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K Kuba

Publications and source records attributed to K Kuba.

At least 19 recordsLinked to original sources
PubMed1992

Basal Ca2+ and the oscillation of Ca2+ in caffeine-treated bullfrog sympathetic neurones.

1. Effects of caffeine on the intracellular free Ca2+ concentration ([Ca2+]i) in single bullfrog sympathetic neurones in excised tissue were studied by recording Fura-2 fluorescence excited at 340, 361 or 380 nm and taking their ratios (R340/380 or R361/380). 2. Caffeine (3-10 mM) produced oscillation of [Ca2+]i and an 'apparent' decrease in the basal level of [Ca2+]i during a period between phasic rises. The mechanism of the latter effect was analysed in relation to the mechanism of the former. 3. Caffeine (3-10 mM) increased Fura-2 fluorescence in a range of excitation wavelength from 330 to 390 nm. The ratios of fluorescences, R340/380 and R361/380, however, were not significantly affected by caffeine. These results suggest that the 'apparent' reduction in the basal [Ca2+]i seen as a decrease in R340/380 or R361/380 results from a true decrease in [Ca2+]i. 4. Caffeine-induced decrease in [Ca2+]i persisted for every period between phasic rises of [Ca2+]i during [Ca2+]i oscillation, and after the blockade of [Ca2+]i oscillation by ryanodine. The decrease in the latter condition lasted for more than 20 min. 5. The decrease in the basal [Ca2+]i depended on the external Ca2+ concentration and was not mimicked by the action of cyclic nucleotides. 6. Possible mechanisms underlying the decrease in the basal [Ca2+]i produced by caffeine (effects on Ca2+ transport at the cell or Ca(2+)-storing organelle membrane) and their significance in relation to the [Ca2+]i oscillation were discussed.

Animals↗
PubMed1992

A patch-clamp study on the muscarine-sensitive potassium channel in bullfrog sympathetic ganglion cells.

1. A voltage-independent K+ channel was characterized and effects of muscarine were studied in cultured bullfrog sympathetic ganglion cells using the cell-attached patch-clamp configuration. 2. Three types of single-channel current were recorded from 2- to 10-day-old cultured cells in the presence of tetraethylammonium (2-20 mM), tetrodotoxin (1-2 microM), Cd2+ (0.1 mM) and apamin (20 nM). 3. The most frequently observed channel was a voltage-independent K+ channel which was open at the resting membrane potential and had a conductance of 52.6, 78.9 and 114.9 pS at a [K+]o of 2, 40 and 100 mM, respectively. This channel was designated background K+ channel. 4. Two other channel types were observed less frequently. One had a conductance of 26 pS (external K+, 118 mM) and a long open time of several seconds at the resting membrane potential. The second channel had a smaller conductance (20 pS) and displayed a voltage-dependent activation. 5. The open probability of the background K+ channel varied between patches, ranging from 0.0005 to 0.486. The open time distribution was fitted by a single exponential with a time constant of 0.51 ms. Both of these parameters were independent of the membrane potential. The closed time distribution consisted of at least four exponentials having time constants of 0.17, 3.7, 120 ms and several seconds. 6. Muscarine (10-20 microM) applied to the membrane outside the patch pipette reversibly enhanced the activity of the background K+ channel. This effect was associated with an increase in the open probability, which resulted from an increase in the mean open time concomitant with a decrease in the mean closed time. Muscarine did not change the single-channel conductance of this channel. 7. The effects of muscarine were blocked by atropine (1 microM). 8. It is concluded that there exists a muscarine-sensitive, voltage-independent K+ channel in cultured bullfrog ganglion cells. This K+ channel appears to contribute to the generation of the resting membrane potential and underlie the slow inhibitory postsynaptic potential of these neurones in situ.

Animals↗
PubMed1992

Intracellular calcium dynamics in response to action potentials in bullfrog sympathetic ganglion cells.

