共查询到20条相似文献,搜索用时 562 毫秒
1.
M.C. Ribeiro M.S. Costa-Alves M. Wengert J.R. Meyer-Fernandes P. Zancan C. Caruso-Neves A.A.S. Pinheiro 《Biochimica et Biophysica Acta (BBA)/General Subjects》2012
Background
The concentration of extracellular nucleotides is regulated by enzymes that have their catalytic site facing the extracellular space, the so-called ecto-enzymes.Methods
We used LLC-PK1 cells, a well-characterized porcine renal proximal tubule cell line, to biochemically characterize ecto-ATPase activity in the luminal surface. The [γ-32P]Pi released after reaction was measured in aliquots of the supernatant by liquid scintillation.Results
This activity was linear with time up to 20 min of reaction and stimulated by divalent metals. The ecto-ATPase activity measured in the presence of 5 mM MgCl2 was (1) optimum at pH 8, (2) insensitive to different inhibitors of intracellular ATPases, (3) inhibited by 1 mM suramin, an inhibitor of ecto-ATPases, (4) sensitive to high concentrations of sodium azide (NaN3) and (5) also able to hydrolyze ADP in the extracellular medium. The ATP:ADP hydrolysis ratio calculated was 4:1. The ecto-ADPase activity was also inhibited by suramin and NaN3. The dose–response of ATP revealed a hyperbolic profile with maximal velocity of 25.2 ± 1.2 nmol Pi x mg− 1 x min− 1 and K0.5 of 0.07 ± 0.01 mM. When cells were submitted to ischemia, the E-NTPDase activity was reduced with time, achieving 71% inhibition at 60 min of ischemia.Conclusion
Our results suggest that the ecto-ATPase activity of LLC-PK1 cells has the characteristics of a type 3 E-NTPDase which is inhibited by ischemia.General Significance
This could represent an important pathophysiologic mechanism that explains the increase in ATP concentration in the extracellular milieu in the proximal tubule during ischemia. 相似文献2.
Tadakatsu Inagaki Tsuyoshi Akiyama Cheng-Kun Du Dong-Yun Zhan Misa Yoshimoto Mikiyasu Shirai 《Free radical research》2016,50(6):645-653
To elucidate the involvement of monoamine oxidase (MAO) in hydroxyl radical production and cardiomyocyte injury during ischemia as well as after reperfusion, we applied microdialysis technique to the heart of anesthetized rats. Dialysate samples were collected during 30?min of induced ischemia followed by 60?min of reperfusion. We monitored dialysate 3,4-dihydrobenzoic acid (3,4-DHBA) concentration as an index of hydroxyl radical production using a trapping agent (4-hydroxybenzoic acid), and dialysate myoglobin concentration as an index of cardiomyocyte injury in the ischemic region. The effect of local administration of a MAO inhibitor, pargyline, was investigated. Dialysate 3,4-DHBA concentration increased from 1.9?±?0.5?nM at baseline to 3.5?±?0.7?nM at 20–30?min of occlusion. After reperfusion, dialysate 3,4-DHBA concentration further increased reaching a maximum (4.5?±?0.3?nM) at 20–30?min after reperfusion, and stabilized thereafter. Pargyline suppressed the averaged increase in dialysate 3,4-DHBA concentration by ~72% during occlusion and by ~67% during reperfusion. Dialysate myoglobin concentration increased from 235?±?60?ng/ml at baseline to 1309?±?298?ng/ml at 20–30?min after occlusion. After reperfusion, dialysate myoglobin concentration further increased reaching a peak (5833?±?1017?ng/ml) at 10–20?min after reperfusion, and then declined. Pargyline reduced the averaged dialysate myoglobin concentration by ~56% during occlusion and by ~41% during reperfusion. MAO plays a significant role in hydroxyl radical production and cardiomyocyte injury during ischemia as well as after reperfusion. 相似文献
3.
