Effect of CaCl2 on growth performance, photosynthetic efficiency and nitrogen assimilation of Cichorium intybus L. grown under NaCl stress

Pot culture experiments were conducted to assess the extent of growth, photosynthetic efficiency and nitrogen assimilation of chicory (Cichorium intybus L.) as affected by NaCl and CaCl₂ alone as well as in combination. Six treatments, i.e., 80 mM and 160 mM NaCl, 5 mM and 10 mM CaCl₂ and 80 mM + 10 mM and 160 mM + 10 mM of NaCl + CaCl₂ were given to the growing plants separately at three developmental stages, viz., the pre-flowering (30 DAS), flowering (120 DAS) and post-flowering (150 DAS) stages. Each NaCl treatment caused a significant reduction in total plant biomass, photosynthetic rate, stomatal conductance, total chlorophyll content, soluble protein content, NR activity and nitrogen content, although nitrate content increased. On the contrary CaCl₂ treatment gave a favorable effect, compared to the control. The effect of combined treatments was similar to that of NaCl but less in magnitude. Thus, the application of CaCl₂ may mitigate the adverse effect caused by NaCl.     

Differentiation-dependent expression of cathepsin D and importance of lysosomal proteolysis in the degradation of UCP1 in brown adipocytes

The lysosomal protease cathepsin D increased markedly in brown adipocytes during differentiation in primary cultures. Differentiated cells had 20 times the amount of immunoreactive cathepsin D found in preadipocytes. Cathepsin D mRNA, as estimated by relative RT-PCR, was also present in higher amounts in differentiated brown fat cells. Cathepsin D expression was not influenced by repeated exposures of brown adipocytes to norepinephrine (NE). Cathepsin D levels were also unchanged when NE was withdrawn for 48 h after cells had been exposed to NE for 7 days. In contrast, exposure of the cells to NE for 7 days increased their UCP1 content by more than twofold, which returned to basal levels within 48 h of withholding NE. The half-life of UCP1 under basal conditions and in cells chronically exposed to NE was estimated from reductions in [35S]methionine-labelled immunoprecipitable UCP1 over 72 h. UCP1 t1/2 under basal conditions was 3.7+/-0.4 days, which was similar to the half-lives of labelled mitochondrial translation products (3.6+/-0.8 days). The turnover rates of both UCP1 and mitochondrial translation products were reduced by NE. The turnover rate of UCP1 in the presence or absence of NE cannot account solely for the rapid loss of UCP1 from brown adipocytes upon withdrawal of NE. This loss was reduced when cells were incubated with inhibitors of phosphatidylinositol 3-kinases (PI 3-kinase), previously shown to block formation of autophagic vacuoles. Thus, brown adipocytes acquire a large capacity for both uncoupled metabolism and for lysosomal proteolysis during differentiation. Withdrawal of NE, as often occurs in vivo from suppression of sympathetic nervous system activity, would not only terminate thermogenesis but also favor formation of autophagic vacuoles to rapidly reduce the cell content of UCP1-containing mitochondria.     

Some characteristics of Rabbit muscle phosphofructokinase-1 inhibition by ascorbate

These studies relate to a working hypothesis that glycogen storage is facilitated in resting muscle by inhibiting glycolysis via inhibition of LDH, AK, and PFK-1 by ascorbate; when muscle is active, these isozymes combine with muscle proteins and are released and protected from inhibition by ascorbate and glycolysis proceeds. Focus in these studies is on the ability of G-actin and aldolase to prevent PFK-1 inhibition by ascorbate. We found that inhibition by ascorbate was PFK-1 concentration dependent; ascorbate does not inhibit above 200 nM PFK-1. We conclude that ascorbate inhibits PFK-1 dimers (and perhaps monomers) but not PFK-1 tetramers. Separation of PFK-1 dimers from tetramers was achieved with centrifugal filter devices and differences in their sensitivity to ascorbate inhibition were demonstrated. Some comparisons are made with attributes of AK inhibitions by ascorbate that, like PFK-1, are also enzyme concentration dependent. Discussions relate findings to cellular infrastructure and the role of ascorbate in glycogen synthesis.     

Growth and Metabolism of Senna as Affected by Salt Stress

Pot culture experiments were conducted using different NaCl concentrations to assess their impact on the growth and metabolic changes in senna (Cassia angustifolia Vahl.). Five treatments (0, 40, 80, 120, and 160 mM NaCl) were given to the plants at three phenological stages, i.e. at pre-flowering, (45 days after sowing, DAS); flowering (75 DAS) and post-flowering (90 DAS) stages. A significant reduction in the biomass and length of the roots and shoots, photosynthetic rate, stomatal conductance, the total chlorophyll content, protein content, nitrate reductase activity, and reduced nitrogen content of the leaves was observed at each phenological stage with each salt concentration applied. Contrary to this, proline and nitrate contents of the leaves increased markedly. The post-flowering stage was most sensitive to NaCl treatment.