Prevalence, Onset, Evolution, and Prediction of Spasticity Poststroke: A Longitudinal Study / Prevalencia, inicio, evolución y predicción de la espasticidad posterior a un ACV: un estudio longitudinal / Prevalência, início, evolução e previsão de espasticidade após AVC: um estudo longitudinal

Introduction: Because of the the complex physiopathology of spasticity, it is distinguished as one of the most significant positive clinical signs of upper motor neuron syndrome, constituting a clinical feature that has great impact in the neurorehabilitation setting. Thus, the current study aimed to determine the prevalence, onset, evolution, and prediction of spasticity after a stroke. Materials and Methods: A correlational, longitudinal design was used. A total of 136 patients were evaluated at the following times: 10 days (T1), 3 months (T2), and 12 months (T3) poststroke. The initial evaluation included sociodemographic and clinical data (T1). Muscle tone was measured (T1, T2, and T3) using the Modified Ashworth Scale. Results: The prevalence of poststroke spasticity in the elbow was 37.5 % at T1 and 57.4 % at T2 and T3. Among patients with motor damage, the onset of spasticity occurred at T1 in 44.7 %, between T1 and T2 in 23.7 %, and between T2 and T3 in 0.9 %. Significant predictors of the alteration in muscular tone for at least two of the evaluation times were ethnic self-classification, type, area, extent of stroke, and number of sessions. Conclusions: Spasticity onset occurs during the first 10 days after a stroke. More clinical than sociodemographic variables predicted spasticity.

Introducción: la espasticidad se destaca como uno de los signos clínicos positivos más significativos del síndrome de motoneurona superior, por su compleja fisiopatología, y constituye una característica clí- nica de gran impacto en el ámbito de la neurorrehabilitación. Por lo tanto, el objetivo fue determinar la prevalencia, el inicio, la evolución y la predicción de la espasticidad después de un accidente cerebro- vascular. Materiales y métodos: se utilizó un diseño longitudinal correlacional. Se evaluaron 136 pacientes: 10 días (T1), 3 meses (T2) y 12 meses (T3) pos-ACV. La evaluación incluyó datos sociodemográficos y clínicos (T1) y se midió el tono muscular (T1, T2 y T3) mediante la Escala de Ashworth Modificada. Resultados: la prevalencia en el codo fue del 37.5 % en T1, y del 57.4 % en T2 y T3. Entre los pacientes con daño motor, el inicio de la espasticidad ocurrió en T1 para el 44.7 % de ellos, entre T1 y T2 para el 23.7 % y entre T2 y T3 para el 0.9 %. La autoclasificación étnica, el tipo, el área, la extensión del ictus y el número de sesiones predijeron significativamente la alteración del tono muscular en al menos dos ocasiones. Conclusiones: el inicio de la espasticidad ocurre durante los 10 primeros días después de un ACV. Más variables clínicas que sociodemográficas predijeron espasticidad.

Introdução: a espasticidade destaca-se como um dos sinais clínicos positivos mais significativos da síndrome do neurônio motor superior, devido à sua fisiopatologia complexa, e constitui uma característica clínica de grande impacto no campo da neurorreabilitação. Portanto, nosso objetivo foi determinar a prevalência, início, evolução e predição da espasticidade após o acidente vascular cerebral. Materiais e métodos: foi utilizado um desenho correlacional longitudinal. Foram avaliados 136 pacientes: 10 dias (T1), 3 meses (T2) e 12 meses (T3) pós-AVC. A avaliação incluiu dados sociodemográficos e clínicos (T1) e o tônus muscular (T1, T2 e T3) foi medido por meio da Escala Modificada de Ashworth. Resultados: a prevalência no cotovelo foi de 37,5 % em T1 e 57,4 % em T2 e T3. Entre os pacientes com prejuízo motor, o início da espasticidade ocorreu em T1 em 44,7 % deles, entre T1 e T2 em 23,7 % e entre T2 e T3 em 0,9 % dos pacientes. A autoclassificação étnica, o tipo, a área, a extensão do AVC e o número de sessões predisseram significativamente as anormalidades do tônus muscular em pelo menos duas ocasiões. Conclusões: o início da espasticidade ocorre durante os primeiros 10 dias após o acidente vascular cerebral. Mais variáveis clínicas do que sociodemográficas previram a espasticidade

Distribución de patrones espásticos en extremidad superior posterior a un daño de motoneurona superior / Distribution of spastic patterns in upper extremity after an upper motor neuron syndrome

