A Bayesian spatiotemporal approach to modelling arboviral diseases in Mexico.

BACKGROUND: The objective of this study was to evaluate the spatial and temporal patterns of disease prevalence clusters of dengue (DENV), chikungunya (CHIKV) and Zika (ZIKV) virus and how socio-economic and climatic variables simultaneously influence the risk and rate of occurrence of infection in Mexico. METHODS: To determine the spatiotemporal clustering and the effect of climatic and socio-economic covariates on the rate of occurrence of disease and risk in Mexico, we applied correlation methods, seasonal and trend decomposition using locally estimated scatterplot smoothing, hotspot analysis and conditional autoregressive Bayesian models. RESULTS: We found cases of the disease are decreasing and a significant association between DENV, CHIKV and ZIKV cases and climatic and socio-economic variables. An increment of cases was identified in the northeastern, central west and southeastern regions of Mexico. Climatic and socio-economic covariates were significantly associated with the rate of occurrence and risk of the three arboviral disease cases. CONCLUSION: The association of climatic and socio-economic factors is predominant in the northeastern, central west and southeastern regions of Mexico. DENV, CHIKV and ZIKV cases showed an increased risk in several states in these regions and need urgent attention to allocate public health resources to the most vulnerable regions in Mexico.

Quantifying Media Effects, Its Content, and Role in Promoting Community Awareness of Chikungunya Epidemic in Bangladesh.

BACKGROUND: Chikungunya is a vector-borne disease, mostly present in tropical and subtropical regions. The virus is spread by Ae. aegypti and Ae. albopictus mosquitos and symptoms include high fever to severe joint pain. Dhaka, Bangladesh, suffered an outbreak of chikungunya in 2017 lasting from April to September. With the goal of reducing cases, social media was at the forefront during this outbreak and educated the public about symptoms, prevention, and control of the virus. Popular web-based sources such as the top dailies in Bangladesh, local news outlets, and Facebook spread awareness of the outbreak. OBJECTIVE: This study sought to investigate the role of social and mainstream media during the chikungunya epidemic. The study objective was to determine if social media can improve awareness of and practice associated with reducing cases of chikungunya. METHODS: We collected chikungunya-related information circulated from the top nine television channels in Dhaka, Bangladesh, airing from 1st April-20th August 2017. All the news published in the top six dailies in Bangladesh were also compiled. The 50 most viewed chikungunya-related Bengali videos were manually coded and analyzed. Other social media outlets, such as Facebook, were also analyzed to determine the number of chikungunya-related posts and responses to these posts. RESULTS: Our study showed that media outlets were associated with reducing cases of chikungunya, indicating that media has the potential to impact future outbreaks of these alpha viruses. Each media outlet (e.g., web, television) had an impact on the human response to an individual's healthcare during this outbreak. CONCLUSIONS: To prevent future outbreaks of chikungunya, media outlets and social media can be used to educate the public regarding prevention strategies such as encouraging safe travel, removing stagnant water sources, and assisting with tracking cases globally to determine where future outbreaks may occur.

Clinical Symptoms of Arboviruses in Mexico.

Arboviruses such as Chikungunya (CHIKV), Dengue (DENV), and Zika virus (ZIKV) have emerged as a significant public health concern in Mexico. The existing literature lacks evidence regarding the dispersion of arboviruses, thereby limiting public health policy's ability to integrate the diagnosis, management, and prevention. This study seeks to reveal the clinical symptoms of CHIK, DENV, and ZIKV by age group, region, sex, and time across Mexico. The confirmed cases of CHIKV, DENV, and ZIKV were compiled from January 2012 to March 2020. Demographic characteristics analyzed significant clinical symptoms of confirmed cases. Multinomial logistic regression was used to assess the association between clinical symptoms and geographical regions. Females and individuals aged 15 and older had higher rates of reported significant symptoms across all three arboviruses. DENV showed a temporal variation of symptoms by regions 3 and 5, whereas ZIKV presented temporal variables in regions 2 and 4. This study revealed unique and overlapping symptoms between CHIKV, DENV, and ZIKV. However, the differentiation of CHIKV, DENV, and ZIKV is difficult, and diagnostic facilities are not available in rural areas. There is a need for adequately trained healthcare staff alongside well-equipped lab facilities, including hematological tests and imaging facilities.

