Development and Long-Term Follow-Up of an Experimental Model of Myocardial Infarction in Rabbits.

A chronic model of acute myocardial infarction was developed to study the mechanisms involved in adverse postinfarction ventricular remodeling. In an acute myocardial infarction (AMI), the left circumflex coronary artery of New Zealand White rabbits (n = 9) was occluded by ligature for 1 h, followed by reperfusion. A specific care protocol was applied before, during, and after the intervention, and the results were compared with those of a sham operated group (n = 7). After 5 weeks, programmed stimulation and high-resolution mapping were performed on isolated and perfused hearts using the Langendorff technique. The infarct size determined by 2,3,5-triphenyltetrazolium chloride inside of the area at risk (thioflavin-S) was then determined. The area at risk was similar in both groups (54.33% (experimental infarct group) vs. 58.59% (sham group), ns). The infarct size was 73.16% as a percentage of the risk area. The experimental infarct group had a higher inducibility of ventricular arrhythmias (100% vs. 43% in the sham group, p = 0.009). A reproducible chronic experimental model of myocardial infarction is presented in which the extent and characteristics of the lesions enable the study of the vulnerability to develop ventricular arrhythmias because of the remodeling process that occurs during cardiac tissue repair.

Egg yolk and glycerol requirements for freezing boar spermatozoa treated with methyl ß-cyclodextrin or cholesterol-loaded cyclodextrin.

Egg yolk (EY) and glycerol are common constituents of extenders used for sperm cryopreservation. It has been demonstrated that using cholesterol-loaded cyclodextrins (CLC) improves sperm cryosurvival in several species. However, standard freezing extenders might not be the most appropriate for CLC-treated sperm. This study evaluated the EY and glycerol requirements for freezing CLC-treated boar spermatozoa. Semen samples from 34 ejaculates coming from 4 boars were used. Each ejaculate was split into three aliquots: one was used untreated (control), and the other two were treated with 1 mg of CLC or methyl-ß-cyclodextrin/120 × 10(6) sperm for 15 min at 22 C prior to cryopreservation. Our results indicated that reducing the concentration of EY was detrimental for sperm viability after thawing (31.57 ± 2 vs. 19.89% ± 2 for 20 and 10% EY, respectively; P <0.05), even in semen treated with CLC. On the other hand, it was observed that the traditional concentration of glycerol (3%) was not the appropriate for freezing CLC-treated sperm (61.10 ± 3 vs. 47.87% ± 3 viable sperm for control and CLC-treated sperm, respectively; P <0.05). Thus, CLC-treated sperm showed a higher tolerance to high glycerol concentrations (5%) in terms of sperm viability (59.19% ± 3) than non-treated sperm (45.58% ± 3; P<0.05). Therefore, it could be necessary to modify the freezing extenders for CLC-treated sperm. Nevertheless, additional studies will be needed to evaluate alternative cryoprotectants and to determine the effect of high glycerol concentrations on sperm functionality.

In vivo fertilising ability of frozen-thawed boar sperm treated with cholesterol-loaded cyclodextrins prior to cryopreservation.

The use of frozen-thawed (FT) sperm for the artificial insemination of pigs is rare. Treating boar sperm with cholesterol-loaded cyclodextrins (CLC) prior to cryopreservation enhances the penetration of immature oocytes in vitro, and this phenomenon has been positively correlated with in vivo fertilisation ability in pigs. The objective of this study was to compare the in vivo fertilising ability of boar sperm treated with 0 (control) or 1mg CLC/120×10(6) sperm (CLC) prior to freezing. The fertilising ability of the FT sperm was compared in hormonally treated (equine/human chorionic gonadotropin hormones; eCG/hCG) weaned sows inseminated once (cervical insemination) at the following fixed-times after hCG administration: 37h (experiment 1) or 30h (experiment 2). In experiment 1, both treatments exhibited similar fertility rates of 67.7 and 55.9% for the control and CLC, respectively (P>0.05); however, the CLC group had a smaller litter size (11.3±0.9) than the control group (13.6±0.8) (P<0.05). In experiment 2, the pregnancy and farrowing rates were 65.2 and 66.7% for the control and CLC groups, respectively, and the litter size was 12.9±1 and 11.3±1 for the control and CLC groups, respectively, which were similar (P>0.05) for both treatments. These results indicate that the timing of insemination developed for the FT control sperm may not be suitable for CLC-treated sperm and that CLC-treated sperm may benefit from a shorter time interval between the hCG treatment and insemination. Moreover, acceptable results can be obtained with FT boar sperm with a single artificial insemination performed 30h after hCG treatment, which is the time interval recommended for fresh sperm.

Treating boar sperm with cholesterol-loaded cyclodextrins widens the sperm osmotic tolerance limits and enhances the in vitro sperm fertilising ability.

Treating sperm with cholesterol-loaded cyclodextrins (CLC) improves the cryosurvival of the sperm of different cold-shock sensitive species. However, the response of boar sperm to this treatment is not fully understood. The aim of this study was to determine how CLC and methyl-ß-cyclodextrin (MßCD, not loaded with cholesterol) affect the parameters for boar sperm functionality, including sperm osmotic resistance, and the ability of the sperm to capacitate and to penetrate the sow's immature oocytes in vitro. Samples treated with CLC or MßCD prior to freezing exhibited similar percentages of motile sperm, live sperm and sperm with intact acrosomes as the control samples (P>0.05). In addition, these treatments did not alter the response of the boar sperm to capacitating conditions. However, when compared to the controls and the MßCD-treated samples, the CLC-treated sperm maintained greater percentages of motile sperm and live sperm in a wide range of osmotic solutions including hypo- (50, 75 and 150 mOsm/kg) and hyper-osmotic (600, 800 mOsm/kg) conditions (P<0.05). In addition, the CLC-treated sperm exhibited greater oocyte penetration ability than the control and the MßCD-treated sperm (P<0.0001). In conclusion, the pre-freezing treatment of boar sperm with CLC does not alter the ability of the sperm to respond to capacitating conditions. Despite not increasing the cryosurvival of the sperm, this treatment widens the sperm osmotic tolerance limits and enhances the in vitro sperm fertilising ability.