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A new family of stabilized benzylic nucleophiles for the palladium-catalyzed decarboxylative allylic alkylation reaction has been developed. Allyl esters derived from 3-carboxyphthalides were found to undergo palladium-catalyzed deallylation and decarboxylation under mild reaction conditions, a process facilitated by the formation of a stabilized aromatic anion. The regioselective allylic coupling of this intermediate afforded a variety of functionalized phthalides in 73-96% yields.

In a study designed to test the effect of molybdenum (Mo) on resistance to trichostrongylosis, the Mo content of the diet during primary infection of 8-month-old Merino lambs with Trichostrongylus colubriformis was found to affect the number of worm eggs found in the faeces during challenge and the total number of worms in the jejunum after six weeks of challenge infection. The optimal intake of Mo in this experiment was in the range of 4-8 mg sheep(-1)day(-1), approximately equivalent to feeding a diet containing 6-10 mg Mo kg(-1)dry matter (DM) and to 0.15-0.30 mg Mo kg(-1)liveweight. Lambs fed Mo at this rate showed a 90 per cent reduction in faecal egg count and total worm count six weeks after challenge compared with lambs fed quantities of Mo outside this range. The mechanism by which Mo exerted these effects was not defined, although the interactions of molybdenum, worm establishment and faecal egg count suggested that this trace element may be acting via an effect on the host's acquired immune response. This hypothesis is supported by the observed enhancement of immune responses (intestinal antibody and granulocyte numbers and in vitro worm-specific proliferation of lymphocytes) associated with Mo intake of 0.15-0.3 mg kg(-1)Lwt., (Copyright 1999 Harcourt Publishers Ltd.)

Dairy cows on 3 New South Wales dairy farms with herd mean blood glutathione peroxidase (GSH-Px) activities of less than 70 U/g haemoglobin, showed a significant improvement in first service conception rates following treatment with oral selenium pellets. Treated cows had significantly higher blood GSH-Px activities compared with control cows, with a lag phase of 4 to 5 months to reach peak mean levels of 88 to 159 U/g haemoglobin.

Serial dilutions of mixtures of the closely related diterpenoid orthoesters simplexin and huratoxin were added to cultures of chicken embryo fibroblast cells and bovine erythroid cells; the mixture was lethal at concentrations of 100 micrograms/ml and 1 microgram/ml, respectively. Morphological changes were observed in the chicken embryo fibroblast cells exposed to concentrations of greater than or equal to 100 ng/ml; 1 microgram/ml caused a loss of definition of the mitochondrial cristae within 2 hr and vacuolation, crenation and shrinkage of the cells within 5 hr. These results support a hypothesis that the lesions and clinical signs shown by cattle affected with chronic Pimelea poisoning are caused by direct cytotoxic effects on the cells of the cardiovascular, haemopoietic, digestive and hepatic systems.

Washed red blood cells from normal cows were incubated as 10 and 20 per cent suspensions in media containing 0, 2.5 and 25 mM phosphate. The results showed that the rate of glycolysis was dependent on the inorganic phosphate concentration. In the absence of phosphate, the consumption of glucose and the production of 2,3-diphosphoglycerate, lactate and adenosine 5'-triphosphate (ATP) were decreased. Incubation without added phosphate also greatly increased the production of fructose-1,6-diphosphate, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. Moderate hypophosphataemia was induced in two pre-ruminant calves. Washed red cells from the blood of these animals showed a depletion of ATP when compared with red cells from a control calf. The results indicate that phosphorus deficiency, leading to hypophosphataemia, may be a mechanism of post parturient and related syndromes of haemoglobinuria by decreasing red cell glycolysis and resultant ATP synthesis. Subnormal concentrations of ATP would predispose red cells to altered structure and function, a loss of normal deformability, and an increase in fragility and haemolysis with resultant haemoglobinuria.

Fourteen dairy herds which had been subjected to the Compton Metabolic Profile test on a total of 29 occasions were selected from the records of the institute for Research on Animal Diseases, United Kingdom, because they had a wide range of mean blood-glucose concentrations. Two herds had to be rejected from the study because of inadequate breeding records, leaving 12 herds (26 profile tests) to be included. The first service non-return rate of each herd was calculated from the breeding records of 10 cows mated closest to the date of each profile test. These rates were positively related to the mean blood-glucose concentrations of the lactating cows (P less than 0.01).

Food was withheld from female rats for 0-72 h at various stages of the oestrous cycle. Withholding food for periods of 24 h ending at 12:00 h on the day of pro-oestrus reduced the mating rate from 61 to 25% (P less than 0.05) but not the pregnancy rate of those rats that mated. Fasting for 24 h ending at 18:00 h on the day of pro-oestrus reduced the pregnancy rate from 82 to 18% (P less than 0.05) without affecting the mating rate and a 48-h fast starting at 12:00 h on the day of pro-oestrus reduced the pregnancy rate from 82 to 25% (P less than 0.05). Withholding food for 23 h ending at 17:00 h on the day of pro-oestrus prevented the LH and prolactin surges normally present at 17:00 h on this day. The treatments had no apparent effect on the ability of the adenohypophysis to release LH in response to injections of GnRH. When ovariectomized female rats fasted for 0-72 h and given 2 injections of oestradiol dibenzoate to test the ability of the hypothalamus to respond to an increasing plasma oestradiol concentration by stimulating the release of LH, a fast for 24 h reduced and a fast for 72 h completely prevented LH release.

The administration of the metabolic inhibitor, 2-deoxy-D-glucose (2DG), to four well fed heifers just before and during the time of expected oestrus, and to another heifer following the removal of the corpus luteum, prevented both the occurrence of oestrus and the formation of corpora lutea in all animals. Plasma progesterone concentrations remained low for at least 10-21 days after the last dose of 2DG. The results suggest that the inhibition of glycolysis is associated with the failure of both oestrus and formation of functional corpora lutea, and they support the hypothesis that hypoglycaemia is the primary biochemical change responsible for infertility induced by acute energy deficiency in lactating cattle.