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Biomedical subjects

I Johnstone

Publications and source records attributed to I Johnstone.

9 recordsLinked to original sources
PubMed1991

Clinical signs, laboratory changes and toxicokinetics of brodifacoum in the horse.

Six horses gavaged with a commercial brodifacoum (BDF)-containing bait (Talone) at a dosage of 0.125 mg of BDF/kg of body weight showed weight loss, severe hypocoagulability and hemogram alterations. Four of the horses became depressed and anorectic; one required vitamin K1 therapy. Increases in clotting times were observed at 24 h in the partial thromboplastin time (PTT) followed by the thrombotest (TBT) and one-stage prothrombin time (PT) at 48 h. Elevated mean PTT, PT and TBT were observed from days 4 to 8 (p less than 0.05) with levels returning to pretreatment levels by day 12. Maximum prolongation was a fourfold increase in PTT (day 4), a 2.5-fold increase in TBT (day 6) and a twofold increase in PT (day 6). Thrombin clotting times remained unchanged. In two horses prolongation in clotting time did not normalize until day 23. The mean hematocrit (0.38 +/- 0.01 L/L) was decreased (p less than 0.05) from day 8 (0.33 +/- 0.02 L/L) to day 14 (0.33 +/- 0.01 L/L). The hemoglobin concentration and erythrocyte numbers were decreased (p less than 0.05) from day 6 (20.1%, 17.6% respectively) to day 14 (22%, 20% respectively). Platelet counts decreased on day 6 (17.2%) to nine (14.6%). No other significant changes were observed in routine hematological and serum biochemical parameters. Peak plasma concentrations of BDF occurred 2 to 3 h after oral administration; two horses had detectable levels of BDF at nine days. Pharmacokinetic evaluation indicated that BDF has a half-life of 1.22 +/- 0.22 days, a body clearance of 1073.1 +/- 53.21 mL/kg/day, a volume of distribution of 1853.7 +/- 26.41 ng-day/mL and closely approximates a one-compartment model in the elimination phase.(ABSTRACT TRUNCATED AT 250 WORDS)

4-Hydroxycoumarins↗
PubMed1989

Congenital toxoplasmosis in Abyssinian cats.

Two of three litter-mate kittens born to an Abyssinian cat died of acute toxoplasmosis. Toxoplasma gondii was found in histologic sections of both kittens and this was confirmed by immunoperoxidase staining.

Animals↗
PubMed1987

Reproductive patterns of pedigree cats.

A survey of Brisbane catteries was carried out to investigate reproductive patterns of pedigree cats. Eighteen breeders supplied data on 751 litters with a total of 3171 kittens covering the Persian, Chinchilla, Siamese, Burmese and Abyssinian breeds. The overall sex ratio at birth was 100 males to 92 females. There was a significant seasonal effect on sex ratio with litters conceived during the wet season (September to February) producing more males than expected and litters conceived during the dry season producing more females than expected. Litter size and breed had no significant effect on the sex ratio. The average litter size varied with the breed with the most prolific being the Burmese (5.0) then the Siamese (4.5), Persian (3.9), Abyssinian (3.5) and Chinchilla (2.8). The average litter size was smaller for the first litter than for the subsequent 3 litters. The maximum average litter size was reached at 6 years with only a moderate decline thereafter. There was a seasonal fluctuation in births with the greatest numbers being born in spring and the least in late autumn. Longhair cats showed a more marked seasonal distribution of births than the shorthairs which reproduced for most of the year, particularly the Burmese breed.

Animals↗
PubMed1984

An aetiological study of 290 XXY males, with special reference to the role of paternal age.

Data on 290 non-mosaic 47,XXY males have been analysed for possible associations with parental ages at birth, season of birth, sex ratio among sibs, and twinning. Comparison with matched population controls revealed a highly significant association with parental age, which was fully explained by dependence on maternal age and maternal age alone. The maternal age effect was determined with greater precision than in an earlier study of the same material, in which siblings were used as controls, and was estimated to result in an increased risk of between 5% and 10% per annum (p.a.). The estimated independent effect of paternal age, after fitting maternal age, was marginally (but not significantly) negative, and excluded an increased risk in excess of 3% p.a. Paternal age therefore appears to have little if any independent significance in the aetiology of 47,XXY. After correcting for seasonal variations in the population birth rate and smoothing, there was a peak of XXY births in March and a trough in November. Though not statistically significant, the pattern resembled that reported in previous studies, and was similar for both younger and older mothers. The twinning rate for both the XXYs and their sibs, and the sex ratio among the latter, were close to the corresponding population values.

