Parathyroid hormone (PTH)-like bioactivity, assayed as adenylate cyclase response in UMR 106-01 osteogenic sarcoma cells, was present in extracts of sheep fetal and maternal parathyroid glands and placenta. Preincubation of extracts with PTH(1-34) antiserum inhibited approximately 40% of the bioactivity in fetal parathyroid extracts, 50% in maternal parathyroid extracts, but only 10% of the bioactivity in the placental extract. Partial purification of placental extracts by chromatography yielded fractions containing PTH-like bioactivity which were similar in behaviour to that of PTH-related protein (PTHrP) from a human lung cancer cell line (BEN). An antiserum against synthetic PTHrP(1-16) partially inhibited the bioactivity of the placental extract and synthetic PTHrP(1-34), but had no effect on the bioactivity of bovine PTH(1-34) or bovine PTH(1-84). The placental PTH-like bioactivity was higher in mid- than in late gestation. Fetal parathyroid glands contained the highest PTH-like bioactivity. Thyroparathyroidectomy of one fetal twin lamb in each of 16 ewes between 110 and 125 days of gestation resulted in decreases of the plasma calcium concentration and reversal of the placental calcium gradient that existed between the ewe and the intact fetus. Perfusion of the placenta of each twin in anaesthetized ewes was carried out sequentially with autologous fetal blood in the absence of the exsanguinated fetus. The plasma calcium concentration in the blood perfusing the placenta of each twin increased, but reached a plateau at a lower concentration in the perfusing blood of thyroparathyroidectomized fetuses than in that of the intact fetuses. Addition of extracts of fetal parathyroid glands or of partially purified PTHrP resulted in further increases in plasma calcium in the autologous blood perfusing the placentae of thyroparathyroidectomized fetuses, but addition of bovine PTH(1-84) or rat PTH(1-34) had no effect. The presence of this PTH-like protein in the fetal parathyroid gland and placenta may contribute to the relative hypercalcaemia of the fetal lamb. This protein, which is similar to PTHrP associated with humoral hypercalcaemia of malignancy, stimulates the placental calcium pump responsible for maintaining a relative fetal hypercalcaemia during gestation.

SUMMARYPerfusion in situ of the placenta of intact or previously parathyroidectomized fetal lambs has been used to assess the ability of three mid-molecule fragments of the human parathyroid hormone-related protein (PTHrP)

SUMMARYPerfusion in situ of the placenta of previously thyroparathyroidectomized fetal lambs has been used to compare the ability of various forms of parathyroid hormone-related protein (PTHrP) to stimulate placental calcium transport. Whereas PTHrP (1-34) was without effect, PTHrP (1-141) was active but usually after a delay of up to 1 h, in common with the effect noted when using extracts of fetal parathyroid glands. In contrast, PTHrP (1-84) and PTHrP (1-108), tended to show a more rapid stimulatory action. It is suggested that post-translational processing of PTHrP (1-141) may occur as an activating step in the placenta in vivo.

Proliferative enteritis (PE) is a common intestinal disease on pig farms. The disease is caused by ileal symbiont (IS) intracellularis (Campylobacter-like organism) bacteria. An enzyme-linked immunosorbent assay (ELISA) was developed to measure IS intracellularis-specific immunoglobulin G (IgG) response in the sera of pigs. The antigen used in the ELISA was filtered, percoll gradient-purified IS intracellularis extracted from the intestines of pigs affected with proliferative hemorrhagic enteropathy. The antibody responses of pigs challenged with intestinal homogenates from pigs affected with proliferative hemorrhagic enteropathy containing IS intracellularis or percoll-gradient purified IS intracellularis were low and variable. The low IgG titers measured in challenged pigs support previous findings that IgG plays a minor role in the immune response of pigs to IS intracellularis. On a farm in which infection was endemic, pigs seroconverted at between 7 and 24 weeks of age. High IgG titers, indicative of maternally acquired antibody, were present in 3-week-old pigs. The IgG titers in piglets were lowest at 6 weeks of age, which approximates the age of onset of clinical disease. These results suggest that IgG plays a role in determining the susceptibilities of pigs to natural infection. Measurements of seroconversion by the ELISA might aid in epidemiological investigations of PE in naturally infected herds. However, the variable antibody responses in experimentally challenged pigs would seem to limit its usefulness as an antemortem diagnostic test for PE.

Serums from 1002 penguins of 4 species on Macquarie Island, a sub-antarctic island in the Southern Ocean, were examined for antibody to Newcastle disease virus (NDV), influenza A virus, avian paramyxovirus, alphavirus and flavivirus. No evidence of haemagglutination-inhibition antibody to influenza A virus or alphavirus was detected. Serums from 6% of royal penguins sampled gave positive reactions to NDV while the other 3 species were negative. Antibody to a flavivirus and an avian paramyxovirus, other than NDV, was detected in 3 of the 4 penguin species. Cloacal swabs from 831 penguins of 4 species were examined for the presence of viruses. Six isolated of paramyxovirus, other than NDV, were obtained from swabs taken from royal and king penguins at 2 widely separated sites on the island.