A Cholinergic Synaptically Triggered Event Participates in the Generation of Persistent Activity Necessary for Eye Fixation

An exciting topic regarding integrative properties of the nervous system is how transient motor commands or brief sensory stimuli are able to evoke persistent neuronal changes, mainly as a sustained, tonic action potential firing. A persisting firing seems to be necessary for postural maintenance after a previous movement. We have studied in vitro and in vivo the generation of the persistent neuronal activity responsible for eye fixation after spontaneous eye movements. Rat sagittal brainstem slices were used for the intracellular recording of prepositus hypoglossi (PH) neurons and their synaptic activation from nearby paramedian pontine reticular formation (PPRF) neurons. Single electrical pulses applied to the PPRF showed a monosynaptic glutamatergic projection on PH neurons, acting on AMPA-kainate receptors. Train stimulation of the PPRF area evoked a sustained depolarization of PH neurons exceeding (by hundreds of milliseconds) stimulus duration. Both duration and amplitude of this sustained depolarization were linearly related to train frequency. The train-evoked sustained depolarization was the result of interaction between glutamatergic excitatory burst neurons and cholinergic mesopontine reticular fibers projecting onto PH neurons, because it was prevented by slice superfusion with cholinergic antagonists and mimicked by cholinergic agonists. As expected, microinjections of cholinergic antagonists in the PH nucleus of alert behaving cats evoked a gaze-holding deficit consisting of a re-centering drift of the eye after each saccade. These findings suggest that a slow, cholinergic, synaptically triggered event participates in the generation of persistent activity characteristic of PH neurons carrying eye position signals

Los líquenes: Definición, características, importancia y usos potenciales

En este artículo se abordan los líquenes, que tradicionalmente son consideradas asociaciones entre un hongo y una o varias algas. En ellas, cada simbionte se beneficia del otro obteniendo nutrientes o protección. La asociación causa un cambio morfofisiológico donde el líquen adquiere una forma diferente al hongo o al alga y nuevas capacidades de síntesis, mejorando con ello sus capacidades adaptativa y competitiva. Existen alrededor de 13,500 especies de líquenes, el nombre de la especie del liquen lo recibe del hongo que participa en la asociación. México cuenta con 2500 especies registradas. La diversidad liquénica obedece a una radiación adaptativa a casi todo tipo de sustratos, desde suelo, rocas, cortezas o carapachos de tortugas, hasta estructuras hechas por el hombre. Los líquenes se identifican tradicionalmente por la consistencia y anatomía de su cuerpo o talo, de modo que los hay homómeros (gelatinosos) y heterómeros; la forma del talo, teniendo bajo este criterio costrosos, foliosos y fruticosos y por poseer ciertas estructuras peculiares que sirven para la fijación al sustrato, para la reproducción asexual o la reproducción sexual. También la presencia de sustancias liquénicas, que se revelan mediante reacciones químicas es diagnóstica de las especies. La importancia biológica de los líquenes radica en que son organismos pioneros en el establecimiento de la cobertura vegetal del suelo y una vez formado, los cianolíquenes lo fertilizan atrapando el nitrógeno atmosférico y cambiándolo de su forma inerte a otra reactiva biodisponible, además, la presencia de líquenes sirve de refugio y alimento a una gran diversidad de fauna. Por otra parte, en diversas culturas los líquenes son consumidos como gelatinas, pan, bebidas, ensaladas o se han utilizado como fuente de colorantes naturales o remedios medicinales. Existen más de 700 sustancias liquénicas, que poseen actividades antineoplásicas, antibióticas, antivirales, antioxidantes y como filtros solares. Su lento crecimiento se ha empleado para fechar la edad de estructuras o formaciones rocosas y la susceptibilidad a la contaminación atmosférica ha permitido usarlos como indicadores de la calidad del aire en áreas urbanas, pero estas útiles características también ponen en riesgo de desaparición a estos bellos seres poco conocidos

Using Kinect to classify Parkinson's disease stages related to severity of gait impairment

