Expression of xyloglucanase sp-Xeg gene from Penicillium canescens accelerates growth and rooting in transgenic aspen plants

The properties of transgenic aspen (Populus tremula) clones carrying the recombinant gene of xyloglucanase sp-Xeg from Penicillium canescens have been analyzed. Complex modifications were revealed both in the composition of the wood and in the plant phenotype. Biometric analysis showed that shoot dimensions increased by 24.8%, 25% and 26% in the PtXIV-Xeg1a, PtXVXeg1a and PtXVXeg1b lines, respectively. The number of internodes in some transgenic clones also increased. Modifications in rhizogenesis have been shown for the first time in the plants with the recombinant gene of xyloglucanase: in vitro rooting efficiency exceeded the control value in 13 out of 25 lines. Maximum rooting efficiency was observed in the PtXVXeg1a line (3.2-fold higher than in the control). A reliable increase in the root system mass (by 20% to 52%) under greenhouse conditions was observed for 8 out of 25 clones. A lower pentosan content in the wood was shown for all lines. The data on xyloglucanase activity and pentosan content generally correlated with phenotypic modifications.     

Some properties of partially purified preparations of cAMP phosphodiesterase from beef heart]

Beef heart cAMP phosphodiesterase (EC 3.1.4.17) was isolated and partially purified using fractionation by ammonium sulfate and gel filtration on the columns with Sephadex G-200 and Sepharose 6B. This method allowed to preserve the enzyme binding to the low-molecular weight thermostable protein regulator of the phosphodiesterase activity. The enzyme preparation was purified 130--180-fold as compared to the original homogenate. The pH-dependence of the enzyme activity in the imidazole and tris -- buffers for the fraction with maximal activity was carried out. The kinetic analysis of this fraction revealed an abnormal kinetic behaviour with two Km values. The enzyme is represented by four forms differing in their molecular weights and possessing different capacity for activation by Ca2+ and protein regulator. No activation was observed in the forms with higher molecular weights, whereas the activity of the forms with lower molecular weights depended on the presence of Ca2+ and protein regulator. It is assumed that some of the above-described forms are capable of interconversions.     

Spreading depression produced in the thalamus,hippocampus, and caudate nucleus by electrical stimulation of the parietal cortex in rats

The parameters of cortical electrical stimulation (ES) producing synaptically-operated spreading depression (SD) were determined in rats. Waves of SD were regularly triggered in the thalamus by brief, high frequency ES (0.02–0.05 sec; 200–500 Hz) of the parietal cortex. Monitoring by EEG confirmed the lack of accompanying convulsive activity in the cortex and the subcortical structures investigated. Use of Nembutal-induced anesthesia led to a higher minimum threshold for onset of SD, without preventing short-latency thalamid SD. Stimulating the parietal cortex was less effective for synaptic excitation of hippocampal and caudate SD. Hippocampal, unlike thalamic SD, was accompanied by spells of epileptiform activity, most pronounced at certain points in the onset and decline of the SD wave. These brief convulsive episodes were not the cause but the result of SD to a large extent. The low, subconvulsive threshold of synaptically triggered subcortical as well as cortical structures should therefore be taken into account when considering the functional significance of the SD reaction.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 22, No. 1, pp. 36–44, January–February, 1990.