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Biomedical subjects

J Alonso

Publications and source records attributed to J Alonso.

At least 145 records · Page 8Linked to original sources
PubMed1998

A generalization of Prentice's law for lenses with arbitrary refracting surfaces.

A generalization of the Prentice's law is presented in this paper. The idea consists of removing some (but not all) of the approximations that comprise the paraxial approach. In that way, we obtain a new formulation that permits us to compute the prismatic power of a lens made up of arbitrary refracting surfaces, and to improve the precision obtained by Prentice's law when applied to monofocal lenses. The resulting formalism is simple and manageable and its derivation leads us to a precise definition of the local dioptric power matrix, introduced in a previous paper, as well as a better understanding of the same.

Humans↗
PubMed1998

Rasch measurement for reducing the items of the Nottingham Health Profile.

The present study aimed to develop a short form of the Spanish version of the Nottingham Health Profile (NHP) by means of Rasch analysis. Data from several Spanish studies that included the NHP since 1987 were collected in a common database. Forty-five different studies were included, covering a total of 9,419 subjects both from the general population and with different clinical pathologies. The overall questionnaire (38 items) was simultaneously analyzed using the dichotomous response model. Parameter estimates, model-data fit and separation statistics were computed. The items of the NHP were additionally regrouped into two different scales: Physical (19 items) and Psychological (19 items). Separated Physical and Psychological parameter estimates were produced using the simultaneous item calibrations as anchor values. Misfitting items were deleted, resulting in a 22 item final short form (NHP22)-11 Physical and 11 Psychological-. The evaluation of the item hierarchies confirmed the construct validity of the new questionnaire. To demonstrate the invariance of the NHP22 item calibrations, Rasch analyses were performed separately for each study included in the sample and for several sociodemographic and health status variables. Results confirmed the validity of using the NHP22 item calibrations to measure different groups of people categorized by gender, clinical and health status.

Health Status Indicators↗
PubMed1997

Chronic obstructive pulmonary disease stage and health-related quality of life. The Quality of Life of Chronic Obstructive Pulmonary Disease Study Group.

BACKGROUND: The American Thoracic Society recently recommended that chronic obstructive pulmonary disease be staged on the basis of the percentage of predicted FEV1. OBJECTIVE: To examine 1) the relation between the american Thoracic Society system for staging chronic obstructive pulmonary disease and health-related quality of life and 2) the effect of self-reported comorbid conditions on health-related quality of life. DESIGN: Cross-sectional study. SETTING: Outpatient clinics of respiratory departments of four hospitals and one primary health care center in spain. PATIENTS: 321 consecutive male patients with chronic obstructive pulmonary disease. MEASUREMENTS: Functional respiratory impairment, FEV1, respiratory symptoms, and health-related quality of life. Respiratory symptoms and health-related quality of life were measured by using the Spanish version of the St. George's Respiratory Questionnaire and the Nottingham Health Profile. RESULTS: Patient scores on the St. George's Respiratory Questionnaire were moderately to strongly associated with disease staging (r = 0.27 to 0.51). Compared with reference values, values for health-related quality of life for patients with stage I disease were substantially higher on the St. George's Respiratory Questionnaire (6 and 34; p < 0.001) and values for impairment were significantly greater in stage 1 patients with comorbid conditions (19 and 36; P = 0.001). At least one concomitant chronic condition was found in 84% of study patients. Comorbid conditions only partly influenced the observed pattern of deterioration of health-related quality of life with worsening stages of disease. CONCLUSION: Staging criteria for chronic obstructive pulmonary disease based on percentage of predicted FEV1 separated groups of patients with varying degrees of impairment in health-related quality of life. Contrary to expectations, even patients with mild disease showed substantially compromised health-related quality of life. Comorbid conditions influenced the relation between chronic obstructive pulmonary disease and health-related quality of life.

Comorbidity↗
PubMed1997

Six-month outcome in patients with myocardial infarction initially admitted to tertiary and nontertiary hospitals. RESCATE Investigators. Recursos Empleados en el Síndrome Coronario Agudo y Tiempos de Espera.