Shigeru Sakurai Yosuke Kuroko Shuji Shimizu Toru Kawada Tsuyoshi Akiyama Toji Yamazaki Masaru Sugimachi Shunji Sano 《Life sciences》2014
Aims
To examine the effects of cariporide, a Na+/H+ exchanger-1 inhibitor, on cardiac norepinephrine (NE) and myoglobin release during myocardial ischemia/reperfusion by applying a microdialysis technique to the rabbit heart.Main methods
In anesthetized rabbits, two dialysis probes were implanted into the left ventricular myocardium and were perfused with Ringer's solution. Cariporide (0.3 mg/kg) was injected intravenously, followed by occlusion of the left circumflex coronary artery. During 30-min coronary occlusion followed by 30-min reperfusion, four consecutive 15-min dialysate samples (two during ischemia and two during reperfusion) were collected in vehicle and cariporide-treated groups. Dialysate myoglobin and NE concentrations were measured by immunochemistry and high-performance liquid chromatography, respectively.Key findings
Dialysate myoglobin and NE concentrations increased significantly during myocardial ischemia/reperfusion in both vehicle and cariporide-treated groups (P < 0.01 vs. baseline). In cariporide-treated group, dialysate myoglobin concentrations were significantly lower than those in vehicle group throughout ischemia/reperfusion (P < 0.01 at 0–15 min of ischemia, P < 0.05 at 15–30 min of ischemia, P < 0.01 at 0–15 min of reperfusion, and P < 0.01 at 15–30 min of reperfusion). However, dialysate NE concentrations in cariporide-treated group were lower than those in vehicle group only during ischemia (P < 0.01 at 0–15 min of ischemia, and P < 0.05 at 15–30 min of ischemia).Significance
When administered before ischemia, cariporide reduces myoglobin release during ischemia/reperfusion and decreases NE release during ischemia. 相似文献4.
Harmanpreet Kaur Rebecca Heeney Rupp Carriveau Gabriel Sosne Bulent Mutus 《Biochimica et Biophysica Acta (BBA)/General Subjects》2010
Background
Thymosin beta 4 (Tβ4) is a major actin sequestering peptide present in most mammalian cells. It also acts as an anti-inflammatory agent and promotes corneal wound healing.Methods
In the present study, we constructed a four channel cylindrical flow chambers out of polydimethylsiloxane (PDMS) on microscope coverslips. The platelet-binding proteins–fibrinogen and collagen–were immobilized onto the middle ~ 25% of the inner cylindrical surface. The flow method introduced here was employed to determine the effect of Tβ4, on the deposition of ADP-activated platelets onto fibrinogen cross-linked flow chambers.Results
The binding data from the flow chambers indicated that the both the rate constant of platelet deposition (average: 0.026 ± 0.0015 s− 1, corresponding to a half-life of 26.7 s) and the total number of deposited platelets were independent of the platelet binding protein and the activating agent. Our results show that low concentrations of Tβ4 (0.2 μM to 0.5 μM) increased both the rate constant of platelet deposition by ~ 1.5-fold (i.e. half-life decreased from 26.7 s to 17.6 s) and the total number of deposited platelets by ~ 3-fold. However at higher concentrations (> 1 μM) the Tβ4-potentiating effect was diminished to near control levels. Tβ4 did interact with fibrinogen with an estimated KD of ~ 126 ± 18 nM or 66 ± 20 nM under equilibrium or flow, respectively.Conclusion
These results suggest that Tβ4 could potentially increase the affinity of platelet receptors for their ligands thus promoting platelet deposition. Tβ4 could also bind to fibrinogen and as its concentration increased would prevent platelet–fibrinogen interactions resulting in the attenuation of platelet deposition.General significance
This work suggests that Tβ4 might have a dual role in platelet function. 相似文献5.
6.
