Abstract: Background: Tropical dry forests (TDF) provide numerous environmental services to its residents; this has led them to be humanized landscapes subjected to chronic disturbance with a high risk of disappearing. Research question: To establish the relationship of vegetation structure and composition of a chronically disturbed TDF, with some environmental factors and the intensity of agricultural land use. Study site and period of research: Our study was conducted during six months (July through November) in the TDF of the community of San Nicolas Zoyatlan (Guerrero, Mexico); a territory with a history of over 500 years of agricultural use. This use has led to a complex mosaic of vegetation fragments. Methods: A selection of 36 fragments was studied to determine vegetation structure and composition as well as environmental factors. Representative plants from sampled areas were collected. Data gathered was explored with regression and multivariate statistical analysis techniques. Results: A total of 59 families, 178 genera and 279 species were recorded. Species richness varied widely among fragments, in general with a low dominance and high turnover of species. Slope was the only factor that showed a solid relationship with vegetation variables. Three groups of fragments were established and the statistical differences between them were explained by the duration of fallow. The fragments with longer fallow period showed the best conditions in vegetation variables and 66.9 % of the species were found in them. Conclusions: Composition and structure of the tropical dry forests were related to intensity of agricultural land use. Although there is a process of impoverishment, vegetation dynamics involving species of the Fabaceae, Asteraceae and Burseraceae families show a potential for their use in the environmental restoration of Zoyatlan.

Resumen: Antecedentes: Los bosques tropicales secos (BTS) aportan numerosos servicios ambientales a sus habitantes, esto los ha llevado a ser paisajes humanizados sujetos a disturbio crónico con riesgo de desaparecer. Pregunta: ¿Cuál es la relación de la composición y estructura de la vegetación de un BTS sujeto a disturbio crónico, con algunos factores del medio físico y la intensidad de uso agrícola del suelo? Sitio de estudio y fecha: El estudio se realizó en la comunidad de San Nicolás Zoyatlan (Guerrero, México) durante seis meses (junio-noviembre). Este territorio cuenta con más de 500 años de uso agropecuario, lo que ha propiciado un complejo mosaico de fragmentos de vegetación. Métodos: Se muestrearon 36 fragmentos para determinar la composición y estructura de la vegetación y los factores ambientales. Se recolectó y herborizó el material botánico representativo de las áreas muestreadas. Utilizando análisis de regresión y técnicas multivariadas se establecieron, tanto relaciones entre la vegetación y los factores ambientales como grupos específicos de fragmentos. Resultados: Se registraron 59 familias, 178 géneros y 279 especies. Entre fragmentos la riqueza específica varío ampliamente presentándose una dominancia baja y un alto recambio de especies. Únicamente la pendiente mostró una relación consistente con las variables de vegetación. Se obtuvieron tres grupos de fragmentos cuyas diferencias estadísticas se explicaron por los periodos de descanso agrícola; las zonas con mayor tiempo de barbecho presentaron 66.9 % de las especies y las mejores condiciones en las variables de vegetación. Conclusiones: La composición y estructura de la vegetación del BTS estuvo relacionada con la intensidad de uso agrícola del suelo. Aunque se presenta un proceso de empobrecimiento de la vegetación, existe una dinámica en la que participan especies de las familias Fabaceae, Asteraceae y Burseraceae, con potencial para utilizarse en la restauración ambiental de Zoyatlan.

Establecer la asociación entre las principales exigencias de trabajo y los daños a la salud en académicos que tienen la opción de participar en los programas de estímulos económicos. Estudio transversal y observacional, participaron 192 académicos universitarios con base en un muestreo aleatorio estratificado. Se recabaron datos sociodemográficos, exigencias laborales, perfil de daños a la salud e implicaciones derivadas de la participación en los programas de becas. Se utilizó el JMP8 y se controlaron variables confusoras (edad, género y antigüedad) estableciendo un nivel de significancia de p<0.05. El 64% cuenta con algún tipo de estímulo económico. El perfil de daños a la salud se caracterizó por trastornos músculo-esqueléticos (42%). Las exigencias de trabajo más representativas fueron: laborar en días de descanso (86%), cubrir una cuota de trabajo (80%) y sobrecarga de trabajo (60%); éstas se asociaron significativamente con: lumbalgia, músculo-esqueléticos, túnel del carpo y disfonía. Prevalecen tasas elevadas de trastornos músculo-esqueléticos, lumbalgia y disfonía, entre 3 y 4 de cada 10 trabajadores. Las exigencias laborales para poder concursar en los estímulos económicos se asociaron más significativamente con los daños a la salud, que los propios estímulos como tal. Es necesario visibilizar estos resultados para prevenirlos y atenderlos en materia de salud de los trabajadores.

