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L Varecka

Publications and source records attributed to L Varecka.

At least 19 recordsLinked to original sources
PubMed2004

Chloride transport in the vegetative mycelia of filamentous fungus Trichoderma viride.

The influx of chlorides into Trichoderma viride vegetative submerged mycelium was measured by means of the radionuclide (36)Cl(-). It was found that the (36)Cl(-) influx was time-dependent (the steady-state was established with t(1/2 )= 25 min at 25 degrees C), pH-dependent (with pH optimum between 4-5.5), temperature-dependent (at about 15 degrees C), and concentration-dependent (K(M)(Cl(-))) = 47.6 +/- 4.2 micromol x l(-1); J(max) = 11.5 +/- 0.7 pmol(Cl(-)) x min(-1). mg(dry mass) (-1)). The (36)Cl(-) influx was inhibited by Br(-) but not F(-), I(-), SO(4)(2-), HPO(3)(2-) and HCO(3)(-). The presence of vanadate (P-type ATPase inhibitor) moderately stimulated the (36)Cl(-) influx but the presence valinomycin (electrogenic K(+) ionophore), salicylate (known to release Ca(2+) from Trichoderma viride internal stores) were without effect on the (36)Cl(-) influx. The results suggest that the (36)Cl(-) influx is mediated by a carrier and that the transport is electroneutral, probably Cl(-)/OH(-) antiport.

Biological Transport↗
PubMed2002

The effect of boromycin on the Ca2+ homeostasis.

A boron-containing antibiotic, boromycin (BM), was found to influence the Ca2+ homeostasis in both excitable and non-excitable cells. In non-excitable cells (human erythrocytes and leucocytes) it inhibited the resting passive 45Ca2+ transport in 10(-6)-10(-5) mol/L concentrations. In human erythrocytes, the passive 15Ca2+ transport induced by the presence of 1 mmol/L NaVO3 was inhibited by boromycin (90% inhibition) as well. The inhibitory effect of BM on the NaVO3-induced passive 45Ca2+ transport was diminished in the presence of inhibitory concentrations of nifedipine (10 micromol/L -60% inhibition) or of those of K+o (75 mmol/L -20% inhibition). On the other hand, in rat brain synaptosomes, and rat cardiomyocytes, BM stimulated the passive 45Ca2+ transport in 'resting' cells at similar concentrations. In rat cardiomyocytes the stimulation was transient. The stimulatory effect on the passive 45Ca2+ transport in rat brain synaptosomes was accompanied with the increase of cytoplasmic Ca2+ concentration measured by means of the entrapped fluorescent Ca2+ chelator fura-2. The stimulatory effect of BM was diminished when synaptosomes were pre-treated with veratridine (10 micromol/L) which itself stimulated the passive 45Ca2+ transport. At saturating concentrations of veratridine, no stimulatory effect of BM was observed. These results could be explained by the indirect interaction of BM with both Ca2+ and Na+ transport systems via transmembrane ionic gradients of monovalent cations and could be useful in determining whether the cells belong to excitable, or non-excitable cells.

Animals↗
PubMed2001

Vegetative growth, aging- and light-induced conidiation of Trichoderma viride cultivated on different carbon sources.

The growth and conidiation of the aged Trichoderma viride culture grown in the dark, and after an induction by a light pulse, was examined in the presence of selected mono-, di(tri)saccharides, amino acids and alcohols as sole carbon sources. Hexoses and disaccharides, but not pentoses and amino acids, promoted proportionally both growth and conidiation induced by aging or light. All compounds but pentoses promoted the conidiation in aged cultures and photoconidiation in a close correlation. Ethanol, glycerol and ethylene glycol supported both growth and conidiation but these processes were not supported equally. Conidia formation with hexoses and amino acids as sole carbon sources seems to be a function of growth promotion, rather than of growth restriction (starvation, stress, aging). With glucose as sole carbon source the conidiation was not triggered by nutrient limitation, nor by the accumulation of waste metabolites. The aging-induced conidiation can be considered to be triggered by the genetic program of the microorganism rather than by its nutrient status.

