Plasma amino-acids in the Nigerian nutritional ataxic neuropathy

Konzo risk factors, determinants and etiopathogenesis: What is new? A systematic review

Konzo is a toxico-nutritional upper motor neuron disease causing a spastic paraparesis in schoolchildren and childbearing women in some African countries. Almost a century since the first description of konzo, its underlying etiopathogenic mechanisms and causative agent remain unknown. This paper aims at refreshing the current knowledge of konzo determinants and pathogenesis in order to enlighten potential new research and management perspectives. Literature research was performed in PubMed and Web of Science databases according to the PRISMA methodology. Available data show that cassava-derived cyanide poisoning and protein malnutrition constitute two well-documented risk factors of konzo. However, observational studies have failed to demonstrate the causal relationship between konzo and cyanide poisoning. Thiocyanate, the current marker of choice of cyanide exposure, may underestimate the actual level of cyanide poisoning in konzo patients as a larger amount of cyanide is detoxified via other unusual pathways in the context of protein malnutrition characterizing these patients. Furthermore, the appearance of konzo may be the consequence of the interplay of several factors including cyanide metabolites, nutritional deficiencies, psycho-emotional and geo-environmental factors, resulting in pathophysiologic phenomena such as excitotoxicity or oxidative stress, responsible for neuronal damage that takes place at sparse cellular and/or subcellular levels.

Brain banking in low and middle-income countries: Raison D'être for the Ibadan Brain Ageing, Dementia And Neurodegeneration (IBADAN) Brain Bank Project

Brain banks are biorepositories of central nervous system (CNS) tissue including fixed and frozen whole brains, brain biopsies and spinal cord, as well as body fluids comprising the cerebrospinal fluid (CSF) and blood stored for research purposes. Though several independent brain banks exist in high income countries, only five low- and middle - income countries (LMIC) have brain banks. The African continent is yet to establish a formalized brain bank despite its huge human genomic diversity, ageing of her populations with concomitant increases in ageing - associated brain disorders and differential phenotypic expression and outcomes of brain disorders. Cellular and molecular clinicopathological studies are vital to shaping our understanding of the interaction between racial (genetic) and geographical (environmental) factors in the natural history and mechanisms of disease, and unravelling frameworks of diagnostic biomarkers, and new therapeutic and preventative interventions. The Ibadan Brain Ageing, Dementia And Neurodegeneration (IBADAN) Brain Bank, the first organized brain tissue biorepository in sub - Saharan Africa, is set up to accrue, process and store unique brain tissues for future research into a broad spectrum of neurological and psychiatric disorders. The potential unique discoveries and research breakthroughs will benefit people of African ancestry and other ancestral populations.

Notes on the Recent History of Neuroscience in Africa

Neuroscience began with neuroanatomy and neurosurgery in Egypt more than 5000 years ago. Knowledge grew over time and specialized neurosurgery centers were established in north Africa in the eleventh century. However, it was not until the twentieth century that neuroscience research became established in sub-Saharan Africa. In most African countries, clinical research focused on understanding the rationale and improving treatment of epilepsy, infections, nutritional neuropathies, stroke and tumors. Significant advances were made. In the twenty-first century, African knowledge expanded to include all branches of neuroscience, contributing to genetic, biochemical and inflammatory determinants of brain disorders. A major focus of basic neuroscience research has been, and is, investigation of plant extracts, drugs and stress in animal models, providing insight and identifying potential novel therapies. A significant event in the history of African neuroscience was the founding of the Society of Neuroscientists of Africa (SONA) in 1993. The International Brain Research Organization (IBRO) supported SONA conferences, as well as workshops and neuroscience training schools in Africa. Thanks to their investment, as well as that of funding agencies, such as the National Institutes of Health (NIH), International Society for Neurochemistry (ISN), World Federation of Neurosurgical Societies (WFNS), World Federation of Neurology (WFN) and the International League Against Epilepsy (ILAE), neuroscience research is well-established in Africa today. However, in order to continue to develop, African neuroscience needs continued international support and African neuroscientists need to engage in policy and decision-making to persuade governments to fund studies that address the unique regional needs in Africa.

