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1.
An electrophoretically detectable variant of lactate dehydrogenase-2 in Mus musculus has been found and used to locate the structural gene, Ldh-2, on chromosome 6. Gene order and recombination frequencies are estimated as Sig—36.0±4.8—Lc 21.0±4.1—Mi
wh—20.0±4.0—Ldh-2. 相似文献
2.
The aim of this study was to characterize the electropharmacological effects of prostacyclin (PGI2) in human atrial fibers and cardiomyocytes. Atrial tissues obtained from the hearts of 28 patients undergoing corrective cardiac surgery were used. Transmembrane action potentials were recorded using a conventional microelectrode technique, and twitch force by a transducer. Effects of PGI2 (1 nM–10 µM) on action potential characteristics and contraction of atrial fibers were evaluated in normal [K]o (4 mM) and high [K]o (27 mM) in the absence and presence of cardiotonic agents. In addition, atrial and ventricular myocytes were isolated enzymatically from atrial tissues and hearts of 4 patients undergoing cardiac transplant. The effects of PGI2 on Na- and Ca-dependent inward currents (INa and ICa) of cardiomyocytes were tested. In 9 human atrial fibers showing fast-response action potentials (mean dV/dtmax = 101 ± 15 Vs–1) in 4 mM [K]o, PGI2 did not influence dV/dtmax of phase 0 depolarization even at 1 µM. However, at a concentration as low as 10 nM, PGI2 depressed spontaneous rhythms or slow-response action potentials in high-K-depolarized fibers. PGI2 also depressed delayed afterdepolarizations and aftercontractions induced by cardiotonic agents. In isolated cardiomyocytes, PGI2 reduced ICa but not INa. The present findings show that, in human atrial fibers and cardiomyocytes, PGI2 induces greater depressant effects on the slow-response action potential, ICa and triggered activity than on the fast-response action potential. It is suggested that PGI2 may act through a selective reduction of transmembrane Ca influx. 相似文献
3.
Summary We have investigated the pacemaker properties of aggregates of cells dissociated from the atria and ventricles of 10 to 14-day-old chick embryonic hearts using a two-microelectrode current and voltage-clamp technique. These preparations usually beat spontaneously and rhythmically in tissue culture medium containing 1.3mm potassium with a beat rate typically in the range of 15–60 beats per minute. The beat rate results show considerable variability, which precludes any statistically significant comparison between the spontaneous activity of atrial and ventricular cell preparations at 10–14 days of development. However, the shapes of pacemaker voltage changes do exhibit differences characteristic of cell type. Spontaneous atrial preparations rapidly depolarize from maximum diastolic potential (–90 mV) to a plateau range of pacemaker potentials (–80 to –75 mV). The membrane subsequently depolarizes more gradually until threshold (–65 mV) is reached. In contrast, spontaneously beating ventricular cell preparations slowly hyperpolarize after maximum diastolic potential to the –100 to –95 mV range before gradually depolarizing toward threshold. Voltage-clamp analysis reveals a virtual lack of any time-dependent pacemaker current in atrial preparations. These preparations are characterized by an approximately linear background current (I
bg) having a slope resistance of 100 K cm2. Ventricular preparations have a potassium ion pacemaker current with slow kinetics (I
K
2), and a second time-dependent component (I
x) which is activated at potentials positive to –65 mV. The background current of these preparations displays inward rectification. Computer simulations of pacemaking reveal that the initial rapid phase of pacemaker depolarization in atrial cells is determined by the membrane time constant, which is the product of membrane capacitance and the slope resistance ofI
bg. The hyperpolarization after maximum diastolic potential of ventricular cells is caused byI
K
2. The final slow phase of depolarization in both cell types is caused in part by the steady-state amplitude of the fast inward sodium current (I
Na). This component has negative slope conductance which effectively increases the slope resistance in the vicinity of threshold compared to TTX-treated preparations. This mechanism is sufficient to produce interbeat intervals several seconds in duration, even in the absence of time-dependent pacemaker current, provided that the background current is at the appropriate level. 相似文献
4.
