Biomedical subjects

A Chavez

Publications and source records attributed to A Chavez.

At least 19 recordsLinked to original sources

PubMed2006

Rabeprazole containing triple therapy to eradicate Helicobacter pylori infection on the Texas-Mexican border.

BACKGROUND: Antibiotic resistance and duration of therapy influence the success of proton-pump inhibitor-containing Helicobacter pylori eradication therapy. Clarithromycin resistance is associated with treatment failure. AIM: To examine the success of a 7-day rabeprazole-clarithromycin-amoxicillin therapy in the study population. METHODS: Adults from Ciudad Juarez with H. pylori infections identified by culture or histology received rabeprazole 20 mg, clarithromycin 0.5 g and amoxicillin 1 g, each b.d. for 7 days. Outcome was assessed by 13C-urea breath test carried out 4+ weeks after treatment. RESULTS: A total of 111 patients were enrolled and evaluated by urea breath test; 102 completed the full 7 days therapy. Two deviated from protocol, and five stopped because of adverse events. The cure rate (intention-to-treat) was 85% (95% CI: 78-91%); the per-protocol cure rate was 85% (95% CI: 78-91%). Side-effects were not serious and only 6.6% of those with adverse events stopped medication. Only three isolates were clarithromycin-resistant and none was cured. Compliance explained most of the successes. CONCLUSIONS: In the study population a 7-day rabeprazole triple eradication therapy was both effective and well-tolerated. Clarithromycin resistance was uncommon. We observed a slightly better outcome but consistent with results from recent large studies in US populations.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2006

Particle size distribution to design and operate an APT process for agricultural wastewater reuse.

Total suspended solids is a parameter commonly used to operate and design coagulation-flocculation processes. Nevertheless, their application for an advanced primary treatment (a high performance but low dose demand coagulation processes coupled with a high rate sedimentator, sometimes called enhanced primary treatment) is not the best option to produce an effluent for agricultural irrigation. This paper compares the best operating conditions obtained using the TSS or the PSD (particle size distribution) as parameters to follow the efficiency. The treatment objective was to remove particles >20 microm, in such conditions that the effluent can contain organic matter and nutrients necessary for crops with a reduced number of helminth ova (with sizes between 20 to 80 microm). Using the TSS as parameter, the best coagulation (460 s(-1), 60 s contact time and 300 micromolAl/L) and flocculation (20 s(-1) with 15 min) conditions produced an effluent with 1.2 HO/L. To obtain a similar results but using operating conditions determined with the PSD at a three times lower coagulant dose can be employed (diminishing operating costs and reducing the quantity of sludge produced), and a reduction on energy consumption of around eight times can be reached. Best operating conditions defined using the PSD (160 s(-1), 60 s contact time and 100 micromolAl/L) produced an effluent with <0.4 HO/L.

Agriculture↗

PubMed2004

Particle size distribution as a useful tool for microbial detection.

Worldwide, raw or treated wastewater is used for irrigation. However, this practice implies that the microbial content must be controlled. Unfortunately, detection techniques for microorganisms are costly, time consuming, and require highly trained personnel. For these reasons, this study used particle size distribution to measure the microbial quality of wastewater through correlations between the number or volume of particles and the concentration of fecal coliforms, Salmonella spp. and helminth ova. Such correlations were obtained for both raw and chemically treated wastewater. The best fit was the one for helminth ova, which applies for both the influent and effluent and also for all the coagulants involved. This technique allows the on-line quantification of helminth ova at a cost of US$3 and it takes only 5 minutes, instead of the US$70 and 5 days for the standard technique. With respect to the coagulants applied, their behavior is different only for particles smaller than 8 microm, and thus this value is considered as the critical size for this particular treatment. The best coagulant was the aluminium polychloride. In addition, this work establishes the distribution of COD, TSS, nitrogen, and phosphorous for particles smaller and larger than 20 microm.

Agriculture↗

PubMed1999

Medicolegal aspects of imaging and Internet communications.

Many facial plastic surgeons have set up their own personal World Wide Web (WWW) pages with an electronic mail link to communicate with and educate prospective patients. The possible dilemma is in that these services are provided without actually meeting patients face to face. Also, despite the growing popularity of computer imaging systems, it is not clear whether the medical and legal advantages of using such a system outweigh the disadvantages. The purpose of this article is to evaluate these aspects and to provide some protective guidelines. An examination of possible causes of actions arising from computer imaging suggests that surgeons who follow a few simple guidelines, and who use computer imaging responsibly and cautiously, minimize their legal liability. Issues surrounding Internet discussion groups, posted medical advice, intellectual property, and the use of an electronic mail link are also discussed.

