Tensor algebra-based geometric methodology to codify central chirality on organic molecules.

A novel mathematical procedure to codify chiral features of organic molecules in the QuBiLS-MIDAS framework is introduced. This procedure constitutes a generalization to that commonly used to date, where the values 1 and -1 (correction factor) are employed to weight the molecular vectors when each atom is labelled as R (rectus) or S (sinister) according to the Cahn-Ingold-Prelog rules. Therefore, values in the range [Formula: see text] with steps equal to 0.25 may be accounted for. The atoms labelled R or S can have negative and positive values assigned (e.g. -3 for an R atom and 1 for an S atom, or vice versa), opposed values (e.g. -3 for an R atom and 3 for an S atom, or vice versa), positive values (e.g. 3 for an R atom and 1 for an S atom) or negative values (e.g. -3 for an R atom and -1 for an S atom). These proposed Chiral QuBiLS-MIDAS 3D-MDs are real numbers, non-symmetric and reduced to 'classical' (non-chiral) QuBiLS-MIDAS 3D-MDs when symmetry is not codified (correction factor equal to zero). In this report, only the factors with opposed values were considered with the purpose of demonstrating the feasibility of this proposal. From QSAR modelling carried out on four chemical datasets (Cramer's steroids, fenoterol stereoisomer derivatives, N-alkylated 3-(3-hydroxyphenyl)-piperidines, and perindoprilat stereoisomers), it was demonstrated that the use of several correction factors contributes to the building of models with greater robustness and predictive ability than those reported in the literature, as well as with respect to the models exclusively developed with QuBiLS-MIDAS 3D-MDs based on the factor 1 | -1. In conclusion, it can be stated that this novel strategy constitutes a suitable alternative to computed chirality-based descriptors, contributing to the development of good models to predict properties depending on symmetry.

[Vertebral fixation with a transpedicular approach. Relevance of anatomical and imaging studies]. / Fijación vertebral por vía transpedicular. Importancia de los estudios anatómicos y de imagen.

The number of patients with spine conditions has grown exponentially in recent years leading to an increase in the number of cases requiring surgical treatment. Currently vertebral fusion surgery with a transpedicular approach represents the most commonly used technique to treat any type of vertebral disorder. The morphometric characteristics of vertebrae, particularly the pedicle, determine the size of pedicular implants, including width and length, as well as the shape and direction of the screw and its ideal angulation at the time of introduction. Knowing these characteristics is important to prevent injuring important adjacent structures and to decrease the postoperative complication rate. In recent decades numerous studies on the morphometric characteristics of the vertebral pedicle have been conducted in different populations to determine its real dimensions by means of direct measurement and imaging methods. These studies have concluded that there are significant differences in these measurements among the different ethnic groups, races, genders, ages and the vertebral regions studied. This paper analyzes the different morphometric studies of the pedicle and all the other vertebral elements studied in Mexico and the rest of the world and explain the importance of their knowledge and surgical application for the correct development of vertebral fusion surgery with a transpedicular approach.

Copula-based regression models for a bivariate mixed discrete and continuous outcome.

This paper is concerned with regression models for correlated mixed discrete and continuous outcomes constructed using copulas. Our approach entails specifying marginal regression models for the outcomes, and combining them via a copula to form a joint model. Specifically, we propose marginal regression models (e.g. generalized linear models) to link the outcomes' marginal means to covariates. To account for associations between outcomes, we adopt the Gaussian copula to indirectly specify their joint distributions. Our approach has two advantages over current methods: one, regression parameters in models for both outcomes are marginally meaningful, and two, the association is 'margin-free', in the sense that it is characterized by the copula alone. By assuming a latent variable framework to describe discrete outcomes, the copula used still uniquely determines the joint distribution. In addition, association measures between outcomes can be interpreted in the usual way. We report results of simulations concerning the bias and efficiency of two likelihood-based estimation methods for the model. Finally, we illustrate the model using data on burn injuries.