Shivali Gupta Vandanajay Bhatia Jian-jun Wen Yewen Wu Ming-He Huang Nisha Jain Garg 《Free radical biology & medicine》2009,47(10):1414-1421
In this study, we investigated the role of Trypanosoma cruzi invasion and inflammatory processes in reactive oxygen species (ROS) production in a mouse atrial cardiomyocyte line (HL-1) and primary adult rat ventricular cardiomyocytes. Cardiomyocytes were incubated with T. cruzi (Tc) trypomastigotes, Tc lysate (TcTL), or Tc secreted proteins (TcSP) for 0–72 h, and ROS were measured by amplex red assay. Cardiomyocytes infected by T. cruzi (but not those incubated with TcTL or TcSP) exhibited a linear increase in ROS production for 2–48 h postinfection (max 18-fold increase), which was further enhanced by recombinant cytokines (IL-1β, TNF-α, and IFN-γ). We observed no increase in NADPH oxidase, xanthine oxidase, or myeloperoxidase activity, and specific inhibitors of these enzymes did not block the increased rate of ROS production in infected cardiomyocytes. Instead, the mitochondrial membrane potential was perturbed and resulted in inefficient electron transport chain (ETC) activity and enhanced electron leakage and ROS formation in infected cardiomyocytes. HL-1 rho (ρ) cardiomyocytes lacked a functional ETC and exhibited no increase in ROS formation in response to T. cruzi. Together, these results demonstrate that invasion by T. cruzi and an inflammatory milieu affect mitochondrial integrity and contribute to electron transport chain inefficiency and ROS production in cardiomyocytes. 相似文献
5.
M. El Gamal 《Netherlands heart journal》2008,16(1):23-26
In patients with sick sinus syndrome and normal atrioventricular conduction, physiological pacing can be accomplished with either a single chamber atrial pacemaker AAI/R or a dual chamber pacemaker DDD/R. The single chamber device has the advantages of simpler implantation and lower initial costs, while the dual chamber device offers protection in case atrioventricular conduction disturbances develop in the future. When rigorous attention is paid to the pre-implantation selection criteria, the incidence of reported second- or third-degree atrioventricular block varied between 0.4 and 1.8% per annum. Medical practice, however, has shifted to predominant implantation of DDD/R pacemakers in more than 95% of patients with sick sinus syndrome. Recent publications have reported an increase in left atrial diameter, decrease in left ventricular fractional shortening and increased incidence of atrial fibrillation in patients with DDD/R pacing as compared with patients with single chamber atrial devices. These changes were proportional to the percentage of ventricular paced beats. New algorithms in dual chamber devices have been developed in order to minimise ventricular stimulation. These are being evaluated at present. In my opinion there is still a place for atrial pacing in selected patients with sick sinus syndrome with a minimum risk of developing complete atrioventricular block. (Neth Heart J 2008;16(suppl 1): S25-S27.) 相似文献
6.
M. Liebregts M. C. E. F. Wijffels M. N. Klaver V. F. van Dijk J. C. Balt L. V. A. Boersma 《Netherlands heart journal》2022,30(5):273
IntroductionThe AcQMap High Resolution Imaging and Mapping System was recently introduced. This system provides 3D maps of electrical activation across an ultrasound-acquired atrial surface.MethodsWe evaluated the feasibility and the acute and short-term efficacy and safety of this novel system for ablation of persistent atrial fibrillation (AF) and atypical atrial flutter.ResultsA total of 21 consecutive patients (age (mean ± standard deviation) 62 ± 8 years, 23% female) underwent catheter ablation with the use of the AcQMap System. Fourteen patients (67%) were treated for persistent AF and 7 patients (33%) for atypical atrial flutter. Eighteen patients (86%) had undergone at least one prior ablation procedure. Acute success, defined as sinus rhythm without the ability to provoke the clinical arrhythmia, was achieved in 17 patients (81%). At 12 months, 4 patients treated for persistent AF (29%) and 4 patients treated for atypical flutter (57%) remained in sinus rhythm. Complications included hemiparesis, for which intra-arterial thrombolysis was given with subsequent good clinical outcome (n = 1), and complete atrioventricular block, for which a permanent pacemaker was implanted (n = 2). No major complications attributable to the mapping system occurred.ConclusionThe AcQMap System is able to provide fast, high-resolution activation maps of persistent AF and atypical atrial flutter. Despite a high acute success rate, the recurrence rate of persistent AF was relatively high. This may be due to the selection of the patients with therapy-resistant arrhythmias and limited experience in the optimal use of this mapping system that is still under development.Supplementary InformationThe online version of this article (10.1007/s12471-021-01636-w) contains supplementary material, which is available to authorized users. 相似文献
7.
