Sugar Compositions, Intrinsic Viscosities and Molecular Weights of Hemicellulosic Polysaccharides of the Coleoptile Cell Walls in a Semi-Brachytic and a Normal Type Barley

The sugar compositions and intrinsic viscosities of the hemicellulosicpolysaccharides of the coleoptile cell wall were determinedin a normal type barley and a semi-brachytic type which producedless IAA than the normal type. The major sugar components ofhemicelluloses for both strains were arabinose (Ara), xylose(Xyl) and glucose (Glc). The Ara and Xyl content per unit lengthin the normal type did not change during growth, while thosein the semi-brachytic type decreased during growth. The Glccontents per unit length and per coleoptile decreased duringgrowth in both types of barley. The intrinsic viscosity of hemicellulosesfrom the coleoptile of the normal type was lower than that ofthe semi-brachytic type. These results suggested that the synthesis of arabinoxylan keptpace with the growth of the coleoptile in the normal type butnot in the semi-brachytic type, and that the average mol wtof the hemicelluloses in the normal type was lower than thatin the semibrachytic type. These chemical and physical changesin the hemicellulosic polysaccharides may account for the stuntedcoleoptile of the semi-brachytic barley with its less amountof endogenous IAA. (Received March 14, 1984; Accepted June 8, 1984)     

Insuppressibility of plasma glucagon by orally or intravenously administered glucose in diabetes mellitus

In order to study the response of pancreatic alpha cells to the change blood glucose, plasma pancreatic glucagon levels were measured after glucose loading given orally (50g) or intravenously (25g) in twenty-two normal controls and eighty untreated diabetics. Basal plasma pancreatic glucagon levels did not differ significantly in the two groups. However, oral or intravenous glucose administration caused a decrease in plasma pancreatic glucagon in normal subjects but not in diabetics. In "moderate" or "severe" diabetics, plasma pancreatic glucagon tended to increase paradoxically following oral glucose loading. To evaluate the sensitivity of pancreatic alpha cells to glucose, we calculated the index, -sigma delta IRG/sigma delta BS, after oral glucose loading. It was 1.96 +/- 0.57 in normal subjects, and significantly higher than in "mild" (0.11 +/- 0.05), "moderate" (-0.002 +/- 0.06) and "severe" (-0.09 +/- 0.07) diabetics. These results demonstrate the insensitivity of alpha cells to hyperglycemia in patients with diabetes mellitus as compared with normal subjects.     

Growth Regulation of Dark-grown Dwarf Barley Coleoptile by the Endogenous IAA Content

Growth curves of dark-grown coleoptiles of 11 isogenic coleoptilardwarf strains of barley (Hordeum vulagare L. cv. Akashinriki:uzu, 5, 77, 97, 105, 125, 131, 133, 136, 145 and 148) were simulatedwith a logistic equation and the endogenous IAA contents ofthe barley strains were determined. Growth analysis of the dwarfbarley coleoptiles revealed that the final coleoptile lengthwas correlated with the growth rate on the 2nd day after germination(r=0.897), when the growth rate was about maximum. The endogenousIAA Content of the barley strains, measured fluorometrically,indicated that on the 2nd day, the dwarf strains contained lessendogenous IAA than the normal Strain. The IAA content on the2nd day was correlated to the growth rate on the 2nd day (r=0.907,except for Strain 145) and the final coleoptile length (r=0.933,except for strains 77 and 145). The correlation, however, wasnot significant on the 3rd day. These results suggested thatthe dwarfism of the dark-grown coleoptiles of the barley Strainsexamined is primarily controlled by the endogenous IAA content. ¹ Present address: Department of Biology, Faculty of Science,Osaka City University, Osaka 558, Japan. (Received February 1, 1982; Accepted April 13, 1982)     

Effect of indole-3-acetic acid on cell wall loosening: Changes in mechanical properties and noncellulosic glucose content of Avena coleoptile cell wall

The effect of indole-3-acetic acid on cell wall loosening andchemical modifications of noncellulosic components of the cellwall in Avena coleoptile segments was studied and the followingresults were obtained. (1) Auxin decreased both the minimum stress-relaxation time(T_o) and the noncellulosic glucose content of the cell wall. (2) Decreases were observed in the absence or presence of mannitolsolution at concentrations lower than 0.20 M which osmoticallysuppressed auxin-induced extension, while at concentrationshigher than 0.25 M, there was little auxin effect, indicatingthat it is turgor-dependent. (3) The decrease in T_o of the cell wall and that in the noncellulosicglucose content caused by auxin in the presence of mannitolsolutions of various concentrations paralleled each other (thecorrelation coefficient was 0.897). (4) Both decreases in T_o and glucose content caused by auxinwere inhibited by nojirimycin (5-amino-5-deoxy-D-glucopyranose)in the presence of mannitol. The results suggest that auxin-induced cell wall loosening iscaused by the degradation of noncellulosic rß-glucanin the cell wall. (Received December 24, 1976; )     

Auxin-indnced changes in barley coleoptile cell wall composition

Auxin induces extension growth of barley coleoptile segments,causing cell extension and cell wall loosening represented bya change in mechanical properties of the cell wall. This responsedecreased after the segments were starved for more than 12 hrin buffer solution. Auxin decreased the noncellulosic glucosecontent of the cell wall of the segments starved for 0 and 6hr, but very little that of segments starved for 12 and 18 hr.The contents of arabinose, xylose and galactose, among noncellulosicpolysaccharides, and -cellulose of the cell wall increased duringthe starvation, but auxin did not affect them. The auxin-induceddecrease in glucose content was inhibited by nojirimycin, apotent inhibitor of ß-glucanase, which inhibited auxin-inducedextension and changes in mechanical properties of the cell wall,suggesting that cell wall loosening, and thus cell extension,resulted from partial degradation of ß-glucan of thecell wall. (Received April 20, 1978; )     

Comparison between the gelsolin and adseverin domain structure.