ANTECEDENTES: la evidencia sobre personas que presentan daño de motoneurona superior y desarrollan un patrón de espasticidad en extremidad superior (EES) es limitada. Este signo positivo de disfunción o secundario al daño de la motoneurona superior se asocia con pérdida de función y disminución de la independencia, provocando discapacidad y alterando la calidad de vida. OBJETIVO: determinar la distribución de frecuencias de los patrones de EES, muñeca, dedos y pulgar posterior a un daño de motoneurona superior. MÉTODO: diseño descriptivo de corte transversal prospectivo. Se realizó una medición a 206 sujetos pertenecientes a 17 centros de salud, quienes cumplieron con los criterios de inclusión y firmaron el consentimiento. La evaluación incluyó datos clínicos y la evaluación del patrón de EES (Clasificación de Hefter), muñeca, dedos (Zancolli adaptado) y pulgar (Clasificación de House). RESULTADOS: El análisis consideró cada una de las taxonomías de los patrones de EES evaluados (Hefter I a V). La distribución de frecuencias fue investigada mediante la prueba χ2 de bondad de ajuste, seguida de la inspección post hoc de los residuos estandarizados (z) en cada celda. Se identificaron frecuencias significativamente mayores en: el patrón III de extremidad superior, el patrón cubitalizado neutro de muñeca, el patrón del flexor profundo y mixto de Zancolli adaptado, y en los patrones 3, 4 del pulgar. Ninguna taxonomía se asoció al tiempo de evolución y tipo de ACV. CONCLUSIÓN: El estudio aporta evidencia relevante sobre la distribución frecuencia de patrones espásticos, posterior a un daño de motoneurona superior. La información proporcionada busca apoyar el proceso de decisión terapéutica potenciando la recuperación funcional de la extremidad superior.

BACKGROUND: The evidence regarding people who present superior motor neuron damage and develop a pattern of spasticity in the upper limb (SUL) is limited. This positive sign of the superior motor neuron is associated with both the loss of function and the decreased independence, causing disability and altering life quality. OBJECTIVE: to determine the frequency distribution of SUL, wrist, finger and thumb patterns after superior motor neuron damage. METHOD: prospective cross-sectional descriptive design, the sample consisted of 206 patients belonging to 17 health centers, who met the inclusion criteria and signed the informed consent, approved by the committee of ethics. The study considered a measurement, including clinical data and evaluation of the pattern of SUL (Hefter´s classification), wrist, fingers (adapted Zancolli) and thumb (House Classification). RESULTS: The analysis considered each of the taxonomies of evaluated patterns (Hefter´s I-V). Frequency distribution was investigated by χ2 goodness of fit tests, followed by post hoc inspection of standardized residues (z) in each cell. Significantly higher frequencies were identified in the upper limb pattern III, the neutral cubitalized wrist pattern, the adapted Zancolli deep flexor pattern and in the thumb patterns 3, 4. No taxonomy was associated with the evolution time and type of stroke. CONCLUSION: The study provides with relevant scientific evidence regarding the frequency distribution of spasticity patterns after superior motor neuron damage. The information provided can support the therapeutic decision process by enhancing the functional recovery of upper limb.

Sociodemographic Characteristics, Gender Identification, and Gender Affirmation Pathways in Transgender People: A Survey Study in Chile.

Understanding the internal diversity of transgender communities is essential for developing optimal, inclusive policies and service provision. To date, research on this topic remains scarce in Chile. We conducted a survey study describing sociodemographic characteristics (age, sex assigned at birth, onset age, nationality, education, sex work, having a partner, having children, sexual orientation, religiousness, gender identification, and gender affirmation pathways). A snowball sample of 377 self-identified transgender adults living in Chile (Mage = 31.88, rangeage = 18-67) was collected for the purpose of this study. According to their sex assigned at birth, 139 participants were female and 238 male. Results revealed that sex assigned at birth was significantly associated with almost all the sociodemographic variables. Eight gender self-identification categories were obtained based on self-declaration. These gender identification categories varied according to sex assigned at birth. Finally, four patterns (clusters) of gender affirmative actions were identified among participants. These patterns indicated that the longer the gender affirmation pathway time, the greater the invasiveness level of the medical procedures used. Sex assigned at birth moderated the association between gender affirmation pathways and gender identity categories. Results were discussed highlighting the heterogeneity found in terms of sociodemographic characteristics, gender identification, and gender affirmation pathways.

Reliability Estimation in Multidimensional Scales: Comparing the Bias of Six Estimators in Measures With a Bifactor Structure.

In the context of multidimensional structures, with the presence of a common factor and multiple specific or group factors, estimates of reliability require specific estimators. The use of classical procedures such as the alpha coefficient or omega total that ignore structural complexity are not appropriate, since they can lead to strongly biased estimates. Through a simulation study, the bias of six estimators of reliability in multidimensional measures was evaluated and compared. The study is complemented by an empirical illustration that exemplifies the procedure. Results showed that the estimators with the lowest bias in the estimation of the total reliability parameter are omega total, the two versions of greatest lower bound (GLB) and the alpha coefficient, which in turn are also those that produce the highest overestimation of the reliability of the general factor. Nevertheless, the most appropriate estimators, in that they produce less biased estimates of the reliability parameter of the general factor, are omega limit and omega hierarchical.

Salud mental en población transgénero y género no conforme en Chile

Background: Transgender population is at a higher risk of suffering mental health problems than cisgender population (people whose sex and gender identity are in agreement) and other sexual minorities (gays, lesbians, and bisexuals), partly due to the greater stress that they suffer or for being victims of sexual prejudice. Aim: To describe positive and negative mental health indicators in a sample of transgender people living in Chile. Material and Methods: An intentional sample of 377 transgender individuals older than 18 years, living in the country's northern, center and southern zones were studied. Sociodemographic and well-being features, negative emotional symptoms, suicidal behavior, and substance consumption were assessed. Results: A precarious mental health was confirmed among participants. A high frequency of depression, ideation and suicide attempts, and high levels of depression, anxiety, and stress symptoms were identified. Also, a high frequency of substance abuse was found. These mental health indicators varied according to the sex assigned at birth and gender self-identification. Conclusions: Transgender people experience precariousness and vulnerability in their mental health.

