Untersuchungen über die Temperaturabhängigkeit der Kohlensäure-Assimilation bei Bohnen

Ohne ZusammenfassungMit 2 Textabbildungen.     

Combination treatment of angiotensin II type I receptor blocker and new oral iron chelator attenuates progression of nonalcoholic steatohepatitis in rats

Angiotensin II type I receptor blocker and iron chelator reportedly exert suppressive effects on nonalcoholic steatohepatitis (NASH) progression, including liver fibrosis and hepatocarcinogenesis. The aim of this study was to elucidate the combined effect of losartan (LOS), an angiotensin II type I receptor blocker, and deferasirox (DSX), a newly developed oral iron chelator, on the progression of NASH in rats. To induce NASH, F344 rats were fed a choline-deficient l-amino acid-defined diet for 12 wk, and the effects of LOS and DSX at clinically comparable low doses were elucidated in conjunction with oxidative stress, neovascularization, and hepatic stellate cells (HSC) activation, all known to play important roles in the progression of NASH. Treatment with both LOS and DSX suppressed choline-deficient L-amino acid-defined diet-induced liver fibrosis development and hepatocarcinogenesis. This combination treatment exerted a stronger inhibitory effect compared with treatment with a single agent. These inhibitory effects occurred almost concurrently with the suppression of oxidative stress, neovascularization, and HSC activation. Our in vitro study demonstrated that LOS and DSX inhibited angiotensin II-induced proliferation, transforming growth factor-β(1) expression of activated HSC, and in vitro angiogenesis. These results indicated that dual inhibition by combined treatment of LOS and DSX attenuated the progression of NASH. Since both agents are widely used in clinical practice, this combination therapy may represent a potential new strategy against NASH in the near future.     

Studies on Sugar-isomerizing Enzyme Purification,Crystallization and Some Properties of Glucose Isomerase from Streptomyces sp.

Glucose isomerase was purified by means of acetone fractionation, DEAE-cellulose column chromatography, DEAE-Sephadex column chromatography and crystallization. The purified enzyme appeared to be homogeneous on ultracentrifugation and electrophoresis. The sedimentation coefficient, s_20,w, the diffusion coefficient, D_20,w, and partial specific volume of the enzyme were 8.0S, 4 × 10^?7cm²/sec and 0.69 ml/g, respectively. The molecular weight of the enzyme was estimated to be 157,000 from the sedimentation and diffusion measurements. The crystalline glucose isomerase contained cobalt and magnesium ions. The properties of the enzyme were also studied.     

Role of the second-largest subunit of DNA polymerase alpha in the interaction between the catalytic subunit and hyperphosphorylated retinoblastoma protein in late S phase

DNA polymerase alpha (pol-alpha) is a heterotetrameric enzyme (p180-p68-p58-p48 in mouse) that is essential for the initiation of chain elongation during DNA replication. The catalytic (p180) and p68 subunits of pol-alpha are phosphorylated by Cdk-cyclin complexes, with p68 being hyperphosphorylated by cyclin-dependent kinases in G(2) phase of the cell cycle. The activity of Cdk2-cyclin A increases during late S phase and peaks in G(2) phase. We have now examined the role of p68 in the interaction between the catalytic subunit of pol-alpha and hyperphosphorylated retinoblastoma protein (ppRb) and in the stimulation of the polymerase activity of pol-alpha by ppRb. With the use of recombinant proteins, we found that nonphosphorylated p68 inhibited the stimulation of pol-alpha activity by ppRb, suggesting that p68 might impede the association of ppRb with p180. Phosphorylation of p68 by Cdk2-cyclin A greatly reduced its inhibitory effect. Immunofluorescence analysis also revealed that ppRb localized at sites of DNA replication specifically in late S phase. These results suggest that Cdk-cyclin A can phosphorylate pol-alpha which may result in a conformational change in pol-alpha facilitating its interaction with and activation by ppRb.     

Haploid plant regeneration via embryogenesis from anther cultures of Hepatica nobilis

An anther culture technique for the production of haploid plants was developed in Hepatica nobilis. Embryos with bipolar meristem regions were induced from microspores within the cultured anthers. Embryo formation was promoted by first culturing anthers on NN medium (Nitsch and Nitsch, 1969) supplemented with 1% activated charcoal (AC) at 5 or 35°C for a few days and by then incubating them in the dark at 25°C. Pre-culturing anthers at 35°C for 4days (thermal-shock treatment) led to the best embryo formation (45 embryos/Petri dish with 30 anthers). Plant regeneration was achieved by culturing the anther-derived embryos on NN medium without AC at 15°C. Flow cytometric analysis of anther-derived embryos and chromosome counts in regenerated plants showed that they were haploid plants.     