To examine the association between the main job demands and adverse health effects among Mexican university faculty who have the option of participating in economic stimulus programs. Cross-sectional, observational study, involving a stratified random sample of 192 university academics. Data were collected on sociodemographics, job demands, adverse health profile implications arising from participation in economic incentive programs. The JMP8 was used and the analysis controlled for confounding variables (age, gender and age); statistical significance level was set at p < 0.05. Sixty-four percent of respondents indicated being eligible for some type of economic stimulus. The adverse health profile was characterized by musculoskeletal disorders (42%). The most representative job demands were working on days off (86%), covering for others (80%) and increased workload (60%). These factors were significantly associated with low back pain, musculoskeletal, carpal tunnel syndrome and dysphonia. The prevailing high rates of musculoskeletal disorders, back pain and dysphonia, affected between 3 and 4 out of 10 workers. Job demands required to participate in the economic stimulus were more significantly associated with adverse health than the economic incentives themselves.

Abstract We assessed a recently applied partial evaluation in the subject of Biochemistry, using this techniques for its validation: 1) Index of difficulty (pi), 2) Index of discrimination (Di), 3) Coefficient of discrimination (rpbis) and 4) Cronbach's alpha. The study was retrospective, descriptive, transversal, and observational, that is, it corresponds to a descriptive survey. The examination was administered to 1321 students and consisted of five themes with a total of 70 items, distributed 5 for thermodynamics, 25 for water, pH, and ions, 15 for proteins, 15 for enzymes, and 10 for laboratory sessions. The index of difficulty indicated 17 items to be either very easy or very difficult, the index of discrimination yielded 11 items that have to be revised, and, finally, the coefficient of discrimination yielded 35 items to be revised. Cronbach's alpha revealed that 28 items have to be removed. Cronbach's alpha was obtained with the SPSS statistics software, and the difficulty and discrimination index, as well as the coefficient of discrimination, were obtained with Excel. We conclude that it is feasible to assess, by means of the proposed techniques, the examinations for the subject of Biochemistry at the School of Medicine (UNAM).

Resumen Se evaluó un examen parcial de bioquímica aplicado recientemente utilizando las siguientes técnicas para su validación: 1) Índice de dificultad (pi), 2) Índice de discriminación (Di), 3) Coeficiente de discriminación (rpbis) y 4) Alfa de Cronbach. El estudio fue retrospectivo, descriptivo, transversal y observacional por lo que pertenece a una encuesta descriptiva. Se evaluaron las respuestas dadas por 1321 estudiantes y el examen constó de cinco temas. El total de reactivos de evaluación fue de 70, de los cuales 5 para termodinámica, 25 para agua pH e iones, 15 para química de proteínas, 15 para enzimas y con 10 se evaluaron las prácticas de laboratorio. Con el estudio de índice de dificultad se encontró que hay 17 reactivos o muy fáciles o muy difíciles, con el índice de discriminación se identificó que hay que revisar 11 reactivos y finalmente con el coeficiente de discriminación, el número a revisar fue de 35. Con el alfa de Cronbach se encontró que 28 reactivos deberán modificarse o eliminarse. El alfa de Cronbach fue obtenida con el paquete estadístico SPSS; el índice de dificultad, el índice y el coeficiente de discriminación se obtuvieron con el programa Excel. Se concluye que es factible evaluar mediante las técnicas aquí propuestas los exámenes de la asignatura de Bioquímica del Departamento de Medicina de la UNAM.

The most important impact of early expressions of neurological damage in children is the difficulty of mixing up in their social environment which at the beginning affects their interactions with their mother. Children with biological risks show great difficulties to begin interactions. When mothers get adjusted to bidirectional relations with neurologically damaged children, an increase in the commencement of interactions by a child is achieved, while fewer responses of the mother to child produce fewer interactions and increases irritability. Early intervention programs which contain in their strategies management of mother-infant interactions have been considered effective for child development. However, further empirical studies are required, concerning the influence of specific patterns of early mother-infant interaction and future development of children with perinatal neurological damage, in terms of prevention of alterations or disability. The present longitudinal study reports the effect of reciprocity of mother-infant interactions in the motor development observed in children of 4, 8, and 12 months old, latent growth curve in structural equation modeling. This model permits the identifications of causal factors that could affect the results in different age groups and provides predictions of the relations in a more complex form than lineal relations. Based on the model designed, it could be shown that mother-infant interactions of reciprocity best characterized children with higher development level while the absence is seen in children with retarded development. We classified mothers and children in two types, respectively: interactive and organized mothers vs. non-interactive and disorganized ones; interactive and responsive children vs. non-interactive and non-responsive ones. Subjecting these two types of mothers and children to four possible combinations, the model results showed different motor development predictions in the children. On one hand, we estimated regression coefficient of four dyadic systems, obtained by combinations of different types of mothers and children: interactive and organized mother with interactive and responsive child (Dyadic system 1); interactive and organized mother with non-interactive and non-responsive child (Dyadic system 2); non-interactive and disorganized mother with interactive and responsive child (Dyadic system 3); and non-interactive and disorganized mother with non-interactive and non-responsive child (Dyadic system 4). Dyadic system 1 was associated with a better motor development in children with a mayor regression coefficient (19.82), followed by System 2 and System 3 (regression coefficient of 17.54 and 11.46, respectively). System 4 had a negative estimate value of regression coefficient (-11.27) in our model. On the other hand, we estimated intercept values according to the interactive type of these mothers and children. Among the four interactive types, solely two of them had statistically significant intercepts (p < .05), <img border=0 width=13 height=18 src="../img/a07n1.gif" > or = 66.13 for interactive children and <img border=0 width=13 height=18 src="../img/a07n1.gif" > or = 42.76, for non-interactive children. To predict the motor development of 4, 8, and 12 months old children, the slope with attenuation permitted to give a mayor model fitting, with the regression coefficient of 0, 1 and 1.5, respectively. This model presented excellent values of model fitting indicators (X² = .96, p = .97, CFI = 1.00, RMSEA = .00). This line of study should be widened, because motor development is the principal domain consolidated in the first months of life. It is fundamental in domain organizations of higher complexity as cognition and language. We conclude that this model showed that in high risk perinatal children, early mother-child interactions represent a good predictor of motor development in the first year of life. Moreover, we found that motor achievements in the first months of life can be a strong predictive indicator of future development of a child. These findings suggest the importance in clinical practice of observation and registration of mother-child interactions as part of an integral strategy of child evaluation.

