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91.
Kubota T Tokuno K Nakagawa J Kitamura Y Ogawa H Suzuki Y Suzuki K Oka K 《Biochemical and biophysical research communications》2003,303(1):332-336
Mg(2+) buffering mechanisms in PC12 cells were demonstrated with particular focus on the role of the Na(+)/Mg(2+) transporter by using a newly developed Mg(2+) indicator, KMG-20, and also a Na(+) indicator, Sodium Green. Carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP), a protonophore, induced a transient increase in the intracellular Mg(2+) concentration ([Mg(2+)](i)). The rate of decrease of [Mg(2+)](i) was slower in a Na(+)-free extracellular medium, suggesting the coupling of Na(+) influx and Mg(2+) efflux. Na(+) influxes were different for normal and imipramine- (a putative inhibitor of the Na(+)/Mg(2+) transporter) containing solutions. FCCP induced a rapid increase in [Na(+)](i) in the normal solution, while the increase was gradual in the imipramine-containing solution. The rate of decrease of [Mg(2+)](i) in the imipramine-containing solution was also slower than that in the normal solution. From these results, we show that the main buffering mechanism for excess Mg(2+) depends on the Na(+)/Mg(2+) transporter in PC12 cells. 相似文献
92.
Westerlund U Moe MC Varghese M Berg-Johnsen J Ohlsson M Langmoen IA Svensson M 《Experimental cell research》2003,289(2):378-383
Recent research communications indicate that the adult human brain contains undifferentiated, multipotent precursors or neural stem cells. It is not known, however, whether these cells can develop into fully functional neurons. We cultured cells from the adult human ventricular wall as neurospheres and passed them at the individual cell level to secondary neurospheres. Following dissociation and plating, the cells developed the antigen profile of the three main cell types in the brain (GFAP, astrocytes; O2, oligodendrocytes; and beta-III-tubulin/NeuN, neurons). More importantly, the cells developed the electrophysiological profiles of neurons and glia. Over a period of 3 weeks, neuron-like cells went through the same phases as neurons do during development in vivo, including up-regulation of inward Na+ -currents, drop in input resistance, shortening of the action potential, and hyperpolarization of the cell membrane. The cells developed overshooting action potentials with a mature configuration. Recordings in voltage-clamp mode displayed both the fast inactivating TTX-sensitive sodium current (INa) underlying the rising phase of the action potential and the two potassium currents terminating the action potential in mature neurons (IA and IK, sensitive to 4-AP and TEA, respectively). We have thus demonstrated that the human ventricular wall contains multipotent cells that can differentiate into functionally mature neurons. 相似文献
93.
A comparative study on effect of dietary selenium and vitamin E on some antioxidant enzyme activities of liver and brain tissues 总被引:5,自引:0,他引:5
Since selenium and vitamin E have been increasingly recognized as an essential element in biology and medicine, current research
activities in the field of human medicine and nutrition are devoted to the possibilities of using these antioxidants for the
prevention or treatment of many diseases. The present study was aimed at investigating and comparing the effects of dietary
antioxidants on glutathione reductase and glutathione peroxidase activities as well as free and protein-bound sulfhydryl contents
of rat liver and brain tissues. For 12–14 wk, both sex of weanling rats were fed a standardized selenium-deficient and vitamin
E-deficient diet, a selenium-excess diet, or a control diet. It is observed that glutathione reductase and glutathione peroxidase
activities of both tissues of the rats fed with a selenium-deficient or excess diet were significantly lower than the values
of the control group. It is also shown that free and bound sulfhydryl concentrations of these tissues of both experimental
groups were significantly lower than the control group. The percentage of glutathione reductase and glutathione peroxidase
activities of the deficient group with respect to the control were 50% and 47% in liver and 66% and 61% in the brain, respectively;
while these values in excess group were 51% and 69% in liver and 55% and 80% in brain, respectively. Free sulfhydryl contents
of the tissues in both experimental groups showed a parallel decrease. Furthermore, the decrease in protein-bound sulfhydryl
values of brain tissues were more pronounced than the values found for liver. It seems that not only liver but also the brain
is an important target organ to the alteration in antioxidant system through either a deficiency of both selenium and vitamin
E or an excess of selenium alone in the diet. 相似文献
94.