Modulation of CYP2E1 metabolic activity in a cohort of confirmed caffeine ingesting pregnant women with preterm offspring.

BACKGROUND: To ascertain interactions of caffeine ingestion, food, medications, and environmental exposures during preterm human gestation, under informed consent, we studied a cohort of Mexican women with further preterm offspring born at ≤ 34 completed weeks. At birth, blood samples were taken from mothers and umbilical cords to determine caffeine and metabolites concentrations and CYP1A2 (rs762551) and CYP2E1 (rs2031920, rs3813867) polymorphisms involved in caffeine metabolism. RESULTS: In 90 pregnant women who gave birth to 98 preterm neonates, self-informed caffeine ingestion rate was 97%, laboratory confirmed rate was 93 %. Theobromine was the predominant metabolite found. Consumption of acetaminophen correlated significantly with changes in caffeine metabolism (acetaminophen R2 = 0.637, p = 0.01) due to activation of CYP2E1 alternate pathways. The main caffeine source was cola soft drinks. CONCLUSION: Environmental exposures, especially acetaminophen ingestion during human preterm pregnancy, can modulate CYP2E1 metabolic activity.

Physiological Effects of Pulsed LED Light Added to a Task Lamp to Improve Alertness on Employees of Hospital or Shift Workers / Efectos Fisiológicos de Pulsos de Luz de Diodo Adicionados a una Lámpara de Trabajo para Mejorar el Estado de Alerta en Personal de Hospitales o Trabajadores por Turnos

Abstract The aim of this study is to investigate the effect of a continuous stream of pulses of monochromatic blue pulsed (BP) and a combination of blue and green pulsed (BGP) light-emitting diode (LED) light conditions on physiological responses. This study is an approach to clarify the most suitable LED combination and flickering frequency to evoke alertness when a continuous stream of pulsed LED light is delivered and may suggest applications of continuous pulsed light as support for task illumination for shift workers, hospital nurses, school students or office employees. Combinations were delivered by exposures of BPLED and BGPLED pulses at 100, 200, and 400 Hertz over two background light colors (BLC). Participants were exposed to 12 different light conditions in a counterbalanced procedure. By integrating measures of electroencephalogram (EEG) and pupil constriction; results suggested significant changes in responses during the interaction of BLC, LED, and EEG. Beta waves exhibited a statistically significance (p < 0.05) in arousal levels when exposed to BG light, although no active task was involved during exposure. Furthermore, pupil reacted with larger constriction towards BGPLED exposure than towards monochromatic BPLED exposure, thus demonstrating that a continuous stream of pulses can deliver the same irradiance as if delivered in a continuous flow and without affecting perception as no flickering was perceived in any of the conditions by a qualitative evaluation.