Los impactos más importantes de las expresiones tempranas del daño neurológico en los niños, son las dificultades para establecer intercambios con su medio social, afectando en la etapa inicial las primeras interacciones con su madre. Niños con riesgo biológico muestran grandes dificultades para iniciar interacciones. Cuando las madres se ajustan en una relación bidireccional se logra un aumento en las iniciaciones del niño; si las madres responden menos, los niños disminuyen las iniciaciones y aumentan la irritabilidad. Los programas de intervención temprana que integran en sus estrategias el manejo de las interacciones madre-niño se han considerado exitosos por sus implicaciones directas en el desarrollo del niño. Se requiere mayor soporte empírico sobre la influencia de patrones específicos de interacciones tempranas madre-hijo y el desarrollo posterior de niños con daño neurológico perinatal, en términos de prevención de alteraciones o discapacidad. Se realizó un estudio longitudinal y se reporta el efecto de las interacciones de reciprocidad madre-hijo en el desarrollo motor observado en niños a los 4, 8 y 12 meses de edad, a través del empleo del Modelo de Ecuaciones Estructurales (Curva de Crecimiento Latente). Se concluye que el modelo permitió mostrar que en niños de riesgo perinatal, las interacciones madre-hijo representan un buen predictor del desarrollo motor en el primer año de vida. Estos hallazgos tienen importantes implicaciones en la práctica clínica como estrategia integral para el diseño de acciones de intervención temprana debido a que los logros motores en los primeros meses representan un indicador predictivo del desarrollo infantil posterior.

Las nuevas formas de organización laboral provocan incertidumbre, precarización y violación de los derechos de los trabajadores. El obrero de la construcción es vulnerable porque tiene que aceptar condiciones de trabajo inhumanas para poder sobrevivir. Este estudio analiza la relación entre esas condiciones y los trastornos musculoesqueléticos, la fatiga y los accidentes. Se aplicó una encuesta validada en población trabajadora mexicana (n=128). Esta industria en México se caracteriza por pésimas condiciones de trabajo: la jornada es al menos de 12 horas, 99% de los trabajadores tiene contrato temporal y 77% no tiene ninguna prestación. Más de 75% está expuesto a múltiples riesgos que se asociaron con trastornos musculoesqueléticos de miembros superiores e inferiores (57,8%), lumbalgia (50%), fatiga crónica (48,4%) y accidentes de trabajo (44,5%). Las interacciones sinérgicas mostraron que la extensión y la intensidad de la jornada se encontraron fuertemente relacionadas con el esfuerzo físico intenso y las posiciones forzadas, para generar los diversos padecimientos.

New forms of work organization cause uncertainty and increased precariousness, and infringe on workers’ rights. Construction workers are vulnerable because they have to accept inhumane working conditions in order to survive. This study analyzes the relationship between these conditions and musculoskeletal disorders, fatigue and accidents. A previously validated survey was administered to a population of Mexcian workers (n=128). Conditions in the construction industry in Mexico are extremely poor: the work shifts are at least 12 hours long, 99% of workers work under temporary contracts, and 77% of workers receive no benefits. More than 75% are exposed to multiple hazards which were associated with musculoskeletal disorders of the limbs (57.8%), low back pain (50%), chronic fatigue (48.8%) and occupational injuries (44.5%). Synergistic interactions showed that the long duration and intensity of the working day were strongly related to intense physical activity and awkward positions in generating the various adverse health effects observed.

El objetivo de esta investigación fue describir las características de la noción de la palabra escrita y la noción gramatical de la oración escrita, en 28 niños de 4 a 8 años con encefalopatías hipóxicoisquémica, hiperbilirrubinémica y mixta en el periodo perinatal. Para tal fin, se aplicaron las pruebas Monterrey y Terman Merrill, y se documentó la secuela neuropsicológica. El 75% de los niños presentó secuela cognoscitiva leve; 82% estuvo en el nivel esperado de las nociones evaluadas acordes con su edad, y del 18% de los niños con atraso en la lectura cuatro tuvieron antecedentes de encefalopatía mixta y uno antecedentes de hiperbilirrubinemia. Se discuten los niveles de conceptualización de lecto-escritura y su relación con variables biológicas y sociales.

