Effects of Left Ventricular Assist and Aortic Graft Angle on Aortic Valve: A Hemodynamic Study / 医用生物力学

Objective To investigate the effect of left ventricular assist device (LVAD) and aortic graft angle on hemodynamics of aortic valve. Methods Three models of aorta and aortic valve with 45°, 60° and 90° anastomosis angles between LVAD and aorta were constructed, and an in vitro pulsating table was built for in vitro experiments. Using particle image velocimetry (PIV) system, three moments in the cardiac cycle ( T1 systolic peak, T rapid closure, T3 diastolic peak), were selected to study the hemodynamic state of aortic valve. Results Velocity vector, vorticity and viscous shear stress were used to evaluate the effect of LVAD anastomosis angle on hemodynamics of aortic valve. During the period of rapid valve closure, with the increase of graft angle, the blood flow velocity near the valve wall, the average vorticity and the maximum viscous shear stress all increased. Conclusions When the graft angle is lower, the impact velocity of blood on the valve is smaller, and the shear force on the valve decreases, so that the valve is in a better hemodynamic environment. This study provides references for the selection of anastomotic angles in clinical operations.

Efeito do cilostazol na produção in vitro de ovinos / Effect of cilostazol on in vitro production of sheep / Efecto del cilostazol en la producción in vitro de ovejas

O objetivo deste estudo foi avaliar o efeito da inclusão de cilostazol no meio de maturação in vitro de oócitos sobre produção in vitro de embriões ovinos. Para isso, foram realizadas colheitas de oócitos oriundos de ovários obtidos em abatedouro por meio do método de aspiração folicular com bomba de vácuo. Os oócitos foram divididos em quatro grupos de maturação: grupo CON, onde os complexos cumulus oócitos foram imersos em TCM-199, suplementado com 500 UI de penicilina, 0,5 mg de estreptomicina, 1,25 µg de anfotericina, 0,2 mM de piruvato de sódio, 10% (v/v) de soro fetal bovino (SFB), 10 ng/mL de fator de crescimento epidérmico (EGF), 10 ug/m de FSH, 10 µg/mL de LH, 10 ug/mL de estradiol e 100 µM de cisteamina; e nos grupos CILO0,3; CILO1 e CILO10, os oócitos foram maturados no meio do grupo CON, mas sem a adição de cisteamina e suplementado com as concentrações de 0,3; 1 e 10 µM, respectivamente. Após 24h, os oócitos foram avaliados quanto a presença ou não de células do cumulus e quanto ao grau de expansão e destinados à fecundação in vitro, em meio FIV, juntamente com espermatozoides. Após a FIV, os presumíveis zigotos seguiram para o cultivo in vitro. Foram avaliadas clivagens no dia 2, sendo dia 0 o dia do início do CIV. Os resultados foram expressos em porcentagem e as variáveis de expansão das células do cumulus e número de estruturas clivadas foram comparadas por meio do teste qui-quadrado do software Epi Info (Epi Info 7.2.5, Atlanta, GA, EUA, 2021). Os resultados foram considerados significativos quando P<0,05. Em relação à expansão das células do cumulus, todos os grupos apresentaram 100% de expansão. Não houve diferenças significativas quanto ao grau de expansão das células do cumulus entre os grupos suplementados com cilostazol e cisteamina (P>0,05), assim como não houve diferenças significativas entre as taxas de clivagem entre os grupos suplementados com cilostazol e cisteamina (P > 0,05).

