Buckthorn neuropathy: effects of intraneural injection of Karwinskia humboldtiana toxins

Neuropathic or systemic chronic intoxication with Karwinskia humboldtiana (Buckthorn) fruit? Histopathological effect in myocardial and skeletal muscle

In accidental intoxicated animals and humans, Karwinskia humboldtiana (Kh) causes lesions in the central and peripheral nervous system and organs like the kidney, liver, and lung. The objective was to evaluate the histology of myocardium and skeletal muscle after experimental chronic intoxication with mature fruit of Kh in Wistar rat. Twenty-five rats were used and divided into five groups (n = 5): four intoxicated and one control. Kh fruit was ground, dried, sieved, and administered by an orogastric tube. Intoxicated rats received 3.5 g/kg body weight fractionated in 5 doses. Control rats received only water. Animals were euthanized at 24, 48, 58, and 112 days, respectively. Samples of the myocardium and skeletal muscle were obtained and processed for light microscopy evaluation. Morphological analyses were performed, including a microdensitometric analysis. Results showed areas of necrosis in the muscle fibers, fibers with vacuolated cytoplasm, and disorganization of myofilaments, as well as staining variations in both myocardium and skeletal muscle time-depending. Zones with loss of continuity of the external lamina were identified with PAS with the diastase histochemical method. Immunolabeling with specific antibodies demonstrated diminution of actin and desmin myofilaments. The microdensitometric analysis showed a statistically significant difference between the intoxicated vs control group. These findings demonstrate that chronic intoxication of Kh fruit also causes damage in myocardial and skeletal muscle, these alterations will be useful to understand that the toxic effects of Kh fruit in accidently intoxicated humans are systemic, and not only over the nervous system.

Toxicity and Anticancer Potential of Karwinskia: A Review

Karwinskia genus consists of shrubs and small trees. Four toxic compounds have been isolated from Karwinskia plants, which were typified as dimeric anthracenones and named T496, T514, T516, and T544. Moreover, several related compounds have been isolated and characterized. Here we review the toxicity of the fruit of Karwinskia plants when ingested (accidentally or experimentally), as well as the toxicity of its isolated compounds. Additionally, we analyze the probable antineoplastic effect of T514. Toxins cause damage mainly to nervous system, liver, lung, and kidney. The pathophysiological mechanism has not been fully understood but includes metabolic and structural alterations that can lead cells to apoptosis or necrosis. T514 has shown selective toxicity in vitro against human cancer cells. T514 causes selective and irreversible damage to peroxisomes; for this reason, it was renamed peroxisomicine A1 (PA1). Since a significant number of malignant cell types contain fewer peroxisomes than normal cells, tumor cells would be more easily destroyed by PA1 than healthy cells. Inhibition of topoisomerase II has also been suggested to play a role in the effect of PA1 on malignant cells. More research is needed, but the evidence obtained so far indicates that PA1 could be an effective anticancer agent.

An experimental model of peripheral neuropathy induced in rats by Karwinskia humboldtiana (buckthorn) fruit

Intoxication by Karwinskia humboldtiana (buckthorn) fruit presents a neurological picture similar to that of Guillain-Barré syndrome. In this report, we describe an experimental animal model of peripheral neuropathy induced by buckthorn fruit. Four groups of Wistar rats received one oral dose of 1.5 g/kg followed by oral doses of 0.5 g/kg at days 3, 7, 10, and 14 of dried and ground buckthorn fruit in aqueous suspension. Rats were sacrificed at 24, 48, 58, and 112 days after initial dose. Treated animals developed progressive paralysis through 58 days, then completely recovered by 112 days. Sciatic nerves showed segmental demyelination and cellular infiltrates until 58 days after exposure and then remyelinating changes at 112 days. This experimental model for peripheral neuropathy is reproducible and easy to handle. Its manipulation is relatively innocuous and allows us to study reversible peripheral nerve damage. This model can be developed in other animal species and may be useful to test new therapies for peripheral neuropathy.

Depression of fast axonal transport in axons demyelinated by intraneural injection of a neurotoxin from K. humboldtiana

Tullidinol, a neurotoxin extracted from the Karwinskia humboldtiana fruit, dissolved in peanut oil was injected into the right sciatic nerve of adult cats. The contralateral sciatic nerve received an equivalent volume of peanut oil alone. The fast axonal transport of labeled ([3H]Leucine) protein was studied in sensory and motor axons of both sciatic nerves. The radioactive label was pressure injected either into the L7 dorsal root ganglion or the ventral region of the same spinal cord segment. Several days after the toxin injection, the cat limped and the Achilles tendon reflex was nearly absent in the right hind limb. The amount of transported label was decreased distal to the site of toxin injection. Proximal to this site, the transported material was damned. Sensory and motor axons showed similar changes. In addition, the toxin produced demyelination and axonal degeneration. Axonal transport and the structure of the axons were normal in the contralateral nerve. Both, Schwann cells and axons of the right sciatic nerve showed globular inclusions, presumably oil droplets containing the toxin. We conclude that Schwann cells and axons as well are tullidinol targets.

