Effect of Osmotic Stress on Turgor Pressure in Mung Bean Root Cells

Turgor pressure in cells of the elongating region of intactmung bean roots was directly measured by using the pressure-probetechnique. After the external osmotic pressure had been increasedfrom 0 MPa to 0.5 MPa, turgor pressure rapidly decreased byabout 0.5 MPa from 0.65 MPa to 0.14 MPa and root elongationstopped. Subsequent turgor regulation was clearly confirmed,which followed the osmotic adjustment to maintain a constantdifference in the osmotic pressure between root-cell sap andthe external medium ( II). It took at least 6 h for turgor pressureto recover to an adjusted constant level of about 0.5 MPa dueto turgor regulation, but rootelongation resumed within onlyan hour after the osmotic treatment. Therefore, the resumptionof root elongation under osmotic stress could not have beendirectly connected with turgor regulation. Furthermore, sincethe amounts of decrease in turgor pressure just after applicationsof various degrees of osmotic stress could be interpreted inrelation to those in II, hydraulic conductivity between theinside and the outside of root cells must be large enough toattain water potential equilibrium rapidly in response to osmoticstress. We conclude that turgor pressure in the cells of theelongating region of mung bean roots is determined mainly by II because of water potential equilibrium. (Received January 27, 1987; Accepted May 21, 1987)     

Cloning and sequence analysis of adrenodoxin reductase cDNA from bovine adrenal cortex

cDNA clones for bovine adrenodoxin reductase were isolated, and the primary structure of the enzyme precursor was deduced from their nucleotide sequences. The precursor consists of 492 amino acids including an extrapeptide of 32 amino acids at the amino terminus. The extrapeptide is hydrophilic [corrected] and rich in arginine. The amino terminal sequence of the precursor is homologous with that of the adrenodoxin precursor. A possible FAD- or NADPH-binding site is present near the amino terminus of the mature enzyme.     

Effects of calcium-antagonists and calmodulin inhibitors on DNA synthesis in cultured rat vascular smooth muscle cells

To investigate the role of intracellular Ca2+ in the mechanism of cellular proliferation of vascular smooth muscle cells (VSMC), the effects of Ca2+-antagonists and calmodulin (CaM) inhibitors on DNA synthesis stimulated by serum-derived growth factors were studied in cultured VSMCs derived from rat aorta. DNA synthesis assessed by incorporation of [3H]thymidine into the cells was significantly stimulated by epidermal growth factor (EGF), platelet-derived growth factor (PDGF) or fetal bovine serum (FBS), of which the effects were dose-dependently inhibited by a variety of Ca2+-antagonists, such as verapamil, diltiazem and nicardipine. Trifluoperazine and W-7, both specific CaM inhibitors, similarly inhibited DNA synthesis stimulated by EGF, PDGF or FBS in a dose-dependent manner, whereas W-5, a less specific CaM inhibitor, was minimally effective. These data suggest that the Ca2+-CaM system plays an important role in the mechanism of growth factor-induced DNA synthesis in VSMCs.     

Cloning of a Vero toxin (VT2) gene from a VT2-converting phage isolated from Escherichia coli 0157: H7

Abstract A Vero toxin (VT2 or Shiga-like toxin II)-converting phage was isolated from Escherichia coli 0157: H7 strain J-2. Nontoxigenic E. coli C600 produced VT2 when lysogenized with the toxin-converting phage. Eco RI fragments of the phage DNA were ligated with Eco RI-digested pBR322 or pUC118 and were transformed into E. coli MC1061 or MV1184. Transformants exhibiting VT2 production commonly contained a 4.6 kb Eco RI fragment. It was found that a 2.3 kb Kpn I- Sph I fragment coded VT2 production and that this fragment hybridized weakly with the 2.1 kb fragment encoding VT1.     