Alcohols↗
PubMed2001

Novel oxindole derivatives and their biological activity.

The antifungal activity of fourteen novel derivatives of oxindole with side chain was studied using representatives of toxinogenic, phytopathogenic and dermatophytic filamentous fungi. Derivatives with exocyclic C=C bond in position C-3 exhibited a higher antifungal activity compared with derivatives with an exocyclic C-C bond in the same position. The strongest antifungal effects were shown by 3-(-2-thienoylmethylidene)-indol-2(3H)-ones.

Antifungal Agents↗
PubMed2001

Glutamate decarboxylase activity in Trichoderma viride conidia and developing mycelia.

Glutamic acid decarboxylase (GAD) activity was measured in homogenates of conidia and both submerged and aerial mycelia of Trichoderma viride. The GAD activity in conidia had a temperature optimum at 30 degrees C and a pH optimum at pH 4. GAD was stimulated by EDTA (2 mM) and was insensitive to treatment with calmodulin antagonists calmidazolium (10 microM) or phenothiazine neuroleptics (60 microM). Cyclosporin A (up to 300 microM) partially inhibited GAD in the homogenate, but not in the supernatant obtained after centrifuging the homogenate. Attempts to release GAD activity from the homogenate using high ionic strength, detergents, or urea failed. Freezing-thawing led to the partial increase of activity in the conidial homogenate. These results indicate that GAD is a membrane-bound enzyme. The highest specific activity of GAD was present in the mitochondrial/vacuolar organellar fraction. Germination of conidia in the submerged culture led to a temporary decrease in GAD activity. After prolonged cultivation, the activity displayed quasi-oscillatory changes. The stationary state was characterized by a high GAD activity. The presence of gamma-aminobutyric acid in the submerged mycelia was demonstrated. In surface culture in the dark, GAD activity increased in a monophasic manner until conidia formation. The illumination of dark-cultivated mycelia by a white-light pulse caused a dramatic increase in GAD activity. Light-induced changes were not observed in mutants with delayed onset of conidiation. In the dark or upon illumination by light pulse, the increase of GAD activity preceded the appearance of conidia. Thus, GAD activity in T. viride is closely associated with its developmental status and may represent a link between differentiation events and energy metabolism.

Cyclosporine↗
PubMed2001

The effect of azalomycin F on Ca2+ homeostasis in Trichoderma viride and Saccharomyces cerevisiae.

Azalomycin F (AMF), a macrocyclic lactone antibiotic, in concentrations of 10(-5) g/ml (10(-6) - 10(-5) mol/l) was found to stimulate both the 45Ca2+ influx and efflux in intact Trichoderma viride submerged mycelium and in cells of Saccharomyces cerevisiae without having Ca2+ ionophoric properties. AMF also inhibited ATP-dependent Ca2+ uptake in membrane fractions prepared from T. viride submerged mycelium. 45Ca2+ which had been accumulated in membrane fractions in an ATP-dependent manner was released upon addition of AMF. This release was observed in light organellar fractions (LOF) of S. cerevisiae and of T. viride submerged mycelium and, to a small extent, in heavy organellar fraction (HOF) of S. cerevisiae. No Ca2+ releasing effect of AMF was observed in HOF from T. viride submerged mycelium. In S. cerevisiae expressing Ca2+-dependent photoprotein aequorin, AMF induced transients of luminescence which reflect changes in the cytoplasmic Ca2+ concentration. The results suggest that the stimulation by AMF of the Ca2+ efflux from the mycelium (cells) could be explained by an increase of the cytoplasmic Ca2+ concentration due to the release of Ca2+ from microsomal membranes or to the stimulation of Ca2+ influx.

Anti-Bacterial Agents↗
PubMed2000

Some biological properties of new quinoline-4-carboxylic acid and quinoline-4-carboxamide derivatives.

