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The mycorrhizal component of revegetated areas after ecological restoration or rehabilitation in arid and semiarid tropical areas has been scarcely assessed, particularly those made after mining disturbance. We evaluated and compared the presence of arbuscular mycorrhizal fungi of a small area of restored tropical dry for est destroyed by sand extraction, with a non-restored area of similar age, at the peninsula of Macanao, Margarita Island (Venezuela). Our study was undertaken in 2009, four years after planting, and the mycorrhizal status was evaluated in four restored plots (8 x 12.5 m) (two were previously treated with hydrogel (R2 and R2'), and two were left untreated (R1 and R1'), and four non-restored plots of similar size (NR1 and NR1' with graminoid physiognomy with some scattered shrubs; and NR2 and NR2', with a more species rich plant community). Apparently the restoration management promoted higher arbuscular mycorrhizal fungi (AMF) species richness and diversity, particularly in restored soils where the hydrogel was added (R2 treatment). Soil of the NR1 treat ment (with a higher herbaceous component) showed the highest spore density, compared to samples of soils under the other treatments. Considering species composition, Claroideoglomus etunicatumand Rhizophagus intraradiceswere found in all treatments; besides, Diversispora spurcaand Funneliformis geosporumwere only found in non-restored plots, while members of the Gigasporaceae (a family associated with little disturbed sites) were commonly observed in the plots with restored soils. Mycorrhizal colonization was similar in the restored and non-restored areas, being a less sensitive indicator of the ecosystem recovery. The trend of higher richness and diversity of AMF in the restored plot with hydrogel suggests that this management strategy contributes to accelerate the natural regeneration in those ecosystems where water plays an essential role.

Myotonia congenita is a muscular disease characterized by myotonia, hypertrophy, and stiffness. It is inherited as either autosomal dominant or recessive known as Thomsen and Becker diseases, respectively. Here we confirm the clinical diagnosis of a family diagnosed with a myotonic condition many years ago and report a new mutation in the CLCN1 gene. The clinical diagnosis was established using ocular, cardiac, neurological and electrophysiological tests and the molecular diagnosis was done by PCR, SSCP and sequencing of the CLCN1 gene. The proband and the other affected individuals exhibited proximal and distal muscle weakness but no hypertrophy or muscular pain was found. The myotatic reflexes were lessened and sensibility was normal. Electrical and clinical myotonia was found only in the sufferers. Slit lamp and electrocardiogram tests were normal. Two affected probands presented diminution of the sensitive conduction velocities and prolonged sensory distal latencies. The clinical spectrum for this family is in agreement with a clinical diagnosis of Becker myotonia. This was confirmed by molecular diagnosis where a new disease-causing mutation (Q412P) was found in the family and absent in 200 unaffected chromosomes. No latent myotonia was found in this family; therefore the ability to cause this subclinical sign might be intrinsic to each mutation. Implications of the structure-function-genotype relationship for this and other mutations are discussed. Adequate clinical diagnosis of a neuromuscular disorder would allow focusing the molecular studies toward the confirmation of the initial diagnosis, leading to a proper clinical management, genetic counseling and improving in the quality of life of the patients and relatives. Rev. Biol. Trop. 56 (1): 1-11. Epub 2008 March 31.La miotonía congénita es una enfermedad muscular caracterizada por miotonía, hipertrofia y rigidez. Se presenta con dos patrones de herencia, autosómica dominante en cuyo caso recibe el nombre de miotonía de Thomsen, o autosómica recesiva conocida como miotonía de Becker. En este trabajo se confirmó el diagnóstico clínico presuntivo hecho hace algunos años en una familia con una condición miotónica y se reporta una nueva mutación en el gen CLCN1. El diagnóstico clínico se estableció después de estudios oculares, cardíacos, neurológicos y electrofisiológicos. El diagnóstico molecular fue hecho mediante la PCR, SSCP y secuenciación del gen CLCN1. El caso índice y los otros individuos afectados exhibieron debilidad muscular proximal y distal, pero no se encontró hipertrofia ni dolor muscular. Los reflejos miotáticos estuvieron disminuidos y la sensibilidad fue normal. Se encontró miotonía clínica y eléctrica solo en los individuos afectados. Las pruebas de lámpara de hendidura y electrocardiograma resultaron normales. Dos individuos afectados presentaron disminución de las velocidades de conducción sensitiva y latencias distales sensoriales prolongadas. El cuadro clínico concuerda con la miotonía de Becker, lo cual se confirmó con el hallazgo de una mutación responsable de la enfermedad en el gen CLCN1 (Q412P), la cual se encontró en la familia y estuvo ausente en 200 cromosomas provenientes de la población general. No se encontró miotonía latente, por lo que probablemente la habilidad de causar este signo subclínico es intrínsica de cada mutación. Afinar el diagnóstico clínico diferencial de las enfermedades neuromusculares permitiría enfocar los estudios moleculares hacia la confirmación del diagnóstico inicial en forma eficiente, lo cual permitiría un manejo clínico y asesoramiento genético más adecuados y una mejora en la calidad de vida de los pacientes y sus familias.

