Quantification of Intact Cytokinin Glucosides in Datura innoxia Crown Gall Tissue by Desorption Chemical Ionisation Mass Spectrometry

Cytokinin glucosides are routinely quantified as their aglycones produced by enzymic or chemical hydrolysis. It is, however, important to be able to measure their levels per se. The present paper illustrates the use of desorption chemical ionisation mass spectrometry coupled with stable isotope dilution for the determination of intact, underivatized N- and O- glucosyl conjugates of cytokinins in Datura innoxia crown gall tissue. A total of six glucosyl conjugates were determined; the two N-glucosides, zeatin-7-glucoside and zeatin-9-glucoside, were present in higher quantities than the O-glucosyl derivatives of zeatin, dihydrozeatin and their ribosides.     

Impaired calcium mobilisation in the 7315a prolactin-secreting pituitary tumour

The 7315a tumour secretes prolactin, but is refractory to enhancement of prolactin release by thyrotrophin-releasing hormone (TRH). In order to investigate further this refractoriness of the 7315a tumour cell, we compared cells from the tumour and from the normal pituitary with regard to TRH-enhanced fractional 45Ca2+ efflux and inositol phosphate production. TRH caused a large efflux of calcium from normal pituitary cells, but only mildly enhanced calcium efflux from the tumour cells. In contrast, TRH enhanced total inositol phosphate generation in both groups of cells to a similar degree. We therefore conclude that prolactin release from 7315a tumour cells is refractory to TRH due, at least in part, to impaired mobilisation of intracellular calcium by inositol phosphates.     

Calmodulin modulates prolactin secretion in vitro: studies with calmodulin containing liposomes

The control of prolactin secretion by Ca calmodulin and cyclic AMP was studied. Ca++ ionophore A23187 stimulated both cyclic AMP accumulation and prolactin release by primary culture of anterior pituitary cells in vitro. The increase of cyclic AMP formation by A23187 preceded that of prolactin release. To test the calmodulin involvement in these processes we used either selective calmodulin antagonist, the naphthalene sulphonamide derivative W7, or calmodulin containing liposomes. W7 dose dependently inhibited both basal or A23187 stimulated cyclic AMP accumulation and prolactin secretion. Insertion of Ca calmodulin within the cells stimulated prolactin secretion without modifying cyclic AMP accumulation. W7 inhibited the Ca calmodulin containing liposomes stimulation of prolactin release. These results suggest that calmodulin participates to the process of prolactin release.     

Internode length in Pisum. Action of gene lw

Jolly, C. J., Reid, J. B. and Ross, J. J. 1987. Internode length in Pisum. Action of gene lw.
Mutant K29 of Pisum sativum L. is shown to possess a recessive gene at a new locus, lw , which results in reduced internode length, delayed flowering and increased symptoms of water congestion compared with the parental cv. Torsdag. The interaction of gene lw with the internode length genes na, le, la and cry ⁵ is examined. Extracts from the shoots of Iw plants are shown to contain similar levels of gibberellin (GA)-like substances to comparable Lw plants, but Iw plants do not elongate to the same extent as Lw plants when treated with GA₁₉ GA₁₉, or GA₂₀. The effect of gene Iw is not graft-transmissible. Unlike essentially isogenic dwarf lines possessing the GA-synthesis genes le, Ih or Is, lw plants show a relative increase in elongation similar to Torsdag in response to photoperiod extensions from sources rich in far-red light. These results suggest that gene lw probably does not reduce elongation by influencing GA-synthesis and that the response to photoperiod extensions with far-red light may depend on the level of GA.