Resumen Este estudio tiene por objetivo determinar cuál es la combinación de luz LED más adecuada y la frecuencia de parpadeo que esta deba tener, para evocar un estado de alerta cuando se emite un flujo continuo de la misma al combinarla con una iluminación de ambiente; y poder sugerir aplicaciones como soporte para la iluminación de tareas para trabajadores por turnos, enfermeras, médicos, estudiantes; o en oficinas y hospitales. Es de original importancia resaltar que en el mercado no existe un producto comercial que se pueda ajustar para apoyar en el trabajo al estado de alerta, se tiene la limitante que estas son pruebas a nivel laboratorio y que posteriores pruebas serán necesarias para validar el producto final. El método usado se basó en las combinaciones que se administraron mediante exposiciones de luz azul pulsada (BPLED) y luz azul y verde combinadas (BGPLED) a frecuencias de 100, 200 y 400 Hz adicionadas a la iluminación ambiental (BLC). Los participantes fueron expuestos a 12 condiciones de luz diferentes en un experimento balanceado y contrapesado. Mediante la integración de medidas electroencefalográficas (EEG) y de constricción pupilar; los resultados sugirieron cambios significativos en las respuestas durante la interacción de BLC, LED y EEG. Las ondas beta mostraron una significancia estadística (p <0.05) en los niveles de activación cuando se expusieron a la luz BGPLED, además, la pupila reaccionó con una mayor constricción hacia la exposición a BGPLED que hacia la exposición BPLED monocromática, adicionalmente se demostró que un flujo continuo de pulsos puede proporcionar una irradiación igual a la que se emite en flujo continuo; se concluyó e identificó además la frecuencia (100 Hz) que mejor evoca estado de alerta encefalográfíca y sin afectar la percepción de los usuarios en cuanto a su percepción del ambiente de acuerdo a la evaluación cualitativa.

Environmental suitability for Aedes aegypti and Aedes albopictus and the spatial distribution of major arboviral infections in Mexico.

BACKGROUND: This paper discusses a comparative geographic distribution of Aedes aegypti and Aedes albopictus mosquitoes in Mexico, using environmental suitability modeling and reported cases of arboviral infections. METHODS: Using presence-only records, we modeled mosquito niches to show how much they influenced the distribution of Ae. aegypti and Ae. albopictus based on mosquito records collected at the municipality level. Mosquito surveillance data were used to create models regarding the predicted suitability of Ae. albopictus and Ae. aegypti mosquitos in Mexico. RESULTS: Ae. albopictus had relatively a better predictive performance (area under the curve, AUC = 0.87) to selected bioclimatic variables compared to Ae. aegypti (AUC = 0.81). Ae. aegypti were more suitable for areas with minimum temperature of coldest month (Bio6, permutation importance 28.7%) -6 °C to 21.5 °C, cumulative winter growing degree days (GDD) between 40 and 500, and precipitation of wettest month (Bio13) >8.4 mm. Minimum temperature range of the coldest month (Bio6) was -6.6 °C to 20.5 °C, and average precipitation of the wettest month (Bio13) 8.9 mm ~ 600 mm were more suitable for the existence of Ae. albopictus. However, arboviral infections maps prepared from the 2012-2016 surveillance data showed cases were reported far beyond predicted municipalities. CONCLUSIONS: This study identified the urgent necessity to start surveillance in 925 additional municipalities that reported arbovirus infections but did not report Aedes mosquito.

Physiological Effects of Blue Pulsed LED in an Indoor Lighting Environment / Efectos Fisiológicos de Luz LED Azul Intermitente en un Ambiente de Iluminación en Interiores

Abstract Purpose: An experiment was conducted to investigate the physiological effects of a continuous blue pulsed light emitting diode (BP-LED) added to a task lamp in an actual indoor lighting environment and its influence in alertness having as a final purpose to develop a commercial product that could be applied in situations similar to those depicted in the present work. Design methodology: Previous research studies have stated that the addition of pulsed light evokes physiological changes that may induce alertness. The participants were exposed to four different lighting conditions. Electroencephalograms (EEG), pupil sizes, heart rates (HR), performance tests, and subjective reactions were measured. Findings: Low colour temperature light and the BP-LED revealed an improved alertness according to the data from the EEG recordings. The intervention of the BP-LED in a high colour temperature ambiance was beneficial in maintaining high levels of alertness compared to the conditions where the BP-LED was not used. It was tested that the use of a BP-LED in a task lamp may be beneficial in improving or maintaining alertness levels in an indoor workplace ambiance. Originality and Value: Designing of an adequate workplace task lamp light that improves alertness for in-house, office, or classroom situations in which it is essential.

