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M F Shuba

Publications and source records attributed to M F Shuba.

At least 19 recordsLinked to original sources
PubMed2006

[Effects of Staphylococcus aureus cell-bound protein A on adenosine triphosphate and nitric oxide inhibitory actions in smooth muscles].

Cell-bound protein A (CBPA), an immune-active substance of Staphylococcus aureus was ascertained to depolarize membrane of taenia coli smooth muscle (SM) cells, depress ATP inhibiting action (or uridinetriphosphate (UTP)) and sodium nitroprusside (SNP). ATP or UTP-induced membrane hyperpolarization increased during first minutes of CBPA exposure. Bacterial substance enhanced and then inhibited fast component of nicotine-induced relaxation of histamine-activated smooth muscles. This enhancement was inhibited by N(omega)-nitro-Larginine, a NO-syntase blocker. CBPA decreased ATP inhibiting action upon histamine-induced contraction, but enhanced cholinergic SM excitation. All these processes are reversible.

Adenosine Triphosphate↗
PubMed2004

[Single nonselective cation channels activated by muscarinic agonists in smooth muscle cells of the guinea-pig small intestine].

The carbachol-evoked inward cationic current in guinea-pig ileum smooth muscle cells is comprised of three types nonselective cationic channels (NSCC) with small (10 +/- 2 pS), medium (56 +/- 8pS) and large (135 +/- 14 pS) unitary conductance. All three types of NSCC could be activated by external application of carbachol as well as by internal application of GTPgS. It was found that behavior of carbachol- and GTPgammaS-evoked whole-cell current is mainly determined by the properties of medium conductance channels. The U-shaped I-V relationship of the whole-cell cationic current at negative potentials range arrives from voltage-dependence of its Po of this channel.

Animals↗
PubMed2002

[Transfer factor modulates inhibitory action of neurotransmitters on intestinal smooth muscles].

It has been shown that Transfer factor (TF) to Staphilococcus aureus antigens blocked ATP-induced component of the inhibitory junction potential in taenia coli smooth muscle from guinea-pig, and converted an inhibitory action of exogenous ATP into an exciting one (instead of the hyperpolarization of the smooth muscle, TF induced its depolarization). TF at 10-6 mg/ml converted the relaxing effects of sodium nitroprusside (nitric oxide donor) into exciting ones in smooth muscle strips. Higher concentrations (10-5-10-3 mg/ml) of TF slightly amplified the relaxing effect of sodium nitroprusside. Both a- and b-adrenergic activation in taenia coli smooth muscle were not sensitive to that agent.

Adenosine Triphosphate↗
PubMed2001

[Spontaneous transient outward currents in smooth muscle cells of the rat tail artery].

Spontaneous transient outward currents (STOCs) were studied in the rat tail artery smooth muscle cells using standard patch-clamp recording techniques in the whole-cell configuration. STOCs evoked by membrane depolarization from -30 to 20 mV varied in size from 50 to 1000 pA, their amplitude increased with membrane depolarization. These currents were inhibited by 1 mM TEA+. Both the frequency and the transferred charge (Q) were decreased in the absence of the extracellular Ca2+ or in the presence of the selective blocker of voltage-gated L-type Ca2+ channels nifedipine. Application of caffeine at 1 mM increased both Q and the frequency of STOCs generation. These results indicate that STOCs are carried by large conductance Ca(2+)-dependent K+ channels and Ca2+ influx plays an important role in their activation.

Animals↗
PubMed2000

Voltage-dependent inhibition of the muscarinic cationic current in guinea-pig ileal cells by SK&F 96365.

The effects of SK&F 96365 on cationic current evoked either by activating muscarinic receptors with carbachol or by intracellularly applied GTPgammaS (in the absence of carbachol) were studied using patch-clamp recording techniques in single guinea-pig ileal smooth muscle cells. SK&F 96365 reversibly inhibited the muscarinic receptor cationic current in a concentration-, time- and voltage-dependent manner producing concomitant alteration of the steady-state I-V relationship shape which could be explained by assuming that increasing membrane positivity increased the affinity of the blocker. The inhibition was similar for both carbachol- and GTPgammaS-evoked currents suggesting that the cationic channel rather than the muscarinic receptor was the primary site of the SK&F 96365 action. Increased membrane positivity induced additional rapid inhibition of the cationic current by SK&F 96365 which was more slowly relieved during membrane repolarization. Both the inhibition and disinhibition time course could be well fitted by a single exponential function with the time constants decreasing with increasing positivity for the inhibition (e-fold per about 12 mV) and approximately linearly decreasing with increasing negativity for the disinhibition. At a constant SK&F 96365 concentration, the degree of cationic current inhibition was a sigmoidal function of the membrane potential with a potential of half-maximal increase positive to about +30 mV and a slope factor of about -13 mV. Increasing the duration of voltage steps at -80 or at 80 mV, increased the percentage inhibition; the degree of inhibition was almost identical at both potentials providing evidence that the same cationic channel was responsible for the cationic current both at negative and at positive potentials. It is concluded that the distinctive and unique mode of SK&F 96365 action on the muscarinic receptor cationic channel is a valuable tool in future molecular biology studies of this channel.

