Improved micro-method for the high-performance liquid chromatographic determination of caffeine and paraxanthine in biological fluids

A high-performance liquid chromatographic procedure is reported for reproducibly and sensitively quantitating caffeine and its N-demethylated metabolite paraxanthine in micro-samples. A 5-μm reversed-phase radial compression column and 214-nm fixed wavelength ultraviolet detector were used to attain a sensitivity sufficient to quantitate these compounds at concentratios as low as 80 ng/ml using only 25 μl of sample. The assay is applicable to microliter samples of whole blood, serum, plasma, saliva, amniotic, cerebro-spinal and gastric fluids such as might be obtained in studies involving small animals or neonates. The utility of the assay is illustrated with caffeine and paraxanthine levels measured in several maternal and fetal fluids following constant-rate intravenous infusion of caffeine into a rabbit throughout pregnancy.     

Use of a radioimmunoassay technique to measure the titer of anti-cow-zona antibodies in marmoset monkeys

A double antibody radioimmunoassay technique is described for the measurement of anti-zona antibodies in the peripheral plasma of marmosets actively immunized against intact cow zonae pellucidae. The method has been shown to be a reliable, repeatable indicator of antibody titer, enabling direct comparison of the response obtained between marmosets. This is the first report of a procedure describing the active immunization of a primate against zona antigens, and the first time a radioimmunoassay technique has been used to monitor profiles of anti-cow zona antibody production following active immunization. The method should prove to be a useful tool in the evaluation of zona antigens as agents for immunocontraception.     

Comparison of whole-cell protein electrophoretic profiles of Haemophilus influenzae: implementation of a microcomputer mainframe linked system and description of a new similarity coefficient

A microcomputer mainframe linked system is described which allows video camera data capture and storage of one-dimensional whole-cell protein electrophoresis gel images, processing of normalized traces to produce a similarity matrix, and analysis of the matrix using the commercial cluster analysis program CLUSTAN. A new similarity coefficient is introduced which takes into account both band position and intensity. Forty-five strains of Haemophilus influenzae, including the eight biotypes and six serotypes, were analyzed using this system. Results demonstrated groupings which are consistent with known genetic relationships.     

Nile crocodiles, Crocodylus niloticus, and estuarine crocodiles, Crocodylus porosus, show similar osmoregulatory responses on exposure to seawater

1. Nile crocodiles, reared in fresh water and exposed acutely to seawater, suffer marked dehydration and hypernatraemia. Cloacal urine osmolarity and potassium concentration increased markedly but urine sodium remains low. 2. Hypernatraemia is increased when secretion from the lingual salt glands is prevented. 3. C. niloticus appears not to drink seawater. 4. Similarities in osmoregulatory response between estuarine and Nile crocodiles suggest that the lingual salt glands of C. niloticus are functional in salt water, playing an important role in sodium balance. 5. Significant differences in the function of the renal/cloacal complex of Alligator and Crocodylus emphasize further the differences between these two groups of crocodilian and provide support for the postulated marine ancestry of many or all of the Crocodylidae.     

Purple pigmentation in leaves of some tropical weed species

The photoacoustic spectroscopic studies of purple pigmented leaves revealed the occurrence of anthocyanins and betalains in some local weed species growing on soils with low moisture levels. The pigmentation intensities were higher in C₄ plants than in C₃ plants. An inverse correlation was observed between pigmentation intensities and soil moisture levels. This work is a part of the UNEP Research Project granted to Prof. D. O. Hall, UNEP Coordinator, Department of Plant Sciences, King’s College; London.     

Factors governing the production of juvenile Atlantic salmon in Scottish streams

Data are presented to show how the number and growth of juvenile salmon in streams in the Scottish Highlands are influenced by various physical (temperature, water chemistry, depth and velocity, type of substratum) and biotic (food resources, competition, recruitment) factors.