Effects of Ipomoea carnea on the liver and on serum enzymes in young ruminants

Alpha-mannosidosis caused by toxic plants in ruminants of Argentina

It is well known that several of the swainsonine-containing plant species found widespread around the world have a negative economic impact in each country. In Argentina, most of the information on the poisonous plant species that produce α-mannosidosis is published in Spanish and thus not available to most English-speaking researchers interested in toxic plants. Therefore, the aim of this review is to summarize the information about swainsonine-containing plants in Argentina, which are extensively distributed throughout different ecoregions of the country. To date, five species from three genera have been shown to induce α-mannosidosis in livestock in Argentina: Ipomoea carnea subsp. fistulosa, Ipomoea hieronymi subsp. calchaquina (Convolvulaceae), Astragalus garbancillo, Astragalus pehuenches (Fabaceae), and Sida rodrigoi (Malvaceae). These species contain the indolizidine alkaloid swainsonine, which inhibits the lysosomal enzyme α-mannosidase and consequently affects glycoprotein metabolism, resulting in partially metabolized sugars. The prolonged consumption of these poisonous plants produces progressive weight loss and clinical signs related to a nervous disorder, characterized by tremors of head and neck, abnormalities of gait, difficulty in standing, ataxia and wide-based stance. Histological lesions are mainly characterized by vacuolation of different cells, especially neurons of the central nervous system. The main animal model used to study α-mannosidosis is the guinea pig because, when experimentally poisoned, it exhibits many of the characteristics of naturally intoxicated livestock.

Clinical and pathological comparison of Astragalus lentiginosus and Ipomoea carnea poisoning in goats

The indolizidine alkaloid swainsonine, found in some Astragalus and Oxytropis (i.e., locoweed) species, is a potent cellular glycosidase inhibitor that often poisons livestock. Other toxic genera such as some Ipomoea species also contain swainsonine as well as calystegines which are similar polyhydroxy alkaloids. The toxicity of calystegines is poorly characterized; however, they are also potent glycoside inhibitors capable of intestinal and cellular glycoside dysfunction. The objective of this study was to directly compare A. lentiginosus and I. carnea poisoning in goats to better characterize the role of the calystegines. Three groups of four goats each were treated with ground alfalfa (control), I. carnea or A. lentiginosus to obtain daily doses of 0.0, 1.5, and 1.5 mg swainsonine/kg bw per day, respectively, for 45 days. Animals were observed daily and weekly body weights, serum enzyme activities, and serum swainsonine concentrations were determined. At day 45 all animals were euthanized and necropsied. Goats treated with A. lentiginosus and I. carnea developed clinical disease characterized by mild intention tremors and proprioceptive deficits. Goats treated with A. lentiginosus developed clinical disease sooner and with greater consistency. No differences in body weight, serum swainsonine concentrations and serum enzyme activity were observed between goats treated with A. lentiginosus and I. carnea. Additionally, there were no differences in the microscopic and histochemical studies of the visceral and neurologic lesions observed between goats treated with A. lentiginosus and I. carnea. These findings suggest that I. carnea-induced clinical signs and lesions are due to swainsonine and that calystegines contribute little or nothing to toxicity in goats in the presence of swainsonine.

Spontaneous and Experimental Glycoprotein Storage Disease of Goats Induced by Ipomoea carnea subsp fistulosa (Convolvulaceae)

Spontaneous and experimental poisoning with the swainsonine-containing and calystegine-containing plant Ipomoea carnea subsp fistulosa is described. Three of 8 goats presenting with emaciation, weakness, symmetrical ataxia, posterior paresis, proprioceptive deficits, abnormal posture, abnormal postural reaction, and muscle hypertonia were necropsied. I fistulosa was suspected to be the cause of the neurologic disease in all cases. An experiment was conducted to confirm the diagnosis using 12 goats and diets containing 3 different concentrations of the plant. All goats fed I fistulosa developed neurological signs that were similar to those observed in the spontaneous intoxication. Muscle atrophy and pallor were the only macroscopic changes observed in spontaneous and in experimental intoxication. Histological lesions of spontaneous and experimental animals were similar. The most prominent lesion was cytoplasmic vacuolation in neurons of the central and the autonomous nervous system, pancreatic acinar cells, hepatocytes, Kupffer cells, follicular epithelial cells of the thyroid gland, and macrophages of the lymphatic tissues. Neuronal necrosis, axonal spheroids formation, and astrogliosis were additionally observed in the brain. Ultrastructurally, the cytoplasmic vacuoles consisted of distended lysosomes surrounded by a single-layered membrane. Nonreduced end-rests or sequence of α-Man, α-Glc, β(1–4)-GlcNAc, and NeuNAc on lysosomal membrane were revealed by lectin histochemistry. Samples of plants used in the experimental trial contained swainsonine and calystegine and their intermediary derivate. We conclude that I fistulosa induces a glycoprotein storage disease primarily based on the inhibition of the lysosomal α-mannosidase by the alkaloid swainsonine.

