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Biomedical subjects

H Rosling

Publications and source records attributed to H Rosling.

At least 55 records · Page 3Linked to original sources
PubMed1992

Cassava cyanogens and konzo, an upper motoneuron disease found in Africa.

Konzo is a distinct form of tropical myelopathy characterised by abrupt onset of spastic paraparesis. Epidemics in East Africa have been attributed to dietary cyanide exposure from insufficiently processed cassava but a study done in Zaire disputed such an aetiology. We investigated a konzo-affected population in rural Zaire and measured the cyanogen content of cassava flour, determined urinary thiocyanate as an indicator of cyanide intake, and compared blood cyanide concentrations in cases and controls. The affected population consumed flour made from short-soaked (one day) cassava roots and thus had high dietary cyanide exposure (urinary thiocyanate in 31 children = 757 mumol/l) compared with the unaffected population (urinary thiocyanate in 46 children = 50 mumol/l) that ate cassava that had been soaked for three days before consumption. 3 konzo patients, but only 2 of 23 controls, had blood cyanide concentrations above 4 mumol/l (p less than 0.01), although serum thiocyanate concentrations were similar. Our findings indicate a causal role in konzo of sustained high blood cyanide concentrations maintained by a deficient sulphur intake impairing cyanide to thiocyanate conversion. The underlying causes of konzo are poverty and food shortage, but a minor improvement of food processing may, as in beri-beri, be preventive.

Adolescent↗
PubMed1992

Diabetes is not caused by cassava toxicity. A study in a Tanzanian community.

OBJECTIVE: To test the hypothesis that consumption of cassava with liberation of cyanide causes diabetes in malnourished individuals. RESEARCH DESIGN AND METHODS: Glucose tolerance was assessed in two rural communities in Tanzania; in one (Nyambori), the main source of calories was cassava; and in the other (Uswaa), cassava was rarely eaten. Undernutrition was prevalent in both communities. The people of Nyambori were known to have high dietary cyanide exposure for many years from consumption of insufficiently processed cassava. Of the 1435 people in Nyambori greater than or equal to 15 yr old, 1067 (74%) were surveyed, and 1429 of 1472 (97%) eligible subjects in Uswaa were surveyed. All had 75-g oral glucose tolerance tests and measurement of BMI. Plasma and urine thiocyanate and blood cyanide also were measured in some subjects. RESULTS: Mean +/- SD plasma and urine thiocyanate levels in Nyambori were 296 +/- 190 and 497 +/- 457 microM (n = 204), respectively, compared with 30 +/- 37 and 9 +/- 13 microM, respectively, in Uswaa (n = 92) (P less than 0.001 for all differences). The mean blood cyanide level in Nyambori was elevated (1.4 [range 0.1-30.2] microM; n = 91). The prevalence of diabetes in the cassava village (Nyambori) was 0.5% compared with 0.9% in Uswaa (NS). The prevalence of IGT was similar in the two villages in the 15- to 34- and the 34- to 54-yr-old age-groups; but in those greater than or equal to 55 yr old, IGT was higher in Nyambori (17.4 vs 7.2%, P = 0.029). Mean fasting and 2-h blood glucose levels were slightly higher in Nyambori village after adjusting for age, sex, and BMI (4.5 vs. 4.2 and 5.0 vs. 4.4 mM, respectively). CONCLUSIONS: High dietary cyanide exposure was not found to have had a significant effect on the prevalence of diabetes in an undernourished population in Tanzania. Cassava consumption is thus highly unlikely to be a major etiological factor in so-called MRDM, at least in East Africa.

Adolescent↗
PubMed1992

[High prevalence of konzo associated with a food shortage crisis in the Bandundu region of zaire].

Konzo is a form of spastic paraparesis reported from several rural areas in Sub-Saharan Africa. It has been attributed to cyanide exposure from exclusive consumption of insufficiently processed bitter cassava roots. We have tested this attribution in a community based epidemiological survey in an area of Bandundu region in Zaire composed of two agro-ecological zones: savanna and forest. In the savanna area with poor soils we found 78 konzo cases in 1,936 inhabitants, a prevalence of 4%; but in the forest area only 9 cases in 5,531 inhabitants (0.2%). This geographical distribution as well as the temporal distribution coincide with frequent short-soaking of cassava roots (only one night) induced by an agro-ecological crisis. High levels of blood cyanide, mean 13.3 mumol/l (range: 0.1-76.3) and serum thiocyanate, mean (+/- SD) 401 (+/- 126) mumol/l, in a sample of 18 subjects from the savanna area confirm high cyanide exposure in this population with high prevalence of konzo. Prevention of konzo in Zaire is possible by promotion of sufficient soaking of cassava with strict adherence to traditional three nights soaking and the use of completely dry flour.

