Sulfur amino acid metabolism in hepatobiliary disorders.

Sulfur amino acid metabolism was studied in patients with mild to severe forms of liver dysfunction and compared with that of healthy controls. Patients with mild liver dysfunction (for example, Gilbert's syndrome) had a normal sulfur amino acid metabolism. With increased inflammatory activity and cirrhosis (for example, chronic active hepatitis, alcohol-induced cirrhosis, and hepatic coma) a decreased ability to metabolize methionine (to cysteine, with cystathionine accumulation) and cysteine (to inorganic sulfate, with thiosulfate and N-acetylcysteine accumulation) was found. In contrast, transaminative metabolism of sulfur amino acids was preserved in patients with advanced forms of liver dysfunction, suggesting that transamination of sulfur amino acids is performed not only in the liver but also in extrahepatic tissues. Some implications of these findings are discussed.

Studies on lipoamidase: characterization of the enzyme in human serum and breast milk.

Lipoamidase activity was detected in human serum with both lipoyllysine (epsilon-N-(DL-lipoyl)-L-Lysine) and lipoylPABA (N-DL-lipoyl-p-aminobenzoate) as substrates, whereas lipoamidase in human milk used lipoylPABA, but not lipoyllysine as substrate. This suggested that lipoamidase activities in serum and milk are due to different enzymes. Studies with activators and inhibitors suggested that lipoamidase in serum using lipoylPABA as substrate may be a different enzyme from that using lipoyllysine as substrate. We suggest that these lipoamidases are named lipoyllysine hydrolase (LLH) and lipoylPABA hydrolase (LPH), respectively. Serum LLH was activated by thiol compounds and EDTA and strongly inhibited by sulfhydryl reagents whereas serum LPH was inhibited by sulfhydryl reagents but not activated by thiol compounds or EDTA. Milk LPH was unaffected by these reagents. We suggest that serum LLH and possibly serum LPH are cysteine proteases. LLH was adsorbed on Concanavalin A-Sepharose, indicating that LLH was a glycoprotein.

The role of hydrogen cyanide and carbon monoxide in fire casualties: a prospective study.

Determinations of blood cyanide and carboxyhemoglobin concentrations were performed in 18 victims found dead in buildings after fires during a 2-year period. The results indicated that 50% of the victims had been exposed to toxic levels of hydrogen cyanide and 90% to toxic levels of carbon monoxide. Lethal concentrations of carbon monoxide were found in 83% of the victims. In one case a lethal blood cyanide but a non-toxic blood carboxyhemoglobin value was found. It is concluded that carbon monoxide appears to be more important than hydrogen cyanide as a toxic agent in the fire atmosphere, but cyanide poisoning without carbon monoxide poisoning may, under certain circumstances, be the cause of death in fire victims.

Bedside diagnosis of alcohol intoxication with a pocket-size breath-alcohol device: sampling from unconscious subjects and specificity for ethanol.

We describe a novel mouth-cup device for sampling breath from unconscious subjects and analysis with a hand-held breath-alcohol instrument, the "Alcolmeter SD-2." This equipment was evaluated in healthy volunteers after they drank a moderate dose of alcohol. Three kinds of breath were analyzed: (a) end-expired air from a conventional mouth-tube, (b) breath sampled from the mouth-cup, and (c) air from a nasal tube supplied with the breath analyzer. The ethanol concentration in breath from the mouth-cup was slightly less than in end-expired air but significantly greater than in nasal air. Results with mouth-tube and mouth-cup correlated highly with blood-ethanol concentration as determined by gas chromatography; nasal-tube air correlated less well. The Alcolmeter responded not only to ethanol but also to methanol, 1-propanol, and 2-propanol, whereas ethylene glycol gave no response. The time-response curve for methanol was different, and this might permit differential diagnosis of methanol poisoning.

A sensitive gas chromatographic method for determination of protein-associated sulfur.