The objective of this research project was to describe the notion of the written word and the grammatical notion of the written sentence in 28 children between the ages of 4 and 8, who suffered hypoxic ischemic, hyperbilirubinemic, or mixed encephalopathy during the perinatal period. For that purpose, the Monterrey and the Terman Merrill instruments were administered, and the neuropsychological sequelae were documented. 75% of the children showed slight cognitive sequelae; 82% were at the expected level for their age regarding the notions evaluated; and of the 18% of the children with reading delays, four had a history of mixed encephalopathy and one of hyperbilirubinemia. The study discusses the levels of conceptualization regarding reading and writing, and their relation to biological and social variables.

O objetivo desta investigação foi descrever as características da noção da palavra escrita e a noção gramatical da oração escrita, em 28 crianças de 4 a 8 anos com encefalopatias hipóxico-isquêmica, hiperbilirrubinêmica e mista no período perinatal. Com esta finalidade, aplicaram-se as provas Monterrey e Terman Merrill, e documentou-se a seqüela neuropsicológica. Apresentam seqüela cognoscitiva leve 75% das crianças; 82% estiveram no nível esperado das noções avaliadas de acordo com sua idade, e entre 18% das crianças com atraso na leitura, quatro têm antecedentes de encefalopatia mista e um antecedente de hiperbilirrubinemia. Discutem-se os níveis de conceitualização de lecto-escritura e sua relação com variáveis biológicas e sociais.

Lung cancer is the leading cause of cancer mortality in Mexico and worldwide. In the past decade, there has been an increase in the number of lung cancer cases in young people, which suggests an important role for genetic background in the etiology of this disease. In this study, we genetically characterized 16 polymorphisms in 12 low penetrance genes (AhR, CYP1A1, CYP2E1, EPHX1, GSTM1, GSTT1, GSTPI, XRCC1, ERCC2, MGMT, CCND1 and TP53) in 382 healthy Mexican Mestizos as the first step in elucidating the genetic structure of this population and identifying high risk individuals. All of the genotypes analyzed were in Hardy-Weinberg equilibrium, but different degrees of linkage were observed for polymorphisms in the CYP1A1 and EPHX1 genes. The genetic variability of this population was distributed in six clusters that were defined based on their genetic characteristics. The use of a polygenic model to assess the additive effect of low penetrance risk alleles identified combinations of risk genotypes that could be useful in predicting a predisposition to lung cancer. Estimation of the level of genetic susceptibility showed that the individual calculated risk value (iCRV) ranged from 1 to 16, with a higher iCRV indicating a greater genetic susceptibility to lung cancer.

Abstract: The addition of non-milk fat (NMF) to milk and its derivates is considered to be an adulteration of the product. The objective of our study was to develop a statistical methodology that will make it possible to detect NMF in mixtures of NMF with milk fat (MF). A sampling was made of raw milk from the Mexican Highlands every 15 d during one year (total, 216 samples). The samples of NMF included two for each oil: fish, sunflower and canola, as well as two of lard and tallow. The percentages (% p/p) of triacylglycerols (TAG) in each fatty material were obtained by gas chromatography with flame ionization detector; the identified TAG varied between 28 and 56 carbon atoms. MF was mixed with the NMF: 95:5, 90:10, 85:15 and 80:20. A linear multiple regression analysis was made and three equations were obtained for the NMF: 1) Y =1.71C42+11.76C44−1.93C46+3.13C52−0.25C54 (fish oil); 2) Y=4.24C38−2.18C40+2.33C42+2.19C44−0.03C48+2.86 C50−0.69C52+2.20C54 (canola and sunflower oils, tallow); 3) Y=2.41C34+1.37C36−0.30C38+2.67C40+3.63C48−0.6 9C50+1.70C52+0.71C54 (lard). With these equations, 75.3 and 98.11% of the cases were detected when the adulterations with NMF were 5 and 10%.

Resumen: La adición de grasa no láctea (GNL) a la leche y sus derivados se considera una adulteración del producto. El objetivo del presente estudio fue desarrollar una metodología estadística que permita detectar GNL en mezclas de GNL con grasa láctea (GL). Se realizó un muestreo de leche cruda del Altiplano Mexicano cada 15 d durante un año (total, 216 muestras). Las muestras de GNL fueron dos para cada aceite: pescado, girasol y canola, así como dos de manteca y sebo. Los porcentajes (% p/p) de contenido de triacilgliceroles (TAG) en cada materia grasa se obtuvieron por cromatografía de gases con detector de ionización de flama; los TAG identificados oscilaron entre 28 y 56 átomos de carbono. Se mezcló GL con las GNL: 95:5, 90:10, 85:15 y 80:20. Se hizo un análisis de regresión lineal múltiple y se obtuvieron tres ecuaciones para las GNL: 1) Y=1.71C42+11.76C44−1.93C46+3.13C52−0.25C54 (aceite de pescado); 2) Y=4.24C38−2.18C40+2.33C42+2.19C44 −0.03C48+2.86C50−0.69C52+2.20C54 (aceites de canola y girasol, sebo); 3) Y=2.41C34+1.37C36−0.30C38+2.67C40 +3.63C48−0.69C50+1.70C52+0.71C54 (manteca). Con esas ecuaciones se detectaron 75.3 y 98.11% de los casos cuando las adulteraciones con GNL fueron 5 y 10%.