Association between postural patterns of spastic upper extremity and functional independence after TBI and stroke.

BACKGROUND: Spastic hypertonia of the upper limb after stroke or traumatic brain injuries (TBI) is a prevalent clinical sign causing abnormal postures and movement patterns due to hyperexcitability of the upper motor neurons and rheological alterations in the affected muscles. These alterations limit the use of the upper limb, restricting its functional activities and affecting the individual's quality of life and social participation. OBJECTIVE: To determine the association between spastic patterns of the upper limb, wrist, fingers and thumb, and independence in everyday activities after a stroke or TBI. METHODS: The design is a cross-sectional descriptive and correlational study. The sample consisted of 206 individuals who complied with the eligibility criteria and signed an informed consent. Clinical evaluation was carried out, including determination of the postural pattern of the upper extremity according to Hefter's taxonomy and postural pattern classification of the wrist, fingers and thumb. Functional independence was evaluated using the Functional Independence Measure (FIM) and the Barthel Index (BI). RESULTS: Univariate between-subject ANOVAs were used to examine associations of the four pattern classifications with the two independence measures, FIM and BI. Results indicate that Pattern I of Hefter's upper limb taxonomy is associated with lesser functional independence according to FIM and BI mean scores. CONCLUSIONS: The postural pattern of the upper limb after TBI or stroke is related to the patient's functional independence. Specifically, Pattern I tends to co-occur with low independence.

Life Satisfaction among Indigenous People from Chile: Evaluation of Measurement Invariance / Satisfacción con la vida en indígenas de Chile: evaluación de la Invarianza de Medida

Abstract Although the Life Satisfaction Scale (SWLS) has been used to establish comparisons among nations/cultures, the measurement invariance of this scale has not always been demonstrated. The forced acculturative experience of indigenous minorities and its differentiation of gender roles could impact how people respond to this scale. The purpose of this study was to examine the measurement invariance of the SWLS when it is applied to a Chilean indigenous group, considering gender and their most frequent acculturative types (i.e., acculturated and bicultural). Eight hundred adults of Mapuche origin answered a Spanish version of the SWLS and the Mapuche Acculturation Scale. The results supported the SWLS strict invariance between acculturated and bicultural and also between acculturated men and women. Partial strict invariance was found between bicultural men and women; specifically, the residual variance of Item 3 was higher in women than in men. Since Spanish is a gendered language, a linguistic explanation is proposed for the non-invariance of this item. The importance of careful wording of the items, when administered in multilanguage acculturation contexts, is discussed.

Resumen Aunque la Escala de Satisfacción con la Vida (SWLS) se ha usado para comparar personas de distintas naciones/culturas, no siempre su invarianza de medición ha sido demostrada. La aculturación forzada de las minorías indígenas y sus particulares roles de género podrían afectar las respuestas de esas personas a esta escala. Este estudio tuvo por objetivo examinar la invarianza de la SWLS en un grupo indígena chileno, considerando el género y los tipos aculturativos más frecuentes (i.e., aculturados y biculturales). Ochocientos adultos mapuches respondieron, en castellano, la SWLS y la Escala de Aculturación Mapuche. Se encontró apoyo para invarianza estricta entre aculturados y biculturales y, además, entre hombres y mujeres aculturados. Se encontró invarianza estricta parcial entre hombres y mujeres biculturales; específicamente, la varianza residual del ítem 3 fue mayor en mujeres que en hombres. Siendo el castellano un idioma con distinción de géneros, se propuso una explicación lingüística para la falta de invarianza de ese ítem. Se discute la importancia de redactar cuidadosamente los ítems cuando son administrados en contextos aculturativos multilingües.

[Mental health in a sample of transgender people]. / Salud mental en población transgénero y género no conforme en Chile.

BACKGROUND: Transgender population is at a higher risk of suffering mental health problems than cisgender population (people whose sex and gender identity are in agreement) and other sexual minorities (gays, lesbians, and bisexuals), partly due to the greater stress that they suffer or for being victims of sexual prejudice. AIM: To describe positive and negative mental health indicators in a sample of transgender people living in Chile. MATERIAL AND METHODS: An intentional sample of 377 transgender individuals older than 18 years, living in the country's northern, center and southern zones were studied. Sociodemographic and well-being features, negative emotional symptoms, suicidal behavior, and substance consumption were assessed. RESULTS: A precarious mental health was confirmed among participants. A high frequency of depression, ideation and suicide attempts, and high levels of depression, anxiety, and stress symptoms were identified. Also, a high frequency of substance abuse was found. These mental health indicators varied according to the sex assigned at birth and gender self-identification. CONCLUSIONS: Transgender people experience precariousness and vulnerability in their mental health.