El cáncer gástrico es la segunda causa de muerte por cáncer en el mundo. Varios factores han sido asociados con el riesgo de llegar a desarrollarlo, entre ellos la predisposición genética. El gen p53 presenta un polimorfismo en el codón 72, el cual ha sido asociado con un mayor riesgo de desarrollar varios tipos de cáncer entre ellos el gástrico. El objetivo de este estudio fue determinar la asociación del polimorfismo localizado en el codón 72 del gen p53 con el riesgo de cáncer gástrico y lesiones gástricas leves en una población de alto riesgo de Costa Rica. El análisis del polimorfismo se llevó a cabo mediante PCR-RFLP, en una muestra de 58 pacientes de cáncer gástrico, 99 personas controles y 41 individuos clasificados como grupos I y II de acuerdo con la clasificación histológica japonesa. No se determinó asociación del polimorfismo del codón 72 de p53 con el riesgo de cáncer gástrico, ni de lesiones gástricas leves en la muestra estudiada. Con base en este estudio y otros que han investigado el polimorfismo del codón 72 del gen p53, no está claro el papel que podría estar jugando dicho polimorfismo en el desarrollo de cáncer gástrico. Mutaciones de novo en el gen p53 producidas durante el desarrollo neoplásico de la enfermedad podrían tener un mayor efecto que polimorfismos de línea germinal de este mismo gen. Existen otros genes polimórficos que también se han asociado con el riesgo de desarrollar cáncer gástrico.Association of the p53 codon 72 polymorphism to gastric cancer risk in a hight risk population of Costa Rica. Gastric cancer is the second most common cancer associated death cause worldwide. Several factors have been associated with higher risk to develop gastric cancer, among them genetic predisposition. The p53 gene has a polymorphism located at codon 72, which has been associated with higher risk of several types of cancer, including gastric cancer. The aim of this study was to determine the association of p53, codon 72 polymorphism, with the risk of gastric cancer and pre-malignant lesions in a high-risk population from Costa Rica. The genotyping was carried out by PCR-RFLP in 58 gastric cancer patients, 99 controls and 41 individuals classified as group I or II, according to the Japanese histological classification. No association was found for p53, codon 72 polymorphism with neither the risk of gastric cancer nor the risk of less severe gastric lesions in the studied population. Based on this study and taking into account other studies carried out with p53, codon 72 polymorphism, the role of this polymorphism in the development of gastric cancer remains unclear. De novo mutations on p53 gene produced during neoplasic development of this disease might play a greater role than germinal polymorphisms of the gene. Other polymorphic genes have been associated with higher risk to develop gastric cancer. Rev. Biol. Trop. 53(3-4): 317-324. Epub 2005 Oct 3.

Las mutaciones inestables constituyen un tipo de alteración genética descubierta en la década de los noventa. En condiciones normales, regiones específicas de los genes están constituidas por repeticiones de una secuencia corta que puede ser de tres, cuatro, cinco o más nucleótidos; por ejemplo CAG, CGG, ATTCT, etc. Este nuevo tipo de mutación consiste en un aumento en la cantidad de éstas repeticiones, lo que causa una alteración en la expresión de dichos genes. Son inestables porque se ha observado que el tamaño de la secuencia repetida varía cuando las células se dividen por mitosis o meiosis, lo cual tiene implicaciones sobre la herencia y por consiguiente sobre el consejo genético que debe brindarse a los afectados. Estas mutaciones se han encontrado en genes importantes para la función neurológica normal del ser humano, donde pueden alterar el transporte de los ARN desde el núcleo al citoplasma, provocar la inactivación del gen o producir una proteína con funciones nuevas. La mayoría de las enfermedades causadas por estas mutaciones afectan el sistema nervioso, son degenerativas y presentan el fenómeno de anticipación genética, es decir que los afectados dentro de una familia se enfermarán más jóvenes y en forma más severa con el paso de las generaciones. La cantidad de repeticiones de la secuencia repetida presenta una correlación negativa con la edad de manifestación, así como una correlación positiva con la severidad de la enfermedad. En este momento existen veinte padecimientos identificados que son causados exclusivamente por este tipo de mutación. Este trabajo es una breve revisión actualizada del tema.Unstable mutations, new challenges for genetic counseling of inherited disorders. Unstable mutations or amplification of DNA tandem repeats sequences constitute a new kind of genetic alteration discovered in the 90´s that cause hereditary diseases. This mutation has been found inside or near important genes involved in the normal neurological function in human beings. In some cases, the presence of the amplification causes altered expression of the genes, their inactivation or the synthesis of a protein with new functions. Some common characteristics of these diseases are that they affect the central nervous system and are degenerative in nature. Most of them show genetic anticipation meaning that the severity of the manifestations increases in each generation and appear at an earlier age. In most cases, the severity of the symptoms is positively correlated with the size of the amplification. Twenty illnesses caused by this kind of mutations have been identified so far. Briefly, this work reviews the current knowledge about this topic. Rev. Biol. Trop. 52(3): 491-499. Epub 2004 Dic 15.