Background: Parkinson’s Disease (PD) is a chronic neurodegenerative disease associated with motor problems such as gait impairment. Different systems based on 3D cameras, accelerometers or gyroscopes have been used in related works in order to study gait disturbances in PD. Kinect has also been used to build these kinds of systems, but contradictory results have been reported: some works conclude that Kinect does not provide an accurate method of measuring gait kinematics variables, but others, on the contrary, report good accuracy results. Methods: In this work, we have built a Kinect-based system that can distinguish between different PD stages, and have performed a clinical study with 30 patients suffering from PD belonging to three groups: early PD patients without axial impairment, more evolved PD patients with higher gait impairment but without Freezing of Gait (FoG), and patients with advanced PD and FoG. Those patients were recorded by two Kinect devices when they were walking in a hospital corridor. The datasets obtained from the Kinect were preprocessed, 115 features identified, some methods were applied to select the relevant features (correlation based feature selection, information gain, and consistency subset evaluation), and different classification methods (decision trees, Bayesian networks, neural networks and K-nearest neighbours classifiers) were evaluated with the goal of finding the most accurate method for PD stage classification. Results: The classifier that provided the best results is a particular case of a Bayesian Network classifier (similar to a Naïve Bayesian classifier) built from a set of 7 relevant features selected by the correlation-based on feature selection method. The accuracy obtained for that classifier using 10-fold cross validation is 93.40%. The relevant features are related to left shin angles, left humerus angles, frontal and lateral bents, left forearm angles and the number of steps during spin. Conclusions: In this paper, it is shown that using Kinect is adequate to build a inexpensive and comfortable system that classifies PD into three different stages related to FoG. Compared to the results of previous works, the obtained accuracy (93.40%) can be considered high. The relevant features for the classifier are: a) movement and position of the left arm, b) trunk position for slightly displaced walking sequences, and c) left shin angle, for straight walking sequences. However, we have obtained a better accuracy (96.23%) for a classifier that only uses features extracted from slightly displaced walking steps and spin walking steps. Finally, the obtained set of relevant features may lead to new rehabilitation therapies for PD patients with gait problems

Morphological identification and characterization of the formation of floral primordium in Vanilla planifolia (Orchidaceae)

ABSTRACT Objective: To study the formation of floral primordia and individual flower development in the inflorescence of vanilla (Vanilla planifolia Jacks Ex. Andrews). Design/methodology/approach: The study site was located at Rancho Xanathtlan, in Barriles, municipality of Gutiérrez Zamora, Veracruz. Inflorescence primordia and young inflorescences (racemes) at different stages of development were sampled from three different stem positions: basal (11-15 internodes), middle (6-10 internodes) and distal (1-5 internodes). Four samplings were made from February to May, and five replicates of each stem position were used per sampling date. Observations and characterization were carried out with a stereo microscope. Results: Seven developmental stages were described for the racemes of V. planifolia: (I) differentiated meristem of the floral inflorescence, (II) appearance of the third bract, (III) initiation of the formation of the racemes, (IV) elongation of the floral primordia, (V) development and growth of the individual floral primordia in the acropetal direction, (VI) anthesis of the inflorescence in the acropetal direction and (VII) complete flowering of the raceme. Five developmental stages of formation of individual flower primordia within the inflorescence were also identified, which occurred from the appearance of the third bract in the acropetal direction. Limitations on study/implications: Although this study denotes the first observations on the floral phenology of V. planifolia, there are still many questions about the biochemical processes and the interaction of environmental aspects in this floral development. Findings/conclusions: First aspects of floral formation within the inflorescence as well as floral phenology in Vanilla planifolia were shown. Keywords: Floral growth, floral phenology, inflorescences, orchids.Objective: To morphologically identify and characterize the formation of floral primordium and the individual flower development in Vanilla planifolia Jacks Ex. Andrews. Design/Methodology/Approach: Inflorescence primordia and young inflorescences in different development stages were sampled from the stem internodes of the following positions: basal (11-15), middle (6-10), and distal (1-5). Four samples were taken from each stem position from February to May, with five repetitions per sampling date. Observations and characterization were made with a stereo microscope. The study site was located at Rancho Xanathtlan, in Barriles, municipality of Gutiérrez Zamora, Veracruz. Results: The development of the V. planifolia raceme is described in seven phases: (I) differentiated meristem of the floral inflorescence; (II) appearance of the third bract; (III) initiation of the racemes formation; (IV) elongation of the floral primordium; (V) development and growth of the individual floral primordium in the acropetal direction, (VI) anthesis of the inflorescence in the acropetal direction; and (VII) complete flowering of the raceme. The development of the buds in the raceme is described in five stages from the appearance of the third bract in the acropetal direction. Study Limitations/Implications: The biochemical processes and the interaction of environmental aspects on the floral development of V. planifolia pose questions that remain unanswered. Findings/Conclusions: The first aspects of floral formation within the inflorescence of Vanilla planifolia were determined, along with its floral phenology

Diversidad de enterobacterias asociadas a frutos de tomate (Lycopersi-cum sculentum Mill) y suelos de invernadero

