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1.
Hypertrophic effect of selective beta(1)-adrenoceptor stimulation on ventricular cardiomyocytes from adult rat 总被引:3,自引:0,他引:3
Schäfer M Frischkopf K Taimor G Piper HM Schlüter KD 《American journal of physiology. Cell physiology》2000,279(2):C495-C503
Weinvestigated whether selective 1-adrenoceptorstimulation causes hypertrophic growth on isolated ventricularcardiomyocytes from adult rat. As parameters for the induction ofhypertrophic growth, the increases of [14C]phenylalanineincorporation, protein and RNA mass, and cell size weredetermined. Isoproterenol (Iso, 10 µM) alone had no growtheffect. In the presence of the 2-adrenoceptor antagonist ICI-118551 (ICI, 10 µM), Iso caused an increase in[14C]phenylalanine incorporation, protein and RNA mass,cell volume, and cross-sectional area. We showed for phenylalanineincorporation that the growth effect of Iso+ICI could be antagonized by1-adrenoceptor blockade with atenolol (10 µM) ormetoprolol (10 µM), indicating that it was caused by selective1-adrenoceptor stimulation. The growth response toIso+ICI was accompanied by an increase in ornithine decarboxylase (ODC)activity and expression. Inhibition of ODC by the ODC antagonistdifluoromethylornithine (1 mM) attenuated this hypertrophic response,indicating that ODC induction is causally involved. The growth responseto Iso+ICI was found to be cAMP independent but was sensitive togenistein (100 µM) or rapamycin (0.1 µM). The reaction was enhancedin the presence of pertussis toxin (10 µM). We conclude thatselective 1-adrenoceptor stimulation causes hypertrophicgrowth of ventricular cardiomyocytes by a mechanism that is independentof cAMP but dependent on a tyrosine kinase and ODC. 相似文献
2.
Identification of P2Y purinoceptors associated with voltage-activated cation channels in cardiac ventricular myocytes of the rat 总被引:5,自引:0,他引:5
Extracellular ATP has vasodilatory and inotropic effects in the heart. We have demonstrated that extracellular ATP, in a concentration-dependent manner (10 nM-0.1 mM), increased [Ca2+]i in suspensions of isolated fura-2-loaded rat cardiac ventricular myocytes (maximum 96 +/- 10% increase over basal levels, SEM, n = 12, P less than 0.01). The increase in [Ca2+]i was often biphasic, with an initial fast phase (less than 1 s) of low amplitude, followed by a slower phase of higher amplitude. A second application of ATP had little effect, and ATP abolished the effect of subsequent electrical stimulations, even through the cells were still able to respond with an increase in [Ca2+]i to KCl-induced depolarization or stimulation by caffeine. Pretreatment of cells with nifedipine, verapamil, caffeine, ryanodine, or 8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride attenuated the effect of extracellular ATP on [Ca2+]i, and binding of extracellular free calcium by excess EGTA completely abolished the effects of extracellular ATP and electrical stimulation. Extracellular ATP increased bisoxonol fluorescence in ventricular myocytes, indicating depolarization of the sarcolemma. Pretreatment of the myocytes with tetrodotoxin (50 microM), or replacement of NaCl in the incubation buffer with the impermeant cation N-methyl-D-glucamine, suppressed the extracellular ATP effect on [Ca2+]i. ADP and AMP had smaller effects on [Ca2+]i than ATP; adenosine had no effect. ATP analogues showed the following rank order of potency in increasing [Ca2+]i or bisoxonol fluorescence: ATP greater than or equal to 2-methylthioATP much greater than adenosine 5'-O-[3-thio]triphosphate greater than adenosine 5'-[alpha, beta-methylene]triphosphate approximately adenosine 5'-[beta, gamma-methylene]triphosphate approximately adenosine 5'-[beta, gamma-imino]triphosphate greater than adenosine. These data are consistent with the presence of purinoceptors (P2Y subtype) on the sarcolemma of cardiac ventricular myocytes of the rat, which upon activation lead to depolarization and activation of cation channels of the sarcolemma and flux of extracellular Ca2+ into the cells. This may result in further flux of Ca2+ into the cytosol from intracellular stores. The effects of extracellular ATP on [Ca2+]i in rat cardiac ventricular myocytes may, in part, explain the direct inotropic effects of extracellular ATP on the mammalian heart. 相似文献
3.