Resumen Propósito: Un experimento fue llevado a cabo para investigar los efectos fisiológicos que una luz azul LED pulsada de manera intermitente (BP-LED), adicionada a una lámpara de escritorio, y en un ambiente interior; pueda influir en el estado de alerta de una persona con la finalidad de desarrollar un producto comercial que pueda ser aplicado para los casos desarrollados y otros posibles escenarios. Metodología de Diseño: En estudios anteriores se establece que la adición de luz en pulsaciones evoca cambios fisiológicos que pueden inducir al estado de alerta. Los participantes experimentaron cuatro escenarios de iluminación. Se registraron mediciones con respecto a encefalografía (EEG), tamaño pupilar, ritmo cardiaco, prueba de performance, así como evaluación subjetiva. Hallazgos: Los datos de EEG revelaron un mayor estado de alerta durante la exposición a iluminación cálida aunado a luz BP-LED. La intervención de luz fría y BP-LED denotó ser benéfica en el nivel de estado de alerta en comparación con las condiciones donde el BP-LED no intervino. Se logró evaluar que el uso de BP-LED en una lámpara de escritorio puede ser benéfico para mejorar o mantener el estado de alerta cuando sea usado en un espacio interior. Originalidad y Valor: Propuesta para diseñar una luminaria de escritorio; para uso casero, laboral o de estudio; que mejore el estado de alerta de las personas.

Are there intracellular Ca2+ oscillations correlated with flagellar beating in human sperm? A three vs. two-dimensional analysis.

STUDY QUESTION: Are there intracellular Ca2+ ([Ca2+]i) oscillations correlated with flagellar beating in human sperm? SUMMARY ANSWER: The results reveal statistically significant [Ca2+]i oscillations that are correlated with the human sperm flagellar beating frequency, when measured in three-dimensions (3D). WHAT IS KNOWN ALREADY: Fast [Ca2+]i oscillations that are correlated to the beating flagellar frequency of cells swimming in a restricted volume have been detected in hamster sperm. To date, such findings have not been confirmed in any other mammalian sperm species. An important question that has remained regarding these observations is whether the fast [Ca2+]i oscillations are real or might they be due to remaining defocusing effects of the Z component arising from the 3D beating of the flagella. STUDY DESIGN, SIZE, DURATION: Healthy donors whose semen samples fulfill the WHO criteria between the age of 18-28 were selected. Cells from at least six different donors were utilized for analysis. Approximately the same number of experimental and control cells were analyzed. PARTICIPANTS/MATERIALS, SETTING, METHODS: Motile cells were obtained by the swim-up technique and were loaded with Fluo-4 (Ca2+ sensitive dye) or with Calcein (Ca2+ insensitive dye). Ni2+ was used as a non-specific plasma membrane Ca2+ channel blocker. Fluorescence data and flagella position were acquired in 3D. Each cell was recorded for up to 5.6 s within a depth of 16 microns with a high speed camera (coupled to an image intensifier) acquiring at a rate of 3000 frames per second, while an oscillating objective vibrated at 90 Hz via a piezoelectric device. From these samples, eight experimental and nine control sperm cells were analyzed in both 2D and 3D. MAIN RESULTS AND THE ROLE OF CHANCE: We have implemented a new system that allows [Ca2+]i measurements of the human sperm flagellum beating in 3D. These measurements reveal statistically significant [Ca2+]i oscillations that correlate with the flagellar beating frequency. These oscillations may arise from intracellular sources and/or Ca2+ transporters, as they were insensitive to external Ni2+, a non-specific plasma membrane Ca2+ channel blocker. LARGE SCALE DATA: N/A. LIMITATIONS REASONS FOR CAUTION: Analysis in 3D needs a very fast image acquisition rate to correctly sample a volume containing swimming sperm. This condition requires a very short exposure time per image making it necessary to use an image intensifier which also increases noise. The lengthy analysis time required to obtain reliable results limited the number of cells that could be analyzed. WIDER IMPLICATIONS OF THE FINDINGS: The possibility of recording flagellar [Ca2+]i oscillations described here may open a new avenue to better understand ciliary and flagellar beating that are fundamental for mucociliary clearance, oocyte transport, fertilization, cerebrospinal fluid pressure regulation and developmental left-right symmetry breaking in the embryonic node. STUDY FUNDING AND COMPETING INTEREST(S): This work was supported by Consejo Nacional de Ciencia y Tecnología (CONACyT) (grants 253952 to G.C.; 156667 to F.M.M. and Fronteras 71 39908-Q to A.D. and Post-doctoral scholarships 366844 to P.H.-H. and 291028 to F.M.) and the Dirección General de Asuntos del Personal Académico of the Universidad Nacional Autónoma de México (DGAPA-UNAM) (grants CJIC/CTIC/4898/2016 to F.M. and IN205516 to A.D.). There are no conflicts of interest to declare.

