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Biomedical subjects

A R Jackson

Publications and source records attributed to A R Jackson.

34 records · Page 2Linked to original sources
PubMed1984

Clinical and pathological changes in sheep experimentally poisoned by the blue-green alga Microcystis aeruginosa.

Fifteen young sheep were inoculated intraruminally with various doses of an algal bloom of Microcystis aeruginosa. Lethally poisoned sheep died between 18 and 48 hours after inoculation. Findings included marked elevation of serum concentrations of certain enzymes and bilirubin, mild elevations of blood urea nitrogen and serum inorganic phosphorus with marked reduction in blood glucose, a mild neutrophilia with a marked left shift and marked changes in coagulation parameters. Necropsy findings included pale swollen, sometimes hemorrhagic, livers, edema involving the body cavities and widespread small hemorrhages. The primary site of toxicity was the liver which had centrilobular to near massive hepatocyte necrosis. Electron microscopic lesions were aggregation of endoplasmic reticulum with displacement of subcellular organelles towards the periphery of the hepatocyte, and vacuolation of the contents of more severely affected cells.

Animals↗
PubMed1981

Keratoconjunctivitis of the koala, Phascolarctos cinereus, caused by Chlamydia psittaci.

Chlamydia psittaci was cultured from 29 of 35 koalas (Phascolarctos cinereus) with keratoconjunctivitis. The disease progressed from acute to chronic stages over some months, with a known duration of at least 2 years. One recovered carrier was found. Up to 29% of koalas in some populations were clinically affected. A seasonal spread of infection was indicated by the high percentage of acutely affected cases found in summer. There was no evidence of susceptibility being related to age or sex. The sera of all chronically affected koalas had complement fixation test titres against chlamydial group antigen of 80 or above; in acute cases the titre ranged from 0 to 320. Of normal koalas, 84% were serologically negative, 16% had chlamydial antibody. A titre of 80 or more considered in conjunction with ocular disease could be taken as presumptive evidence of a chlamydial etiology. Chlamydial keratoconjunctivitis may be the ocular disease which was associated with the decline of koala numbers between the years 1885 and 1930.

Animals↗
PubMed1978

Isolation, characterization and pathology of the toxin from a Microcystis aeruginosa (= Anacystis cyanea) bloom.

The nature of the toxicity of a bloom of blue-green alga, M. aeruginosa (= Anacystis cyanea), that occurred in a man-made lake was investigated. Crude algal bloom extracts were toxic to laboratory mice when injected intraperitoneally. The lethal dose (LD100) of these extracts was 15-30 mg of lyophilized algal bloom per kilogram body weight. The toxin was purified by a procedure that included ammonium sulphate fractionation, solvent extraction, acid precipitation, Sephadex G25 and DEAE-Sephadex chromatography, and high-voltage electrophoresis at pH 6.5. The preparation gave a single spot on high-voltage electrophoresis at pH 9.0, had no free amino group, and was characterized by a simple amino acid composition of equimolar quantities of L-methionine, L-tyrosine, D-alanine, D-glutamic acid, erythro beta-methyl aspartic acid and methylamine. The LD50 for the purified toxin was estimated to be 0.056 mg/kg of mice, and the approximate LD100 is 0.070 mg/kg, based on the total material found from amino acid analysis. Parenteral administration of the purified toxin to mice produced extensive liver lobular haemorrhage and death within 1-3 h. Repeated inoculation of sublethal doses daily over some weeks produced progressive hepatocyte degeneration and necrosis and the development of fine hepatic fibrosis.

Amino Acids↗
PubMed1977

Studies on nematode infections of beef cattle in New South Wales.

The occurrence and seasonal trends of nematode parasite infections in beef cattle on the Tablelands and North Coast regions of New South Wales are described, based on worm counts from 627 spring-born steers slaughtered at 2-monthly intervals from 6 to 24 months of age. The predominant parasites were Ostertagia ostertagi, Trichostrongylus axei and Cooperia spp. Large burdens of adult Ostertagia were seen in 12-month-old animals in late winter and early spring, and later in 18- to 20-month-old cattle in the following late summer and autumn. These infections often resulted in outbreaks of clinical parasitism. Massive numbers of inhibited early fourth stage larvae (EL4) also accumulated in the yearlings during their first spring, reached peaks in mid-summer and then declined. The possibility of their resumption of development to mature worms in the late summer and autumn period is discussed. Adult T. axei showed a similar seasonal trend to Ostertagia and may have increased the severity of outbreaks of clinical disease. Cooperia populations of EL4 and adult worms were highest in weaners during winter, but lower numbers thereafter indicated a strong resistance to re-infection. In addition, Haemonchus placei occurred frequently on the North Coast both as EL4 and adults in cattle of all ages up to 20 months. Of the other cattle nematodes, Oesophagostomum radiatum and Trichuris spp occurred in low numbers, mainly in weaners. Bunstomum phlebotomum and H. contortus occurred sporadically on the North Coast and Tablelands respectively. Intestinal Trichostronglyus spp, Oesophagostomum venulosum and Dictyocaulus viviparus were seen occasionally and Nematodirus spp were not seen. There was a poor relationship between worm counts and faecal egg counts. Cooperia spp dominated the egg counts, while those for other genera were generally low and did not reflect the relative abundance or seasonal changes in worm numbers.

Animals↗
PubMed1977

Bone thinning in frontal mucocele.

Sixteen cases of frontal mucocele are reviewed. Bone thinning leading to destruction of the sinus floor was shown to be a feature. It usually affects the superomedial margin of the orbital roof first, due to pressure on the area where the sinus wall is thinnest. Demonstrable thinning of either anterior or posterior sinus walls--a cardinal sign of frontal mucocele, is best shown by means of underpenetrated lateral radiographs. All other conventional radiographic signs of frontal mucocele, including lucency of the affected sinus, were found to be non-specific. The presence of an osteoma in a site likely to obstruct the frontonasal duct is a valuable adjunct to diagnosis.

Adult↗