Adseverin (74-kDa protein, scinderin) is a calcium- and phospholipid-modulated actin-binding protein that promotes actin polymerization, severs actin filaments, and caps the barbed end of the actin filament, with its NH2-terminal half retaining these properties (Sakurai, T., Kurokawa, H., and Nonomura, Y. (1991) J. Biol. Chem. 266, 4581-4585). Further proteolysis of this NH2-terminal half generated five fragments, and two of them (Mr 15,000 and 31,000) showed Ca(2+)-dependent binding to monomeric actin. The Mr 31,000 fragment especially caused actin filament fragmentation, although its severing activity was also inhibited by several acidic phospholipids as was found in adseverin and its NH2-terminal half. Amino acid sequencing demonstrated that the two fragments' NH2 terminus were blocked in the same manner as the NH2 terminus of adseverin, and thus these two fragments are possibly located at the NH2-terminal of the adseverin molecule. This would then indicate that NH2-terminal fragments had a Ca(2+)-sensitive actin-binding function that relates to actin severing. The other two fragments' NH2-terminal sequencing showed a similar homology to the amino acid sequences of gelsolin and villin. Based on these observations, we propose that adseverin has a functional domain structure similar to that of the gelsolin and villin core.     

Inhibitory effect of calcium-binding protein regucalcin on Ca2(+)-activated DNA fragmentation in rat liver nuclei

Incubation of isolated rat liver nuclei with ATP, NAD+, and micromolar Ca2+ concentrations of various metal ions resulted in extensive DNA hydrolysis. Half-maximal activity occurred with 1.0 microM Ca2+ added, and saturation of the process was observed with 10 microM Ca2+. The Ca2+ (10 microM)-activated DNA fragmentation was inhibited by the presence of Ca2(+)-binding protein regucalcin isolated from rat liver cytosol. The inhibitory effect of regucalcin was complete at 0.5 microM. At 25 microM Ca2+ added, such an effect of regucalcin (1.0 microM) was not seen. Regucalcin also inhibited Ca2(+)-activated DNA fragmentation in the presence of calmodulin (10 and 20 micrograms). The results show that regucalcin can inhibit the Ca2(+)-activated DNA fragmentation due to binding the metal, suggesting a role in regulation of liver nuclear functions.     

Recognition of a 56 kDa protein in partially purified rat hepatic nuclear thyroid hormone receptor by anti-human c-erb A beta antibody.

Human beta thyroid hormone receptor (c-erb A beta protein) produced by an Escherichia coli expression system was purified by sequential column chromatography followed by electroelution from an electrophoresis gel and an antibody was prepared. The antibody recognized a 56 kDa protein band in a partially purified rat hepatic nuclear thyroid hormone receptor fraction on Western blotting. Although multiple bands appeared on Western blotting of crude rat hepatic receptor preparations, a 56 kDa band was the most prominent and preadsorption of the antibody by purified c-erb A protein resulted in almost complete disappearance of the 56 kDa band, indicating that the 56 kDa band was formed by a specific antigen-antibody interaction. Furthermore, the 56 kDa protein appeared to co-elute with 3, 5, 3'-triiodo-L-thyronine binding activity in hydroxylapatite, Sephacryl S-200, and DNA-cellulose column chromatography of rat hepatic nuclear receptor, and sequential column purification resulted in selective enrichment of the 56 kDa band. These results suggest that the 56 kDa protein may be the major component of the rat hepatic thyroid hormone receptor.     

Hydration of oligosaccharides: anomalous hydration ability of trehalose.

The disaccharide trehalose extensively exists in anhydrobiotic organism and is considered to play an important role in preserving the integrity of biomembrane. However, the preserving mechanism remains unclear. In this report, we examine the hydration abilities of trehalose and several oligosaccharides composed of alpha-D-glucopyranosyl residues. The unfrozen water fraction per molecule was determined from differential scanning calorimetry measurements of their aqueous solutions. Further, the NMR relaxation time of the natural abundance 17O of water is measured for several saccharide solutions. These results indicate that trehalose has the highest hydration ability among the saccharides studied. In other words, trehalose can effectively lower the mobility of water molecules hydrogen-bonded with saccharides. It is thus reasonable that, among the disaccharides studied, trehalose exhibits the maximum stabilizing effect on the bilayer structure of lipid whose acyl chains are bonded with each other by the apolar interaction, because the apolar interaction is strengthened with the stabilization of the surrounding water structure.     

Oxidative modification of glycated low density lipoprotein in the presence of iron

This is the first observation for contributing to the glycation of low density lipoprotein (LDL) to oxidative modification of its own lipids and protein. Human plasma LDL was glycated by incubation with glucose (G-LDL). Glucose incorporated into apoprotein B was approximately 10 mol/mol of apoprotein (2.8% modification of lysine residues) and 84% of G-LDL was adsorbed on phenylboronate affinity column. G-LDL incubated with Fe3+ for 4 h caused a significantly higher level of lipid peroxidation than U-LDL (untreated with glucose), and a higher molecular weight protein was observed in apoprotein B on SDS-polyacrylamide gel electrophoresis (SDS-PAGE), increasing with incubation period. Corresponding to change on SDS-PAGE, G-LDL exposed to Fe3+ moved faster than G-LDL per se or U-LDL to anode on agarose gel electrophoresis. The higher the Fe3+ concentration, the more lipid peroxidation was caused. Alpha-tocopherol or probucol suppressed the lipid peroxidation of G-LDL exposed to Fe3+.