Effects of NaCl and iso-osmotic PEG stress on growth,osmolytes accumulation and antioxidant defense in cultured sugarcane cells

In order to discriminate between the ionic and osmotic components of salt stress, sugarcane (Saccharum officinarum L. cv. Co 86032) calli were cultured on media containing NaCl or polyethylene glycol (PEG) 8000 that exerted the same osmotic pressure (−0.7 MPa). PEG stress exposure for 15 days led to significant growth reduction and loss in water content than salt stressed and control tissues. Osmotic adjustment (OA) was observed in callus tissues grown on salt, but was not evident in callus grown on PEG. Oxidative damage to membranes, estimated in terms of accumulation of thiobarbituric acid reactive substances-TBARS and electrolytic leakage was significantly higher in both the stressed calli than the control however, the extent of damage was more in the PEG stressed calli. The stressed callus tissues showed inhibition of ascorbate peroxidase activity, while catalase activity was increased. These results indicate sensitivity of cells to PEG-mediated stress than salt stress and differences in their OA to these two stress conditions. The sensitivity to the osmotic stress indicate that expression of the stress tolerance response requires the coordinated action of different tissues in a plant and hence was not expressed at the cellular level.     

The isolation and immunolocalization of iron-binding compounds produced by Gloeophyllum trabeum

Summary Low molecular weight iron-binding compounds are produced by the brown-rot fungus Gloeophyllum trabeum. These chelators may function in scavenging transition metals for fungal metabolism and extracellular enzyme production. Because of the low molecular mass of the chelate-metal complex (below 1000 Da), and the oxidizing potential of the bound transition metals, certain chelating compounds could also play a role in the early stages of cellulose depolymerization by brown-rot fungi. High-affinity iron-binding compounds were isolated and partially purified from both liquid cultures of the brown-rot Gloeophyllum trabeum and from infected wood. Chelating compounds purified by thin-layer chromatography were used to prepare specific antibodies. These antibodies were shown to detect the chelator in infected wood and liquid fungal cultures by enzyme-linked immunosorbent assay and could be used in immunotransmission electron microscopy to visualize the high-affinity iron-binding compounds in situ. Elucidating the physiological roles of fungal chelate-metal complexes and determining their function in lignocellulose depolymerization will help us to better understand the mechanism of wood biodegradation.Publication no. 1549 Maine Agricultural Experiment Station Offprint requests to: J. Jellison     

The role of dendritic cells in the initiation of immune responses to contact sensitizers. I. In vivo exposure to antigen

Twenty-four hours after skin painting mice with picryl chloride (PIC) there was a four- to fivefold increase in the numbers of dendritic cells (DC) isolated from the lymph nodes. These DC initiated primary proliferative and cytotoxic responses when added to cultures of normal syngeneic lymph node cells. The proliferative response was enhanced when the donors of the responding lymph node cells were sensitized with the same antigen. Contact sensitivity developed in syngeneic mice injected into the footpads with 30,000-50,000 DC from lymph nodes of mice painted with picryl chloride 1 day previously. Thus, 1 day after skin painting mice, there were dendritic cells in the draining lymph nodes which were able both to initiate primary stimulation of lymphocytes in vitro and to sensitize recipient mice to give specific delayed hypersensitivity reactions.     

Foreign protein expression from S phase specific promoters in continuous cultures of recombinant CHO cells

Foreign protein expression from the commonly used SV40 promoter has been found to be primarily during the S-phase of the cell cycle. Simple mathematical models with this cell cycle phase dependent expression of foreign protein suggest that the specific production rate will be proportional to the cell growth rate, which is particularly disadvantageous in high cell density fed-batch or perfusion bioreactors. In this study we investigate this predicted relationship between the production rate and growth rate by culturing recombinant CHO cells in a continuous suspension bioreactor. One CHO cell line, GS-26, has been stably transfected with the plasmid pSVgal, which contains the E. coli lac Z gene under the control of the SV40 promoter. This GS-26 cell line was grown in suspension cultures over a range of specific growth rates in batch and continuous modes. The intracellular -galactosidase activity was assayed using a standard spectrophotometric method after breaking the cells open and releasing the enzyme. A strong growth associated relationship is found between the intracellular -galactosidase content and the specific growth rate in batch and continuous cultures, as predicted.     

