Effect of onion (Allium cepa) root exudates on the hyphal growth of Gigaspora margarita

 The effect of root exudates from onions differing in P status on spore germination and hyphal growth of arbuscular mycorrhizal fungi was investigated. Onion (Allium cepa) was grown in solution culture at different phosphorus concentrations (0, 0.1, 1.0, 8.0 and 24.0 mg P l^–1) and root exudates were collected. When spores of the arbuscular mycorrhizal fungus, Gigaspora margarita were incubated with these root exudates, spore germination was only slightly affected but hyphal growth was greatly affected, particularly with exudates from P-deficient plants. This suggests that the P nutrition of host plants influences the composition of root exudates and thereby the hyphal growth of arbuscular mycorrhizal fungi. Accepted: 25 June 1995     

Isolation of mutants of Arabidopsis thaliana in which accumulation of tobacco mosaic virus coat protein is reduced to low levels.

Summary We have found that Arahidopsis thaliana is susceptible to infection with a crucifer strain of tobacco mosaic virus (TMV-Cg); the coat protein of TMV-Cg accumulated to a high level in uninoculated rosette leaves several days after inoculation. As a first step in the search for host-coded factors that are involved in virus multiplication, we isolated mutants of A. thaliana in which the accumulation of TMV-Cg coat protein was reduced to low levels. Of 6000 M₂ plants descended from ethyl methanesulfonate-treated seeds, two such lines (PD 114 and PD378) were isolated. Genetic analyses suggested that the PD 114 phenotype was caused by a single nuclear recessive mutation, and that PD114 and PD378 belonged to the same complementation group. The coat protein accumulation of a tomato strain of TMV (TMVL) was also reduced in PD 114 plants compared to that in the wild-type plants. In contrast, PD114 plants infected with turnip crinkle or turnip yellow mosaic viruses, which belong to taxonomic groups other than Tobamovirus, expressed similar levels of these coat proteins as did infected wild-type plants.In this paper, we use the term multiplication (of a virus in a plant) to mean a substantial increase in virus concentration in the uninoculated leaves of the infected plant. Therefore, the efficiency of each process of invasion of the plant by the virus, uncoating, replication and degradation of the virus genome, formation and degradation of the virus particles, and spreading of the virus in the plant will affect the degree of multiplication     

Analysis of integrated human papillomavirus type 16 DNA in cervical cancers: amplification of viral sequences together with cellular flanking sequences.

We have isolated four clones of integrated human papillomavirus type 16 (HPV-16) DNA from four different primary cervical cancer specimens. All clones were found to be monomeric or dimeric forms of HPV-16 DNA with cellular flanking sequences at both ends. Analysis of the viral sequences in these clones showed that E6/E7 open reading frames and the long control region were conserved and that no region specific for the integration was detected. Analysis of the cellular flanking sequences revealed no significant homology with any known human DNA sequences, except Alu sequences, and no homology among the clones, indicating no cellular sequence specific for the integration. By probing with single-copy cellular flanking sequences from the clones, it was demonstrated that the integrated HPV-16 DNAs, with different sizes in the same specimens, shared the same cellular flanking sequences at the ends. Furthermore, it was shown that the viral sequences together with cellular flanking sequences were amplified. The possible process of viral integration into cell chromosomes in cervical cancer is discussed.     

Unique response of Cyanophyceae to copper

A study was made of the tolerance to Cu of 11 strains of Cyanophyceae and 7 strains of eukaryotes. These had all been tested within 6 months after isolation for their photosynthetic activity when exposed to Cu (Takamuraet al., 1989) and had repeatedly been subcultured in the medium without Cu for 2 years. Photosynthetic measurements were made in two ways: precultured in medium without Cu or precultured (for one subculture) in medium containing Cu (645 g 1^–1). The results were compared with those obtained within 6 months of isolation. The tolerance of the eukaryotes did not change significantly in any case, but most strains of Cyanophyceae lost their tolerance to Cu within a few subcultures in medium without Cu; however tolerance recovered following one subculture in medium containing an intermediate level of Cu. This rapid adaptation cannot be explained by a constitutive mutation.     