1. Dynamic changes in the intracellular free Ca2+ concentration ([Ca2+]i) following electrical membrane activity, were recorded from the neurone soma of the excised bullfrog sympathetic ganglion, using Fura-2 fluorescence and compared with the accompanying Ca(2+)-dependent electrical membrane responses. 2. The resting [Ca2+]i was about 100 nM, a value little changed by penetration with an intracellular electrode. 3. A net rise in fluorescence at a wavelength of 340 nm (Ca2+ transient) induced by a single action potential in Ringer solution rose almost in parallel with the initial decay phase of a slow Ca(2+)-dependent after-hyperpolarization; decayed in parallel with the late phase; and increased in amplitude and duration in the presence of tetraethylammonium (20 mM). 4. A Ca2+ transient induced by repetitive action potentials was increased asymptotically in amplitude and progressively in duration by increasing the number of spikes, and was slower in time course than the associated Ca(2+)-dependent K+ current. 5. Scanning a single horizontal line across the cytoplasm with an ultraviolet argon ion laser (351 nm) and recording Indo-1 fluorescence with a confocal microscope demonstrated an inward spread of a rise in [Ca2+]i following a tetanus. 6. Both single spike- and tetanus-induced Ca2+ transients were abolished in a Ca(2+)-free solution, while single or repetitive transient rises in [Ca2+]i induced by caffeine (5-10 mM) were generated under the same conditions. 7. Ryanodine (10-50 microM) did not affect tetanus-induced Ca2+ transients, whereas it blocked completely the caffeine-induced oscillation of [Ca2+]i. 8. Ca2+ transients induced by a tetanus in Ringer solution were independent of the interval from the preceding tetanus. The amplitude of Ca2+ transients induced by a tetanus in the presence of caffeine (5 mM) was equal to, or greater than, that generated in Ringer solution in any of the phases of [Ca2+]i oscillation. 9. It is suggested that under the physiological conditions here, the induction of action potentials does not cause the release of Ca2+ in the cells of the freshly excised bullfrog sympathetic ganglion, and that Ca(2+)-buffering systems contribute not only to lowering a transient rise in [Ca2+]i but also to sustaining an increased [Ca2+]i after a large Ca2+ load into the cell.

Action Potentials↗
PubMed1992

Intracellular Ca2+ dynamics in response to Ca2+ influx and Ca2+ release in autonomic neurones.

Spatial and temporal changes in the intracellular free Ca2+ concentration in response to Ca2+ influx at the cell membrane and to Ca2+ release from intracellular organelles were studied by recording fluorescence of Ca(2+)-sensitive probes, fura 2 or indo 1, with conventional epifluorescence or confocal laser-scanning microscopy combined with recordings of Ca(2+)-dependent membrane responses in bullfrog sympathetic ganglion cells. It was found that an increase in the intracellular Ca2+ induced by (an) action potential(s) in freshly ganglion cells bathed in Ringer's solution was solely a result of Ca2+ influx, while a rise in the intracellular Ca2+ by Ca2+ current in voltage-clamped cultured neurones was caused by not only Ca2+ influx but also Ca2+ release. This Ca2+ release was suggested to occur by a voltage-dependent (and graded) mode of activation of a Ca(2+)-induced Ca2+ release mechanism, explaining the lack of Ca2+ release by action potentials (because of their short-lasting depolarization) in freshly isolated neurons. In both cases, there was an inward spread of an increase in intracellular Ca2+. On the other hand, all or nothing activation of Ca(2+)-induced Ca2+ release occurred in the presence of caffeine, leading to the oscillation of Ca2+ in the cells. Characteristics of this mode of Ca2+ release and unique properties of drugs to block Ca2+ release were described. Finally, the physiological significance of different types of Ca2+ release was discussed.

Animals↗
PubMed1992

[The effect of breast feeding on morbidity in children].