4.
Effects of zinc ex vivo and intracellular zinc chelator in vivo on taurine uptake in goldfish retina
Taurine and zinc exert neurotrophic effects. Zinc modulates Na+/Cl−-dependent transporters. This study examined the effect of zinc (ZnSO4) ex vivo and zinc chelator N,N,N′,N′-tetrakis-(2-pyridylmethyl) ethylenediamine (TPEN) in vivo on [3H]taurine transport in goldfish retina. The effect of TPEN in vivo on taurine and zinc levels was determined. Isolated cells
were incubated in Ringer with zinc (0.1–100 μM). Taurine transport was done with taurine (0.001–1 mM) and 50 nM [3H]taurine. Zinc (100 μM) noncompetitively inhibited taurine transport. TPEN was administered intraocularly and retinas extracted
3, 5 and 10 days later. Taurine was determined by HPLC (nmol/mg protein) and zinc by spectrophotometry ICP (mg/mg protein).
Taurine and zinc levels decreased at 3 days and increased at 10 days after TPEN administration. At 10 days after intraocular
TPEN, taurine transport affinity increased (K
s = 0.018 ± 0.006 vs. 0.028 ± 0.008 mM). Apparently, zinc deficiency affects the taurine–zinc complex and taurine availability.
The increased taurine uptake affinity by TPEN was possibly associated with a response to maximize retinal taurine content
at low zinc concentration. 相似文献
5.
《The Journal of general physiology》1993,102(3):575-597
Acidosis increases resting cytosolic [Ca2+], (Cai) of myocardial preparations; however, neither the Ca2+ sources for the increase in Cai nor the effect of acidosis on mitochondrial free [Ca2+], (Cam) have been characterized. In this study cytosolic pH (pHi) was monitored in adult rat left ventricular myocytes loaded with the acetoxymethyl ester (AM form) of SNARF-1. A stable decrease in the pHi of 0.52 +/- 0.05 U (n = 16) was obtained by switching from a bicarbonate buffer equilibrated with 5% CO2 to a buffer equilibrated with 20% CO2. Electrical stimulation at either 0.5 or 1.5 Hz had no effect on pHi in 5% CO2, nor did it affect the magnitude of pHi decrease in response to hypercarbic acidosis. Cai was measured in myocytes loaded with indo- 1/free acid and Cam was monitored in cells loaded with indo-1/AM after quenching cytosolic indo-1 fluorescence with MnCl2. In quiescent intact myocytes bathed in 1.5 mM [Ca2+], hypercarbia increased Cai from 130 +/- 5 to 221 +/- 13 nM. However, when acidosis was effected in electrically stimulated myocytes, diastolic Cai increased more than resting Cai in quiescent myocytes, and during pacing at 1.5 Hz diastolic Cai was higher (285 +/- 17 nM) than at 0.5 Hz (245 +/- 18 nM; P < 0.05). The magnitude of Cai increase in quiescent myocytes was not affected either by sarcoplasmic reticulum (SR) Ca2+ depletion with ryanodine or by SR Ca2+ depletion and concomitant superfusion with a Ca(2+)-free buffer. In unstimulated intact myocytes hypercarbia increased Cam from 95 +/- 12 to 147 +/- 19 nM and this response was not modified either by ryanodine and a Ca(2+)-free buffer or by 50 microM ruthenium red in order to block the mitochondrial uniporter. In mitochondrial suspensions loaded either with BCECF/AM or indo-1/AM, acidosis produced by lactic acid addition decreased both intra- and extramitochondrial pH and increased Cam. Studies of mitochondrial suspensions bathed in indo- 1/free acid-containing solution showed an increase in extramitochondrial Ca2+ after the addition of lactic acid. Thus, in quiescent myocytes, cytoplasmic and intramitochondrial buffers, rather than transsarcolemmal Ca2+ influx or SR Ca2+ release, are the likely Ca2+ sources for the increase in Cai and Cam, respectively; additionally, Ca2+ efflux from the mitochondria may contribute to the raise in Cai. In contrast, in response to acidosis, diastolic Cai in electrically stimulated myocytes increases more than resting Cai in quiescent cells; this suggests that during pacing, net cell Ca2+ gain contributes to enhance diastolic Cai. 相似文献
6.
