The cryopreservation of mammalian embryos has become an integral part of method s to control animal reproduction. Numerous vitrification solutions have been formulated with ethylene glycol in combination with macromolecules, sugars and other cryoprotective agents. These indicate that a study of ethylene glycol as a cryoprotectant of choice in vitrification studies would be promising. To understand the cryobiology of ethylene glycol, several factors have to be studied. These are : cryoprotectant toxicity, osmotic stress and temperature at exposure. Understanding these factors could lead to the formulation of vitrification protocols that would lead to higher viability rates after cooling. First, ethylene glycol must be used as the sole cryoprotectant in a solution without macromolecules and sugars. Second, partial dehydration and permeation prior to cooling to subzero temperatures must be studied to achieve accurate exposure and a one-step dilution method. Third, the toxic effects of ethylene glycol must be overcome without sacrificing its vitrification properties by combining step-wise exposure at appropriate temperatures, low concentration and decreased volume. Fourth, the long-term effects of ethylene glycol on exposed or vitrified embryos must be determined. Lastly, the influence of culture on the viability of vitrified embryos must be studied to improve viability rates after warming

Ovulated mouse oocytes denuded of their cumulus cells, were vitrified in a solution containing 7 M ethylene glycol as the sole cryoprotectant using one or two steps of exposure before vitrification and were diluted in 1 M sucrose solution in 5 or 10 min after warming. The results proved that the viability of oocytes are detrimentally affected by exposure to the vitrification solution even without vitrification. At 5 min dilution time, the two-step exposure was superior to the one-step in terms of the post-warming recovery rate of vitrified oocytes with normal morphology and their subsequent development to the blastocyst stage (p0.001) after fertilization in vitro. At 10 min dilution time, no significant difference between one or two-step exposure was found. The effect of the addition of 0.5 M sucrose to the vitrification solution was also determined and did not result in a significant improvement in the viability of oocytes vitrified in one-step and diluted for 10 min. In conclusion, the results in this study indicate that oocytes can be vitrified with 7 M ethylene glycol as the sole cryoprotectant in the vitrification solution, and that the recovery of normal oocytes after one-step exposure in the vitrification solution can be improved by 10 min dilution time. However, the improvement in the recovery rate of oocytes with normal morphology and their subsequent developmental in vitro was not improved by the addition of 0.5 M sucrose to the vitrification solution

Forty-seven Newcastle disease virus (NDV) strains isolated from fecal samples of waterfowls in Alaska and Siberia from 1991 to 1996 were analyzed for their virulence. None of the viruses formed plaques on MDBK cells in the absence of trypsin. Of these, 29 strains showed virulent character by the mean death time with the minimum lethal dose in chicken embryos comparable to velogenic NDV strains. Of the 29 strains, 11 were sequenced for their fusion protein (F) gene. The results showed that 5 of them contained a pair of dibasic amino acids at the cleavage site of the F, which is of a virulent type. The present results suggest that potentially virulent strains of NDV are maintained in migratory waterfowl populations in nature, and that some of those may be transmitted to domestic poultry and acquire pathogenicity during passages in chicken population

The purpose of this study was to evaluate the relationship between the results of laboratory examinations and ultrasonographic findings, especially portal vein hemodynamics in experimentally bile duct ligated dogs. Biliary obstruction was accomplished by surgically occluding the common bile duct in five dogs. All the dogs became visibly jaundiced within 24 hours after surgery. The total protein and albumin/globulin ratio showed a gradual decrease throughout the examination period, while blood urea nitrogen reached its peak in the 6th week and decreased to pre ligation values by the 10th week. Similar trends were noted in the alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, and direct and total bilirubin. Total cholesterol and fasting serum bile acid levels rapidly increased after surgery to peak values between the 2nd and 4th week, and then gradually decreased, but still remained high throughout the experiment period. The portal flow volume and velocity significantly (p0.05) decreased while only a slight increase was noted in the congestion index after bile duct ligation. The cross sectional area of the portal vein changed insignificantly. Bile duct and gallbladder distention was evident within the 1st week after ligation but there was little change in the echogenicity of the liver parenchyma. The results of this study suggest that the determination of Doppler ultrasound parameters of hepatic hemodynamics, especially the portal vein flow indices, may contribute to a better noninvasive assessment of the canine patient with biliary obstructive disease

A study was made to determine if mouse zygotes can be effectively vitrified in 7 M ethylene glycol in modified Dulbecco's phosphate buffered saline (PB1) and to find out if the development of vitrified-warmed zygotes in vitro can be improved by renewing the culture medium. The results showed that without medium change, vitrification reduced the development of zygotes to the expanded blastocyst stage (p0.01). With medium change, the development rate of vitrified-warmed zygotes exposed in 7 M ethylene glycol for 1 or 2 min was similar to that of unvitrified zygotes. However, prolonged exposure (5 min) markedly reduced the development rates of vitrified-warmed zygotes to the expanded blastocyst stage (p0.05). When the zygotes were vitrified in 7 M ethylene glycol and diluted at 18 degree C to 22 degree C, a slower efflux of ethylene glycol from the cell might have occurred, leading to a toxic effect of ethylene glycol in culture. The development rates of vitrified embryos cultured with medium change at 24 hr did not significantly differ from the untreated control (89.0% vs 96.5%). In conclusion, this study showed that mouse zygotes can be vitrified in 7 M ethylene glycol in PB1 and that changing the culture medium can improve the in vitro development rates of vitrified-warmed zygotes to the expanded blastocyst stage

This paper reviews the alkaline phosphatases in canine serum, the analytical methods used for qualitative and/or quantitative detection of these isoenzymes, and the diagnostic significancy of each of these isoenzymes. The paper further describes some of the latest advances of our knowledge of the canine alkaline phosphatases and possible areas of future research

The in vitro differentiative potential of mouse parthenogenetic (PG) embryonic stem (PGES) cells were investigated in the formation of embryoid bodies (EBs). EBs derived from PGES cells retarded in growth and showed restricted differentiation compared to their fertilized counterpart. In chimeric EBs from the aggregation of PGES and fertilized ES cells, morphological examination revealed that PGES cells were reduced in their population and distributed in endodermal layer as culture periods proceeded. These findings were comparable to those in aggregation chimeras of fertilized and PG embryos, and suggest that the differentiation of PGES cells in vitro is restricted in the formation of EBs