Mariana Chávez-Pantoja Mariella López-Mendoza Percy Mayta-Tristán 《Revista espa?ola de geriatría y gerontología》2014
Objective
To evaluate changes in physical performance in institutionalized older adults through a program of physiotherapy exercises.Materials and methods
A quasi-experimental study was conducted on adults over 60 years-old, institutionalized in Lima, Peru. The exercise program was implemented in 45 minutes sessions included warming-up, muscle strengthening exercises, balance, gait training and cooling phase, three times a week for 12 weeks. Physical performance was measured with the Short Physical Performance Battery (SPPB) one week before and after the intervention. It included 45 participants, of whom 16 did not attend any of the sessions and was used as a control group.Results
The mean age was 77.6 ± 7.1 years, and 62.2% were women. The mean baseline SPPB was 7.0 ± 1.6 in the intervention group, and 6.9 ± 1.9 in the control group (P=.90). A change of 2.6 ± 1.8 was observed in the SPPB of the intervention group versus -1.4 ± 2.0 in the control group (P<.001).Conclusions
The development of a physiotherapy exercise program for institutionalized elderly increases physical performance, which could be implemented in care centers for elderly. 相似文献7.
Hussein Kaddour Jacques Vergne Guy Herve Marie-Christine Maurel 《Biochimica et Biophysica Acta (BBA)/General Subjects》2014
Background
Viroids are the smallest pathogens known to date. They infect plants and cause considerable economic losses. The members of the Avsunviroidae family are known for their capability to form hammerhead ribozymes (HHR) that catalyze self-cleavage during their rolling circle replication.Methods
In vitro inhibition assays, based on the self-cleavage kinetics of the hammerhead ribozyme from a Chrysanthemum chlorotic mottle viroid (CChMVd-HHR) were performed in the presence of various putative inhibitors.Results
Aminated compounds appear to be inhibitors of the self-cleavage activity of the CChMVd HHR. Surprisingly the spermine, a known activator of the autocatalytic activity of another hammerhead ribozyme in the presence or absence of divalent cations, is a potent inhibitor of the CChMVd-HHR with Ki of 17 ± 5 μM. Ruthenium hexamine and TMPyP4 are also efficient inhibitors with Ki of 32 ± 5 μM and IC50 of 177 ± 5 nM, respectively.Conclusions
This study shows that polyamines are inhibitors of the CChMVd-HHR self-cleavage activity, with an efficiency that increases with the number of their amino groups.General significance
This fundamental investigation is of interest in understanding the catalytic activity of HHR as it is now known that HHR are present in the three domains of life including in the human genome. In addition these results emphasize again the remarkable plasticity and adaptability of ribozymes, a property which might have played a role in the early developments of life and must be also of significance nowadays for the multiple functions played by non-coding RNAs. 相似文献8.
Background
Trypanosoma brucei, responsible for African sleeping sickness, is a lethal parasite against which there is need for new drug protocols. It is therefore relevant to attack possible biomedical targets with specific preparations and since arginine kinase does not occur in humans but is present in the parasite it becomes a suitable target.Methods
Fluorescence quenching, thermodynamic analysis and FRET have shown that arginine kinase from T. brucei interacted with silver or gold nanoparticles.Results
The enzyme only had one binding site. At 25 °C the dissociation (Kd) and Stern–Volmer constants (KSV) were 15.2 nM, 0.058 nM− 1 [Ag]; and 43.5 nM, 0.052 nM− 1 [Au] and these decreased to 11.2 nM, 0.041 nM− 1 [Ag]; and 24.2 nM, 0.039 nM− 1 [Au] at 30 °C illustrating static quenching and the formation of a non-fluorescent fluorophore–nanoparticle complex. Silver nanoparticles bound to arginine kinase with greater affinity, enhanced fluorescence quenching and easier access to tryptophan molecules than gold. Negative ΔH and ΔG values implied that the interaction of both Ag and Au nanoparticles with arginine kinase was spontaneous with electrostatic forces. FRET confirmed that the nanoparticles were bound 2.11 nm [Ag] and 2.26 nm [Au] from a single surface tryptophan residue.Conclusions
The nanoparticles bind close to the arginine substrate through a cysteine residue that controls the electrophilic and nucleophilic characters of the substrate arginine–guanidinium group crucial for enzymatic phosphoryl transfer between ADP and ATP.General significance
The nanoparticles of silver and gold interact with arginine kinase from T. brucei and may prove to have far reaching consequences in clinical trials. 相似文献9.