The aim of this study was to evaluate the diversity of Enterobacteriaceae present in soil and tomato fruits from three greenhouses with fertirigation system. These crop systems are an important alternative for production in protected agriculture; however, there is little information about the microbiological quality of the fruit and its relationship with chemical soil characteristics. Soil evaluations consisted of analyzing organic matter content and pH. In the microbiological analysis were isolated and identified enterobacterias organisms from composite samples of soil and fruits at different stages of maturity (0, 50 and 100%). Culture media used was selective, differential and confirmatory testing with VITEK system. Enteropathogenic E. coli (EPEC) and enterotoxigenic E. coli (ETEC) were characterized genotypically, amplifying the lngA and bfpA genes by the technique of polymerase chain reaction (PCR). Diversity index (Simpson (D), Shannon-Wiener (H') and Chao estimator (SChao1) were calculated with the identified species. The species Enterobacter cloacae, Citrobacter freundii and C. brakii had a higher frequency of isolation, EPEC and ETEC were identified in soil samples and in fruits with 100% maturity. In soil, H' indices were positively correlated with the highest organic matter percentages. In fruit, although H 'and D showed less diverse bacterial communities, the isolation of ETEC and Shigella boydii on the fruit surface compromise their safety because they are usually consumed raw.El objetivo de este trabajo fue determinar la diversidad de enterobacterias presentes en suelo y tomates provenientes de tres invernaderos de fertirrigación. Estos sistemas de cultivo son una alternativa importante de producción en agricultura protegida, sin embargo, existe escasa información acerca de la calidad microbiológica de los frutos y su relación con las características químicas del suelo. Las evaluaciones del suelo consistieron en analizar el contenido de materia orgánica y pH. En los análisis microbiológicos se aislaron e identificaron enterobacterias en muestras compuestas de suelo y frutos con diferentes grados de madurez (0, 50 y 100%), utilizando medios de cultivo selectivos, diferenciales y pruebas confirmatorias con el sistema VITEK. Los patogrupos de Escherichia coli enteropatogena (EPEC) y enterotoxigénica (ETEC) se caracterizaron genotípicamente mediante la técnica de reacción en cadena de la polimerasa (PCR), amplificándose los genes bfpA y lngA. Con las especies identificadas se calcularon los índices de diversidad Simpson (D) y Shannon-Wiener (H´) y estimador de Chao (SChao1). Las especies Enterobacter cloacae, Citrobacter freundii y C. brakii presentaron mayor frecuencia de aislamiento, EPEC y ETEC fueron identificadas en muestras de suelo y en frutos con 100% de madurez. En suelo, los porcentajes de materia orgánica se correlacionaron positivamente con los índices H´. En fruto, aunque H´ y D reflejaron comunidades bacterianas menos diversas, el aislamiento de ETEC y Shigella boydii sobre la superficie del fruto comprometen su inocuidad debido a que habitualmente se consume en forma cruda

Diversidad de enterobacterias asociadas a frutos de tomate (Lycopersi-cum sculentum Mill) y suelos de invernadero

The aim of this study was to evaluate the diversity of Enterobacteriaceae present in soil and tomato fruits from three greenhouses with fertirigation system. These crop systems are an important alternative for production in protected agriculture; however, there is little information about the microbiological quality of the fruit and its relationship with chemical soil characteristics. Soil evaluations consisted of analyzing organic matter content and pH. In the microbiological analysis were isolated and identified enterobacterias organisms from composite samples of soil and fruits at different stages of maturity (0, 50 and 100%). Culture media used was selective, differential and confirmatory testing with VITEK system. Enteropathogenic E. coli (EPEC) and enterotoxigenic E. coli (ETEC) were characterized genotypically, amplifying the lngA and bfpA genes by the technique of polymerase chain reaction (PCR). Diversity index (Simpson (D), Shannon-Wiener (H') and Chao estimator (SChao1) were calculated with the identified species. The species Enterobacter cloacae, Citrobacter freundii and C. brakii had a higher frequency of isolation, EPEC and ETEC were identified in soil samples and in fruits with 100% maturity. In soil, H' indices were positively correlated with the highest organic matter percentages. In fruit, although H 'and D showed less diverse bacterial communities, the isolation of ETEC and Shigella boydii on the fruit surface compromise their safety because they are usually consumed raw.El objetivo de este trabajo fue determinar la diversidad de enterobacterias presentes en suelo y tomates provenientes de tres invernaderos de fertirrigación. Estos sistemas de cultivo son una alternativa importante de producción en agricultura protegida, sin embargo, existe escasa información acerca de la calidad microbiológica de los frutos y su relación con las características químicas del suelo. Las evaluaciones del suelo consistieron en analizar el contenido de materia orgánica y pH. En los análisis microbiológicos se aislaron e identificaron enterobacterias en muestras compuestas de suelo y frutos con diferentes grados de madurez (0, 50 y 100%), utilizando medios de cultivo selectivos, diferenciales y pruebas confirmatorias con el sistema VITEK. Los patogrupos de Escherichia coli enteropatogena (EPEC) y enterotoxigénica (ETEC) se caracterizaron genotípicamente mediante la técnica de reacción en cadena de la polimerasa (PCR), amplificándose los genes bfpA y lngA. Con las especies identificadas se calcularon los índices de diversidad Simpson (D) y Shannon-Wiener (H´) y estimador de Chao (SChao1). Las especies Enterobacter cloacae, Citrobacter freundii y C. brakii presentaron mayor frecuencia de aislamiento, EPEC y ETEC fueron identificadas en muestras de suelo y en frutos con 100% de madurez. En suelo, los porcentajes de materia orgánica se correlacionaron positivamente con los índices H´. En fruto, aunque H´ y D reflejaron comunidades bacterianas menos diversas, el aislamiento de ETEC y Shigella boydii sobre la superficie del fruto comprometen su inocuidad debido a que habitualmente se consume en forma cruda

