The Association of Ascorbate and Ascorbate Oxidase in the Apoplast with IAA-Enhanced Elongation of Epicotyls from Vigna angularis

The level of (ascorbic acid (AA) plus dehydroascorbic acid (DHA))and the ratio of the level of AA to that of AA plus DHA in intercellularwashing fluid (IWF) of epicotyl segments from Vigna angularisdecreased from 2.8±0.3 to 1.2±0.5nmol (g fr wt)^–1and from 0.23±0.03 to 0.13±0.01, respectively,after incubation of the segments without IAA for 20 h at 27°C.However, these values changed to 5.3±1.7 nmol (g fr wt)^–1and 0.07±0.05 after incubation with 0.1 mM IAA. The activityof cell wall-bound ascorbate oxidase increased by about 20%and 70% after incubation without IAA and with IAA, respectively.However, the activity of cell wall-bound peroxidase was notaffected by incubation with or without IAA. The activities ofascorbate oxidase and peroxidase in IWF decreased by about 85and 75% after incubation without IAA. IAA did not affect thesedecreases to any great extent. A lignin-like compound was formedduring the incubation of epicotyl segments in the absence ofIAA. Formation of this compound was inhibited by IAA. The resultssuggest that one of the causes of the enhancement of elongationgrowth by IAA is the inhibition of peroxidase-dependent lignificationas a result of increases in levels of AA and DHA and in ascorbateoxidase activity. (Received August 16, 1993; Accepted December 6, 1993)     

Fractal property of eye movements in schizophrenia

 On the basis of a temporal model of animal behavior we conducted temporal analysis of eye movements in schizophrenic subjects (n=10) and normal controls (n=10). We found a fractal property in schizophrenic subjects, the fixation time of eye movement during reading ambiguous and difficult sentences showing a clear inverse power law distribution. An exponential distribution of a nonfractal nature was found in normal controls. Received: 21 July 1995/Accepted in revised form: 30 April 1996     

Conformation of NAD+ bound to allosteric L-lactate dehydrogenase activated by chemical modification

On modification of arginine residues with 2,3-butanedione, the Thermus caldophilus L-lactate dehydrogenase is converted to an activated form that is independent of an allosteric effector, fructose 1,6-bisphosphate (Fru-1,6-P2). The conformation of NAD+ bound to the modified enzyme in the absence of Fru-1,6-P2 was investigated by means of proton NMR, analyzing the time dependence of the transferred nuclear Overhauser effect (TRNOE) and TRNOE action spectra. The inter-proton distances determined on TRNOE analysis indicated that both the nicotinamide riboside moiety and the adenosine moiety of NAD+ were in the anti conformation, the ribose rings being in the C3'-endo form. This conformation was almost the same as that of NAD+ bound to the native enzyme-Fru-1,6-P2 complex, rather than that of NAD+ bound to the free native enzyme. These results suggest that the C3'-endo-anti form of the enzyme-bound NAD+ is essential for the activation of the T. caldophilus L-lactate dehydrogenase.     

Dermatan sulfate isomers in human articular cartilage characterized by high-performance liquid chromatography

The Constituents of dermatan sulfate isomers in human articular cartilage were studied at the disaccharide level by high-performance liquid chromatography. Appreciable amounts of dermatan sulfate components, i.e., dermatan sulfate, chondroitin sulfate types G and B, could be detected after digestion with chondroitinases-B or -ABC. The oversulfated dermatan sulfate isomers were isolated only after digestion with chondroitinase-ABC but not with the AC-lyase. The dermatan sulfate isomers were found to be markedly increased in weight loading parts of articular cartilage. It is postulated that the dermatan sulfate isomers are formed as a result of the weight loading reaction, which may be responsible for the fibrosis of articular cartilage.     

Inhibiting Effect of Auxin on Glucosamine Incorporation into Cell Walls of Rice Coleoptiles

Auxin induced growth and decreased the hexosamine content ofthe cell walls of rice coleoptile sections. Indole-3-aceticacid (IAA) at 10^–5 M inhibited the incorporation of ¹⁴C-glucosamineinto the cell walls. IAA did not affect the ¹⁴C-incorporationinto the cytoplasm, while inhibitors of glycoprotein synthesis,unicamycin and monensin, suppressed the incorporation into boththe cytoplasm and the cell walls. The radioactivity due to labeledglucosamine in the cell walls increased during the chase, butthis increase was inhibited by IAA. Among the cell wall fractions,the increase in radioactivity and its inhibition by IAA wereconspicuous in the hemicellulose I fraction. The inhibitoryeffect of IAA on glucosamine incorporation into the cell wallswas observed even in the presence of 0.15 M mannitol solutionwhich completely suppressed the IAA-induced growth. These resultssuggest that auxin induces growth at least partly by inhibitingthe transport of asparagine-linked glycoproteins from the cytoplasmto the cell walls. ¹ Present address: Department of Biology, Faculty of Science,Osaka City University, Sumiyoshi-ku, Osaka 558, Japan (Received July 23, 1986; Accepted December 22, 1986)     

An ultrastructural study of HeLa cell invasion with Salmonella typhi GIFU 10007

Scanning electron micrograph of HeLa S3 monolayered cells, inoculated with viable bacteria of a Salmonella typhi strain GIFU 10007, revealed that the extended microvilli tangled the bacteria within 10 min after inoculation. The micrographs of HeLa cells, at 1 hr after inoculation, indicate the following: shortening of bacterium-attached microvilli, subsiding of tangled bacteria into microvilli bush, and then attachment of bacterial soma to cell surface making the cell membrane depressed. The transmission electron micrographs, at 1 hr after inoculation, demonstrated the findings of interaction between HeLa cell and S. typhi 10007, similar to those observed on scanning electron micrographs. Hair-like fine structures from the soma of challenge organisms were also observed. They were in contact with HeLa cell microvilli and cell membrane. The bacteria were first partially and then totally surrounded by the HeLa cell plasma membrane. One, two, or several bacteria with intact outer membrane were enclosed in intracytoplasmic membrane-bound vacuoles. Fragmented vacuolar membrane was still visible around the intracellularly accumulated bacteria at 24 hr after inoculation. The viable cells of S. typhi 10007 are regarded as internalizing into HeLa cells by a process of endocytosis and to multiply within the membrane-bound vacuoles.     

Molecular evolution of mammalian class I alcohol dehydrogenase

Phylogenetic relationship and the rates of evolution of mammalian alcohol dehydrogenases (ADHs) have been studied by using the amino acid sequences from the human (ADH alpha, ADH beta, and ADH gamma), rat, mouse, and horse (ADH E and ADH S). With the maize ADH1 and ADH2 used as references, the patterns of the amino acid replacements in the beta-sheets, alpha-helices, and random coils in each of the catalytic and coenzyme-binding domains were analyzed separately. The phylogenetic trees based on the different sets of amino acid substitutions consistently showed that (1) multiple ADHs in human and horse have arisen after mammalian radiation, (2) the common ancestor of human ADHs alpha and beta diverged from the ancestor of ADH gamma first and the former two ADHs diverged from each other more recently, and (3) the human ADHs are more closely related to the rodent ADHs than to the horse ADHs. Furthermore, the estimated branch lengths showed that the rodent ADHs are evolving faster than the other ADHs. This difference in evolutionary rate between the two groups of organisms is explainable either in terms of the difference in the number of cell generations per year or in terms of reduction of functional constraints.