A gene (arf) encoding an α-l-arabinofuranosidase (ARF) that hydrolyzes arabinose substituted on xylan was isolated from Penicillium sp. The gene was predicted to encode 339 amino acid residues showing 71–75% homology to GH family 54. E. coli expressed ARF showed optimal activity at 50°C and pH 5–6 on wheat arabinoxylan. The hydrolysis activities on oat spelt xylan
by ARF and xylanase were 1.67-fold higher than that of xylanase alone. The synergistic effects of ARF and commercial enzymes
(xylanase and cellulase) on popping-pretreated rice straw were 1.15–1.51-fold higher amounts of sugars released in the [ARF + xylanase + cellulase]
mixture than in the mixtures [ARF + xylanase], [ARF + cellulase], and [xylanase + cellulase]. Moreover, the liberation of
arabinose by ARF was enhanced 2.1–2.9-fold in a reaction with xylanase and cellulase as compared with [xylanase + cellulase]
and ARF alone. 相似文献
7.
To investigate the importance of the overall size of the total adenine nucleotide pool for the regulation of primary metabolism
in growing potato tubers, freshly cut discs were provided with zero or 2 mM adenine in the presence of 1 or 100 mM [U-14C]glucose or 100 mM [U-14C]sucrose in the presence and absence of 20 mM orthophosphate (Pi). Adenine led to a 150–250% increase of the total adenine
nucleotide pool, which included an increase of ADP, a larger increase of ATP and an increase of the ATP:ADP ratio. There was
a 50–100% increase of ADP-glucose (ADPGlc), and starch synthesis was stimulated. Respiratory oxygen uptake was stimulated,
and the levels of glycerate-3-phosphate, phosphoenolpyruvate and α-ketoglutarate decreased. The response to adenine was not
modified by Pi. It is proposed that increased ATP stimulates ADPGlc pyrophosphorylase, leading to a higher rate of starch
synthesis. The impact on starch synthesis is constrained, however, because increased ADP can lead to a stimulation of respiration
and decline of glycerate-3-phosphate, which will inhibit ADPGlc pyrophosphorylase. The quantitative impact depends on the
conditions. In the presence of 1 mM glucose, the levels of phosphorylated intermediates and the rate of starch synthesis were
low. Adenine led to a relatively large stimulation of respiration, but only a small stimulation of starch synthesis. In the
presence of 100 mM glucose, discs contained high levels of phosphorylated intermediates, low ATP:ADP ratios (<3) and low rates
of starch synthesis (<20% of the metabolised glucose). Adenine led to marked increase of ATP and 2- to 4-fold stimulation
of starch synthesis. Discs incubated with 100 mM sucrose already had high ATP:ADP ratios (>8) and high rates of starch synthesis
(>50% of the metabolised sucrose). Adenine led to a further increase, but the stimulation was less marked than in high glucose.
These results have implications for the function of nucleotide cofactors in segregating sucrose mobilisation and respiration,
and the need for energy conservation during sugar-starch conversions.
Received: 9 February 2000 / Accepted: 9 June 2000 相似文献
8.
Yoval-Sánchez B Jasso-Chávez R Lira-Silva E Moreno-Sánchez R Rodríguez-Zavala JS 《Journal of bioenergetics and biomembranes》2011,43(5):519-530
Ethanol is one of the most efficient carbon sources for Euglena gracilis. Thus, an in-depth investigation of the distribution of ethanol metabolizing enzymes in this organism was conducted. Cellular
fractionation indicated localization of the ethanol metabolizing enzymes in both cytosol and mitochondria. Isolated mitochondria
were able to generate a transmembrane electrical gradient (Δψ) after the addition of ethanol. However, upon the addition of
acetaldehyde no Δψ was formed. Furthermore, acetaldehyde collapsed Δψ generated by ethanol or malate but not by D-lactate.
Pyrazole, a specific inhibitor of alcohol dehydrogenase (ADH), abolished the effect of acetaldehyde on Δψ, suggesting that
the mitochondrial ADH, by actively consuming NADH to reduce acetaldehyde to ethanol, was able to collapse Δψ. When mitochondria
were fractionated, 27% and 60% of ADH and aldehyde dehydrogenase (ALDH) activities were found in the inner membrane fraction.
