Improvement of short straws for sperm cryopreservation: installing an air-permeable filter facilitates handling.

Saving space for sperm cryopreservation would aid mouse genetics research. We previously developed the ST (sperm freezing in ShorT STraw to reduce STorage space) method for cryopreserving mouse sperm in a smaller storage space than conventional methods. However, our ST method has two drawbacks: difficulties during freeze-thaw procedures and the potential risk of sperm loss during storage. Here, we refine ST, terming the new method improved ST (iST). In iST, the straw has an air-permeable filter and the straw container (2-ml cryotube) is endowed with air vents. As in our ST method, iST frozen-thawed sperm showed good performance upon in vitro fertilization. Moreover, up to nine straws can be stored in one cryotube, occupying less storage space than conventional methods. This method provides an easy and space-saving cryopreservation method for mouse sperm, and thus will be valuable for mouse genetics researchers.

Freezing sperm in short straws reduces storage space and allows transport in dry ice.

Efficient cryopreservation and transportation of mouse sperm are among the most desirable strategies for current and future research on mouse genetics. However, the current method for sperm cryopreservation uses an 11-cm plastic straw, which is a bulky and fragile container. Developing an alternative to overcome the limitations associated with this method would accelerate biomedical research. Here, we developed the ST (sperm-freezing in ShorT STraw to reduce STorage space) method for cryopreserving mouse sperm in short 3.8-cm plastic straws. Up to nine short straws can be stored in a cryotube, reducing storage space. We further show that sperm frozen by the ST method can be transported in liquid nitrogen or dry ice without any detrimental effects on subsequent fertilization and the birth rate. Our findings suggest that this sperm-freezing method is beneficial not only for individual laboratories but also for large-scale mutagenesis/knockout and phenotyping programs.

Littermate influence on infant growth in mice: comparison of SJL/J and ICR as cotransferred carrier embryos.

In mice, a minimum number of healthy embryos is required to trigger and maintain pregnancy. Therefore, when recovering mouse embryos from a limited litter, one useful technique is to transfer carrier ICR embryos along with the embryos of interest, a technique referred to as cotransfer. In this study, we examined suitable mouse strains for cotransfer with C57BL/6J (B6) embryos in regards to the maintenance of pregnancy, number of pups born, intrauterine growth, and postnatal growth. Because the coat color of B6 is black, we compared two white coat-colored strains, SJL/J and ICR. Cotransfer of SJL/J and ICR embryos had similar effects on maintenance of pregnancy, number of pups born, and intrauterine growth. However, the postnatal growth of B6 mouse pups cotransferred and grown with SJL/J pups was better than for B6 mouse pups cotransferred and grown with ICR pups, suggesting competition among littermates. These results demonstrate that cotransfer of SJL/J embryos will be useful not only as carrier embryos with B6-background embryos but also as a model system to examine littermate competition.

Oxygen inhalation using an oxygen concentrator in a low-pressure environment outside of a hospital.

Supplementation with oxygen is fundamental in rescue and emergency medicine. However, transportation of oxygen cylinders or a rigid hyperbaric chamber requires large work forces. Also, oxygen in a cylinder may be completely consumed during a rescue action. The oxygen concentrators, which enrich the oxygen percentage of ambient air, may free rescuers from carrying heavy oxygen cylinders. In the present study, 2 types of oxygen concentrators were tested in a mountain hut located at an altitude of 3776 m. Oxygen concentration of the generated gas was 28.6% +/- 0.8% with the first machine, which was powered by an internal battery. Arterial oxygen saturation of the volunteers inhaling through the machine increased from the original 79% +/- 6% to 82% +/- 6%. When the machine was used with a semi-closed circuit, the value increased further to 90% +/- 3%. The second concentrator, which was powered by an external electric generator, outputted 90% +/- 2% oxygen. Arterial oxygen saturation of the volunteers increased to 95% +/- 1%. It is concluded that both types of oxygen concentrators were efficient at high altitude.