Compartment Analysis of Nitrogen Flows through Mature Leaves

Nitrogen flows in mature leaves of rice, sunflower and cornwere analyzed by multicompartment analyses of data from ¹⁵Ntracer experiments. The fourcompartment model fit the measureddata better than the two- or three-compartment models. Rateconstants of the nitrogen flows, transfers with or without proteinturnover and flow through a storage pool of soluble-N, werederived from a least-squares fit between the mathematical expressionsand the corresponding measured data. Results of computations indicated the following: The flow ofnitrogen through the protein pool was larger than the directflow in recently matured leaves, whereas the reverse was truein senescent leaves. The presence of a temporary storage poolof soluble N was suggested, and the half-life of the N exchangein that pool was estimated to be roughly the amount of the insolubleN present in three of the four cases examined. The half-livesof insoluble N (protein) pools were 35 to 150 h. The pool forthe N efflux from the leaves was small with the shortest half-lives(most less than 2 h) of N turnover. Some recycling of N duringprotein turnover was suggested in sunflower leaves, but theextent in the leaves of rice seedlings was estimated to be little. (Received April 28, 1983; Accepted October 6, 1983)     

The primary structure of teichuronic acid in Bacillus subtilis AHU 1031

Structural studies were carried out on the acidic polysaccharide fraction obtained from lysozyme digest of the cell walls of Bacillus subtilis AHU 1031. The polysaccharide fraction contained N- acetylmannosaminuronic acid ( ManNAcA ), N-acetylglucosamine (GlcNAc), glucose, glycerol and phosphorus in a molar ratio of 2:2:4:1:1, together with glycopeptide components. The results of analyses involving Smith degradation, chromium trioxide oxidation, methylation and proton magnetic resonance spectroscopy led to the conclusion that the backbone chain of the polysaccharide has the repeating unit----6)Glc(alpha 1----3/4) ManNAcA (beta 1----4)GlcNAc(beta 1----. About 50% of the N-acetylglucosamine residues in the backbone chain seem to be substituted at C-3 by the glycosidic branches, glycerol phospho-6-glucose, while the other half seem to be substituted by glucose.     

Hemoglobin M: effect of the proximal or distal histidine replacement on circular dichroism in the visible region

To examine the effects of a replacement of the proximal or the distal histidine on the structure of hemoglobin (Hb), absorption and circular dichroic (CD) spectra of five species of Hbs M in the visible region were measured. Four Hbs M had a characteristic but a similar absorption spectrum upon amino acid substitution, however, the proximal histidine replaced Hbs M (Hb M Iwate and Hb M Hyde Park) showed considerably different CD spectra from those of the distal histidine replaced ones (Hb M Boston and Hb M Saskatoon). The former exhibited large positive CD but the latter gave a complex CD spectrum with positive and negative extrema. On the other hand, absorption and CD spectra of Hb M Milwaukee did not changed very much from those of Hb A.     

Effect of inoculation withKlebsiella oxytoca andEnterobacter cloacae on dinitrogen fixation by rice-bacteria associations

The influence ofKlebsiella oxytoca andEnterobacter cloacae inoculation on dinitrogen fixation by the rice-bacteria association was examined in pots in a greenhouse. For inoculation,K. oxytoca NG13 isolated from a Japan paddy soil,E. cloacae E26 isolated from a China soil and following three strains were employed.K. oxytoca NG1389 is a mutant from NG13 and has no nitrogenase activity (nif). K. oxytoca NG13/pMC71A andE. cloacae E26/pMC71A were produced by inserting anif A containingK. pneumoniae plasmid (pMC71A) to NG13 and E26, respectively. These two strains were able to fix dinitrogen fixation in the presence of ammonium, whereas nitrogenase activity of wild strains (NG13 and E26) were repressed under this condition. Inoculation effects were tested on two rice (Oryza sativa L.) varieties, a Indica type C5444 and a Japonica type T65. Rice seedlings were planted to nonsterilized potted soil, and grown under flooded conditions. Upon inoculation with NG13 and E26, growth and N increment of plants particularly in T65 were stimulated above NG1389 inoculated plants. Assay by¹⁵N dilution and acetylene reduction techniques indicated that this N increment may be due to fixed N. Inoculation with NG13/pMC71A and E26/pMC71A resulted in more dry weight and fixed N than those of NG13 and E26 inoculated plants. Dr Y. Hirota died on 23 December 1986.     