Humans↗

PubMed1999

A comparison of cycle control with monophasic levonorgestrel/ethinylestradiol 100 micrograms/20 micrograms versus triphasic norethindrone/ethinylestradiol 500-750-1000 micrograms/35 micrograms: a multicenter, randomized, open-label study.

OBJECTIVES: This multicenter, randomized, open-label study was undertaken to compare the effects on menstrual cycle control of two oral contraceptive regimens: monophasic levonorgestrel (LNG) 100 micrograms/ethinylestradiol (EE) 20 micrograms (Alesse or Loette) and triphasic norethindrone (NET) 500-750-1000 micrograms/EE 35 micrograms (OrthoNovum 7/7/7). METHODS: Healthy women with normal menstrual cycles were enrolled and completed up to four cycles of study medication. A total of 384 cycles in the LNG/EE group and 400 cycles in the NET/EE group were evaluable for analysis of cycle control. RESULTS: For all treatment cycles, the percentage of cycles classified as normal was consistently higher in the LNG/EE group than in the NET/EE group. By cycle 4, 69.9% of cycles with LNG/EE and 54.4% with NET/EE (p < 0.05) were normal. In individual cycles, consistently lower occurrences of intermenstrual bleeding (total bleeding and/or spotting) were seen for the LNG/EE group, although these differences were not statistically significant. Withdrawal bleeding characteristics were comparable between the two groups, except for the length of the latent period, which was significantly longer in the LNG/EE group. The incidence of treatment-emergent adverse events was similar in the two groups. CONCLUSION: This study indicates that the monophasic LNG/EE 100 micrograms/20 micrograms provides better cycle control than the multiphasic NET/EE product, despite its lower EE dose.

Adolescent↗

PubMed1998

Advantages and disadvantages of computer imaging in cosmetic surgery.

BACKGROUND: Despite the growing popularity of computer imaging systems, it is not clear whether the medical and legal advantages of using such a system outweigh the disadvantages. OBJECTIVE: The purpose of this report is to evaluate these aspects, and provide some protective guidelines in the use of computer imaging in cosmetic surgery. METHODS: The positive and negative aspects of computer imaging from a medical and legal perspective are reviewed. Also, specific issues are examined by a legal panel. RESULTS: The greatest advantages are potential problem patient exclusion, and enhanced physician-patient communication. Disadvantages include cost, user learning curve, and potential liability. CONCLUSION: Careful use of computer imaging should actually reduce one's liability when all aspects are considered. Recommendations for such use and specific legal issues are discussed.

Communication↗

PubMed1997

Risk analysis of coronary bypass surgery after acute myocardial infarction.

BACKGROUND: Current strategies for management of acute myocardial infarction (MI) include thrombolysis, angioplasty, and coronary bypass surgery singly or in combination. This study was designed to identify contemporary risk factors for coronary bypass surgery among patients in this high-risk group. METHODS: Between June 1992 and December 1995, 1181 consecutive patients underwent isolated coronary bypass surgery. Of these, 316 underwent coronary bypass surgery within 21 days of MI. Mean age was 65 years (range, 33 to 87 years), and 73% were male. There were 166 patients with stable angina (group 1), 107 patients with unstable angina requiring intravenous nitroglycerin for a control of ischemia (group 2), 20 patients with angina requiring intraaortic balloon counterpulsation for stabilization (group 3), and 23 patients with severe postinfarction ischemia complicated by cardiogenic shock (group 4). RESULTS: The overall in-hospital mortality rate was 5.1% (16 of 316), which was higher (p < 0.05) than the 2.5% (22 of 865) among patients undergoing coronary bypass surgery without recent myocardial infarction. Mortality increased with severity of clinical preoperative status and was 1.2% in group 1, 3.7% in group 2, 20.0% in group 3, and 26% in group 4. Serious postoperative morbidity occurred in 7.3% of patients. Multivariate logistic regression analysis identified preoperative intraaortic balloon counterpulsation, left ventricular dysfunction, and renal insufficiency as the only independent correlates of mortality. CONCLUSIONS: Coronary bypass surgery can be safely performed in stable patients at any time after acute MI, with an operative mortality similar to elective surgery. Thus, in this era of medical cost containment, there is no apparent indication for prolonged stabilization attempts that delay surgery.

Adult↗

PubMed1997

Assessment of the economic impact of an overage reduction program in the operating room.

