High-performance liquid chromatographic assay for N2-[5-(hypoxanthin-9-yl)pentyloxycarbonyl]-L-arginine (ST 789) in plasma by cyclization with benzoin and fluorimetric detection.
This paper describes a new highly sensitive assay for N2-[5-(hypoxanthin-9-yl)pentyloxycarbonyl]-L-arginine, an immunomodulatory agent, required for clinical pharmacokinetic investigation. A pre-column derivatization by cyclization with benzoin in aqueous medium produces the fluorescent 2-substituted amino-4,5-diphenylimidazole fluorescing at 450 nm (excitation wavelength 310 nm). L-Arginine-acetyl-L-carnitinamide chloride (ST 857, II), another arginine derivative, was used as an internal standard. A C18 DB column (5 microns, 250 mm x 4.6 mm I.D.) and a 45:55 (v/v) mixture of 0.05 M ammonium phosphate at pH 7.2 and methanol as mobile phase were used. Linearity was ascertained in the range 5-100 ng. Extraction recovery from plasma proved to be higher than 90% in the range 5-50 ng/ml. Intra-day precision, expressed as coefficient of variation, was in the range 4.7-6.0%. The limit of quantification proved to be 5 ng/ml and the limit of detection 2 ng/ml at a signal-to-noise ratio of 5. The method is specific.
High-performance liquid chromatographic evaluation of PCF 39, a new immunomodulator agent.
An high-performance liquid chromatographic analysis of PCF 39, N2-[5-(hypoxanthin-9-yl)pentyloxycarbonyl]-L-arginine, with ultraviolet detection, has been devised and validated. The main pharmacokinetic results encountered for rats treated intravenously with PCF 39 at a dose of 100 mg/kg are described.
The infection process, sporulation and survival of Alternaria helianthi on sunflower
SUMMARY 
 
Electron microscopy was used to study the infection of sunflower leaves by Alternaria helianthi. Conidia germinated by producing one to many germ tubes which grew across the leaf surface before forming appressoria. The fungus directly penetrated its host through the cuticle and epidermis. Entry into the host through wounds and stomates was also observed. Extracellular sheaths were found to be associated with germ tubes and intercellular hyphae of A. helianthi. Conidiophores developed through collapsed stomates, from leaf veins, trichomes and also from mycelium growing across the host leaf surface. Microcylic conidia were produced directly from parent conidia under certain conditions. Studies using a volumetric spore trap showed that the airborne spore concentration followed a distinct periodicity with peaks occurring between 0900 and 1100 h each day. Laboratory studies showed that safflower, noogoora burr and bathurst burr could serve as alternative hosts for A. helianthi. The pathogen was readily isolated from sunflower crop debris from a diseased crop that had been harvested 1 yr earlier.