Clinical and spatial features of Zika virus in Mexico.

BACKGROUND: Zika virus (ZIKV) is an emerging arbovirus transmitted to humans by Aedes mosquitoes, the same vectors that transmit dengue virus and chikungunya. Recent work has suggested that prior infection with dengue could lead to more severe clinical disease in ZIKV patients. Here, we describe the spatial distribution of and clinical symptoms experienced by ZIKV cases in Mexico. METHODS: We performed Fisher's Exact test and Pearson's Chi-Square tests on data from Mexico's national surveillance system on the demographic and clinical characteristics of ZIKV patients (N=84), and then a multivariate logistic regression analysis to determine demographic risk factors for patients presenting with at least 9 symptoms. We also mapped the cases to describe the spatial distribution of ZIKV in Mexico. RESULTS: Results from the multivariate logistic regression analysis indicate that, controlling for all covariates, sex (male) is a significant protective factor in reporting a high number of symptoms (OR=0.36, 95% CI: 0.14, 0.92), and that a one-year increase in age is associated with a 4% increase in odds of having at least 9 symptoms (95% CI: 1.00, 1.08). Spatial analysis revealed more than 50% cases reported within 50km of railways. CONCLUSION: We found that sex and age are both significant risk factors for ZIKV infection severity, using number of reported symptoms as a proxy. The presence of cases along railways indicates that transportation networks within Mexico may be relevant for the national and international spread of the disease.

Carbonic anhydrases and their functional differences in human and mouse sperm physiology.

Fertilization is a key reproductive event in which sperm and egg fuse to generate a new individual. Proper regulation of certain parameters (such as intracellular pH) is crucial for this process. Carbonic anhydrases (CAs) are among the molecular entities that control intracellular pH dynamics in most cells. Unfortunately, little is known about the function of CAs in mammalian sperm physiology. For this reason, we re-explored the expression of CAI, II, IV and XIII in human and mouse sperm. We also measured the level of CA activity, determined by mass spectrometry, and found that it is similar in non-capacitated and capacitated mouse sperm. Importantly, we found that CAII activity accounts for half of the total CA activity in capacitated mouse sperm. Using the general CA inhibitor ethoxyzolamide, we studied how CAs participate in fundamental sperm physiological processes such as motility and acrosome reaction in both species. We found that capacitated human sperm depend strongly on CA activity to support normal motility, while capacitated mouse sperm do not. Finally, we found that CA inhibition increases the acrosome reaction in capacitated human sperm, but not in capacitated mouse sperm.

Membrane hyperpolarization during human sperm capacitation.