Summary As the environment is a crucial source in an infant’s development, it is important to assess the proximal environment where a variety of social relationships take place. Experiences derived from the home environment allow the specific activities that a child builds actively. These opportunities have an outstanding impact on an infant’s development. The home concept and its influence on development led to the discovery and interrelations of several dimensions and today’s emphasis relies on identifying the mechanisms of the variability of environment that exert an influence on the variability of development. Under this perspective, at the end of the 1960’s the Infant/Toddler HOME Inventory was developed by Caldwell and Bradley. Very soon, Cravioto adapted it for its use in a Mexican population according to the characteristics of typical families and cultural aspects. The purpose of this investigation was to establish the internal consistency of the Infant/Toddler HOME Inventory in the version adapted by Cravioto through the assessment of the precision of its scoring in terms of internal consistency. Cohort: 62 infants and their mothers were contacted in the first 72 hours after delivery through a Research Program from the Child Psychiatry Hospital Dr. Juan N. Navarro (Environmental Modulation of Infancy Development). They were born in two Mexico City hospitals: a state public hospital, Hospital de la Mujer (Women’s Hospital) and in the Mother-infant Research Center from the Birth Study Group (CIMIGEN). All of them were low-risk infants who met the criteria for a one year follow up and whose parents gave their informed consent and accepted to be visited at their homes. The distribution of the infants group by sex was: 30 infants (48%) were female and 32 (52%) were male. Families were classified as follows: 72.5% were nuclear and 27.5% were extended. According to their socioeconomic profile, a high relationship was found between income and housing: seven (11.3%) of the highest income families lived in houses or apartments of their own or rented, where there were more rooms than inhabitants, whereas all others were living as follows: crowded houses or apartments (23 families, 37.1%), houses with of only one room (4 families, 6.5%) and the poorest houses with collective bathroom (28 families, 45.2%). All households had electrical lighting and most of them had also drinkable water inside their homes (98.4%); one shared water from a deep pond with their community. Bathrooms were: 35.5% with running water, 59.7% used a bucket for carrying water and 4.8% had latrine. Instrument: The Infant/Toddler HOME Inventory, version adapted by Cravioto, with 62 items in a binary format response was used. Subscale VII, Play Materials, asked about color, size, consistency or texture and type of toys. The instrument is administered by having a person calling the home at a time when the infant is awake and can be observed interacting with the mother or principal caregiver. The internal consistency of the Infant/Toddler HOME Inventory was monthly assessed for each of its subscales and the total scale, until the child’s first year of life (12 months), applying Cronbach’s alpha. Results showed that alpha coefficient’s values higher than 0.60 throughout the 12 months were observed in the VII Play Materials shoed a range of 0.64 and 0.84, and 0.60 and 0.83 for the Total Scale. On the other hand, subscale VI, Physical Environment, showed a less than 0.60 value with an internal consistency coefficient of 0.56 in the first month of life; nevertheless the remaining months had values between 0.60 and 0.70. This was also observed with subscale II, Mental Development and Vocal Stimulation, with a 0.58 value for the first month of life and alpha values between 0.63 and 0.74 for the remaining eleven assessments. Subscale III, Emotional Climate, exhibited seven evaluations in a range between 0.61 and 0.76; this is the second with a 0.61, fourth with 0.69, sixth with 0.76, seventh with 0.67, ninth with 0.63, tenth with 0.69 and eleventh 0.63. Non-acceptable internal consistency, it is less than 0.60 in most of their scorings were observed for the following scales: I. Adult Contact, V. Breadth of Experience. Only in the sixth month’s a value of 0.64 was observed, and the rest of scales exhibited a range within a 0.38 as inferior limit and 0.56 superior limit in the former and a 0.65 value in the tenth month and 0.60 in the eleventh. Subscale IV, Avoidance of Restriction, showed the lowest coefficient with values between 0.24 and 0.49. These results suggest that most of the subscales had adequate reliabilities, except for subscales I, Adult Contact; IV, Avoidance of Restriction; and V, Breadth of Experience. The purpose of this study was to evaluate the internal consistency of an instrument which measures the home environment quality in infants during their first year of life. Results showed the Infant/Toddler HOME Inventory had high internal consistency values in the Total Scale. These results are similar to those obtained by Banard, Bee & Hammond with a group of 179 children in Seattle, where they found 0.77 values at fourth months, 0.81 at eight and 0.86 at twelve. Our findings were within a rank of 0.68 and 0.83. Cronbach’s alpha value obtained for the different subscales showed intersubscale differences. Subscales II, III, VI and VII showed internal consistency values equal or higher than 0.60 in most of the assessments during the 12 months of life. This implies measurements are precise and reliable when using them in low risk Mexican infants. Lower values found in subscales I, Adult Contact, IV, Avoidance of Restriction and V, Breadth of the Experience, may be due to the low number of items. According to Nunnally and Bernstein, it is recommended that measurements with a low internal consistency should be used with initial, non-crucial decisions, and with temporary and reversible effects susceptible to replication and rectification. It is very important to stress the fact that this Infant/Toddler HOME Inventory version is not comparable with other in the literature because the structure was notably modified. Limitations in this study are not only this modification, but the size sample, and future research efforts should overcome this fact by trying to sample infants from different Mexican regions. This study points out the need to adapt, develop and evaluate psychometrically instruments that measure specific aspects of the environment of infant’s homes. Our results may be an initial step for those interested in measurements of Mexican families homes, or in those interested in the Infant/Toddler HOME Inventory as an indicator of the environmental aspects in early infancy.

