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Biomedical subjects

I Mendoza

Publications and source records attributed to I Mendoza.

At least 19 recordsLinked to original sources
PubMed2001

Self-rated health and its relationship to functional status and well-being in a group of elderly Guatemalan subjects.

This study examined the association of self-rated health with physical function and emotional well-being, while controlling for differences in sex, age and anthropometry. Subjects were participants in a multicentre study originated by the International Union of Nutritional Sciences (IUNS). A total of 151 elderly Guatemalan subjects were examined using a questionnaire which included information on self-rated health, activities of daily living, well-being, and a common battery of anthropometric variables. Adjusted odds ratios (OR) obtained with polytomous logistic regression showed that subjects with the highest score on the well-being index compared with those with the lowest were 1.67 times more likely (P-value <0.001, confidence interval (C.I.) = 1.31-2.14) to rate themselves in 'good' health versus 'fair' and 'poor' health. Subjects with the highest score versus those with the lowest on the mobility index were 1.15 times more likely (P-value <0.05, (C.I.) = 1.00-1.32) to rate themselves in 'good' health versus the other health ratings. These are the first results to examine the relationship of self-rated health to physical function and emotional well-being of elderly, free-living Guatemalans.

Activities of Daily Living↗
PubMed2001

Paradoxical behavior of PR interval dynamics during exercise and recovery and its relationship to cardiac memory at the atrioventricular node.

This preliminary study deals with the dynamics of the PR interval during exercise testing by using a Bruce protocol in 31 nonmedicated, normal patients with ages of 33 +/- 14 years. The behavior of the PR interval permitted its categorization into 2 groups. In Group I (27 of 31, 87.1% of patients) the PR interval showed the expected biphasic behavior with a gradual shortening with increasing exercise and a gradual lengthening during recovery. In contrast, the PR interval in Group II (4 of 31, 12.9% of patients) showed a triphasic behavior since, toward the end of recovery, there was a second decrease in duration. Because of this temporal relation to the phases of exercise, this paradoxical response, in analogy to what happened to the QT interval during exercise, could have been caused by a form of short-term memory or to varying, but normal, intergroup differences in autonomic function. However, further studies involving a greater number of patients are required to reach definite conclusions.

Adult↗
PubMed2001

Can the degree of concordance with recommendations for a cancer prevention diet and lifestyle be assessed from existing survey information data?

BACKGROUND: The World Cancer Research Fund convened an expert committee who analyzed the literature related to the causation of human cancers. Recommendations for preventing cancer through behavioral practices were formatted into a 14-point guideline. OBJECTIVE: We parsed the cancer prevention guidelines to determine to what extent relevant information on individual behavior could be assessed from conventional food-frequency questionnaires, which are being used in surveys conducted in developing countries. DESIGN: We examined a convenience sample of archival forms completed during 2 independent studies (a case-control and a field study) that used an adapted Willett food-frequency questionnaire that was translated into Spanish for use in Guatemala. RESULTS: All dietary related guidelines, except for salt, were evaluated by both questionnaires. Physical activity, food handling, and food preparation were not addressed by either of the questionnaires, although body mass index and dietary supplements were addressed in the case-control study and field-study questionnaires, respectively. CONCLUSIONS: Although concordance with some of the cancer prevention goals and guidelines can be evaluated from the existing questionnaires, adjustments and additions must be made with respect to salt and supplement use, physical activity, and food handling. Actual weight and height measurements are also needed, particularly in low-income populations.

Adult↗
PubMed1999

Paradoxical behavior of the QT interval during exercise and recovery and its relationship with cardiac memory.

BACKGROUND: Few studies have dealt with the behavior of the corrected (QTc) and uncorrected QT intervals during exercise and recovery. HYPOTHESIS: Based on previously published dynamics of the QT interval during treadmill testing, this study attempted to reevaluate the computer-proposed underlying mechanisms of these dynamics and to determine whether the so-called memory phenomenon could be operative in some subjects without evidence of structural heart disease. METHODS: This study included 42 unmedicated healthcare volunteers, 23 men and 19 women aged between 20 and 42 (mean 31.7) years. All had normal physical examinations, x-rays, and transthoracic echocardiograms. The electrocardiograms were also normal with 12-lead QT interval dispersions of < 90 ms. RESULTS: During exercise and recovery, the behavior of the QT intervals permitted the categorization into two groups. In Group 1 (31/42; 73.8% of subjects) the uncorrected QT interval showed a biphasic pattern consisting of a gradual decrease during incremental exercise followed by a gradual increase during recovery. In contrast, the QTc interval had a triphasic pattern resulting from a slight increase during the early phase of exercise, a gradual decrease at the highest rates, and a final increase during recovery as the rate slowed to control values. In Group 2 (11/42; 36.2% of subjects) the behavior was considered as paradoxical since the uncorrected QT interval displayed in a triphasic pattern whereas the QTc interval yielded a tetraphasic pattern due to the fact that both showed a second decrease during recovery while the rate was decreasing. CONCLUSIONS: Analysis of dynamics behavior of the QTc and the uncorrected QT intervals during exercise showed that some normal subjects had a paradoxical behavior which, because of its temporal relation to the phases of exercise, could be an expression of the so-called memory phenomenon.