ADH activity showed two kinetic components, suggesting the presence of two isozymes in the membrane fraction, while ALDH kinetics
was monotonic. The ADH Km values were 0.64–6.5 mM for ethanol, and 0.16–0.88 mM for NAD+, while the ALDH Km values were 1.7–5.3 μM for acetaldehyde and 33–47 μM for NAD+. These novel enzymes were also able to use aliphatic substrates of different chain length and could be involved in the metabolism
of fatty alcohol and aldehydes released from wax esters stored by this microorganism. 相似文献
9.
Birkedal R Shiels HA 《American journal of physiology. Regulatory, integrative and comparative physiology》2007,293(2):R861-R866
Intracellular Na(+)-concentration, [Na(+)](i) modulates excitation-contraction coupling of cardiac myocytes via the Na(+)/Ca(2+) exchanger (NCX). In cardiomyocytes from rainbow trout (Oncorhyncus mykiss), whole cell patch-clamp studies have shown that Ca(2+) influx via reverse-mode NCX contributes significantly to contraction when [Na(+)](i) is 16 mM but not 10 mM. However, physiological [Na(+)](i) has never been measured. We recorded [Na(+)](i) using the fluorescent indicator sodium-binding benzofuran isophthalate in freshly isolated atrial and ventricular myocytes from rainbow trout. We examined [Na(+)](i) at rest and during increases in contraction frequency across three temperatures that span those trout experience in nature (7, 14, and 21 degrees C). Surprisingly, we found that [Na(+)](i) was not different between atrial and ventricular cells. Furthermore, acute temperature changes did not affect [Na(+)](i) in resting cells. Thus, we report a resting in vivo [Na(+)](i) of 13.4 mM for rainbow trout cardiomyocytes. [Na(+)](i) increased from rest with increases in contraction frequency by 3.2, 4.7, and 6.5% at 0.2, 0.5, and 0.8 Hz, respectively. This corresponds to an increase of 0.4, 0.6, and 0.9 mM at 0.2, 0.5, and 0.8 Hz, respectively. Acute temperature change did not significantly affect the contraction-induced increase in [Na(+)](i). Our results provide the first measurement of [Na(+)](i) in rainbow trout cardiomyocytes. This surprisingly high [Na(+)](i) is likely to result in physiologically significant Ca(2+) influx via reverse-mode NCX during excitation-contraction coupling. We calculate that this Ca(2+)-source will decrease with the action potential duration as temperature and contraction frequency increases. 相似文献
10.
Pacing rate, halothane, and BDM affect fura 2reporting of [Ca2+]i in intact rat trabeculae 总被引:1,自引:0,他引:1
Experiments weredone on intact trabeculae from rats. Fura 2 in the salt form wasmicroinjected directly into the myoplasm. The experiments wereconducted at 30°C, with 2 mM extracellular Ca2+ concentrationand pacing at either 0.5 or 5 Hz. The aims were to establish a newmethod for in vivo calibration of fura 2 and to determine the effect ofautofluorescence changes on intracellular Ca2+ concentration([Ca2+]i)reported by fura 2. Autofluorescence was recorded under optimal conditions for fura 2 fluorescence (emission at 510 nm). By alteration of the oxidation-reduction state, it was shown that NADH is the maincomponent of autofluorescence in heart. An increase in pacing frequencycaused a decrease in autofluorescence. Both halothane and2,3-butanedione monoxime (BDM) at 5-Hz pacing produced a substantial rise in autofluorescence, approaching the levels observed at 0.5-Hz pacing. The values for the dissociation constant (678 nM) and maximumfluorescence ratio of fura 2 forCa2+ for the in vivo calibrationare 3.4 times larger and 2.6 times smaller, respectively, than thosefound in vitro. Using the parameters obtained in vivo, we found thatthe diastolic and systolic[Ca2+]iof a twitch at 30°C were 0.2 and 2.4 µM, respectively. Proper correction of the autofluorescence change unmasks the[Ca2+]ielevation caused by 5-Hz pacing. It was concluded that autofluorescence is not constant and that interventions affecting autofluorescence needcorrection if fura 2 is used to report[Ca2+]i. 相似文献
11.