STUDY OBJECTIVES: To delineate excessive supply preparation in the operating rooms (ORs) of Yale-New Haven Hospital, and to measure the reduction in such overage as a result of nursing and administration cost-containment efforts. DESIGN: Before and after trial. SETTING: Inpatient ORs of Yale-New Haven Hospital. INTERVENTIONS: After the initial documentation of overage, several cost-containment measures were instituted, including nursing education, review of overage data, and updating of surgical request lists. MEASUREMENTS AND MAIN RESULTS: The hospital cost of case-specific overage generated by all surgical procedures performed during two 2.5-month periods in 1992 and 1994 (before and after the interventions) were compared. One-thousand three hundred eighteen cases in 1992 were compared with 1,367 cases in 1994. A 45% reduction in mean per case overage occurred between the two assessment periods. Extrapolation of the data to the incidence of similar cases throughout the United States projected a comparable savings. CONCLUSIONS: Efforts to increase the efficiency of OR supply management can be measured, in part, by overage evaluation, which can serve as a resource for focusing efforts at cost-containment.

Cost Control↗

PubMed1997

Inhibition of inducible nitric oxide synthase ameliorates endotoxin-induced gut mucosal barrier dysfunction in rats.

BACKGROUND & AIMS: The permeability of intestinal epithelial monolayers increases after exposure to nitric oxide. The aim of this study was to investigate the role of excessive NO production on intestinal barrier function in rats injected with lipopolysaccharide (LPS). METHODS: Rats were injected with saline or LPS (5 mg/ kg). Bacterial translocation to mesenteric lymph nodes, liver, and spleen was assessed 24 hours after LPS injection. Mucosal permeability was determined by loading fluorescein-labeled dextran (mol wt, 4000 daltons) into an intestinal segment and measuring its appearance in plasma. Intestinal mucosal mitochondrial respiration was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. RESULTS: Intestinal tissue from LPS-challenged rats showed upregulation of inducible NO synthase (iNOS) messenger RNA expression and subsequent up-regulation of iNOS enzymatic activity. Plasma concentrations of nitrite plus nitrate (NO2-/NO3-) were increased for at least 24 hours after injection of LPS. Treatment with the selective iNOS inhibitor, aminoguanidine, inhibited iNOS enzymatic activity and overproduction of NO2-/NO3-. LPS-induced bacterial translocation was reduced by aminoguanidine. LPS-induced intestinal hyperpermeability was ameliorated by both aminoguanidine and another selective iNOS inhibitor, S-methylisothiourea. LPS depressed intestinal mucosal mitochondrial function, and this effect was ameliorated by aminoguanidine. CONCLUSIONS: Overproduction of NO may contribute to intestinal barrier dysfunction in LPS challenged rats, possibly by interfering with mitochondrial oxidative metabolism.

Animals↗

PubMed1997

Molecular epidemiology of human rotaviruses in Santiago, Chile.

BACKGROUND: Protective immunity against rotavirus infection is directed against antigenic epitopes on the outer capsid proteins VP7 and VP4. Our aim was to characterize the epidemiology of rotavirus antigenic types over time in Santiago, Chile. METHODS: We prospectively obtained 2097 stool samples for rotavirus testing, VP7 (G1 to G4) and VP4 (P4, P6, P8, P9) typing from children with diarrhea evaluated in emergency rooms of 5 base hospitals of Santiago. In addition 256 rotavirus-positive samples collected between 1985 and 1987 in the north health care area of Santiago were studied. RESULTS: Of 995 rotavirus-positive samples obtained 825 (82%) were typable for 1 or more VP7 types. G1 represented 81% of the G-typed samples during 1993 through 1995 and 77% during 1985 through 1987, predominating in all health care areas. G2 was next most common in all 5 areas, representing 6 to 23% of typed samples, with 1 area, the Southeast concentrating a significantly higher number of G2 infections. G2 declined from 35% of rotavirus-positive samples in 1993 to 0% in 1995 (P < 0.001), and from 25% to 2% in the north health care area from 1985 to 1987 (P < 0.001). G4 was uncommon and significantly more prevalent in 1985 through 1987 than in 1993 through 1995 (7% vs. 3%, P = 0.015). G3 was not detected. G1P8 (53%) and G2P4 (16%) combinations were by far the most commonly detected G-P associations. CONCLUSIONS: In Santiago, Chile, rotavirus antigenic type G1P8 has been highly prevalent and G2P4 has circulated in cycles. Differences in epidemiology of rotavirus antigenic types worldwide may prove to be relevant in efficacy of rotavirus vaccines.