Animals↗
PubMed2000

[The role of voltage gated K(+) channels in the modulation of resting membrane potential of myocytes isolated from rat resistance arteries].

K+ current which take part in the controlling of membrane potential in myocytes isolated from rat resistance mesenteric arteries have been investigated using conventional patch clamp method. The mean resting potential of myocytes was--37 mV. Charybdotoxin (200 nM)--selective blocker of large conductance Ca(2+)-activated K+ (KCa) channels--inhibited transmembrane outward K+ current by 60%. 1 mM of tetraethylammonium inhibited outward K+ current same as 200 nM of charybdotoxin, also it inhibited spontaneous spike-like hyperpolarizations and did not affect the membrane potential. Transmembrane current had a 4 aminopyridine (4-AP) sensitive component of delayed rectifier current (KV). Addition of 5 mM of 4-AP evoked membrane depolarization with mean significance of 12.0 +/- 1.5 mV in 5 from 7 single myocytes which had resting potential in the range of -50 ... -35 mV. The obtained results suggest that large conductance KCa channels do not determine the resting potential, but may serve as a negative feedback mechanism at the considerable membrane depolarization. In contrast, 4-AP sensitive KV current take part in the controlling of the resting membrane potential of single myocytes from rat resistance mesenteric arteries.

Animals↗
PubMed2000

[Transmembrane ionic currents in smooth muscle cells of rat tail artery].

Whole-cell currents in single smooth muscle cells freshly isolated from the rat tail artery have been studied using patch-clamp recordings techniques. Outward current evoked by depolarizing steps from -70 mV consisted of the initial fast and subsequent sustained components. The former was inhibited by 10 mM nifedipine and Ca(2+)-free solution application whereas the latter decreased by only 16% under these conditions. Caffeine at 4 mM abolished the fast component and only slightly reduced the sustained component. Both component were inhibited by 1 mM TEA+. Adding 10 mM EGTA to the pipette solution abolished the fast outward current. In the presence of 10 mM TEA+ and 4 mM 4-AP an inward current was unmasked. These results suggest that the outward current in these cells is carried mainly via delayed rectifier and Ca(2+)-activated K(+)-channels. 4-AP inhibited the sustained component and had no effect on the initial fast outward current, thus A-current is apparently absent.

Animals↗
PubMed1999

TTX-sensitive Na(+) and nifedipine-sensitive Ca(2+) channels in rat vas deferens smooth muscle cells.

The inward currents in single smooth muscle cells (SMC) isolated from epididymal part of rat vas deferens have been studied using whole-cell patch-clamp method. Depolarising steps from holding potential -90 mV evoked inward current with fast and slow components. The component with slow activation possessed voltage-dependent and pharmacological properties characteristic for Ca(2+) current carried through L-type calcium channels (I(Ca)). The fast component of inward current was activated at around -40 mV, reached its peak at 0 mV, and disappeared upon removal of Na ions from bath solution. This current was blocked in dose-dependent manner by tetrodotoxin (TTX) with an apparent dissociation constant of 6.7 nM. On the basis of voltage-dependent characteristics, TTX sensitivity of fast component of inward current and its disappearance in Na-free solution it is suggested that this current is TTX-sensitive depolarisation activated sodium current (I(Na)). Cell dialysis with a pipette solution containing no macroergic compounds resulted in significant inhibition of I(Ca) (depression of peak I(Ca) by about 81% was observed by 13 min of dialysis), while I(Na) remained unaffected during 50 min of dialysis. These data draw first evidence for the existence of TTX-sensitive Na(+) current in single SMC isolated from rat vas deferens. These Na(+) channels do not appear to be regulated by a phosphorylation process under resting conditions.

Animals↗
PubMed1994

Activation of the non-actomyosin component of aortic wall contraction by phorbol ester.