Adolescent↗
PubMed1991

Epidemiological evidence from Zaire for a dietary etiology of konzo, an upper motor neuron disease.

A clear association between seasonal outbreaks of a paralytic disease called konzo and toxic effects from consumption of insufficiently processed bitter cassava roots has been demonstrated in Bandundu region, Zaire. A community-based survey of 6764 inhabitants identified 110 live and 24 dead konzo-affected persons with a history of isolated non-progressive spastic paraparesis of abrupt onset. The start of these annual outbreaks of konzo in 1974 coincided with the completion of a new tarmac road to the capital, which facilitated the transport of cassava and made it the main cash crop. The extensive cassava sales encouraged the consumption by the peasant families of roots that had not been adequately processed; frequent acute cyanide intoxications resulted when the naturally occurring cyanogens in the roots were eaten. The disease mainly appeared in the dry season when there was high consumption of insufficiently processed cassava and the diet lacked supplementary foods with sulfur-containing amino acids which promote cyanide detoxification. These results, which confirm the earlier findings in East Africa, show that, owing to the high cyanide and low sulfur dietary intake, there is an increased risk of konzo outbreaks in cassava-growing areas during periods of adverse agro-economic changes.

Adolescent↗
PubMed1990

Konzo, an epidemic upper motor neuron disease studied in Tanzania.

An epidemic of spastic paraparesis was studied in a drought-affected rural area of Tarime district in northern Tanzania. The uniform clinical findings in 39 cases, aged 4-46 yrs, indicated abrupt symmetric isolated and permanent but not progressive damage to the upper motor neurons. Due to the failure of other food crops, the diet at onset consisted almost exclusively of bitter cassava roots, a drought-tolerant starchy root crop widely cultivated in Africa. The drought increased the natural occurrence of cyanogenic glucosides in the cassava roots, and the processing procedure normally applied in order to remove cyanide before consumption was shortened because of food shortage. The resulting high dietary cyanide exposure was confirmed by very high serum levels of thiocyanate, the detoxification product of cyanide. Tests for HTLV-1 antibodies were negative and no other findings supported an infectious aetiology. The clinical findings and the associations with cassava toxicity are almost identical to those reported from outbreaks of spastic paraparesis in Mozambique and in Zaire, where this disease was first reported under the name 'konzo'. We thus conclude that konzo constitutes a distinct upper motor neuron disease entity, probably caused by a toxic effect from insufficiently processed cassava under adverse dietary circumstances.

Adolescent↗
PubMed1989

Cyanide release from sodium nitroprusside during coronary bypass in hypothermia.

Erythrocyte cyanide levels were determined by a sensitive fluorimetric method on four occasions during coronary bypass in hypothermia in 18 consecutive patients treated with sodium nitroprusside (SNP) with an infusion rate less than 1 microgram x kg-1 x min-1. Every second patient received the cyanide antidote thiosulphate simultaneously with the SNP-infusion. At normal body temperature, as well as during hypothermia in cases receiving thiosulphate, the cyanide levels rose slowly but significantly with the infusion rate. Higher erythrocyte cyanide levels in relation to the infusion rates, up to 8.0 mumol/l, were found during hypothermia in two of the cases not receiving thiosulphate. We conclude that SNP is broken down to cyanide even under hypothermia and that low body temperature may impair the conversion of cyanide to thiocyanate, probably by affecting the metabolic pathways providing the sulphur substrate. This effect may add to other factors decreasing sulphur availability in critically ill patients, and simultaneous administration of thiosulphate is therefore recommended to ensure a safe SNP treatment during and after coronary bypass operations.

Adult↗
PubMed1989

Human retroviruses HTLV-I, HIV-1, and HIV-2 and neurological diseases in some equatorial areas of Africa.

HTLV-I is associated with tropical spastic paraparesis (TSP) in the Caribbean area and with certain chronic myelopathies termed HAM (HTLV-I-associated myelopathy) in Japan. In order to investigate the situation in Africa, we tested for HTLV-I, but also for HIV-1 and HIV-2 antibodies, 94 patients with epidemic spastic paraparesis (ESP) from Zaire and Tanzania, 26 cases of sporadic spastic paraparesis (SSP) and 21 cases of tropical ataxic neuropathy (TAN), both from Ivory Coast, and 319 unselected neurological patients from Ivory Coast, Congo, and Tanzania. While none of the 94 ESP cases nor any of the 21 TAN patients exhibited antibodies to any retrovirus, 4 of the 26 sporadic spastic paraparesis patients had high HTLV-I antibodies in their sera and cerebrospinal fluid (CSF). Three of those were clinically and immunologically identical to TSP, as observed in persons from the Caribbean region, and the fourth case, a poorly explored chronic pyramidal syndrome, could also represent a TSP. Only one of these four cases originally had HIV-1 antibodies. Among the 319 unselected patients, only 5 (1.6%) had HTLV-I antibodies, but 32 (10%) had HIV-1 antibodies and 14 (4.4%) had HIV-2 antibodies, with a number of combined infections, indicating that retroviruses represent potentially important etiological agents for African neurological diseases.

