In recent years, hydrogels have been introduced as new materials suitable for applications in areas such as biomedical engineering, agriculture, etc. The rate and degree of hydrogel swelling are important parameters t...In recent years, hydrogels have been introduced as new materials suitable for applications in areas such as biomedical engineering, agriculture, etc. The rate and degree of hydrogel swelling are important parameters that control the diffusion of drugs or solvents inside a polymer network. Therefore, the description of the dynamic swelling process of the hydrogels is very important in applications that require precise control of the absorption of solvents inside the hydrogel structure. To date, most of the numerical models developed for describing the swelling process are based in the finite difference methods. Even though numerical models supported in finite differences can be easily implemented, their use is limited to samples with very simple shapes. In this paper, a new model based on the finite element method is proposed. The diffusion equation is solved in a time-deformable grid. An original procedure is proposed to numerically solve the non-linear algebraic equation system that permits computing a new grid for each time-step. Hydrogel samples of different shapes were prepared in order to conduct experimental tests to validate the numerical proposed model. Numerical results show that the new model is able to describe the mass and shape changes in the hydrogel samples in time. An application of the numerical model to determine the relation between diffusion coefficients and density in Poly-acrylamide samples allows verifying the versatility of the model.展开更多
Aim： To investigate if interleukin-6 （IL-6）, interleukin-8 （IL-8）, interleukin- 10 （IL-10）, interferon-gamma （IFN-γ） or tumor necrosis factor-alpha （TNF-α） are able to stimulate the level of lipid peroxid...Aim： To investigate if interleukin-6 （IL-6）, interleukin-8 （IL-8）, interleukin- 10 （IL-10）, interferon-gamma （IFN-γ） or tumor necrosis factor-alpha （TNF-α） are able to stimulate the level of lipid peroxidation of sperm membranes, either alone or in the presence of leukocytes. Methods： Semen samples from normozoospermic donors were prepared by density gradient. The sperms were exposed to the indicated cytokines, at physiological and infection-inflammation concentrations, in the absence or presence of leukocytes. Lipid peroxidation of the sperm membranes was determined by measuring malondialdehyde （MDA） and 4-hydroxialkenals （HAE） formation. Results： TNF-α, IL-8 and IFN-γ increased the level of sperm membrane lipid peroxidation when tested at physiological concentrations. At infectioninflammation concentrations, only IL-8 was able to produce a higher effect. When assayed in the presence of leucocytes, IL-8 and TNF-α showed a higher effect at infection-inflammation concentrations than at physiological concentrations. Finally, IL-8 showed a higher effect in the presence of leukocytes than in their absence at both physiological and infection-inflammation concentrations. TNF-α also showed a higher effect when assayed in the presence of leuko- cytes than in their absence, but only at infection-inflammation concentrations. There was no effect of IL-6 or IL-10 in any of the tested conditions. Conclusion： Several pro-inflammatory cytokines at physiological concentrations increase the level of lipid peroxidation of sperm membranes, which could be important for the sperm fecundation process. However, infection-inflammation concentrations of some cytokines, such as IL-8 and TNF-α, either alone or in the presence of leukocytes, could drive the lipid peroxidation of the spermatozoa plasma membrane to levels that can affect the sperm fertility capacity.展开更多
<abstract>Aim: To relate the presence of anti-Chlamydial trachomatis IgA in semen with sperm lipid membrane peroxidation and changes in seminal parameters. Methods: Semen samples of the male partners of 52 coupl...<abstract>Aim: To relate the presence of anti-Chlamydial trachomatis IgA in semen with sperm lipid membrane peroxidation and changes in seminal parameters. Methods: Semen samples of the male partners of 52 couples assessed for undiagnosed infertility were examined for the presence of IgA antibody against C. trachomatis. The level of sperm membrane lipid peroxidation was estimated by determining the malondialdehyde (MDA) formation. Results: Sperm membrane of infertile males with positive IgA antibodies against C. trachomatis showed a higher level of lipid peroxidation than that of infertile males with negative IgA antibody (P<0.05). There was a positive correlation (P< 0.01) between the level of C. trachomatis antibody and the magnitude of sperm membrane lipid peroxidation. All the other tested semen parameters were found to be similar in the two groups. Conclusion: The activation of immune system by C. trachomatis may promote lipid peroxidation of the sperm membrane. This could be the way by which C. trachomatis affects fertility.展开更多
It has long been recognized that plant invasions may alter carbon(C) and nitrogen(N) cycles, but the direction and magnitude of such alterations have been rarely quantified. In this study, we quantified the effects ca...It has long been recognized that plant invasions may alter carbon(C) and nitrogen(N) cycles, but the direction and magnitude of such alterations have been rarely quantified. In this study, we quantified the effects caused by the invasion of a noxious exotic plant,Kalanchoe daigremontiana(Crassulaceae), on C and N mineralization and enzymatic and microbial activities in the soil of a semiarid locality in Venezuela. We compared soil parameters associated with these processes(C and N mineralization time and the cumulative values, fluorescein diacetate hydrolytic activity, and activities of dehydrogenase, β-glucosidase, glucosaminidase, and urease) between invaded and adjacent non-invaded sites. In addition, correlations among these parameters and the soil physical-chemical properties were also examined to determine if a positive feedback exists between nutrient availability and K. daigremontiana invasion. Overall,our results showed that C mineralization and transformation of organic compounds to NH_4^+ were favored at sites colonized by K.daigremontiana. With this species, we found the highest cumulative amounts of NH_4^+-N and C and the lowest mineralization time.These results could be explained by higher activities of urease and glucosaminidase in soils under the influence of K. daigremontiana.In addition, higher amounts of organic matter and moisture content in invaded soils might favor C and N mineralization. In conclusion,invasion of Neotropical semiarid zones by K. daigremontiana may influence the chemical and biological properties of the soils covered by this species, increasing nutrient bioavailability, which, in time, can facilitate the invasion process.展开更多
文摘In recent years, hydrogels have been introduced as new materials suitable for applications in areas such as biomedical engineering, agriculture, etc. The rate and degree of hydrogel swelling are important parameters that control the diffusion of drugs or solvents inside a polymer network. Therefore, the description of the dynamic swelling process of the hydrogels is very important in applications that require precise control of the absorption of solvents inside the hydrogel structure. To date, most of the numerical models developed for describing the swelling process are based in the finite difference methods. Even though numerical models supported in finite differences can be easily implemented, their use is limited to samples with very simple shapes. In this paper, a new model based on the finite element method is proposed. The diffusion equation is solved in a time-deformable grid. An original procedure is proposed to numerically solve the non-linear algebraic equation system that permits computing a new grid for each time-step. Hydrogel samples of different shapes were prepared in order to conduct experimental tests to validate the numerical proposed model. Numerical results show that the new model is able to describe the mass and shape changes in the hydrogel samples in time. An application of the numerical model to determine the relation between diffusion coefficients and density in Poly-acrylamide samples allows verifying the versatility of the model.
