TIP GROWTH OF NEUROSPORA CRASSA IN THE CONDITIONS OF THE RESOURCE DEFICIENCY: IMPAIRMENTS IN THE COHERENCE OF ELONGATION, BRANCHING, AND SEPTATION.

With the aid of intracellular fluorescent probes, peculiarities of elongation, branching, septation, and nucleus morphology have been studied in isolated 400-µm-long apical fragments of Neurospora crassa hyphae growing for several hours without the influx of the nutrient materials from the mycelium. We found that: 1) the diameter and growth rate of newly developing branches decreased as compared to intact mycelium (from 10-20 to 6.5 ± 0.4 µm and from 24 ± 1 to 6.7 ± 0.5 µm/min, respectively), but the initial orientation of growth did not change; 2) the branching rhythm was altered; abnormally long internode distances appeared (up to 1471 µm), and the development of some side-branch buds ceased; 3) the character of the septation remained unchanged, as well as the hyphal segment length (68 ± 2 µm). In hyphae growing for 4.5-5.0 h in isolation from the whole mycelium, the distance between the tip and the first septum was 210 ± 15 µm, which was comparable with the respective value in intact mycelium, whereas the mean distance between the growth tip and the first side branch (492 ±127 µm) and the dispersion of this parameter was considerably higher than in intact mycelium. In branches growing in isolation from the intact mycelium for 1.5-4.5 h, the length of the nucleus- free apical zones near the growth tip (from 5 to 33 µm) and the nucleus morphology were similar to the respective characteristics known for the N. crassa mycelium. The experimental model described here can be used for the investigations of molecular and genetic mechanisms regulating the interactions between intracellular structures involved in the tip growth of N. crassa.

Structural and functional organization of growing tips of Neurospora crassa Hyphae.

Data are presented on a variety of intracellular structures of the vegetative hyphae of the filamentous fungus Neurospora crassa and the involvement of these structures in the tip growth of the hyphae. Current ideas on the molecular and genetic mechanisms of tip growth and regulation of this process are considered. On the basis of comparison of data on behaviors of mitochondria and microtubules and data on the electrical heterogeneity of the hyphal apex, a hypothesis is proposed about a possible supervisory role of the longitudinal electric field in the structural and functional organization of growing tips of the N. crassa hyphae.

[Organization of mitochondria in the growing hyphae of Neurospora crassa].

In vivo fluorescent labeling of mitochondria in Neurospora crassa showed the concentration of filamentous mitochondria within 30 µm of apex in growing hyphae. These mitochondrial assemblies propagated forward with the elongation of hyphae, split and segregated as the growing tip bifurcated and formed de novo when new branches formed farther away from the apex. The efficiency of the mitochondria concentration in the apical 30 µm zone is related to the growth rate and identical in hyphae cultivated in glucose- and sorbitol-containing media. The obtained data are discussed in connection with the behavior of microtubules in growing hyphae as well as with the electric heterogeneity of N. crassa hyphal apex described previously.

[Effect of superficial reflexotherapy (redox-therapy) on the psychophysiological status of athletes].

The objective of this study was to evaluate the influence of superficial reflexotherapy (redox-therapy) on the psychophysiological status of athletes. It was shown to have positive effect on central and peripheral hemodynamics and beneficial action on neurovegetative regulation of the blood circulatory system. These effects depend on the choice of applicators and the duration of therapy. Superficial reflexotherapy can be used alone or in combination with physiotherapy.

[Children's health as a subject to sanitary and hygienic monitoring]. / Zdorov'e detei kak ob"ekt sotsial'no-gigienicheskogo monitoringa.

Sanitary and hygienic monitoring in town near Moscow evaluated health of children living in areas under various ecologic circumstances. The results proved that living near automobile roads and in town's industrial district is associated with considerably lower health state of the children. Increased level of acoustic exposure in the district corresponds to more frequent appeals to medical establishments for cardiovascular care.

Structure, function, regulation: experimental analysis in groups of non-excitable cells coupled via permeable junctions.

This presentation reviews the functional properties of different permeable junctions (microplasmodesmata of filamentous cyanobacteria, septal pores of fungi, and gap junctions of animals). Examples of the distribution of power by ionic fluxes and electric current through permeable cell-cell junctions are considered. Based on the analysis of intercellular communication occurring during apical growth of hyphae of wild-type and mutant lines of the mycelial fungus Neurospora crassa, approaches to studies of the molecular and genetic mechanisms of self-organization in systems of cells with permeable junctions are discussed.

A possible role of cold-induced ionic stress in cold-induced cell death.

Analysis of experimental results and published data within the framework of the suggested mathematical model of ion-osmotic homeostasis revealed the dependence of a variety of cell parameters on temperature. It was shown that the cold-induced drastic increase in the basal concentration of cytoplasmic Ca was determined, on the one hand, by the suppression of transport processes responsible for Ca removal from the cytoplasm, and, on the other hand, by the increase of calcium fluxes, both from the outer medium and from cell organelles. The cold-induced variation in the ratio of permeabilities for Na and K ions was found, which can be due to the activation of different calcium- and potential-dependent channels or by formation of membrane defects. Besides the flow of calcium ions through appropriate selective channels, its delivery into the cytosol through membrane defects actively induced by cell cooling can not be excluded. Formation of nonselective transmembrane channels was promoted by lipid peroxidation and proteolysis induced by an increase in the basal concentration of calcium. The new approaches to protecting the cell from cold injury are discussed.