Selenium is known to play an important role in the physiology of many different cell types and extracellular application of
selenite causes cellular dysfunction in many different types of tissues. In a previous study, we have shown that in rat ventricles,
sodium selenite (≥1 mM) caused an increase in the resting tension and a decrease in contractile force, in a time-dependent manner. In the present
study, we have shown that sodium selenite caused a contracture state both in Langendorff perfused hearts and isolated papillary
muscles. We also showed that the application of extracellular ATP (0.1 mM) markedly reduced this detrimental effect of sodium selenite on ventricular contraction in Langendorff perfused hearts and
delayed it in isolated papillary muscle preparations. In contrast, isoproterenol (0.1 μM) did not seem to influence this action of sodium selenite in papillary muscle preparations. Possible reasons for this protective
effect of ATP to selenite-induced contracture are also discussed. 相似文献
95.
Effect of epidermal growth factor on intestinal adaptation after allogeneic small bowel transplantation in rats 总被引:1,自引:0,他引:1
We reported that epidermal growth factor (EGF) stimulated graft adaptation in a rat model of syngeneic small bowel transplantation. However, graft rejection is a severe problem with clinical small bowel transplantation, because small intestinal wall contains large amounts of lymphoid tissue. Studies were performed to investigate the effect of EGF on allogeneic graft adaptation after small bowel transplantation in rats treated with an immunosuppressant FK506. The transplanted animals received intraperitoneally EGF or saline (untreated) after surgery and were examined for analysis one week later. EGF-treated group markedly enhanced the water absorption and induction of sodium glucose cotransporter (SGLTI) as compared with EGF-untreated group. EGF-treated group also increased the mucosal crypt depth and its cell proliferating rate, although there was no significant difference in the mucosal villus height between the two groups. These results indicate that EGF accelerates intestinal allograft adaptation in part by the recovery of mucosal structure and function after small bowel transplantation in rats. EGF may have relevance to promote graft function in clinical small intestinal transplantation. 相似文献
96.
Pederzoli A Gambarelli A Gabbay S Rozman A Katz U 《Biology of the cell / under the auspices of the European Cell Biology Organization》2002,94(3):187-196
Morphological, cytological and transport properties of the integument of Salamandra salamandra were investigated during natural ontogenetic development, from birth to adult. Three stages were operationally defined: I, larvae, from birth to metamorphosis; II, metamorphosis (judged externally by the colour change and loss of the gills); and III, post-metamorphosis to adult. Pieces of skin were fixed at various stages for immunocytochemical examinations, and the electrical properties were investigated on parallel pieces. Distinct cellular changes take place in the skin during metamorphosis, and lectin (PNA, WGA and ConA) binding indicates profound changes in glycoprotein composition of cell membranes, following metamorphosis. Band 3 and carbonic anhydrase I (CA I) were confined to mitochondria-rich (MR)-like cells, and were detected only in the larval stage. CA II on the other hand, was detected both in MR-like and in MR cells following metamorphosis. The electrical studies show that the skin becomes more tight (transepithelial resistance increases) upon metamorphosis, followed by manifestation of amiloride-sensitive short-circuit current (I(SC)) indicating that functional Na+ uptake has been acquired. The skin of metamorphosed adults had no finite transepithelial Cl- conductance, and band 3 was not detected in its MR cells. The functional properties of MR-like and MR cells remain to be established. 相似文献
97.