For purposes of correct treatment it is important to recognize that patients with complete atrioventricular dissociation fall into three groups: Group I—established third-degree heart block with and without Stokes-Adams attacks; Group II—periodic third-degree heart block with and without Stokes-Adams attacks; Group III—established third-degree heart block with cardiac failure. Most patients in Group I present no technical problems when a pacemaker is implanted. In Group II it is advisable to insert a temporary intracardiac catheter electrode and maintain a rate of 60 to 64 during the periods of third-degree heart block. Sudden reversion, in this group, from sinus rhythm can be fatal. Group III patients will often require a pacemaker set in excess of 74 beats until they are free of cardiac failure. Fifteen of 20 patients with complete atrioventricular dissociation showed marked functional improvement after insertion of a pacemaker. The development, in our laboratory, of a 4″ portable pacemaker impulse detector has been invaluable in locating the cause of failure in an implanted pacemaker. 相似文献
8.
K. Barth C. Pfleger A. Linge J. A. Sim A. Surprenant N. Steinbronn R. H. Strasser M. Kasper 《Histochemistry and cell biology》2010,134(1):31-38
It has recently been shown in epithelial cells that the ATP-gated ion channel P2X7R is in part, associated with caveolae and
colocalized with caveolin-1. In the present study of the mouse heart, we show for the first time, using immunohistochemistry
and cryoimmunoelectron microscopy, that P2X7R is expressed in atrial cardiomyocytes and in cardiac microvascular endothelial
cells, but not in the ventricle cardiomyocytes. Furthermore, biochemical data indicate the presence of two forms of P2X7R,
the classical glycosylated 80 kDa isoform and a protein with the molecular weight of 56 kDa, in both cardiomyocytes and endothelial
cells of the mouse heart. The functionality of both proteins in heart cells is still unclear. In cardiac tissue homogenates
derived from caveolin-1 deficient mice (cav-1
−/−), an increase of the P2Xrx7 mRNA and P2X7R protein (80 kDa) was found, particularly in atrial samples. In addition, P2rx7
−/− mice showed enhanced protein levels of caveolin-1 in their atrial tissues. Although the details of cellular mechanisms that
underlie the relationship between caveolin-1 and P2X7R in atrial cardiomyocytes and the electrophysiological consequences
of the increased P2X7R expression in atrial cells of cav-1
−/− mice remain to be elucidated, the cardiomyopathy detectable in cav-1
−/− mice is possibly related to a disturbed crosstalk between P2X7R and caveolin-1 in different heart cell populations. 相似文献
9.
Takeo Tadano 《Biochemical genetics》1987,25(5-6):375-384
Hexokinases (EC 2.7.1.1) were genetically analyzed in the mosquitoAedes togoi by agar gel electrophoresis. Enzyme activity was observed anodally in one major banding region (HK-1) on the gel and in another faintly stained region (HK-2). A total of six bands was detected in the HK-1 region. All six bands could be detected in three body parts, head, thorax, and abdomen, of adults with different banding intensities. The third and fourth bands, numbered from the more anodal side, showed the broadest substrate specificity and the greatest enzyme activity throughout development. Genetic analysis of the six HK-1 bands was undertaken on the hypothesis of a single gene locus (or three extremely tightly linked loci). The analysis gave the following gene order:HK-1—4.2±1.8 (recombination units±SE)—To-2—Odh-2—29.5±2.5—sex (M/m)—s. A comparison is made of gene loci for hexokinases among the mosquito speciesCulex pipiens, Aedes aegypti, and this species, along with a comment on linkage relationships betweenHk andOdh (octanol dehydrogenase) loci in threeAedes species.This research was supported by National Institutes of Health Grant AI 16983 and a Grant-in-Aid for Co-operative Research (57340033) from the Ministry of Education, Science and Culture, Japan. 相似文献
10.
-Mimosine (β-N-[3-hydroxy-4-pyridone]-α-aminopropionic acid)—a rare amino acid derived fromMimosaandLeucaenaplants—arrests cells reversibly late during G1 phase or at the beginning of S-phase. If mimosine were to arrest cells immediately before S-phase, it would provide a superb tool for the investigation of the initiation of DNA synthesis. Therefore, we reexamined the point of action of mimosine. Mitotic HeLa cells were released into 200 μMmimosine and grown for 10 h to block them, before the cells were permeabilized and the amino acid removed by washing them thoroughly. On addition of the appropriate triphosphates, DNA synthesis—measured by the incorporation of [32P]dTTP—began immediately; as it is known that such permeabilized cells cannot initiate DNA synthesis but can only resume elongating previously initiated chains, mimosine must arrest after DNA synthesis has begun. Moreover, cells grown in mimosine assembled functional replication factories—detected by immunolabeling after incorporation of biotin–dUTP—that were typical of those found early during S-phase. Disappointingly, it seems that mimosine—like aphidocolin—blocks only after cells enter S-phase. 相似文献
11.
