George E. Boxer

Studies on the metabolism of the carbon of cyanide and thiocyanate

Abstract Radioactive cyanide injected into the dog appears in the “free” cyanide, vitamin B 12 -bound cyanide, and the thiocyanate of the urine. Data are presented which indicate that the cyano group of vitamin B 12 is rapidly taking up injected cyanide and that the vitamin B 12 comes into equilibrium with a small metabolically active pool of cyanide. Cyanide and thiocyanate are in a dynamic equilibrium as demonstrated by the specific activity of hydrogen cyanide exhaled by rats after injection of radioactive cyanide and of radioactive thiocyanate. Cyanide as well as thiocyanate carbon is converted to carbon dioxide in the rat. The carbon of thiocyanate has a biological half life of 3.6 days and is replaced at a rate of 19% per day in the rat. About two-thirds of the thiocyanate carbon replaced are excreted as thiocyanate in the urine and one third as carbon dioxide in the respiratory air. Cyanide carbon, and therefore by metabolic equilibrium thiocyanate carbon, appears in the methyl carbons of choline and methionine, and in the ureide carbons of allantoin. The specific activity of the isolated formate makes it a very probable intermediate for this conversion. Relatively high activity has been observed in the carbon of liver proteins, and possible interpretations are discussed. The liver fatty acids show a low order of activity which is probably derived from carbon dioxide. Evidence is presented that to a large extent cyanide and thiocyanate carbon are oxidized directly to carbon dioxide, possibly via cyanate.

Antidotal efficacy of vitamin B12a (hydroxo-cobalamin) in experimental cyanide poisoning.

Summary and Conclusion 1. Vit. B12a (hydroxo-cobalamin), but not vitamin B12a (cyano-cobalamin), has been found to be capable of preventing in mice the toxic symptoms and death due to cyanide administration. 2. When injected into mice exhibiting complete respiratory arrest and coma due to cyanide poisoning, vit. B12a effected rapid recovery of most animals. 3. In mice injected with potassium cyanide followed by vit. B12a some of the cyanide appears in the urine as thiocyanate, but a greater percentage of the cyanide appears as vit. B12 having formed this compound by reacting with the vit. B12a.

Incorporation of 3′-deoxyadenosine-5′triphosphate into RNA by RNA polymerase from Micrococcuslysodeikticus☆

Abstract 14C labeled 3′-deoxyadenosine-5′triphosphate was found to be incorporated to a limited extent into RNA by partially purified RNA polymerase from Micrococcus lysodeikticus . Upon alkaline hydrolysis and subsequent fractionation of the RNA hydrolysate, practically all of the redioactivity was found to be present in the nucleoside fraction. The results indicated that incorporation of 3′-deoxyadenosine into nascent polynucleotide prevented the further elongation of the polymer.

Determination of thiocyanate in body fluids.

Abstract A specific and sensitive method for the determination of thiocyanate in plasma or serum, cerebrospinal fluid, urine, gastric juice, and saliva is described. The method is based on the rapid oxidation of thiocyanate to cyanide under mild conditions at room temperature and determination of the cyanide formed by a sensitive colorimetric method (12).

Metabolism of 2-fluoroadenosine by Ehrlich ascites cells☆

Abstract 2-Fluoroadenosine was found to inhibit the incorporation of various labeled precursors into ribonucleic acid in whole Ehrlich ascites cells. Upon incubation with ascites cells, the nucleoside was readily converted to the 5′-mono-, 5′-di-, and 5′-triphosphates. 2-Fluoroadenosine-5′-triphosphate inhibited the DNA-dependent syntheses of RNA and polyadenylate catalyzed by RNA polymerase obtained from Micrococcus lysodeikticus . The results suggested that the inhibition was due to the incorporation of the analogue into RNA.

Determination of traces of hydrogen cyanide in respiratory air.

Abstract A procedure for the quantitative determination of hydrogen cyanide in respiratory air is described. By means of this procedure it has been demonstrated that traces of hydrogen cyanide are normally excreted in the respiratory air of man and rats.