The mechanisms of smooth muscle tissue contractile system functioning are in many respects unexplained. According to the existing hypothesis, the mechanism of smooth muscle contraction is based on the interaction between myosin and actin. The change of muscle tissue stiffness during the contractive process is the important and obligatory feature of this actomyosin interaction. Earlier we have shown that, together with the smooth muscle cells, the connective tissue matrix can also produce the active mechanical strength. This process is not accompanied by changes of stiffness. We suggested that in some cases the induced contraction of smooth muscles is fulfilled, entirely or in part, by the connective tissue matrix. We report here that contractive reaction induced by the phorbol ester--activator of protein kinase C, which is one of the most important enzymes involved in the regulation of the smooth muscle contraction--occurs without any stiffness changes. The results obtained can not be explained in terms of the generally accepted hypothesis of actomyosin interaction. The conclusion is made that phorbol ester during the action on the smooth muscle tissue activates the mechanical strength generation by the connective tissue matrix.

Actomyosin↗
PubMed1994

[The "non-actomyosin" component of vascular wall contraction].

The matrix of connective tissue was found to take part in generation of the mechanical strength in isolated strips of the v. cava posterior wall under the effect of increased temperature. The finding corroborates the concept of the actomyosin interaction. The vessel tissue response to temperature seems to be formed by three mechanisms, two of them being of a non-actomyosin nature.

Actomyosin↗
PubMed1992

Potential-dependent inward currents in single isolated smooth muscle cells of the rat ileum.

1. Calcium (ICa) and sodium (INa) currents were studied in single smooth muscle cells freshly isolated from both the newborn (1-3 days old) and adult rat ileum, using the patch-clamp technique (whole-cell configuration). 2. Under conditions when INa was blocked, two components of ICa, low-voltage activated or ICa,low and high-voltage activated or ICa,high, were observed in the newborn rat ileal cells. ICa,high and ICa,low have differing voltage ranges of activation and steady-state inactivation and time courses of recovery from inactivation. Potential dependence of ICa,low was much steeper and shifted toward negative membrane potential than that for ICa,high (slope factors and the potential of half-maximal inactivation were 13.6 and -60.6 and 8.8 and -49 mV for ICa,low and ICa,high, correspondingly). 3. Nifedipine at the high concentration of 30 microM exerted no effect on ICa,low and only slightly suppressed ICa,high, decreasing its peak to 0.81 +/- 0.04 (n = 7) at the holding potential of -80 mV and to 0.66 +/- 0.05 (n = 3) at -50 mV. ICa,high was suppressed significantly by Cd2+ ions, while ICa,low was more sensitive to Ni2+ ions. 4. Results presented here suggest that the properties of high-voltage-activated (HVA) Ca2+ channels in the rat small intestine are quite different to those described for L-type Ca2+ channels found in other smooth muscles. It is proposed that HVA Ca2+ channels are similar to N-type Ca2+ channels. 5. Comparison of Ca2+ currents in newborn and adult rat ileal cells showed that the contribution of ICa,low to the net Ca2+ current was negligible in adults, whereas the properties of HVA Ca2+ channels were similar in the neonatal and adult animals. 6. INa, studied in nominally Ca(2+)-free physiological salt solution, activated in the voltage range between -50 and -40 mV and reached its peak at -10 mV. INa was blocked in a dose-dependent manner by TTX with an apparent dissociation constant of 4.5 nM. 7. INa decay was monoexponential in the voltage range studied and its time constant decreased monotonically with membrane depolarization from 4.7 +/- 0.2 ms (n = 6) at -30 mV to 0.51 +/- 0.03 ms (n = 7) at 20 mV.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

A potential-dependent fast outward current in single smooth muscle cells isolated from the newborn rat ileum.