Sperm capacitation is a complex and indispensable physiological process that spermatozoa must undergo in order to acquire fertilization capability. Spermatozoa from several mammalian species, including mice, exhibit a capacitation-associated plasma membrane hyperpolarization, which is necessary for the acrosome reaction to occur. Despite its importance, this hyperpolarization event has not been adequately examined in human sperm. In this report we used flow cytometry to show that a subpopulation of human sperm indeed undergo a plasma membrane hyperpolarization upon in vitro capacitation. This hyperpolarization correlated with two other well-characterized capacitation parameters, namely an increase in intracellular pH and Ca(2+) concentration, measured also by flow cytometry. We found that sperm membrane hyperpolarization was completely abolished in the presence of a high external K(+) concentration (60 mM), indicating the participation of K(+) channels. In order to identify, which of the potential K(+) channels were involved in this hyperpolarization, we used different K(+) channel inhibitors including charybdotoxin, slotoxin and iberiotoxin (which target Slo1) and clofilium (a more specific blocker for Slo3). All these K(+) channel antagonists inhibited membrane hyperpolarization to a similar extent, suggesting that both members of the Slo family may potentially participate. Two very recent papers recorded K(+) currents in human sperm electrophysiologically, with some contradictory results. In the present work, we show through immunoblotting that Slo3 channels are present in the human sperm membrane. In addition, we found that human Slo3 channels expressed in CHO cells were sensitive to clofilium (50 µM). Considered altogether, our data indicate that Slo1 and Slo3 could share the preponderant role in the capacitation-associated hyperpolarization of human sperm in contrast to what has been previously reported for mouse sperm, where Slo3 channels are the main contributors to the hyperpolarization event.

Characterization of NAADP-mediated calcium signaling in human spermatozoa.

Ca(2+) signaling in spermatozoa plays a crucial role during processes such as capacitation and release of the acrosome, but the underlying molecular mechanisms still remain unclear. Nicotinic acid adenine dinucleotide phosphate (NAADP) is a potent Ca(2+)-releasing second messenger in a variety of cellular processes. The presence of a NAADP synthesizing enzyme in sea urchin sperm has been previously reported, suggesting a possible role of NAADP in sperm Ca(2+) signaling. In this work we used in vitro enzyme assays to show the presence of a novel NAADP synthesizing enzyme in human sperm, and to characterize its sensitivity to Ca(2+) and pH. Ca(2+) fluorescence imaging studies demonstrated that the permeable form of NAADP (NAADP-AM) induces intracellular [Ca(2+)] increases in human sperm even in the absence of extracellular Ca(2+). Using LysoTracker, a fluorescent probe that selectively accumulates in acidic compartments, we identified two such stores in human sperm cells. Their acidic nature was further confirmed by the reduction in staining intensity observed upon inhibition of the endo-lysosomal proton pump with Bafilomycin, or after lysosomal bursting with glycyl-l-phenylalanine-2-naphthylamide. The selective fluorescent NAADP analog, Ned-19, stained the same subcellular regions as LysoTracker, suggesting that these stores are the targets of NAADP action.

The anti-inflammatory drug celecoxib inhibits T-type Ca2+ currents in spermatogenic cells yet it elicits the acrosome reaction in mature sperm.

Celecoxib (Cx), an anti-inflammatory drug designed to inhibit COX2, can affect some ion channels. T-type (CaV3) channels have been implicated in sperm physiology. Here we report and characterize the Cx induced inhibition of T-type channels in mouse spermatogenic cells. Unexpectedly, Cx can also induce the acrosome reaction (AR), an intracellular Ca(2+) ([Ca(2+)]i) increase and a sperm depolarization. This [Ca(2+)]i increase possibly results from the ability Cx has to alkalinize intracellular pH (pHi), which is known to activate the sperm specific Ca(2+) channel CatSper. As the Cx induced [Ca(2+)]i increase is sensitive to mibefradil, a CatSper blocker, this channel may mediate the Cx-induced Ca(2+) entry leading to the AR. Our observations demonstrate that Cx can compromise fertilization.