resumen está disponible en el texto completo

Abstract In the management of fragmented ecosystems, it is of great relevance to understand the repercussions that the edge effect has on the remnant vegetation of these fragments. In this experiment, an analysis was made of how seedlings of Caesalpinea platyloba and cuttings of Spondias purpurea respond to the environmental gradient generated on the edge of two fragments of tropical dry forest bordering on grasslands. Thirty individuals of C. platyloba, 8 months of age, and the same number of cuttings of S. purpurea, were transplanted along 5 corridors of 5 by 50 m parallel to the edge, at distances of 0-5, 30-35 and 75-80 m from the edge toward the inner forest, and at 0-5 and 35-40 m toward the pasture. Measurements were taken of the height increase of each plant, and its survival was registered during 14 months after transplanting. It was found that the survival of the plants was differential among species, with different thresholds of tolerance to disturbance. C. platyloba showed a higher percentage of survival in the corridors of the inner forest, although the heterogeneity of the micro-environmental conditions appears to have greater influence than the effect of the distance with respect to the edge. C. platyloba showed a greater response to the factors of the quality of the site that regulate its height increase.

Resumen En el manejo de ecosistemas fragmentados, es de gran relevancia comprender las repercusiones que el efecto de borde tiene sobre la vegetación remanente de dichos fragmentos. En este experimento se analizó cómo plántulas de Caesalpinea platyloba y estacas de Spondias purpurea responden al gradiente ambiental generado en el borde de dos fragmentos de bosque tropical caducifolio colindantes con potreros. Se trasplantaron 30 individuos de 8 meses de edad de C. platyloba e igual número de estacas de S. purpurea, a lo largo de 5 corredores de 5 por 50 m paralelos al borde, a distancias de 0-5, 30-35 y 75-80 m desde el borde hacia el interior del bosque, y a 0-5 y 35-40 m hacia el potrero. A cada planta se le tomaron medidas del incremento en altura y se registró su supervivencia durante 14 meses después del trasplante. Se encontró que la supervivencia de las plantas fue diferencial entre especies, con diferentes umbrales de tolerancia a la perturbación. C platyloba mostró un mayor porcentaje de supervivencia en los corredores del interior del bosque, aunque la heterogeneidad de las condiciones microambientales parece tener mayor influencia que el efecto de la distancia respecto al borde. C. platyloba mostró una mayor respuesta a los factores de la calidad del sitio que regulan su incremento en altura.

The aim of this work was to propose an adjustment to the Model of Andersen who answers better to the social inequality of the population in the Mexico City and allows to evaluate the effect of socioeconomic factors in the access to the prenatal care of a sample stratified according to degree of marginalization. MATERIAL AND METHODS: The data come from a study of 663 women, randomly selected from a framework sample of 21 421 homes in Mexico City. This work collects information about factors that affect utilization of health services, as well as predisposing factors (age and socioeconomic level), as enabling factors (education, social support, entitlement, pay out of pocket and opinion of health services), and need factors. The sample was ranked according to exclusion variables into three stratums. The data were analyzed through the technique of path analysis. RESULTS: The results indicate that socioeconomic level takes part like predisposed variable for utilization of prenatal care services into three stratums. Otherwise, education and social support were the most important enabling variables for utilization of prenatal care services in the same three groups. In regard to low stratum, the most important enabling variables were education and entitlement. For high stratum the principal enabling variables were pay out of pocket and social support. The medium stratum shows atypical behavior which it was difficult to explain and understand. There was not mediating role with need variable in three models. This indicated absence of equality in all stratums. However, the most correlations in high stratum perhaps indicate less inequitable conditions regarding other stratums.

