Utilização da lipoproteína de baixa densidade, em diferentes concentrações, em meio diluidor para criopreservação do sêmen ovino / Use of low density lipoprotein in different concentrations in diluent medium for cryopreservation of ovine semen

A utilização da gema de ovo dificulta a padronização de meios diluidores e apresenta riscos biológicos. Assim, este estudo avaliou diferentes concentrações da lipoproteína de baixa densidade (LDL), em substituição à gema de ovo, para a confecção de diluentes para criopreservação espermática em ovinos. Foram utilizados um diluidor controle (CTR= 20% de gema de ovo) e cinco tratamentos, substituindo-se a gema pelas diferentes proporções de LDL (T1=6%; T2=8%; T3=12%; T4=16%; T5=20%), todos à base de TRIS-glicerol. Para o estudo, utilizaram-se dois ejaculados, de seis reprodutores da raça Santa Inês. Sessenta dias após a criopreservação, as amostras foram descongeladas e avaliadas subjetivamente quanto à motilidade total (MT, %) e progressiva (MP, %), ao vigor (1-5) e à integridade funcional (choque hisposmótico com água destilada, %) e estrutural (corante supravital eosina, %) das membranas espermáticas. As avaliações de vigor e funcionalidade de membrana não diferiram (P>0,05) entre os grupos. Entretanto, os grupos T4 (P<0,01) e T5 (P<0,05) foram superiores ao CTR para os parâmetros MT, MP e integridade estrutural de membrana, o que confirma que as LDLs podem ser alternativas eficientes para substituição da gema de ovo em diluidores para criopreservação de sêmen ovino.(AU)

The use of egg yolk makes it difficult to standardize extenders and presents biological hazards. Thus, this study evaluated different concentrations of low-density lipoprotein (LDL) to replace yolk extenders for production of sperm for cryopreservation in ovine. A control extender was used (CTR= 20% yolk) and five treatments, replacing the yolk by different ratios of LDL (T1= 6%; T2= 8%, T3= 12%; T4= 16%; T5= 20%) all based on TRIS-glycerol. For the study, two ejaculates from six Santa Ines breeding were used. Sixty days after cryopreservation, the samples were thawed and evaluated for total motility (MT, %) and progressive motility (MP, %), vigor (1-5) and the functional integrity (hyposmotic shock with distilled water, %) and structural (supravital dye eosin, %) of the sperm membranes. The evaluations of strength and membrane functionality didn't differ (P> 0.05) between groups. However, T4 (P< 0.01) and T5 (P< 0.05) groups were superior to the CTR for the MT, MP, and membrane structural integrity parameters, which confirms that LDLs can be efficient alternatives for yolk replacement in extenders for cryopreservation of ovine semen.(AU)

Antibodies against electronegative LDL inhibit atherosclerosis in LDLr-/- mice

In order to determine the effect of antibodies against electronegative low-density lipoprotein LDL(-) on atherogenesis, five groups of LDL low receptor-deficient (LDLr-/-) mice (6 per group) were immunized with the following antibodies (100 µg each): mouse anti-LDL(-) monoclonal IgG2b, rabbit anti-LDL(-) polyclonal IgG or its Fab fragments and mouse irrelevant monoclonal IgG and non-immunized controls. Antibodies were administered intravenously one week before starting the hypercholesterolemic diet (1.25 percent cholesterol) and then every week for 21 days. The passive immunization with anti-LDL(-) monoclonal IgG2b, polyclonal antibody and its derived Fab significantly reduced the cross-sectional area of atherosclerotic lesions at the aortic root of LDLr-/- mice (28.8 ± 9.7, 67.3 ± 17.02, 56.9 ± 8.02 µm² (mean ± SD), respectively) compared to control (124.9 ± 13.2 µm²). Vascular cell adhesion molecule-1 protein expression, quantified by the KS300 image-analyzing software, on endothelium and the number of macrophages in the intima was also decreased in aortas of mice treated with anti-LDL(-) monoclonal antibody (3.5 ± 0.70 per field x 10) compared to controls (21.5 ± 3.5 per field x 10). Furthermore, immunization with the monoclonal antibody decreased the concentration of LDL(-) in blood plasma (immunized: 1.0 ± 1.4; control: 20.5 ± 3.5 RLU), the amount of cholesterol oxides in plasma (immunized: 4.7 ± 2.7; control: 15.0 ± 2.0 pg COx/mg cholesterol) and liver (immunized: 2.3 ± 1.5; control: 30.0 ± 26.0 pg COx/mg cholesterol), and the hepatic content of lipid hydroperoxides (immunized: 0.30 ± 0.020; control: 0.38 ± 0.15 ng/mg protein). In conclusion, antibodies against electronegative LDL administered intravenously may play a protective role in atherosclerosis.