1. Whole-cell outward currents have been studied in single smooth muscle cells isolated from newborn and adult rat ileum, using fire-polished glass micropipettes. 2. Two major outward currents, delayed (I(do)) and fast inactivating potential-dependent (I(fo)), have been observed in the newborn rat ileal cells. I(fo) is activated between -50 and -40 mV from the holding potential of -80 mV, whereas I(do) usually starts to activate at membrane potentials positive to -20 mV. Activation of I(do) was fast, its time-to-peak decreased from 10.8 +/- 0.9 ms (n = 5) at -30 mV to 4.5 +/- 0.7 ms (n = 4) at 20 mV. 3. I(fo) decay was monoexponential and its time constant did not depend on the membrane potential. Dependence of I(fo) inactivation on membrane voltage in normal physiological salt solutions (PSS) could be described by the Boltzmann equation with the following parameters: a half-inactivation potential, V0.5 = -70.8 mV and slope factor, k = 7.7 mV. 4. Recovery of I(fo) from inactivation was fitted by a single exponential and was potential dependent. The average time constant was 28.4 +/- 2.4 ms (n = 11) at -120 mV, 47.7 +/- 3.0 ms (n = 6) at -100 mV and 89.6 +/- 5.3 ms (n = 13) at -80 mV. 5. Removal of Ca2+ ions from the PSS (in the presence of 5 mM-Mg2+) increased I(fo) amplitude by about two times, and shifted its voltage dependence of inactivation towards negative membrane potentials by about 16 mV (V0.5 = -87.2 mV). Removal of Mg2+ from the PSS (in the presence of 2.5 mM-Ca2+) exerted no effects upon either inactivation dependence (V0.5 = -74.2 mV) or I(fo) amplitude. 6. I(do) and I(fo) had different sensitivities to K+ channel blockers. With 10 mM-external TEA+ I(do), was preferentially suppressed, while 5 mM-4-aminopyridine (4-AP) completely blocked I(fo). I(fo) was also partially blocked by a higher TEA+ concentration (30 mM), which suppressed I(fo) to 0.55 +/- 0.02 (n = 9). The blocking effect of 4-AP on I(fo) was potential, use and time dependent. 7. Ileal cells isolated from the adult rat demonstrated the presence of two populations of smooth muscle cells. One has an outward current which seems to be similar to that described in the newborn rat. However, in other cells spontaneous transient outward currents, well described in other single smooth muscle cells, but not found in newborn rat ileal cells, have been observed.

4-Aminopyridine↗
PubMed1992

Some properties of Ca(2+)-induced Ca2+ release mechanism in single visceral smooth muscle cell of the guinea-pig.

1. Late transient outward Ca(2+)-dependent K+ current (ILTO) correlated with Ca(2+)-induced Ca2+ release mechanism was studied in relation to the calcium inward current (ICa) in single isolated smooth muscle cells of the guinea-pig ileum using the whole-cell patch-clamp technique. 2. The voltage dependencies of peak ICa and ILTO were both bell shaped. However, the I-V curve of the outward current was shifted toward more positive potentials by about 60 mV in comparison to that for ICa. 3. Reduction in the external Ca2+ concentration resulted in a decrease of peak amplitude of both ICa and ILTO. However, caffeine-induced outward current was also decreased abruptly suggesting a rapid loss of stored Ca2+ upon lowering the external Ca2+ concentration. 4. Investigation of the relation of ILTO to partially inactivated ICa showed that inactivation of ICa by approximately 65, 80 or 84% of control (produced by prepulse to -20 mV for 2 s, shifting the holding potential to -20 mV for 30 s or by the ramp voltage command from -50 to +10 mV, respectively) was without detectable effect on the ILTO generation. 5. Bath application of the Ca2+ antagonist nifedipine (300 nM) inhibited ICa by 81% without affecting ILTO peak amplitude (92.0 +/- 5.6% of control in six cells). The mean concentration-response curve for ICa inhibition was sigmoidal with the apparent dissociation constant of 86.9 nM, whereas that for the ILTO had a characteristic sharp transition indicating a definite threshold of Ca2+ influx for ILTO generation. 6. Application of Ca(2+)-free external solution during 500 ms of the time when ICa peaked inhibited the current by about 76% whereas the ILTO during such an intervention remained virtually unchanged. 7. In double-pulse experiments, with conditioning and test pulses to +10 mV from -50 mV and an interpulse interval of 600 ms, most of the cells (about 80%) showed larger outward current at the test pulse suggesting continued Ca2+ release triggered by Ca2+ influx during a short (50-200 ms) depolarizing prepulse. The outward current could also be evoked at large positive potentials (presumably near the calcium equilibrium potential) where it did not occur normally by a prepulse to +10 mV for 50 ms. The charge transferred by Ca2+ current necessary to activate Ca2+ release in most of the cells was estimated to be from 6 to 20 pC. 8. The data are interpreted to suggest that the Ca(2+)-induced Ca2+ release mechanism operates in single ileal cells in a regenerative manner.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Patch-clamp recording in myenteric neurons of guinea pig small intestine.

The results of our research established the feasibility of applying patch-clamp methods in the study of the cellular neurophysiology of myenteric neurons enzymatically dissociated from adult guinea pig small intestine. Recording in current-clamp mode revealed two populations of neurons. One population discharged repetitively during depolarizing current pulses and displayed anodal-break excitation reminiscent of S/type 1 myenteric neurons. In the second population, spike discharge was limited to one or two spikes at the onset of depolarizing pulses and was similar to the behavior of AH/type 2 neurons. Recording in voltage-clamp mode revealed a complex of overlapping inward and outward whole cell currents. Fast and slow components of inward current were interpreted as sodium and calcium currents, respectively. Outward currents were blocked by cesium and consisted of components with properties of delayed rectifier current and A-type potassium current.

Animals↗