The objective of this study was to evaluate the effect of including cilostazol in the in vitro maturation medium of oocytes on the in vitro production of sheep embryos. Oocytes were collected from ovaries obtained from a slaughterhouse by follicular aspiration with a vacum pump. The oocytes were divided into four maturation groups: the CON group, where the cumulus-oocyte complexes were immersed in TCM-199 supplemented with 500 IU of penicillin, 0.5 mg of streptomycin, 1.25 µg of amphotericin, 0.2 mM of sodium pyruvate, 10% (v/v) fetal bovine serum (FBS), 10 ng/mL of epidermal growth factor (EGF), 10 µg/mL of FSH, 10 µg/mL of LH, 10 µg/mL of estradiol, and 100 µM of cysteamine; and in the CILO0.3, CILO1, and CILO10 groups, the oocytes were matured in the CON group medium without the addition of cysteamine and supplemented with concentrations of 0.3, 1, and 10 µM of cilostazol, respectively. After 24 hours, the oocytes were evaluated for the presence or absence of cumulus cells and the degree of expansion and then subjected to in vitro fertilization (IVF) with sperm in FIV medium. After IVF, the presumptive zygotes were cultured in vitro. Cleavage was evaluated on day 2, with day 0 being the start of IVF. Results were expressed as a percentage, and variables such as cumulus cell expansion and the number of cleaved structures were compared using the chi-square test in the Epi Info software (Epi Info 7.2.5, Atlanta, GA, USA, 2021). Results were considered significant when P < 0.05. All groups showed 100% cumulus cell expansion, and there were no significant differences in cumulus cell expansion degree between the cilostazol- and cysteamine-supplemented groups (P > 0.05), as well as no significant differences in cleavage rates between the cilostazol- and cysteamine-supplemented groups (P > 0.05).

El objetivo de este estudio fue evaluar el efecto de la inclusión de cilostazol en el medio de maduración in vitro de ovocitos sobre la producción in vitro de embriones ovinos. Para ello, se realizaron recolecciones de ovocitos provenientes de ovarios obtenidos en un matadero mediante el método de aspiración folicular con bomba de vacío. Los ovocitos se dividieron em cuatro grupos de maduración: grupo CON, donde los complejos cúmulus ovocitos se sumergieron en TCM-199, suplementado con 500 UI de penicilina, 0,5 mg de estreptomicina, 1,25 ug de anfotericina, 0,2 mM de piruvato de sodio, 10% (v/v) de suero fetal bovino (SFB), 10 ng/mL de factor de crecimiento epidérmico (EGF), 10 ug/m de FSH, 10 µg/mL de LH, 10 µg/mL de estradiol y 100 µM de cisteamina; y en los grupos CILO0,3; CILO1 y CILO10, los ovocitos se maduraron en el medio del grupo CON, pero sin la adición de cisteamina y suplementado con las concentraciones de 0,3; 1 y 10 µM, respectivamente. Después de 24 horas, los ovocitos se evaluaron en cuanto a la presencia o no de células del cúmulus y em cuanto al grado de expansión y se destinaron a la fecundación in vitro, en medio FIV, junto con espermatozoides. Después de la FIV, los presuntos cigotos siguieron para el cultivo in vitro. Se evaluaron las clivajes en el día 2, siendo el día 0 el día del início del CIV. Los resultados se expresaron en porcentaje y las variables de expansión de las células del cúmulos y número de estructuras clivadas se compararon mediante la prueba del chi-cuadrado del software Epi Info (Epi Info 7.2.5, Atlanta, GA, EE. UU., 2021). Los resultados se consideraron significativos cuando P < 0,05. En relación a la expansión de las células del cúmulus, todos los grupos presentaron el 100% de expansión. No hubo diferencias significativas en cuanto al grado de expansión de las células del cúmulus entre los grupos suplementados con cilostazol y cisteamina (P > 0.05), así como no hubo diferencias significativas entre las tasas de clivaje entre los grupos suplementados con cilostazol y cisteamina (P>0,05).

Research Progress of Micro-PIV in Biomedical Engineering Field / 医用生物力学

Blood is an important component of living organism which is responsible for material transportation. The microenvironment of blood flow plays an important role in physiological and pathological processes of angiogenesis and cardiac development, erythrocytes aggregation and blood viscosity, tumor metastasis and atherosclerosis. Besides, micro-fluid environment significantly affects drug delivery, cell screening, and artificial organ design. Thus, the measurement and quantitative analysis of micro-fluid contribute to the biomedical engineering filed. Micro-particle imaging velocimetry (Micro-PIV) combines conventional PIV with microscopy technique. Correlation analysis is conducted in two groups of images captured by high speed camera at different time intervals, and the velocity profiles in micro-fluid environment are successfully measured. Compared with other velocity measurement methods, Micro-PIV has high temporal resolution and spatial resolution. The main setup of Micro-PIV and its principle analysis method were introduced in this review. Recent studies of Micro-PIV applications in biomedical engineering field were then summarized. Moreover, the drawbacks of Micro-PIV technique and prospect of its applications were discussed.