OBJETIVO: Proponer una adaptación al modelo de Andersen que responda mejor a la desigualdad social de la población en la Ciudad de México y permita evaluar el efecto de factores socioeconómicos en el acceso a la atención prenatal de una muestra estratificada según grado de marginación. MATERIAL Y MÉTODOS: En la Ciudad de México, el marco muestral estuvo conformado por 21 421 hogares y la muestra probabilística quedó constituida por 663 casos. En la encuesta se obtuvo información de factores predisponentes al uso de servicios (edad y estrato socioeconómico), factores mediadores (escolaridad, apoyo social, seguridad social, pago de bolsillo y calidad de los servicios de salud) y de necesidad percibida. La muestra se distribuyó en tres estratos, de acuerdo con un índice de marginalidad. Para analizar la información se recurrió al análisis multivariado de senderos (path analysis). RESULTADOS: El modelo mostró ser eficiente para evaluar el efecto de la desigualdad social en el acceso a la atención prenatal pues en los tres estratos se observó que el nivel socioeconómico interviene como predisponente de la utilización de servicios de atención prenatal. De igual forma, la escolaridad y el apoyo social fueron las variables mediadoras más importantes para el uso de servicios de salud de control prenatal en los tres estratos. En relación con el estrato bajo, las variables mediadoras más importantes fueron escolaridad y seguridad social. El estrato medio mostró un comportamiento atípico difícil de caracterizar, y en el estrato alto las principales variables fueron pago de bolsillo y apoyo social.

The aim of this work was to propose an adjustment to the Model of Andersen who answers better to the social inequality of the population in the Mexico City and allows to evaluate the effect of socioeconomic factors in the access to the prenatal care of a sample stratified according to degree of marginalization. MATERIAL AND METHODS: The data come from a study of 663 women, randomly selected from a framework sample of 21 421 homes in Mexico City. This work collects information about factors that affect utilization of health services, as well as predisposing factors (age and socioeconomic level), as enabling factors (education, social support, entitlement, pay out of pocket and opinion of health services), and need factors. The sample was ranked according to exclusion variables into three stratums. The data were analyzed through the technique of path analysis. RESULTS: The results indicate that socioeconomic level takes part like predisposed variable for utilization of prenatal care services into three stratums. Otherwise, education and social support were the most important enabling variables for utilization of prenatal care services in the same three groups. In regard to low stratum, the most important enabling variables were education and entitlement. For high stratum the principal enabling variables were pay out of pocket and social support. The medium stratum shows atypical behavior which it was difficult to explain and understand. There was not mediating role with need variable in three models. This indicated absence of equality in all stratums. However, the most correlations in high stratum perhaps indicate less inequitable conditions regarding other stratums.

OBJETIVO: Proponer una adaptación al modelo de Andersen que responda mejor a la desigualdad social de la población en la Ciudad de México y permita evaluar el efecto de factores socioeconómicos en el acceso a la atención prenatal de una muestra estratificada según grado de marginación. MATERIAL Y MÉTODOS: En la Ciudad de México, el marco muestral estuvo conformado por 21 421 hogares y la muestra probabilística quedó constituida por 663 casos. En la encuesta se obtuvo información de factores predisponentes al uso de servicios (edad y estrato socioeconómico), factores mediadores (escolaridad, apoyo social, seguridad social, pago de bolsillo y calidad de los servicios de salud) y de necesidad percibida. La muestra se distribuyó en tres estratos, de acuerdo con un índice de marginalidad. Para analizar la información se recurrió al análisis multivariado de senderos (path analysis). RESULTADOS: El modelo mostró ser eficiente para evaluar el efecto de la desigualdad social en el acceso a la atención prenatal pues en los tres estratos se observó que el nivel socioeconómico interviene como predisponente de la utilización de servicios de atención prenatal. De igual forma, la escolaridad y el apoyo social fueron las variables mediadoras más importantes para el uso de servicios de salud de control prenatal en los tres estratos. En relación con el estrato bajo, las variables mediadoras más importantes fueron escolaridad y seguridad social. El estrato medio mostró un comportamiento atípico difícil de caracterizar, y en el estrato alto las principales variables fueron pago de bolsillo y apoyo social.

Introduction. The inhibitory masseteric reflex (IMR) evoked by means of stimulation of diverse intra or extra oral sites and during voluntary contraction of elevators muscles of the jaw; the main observed phenomenon is a period of silence or inhibitory wave in electromyogram of the mentioned muscles, whose function is to protect the oral structures and to control the bite force, followed by a potentiation wave that, in healthy adult subjects, is always minor that the inhibitory one. Material and methods. Twenty eight children were studied with temporary, mixed and permanent dentition, 17 without dental malocclusion and 11 with occlusal interferences. The IMR was registered by electromyography techniques, applying stimulus on the chin. Twenty stimuli were applied and averaged to obtain a reflexigram in which was measured: latency, duration and amplitude of the inhibitory wave and potentiation wave on both sides. Results. Clusters analysis identified interaction between IMR with dentition and occlusal interferences with statistically significative differences regarding occlusal interferences (P =0.05). Conclusions. It was observed influence of oclusal interferences on IMR, modifying its physiological protector effect, it was not observed regarding the dentition stages