Adolescent↗
PubMed1988

The origin of hydrogen cyanide in breath.

The excretion of hydrogen cyanide in breath and blood concentrations of cyanide were measured in eight normal subjects. There was no correlation between breath and blood levels of cyanide. Furthermore, breath cyanide concentrations calculated from blood values were much lower than measured values, which suggested a local production of hydrogen cyanide in the oropharynx. When saliva was incubated at 37 degrees C hydrogen cyanide was formed in the presence of air but not in a nitrogen atmosphere. No hydrogen cyanide was formed with boiled saliva and the production of hydrogen cyanide by native saliva was inhibited by catalase and by 6-n-propyl-thiouracil. Centrifugation of saliva resulted in a supernatant and a sediment, which were both required for the formation of hydrogen cyanide. Dialysis of the supernatant abolished its cyanide forming ability, which could be restored by addition of thiocyanate. We conclude that most of the hydrogen cyanide found in breath from normal human beings originates from oxidation of thiocyanate by salivary peroxidase in the oropharynx. As a consequence measurements of breath hydrogen cyanide can only be used to detect heavy exposure to cyanide.

Adult↗
PubMed1988

A simple method for determination of plasma thiocyanate.

We describe a method for the determination of thiocyanate in plasma from blood collected under field conditions in heparinised glass capillary tubes. After deproteinisation of plasma with perchloric acid, thiocyanate is directly determined colorimetrically by the König reaction with sodium hypochlorite as the chlorinating reagent and barbituric acid as the coupling agent. This simple method cannot be applied to urine as the latter contains interfering compounds.

Humans↗
PubMed1987

Cyanide concentrations in blood after cigarette smoking, as determined by a sensitive fluorimetric method.

Using the sensitive fluorimetric method described here, we evaluated the determination of blood cyanide as a method for monitoring exposure to tobacco smoke. The mean concentration of cyanide in blood from eight nonsmokers was 0.098 (SD 0.036) mumol/L. The concentration of cyanide in blood of smokers who had refrained from smoking for at least 2 h before sampling peaked immediately after the subjects smoked a cigarette, then rapidly declined, with a half-life of about 4 min. Its rapid disappearance from blood makes cyanide an unsuitable marker of exposure to tobacco smoke. Because the ability of patients with hepatic dysfunction to detoxify cyanide has been presumed to be impaired, we monitored the concentrations of cyanide in the blood of four patients with severe hepatic insufficiency who smoked a cigarette. The rate of elimination of cyanide from blood after smoking was only slightly less in these patients than in the controls, and the difference was not statistically significant.

Adult↗
PubMed1986

Thyroid function in a cassava-eating population affected by epidemic spastic paraparesis.

Thyroid function was studied in a rural population in Mozambique that had been affected by an epidemic of spastic paraparesis attributed to dietary cyanide exposure from cassava. Laboratory investigation on a sample of this population demonstrated very high levels of serum and urinary thiocyanate, indicating a heavy exposure to cyanide. The urinary excretion of iodine was within normal limits, indicating an adequate intake of iodine. The serum levels of FT4I were somewhat decreased and serum FT3I, T3/T4 ratio and TSH were somewhat raised. This hormone pattern suggests an adaptation to the antithyroid effect of thiocyanate, but not overt hypothyroidism. A follow-up study on school children was performed, and it also demonstrated high thiocyanate exposure, adequate intake of iodine, and absence of endemic goitre. The results show that if iodine supply is adequate, the thyroid gland is capable of adaptation to a heavy body burden of thiocyanate without development of overt hypothyroidism or goitre.

Adolescent↗
PubMed1985

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.

Child↗
PubMed1985

Determination of cyanide in whole blood, erythrocytes, and plasma.

We describe a method for determination of cyanide in whole blood, erythrocytes, and plasma after stabilization of cyanide by addition of silver ions. The cyanide is then transferred from the acidified sample, by aeration, into sodium hydroxide and quantified by the König reaction, with sodium hypochlorite as the chlorinating agent. A rapid loss of measurable cyanide found when cyanide was added to plasma in the absence of silver ions was attributed to a reaction with serum albumin. Cyanide added to whole blood was bound to a saturable component in erythrocytes, which we identified as methemoglobin.

Cyanides↗