A. Anitha N. DeepaK.P. Chennazhi Vinoth-Kumar LakshmananR. Jayakumar 《Biochimica et Biophysica Acta (BBA)/General Subjects》2014
Background
Evaluation of the combinatorial anticancer effects of curcumin/5-fluorouracil loaded thiolated chitosan nanoparticles (CRC-TCS-NPs/5-FU-TCS-NPs) on colon cancer cells and the analysis of pharmacokinetics and biodistribution of CRC-TCS-NPs/5-FU-TCS-NPs in a mouse model.Methods
CRC-TCS-NPs/5-FU-TCS-NPs were developed by ionic cross-linking. The in vitro combinatorial anticancer effect of the nanomedicine was proven by different assays. Further the pharmacokinetics and biodistribution analyses were performed in Swiss Albino mouse using HPLC.Results
The 5-FU-TCS-NPs (size: 150 ± 40 nm, zeta potential: + 48.2 ± 5 mV) and CRC-TCS-NPs (size: 150 ± 20 nm, zeta potential: + 35.7 ± 3 mV) were proven to be compatible with blood. The in vitro drug release studies at pH 4.5 and 7.4 showed a sustained release profile over a period of 4 days, where both the systems exhibited a higher release in acidic pH. The in vitro combinatorial anticancer effects in colon cancer (HT29) cells using MTT, live/dead, mitochondrial membrane potential and cell cycle analysis measurements confirmed the enhanced anticancer effects (2.5 to 3 fold). The pharmacokinetic studies confirmed the improved plasma concentrations of 5-FU and CRC up to 72 h, unlike bare CRC and 5-FU.Conclusions
To conclude, the combination of 5-FU-TCS-NPs and CRC-TCS-NPs showed enhanced anticancer effects on colon cancer cells in vitro and improved the bioavailability of the drugs in vivo.General significance
The enhanced anticancer effects of combinatorial nanomedicine are advantageous in terms of reduction in the dosage of 5-FU, thereby improving the chemotherapeutic efficacy and patient compliance of colorectal cancer cases. 相似文献10.
Horia Nicolae Roman Nedjma B. Zitouni Linda Kachmar Gijs IJpma Lennart Hilbert Oleg Matusovsky Andrea Benedetti Apolinary Sobieszek Anne-Marie Lauzon 《Biochimica et Biophysica Acta (BBA)/General Subjects》2013
Background
Smooth muscle has the distinctive ability to maintain force for long periods of time and at low energy costs. While it is generally agreed that this property, called the latch-state, is due to the dephosphorylation of myosin while attached to actin, dephosphorylated-detached myosin can also attach to actin and may contribute to force maintenance. Thus, we investigated the role of calponin in regulating and enhancing the binding force of unphosphorylated tonic muscle myosin to actin.Methods
To measure the effect of calponin on the binding of unphosphorylated myosin to actin, we used the laser trap assay to quantify the average force of unbinding (Funb) in the absence and presence of calponin or phosphorylated calponin.Results
Funb from F-actin alone (0.12 ± 0.01 pN; mean ± SE) was significantly increased in the presence of calponin (0.20 ± 0.02 pN). This enhancement was lost when calponin was phosphorylated (0.12 ± 0.01 pN). To further verify that this enhancement of Funb was due to the cross-linking of actin to myosin by calponin, we repeated the measurements at high ionic strength. Indeed, the Funb obtained at a [KCl] of 25 mM (0.21 ± 0.02 pN; mean ± SE) was significantly decreased at a [KCl] of 150 mM, (0.13 ± 0.01 pN).Conclusions
This study provides direct molecular level-evidence that calponin enhances the binding force of unphosphorylated myosin to actin by cross-linking them and that this is reversed upon calponin phosphorylation. Thus, calponin might play an important role in the latch-state.General significance
This study suggests a new mechanism that likely contributes to the latch-state, a fundamental and important property of smooth muscle that remains unresolved. 相似文献11.