Determinants of cognitive performance in children relying on cyanogenic cassava as staple food

While risk factors for konzo are known, determinants of cognitive impairment in konzo-affected children remain unknown. We anchored cognitive performance (KABC-II scores) to serum levels of free-thyroxine (free-T4), thyroid-stimulating hormone (TSH), albumin, and motor proficiency (BOT-2 scores) in 40 children including 21 with konzo (median age: 9 years) and 19 without konzo (median age: 8 years). A multiple regression model was used to determine variables associated with changes in KABC-II scores. Age (β: -0.818, 95% CI: -1.48, -0.152) (p = 0.018), gender (β: -5.72; 95% CI: -9.87, -1.57 for females) (p = 0.009), BOT-2 score (β: 0.390; 95% CI: 0.113, 0.667) (p = 0.008), and free-T4 (β: 1.88; 95% CI: 0.009, 3.74) (p = 0.049) explained 61.1 % of variation in KABC-II scores. Subclinical hypothyroidism was not associated with poor cognition. A crude association was found between serum albumin and KABC-II scores (β: 1.26; 95 % CI: 0.136, 2.39) (p = 0.029). On spot urinary thiocyanate reached 688 μmol/l in children without konzo and 1,032 μmol/L in those with konzo. Female gender and low serum albumin are risk factors common to cognitive and proportionally associated motor deficits in children exposed to cassava cyanogens. The two types of deficits may share common mechanisms.

Cassava interspecific hybrids with increased protein content and improved amino acid profiles

Cassava (Manihot esculenta) is a principal food for large populations of poor people in the tropics and subtropics. Its edible roots are poor in protein and lack several essential amino acids. Interspecific hybrids may acquire high protein characteristics from wild species. We analyzed 19 hybrids of M. esculenta with its wild relative, M. oligantha, for crude protein, amino acid profile, and total cyanide. Some hybrids produced roots with high protein content of up to 5.7%, while the common cultivar that we examined had just 2.3% crude protein. The essential amino acids alanine, phenylalanine, and valine were detected in the hybrids. The sulfur-containing amino acids cysteine and methionine were found at relatively high concentrations in the roots of 4 hybrids. The proportion of lysine in one hybrid was 20 times higher than in the common cultivar. The levels of total cyanide ranged from 19.73 to 172.56 mg/kg and most of the roots analyzed were classified as "non-toxic" and "low toxic". Furthermore, 2 progenies showed reasonable levels of cyanide, but higher protein content and amino acid profile more advantageous than the common cassava.

Neurological disorders associated with cassava diet: a review of putative etiological mechanisms

Tropical ataxic neuropathy (TAN) and epidemic spastic paraparesis (konzo) are two neurological disorders associated with the consumption of cassava (Manihot esculenta) in several African countries. TAN is characterized by sensory polyneuropathy, sensory ataxia, bilateral optic atrophy and bilateral sensori-neural deafness. It occurs in elderly individuals subsisting on a monotonous cassava diet with minimal protein supplementation. Konzo is a syndrome of symmetrical spastic paraparesis with a predilection for children and young women and invariably associated with consumption of inadequately processed bitter cassava roots with minimal protein supplementation. Despite numerous epidemiological, clinical and biochemical studies aimed at elucidating the etiological mechanisms of these disorders, their etiologies remain unknown, and there is no known treatment. The diseases continue to be prevalent in endemic areas, causing significant disability and increased mortality. A fresh appraisal of the putative etiologic mechanisms proposed for these intriguing and enigmatic syndromes is presented in this paper. Evidences against a causal role for cyanide intoxication are discussed, and evidences implicating thiamine deficiency as a unifying etiological mechanism for these neurological syndromes are presented. It is concluded that urgent research is needed to evaluate thiamine status and implement a therapeutic trial of thiamine in these debilitating neurological disorders.

Brain glutathione as a target for aetiological factors in neurolathyrism and konzo

Both neurolathyrism and konzo are associated with the nutritional dependence of human populations on a single plant food. These diseases express themselves as chronic disorders of upper motor neurones, leading to signs and symptoms that characterise amyotrophic lateral sclerosis (motor neurone disease). The plant food associated with neurolathyrism is grass pea, which contains the neurotoxic β-N-oxalyl-α,β-diaminopropionic acid (β-ODAP). The plant food associated with konzo is cassava, which may contain significant concentrations of cyanogenic glycosides and their degradation products. A monotonous diet of grass pea is likely to generate nutritional deficiencies; it is proposed that one of these, plasma methionine deficiency, may predispose neurones to the neurotoxic effects of β-ODAP. Subjects suffering from konzo also have low concentrations of plasma methionine as a result of a dietary deficiency of this amino acid. However, the plasma cystine concentration is also compromised because cyanide released from cyanogenic glycosides in cassava probably reacts with plasma cystine non-enzymatically. The product of this reaction is 2-imino-4-thiazolidine carboxylic acid. Since both plasma methionine and cystine are used for glutathione synthesis it seems likely that one common feature that leads to motor neurone death in neurolathyrism and konzo is the depletion of glutathione in the central nervous system.