Tenacidad en estudiantes universitarios chilenos: Un estudio inicial de su estructura y red nomológica / Grit in Chilean university students: An initial study of its structure and nomological network

En los últimos años ha surgido un creciente interés por indagar el rol de las habilidades no cognitivas, como la tenacidad, en el desempeño académico. Si bien la investigación sobre tenacidad no ha generado aún conclusiones definitivas, debe considerarse que ella no ha incluido a poblaciones latinoamericanas. Ante este panorama, este estudio inicial se propuso examinar en estudiantes universitarios chilenos de pedagogía en matemáticas: (1) la estructura interna de la tenacidad y (2) su posición en una red nomológica integrada por desempeño académico, sexo, edad y años en el programa educativo. Un total de 153 estudiantes de la Universidad de La Frontera, una institución estatal chilena, respondió la Escala Corta de Tenacidad y un cuestionario sociodemográfico. Análisis factoriales exploratorios revelaron que la tenacidad adquiere una configuración unidimensional que posee una adecuada consistencia interna. Además, adoptando una relación no lineal semejante a una curva hiperbólica, niveles altos de tenacidad se vincularon con desempeño académico alto, en tanto que niveles bajos o moderados se vincularon con desempeño bajo. Finalmente, la tenacidad apareció asociada con sexo (las mujeres mostraron más tenacidad que los hombres) y, en una relación directa, con los años en el programa. Tenacidad no correlacionó significativamente con edad. Este conjunto de hallazgos, que discrepan mayormente de aquellos reportados en la literatura, son discutidos principalmente en términos del dominio disciplinar previo de los participantes y/o de la dificultad del programa educativo. Se proponen explicaciones para estos hallazgos a fin de que sean evaluadas en estudios futuros, empleando un enfoque confirmatorio.

Traditionally, academic performance has been linked to intelligence and some other student´s cognitive abilities. However, in recent 4 years we have witnessed a growing interest in expanding this view by investigating the role that other non-cognitive skills, such as tenacity, may play in academic achievement. Grit can conceptually be conceived as perseverance and passion aimed at achieving long-term goals. A review of the literature shows that grit does not appear to be configured, as some authors claim, as a hierarchical structure with a general second-order construct and two first-order facets (perseverance of effort and consistency of interest). The literature also points out that grit is only a modest predictor of academic performance and that it presents a slightly positive correlation with age and a very weak one with sex and the students' number of years in an academic program. While research on grit has not yet generated any definitive conclusions, it must be considered that it has not included Latin American populations. Given this scenario, this initial study aimed to examine in mathematics teacher Chilean students (1) the internal structure of grit and (2) their position in a nomological network integrated by academic achievement, sex, age and years enrolled in the program. Participants consisted in the total population (n = 153) of students enrolled in a mathematics teacher program at Universidad de La Frontera, a public institution located in the Central-South area from Chile. The program was selected because it presents a high level of difficulty to its students and because it includes highly formalized tasks, as part of its disciplinary courses. Participants responded the Short Grit Scale (Grit-S) and a demographic questionnaire. In this study, Grit-Swas previously translated and adapted into Spanish from the original English version. Grit-Scontains eight items intended to measure the two facets of grit. Exploratory factorial analysis revealed that, after excluding two items due to low factor loadings (items No. 1 and 2), grit presented a one-dimensional configuration, with an adequate internal consistency (ordinal Alpha: .80). A positive linear correlation, although marginally significant, was obtained between grit and academic achievement, r(143)= .12, p =.069, d = .24. However, a planned contrast revealed that a nonlinear relationship, similar to a hyperbolic curve, better explains the link between these two variables. Specifically, this analysis showed that students in the upper grit quintile obtained a significantly higher grade point average than the combined grade point average of the remaining grit quintiles, t(138) =1.87, p = .032, d = .32. This result suggests that academic achievement remains reduced when grit level is low or moderate and only increases when grit level is high. A multiple regression analysis indicated that sex, age and number of years in the program account for 12.6% of grit variance, F(3, 149) = 7.15, p < .001, d = .76. Sex significantly contributed to the prediction (β =.198, p = .011, d = .38) with women, (M = 3.77,dt = .61) reporting higher levels of grit than men (M = 3.53, dt = .69). Whereas age did not significantly contribute to the prediction (β =.102, p = .206), the number of years in the program showed a significant direct association with grit (β = .261, p = .001, d = .60. Due to the originality of these findings, most differing from those reported in the literature, this study offers tentative explanations that future research could use to formulate and empirically test new hypotheses using, hopefully, a confirmatory approach. These possible explanations mainly refer to the participants' previous level of mathematic mastery and/or the level of difficulty demanded by the educational program.

The Schizotypal Personality Questionnaire-Brief lacks measurement invariance across three countries.

The Schizotypal Personality Questionnaire-Brief (SPQ-B) is a commonly-used tool for measuring schizotypal personality traits and due to its wide application, its cross-cultural validity is of interest. Previous studies suggest that the SPQ-B either has a three- or four-factor structure, but the majority of studies have been conducted in Western contexts and little is known about the psychometric properties of the scale in other populations. In this study factorial invariance testing across three cultural contexts-Australia, China and Chile was conducted. In total, 729 young adults (Mean age = 23.99 years, SD = 9.87 years) participated. Invariance testing did not support the four-factor model across three countries. Confirmatory Factor Analyses revealed that neither the four- nor three-factor model had strong fit in any of the settings. However, in comparison with other competing models, the four-factor model showed the best for the Australian sample, while the three-factor model was the most reasonable for both Chinese and Chilean samples. The reliability of the SPQ-B scores, estimated with Omega, ranged from 0.86 to 0.91. These findings suggest that the SPQ-B factors are not consistent across different cultural groups. We suggest that these differences could be attributed to potential confounding cultural and translation issues.

