Evaluation of orf virus (ORFV) isolation in continuous lamb testis cells (OA3.Ts) and development of a co-culture method with infected cells to increase infectivity

Continuous foetal lamb testis cells OA3.Ts was used to compare the isolation of a vaccine orf virus (ORFV) strain that had been adapted to primary lamb testes cells, with scab derived wild-type/field ORFV isolates. The wild type virus showed an accelerated and exaggerated cyto-pathic effect (CPE) than the vaccine virus as has been demonstrated by immunofluorescent detection of viral antigen using ORFV monoclonal antibodies. ORFV could be successfully isolated in OA3.Ts foetal lamb testes cells and can be used for direct isolation of the virus from clinical samples.Two different methods of cell culture infection were also compared during sub-culture, one using infected supernatant as the inoculum and the other using infected cells as a modified method for infecting healthy culture cells. The present study also indicates that a higher infection can probably be achieved with inoculating infected cells together with healthy ones as a co-culture method during propagation of ORFV. This has been revealed as visibly pronounced CPE and presence of larger and multiple aggregates of cytoplasmic inclusions than cells infected with infected supernatant alone.

Desmosome-like structure between lymphocytes of developing thymus of foetal lamb

The foetal thymuses of sheep from 40 days to full term gestation were studied. The earliest thymuses that were studied were obtained from foetuses of 40 days gestation. At this stage of development the thymic tissue was formed of cords of condensed epithelial cells. Lymphopoiesis occurred in these thymuses between the thymus of 40 day old foetus and those of 42 days was striking and indicated that the onset of lymphopoiesis in the foetal sheep occurred abruptly. From 42 days onwards there was a rapid increase in the size of the thymus and in the extent of the lymphopoiesis (Fig. 1). By 45 days gestation the distribution of the lymph cells in the thymus had begun to define the cortex and medulla, and the organ was plainly lymphoid.Apart from lymphoid and epithelial cells, macrophages, erythroblasts and granulocytic myelocytes were sometimes found in the thymus (Fig. 2). Many of die lymphocytes within the cortex were closely attached to one another, the point of attachment resembling tight junctional complexes that normally found between epithelial cells (Fig. 3 and 4).

Ontogenesis of thyroid hormone receptor in foetal lambs

Affinity and concentration of T3 receptor sites have been measured in nuclear extracts from the brain, lung, and liver of foetal lamb tissues at 50, 82 and 100 days of gestational age. Control experiments indicated that the concentration of sites was similar when nuclear extracts or purified nuclei were used, and that maximal binding capacity was obtained after 2 h of incubation at 22°C. The pattern of receptor binding affinity when different thyroid hormone analogs were used in competition assays with [125I]T3 was T3 > 3,5,3'-triiodothyroacetic acid (Triac) > T4 in the lung and brain. In the liver, Triac had the same affinity as T3. The sedimentation coefficient of the receptor was 3.6 S in lung. There were minor changes of receptor affinity in the brain, but not in the lung or liver, during development with the highest value at 82 days. Receptor concentration increased twice from 50 to 82 days. Since in the brain this is the period of neuroblast proliferation, the results suggest that thyroid hormone is required for proper foetal lamb development and, in particular, for neuroblast proliferation and/or differentiation.