Equine dysautonomia (grass sickness) is associated with altered plasma amino acid levels and depletion of plasma sulphur amino acids

To determine whether equine dysautonomia (ED) is associated with alterations in plasma amino acid metabolism, plasma amino acid profiles were determined for horses with acute (n = 10), subacute (n = 6) and chronic (n = 7) ED and for healthy cograzing horses (n = 6) and control horses (n = 10). Horses with acute ED had perturbations in plasma amino acid profiles resembling those of severe protein malnutrition. In addition, horses with ED and cograzing healthy horses had depletion of the plasma sulphur amino acids cyst(e)ine and methionine. As similar plasma amino acid perturbations occur in subacute/chronic cyanide toxicity, the role of cyanogenic glycosides in the aetiology of ED warrants further study. Unfortunately, amino acid analysis cannot be used as a definitive premortem diagnostic test for ED, since there was overlap in the individual amino acid levels of control, cograzing and ED horses.

Thiocyanate levels of mainly dietary origin in serum and urine from a human population sample in Port Harcourt, Nigeria

Thiocyanate levels were determined in serum and urine samples obtained from a human population sample of healthy non-smoking volunteers (aged between 14 and 30 years) of both sexes known to eat gari-based meals at least once a day. The samples were collected before and 3-4 hours after a gari- or rice-based meal. The values obtained before the test meals showed a wide variation, ranging between 39.20 +/- 1.95 to 160.95 +/- 8.06 mumol/l of serum, and 81.92 +/- 9.78 to 294.01 +/- 14.70 mumol/l of urine. For each volunteer, the serum and urine thiocyanate were affected by the test meals. Average increases of 18 and 20% were observed for serum and urine thiocyanate, respectively, following a gari-based meal. A rice-based meal produced, on the average, 10% decrease in both serum and urine thiocyanate. No significant effect of sex or age on the thiocyanate levels was observed. The gari samples used in the study, as well as random samples from the locality of study, had no detectable thiocyanate but contained between 0.013 and 0.015 mg cyanide per kg of gari. These findings indicate that conversion to thiocyanate is a significant pathway in the metabolism of HCN and contributes significantly to thiocyanate found in body fluids and tissues of man. In addition, support is provided for the possible involvement of the sulphur-transferases in the process of cyanide detoxication.

Cyanide and arsenic poisoning by intravenous injection

A 29-year-old man was found unresponsive a few minutes after self-injecting undetermined amounts of potassium cyanide and sodium arsenite intravenously in a suicide attempt. Treatment with the Lilly Cyanide Antidote kit rapidly resolved the initial coma, despite a whole blood cyanide level of 4.4 micrograms/mL. A 12-hour urine arsenic collection begun on admission showed 10,065 micrograms arsenic/12 hr. The patient received intramuscular BAL initially, which was followed by two ten-day courses of oral D-penicillamine. Complications included upper gastrointestinal tract bleeding requiring transfusion, transient elevations of liver function tests, self-limited complaints of decreased vision with conjunctival hyperemia and photophobia, and an abscess at the injection site. Although specific antidote therapy completely resolved the cyanide toxicity, early and prolonged arsenic chelation did not prevent a mild sensory peripheral neuropathy from developing with onset about 17 days after self-injection.

Clinical toxicology of cyanide

Cyanide poisoning causes a high incidence of severe symptomatology and fatality. There are numerous sources of potential cyanide exposure. Without the history of cyanide exposure, diagnosis is often difficult. Treatment with supportive measures and available specific and efficacious antidotes frequently allows survival. The toxicology of cyanide, including sources, clinical features, diagnosis, and treatment, is reviewed.

Association of high cyanide and low sulphur intake in cassava-induced spastic paraparesis

Urinary excretion of sulphur compounds was studied in children from a population in Mozambique that had been affected, during a drought, by an epidemic of spastic paraparesis attributed to cyanide exposure from cassava. The children had increased thiocyanate and decreased inorganic sulphate excretion, indicating high cyanide and low sulphur-containing amino-acid intake. Children from a neighbouring cassava-eating area, where no cases of spastic paraparesis had occurred, had lower thiocyanate excretion but higher inorganic sulphate excretion. These results support the hypothesis that the epidemic was due to the combined effects of high dietary cyanide exposure and sulphur deficiency.