Alexander E. Egger Christian G. Hartinger Anna K. Renfrew Paul J. Dyson 《Journal of biological inorganic chemistry》2010,15(6):919-927
Abstract
The anticancer ruthenium–arene compound [Ru(η6-C6H5CF3)(pta)Cl2] (where pta is 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane), termed RAPTA-CF3, with the electron-withdrawing α,α,α-trifluorotoluene ligand, is one of the most cytotoxic RAPTA compounds known. To rationalize the high observed cytotoxicity, the hydrolysis of RAPTA-CF3 in water and brine (100 mM sodium chloride) and its reactions with the protein ubiquitin and a double-stranded oligonucleotide (5′-GTATTGGCACGTA-3′) were studied using NMR spectroscopy, high-resolution Fourier transform ion cyclotron resonance mass spectrometry, and gel electrophoresis. The aquation of the ruthenium–chlorido complex was accompanied by a loss of the arene ligand, independent of the chloride concentration, which is a special property of the compound not observed for other ruthenium–arene complexes with relatively stable ruthenium–arene bonds. Accordingly, the mass spectra of the biomolecule reaction mixtures contained mostly [Ru(pta)]–biomolecule adducts, whereas [Ru(pta)(arene)] adducts typical of other RAPTA compounds were not observed in the protein or DNA binding studies. Gel electrophoresis experiments revealed a significant degree of decomposition of the oligonucleotide, which was more pronounced in the case of RAPTA-CF3 compared with RAPTA-C. Consequently, facile arene loss appears to be responsible for the increased cytotoxicity of RAPTA-CF3. 相似文献12.
V V Kupriyanov V L Lakomkin O V Korchazhkina V A Stepanov V I Steinschneider AYaKapelko 《Biochimica et biophysica acta》1991,1058(3):386-399
In order to investigate the potential role of cytosolic phosphates ([ATP], [ADP] and [Pi]) in the integration of mitochondrial respiration and mechanical function in the perfused heart, inhibition of the substrate end of the respiratory chain by amytal has been employed. A stepwise increase in amytal concentration (from 0.2 to 1.2 mM) resulted in the progressive abolition of the cardiac oxygen consumption, rate (VO2) in hearts oxidizing pyruvate (5 mM). The inhibition curve for VO2 was S-shaped, with K0.5 = 1.1 mM, and independent of the initial VO2 values varied by coronary flow and isoproterenol (Iso) addition. ADP-stimulated respiration of isolated mitochondria (malate + pyruvate) was twice as sensitive to amytal inhibition, whereas state 2 respiration (before ADP addition) had the same sensitivity as cardiac VO2. Decrease in VO2 was followed by a decline in phosphocreatine (PCr) content and augmentation of Pi at nearly constant ATP level and intracellular pH as assessed by the 31P-NMR method. These changes were associated with an elevation of cytosolic free [ADP] and a reduction of the [ATP]/[ADP] ratio and ATP affinity calculated from creatine kinase equilibrium. Concomitantly, pressure-rate product (PRP), maximal rates of contraction and relaxation fell down and the end diastolic pressure (EDP) rose at all initial loads. Amytal-inhibited hearts retained the capability to respond to Iso stimulation (0.1 microM, about 50% enhancement of PRP) even at 1 mM amytal, but their response to elevation of coronary flow was greatly diminished. Alterations in the PRP value induced by the inhibitor at a fixed coronary flow correlated negatively with cytosolic [ADP] and [Pi], and positively with [ATP]/[ADP] and A(ATP). In contrast, EDP correlated with all these parameters in the opposite manner. However, when PRP was varied by coronary flow in the absence of the inhibitor or at its fixed concentrations, such correlations were absent. These data imply that cytosolic phosphates can serve as a feedback between energy production and utilization when the control point(s) is (are) at the mitochondria. In contrast, other regulatory mechanisms should be involved when control is distributed among different steps located both in energy producing and utilizing systems. 相似文献
13.