Temperature plays an important role in the electrophysiology of cardiomyocytes. Pulmonary veins (PVs) are known to initiate paroxysmal atrial fibrillation. The effects of temperature on the arrhythmogenic activity of rabbit single PV and atrial cardiomyocytes were assessed using the whole-cell clamp technique. PV cardiomyocytes had different beating rates at low (22-25 degrees C), normal (38-39 degrees C) and high (40-41 degrees C) temperatures (0.9 +/- 0.1, 3.2 +/- 0.4, 6.4 +/- 0.6 Hz, respectively; p < 0.001). There were different action potential durations and incidences of delayed afterdepolarization in PV cardiomyocytes with pacemaker activity (31, 59, 63%; p < 0.05), PV cardiomyocytes without pacemaker activity (16, 47, 60%; p < 0.001), and atrial myocytes (0, 0, 21%; p < 0.05). However, oscillatory afterpotentials were only found in PV cardiomyocytes with pacemaker activity at normal (50%) or high (68%) temperatures, but not at low temperatures (p < 0.001). Both PV and atrial cardiomyocytes had larger transient inward currents and inward rectified currents at high temperatures. Additionally, PV cardiomyocytes with and without pacemaker activity had larger pacemaker currents at higher temperatures. This study demonstrated that PV cardiomyocytes have an increase in arrhythmogenic activity at high temperatures because of enhanced automaticity, induced triggered activity, or shortening of action potential duration. 相似文献
12.
Reza Rafie Salima Qamruddin Ali Ozhand Nima Taha Tasneem Z Naqvi 《Cardiovascular ultrasound》2012,10(1):1-11
Background
Use of rate adaptive atrioventricular (AV) delay remains controversial in patients with biventricular (Biv) pacing. We hypothesized that a shortened AV delay would provide optimal diastolic filling by allowing separation of early and late diastolic filling at increased heart rate (HR) in these patients.Methods
34 patients (75 ± 11 yrs, 24 M, LVEF 34 ± 12%) with Biv and atrial pacing had optimal AV delay determined at baseline HR by Doppler echocardiography. Atrial pacing rate was then increased in 10 bpm increments to a maximum of 90 bpm. At each atrial pacing HR, optimal AV delay was determined by changing AV delay until best E and A wave separation was seen on mitral inflow pulsed wave (PW) Doppler (defined as increased atrial duration from baseline or prior pacemaker setting with minimal atrial truncation). Left ventricular (LV) systolic ejection time and velocity time integral (VTI) at fixed and optimal AV delay was also tested in 13 patients. Rate adaptive AV delay was then programmed according to the optimal AV delay at the highest HR tested and patients were followed for 1 month to assess change in NYHA class and Quality of Life Score as assessed by Minnesota Living with Heart Failure Questionnaire.Results
81 AV delays were evaluated at different atrial pacing rates. Optimal AV delay decreased as atrial paced HR increased (201 ms at 60 bpm, 187 ms at 70 bpm, 146 ms at 80 bpm and 123 ms at 90 bpm (ANOVA F-statistic = 15, p = 0.0010). Diastolic filling time (P < 0.001 vs. fixed AV delay), mitral inflow VTI (p < 0.05 vs fixed AV delay) and systolic ejection time (p < 0.02 vs. fixed AV delay) improved by 14%, 5% and 4% respectively at optimal versus fixed AV delay at the same HR. NYHA improved from 2.6 ± 0.7 at baseline to 1.7 ± 0.8 (p < 0.01) 1 month post optimization. Physical component of Quality of Life Score improved from 32 ± 17 at baseline to 25 ± 12 (p < 0.05) at follow up.Conclusions
Increased heart rate by atrial pacing in patients with Biv pacing causes compromise in diastolic filling time which can be improved by AV delay shortening. Aggressive AV delay shortening was required at heart rates in physiologic range to achieve optimal diastolic filling and was associated with an increase in LV ejection time during optimization. Functional class improved at 1 month post optimization using aggressive AV delay shortening algorithm derived from echo-guidance at the time of Biv pacemaker optimization. 相似文献13.
