The effect of dietary spray-dried porcine plasma on clinical response in weaned piglets challenged with a pathogenic Escherichia coli.

Weaned piglets were used to determine the effect of dietary spray-dried porcine plasma (SDPP) on the clinical response to an infection with a pathogenic Escherichia coli (E. coli) O139:K82 LT(-). The piglets were divided into two groups of 10 animals each. One group was fed the control diet containing soybean(meal) plus whey powder. The test piglets were fed a diet with 8% SDPP. Piglets were orally infected with the challenge strain on days 6 and 7 after weaning. The experimental period lasted 14 days after which the piglets were euthanised and necropsied. Faecal samples were collected daily for bacteriological analysis. Segments of jejunum, caecum and rectum were removed for bacteriological analysis post mortem. Feed intake and weight gain, faecal and condition scores and body temperature were measured daily. In the control and SDPP groups, 6 and 7 piglets died from diarrhoea. The average daily feed intake (ADFI) and average daily gain (ADG) were substantially higher in the SDPP group than in the control group. SDPP-fed piglets generally had a more favourable faecal score and a healthier appearance than did the control piglets. The faecal excretion of E. coli O139:K82 was similar for control and test piglets. There were no diet effects on the E. coli O139:K82 counts at different sites of the intestine. In this experiment, the inclusion of SDPP at an economically acceptable percentage in the diet could not prevent piglet losses due to challenge with a pathogenic E. coli, but improvements of ADG, ADFI and faecal and condition scores were achieved.

Small intestinal morphology in weaned piglets fed a diet containing spray-dried porcine plasma.

The hypothesis tested in this study was that the reported beneficial effects of spray-dried porcine plasma (SDPP) on piglet post-weaning performance and health are associated with a trophic effect on small intestinal mucosa. At 24 days of age, the piglets of seven sows were assigned to one of three treatment groups. One group continued to be suckled. The other two groups were weaned and offered a diet containing either 15 per cent SDPP or casein. From each treatment group, one piglet was anaesthetised and samples were taken from the small intestinal wall at 26, 28 and 31 days of age. There were no significant effects of SDPP versus casein on villus length. On average, there was less mitotic activity in the SDPP -fed piglets than in those fed casein on days 4 and 7 after weaning. As less mitotic activity leads to less immature enterocytes, this may provide a mechanism for the reported beneficial effects of SDPP on performance and health.

Glucocorticoid-induced changes in synaptic vesicles of rat phrenic nerve terminals.

The mean cross sectional area of synaptic vesicle profiles of the myoneural junction of rat diaphragm is increased significantly when rats are injected i.p. with single doses of 200 micrograms/kg dexamethasone 1/2 hr to 8 hr previously to a control injection of 0.9% NaCl. A maximum effect is observed at 8 hr after pretreatment with dexamethasone. The treatment of rats with hemicholinium-3 (300 micrograms/kg) induces a significant reduction of the vesicle size. Complete prevention of this decrease in vesicle size is already observed when the animals are pretreated with a single dose of 200 micrograms/kg dexamethasone 1/2 hr before treatment with 300 micrograms/kg hemicholinium-3. Dexamethasone in the same dose causes an optimum increase of the mean cross sectional area when it is given 1 hr before treatment of the animals with hemicholinium-3. It is concluded that glucocorticoids have direct actions in both "normal" motor nerve terminals and in motor nerve terminals with a deficient choline transport system, which may contribute to their proposed beneficial effects in certain cases of muscle weakness.

Effects of corticosteroids on the myoneural junction. A morphometric and electrophysiological study.

The mean size of the synaptic vesicles in the nerve endings of the isolated rat diaphragm was significantly increased after incubation with the glucocorticoids prednisolone (10(-5) mol/l) and dexamethasone (2 X 10(-7) mol/l). The shape of the vesicles was also changed, i.e. they became rounder. Similar increases in the mean size of the diaphragm synaptic vesicles were seen when the rats were injected with prednisolone (i.p., 2 mg/kg) and dexamethasone (i.p., 50 micrograms/kg) 2-4 h previously. The amplitude of the miniature endplate potentials was also significantly increased in diaphragms isolated from rats which had been injected with prednisolone or with dexamethasone. Changes in frequency of the MEPPs were less marked after injection of prednisolone, but a significant increase was seen after injection of dexamethasone. It is concluded that relatively low concentrations of glucocorticoids have direct effects on the motor endplate in rat diaphragm both in vitro and in vivo. We tentatively suggest that presynaptic effects may contribute to the beneficial effect of corticosteroids in deficient neuromuscular transmission, e.g. in myasthenia gravis.

Are muscarinic receptors in the central and peripheral nervous system different?

The concentration-dependent binding of atropine-3 H to membrane fractions from bovine tracheal muscle, parotid gland and caudate nucleus, measured by equilibrium dialysis, revealed the presence of virtually identical high affinity binding sites in all three tissues. Sch 1000 and Sch 1178 geometrical isomers of N-isopropylatropine bromide with a large potency ratio as antimuscarinics, inhibited atropine binding identically in all three tissues. Differences in properties of muscarinic receptors in these tissues are either non-existent or too small to be detected by the applied techniques.