Conditioned feed aversion as a means to prevent tulp (Homeria pallida) poisoning in cattle.

Conditioned feed aversion was investigated as a means to prevent tulp (Homeria pallida) poisoning in cattle on tulp-infested grazing. Aversion treatment with a combination of epoxyscillirosidin and lithium chloride together with a tulp-hexane extract, which served as identification factor for tulp, resulted in a significantly lower (P < 0.001) proportion of severe tulp poisoning. In a first trial where 21 averted and 21 non-averted control cattle were exposed to a tulp-infested grass pasture, only two of the averted cattle were severely poisoned compared to 13 of the non-averted control cattle. In a second trial, with cattle being exposed to a pure stand of tulp supplemented with maize residues, only two of 21 averted cattle were severely poisoned compared to 14 of 21 non-averted control cattle. Occurrence of mild tulp poisoning, however, did not differ much between averted and non-averted control cattle. The results show that conditioned feed aversion effectively restricted severe poisoning in cattle on tulp-infested grazing.

Effect of pavetamine on protein synthesis in rat tissue.

Pavetamine, the active principle of plants causing gousiekte in ruminants, was found in this study to be an inhibitor of protein synthesis in the rat heart. Sprague-Dawley rats were injected intra-peritoneally with 8-10 mg/kg pavetamine and the levels of protein synthesis in different organs determined utilizing L-[4-3H]phenylalanine incorporation. In contrast to the more than 23% inhibition found in heart tissue at 4, 24 and 48 h after administration of pavetamine, the effect on the kidney, liver, spleen, intestine and skeletal muscle was minimal or returned to pretreatment levels within 48 h. These results may offer an explanation for the clinical signs observed in ruminants with gousiekte, where the heart only is affected.

Poisoning of wildlife in South Africa.

Over a period of 7 years the Toxicology Diagnostic Laboratory at the Onderstepoort Veterinary Institute investigated 370 suspected incidents of poisoning of wildlife. A diagnosis was made in 166 of the outbreaks. Synthetic organic pesticides were responsible for 82.5% of the poisonings. More than 90% of the poisonings were maliciously intended and monocrotophos was the chemical most often used. The data were derived from authenticated outbreaks of poisoning and indicate the chemicals most often incriminated in acute poisoning of wildlife. Of all wild animals, birds are the most frequent victims of poisoning. Uncommon toxicities such as ionophore, cardiac glycoside poisoning and chronic fluorosis are also described.

A fluorescent investigation of subcellular damage in H9c2 cells caused by pavetamine, a novel polyamine.

Gousiekte, which can be translated literally as "quick disease", is one of the six most important plant toxicoses that affect livestock in South Africa. It is a plant-induced cardiomyopathy of domestic ruminants characterised by the sudden death of animals within a period of 4-8weeks after the initial ingestion of the toxic plant. The main ultrastructural change in sheep hearts is degradation of myofibres. In this study, fluorescent probes were used to investigate subcellular changes induced by pavetamine, the toxic compound that causes gousiekte, in H9c2 cells. The sarcoplasmic reticula (SR) and mitochondria showed abnormalities that were not present in the control cells. The lysosomes of treated cells were more abundant and enlarged than those of the control cells. There was increased activity of cytosolic hexosaminidase and acid phosphatase, indicating increased lysosomal membrane permeability. Lysosomes play an important role in both necrosis and apoptosis. The degradation of the myofibres may be a consequence of the increased lysosomal membrane permeability. Pavetamine was also found to cause alterations in the organisation of F-actin. F-actin in the nucleus is a transcription regulator and can therefore influence protein synthesis. Actin filament organisation also regulates the cardiac L-type Ca(2+) channels. Fluorescent staining demonstrated that pavetamine may damage a number of organelles, all of which can influence the proper functioning of the heart.

Damage to some contractile and cytoskeleton proteins of the sarcomere in rat neonatal cardiomyocytes after exposure to pavetamine.

Pavetamine, a cationic polyamine, is a cardiotoxin that affects ruminants. The animals die of heart failure after a period of four to eight weeks following ingestion of the plants that contain pavetamine. This immunofluorescent study was undertaken in rat neonatal cardiomyocytes (RNCM) to label some of the contractile and cytoskeleton proteins after exposure to pavetamine for 48 h. Myosin and titin were degraded in the RNCM treated with pavetamine and the morphology of alpha-actin was altered, when compared to the untreated cells, while those of beta-tubulin seemed to be unaffected. F-actin was degraded, or even absent, in some of the treated cells. On an ultrastructural level, the sarcomeres were disorganized or disengaged from the Z-lines. Thus, all three contractile proteins of the rat heart were affected by pavetamine treatment, as well as the F-actin of the cytoskeleton. It is possible that these proteins are being degraded by proteases like the calpains and/or cathepsins. The consequence of pavetamine exposure is literally a "broken heart".

Cytotoxicity and ultrastructural changes in H9c2(2-1) cells treated with pavetamine, a novel polyamine.

Intake of pavetamine, a novel polyamine, synthesized by certain rubiaceous plants, is the cause of gousiekte ("Quick disease") in ruminants. The disease is characterized by a latent period of 4-8 weeks, followed by heart failure. The aim of this study was to firstly investigate the cytotoxicity in H9c2(2-1) cells using the MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) and LDH (lactate dehydrogenase) release assays. Maximum cell death occurred after pavetamine exposure of cells for 72h at a concentration of 200muM (55%+/-9.84), as measured by the MTT assay. LDH release was only observed after 72h exposure to pavetamine. Secondly, the ultrastructural changes induced by pavetamine in H9c2(2-1) cells were investigated. Changes in the mitochondria and sarcoplasmic reticula were observed. The nucleus was not affected during the first 48h exposure of cells to pavetamine and no chromatin condensation occurred. However, after 72h exposure to pavetamine, the nucleus became fragmented and membrane blebbing occurred. It was concluded that the ultimate cell death of H9c2(2-1) cells treated with pavetamine, was through necrosis and not apoptosis. Thirdly, the effect of pavetamine on the mitochondrial membrane potential (DeltaPsi) was evaluated by using the JC-1 (5,5',6,6'-Tetrachloro-1,1',3,3'-tetraethyl-imidacarbocyanine iodide) and TMRM (tetramethylrhodamine methyl ester perchlorate) probes. Pavetamine treatment led to significant hyperpolarization of the mitochondrial membrane potential. Cyclosporin A (CsA), an inhibitor of the mitochondrial permeability transition pore, did not reduce the cytotoxicity of pavetamine significantly, indicating that the MPTP (mitochondrial permeability transition pore) plays no role in the cytotoxicity of pavetamine.