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)     

Ultrastructure of a Hexagonal Array in Exosporium of a Highly Sporogenic Mutant of Clostridium botulinum Type A Revealed by Electron Microscopy Using Optical Diffraction and Filtration

The ultrastructure of a hexagonal array in the exosporium from spores of a highly sporogenic mutant of Clostridium botulinum type A strain 190L was studied by electron microscopy of negatively stained exosporium fragments using optical diffraction and filtration. The exosporium was composed of three or more lamellae showing an equilateral, hexagonal periodicity. Images of the single exosporium layer from which the noise had been filtered optically revealed that the hexagonally arranged, morphological unit of the exosporium was composed of three globular subunits about 2.1 nm in diameter which were arranged at the vertices of an equilateral triangle with sides of about 2.4 nm. The morphological units were arranged with a spacing of about 4.5 nm. The adjacent globular subunits appeared to be interconnected by delicate linkers.     

The APC/C activator Cdh1 regulates the G2/M transition during differentiation of placental trophoblast stem cells

Differentiation of placental trophoblast stem (TS) cells to trophoblast giant (TG) cells is accompanied by transition from a mitotic cell cycle to an endocycle. Here, we report that Cdh1, a regulator of the anaphase-promoting complex/cyclosome (APC/C), negatively regulates mitotic entry upon the mitotic/endocycle transition. TS cells derived from homozygous Cdh1 gene-trapped (Cdh1^GT/GT) murine embryos accumulated mitotic cyclins and precociously entered mitosis after induction of TS cell differentiation, indicating that Cdh1 is required for the switch from mitosis to the endocycle. Furthermore, the Cdh1^GT/GT TS cells and placenta showed aberrant expression of placental differentiation markers. These data highlight an important role of Cdh1 in the G2/M transition during placental differentiation.     

Polyclonal Antibody Production in Murine Spleen Cells Induced by Staphylococcus

Polyclonal plaque-forming cell (PFC) responses in murine spleen cells induced by Staphylococcus aureus and S. epidermidis were studied. Injection of Balb/c mice with S. aureus strain 248βH resulted in the generation of anti-trinitrophenyl (TNP) and anti-sheep red blood cell PFC in their spleens. Cultures of Balb/c spleen cells in the presence of S. aureus 248βH, Cowan I, or a protein A-deficient mutant yielded many anti-TNP PFC. The larger the number of organisms that were added to the cultures, the better was the PFC response. Both living and killed organisms, were capable of inducing the response, but an excess of living 248βH organisms in the cultures abrogated the response. All of the organisms (12 strains of S. aureus and 11 strains of S. epidermidis) freshly isolated from patients had the ability to induce the polyclonal PFC response in cell cultures. These organisms stimulated cultured C3H/HeJ mouse spleen cells, which were unresponsive to bacterial lipopolysaccharide (LPS). Cultured cells from the spleens of athymic nu/nu mice also responded to these organisms, and the number of PFC in nu/nu cell cultures was always greater than that in nu/+ cells prepared from a haired litter mate. Moreover, the responses of nu/nu spleen cell cultures to which nylon wool column-filtered splenic nu/+ T cells were added were lower than expected. These findings suggest that the polyclonal PFC response to staphylococci is thymus independent, but that the magnitude of the response is regulated by mature T cells. Cultures of macrophage-depleted spleen cells responded to the organisms to an extent similar to that of the control. The 248βH organisms were less capable of stimulating spleen cells of 2-week-old mice (i.e., early maturing B cells) than LPS. However, spleen cells from adult (7-week-old) and aged (9-month-old) mice responded well to both the organisms and LPS. Previous sensitization with the organisms in vivo did not affect any polyclonal responses of spleen cells in vitro to either the organisms or LPS. The role of staphylococcal protein A in the polyclonal PFC response to staphylococci is discussed.     

Mitochondrial DNA haplogrouping of the brown bear,Ursus arctos (Carnivora: Ursidae) in Asia,based on a newly developed APLP analysis

Sequence analyses of the complete brown bear, Ursus arctos, mitochondrial DNA (mtDNA) genome have detected scattered single nucleotide polymorphisms (SNPs) that define distinct mtDNA haplogroups in phylogeographical studies. The degraded DNA in historical samples, such as stuffed or excavated specimens, however, is often not suitable for sequence analyses. To address this problem, we developed an amplified product length polymorphism (APLP) analysis for mtDNA‐haplogrouping U. arctos specimens by detecting haplogroup‐specific SNPs. We verified the validity and utility of this method by analysing up to 170‐year‐old skin samples from U. arctos specimens collected widely across continental Eurasia. We detected some of the same haplogroups as those occurring in eastern Hokkaido (Japan) and eastern Alaska in continental Eurasia (the Altai and the Caucasus). Our results show that U. arctos in eastern Hokkaido and eastern Alaska descended from a common ancestor in continental Eurasia, and suggest that U. arctos occupied several refugia in southern Asia during the Last Glacial Maximum. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 627–635.     

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)