Hazardous faults of South America; compilation and overview

The heterogeneous South American geology has coined a wide variety of neotectonic settings where crustal seismogenic sources do occur. This fact has led to different approaches for mapping and inventory neotectonic structures. The South American Risk Assessment project promoted the discussion and update under uniform standards of the available information on neotectonic deformation, for its application in regional Probabilistic Seismic Hazard Assessments. As a result, 1533 hazardous faults have been inventoried onshore South America, 497 of them qualifying to feed the engine model driving probabilistic maps. Main hazardous structures are concentrated throughout the eastern boundary of the Northern Andean Sliver and along the foreland-facing Andean Thrust Front. Space geodesy and seismicity illuminate the seismogenic significance of these deformation belts, although few neotectonic surveys have been conducted to date in the latter region. The characteristics of the main structures or deformation zones are here outlined according to their filiation to neotectonic domains, which are dependant on the geologic, seismotectonic, or morphotectonic settings in Andean and extra-Andean regions. The knowledge accrued on the hazardous faults in South America here compiled, reinforces the fact that some of these structures constitute significant hazard sources for many urban areas and critical facilities and should be incorporated in seismic hazard assessments. However, the available fault data are insufficient in many cases or carry significant epistemic uncertainties for fault source characterization. This contribution aims to summarize the present knowledge on the South American hazardous faults as well as the main challenges for successful fault data incorporation into seismic hazard models

Seroepidemiology of Toxoplasma gondii infection in psychiatric inpatients in a northern Mexican city

BACKGROUND: Patients with psychiatric disorders were found to show a high seroprevalence of Toxoplasma gondii infection. There is scarce information about the epidemiology of T. gondii infection in psychiatric patients in Mexico. Therefore, we sought to determine the prevalence of T. gondii infection and associated socio-demographic, clinical and behavioural characteristics in a population of psychiatric patients in Durango City, Mexico. Seroprevalence in patients was compared with that obtained in a control population. METHODS: One hundred and thirty seven inpatients of a public psychiatric hospital and 180 controls were examined for the presence of IgG and IgM antibodies against T. gondii by enzyme-linked immunoassay (Diagnostic Automation Inc., Calabasas, CA, USA). The control population consisted of blood donors of a public blood bank and elderly persons attending a senior center in the same city. Age in controls (42 years +/- 20.2) was comparable with that of the psychiatric patients (43.7 years +/-13.8) (p = 0.42). Socio-demographic, clinical and behavioral characteristics from the patients were also obtained. RESULTS: Anti-T. gondii IgG antibodies indicating latent infection with T. gondii was found in 25 (18.2%) of 137 psychiatric inpatients and 16 (8.9%) of 180 controls (p = 0.02). Ten (26.3%) of 38 schizophrenic patients had latent infection and this prevalence was also significantly higher than that observed in controls (p = 0.005). Prevalence of anti-T. gondii IgM antibodies was comparable among patients and controls (4.4% vs 2.2%, respectively, p = 0.22). Multivariate analysis showed that T. gondii infection in inpatients was positively associated with sexual promiscuity (adjusted OR = 15.8; 95% CI: 3.8–64.8), unwashed raw fruit consumption (adjusted OR = 5.19; 95% CI: 2.3–11.3), and a history of surgery (adjusted OR = 6.5; 95% CI: 2.6–16), and negatively associated with lamb meat consumption (adjusted OR = 0.26; 95% CI: 0.10–0.63). CONCLUSION: In the present study, psychiatric inpatients in Durango, Mexico, in general and schizophrenia inpatients in particular had a significantly higher prevalence of T. gondii infection than the control group. Results suggest that unwashed raw fruit consumption might be the most important route of T. gondii transmission in our psychiatric inpatients while lamb meat consumption the less important. Additional studies will have to elucidate the causative relation between infection with T. gondii and psychiatric disorders