Effects of Cryopreservation on the Quality and Ultrastructure of Tibetan Mastiff Sperm

[Objective] This study aimed to investigate the effects of cryopreservation on the quality and ultrastructure of Tibetan Mastiff sperm. [Method] The effects of cryopreservation on the quality of Tibetan Mastiff sperm were evaluated via motility, membrane integrity rate and acrosome intact rate. On that basis, the effects of cryopreservation on ultrastructure of sperm were observed under SEM and TEM. [Result] In Experiment 1, EG gave the best results not only in post-thaw motility rate （36.3%）, but also in low membrane integrity rate （38.0%） and acrosome intact rate （42.0% ）, but there was no significant difference between EG group and Glycerol group （P0.05）. In Experiment 2, the 5 cm freezing height obtained the best freezing-thawing results, but there was no significant difference between 2 and 5 cm height （P 0.05）, besides in acrosome intact rate. In Experiment 3, SDS and Vc added separately or together into extenders could improve freezing-thawing results, but there was not obvious difference between SDS group and Vc group （P0.05）, besides the lower motility of Vc group （P0.05）. Addition of SDS and Vc obtained the best results in post-thaw motility rate （44.1%）, and also in membrane integrity rate （48.0%） and acrosome intact rate （48.2%）. The ultrastructure of frozen-thawed sperm was also evaluated under SEM and TEM, results showed that cryopreservation caused various degrees of damage to Tibetan Mastiff sperm, more serious damages were observed in the acrosome such as swelling, vesiculation and even disappearance. [Conclusion] This study confirms that EG, horizontal height of 0.25 ml straw above LN 2 surface and additives SDS and Vc together can improve freezing effect. However, cryopreservation has certain damage to ultrastructure of sperm.

Effects of Low Temperature and Ultra-low Temperature on Pollen Viability of Tomato(Lycopersicon esculentum Mill.)

The pollen of two tomato varieties, Ryau961721 and Ryau9327D, was adopted in our research. The two tomato varieties were bred by College of Land- scape and Horticulture, Yunnan Agricultural University. The collected pollen was stored in low-temperature （4 ℃） and ultra-low-temperature （-196 ℃） circumstances. Then it was inoculated to the medium and cultured at 28 ℃ in thermostat incubator. The pollen viability was determined by electron microscope. The results showed that compared to that of pollen stored in control （25 ℃） circumstance, the viability of pollen stored in low-temperature （4 ℃） and ultra-low-temperature （-196 ℃） circum- stances for 1 -3 d did not change significantly. In addition, pollen viability trended to decrease with the increase of freeze-thaw cycle and storage time. The pollen lost basically the viability by the 7th d in the storage.

Cryopreservation of Veliger Larvae of Trumpet Shell, Charonia sauliae: an Essential Preparation to Artificial Propagation

Trumpet shell, Charonia sauliae, is an endangered and valuable species, but its artificial propagation protocol has not been successfully established. To estimate the possibility of cryopreservation for larvae of C. sauliae, which is a potential preparation for its artificial reproduction and further research, in this study a protocoi for the cryopreservation of veliger larvae of trumpet shell was optimized. Through a two-step cryopreservation procedure, four kinds of cryoprotectants （ethylene glycol, 1, 2-propanediol, dimethyl sulfoxide and glycerol） were employed at three concentrations （1.0, 1.5 and 2.0molL^-1） respectively and survival rates of larvae were determined after a storage of lh. The larvae frozen with these four cryoprotectants after 1 h storage were cultured, and then survival rates were determined at 24, 72 and 120 h after thawing. Dimethyl sulfoxide at a concentration of 1.5 molL^-1 showed the best protective effect in all experiments （p〈0.05）. And survival rates of larvae frozen with dimethyl sulfoxide were determined after 1, 7 and 15 d of storage. The survival rates of larvae frozen with 1.5 molL^-1 dimethyl sulfoxide after 1 h, 1 d, 7 d and 15 d of storage were 80.77% ±7.51%, 80.34%±11.28%, 83.10%±9.14% and 77.23%±6.22% respectively. No significant differences in survival rates of larvae frozen with dimethyl sulfoxide were observed after various storage periods （p〉0.05）.

Protection of ultrastructure in chilling-stressed banana leaves by salicylic acid

Objective： Chilling tolerance of salicylic acid （SA） in banana seedlings （Musa acuminata cv., Williams 8818） was investigated by changes in ultrastructure in this study. Methods： Light and electron microscope observation. Results： Pretreatment with 0.5 mmol/L SA under normal growth conditions （30/22 ℃） by foliar spray and root irrigation resulted in many changes in ultrastructure of banana cells, such as cells separation from palisade parenchymas, the appearance of crevices in cell walls, the swelling of grana and stromal thylakoids, and a reduction in the number of starch granules. These results implied that SA treatment at 30/22 ℃ could be a type of stress. During 3 d of exposure to 7 ℃ chilling stress under low light, however, cell ultrastructure of SA-pretreated banana seedlings showed less deterioration than those of control seedlings （distilled water-pretreated）. Conclusion： SA could provide some protection for cell structure of chilling-stressed banana seedling.

我国家畜主要保种方法及应用现状

近几十年来,各个养殖场引进了大量外国品种与我国优良地方品种进行广泛杂交,导致地方品种优良基因的流失。为了更好保存我国畜禽的优良基因,在生产中采取了活体保种、超低温保种等方法。笔者就应用比较多的几种方法进行了介绍。