Kenneth R. Courtney Ph.D. William T. Colwell Ph.D. Richard A. Jensen Ph.D. 《Prostaglandins & other lipid mediators》1978,16(3):451-459
Prostaglandins PGE2, PGE1, PGF2α, and PGA1 substantially increase automaticity in SA-nodal, right atrial preparations excised from guinea pigs. This natural pacemaker tissue is sensitive to nanomolar doses of PG with, for example, 10−8 M PGE2, increasing SA rate by about 20%. If these preparations are pretreated with 2 μM indomethacin, a blocker of endogenous prostaglandin synthesis, then spontaneous rate drops and subsequent rate increases due to PGE2 administration can be more easily demonstrated. Guinea pig pacemaker tissue differs from similar rabbit tissue not only in that it is directly responsive to PGE2, but also in that PGE2 does not depress the absolute response to transmural stimulation (adrenergically mediated rate increase). The positive chronotropic responses to PGE2 also occur when the guinea pig tissue is pretreated in 0.6 μM propranolol, which causes blockade of beta-adrenergic receptors.The pacemaker myocardium in the guinea pigs thus appears to be directly stimulated by exogenous PGE2 at very low doses. The observation that 2 μM indomethacin reduces SA-nodal rate suggests the presence of a very sensitive, functionally important, PGE-like system which modulates heart rate in this mammalian species. 相似文献
14.
Kousik Krishnan Akshay Gupta Sean M Halleran Dave Chawla Elizabeth F Avery Julia L Bienias Richard G Trohman 《Indian pacing and electrophysiology journal》2009,9(3):167-173
Background
Right atrial flutter cycle length can prolong in the presence of antiarrhythmic drug therapy. We hypothesized that the cycle length of right atrial isthmus dependent flutter would correlate with right atrial cross-sectional area measurements.Methods
60 patients who underwent ablation for electrophysiologically proven isthmus dependent right atrial flutter, who were not on Class I or Class III antiarrhythmic drugs and had recent 2-dimensional echocardiographic data comprised the study group. Right atrial length and width were measured in the apical four chamber view. Cross-sectional area was estimated by multiplying the length and width. 35 patients had an atrial flutter rate ≥ 250 bpm (Normal Flutter Group) and 25 patients had an atrial flutter rate < 250 bpm (Slow Flutter Group).Results
Mean atrial flutter rate was 283 bpm in the normal flutter group and 227 bpm in the slow flutter group. Mean atrial flutter cycle length was 213 ms in the Normal Flutter Group and 265 ms in the Slow Flutter Group (p< 0.0001). Mean right atrial cross sectional area was 1845 mm2 in the Normal Flutter group and 2378 mm2 in the Slow Flutter Group, (p< 0.0001). Using linear regression, CSA was a significant predictor of cycle length (β =0.014 p = 0.0045). For every 1 mm2 increase in cross-sectional area, cycle length is 0.014 ms longer.Conclusions
In the absence of antiarrhythmic medications, right atrial cross sectional area enlargement correlates with atrial flutter cycle length. These findings provide further evidence that historical rate-related definitions of typical isthmus dependent right atrial are not mechanistically valid. 相似文献15.
Terence J. Campbell 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1989,158(6):759-762
Summary Standard microelectrode techniques were used to record action potentials from single atrial, ventricular and Purkinje fibers of hearts taken from three species of marsupial (Macropus rufus, Macropus robustus andMacropus eugenii) and from dogs, sheep and guinea-pigs. The major electrophysiological parameters of marsupial potentials were qualitatively similar to the values for placental mammals. The grouped data for ventricular action potentials from studies on 6 adult male red kangaroos (Macropus rufus) were (mean ±SD): Resting potential –69.5±5.0 mV; action potential amplitude 92.7±5.7 mV; action potential duration (to 90% repolarization): 182.5±17.5 ms; maximum rate of depolarization: 196.5±80.1 V/s. The major point of difference was the short duration of the red kangaroo ventricular action potential compared to those of the placental mammals, and compared to atrial cells from the kangaroos. It is suggested that this explains the short QT interval reported by others for kangaroo electrocardiograms, and that it may also be implicated in the high frequency of sudden death previously noted in these animals. 相似文献
16.