Temporal relationship between cytosolic free Ca(2+) and membrane potential during hypotonic turgor regulation in a brackish water Charophyte Lamprothamnium succinctum

Internodal cells of a brackish water charophyte, Lamprothamnium succinctum, regulate turgor pressure in response to changes in external osmotic pressure by modifying vacuolar concentrations of KCl. An increase in cytosolic concentration of free Ca(2+) ([Ca(2+)](c)) is necessary for the progress of turgor regulation induced by hypotonic treatment. Initial changes in membrane potential and [Ca(2+)](c) upon hypotonic treatment were measured to examine the temporal relationship between the two parameters. Fura-dextran (potassium salt, M(r) 10,000, anionic) that had been injected into the cytosol was used to measure [Ca(2+)](c). Membrane potential and membrane conductance under a current-clamp condition were also measured. Decrease in external osmotic pressure by 0.16 Osm induced a simultaneous increase in [Ca(2+)](c) with both depolarization of the membrane and increase in the membrane conductance. Decrease in external osmotic pressure by 0.05 Osm induced a simultaneous increase in [Ca(2+)](c) with membrane depolarization but the increase in membrane conductance started later than the other two processes. There was a close temporal relationship between the increase in [Ca(2+)](c) and membrane depolarization on the initial response of turgor regulation induced by hypotonic treatment.     

Blue light inactivates plasma membrane H(+)-ATPase in pulvinar motor cells of Phaseolus vulgaris L

Unilateral blue light irradiation induces bending of pulvini of Phaseolus vulgaris towards the source of light. The pulvinar bending is caused by a decrease in turgor pressure of motor cells that are irradiated with blue light. Decrease in the turgor pressure is caused by the net efflux of K(+) and counter anions, accompanying membrane depolarization. In the present study the effect of blue light on the activity of plasma membrane H(+)-ATPase was studied in relation to the membrane depolarization. The activity of the plasma membrane H(+)-ATPase was measured using protoplast suspensions prepared from laminar pulvini from primary leaves. A pulse of blue light under continuous red light irradiation induced both a transient increase in the external pH and transient inhibition of the vanadate-sensitive ATPase. Continuous blue light irradiation under continuous red light irradiation induced both a sustained increase in the external pH and sustained inhibition of the vanadate-sensitive ATPase. These results show that blue light inhibits the activity of the plasma membrane H(+)-ATPase. Inactivation of the plasma membrane H(+)-ATPase supports the membrane depolarization induced by the blue light irradiation.     

Reduction in the extent of atherosclerosis in apolipoprotein E-deficient mice induced by electroporation-mediated transfer of the human plasma platelet-activating factor acetylhydrolase gene into skeletal muscle

The effect of increasing the activity of plasma platelet-activating factor (PAF) acetylhydrolase (AH) (PAF-AH) on the progression of atherosclerosis in apolipoprotein E-deficient (apoE(-/-)) mice was examined by gene delivery to skeletal muscle. The expression vector pcDNA3.1 containing either human PAF-AH cDNA (pcDNA/PAF-AH) or green fluorescent protein cDNA (pcDNA/GFP) was introduced into the skeletal muscle of both hind legs of 6-week-old apoE(-/-) mice by electroporation. The activity of PAH-AH in plasma was significantly increased 4-16 weeks after electroporation of apoE(-/-) mice with 120 microg of pcDNA/PAF-AH; the maximal (2.5-fold) increase was apparent after 8 weeks. The mean thickness of the aortic wall, determined by 160 measurements in each mouse, was significantly reduced in apoE(-/-) mice 8-16 weeks after exposure to pcDNA/PAF-AH compared with that in corresponding control animals that received pcDNA/GFP. These results suggest that the electrotransfer of the plasma PAF-AH gene to skeletal muscle reduces the extent of atherosclerosis in apoE(-/-) mice.     

Effects of a Pulse of Blue Light on the Extracellular pH in the Pulvinus of Phaseolus vulgaris L.: Measurements with a Double-Barreled pH-Sensitive Electrode

Effects of a pulse of blue light on the extracellular pH inthe pulvinus of Phaseolus vulgaris L. were studied with double-barreledpH-sensitive microelectrodes. A blue-light pulse (30 s) inducedtransient alkalization, sometimes with initial acidification.This result is consistent with the hypothesis that blue lightinactivates the plasmalemma H⁺-ATPase. (Received January 17, 1995; Accepted May 29, 1995)     

Turgor Regulation in a Brackish Charophyte, Lamprothamnium succinctum I. Artificial Modification of Intracellular Osmotic Pressure

Internodal cells of Lamprothamnium succinctum cultured in freshwater and brackish water of different salinities maintainedalmost the same turgor pressure at steady state. When the turgorpressure was increased by decreasing the external osmolality,the cells recovered their original turgor pressure within 2h. However, the recovery from decreased turgor pressure required1 day. When salts of the external medium were replaced with sorbitol,the cells still regulated the turgor pressure, indicating thatthe essential factor for the turgor regulation is not the salinitybut the osmolality. Internodal cells with osmotic pressure andion concentrations artificially modified to higher or lowervalues also regained the original turgor pressure by changingtheir intracellular osmotic pressure, whether the cells werecultured in brackish water or fresh water. These results indicate that turgor regulation is intrinsic toLamprothamnium and is initiated by a deviation of turgor pressurefrom the reference value, which is about 0.35 Osm. (Received November 28, 1983; Accepted March 14, 1984)