The antimicrobial and morphogenetic effects of fourteen newly synthesized 2-substituted derivatives of quinoline-4-carboxylic acid and quinoline-4-carboxamide were studied using G+ and G- bacteria, yeasts and filamentous fungi. The highest antimicrobial effects were found with substituted quinoline-4-carboxylic acid derivatives. Quinoline-4-carboxamides only weakly influenced the growth of the tested microorganisms. Some derivatives of quinoline-4-carboxylic acid elicited profound changes in the morphology of hyphal tips of Botrytis cinerea, mainly their branching and the release of the cytoplasmic content. Quinoline derivatives, which elicited morphological changes, increased also the permeability of the plasmalemma of plant cells.

Anthocyanins↗
PubMed2000

Ca2+ fluxes in developing Trichoderma viride mycelium.

The properties of both Ca2+ influx and efflux in the mycelium during the life cycle of Trichoderma viride were studied by means of 45Ca2+ and by X-ray fluorescence spectroscopy measurements. The properties of the 45Ca2+ influx and effluxes indicate that they are mediated by different transport systems. The Ca2+ influx could be mediated by an electrogenic Ca2+/nH+ antiport, or by an Ca2+ uniport system. Both Ca2+ influx and efflux were stimulated by the uncouplers (and the treatment leading to the suppression of energy metabolism) and by azalomycin F, an antifungal agent. Salicylate stimulated the Ca2+ efflux, but inhibited the Ca2+ influx. In the isolated preparation of crude vacuolar/mitochondrial fraction, salicylate induced the Ca2+ release, as did A23187. Azalomycin F moderately released Ca2+ from the microsomal fraction. On the other hand, uncouplers did not release Ca2+ from the isolated organelles, but inhibited to a different extent the ATP-dependent and -independent Ca2+ influx. The results could be explained in terms of the capacitative Ca2+ influx mechanism. The rate of 45Ca2+ influx, or of the 40Ca2+ content, was maximal after about 30 h of submerged cultivation, and then decreased. The results show that loading of internal Ca2+ stores occurs in the early stages of the development of mycelium only, and the Ca2+ influx mechanism is developmentally down-regulated, being almost nonexistent during its later stages. In older mycelium, growth seems to be autonomous of the extracellular Ca2+ until the onset of conidiation.

Anti-Bacterial Agents↗
PubMed1999

Properties of uracil transport by vegetative mycelium of Trichoderma viride.

The transport of radioactively labelled uracil into submerged mycelium of T. viride was measured by means of a membrane filtration technique. It was found to be time-dependent (up to 90 min) and concentration-dependent (up to 8 mmol l-1). Its concentration dependence was biphasic and consisted from the saturatable part (at the uracil concentration below 0.2 mmol l-1) with KM = 0.08 +/- 0.02 mmol l-1 and Vmax = 1.74 +/- 0.3 nmol (mg dry wt.)-1 h-1, and from the region at higher uracil concentration which showed only a weak saturatability with the substrate. The transport measured in the saturatable part of the curve was also pH- and temperature-dependent. The optimal pH was between 5.4 and 6.4 and the optimal temperature was at 37 degrees C. The activation energy of 54 kJ mol-1 and the temperature quotient of Q10 = 2.1 could be calculated from the temperature dependence. The entry of uracil was in part inhibited by nucleobases and their analogues, nucleosides, nucleotides and amino acids. The inhibitors had similar inhibitory efficiency about 50% at 0.2 mmol l-1. 3,3',4',5-tetrachlorosalicylanilide (TCS), the uncoupling agent, significantly inhibited the uracil transport, but its inhibitory efficiency decreased upon increasing the uracil concentration. Ionophore antibiotics valinomycin and monensin also inhibited the uracil transport. Inhibitors of RNA-polymerase, rifamycin and rifampicin were without effect. The results suggest that at low uracil concentrations (below 0.2 mmol l-1), its transport is mediated by a carrier and is driven by the electrochemical potential of protons. At higher uracil concentrations, the transport may be driven by the concentration difference of uracil with the contribution of the protonmotive force. It is feasible that inhibitors of uracil transport tested exert their inhibition by the dissipation of the driving force rather than by the direct competition with the substrate-binding site.

Biological Transport↗
PubMed1998

Properties of the Ca2+ influx reveal the duality of events underlying the activation by vanadate and fluoride of the Gárdos effect in human red blood cells.