Oxygen and temperature dependence of stimulated insulin secretion in isolated rat islets of Langerhans 总被引:3,自引:0,他引:3
M Ohta D Nelson J Nelson M D Meglasson M Erecińska 《The Journal of biological chemistry》1990,265(29):17525-17532
The effects of lowered O2 tension on insulin secretion and changes in cellular energy parameters were investigated in isolated rat pancreatic islets perifused with buffers equilibrated with 21, 9, 5, and 1% oxygen and containing 5 mM glucose. Decreasing the external [O2] reduced the amount of insulin released in response to 16 mM glucose, 20 mM alpha-ketoisocaproic acid, and 40 mM KCl. Secretion elicited by high glucose or KCl had declined significantly at 9% oxygen, whereas that caused by alpha-ketoisocaproic acid became inhibited below 5% O2. Lowering the oxygen tension also decreased the ability of islets to respond with a rise in [ATP]/[ADP] upon stimulation with metabolic secretagogues. This reduction in the evoked increase in the nucleotide ratios paralleled the inhibition of stimulated insulin secretion. Addition of 2 mM amytal markedly decreased the islet energy level and eliminated the secretory response to 16 mM glucose. The results suggest that enhancement of B-cell energy production and a consequent rise in [ATP] (or [ATP]/[ADP]) are a necessary event for the hormone release elicited by high glucose and alpha-ketoisocaproic acid. A decrease in temperature inhibited insulin secretion with all three secretagogues tested. The energies of activation were similar for high glucose and KCl-induced secretion, about 20 kcal/mol, but were higher for alpha-ketoisocaproic acid, about 35 kcal/mol. At 28 degrees C, the [ATP]/[ADP] was larger than that at 38 degrees C (8 versus 5) and was not increased further upon addition of 16 mM glucose. It is suggested that a decrease in the rate of energy production at lowered temperatures may contribute to the inhibition of insulin release caused by metabolic secretagogues. 相似文献
14.
Warren Gordon L. III; Williams Jay H.; Ward Christopher W.; Matoba Hideki; Ingalls Christopher P.; Hermann Karl M.; Armstrong R. B. 《Journal of applied physiology》1996,81(6):2555-2564
Warren III, Gordon L., Jay H. Williams, Christopher W. Ward,Hideki Matoba, Christopher P. Ingalls, Karl M. Hermann, and R. B. Armstrong. Decreased contraction economy in mouse EDL muscleinjured by eccentric contractions. J. Appl.Physiol. 81(6): 2555-2564, 1996.The objective ofthis study was to find out whether basal and/or active energymetabolism are altered in isolated mouse extensor digitorum longusmuscle injured by eccentric (Ecc) contractions. Measurements of basalO2 consumption and isometric tetanus O2 recovery cost were madeat 25°C on muscles that had done either 10 Ecc, 10 isometric (Iso),or no contractions (No). In parallel experiments, rates of lactate andpyruvate production were measured to estimate the anaerobiccontribution. Basal O2 consumptionwas unaffected by the type of protocol performed(P = 0.07). However, the tetanusO2 cost per force-time integral was elevated by 30-36% for the Ecc protocol muscles over that forthe Iso and No protocol muscles. When including the increased lactateproduction by the Ecc protocol muscles, the total energetic cost perforce-time integral was 53% higher than that for the Iso protocolmuscles [2.35 ± 0.17 vs. 1.54 ± 0.18 µmolO2/(N · m · s)].The decreased economy was attributed to two factors. First, in skinnedfibers isolated from the injured muscles, the ratio of maximalactomyosin adenosinetriphosphatase activity to force production was upby 37.5%, suggesting uncoupling of ATP hydrolysis from forceproduction. Second, increased reliance on anaerobic metabolism alongwith the fluorescent microscopic study of mitochondrial membranepotential and histochemical study of ATP synthase suggested anuncoupling of oxidative phosphorylation in the injured muscles. 相似文献
15.
Palmer Bradley M.; Thayer Anne M.; Snyder Steven M.; Moore Russell L. 《Journal of applied physiology》1998,85(6):2159-2168
The effects of run endurance training and fura 2 loading on the contractile function andCa2+ regulation of rat leftventricular myocytes were examined. In myocytes not loaded with fura 2, the maximal extent of myocyte shortening was reduced with trainingunder our pacing conditions [0.5 Hz at 2.0 and 0.75 mM externalCa2+ concentration([Ca2+]o)], although training had noeffect on the temporal characteristics. The "light" loading ofmyocytes with fura 2 markedly suppressed (~50%) maximal shorteningin the sedentary and trained groups, although the temporalcharacteristics of myocyte shortening were significantly prolonged inthe trained group. No discernible differences in the dynamiccharacteristics of the intracellularCa2+ concentration([Ca2+]) transientwere detected at 2.0 mM[Ca2+]o, althoughpeak [Ca2+] and rateof [Ca2+] rise duringcaffeine contracture were greater in the trained state at 0.75 mM[Ca2+]o. We concludethat training induced a diminished myocyte contractile function underthe conditions studied here and a more effective coupling of inwardCa2+ current to sarcoplasmicreticulum Ca2+ release at low[Ca2+]o,and that fura 2 and its loading vehicle DMSO significantly alter theintrinsic characteristics of myocyte contractile function andCa2+ regulation. 相似文献
16.