Association between idiopathic achalasia and IL23R gene.

BACKGROUND: Idiopathic achalasia is a primary esophageal motor disorder of unknown etiology. Different evidences have been reported in support of achalasia as the result of an autoimmune and inflammatory process leading to neuronal cell loss. According to this, idiopathic achalasia has been significantly associated with specific alleles of the human leukocyte antigen system class II, although few reports studying association with other loci can be found in the literature. Recent studies have shown association of a non-synonymous polymorphism within the IL23R gene with different chronic inflammatory disorders, including Barrett's esophagus. The purpose of this study was to assess whether the IL23R coding variant Arg381Gln polymorphism is involved in susceptibility to idiopathic achalasia. METHODS: We performed a case-control study including 262 patients with idiopathic achalasia and 802 healthy subjects, all of them white Spaniards. Achalasia patients were diagnosed on the basis of clinical, radiographic, endoscopic, and manometric criteria. All samples were genotyped for the IL23R Arg381Gln polymorphism using TaqMan technology. KEY RESULTS: The minor allele of the Arg381Gln polymorphism was significantly increased in patients compared with healthy controls (OR = 1.46, 95% CI = 1.01-2.11, P = 0.036). This association seems to be specific to male patients with disease onset after 40 years (OR = 2.33, 95% CI = 1.29-4.16, P = 0.002). CONCLUSIONS & INFERENCES: Our results suggest a role of IL23R in idiopathic achalasia predisposition and extend the evidence of the general influence of this gene in autoimmune and inflammatory diseases.

A likelihood approach to estimating sensitivity and specificity for binocular data: application in ophthalmology.

Binocular data typically arise in ophthalmology where pairs of eyes are evaluated, through some diagnostic procedure, for the presence of certain diseases or pathologies. Treating eyes as independent and adopting the usual approach in estimating the sensitivity and specificity of a diagnostic test ignores the correlation between eyes. This may consequently yield incorrect estimates, especially of the standard errors. The paper proposes a likelihood-based method of accounting for the correlations between eyes and estimating sensitivity and specificity using a model for binocular or paired binary outcomes. Estimation of model parameters via maximum likelihood is outlined and approximate tests are provided. The efficiency of the estimates is assessed in a simulation study. An extension of the methodology to the case of several diagnostic tests, or the same test measured on several occasions, which arises in multi-reader studies, is given. A further extension to the case of multiple diseases is outlined as well. Data from a study on diabetic retinopathy are analysed to illustrate the methodology.

Comparison of patient-controlled and operator-controlled conscious sedation for restorative dentistry.

BACKGROUND AND OBJECTIVE: The use of midazolam for conscious sedation is an accepted method of anxiety control in restorative dentistry. A lack of predictability in its effects requires the dose of midazolam to be adjusted to individual patient's requirements. We determined whether patient-controlled sedation was a suitable alternative to operator-controlled sedation in restorative dentistry. METHODS: A randomized crossover clinical trial involving 35 consecutive patients undergoing similar dental procedures. Patients were randomly given midazolam, administered either by the patient or by the operator at the first visit and the alternative option on the second visit. All patients were ASA I-II and their ages ranged between 20 and 48 yr. Blood pressure, heart rate, oxygen saturation and patient satisfaction were recorded. RESULTS: The onset time and initial dose for sedation were similar with the two methods of administration and the sedation scores and vital signs were satisfactory. In the patient-controlled group the mean total dose of midazolam was 7.9 (+/- 4.2 SD) mg cf. 4.2 (+/- 1.8 SD) mg in the operator-controlled group (P < 0.05). The time to fitness for discharge (15.4 (+/- 11.9 SD) min) was greater in the patient-controlled group cf. the operator-controlled group (8.5 (+/- 9.5 SD) min), P < 0.05. CONCLUSION: This study shows that patient-controlled sedation is a suitable alternative to operator-controlled sedation in the management of anxious dental patients.