La distrofia miotónica tipo1 (DM1) y el síndrome del cromosoma X frágil (FRAXA) son dos enfermedades hereditarias relativamente comunes. Ambas constituyen ejemplos de un nuevo tipo de mecanismo mutacional, llamado mutaciones inestables o dinámicas, expansión de tripletas, o amplificación del ADN. La DM1 se considera como la distrofia muscular más frecuente en los adultos y FRAXA es la principal causa de retardo mental hereditario. Este trabajo presenta resultados actualizados de un estudio prospectivo no aleatorio en pacientes clínicamente afectados, que se realiza con el objetivo de confirmar el diagnóstico con técnicas moleculares (Hibridación de Southern y reacción en cadena de la polimerasa, PCR), y llevar a cabo el tamizaje en cascada del resto de la familia para ofrecerles consejo genético adecuado. Se confirmó el diagnóstico clínico inicial en la mayoría de los casos de distrofia miotónica, pero en los casos con retardo mental, más de la mitad de los análisis resultaron negativos para la amplificación en el gen FMR1, específica de FRAXA. La razón principal para esto podría ser el cuadro clínico muy sutil que muestran los niños afectados antes de la pubertad. Los únicos métodos disponibles para prevenir estas discapacidades por el momento son, el tamizaje en cascada, el consejo genético y el aborto selectivo. De los cuales, el último no se puede llevar a cabo según las leyes vigentes en Costa Rica.

Con el objetivo de conocer si la exposición ocupacional a los plaguicidas utilizados en las plantas empacadoras de banano provoca daño genético en las células somáticas de las trabajadoras, se estudió la frecuencia de aberraciones cromosómicas en linfocitos de un grupo de diez trabajadoras expuestas y diez mujeres no expuestas. Las trabajadoras se captaron en fincas independientes de los cantones de Guácimo y Pococí, Costa Rica, entre enero y junio de los años 1996 y 1997. El grupo de expuestas tenían un mínimo de tres meses de trabajo, no habían recibido quimioterapia o radioterapia, y realizaban alguna de las siguientes labores: sellar, atomizar y/o pesar la fruta. El grupo de no expuestas estuvo formado por mujeres residentes de la misma zona, con edades similares; tanto ellas como sus esposos o compañeros no trabajaban en labores relacionadas con plaguicidas. Se analizaron 100 figuras mitóticas por persona y se registraron las aberraciones siguientes: fragmentos acéntricos, cromosomas dicéntricos, anillos, lagunas y fracturas cromosómicas. El 16% de las células (n = 1000) pertenecientes a las trabajadoras tenían una o más anormalidades contra el 6% (n = 1000) en el grupo de mujeres no expuestas (p Chromosomic aberrations in female workers exposed to pesticides. The purpose of this work was to determine if the occupational exposure to those pesticides used at banana plantations’ packaging plants produces genetic damage to somatic cells of female workers. Chromosomal aberrations were scored in lymphocytes of 20 women, 10 female exposed workers and 10 female controls. Workers were recruited from independent farms from two locations in Costa Rica, during January through June in 1996 and 1997. These females had a minimum of three months of work, had never received chemotherapy or radiotherapy and did some of these labors: sealing, spraying or weighting of bananas. Control unexposed females lived in the same area, were of similar age and neither them nor their husbands/mates had ever worked in pesticide related labors. For each female, 100 mitotic figures were scored. The kind of aberrations detected were acentric fragments, dicentric chromosomes, rings, gaps and breaks. Among workers, 16% of cells (n=1000) had one or more abnormalities, whereas control unexposed females had 6% of cells (n=1000) with comparable anomalies (p