OBJECTIVES: The aim of the present study was to ascertain whether the degree of accessibility to coronary angiography and revascularization results in differing usages or outcomes, or both, in the setting of a high coverage national health system. BACKGROUND: The selective use of coronary angiography and revascularization procedures in the management of acute myocardial infarction (MI) remains controversial. METHODS: A cohort of 1,460 consecutive patients with a first MI admitted to four referral teaching hospitals (one with tertiary facilities) were followed up for 6 months after admission. Only patients initially admitted to each of the study hospitals were retained for analysis in the original hospital's cohort. End points were 6-month mortality and readmission for reinfarction, unstable angina, heart failure or severe ventricular arrhythmia. RESULTS: Patients admitted to the tertiary hospital were more likely to undergo coronary angiography (adjusted relative risk 4.22, 95% confidence interval [CI] 3.37 to 5.45) than those admitted to the nontertiary sites (use rate: 22.1% for nontertiary care, 55.5% for tertiary care). Revascularization procedures were performed in 21.2% of patients in the tertiary hospital and in 8.3% in the nontertiary hospitals (p < 0.0001). Median delay for emergency coronary angiography was shorter in the tertiary hospital (within 1 vs. 2 days, p < 0.0001). Six-month mortality or readmission rates were similar (23.7% and 24.7% for tertiary and nontertiary care, respectively). After adjustment for comorbidity and disease severity, the relative risk of death or readmission for the tertiary hospital was 1.03 (95% CI 0.69 to 1.53) times that of the nontertiary hospitals. CONCLUSIONS: Selective use of coronary angiography and revascularization procedures may be as effective as less restricted use in the management of acute MI.

Aged↗
PubMed1997

[Clinical results and perceived health among patients with hip prosthesis].

BACKGROUND: Assessment of total hip replacement has been performed without careful attention to the patients' perceived health. The objective of this study is to assess, in a standardized way, the benefit of hip replacement in terms of hip pain, mobility, and function and as an increase in general perceived health. And to quantify clinical complications of the procedure. PATIENTS AND METHODS: Observational study of a series of 131 consecutive patients of a tertiary hospital to whom two health questionnaires (one specific and the other generic) were administered before and one year after total hip replacement. The specific instrument, the Hip Pain and Function (HPF) scale, measures the functional capacity of the hip gathering information on pain, function and mobility. Scores for the HPF range from 0 (maximal limitation of functional capacity) to 85 (no limitation). The generic instrument used, the Nottingham Health Profile (NHP) measures perceived health and scores range from 0 (best health status) to 100 (worse). RESULTS: Mean age of patients was 63 years; ostheo-arthritis was the most frequent diagnosis (78%), with 42% of the patients with associated pathology. An improvement in both hip functional capacity and perceived general health was observed after one year. HPF scores increased from 26.6 at baseline to 69.9 (p < 0.001). Improvements was important and statistically significant in each of the three dimensions of the specific instrument: Pain, Function and Mobility. Overall score for the NHP changed from 50.9 (at baseline) to 18.1 (p < 0.001). Regression analysis showed only two variables associated with improvement: a higher improvement hip function for patients with no other joints affected; and a higher improvement of perceived health in patients over 70 years with cemented prosthesis, that had a worse initial perceived health status. CONCLUSION: Total hip replacement decreases pain and significantly improves hip mobility and function, as well as the general perceived health. The improvement of perceived health was higher in patients over 70 years.

Adult↗
PubMed1997

[Assessment of quality of life related to health 2 years after coronary surgery].