[Health needs of the diabetic user of primary care]. / Necesidades en salud del diabético usuario del primer nivel de atención.

OBJECTIVE: To determine the extent and importance of unmet health needs of type 2 diabetic patients seen at primary care services. MATERIAL AND METHODS: A cross-sectional study was conducted in 1999, among rural and urban patients of the Mexican Institute of Social Security, in Nuevo Leon, Mexico. The study population consisted of 256 subjects selected at random, diagnosed with type-II diabetes for at least two years. Data were obtained by interview and complemented with medical charts and provider interviews. Five health areas and four health determinants were evaluated, through Mexican Official Standards and American Diabetes Association standards of medical care for diabetic patients. Analysis consisted of descriptive statistics and estimation of z scores. RESULTS: Health needs were met in 49% of cases. A lower mean of health need satisfaction was found in rural regions as compared to urban regions (36.8% vs. 53.3%, p < .01). Nutrition was the most affected health area (z score = -6), followed by the physical exercise (z score = -1), the metabolic health area (z score = +1), the non-smoking health area (z score = +2), the prevention and early detection of complications health area (z score = +2), and the cognitive health area (z score = +3). The health determinant with the highest requirement corresponded to utilization (z score = -5), followed by resource availability (z score = -4), perceived health need (z score = +4), and access barriers (z score = +6). CONCLUSIONS: Health need measurement allows evaluating the effectiveness of existing interventions, in addition to identifying areas with higher unmet health needs. These findings facilitate analysis and decision-making to devise specific health policies and actions directed at improving the quality of care for diabetic patients. The English version of this paper is available at: http://www.insp.mx/salud/index.html

Bradyarrhythmias, temporary and permanent pacing.

Bradycardia is common in critical care units. It may be transient, asymptomatic and of little consequence, or life-threatening. Bradycardia may result from abnormalities of the sinus node, atrioventricular node, or the His-Purkinje system. It may also be precipitated by drug effects or enhanced vagal tone. Proper diagnosis is pivotal to determining prognosis and management. Temporary and permanent pacing is now readily available, markedly improving the morbidity and mortality associated with bradyarrhythmias.

[Prevalence of nosocomial infections in children: survey of 21 hospitals in Mexico]. / Prevalencia de infecciones nosocomiales en niños: encuesta de 21 hospitales en México.

OBJECTIVE: The purpose of this study was to determine the prevalence of nosocomial infections, associated risk factors, microbiology, use of antibiotics, and associated mortality among hospitalized children. MATERIAL AND METHODS: A 1-day prevalence survey was conducted among 1,183 children hospitalized in a nationwide network of 21 public hospitals caring for children. To attain consistency between hospitals, CDC nosocomial infection definitions were used. Adjusted relative odds of bacteremia were estimated using logistic regression analysis. RESULTS: The prevalence of nosocomial acquired infection was 9.8% (CI 95%, 8.1-11.6). The more prevalent infections were pneumonia (25%), sepsis/bacteremia (19%), and urinary tract infection (5%). The main microorganism isolated in blood cultures drown from patients with nosocomial infection was K. pneumoniae (31%). The prevalence of antibiotics use was 49% with substantial variation between hospitals (range 3-83%). Using logistic regression analysis, four factors were independently associated with the risk of nosocomial infection: central venous catheters (OR 3.3; CI 95% 1.0-5.9), total parenteral nutrition (OR 2.1; CI 95% 1.0-4.5) mechanical ventilation (OR 2.3; CI 95% 1.2-4.1), and low birth weight (OR 2.6; CI 95% 1.0-6.8). The overall mortality was 4.8%; however, patients with nosocomial infection had two times greater risk to die as compared to non-infected children (OR 2.6; CI 95% 1.3-5.1). CONCLUSIONS: This rapid assessment survey using a standard methodology allows to document the prevalence of nosocomial infections in children. The results were used to develop targeted programs on central catheters and mechanical ventilation aimed to reduce bacteremia/sepsis and pneumonia, two nosocomial infections characterized by high prevalence and mortality.

