Differences in resistance against osmotic challenge among C57BL/6, DBA/2 and their hybrid mice metaphase II (MII) stage oocytes

SummaryOocytes of B6D2F1 (BDF1) mice are often used as recipients for intracytoplasmic sperm injection because of their cell membrane resistance against capillary penetration. It is assumed that oocytes of BDF1 mice have superior traits because of their hybrid vigour. However, the mechanisms of hybrid vigour are unclear. In this study, we focused on the membrane resistance of MII stage oocytes against changes in extracellular osmotic pressure. As a result, MII stage oocytes of inbred C57BL/6 and DBA/2 mice showed high tolerance in either a hypertonic or a hypotonic environment. Conversely, MII stage oocytes of hybrid BDF1 and D2B6F1 mice showed high tolerance in both hypertonic and hypotonic environments. Therefore, it is considered that MII stage oocytes of hybrid mice have superior traits than those of inbred mice. Our findings demonstrated that the hybrid vigour exists in the form of resistance to extracellular osmotic environment in hybrid MII stage oocytes.

Antimicrobial Activity of Chitosan against Campylobacter spp. and Other Microorganisms and Its Mechanism of Action

The antimicrobial activities of three chitosans with different molecular masses against six gram-negative and three gram-positive bacteria were examined. Campylobacter spp. were the microorganisms most sensitive to chitosan, regardless of their molecular mass. The MIC of chitosan for Campylobacter ranged from 0.005 to 0.05%, demonstrating the global sensitivity of campylobacters to chitosan. Chitosan caused a loss in the membrane integrity of Campylobacter, measured as an increase in cell fluorescence due to the uptake of propidium iodide, a dye that is normally excluded from cells with intact membranes. As cells entered the stationary phase, there was a change in cell membrane resistance toward a loss of integrity caused by chitosan. This study demonstrates that chitosans could be a promising antimicrobial to control Campylobacter.

Haematological, Blood and Rumen Chemistry Changes in Lambs Following Supplementation with Se-yeast

The effects of feed supplementation with organic form of selenium (Se) on ruminal enzyme activities (ALT, AST, GGT, ALP and GDH), blood enzyme activity (GPx), serum enzyme activities (LDH, CK) and haematological indicators were examined in lambs. Ten animals were divided into two groups and fed experimental diets for 3 months. The first group received a basic diet (BD) providing a daily intake 50.6 μg of Se only. The diet for the second group consisted of BD supplemented with selenium 0.3 mg kg-1 DM in the form of Se-enriched yeast and giving a total daily intake 278 μg of Se per animal. Lambs of the second group which were fed additional Se had increased concentrations of Se in plasma (P < 0.001), greater activity of blood glutathione peroxidase (GPx) (P < 0.001) and lower activity of creatine kinase (CK) (P < 0.05) in serum. The activity of alkaline phosphatase (ALP) (P < 0.001) and glutamate dehydrogenase (GDH) (P < 0.001) in ruminal fluid were found to be significantly higher in Se-yeast group of lamb compared with the group given BD with no differences for Se concentration in ruminal fluid and ALT, AST and GGT activities. Total erythrocyte count and osmotic resistance of red blood cells were significantly higher (P < 0.01) in selenium-supplemented animals. White blood cell count was increased in lambs given BD (P < 0.05). It was concluded that Se supplementation can influence ruminal enzyme activities and cell membrane resistance of lambs.

Electrical Resistance and Volume Flow in Glass Microelectrodes

The electrical resistance and the flow of solution in glass microelectrodes has been studied as function of the concentration of internal and external solution (KCl, 3–10−5 M), and as a function of pressure between the inside and outside solutions. The study demonstrates the usefulness of using microelectrodes for measuring cell membrane resistance and also the dangers in using them as microejectors because of anomalous flow effects. Electrokinetic effects and tip potentials are briefly described; they offer a means of investigating the surface condition of the glass wall inside the tip of the electrode and its variation with the outside solution.