Pre-incubation of porcine semen reduces the incidence of polyspermy on embryos derived from low quality oocytes / Pré-incubação dos espermatozoides suínos diminui polispermia e aumenta a produção embrionária em oócitos de baixa qualidade

ABSTRACT: The main cause of low efficiency of in vitro produced porcine embryos is the high polyspermic penetration rates at fertilization, which is aggravated in low quality oocytes. Experiment 1 evaluated the embryo development in high and low quality oocytes. Experiment 2 evaluated the embryo development and quality of low quality oocytes fertilized with sperm pre-incubated during 0h (control), 0.5h, 1h and 1.5h. Experiment 3 investigated fertilization and monospermic rates of the same groups of Experiment 2. Experiment 4 evaluated embryo development, cell density, fertilization and monospermic rates of high quality oocytes using semen pre incubated during the best time observed in the previous experiments. Cleavage and blastocyst rates were analyzed by chi-square test, and remaining data by ANOVA and Tukey test (P≤0.05). The cleavage (74.8 vs 51.7%) and blastocyst (33.7 vs 9.8%) rates were greater in oocytes of high versus low quality, with no differences in cell density. Fertilization rates (65.6 to 79.5%) were not influenced by pre-incubation time. However, semen pre-incubation during 1.5h increased monospermic penetration (53.3%) and cleavage rates (92.5%) in low quality oocytes. Blastocyst rate was improved with 1.5h of semen pre incubation; however they were still lower than that observed with high quality control oocytes. Ultimately, pre-incubation did not influence fertilization, monospermic penetration, embryo development rates, nor cell density in oocytes of high quality. Low-quality porcine oocytes resulted in better rates of embryo development if in vitro fertilized with sperm pre-incubated for 1.5 hour.

RESUMO: A principal causa da baixa eficiência na PIV de embriões suínos é a elevada taxa de polispermia, que é exacerbada em oócitos de baixa qualidade. O experimento 1 avaliou o desenvolvimento embrionário de oócitos de baixa e alta qualidade. O experimento 2 avaliou a qualidade e o desenvolvimento embrionário de oócitos de baixa qualidade fecundados com sêmen pré-incubado por 0h (controle), 0,5h, 1h e 1,5h. O experimento 3 investigou a fecundação e as taxas de monospermia dos mesmos grupos do experimento 2. O experimento 4 avaliou o desenvolvimento embrionário, a densidade celular, a fecundação e as taxas de monospermia de oócitos de alta qualidade, fecundados com sêmen pre-incubado com o melhor tempo observado nos experimentos anteriores. As taxas de clivagem e de blastocistos foram submetidas ao teste de Qui-quadrado e os demais dados submetidos à ANOVA e teste de Tukey (P≤0,05). As taxas de clivagem (74,8 vs 51,7%) e de blastocistos (33,7 vs 9,8%) foram superiores nos oócitos de alta qualidade, comparados aos de baixa qualidade, não havendo diferenças na quantidade de células embrionárias. As taxas de fecundação (65,6 vs 79,5%) não foram influenciadas pelo tempo de pré-incubação. Todavia, a pré-incubação do sêmen por 1,5h aumentou a penetração monospérmica (53,3%) e a taxa de clivagem (92,5%), nos oócitos de baixa qualidade. As taxas de blastocisto aumentaram com sêmen pré-incubado por 1,5h, que foram ainda inferiores às obtidas dos oócitos de alta qualidade do grupo controle. Finalmente, a pré-incubação do sêmen não influencia na fecundação, na penetração monospérmica, no desenvolvimento embrionário, nem na quantidade de células embrionárias com oócitos de alta qualidade. Oócitos suínos de baixa qualidade produzem melhores taxas de desenvolvimento embrionário se fecundados in vitro com sêmen pré-incubado por 1,5 horas.