Aims
Dietary flavonoid intake shows a significant inverse association with mortality from coronary heart disease, incidence of myocardial infarction and stroke. Quercetin is one of the most common flavonoids in our diet and has several favorable biological activities. Quercetin glucosides, which are enzymatically trans-glycosylated isoquercitrin, have high water-solubility and bioavailability compared with quercetin. Here, we investigated the effects of quercetin glucosides on collateral development in a murine hindlimb ischemia model.Main methods
We induced hindlimb ischemia in 24- to 32-week-old male C3H/HeJ mice by resecting the right femoral artery. Then, 0.5% carboxymethyl cellulose (control) or quercetin glucosides (100 mg/kg/day) were administered daily by gavage. Blood flow was monitored weekly by laser Doppler imaging.Key findings
Recovery of blood flow to the ischemic leg was significantly enhanced by quercetin glucosides (blood flow ratio at 4 weeks: control, 0.57 ± 0.11; quercetin glucosides, 0.95 ± 0.10, p < 0.05). Furthermore, anti-CD31 immunostaining revealed that quercetin glucosides increased capillary density in the ischemic muscle (control, 200 ± 24/mm2; quercetin glucosides, 364 ± 41/mm2, p < 0.01). Quercetin glucosides did not promote tumor growth. The beneficial effect of quercetin glucosides was abrogated in eNOS-deficient mice.Significance
These results suggest that quercetin glucosides may have therapeutic potential to promote angiogenesis in ischemic tissue. 相似文献12.
Jhon Fredy Ramírez Villada Henry Humberto León Ariza 《Revista espa?ola de geriatría y gerontología》2012
Objective
To analyze the relationship between different test measuring explosive strength and functionality of active women participating in a leisure sport program in order to describe the caracteristics of health status and look for tools for diagnosing and monitoring degenerative process.Methods
This study was conducted on 102 women physically active and without risk factors. Anthropometric, functional independence and explosive strength tests were applied.Results
Mean age 60.08±5.35 years; body mass index: 26.81±3.91; percentage of fat: 52.45±4.75; percentage of muscle mass: 37.24±6.77; tests of functional independence: maximum speed (30 meters): 9.39±1.92 s; speed-agility (30 meters): 12.93±1.59 s, and dynamic balance (6 meters): 21.9±8.01 s. Explosive Strength (Bosco test): Squat Jump: 12.23±3.05 cm, Countermovement Jump: 13.18±3.04 cm and Countermovement Jump Arm swing: 14.80±4.01 cm.Conclusion
The statistical relationships found between body composition, explosive strength and functionality tests, are important tools for diagnosing and monitoring, and could improve the intervention models on the elderly. 相似文献13.