The authors investigated in a group of 4210 children from birth to three years from Southern Moravia the morbidity from respiratory infections, diarrhoea and other infections. There were bisexual differences in morbidity, girls were less frequently ill. Children from child communities had a two old morbidity. Birth order was also important. The influence of natural nutrition was apparent in particular during the first year when infants breastfed for more than 4 months had significantly fewer spells of illness. These results were influenced by sex and birth order. At the age of two and three years the differences between children breastfed for a short and long time disappeared. Similar results were found also in other morbidity indicators such as administration of antibiotics, number of hospital admissions and mean number of days spent in hospital.

Breast Feeding↗
PubMed1992

[The effect of breast feeding on anthropometric indicators in very young children].

In a group of 4,217 children from Southern Moravia the authors evaluated growth from birth to the age of three years in relation to breastfeeding. The basic anthropometric data were evaluated in sub-groups made with regard to birth weight. Infants who were breastfed longer than four months were lighter during the first half year, as compared with those breastfed for a shorter period; at the age of one year this difference disappeared, in the second year they tended to have a higher weight, in the third year the differences were balanced. The same was manifested in weight increments. The influence on height was not so marked and was manifested mainly in the difference of increments. The head circumference and chest circumference was not much influenced. Evaluation of indices of proportionality revealed a more harmonious growth in children who were breastfed for a longer period.

Birth Weight↗
PubMed1992

[Persistent ductus omphaloentericus as a cause of ileus in children].

The authors describe a case of ileus in a 16-month-old child caused by Meckel's diverticulum. The symptoms leading to diagnosis were vague, partly masked by concurrent respiratory disease. In the discussion the authors mention possible complications associated with this anomaly.

Humans↗
PubMed1991

Ultraviolet light activates blocking actions of dantrolene on intracellular Ca2+ release in bullfrog sympathetic neurones.

Effects of dantrolene, a blocker of intracellular Ca2+ release, on the oscillation of the intracellular Ca2+ ([Ca2+]i) induced by caffeine were studied in bullfrog sympathetic ganglion cells, using a Fura-2 fluorescence technique. Dantrolene blocked the Ca2+ oscillation only in the cell illuminated by ultraviolet light (335-385 nm). Likewise, the blocking effects on rhythmic Ca(2+)-dependent hyperpolarizations, representing Ca2+ oscillations via activation of Ca(2+)-dependent K+ channel, occurred only under the illumination with ultraviolet light (335-385 nm), but not with visible light (404-417 nm). This wavelength dependence differs from the absorbance spectrum of dantrolene. On the other hand, dantrolene preirradiated with ultraviolet light under dark condition or ultraviolet light itself did not affect the [Ca2+]i oscillation. The blocking action was not prevented by the pretreatment of the cells with reducing agents. These results indicate that illumination of the Ca2+ release channel or dantrolene itself with ultraviolet light (possibly the former) is necessary for the drug to exert its blocking effect. Furthermore, dantrolene was found to decrease Fura-2 fluorescence and to increase cell autofluorescence, leading sometimes to a false decrease in the basal [Ca2+]i.

Animals↗
PubMed1991

A muscarine-activated voltage-independent K+ channel in cultured bullfrog sympathetic neurones.

In cultured bullfrog sympathetic neurones, cell-attached patch clamp revealed a voltage-independent K+ channel having a conductance of 46-113 pS at an external K+ of 2-120 mM. Muscarine (10-20 microM), applied to the cell membrane outside a recording pipette, increased its open probability and mean open time in an atropine-sensitive manner. This muscarine-activated K+ channel could underlie some of the muscarinic inhibitory postsynaptic potentials in both central and peripheral nervous systems.

Animals↗
PubMed1991

Spatial and dynamic changes in intracellular Ca2+ measured by confocal laser-scanning microscopy in bullfrog sympathetic ganglion cells.