The properties of the 45Ca2+ influx by human red blood cells (RBC) induced by NaVO3 or NaF were compared. The NaVO3-induced 45Ca2+ influx was slower and less extensive than that induced by NaF. Both processes were saturable with Ca2+. Substitution of Na+ by K+ inhibited the 45Ca2+ influx induced by NaVO3 but stimulated that by NaF. The NaVO3-induced Ca2+ influx was sensitive to nifedipine (IC50 = 50 mol/l), Cu2+ (IC50=9 mol/l), DTNB (5,5'-dithiobis-(dinitrobenzoic acid)) (IC50 = 12 mol/l) (maximal inhibition 16%, 18%, and 28%, respectively, if NaF was used as inducer). On the other hand, tetrodotoxin (TTX) and cyclosporin A inhibited only the NaF-induced 45Ca2+ influx (IC50 = 21 mol/l and 28 mol/l, respectively). Pig RBC, known not to display the NaVO3-induced Ca2+ influx, exhibited Ca2+ influx induced by NaF. The results show that NaVO3 activates the Ca2+ influx via a pathway homologous to the L-type Ca2+ channel while the NaF-induced Ca2+ influx is mediated via the TTX-sensitive Na+ channel in the presence of NaF with possible participation of calcineurin or cyclophilin. Thus, the Gardos effect induced by NaVO3 and NaF represents two phenomena activated by different mechanisms present in the cryptic state in the RBC membrane.

Calcium↗
PubMed1997

Ca(2+)-activated K+ channel and the activation of Ca2+ influx in vanadate-treated red blood cells.

The mechanism by which K+ inhibits vanadate-induced 45Ca2+ influx by human red blood cells (RBC) was studied using several independent approaches. The following results were found: 1. The inhibitory effect of K+ was absent when RBC were loaded with a Ca(2+)-chelator. This treatment at the same time inhibited the vanadate-induced K+ efflux, and the membrane hyperpolarization induced by Ca2+ in vanadate-treated cells. 2. The potency of K+, Rb+, and Cs+ to inhibit vanadate-induced Ca2+ influx corresponded to their ability to depolarize the RBC membrane via the Ca(2+)-activated K+ channel (K(Ca)). 3. Inhibition of the vanadate-induced 45Ca2+ influx by a protonophore proceeded in parallel with the inhibition of the vanadate-plus-Ca(2+)-induced membrane hyperpolarization. 4. Valinomycin in part released the inhibition of the vanadate-induced Ca2+ influx by known K(Ca) inhibitors (quinine, oligomycin, 4-aminopyridine) but not by inhibitors of the Ca2+ channel (Cu2+, HS-reagents, organic Ca2+ channel blockers). 5. K+ did not inhibit the vanadate-induced Ca2+ influx in dog RBC which have K(Ca) but no transmembrane K+ gradient. The inhibition of the vanadate-induced Ca2+ influx by external K+ appears to be due to the elimination of the electrical component of the Ca(2+)-motive force imposed by opening of the K(Ca). This implies that the Ca2+ carrier mediating the influx of Ca2+ in the presence of vanadate is of uniport type, and that the activity of K(Ca) may serve as a supporting element for Ca2+ influx.

Aminoquinolines↗
PubMed1997

Vanadate changes Ca2+ influx pathway properties in human red blood cells.