Stereoscopic particle image velocimetry measurements of the three-dimensional flow field of a descending autorotating mahogany seed (Swietenia macrophylla).

An experimental investigation of near field aerodynamics of wind dispersed rotary seeds has been performed using stereoscopic digital particle image velocimetry (DPIV). The detailed three-dimensional flow structure of the leading-edge vortex (LEV) of autorotating mahogany seeds (Swietenia macrophylla) in a low-speed vertical wind tunnel is revealed for the first time. The results confirm that the presence of strong spanwise flow and strain produced by centrifugal forces through a spiral vortex are responsible for the attachment and stability of the LEV, with its core forming a cone pattern with a gradual increase in vortex size. The LEV appears at 25% of the wingspan, increases in size and strength outboard along the wing, and reaches its maximum stability and spanwise velocity at 75% of the wingspan. At a region between 90 and 100% of the wingspan, the strength and stability of the vortex core decreases and the LEV re-orientation/inflection with the tip vortex takes place. In this study, the instantaneous flow structure and the instantaneous velocity and vorticity fields measured in planes parallel to the free stream direction are presented as contour plots using an inertial and a non-inertial frame of reference. Results for the mean aerodynamic thrust coefficients as a function of the Reynolds number are presented to supplement the DPIV data.

K+ and Cl- channels and transporters in sperm function.

To succeed in fertilization, spermatozoa must decode environmental cues which require a set of ion channels. Recent findings have revealed that K(+) and Cl(-) channels participate in some of the main sperm functions. This work reviews the evidence indicating the involvement of K(+) and Cl(-) channels in motility, maturation, and the acrosome reaction, and the advancement in identifying their molecular identity and modes of regulation. Improving our insight on how these channels operate will strengthen our ability to surmount some infertility problems, improve animal breeding, preserve biodiversity, and develop selective and secure male contraceptives.

Thermal nonlinear oscillator in mixed convection.

A detailed numerical simulation is carried out for transient laminar flow opposing mixed convection in a downward vertical channel flow with both walls suddenly subjected to isothermal heat sources over a finite portion of the channel walls, by solving the unsteady two-dimensional Navier-Stokes and energy equations. The dynamical behavior of the system is influenced by, in addition to the geometrical parameters, three nondimensional parameters: the Reynolds, Richardson, and Prandtl numbers. Numerical experiments were performed for fixed values of the geometrical parameters, the Reynolds number (Re=100) and the Prandtl number (Pr=7). With variation in the value of the buoyancy (Richardson number), the nonlinear dynamical response of the system can reach (i) a stationary solution, (ii) a local and then a global periodic solution where the system executes self-sustained relaxation oscillations, or (iii) a solution in which the relaxation oscillation is destroyed leading to a chaotic state. In this study, bifurcations between different states, phase-space plots of the self-oscillatory system, characteristic times of temperature oscillations, and an exact description of the oscillations are presented quantitatively for a range of values of the buoyancy parameter. The results include the effects of the Reynolds and Prandtl numbers on the evolution of the different transitions.

Ion channels in sperm motility and capacitation.

Spermatozoa depend upon ion channels to rapidly exchange information with the outside world and to fertilise the egg. These efficient ion transporters participate in many of the most important sperm processes, such as motility and capacitation. It is well known that sperm swimming is regulated by [Ca2+]i. In the sea urchin sperm speract, a decapeptide isolated from egg outer envelope, induces changes in intracellular Ca2+ ([Ca2+]i), Na+, cAMP and cGMP, membrane potential (Em) and pH (pHi). Photoactivation of a speract analogue induces Ca2+ fluctuations that generate turns that are followed by straighter swimming paths. A fast component of the [Ca2+], increase that most likely occurs through voltage dependent Ca2+ channels (Ca(v)s) is essential for these turns. The Ca(v)s involved are modulated by the Em changes triggered by speract. On the other hand, mammalian sperm gain the ability to fertilise the egg after undergoing a series of physiological changes in the female tract. This maturational process, known as capacitation, encompasses increases in [Ca2+]i and pHi, as well as an Em hyperpolarization in mouse sperm. Our electrophysiological, immunological and molecular-biological experiments indicate that inwardly rectifying K+ channels regulated by ATP (KATP channels) and epithelial Na+ channels (ENaCs) are functionally present in mouse spermatogenic cells and sperm. Notably, pharmacological experiments indicate that the opening of KATP channels and closure of ENaCs may contribute to the hyperpolarization that accompanies mouse sperm capacitation. Remarkably, both in the sea urchin sperm speract response and in the mouse sperm capacitation, Em hyperpolarization seems necessary to remove inactivation from Ca(v) channels so they can then open.

