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231.
The leaf of the NADP-malic enzyme type C(4) grass, Arundinella hirta, has not only mesophyll cells (MCs) and bundle sheath cells (BSCs, usual Kranz cells) but also another type of Kranz cells (distinctive cells; DCs) that are not associated with vascular bundles. We investigated photosynthetic enzyme accumulation along the base-to-tip maturation gradient of developing leaves by immunogold electron microscopy. In mature leaves, phosphoenolpyruvate carboxylase (PEPC) and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) were detected in the MC cytosol and in the BSC and DC chloroplasts, respectively. Pyruvate, P(i) dikinase (PPDK) was present in the chloroplasts of all photosynthetic cells but with higher levels in the MCs. Rubisco was first detected in the basal region of emerging leaf blades where the BSCs and DCs became discernable. Subsequently, the accumulation of PEPC and PPDK was initiated in the region where the granal proliferation in the chloroplasts was conspicuous; and, suberized lamellae were formed in the cell walls of the Kranz cells. There was no difference in the patterns of cellular development and enzyme accumulation between the BSCs and DCs or between the MCs adjacent to each type of Kranz cells. These results demonstrate that, although the DCs are not associated with veins, they behaved like BSCs with respect to enzyme induction and cellular differentiation. 相似文献
232.
Kashiwakura I Inanami O Takahashi K Takahashi TA Kuwabara M Takagi Y 《Radiation research》2003,160(2):210-216
In previous studies we characterized the radiosensitivity of CFU-megakaryocytes from human placental and umbilical cord blood and the effects of various early-acting cytokines. We found that the maximal clonal growth of CFU-megakaryocytes in vitro and maximal protection against X-ray damage were supported by a combination of thrombopoietin and stem cell factor. However, the mechanism by which the two cytokines exert a synergistic effect remained unclear, so we extended these studies to investigate the radioprotective action of synergistic thrombopoietin and stem cell factor on the survival of X-irradiated CD34(+) CFU-megakaryocytes. A combination of thrombopoietin and stem cell factor led to activation of mitogen-activated protein kinase and extracellular signal-regulated protein kinase and to suppression of caspase 3 in X-irradiated CD34(+) cells. When PD98059 and various synthetic substrates-specific inhibitors of these proteins-were used, the combination had less effect on the clonal growth of X-irradiated CD34(+) CFU-megakaryocytes. However, the addition of wortmannin, a specific inhibitor of the phosphatidylinositol-3 kinase pathway, did not alter the synergistic action of thrombopoietin plus stem cell factor. We suggest that part of this synergistic effect can be explained by activation of mitogen-activated protein kinase and extracellular signal-regulated protein kinase and by suppression of the caspase cascade. 相似文献
233.
234.
Dietary Zn deficiency does not influence systemic blood pressure and vascular nitric oxide signaling in normotensive rats 总被引:1,自引:1,他引:0
Sato M Kurihara N Moridaira K Sakamoto H Tamura J Wada O Yanagisawa H 《Biological trace element research》2003,91(2):157-171
Because zinc (Zn) is an important component for cell protection against certain oxygen species, it has been suggested that
Zn deficiency impairs the potent oxidant defense capacity, which is constitutively provided in the vascular system. However,
the influence of dietary Zn deficiency on systemic blood pressure and vascular system is controversial and unclear. We therefore
examine the effect of dietary Zn deficiency on systemic blood pressure, a potent superoxide scavenger, aortic Cu/Zn superoxide
dismutase (SOD) activity, a most representative synthase of the endothelium-derived relaxing factor, and aortic endothelial
nitric oxide synthase (eNOS) expression. Furthermore, the direct effects of intravenous administration of NOS inhibitor, N
ω-nitro-l-arginine methyl ester (l-NAME), and a SOD mimetic compound, tempol, in normotensives were tested in Wistar-Kyoto (WKY) rats. A Zn-deficient diet (4
wk) contributed to growth retardation, the decrease in thymus weight, and the lower levels of serum Zn compared with the standard
diet group. However, no significant difference in conscious systolic and diastolic blood pressure was found in the Zn-deficiency
group. The administration of l-NAME caused an increase in the mean arterial pressure (MAP) levels in the two groups of rats and the involvement of the vasodilator
nitric oxide (NO) in the regulation of systemic BP in the normotensive state. On the other hand, administration of the superoxide
scavenger, tempol, led to a decrease in MAP levels in the two groups of rats, indicating the participation of the oxygen free
radical, superoxide, in the maintenance of the systemic BP in a normotensive state. There were no significant differences
between the Zn-deficient diet group and the standard diet group in the normotensive state. eNOS expression and Cu/Zn SOD activity
in the aorta were also intact in Zn-deficient normotensive rats. These findings suggest that the 4 wk of Zn deficiency was
inadequate to alter systemic blood pressure and focal NO signaling in the normotensive state. Long-term Zn deficiency affects
the neuronal, immune, and hematopoietic systems, which contribute to systemic and/or local circulation. However, Zn deficiency
alone does not cause hypertension and local vascular dysfunction in the normotensive state. 相似文献
235.