Confocal laser scanning microscopy (CLSM) was used to record spatial and dynamic changes in the intracellular Ca2+ [(Ca2+]i) of bullfrog sympathetic ganglion cells in excised tissue or in culture. A CLSM utilizing Ar ion laser (488 nm) and recording fluo-3 fluorescence yielded the sliced image of ganglion cells, while conventional epifluorescence microscopy provided the cell image of a convex structure. A high K+ (50 mM) solution, caffeine (3-10 mM) and electrical stimulation (10-20 Hz, 0.5-10 s) caused a homogeneous increase in fluo-3 fluorescence with or without regional differences, possibly due to intracellular organelles and other constituents. Scanning a single horizontal line across the cytoplasm with He-Cd laser (325 nm) and recording indo-1 fluorescence demonstrated that the rate of rise in [Ca2+]i following action potentials depends on the distance from the cell membrane and on the cytoplasmic constituents, showing an inward spread of 'Ca(2+)-wave' at variable speeds of 17-219 microns/s. These results suggest that heterogeneity of the cytoplasmic structures and constituents affects dynamic and spatial changes of [Ca2+]i in response to stimuli in neurones. Such heterogenic changes in [Ca2+]i would better be studied by CLSM.

Aniline Compounds↗
PubMed1991

Long-term potentiation induced by a sustained rise in the intraterminal Ca2+ in bull-frog sympathetic ganglia.

1. The mechanism of a long-term potentiation of transmitter release (pre-LTP) induced by a tetanic stimulation (33 Hz for 1-30 s) applied to the preganglionic nerve was examined by intracellularly recording the fast excitatory postsynaptic potentials (fast EPSPs) in bull-frog sympathetic ganglia. 2. Short-term facilitation induced by paired pulses was decreased during the course of pre-LTP; the extent of reduction paralleled with the magnitude of pre-LTP. 3. The frequency of miniature EPSPs increased after tetanic stimulation that produced the pre-LTP. 4. The Ca2+ ionophore, A23187, increased both the amplitude and quantal content of fast EPSPs and frequency of miniature EPSPs while it decreased short-term facilitation. 5. A Ca2+ chelating agent, Quin-2, loaded as acetoxymethyl ester, reduced the amplitude and quantal content of fast EPSPs and short-term facilitation, and blocked the generation of pre-LTP. 6. Activators of protein kinase C, phorbol 12,13-dibutyrate and 1-oleoyl-2-acetyl-rac-glycerol, and its inhibitors, H-7 and staurosporine, did not block the generation of pre-LTP, while the activators enhanced transmitter release. 7. Inhibitors of calmodulin, trifluoperazine and W-7, blocked the generation of pre-LTP, whereas the amplitude and quantal content of fast EPSPs were not influenced. 8. These results suggest that the pre-LTP results from a sustained rise in the basal level of intraterminal Ca2+ and an activation of the Ca(2+)-calmodulin-dependent process in the preganglionic nerve terminals.

Animals↗
PubMed1989

Patch clamp experiments on nicotinic acetylcholine receptor-ion channels in bullfrog sympathetic ganglion cells.

Nicotinic acetylcholine-receptor ion channels (AChR channels) were studied in bullfrog sympathetic ganglion cells cultured for 1 day to 3 weeks, using a patch clamp technique. Microsuperfusion of ACh (2-10 microM) to the ganglion cell under the whole cell clamp produced an inward current at membrane potentials negative to -60 mV, which had a fast onset and decay. This rapid ACh-induced current was accompanied by a large current fluctuation, decreased and increased in amplitude by membrane depolarization and hyperpolarization, respectively, and blocked by d-tubocurarine. Thus, this current must be induced by the nicotinic action of ACh, but not by a muscarinic effect to activate a slow cation-selective current. At depolarized levels more than -50 mV, ACh induced an additional inward current which was slow in time course, accompanied by no or decreased current fluctuation and increased in amplitude by membrane depolarization. Accordingly, this slow ACh-induced current could result from the suppression of a voltage-dependent K+ current (M-current: Brown and Adams 1980) by the muscarinic action of ACh. Fluctuation analysis of the rapid ACh-induced current at potentials negative to -50 mV revealed the elementary conductance of 14 pS and a power spectral density distribution of the double Lorentzian function which yielded the time constants of 5.4 and 62.5 ms at -60 to -80 mV. The variance of either component was independent of the mean current.