The role of acid phosphatases in plant phosphorus metabolism

Hydrolysis of phosphate esters is a critical process in the energy metabolism and metabolic regulation of plant cells. This review summarizes the characteristics and putative roles of plant acid phosphatase (APase). Although immunologically closely related, plant APases display remarkable heterogeneity with regards to their kinetic and molecular properties, and subcellular location. The secreted APases of roots and cell cultures are relatively non-specific enzymes that appear to be important in the hydrolysis and mobilization of P_i from extracellular phosphomonoesters for plant nutrition. Intracellular APases are undoubtedly involved in the routine utilization of P_i reserves or other P_i-containing compounds. A special class of intracellular APase exists that demonstrate a clear-cut (but generally nonabsolute) substrate selectivity. These APases are hypothesized to have distinct metabolic functions and include: phytase, phosphoglycolate phosphatase, 3-phosphoglycerate phosphatase, phosphoenolpyruvate phosphatase, and phosphotyrosyl-protein phosphatase. APase expression is regulated by a variety of developmental and environmental factors. P_i starvation induces de novo synthesis of extra- and intracellular APases in cell cultures as well as in whole plants. Recommendations are made to achieve uniformity in the analyses of the different APase isoforms normally encountered within and between different plant tissues.     

A neural network model for kindling of focal epilepsy: basic mechanism

A simple neural network model is proposed for kindling — the phenomenon of generating epilepsy by means of repeated electrical stimulation. The model satisfies Dale's hypothesis, incorporates a Hebb-like learning rule and has low periodic activity in absence of shocks. Many of the experimental observations are reproduced and some new experiments are suggested. It is proposed that the main reason for kindling is the formation of a large number of excitatory synaptic connections due to learning.     

Speed Breeding Opportunities and Challenges for Crop Improvement

Journal of Plant Growth Regulation - Crop improvement in light of the rapidly changing climate and the increasing human population continues to be one of the primary concerns for researchers across...     

Chemodiversity and α-Glucosidase Activity of Eucalyptus Species from Northwestern Himalaya,India

The aim of current work was to determine essential oils (EOs) composition from three Eucalyptus species, including E. citriodora, E. camaldulensis and E. globulus and assess their α-glucosidase inhibitory activity. The EOs were collected using the hydrodistillation technique and characterized by GC/MS, GC-FID and NMR. The isolated EOs from leaves parts of Eucalyptus species varied from 0.56 to 1.0 % on fresh weight basis. The content of the EOs was distinct according to the species. The most abundant metabolites were identified as citronellal (0–83.0 %), 1,8-cineole (0.2–44.8 %), spathulenol (0.4–16.1 %) α-pinene (0.4–15.9 %), p-cymene (3.7–11.9 %), citronellol (0–8.6 %), β-eudesmol (5.3–8.6 %) and β-pinene (0–7.1 %). The EOs obtained from targeted samples exhibited strong α-glucosidase inhibitory activity. These results are encouraging and underline that the EOs of Eucalyptus species may be a promising alternative source of natural antidiabetic.     

Short communication: Protoplast formation from the thermophilic fungus Malbranchea sulfurea,using the thermostable chitinase and laminarinase of Paecilomyces varioti

Two thermostable enzymes produced by the thermophilic fungus Paecilomyces varioti, a chitinase and laminarinase, were used to isolate protoplasts of a thermophilic fungus, Malbranchea sulfurea. The frequency of protoplast regeneration observed (35%) was considerably higher than that obtained using commercial lytic enzymes.