Introducción. El reflejo inhibitorio masetérico (RIM) se evoca mediante estimulación de diversos sitios intra o extrabucales y durante contracción voluntaria de los músculos elevadores de la mandíbula; el principal fenómeno observado es un período de silencio u onda inhibitoria en el electromiograma de los músculos mencionados, cuya función es proteger las estructuras bucales y controlar la fuerza de mordida, seguida por una onda potenciadora que, en sujetos adultos sanos, siempre es menor que la inhibitoria. Objetivo: identificar los cambios del RIM que se asocian con las etapas de dentición (primaria, mixta o permanente) y con las interferencias oclusales. Material y métodos. Se estudió el RIM en 28 niños, 17 con oclusión normal y 11 con interferencias oclusales, en las 3 etapas de dentición. El RIM se registró con técnicas electromiográficas, aplicando estímulo sobre el mentón para evocar el reflejo; se realizaron 20 réplicas que fueron promediadas obteniendo el reflexigrama en el que se midió latencia, duración y amplitud de las ondas inhibitorias y potenciadoras derechas e izquierdas. Resultados. Mediante análisis de conglomerados, se identificó la interacción del RIM con la dentición y las interferencias oclusales y se encontró diferencia estadística significativa respecto de las últimas (P =0.05). Conclusiones. Hubo influencia de las interferencias oclusales sobre el RIM, modificando su efecto fisiológico protector, situación no observada respecto de la dentición

Lower back pain has a high prevalence among the Mexican working population, with extensive social and economic repercussions. Official figures show that lower back pain accounts for 10.0 to 15.0% of sick leave excuses. However, this fails to identify any relationship between lower back pain and job conditions, since such leave is only granted if it can be shown that the condition was not work-related. The present study shows that such a relationship does in fact exist. A retrospective study examined all cases (n = 210) in which workers were granted sick leave for lower back pain in an IMSS (Mexican Government Health Insurance) hospital in Mexico City during a seven-year period. The results show the association and interactions between debilitating lower back pain and several work-related variables: job position, time-on-the-job, and physical effort and weight-carrying associated with the position. Causes of lower back pain and the difficulty in obtaining accurate, precise back pain diagnosis are discussed. A number of clinical, epidemiological, and legal strategies for the study and prevention of back pain are suggested.

La lumbalgia es un padecimiento de alta prevalencia en la población trabajadora mexicana y tiene repercusiones económico-sociales de enorme alcance. Las cifras oficiales muestran que por lo menos entre el 10,0 y 15,0% de los dictámenes de invalidez se deben a ella. Este dictamen se otorga sólo cuando se ha demostrado que la enfermedad no tuvo relación con el trabajo. Sin embargo, esta investigación muestra que existe tal relación. El estudio fue retrospectivo y se consideraron a todos los trabajadores con dictamen de invalidez por lumbalgia (210 casos), en un hospital del IMSS de la Ciudad de México, durante un periodo de 7 años. Los resultados muestran la asociación e interacciones entre la lumbalgia invalidante y variables laborales como: puesto de trabajo, antigüedad, esfuerzo físico y levantamiento de cargas. Se discute sobre las dificultades y la precisión diagnósticas de la lumbalgia, así como sobre la causalidad del síndrome. Se sugieren algunas vías clínicas, epidemiológicas y legales para su estudio y prevención.

Lower back pain has a high prevalence among the Mexican working population, with extensive social and economic repercussions. Official figures show that lower back pain accounts for 10.0 to 15.0% of sick leave excuses. However, this fails to identify any relationship between lower back pain and job conditions, since such leave is only granted if it can be shown that the condition was not work-related. The present study shows that such a relationship does in fact exist. A retrospective study examined all cases (n = 210) in which workers were granted sick leave for lower back pain in an IMSS (Mexican Government Health Insurance) hospital in Mexico City during a seven-year period. The results show the association and interactions between debilitating lower back pain and several work-related variables: job position, time-on-the-job, and physical effort and weight-carrying associated with the position. Causes of lower back pain and the difficulty in obtaining accurate, precise back pain diagnosis are discussed. A number of clinical, epidemiological, and legal strategies for the study and prevention of back pain are suggested.

La lumbalgia es un padecimiento de alta prevalencia en la población trabajadora mexicana y tiene repercusiones económico-sociales de enorme alcance. Las cifras oficiales muestran que por lo menos entre el 10,0 y 15,0% de los dictámenes de invalidez se deben a ella. Este dictamen se otorga sólo cuando se ha demostrado que la enfermedad no tuvo relación con el trabajo. Sin embargo, esta investigación muestra que existe tal relación. El estudio fue retrospectivo y se consideraron a todos los trabajadores con dictamen de invalidez por lumbalgia (210 casos), en un hospital del IMSS de la Ciudad de México, durante un periodo de 7 años. Los resultados muestran la asociación e interacciones entre la lumbalgia invalidante y variables laborales como: puesto de trabajo, antigüedad, esfuerzo físico y levantamiento de cargas. Se discute sobre las dificultades y la precisión diagnósticas de la lumbalgia, así como sobre la causalidad del síndrome. Se sugieren algunas vías clínicas, epidemiológicas y legales para su estudio y prevención.