Analysis of electrical phenomena accompanying the growth of Neurospora crassa hyphae: theory and experiment.

To describe electrical phenomena observed in growth of Neurospora crassa hyphae, a theoretical model was developed considering the hypha as a one-dimensional electric cable with non-uniform longitudinal distribution of current sources reflecting the activity of proton pumps. A profile of the density of the pump current along the hypha is proposed, at which the results of simulation quantitatively coincide with the results of physiological experiments. The model values of energy coupling in the growth zones were estimated. The experimental dependence of the elongation rate of regenerating apical hypha fragments on their lengths was determined. Based on the comparison of these experimental results with the results of analysis of the model, the contribution of the axial metabolite transport, from the distal parts of the hypha to the apical part, to the dynamics of the apical cell growth was estimated. The possibility of evaluating the intensity of high-molecular-weight syntheses and/or accumulation of substances in granules was demonstrated. The growth rate of the regenerating hypha fragments was shown to correlate with the electric current flowing into the apical fragment 0.2-mm in length.

[Populations of higher plants found in the area of influence of the Semipalatinsk proving grounds]. / Izuchenie populiatsii vysshikh rastenii, nakhodiashchikhsia v zone vliianiia Semipalatinskogo poligona.

Population of Scotch pine and crested wheat grass growing on the territories of Semipalatinsk testing ground and contaminated during the traits of nuclear weapon, and in the control region differ by a number of genetic and cytogenetic trials. Besides, it is evident that the investigation of the nature of genetic anomalies and their association with radiation factors in the problem more complicated than merely to recognize the fact of their availability. This calls for further investigations.

Energetic cooperation via ion-permeable junctions in mixed animal cell cultures.

Low ouabain concentration (1 x 10(-6) M) is shown to decrease intracellular K+ (K+in) and to increase intracellular Na+ (Na+in) in human fibroblast cell cultures. The same ouabain concentration was without effect upon K+in ad Na+in in rodent cultures such as BHK-21, mouse fibroblasts and rat glyoma C6 cells. K+in and Na+in in the mixed cultures of human and BHK-21 fibroblasts or human and mouse fibroblasts were found to be resistant to 1 x 10(-6) M ouabain whereas that of the mixtures of human and rat glyoma C6 cells proved to be ouabain-sensitive. The gap-junction-mediated dye transfer was revealed between human and BHK-21 cells. Such an effect was very small in the human-C6 cell mixed culture. It is concluded that cells with active ion pumps can support the maintenance of K+ and Na+ gradients in cells with inactive pumps, provided that effective ion transport via gap junctions takes place.

Competition of contacting heterotypic epithelial sheets for the territory in culture.

Co-cultured epithelial cells of various lines formed mixed cohesive sheets. Contact interactions of different cells in the sheets were studied by phase contrast and interference reflection microscopy, time-lapse microcinematography, transmission and scanning electron microscopy. It was found that heterotypic cells in the combined sheets were locked together by the complexes of specialized contacts and were metabolically coupled, as shown by the dye transfer. At the same time heterotypic cells continued to extend pseudopods at the contacting lateral surfaces and to attach these pseudopodies to substratum. Due to competition of pseudopod attachments one group of cells in the sheet often progressively pushed another group from the substratum. This competition of cells for substratum may provide an important mechanism for morphogenetic reorganisation of epithelial sheets and of other groups of interacting cells in vivo.

Energy transfer via cell-to-cell junctions. Ouabain-resistant cells maintain a membrane potential in ouabain-sensitive cells.

Animal cell cooperation has been studied in a mixed cell culture. Membrane potentials of human embryonic cells and hamster BHK-21 cells were recorded by intracellular microelectrodes. The Na+/K(+)-ATPase inhibitor ouabain (1 x 10(-6) M; 2 h) caused strong depolarisation of the human cells in pure culture. The same treatment reduced only slightly the membrane potential in the hamster cells in pure or mixed cultures, as well as in the human cells in mixed culture. The above data can be explained by effective ion fluxes through heterotypic gap junctions in mixed culture. Thus, in the presence of ouabain the Na+/K(+)-ATPase of hamster cells creates transmembrane differences of the electrochemical potential of ions not only in the hamster cells, but in the human cells as well.

Transcellular ionic currents studied by intracellular potential recordings in Neurospora crassa hyphae. Transfer of energy from proximal to apical cells.

Membrane potentials, input resistances, and electric coupling in the apical parts of N. crassa growing hyphae were recorded with the aid of intracellular microelectrodes. It was revealed that the apical cells were always depolarized by 10 to 30 mV as compared to the adjacent proximal cells. The septal pore maintained an electrical resistance of 4 to 6 M omega. The calculated values of the endogenous electrical current passing through the septal pore varied between 0.5 and 1 nA. Electrical isolation of the apical cells resulted in their depolarization from 120-150 mV to 40-60 mV, characteristics of the membrane potential value of N. crassa adult hyphae with completely blocked electrogenic pumps. A simultaneous increase in the input resistance value from 15-20 M omega to 40-80 M omega was observed. The above data can be explained assuming that H+-ATPase activity was greatly lowered in the apical cells. Thus in the intact hyphae with electrically coupled cells energy is transferred from the proximal hyphal compartments to the apical ones.