The dissociation of noncovalently associated protein-protein complexes in human plasma was examined by comparing two-dimensional gel electrophoresis (2-DE) patterns obtained in two different electrophoretic conditions. A type I 2-DE pattern was obtained running nondenaturing isoelectric focusing (IEF) followed by nondenaturing gel electrophoresis and a type II 2-DE pattern was nondenaturing IEF followed by sodium dodecyl sulfate gel electrophoresis. Micro-sized gels (internal diameter(id) 1.3 x 35 mm polyacrylamide IEF gels and 38 x 38 x 1 mm polyacryamide slab gels) were used to follow the dissociation processes of major plasma proteins. Larger gel sizes (id 3.4 x 160 mm agarose IEF gels and 160 x 120 x 2.8 mm polyacrylamide slab gels) were used to detect minor plasma proteins dissociated from major proteins. About 110 spots, which have not been detected on type I (nondenaturing) 2-D gels, newly appeared on type II large-sized 2-D gels at molecular masses smaller than 67 kDa. Some of these spots had been analyzed and identified, but about 70 minor spots (isoelectric point 5.5-7.5 and relative molecular mass 8-45 kDa) were detected for the first time by applying large volumes of human plasma samples to the large type II 2-D gels. These minor spots could be concentrated on type II 2-D gels by enriching the immunoglobulin G (IgG) fraction under nondenaturing conditions, and they disappeared when IgG was removed from the fraction. These results strongly suggest that many of the minor spots newly detected were bound to IgG in physiological conditions. 相似文献
236.
Chiba T Li YH Yamane T Ogikubo O Fukuoka M Arai R Takahashi S Ohtsuka T Ohkubo I Matsui N 《Peptides》2003,24(5):773-778
In order to find the most effective antagonist for dipeptidyl peptidase III degrading enkephalin, we synthesized hemorphin-like pentapeptides with aliphatic or aromatic amino acids at the N-termini, such as VVYPW, LVYPW, IVYPW, YVYPW, FVYPW and WVYPW. Among those pentapeptides, IVYPW and WVYPW showed the strongest inhibitory activity toward rDPP III. The K(i) values of IVYPW and WVYPW were 0.100+/-0.011 and 0.126+/-0.015 microM (mean+/-S.E.), respectively. The order of K(i) values was Ile> or =Trp>Phe> or =Tyr>Leu>Ala>Val>Ser>Gly. rDPP III activity is inhibited in a non-competitive manner by these peptides. The peptide VYPW did not inhibit rDPP III activity, but the sequence is essential for the expression of inhibitory activity. 相似文献
237.
Yamamoto S Nakanishi O Matsui T Shinohara N Kinoshita H Lambert C Ishikawa T 《Cellular and molecular neurobiology》2003,23(2):175-185
The analgesia effects of intrathecal adenosine A1 receptor agonist, R-PIA, on the hyperalgesia and CSF-glutamate release after formalin injection into the rat paw were evaluated. R-PIA significantly and dose-dependently attenuated increases in flinching behavior, and this attenuating effect was reversed by the adenosine A1 receptor antagonist, aminophylline. Morphine blocked flinchs, however MK-801 partially abolished. The increase in CSF-glutamate release evoked by formalin stimulation was inhibited by morphine but not by either R-PIA or MK-801. These findings suggest that the intrathecal adenosine A1 receptor agonist provokes analgesic effect via the postsynaptic action independent of an effect upon spinal glutamate release. 相似文献
238.
Ueda A Nagase S Yokoyama H Tada M Noda H Ohya H Kamada H Hirayama A Koyama A 《Molecular and cellular biochemistry》2003,244(1-2):119-124
Spin probing methods using an electron spin resonance (ESR) spectrometer are used extensively and bring us a lot of information about in vivo redox mechanisms. However, the in vivo reducing mechanisms of exogenous nitroxide radicals, which serve as typical spin probing reagents are not clear. To clarify this, we examined the sequential kinetics of a spin probe, 4-hydroxy 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL) in the in vivo organs, tissue homogenates and subcellular fractions of kidney and liver using an in vivo and X-band ESR spectrometers. As a parameter of reducing activity, we calculated the half-life of TEMPOL from the decay curve of ESR signal intensity. The half-life of TEMPOL in the whole organs and homogenates of the kidney was significantly shorter than that of the liver, this indicates that the kidney has more reducing activity against TEMPOL as compared to the liver. Subcellular fractional studies revealed that this reducing activity of the kidney mainly exists in the mitochondria. Contrarily, in addition to reduction in the mitochondria, TEMPOL in the liver was reduced by the microsome and cytosol. 相似文献
239.
An asymmetric carbon-carbon bond-forming reaction at the 2-position of a piperidine skeleton was exploited. This method consisted of a reaction between 1-(4-methoxybenzoyl)-3,4-didehydro-2-methoxypiperidines and dimethyl malonate catalyzed by Cu(II)-chiral 2,2'-isopropylidenebis(4-phenyl-2-oxazoline) to afford a 2-substituted piperidine skeleton with moderate enantioselectivity. 相似文献
240.
Inagaki K Aki T Shiota T Kawamoto S Shigeta S Suzuki O Ono K 《Bioscience, biotechnology, and biochemistry》2003,67(2):451-454
The expression of delta6 fatty acid desaturase, previously identified, was suppressed almost completely by hyper expression of the corresponding antisense gene in a transformant of the rat hepatic cell line BRL-3A. Conversion rates of [1-14C] linoleic acid, alpha-linolenic acid, and tetracosapentaenoic acid into the respective delta6 fatty acids were equivalent to those in control cells. This finding suggested that all of these reactions were catalyzed by at least two delta6 desaturase isozymes in rat hepatocytes. 相似文献