BACKGROUND: The determinants of quality of life after coronary artery surgery in well defined health care populations are still incompletely understood. The aim of the present study was to assess the health related quality of life associated with coronary artery bypass surgery as performed in a tertiary public hospital, and also to investigate its association with clinical variables. PATIENTS AND METHODS: All survivors of a first coronary artery bypass grafting operation performed during a calendar year in a single center (100 patients) were included for assessment two years after surgery. Assessment included a review of the clinical records, a structured clinical interview and the administration of three questionnaires of perceived health (Nottingham Health Profile, Duke Activity Status Index and SF-36 Health Survey). RESULTS: The mean scores of the administered questionnaires corresponded to a moderate overall impairment of perceived health, with wide individual variations. Chronic stable postoperative angina pectoris (28% of patients), worse clinical functional grade (either due to angina or to others causes), comorbidity (51% of patients) and female sex were significantly associated with worse scores. CONCLUSIONS: In the study population, postoperative angina, impairment of the clinical functional grade (due to angina or to other conditions), and female gender were the major determinants of impaired health related quality of life after coronary artery bypass surgery. As such determinants are associated with anatomoclinical variables in the population undergoing coronary bypass surgery and also with perioperative variables, appropriate effectively studies appear to be indicated for the assessment of this surgical procedure.

Aged↗
PubMed1997

Crystallization and preliminary X-ray diffraction analysis of proline iminopeptidase from Xanthomonas campestris pv. citri.

Proline iminopeptidase from Xanthomonas campestris pv. citri, displaying no significant sequence homology to any protein previously analyzed by X-ray crystallography, has been crystallized using the vapour diffusion method. Two different orthorhombic crystal forms (space group C222 and I222) were obtained from a solution containing NaCl or polyethylene glycol monomethyl ether (MW 5000) as precipitating agent for the native and lanthanum-derivatized protein, respectively. Complete diffraction data sets have been collected up to 2.6 A (native) and 3.0 A (lanthanum derivative) resolution. Cell dimensions are a= 147.2 A, b = 167.8 A, and c = 85.6 A (C222) and a = 146.7 A, b = 167.7 A, and c = 171.4 A (I222), respectively. Considerations of the possible values of V(m) and analysis of the self-rotation function of the native crystals account for the presence of one dimer per asymmetric unit, whereas a tetramer probably would occupy the smallest crystallographically independent crystal portion in the lanthanum-derivatized protein crystals.

Aminopeptidases↗
PubMed1997

International variation in ophthalmologic management of patients with cataracts. Results from the International Cataract Surgery Outcomes Study.

OBJECTIVES: To describe international variation in the management of patients with cataacts in 4 health care systems and to discuss the potential implications for cost and utilization of services. DESIGN: To characterize current clinical practice on patients with no coexisting medical or ocular conditions, a standardized questionnaire was sent to random samples of ophthalmologists in the United States (response rate, 82.5%), Canada (66.9%), and Barcelona, Spain (70.4%), and to all ophthalmologists in Denmark (80.1%). From the United States, 526 ophthalmologists who performed cataract surgery participated in the study; there were 276 from Canada, 89 from Barcelona, and 82 from Denmark. RESULTS: Although in all 4 sites most surgeons reported that they performed A-scanning, fundus examination, and refraction routinely before surgery, significant crossnational variation was observed in preoperative ophthalmic and medical testing. While preoperative medical tests were virtually unused in Denmark, they were widely used in the other sites. A significantly higher proportion of the surgeons in the United States and Barcelona reported that they performed less than 100 extractions per year compared with surgeons in Canada and Denmark (P < .001). A significantly higher proportion of the surgeons in the United States and Canada were performing predominantly phacoextraction compared with surgeons in Denmark and Barcelona (P < .001). Both within and across sites, considerable variation in number of follow-up visits and postoperative tests was observed. CONCLUSIONS: Significant international variation in the management of healthy patients with cataracts has been observed. If less intensive care is not associated with poorer outcomes, there is the potential for less costly care of patients with cataracts. Further research identifying the most cost-effective practices is needed.

Adult↗
PubMed1997

International variation in anesthesia care during cataract surgery: results from the International Cataract Surgery Outcomes Study.

