO2 congruent to 150 Torr). During air breathing, pulmonary vascular resistance was elevated at rest and did not change with exercise. Pulmonary arterial pressure rose less at rest with UPAO than during exercise without UPAO, and pulmonary vascular resistance was less in the former. Raising PaO2 to normal sea-level values had no effects on the pulmonary circulation at rest but prevented to a large extent the rise in pulmonary arterial pressure during exercise. Hence pulmonary vascular resistance during exercise was lower with oxygen than without. Thus, hypoxic vasoconstriction contributed to the pulmonary hypertension during exercise in normal highlanders. Circumstantial evidence suggests that this is related to the profound mixed venous hypoxemia caused by exercise in a hypoxic environment.

Adolescent↗
PubMedDate not supplied

Helping patterns and reproductive success in Aymara communities.

"Helpers at the nest," young adults remaining in their parents home to take care of younger siblings, are known in many species of birds and mammals. Similar behaviors are occasionally observed in human societies but their frequency and significance for parental reproductive success are still not fully appraised. This study was designed to document this issue in a traditional Aymara peasant society of the Bolivian Altiplano, It is based on 359 reproductive life histories of women 45 years of age or older and on a survey of children's workload in 1998 and 1999. The presence of "potential helpers" in the household is significantly associated with higher fertility and with improved survival of siblings to sexual maturity. Caretaking is not particularly assigned to older daughters. The positive relationship between the availability of offspring help and reproductive success does not demonstrate a causal role for child caretaking because, in contrast with nonhuman helpers, workloads of children range from housekeeping to agricultural tasks, instead of being focused on feeding or protecting younger siblings. Correlation and multiple regression analyses, however, suggest that the total amount of care given by the older offspring and the amount of care received by each recipient are, along with offspring contribution to household economy, among the determinants of parental reproductive success.

Adult↗
PubMedDate not supplied

Preference for sons and sex ratio in two non-Western societies.

Moroccan Berbers and the Bolivian Aymara are two unrelated peasant groups living in adverse environments with a still rather traditional agriculture. Precarious life conditions may be responsible for the importance given to male labor and hence for the cultural preference conferred on male descent. This preference, expressed in the social valorization of sons to the detriment of daughters, is more emphasized if the socioeconomic status of the family is lower. Interpreted according to the cost/benefit approach of Fisher (1958 Genetical Theory of Natural Selection, New York: Dover) of variations in the sex ratio and to its later developments (Trivers and Willard 1973 Science 179:90-91; Trivers 1985 Social Evolution, Menlo Park: Benjamin/Cummings; Hewlett 1991 J. Anthropol. Res. 47:1-37; Smith 1993 Ethol. Sociobiol. 14:39-44), these cultural characteristics could determine that parents bias the care allocated to their progeny in favor of sons, to the detriment of daughters. This could eventually affect their respective survival and finally modify the offspring tertiary sex ratio. This study compares differences in survival as indicators of parental care according to a child's sex and across three economic strata: poor, medium, and high. The Moroccan data express no other sex differences in survival than an advantage for daughters during the preweaning period in the medium and high strata. Within the same sex and across economic strata, a greater mortality between age 10-20 years is observed for boys of the poorest stratum. The Aymara data do not show sex differences by economic stratum, except for an advantage to daughters between birth and 5 years in the medium group, and no survival differences within the same sex across economic strata. These results suggest either that despite the social valorization of male progeny no differences in parental care according to sex occur, or that their magnitude is not great enough to contrast the survival of sons and daughters.

Adolescent↗
PubMedDate not supplied

The short-term effect of a switch from glibenclamide to metformin on blood pressure and microalbuminuria in patients with type 2 diabetes mellitus.

BACKGROUND: Renal hyperfiltration and albuminuria have a deleterious effect on kidney function. Therefore, we studied the effect of metformin on blood pressure, renal hemodynamics, and microalbuminuria in type 2 diabetic patients. METHODS: A clinical trial was designed in type 2 diabetic patients with incipient nephropathy. All patients were below the age of 65, normotensive, and without evidence of malignant, hepatic, or cardiovascular disorders. They were randomly allocated to receive glibenclamide or metformin. At baseline and 12 weeks thereafter we measured body mass index (BMI), serum insulin, blood glucose, lipid profile, glycosylated hemoglobin, blood pressure, glomerular filtration rate, renal plasma flow, and urine albumin. RESULTS: We studied 23 patients in the glibenclamide group and 28 in the metformin group. There was no difference in baseline variables between the groups. Metabolic control was obtained in both groups. In the metformin group, all the following variables decreased: microalbuminuria was reduced by a mean of 24.2 mg/day (p = 0.008); systolic and diastolic blood pressure by a mean of 5.3 mmHg (p = 0.002) and 3.93 mmHg (p = 0.009), respectively; insulin levels by an average of 11.8 microIU/mL (p = 0.001), and total cholesterol levels and triglycerides by an average of 0.45 and 0.18 mmol/L, respectively. Insulin resistance measured by the homeostasis model decreased more in the metformin group than in the glibenclamide group. Patients treated with glibenclamide had an increase in HDL cholesterol of 0.082 mmol/L (p = 0.01). CONCLUSIONS: Metformin significantly decreased the urine albumin excretion rate with none of the expected changes in renal hemodynamics, probably due to its favorable effects on blood pressure, lipid profile, metabolic control, and insulin resistance.