Yu Yokoyama Kazuichi Maruyama Kotaro Yamamoto Kazuko Omodaka Masayuki Yasuda Noriko Himori Morin Ryu Koji M. Nishiguchi Toru Nakazawa 《Biochemical and biophysical research communications》2014
Purpose
In this study, we set out to establish an in vivo animal model of oxidative stress in the retinal ganglion cells (RGCs) and determine whether there is a link between oxidative stress in the RGCs and the activation of calpain, a major part of the apoptotic pathway.Materials and methods
Oxidative stress was induced in the RGCs of C57BL/6 mice by the intravitreal administration of 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH, 30 mM, 2 μl). Control eyes were injected with 2 μl of vehicle. Surviving Fluorogold (FG)-labeled RGCs were then counted in retinal flat mounts. Double staining with CellROX and Annexin V was performed to investigate the co-localization of free radical generation and apoptosis. An immunoblot assay was used both to indirectly evaluate calpain activation in the AAPH-treated eyes by confirming α-fodrin cleavage, and also to evaluate the effect of SNJ-1945 (a specific calpain inhibitor: 4% w/v, 100 mg/kg, intraperitoneal administration) in these eyes.Results
Intravitreal administration of AAPH led to a significant decrease in FG-labeled RGCs 7 days after treatment (control: 3806.7 ± 575.2 RGCs/mm2, AAPH: 3156.1 ± 371.2 RGCs/mm2, P < 0.01). CellROX and Annexin V signals were co-localized in the FG-labeled RGCs 24 h after AAPH injection. An immunoblot assay revealed a cleaved α-fodrin band that increased significantly 24 h after AAPH administration. Intraperitoneally administered SNJ-1945 prevented the cleavage of α-fodrin and had a neuroprotective effect against AAPH-induced RGC death (AAPH: 3354.0 ± 226.9 RGCs/mm2, AAPH+SNJ-1945: 3717.1 ± 614.6 RGCs/mm2, P < 0.01).Conclusion
AAPH administration was an effective model of oxidative stress in the RGCs, showing that oxidative stress directly activated the calpain pathway and induced RGC death. Furthermore, inhibition of the calpain pathway protected the RGCs after AAPH administration. 相似文献14.
15.
Zheng Wang Akira Sato Daiki Akiyama Taizo Kimura Kazuko Tajiri Tomoya Hoshi Satoshi Sakai Akira Koike Takashi Miyauchi Kazutaka Aonuma 《Life sciences》2014
Aims
Post-procedural myocardial necrosis manifested by elevated cardiac troponin T (cTnT) often complicates percutaneous coronary intervention (PCI). Plasma pentraxin 3 (PTX3) levels are increased in patients with arterial inflammation and especially unstable angina pectoris (UAP). This study tested whether plasma PTX3 levels can predict post-PCI cTnT elevation.Main methods
We evaluated 94 consecutive patients with AP and normal pre-PCI cTnT levels who underwent PCI. Pre-PCI virtual histology-intravascular ultrasound was performed to assess culprit plaque composition. Plasma PTX3 and serum hs-CRP levels were measured pre-PCI. Patients were divided into 2 groups according to presence (Group I, n = 34) or absence (Group II, n = 60) of post-PCI cTnT elevation > 3 × the upper limit of normal at 24 h after PCI.Key findings
Plasma PTX3 (4.06 ± 2.05 ng/ml vs 2.17 ± 1.02 ng/ml, p < 0.001), serum hs-CRP levels (0.25 ± 0.03 vs 0.16 ± 0.03 mg/dl, p = 0.048), plaque burden (80.9 ± 5.3 vs 75.4 ± 10.6%, p = 0.047), presence of positive remodeling (59 vs 25%, p = 0.034), and percent necrotic core area (19.0 ± 7.4 vs 14.0 ± 5.9%, p = 0.046) were significantly higher in Group I than in Group II. Receiver-operating characteristic curve analysis showed that with a best cut-off value of 2.83 ng/ml, plasma PTX3 level (AUC 0.823) predicted post-PCI cardiac TnT elevation better than did serum hs-CRP level (AUC 0.618). Multiple logistic regression analysis showed that plasma PTX3 level was the most independent predictor of post-PCI cardiac cTnT elevation (OR: 2.65; 95% CI: 1.56–10.1; p = 0.003).Significance
Plasma PTX3 level may be a useful marker for predicting post-PCI cardiac cTnT elevation, which is associated with inflammatory status of culprit lesions. 相似文献16.