Cassava as a food

This review has attempted to examine information pertaining to the role of cassava (Manihot esculenta) as a major food source for a large part of the world population, particularly the countries of South America, Africa, and Asia, where it is primarily a major source of energy for 300 to 500 million people. Its cultivation, usually on small farms with little technology, is estimated to cover on an annual basis about 11 million hectares providing about 105 million tons, more than half of which is consumed by humans. The importance of cassava as an energy source can be seen by its growing demand in the European economic community countries where it forms up to 60% of the balanced diets for swine. Cassava is one of the crops that converts the greatest amount of solar energy into soluble carbohydrates per unit of area, thus 1 kg of moisture-free cassava meal may yield up to about 3750 kcal which would mean that a yearly production of 15 tons of cassava meal per hectare would yield some 56 million kcal. The major limitations of cassava as food appear to be its poor protein content and quality and the rapid post harvest deterioration of its roots which usually prevents their storage in the fresh state for more than a few days. However, in addition to its use for culinary purposes, cassava finds application in industrial products such as an adhesive for laundry purposes, for manufacturing paper, alcohol, butanol, dextrin, adhesive tape, textile sizing, and glue.

Tobacco-alcohol amblyopia: a proposed biochemical basis for pathogenesis

Tobacco-alcohol or nutritional amblyopia is a rare disorder of decreased central vision associated with nutritional deficiencies and tobacco smoking. although folate deficiency is common in patients with tobacco-alcohol amblyopia, the role of folic acid in this disorder has been underplayed. The role of cyanide from tobacco smoke, folate and other dietary deficiencies will be reviewed. A new model of the pathogenesis of tobacco-alcohol amblyopia is proposed based on the presumptive alteration of methionine and S-adenosyl-L-methionine metabolism.

Cyanide poisoning

In recent years, the increasing use of laetrile has been added to the traditional sources of exposure to cyanide in industry, chemistry labs, and fumigation. The events in Jonestown in 1978 were a grim reminder of the lethality of cyanide. Nonetheless, advancement in new modes of treatment has been slow. The traditional method of treatment used in the United States is effective, but not without its own morbidity and mortality. Using two case reports as models, we review here the topic of cyanide poisoning including sources of exposure, pathophysiology, clinical manifestations of both acute and chronic exposure, and modes of treatment. Although there is currently no accepted alternate treatment in this country, review of the literature shows promise in other modalities being investigated in Europe, including hydroxocobalamin, cobalt salts, and particularly aminophenols.

Amino acid metabolism in Friedreich's ataxia

A study of amino acids determined by sequential Multi-sample Amino Acid Automatic Analyzer in plasma, urine and cerebrospinal fluid (CSF) in patients with Friedreich's ataxia and control subjects has revealed a number of mathematically significant variations from normal. Of practical physiological importance are the following: a high urinary excretion of alanine with slightly elevated plasma levels; a low plasma and CSF concentration of aspartic acid in the presence of normal urinary values and finally a low CSF concentration of taurine accompanied by normal plasma levels, but elevated urinary output and renal clearance rates. We postulate that the modifications in alanine and aspartic acid are less specific and probably secondary, but there could be a genetic defect in the membrane transport of taurine and the other beta-amino acids in Friedreich's ataxia.

Controlled trial of combinations of hydroxocobalamin-cystine and riboflavine-cystine, in Nigerian ataxic neuropathy

Chronic cyanide intoxication of dietary origin and riboflavine deficiency are believed to be major aetiological factors in Nigerian tropical ataxic neuropathy. The results are presented of a double-blind controlled therapeutic trial of combinations of large doses of hydroxocobalamin and cystine as cyanide binding agents together with riboflavine or placebos in Nigerian patients suffering from the tropical ataxic neuropathy. No clinical benefit was demonstrable with any of the treatments.

Biochemical studies in Tanzanian patients with ataxic tropical neuropathy

Data on thiocyanate and vitamin B(12) concentrations in plasma from Tanzanian patients with ataxic tropical neuropathy are presented and support the hypothesis that, as in Nigeria, the condition may result from chronic exposure to cyanide or cyanogens from a diet including large amounts of cassava.

Relationship of a degenerative tropical neuropathy to diet: report of a field survey

A survey of neurological abnormalities in two Nigerian villages preselected for their differing consumption of cassava has shown that a degenerative neuropathy occurs with relatively high frequency in the village (Ososa) where cassava consumption was high.It is suggested that eating cassava results in exposure to cyanide, as shown by a raised plasma thiocyanate level, and that the latter, together with other factors, may contribute to the pathogenesis of "tropical neuropathy."