Se evaluó la genotoxicidad in vitro de los fungicidas imazalil y tiabendazol y del insecticida clorpirifos, formulaciones empleadas en las bananeras costarricenses, utilizando la técnica de electroforesis de células únicas (ensayo cometa). El ensayo cometa es una técnica simple, rápida y de bajo costo para la cuantificación de daños en el ADN, en términos de rupturas y sitios álcalilábiles, en la hebra simple del ADN de células individuales. Se expusieron linfocitos humanos a concentraciones de 0, 25, 50, 75 y 100 µg/ml de los plaguicidas, por 30 min a 37°C. Las células fueron embebidas en agarosa, se provocó la lisis de sus membranas citoplasmáticas y se sometieron a electroforesis alcalina durante 20 min a 25V. Por último, las preparaciones se neutralizaron y se deshidrataron, para el posterior teñido de las láminas con el fluorocromo y la visualización de los cometas en el microscopio de epifluorescencia. El clorpirifos y el imazalil inducen daños significativos en la hebra sencilla del ADN en forma dependiente de la concentración, siendo el clorpirifos el mayor inductor de rupturas en el material genético. Estos resultados indican que ambos se comportan como compuestos genotóxicos in vitro. El fungicida tiabendazol mostró resultados negativos en las concentraciones empleadas.Genotoxicity of three pesticides used in Costa Rican banana plantations. The in vitro genotoxicity of imazalil and thiabendazole fungicides and the insecticide chlorpyrifos, compounds used in Costa Rican banana plantations, was evaluated with the single-cell gel electrophoresis technique (comet assay). The comet assay is a simple, rapid and low cost technique for quantification of DNA damage. This assay detects DNA single- strand breaks and alkalilabile sites in individual cells. The effects were analyzed by using human lymphocytes exposed to doses of 0, 25, 50, 75 and 100 µg/ml of each pesticide for 30 min at 37°C. The cells were embedded in agarose, lysed, subjected to alkaline electrophoresis (pH> 13) for 20 min at 25V, neutralized and dehydrated to be stained with a fluorescent dye and later comets visualization with the epifluorescence microscope. Chlorpyrifos and imazalil induced significant DNA damage in a dose-dependent manner. Chlorpyrifos was the major inductor of DNA breaks. These results indicate that both are genotoxic compounds in vitro. Thiabendazole fungicide did not induced DNA damage using the comet assay for all concentrations tested. Rev. Biol. Trop. 52(3): 601-609. Epub 2004 Dic 15.

La mutagénesis ambiental o genética toxicológica es una disciplina que tiene como objetivo estudiar el daño genético que conduce a mutaciones, producido por agentes físicos, químicos y biológicos, identificar estos agentes, analizar sus interacciones y mecanismos de acción. Existen suficientes evidencias experimentales y epidemiológicas que demuestran que el proceso cancerígeno se inicia y se favorece por la presencia de mutaciones en los oncogenes, los genes supresores de tumores y los que codifican para los sistemas de reparación del ADN. Una herramienta valiosa en salud pública y ocupacional es el monitoreo de grupos de población expuestos a agentes potencialmente dañinos para el ser humano. Tiene como objetivo preservar la salud y la calidad de vida en aquellos grupos que son de alto riesgo por la naturaleza de las sustancias a que están expuestos. Se vislumbra al monitoreo del efecto genotóxico en poblaciones expuestas, en conjunto con el análisis de polimorfismos de susceptibilidad, como herramientas clave en la salud pública y ocupacional del futuro, para prevenir la ocurrencia de tumores de origen ambiental y especialmente laboral. En este trabajo se revisan los principales conceptos sobre este tema y se hace referencia a los trabajos realizados sobre exposición laboral a potenciales cancerígenos y a la que existe en el monitoreo de poblaciones expuestas en Costa Rica.Environmental mutagenesis and use of biomarkers in cancer risk prediction. The field of environmental mutagenesis or toxicology genetics aims to study the genetic damage that leads to mutations produced by physical, chemical and biological agents, to identify these agents and analyze their interactions and ways of action. There are enough experimental and epidemiological evidences implicating mutations in oncogenes, tumor suppressor genes and DNA repair genes as determinants in the onset and progression of the neoplastic process. A valuable tool in public and occupational health is the monitoring of populations exposed to potentially hazardous agents. The objective is to protect the health and quality of life of high risk groups on account of the nature of the agents of exposure. Monitoring of genotoxic effects in exposed populations as well as the analysis of susceptibility polymorphism are visualized as key tools in the realm of future public and occupational health in order to prevent the occurrence of environmental and specially occupational origin of tumors. This paper reviews the main concepts concerning this issue and refers to studies on the subject in Costa Rica. Rev. Biol. Trop. 52(3): 585-590. Epub 2004 Dic 15.

