Analysis of water in Autonomous Biological Systems (ABS) samples.

Several soluble components, peptidase and amino acids, and carbon isotopic ratio in the water retrieved from flight experiments of Autonomous Biological Systems (ABS) as well as ground control samples are analyzed to interpret the condition, dynamics, material balance of the ABS ecosystems. Organic carbons in flight samples were found to be more abundant compared with the control ones, which suggested the uniform ecosystems in low gravity might easily dissolve more soluble components. The Mir-1997 flight sample showed higher C/N ratio probably because of the dissolution of carbon-rich plant materials.     

Domains required for nucleic acid binding activities in chloroplast ribonucleoproteins.

Five ribonucleoproteins (or RNA-binding proteins) from tobacco chloroplasts have been identified to date; each of these contains an acidic N-terminal domain (24-64 amino acids) and two conserved RNA-binding domains (82-83 amino acids). All five ribonucleoproteins can bind to ssDNA and dsDNA but show high specificity for poly(G) and poly(U). Here we present the nucleic acid binding activity of each domain using a series of deletion mutant proteins made in vitro from the chloroplast 29 kDa ribonucleoproteins. The acidic domain does not have a positive effect on binding activities and proteins lacking this domain show higher affinities for nucleic acids than the wild-type proteins. Mutant proteins containing single RNA-binding domains can bind to poly(G) and poly(U), though with lower affinities than proteins containing two RNA-binding domains. The spacer region (11-37 amino acids) between the two RNA-binding domains does not interact with poly(G) or poly(U) by itself, but is required for the additive activity of the two RNA-binding domains. Proteins consisting of two RNA-binding domains but lacking the spacer have the same activity as those containing only one RNA-binding domain. Possible roles for each domain in chloroplast ribonucleoproteins are discussed.     

Coenzyme A-dependent transacylation system in rabbit liver microsomes

The activities of cofactor-independent and CoA-dependent transacylation were examined for various rabbit tissues. Liver microsomes were found to exhibit relatively high CoA-dependent transacylation activity, while the cofactor-independent transacylation activity was low. The apparent Km values for CoA were 1.4 microM (acceptor, 1-acyl-sn-glycero-3-phosphocholine (1-acyl-GPC] and 3.8 microM (acceptor, 1-acyl-sn-glycero-3-phosphoethanolamine (1-acyl-GPE], respectively. The apparent Vmax values were 2.6 nmol/min/mg (1-acyl-GPC) and 1.2 nmol/min/mg (1-acyl-GPE), respectively. The CoA-dependent transacylation reaction shows a distinct fatty acid specificity. [14C]18:2 and [14C]20:4 at the 2-positions and [14C]18:0 at the 1-positions of donor phospholipids were transferred to lysophospholipids in the presence of CoA. We observed the formation of considerable amounts of acyl-CoA from these fatty acids during the reaction, without the participation of ATP. The transfer of other fatty acids between phospholipids was shown to be almost nil. The very low transfer of 18:1 was in marked contrast to the effective utilization of 18:1-CoA by acyl-CoA:1-acyl-GPC acyltransferase. The effects of several compounds and heat treatment on these two acylation reactions were also examined. The CoA-dependent transacylation reaction may be important for the selective acylation of certain lysophospholipids, such as 1-acyl-GPE, in living cells with the cooperation of acyl-CoA:lysophospholipid acyltransferase, which generates CoA for the former reaction.     

Mycological survey of Korean cereals and production of mycotoxins by Fusarium isolates.

The fungal species isolated from Korean cereals (barley, polished barley, wheat, rye, and malt) were Alternaria spp., Aspergillus spp., Chaetomium spp., Drechslera spp., Epicoccum sp., Fusarium spp., and Penicillium spp., etc. The number of Fusarium strains isolated was 36, and their ability to produce Fusarium mycotoxins on rice was tested. Nivalenol (NIV) was produced by Fusarium graminearum (7 of 9 isolates), Fusarium oxysporum (3 of 10 isolates), and Fusarium spp. (7 of 15 isolates). Of 15 isolates of Fusarium spp., 6 formed deoxynivalenol (DON). Fusarenon-X and 3-acetyl-DON were produced by most NIV- and DON-forming isolates, respectively. Zearalenone was produced by 3 isolates of F. graminearum, 1 isolate of Fusarium equiseti, and 11 isolates of Fusarium spp. T-2 toxin was not produced by any Fusarium isolates. The highest concentrations of mycotoxins produced by Fusarium isolates were 77.4 (NIV), 5.3 (DON), 138.3 (fusarenon-X), 40.6 (3-acetyl-DON), and 23.2 (zearalenone) micrograms/g.     

