Biomedical subjects

M Simkovic

Publications and source records attributed to M Simkovic.

7 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

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

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↗

PubMed1993

[The theoretical basis of "process-oriented psychotherapy"].

Process-oriented psychotherapy /POP/ is an eclectic trend. It is based on Jungian psychology but is inspired also by some dynamic schools and oriental philosophy, in particular Taoism. The essence of the psychotherapeutic method is work with signals in the communication channels. By their reinforcement the personality attains contact with the secondary process behind the borderline of identity. In addition to psychopathological indications it uses somatic symptoms and diseases which are considered a purposeful message of the dream body.

Humans↗