Child↗

PubMed1996

Recovery of unused operating room supplies for overseas orthopedic surgery.

Recovery of surplus operating room (OR) materials may contribute needed supplies to volunteer overseas surgical efforts. However, recovery often generates supplies that are highly heterogeneous in nature. In order to evaluate the nature and quantity of supplies useful to orthopedic surgical missions, the present investigation evaluated the material generated from 381 consecutive orthopedic cases performed during three 3-month assessment periods over 3 years. The amount of recovered material varied markedly within and among procedure types as well as surgeons. Nevertheless, the long-term, OR-wide recovery program at Yale-New Haven Hospital has provided a highly reliable source of usable materials over the 4-year life of the program.

Equipment and Supplies↗

PubMed1994

LOCALIZATION OF ANGIOTENSIN II RESPONSES IN THE TROUT CARDIOVASCULAR SYSTEM

The renin/angiotensin system (RAS) is a tonic anti-drop regulator of arterial blood pressure in many teleosts. In trout, angiotensin II (ANG II) has no direct constrictor effect on large arteries or veins and the identity of specific cardiovascular pressor effectors is unknown. Potential targets of angiotensin activation were examined in the present experiments using perfused organs and isolated tissues from the rainbow trout Oncorhynchus mykiss. Perfused gill (arches 2 and 3), perfused skeletal muscle-kidney (via the dorsal aorta; PDA) and perfused splanchnic (via the celiacomesenteric; PCM) circulations vasoconstrict in response to salmonid ANG II in a dose-dependent manner. ANG II was significantly (P¾0.05) more potent in the PCM than in the PDA, and both preparations were more responsive than the gills: pD2=8.0±0.20 (10) for PCM; pD2=7.5±0.07 (13) for PDA; pD2=6.9 ±0.21 (8) for gill arch 3; pD2=6.7±0.23 (8) for gill arch 2; mean ± s.e.m. (N), respectively. Salmonid angiotensin I (ANG I) also produced a dose-dependent constriction of the PDA and PCM. Angiotensin converting enzyme (ACE) activated nearly 100 % of ANG I to ANG II in a single pass through the PDA, whereas PCM conversion was estimated to be less than 10 %. Inhibitors of adrenergic constriction partially prevented ANG II responses in the PDA but did not affect PCM responses. ANG II did not affect paced rings of ventricular muscle in the presence of high or low [Ca2+] or epinephrine concentrations, nor did it have any inotropic or chronotropic effects in the in situ perfused heart. Red blood cell swelling was unaffected by ANG II. Similarly, the effects of ANG II on gut, urinary bladder and gall bladder smooth muscle were negligible or non-existent; thus, an increase in splanchnic resistance due to extravascular compression can be discounted. These results indicate that, in trout, the systemic microcirculation is the major cardiovascular effector of angiotensin-mediated pressor responses. In addition, the RAS has little direct effect on non-vascular smooth muscle or the heart. From an evolutionary perspective, the initial site of direct systemic RAS action appears to be the vascular microcirculation.

Journal Article↗

PubMed1991

Household size, food intake and anthropometric status of school-age children in a highland Mexican area.

Large household size is widely regarded as a risk factor for malnutrition in developing countries, particularly for infants and young children. This study examines the extent to which household size is related to nutritional status in school-age children in the Solis Valley in highland Mexico. The relationships of food intake, anthropometric measures, and household size are assessed in a sample of 110 children (7-9 years of age), who were followed longitudinally for a minimum of one year as part of the Collaborative Research Support Program on Food Intake and Human Function. Diets in the valley are characterized by very low intake of animal food products and are heavily dependent on maize, which is primarily home-produced. Growth faltering is pervasive; the mean Z score for height-for-age in the sample is--1.6 of the NCHS reference standard. Children from larger households are significantly shorter and consume diets of poorer quality, as assessed by intake of foods from animal sources. These relationships remain statistically significant in regression analyses that control for household economic status. It therefore appears that the resources available to households in the Solis Valley are inadequate to buffer children in even more advantaged households from the stresses of maintaining large families.

Anthropometry↗

PubMed1991

Nutritional supplementation and the development of linear enamel hypoplasias in children from Tezonteopan, Mexico.