Las enzimas de las familias P450 y Glutation S-transferasa están relacionadas en la activación y desintoxicación de sustancias que podrían actuar como cancerígenas. Polimorfismos genéticos en estas enzimas han sido asociados con un incremento en el riesgo de desarrollar cáncer específicamente con un mayor riesgo de desarrollar cáncer gástrico. En esta investigación se estudió un grupo de costarricenses con alto riesgo de cáncer gástrico. Se estudiaron 31 individuos con cáncer gástrico, 51 controles normales confirmados por rayos X (serie gastroduenal de doble contraste) o por endoscopía y 58 individuos con otras lesiones gástricas. Se estudiaron los polimorfismos de desintoxicación química CYP1A1 MspI y CYP2E1 PstI, los cuales presentan una mayor expresión enzimática y los polimorfismos de los genes GSTT1 y GSTM1 que carecen de un producto proteínico funcional y su relación con lesiones gástricas leves y cáncer gástrico. El ADN de los pacientes fue aislado a partir de leucocitos de sangre periférica. Los polimorfismos de los genes GSTT1 y GSTM1 fueron evaluados mediante un PCR múltiple y para los polimorfismos CYP2E1 PstI y CYP1A1 MspI se realizó un PCR seguido por la digestión con las enzimas de restricción PstI y MspI respectivamente. La prevalencia del polimorfismo CYP1A1 MspI, y de los polimorfismos GSTT1 y GSTM1 sin actividad enzimática, fue similar en los tres grupos estudiados (p=0.73, p=0.88 y p= 0.89 respectivamente). Los resultados sugieren que el alelo CYP2E1 Pst1 podría actuar como factor protector contra el cáncer gástrico (OR=0.09, IC al 95%: 0.01-0.83).Polymorphisms in detoxification genes CYP1A1, CYP2E1, GSTT1 and GSTM1 in gastric cancer susceptibility. Cytochrome P450 (CYP) and glutathione S-transferase (GST) enzymes are involved in activation and detoxification of many potential carcinogens. Genetic polymorphisms in those enzymes have been found to influence the interindividual susceptibility to cancer. Some polymorphisms of those enzymes have been associated specifically with susceptibility to gastric cancer. We conducted a study in a Costa Rican population, where gastric cancer incidence and mortality rates are among the highest in the world. We investigated whether such variations affected the risk of developing gastric cancer. Subjects included 31 with gastric cancer, 58 controls with gastric injures others than cancer and 51 normal controls confirmed by X-rays (double-contrast) or endoscopic diagnostic. DNA from peripheral white blood cell was obtained from all subjects. Deletion of GSTT1 and GSTM1 was assessed by multiplex PCR and genotyping of CYP2E1 was performed using a PCR-based restriction fragment length polymorphism assay with the restriction enzyme PstI and the gene CYP1A1 using the restriction enzyme MspI. The prevalence of CYP1A1 MspI polymorphism, GSTT1 and GSTM1 null genotype was similar in the three groups of individuals (p=0.73, p=0.88 y p= 0.89 respectively). Our findings suggest that the polymorphism CYP2E1 PstI could be associated with a reduced risk of having gastric cancer (OR=0.09, IC95% :0.01 - 0.83). Rev. Biol. Trop. 52(3): 591-600. Epub 2004 Dic 15.

Para determinar si la exposición laboral a plaguicidas produce daño al material genético se utilizó como biomarcador de efecto la presencia de micronúcleos en células del epitelio oral de trabajadoras de Guápiles y Siquirres, Costa Rica. También se analizaron otras anormalidades nucleares que pueden ser indicio de genotoxicidad o de citotoxicidad. El grupo de mujeres expuestas a plaguicidastrabajaban en plantas empacadoras de diferentes fincas bananeras independientes. El grupo de mujeres no expuestas nunca habían trabajado en labores agrícolas, no vivían dentro de una finca bananera, así como tampoco sus esposos o compañeros. Se obtuvo información acerca del estilo de vida, historia médica y familiar de las participantes mediante una entrevista. No se encontró un aumento significativo en la frecuencia de micronúcleos en el grupo de expuestas con respecto a las no expuestas. Las otras anormalidades nucleares mostraron indicios de citotoxicidad y genotoxicidad en el grupo de no expuestas, asociados a ingesta de café y a radiografías dentales. Estos resultados no descartan a los plaguicidas como agentes capaces de causar daño genético, sino que más bien los micronúcleos de la mucosa oral no parecen ser el biomarcador más adecuado para medirlo.Micronuclei and other nuclear abnormalities in the oral epithelium of female workers exposed to pesticides. In order to study if banana fields labour exposure to pesticides produces some kind of DNA damage, we determine the presence of micronuclei in epithelial oral cells in working women in Guapiles and Siquirres, Costa Rica, as an effect biomarker. We also analyzed other abnormalities in the nucleus of those cells such as broken-egg, karyolysis or kariorrhexis, to see if there was some kind of genotoxicity or citotoxicity. The women group exposed to pesticides worked in packing bananas plant from different independent farms. The control group of women had never done any farming tasks; they did not live in the banana fields, neither their husband. We got information about the life style, medical and familial history of the participants through an interview. We did not found any significant increment in the frequency of micronuclei form the exposed group compared with the controls. The other nuclei abnormalities showed signs of citotoxicity or genotoxicity in the controls, associated with the intake of coffee and dental x-rays. These results do not rule out at that pesticides used in packing bananas are agents capable of producing damage to the DNA, but it seems that micronuclei from the oral epithelium is not the most adequate marker to measure it. Rev. Biol. Trop. 52(3): 611-621. Epub 2004 Dic 15.

