Brain cortex gangliosides and (Na+, K+)ATPase system of the stria vascularis in guinea pig

Histopathological analysis of gangliosides use in peripheral nerve regeneration after axonotmesis in rats

PURPOSE: To analyze the action of gangliosides in peripheral nerve regeneration in the sciatic nerve of the rat. METHODS: The sample was composed of 96 male Wistar rats. The animals were anaesthetized and, after identification of the anaesthesic plane, an incision was made in the posterior region of the thigh, followed by skin and muscle divulsion. The right sciatic nerve was isolated and compressed for 2 minutes. Continuous suture of the skin was performed. The animals were randomly divided into two groups: the experimental group (EG), which received subcutaneous injection of gangliosides, and the control group (CG), which received saline solution (0.9%) to mimic the effects of drug administration. RESULTS: No differences were observed between the experimental and control groups evaluated on the eighth day of observation. At 15 and 30 days the EG showed an decrease in Schwann cell activity and an apparent improvement in fibre organization; at 60 days, there was a slight presence of Schwann cells in the endoneural space and the fibres were organized, indicating nerve regeneration. At 15 and 30 days, the level of cell reaction in the CG had diminished, but there were many cells with cytoplasm in activity and in mitosis; at 60 days, hyperplastic Schwann cells and mitotic activity were again observed, as well as nerve regeneration, but to a lesser extent than in the EG. CONCLUSION: The administration of exogenous gangliosides seems to improve nerve regeneration.

Auditory brainstem responses of CBA/J mice with neonatal conductive hearing losses and treatment with GM1 ganglioside

Exogenous administration of GM1 ganglioside to CBA/J mice with a neonatal conductive hearing loss ameliorates the atrophy of spiral ganglion neurons, ventral cochlear nucleus neurons, and ventral cochlear nucleus volume. The present investigation demonstrates the extent of a conductive loss caused by atresia and tests the hypothesis that GM1 ganglioside treatment will ameliorate the conductive hearing loss. Auditory brainstem responses were recorded from four groups of seven mice each: two groups received daily subcutaneous injections of saline (one group had normal hearing; the other had a conductive hearing loss); the other two groups received daily subcutaneous injections of GM1 ganglioside (one group had normal hearing; the other had a conductive hearing loss). In mice with a conductive loss, decreases in hearing sensitivity were greatest at high frequencies. The decreases were determined by comparing mean ABR thresholds of the conductive loss mice with those of normal hearing mice. The conductive hearing loss induced in the mice in this study was similar to that seen in humans with congenital aural atresias. GM1 ganglioside treatment had no significant effect on ABR wave I thresholds or latencies in either group.

Localization of the GM1 ganglioside in the vestibular system using cholera toxin

Cholera toxin is an ubiquitous activator of intracellular adenylate cyclase and is divided in two major components: A and B. The B-component consists of several subunits that specifically bind to the external cell membrane. The receptor for the toxin, the GM1 ganglioside, is concentrated in nervous tissues. The B subunit of the cholera toxin, conjugated to different molecules (i.e., choleragenoid) is therefore a sensitive anatomical tracer and has been used to detect the presence of GM1 in mammalian tissues. Using choleragenoid, unlabeled and labeled with FITC, we have determined the distribution of the GM1 ganglioside in the vestibular system of the chinchilla. Vestibular tissues were fixed in 4% paraformaldehyde in phosphate buffer, decalcified in 10% EDTA and prepared as either whole-mount, surface-preparations, or for radial cryosections. Positive control tissue consisted of binding to normal brain tissues. Negative controls consisted of several treatments: masking of the GM1 receptors with unlabeled choleragenoid, tissue extraction of GM1 using ethanol, and preabsorbing the choleragenoid with bovine GM1. In addition, to exclude staining of glycoproteins that may have a carbohydrate structure similar to GM1, tissues were digested with trypsin prior to choleragenoid exposure. In the vestibular system, a strongly positive reaction was observed in: the sensory stereocilia and supporting cells of the maculae and cristae, epithelial cells of the planum semilunatum, and polygonal cells of the semicircular canal. Positive but less strong reactivity was observed in the sensory cell body of maculae and cristae, nerve fibers, epithelial cells of utricle and ampulla walls and flattened epithelial cells of the semicircular canals. No reactivity was present in the supporting connective tissue cells and fibrils, blood vessels, gelatinous cupula of the cristae ampullaris and statoconial membranes. Brain tissue showed strong choleragenoid reactivity. The negative controls showed no or greatly reduced reactivity to choleragenoid. Trypsin digestion did not decrease reactivity to choleragenoid.