Experimental poisoning of goats by Ipomoea carnea subsp. fistulosa in Argentina: a clinic and pathological correlation with special consideration on the central nervous system

Ipomoea carnea subsp. fistulosa, aguapei or mandiyura, is responsible for lysosomal storage in goats. The shrub contains several alkaloids, mainly swansonine which inhibits lysosomal α-mannosidase and Golgi mannosidase II. Poisoning occurs by inhibition of these hydrolases. There is neuronal vacuolation, endocrine dysfunction, cardiovascular and gastrointestinal injury, and immune disorders. Clinical signs and pathology of the experimental poisoning of goats by Ipomoea carnea in Argentina are here described. Five goats received fresh leaves and stems of Ipomoea. At the beginning, the goats did not consume the plant, but later, it was preferred over any other forage. High dose induced rapid intoxication, whereas with low doses, the course of the toxicosis was more protracted. The goats were euthanized when they were recumbent. Cerebrum, cerebellum, medulla oblongata, pons and colliculi, were routinely processed for histology. In nine days, the following clinical signs developed: abnormal fascies, dilated nostrils and abnormal postures of the head, cephalic tremors and nystagmus, difficulty in standing. Subsequently, the goats had a tendency to fall, always to the left, with spastic convulsions. There was lack in coordination of voluntary movements due to Purkinje and deep nuclei neurons damage. The cochlear reflex originated hyperreflexia, abnormal posture, head movements and tremors. The withdrawal reflex produced flexor muscles hypersensitivity at the four legs, later depression and stupor. Abnormal responses to sounds were related to collicular lesions. Thalamic damage altered the withdrawal reflex, showing incomplete reaction. The observed cervical hair bristling was attributed to a thalamic regulated nociceptive response. Depression may be associated with agonists of lysergic acid contained in Ipomoea. These clinical signs were correlated with lesions in different parts of the CNS.

The Comparative Pathology of the Glycosidase Inhibitors Swainsonine, Castanospermine, and Calystegines A3, B2, and C1 in Mice

To study various polyhydroxy-alkaloid glycosidase inhibitors, 16 groups of 3 mice were dosed using osmotic minipumps with swainsonine (0, 0.1, 1, and 10 mg/kg/day), castanospermine, and calystegines A3, B2, and C1 (1, 10, and 100 mg/kg/day). After 28 days, the mice were euthanized, necropsied, and examined using light and electron microscopy. The high-dose swainsonine–treated mice developed neurologic disease with neuro-visceral vacuolation typical of locoweed poisoning. Castanospermine- and calystegines-treated mice were clinically normal; however, high-dose castanospermine–treated mice had thyroid, renal, hepatic, and skeletal myocyte vacuolation. Histochemically, swainsonine- and castanospermine-induced vacuoles contained mannose-rich oligosaccharides. High-dose calystegine A3–treated mice had increased numbers of granulated cells in the hepatic sinusoids. Electron microscopy, lectin histochemistry, and immunohistochemistry suggest these are pit cells (specialized NK cells). Histochemically, the granules contain glycoproteins or oligosaccharides with abundant terminal N-acetylglucosamine residues. Other calystegine-treated mice were histologically normal. These findings indicate that swainsonine produced lesions similar to locoweed, castanospermine caused vacuolar changes with minor changes in glycogen metabolism, and only calystegine A3 produced minimal hepatic changes. These also suggest that in mice calystegines and castanospermine are less toxic than swainsonine, and as rodents are relatively resistant to disease, they are poor models to study such induced storage diseases.

The role of alkaloids in Ipomoea carnea toxicosis: A study in rats

Ipomoea carnea promotes in livestock a toxicosis histologically characterized by vacuolated cells in different organs. The toxic principles of I. carnea are the alkaloids swainsonine and calystegines B1, B2, B3 and Cl. However, it has not been determined whether the effects observed in rats treated with this plant are only due to swainsonine or if the calystegines have some additive toxic effect. Thus, the aim of the present study was to evaluate in rats the toxic effects of the L carnea aqueous fraction (AF) and of its different alkaloids when administered individually at the same concentration as in this fraction, for 14 days. No anorexic effect and/or alteration in body weight was observed in any group. The histopathologic study showed that while calystegines did not produce any toxic effects, swainsonine and I carnea AF promoted vacuolation in different organs, being more severe in the animals from the I. carnea AF group and extensible to other organs evaluated. No alterations were detected in the central nervous system of rats of any group assayed. The results obtained here suggest that calystegines may act as coadjuvants of swainsonine in I carnea toxicosis; however, little can be proposed about the neurotoxic effect of I. carnea since rats did not prove to be a good model for the reproduction of neuronal storage disease.