Cytotoxicity of Fusarium T-2 in cultured Madin-Darby bovine kidney (MDBK) and primary fetal bovine kidney (PFBK) cells

Cytotoxicity of Fusarium T-2 toxin was evaluated in cultured Madin-Darby bovine kidney (MDBK) and primary fetal bovine kidney (PFBK) cells. The criteria for evaluation included number of adherent cells, phase contrast microscopy, and the scanning and transmission electron microscopy. The primary cells were more sensitive to the toxic effects of T-2 toxin than MDBK cultures. Cytotoxicity was observed when the cultures were exposed to the toxin for only 1 hour and then incubated with untreated media. Cell multiplication was decreased in both systems in 72 hour cultures. Scanning electron microscopy indicated loss of inter-cell contact and marked alterations in cell shape. Transmission electron microscopy indicated extensive proliferation of lysosomal bodies and proliferation of endoplasmic reticulum. The membrane system and mitochondria were not affected. Results indicated the kidney cells are highly sensitive to the toxic effects of T-2 toxin.     

Spectral changes upon subunit association in valency hybrid hemoglobins

The absorption, circular dichroism (CD) and magnetic circular dichroism (MCD) spectra of valency hybrid hemoglobins and their constituents (alpha + and beta chains for alpha 2+beta 2, alpha and beta + chains for alpha 2 beta 2+: + denotes ferric heme) were measured in the Soret region for F-, H2O, N3- and CN- derivatives. Absorption and MCD spectra of valency hybrid hemoglobins were very similar to the arithmetic mean of respective spectra of their corresponding component chains in all derivatives. The Soret MCD intensity around 408 nm for various complexes of valency hybrid hemoglobins seems to reflect the spin state of ferric chains. Upon ferric and deoxy ferrous subunit association to make the deoxy valency hybrid hemoglobins, only the high-spin forms bound with F- and H2O of alpha 2+beta 2 displayed a blue shift in the peak position around 430 nm and those of alpha 2 beta 2+ an increase in intensity around 430 nm. The blue shift and the increase in intensity were considered to be caused by the structural changes in deoxy beta chains of alpha 2+beta 2 and deoxy alpha chains of alpha beta 2+, respectively. These spectral changes were interpreted on the basis of their oxygen-equilibrium properties. In contrast to absorption and MCD spectra, the CD spectra of valency hybrid hemoglobins were markedly different from the simple addition of those of their component chains in all derivatives examined. The large part of CD spectral changes upon subunit association were interpreted as changes in the heme vicinity accompanied by formation of the alpha 1 beta 1 subunit contact.     

A kinetic study of the assimilation of 15N-labelled nitrate in rice seedlings

A ¹⁵N kinetic-analysis of the assimilation of nitrate nitrogenin the roots of rice seedlings indicated that (1) nitrate wasrapidly reduced to ammonia in the roots, where it was incorporatedinto glutamine and glutamic acids; (2) the pattern of nitrateassimilation into amino acids was very similar to that of ammoniumassimilation; and (3) the pattern of nitrogen incorporationinto protein was also similar to that of the incorporation withNH₄-feeding. In the shoots, alanine, serine, glutamic acid, -amino butyricacid and aspartic acid were relatively strongly labelled with¹⁵N as compared with the other amino acids. A different mechanismof nitrogen assimilation seems to operate in between the photosyntheticand non-photosynthetic organs of the plants. (Received August 19, 1974; )