The role of the cysteine-rich region of the β2 integrin subunit in the leukocyte function-associated antigen-1 (LFA-1, αLβ2, CD11a/CD18) heterodimer formation and ligand binding

The cysteine-rich region (CRR) of the β2 integrin subunit was replaced by that of β1 to give the chimera β2NV1. β2NV1 can combine with αL to form a variant leukocyte-function-associated antigen (LFA)-1 on COS cell surface, suggesting that the specificity of the β2 interaction with αL does not lie in the CRR. Unlike those expressing wild-type LFA-1, COS cells expressing αLβ2NV1 are constitutively active in intercellular adhesion molecule (ICAM)-1 adhesion. These results suggest that activation of LFA-1 involves the release of an intramolecular constraint, which is maintained, in part, by the authentic β2 CRR.     

Internode length in Pisum. I. The effect of the Le/le gene difference on endogenous gibberellin-like substances

The allelopathic potential of the dry fruits of Washingtonia filifera (L. Linden) H. Wendl. was investigated. Leachates from fruits inhibited the germination of lettuce, wheat, red cabbage and cucumber seeds. The inhibitory effect was partly neutralized by kinetin (20 mg 1⁻¹) and gibberellic acid (50 mg 1⁻¹). The effect of kinetin was more pronounced at 25°C than at 20°C. Substances inhibiting germination were localized in the pericarp of the fruit and were resistant to high temperature.     

The discrimination between Rb+ and K+ by Escherichia coli is changed after bacteriophage T7 infection

Rb+ and K+ have similar chemical properties. They share the uptake systems in Escherichia coli and can replace each other inside the cell. These common features led to experiments in which the radioactive isotope 86Rb was used to trace intracellular K+ fluxes. However, the E. coli pumps discriminate between these two ions and one should thus be cautious using 86Rb+ as a tracer for K+. We now report that T7 infection alters the degree of discrimination in such a way that changes of intracellular Rb+ do not reflect changes of K+. It has been observed that shortly after infection the 86Rb+ level was strongly reduced (Ponta, H., Altendorf, K.-H. and Schweiger, M. (1976) Mol. Gen. Genet. 149, 145-150). In contrast, determination of the K+ content showed no change directly after infection (Kuhn, A., Jütte, H. and Kellenberger, E. (1983) J. Virol. 47, 540-552). The efflux of 86Rb was only evident when Rb+ was used in trace amounts. In media conditions under which intracellular K+ was mainly replaced by Rb+, 86Rb+ efflux was not observed.     

The Enucleation of Cells on Plastic Leighton Coverslips

A simple enucleation technique that facilitates autoradiographic and electron microscopic examination of cytoplasms is described. Cells were grown on commercially available plastic Leighton coverslips and these were centrifuged in the presence of cytochalasin B. The centrifugation requires no special holders and only a high speed centrifuge. Enucleation frequencies of greater than 90% were obtained for Chinese hamster fibroblasts and mouse B-82 cells.     

Evaluation of the establishment of Aphidius ervi Haliday (Hymenoptera: Braconidae) in lucerne aphid populations in New South Wales

The aphid parasitoid Aphidius ervi was released in the major lucerne-growing areas of New South Wales (NSW), Australia, between 1978 and 1981. With the collaboration of district agronomists of the New South Wales Department of Agriculture, five State-wide surveys were conducted in 1982–1983 to determine the success of the release program. In each survey, the distribution of the parasitoid was checked in relation to populations of the aphids Acyrthosiphon kondoi Shinji and Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae). The surveys confirmed the successful dispersal and establishment of A. ervi in the major lucerne-growing areas of NSW. They demonstrated its ability to survive and recover rapidly after a severe and widespread drought.