Photosensitive DNA cleavage and phage inactivation by copper(II)-camptothecin

Upon irradiation with 365-nm light, copper(II)-camptothecin significantly produced single- and double-strand breaks of DNA and also induced a marked inactivation of bacteriophage. The nucleotide sequence analysis exhibited considerably random DNA cleavage. The DNA strand scission by the camptothecin-Cu(II)-UV light system, as well as the phage inactivation, was strongly suppressed by bathocuproine and catalase, indicating participation of cuprous species and hydrogen peroxide in the reaction. The present results suggest that (1) Cu(II) ion may play an important role as a cofactor in antitumor action of camptothecin and (2) the combination of copper-camptothecin plus long-wave ultraviolet light is useful against certain cancer treatment as a new photochemotherapy.     

Intercellular CO2 concentration and water-use efficiency of temperate plants with different life-forms and from different microhabitats

Summary Photosynthesis and transpiration were measured simultaneously, under near-optimum and constant environmental conditions, in intact leaves of plants native to the temperate forest region. A linear relationship between photosynthetic rate and stomatal conductance was found in every species tested irrespective of leaf age or season, indicating that the calculated intercellular CO₂ concentration and water-use efficiency were fairly constant within a species. The values of intercellular CO₂ concentration and water-use efficiency ranged from 221 to 271 l l^–1 and 4.46 to 8.20 mol CO₂ mmolH₂O^–1 (6.24±0.90 mol CO₂ mmolH₂O^–1), respectively. The variations in intercellular CO₂ concentration and water-use efficiency were not directly related to photosynthetic capacities, life-forms, or microhabitat preferences. The intercellular CO₂ concentrations found in this study were close to values reported from cultivated plants and plants native to more arid regions, suggesting a common mechanism to maintain the stomatal conductance proportional to photosynthetic capacity over a wide variety of C₃ plants.     

Binding and crosslinking of 125I-labeled recombinant human tumor necrosis factor to cell surface receptors

Highly purified recombinant human tumor necrosis factor (TNF) (molecular mass determined as 17 kilodaltons (kDa) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and as 36 kDa by Sephadex G-100 gel chromatography) was labeled with 125I to a specific activity of 5 microCi/micrograms without appreciable loss of activity. The binding of 125I-TNF to eighteen human and twelve animal cell lines was examined. The binding varied considerably among different cell lines. In most cell lines, the binding was inhibited up to greater than 90% by the addition of a 100-fold excess of unlabeled TNF. Some human and mouse cell lines showed no significant binding above background levels, suggesting that these cell lines had no receptors for TNF. Among the TNF receptor-positive cell lines, there was no direct correlation between the level of specific TNF binding and the level of sensitivity to the cytotoxic or cytostatic effect of TNF. Some cell lines were sensitive to TNF, whereas others were not affected at all by TNF. The TNF receptor-negative cell lines were also resistant to TNF. Therefore, although the existence of TNF receptor seems to be necessary, it does not alone determine cellular sensitivity to TNF. Scatchard analysis of the binding data revealed that human HeLa S3 and THP-1 had about 50,000 and 10,000 receptors/cell with a dissociation constant (KD) of 0.3-0.5 nM, respectively. Similarly, mouse L-929 and L-M cells had about 5,000 receptors/cell with KD of 3-5 nM. 125I-TNF bound to HeLa S3 cells was rapidly internalized at 37 degrees C, presumably by receptor-mediated endocytosis, and degraded to acid-soluble products. The turnover of TNF receptors on HeLA S3 cells seemed to be rapid, since the level of specific binding quickly decreased after treatment with 100 micrograms/ml of cycloheximide at 37 degrees C with a half-life of about 1.5 h. The crosslinking of the cell-bound 125I-TNF with the use of disuccinimidyl suberate yielded a complex of 105 kDa for HeLa S3 and THP-1 cells, and a complex of 100 kDa for U937 cells. The crosslinking was completely inhibited by the addition of a 100-fold excess of unlabeled TNF. Assuming that the complex was due to a one-to-one association of the dimeric form of TNF (34 kDa) with the receptor, we estimated the molecular size of the human TNF receptor to be 71 kDa for HeLa S3 and THP-1, and 66 kDa for U937.     

Proline production by regulatory mutants of Serratia marcescens

Summary Proline-producing strains of Serratia marcescens Sr41 were constructed by three rounds of mutagenesis. A strain SP103 which did not degrade l-proline carried the putA mutation leading to lack of proline oxidase. A 3,4-dehydroproline-resistant mutant SP105, derived from strain SP103, carried the dpr-1 mutation which resulted in desensitization of the feedback inhibition of glutamate kinase. Strain SP103 produced 5.5 mg of l-proline per ml of fermentation medium containing sucrose and urea. Growth inhibition by proline analogs was enhanced when succinate was used as a carbon source in the medium. A thiazolidine-4-carboxylate-resistant mutant SP126 derived from strain SP105 produced 20.5 mg of l-proline per ml of medium. The mutation carried by strain SP126 might be distant from dpr-1 and putA mutations on the chromosome. Pyrroline-5-carboxylate reductase was not repressed by proline in S. marcescens Sr41.