Biomedical subjects
Publications and source records attributed to Amir Arav.
This is the first report of successful cryopreservation and transplantation of an intact ovary in a large animal (sheep). Three of eight transplanted sheep had resumed hormonal cyclicity.
We developed new techniques to improve freezing and vitrification of sperm, oocytes and embryos. Our novel freezing technology is based on 'Multi-Thermal-Gradient' (MTG) freezing that is used for sperm. The freezing apparatus has the ability to control ice crystals propagation by changing thermal gradient or the liquid-ice interface velocity which optimizes ice crystals morphology during freezing of cells and tissue. Using this apparatus we were able to freeze bull, stallion, boar, ram, fowl and human sperm with normal post-thaw motility/pre-freezing motility of 70-100%. The vitrification method includes the cooling of nanoliter sample (the 'Minimum Drop Size' technique) in 'super-cooled' liquid nitrogen (-210 degrees C), which maximized cooling rate to the highest physically possible (24-130000 degrees C/min). Using this method we achieved very high survival of bovine oocytes and embryos. Vitrification of oocytes at the MII stage resulted with cleavage and blastocyst rate of 50 and 20%, respectively. The vitrification of in-vitro production (IVP) of bovine embryos allowed the production of a healthy calf after embryo-transfer carrying the name 'Zegugit' (in Hebrew: made from glass).
Fat supplementation in the diet influences reproductive performance of lactating ruminants. Changes in the fat supply alter fatty acid composition and this can affect physical properties of cell membranes. This study examined the effect of rumen bypass polyunsaturated fatty acid (PUFA) supplementation on oocyte quality, chilling sensitivity, and lipid phase transition in oocytes of the sheep. Ewes were fed a diet supplemented with calcium soaps of fish oil for 13 weeks. More follicles and oocytes were found in the ovaries of ewes supplemented with PUFA than in control ewes. The number of high-quality oocytes was higher in ewes fed PUFA than in control ewes (74.3 and 57.0%, P < 0.05, respectively). Evaluation of phospholipid fatty acid composition indicated that PUFA were present in small proportions in oocytes, and eicosapentaenoic acid and docosahexaenoic acid were absent. Supplementation with PUFA increased the proportion of long chain unsaturated fatty acid in the plasma and cumulus cells phospholipids by 7.4 and 12.7%, respectively (P < 0.05). Integrity of oocyte membranes following chilling (16 degrees C, 15 min) was improved by PUFA supplementation increasing from 62.5 to 90.0% (P < 0.05). Due to changes in the oocyte's fatty acid profile, physical properties of the membrane were changed and the midpoint temperature of lipid transition reduced by 11 degrees C. These results suggest that supplementation of rumen bypass PUFA to ruminant diets can change fatty acid composition of follicle components and influence parameters such as number and quality of oocytes and their chilling resistance.
OBJECTIVE: To report an ongoing twin pregnancy after transfer of embryos that were vitrified at the 2-pronuclei stage in a new vitrification solution. DESIGN: Case report. SETTING: A tertiary-care infertility clinic. PATIENT(S): A 26-year-old infertile woman in whom two previous IVF implantations failed. INTERVENTION(S): Vitrification of 2-pronuclei embryos, in vitro culture for 48 hours, and transfer into the uterus. MAIN OUTCOME MEASURE(S): Survival and cleavage after vitrification and achievement of clinical pregnancy. RESULT(S): Six zygotes were vitrified by using a three-step protocol (4% ethylene glycol for 3 minutes, 20% ethylene glycol for 1 minute, and 38% ethylene glycol and 1.2 M trehalose for 0.5 minute). After 2 months of storage in a double-straw system in liquid nitrogen, two zygotes were warmed and cryoprotectants were removed by using a four-step protocol (1 M, 0.5 M, 0.25 M, and 0.125 M of trehalose). Two embryos were transferred after 48 hours of in vitro culture, cleaving to 5 and 6 cells. The resulting twin pregnancy was confirmed by ultrasonography at the sixth week. CONCLUSION(S): Vitrification by using ethylene glycol and trehalose appears to be a safe, promising method for cryopreservation of human zygotes. Storage of vitrified zygotes in a double-straw system does not compromise their subsequent potential for survival and development.
The objective of the following paper is to describe a new technology for large volume and double freezing of semen in 12 mL test tubes. Semen from two different bulls was frozen with a new technique using 12 mL test tubes and was refrozen after thawing in mini straws. All freezing was done in a "Multi thermal gradient" (MTG) freezing apparatus, which moves the container at a constant velocity (V) through a thermal gradient (G) producing a controlled cooling rate B = (G) x (V). Each of the two bulls ejaculated were evaluated for post thaw motility in the lab and then in a field trial which was carried out in a split sample mode. We inseminated 105 cows after a double freezing/thawing cycle, and another 123 cows were inseminated with semen frozen in mini-straws and a conventional method. The results showed a 75 +/- 5% post thaw motility after freezing a 12 mL test tube and 50 +/- 5% after a second freezing/thawing in mini-straws, respectively. Controlled vapour freezing showed a 60 +/- 10% post thaw motility. The results of the field trial showed a pregnancy rate of 44% (47/105) for the double freezing group in comparison to 45.5% (56/123) for the controlled group. These results can be beneficial for large volume freezing, and therefore for bull semen cryobanking in a large volume which will be followed by second freezing in a regular insemination volume.