Regulation of Levels of Proline as an Osmolyte in Plants under Water Stress

Compatible osmolytes are potent osmoprotectants that play arole in counteracting the effects of osmotic stress. Proline(Pro) is one of the most common compatible osmolytes in water-stressedplants. The accumulation of Pro in dehydrated plants is causedboth by activation of the biosynthesis of Pro and by inactivationof the degradation of Pro. In plants, L-Pro is synthesized fromL-glutamic acid (l-G1u) via     

Cytomorphogenesis in cenocytic green algae. V. Segregative cell division and cortical microtubules in Dictyosphaeria cavernosa (Siphonocladales,Chlorophyceae)*

Disassembly and reassembly of cortical microtubules (MT) during and after segregative cell division (SCO) in Dictyosphaeria cavernosa (Forssk.) Børgesen were observed using fluorescence microscopy. Parallel cortical MT in a mother cell were intact just after the initiation of SCD, but soon circular, MT-free patches appeared. Protoplasmic contraction enlarged the patches, and in these areas, the protoplasm eventually became perforated. Long and undulating cortical MT were arranged densely in the reticulate protoplasm. During further protoplasmic contraction, cortical MT appeared to be random and decreased in density. Finally, short and random cortical MT were present in the segregated protoplasts. Parallel cortical MT reassembled in the expanding daughter cells. After the daughter cells came in contact with one another, a radial system of cortical MT was constructed at the side that faced the inside of the mother cell wall. A microtubule inhibitor (amiprophos methyl, APM) had no effect on SCO. Segregative cell division was not induced directly by mechanical wounding. A comparison between SCO and wound-induced protoplasmic contraction was made.     

Characterization of the gene for Δ1-pyrroline-5-carboxylate synthetase and correlation between the expression of the gene and salt tolerance in Oryza sativa L.

A cDNA for ¹-pyrroline-5-carboxylate (P5C) synthetase (cOsP5CS), an enzyme involved in the biosynthesis of proline, was isolated and characterized from a cDNA library prepared from 14-day-old seedlings of Oryza sativa cv. Akibare. The deduced amino acid sequence of the P5CS protein (OsP5CS) from O. sativa exhibited 74.2% and 75.5% homology to that of the P5CS from Arabidopsis thaliana and Vigna aconitifolia, respectively. Northern blot analysis revealed that the gene for P5CS (OsP5CS) was induced by high salt, dehydration, treatment of ABA and cold treatment, while it was not induced by heat treatment. Simultaneously, accumulation of proline was observed as a result of high salt treatment in O. sativa. Moreover, the levels of expression of OsP5CS mRNA and content of proline under salt stress condition were compared between a salt-tolerant cultivar, Dee-gee-woo-gen (DGWG) and a salt-sensitive breeding line, IR28. It was observed that the expression of the P5CS gene and the accumulation of proline in DGWG steadily increased, whereas those in IR28 increased slightly.     

A comparison of the genotoxicity of ethylnitrosourea and ethyl methanesulfonate in lacZ transgenic mice (Muta™Mouse)

We compared the induction of gene mutations and chromosomal aberrations by ethylating agents in lacZ transgenic mice (Muta™Mouse). Chromosomal aberrations were detected by the peripheral blood micronucleus assay. Gene mutations were detected in the lacZ transgene. A small amount of blood was sampled from a tail vessel during the expression time for fixation of gene mutations in vivo; this enabled us to detect and compare clastogenicity and gene mutations in the identical mouse. Single intraperitoneal injections of ENU (50–200 mg/kg) and EMS (100–400 mg/kg) strongly induced micronucleated reticulocytes (MN) detectable in peripheral blood 48 h after treatment. The maximum MN frequencies induced were 6.6% and 3.3% for ENU (100 mg/kg) and EMS (400 mg/kg), respectively (the control value was 0.3%). lacZ mutant frequency (MF) was analyzed in bone marrow and liver 7 days after treatment. Spontaneous MFs were 2.0–4.6x10⁻⁶. MF in bone marrow was increased by ENU to 3.4x10⁻⁵ at 200 mg/kg and induced by EMS to 1.8x10⁻⁵ at 400 mg/kg. In liver, however, both chemicals at their highest doses induced only slight increases in MF. The induction of both micronuclei and lacZ mutations in bone marrow by both ENU and EMS correlated better with O⁶-ethylguanine adducts than with N7-ethylguanine adducts. The mutants (19 for ENU and 12 for EMS) were subjected to DNA sequence analysis. Among EMS-induced mutations, 75% were GC to AT transitions, which were probably caused by O⁶-ethylguanine. Among ENU-induced mutations, in contrast, 40% occurred as AT base pair substitutions (6 AT to TA transversions and 2 AT to GC transitions) (no such mutations were induced by EMS). These results, together with the known reactivity of ENU to thymine suggest that thymine adducts play a significant role in the ENU mutagenesis.     