Percentage Incidence, Morphology and Morphometry of Myocardial Bridges: A Cadaveric Study.

Introduction: Myocardial bridging is the term used when a segment of major epicardial coronary artery runs intramuscularly under the tunnel formed by fibers of myocardium that bridges instead of it’s normal or routine epicardial path. In the literature there are varying reports on clinical implications of myocardial bridges from protection against atherosclerosis to myocardial ischemia, as well as leading to infarction and sudden cardiac death. Materials and Methods: 150 adult formalin fixed human hearts which were available in the department of Anatomy and Forensic Medicine, S.V.Medical College, Tirupati, Andhra Pradesh, India. These hearts were dissected and observed for the presence, location, type, number and direction of myocardial bridges and their association with coronary dominance. With the help of digital calipers morphometric parameters (length, width& thickness) of myocardial bridges and length of blood vessel underneath the myocardial bridge were measured, noted and photographs were taken. Results: The overall incidence of myocardial bridges was 20.6%( 31/150). Among these 18.6% (28/31) were on left anterior descending (LAD) artery and 2% (03/31) were on posterior interventricular (PIV) artery. The direction of muscle fibers in the bridges were oblique to the direction of the coronary vessels in majority of cases. Length, width and thickness of myocardial bridges were in the range of 12-69.7mm, 3.74-8.6mm and 1.3-3.87mm respectively. Conclusions: Myocardial bridges may be associated with wide range of clinical problems. Contraction of myocardial bridge may results in vascular compression and myocardial ischemia. Knowledge on morphology and morphometric details of myocardial bridges facilitates cardiologists in diagnosis, planning therapeutic strategies and prognostic predictions.

Laparoscopic ovum pick up (LOPU) in goats: from hormonal treatment to oocyte possible destinations / Colheita de oócitos por laparoscopia em caprinos: do tratamento hormonal aos possíveis destinos dos oócitos

Whether we are collecting oocytes from donors as part of a program of in vitro embryo production (IVP) and/or to promote advances in emerging biotechnologies as cloning and transgenesis, the success rate depends on the development of methodological aspects of recovering oocytes. To succeed, sufficient number of good quality oocytes is the prerequisite for various reproductive techniques and laparoscopic ovum pick up (LOPU) is the recommended technique for obtaining them from live goats. However, the variability of the quantity and quality of the oocytes collected still limits the large-scale use of this technology. Under the current conditions, too large variability is reported with oocyte recovery rates ranging from 40 to 90%, and the number of harvested oocytes per female between 4 and 14, in different laboratories. This variability can depend on either intrinsic characteristic of the donors, suchas breed, age, individual response or on aspects that we might be able to control, such as stimulation treatment, type of needle, aspiration pressure, among others. We believe that new investigations should contribute to significant improvement of LOPU yield. This review aims to report different factors influencing goat donor response for LOPU, presenting main steps for oocytes recovery as well as technical alternatives for improving LOPU efficiency. Furthermore, it is aimed to discuss about the potential use of goatoocytes after their recovery by LOPU and present overall results in goat IVP worldwide.

Independentemente se a coleta de oócitos é parte de um programa de produção in vitro de embriões (PIVE) e/ou promoverá avanços biotecnológicos como clonagem e transgênese, os aspectos metodológicos nas técnicas de recuperação de oócitos são imprescindíveis. Para alcançar sucesso de forma ótima, número suficiente de oócitos de boa qualidade é pré-requisito para diversas técnicas reprodutivas e a colheita de oócitos por laparoscopia (COL) é a técnica recomendada para obtê-los de cabras saudáveis. Entretanto, a variabilidade na quantidade e qualidade de oócitos coletados ainda limita o uso desta tecnologia em grande escala. Sob as condições atuais, uma grande variação é relatada na literatura com taxas de recuperação de oócitos variando de 40 a 90% e o número de estruturas coletadas por fêmea entre 4 e 14 oócitos em diferentes laboratórios. Esta variabilidade pode ocorrer tanto em função de variáveis não controláveis, como raça, idade e características intrínsecas da cabra, como devido a aspectos controláveis, como o tratamento superestimulatório, tipo da agulha, pressão de aspiração, dentre outros. Acredita-se que novas pesquisas devam contribuir significativamente para a melhoria da técnica de COL. Esta revisão objetiva relatar os diferentes fatores que influenciam a resposta de cabras doadoras após COL, apresentando as principais etapas para recuperação oocitária assim como modificações técnicas propostas para melhoria da eficiência da COL. Além disso, discutir sobre potencias aplicações de oócitos caprinos depois de sua recuperação por COL e resultados gerais sobre a técnica no mundo.