A sensitive method for the determination of elemental sulfur bound to serum albumin and other proteins has been devised. The sample is treated with a hexane solution of triphenylphosphine, and the triphenylphosphine sulfide formed is determined by gas chromatography with a flame photometric sulfur detector. The detection limit of the method is 0.3 microM albumin-associated sulfur. Protein-associated sulfur was not detected in plasma from rats or normal human beings, findings that do not support an earlier suggested transport function of serum albumin for sulfur. Significant amounts of protein-associated sulfur, however, were found in certain rat tissues.

Rapid determination of toxic cyanide concentrations in blood.

This method for the rapid colorimetry of cyanide in blood, applicable to patients exposed to toxic levels of cyanide, is based on the König reaction, which produces a chromophore from cyanide as well as thiocyanate. The latter compound, normally present in blood, is confined to plasma. Thus, its interference with determination of cyanide was eliminated by performing the assay on the erythrocytes, which contain most of the blood cyanide. Furthermore, cyanide was trapped in the erythrocytes and stabilized during the initial washing steps by conversion of hemoglobin to methemoglobin with inorganic nitrite.

Hyposelenaemia: patients with gastrointestinal diseases are at risk.

A retrospective study of serum selenium determinations performed in a hospital laboratory revealed 47 cases of hyposelenaemia (defined as a serum selenium level below 0.74 mumol l-1). Moderate hyposelenaemia (serum selenium 0.30-0.55 mumol l-1) was found in 11 patients and seven of these suffered from gastrointestinal diseases. Furthermore severe hyposelenaemia (serum selenium below 0.30 mumol l-1) was detected in three patients, who were all affected by gastrointestinal disease. We concluded that patients with gastrointestinal diseases are especially at risk of developing selenium deficiency and should be monitored by repeated determinations of serum selenium. Patients with moderate or severe hyposelenaemia should receive selenium treatment.

Mercaptoethanol poisoning: report of a fatal case and analytical determinations.

A suicide due to oral intake of 2-mercaptoethanol is reported. High concentrations of 2-mercaptoethanol and its metabolite 2-mercaptoacetate were found by gas chromatography in the urine and gastric content of the victim. These compounds were also identified by gas chromatography/mass spectrometry. Increased amounts of inorganic sulfate were furthermore found in the urine. Case history and autopsy findings are presented, and the metabolism of 2-mercaptoethanol is discussed.

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.

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.

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.

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.

A possible involvement of glutathione in the detoxication of sulfite.

Inorganic sulfite may be detoxified by conversion to S-sulfocysteine. We demonstrate this conversion by a series of enzyme-catalyzed steps as follows. Inorganic sulfite reacts with glutathione disulfide by a thiol transferase catalyzed reaction as previously demonstrated. The S-sulfoglutathione formed is then converted by gamma-glutamyltranspeptidase to S-sulfocysteinylglycine and the latter finally hydrolyzed to S-sulfocysteine by a renal dipeptidase. S-Sulfoglutathione is a substrate for gamma-glutamyl-transpeptidase as effective as glutathione itself. Furthermore, S-sulfocysteinylglycine is cleaved as efficiently as cysteinylglycine by a renal dipeptidase at high substrate concentrations but somewhat less efficiently at low substrate concentrations.

Serum concentrations of 25-hydroxyvitamin D and vitamin D-binding protein in elderly people. Effects of institutionalization, protein-energy malnutrition and inflammation.

Serum concentrations of 25-hydroxyvitamin D (25-OH-D) and vitamin D-binding protein (DBP) were measured in institutionalized and non-institutionalized elderly people. The institutionalized subjects were found to have low serum 25-OH-D in confirmation of other studies, but their serum DBP levels were similar to those found in non-institutionalized elderly subjects. Serum DBP concentrations were slightly higher in elderly females than in males, while no age dependence was found for DBP. Elderly people with protein-energy malnutrition who lived in their own homes had slightly reduced serum DBP and 25-OH-D levels. Elderly subjects with infections or other diseases causing acute inflammation, as indicated by an elevated serum haptoglobin and C-reactive protein, had normal levels of DBP.

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.