Female↗
PubMed1984

Electroejaculation in the domestic cat.

A method of electroejaculation for tomcats is described. Normal sperm counts in 4 cats ranged from 6 to 13 X 10(6)/ejaculate. There was a great deal of variation between collections from the same cat indicating the necessity for at least 5 collections when assessing the fertility of a tomcat. Sperm counts were higher in the latter half of the year, at the time of increased sexual activity for cats in the Brisbane area. The volume of semen collected by electroejaculation increased in direct proportion to the length of electrical stimulation, hence, volume is not a reliable criterion for the appraisal of semen. However, results have indicated that semen volume tends to increase from July to December, thus indicating increased accessory gland activity during the breeding season. As this procedure does not cause any apparent discomfort or harmful effects there seems no reason to assume that it could not be used routinely on stud cats.

Animals↗
PubMed1983

Enhanced incorporation of exogenous arachidonic acid into phosphatidylinositol and other phospholipids during the early stages of thrombin-induced aggregation in gerbil platelets.

The degradation of platelet phospholipids via phospholipase activity is known to occur during thrombin-induced platelet aggregation. Both phosphatidylinositol and phosphatidylcholine are considered to be sources of the released arachidonic acid which becomes a substrate for prostaglandin and thromboxane A2 formation. In this work, the effect of thrombin on the incorporation of exogenous arachidonic acid into platelet membrane phospholipids was studied. Suspensions of gerbil platelets were incubated in aggregometer cuvettes with [14C] arachidonic acid in the absence or presence of thrombin, and product formation was monitored by thin layer chromatography and scintillation counting. Within 30 sec, the entry of arachidonic acid into phosphatidylinositol was increased by 165% in thrombin-stimulated platelets over controls. Under identical conditions, the incorporation into phosphatidylcholine was increased by only 57%. These results suggest that the incorporation of exogenous arachidonic acid via lysophosphatidylinositol and lysophosphatidylcholine acyltransferase activities may be intimately associated with thrombin-induced platelet aggregation in the gerbil.

Animals↗
PubMed1983

The metabolism of the anti-inflammatory drug eterylate in rat, dog and man.

Oral doses of 14C-eterylate were well absorbed by rat and man and excreted mainly in the urine (94% dose by rat in three days and 91% by man in five days). Oral doses to dogs were excreted in similar proportions in both the urine and faeces, although faecal 14C was probably derived in part, from biliary-excreted material. Peak plasma 14C and drug concn. were generally reached between one and three hours after oral doses. In humans, only two metabolites, salicylic acid and 4-acetamido-phenoxyacetic acid, were detected in plasma. The latter was cleared more rapidly than the former and hence plasma salicyclate concn. reached a peak (10.9 and 19.8 micrograms/ml in Subjects 1 and 2, respectively) and initially declined with a half-life of about two-three hours. Plasma 4-acetamidophenoxyacetic acid concn. reached a peak (4.3, 10.0 micrograms/ml, respectively) and declined with a half-life of about one hour. Tissue concn. of 14C were generally greater in dogs than in rats. Highest conc. occurred at three hours in dogs and at one hour in rats. Apart from those in the liver and kidneys, tissue concn. were lower than those in the corresponding plasma. Unchanged drug was not detected in urine or plasma of any species and was rapidly metabolized in human plasma. The major 14C components in human urine were identified as salicyluric acid and 4-acetamidophenoxyacetic acid; minor metabolites were salicylic acid, gentisic acid and paracetamol. These metabolites were also detected in rat urine albeit in different proportions to those in human urine. Dog urine contained less of these metabolites and a major proportion of the 14C was associated with relatively non-polar components. Although salicylic acid and 4-acetamidophenoxyacetic acid were the only major circulating metabolites in man and rat, dog plasma also contained the non-polar urine metabolites.

Acetanilides↗