Jaqueline Soares da Silva Sharlene Lopes Pereira Rodolfo do Couto Maia Sharon Schilling Landgraf Celso Caruso-Neves Arthur Eugen Kümmerle Carlos Alberto Manssour Fraga Eliezer Jesus Barreiro Roberto Takashi Sudo Gisele Zapata-Sudo 《Life sciences》2014
Aims
This work investigated the effects of 3,4-methylenedioxybenzoyl-2-thienylhydrazone (LASSBio-294) treatment on the contractile response of soleus (SOL) muscle from rats submitted to myocardial infarction (MI).Main methods
Following coronary artery ligation, LASSBio-294 (2 mg/kg, i.p.) or vehicle was administrated once daily for 4 weeks.Key findings
The run time to fatigue for sham rats was 17.9 ± 2.6 min, and it was reduced to 3.3 ± 0.8 min (P < 0.05) in MI rats. In MI rats treated with LASSBio-294, the time to fatigue was 15.1 ± 3.6 min. During the contractile test, SOL muscles from sham rats showed a response of 7.12 ± 0.54 N/cm2 at 60 Hz, which was decreased to 5.45 ± 0.49 N/cm2 (P < 0.05) in MI rats. The contractility of SOL muscles from the MI-LASSBio-294 group was increased to 9.01 ± 0.65 N/cm2. At 16 mM caffeine, the contractility was reduced from 2.31 ± 0.33 to 1.60 ± 0.21 N/cm2 (P < 0.05) in the MI group. In SOL muscles from MI-LASSBio-294 rats, the caffeine response was increased to 2.62 ± 0.33 N/cm2. Moreover, SERCA2a expression in SOL muscles was decreased by 0.31-fold (31%) in the MI group compared to the Sham group (P < 0.05). In the MI-LASSBio-294 group, it was increased by 1.53-fold (153%) compared to the MI group (P < 0.05). Meanwhile, the nuclear density in SOL muscles was increased in the MI group compared to the Sham group. Treatment with LASSBio-294 prevented this enhancement of cellular infiltrate.Significance
LASSBio-294 treatment prevented the development of muscular fatigue and improved exercise intolerance in rats submitted to MI. 相似文献17.
Horia Nicolae Roman Nedjma B. Zitouni Linda Kachmar Andrea Benedetti Apolinary Sobieszek Anne-Marie Lauzon 《Biochimica et Biophysica Acta (BBA)/General Subjects》2014
Background
Studies conducted at the whole muscle level have shown that smooth muscle can maintain tension with low Adenosine triphosphate (ATP) consumption. Whereas it is generally accepted that this property (latch-state) is a consequence of the dephosphorylation of myosin during its attachment to actin, free dephosphorylated myosin can also bind to actin and contribute to force maintenance. We investigated the role of caldesmon (CaD) in regulating the binding force of unphosphorylated tonic smooth muscle myosin to actin.Methods
To measure the effect of CaD on the binding of unphosphorylated myosin to actin (in the presence of ATP), we used a single beam laser trap assay to quantify the average unbinding force (Funb) in the absence or presence of caldesmon, extracellular signal-regulated kinase (ERK)-phosphorylated CaD, or CaD plus tropomyosin.Results
Funb from unregulated actin (0.10 ± 0.01 pN) was significantly increased in the presence of CaD (0.17 ± 0.02 pN), tropomyosin (0.17 ± 0.02 pN) or both regulatory proteins (0.18 ± 0.02 pN). ERK phosphorylation of CaD significantly reduced the Funb (0.06 ± 0.01 pN). Inspection of the traces of the Funb as a function of time suggests that ERK phosphorylation of CaD decreases the binding force of myosin to actin or accelerates its detachment.Conclusions
CaD enhances the binding force of unphosphorylated myosin to actin potentially contributing to the latch-state. ERK phosphorylation of CaD decreases this binding force to very low levels.General significance
This study suggests a mechanism that likely contributes to the latch-state and that explains the muscle relaxation from the latch-state. 相似文献18.