El uso de plaguicidas en los países en desarrollo es extenso en cantidad y en tiempo. Un gran porcentaje de lo que se aplica queda en el entorno y en los organismos que ahí habitan, lo que acarrea problemas de contaminación ambiental y deterioro de la salud de las personas que están en contacto con ellos. Los efectos se pueden manifestar a corto o a largo plazo y los síntomas varían desde un dolor de cabeza hasta el desarrollo de cáncer. La mayoría de los estudios en esta área se han orientado hacia los efectos agudos o crónicos y recientemente se inicia el estudio del efecto genotóxico de los plaguicidas. En e1 presente trabajo se evaluó el efecto genotóxico de los plaguicidas utilizados en las empacadoras de banano, usando como marcador biológico la electroforesis de células únicas (conocido como ensayo cometa) en linfocitos aislados de sangre periférica. La población en estudio correspondió a 30 trabajadoras expuestas a plaguicidas, procedentes de 15 fincas bananeras y 28 mujeres sin antecedentes de exposición ocupacional a plaguicidas, de la misma área geográfica. Las trabajadoras que tenían entre cinco y quince años de trabajo presentaron mayor daño en la hebra sencilla del ADN (R² =0.12). Se desconoce si este efecto se debe a los plaguicidas que se utilizan actualmente o a plaguicidas empleados en el pasado. Tampoco fue posible correlacionar las dosis y las frecuencias de exposición a los plaguicidas con el daño al ADN, debido a que no existe un registro histórico sobre los productos empleados en el cultivo de banano, no se sabe por cuánto tiempo y las épocas en que fueron utilizados. Se recomienda el ensayo cometa para monitoreo genético en poblaciones expuestas a plaguicidasPesticide use in Costa Rica is very high and all year round. A high percentage of what is sprayed remains in the environment and in the living organisms around. This situation brings contamination and health problems to people in contact with them. The onset of adverse effects may be in the short or the long term, and symptoms vary widely, from headaches to cancer. Much research in this area has been devoted to acute or chronic effects, and not until recently to the genotoxic effect of pesticides. This study evaluated the genotoxic effect of pesticides used in banana packing activities, using the comet assay (single cell electrophoresis) as the biological marker in lymphocytes. This was a case-control double blind study of 30 exposed women from 15 banana farms and 28 women not occupationally exposed to pesticides from the same geographic area. Results show damage to single stranded DNA after working from 5 to 15 years (R 2 =0.12). In Costa Rica we do not have an historical record of the kind of pesticides used in banana farms, the period of time and for how long were they used. This prevented further analysis concerning dose, frequency of exposure and use of new or old kind of pesticides in the farms in relation to DNA damage. The comet assay is of value in the genetic monitoring of pesticide exposed populations

Pesticides have been widely used in developing countries over the years. A large amount of these remains in the environment and organisms. Pesticide pollution is detrimental to human health. The effects can be seen on a short or a long-term basis and the symptoms can vary from headache to cancer. Only a minority of studies focuses on their genotoxic effect. This study assesses the genotoxic effect of the pesticides used at banana-packaging plants with binucleate micronuclei assay using cultured lymphocytes. The studied population included 32 exposed and 37 unexposed women from Costa Rica. There is no significant difference between the two groups. However, women who worked at the packaging plant and had stillbirths or spontaneous abortions were 1.45 times more (α= 0.06) likely to have an increased micronuclei frequency than their coworkers who lacked those disorders; this may indicate genetic susceptibility. In vitro pesticides studies and susceptibility biomarkers are needed to identify subgroups with higher risks.

Myotonia congenita is a muscular disease characterized by myotonia, hypertrophy, and stiffness. It is inherited as either autosomal dominant or recessive known as Thomsen and Becker diseases, respectively. Here we confirm the clinical diagnosis of a family diagnosed with a myotonic condition many years ago and report a new mutation in the CLCN1 gene. The clinical diagnosis was established using ocular, cardiac, neurological and electrophysiological tests and the molecular diagnosis was done by PCR, SSCP and sequencing of the CLCN1 gene. The proband and the other affected individuals exhibited proximal and distal muscle weakness but no hypertrophy or muscular pain was found. The myotatic reflexes were lessened and sensibility was normal. Electrical and clinical myotonia was found only in the sufferers. Slit lamp and electrocardiogram tests were normal. Two affected probands presented diminution of the sensitive conduction velocities and prolonged sensory distal latencies. The clinical spectrum for this family is in agreement with a clinical diagnosis of Becker myotonia. This was confirmed by molecular diagnosis where a new disease-causing mutation (Q412P) was found in the family and absent in 200 unaffected chromosomes. No latent myotonia was found in this family; therefore the ability to cause this subclinical sign might be intrinsic to each mutation. Implications of the structure-function-genotype relationship for this and other mutations are discussed. Adequate clinical diagnosis of a neuromuscular disorder would allow focusing the molecular studies toward the confirmation of the initial diagnosis, leading to a proper clinical management, genetic counseling and improving in the quality of life of the patients and relatives.

