Flow cytometric analysis of T cell response in mice infected with Cowdria ruminantium.

A 3-fold increase in the numbers of Lyt-2+ T cells in the circulating blood of mice infected and re-infected with the Welgevonden stock of Cowdria ruminantium, as determined by flow cytometry, is supportive evidence that immunity in heartwater is cell-mediated. The rise in Lyt-2+ cells only after re-infection of the mice is further evidence that the development of immunity in heartwater is dependent on the unhindered and adequate replication of C. ruminantium.     

An improved ferritin assay for canine sera

An improved serum ferritin assay for canine serum has been developed. It uses two monoclonal antibodies in a sandwich arrangement. Serum ferritin can be determined on undiluted canine sera with this assay. The recovery of ferritin added to canine serum ranged from 98 to 106%, the within-assay coefficient of variability was 3.3 to 4.5%, and the assay-to-assay variability was 9.8 to 10.2%. Serum ferritin from 61 apparently healthy dogs had a geometric mean of 252 ng/ml, with a range of 80 ng/ml to 800 ng/ml.     

The relationship between the pharmacokinetics of intravenous cismethrin and bioresmethrin and their mammalian toxicity

The distribution and excretion of [¹⁴C]alcohol-labeled cismethrin and bioresmethrin was determined after intravenous administration to rats. Initially the label distribution of both isomers was similar, but differences occurred at later times mainly due to the retention of 5-benzyl-3-furylcarboxylic acid, a metabolite of bioresmethrin, in high concentration in the blood. Retention of this metabolite accounted for the slower excretion of bioresmethrin label compared to cismethrin. After administration of either isomer, parent pyrethroid was rapidly cleared from the blood and liver, and both isomers rapidly entered the central nervous system reaching peak concentrations within 2–5 min. Brain cismethrin concentrations exceeding 3.5 nmol/g were associated only with animals showing tremors. These levels of cismethrin are maintained for up to 30 min but bioresmethrin was depleted more rapidly possibly due to brain metabolism. It is concluded that the low toxicity of bioresmethrin is possibly due to the inability of this isomer to interact with the site of action in the central nervous system and not, as previously suggested, primarily because of more rapid metabolism in the liver.     

Biochemical markers of bone metabolism in growing thoroughbreds: a longitudinal study

This study describes longitudinal changes in serum levels of biochemical markers of bone cell activity in a group of 24 thoroughbred foals from birth to 18 months of age. The markers of bone formation included the type I collagen carboxy-terminal propeptide (PICP), the bone-specific isoenzyme of alkaline phosphatase (BAP), and osteocalcin (OC). Levels of the cross-linked telopeptide of type I collagen (ICTP), a marker of bone resorption, and the N-terminal propeptide of type III collagen (PNIIIP), a marker of soft tissue turnover, were also measured. Levels of all markers fell significantly between birth and 18 months of age (70-80 per cent); this decrease being most marked between 0 and 6 months. However, a transient increase in levels of the markers then occurred between 6 and 14 months of age. The timing of this increase was specific for each parameter. ICTP and OC concentrations increased between October and December. PICP concentrations increased between December and April whereas the increase in PIIINP was coincident with the peak in weight gain between April and June. Changes in BAP concentration were less distinct at this time. Season was shown to have significant effects on the biochemical markers independent from the effect of age. Concentrations of all markers decreased with increasing body weight and at any given age heavier horses had lower marker levels. These results show that biochemical markers of bone cell activity and soft tissue turnover follow characteristic patterns of change in growing thoroughbreds influenced by age, season and bodyweight. The demonstration that the reference ranges for the biochemical markers change from month to month means that single samples from individuals are of little value for monitoring bone cell activity in growing thoroughbreds.     

The dietary toxicity of flocoumafen to hens: Elimination and accumulation following repeated oral administration

In a dietary toxicity study, laying hens received a diet containing the rodenticide flocoumafen at concentrations of 1.5, 5, 10 and 50 mg kg^?1 for five consecutive days. The LC₅₀ at termination following a 28-day observation period was 16.4 mg kg^?1. Livers of birds which received doses of flocoumafen between 5 and 50 mg kg^?1 had concentrations of flocoumafen (1.5 nmol g^?1) that were independent of dose. The data indicate the presence in hen liver of a saturable high-affinity flocoumafen binding site with similar characteristics and capacity to that of the quail and rat. Residues of flocoumafen in samples of breast and leg muscle were low in all exposure groups. Higher, dose-related residues were found in samples of abdominal fat and skin-associated fat and there was a clear demonstration of the transfer of dose-related residues into eggs. In a separate study in which hens were dosed with [¹⁴C]flocoumafen for five consecutive days at a daily rate of 1 and 4 mg kg^?1 body weight, the majority (68 %) of the daily radioactive dose was eliminated over the following 24 hours via excreta. Residues in liver at death or when killed accounted for < 1 % of the cumulative administered radioactivity. Residues in eggs were located primarily in the yolk with maximum concentrations 1.0 mg kg^?1 or 0.18% of the low dose; 2.1 mg kg^?1 or 0.06% of the high dose as [¹⁴C]flocoumafen equivalents were observed at 10 days after start of dosing. Some 40 % of the total activity in the yolk was unchanged flocoumafen.