OBJECTIVES: To describe international variation in anesthesia care and monitoring during cataract surgery and to discuss its implications for cost and safety. METHODS: A standardized questionnaire was sent to random samples of ophthalmologists in the United States, Canada, and Barcelona, Spain, and to all ophthalmologists in Denmark. The survey was conducted in 1993 and 1994. Certified ophthalmologists who had performed 1 or more cataract extractions in the previous year were eligible for enrollment. RESULTS: The response rates were 62% in the United States (n=148), 67% in Canada (n=276), 70% in Barcelona (n=89), and 80% in Denmark (n=82). The anesthetic technique for cataract surgery varied significantly between sites (P<.001). Surgeons reported that retrobulbar blocks were used for 46% of the cataract extractions in the United States, 70% in Canada, 66% in Denmark, and 31% in Barcelona. In Barcelona, general anesthesia was used for 23% of the cataract extractions; it was used for less than 3% of the extractions at the other 3 sites. Peribulbar blocks or topical anesthesia was used for the remaining extractions. In the United States, Canada, and Barcelona, surgeons reported that vital functions were monitored during more than 97% of the extractions and anesthesia surveillance was used during more than 78% of the extractions. In Denmark, ophthalmologists reported that vital functions were monitored and anesthesia surveillance was used for 1% of the cataract extractions (P<.001). CONCLUSIONS: Substantial international variation in anesthesia care and monitoring during cataract surgery was observed. The findings suggest a need for further research to determine whether less intensive monitoring is cost-effective.

Anesthesia↗
PubMed1997

Regioselectivity of the enzymatic transgalactosidation of D- and L-xylose catalysed by beta-galactosidases.

The regioselectivity of enzymatic transgalactosidation depends on the source of the beta-galactosidase used. When the galactosyl acceptor only contains secondary hydroxyl groups, e.g., D- or L-xylose, it is possible to find an enzyme that catalyses preferentially the synthesis of any of the three regioisomers 4-, 3- and 2-O-beta-D-galactopyranosyl-D-xylose (1, 2 and 3, respectively) or 4-, 3- and 2-O-beta-D-galactopyranosyl-L-xylose (4, 5 and 6, respectively). Enriched mixtures in 1, 2 or 3 were obtained using beta-galactosidases from Escherichia coli, bovine testes or Aspergillus oryzae, respectively, by transgalactosidation reaction of O-nitrophenyl-beta-D-galactopyranoside and D-xylose, and enriched mixtures in 4, 5 or 6 were obtained in a similar way using beta-galactosidases from Aspergillus oryzae, lamb small-intestine (intestinal lactase-phloridzin hydrolase) or Saccharomyces fragilis, respectively, using L-xylose as acceptor.

Animals↗
PubMed1997

International applicability of the VF-14. An index of visual function in patients with cataracts.

PURPOSE: There is increased recognition that a rigorous approach to functional assessment should complement the assessment of clinical status. The authors compare the reliability, validity, and responsiveness to clinical change of a visual function index (VF-14) in non-U.S. and in U.S. patients with cataracts. DESIGN: An observational longitudinal study was performed. PARTICIPANTS: One thousand four hundred seven first eye cataract surgery patients were recruited in four international sites: Manitoba (Canada), Denmark, Barcelona (Spain), and the United States. INTERVENTION: Patients were evaluated before cataract surgery and at a 4-month postoperative follow-up visit. Patients completed the preoperative interview and the clinical examination (766 in the United States, 152 in Manitoba, 291 in Denmark, and 198 in Barcelona), and 91.3% of those (1284) also completed the 4-month postoperative follow-up interview and were evaluated postoperatively by an ophthalmologist. MAIN OUTCOME MEASURES: The authors used the following measures: the visual function index (VF-14), the Sickness Impact Profile (SIP), global measures of patients' trouble and satisfaction with vision, and best-corrected visual acuity (VA) in each eye. RESULTS: The VF-14 showed a high internal consistency reliability level in all sites (Cronbach's alpha coefficients > or = 0.84). Correlation of preoperative visual function index scores with the Vision-Related SIP was strong (r = -0.68 in non-U.S. and r = -0.57 in U.S. patients) and with VA in the eye with better vision was moderate (r = 0.40 and r = 0.27, respectively), the pattern of relationships being very similar among U.S. and non-U.S. patients. In patients with only first-eye surgery who reported that their initial trouble with vision had improved, the amount of change in visual function as assessed by the VF-14 (effect size) was large (1.01 for the non-U.S. patients and 1.17 for the U.S. patients). CONCLUSIONS: The non-U.S. versions of the visual function index (VF-14) analyzed are as reliable, valid, and responsive to clinical change as the original U.S. version. These versions are appropriate for international studies of cataract patients outcomes and possibly in routine clinical practice.