Mechanical effects of ET-1 in cardiomyocytes isolated from normal and heart-failed rabbits 总被引:1,自引:0,他引:1
Elizabeth J. Kelso Robert F. Geraghty Barbara J. McDermott Elisabeth R. Trimble D. Paul Nicholls Bernard Silke 《Molecular and cellular biochemistry》1996,157(1-2):149-155
Endothelin (ET-1) is found at elevated concentrations in the plasma of patients with heart failure and in animal models of cardiomyopathy. The peptide is a potent positive inotropic agent, the effects of which are mediated by increases in cytosolic Ca2+ in cardiomyocytes. The object of this study was to investigate at the cellular level, the actions of ET-1 on contractile function and on Ca2+ currents in heart-failed ventricular myocardium. Male New Zealand White rabbits (8 wks) were treated with twice weekly injections of epirubicin (4 mg/kg/wk, n=7) or with saline (n=7) for 6 wks, followed by a washout period of 2 wks. Ventricular cardiomyocytes were isolated from rabbit hearts using Langendorff perfusion with collagenase; contractile function was examined using a video microscopy method, and L-type Ca2+ currents were recorded using a whole-cell patch-clamp technique. ET-1 produced a concentration-dependent increase in contractile response (% increase from basal value) to a maximum at 1 nM ET-1 of 69 ± 11% (mean ± S.D.) in control cardiomyocytes and 33 ± 6% in heart-failed cells. However, there was no significant change in the EC50 obtained with ET-1 for healthy (0.31 ± 0.1 nM) and for failed cardiomyocytes (0.24 ± 0.1 nM). The effects of ET-1 on L-type Ca2+ channels were similar with a peak amplitude at 1 nM ET-1 of –3.26 ± 0.8 in control cardiomyocytes and –3.32 ± 0.9 nA in heart-failed cells. The attenuation of the contractile response to ET-1 in heart-failed cells may reflect a desensitization of ET receptors as a consequence of elevated circulating levels of ET and was not reflected by alteration of transmembrane Ca2+ conductance. It is probable, therefore, that multiple signalling pathways are involved in the actions of ET on ventricular myocardium.Recipient of Servier Investigator Award 相似文献
17.
Treatment of the “sick sinus syndrome” is based on artificial pacemakers. These bear hazards such as battery failure and infections. Moreover, they lack hormone responsiveness and the overall procedure is cost-intensive. “Biological pacemakers” generated from PSCs may become an alternative, yet the typical content of pacemaker cells in Embryoid Bodies (EBs) is extremely low. The described protocol combines “forward programming” of murine PSCs via the sinus node inducer TBX3 with Myh6-promoter based antibiotic selection. This yields cardiomyocyte aggregates consistent of >80% physiologically functional pacemaker cells. These “induced-sinoatrial-bodies” (“iSABs”) are spontaneously contracting at yet unreached frequencies (400-500 bpm) corresponding to nodal cells isolated from mouse hearts and are able to pace murine myocardium ex vivo. Using the described protocol highly pure sinus nodal single cells can be generated which e.g. can be used for in vitro drug testing. Furthermore, the iSABs generated according to this protocol may become a crucial step towards heart tissue engineering. 相似文献
18.
Sonya Anderson Tom Brismar Elisabeth Hansson 《Cellular and molecular neurobiology》1995,15(4):439-450
Summary 1. The purpose of this study was (a) to identify if astrocytes show a similar non-Nernstian depolarization in low K+ or low Ca2+ solutions as previously found in human glial and glioma cells, and (b) to analyze the influence of the K+ conductance on the membrane potential of astrocytes.2. The membrane potential (Em) and the ionic conductance were studied with whole-cell patch-clamp technique in neonatal rat astrocytes (5–9 days in culture) and in human glioma cells (U-251MG).3. In 3.0 mM K+, Em was –75 ± 1.0 mV (mean ± SEM,n=39) in rat astrocytes and –79 ± 0.7 mV (n=5) in U-251MG cells. In both cell types Em changed linearly to the logarithm of [K+]0 between 3.0 and 160 mM K+. K+ free medium caused astrocytes to hyperpolarize to –93 ± 2.7 mV (n=21) and U-251MG cells to depolarize to –27 ± 2.1 mV (n=3).4. The I-E curve did not show inward rectification in astrocytes at this developmental stage. The slope conductance (g) exhibited only a small decrease (–19%) in K+ free solution and no significant change in 160 mM K+.5. Ba2+ (1.0 mM) depolarized astrocytes to –45 ± 2.9 mV (n=11), decreasing the slope conductance (g) by 42.4 ± 8.3% (n=11). Ca2+ free solution depolarized astrocytes to –53 ± 3.4 mV (n=12) and resulted in a positive shift of the I-E curve, increasing g by 15.3 ± 8.2% (n=8).6. Calculations indicated that a block of K+ channels explains the depolarizing effect of Ba2+. The effects of K+ free or Ca2+ free solutions on Em can be explained by a transformation of K+ channels to non-specific leakage channels. That astrocytes show a different reaction to low K+ than glioma cells can be related to the lack of inwardly rectifying K+ channels in astrocytes at this developmental stage. 相似文献
19.