PIV experiment on flow fields of the real human upper respiratory tract gauge model / 医用生物力学

Objective To investigate the airflow distribution mode in human upper respiratory tract model for understanding the characteristics of the airflow in human upper respiratory tract, and provide scientific basis for analyzing the diffusion, transition and deposition patterns of aerosol in human upper respiratory tract. Methods PIV（particle image velocimetry）technology was adopted to study flow fields of the real human upper respiratory tract model. The airflow state in oral cavity，pharynx and trachea was analyzed. Results The flow velocity was relatively high at the upper tongue coating and in the middle of the oral cavity; when the airflow reached the pharynx, the velocity was increased rapidly due to the reduction of sectional area; the maximum velocity (10.24 m/s) appeared in the glottis, and the velocity in the anterior wall was higher than that in the posterior wall of the trachea; as the airflow injected at the glottis, the velocity gradient was increased, and the vorticity was concentrated at the anterior and posterior wall of the glottis, resulting in a significantly higher vorticity value at anterior wall of the trachea than that at the posterior wall. Conclusions PIV technology is an effective way to investigate the airflow distribution mode in human upper respiratory tract, and it is of great importance for exploring the harm of toxic aerosol to human body and the therapeutic effect of inhalation drug aerosol, as well as for researching the pathogenesis of respiratory system.

Numerical and experimental study on steady flow in the model of internal carotid artery siphon / 医用生物力学

Objective To investigate the hemodynamic factors in internal carotid arteries (ICA) with different shapes, and analyze the relationship between the arterial geometry and atherosclerotic stenosis to provide the hemodyanmic basis for the risk prediction and early diagnosis of ICA stenosis. Methods The flow field in the most two common types of ICAs, U and V-shaped ICA, were investigated by numerical simulation and particle image velocimetry (PIV) experiment under the condition of steady flow. Results At the upstream bend of ICA, the hemodynamic factors were monotonically associated with the curvature of the bend. As a result, the risk for stenosis here was smaller in the V-shaped ICA, as compared to U-shaped ICA. But at the downstream bend, such monotonic relationship didn’t exist due to the synergistic effect of the two bends. ConclusionsThe curvature of the artery is positively related to the risk for stenosis, but the synergistic effect of bends needs to be considered for studying arteries with the serial bends. The research on the synergistic effect may explain why the stenosis is frequently observed in arteries with multiple bends.

Experimental apparatus for measuring flow field of human upper respiratory tract with PIV technology / 医用生物力学

Objective To develop a measurement device and provide a platform for researching the characteristics of human upper respiratory tract flow field based on PIV (particle image velocimetry) technology with respect to the characteristics that human upper respiratory tract flow may form the vortex structure, flow shunt and secondary flow. Methods A transparent physical model of human upper respiratory tract was prepared based on the completely scanned medical images. By means of selecting appropriate air pressure system, combined with two-dimensional PIV system, a complete experimental apparatus was established. Based on the apparatus, preliminary experiment on air velocity in human upper respiratory tract flow field was conducted, and the experiment result was compared with the numerical simulation result. Results Under the steady breathing pattern at respiratory flow of 30 L/min, respiratory air flow measured by the experimental apparatus led to the formation of vortex structure in the front part of oral cavity. Air velocity was relatively higher both in the lower part of oral cavity near the upper tongue and in the middle part of oral cavity, while the velocity was relatively lower in the other parts of oral cavity. The results were in accordance with numerical simulation. Conclusions The experimental apparatus for human upper respiratory tract flow measurement based on PIV technology is practical and reliable, which can be applied in the measurement of airflow organization patterns and vorticity distributions in human upper respiratory tract, and realize the verification of numerical simulation results.