Adult↗
PubMed1997

Progressive sensorineural hearing loss, subjective tinnitus and vertigo caused by elevated blood lipids.

The otologist frequently sees patients with progressive sensorineural hearing loss, subjective aural tinnitus and vertigo with no apparent cause. Elevated blood lipids may be a cause of inner ear malfunction on a biochemical basis. To establish the true incidence of this condition, all new patients (4,251) seen during an eight-year period were evaluated; of these, 2,332 patients had complaints of inner ear disease. All had a complete neurotologic examination, appropriate audiometric and vestibular studies and imaging, and blood tests including lipid phenotype studies. Hyperlipoproteinemia was found in 120 patients (5.1%). Most patients were found to be overweight and had additional coexisting conditions such as diabetes mellitus. Treatment with vasodilators and a 500-calorie, high-protein, low-carbohydrate diet yielded improvement of symptoms in 83% of patients within five months of initiation of treatment.

Adult↗
PubMed1996

Activated calcineurin confers high tolerance to ion stress and alters the budding pattern and cell morphology of yeast cells.

The PP2B protein phosphatase, also known as calcineurin, is a regulator of ion homeostasis in yeast cells. We have investigated the physiological consequences of constitutive expression of a recombinant form of calcineurin in which the Ca2+/calmodulin-binding and autoinhibitory domains of the catalytic subunit were deleted. The concomitant expression of the regulatory subunit along with the truncated catalytic subunit resulted in high tolerance to toxic levels of Na+ and Li+. This activated form of calcineurin substituted for the Na+ stress signal to promote the expression of the ENA1 gene, encoding a P-ATPase pump, and to induce the transition of the K+ uptake system to the high affinity mode that restricts influx of Na+ and Li+. In addition, the transcriptional responsiveness of ENA1 to Na+ stress was enhanced. These results demonstrate that calcineurin has a pivotal role in a signaling cascade activated by ion stress in yeast. Moreover, we found that changes in the level of calcineurin activity affected budding pattern and cell morphology. Cells expressing the truncated calcineurin were elongated and budded in an unipolar pattern, whereas calcineurin-deficient mutants budded randomly. These results suggest that calcineurin may also act in the establishment of cell polarity.

Biological Transport↗
PubMed1996

Characterization of spontaneous recurrent ventricular arrhythmias detected by electrogram-storing defibrillators in sudden cardiac death survivors with no inducible ventricular arrhythmias at baseline electrophysiologic testing.

This retrospective study characterized the recurring ventricular arrhythmias with an electrogram-storing defibrillator in survivors of sudden cardiac death who had no inducible sustained ventricular arrhythmias at baseline electrophysiologic testing (EPS). The study group was composed of 24 selected patients with documented ventricular fibrillation (VF) without need of revascularization or chronic antiarrhythmic therapy. The EPS protocol usually consisted of three extrastimuli at two drive cycles at two right ventricular sites. Nonischemic cardiomyopathy was the most frequent structural abnormality (n = 11) followed by coronary artery disease (n = 7). The mean ejection fraction was 0.37 +/- 0.13. Cardiac status did not appear to change during a mean follow-up period of 16.4 +/- 12.5 months, and eight (33%) patients received appropriate shocks in that time period. On the basis of intracardiac electrograms, 7 (88%) patients experienced VF and 1 (12%) patient had ventricular tachycardia as the first recurring arrhythmia. Four patients had additional recurrences and all were VF episodes. VF was usually present from the onset of the arrhythmia. In addition, 9 (38%) patients had nonsustained ventricular arrhythmias that were solely VF in 6 (67%). In conclusion, VF of sudden onset was the most frequent recurring sustained ventricular arrhythmia in this group.

Aged↗
PubMed1996

A comparison of body fat estimates using anthropometry and bioelectrical impedance analysis with distinct prediction equations in elderly persons in the Republic of Guatemala.

