The isolation of abscisic acid (ABA) deficient mutants by selection of induced revertants in non-germinating gibberellin sensitive lines of Arabidopsis thaliana (L.) heynh.

Summary By selecting for germinating seeds in the progeny of mutagen-treated non-germinating gibberellin responsive dwarf mutants of the ga–1 locus in Arabidopsis thaliana, germinating lines (revertants) could be isolated. About half of the revertants were homozygous recessive for a gene (aba), which probably regulates the presence of abscisic acid (ABA). Arguments for the function of this gene were obtained from lines homozygous recessive for this locus only, obtained by selection from the F₂ progeny of revertant X wild-type crosses. These lines are characterized by a reduced seed dormancy, symptoms of withering, increased transpiration and a lowered ABA content in developing and ripe seeds and leaves.Abbreviations ABA Abscisic acid - GA₄₊₇ Mixture of gibberellin A₄ and A₇ - EMS Ethylmethanesulfonate - NG Non-germinating - G Germinating     

Evidence for substrate guidance of primordial germ cells

Primordial germ cells (PGCs) have been removed from their normal migratory route in early embryos of Xenopus laevis, and their behaviour studied in vitro. They adhere to, and move over the upper surface of, layers of outgrowing cells from expiants of adult Xenopus mesentery. They move by the extrusion of single filopodia, elongation, forward streaming of the yolky cytoplasm and retraction of their trailing ends. When the underlying cells are polarized in one direction only, PGCs always elongate and move along the same direction. Furthermore, when PGCs elongate and move over less obviously polarized cells, they always do so in the direction of ‘stress fibres’ (actin bundles) in the underlying cells. A substrate-guidance hypothesis for PGC migration is only tenable if there is some orientation in their natural substrate in vivo. Using the scanning electron microscope, we demonstrate that the coelpmic lining cells, beneath which PGCs migrate up the dorsal mesentery of the gut, are orientated in the direction of travel. Furthermore, this orientation changes at the time of gonadal ridge formation. This raises the intriguing possibility that PGCs are guided for at least part of their migration in Xenopus laevis embryos by a substrate-guidance mechanism.     

Physical structures of Tn10-promoted deletions and inversions: role of 1400 bp inverted repetitions.

We report here the physical structures of deletions and inversions promoted by the translocatable tetracycline-resistance element Tn10. DNA/DNA heteroduplex and restriction enzyme analyses of alterations in the genome of bacteriophage lambda suggest that both types of DNA alterations almost always originate at the internal termini of the 1400 bp terminal inverted repetitions of Tn10. Tn10-promoted deletions remove a single contiguous DNA segment beginning at one such terminus; Tn10-promoted inversions are more complex, and involve both an inversion and a specific deletion of Tn10 DNA.     

Determination of acid α-naphthyl acetate esterase enzyme activity in peripheral blood leukocytes of gazelles (Gazella subgutturosa)

We examined gazelle peripheral blood leucocytes using the α-Naphthyl acetate esterase (ANAE) staining technique (pH 5.8). Our purpose was to determine the percentage of ANAE positive lymphocytes. The proportion of ANAE positive T-lymphocytes was 72%. T-lymphocytes showed an ANAE positive reaction, but eosinophilic granulocytes and monocytes also showed a positive reaction. By contrast, no reaction was detected in B-lymphocytes, neutrophil granulocytes or platelets. The reaction observed in T-lymphocytes was a red-brown coloration, usually 1–2 granules, but enough granules to fill the cytoplasm were detected rarely. As a result of ANAE enzyme staining, we concluded that the staining technique can be used as a cytochemical marker for gazelle T-lymphocytes.     

Development and application of microwave-assisted extraction technique in biological sample preparation for small molecule analysis

Microwave-assisted extraction (MAE) has emerged as an efficient extraction technique for various kinds of biological samples due to its low usage of extraction solvents and shorter extraction time. This review will focus on the recent developments and advantages of incorporating MAE in sample preparation protocols for the analysis of small molecules in plant, food and clinical samples in recent years. The operating principles of this technique and the key parameters influencing its extraction efficiency, including the nature of solvent, temperature, power and extraction time and their limitations are first mentioned. This is followed by a discussion on the advantages of applying MAE to extract organic contaminants in food for routine food safety analysis and active ingredients recovery. The successful application of MAE technique to recover bioactive compounds from plants in drug discovery studies and quality control purposes is then described. Additionally, the feasibility of using green solvents such as water, micelle and ionic liquids with MAE for plant metabolite profiling studies is evaluated and the associated challenges discussed. Finally, the application of MAE in clinical samples is highlighted. The use of MAE in this field is currently limited to the targeted detection of small molecules in human samples, due to a lack of knowledge of its effects on thermally labile metabolites. Consequently, the need for additional studies on how MAE impacts the recoveries of different metabolite classes in mammalian samples is discussed. The outcome of these studies can potentially broaden MAE applications in the clinical field.     

Book reviews

THE ORIGINS OF ANGIOSPERMS AND THEIR BIOLOGICAL CONSEQUENCES by E. M. Friis, W. G. Chaloner and P. R. Crane (Eds). Cambridge University Press. Paperback Version 1989. ISBN 0 521 31173X. Price £15.

ARGUMENTS ON EVOLUTION. A PALEONTOLOGIST'S PERSPECTIVE by Antoni Hoffman. Oxford University Press. 1989. 274 pages.

HETEROCHRONY IN EVOLUTION: A MULTDDISCIPLINARY APPROACH. Editon M.L. McKinney. Plenum Press, New York. 1988. 348 pp. ISBN 0–306–42947–0. $95.40 £79.50