Impacto de la rehabilitación neurológica a través de la terapia de restricción inducida modificada en la mejora del apoyo social en usuarios con ataque cerebro vascular / Impact of neurological rehabilitation through modified constraint induced therapy in improving social support patients with stroke

Introduction: Access to rehabilitation in stroke patients is critical, considering the physical and psychological disabilities and generates social impact involved. Purpose: Evaluate the effectiveness of neurorehabilitation in collective mode, compared to the individual mode, in improving social support among patients with stroke, after application of the constraint induced of movement therapy. Methods: A randomized controlled trial of 36 patients who had a stroke were divided into two intervention groups. The independent variable was the implementation of collective or individual therapy for 3 hours for 10 consecutive days and the dependent variable was social perception evaluated by the Medical Outcomes Study-Social Support Survey (MOS-SSS) at baseline (pre-test) and end (post-test). Results: After controlling the pre-test scores, analysis of covariance revealed significant differences in favor of the collective mode in all post-test social support dimensions. Conclusions: Compared with the individual mode, the collective mode significantly improves several aspects of the patient’s perceived social support, thus providing evidence of its clinical and practical effectiveness.

Introducción: El acceso a rehabilitación en usuarios con ataque cerebro vascular es fundamental, considerando las discapacidades físicas y psicológicas que genera y el impacto social que conlleva. Objetivo: Evaluar la efectividad de la neurorehabilitación en modalidad colectiva, comparada con la modalidad individual, en la mejora del apoyo social en usuarios con ACV, después de la aplicación de la terapia de restricción inducida de movimiento. Método: Se realizó un ensayo clínico aleatorizado con 36 usuarios con ACV divididos en dos grupos de intervención. La variable independiente fue la implementación de la terapia en modalidad colectiva o individual por 3 horas diarias durante 10 días consecutivos y la variable dependiente fue el apoyo social percibido evaluado mediante la Medical Outcomes Study-Social Support Survey (MOS-SSS) antes (pretest) y después (post-test) de la intervención. Resultados: Controlando los puntajes pre-test, análisis de covarianza revelaron diferencias significativas a favor de la modalidad colectiva en todas las dimensiones post-test del apoyo social. Conclusiones: La rehabilitación en modalidad colectiva, en comparación con la modalidad individual, mejora significativamente diversos aspectos del apoyo social percibido del usuario, apoyando así su efectividad clínica y práctica.

Aprendizaje autodirigido en estudiantes de pedagogía chilenos: un análisis psicométrico / Self-directed learning in Chilean student teachers: A psychometric analysis

Este estudio examinó la validez estructural y confiabilidad de la Escala de Aprendizaje Auto-dirigido en una muestra representativa de estudiantes de pedagogía de una universidad chilena. Adicionalmente, este estudio estableció niveles de desempeño en la escala y exploró su variación según sexo y antigüedad en la carrera. Usando el análisis factorial exploratorio se retuvo una solución de 3 factores oblicuos (autocontrol, autogestión y deseos de aprender) muy semejante a, y teóricamente coherente con, la estructura original de la escala. Estos 3 factores y la escala total presentaron una adecuada consistencia interna. Las mujeres exhibieron niveles de desempeño significativamente mayores que los hombres en autogestión, sin diferencias en los otros factores. Las 3 dimensiones correlacionaron de modo directo y significativo con la antigüedad en la carrera. Se discuten estos resultados como evidencia inicial que respalda la validez y confiabilidad de la escala en esta población de estudiantes de pedagogía.

This study examined the structural validity and reliability of the Self-Directed Learning Scale, in a representative sample of student teachers enrolled at a Chilean university. Additionally, this study established performance levels within the scale and explored its variation in accordance to gender and the number of years spent in the program. Using exploratory factor analyses, an oblique 3-factor solution (self-control, self-management, and desire for learning) was retained, being very similar to-and theoretically coherent with- the original structure of the scale. Both the factors’ scores and the total scale score showed adequate indices of internal consistency. Women outperformed men in self-management, and no differences were observed in the other 2 factors. The 3 dimensions correlated directly and significantly with the number of years spent in the program. These results are discussed as initial evidence to support the validity and reliability of the scale in this population of student teachers.

El coeficiente K² de Livingston y la fiabilidad de una decisión dicotómica en un test psicológico / Livingston K² Coefficient and the Reliability of a Dichotomous Decision in a Psychological Test

La fiabilidad de los puntajes es una de las propiedades psicométricas más importantes de un test psicológico. Sin embargo, a menudo los test son utilizados para hacer clasificaciones dicotómicas de personas, como sucede en las pruebas de screening psicopatológico o en selección de personal. En esos casos, los coeficientes de fiabilidad convencionales no resultan apropiados para estimar la precisión de las clasificaciones. En este trabajo se presenta el coeficiente K² de Livingston (1972, 1973) y se demuestra su uso a través de dos ejemplos empíricos, para estimar la fiabilidad de una clasificación realizada a partir de un test psicológico.