Berry S 《Journal of molecular evolution》2002,54(5):595-613
All organisms rely on chemiosmotic membrane systems for energy transduction; the great variety of participating proteins
and pathways can be reduced to a few universal principles of operation. This chemical basis of bioenergetics is reviewed with
respect to the origin and early evolution of life. For several of the cofactors which play important roles in bioenergetic
reactions, plausible prebiotic sources have been proposed, and it seems likely that these cofactors were present before elaborate
protein structures. In particular, the hydrophobic quinones require only a membrane-enclosed compartment to yield a minimum
chemiosmotic system, since they can couple electron transport and proton translocation in a simple way. It is argued that
the central features of modern bioenergetics, such as the coupling of redox reactions and ion translocation at the cytoplasmic
membrane, probably are ancient features which arose early during the process of biogenesis. The notion of a thermophile root
of the universal phylogenetic tree has been discussed controversially, nevertheless, thermophiles are interesting model organisms
for reconstructing the origin of chemiosmotic systems, since they are often acidophiles and anaerobic respirers exploiting
iron–sulfur chemistry. This perspective can help to explain the prominent role of iron–sulfur proteins in extant biochemistry
as well as the origin of both respiration and proton extrusion within the context of a possible origin of life in the vicinity
of hot vents.
Received: 6 June 2001 / Accepted: 16 October 2001 相似文献
98.
Maejima H Kinoshita E Yuki T Yakehiro M Seyama I Yamaoka K 《Biochemical and biophysical research communications》2002,295(2):452-457
We located a novel binding site for grayanotoxin on the cytoplasmic linkers of voltage-dependent cardiac (rH1) or skeletal-muscle (mu 1) Na(+) channel isoforms (segments S4-S5 in domains D1 and D4), using the alanine scanning substitution method. GTX-modification of Na(+) channels, transiently expressed in HEK 293 cells, was evaluated under whole-cell voltage clamp, from the ratio of maximum chord conductance for modified and unmodified Na(+) channels. In mu 1, mutations K237A, L243A, S246A, K248A, K249A, L250A, S251A, or T1463A, caused a moderate, but statistically significant decrease in this ratio. On making corresponding mutations in rH1, only L244A dramatically reduced the ratio. Because in mu 1, the serine at position 251 is the only heterologous residue with respect to rH1 (Ala-252), we made a double mutant L243A&S251A to match the sequence of mu 1 and rH1 in S4-S5 linkers of both domains. This double mutation resulted in a significant decrease in the ratio, to the same extent as L244A substitution in rH1 did, indicating that the site at Leu-244 in rH1 or at Leu-243 in mu 1 is a novel one, exhibiting a synergistic effect of grayanotoxin. 相似文献
99.
Streptococcus pyogenes grown in the presence of subinhibitory concentrations of sodium fluoride had a diminished ability, compared to control cells, to adhere to buccal cells, collagen, fibronectin, and laminin. In addition, sodium fluoride was a competitive inhibitor of streptococcal adhesion to collagen and fibronectin, but not laminin. It is suggested that sodium fluoride may be useful in therapy or prophylaxis in infections involving group A streptococci. 相似文献
100.
Reactive oxygen species from mitochondria mediate SW480 cells apoptosis induced by Na2SeO3 总被引:3,自引:0,他引:3
A number of selenium compounds have been found to inhibit tumorigenesis in a variety of animal and cell models. In order to
explore the molecular mechanism involved in the anticarcinogenesis activity of selenium, we examined the effects of sodium
selenite on cell viabilty, generation of reactive oxygen species (ROS), and mitochondrial transmembrane potential (Δω
m
) in human colonic carcinoma cells SW480. The result from MTT test showed that sodium selenite reduced cell viability. Morophologic
and flow cytometric results indicated that Na2SeO3 induced the apoptosis of SW480 cells. Na2SeO3 increased the generation of intracellular ROS, whereas BAPTA-AM, rotenone, and NaCN completely inhibited the increase of
ROS induced by Na2SeO3. Na2SeO3 also caused the disruption of Δω
m
. The intracellular ROS increase and apoptosis induced by Na2SeO3 were significantly decreased by superoxide dismutase (SOD), catalase. These data suggest that the ROS mediate apoptosis induced
by Na2SeO3 and mitochondria may be a major source of Na2SeO3-induced ROS. 相似文献