Experimental design on flow characteristics of aqueous humor based on PIV method / 医用生物力学

Objective To visualize the process of introcular flow caused by injection into the posterior chamber of the impermeable vitro eyeball with particle image velocimetry (PIV) technology, and calculate the flow fields at different moments, so as to investigate PIV experimental scheme for low-speed flow field measurement in the eye and provide basis for the in vivo measurement of aqueous humor flow under physiological status. Methods In an impermeable vitro eyeball, the introcular flow would be slow enough when the injection pump was driven at the rate of 0.2, 0.4, 0.6, 0.8, 1.0, 1.5 mL/min. Fluorescent particle solution, with a certain concentration and particle diameter of 10 μm, was injected into the posterior chamber of the vitro rabbit eye, and the sheet laser was projected to the medial frontal plane of the eye. Then clear particle images were captured by camera, and the velocity field was recorded and calculated by PIV system. Results The fluid into the posterior chamber first filled in the posterior chamber and the pupil, then passed the pupillary margin and flowed into the anterior chamber, which was consistent with the theoretical flow process of aqueous humor under physiological conditions. Based on analysis of the particle images, the velocity inside an impermeable eyeball was calculated at the magnitude of a few millimeters per second. Conclusions PIV method can be applied to low-speed flow field measurement, and the flow characteristics inside the eyeball can also be measured by PIV method, which contributes to the measurement of aqueous flow under both physical and pathological conditions, provides experimental verification for numerical simulations on aqueous humor field, and offers a new diagnostic and treatment perspective for shear force damage and destructions of corneal endothelial cells, the iris and lens under different flow fields.

Turbulência induzida por jatos bifásicos do tipo gás-líquido em tanques de aeração / Turbulence induced by two-phase gas-liquid jets in aeration tanks

Jatos bifásicos do tipo gás-líquido são bastante usados nas engenharias sanitária e ambiental para fins de aeração artificial e mistura turbulenta. O presente trabalho investiga a turbulência gerada por meio desses jatos em um tanque de água, utilizando velocimetria por imagem de partículas. As condições experimentais incluíram jatos bifásicos com frações volumétricas de ar de até 70 por cento e números de Reynolds variando entre 10.600 e 17.700. Os resultados dos ensaios indicaram que a fração volumétrica de ar afeta consideravelmente as propriedades turbulentas da fase líquida, enquanto o número de Reynolds apresenta efeito secundário. Correlações adimensionais foram então obtidas para expressar a energia cinética turbulenta e a taxa de dissipação de energia em função desses dois parâmetros. Finalmente, são apresentadas possíveis aplicações dos resultados deste trabalho.

Two-phase gas-liquid jets are widely used in the sanitary and environmental engineering field for artificial aeration and turbulent mixing. The present work investigates the turbulence generated by these jets in a water tank, using particle image velocimetry. The experimental conditions included two-phase jets with gas volume fractions of up to 70 percent and Reynolds numbers ranging from 10,600 to 17,700. The results indicated that the gas volume fraction affects significantly the turbulent properties of the liquid phase, while the Reynolds number presents a secondary effect. Dimensionless correlations were then obtained to express the turbulent kinetic energy and dissipation rate as a function of these two parameters. Finally, possible applications of the results obtained in this work are presented.

Estudos de Reaeração com Velocimetria por Imagens de Partículas - Sistema S-PIV-3D / Rearation Studies with Particle Image Velocimetry - S-PIV-3D System

Particle Image Velocimetry (PIV) é uma técnica recente de medição não-intrusiva de campos de velocidades em escoamentos. Neste trabalho, foi desenvolvido um equipamento de medição com características similares aos convencionais, porém com algumas características exclusivas, como o método óptico de aquisição de imagens e a calibração de coordenadas, que resultaram na utilização de uma única câmera convencional para obtenção de imagens e dados tridimensionais em escoamentos de baixa turbulência, proporcionando significativa economia na implantação. Foi desenvolvido um software específico e os resultados consistem em campos de velocidades tridimensionais. A aplicação destinou-se à medição de velocidades na superfície do escoamento em um tanque de grades oscilantes de forma a correlacionar a turbulência superficial com a capacidade de reaeração dos corpos da água.