Effects of gangliosides on the methionine uptake in crushed sciatic nerves of rats with alloxan diabetes

Effect of gangliosides on the transmembrane transport of methionine in crushed sciatic nerves was studied in alloxan diabetic and control rats until the 4th day after nerve crushing. Methionine uptake rate decreases while time passes after injury in both control and diabetic rats, but the decrement is greater in diabetic rats than in controls. Ganglioside treatment causes an enhancement on the transmembrane transport in both diabetic and control animals, but the effect in time was greater in diabetic rats than in controls.

Investigations on the incorporation of a tritiated ganglioside, GM1, in the injured and intact sciatic nerves of the rat

Following injury of their left sciatic nerves by means of a standardized procedure, male rats received intravenous injections of a tritiated ganglioside. GM1, on different days during the process of regeneration. The rats were killed at two different times after the injection and the concentrations of the total radioactivity, nonvolatile radioactivity, and labelled GM1 were estimated in six segments of the crushed and intact sciatic nerves. The segments of the damaged nerves showed higher concentrations of radioactivity and a higher content of GM1 than the corresponding segments of the contralateral nerves. Within the immediate area of the lesion the highest levels were found on the 3rd and 6th days after the injury; the segments distal from the lesion showed the highest levels of activity on days 9 and 12. The nerve segments proximal to the site of the injury showed a low rate of radioactivity incorporation. The higher concentrations of [3H]GM1 in damaged nerves as well as the rate of incorporation as a function of time indicate that exogenous gangliosides may be involved in the processes of regeneration and have a bearing on the latter.

The facilitating effect of gangliosides on the electrogenic (Na+/K+) pump and on the resistance of the membrane potential to hypoxia in neuromuscular preparation

The effects have been investigated of a mixture of gangliosides from beef brain cortex (GM1, GD1a, GD1b and GT1) either added to the bathing medium or injected intraperitoneally on muscle fibres and nerve terminals in mouse diaphragm. The electrogenic (Na+/K+) pump activity of muscle fibres enriched with sodium was increased by 38% after 2-h pretreatment with gangliosides (5 X 10(-8) mol X 1(-1]. Muscles from animals treated with gangliosides did not show the substantial depolarization of the resting membrane potential (RMP) in K+-free solution (6 h) shown by control muscles. Further, treatment with gangliosides slowed the changes in muscle fibre RMP and frequency of the miniature end-plate potentials in oxygen deprived muscles.

Development of diabetic neuropathy in the C57BL/Ks (db/db) mouse and its treatment with gangliosides

We studied the development of diabetic neuropathy and its treatment with gangliosides using the C57BL/Ks mouse. The results of axonal morphometry showed the presence of a progressive axonal atrophy which was maximal at 180 days of age. To 400 days of age there was no longer any significant difference, perhaps due to aging processes. Nerve conduction velocity changed significantly from the early days of life. Thirty-day treatment with gangliosides significantly improved nerve conduction velocity and axonal morphometry at 180 and 280 days of life. No effect was observed with treatments at 30 or 60 days. It was previously shown that the early phase of the C57BL/Ks mouse neuropathy was reversed by insulin, whereas the late phase (180 days) was not. We showed elsewhere that at 180 days of age in the C57BL/Ks mouse there was a drastic decrease in slow transport of AChE (G1 and G2 molecular forms) indicating a shift in neuronal metabolism and suggesting that the disease was then more intrinsically neuronal. Using the suggestion of Robertson and Sima (Diabetes 29: 60-67, 1980) we label the first phase of the neuropathy "metabolic" (treatable with insulin) and the second phase "neuronal" (treatable with gangliosides). This "neuronal" phase could be related to the degenerative stage of human diabetic neuropathy.