Serologic survey of domestic animals for zoonotic arbovirus infections in the Lacandón Forest region of Chiapas, Mexico.

A serologic survey in domestic animals (birds and mammals) was conducted in four communities located in the Lacandón Forest region of northeastern Chiapas, Mexico, during June 29 to July 1, 2001, with the objective to identify zoonotic arboviruses circulating in this area. We collected 202 serum samples from healthy domestic chickens, geese, ducks, turkeys, horses and cattle. The samples were tested by plaque-reduction neutralization test for antibodies to selected mosquito-borne flaviviruses (family Flaviviridae), including St. Louis encephalitis (SLE), Rocio (ROC), Ilheus (ILH), Bussuquara (BSQ), and West Nile (WN) viruses, and selected alphaviruses (family Togaviridae), including Western equine encephalitis (WEE), Eastern equine encephalomyelitis (EEE), and Venezuelan equine encephalitis (VEE) viruses. Neutralizing antibodies to SLE virus were detected in two (8%) of 26 turkeys, 15 (23%) of 66 cattle, and three (60%) of five horses. Antibodies to VEE virus were detected in 29 (45%) of 65 cattle. Because some of these animals were as young as 2 months old, we demonstrated recent activity of these two viruses. Sub-typing of the VEE antibody responses indicated that the etiologic agents of these infections belonged to the IE variety of VEE, which has been reported from other regions of Chiapas. WN virus-neutralizing antibodies were detected in a single cattle specimen (PRNT(90) = 1:80) that also circulated SLE virus-neutralizing antibodies (PRNT(90) = 1:20), suggesting that WN virus may have been introduced into the region. We also detected weak neutralizing activity to BSQ virus in four cattle and a chicken specimen, suggesting the presence of this or a closely related virus in Mexico. There was no evidence for transmission of the other viruses (ROC, ILH, EEE, WEE) in the study area.

Identification of mouse trp homologs and lipid rafts from spermatogenic cells and sperm.

Intracellular Ca(2+) has an important regulatory role in the control of sperm motility, capacitation, and the acrosome reaction (AR). However, little is known about the molecular identity of the membrane systems that regulate Ca(2+) in sperm. In this report, we provide evidence for the expression of seven Drosophila transient receptor potential homolog genes (trp1-7) and three of their protein products (Trp1, Trp3 and Trp6) in mouse sperm. Allegedly some trps encode capacitative Ca(2+) channels. Immunoconfocal images showed that while Trp6 was present in the postacrosomal region and could be involved in sperm AR, expression of Trp1 and Trp3 was confined to the flagellum, suggesting that they may serve sperm to regulate important Ca(2+)-dependent events in addition to the AR. Likewise, one of these proteins (Trp1) co-immunolocalized with caveolin-1, a major component of caveolae, a subset of lipid rafts potentially important for signaling events and Ca(2+) flux. Furthermore, by using fluorescein-coupled cholera toxin B subunit, which specifically binds to the raft component ganglioside GM1, we identified caveolin- and Trp-independent lipid rafts residing in the plasma membrane of mature sperm. Notably, the distribution of GM1 changes drastically upon completion of the AR.