A comparison of ventricular function during high right ventricular septal and apical pacing after his-bundle ablation for refractory atrial fibrillation.

This study compares LV performance during high right ventricular septal (RVS) and apical (RVA) pacing in patients with LV dysfunction who underwent His-bundle ablation for chronic AF. We inserted a passive fixation pacing electrode into the RVA and an active fixation electrode in the RVS. A dual chamber, rate responsive pulse generator stimulated the RVA through the ventricular port and the RVS via the atrial port. Patients were randomized to initial RVA (VVIR) or RVS (AAIR) pacing for 2 months. The pacing site was reversed during the next 2 months. At the 2 and 4 month follow-up visit, each patient underwent a transthoracic echocardiographical study and a rest/exercise first pass radionuclide ventriculogram. We studied nine men and three women (mean age of 68 +/- 7 years) with congestive heart failure functional Class (NYHA Classification): I (3 patients), II (7 patients), and III (2 patients). The QRS duration was shorter during RVS stimulation (158 +/- 10 vs 170 +/- 11 ms, P < 0.001). Chronic capture threshold and lead impedance did not significantly differ. LV fractional shortening improved during RVS pacing (0.31 +/- 0.05 vs 0.26 +/- 0.07, P < 0.01). RVS activation increased the resting first pass LV ejection fraction (0.51 +/- 0.14 vs 0.43 +/- 0.10, P < 0.01). No significant difference was observed during RVS and RVA pacing in the exercise time (5.6 +/- 3.2 vs 5.4 +/- 3.1, P = 0.6) or the exercise first pass LV ejection fraction (0.58 +/- 0.15 vs 0.55 +/- 0.16, P = 0.2). The relative changes in QRS duration and LV ejection fraction at both pacing sites showed a significant correlation (P < 0.01). We conclude that RVS pacing produces shorter QRS duration and better chronic LV function than RVA pacing in patients with mild to moderate LV dysfunction and chronic AF after His-bundle ablation.

Transvenous cardioverter defibrillator lead malfunction due to terminal connector damage in pectoral implants.

Lead failure places patients with implantable cardioverter defibrillators (ICD) at risk for sudden cardiac death or results in delivery of inappropriate shocks. This study describes a mechanism of lead malfunction occurring at the junction of the terminal ring with the conductor coil of the rate sensing terminal connector in one specific model of a transvenous ICD lead. We detected the problem in a population of 179 patients with a mean age of 61 +/- 10 years and a mean lead implant duration of 16 +/- 11 months. All patients underwent pectoral ICD implantation using a submuscular approach. The implanting physician chose to place the ICD on the left side in 155 patients (87%) and on the right side in 24 patients (13%). Cephalic vein cutdown provided central venous access in 147 patients (82%), and subclavian vein puncture provided access in 32 patients (18%). Follow-up examination detected lead failure in six patients (3.5% over 31 months) due to insulation damage with or without conductor coil fracture at the junction of the terminal ring and conductor coil of the IS-1 rate sense terminal. We detected lead disruption 17 +/- 9 months (range 5-31 months) after implantation. Multiple nonsustained arrhythmia episodes exhibiting nonphysiologic intervals associated with noisy rate sensing electrograms during pocket manipulation led to discovery in three patients. The other three patients presented with inappropriate device discharges confirmed by stored high-energy lead electrograms showing normal rhythm. Pacing lead impedance abnormally dropped in two patients. Impedance remained stable in the other four patients. In conclusion, the generator pocket represents an important site of ICD transvenous lead vulnerability. Lead failure may result from conductor coil and/or insulation disruption at the interface with the rate sensing terminal connector.

