Increased chilling tolerance and altered carbon metabolism in tomato leaves following application of mechanical stress

We investigated the effects of brushing on the chilling tolerance and metabolism of nonstructural carbohydrates (soluble sugars and starch) in tomato leaves before, during and after a chilling stress. Tomato plants ( Lycopersicon esculentum Mill. cv. Caruso) were cultivated either without mechanical stress application (control plants) or with daily brushing treatments for 15 days (brushed plants), prior to a 7-day chilling treatment (8/5°C day/night). Brushing resulted in shorter plants with a 34% reduction in leaf dry weight per area and a 59% reduction of soluble sugars and starch, on a dry weight basis. The sugar to starch ratio was not affected by brushing. A greater chilling tolerance in the brushed plants was demonstrated by the maintenance of a significantly higher PSII efficiency in brushed plants (42%) compared to that of the control plants (30%) after 7 days of chilling treatment, less visible damage to the leaf tissue, and a more rapid resumption of growth during 3 days of recovery as compared to control plants. During the chilling treatment levels of soluble sugars per leaf dry weight increased 15-fold in the brushed plants and 5-fold in control plants. In the present study we have demonstrated that brushing can increase chilling tolerance in tomato plants. The observed differences in chilling tolerance and concentration of soluble sugars in the leaves may indicate an involvement of soluble sugar levels in acclimation to chilling.     

BBReader: A computer program for the combined use of the BioMagResBank and PDB databases

A computer program (BBReader) was developed which performs an inverse search in theBioMagResBank database. Given (cross) peak positions of a protein, the program searchesfor atoms with matching chemical shifts and suggests possible assignments for user-specifiedhomo- and heteronuclear one- to three-dimensional COSY- and NOESY-type experiments.It can handle 1H, 13C and 15N spectra. Distance information from PDB files can be utilizedfor filtering possible NOESY cross peak assignments.     

Cholinergic Control of Nerve Growth Factor in Adult Rats: Evidence from Cortical Cholinergic Deafferentation and Chronic Drug Treatment

Abstract: It is well documented that nerve growth factor (NGF) plays an important role in maintaining functions of cholinergic basal forebrain neurons. In the present study, we tested the hypothesis that cholinergic activity controls NGF levels in cholinoceptive neurons of the cerebral cortex and hippocampus. To address that question, we used both cholinergic deafferentation of cerebral cortex and hippocampus by cholinergic immunolesion with 192IgG-saporin and chronic pharmacological treatment of sham-treated and immunolesioned rats with the cholinergic agonist pilocarpine and the cholinergic antagonist scopolamine. We observed an increase in NGF protein levels in the cortex and hippocampus after cholinergic immunolesions and also after muscarinic receptor blockade by chronic intracerebroventricular scopolamine infusion in sham-treated rats after 2 weeks. There was no further increase in the accumulation of NGF after scopolamine treatment of immunolesioned rats. Chronic infusion of pilocarpine had no effect on cortical and hippocampal NGF protein levels in sham-treated rats. In rats with cholinergic immunolesions, however, pilocarpine did prevent the lesion-induced accumulation of NGF. There was no effect of cholinergic lesion and drug treatment on cortical or hippocampal NGF mRNA levels, consistent with the importance of NGF retrograde transport as opposed to its de novo synthesis. This study provides strong evidence for the hypothesis that there is cholinergic control of cortical and hippocampal NGF protein but not mRNA levels in adult rats.     

Isolation of pure myocardial subcellular organelles.

A procedure is outlined for the isolation of three pure myocardial subcellular fractions by sucrose gradient ultracentrifugation. The purity of the sarcolemmal (SL) and sarcoplasmic reticulum (SR) fragments and mitochondria were documented by marker enzyme assays and SL purity by electronmicroscopy.     

Temperature acclimation in the Mongolian gerbil (Meriones unguiculatus): biochemical and organ weight changes.

1. Adult Mongolian gerbils (Meriones unguiculatus) were acclimated to 5 +/- 1, 24 +/- 1 and 34 +/- 1 degrees C for 6-8 weeks. 2. Body weights of temperature acclimated gerbils did not differ significantly from controls. Organ wt/body wt ratios of liver, kidney and heart increased in cold-acclimated and decreased in heat-acclimated gerbils. Adrenal wt/body wt ratio increased in the cold and was unchanged in the heat. Relative weights of brain, spleen, lungs, brown fat and ovaries + uterus did not change with temperature acclimation. 3. Cold acclimation produced significant increases in specific and total activity of brown fat alpha GPO and liver SO and AAO and in total activity of kidney SO; a significant decrease in liver mitochondrial ADP/O ratio with succinate as substrate; and no change in brown fat SO or liver alpha KGO. 4. Heat acclimation produced significant decreases in specific and total activity of liver and kidney SO, and in total activity of brown fat SO and alpha GPO, and liver AAO and alpha KGO. 5. The combined biochemical and organ wt changes seen in temperature-acclimated gerbils suggest that this species is capable of altering its metabolic thermogenic potential in response to a wide range of ambient temperatures.     

Aggregation of sponge cells. XX. Self-aggregation of the circular proteid particle.

In the extracellular space of the tissue of the sponge Geodia cydonium, circular proteid particles are found which carry as subunits the aggregation factor and a series of glycosyltransferases. Using the technique of velocity sucrose gradient centrifugation, the sedimentation coefficient (S020,w) of the particle-monosomes was determined to be 90. By means of the Svedberg equation a molecular weight of 1.3 . 10(8) daltons could be estimated. The monosomes aggregate in the presence of Ca2+ to higher complexes via disomes, trisomes, and pentasomes. The complexes can be redissociated by dodecyl sulfate but not by EDTA. During the Ca2+-mediated self-aggregation, the particles lose their biological activity with respect to their aggregation promoting function.     

Steroidogenesis in isolated adrenocortical cells. Correlation with receptor-bound adenosine 3′:5′-cyclic monophosphate

Because several groups have recently questioned a mediating role for cyclic AMP in adrenocortical steroidogenesis, we analysed the problem in more detail by measuring three different cyclic AMP pools in cells isolated from decapsulated rat adrenals. Extra-cellular, total intracellular and bound intracellular cyclic AMP were determined by radioimmunoassay in comparison with corticosterone production induced by low corticotropin concentrations. The increase in extracellular and total intracellular cyclic AMP with low corticotropin concentrations was dependent on the presence of a phosphodiesterase inhibitor and short incubation times. Bound intracellular cyclic AMP was less dependent on these two parameters. In unstimulated cells cyclic AMP bound to its receptor represents only a small fraction of the total intracellular cyclic AMP. After stimulation by a concentration of corticotropin around the threshold for corticosterone production, an increase in bound cyclic AMP was observed which correlated very well with steroidogenesis both temporally and with respect to corticotropin concentration. This finding was complemented by measuring a concomitant decrease in free receptor sites. Full occupancy of the receptors was not necessary for maximal steroidogenesis. Binding kinetics of cyclic [(3)H]AMP in concentrations equivalent to the intracellular cyclic AMP concentration suggest the presence of at least three different intracellular cyclic AMP pools. These observations are in agreement with a possible role for cyclic AMP as a mediator of acute steroidogenesis induced by low corticotropin concentrations.