The properties of the basal Ca2+ influx (measured using cells labelled with 45Ca2+) in intact human red blood cells (RBC) were compared with those of 45Ca2+ influx induced by vanadate. The basal Ca2+ influx was not sensitive to inhibitors of vanadate-induced Ca2+ influx such as the HS-reagent p-chloromercuribenzoate and low concentrations of Cu2+, and also the sensitivity to nifedipine was significantly weaker. High K+ known to suppress vanadate-induced 45Ca2+ influx had no effect on the basal Ca2+ influx. Both processes were saturated with Ca2+ but the latter was saturated at higher Ca2+ concentrations (KM(Ca) 2.1 vs. 0.5 mmol/l). These experiments favour the notion that vanadate changes the properties of the inward-directed Ca(2+)-transport pathway in human RBC membrane. Vanadate-induced 45Ca2+ influx was insensitive to pertussis toxin and cholera toxin, and several non-steroidal antiinflammatory agents did not influence it in a consistent manner. Li+ partly inhibited the 45Ca2+ uptake. Vanadate stimulated the incorporation of 32P(in) into PIP2 in human but not in pig RBC which are known to be defective in the phosphoinositide metabolism and in the vanadate-induced 45Ca2+ uptake. These results suggest that the change in the Ca2+ influx pathway properties induced by vanadate may involve changes in the metabolism of phosphoinositides but not of the arachidonate metabolism nor G-protein activation.

Animals↗
PubMed1996

The presence of H+ and Na+ -linked Ca2+ extruding systems in Methanobacterium thermoautotrophicum.

The effects of monovalent cations (Na+, K+ and choline+) and the uncoupler 3,3',4',5-tetrachlorosalicylanilide (TCS) were tested on 45Ca2+ uptake by non-energized cells of Methanobacterium thermoautotrophicum. 45Ca2+ uptake was stimulated by the addition of K+ and (less) by choline+ while Na+ slowed down and even reversed it, thereby mimicking the energization of cells. The uncoupler agent, TCS, suppressed 45Ca2+ uptake in non-energized cells in the presence or absence of Na+ but in cells energized in an atmosphere of CO2+H2 it exerted a stimulating effect. Uncoupled 45Ca2+ efflux was measured in cells pre-loaded with 45Ca2+ by means of the divalent ionophore A23187 following its washing out by buffer containing serum albumin. The efflux was temperature-dependent and was stimulated by external 40Ca2+ and Na+. In the absence of Na+, the uncoupled efflux was completely inhibited by TCS, whereas in the presence of Na+, TCS was without any effect. The results are in agreement with the model in which the Ca2+ influx pathway is represented by a membrane potential-driven uniport whereas Ca2+ efflux is mediated by two transport systems - Na+/Ca2+ and H+/Ca2+ antiporters - whose participation in the total efflux is dependent on the energy of the corresponding gradients of driving ions.

Calcium↗
PubMed1995

The Ca(2+)-dependent activation by fluoride of human red cell membrane sodium permeability: evidence for a chemically activated tetrodotoxin-sensitive Na+ channel.

Fluoride (NaF) (5-15 mM) activated the 22Na+ uptake by human red blood cells (RBC). The effect was Ca(2+)-dependent. Sr2+, but not Ba2+, Mg2+, Mn2+, substituted Ca2+ in supporting the 22Na+ uptake. The NaF-induced 22Na+ uptake was sensitive to tetrodotoxin (TTX), pertussis toxin but not to amiloride nor valinomycin. The value of the influx was 8.6 +/- 5.0 mmol/l cells. Thus, the TTX-sensitive Na(+)-transport system is present in the RBC membrane in an inactive form which could be activated with NaF by a mechanism involving G-protein(s) but not the depolarization.

Calcium↗
PubMed1995

The 45Ca2+ uptake by Trichoderma viride mycelium. Correlation with growth and conidiation.