The reliability of test scores is one of the most important psychometric properties of a psychological test. However, the tests are often used for dichotomous classifications of people, as in tests used for screening or recruitment purposes. In such cases, the conventional reliability coefficients are not suitable for estimating the accuracy of the classifications. This paper introduces the coefficient K² of Livingston (1972, 1973) and demonstrates its use through two empirical examples to estimate the reliability of a classification based on psychological tests.

N-domain of human adhesion/growth-regulatory galectin-9: preference for distinct conformers and non-sialylated N-glycans and detection of ligand-induced structural changes in crystal and solution.

Human tandem-repeat-type galectin-9 is a potent adhesion/growth-regulatory effector via lectin capacity of its N- and C-terminal domains. This bioactivity prompted further crystallographic study of the N-domain, combined with analysis in solution. Binding of lactose markedly increased the N-domain's resistance to thermal denaturation. Crystallography revealed its intimate contact profile, besides detecting an extension of the beta-sandwich fold by an antiparallel beta-strand F0 aligned to the C-terminal F1 strand. Ligand accommodation in its low-energy conformation leads to a movement of Arg87's side chain. As consequence, the ligand's glucose moiety and Arg87 become hydrogen bonded. The resulting predictions for spatial parameters in solution were verified by determining (a) the pattern of magnetization transfer from the protein to protons of lactose and Forssman disaccharide by NMR spectroscopy and (b) the ellipticity changes at wavelengths characteristic for Trp/Tyr residues in near-UV CD spectroscopy. Whereas solid-phase assays confirmed a previously noted tendency for homo- and heterotypic aggregation, gel filtration and ultracentrifugation disclosed monomeric status in solution, in line with crystallographic data. Using cell mutants with defects in glycosylation, this lectin domain was shown to preferentially bind N-glycans without alpha2,3-sialylation. Since proximal promoter sequences were delineated to diverge markedly among galectin genes and resulting differences in expression profiles were exemplarily documented immunohistochemically, the intrafamily diversification appears to have assigned this protein to a characteristic expression and activity profile among galectins. Our data thus take the crystallographic information to the level of the lectin in solution and in tissues by a strategic combination of spectroscopic and cell/histochemical assays.

Meta-estereotipos sobre los indígenas mapuches de Chile / Meta-stereotypes of Mapuche indigenous people from Chile

Se examinaron los meta-estereotipos sobre los mapuches chilenos, esto es, la percepción que miembros de este pueblo originario tienen sobre los estereotipos que los chilenos no indígenas les asignan. Se analizaron cinco aspectos de los meta-estereotipos: contenido (atributos), rótulos (etiquetas grupales), precisión (congruencia con estereotipos), uniformidad (consenso) y estructura (configuración de atributos y rótulos). Una muestra de 39 adultos mapuches de la Ciudad de Temuco (Chile) respondió una entrevista semi-estructurada destinada a indagar experiencias de interacción con chilenos no indígenas. Un análisis de contenido de las entrevistas reveló que los mapuches perciben 10 atributos meta-estereotípicos, todos negativos, relativamente precisos y uniformes: inferior, ignorante, flojo, incapaz, primitivo, conflictivo, sucio, pobre, tonto y borracho. Además, los entrevistados señalaron ser denominados con dos rótulos agraviantes: indio y mapuchito. Un análisis de espacio menor (Guttman, 1968) reveló una estructura compuesta por dos regiones de atributos: una, en torno a mapuchito, con atributos de naturaleza modificable, congruentes con una visión paternalista y otra en torno a indio, con atributos difícilmente modificables, compatibles con una posición extremadamente ofensiva y deshumanizadora. Como se esperaba desde el modelo de contenido de los estereotipos (Fiske, Cuddy, Glick & Xu, 2002), es ta estructura parece reflejar imágenes de personas que difieren a lo largo de las dimensiones de calidez y habilidad. Mientras que los atributos en torno a mapuchito describirían a personas potencialmente cálidas pero incompetentes, los atributos cercanos a indio describirían a personas definitivamente frías e inhábiles. Se discuten las limitaciones del presente estudio y las implicaciones de sus hallazgos.