The exchange of Ca2+-receptive protein complex (troponin) in the myofibrils of fast and slow skeletal muscles

In order to compare the role of the Ca²⁺-receptive protein (troponin), in the characteristic myofibrillar contractile response of chicken fast and slow skeletal muscles, the troponin in both kinds of myofibrils were partially exchanged, under slightly acidic conditions. The Ca²⁺- or Sr²⁺-activation of the ATPase of fast (or slow) skeletal myofibrils hybridized with slow (or fast) skeletal troponin profiles were also investigated. The results indicated that the Ca²⁺- or Sr²⁺-affinity of the myofibrillar ATPase activity were related to the species of troponin. This procedure for replacing troponin in myofibrils under physiological conditions in thus considered to be useful for the study of the Ca²⁺-regulatory mechanism in myofibrillar contraction.     

Isolation and characterization of outer and inner envelope membranes of cyanelles from a glaucocystophyte, Cyanophora paradoxa

Envelope membranes were isolated by sucrose density gradient floatation centrifugation from the homogenate of cyanelles prepared from Cyanophora paradoxa. Two yellow bands were separated after 40 h of centrifugation. The buoyant density of one of the two fractions (fraction Y2) coincided with that of inner envelope membranes of spinach or plasma membranes of cyanobacteria. The other yellow fraction (fraction Y1) migrated to top of sucrose-gradient even at 0% sucrose. Pigment analysis revealed that the heavy yellow fraction was rich in zeaxanthin while the light fraction was rich in β-carotene, and the both fractions contained practically no chlorophylls. Another yellow fraction (fraction Y3) was isolated from the phycobiliprotein fraction, which was the position where the sample was placed for gradient centrifugation. Its buoyant density and absorption spectra were similar to outer membranes of cyanobacteria. We have assigned fractions Y2 and Y3 as inner and outer envelope membrane fractions of cyanelles, respectively. Protein compositions were rather different between the two envelope membranes indicating little cross-contamination among the fractions. H. Koike and Y. Ikeda contributed equally.     

Activation of calcium-sensing receptor accelerates apoptosis in hyperplastic parathyroid cells

Calcimimetic compounds inhibit not only parathyroid hormone (PTH) synthesis and secretion, but also parathyroid cell proliferation. The aim of this investigation is to examine the effect of the calcimimetic compound NPS R-568 (R-568) on parathyroid cell death in uremic rats. Hyperplastic parathyroid glands were obtained from uremic rats (subtotal nephrectomy and high-phosphorus diet), and incubated in the media only or the media which contained high concentration of R-568 (10(-4)M), or 10% cyclodextrin, for 6h. R-568 treatment significantly suppressed medium PTH concentration compared with that of the other two groups. R-568 treatment not only increased the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay-positive cells, but also induced the morphologic changes of cell death determined by light or electron microscopy. These results suggest that CaR activation by R-568 accelerates parathyroid cell death, probably through an apoptotic mechanism in uremic rats in vitro.     

Endogenous expression of angiogenesis-related factors in response to muscle injury

Gene therapy has developed a new strategy to treat a variety of ischemic diseases using angiogenic growth factors. However, the endogenous expression pattern of angiogenesis-related factors in response to muscle injury is not fully characterized. In the present study, we investigated the expression of angiogenesis-related factors, vascular endothelial growth factor, angiopoietin-1, -2, monocyte chemoattractant protein-1, and their receptors during muscle regeneration. Mice underwent freeze injury, and then the gastrocnemius muscles were isolated 1, 3, 5, 7, 10, 14, and 28 days after surgery. Generally, changes in gene expression were most dramatic during the early stage of muscle regeneration, and were attenuated as angiogenesis progressively developed and then returned to steady-state levels. VEGF mRNA began to increase from day 3 and peaked at day 5 after muscle injury. VEGF receptors, Flt-1, KDR/Flk-1, and neuropilin-1 mRNAs were increased from 3- to 9-fold at day 3 after muscle injury. At the same time, angiopoietin-1 and angiopoietin-2 mRNA were increased by 3- and 15-fold respectively, concomitantly with an increase in their receptors and Tie-2 mRNA. Finally, MCP-1 and CC-chemokine receptor 2 mRNAs were sharply up-regulated by 1600- and 100-fold, respectively, at day 3 after muscle injury. These results suggest that the molecular events implicated in angiogenesis occur at an early stage of muscle regeneration.     

Emission of characteristic fluorescence from the ligand-cytosine complex in U_A/ACU bulged RNA duplex

Here we show that N,N-bis(3-aminopropyl)-2,7-diamino-1,8-naphthyridine (DANP) binds to the single cytosine bulge in RNA duplexes. When the base pairs flanking the C-bulge were A-U base pairs, a characteristic fluorescence was emitted from the DANP-C-bulge complex. The fluorescence would be useful for detecting the C-bulge in RNA secondary structures.