We report the ATP-mediated activation of sucrose-phosphate synthase in bundle sheath cells prepared from C4 species. Sucrose synthesis was followed by measuring the incorporation of [14C]fructose 6-phosphate into sucrose in bundle sheath cells also provided with uridine 5′-diphosphoglucose (UDPGlc). Studies
with Panicum miliaceum L. cells showed that activation was largely due to an increase in the affinity for UDPGlc and was therefore only evident
at limiting UDPGlc concentrations. The apparent K
m UDPGlc for sucrose synthesis by cells pretreated and assayed with ATP was about 0.7 mM compared with 7–8 mM for control cells
without ATP. The γ-thio derivative of ATP had a similar effect to ATP. The effect was also evident when ATP was rapidly removed
from cells prior to assay. Sucrose-phosphate synthase activity in extracts from cells pretreated with or without ATP showed
similar differences in K
m UDPGlc. These observations support the view that ATP is inducing a covalent modification of the enzyme. However, several
protein kinase inhibitors did not prevent activation. Changes of more than threefold were observed for the K
m UDPGlc with sucrose-phosphate synthase extracted from bundle sheath cells rapidly isolated from attached leaves that were
subjected to dark/light treatments. The possible relationship between these changes and those induced by ATP with isolated
cells is discussed.
Received: 22 October 1996 / Accepted: 7 January 1997 相似文献
17.
Vincourt V Escriou V Largeau C Bessodes M Scherman D Chaumeil JC Dumortier G 《Cell biology and toxicology》2011,27(5):363-370
Energetic failure which occurs in both ischemia/reperfusion and acute drug-induced hepatotoxicity is frequently associated
with oxidative stress. This study displays the setting of a new cell culture model for hepatic energetic failure, i.e., HepG2
models modified by etomoxir [ETO] addition [0.1 mM to 1 mM] and compares the cell impact versus tert-butylhydroperoxide [TBOOH; 0.2 mM], an oxidative stress inducer. As it was observed with Minimum Essential Medium (MEM) without
any interfering agent, decreasing temperature drastically lowered adenosine triphosphate (ATP) levels, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl
tetrazolium bromide (MTT) viability test, and protein content, compared to 37°C (p = 0.02, p < 0.001 and p < 0.001, respectively), but to a larger extent in the presence of ETO or TBOOH. The alteration was generally highly dependent
on the ETO concentration, time, and temperature. At 37°C 24 h after (T24h), regarding ETO concentration, R2 correlation ratio was 0.65 (p < 0.001), 0.70 (p < 0.001), and 0.89 (p < 0.001) for ATP levels, protein content, and viability, respectively. The lowest ETO concentration producing a significant
effect was 0.25 mM. Concerning time dependency (i.e., T24h versus after 5 h (T5h)), at 37°C with ETO, ATP level continued
to significantly decrease between T5h and T24h. In a similar way, at 37°C, the MTT viability test decrease was accelerated
only between T5h and T24h for ETO concentrations higher than 0.5 mM (p = 0.016 and p = 0.0001 for 0.75 and 1 mM, respectively). On the contrary, with TBOOH, comparing T24h versus T5h, cellular indicators were
improved but generally remained lower than MEM without any interfering agent at T24h, suggesting that TBOOH action was time
limited probably in relation with its oxidation in cell medium. This study confirms the interest of altered ETO cell model
to screen agents (or formulation) prone to prevent or treat energetic depletion in relation with oxidative stress. 相似文献
18.