Extensive evidence shows that members of the mainstream (non indigenous) Chilean society ascribe stereotypes to the Mapuche indigenous mainly through negative trait attributions (e.g., Merino, Millamán, Quilaqueo & Pilleux, 2004, among others). Additional research (e.g., Quilaqueo, 2005) indicates that Mapuches are conscious about being stereotyped, suggesting that this indigenous group may hold meta-stereotypes. According to Vorauer, Main, and O'Connell (1998), meta-stereotypes refer to those beliefs that members of an in-group hold about the stereotypes that members of an out-group assign to them. Some authors have suggested or demonstrated that meta-stereotypes influence in-group affective reactions (Finchilescu, 2005) and prejudice toward out-groups (Vorauer et al., 1998), in-group self-definition (Klein & Assi, 2001), and stereotypes that in-group ascribes to out-groups (Finchilescu, 2005). Providing that research in this topic and within this intergroup context is almost nonexistent, the aim of the present study was to examine Mapuches' meta-stereotypes considering this native group as in-group and Chilean non indigenous as outgroup. Five aspects of meta-stereotypes were studied: content (attributes), labels (in-group names), accuracy (congruence with stereotypes), uniformity (agreement among in-group members), and structure (attribute configuration). A purposive sample of 39 Mapuche adults from the city of Temuco ( Chile), answered a semi-structured survey designed to inquire into interaction experiences with members of the mainstream society. Sample selection criteria were: self-identification as Mapuche, having at least one Mapuche family name, being 18-year-olds or more, and having resided in Temuco for more than five years. The city of Temuco is located in the region that holds the largest Mapuche community in Chile (almost 24% of the regional population). A content analysis of the surveys revealed that mapuches perceive 10 meta-stereotypic attributes, all negatives: inferior, ignorant, lazy, incompetent, primitive, conflictive, dirty, poor, stupid, and drunk. In addition, participants reported having being labeled with two derogatory names as indio and mapuchito. Whereas the label indio was mainly related to intergroup contexts perceived by participants as highly humiliating, the label mapuchito was usually associated with paternalistic attitudes and behaviors that non indigenous Chileans exhibit toward members of this ethnic minority. The 10 meta-stereotypic traits tended to be accurate, that is, they were the same attributes reported in the literature as constituting the unfavorable stereotypes that the out-group assign to Mapuches (e.g., Pilleux, 2005). Also, the report of these attributes and labels tended to be independent from several sociodemographic variables, suggesting a high degree of agreement (uniformity) among Mapuches that out-group members perceive them as possessing these metastereotypes. The sociodemographic variables included in these analyses were: gender, age, marital status, Mapuche origin of the participant's spouse, religion, education level, occupational category, time living in the city of Temuco, and membership in Mapuche organizations. A small space analysis (Guttman, 1968) revealed a structure composed by two attribute clusters. One cluster, located around the label mapuchito, includes six traits of a changeable nature (lazy, conflictive, dirty, poor, stupid, drunk), in line with a paternalistic view of this native group. The second cluster, located close to the label indio, includes four attributes (inferior, ignorant, incompetent, primitive), having a more fixed nature, compatible with an extremely offensive and dehumanizing perspective. These findings show that the labels assigned to the ingroup tend to be coherent with the contents of meta-stereotypic attributes. As expected from the stereotype content model proposed by Fiske, Cuddy, Glick, and Xu (2002), the two clusters seem to reflect images of persons differing along the dimensions of warmth and competence. Attributes around mapuchito would describe potentially warm but incompetent people while attributes near to indio would describe definitely cold and unskilled persons. Finally, limitations and implications from the present study are discussed.

Zinc ions induce the unfolding and self-association of boar spermadhesin PSP-I, a protein with a single CUB domain architecture, and promote its binding to heparin.

Spermadhesins are a family of seminal plasma proteins composed of a single CUB domain, which appear to be involved in various aspects of the fertilization process in pigs. PSP-I and PSP-II, the most abundant porcine spermadhesins, occur in seminal plasma as noncovalent heterodimers devoid of heparin-binding capability. Of note is the stability of this dimer, which is significantly affected by physiologically relevant conditions such as Zn2+ ions. Here, we show that PSP-I and PSP-II when separated appear to conserve the overall fold of the CUB domain observed in the crystal structure of the PSP-I/PSP-II heterodimer, as concluded from gel filtration, analytical ultracentrifugation, differential scanning calorimetry, and circular dichroism analyses. However, Zn2+ concentrations in the range of those found in boar seminal plasma induce the unfolding and self-association of PSP-I, apparently as a consequence of the exposure of hydrophobic core residues, whereas they have no effect on PSP-II. Remarkably, Zn2+-denatured and self-associated (but not structured monomeric) PSP-I is retained on a heparin column, resembling the behavior of free PSP-I and homologous spermadhesins of the heparin-binding fraction of boar seminal plasma, which also exhibit different aggregation states. Thus, the modulation of the structural organization and heparin-binding ability of PSP-I by Zn2+ might be a physiological phenomenon in seminal plasma.

Pneumococcal phosphorylcholine esterase, Pce, contains a metal binuclear center that is essential for substrate binding and catalysis.

The phosphorylcholine esterase from Streptococcus pneumoniae, Pce, catalyzes the hydrolysis of phosphorylcholine residues from teichoic and lipoteichoic acids attached to the bacterial envelope and comprises a globular N-terminal catalytic module containing a zinc binuclear center and an elongated C-terminal choline-binding module. The dependence of Pce activity on the metal/enzyme stoichiometry shows that the two equivalents of zinc are essential for the catalysis, and stabilize the catalytic module through a complex metal-ligand coordination network. The pH dependence of Pce activity toward the alternative substrate p-nitrophenylphosphorylcholine (NPPC) shows that k(cat) and k(cat)/K(m) depend on the protonation state of two protein residues that can be tentatively assigned to the ionization of the metal-bound water (hydrogen bonded to D89) and to H228. Maximum activity requires deprotonation of both groups, although the catalytic efficiency is optimum for the single deprotonated form. The drastic reduction of activity in the H90A mutant, which still binds two Zn2+ ions at neutral pH, indicates that Pce activity also depends on the geometry of the metallic cluster. The denaturation heat capacity profile of Pce exhibits two peaks with T(m) values of 39.6 degrees C (choline-binding module) and 60.8 degrees C (catalytic module). The H90A mutation reduces the high-temperature peak by about 10 degrees C. Pce is inhibited in the presence of 1 mM zinc, but this inhibition depends on pH, buffer, and substrate species. A reaction mechanism is proposed on the basis of kinetic data, the structural model of the Pce:NPPC complex, and the currently accepted mechanism for other Zn-metallophosphoesterases.