Distribución de los fenotipos y genotipos del sistema secretor en la población de Costa Rica / Distribution of the phenotypes and genotypes of the secretor system in the Costa Rica population

Se analizaron 1067 muestras de saliva, de personas procedentes de las siete provincias de Costa Rica, para investigar la distribución de los fenotipos y genotipos del sistema secretor. Se encontró un 86 por ciento de secretores y un 14 por ciento de o secretores que corresponden a una frecuencia genotípica de 0,3924 para Se/Se, de 0,4680 para Se/Se y de 0,1396 para se/se. La distribución alélica es de 0,6264 para Se y 0,3736 para se. El tamaño de la muestra se determinó de acuerdo con la fórmula n = Z2 pq/d2 y la frecuencia alélica por el método de conteo de genes. A un nivel de significancia de 0,05 y 2 grados de libertad el valor de x a la 2 = 5,991 (p>0,05), lo que indica que no hay diferencias estadísticamente significativas entre la distribución observada y la esperada.

Catheter ablation of atrial flutter using radiofrequency energy.

Sixteen patients with type I atrial flutter underwent an attempt at radiofrequency catheter ablation (8 women, 8 men, mean age 53 +/- 11 years). The primary criterion used to identify sites for radiofrequency energy delivery was the identification of a fractionated electrogram. Radiofrequency energy was delivered for 20 to 30 seconds. Radiofrequency catheter ablation was acutely successful in 13 patients and unsuccessful in 3. During a mean follow-up of 10 +/- 4 months, 9 of 13 patients with a successful acute result (69%) remained free of recurrent atrial flutter or atrial fibrillation. The ability to induce nonclinical types of atrial flutter was associated with an unsuccessful outcome. A greater proportion of electrograms recorded at successful sites demonstrated electrogram stability compared with unsuccessful ablation sites. None of the electrograms recorded at successful ablation sites were fractionated or had a double potential. This study demonstrates that radiofrequency catheter ablation of type I atrial flutter can be achieved safely.

Radiofrequency catheter ablation of right ventricular outflow tract tachycardia late after complete repair of tetralogy of Fallot using the pace mapping technique.

While surgical repair of tetralogy of Fallot has improved the long-term outlook for this patient population, sudden death late after repair remains a problem. Ventricular tachycardia (VT) originating in the right ventricular outflow tract (RVOT) is a well described, clinically important finding following surgical repair of tetralogy and a number of investigators suggest that this VT plays a critical role in the etiology of sudden death. We report two patients with RVOT VT late after repair of tetralogy who underwent successful radiofrequency ablation of their tachycardia.

Apparent change in cardiac geometry during single-photon emission tomography thallium-201 acquisition: a complex phenomenon.

We investigated the frequency and extent of changes in heart position and geometry independent of body motion during stress single-photon emission tomography (SPET) thallium-201 myocardial perfusion imaging. Following an exercise treadmill test, patients had a 22.1-min SPET acquisition which was followed immediately by a static image acquisition for 1 min with the camera position identical to the first view of the SPET study. Point sources were placed on the body to monitor patient motion. Cardiac motion was assessed by an approach which mimicked a cross-correlation technique applied to cardiac count profiles along the horizontal and vertical directions from the first view of the SPET study and the static image. A large percentage (87.5%) of cases had some degree of horizontal or vertical motion. Pixel shifts in cardiac position of > or = 2 pixels (12 mm) occurred in 60% of patients. In 37% of patients who moved the cardiac motion was consistent with simple translation of the heart and thus amenable to correction using proposed SPET motion-correction programs. The peak heart rate achieved during stress and the ratio of the heart rate immediately before SPET acquisition to the resting heart rate were determined to be independent predictors of patient motion during SPET acquisition. Cardiac motion changes were minimal at (13.3 +/- 2.2) min after cessation of exercise. The implications of these findings for the accuracy of SPET 201Tl require further investigation.

Inhomogeneity of gated and ungated SPECT technetium-99m-sestamibi bull's-eyes in normal dogs: comparison with thallium-201.