Particle Image Velocimetry (PIV) is a recent technique of flow measurement labeled as a non-intrusive methodology. The system developed in this paper used principles similar to conventional systems including some exclusive characteristics as the optical method of image acquisition and the calibration process of the coordinate system. The measurement system, resulted from these characteristics, uses a single conventional digital video camera to obtain three-dimensional data in low turbulence flow, which provided significant economy in the system implantation. A specific software was developed and the results consist of fields of three-dimensional velocities obtained from the digital video file. The application was destined to the measurement of velocities on the flow surface in a tank of oscillating grids in order to correlate the surface turbulence with the rearation capacity of the bodies of water.

Numerical Simulation Analysis of Single-phase Flow Field in Micro-flow-channels of the Small Square Cylinders in the Electrolysis Oxygen Generation / 航天医学与医学工程

Objective To study the flow fields of electrolysis oxygen generation with micro-flow-channels of small square cylinders and the key structure factors impacting on the uniform distribution of the water flow in the micro-flow-channels.Methods The low Renault k-? model was used to represent the characteristics of the flow field in the micro-flow-channels.And the simulation results of the flow fields by CFD were calibrated by comparing with that of the particle image velocimetry(PIV) experiments,which showed that the low Renault k-? model was suitable to describe the flow field of the micro-flow-channels.Results The flow fields of variable flow were obtained.Conclusion The flow fields of variable flow rates distribute non-uniformly.The velocity magnitude is 10-3m/s,and the inlet structure of the electrolysis oxygen generation is a key factor impacting on the uniform distribution of the water flow.

Secreção de interferon-tau em embriões bovinos produzidos in vitro frescos e congelados / Interferon tau secretion in cattle embryos in vitro fertilized before and after cryopreservation

Avaliou-se a interferência da criopreservação sobre a secreção de interferon-tau (IFN-t) por embriões bovinos produzidos in vitro. Usaram-se dois grupos de tratamentos: I) constituído por embriões não criopreservados (fresco) e II) embriões criopreservados. Os embriões, após atingirem a fase de blastocisto (fresco ou imediatamente após o descongelamento dos criopreservados), continuaram a ser cultivados individualmente por mais sete dias. Do meio de cultivo em que se mantiveram os blastocistos retiraram-se alíquotas com três e sete dias do início do cultivo, para a avaliação da secreção de IFN-t pelos embriões cultivados. Os embriões congelados secretaram menos IFN-t do que aqueles não criopreservados (P<0,05), e com sete dias houve maior secreção do interferon do que com três dias (P<0,05). A criopreservação prejudicou a produção de IFN-t pelo trofoblasto e pode comprometer o reconhecimento materno da gestação e o desenvolvimento do embrião pós-descongelamento.

The effect of cryopreservation in IFN-tau, from bovine embryos produced in vitro was evaluated. Two treated groups (G1= fresh bovine embryos, n=59 and G2= freezed embryos, n=84) were used to study the effect of cryopreservation on IFN-tau secretion. After reaching the blastocyst phase, the embryos were kept on individual culture for additional period of 7 days. On days 3 and 7 after the beginning of embryos cultivation, samples of the media culture were taken for IFN-tau secretion titration. Oocysts taken from follicles ranging from 3 to 5mm in diameter were obtained from ovaries of females at slaughterhouse. The embryos were frozen, after being dehydrated with ethylene glycol (1.8m), conditioned on 0.5ml palletes and frozen. Frozen embryos secreted lower IFN-tau than fresh embryos (P<0.05). At day 7 it was registered higher IFN-tau secretion from trophoblast than at day 3 (P<0.05). The increasing of IFN-tau secretion was observed when the blastocyst began to longed and it was directly related to the embryos development. The synthesis of IFN-tau is related to the capability of development of the blastocyst. Cryopreservation is a method that affects the maternal recognition of pregnancy and the post-freezing embryo development.