Gastric cancer is the second most common cancer associated death cause worldwide. Several factors have been associated with higher risk to develop gastric cancer, among them genetic predisposition. The p53 gene has a polymorphism located at codon 72. which has been associated with higher risk of several types of cancer, including gastric cancer. The aim of this study was to determine the association of p53, codon 72 polymorphism. with the risk of gastric cancer and pre-malignant lesions in a high-risk population from Costa Rica. The genotyping was carried out by PCR-RFLP in 58 gastric cancer patients, 99 controls and 41 individuals classified as group I or II. according to the Japanese histological classification. No association was found for p53. codon 72 polymorphism with neither the risk of gastric cancer nor the risk of less severe gastric lesions in the studied population. Based on this study and taking into account other studies carried out with p53, codon 72 polymorphism. the role of this polymorphismn in the development of gastric cancer remains unclear. De novo mutations on p53 gene produced during neoplasic development of this disease might play a greater role than germinal polymorphisms of the gene. Other polymorphic genes have been associated with higher risk to develop gastric cancer.

Cytochrome P450 (CYP) and glutathione S-transferase (GST) enzymes are involved in activation and detoxification of many potential carcinogens. Genetic polymorphisms in those enzymes have been found to influence the interindividual susceptibility to cancer. Some polymorphisms of those enzymes have been associated specifically with susceptibility to gastric cancer. We conducted a study in a Costa Rican population, where gastric cancer incidence and mortality rates are among the highest in the world. We investigated whether such variations affected the risk of developing gastric cancer. Subjects included 31 with gastric cancer, 58 controls with gastric injures others than cancer and 51 normal controls confirmed by X-rays (double-contrast) or endoscopic diagnostic. DNA from peripheral white blood cell was obtained from all subjects. Deletion of GSTT1 and GSTM1 was assessed by multiplex PCR and genotyping of CYP2E1 was performed using a PCR-based restriction fragment length polymorphism assay with the restriction enzyme PstI and the gene CYP1A1 using the restriction enzyme MspI The prevalence of CYP1A1 Msp1 polymorphism, GSTT1 and GSTM1 null genotype was similar in the three groups of individuals (p = 0.73, p = 0.88 y p = 0.89 respectively). Our findings suggest that the polymorphism CYP2E1 PstI could be associated with a reduced risk of having gastric cancer (OR = 0.09, IC95%:0.01 - 0.83).

The in vitro genotoxicity of imazalil and thiabendazole fungicides and the insecticide chlorpyrifos, compounds used in Costa Rican banana plantations, was evaluated with the single-cell gel electrophoresis technique (comet assay). The comet assay is a simple, rapid and low cost technique for quantification of DNA damage. This assay detects DNA single-strand breaks and alkali-labile sites in individual cells. The effects were analyzed by using human lymphocytes exposed to doses of 0, 25, 50, 75 and 100 microg/ml of each pesticide for 30 min at 37 degrees C. The cells were embedded in agarose, lysed, subjected to alkaline electrophoresis (pH >13) for 20 min at 25V, neutralized and dehydrated to be stained with a fluorescent dye and later comets visualization with the epifluorescence microscope. Chlorpyrifos and imazalil induced significant DNA damage in a dose-dependent manner. Chlorpyrifos was the major inductor of DNA breaks. These results indicate that both are genotoxic compounds in vitro. Thiabendazole fungicide did not induced DNA damage using the comet assay for all concentrations tested.

Unstable mutations or amplification of DNA tandem repeats sequences constitute a new kind of genetic alteration discovered in the 90's that cause hereditary diseases. This mutation has been found inside or near important genes involved in the normal neurological function in human beings. In some cases, the presence of the amplification causes altered expression of the genes, their inactivation or the synthesis of a protein with new functions. Some common characteristics of these diseases are that they affect the central nervous system and are degenerative in nature. Most of them show genetic anticipation meaning that the severity of the manifestations increases in each generation and appear at an earlier age. In most cases, the severity of the symptoms is positively correlated with the size of the amplification. Twenty illnesses caused by this kind of mutations have been identified so far. Briefly, this work reviews the current knowledge about this topic.

Motonic dystrophy and fragile X syndrome are two genetically determined relatively common disabilities. Both are examples of a new type of mutation mechanism called unstable or dynamic mutations, triple repeats expansions or DNA amplification. Fragile X syndrome is recognized as the main cause of hereditary mental retardation and myotonic dystrophy is considered the most common muscular dystrophy of adults. This is a prospective non randomized study of clinically affected people, in order to confirm the diagnosis with molecular techniques (Southern blot and PCR) and to perform cascade screening of the rest of the family to offer them adequate genetic counseling. We were able to corroborate the initial diagnosis in most clinical cases of myotonic dystrophy, but in the cases of mental retardation more than half studies were negative for fragile X syndrome, stressing the difficulties encountered by medical practitioners to diagnose this syndrome. The reasons for this are several; probable the main culprit is the subtle and unspecific clinical picture affected individuals exhibit, particularly children before puberty. Cascade screening, genetic counseling and selective abortion are the only tools available to prevent these disabling diseases for the moment.

