The histochemical location of three diagnostic enzymes in the marmoset liver.

The histochemical locations of alkaline phosphate (ALP), leucine aminopeptidase (LAP) and gamma glutamyltransferase (GGT) were demonstrated in the liver of the marmoset (Callithrix jacchus). Although all three enzymes were located in cell membranes, the location of LAP was demonstrated by a chromogenic substrate, in the canalicular membrane. GGT was seen in a vascular network, provisionally identified as the peribiliary arterial plexus. Possible diagnostic applications in toxicology are discussed.

The diagnostic usefulness of isocitrate dehydrogenase (ICDH) in the marmoset (Callithrix jacchus).

Marmosets were given either a hepatotoxin, carbon tetrachloride, orally or an i.m. injection of a mytoxin, chlorpromazine. Although muscle damage alone caused small increases in the plasma levels of lactate dehydrogenase, alanine aminotransferase, aspartate aminotransferase and isocitrate dehydrogenase (ICDH), only the isoenzyme analysis of ICDH can differentiate definitely between liver and muscle damage. Only very severe muscle damage can increase the plasma concentration of this enzyme but, in this case, the elevation of plasma creatinine kinase levels helps differentiation. It is recommended that the elevation of ICDH is the most specific indicator of hepatic damage in the marmoset.

Tissue activities of enzymes of diagnostic interest in the marmoset and rat.

The activities of enzymes of diagnostic interest were investigated in the liver, heart, kidney and muscle of the marmoset (Callithrix jacchus) and the rat. Methods of tissue extraction which gave maximal enzyme activity were used and comparison between the species showed some major differences. AST, LDH and GDH showed a similar distribution in both species but ICDH activity was much higher in the rat heart than in any other rat or marmoset organ. ALP, LAP and GGT were present in much higher activities in the rat kidney than in the marmoset kidney, a finding which was reversed in the liver of these animals. The major ALT-containing organ in the rat was the liver but, in the marmoset, this enzyme was found in relatively large quantities in the heart and muscle also. These differences can be of importance when plasma enzyme activities are measured following tissue damage.

Local myotoxicity of ketamine hydrochloride in the marmoset.

An investigation of raised plasma aspartate aminotransferase (AST) in marmosets after intramuscular ketamine injection suggested a local myotoxicity. This was confirmed by a range of histopathological findings from myofibrillar striation loss to necrosis. In addition to the elevations in AST levels, creatine kinase and the lactate dehydrogenase-5 isoenzyme levels were elevated. It was further demonstrated that, although the physical properties of the injectable solution (pH, osmolality) and to a lesser extent the injection procedure itself caused slight changes in plasma enzyme levels, the ketamine was predominantly responsible for the lesion. No hepatic interactions were seen. This effect should be taken into consideration when this anaesthetic is used in the marmoset if the primary objectives of the experiment entail routine blood analyses.

Experimental and field studies with thiophanate in pigs.

Thiophanate, administered at a dosage of 50 mg per kg to artifically infected pigs, removed 96 to 99 per cent of adult Oesophagostomum spp, Hyostrongylus rubidus and Trichuris suis. Activity was also high against larval stages of these nematodes, except for 26-day-old T suis. Thiophanate also showed ovicidal and larvicidal activity against H rubidus and Oesophagostomum spp. At 50 mg per kg thiophanate administered alone was inactive against Ascaris suum and Metastrongylus apri, the former species also being refractory at 200 mg per kg. Field trials confirmed these efficacy results in naturally infected animals. Pellet formulations providing mean dosages of 63 mg thiophanate per kg for adult pigs and 75 mg thiophanate per kg with 83 mg piperazine base per kg for growing pigs were highly effective in reducing the faecal output of Oesophagostomum spp, H rubidus and T suis eggs. In growing pigs, A suum was controlled by the thiophanate/piperazine product. No palatability or tolerance problems were observed when thiophanate or thiophanate/piperazine mixtures were administered at recommended dosage or multiples thereof in experimental or field studies.