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Molecular mechanisms of LDL-cholesterol induced endothelial dysfunction
Rojková, Tereza ; Petrezsélyová, Silvia (advisor) ; Šeda, Ondřej (referee)
Hypercholesterolemia, defined as elevated LDL-cholesterol levels in the blood, develops either as a result of genetic predispositions, unhealthy lifestyle, underlying diseases, or as a result of a combination of these factors. LDL-cholesterol is sometimes called "bad" cholesterol because its excess negatively affects the vessel`s innermost layer - endothelium, Endothelium is unique for its vasodilatory, vasoconstrictive, anti-inflammatory, and anti- coagulant function but also for its ability to control vascular permeability. In the case of hypercholesterolemia, cholesterol gradually accumulates in the subendothelial space and reduces levels of the main modulatory molecule of the endothelium - nitric oxide by several mechanisms. In endothelial dysfunction, oxidative stress increases, LDL-cholesterol is oxidized, endothelial cells are activated and produce proinflammatory cytokines and adhesive molecules. Endothelial dysfunction is considered the first stage of atherosclerosis, as monocytes enter the site of inflammation and differentiate into macrophages, which subsequently turn into foam cells by endocytosis of oxidized LDL-cholesterol. In this way, atherosclerotic plaques are formed, which not only narrow the blood vessels, but plaques can erupt, causing subsequent thrombosis, which can result...
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Factors influencing the bull sperm freezability
Dvorská, Tereza ; Rajmon, Radko (advisor) ; Marie, Marie (referee)
An egg yolk is a common component of diluents used as protectants of sperm cells during the process of cryopreservation. Its substitution by low density lipoproteins (LDL) has shown that it is the LDL that provides the egg yolk with its cryoprotective characteristics: it protects sperms against cold shock and other changes, thus helping to preserve their fertilization ability even after the freezing-thawing process. However, the sperm quality is affected by many other internal and external factors. Therefore, the aim of this study was to evaluate if the effect of the addition of LDL to the diluent of the ejaculate is significantly influenced by the following selected factors - the type of used diluent, the bull´s breed and its individuality and the date of the sampling.
Experimental insemination doses were repetitively (four times) obtained from a group of six bulls (three Holstein bulls and three Czech Fleckvieh bulls) at the Natural Hradišťko insemination service s.r.o. The samples of semen were diluted with two types of non-egg diluents containing soybean lecithin extracts (AndoMed and BioXCell). To each of these diluents, LDL at 4, 6, and 8% concentration was added; a non-LDL diluent served as a check. All the insemination doses were frozen by a standard procedure and then stored in liquid nitrogen. The CASA system (Computer Assisted Sperm Analysis) was selected for the evaluation of the sperm motility. Immediately after thawing and then after two hours of incubation in water bath (37 °C), the values of kinematic parameters were obtained from the samples - the total percentage of motile sperm and the percentage of progressively motile sperm. These data were then statistically processed; based on the outputs, VAP, VCL, ALH and the percentage of progressively motile sperm (PMOT) were chosen as representative kinematic parameters.
The values of the parameters were higher in almost all evaluated samples diluted with BioXCell, compared to those diluted with AndroMed. Even though we demonstrated the existence of a high variability of results depending on the time of incubation, bull breed, the individuality of the bull and the date of the sampling, it could be said that the best concentration of added LDL is 6 % for BioXCell and 8 % for AndroMed.
It would be useful to perform more experiments evaluating the effect of adding LDL to non-egg diluents on the quality of the thawed sperm. In these experiments, more sperm quality parameters should be examined and factors influencing the variability of results demonstrated in this work should be taken into consideration.
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