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Potentially virulent newcastle disease viruses are maintained in migratory waterfowl populations
1998
Takakuwa, H. (Hokkaido Univ., Sapporo (Japan)) | Ito, T. | Takada, A. | Okazaki, K. | Kida, H.
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
Mostrar más [+] Menos [-]Current status of vitrification of embryos and oocytes in domestic animals: Ethylene glycol as an emerging cryoprotectant of choice
1998
Bautista, J.A.N. (Hokkaido Univ., Sapporo (Japan)) | Kanagawa, H.
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
Mostrar más [+] Menos [-]Differentiative potential of a mouse parthenogenetic embryonic stem cell line revealed by embryoid body formation in vitro
1998
Park, J.I. (Hokkaido Univ., Sapporo (Japan)) | Yoshida, I. | Tada, T. | Takagi, N. | Takahashi, Y. | Kanagawa, H.
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
Mostrar más [+] Menos [-]Trisomy 8 does not affect differentiative potential in a murine parthenogenetic embryonic stem cell line
1998
Park, J.I. (Hokkaido Univ., Sapporo (Japan)) | Yoshida, I. | Tada, T. | Takagi, N. | Takahashi, Y. | Kanagawa, H.
Murine parthenogenetic embryonic stem (ES) cell lines expressing lac zeta reporter gene were isolated after co-transfection with lac zeta reporter gene (pENL) and neoR gene (pSTneo) to TMA-48P cell line of 129/Sv origin. Karyotype analyses showed that all of four transfected cell lines examined contained 41 chromosomes with trisomy 8. Bacterial neoR transgene required for G418 selection were integrated into several chromosomes including chromosome 8. Histological studies of teratomas formed in syngenic mice and embryoid bodies grown in vitro showed that the differentiative potential remained almost identical in chromosomally normal parental cell line and its derivative cell lines trisomic for chromosome 8
Mostrar más [+] Menos [-]In vitro viability of mouse oocytes vitrified in an ethylene glycol-based solution
1998
Bautista, J.A.N. (Hokkaido Univ., Sapporo (Japan)) | Pena, E.C.D. | Katagiri, S. | Takahashi, Y. | Kanagawa, H.
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
Mostrar más [+] Menos [-]Three new species of ciliated Protozoa from the hindgut of both white and black wild African rhinoceroses
1998
Van Hoven, W. | Gilchrist, F.M.C. (Pretoria Univ. (South Africa). Centre for Wildlife Management) | Liebenberg, H. | Van der Merwe, C.F.
Ixodid tick infestations of wild birds and mammals on a game ranch in Central Province, Zambia
1998
Zieger, U. (Pretoria Univ. (South Africa). Centre for Wildlife Management) | Horak, I.G. | Cauldwell, A.E. | Uys, A.C.
Isolation and characterization of a Babesia species from Rhipicephalus evertsi evertsi ticks picked off a sable antelope (Hippotragus niger) which died of acute babesiosis
1998
Hove, T. (Zimbabwean Univ., Harare (Zimbabwe). Dept. of Paraclinical Veterinary Studies) | Sithole, N. | Munodzana, D. | Masaka, S.
Comparison of immune responses of two Salmonella gallinarum strains viewed as possible vaccines for fowl typhoid in Kenya
1998
Bebora, L.C. | Nyaga, P.N. | Kimoro, C.O. (Nairobi Univ., Kabete (Kenya). Dept. of Veterinary Pathology and Microbiology)
Distribution of endocrine cells in the gut of the impala (Aepyceros melampus)
1998
Schoeman, J.H. (Pretoria Technikon (South Africa). Dept. of Biological Sciences) | De Vos, V. | Van Aswegen, G.