1. Nicotinic acid-deficient rats were given a dose of niacytin or an equivalent one of free nicotinic acid or hydrolysed niacytin. 2. The excretion of N'-methylnicotinamide and of tertiary nicotinoyl derivatives in urine showed that niacytin was not metabolized as free nicotinic acid, although hydrolysed niacytin was equivalent to free nicotinic acid. 3. Little or none of the niacytin dose was recovered as tertiary nicotinoyl derivatives in faeces. This result was not affected by fitting rats with tail-cups to prevent coprophagy. 4. At the high doses used niacytin restored the growth rate of the deficient animals because of a small degree of hydrolysis of the bound nicotinic acid.

Animals↗

PubMed1970

The metabolism of niacytin in the rat. Trigonelline as a major metabolite of niacytin in the urine.

1. To investigate the fate of orally administered niacytin, urine and faeces of rats given single niacytin doses were examined for nicotinic acid derivatives methylated on the pyridine nitrogen atom, determined as trigonelline. 2. Methods were devised for the extraction of trigonelline from urine and faeces and for its differentiation from N'-methylnicotinamide. 3. A prolonged elevation of the excretion of trigonelline in the urine of rats dosed with niacytin was detected colorimetrically, in contrast with the urinary excretion in control groups given free nicotinic acid or hydrolysed niacytin. The total conversion of the nicotinoyl moiety of niacytin into trigonelline was 30-40%. 4. The identity of this metabolite as trigonelline was established by t.l.c., by its u.v. spectrum and by g.l.c. after conversion into methyl nicotinate. 5. The excretion of Ehrlich-positive substances was also increased in urine after administration of niacytin, the increase being approximately parallel to the trigonelline excretion. 6. No increase in the excretion of trigonelline in faeces was found after administration of niacytin. 7. These results suggest a metabolic path-way for niacytin in the rat involving methylation of the pyridine nitrogen without prior release of free nicotinic acid. This hypothesis explains the absence of biological activity of niacytin. An endogenous source of urinary trigonelline was also demonstrated.

Animals↗

PubMed1969

A product from the reaction of pyridine with acetic anhydride.

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Acetates↗

PubMedDate not supplied

The vitamin K content of intravenous lipid emulsions.

Commercially available intravenous lipid emulsions are largely derived from vegetable oils, a natural source of phylloquinone (vitamin K1). We therefore examined the concentration of vitamin K1 in two widely used intravenous lipid emulsions by using a previously validated high performance liquid chromatography technique. The vitamin K1 concentrations of 10% emulsions of Intralipid and Liposyn II were 30.8 and 13.2 micrograms/dL, respectively. The concentration of vitamin K1 in the 20% emulsions of these products was essentially double that in the 10% emulsions. The coefficients of variation between the vitamin K1 content in three different lots of each product were consistently less than 7.0%. The observed concentrations of the vitamin in these lipid emulsions paralleled the predicted content on the basis of the type of vegetable oil(s) used to make the product. The type of vegetable oil used for production therefore seems to be a major determinant of the final vitamin K1 content. The vitamin K1 contained in these intravenous lipid emulsions is substantial and may have great impact on the vitamin K status of the recipient.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

A prospective survey for central line skin-site colonization by the pathogen Malassezia furfur among hospitalized adults receiving total parenteral nutrition.

BACKGROUND: Over 50 case reports suggest that Malassezia furfur is an emerging systemic pathogen in neonates who receive IV lipid emulsions. Because isolation of this fungus requires special culture techniques, which are not routinely used, the authors of many case reports of M. furfur infections in adults question whether infections caused by this organism are being underdiagnosed in older patients. METHODS: Catheter insertion site colonization rates in adults receiving total parenteral nutrition (TPN) were prospectively evaluated in 149 hospitalized patients with 928 cultures handled specifically for M. furfur detection. Positive control samples consisted of M. furfur cultures in neonates and in adults, who had not been enrolled in the study, and of a separate positive culture obtained from a skin site inoculated with M. furfur. RESULTS: M. furfur was not cultured from any of the 928 study samples (95% confidence interval [CI] -0.4% to +0.4%). CONCLUSIONS: These results suggest that M. furfur is less of a threat to hospitalized adults receiving TPN than has been otherwise postulated. These data do not support the inclusion of special cultures for M. furfur in routine skin-site surveillance programs among hospitalized adults receiving TPN.

Adult↗