Acetylcholine↗
PubMed1989

Nicotinic acetylcholine receptor-ion channels involved in synaptic currents in bullfrog sympathetic ganglion cells and effects of atropine.

The nicotinic acetylcholine receptor-ion channels (AChR channels) of the bullfrog sympathetic ganglion cells were studied with a two-electrode voltage clamp technique. The decay phase of the fast excitatory postsynaptic current (fast e.p.s.c.) in B-type neurones followed a double exponential function whose time constants were 3.2 and 8.0 ms at -60 mV and increased with membrane hyperpolarization. Likewise, the decay phase of the fast e.p.s.c. in C-type neurones was double-exponential with time constants of 4.4 and 12.3 ms (at -60 mV). The miniature e.p.s.c. in B-type neurones also decayed with a double exponential function (2.7 and 15.4 ms at -100 mV). Analysis of acetylcholine-induced current fluctuations revealed the power spectral density distribution of a double Lorentzian function which yielded the time constants of elementary events [tau noise(f) and tau noise(s): 1.7 and 29.7 ms, respectively, at -100 mV] and the averaged elementary conductance (gamma: 7.8 pS). The amplitude of fast e.p.s.c. and the time constant of the fast component of its decay phase decreased during the initial ("acute") phase (within 15 min) of the action of atropine (3 microM), but recovered during the later ("chronic") phase (more than 30 min after application) of the action. The slow component was affected by atropine in a manner similar to the fast component during the "acute" phase. During the "chronic phase", however, the slow time constant recovered and exceeded the control value. Furthermore, this prolongation remained for at least 1 h after the removal of atropine.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1989

Synaptic structure and axon collaterals of type B neurons in bullfrog sympathetic ganglia: intracellular horseradish peroxidase (HRP)-labeling study.

Type B neurons of the bullfrog sympathetic ganglia were examined to confirm the existence of axon collaterals and the distribution of synaptic contacts using the intracellular horseradish peroxidase (HRP) labeling method. The mean diameter of the perikarya was 60.8 (+/- 11.5 standard deviation; n = 36) X 43.8 (+/- 11.3) microns and the mean diameter of the initial segments of axons was 6.0 (+/- 1.8; n = 36) microns. Axon collaterals were found in 6 cells among 36 examined. They branched from axons at 61-167 microns from the perikaryon of origin. Short-axon collaterals containing vesicles (diameter: about 70 nm) were also observed to protrude from the stem axons. Spine-like processes were observed from the cell soma, axon hillock and the initial segment of the axon. They enclosed synaptic axon varicosities, or extended into the extracellular space without any synaptic contact. Serial sections revealed 171 axon varicosities in contact with a single ganglion cell; 32 (18.7%) varicosities were seen on the somata. 66 (38.6%) on the axon hillock and 73 (42.7%) on the initial segment of the axon which extended 100 microns from the perikaryon. Synaptic terminals were also found on the axon as far as 494 microns from the cell body of origin. These findings would provide a morphological basis for interaction between bullfrog sympathetic neurons at pre- or postsynaptic sites.

Animals↗
PubMed1987

Regulation of two ion channels by a common muscarinic receptor-transduction system in a vertebrate neuron.

In bullfrog sympathetic ganglion cells, muscarine produced an inward current (Imus) through the activation of a subtype (M1) of muscarinic acetylcholine receptor (mAChR) by suppressing an outward M-current (IM), and/or activating cation-selective current (ID; see below). The former was induced with a potency (Kd = 0.5 microM) higher than the latter (Kd = 5 microM) before and after blocking a fraction of the receptor with an irreversible blocker. Activators of protein kinase C mimicked muscarine's actions. Blocking IM by Ba2+ increased ID. These results suggest that activation of M1-mAChR both closes M-channel and opens cation-selective D-channel through phosphoinositide breakdown and the subsequent activation of protein kinase C and that a difference in potency at the last step of the cascade determines the order in which channels are regulated.

