Assay for both ascorbic and dehydroascorbic acid in dairy foods by high-performance liquid chromatography using precolumn derivatization with methoxy- and ethoxy-1,2-phenylenediamine.

A procedure for the simultaneous determination of both ascorbic and dehydroascorbic acid in dairy foods by high-performance liquid chromatography using precolumn derivatization with 4-methoxy- and 4-ethoxy-1,2-phenylenediamine is presented. The derivatives are isolated by solid-phase extraction and analysed by fluorescence detection on a resin-type reversed-phase column at pH 9. Retention times are 2 and 3.2 min for the derivatives of ascorbic and dehydroascorbic acid, respectively. Relative standard deviations of the within- and between-assay tests are 7.1 and 5.5%, respectively, for ascorbic and 11 and 9%, respectively, dehydroascorbic acid. The limits of detection are 50 and 70 fmol per 5-microl injection for ascorbic and dehydroascorbic acid, respectively.

[Determination of retinol and alpha-tocopherol in milk and milk products using high-pressure liquid chromatography after saponification in serum vials]. / Bestimmung von Retinol und alpha-Tocopherol in Milch und Milchprodukten mit Hilfe der Hochdruck-Flüssigchromatographie (HPLC) nach Verseifung in Serumfläschchen.

An improved procedure is described for the determination of retinol and alpha-tocopherol in milk and dairy products using high-pressure liquid chromatography (HPLC). Samples are saponified in sealed 10-ml serum vials in the absence of oxygen, cooled and neutralized by injecting glacial acetic acid into the system. Retinyl acetate and 5,7-dimethyltocol respectively are used as the internal standards. The solution is extracted with hexane and the organic phase is cleaned up on a sodium sulphate/aluminium oxide column. The solution is evaporated under vacuum and dissolved in ethanol for HPLC analysis. A short reversed-phase column packed with RP-18, using methanol as the eluent, allows fast separations of both the vitamins.

Iron-dependent binding of 8-anilinonaphthalene-1-sulphonate by both lactoferrin and transferrin.

Fluorescence of 8-anilinonaphthalene-1-sulphonate is enhanced by both lactoferrin and transferrin. The enhancement is relatively low between pH 4 and 8, and high at below pH 4. At physiological pH the fluorescence enhancement is higher with the iron-deprived than with the iron-saturated proteins. Binding of iron by lactoferrin is associated with lowering affinity for the dye.

Mechanism of action of narcotics in the production of menstrual dysfunction in women.

The ability of morphine to block ovulation in animals prompted investigation of the frequency and mechanisms of menstrual abnormalities in women addicted to narcotic analgesics. Menstrual histories obtained from 76 former heroin addicts receiving daily methadone maintenance revealed that more than one-half of these women had experienced menstrual abnormalities while taking heroin or methadone. In order to determine the specific physiologic effects of narcotic analgesics on reproductive function, detailed endocrinologic studies were carried out in seven of these patients who complained of amenorrhea or irregular menses while receiving methadone. Four of the seven women manifested abnormalities of the control of gonadotropin secretion. Three of these four failed to exhibit cyclic gonadotropin release, as evidenced by an absence of increased levels of follicular phase follicle-stimulating hormone, midcycle gonadotropin peaks or luteal phase progesterone increments. In the fourth patient a prolonged follicular phase (30 days) of the menstrual cycle was detected. One of these four patients also had low basal gonadotropin levels and failed to exhibit luteinizing hormone increments greater than control levels in response to ethinyl estradiol (positive feedback). The remaining three women exhibited normal patterns of gonadotropin secretion during the observation period. In these women, menstrual bleeding occurred in response to withdrawal from luteal phase (10 to 20 ng/ml) progesterone levels and to exogenous ethinyl estradiol, suggesting normal uterine responsivity to progesterone and estrogen. Although not documented, it is likely that oligo-ovulation was the cause of the irregular menses in these three patients. Amenorrhea is commonly associated with methadone ingestion or heroin addiction and appears to be related to an alteration of the hypothalamic mechanisms controlling gonadotropin secretion. Tolerance to these effects of methadone may develop after chronic ingestion.

The mechanism of alloxan toxicity: an indication for alloxan complexes in tissues and alloxan inhibition of 4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulphonic acid (SITS) binding for the liver cell membrane.

It is shown that alloxan inhibits binding of SITS to liver cells. This indicates the cell membrane as a site of alloxan action. Alloxan is found to react with tissues to form complexes that are detectable up to 3 hrs after alloxan treatment. On the basis of the present findings, an assumption is made that alloxan inhibits a cell membrane processes by blockade of functionally importnat groups.