The properties of Ca2+ uptake by Trichoderma viride were studied using radionuclide 45Ca2+ in conjunction with the study of effects of agents influencing the Ca2+ homeostasis on the 45Ca2+ uptake, vegetative growth and conidiation. Mycelium of T. viride was found to take up 45Ca2+ in time- and temperature-dependent manner. The 45Ca2+ uptake could be distinguished from the 45Ca2+ binding by the insensitivity to washing with EGTA (ethylene glycol-bis(2-amino ethyl ether)-N,N,N',N'-tetraacetic acid)-containing solution. The 45Ca2+ uptake was only slightly suppressed by the treatment used to de-energize cells. Agents known to influence Ca2+ homeostasis in animal and plant cells were also active in perturbing the Ca2+ homeostasis in T. viride. In this respect, the agents tested had dual (stimulatory or inhibitory) effects on the 45Ca2+ uptake. No clear correlation among the perturbation of the 45Ca2+ uptake and the inhibition of growth and conidiation was found for the group of compounds tested. Sr2+ and Mg2+ inhibited 45Ca2+ uptake but did not inhibit growth and conidiation. Co2+, Cd2+ inhibited both 45Ca2+ uptake and growth. Other agents tested (Cu2+, Ni2+, La3+, dihydropyridines), which inhibited growth of T. viride, induced massive 45Ca2+ uptake by its mycelium. Ba2+ and Mn2+ showed a biphasic effect on 45Ca2+ uptake-inhibition at lower, and stimulation at higher concentrations, but they had only a slight inhibitory effect on the growth or conidiation at higher concentrations. The 45Ca2+ uptake was influenced by addition of monovalent cations to a small extent only. Na+ (up to 75 mmol.l-1), less than K+, slightly suppressed the 45Ca2+ uptake leaving both growth and conidiation unaffected. Upon depriving the fungus of Ca2+ by chelation of extracellular Ca2+ (not Mg2+ or divalent trace metals) by EGTA, which interfered with Ca2+ homeostasis, vegetative growth rate, and starvation-induced conidiation were restricted. These results suggest that the sustained Ca2+ influx occurs across the T. viride plasma membrane which may be a target site for the antifungal action of heavy metal ions, and its perturbation may lead to disturbances in physiological processes including growth and conidiation. The properties of the Ca2+ influx in T. viride observed substantially differ from those observed in animal cells.

Biological Transport↗
PubMed1994

GABAA/benzodiazepine receptor alpha 6 subunit mRNA in granule cells of the cerebellar cortex and cochlear nuclei: expression in developing and mutant mice.

The gamma aminobutyric acidA/benzodiazepine (GABAA/BZ) receptor is a multisubunit (alpha, beta, gamma, delta, and rho) ligand-gated chloride channel; there are several variants of the alpha, beta, and gamma subunits, each of which has been localized throughout the central nervous system. A large number of GABAA/BZ subunit variants are expressed within the cerebellar cortex. In previous studies from other laboratories, alpha 6 subunit mRNA has been reported to be present exclusively in cerebellar granule cells. The developmental expression of alpha 6 mRNA in cerebellar and cochlear granule cells is of interest because it has been suggested that each of these cell types is derived from a common precursor pool. The polymerase chain reaction was used to generate a cDNA fragment encoding a portion of the M3-M4 intracellular loop of the alpha 6 subunit of the GABAA/BZ receptor. A [35S] riboprobe, transcribed from this cDNA fragment, was used to examine the expression of the alpha 6 subunit mRNA by in situ hybridization in developing normal mice and in adult mutant mice with known deficits in synaptic circuitry. A strong hybridization signal was observed over the granule cell layers of both the cerebellum and cochlear nuclei in adult mice. The signal over the cochlear nuclei appeared after birth toward the end of postnatal week 1, coinciding with the appearance of labeling in the cerebellar cortex. The intensity of the hybridization signal in both regions increased rapidly until postnatal day 14, after which it increased more gradually, reaching adult levels during postnatal week 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Growth and conidiation of Trichoderma viride are affected by non-steroidal antiinflammatory agents.

Nonsteroid antiinflammatory agents (NSAIA's) (inhibitors of cyclooxygenase and lipoxygenase) of several structural series inhibited growth of Trichoderma viride. The most potent growth inhibitors were indomethacin and its derivative repanidal which inhibited in the range of 0.1 mmol/L. The weakest inhibitors were acetylsalicylic acid and lysine salicylate which exerted only a weak effect at concentrations above 1 mmol/L. The inhibition of growth was accompanied by a stimulation of conidiation in the dark. A light pulse increased the efficiency of these drugs to stimulate the conidiation. Saccharomyces cerevisiae was as sensitive to NSAIA's as T. viride while Botrytis cinerea was less sensitive. The results indicate that arachidonate metabolism may play a role in the growth of fungi and may participate also in the process of conidiation.

Anti-Inflammatory Agents, Non-Steroidal↗