Animals↗
PubMed1987

The Ca2+-sensitive K+-currents underlying the slow afterhyperpolarization of bullfrog sympathetic neurones.

Ca2+-sensitive K+ currents involved in the slow afterhyperpolarization (a.h.p.) of an action potential of bullfrog sympathetic neurones were studied with a single-electrode voltage clamp method. The outward tail current (IAH) generated after the end of a depolarizing command pulse (from the holding potential of -60 mV to 0 mV, 5-20 ms in duration), mimicking an action potential, was separated into at least two exponential components (IAHf and IAHs). They were identified as K+ currents, since their reversal potentials were close to the K+ equilibrium potential and they were sensitive to external K+. The time constant of IAHf (tf; 44 ms at -60 mV) was decreased by membrane hyperpolarization from -40 to -80 mV, while that of IAHs (ts; 213 ms) remained constant. Removal of external Ca2+ or addition of Cd2+ significantly decreased the IAHs amplitude (As) and tf without a change in ts and the IAHf amplitude (Af). On the other hand, increasing Ca2+ influx by applying repetitive command pulses enhanced both Af and As with negligible effects on tf and ts, and produced a much slower component. Intracellular injection of EGTA reduced Af with no effect on tf, and increased As with a decreased ts. Both muscarine and (+/-)-tubocurarine, which reduced IAHs, hardly affected IAHf. These results indicate that a.h.p. is induced by the activation of two distinct Ca2+-dependent K+ channels, which differ in voltage sensitivity, Ca2+-dependence and pharmacology.

Action Potentials↗
PubMed1987

Role of ion conductance changes and of the sodium-pump in adrenaline-induced hyperpolarization of rat diaphragm muscle fibres.

The ionic mechanism of membrane hyperpolarization induced by adrenaline in rat diaphragm muscle fibres was studied. Removal of the extracellular K+ ([K+]o) from Krebs-Ringer solution initially increased the resting membrane potential and then caused an increase in the intracellular Na+ activity ([Na+]i) and a decrease in the intracellular K+ activity ([K+]i). All the changes were maintained for more than 3 h. Application of ouabain (0.1 mM) or lowering the temperature rapidly reduced the resting potential by about 10 mV in the K+-free solution. It then produced further progressive decreases in resting potential and in [K+]i and a progressive increase in [Na+]i. These observations indicate that an electrogenic Na-pump operates in the K+-free solution. Removal of most of the Cl- in the K+-free solution did not affect the resting potential or the magnitude of the initial decrease produced by ouabain, despite an increased input resistance; this result implies a passive distribution of Cl-. Adrenaline (30-60 microM) either added to the bathing solution or applied to the membrane by ionophoresis produced a hyperpolarization (3-10 mV: adrenaline hyperpolarization), the amplitude of which was decreased with a rise in [K+]o and increased with a reduction in [K+]o, but unaffected by the removal of Cl-. Adrenaline produced an increase in input resistance, the relative magnitude (17-18%) of which was constant whether external K+ or Cl- was removed. In contrast, a conditioning membrane hyperpolarization hardly affected the resistance. Ouabain (0.1 mM) or low temperature (8-10 degrees C) abolished both the hyperpolarization and the increased input resistance induced by adrenaline. The [K+]i, [Na+]i and the peak of the action potential remained unchanged after a 20 min exposure to adrenaline (30 microM). The hyperpolarization induced by the replacement of all Na+ with Tris (Tris-hyperpolarization) in the K+-free solution was depressed by 39% during the early period (4-31 min) of exposure to adrenaline (30 microM), while it was enhanced by 26% during the later period (80-130 min). The initial depression suggested a decrease in the ratio of the membrane permeability for Na+ (PNa) to that for K+ (PK). These results suggest that the adrenaline hyperpolarization is generated largely by a decrease in PNa/PK, which is associated with the activity of the Na-pump.

Animals↗