Efficient method for the quantitation of urinary leukotriene E4: extraction using an Empore C18 disk cartridge

We describe here an efficient procedure for the precise quantitation of leukotriene E₄ (LTE₄) in a small volume of urine, which was achieved mainly by the use of an Empore extraction disk cartridge. After addition of [³H]LTE₄ to 2 ml of urine, an Empore C₁₈ cartridge was used for initial extraction of the urine, which resulted in the extraction of LTE₄ in a small volume of solvent. The eluate could then be injected onto a high-performance liquid chromatography column without further concentration. After separation by high-performance liquid chromatography, LTE₄ was extracted from the effluent using an Empore C₁₈ cartridge. The concentration of LTE₄ was subsequently quantified by enzyme immunoassay. LTE₄ can be recovered from urine with sufficient efficiency (69.9±4.7%, mean±S.D., n = 101). The coefficient of variation of the assay procedure was less than 10%. When urine was spiked with different amounts of LTE₄, the recovery of LTE₄ added to the urine specimen was less than 120%. The concentration of LTE₄ in urine from normal healthy subjects was 48.0±15.3 pg/mg creatinine (n = 15).     

Biosynthesis of a blood group H1 antigen by α1,2-fucosyltransferase in PC12 cells

We have examined the expression of GDP-fucose: glycosphingolipid fucosyltransferase activity in PC12 cells and PC12 sublines in relation to the neuronal differentiation induced by nerve growth factor (NGF) or dexamethasone. Transfer of fucose to paragloboside (nLc₄Cer) yielded a product which was determined to be a blood group H₁ antigen (Fuc1-2Gal1-4GlcNAc1-3Gal1-4Glc-Cer) by gas chromatography/mass spectrometry analysis and enzymatic hydrolysis, suggesting that PC12 cells have an 1,2-fucosyltransferase. Lactosylceramide was also fucosylated at a reduced rate. When the differentiation of PC12 cells and PC12 subline cells, PC12D and MR31, was induced by exposure to either NGF or dexamethasone, the fucosyltransferase activity for nLc₄Cer was found to decrease in both cell lines, suggesting the association with cell differentiation. This is the first report of the presence of an 1,2-fucosyltransferase in cultured neuronal cell lines which catalyses thein vitro biosynthesis from nLc₄Cer of a type-2 chain glycosphingolipid having the blood group H₁ determinant. The disaccharides, -lactose andN-acetyllactosamine, were also fucosylated by PC12 cell enzyme, although the specificity for the carbohydrate structure was different from that for glycosphingolipids.Abbreviations Glc d-glucose - Gal d-galactose - GlcNAc N-acetyl-d-glucosamine - Fuc l-fucose - Cer ceramide - nLc₄Cer neolactotetraosylceramide (paragloboside) - GDP guanosine diphosphate - CDP cytidine diphosphate - CTP cytidine triphosphate - NGF nerve growth factor - DX dexamethasone - GC/MS gas chromatography/mass spectrometry     

Seroepidemiological Survey of Lymphocytic Choriomeningitis Virus in Wild House Mice in China with Particular Reference to Their Subspecies

Serum samples from 337 wild house mice (Mus musculus) from 35 sites in China, collected in 1992 and 1993, were examined for antibodies against lymphocytic choriomeningitis virus (LCMV). Ten samples from eight sites were found to contain such antibodies. Six of the eight positive sites were located in the territory of M. m. gansuensis. One of the other two sites was located in the territory of M. m. castaneus in southern China and the other site was in a habitat of M. m. castaneus which had invaded into the western end of the territory of M. m. homourus. It seems likely that LCMV is distributed in the territories of M. m. gansuensis and M. m. castaneus in China. This is the first report of detection of these antibodies in wild house mice in China and specifically in the territories of M. m. gansuensis and M. m. castaneus.     

Human orosomucoid polymorphism: molecular basis of the three common ORM1 alleles, ORM1*F1, ORM1*F2, and ORM1*S

The human orosomucoid (ORM) is controlled by two closely linked loci, ORM1 and ORM2, and two tandem genes, AGP1 and AGP2, encoding the proteins produced by the two loci, have been cloned. In this study the molecular basis of ORM1 polymorphism was investigated. For the detection of mutations the products of the six exons of each gene, amplified by the polymerase chain reaction (PCR), were screened by single-strand conformation polymorphism analysis. Subsequently, the exons with an altered migration pattern were gene-specifically amplified by nested PCR. Sequencing of the gene-specific PCR products showed that the three common ORM1 alleles result from A→G transitions at the codons for amino acid positions 20 in exon 1 and 156 in exon 5 of the AGP1 gene: ORM1*F1 was characterized by CAG (Gln) and GTG (Val), ORM1*F2, by CAG (Gln) and ATG (Met), and ORM1*S, by CGG (Arg) and GTG (Val). The phylogenesis of the genes encoding these three ORM1 alleles is discussed. Received: 5 September 1996