Bioelectrical impedance analysis (BIA) has been proposed as a technique to estimate body composition. Its application has extended beyond the clinical setting, however, it remains to be determined if the BIA prediction formulas published to date provide comparable body composition estimates in elderly populations. The objective of this study was to compare the estimates of body fat derived from published prediction equations in a developing country's population such as Guatemala. A total of 234 elderly persons were studied (108 males and 126 females), with ages of 78 +/- 7 and 77 +/- 8 (mean +/- SD) yr, respectively. The height and weight averaged 156.4 +/- 7.9 and 144.0 +/- 7.0 cm, and 54.5 +/- 9.4 and 49.4 +/- 10.6 kg, for males and females, respectively. Measurements included skinfolds (triceps, biceps, subscapular, and suprailiac), and body resistance (BIA). Body fat estimates were derived from four BIA-prediction formulas and three equations based on anthropometry. Mean percent body fat estimates for the overall population obtained from anthropometry and BIA prediction formulas ranged from 22 to 50%. Females had higher estimates compared to males without regard for the method used. Highly significant intermethod correlations were seen, but differences in fat estimation among prediction formulas were noticed and the magnitude of the differences were BIA-formula dependent.

Adipose Tissue↗
PubMed1995

Blood retinol and beta-carotene levels in rural Guatemalan preschool children.

Plasma retinol and beta-carotene levels were measured in 502 preschool Guatemalan children from five rural hamlets. Their ages ranged from 6 to 78 months (mean: 42.9 +/- 19.2 months); 45% males and 55% females. The mean retinol value in the whole group was 0.9 +/- 0.4 mumol/l (range: 0.1 to 8.4 mumol/l). There was no significant difference between sexes in retinol mean values nor in the incidence of retinol values less than 0.7 mumol/l (22% in males, 18% in females). When grouped by age and community, significant low retinol mean values were found in two hamlets in the youngest age group (12 to 23 months) as compared to the other age-groups (p < 0.05). In the other two hamlets, there were no significant differences among retinol means by age-group. The highest prevalence of deficient retinol values by age-group was in the 12 to 23 months group (40%), and decreased as age increased. The mean value for beta-carotene in the whole group was 0.13 +/- 0.18 mumol/l (range: 0.01 to 2.23 mumol/l). There were no significant differences in beta-carotene means between sexes in the whole group. Stratifying the beta-carotene data by age-groups and community, values were significantly higher in the 48-59 months and 72-83 months groups, as compared with the other age groups in two of the communities (p < 0.05). Significant differences across communities for beta-carotene were found only in the 12 to 23 months group.

Age Factors↗
PubMed1994

The protein phosphatase calcineurin is essential for NaCl tolerance of Saccharomyces cerevisiae.

NaCl-sensitive yeast mutants were isolated to identify genes essential for NaCl tolerance. Complementation of a mutant highly sensitive to Na+ and Li+ led to the isolation of the CNB1 gene. This gene encodes the regulatory subunit (CNB) of the Ca2+/calmodulin-dependent protein phosphatase calcineurin. Cells deficient in CNB accumulated Li+ due to reduced expression of ENA1, a gene encoding a P-type ATPase involved in Na+ and Li+ efflux. In addition, the K+ transport system of cnb1 delta cells was not converted to the high affinity state that facilitates better discrimination of K+ over Na+. Thus the cnb1 delta strain resembled a trk1 mutant. These results indicate that adaptation to NaCl stress in Saccharomyces cerevisiae requires a signal transduction pathway involving Ca2+ and protein phosphorylation-dephosphorylation. In this pathway, calcineurin would coordinate gene expression and activity of ion transporters to facilitate ion homeostasis.

Adenosine Triphosphatases↗
PubMed1994

[Relationship between plasmatic lipids and fat soluble vitamins in Guatemalan periurban elderly].

The levels of plasmatic lipids and fat liposoluble vitamins were measured in 107 elderlies (29% males, 71% females) who were residents of a poor periurban neighborhood of Guatemala City. The age ranged between 60-103 years (means +/- sd 69 +/- 8). The mean and sd for the plasmatic levels of lipids and vitamins were (ranges in parenthesis): cholesterol 220 +/- 42 mg/dl (128 to 428); triglycerides: 189 +/- 92 mg/dl (54 to 513); retinol 50 +/- 16 ug/dl (4.5 to 103); beta-carotene 17 +/- 12 ug/dl (12 to 60), tocopherol 1.32 +/- 0.36 mg/dl (0.54 to 2.46). A significant correlation was found in both sexes between cholesterol and retinol (r = 0.3, p < 0.05) and cholesterol and tocopherol (r = 0.4, p < 0.05), triglycerides and retinol (r = 0.3, p < 0.05). Cholesterol and beta-carotene was also significant in women (r = 0.5, p < 0.05). The correlation between triglycerides and beta-carotene by gender was not significant.

Aged↗
PubMed1993

Prevalence of riboflavin deficiency among Guatemalan elderly people and its relationship to milk intake.