In order to study if banana fields labour exposure to pesticides produces some kind of DNA damage, we determine the presence of micronuclei in epithelial oral cells in working women in Guapiles and Siquirres, Costa Rica, as an effect biomarker. We also analyzed other abnormalities in the nucleus of those cells such as broken-egg, karyolysis or kariorrhexis, to see if there was some kind of genotoxicity or citotoxicity. The women group exposed to pesticides worked in packing bananas plant from different independent farms. The control group of women had never done any farming tasks; they did not live in the banana fields, neither their husband. We got information about the life style, medical and familial history of the participants through an interview. We did not found any significant increment in the frequency of micronuclei form the exposed group compared with the controls. The other nuclei abnormalities showed signs ofcitotoxicity or genotoxicity in the controls, associated with the intake of coffee and dental x-rays. These results do not rule out at that pesticides used in packing bananas are agents capable of producing damage to the DNA, but it seems that micronuclei from the oral epithelium is not the most adequate marker to measure it.

The field of environmental mutagenesis or toxicology genetics aims to study the genetic damage that leads to mutations produced by physical, chemical and biological agents, to identify these agents and analyze their interactions and ways of action. There are enough experimental and epidemiological evidences implicating mutations in oncogenes, tumor suppressor genes and DNA repair genes as determinants in the onset and progression of the neoplastic process. A valuable tool in public and occupational health is the monitoring of populations exposed to potentially hazardous agents. The objective is to protect the health and quality of life of high risk groups on account of the nature of the agents of exposure. Monitoring of genotoxic effects in exposed populations as well as the analysis of susceptibility polymorphism are visualized as key tools in the realm of future public and occupational health in order to prevent the occurrence of environmental and specially occupational origin of tumors. This paper reviews the main concepts concerning this issue and refers to studies on the subject in Costa Rica.

The purpose of this work was to determine if the occupational exposure to those pesticides used at banana plantations' packaging plants produces genetic damage to somatic cells of female workers. Chromosomal aberrations were scored in lymphocytes of 20 women, 10 female exposed workers and 10 female controls. Workers were recruited from independent farms from two locations in Costa Rica, during January through June in 1996 and 1997. These females had a minimum of three months of work, had never received chemotherapy or radiotherapy and did some of these labors: sealing, spraying or weighting of bananas. Control unexposed females lived in the same area, were of similar age and neither them nor their husbands/mates had ever worked in pesticide related labors. For each female, 100 mitotic figures were scored. The kind of aberrations detected were acentric fragments, dicentric chromosomes, rings, gaps and breaks. Among workers, 16% of cells (n=1000) had one or more abnormalities, whereas control unexposed females had 6% of cells (n=1000) with comparable anomalies (p < 0.05). In conclusion, the pesticide exposure is a risk factor for chromosome aberrations in female somatic cells.

Pesticide use in Costa Rica is very high and all year round. A high percentage of what is sprayed remains in the environment and in the living organisms around. This situation brings contamination and health problems to people in contact with them. The onset of adverse effects may be in the short or the long term, and symptoms vary widely, from headaches to cancer. Much research in this area has been devoted to acute or chronic effects, and not until recently to the genotoxic effect of pesticides. This study evaluated the genotoxic effect of pesticides used in banana packing activities, using the comet assay (single cell electrophoresis) as the biological marker in lymphocytes. This was a case-control double blind study of 30 exposed women from 15 banana farms and 28 women not occupationally exposed to pesticides from the same geographic area. Results show damage to single stranded DNA after working from 5 to 15 years (R2 = 0.12). In Costa Rica we do not have an historical record of the kind of pesticides used in banana farms, the period of time and for how long were they used. This prevented further analysis concerning dose, frequency of exposure and use of new or old kind of pesticides in the farms in relation to DNA damage. The comet assay is of value in the genetic monitoring of pesticide exposed populations.

Pesticides have been widely used in developing countries over the years. A large amount of these remains in the environment and organisms. Pesticide pollution is detrimental to human health. The effects can be seen on a short or a long-term basis and the symptoms can vary from headache to cancer. Only a minority of studies focuses on their genotoxic effect. This study assesses the genotoxic effect of the pesticides used at banana-packaging plants with binucleate micronuclei assay using cultured lymphocytes. The studied population included 32 exposed and 37 unexposed women from Costa Rica. There is no significant difference between the two groups. However, women who worked at the packaging plant and had stillbirths or spontaneous abortions were 1.45 times more (alpha = 0.06) likely to have an increased micronuclei frequency than their coworkers who lacked those disorders; this may indicate genetic susceptibility. In vitro pesticides studies and susceptibility biomarkers are needed to identify subgroups with higher risks.