Polymorphism of T-cell receptor genes among laboratory and wild mice: Diverse origins of laboratory mice

Southern blots of genomic DNA from 23 strains of laboratory mice and 19 individual wild mice were examined for restriction fragment length polymorphisms in their loci encoding the T-cell receptors (Tcr): the constant regions of the α, β, and γ chains (C _α,C _β, andC _γ) and a variable region family of the β chain (V _β8). Only a few polymorphisms were observed for each locus in the laboratory mice after using three restriction enzymes,Bam HI,Eco RI, andHind III. All the laboratory mice examined fall into one of two types for theC _α,C _β andV _β8 loci and one of three types for theC _γ. These types are found in some of the wild mice studied, indicating that they were already present in the founder mice of laboratory mouse strains. In contrast, theTcr genes are highly polymorphic among wild mice. Analysis of the polymorphisms in these loci suggests that laboratory mice have inherited their genes not only fromMus musculus domesticus, but also from other subspecies, and much more than previously believed from Asian subspecies.     

Detection of point mutation in the tyrosinase gene of a Japanese albino patient by a direct sequencing of amplified DNA

Summary Enzymatic DNA amplification and direct DNA sequencing were used to detect a mutation in the tyrosinase gene of an albino patient. Single-base change could be detected by direct sequencing. This base change (G to A) is thought to result in an amino acid change (Arg to Gln) in tyrosinase of the patient.     

Regional distribution of DNA and RNA in rat brain: A sensitive determination using high-performance liquid chromatography with electrochemical detection

DNA and RNA contents in 20 brain regions or nuclei of the rat were determined by a highly sensitive method using high-performance liquid chromatography with electrochemical detection. The high DNA and RNA contents were found in the hypothalamic nuclei, especially the median eminence-arcuate nucleus. These results may be available for the preparation of nucleic acids as the regional control.     

Identification of a novel alpha-amylase by expression of a newly cloned human amy3 cDNA in yeast

A novel amylase gene (amy3) that differs in nucleotide sequence from salivary amylase gene (amy1) and pancreatic amylase gene (amy2) has been described [Tomita et al., Gene 76 (1989) 11-18], but whether this gene can ever code for an active enzyme has not been shown. We prepared cDNA of this gene from an mRNA obtained from lung carcinoid tissue, and expressed it in Saccharomyces cerevisiae under the control of an acid phosphatase promoter. The product was secreted into culture media, and showed enzymatic activity, demonstrating that this novel alpha-amylase gene (amy3) can code for a functional isozyme. We purified this enzyme, and compared its biological properties with those of salivary and pancreatic human amylases similarly expressed in yeast. We observed that the novel amylase isozyme is more heat-sensitive than others, and that its substrate specificity is different from the other two isozymes.     

Structure of cDNA clones for the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase from a fern (Asplenium cataractarum rosenstock,aspleniaceae), and its comparison with those of various seed plants

We isolated the small subunit of ribulose-1, 5-bisphosphate carboxylase/oxygenase (RuBisCO SSu) from a fern,Asplenium cataractarum and determined its 34 N-terminal amino acid sequence. We obtained a cDNA clone that contains the entire coding region of the SSu from the same fern species, using synthetic oligonucleotide probes derived from the above amino acid sequence. It contains a 525 bp open reading frame capable of coding for a polypeptide with 174 amino acids, 31 bp 5′-and 206 bp 3′-noncoding regions. It was also elucidated that the precursor to the SSu contains a transit peptide of 53 amino acid residues and a mature protein of 121 residues. We compared the deduced amino acid sequence of the fern SSu with those of 11 other vascular plant species (including gymnosperms, monocots and dicots). As low as 55% homology was observed between those of a fern and seed plants. Constancy of the amino acid substitution rate in RuBisCO SSu was supported by our relative rate test. Amino acid substitution rate per year per site for RuBisCO SSu was calculated to be 0.81×10⁻⁹ assuming that the separation between pteridophytes and seed plants arose 380 million years ago.