Aged↗
PubMed1997

Patients' acceptance of waiting for cataract surgery: what makes a wait too long?

The patient's perspective about waiting for elective surgery is an important consideration in the management of waiting lists, yet it has received little attention to date. This study was undertaken to assess the acceptability of personal waiting times from the perspective of patients, and to examine waiting time and patient characteristics associated with the perception that a wait for cataract surgery is too long. The international prospective study was conducted in three sites with explicit waiting systems: Manitoba, Canada; Denmark; and Barcelona, Spain. Patients over the age of 50 years were recruited consecutively from ophthalmologists' practices at the time of their enlistment for first-eye cataract surgery. Anticipated waiting time, opinions about personal waiting time, and patients' visual and health characteristics were identified by means of telephone interviews. The 550 patients interviewed at the time of enlistment for surgery anticipated waits varying from < 1 to 24 months. Clinical visual acuity measures were obtained from patients' ophthalmologists/cataract surgeons. Results indicated that anticipated waiting time was the strongest predictor of patients' tolerance of waiting for cataract surgery. Patient dissatisfaction increased with the duration of the anticipated wait. Patients in all three sites were accepting of waits of three months or less, and considered waits exceeding six months to be excessive. Response to waits between three and six months varied across study sites. Patients with low tolerance for waiting had greater self-reported difficulty with vision, as assessed by a Cataract Symptom Score and expressed trouble with vision. Patients' acceptance of waiting was not associated with clinical visual acuity measures or socio-demographic characteristics. The patient perspective on acceptability of waiting times for cataract surgery suggests that restricting waiting times to less than six months and preferably less than three months and utilizing self-reported measures of visual difficulty in prioritizing patients may contribute to improved management of waiting systems. Patients are more tolerant of their personal waiting times than responses to questions about waiting for elective surgery in general would indicate, and appear to accept waiting times that are longer than those identified as reasonable by specialists.

Aged↗
PubMed1997

Right ventricular asynergy during dobutamine-atropine echocardiography.

OBJECTIVES: We sought to analyze right ventricular contractility during dobutamine infusion in patients with right coronary artery disease and to elucidate whether the development of right ventricular asynergy aids in characterizing a right coronary artery stenosis. BACKGROUND: Clinical investigations are emphasizing the importance of right ventricular function in patients with coronary artery disease. Thus, prognosis of patients with inferior myocardial infarction is influenced by right ventricular function. This study describes the echocardiographic and electrocardiographic findings during dobutamine-atropine echocardiography in patients with right coronary artery disease. METHODS: We studied 31 patients with isolated right coronary artery disease and no previous myocardial infarction. Six patients with poor acoustic window were excluded (feasibility 80%). The remaining 25 patients underwent dobutamine-atropine echocardiography. A right coronary artery stenosis located before the origin of the right ventricular branches was considered proximal; otherwise, it was considered distal. RESULTS: Right ventricular asynergy during dobutamine-atropine testing developed in 17 patients (sensitivity 68%); 14 had proximal and 3 had distal right coronary artery disease. The following segments were involved: inferior (n = 17), lateral (n = 5) and outflow tract (n = 1). No patient showed anterior asynergy. All 17 patients had left ventricular asynergy as well. Ischemia-free time was 10.7 +/- 6.2 (mean +/- SD) min for the right ventricle and 8.9 +/- 5.2 min for the left ventricle (p < 0.05). Ischemic ST changes were recorded in 15 patients (in standard leads in 14 and in right precordial leads in 8). All patients with right precordial changes showed ST elevation and had right ventricular asynergy (sensitivity and specificity for right ventricular asynergy 47% and 100%, respectively). A control group of 25 patients with no right coronary artery disease (5 with no disease, 15 with left anterior descending and 5 with left circumflex coronary artery disease) underwent dobutamine echocardiography. Right ventricular asynergy developed in two patients with left anterior descending artery stenosis (specificity 92%); in both, the anterior wall was affected. CONCLUSIONS: Echocardiography during dobutamine infusion is a reliable technique for assessing right ventricular dysfunction in patients with right coronary artery disease. Right ventricular contractility can be assessed during dobutamine echocardiography in selected patients.