文摘Aim： To investigate if interleukin-6 （IL-6）, interleukin-8 （IL-8）, interleukin- 10 （IL-10）, interferon-gamma （IFN-γ） or tumor necrosis factor-alpha （TNF-α） are able to stimulate the level of lipid peroxidation of sperm membranes, either alone or in the presence of leukocytes. Methods： Semen samples from normozoospermic donors were prepared by density gradient. The sperms were exposed to the indicated cytokines, at physiological and infection-inflammation concentrations, in the absence or presence of leukocytes. Lipid peroxidation of the sperm membranes was determined by measuring malondialdehyde （MDA） and 4-hydroxialkenals （HAE） formation. Results： TNF-α, IL-8 and IFN-γ increased the level of sperm membrane lipid peroxidation when tested at physiological concentrations. At infectioninflammation concentrations, only IL-8 was able to produce a higher effect. When assayed in the presence of leucocytes, IL-8 and TNF-α showed a higher effect at infection-inflammation concentrations than at physiological concentrations. Finally, IL-8 showed a higher effect in the presence of leukocytes than in their absence at both physiological and infection-inflammation concentrations. TNF-α also showed a higher effect when assayed in the presence of leuko- cytes than in their absence, but only at infection-inflammation concentrations. There was no effect of IL-6 or IL-10 in any of the tested conditions. Conclusion： Several pro-inflammatory cytokines at physiological concentrations increase the level of lipid peroxidation of sperm membranes, which could be important for the sperm fecundation process. However, infection-inflammation concentrations of some cytokines, such as IL-8 and TNF-α, either alone or in the presence of leukocytes, could drive the lipid peroxidation of the spermatozoa plasma membrane to levels that can affect the sperm fertility capacity.
文摘<abstract>Aim: To relate the presence of anti-Chlamydial trachomatis IgA in semen with sperm lipid membrane peroxidation and changes in seminal parameters. Methods: Semen samples of the male partners of 52 couples assessed for undiagnosed infertility were examined for the presence of IgA antibody against C. trachomatis. The level of sperm membrane lipid peroxidation was estimated by determining the malondialdehyde (MDA) formation. Results: Sperm membrane of infertile males with positive IgA antibodies against C. trachomatis showed a higher level of lipid peroxidation than that of infertile males with negative IgA antibody (P<0.05). There was a positive correlation (P< 0.01) between the level of C. trachomatis antibody and the magnitude of sperm membrane lipid peroxidation. All the other tested semen parameters were found to be similar in the two groups. Conclusion: The activation of immune system by C. trachomatis may promote lipid peroxidation of the sperm membrane. This could be the way by which C. trachomatis affects fertility.
基金supported by the Venezuelan Institute for Scientific Research to the first author
文摘It has long been recognized that plant invasions may alter carbon(C) and nitrogen(N) cycles, but the direction and magnitude of such alterations have been rarely quantified. In this study, we quantified the effects caused by the invasion of a noxious exotic plant,Kalanchoe daigremontiana(Crassulaceae), on C and N mineralization and enzymatic and microbial activities in the soil of a semiarid locality in Venezuela. We compared soil parameters associated with these processes(C and N mineralization time and the cumulative values, fluorescein diacetate hydrolytic activity, and activities of dehydrogenase, β-glucosidase, glucosaminidase, and urease) between invaded and adjacent non-invaded sites. In addition, correlations among these parameters and the soil physical-chemical properties were also examined to determine if a positive feedback exists between nutrient availability and K. daigremontiana invasion. Overall,our results showed that C mineralization and transformation of organic compounds to NH_4^+ were favored at sites colonized by K.daigremontiana. With this species, we found the highest cumulative amounts of NH_4^+-N and C and the lowest mineralization time.These results could be explained by higher activities of urease and glucosaminidase in soils under the influence of K. daigremontiana.In addition, higher amounts of organic matter and moisture content in invaded soils might favor C and N mineralization. In conclusion,invasion of Neotropical semiarid zones by K. daigremontiana may influence the chemical and biological properties of the soils covered by this species, increasing nutrient bioavailability, which, in time, can facilitate the invasion process.