Six groups of elderly subjects from central Guatemala were assessed for riboflavin status by using the erythrocyte glutathione reductase activity coefficient (EGRAC). The prevalence of riboflavin deficiency ranged from 50% to 76% among the free-living rural elderly subjects. Milk intake data that were collected from some of the subjects showed a significant correlation (P < 0.0001) between frequency of milk intake and riboflavin status. In a short-term riboflavin supplementation experiment in which nine riboflavin-deficient subjects were given 10 mg riboflavin/d for 3 d, all the subjects' EGRACs were normalized by the supplementation. However, they returned to a state of deficiency within 2 wk while consuming their usual diets without supplementation. It appears that the high prevalence of riboflavin deficiency in elderly Guatemalan people is caused by inadequate intake of riboflavin-rich foods such as dairy products, and that sufficient amounts of riboflavin need to be ingested regularly to maintain satisfactory riboflavin status.

Aged↗
PubMed1993

Riboflavin requirement of healthy elderly humans and its relationship to macronutrient composition of the diet.

The riboflavin requirements of two groups of riboflavin-deficient, but otherwise healthy, Guatemalan elderly persons over the age of 60 y were studied by varying the fat:carbohydrate ratio in two diets. The first group consumed a diet similar in macronutrient content to a Western-type diet with low carbohydrate and high fat; the second group consumed a typical Guatemalan diet with high carbohydrate and low fat. Energy and protein intakes of both groups were similar. Riboflavin status was monitored by weekly measurements of erythrocyte glutathione reductase activity coefficient (EGRAC) and urinary riboflavin excretion. Increasing increments of riboflavin were added to the subjects' diets until their status was normalized, as indicated by EGRAC of < 1.34 and a sharp increase in urinary riboflavin excretion. Using the EGRAC method, the mean value of riboflavin intake at which the subjects' EGRAC reached the limit of normality was 1.37 +/- 0.03 mg/d in the first phase and 1.29 +/- 0.03 mg/d in the second phase. The sharp increase in urinary excretion occurred at riboflavin intakes of 1.13 and 1.03 mg/d for Groups 1 and 2, respectively. Thus, the differences between the two groups suggest that diets with a lower fat:carbohydrate ratio can decrease the dietary need for riboflavin. The dietary requirement of riboflavin, as estimated by the more reliable urinary excretion method, was 1.1-1.3 mg/d for those consuming the Western-type diet, which is similar to values found over 40 y ago in young adults. We conclude that the dietary requirements of riboflavin in the elderly do not differ from those of young adults.

Adult↗
PubMed1986

Sustained ventricular tachycardia in chronic chagasic myocarditis: electrophysiologic and pharmacologic characteristics.

Sustained ventricular tachycardia (VT) develops in many patients with chronic Chagasic myocarditis. Programmed stimulation was used to study the electrophysiologic characteristics of VT in 15 patients with Chagas' cardiomyopathy. Nine patients were in New York Heart Association functional class I, 5 were in class II and 1 patient was in class III. The average ejection fraction was 56 +/- 7%, which is somewhat better than that reported in patients with VT owing to idiopathic cardiomyopathy. In 11 patients VT could be reproducibly initiated and terminated by programmed stimulation. Intravenous mexilitene prevented induction of VT in 7 of 8 patients; amiodarone did not prevent induction in 3 of 4 patients. Our data indicate that the mechanism of VT is likely to be reentrant in many patients, and therefore VT can be produced by extrastimuli. Electrophysiologic study is therefore useful for establishing the diagnosis of sustained VT and may be useful for guiding initial therapy in selected cases of Chagas' disease.

Adolescent↗
PubMed1983

Radionuclide evaluation of left-ventricular function in chronic Chagas' cardiomyopathy.

Left-ventricular ejection fraction (LVEF) and abnormalities of regional wall motion (WMA) were studied by means of radionuclide ventriculography in 41 patients prospectively diagnosed as having chronic Chagas' disease. Thirteen patients were asymptomatic (ASY), 16 were arrhythmic (ARR), and 12 had congestive heart failure (CHF). Mean LVEF was normal in ASY (0.64 +/- 0.06) but markedly depressed in CHF (0.28 +/- 0.08). Regional WMAs were minimal in ASY and their severity increased in ARR. Most CHFs (75%) had diffuse hypokinesia of the left ventricle. The region most frequently affected was the infero-apical (63%). Seven patients had a distinct apical aneurysm. Correlation between radionuclide and contrast ventriculography data was good in 17 patients. For LVEF, r = 0.90. For WMA there was agreement between the two techniques in 77% of 65 segments compared. Best agreement occurred with infero-apical lesions (88%), and worst with septal (69%). Selective coronary arteriography showed normal arteries in all patients. Therefore, chronic Chagas' heart disease joins ischemic heart disease as a cause of regional WMA.

Adult↗