Aged↗
PubMed1997

Are results of the SF-36 health survey and the Nottingham Health Profile similar? A comparison in COPD patients. Quality of Life in COPD Study Group.

A number of questionnaires have been used to assess the health-related quality of life of patients with chronic obstructive pulmonary disease (COPD). The study compares the performance of the SF-36 and the Nottingham Health Profile (NHP) in a sample of 321 male patients with COPD. Score distributions, reliability estimates, and several item scaling tests, including Rasch analysis were compared. Finally, we assessed the relative ability of the two instruments considered in discriminating different levels of disease severity by comparing: (a) their correlations with dyspnea and %FEV1; the receiver operating characteristic (ROC) curves; and the F-statistics. The SF-36 scores were less skewed and more homogeneously distributed than NHP scores. Item scaling tests and reliability estimates showed a better performance of SF-36 items and scales. Nevertheless, results of Rasch analysis evidenced that both instruments have very similar scaling characteristics. Validity results did not show a consistent pattern of superiority for either of the instruments. For the physical domain, correlations of NHP and SF-36 scores with %FEV1 and dyspnea were very similar and substantial (tau > or = 0.30). F-statistics showed that SF-36 physical scale was more precise (86%) than the NHP counterpart in discriminating among levels of dyspnea and %FEV1 impairment. Nevertheless, the ROC curve and its associated area under the curve did not show a significant difference (p > 0.10). Overall results suggest that both instruments are similar in discriminating among different levels of respiratory impairment.

Data Interpretation, Statistical↗
PubMed1997

Measuring functional status of chronic coronary patients. Reliability, validity and responsiveness to clinical change of the reduced version of the Duke Activity Status Index (DASI).

AIMS: Health-related quality of life assessment may be useful for understanding the variability in functioning of patients with a similar level of clinical impairment. We assessed the reliability, validity and responsiveness to clinical change of a reduced version of the Duke Activity Status Index (DASI) in chronic coronary patients. METHODS AND RESULTS: The reduced version of the DASI, a measure of self-reported functional capacity, was administered twice to two groups of patients: 46 stable coronary heart disease outpatients were tested and re-tested 2 weeks after their initial visit; and 44 patients undergoing elective angioplasty for angina pectoris were evaluated the day before and one month after the procedure. The Canadian Cardiovascular Society (CCS) functional grade was assessed in all patients, and a treadmill exercise test was performed sequentially (before and after the procedure) in angioplasty patients. Cronbach's alpha reliability coefficients for reduced DASI scores were high (between 0.81 and 0.89). Correlations of the reduced DASI scores with CCS grade and exercise test duration were moderately high (r = -0.51 and r = 0.45, respectively). Improvement after angioplasty as assessed by the reduced DASI scores was important (effect size = 0.75, P < 0.001). CONCLUSION: The reduced DASI is reliable, valid and responsive to clinical changes. Health-related quality of life measures may be useful in monitoring coronary patients.

Activities of Daily Living↗
PubMed1997

Endothelial cytosolic proteins bind to the 3' untranslated region of endothelial nitric oxide synthase mRNA: regulation by tumor necrosis factor alpha.

Changes in endothelial nitric oxide synthase (eNOS) expression may be involved in the endothelium-dependent vasorelaxation dysfunction associated with several vascular diseases. In the present work, we demonstrate that eNOS mRNA contains a previously undescribed cis element in the 3' untranslated region (3' UTR). A U+C-rich segment in the 3' UTR is critical in complex formation with bovine aortic endothelial cell cytosolic proteins. Tumor necrosis factor alpha (TNF-alpha), which destabilizes eNOS mRNA, increased the binding activity of the cytosolic proteins in a time-dependent manner. These data suggest that endothelial cytosolic proteins bind to the 3' UTR of eNOS mRNA. These proteins may play a role in TNF-alpha-induced eNOS mRNA destabilization.

Animals↗