Changes in coenzyme A concentration during vitamin B12 deficiency

Abstract The coenzyme A concentration in the liver and kidney of vitamin B12-deficient rats is 2–3 times higher than in normal or pair-weighed controls. This increase can be demonstrated in male as well as in female animals and is independent of the added stress of thyroid powder feeding. The increase in CoA concentration is due to an increase in the catalytically active, reduced form of CoA. The rate of degradation of CoA is the same in homogenates of livers from deficient and normal animals. Data on the influence of this increase in CoA level on the oxidation of α-ketoglutarate, succinate, pyruvate, and acetate by kidney and liver homogenates are reported. No marked differences were observed with homogenates from B12-deficient or sufficient animals.

Comparison of glycolytic enzyme activities in a series of human and rodent hepatomas

Abstract Activities of all the enzymes of the glycolytic pathway were determined under concordant conditions in a series of rat hepatomas of varying growth rates and in a group of human hepatomas. Similar determinations were done for comparison on normal human and rat livers. Human and rat liver on the whole are similar with respect to the glycolytic enzymes, both on an absolute and relative basis. In human liver the activities of glucose-6-phosphate dehydrogenase, glycerolphosphate dehydrogenase and fructose-1,6-diphosphatase are lower than in rat liver, while phosphoglucomutase is higher in the human tissue than in the rat tissue. Glucokinase of low glucose affinity was readily demonstrable in normal rat livers, but only glucokinase with high glucose affinity could be demonstrated in normal human livers. In a series of ten human hepato-cellular carcinomas an attempt was made to compare the abnormalities of glycolytic enzymes with those found in a series of slowly and rapidly growing rat hepatomas. Glucokinase and phosphofructokinase showed patterns similar to those of the slowly growing rat hepatomas, that is, levels similar to those found in normal liver. The majority of the human hepatomas had pyruvate kinase activities similar to those of the liver, a pattern that had also been found for the slowly growing rat hepatomas. Some of the human tumors had clearly increased pyruvate kinase levels, which are characteristic of rapidly growing rat hepatomas. Glycerolphosphate dehydrogenase was drastically reduced or absent in the human hepatomas in a pattern closely similar to that observed for the rapidly growing rat hepatomas. Fructose-diphosphatase was predominantly depressed in the human hepatomas similar to the finding in rapidly growing rat hepatomas. Glucose-6-phosphate dehydrogenase is either normal or elevated in both fast- and slow-growing rat hepatomas, but it is drastically reduced or absent in the majority of the human hepatomas. With respect to phosphoglucomutase the human hepatomas are similar to the fast-growing rat hepatomas showing generally quite low levels. Even within the group of the glycolytic enzymes, it is not possible to fit the abnormalities found in the human hepatomas uniformly into the pattern found in either the slowly or rapidly growing hepatomas. Extrapolation from the enzyme pattern of either type of rat hepatoma to the pattern of the human tumor, therefore, is quite uncertain and extrapolation to other types of human malignant tissues should not be attempted.

Concentration of streptomycin in brain and other tissues of cats after acute and chronic intoxication.

Summary Streptomycin was found in the brain, lungs and liver of cats for as long as 3 days after a single injection of 400 mg per kg. At this time the drug had virtually disappeared from the blood and CSF. The concentration in the brain was small compared with that in the other organs. In cats showing typical chronic intoxication during treatment with streptomycin in daily doses of 100 mg per kg, no accumulation of the drug was found in the serum, CSF or brain 24 hours after last dose. Significant concentrations of the drug were present in other tissues, especially in the kidney. It is concluded that the chronic neurotoxic action of streptomycin cannot be attributed to accumulation of the drug in the brain as a whole or in the brain stem.

Chemical determination of vitamin B12. V. A modified procedure for the determination of cobalamins in liver concentrates

A modification of the colorimetric procedure for the determination of vitamin B12 in liver concentrates is described. The modification is based on collection of cyanide, released on illumination from vitamin B12, in an acidic solution of silver sulfate, thus separating cyanide from substances interfering with the colorimetric determination.