Spectrophotometric and chromatographic detection of Karwinskia humboldtiana (tullidora) toxin in rat serum after tullidora ingestion

The absorbance spectrum of tullidinol, a tullidora (Karwinskia humboldtiana) toxin, showed peaks at 260 and 410 nm when dissolved in ethanol; the second peak was linearly related to toxin concentration. Silica gel thin layer chromatograms of tullidinol solutions showed a single, yellow spot with an Rf of 0.76. A single dose of tullidora fruit homogenate was orally given to male Wistar rats; the absorbance spectrum of serum from tullidora-treated rats showed peaks at 300 nm and at 410 nm; the second peak was absent in serum from control rats. No spots were detected in chromatograms of normal serum, but a yellow spot with the same Rf as that of tullidinol was found in the serum of tullidora-treated rats. We conclude that tullidinol was detected in the serum of treated animals and that the methods we used for its detection may also help to diagnose accidental tullidora poisoning in cattle and human beings.

Depression of fast axonal transport produced by tullidora

The fast axoplasmic transport of labeled proteins was studied in cats showing hindlimb paralysis 4-7 weeks after a single oral dose of tullidora (Karwinskia humboldtiana) toxins. The isotope (3H-leucine) was injected into the spinal ganglion and the contralateral spinal cord of the seventh lumbar segment in order to study transport in sensory and motor fibers. The axoplasmic transport in motor fibers of the sciatic nerve was clearly altered in tullidora-treated cats. The majority of these animals showed a gradual decline of radioactivity from the cord to the periphery instead of the clear-cut wave front always seen in normal cats. An apparent wave was seen in three treated cats but the wave peak was behind the normal position and the slope of the wave front was reduced. While the rate of transport indicated by the farthest extent of the foot of the slope was not in all cases significantly changed, the results all indicated a hindered transport by the reduced slope front in the distal segments of the motor axons. In contrast, the axoplasmic transport appeared normal in the sensory fibers of all but one tullidora-treated cat. Light and electron microscopy of medial gastrocnemius and sural (cutaneous) nerves revealed axonal constrictions and axolemal irregularities associated with organelle retention after tullidora treatment. Also, some mitochondria appeared swollen. These changes were more frequent and intense in the motor nerve fibers than in the cutaneous nerve fibers.

Axon-to-axon transmission in tullidora (buckthorn) neuropathy

Oral administration of ether extracts of the tullidora ( Karwinskia humboldtiana ) fruit, which contains an identified neurotoxin, produced flaccid hind limb paralysis in cats after a latency of 4 to 7 weeks. Acute experiments were conducted after the paralysis was evident. Spinal roots of lumbar and sacral segments were transected as close as possible to the spinal cord and divided into several filaments. Stimulation of some filaments distal to the transection evoked action potentials in other filaments (axon-to-axon transmission or cross talk) after a latency of at least 8 ms. Cross-talk responses frequently consisted of multiple discharges. Axon-to-axon transmission was seen only between motor axons and disappeared when hind limb nerves were transected 10 to 15 cm from the spinal cord. Twin pulses were applied to a filament at various intervals; the pulse intensity was adjusted so that the conditioning pulse was subthreshold to elicit cross talk, but the test pulse frequently elicited it (temporal facilitation). In three fully studied fibers the facilitation was prolonged to 50 to 80 ms. In some cases, no cross talk was evoked in a given filament by individual stimulation of two other filaments, but simultaneous stimulation of the same filaments did evoke cross talk (spatial facilitation). Series of periodic bursts of activity spontaneously occurred in those axons responding with multiple discharges to single stimulation of other axons. At low temperatures (about 30 degrees C) the stimulus could trigger essentially similar series of bursts. Single motoneurons were intracellularly stimulated by brief depolarizing pulses. The action potential elicited by the stimulus was followed after several msec by a secondary train of discharges generated at the periphery ("back firing").

Tullidora (Karwinskia humboldtiana) toxin mainly affects fast conducting axons

Cats were given a single oral dose of ether extracts from tullidora (Karwinskia humboldtiana) fruit which contains an identified neurotoxin. Acute experiments were performed 4-7 weeks after toxin administration when flaccid limb paralysis was evident. Normal cats were used as controls. The medial gastrocnemius, the soleus and the sural nerves were electrically stimulated and the unitary potentials evoked by the stimuli were extracellularly recorded from spinal root filaments to measure the conduction velocity of single fibres. In control cats, the average conduction velocity (CV) was greater in medial gastrocnemius motor fibres than in the afferent ones of the same nerve and the soleus motor axons, whereas in the sural nerve CV was less than in the aforementioned cases. The CV values and the proportion of fast conducting fibres (greater than 80 m/s) in each nerve were directly related (r = 0.99). In treated cats, CV diminished in all the nerves studied, but the conduction velocity was further reduced in the faster fibres. Consequently, the motor division of the medial gastrocnemius nerve, normally composed of a high proportion (57%) of fast fibres, was more affected by tullidora and the sural nerve, which has the lowest proportion (0.7%) of these type of fibres, was the less affected. Our findings suggest that the preferential involvement of motor nerves in the experimental tullidora (buckthorn) neuropathy, as well as the preservation of somatic sensation in quadriplegic children accidentally poisoned with tullidora, are related to the distribution of axonal diameters in peripheral nerves.