By computer simulation, we have previously hypothesized, independent of the isotope imaged, that differences in view-to-view resolution and attenuation patterns predictably cause count density distortions in SPECT images. We tested the simulation predictions for both ECG-gated and ungated SPECT 99mTc-sestamibi and SPECT 201Tl myocardial perfusion images in normal dogs. In agreement with the predictions of the computer model, distortions in SPECT 99mTc-sestamibi myocardial perfusion images are virtually equivalent to SPECT 201Tl, dependent on the exact SPECT acquisition orbit and markedly different for a posterior 180 degrees acquisition arc compared to an anterior 180 degrees acquisition arc. Furthermore, ungated and gated SPECT 99mTc-sestamibi images show similar count inhomogeneities. These results suggest that little is to be gained from a 360 degrees acquisition with SPECT 99mTc-sestamibi, and that image distortions from gated or ungated SPECT 99mTc images with 180 degrees orbits will be similar to those in SPECT 201Tl images.

Comparison of single-photon emission computed tomographic (SPECT) myocardial perfusion imaging with thallium-201 and technetium-99m sestamibi in dogs.

OBJECTIVES: The purpose of the present study was to compare single-photon emission computed tomographic (SPECT) myocardial images of technetium-99m (Tc-99m) sestamibi and thallium-201 (Tl-201) isotopes in the same dog undergoing partial coronary occlusion during pharmacologic vasodilation. BACKGROUND: To date, no controlled study has been reported comparing SPECT Tc-99m sestamibi with SPECT Tl-201 imaging during stress with anatomic and physiologic standards. METHODS: Mongrel dogs were anesthetized with chloralose and instrumented to record left anterior descending coronary blood flow and aortic pressure. Partial coronary occlusion with a hydraulic cuff reduced coronary vascular conductance, which is equal to the coronary blood flow normalized to aortic pressure during peak vasodilation with intravenous adenosine. Each dog received 5 mCi of Tl-201, then 30 mCi of Tc-99m sestamibi during partial coronary occlusion at peak vasodilation. Tomographic myocardial imaging was performed in a 180 degrees anterior arc scan for 33.5 min, first with Tl-201, and later, without moving the dog, for 33.5 min with Tc-99m sestamibi. Postmortem staining defined the region underperfused because of its dependence on the artery that was partially occluded. RESULTS: In seven dogs with moderate reduction in coronary blood flow, coronary vascular conductance decreased with partial coronary occlusion (47 +/- 12%) during Tl-201 imaging and (47 +/- 8%, p = NS) during Tc-99m sestamibi imaging. The underperfused region was 23.9 +/- 6.4% of total left ventricular mass. Counts in the defects were 39% higher (0.86 +/- 0.08 of normal counts) for Tc-99m sestamibi than for Tl-201 (0.64 +/- 0.09 of normal counts, p < 0.001), and the defect on SPECT Tc-99m sestamibi images occupied only a fraction (0.37 +/- 0.30) of the area of the defect on the Tl-201 images of the same dog. Bull's-eye displays constructed from the pathologic slices showed that the Tl-201 defect size was closer to the underperfused region of the left ventricular mass determined pathologically than was the Tc-99m sestamibi defect size. In four additional dogs a severe, near total coronary occlusion was created during Tl-201 and Tc-99m sestamibi administration. In these dogs, similar defect contrast (0.55 +/- 0.12 vs. 0.62 +/- 0.09, p = NS) and areas (0.18 +/- 0.07 vs. 0.18 +/- 0.11, p = NS) were observed with Tl-201 and Tc-99m sestamibi, respectively. CONCLUSIONS: Tomographic myocardial imaging with Tc-99m sestamibi during moderately severe partial coronary occlusion underestimated the area of the defect relative to Tl-201 or to the pathologic reference standard in dogs. Defect contrast was sharper with tomographic myocardial Tl-201 than with tomographic myocardial Tc-99m sestamibi during moderately severe partial coronary occlusion.