Jinxia Yang Minyan He Gejiao Wang 《World journal of microbiology & biotechnology》2009,25(9):1579-1587
Chromate-reducing microorganisms with the ability of reducing toxic chromate [Cr(VI)] into insoluble trivalent chromium [Cr(III)]
are very useful in treatment of Cr(VI)-contaminated water. In this study, a novel chromate-reducing bacterium was isolated
from Mn/Cr-contaminated soil. Based on morphological, physiological/biochemical characteristics and 16S rRNA gene sequence
analyses, this strain was identified as Intrasporangium sp. strain Q5-1. This bacterium has high Cr(VI) resistance with a MIC of 17 mmol l−1 and is able to reduce Cr(VI) aerobically. The best condition of Cr(VI) reduction for Q5-1 is pH 8.0 at 37°C. Strain Q5-1
is also able to reduce Cr(VI) in resting (non-growth) conditions using a variety of carbon sources as well as in the absence
of a carbon source. Acetate (1 mmol l−1) is the most efficient carbon source for stimulating Cr(VI) reduction. In order to apply strain Q5-1 to remove Cr(VI) from
wastewater, the bacterial cells were immobilized with different matrices. Q5-1 cells embedded with compounding beads containing
4% PVA, 3% sodium alginate, 1.5% active carbon and 3% diatomite showed a similar Cr(VI) reduction rates to that of free cells.
In addition, the immobilized Q5-1 cells have the advantages over free cells in being more stable, easier to re-use and minimal
clogging in continuous systems. This study provides potential applications of a novel immobilized chromate-reducing bacterium
for Cr(VI) bioremediation. 相似文献
19.
Natalia Timohhina Rita Guzun Kersti Tepp Claire Monge Minna Varikmaa Heiki Vija Peeter Sikk Tuuli Kaambre Dan Sackett Valdur Saks 《Journal of bioenergetics and biomembranes》2009,41(3):259-275
The aim of this study was to measure energy fluxes from mitochondria in isolated permeabilized cardiomyocytes. Respiration
of permeabilized cardiomyocytes and mitochondrial membrane potential were measured in presence of MgATP, pyruvate kinase –
phosphoenolpyruvate and creatine. ATP and phosphocreatine concentrations in medium surrounding cardiomyocytes were determined.
While ATP concentration did not change in time, mitochondria effectively produced phosphocreatine (PCr) with PCr/O2 ratio equal to 5.68 ± 0.14. Addition of heterodimeric tubulin to isolated mitochondria was found to increase apparent Km
for exogenous ADP from 11 ± 2 μM to 330 ± 47 μM, but creatine again decreased it to 23 ± 6 μM. These results show directly
that under physiological conditions the major energy carrier from mitochondria into cytoplasm is PCr, produced by mitochondrial
creatine kinase (MtCK), which functional coupling to adenine nucleotide translocase is enhanced by selective limitation of
permeability of mitochondrial outer membrane within supercomplex ATP Synthasome-MtCK-VDAC-tubulin, Mitochondrial Interactosome. 相似文献
20.
Anu Vikman Sakari Sarkkola Harri Koivusalo Tapani Sallantaus Jukka Laine Niko Silvan Hannu Nousiainen Mika Nieminen 《Hydrobiologia》2010,641(1):171-183
We studied the nitrogen retention capacity of six peatland buffer areas constructed in forested catchments in southern and
central Finland. The buffers (0.1–4.9% of the total catchment area) were either undrained mires or drained peatlands rewetted
4–7 years before the present study. The N retention capacity was studied by adding ammonium nitrate (NH4NO3–N) solution into the inflow waters of the buffers once (one area) or twice (five areas) during a period of 4–6 years. Except
for the first N addition in one area, the three largest buffer areas (relative size > 1%) retained the added inorganic N almost
completely; their retention efficiencies during the year of addition were >93% for both NO3–N and NH4–N. Two of the three small buffers (relative size < 0.25%) were also able to reduce inorganic N from the through-flow waters
effectively; their retention capacities for inorganic nitrogen varied between 58 and 89%. However, one small buffer area had
a retention capacity of only <20%. The factors contributing to efficient N retention were hydrological load during N addition,
relative size of the buffer area, and its length, i.e. the distance between the inflow and outflow points. If there was any
release of the added N, it mostly occurred within a relatively short-time period (<100 days) after the treatment. The buffer
areas appeared to be efficient and long-term sinks for inorganic nitrogen because the release of N during the 2–4 years after
N addition was minor. 相似文献