Adult↗
PubMedDate not supplied

[Cost-effectiveness analysis of the use of celecoxib for the treatment of osteoarthritis].

BACKGROUND: Non-steroidal anti-inflammatory drugs (NSAIDs), used for the treatment of osteoarthritis, can produce serious gastrointestinal (GI) adverse reactions.Celecoxib, a specific COX-2 inhibitor, has a proven efficacy equivalent to that of traditional NSAIDs with an improved tolerance and safety profile. OBJECTIVE: The objective of this study was to perform a cost-effectiveness analysis on the use of celecoxib versus traditional NSAIDs in the treatment of osteoarthritis. MATERIAL AND METHODS: This cost-effectiveness analysis was designed through a pharmacoeconomic model; each effectiveness unit was defined as each year of life gained after the ingestion of celecoxib or NSAIDs. The probability of different clinical results appearing was obtained from published articles and incorporated assumptions. Only direct medical costs were evaluated (medication, hospitalization, additional tests, analyses, extra visits, etc.) and other costs were excluded. The study perspective was the national health system and the time horizon chosen was 6 months. RESULTS: The additional cost for each year of life gained through the use of celecoxib compared with that of traditional NSAIDs amounted to 8017; (1,333,834 ptas). Sensitivity analysis demonstrated how these values were sensitive to changes in the costs of NSAIDs and gastroprotective agents as well as to the inclusion of younger population groups. CONCLUSION: Celecoxib can be considered as a cost-effective option in the treatment of osteoarthritis because its use prevents deaths and increases survival rate and the additional cost is reasonable and moderate compared with that of NSAIDs. Its efficiency increases in proportion to its use in younger patients and probably in those at high risk for developing GI complications.

Aged↗
PubMedDate not supplied

Arsenic resistance determinants from environmental bacteria.

Arsenic resistance determinants from 42 environmental bacterial isolates (32 Gram negative) were analyzed by DNA: DNA hybridization using probes derived from Escherichia coli and Staphylococcus plasmid or chromosomal arsenic resistance (ars) genes. In colony hybridization assays, 11 and 1 Gram negative strains hybridized with the E. coli chromosome and plasmid probes, respectively. No hybridization was detected using a probe containing only the arsA (ATPase) gene from E. coli plasmid or with a Staphylococcus plasmid ars probe. From Southern hybridization tests of some of the positive strains it was concluded that homology to ars chromosomal genes occurred within chromosome regions, except in an E. coli isolate where hybridization occurred in both the chromosome and a 130-kb plasmid. Our results show that DNA sequences homologous to E. coli ars chromosomal genes are commonly present in the chromosomes of environmental arsenic-resistant Gram negative isolates.

Adenosine Triphosphatases↗
PubMedDate not supplied

[Bacterial systems for expelling toxic metals].

Bacteria have developed diverse resistance strategies towards toxic metals with which they interact in the environment. The mechanisms of tolerance include extracellular precipitation, sequestration by cell envelopes, intracellular accumulation, redox transformations and membrane efflux systems. Genes responsible for these processes may be encoded by the chromosome or by plasmids. Since some toxic metals are also essential micronutrients (i.e. copper, cobalt, zinc, nickel), bacteria must precisely adjust the functioning of uptake and efflux systems to maintain their adequate intracellular levels. In the case of metals with no biological function (i.e. cadmium, silver), transport systems must be oriented only to the extrusion of the toxic ions. In the last few years, several bacterial systems devoted to the efflux of toxic metals were analyzed at the molecular level resulting in a detailed understanding of the biochemical mechanisms of resistance. Among these are the membrane pathways that extrude cations derived from copper, cadmium, zinc, nickel, cobalt and silver. Two general mechanisms have been found: those involving P-type ATPases, and some using proton antiporter systems.

Adenosine Triphosphatases↗
PubMedDate not supplied

[Double-blind study on the action of almitrine in patients with polycythemia of high altitude].

Chronic polycythaemia in people living at high altitude is associated with hypoxaemia due to a marked reduction in hypoxic and hypercapnic drives. The effect of almitrine, a chemoreceptor stimulant, was evaluated in 40 patients, with haematocrit values over 57%, living in La Pa2 (3,600-4,000 m). Two studies were carried out. The aim of the first was to assess the ventilatory response, and the increase in PaO2 due to almitrine in a double blind, placebo controlled protocol including 40 patients (mean haematocrit 66.8%). Almitrine was given orally at a dose of 3 mg X kg-1. Variance analysis showed that three hours later there was a significant increase in PaO2 (+0.46 kPa), pH and respiratory frequency, with a significant reduction in PaCO2 (-0.4 kPa). The increase in ventilation (+17%) was not significant. The aim of the second study was to assess the effect of almitrine on the polycythaemia. It was given orally at a dose of 1.5 mg X kg-1 X day-1 to twelve patients over a four week period. Blood gases, ventilation (VE), oxygen consumption (VO2), carbon dioxide, production (VCO2) and haematocrit were measured every week. There was a slight but significant reduction in haematocrit (-3.5%). PaO2 and all the other measured parameters (VE, PaCO2, pH, VO2 VCO2) remained constant. The reduction in haematocrit was not therefore due to an increase in diurnal PaO2 but is perhaps due to the improvement in pulmonary ventilation during sleep.

Adult↗