The purpose of this study was to compare the effect of nutritional intake during tooth-crown formation on the subsequent development of linear enamel hypoplasias (LEHs) in Mexican nonsupplemented (control) adolescents (n = 42) and adolescents who had received daily nutritional supplements since birth (n = 42). The proportion of individuals with LEHs was nearly two-fold greater (74.4%; 95% CI 64.7-84.1%) in the control than in the supplemented group (39.5%; 95% CI 28.6-50.4%; chi 2 = 9.44; P = 0.001). Although the estimated peak age at formation, approximately 2-2.5 y, is similar in both groups, the proportion of early (before 1.5 y) and late (after 3.0 y) LEHs was greater in the control group. LEH was also more common in females and was associated with an increase in illness days and a decrease in growth velocity. Results of this study suggest that mild to moderate undernutrition during enamel formation is causally linked to the formation of LEHs.

Anthropometry↗

PubMed1991

Comparative research in social epidemiology: measurement issues.

The aim of comparative research in social epidemiology is to determine how risk factors for disease may vary within and between sociocultural and ethnic groups and in relation to outcomes. This aim assumes that measurement equivalence within and between social groups can be established, an assumption usually left untested. A model is presented here for deriving cross-culturally valid measures that are also intraculturally sensitive. Measurements so derived can then be used to compare cross-cultural and intracultural effects in a single analytic model. This approach is illustrated by pooling data on social stressors, social supports, and blood pressure from three studies.

Adult↗

PubMed1989

A cautionary note on the use of autoregressive models in analysis of longitudinal data.

Rosner et al. presented a simple, easily implemented modelling method for retaining time order relationships in analyses of longitudinal data when successive measures are correlated. Evaluation of time order is particularly useful in epidemiologic studies concerned with exposure to potentially toxic substances and subsequent outcome, but may also have use in more traditional growth studies that relate intake to subsequent development. The analysis allows for unequally spaced measures and missing data. The estimation method permits varying numbers of observations per subject and, with measures equally spaced, one can fit the model with use of ordinary least squares regression software. We report on a potential false association that can result when both exposure and outcome are related to time. We illustrate this problem with a small scale simulation and example. We also note a more serious problem with Rosner's approach in interpreting parameters. Although the model may be useful for prediction, parameters depend on the autocorrelation and are not readily interpretable. We recommend alternative modelling strategies be used when autocorrelation of errors is suspected.

Age Factors↗

PubMed1989

[Are there any differences between myocardial infarction with Q and non-Q in ECG].

Recent literature provides evidence that Non-Q wave myocardial infarction (Non-Q MI) has a different intrahospital course and prognosis than Q-wave myocardial infarction (Q-MI). We evaluated clinical and laboratory characteristics, complications and therapeutic requirements of 557 consecutive patients, 440 with Q-MI and 117 with Non-Q MI. Risk factors for coronary artery disease did not differ among groups. Non-Q MI patients had a significantly higher incidence of previous cardiac events such as myocardial infarction, angina pectoris and heart failure. Peak CPK enzyme values were significantly lower in Non Q MI patients (952 +/- 753 vs 1,743 +/- 1,425 VI/l p less than 0.05). Early complications were different for both groups: The incidence of heart failure, ventricular arrhythmias and conduction defects was lower in Non-Q MI patients while the incidence of unstable angina pectoris and need for aorto coronary by-pass surgery was higher (18 vs 12%, 17 vs 7% respectively, p less than 0.05). Mortality was not different (8.4% in Non-Q MI vs 12.3% in Q MI). Thus, Non Q MI appears to have a more benign clinical course than Q-MI in terms of less complications such as heart failure, ventricular arrhythmias and conduction defects. However, Non-Q MI is a potentially unstable clinical entity with a higher incidence of early post MI angina pectoris requiring a more aggressive medical and surgical therapy.

Aged↗

PubMed1987

Arterial blood pressure and individual modernization in a Mexican community.

The relationship between changes in individual behavior and arterial blood pressure was studied in a town in central Mexico. Two models relating modern behaviors and blood pressure were examined. The first, or 'accretion model' suggests that any adoption of modern behaviors results in stress and deleterious health change. The second, or 'discrepancy model', suggests that the adoption of modern behaviors is problematic only when the individual has limited access to economic resources. Empirical support for both models was found, but the best predictor of blood pressure was a single index of modern lifestyle, including acquisition of material culture and engaging in cosmopolitan behaviors. The effect of modern lifestyle on blood pressure was independent of the effects of age, sex, sodium intake, and body mass index. Overall the results are consistent with a model in which degree of community modernization, especially as it influences social class structure, is a boundary condition determining the relationship between the adoption of modern behaviors and health status.

Adult↗