Distal reduction of the conduction velocity of alpha-axons in tullidora (buckthorn) neuropathy

Cats were given a single oral dose of ether extracts of the tullidora (Karwinskia humboldtiana) fruit. Three to five weeks later these animals developed the tullidora (buckthorn) neuropathy. Acute experiments were conducted in control cats as well as in treated cats which showed hind limb paralysis. Spinal motoneurons of the medial gastrocnemious and the soleus nerves were recorded intracellularly and their axons were electrically stimulated at two points, near the entry to the muscle and at the hip level. The conduction velocity was determined for the segment between the two stimulating electrodes [distal conduction velocity; (DCV)] and for the segment between the electrode at the hip level and the spinal cord [proximal conduction velocity (PCV)]. In untreated animals, DCV was higher than PCV so that the ratio DCV:PCV was, on the average, larger than 1. In treated animals, DCV was reduced, but PCV remained within normal limits and DCV:PCV was lower than 1. In addition, there was a relative deficit of the faster velocities suggesting that the thicker fibers were preferentially affected. These observations are in agreement with previous ones indicating that demyelination induced by tullidora is restricted to distal nerve segments.

Denervation caused by tullidora (Karwinskia humboldtiana)

Crude homogenate of the seed of the tullidora (Coyotillo, buckthorn; Karwinskia humboldtiana) fruit or a purified neurotoxin extracted from it was administered orally to male Wistar rats. Three to 5 weeks later, gait disturbances and progressive flaccid paralysis of the hindlimbs appeared in these animals which were then submitted to acute experiments. Single twitch and tetanic contractions of the soleus muscle were studied in the tullidora treated rats. The twitch tension elicited by direct stimulation of the muscle was greater than that produced by nerve stimulation. In addition, the tension of nerve-elicited twitches diminished as the stimulating electrode was moved towards the spinal cord, suggesting failure of nerve conduction. When the muscle was directly stimulated, contraction and relaxation were slower than normal and the tetanus/twitch tension ratio was subnormal. These data suggest partial denervation of the soleus muscle under the action of the toxin. Electron microscopy revealed abnormal motor-nerve endings with few synaptic vesicles and denervated end-plates. Degenerative changes of axons and myelin disturbances were frequently seen in the intramuscular branches of the soleus nerve. However, alterations of this type were less severe in the nerve sections closer to the spinal cord and no significant changes were detected at the upper portion of the sciatic nerve. It is concluded that the paralysis produced by the tullidora toxin is the result of both conduction block of the nerve impulses and muscle denervation.

Degeneration of non-myelinated axons in the rat sciatic nerve following lysolecithin injection

Lysolecithin has been used in many studies to induce demyelination in peripheral nerves. In the present investigation lysolecithin (lysophosphatidyl choline) was injected into rat sciatic nerves at a dose of 2-3 microns of a 10 mg/ml solution in order to study the effects of this lipid on cellular elements other than myelin within the nerve. Twenty-four hours after injection, there was splitting of myelin, lysis of Schwann cells, and complete loss of non-myelinated axons and their Schwann cells at the site of injection. Numerous swollen non-myelinated axons containing accumulated organelles were seen just proximal to the site of injection at 48 h. Loss of non-myelinated axons from the distal part of the nerve was also noted at 3 days after injection but 7 days regenerating non-myelinated axons had re-appeared in the distal part of the nerve. Although demyelination, followed by remyelination was prominent feature in the injected segment of the nerve, no damage to myelinated axons was detected. These results suggest that the presence of the myelin sheath protects the large myelinated axons against the action of lysolecithin, but with lysis of Schwann cells, the non-myelinated axons are exposed to the action of lysolecithin. Apart from selective damage to non-myelinated fibres with subsequent degeneration, it is also possible that lysolecithin interferes with axoplasmic flow in non-myelinated axons.

Peripheral neuropathy following intraneural injection of mercury compounds

Between 0.25-25 micrograms of an aqueous solution of either mercuric chloride or methyl mercuric acetate was injected directly into the sciatic nerve of 28 adult Wistar rats. The resultant pathological changes in the nerve were examined by teasing individual fibres and by light and electron microscopy. In most respects mercuric chloride was more toxic than methyl mercuric acetate. The large doses of mercuric chloride produced a hind limb paresis within 24 h but no clinical signs followed injection of organic mercury. The predominant effect of mercuric chloride was on Schwann cells which showed cytoplasmic swelling and necrosis, associated with extensive segmental demyelination. In contrast methyl mercuric acetate caused axonal degeneration in many of the large myelinated fibres but only minor alterations were observed in Schwann cells.

50ppm MnBK subclinical neuropathy in rats

40 rats were subjected daily for 6 months to an atmosphere containing 50ppm MnBK. 32 of the rats presented with demyelination of the sciatic nerve and 2 of these with axonal hypertrophy.