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Biomedical subjects

J G Allen

Publications and source records attributed to J G Allen.

At least 127 records · Page 7Linked to original sources
PubMed1979

Spongy transformation of the brain in sheep with lupinosis.

Spongy transformation in the brain of sheep affected with chronic lupinosis in the field is described. Identical lesions were reproduced in sheep with experimental acute and chronic lupinosis. The primary brain lesion was vacuolation of the white matter of the brain stem with no malacia, neuronal damage or gliosis being present. The extent and severity of the vacuolation was related to the severity of the liver lesion.

Animals↗
PubMed1979

Phosphonopeptides as antibacterial agents: alaphosphin and related phosphonopeptides.

Alaphosphin, l-alanyl-l-1-aminoethylphosphonic acid, was selected from a range of phosphonopeptides for evaluation in humans on the basis of its antibacterial activity, pharmacokinetics, and stability to intestinal and kidney peptidases. In vitro, the antibacterial action was antagonized by small peptides, resulting in low activity on peptone media. On an antagonist-free medium alaphosphin was bactericidal and rapidly lysed most susceptible gram-negative bacteria, but it was largely bacteriostatic and essentially nonlytic against gram-positive organisms. Its spectrum included most strains normally isolated from urinary tract infections, but potency was greatly reduced by very high inoculum levels and by alkaline pH. Although strains of Proteus and Pseudomonas were less susceptible to alaphosphin than were other common gram-negative bacteria, like other species they formed spheroplasts when exposed under appropriate conditions. Alaphosphin was equally effective against penicillin-susceptible and -resistant strains and showed no cross-resistance with known antibiotics. Good synergy and increased bactericidal activity were demonstrated with combinations of alaphosphin and d-cycloserine or beta-lactam antibiotics.

Alanine↗
PubMed1979

Phosphonopeptides as antibacterial agents: metabolism and pharmacokinetics of alafosfalin in animals and humans.

The metabolism and pharmacokinetics of a synthetic antibacterial phosphonodipeptide, alafosfalin, have been studied in rats, baboons, and human volunteers. The compound was rapidly absorbed from the injection site after subcutaneous and intramuscular administration and gave peak plasma concentrations at 15 to 20 min after dosing. Distribution studies showed that high drug concentrations were produced in inflammatory exudates and most tissues except brain. Alafosfalin was rapidly cleared from the general circulation, mainly by the kidney. Plasma half-lives were 20 min in rats and approximately 1 h in baboons and humans. Alafosfalin was well absorbed after oral administration, but was extensively hydrolyzed to alanine and L-1-aminoethylphosphonic acid before it reached the general circulation. This first-pass metabolism was less marked in humans than in animals. Administration of 200-mg intramuscular and 500-mg oral doses produced concentrations of intact phosphonodipeptide in human plasma and urine which were in excess of the in vitro minimal inhibitory concentrations for many pathogenic organisms. The rate of absorption and elimination of alafosfalin in humans were also very similar to published data on beta-lactam antibiotics. This suggests that the pharmacokinetics can be matched to provide synergistic combinations for clinical use.

Alanine↗
PubMed1978

Control of ovine lupinosis: experiments on the making of lupin hay.

Lupin hay was prepared at 2 locations and conserved in fodder rolls and bales until late summer. At this time it was found that the lupin hay had lower levels of infection with P. leptostromiformis and had developed virtually no toxicity, when compared with adjacent normal lupin stubble which was very heavily infected with Phomopsis and very toxic. No additional advantage was gained by spraying cut lupins with formalin before rolling or bailing. It is suggested that the preparation of lupin hay as described provides farmers who do not harvest their lupins for seed with a way of utilising lupin crops for summer feed, while significantly reducing the risk of lupinosis in stock.

Animal Feed↗
PubMed1978

An investigation of the removal of coarse plant material from lupin stubble paddocks for the control of ovine lupinosis.

The removal of course lupin material from lupin stubble paddocks did not reduce the incidence or severity of liver damage caused by the toxins of Phomopsis leptostromiformis. Furthermore, sheep grazing paddocks from which the coarse lupin material had been removed showed body weight changes no different to sheep grazing normal lupin stubbles. In addition, it was found that 6-month old wethers suffered more severe liver damage than 18-month-old wethers, and that lupin material in the paddock remained toxic for a least 6 weeks.

Animal Feed↗
PubMed1978

The toxicity of myoporum tetrandrum (Boobialla) and myoporaceous furanoid essential oils for ruminants.

Boobialla (Myoporum tetrandrum)leaf contains from 0.25 to 0.5% wet weight of furanoid sesquiterpene essential oils of which the main component is dehydrongaione. The plant was toxic when dosed to calves at equivalent dose rates of oils of from 50 to 134 mg/kg, causing mainly extensive haemorrhagic centrillobular necrosis; and to sheep at equivalent dose rates of oil of from 55 to 66 mg/kg, causing either centrilobular or periportal liver lesions with or without acute pulmonary oedema. An essential oil mixture of similar composition derived from Myoporum deserti produced similar syndromes. In addition, treatment of calves with phenobarbitone or Melaleuca linariifolia essential oils prior to dosing with the Myoporum oils caused periportal hepatic necrosis rather than the centrilobular lesion which occurred usually in this species. The liver lesions found in the experimental calves and sheep respectively, were thus similar to those reported in suspected field cases of Boobialla poisoning in cattle and goats in Western Australia. The liver injury that may be expected in intoxication of livestock by myoporaceous plants containing this type of essential oils can thus be either periportal, midzonal or centrilobular necrosis, depending, probably, on the nutritional regime of the animal immediately prior to consumption of the toxic plant.

Animals↗
PubMed1976

Letter: Volunteer?

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Blood Donors↗