Ganglioside treatment of genetic and alloxan-induced diabetic neuropathy

Peripheral neuropathy is a common complication of diabetes. Using the mutant diabetic mouse C57BL/ks (db/db) and alloxan-treated rats, 30 days after intoxication, we investigated development and treatment with gangliosides of such a disease. The db/db mouse develops a neuropathy characterized by a loss in conduction velocity shown as early as 80-90 days after birth and maintained throughout life. At later stages (5-6 months of age) there is a drop in slow transport and myelin particle density. These changes are correlated by a lack of response to insulin treatment, which, prior to this stage, is capable of improving nerve conduction velocity (NCV). On the other hand gangliosides became effective, improving NCV, myelin particle density and sensory perception (auditory deficit) at 5 months of age in the db/db mouse. We presume that this differential neuronal response to insulin and gangliosides indicates a change of the neuropathy from a metabolic stage to neuronal. Alloxan induced diabetic neuropathy is treatable with gangliosides even 30 days after intoxication.

Ganglioside treatment improves recovery of alternation behavior after unilateral entorhinal cortex lesion

Exogenous gangliosides have been reported to enhance neurite formation in vitro and in vivo after damage to peripheral nerves. We report here the effects of ganglioside treatment on the course of recovery of alternation behavior that follows a unilateral lesion of the rat entorhinal cortex. The recovery of this function is known to parallel rapid synaptic reinnervation (collateral sprouting) into the partially denervated dentate gyrus of the hippocampus which previously received afferent input from the entorhinal region. Rats trained on an alternation behavior were subjected to a unilateral entorhinal lesion and subsequently given daily injections of total ganglioside (50 mg/kg, i.m.). Testing of the behavior continued for 2 weeks to assess the extent of behavioral impairment and the rate of recovery. Rats treated with gangliosides showed reduced behavioral impairment, accelerated recovery of the learned behavior, and final performance levels greater than controls. We hypothesize that the gangliosides may be interacting with regenerating neuronal membranes, either acting as receptors for trophic growth factors or altering membrane structure itself.

Ganglioside treatment of alcoholic neuropathies: experimental and clinical aspects

Recent research results indicate that gangliosides, complex glycolipids present in neuronal membranes, play an important functional role in nervous transmission. Physiological and pharmacological investigations have shown that the parenteral administration of a bovine cerebral cortex ganglioside preparation exerts a reinnervation-stimulating activity, due to enhanced nerve sprouting, in peripheral neuropathies. Experimental data are presented showing that the administration of ganglioside prevents the decrease of the conduction velocity, measured in the sciatic nerve of laboratory animals chronically intoxicated with ethanol. Gangliosides are also able to improve the conduction velocity in the sciatic nerve of animals already damaged by the same neurotoxic agent. With regard to therapeutical aspects in alcoholic patients with sensory or motor-sensory polyneuropathy, a review is presented covering 114 patients studied in several clinical trials by means of clinical and instrumental investigations. The clinical parameters, especially the sensory disturbances, turn out to be very responsive to ganglioside treatment. Also, the electrophysiological effects are positively influenced, even though this kind of investigation presents methodological difficulties connected with the great variability of baseline data.

Monosialoganglioside (GM1) treatment of ouabain-induced retinopathy in the rabbit

The mammalian retina is markedly influenced by cardiac glycosides. When nanomolar concentrations of ouabain are intravitreously injected into the rabbit, the visually evoked response completely disappears within 90 min, while scotopic ERG recordings show a remarkably decreased amplitude of the principal waves. When 33 nmol/kg monosialoganglioside are injected intravenously 30 min before topical intoxication, this functional impairment is significantly reduced. The electroretinographic response shows a limited amplitude reduction, while the cortical potential never disappears completely. Histological observations of intoxicated retinas show that a degenerative process begins in photoreceptor outer segment 24 h after the intravitreal ouabain injection. Presently, this process involves both the outer and inner nuclear layers and, finally, the ganglion cell layer. Comparing the intoxicated treated and untreated retinas, no difference is found in the degenerative pattern of the two groups. Autoradiographic studies are also reported to correlate the protective effect of monoganglioside (GM1) on this toxic retinopathy with its preferential accumulation in different retinal tissues.