Chunmei Ma Ailian Liu Yuanyuan Wang Xiaoling Geng Li Hao Qingwei Song Bo Sun Heqing Wang Gang Zhao 《Life sciences》2014
Aims
To evaluate the hepatocyte phase of Gd-EOB-DTPA-enhanced MRI in the early diagnosis of hepatic fibrosis and cirrhosis and assessment of liver function in a rat model.Main methods
In 2 groups of SD rats, liver fibrosis was induced in experimental animals by repetitive carbon tetrachloride injections, while the control group received saline injections. Five experimental rats and 2 control rats were randomly selected at weeks 4, 8, 12. One week after carbon tetrachloride administration, MRI (FIRM T1WI) scan was performed. Gd-EOB-DTPA (0.08 mL) was injected into the rat's tail vein and hepatocyte phase images were obtained after 20 min. The pre-enhanced phase and hepatocyte phase signal intensities (SI) were measured, and the relative contrast enhancement index (RCEI) was calculated. ANOVA analysis (LSD) of RCEI values in controls (n = 6), hepatic fibrosis (n = 7), and histopathologically-determined early cirrhosis group (n = 6) was performed.Key findings
RECI values showed a decreasing trend in the control group, hepatic fibrosis and early cirrhosis groups (1.11 ± 0.43, 0.96 ± 0.22, and 0.57 ± 0.33, respectively). While the difference between the control and early cirrhosis groups was statistically significant (p = 0.013), there was no significant difference in the hepatic fibrosis group vs the control (p = 0.416) and the hepatic fibrosis group vs the early cirrhosis group (p = 0.054).Significance
Hepatocyte phase RCEI values obtained with Gd-EOB-DTPA-enhanced MRI scan indicate liver injury in hepatic fibrosis and early cirrhosis. RCEI values are helpful for early diagnosis of liver cirrhosis. 相似文献19.
Yasushi Sakai Michio Hashimoto Budbazar Enkhjargal Hisashi Mitsuishi Hiromi Nobe Ichiro Horie Takahiro Iwamoto Kenichi Yanagimoto 《Life sciences》2014
Aims
To investigate the effects of n − 3 polyunsaturated fatty acids on cerebral circulation, ovariectomized (OVX) rats were administered with phospholipids in krill oil (KPL) or triglycerides in fish oil (FTG); effects on the Ca2 + regulating system in their basilar artery (BA) were then analyzed.Main methods
The rats were divided into 4 groups: control, OVX, OVX given KPL (OVXP), and OVX given FTG (OVXT) orally, daily for 2 weeks. Time dependent relaxation (TDR) of contractile response to 5HT in BA was determined myographically, Na+/Ca2 + exchanger (NCX) 1 mRNA expression was determined by real time PCR, and nucleotides were analyzed by HPLC.Key findings
The level of TDR in OVX that was significantly lower in the control was inhibited by l-NAME and indomethacin; TEA inhibited TDR totally in the control but only partly in OVXP and OVXT. Relaxation induced by the addition of 5 mM KCl to the BA pre-contracted with 5-HT was inhibited by TEA in the controls, OVXP and OVXT, but not in OVX. Overexpression of NCX1 mRNA in the BA from OVX was significantly inhibited by FTG. The ratio of ADP/ATP in cerebral arteries from OVX was significantly inhibited by KPL and FTG. Levels of triglyceride and arachidonic acid in the plasma of OVX increased, but were significantly inhibited by KPL and FTG.Significance
Ovarian dysfunction affects Ca2 + activated-, ATP-sensitive-K+ channels and NCX1, which play crucial roles in the autoregulation of cerebral blood flow. Also, KPL may become as good a supplement as FTG for postmenopausal women. 相似文献20.
Andrea Ilari Flaminia Alaleona Giancarlo Tria Patrizia Petrarca Andrea Battistoni Carlotta Zamparelli Daniela Verzili Mattia Falconi Emilia Chiancone 《Biochimica et Biophysica Acta (BBA)/General Subjects》2014