Cyclic stretch induces the release of growth promoting factors from cultured neonatal cardiomyocytes and cardiac fibroblasts 总被引:9,自引:0,他引:9
Ruwhof C van Wamel AE Egas JM van der Laarse A 《Molecular and cellular biochemistry》2000,208(1-2):89-98
Growth factors and hormones may play an autocrine/paracrine role in mechanical stress-induced cardiac hypertrophy. Using an in vitro model of mechanical stress, i.e. stretch of cardiomyocytes and cardiac fibroblasts, we tested the involvement of growth factors and hormones in this process.We found that conditioned medium (CM) derived from 4 h cyclicly (1 Hz) stretched cardiomyocytes increased the rate of protein synthesis in static cardiomyocytes by 8 ± 3%. Moreover, CM derived from 2 h stretched fibroblasts increased the rate of protein synthesis in static fibroblasts as well as in static cardiomyocytes by 8 ± 2 and 6 ± 2%, respectively. Analysis of CM using size-exclusion HPLC showed that cardiomyocytes and fibroblasts released at least three factors with MW 10 kD, their quantities being time-dependently increased by stretch. Subsequent analyses using immunoassays revealed that cardiomyocytes released atrial natriuretic peptide (ANP) and transforming growth factor-beta1 (TGF1) being increased by 45 ± 17 and 21 ± 4% upon 4 h of stretch, respectively. Fibroblasts released TGF1 and very low quantity of endothelin-1 (ET-1). The release of TGF1 was significantly increased by 18 ± 4% after 24 h of stretch in fibroblasts. Both cell types released no detectable amount of angiotensin II (Ang II).In conclusion, upon cyclic stretch cardiomyocytes and fibroblasts secrete growth factors and hormones which induce growth responses in cardiomyocytes and fibroblasts in an autocrine/paracrine way. TGF secreted by cardiomyocytes and fibroblasts, and ANP secreted by cardiomyocytes are likely candidates. We found no evidence for the involvement of Ang II and ET-1 in autocrine/paracrine mechanisms between cardiac cell types. 相似文献
20.
Y. Rechav S. Mnqandi E. T. Mwase A. Heller-Haupt M. G. R. Varma 《Experimental & applied acarology》1991,11(4):317-321
Guinea-pigs infested with male ticks of the speciesRhipicephalus appendiculatus, and rabbits infested withR. evertsi evertsi, acquired immunity to conspecific female ticks. The hosts were first infested with male ticks and thereafter were challenged with males and females of the same species. The mean weight of the engorged females ofR. appendiculatus fed on guinea pigs previously infested with male ticks was 509.0 (±41.4) mg compared with that of females fed on control guinea pigs (651.2±31.8 mg). Similar weight differences were observed forR.e. evertsi females which fed on rabbits previously infested three times with male ticks. The mean weight of the female ticks which fed on these rabbits was 520.1 (±29.8) mg compared with 640.7 (±30.2) mg ofR.e. evertsi females which fed on control hosts. The concentration of gammaglobulins in the sera of rabbits was monitored at various intervals after the first infestation. It was found, for the first time, that infestation of laboratory animals with male ticks conferred immunity, but to a lesser degree than infestation with both sexes. It was also shown that the level of gammaglobulins increased from 3.4±0.28 g l–1 to 7.3±0.24 g l–1 in sera of rabbits hosts as a result of the feeding activity of males, but to a lesser extent than in sera of rabbits on which both sexes had fed (10.8±2.4 g l–1). 相似文献