In rodents, chimaeric blastocysts produced by combining embryonic cells of two different species have been used in investigations of cell lineage and interaction during development (Mus musculus-Rattus norvegicus, M. musculus-Clethrionomys glareolus, M. musculus-Mus caroli). However, interspecific chimaerism also offers new approaches to the study of reproductive incompatibilities between species and may even allow such incompatibilities to be neutralized, thus improving the chances of successful hybridization and interspecific embryo transplantation. We report here the production of sheep-goat chimaeras by embryo manipulation and the use of interspecific chimaerism to allow successful interspecific embryo transplantation in sheep and goats.

1. Uptake rates for 23 amino acids were measured for both normal (high-GSH) and GSH-deficient (low-GSH) erythrocytes from Finnish Landrace sheep. 2. Compared with high-GSH cells, low-GSH cells had a markedly diminished permeability to D-alanine, L-alanine, alpha-amino-n-butyrate, valine, cysteine, serine, threonine, asparagine, lysine and ornithine. Smaller differences were observed for glycine and proline, whereas uptake of the other amino acids was not significantly different in the two cell types.

SUMMARYSix interspecific hybridomas (heterohybridomas) secreting bovine monoclonal antibodies (MAbs) against respiratory syncytial (RS) virus were produced. Four of the heterohybridomas were formed using the mouse myeloma cell line NS1 as the fusion partner, one using NS0, and the remaining heterohybridoma was formed using a bovine × murine hybridoma as the fusion partner. Five heterohybridomas secreted bovine IgG1 and one secreted IgG2. All six MAbs recognized human subtype A and B viruses as well as bovine RS virus. They were specific for the fusion glycoprotein and reacted with a 140K dimer and a 70K monomer in a Western blot of native antigen; three also bound to the 46K F~ component and its 22K cleavage product in a blot of reduced antigen. Two of these MAbs neutralized RS virus infectivity, inhibited virusinduced fusion, lysed RS virus-infected cells in the presence of complement and protected mice against RS virus challenge.

Hybridomas made by fusing NSO (subline NSI Ag 4-1) mouse myeloma cells with lymph node cells from a calf immunized with sheep red blood cells failed to maintain antibody secretion in culture. However, when two of these hybridomas were selected in 8-azaguanine and then re-fused with immunized calf lymph node cells, several lines were obtained that secreted bovine Ig. One cloned line, producing bovine IgG1 (strongly lytic in the presence of rabbit complement and presumed to be an anti-Forssman) was maintained in culture for five months. Cytogenetic studies confirmed that the mouse/calf hybridomas lost bovine chromosomes as they proliferated, but that re-fusion increased the bovine complement from a mean of 5 (2 n) to 11 (2 n) bovine chromosomes per cell. It is proposed that the selected hybridoma lines may be suitable fusion partners for the production of further monoclonal bovine antibodies.