Possible involvement of cholinergic and adrenergic mechanisms in changing contractility of guinea pig ileum by Ipomoea carnea

The study aimed to elucidate the mechanism (s) of action of Ipomoea carnea leaf juice (ILJ) in changing contractility of guinea pig ileum. ILJ produced dose-dependent (10-10000 microg/ml) triphasic responses. The initial contractile phase was blocked by atropine (1 microg/ml) but had additive effect with acetylcholine (2 ng/ml) or carbachol (2 ng/ml). Neostigmine (30 ng/ml) or lignocaine (50 microg/ml) failed to alter the response. In cold-induced denervated preparations, this phase was augmented. The relaxatory phase of ILJ was not modified by phenoxybenzamine (35 microg/ml) but was reduced by propranolol (1 microg/ml) and abolished by lignocaine (50 microg/ml). The final contractile phase of ILJ was not affected by atropine (1 microg/ml). These results suggest that the triphasic response of ILJ is possibly mediated through cholinergic, adrenergic and non-cholinergic mechanisms, respectively.

A lysosomal storage disease induced by Ipomoea carnea in goats in Mozambique

A novel plant-induced lysosomal storage disease was observed in goats from a village in Mozambique. Affected animals were ataxic, with head tremors and nystagmus. Because of a lack of suitable feed, the animals consumed an exotic hedge plant growing in the village that was identified as Ipomoea carnea (shrubby morning glory, Convolvulaceae). The toxicosis was reproduced by feeding I. carnea plant material to goats. In acute cases, histologic changes in the brain and spinal cord comprised widespread cytoplasmic vacuolation of neurons and glial cells in association with axonal spheroid formation. Ultrastructurally, cytoplasmic storage vacuoles in neurons were membrane bound and consistent with lysosomes. Cytoplasmic vacuolation was also found in neurons in the submucosal and mesenteric plexuses in the small intestine, in renal tubular epithelial cells, and in macrophage-phagocytic cells in the spleen and lymph nodes in acute cases. Residual alterations in the brain in chronic cases revealed predominantly cerebellar lesions characterized by loss of Purkinje neurons and gliosis of the Purkinje cell layer. Analysis of I. carnea plant material by gas chromatography-mass spectrometry established the presence of the mannosidase inhibitor swainsonine and 2 glycosidase inhibitors, calystegine B2 and calystegine C1, consistent with a plant-induced alpha-mannosidosis in the goats. The described storage disorder is analogous to the lysosomal storage diseases induced by ingestion of locoweeds (Astragalus and Oxytropis) and poison peas (Swainsona).

Neuromuscular blocking activity of a crude aqueous extract of Ipomoea fistulosa

The rat phrenic nerve hemidiaphragm and chick biventer-cervicis preparations were used to investigate the effect of a crude aqueous extract of Ipomoea fistulosa. Electrically-induced skeletal muscle twitches of the hemidiaphragm were blocked by the extract and by tubocurarine. The anticholinesterase, physostigmine, intensified the blockade by the extract. The extract produced contracture of the chick biventer-cervicis preparation. It is suggested that the extract possesses neuromuscular blocking activity of a depolarizing nature.

Effects of Jatropha curcas on calves

Jatropha curcas seed was fed to six calves at doses of 2.5, 1 and 0.25 g/kg once and to two other calves at 0.025 g/kg up to 14 days. The onset of toxic manifestations in the six calves was rapid and death occurred within 19 hours of administration. The two calves that received daily the lowest dose of J. curcas showed signs of poisoning and died within 10 to 14 days. The clinical signs of diarrhoea, dyspnoea, dehydration and loss of condition were well correlated with the pathological findings. There was an increase in aspartate aminotransferase, ammonia and potassium and a decrease in total protein and calcium in the serum of jatropha-poisoned calves.

Toxicity of Jatropha cucurcas for goats

Eleven Nubian goats were fed with Jatropha curcas seeds at doses ranging from 0.25 g to 10g/kg/day. All dose levels were found to be toxic with fatal conswquences within 2 to 21 days. Liver biopsy samples taken 2 days after the start of feeding and subsequent biopsies showed congestion, varying degrees of fatty change, considerable reduction in glycogen content and necrosis of the hepatocytes. Lack of appetite, reduced water consumption, diarrhoea, dehydration, sunken eyes and a steadily deteriorating condition were important clinical signs of Jatropha intoxication goats. In all animals there was a decrease in the level of glucose and a marked rise in the concentration of arginase and glutamate oxaloacetate transminase (GOT) in the serum. Post-mortem examination revealed haemorrhage in the rumen, reticulum, kidney, spleen and heart, catarrhal or haemorrhagic abomasitis and enteritis, congestion and oedema of the lung and excessive fluid in serous cavities.