Monomer/dimer equilibrium of the AB-type lectin from mistletoe enables combination of toxin/agglutinin activities in one protein: analysis of native and citraconylated proteins by ultracentrifugation/gel filtration and cell biological consequences of dimer destabilization.

The biological activity of a lectin is influenced by its quaternary structure. Viscumin is special among the family members of toxic AB-type plant lectins, because it triggers mitogenicity, toxicity, and agglutination. Its activity profile is dependent on the concentration, motivating a thorough inspection of the status of quaternary structure. Over a broad range of protein concentrations (0.01-25 mg/mL), viscumin occurs as a dimer. At high concentrations, the solutions exhibited nonideality, self-association, and polydispersity in sedimentation equilibrium and velocity experiments caused by irreversible aggregation. Calculation of viscumin's overall shape based on sedimentation velocity data resulted in an elongated dimer form resembling that of crystallized agglutinin. Appearance of monomers was restricted to concentrations in the submicrogram/mL level, as demonstrated by fast protein liquid chromatography gel-filtration analysis. To shift the equilibrium to the monomer for comparative cell biological assays, we performed chemical modification under conditions protecting the lectin activity. Citraconylation was effective to destabilize the dimer. Binding studies by fluorescence-activated cell scan analysis revealed a reduction in cell association upon modification and a tendency for increased sensitivity towards haptenic inhibitors at microg/mL concentrations. Nonetheless, growth inhibition continued to be potent for the ricin-like monomer despite reduced extent of binding. Occurrence of a concentration-dependent monomer/dimer equilibrium appears to achieve the same objectives as the development of two separate protein entities in Ricinus communis, an alternative strategy to emergence of a monomeric toxin, and cell cross-linking dimeric agglutinin.

Unravelling the structure of the pneumococcal autolytic lysozyme.

The LytC lysozyme of Streptococcus pneumoniae forms part of the autolytic system of this important pathogen. This enzyme is composed of a C-terminal CM (catalytic module), belonging to the GH25 family of glycosyl hydrolases, and an N-terminal CBM (choline-binding module), made of eleven homologous repeats, that specifically recognizes the choline residues that are present in pneumococcal teichoic and lipoteichoic acids. This arrangement inverts the general assembly pattern of the major pneumococcal autolysin, LytA, and the lytic enzymes encoded by pneumococcal bacteriophages that place the CBM (made of six repeats) at the C-terminus. In the present paper, a three-dimensional model of LytC built by homology modelling of each module and consistent with spectroscopic and hydrodynamic studies is shown. In addition, the putative catalytic-pair residues are identified. Despite the inversion in the modular arrangement, LytC and the bacteriophage-encoded Cpl-1 lysozyme most probably adopt a similar global fold. However, the distinct choline-binding ability and their substrate-binding surfaces may reflect a divergent evolution directed by the different roles played by them in the host (LytC) or in the bacteriophage (Cpl-1). The tight binding of LytC to the pneumococcal envelope, mediated by the acquisition of additional choline-binding repeats, could facilitate the regulation of the potentially suicidal activity of this autolysin. In contrast, a looser attachment of Cpl-1 to the cell wall and the establishment of more favourable interactions between its highly negatively charged catalytic surface and the positively charged chains of pneumococcal murein could enhance the lytic activity of the parasite-encoded enzyme and therefore liberation of the phage progeny.

Structural stability of the PsbQ protein of higher plant photosystem II.

We have characterized the stability and folding behavior of the isolated extrinsic PsbQ protein of photosystem II (PSII) from a higher plant, Spinacia oleracea, using intrinsic protein fluorescence emission and near- and far-UV circular dichroism (CD) spectroscopy in combination with differential scanning calorimetry (DSC). Experimental results reveal that both chemical denaturation using guanidine hydrochloride (GdnHCl) and thermal unfolding of PsbQ proceed as a two-state reversible process. The denaturation free-energy changes (DeltaG(D)) at 20 degrees C extrapolated from GdnHCl (4.0 +/- 0.6 kcal mol(-1)) or thermal unfolding (4.4 +/- 0.8 kcal mol(-1)) are very close. Moreover, the far-UV CD spectra of the denatured PsbQ registered at 90 degrees C in the absence and presence of 6.0 M GdnHCl superimpose, leading us to conclude that both denatured states of PsbQ are structurally and energetically similar. The thermal unfolding of PsbQ has been also characterized by CD and DSC over a wide pH range. The stability of PsbQ is at its maximum at pH comprised between 5 and 8, being wider than the optimal pH for oxygen evolution in the lumen of thylakoid membranes. In addition, no significant structural changes were detected in PsbQ between 50 and 55 degrees C in the pH range of 3-8, suggesting that PsbQ behaves as a soluble and stable particle in the lumen when it detaches from PSII under physiological stress conditions such as high temperature (45-50 degrees C) or low pH (<5.0). Sedimentation experiments showed that, in solution at 20 degrees C, the PsbQ protein is a monomer with an elongated shape.