Formation of band-type electric patterns in Characean cells

It is observed by experiments that band patterns of alternating acid and alkaline zones are formed on the surface of Characean cells under illumination. In order to understand theoretically such pattern formation, we employ a reaction-diffusion equation model with activator-inhibitor interaction. We study the existence problem of band patterns and hysteresis phenomena such as patterns appearing and disappearing with changing light intensity by using singular perturbation methods.     

Electric inhomogeneity in membranes of Characean internode influenced by light/dark transition, O2, N2, CO2-free air and extracellular pH

The electric membrane potential as functions of position and time of Characean internode has been studied using a modified water-film electrode technique. Between the low-conductance hyperpolarized region (called the H-region or acidic region) and the high-conductance depolarized region (D-region), there is a difference in the direction of responses to light-off and -on stimulations. In darkness the membrane potential becomes hyperpolarized in the D-region, whereas it is depolarized in the H-region at the steady state. The potential difference between D- and H-regions, delta Vm, is increased by exposure to pure O2, N2, or CO2-free air. When the amount of water surrounding the internode is limited, the formation of an electric pattern occurs rapidly. In contrast, the recovery is delayed. The membrane potential of the D-region is sometimes hyperpolarized significantly with lowering of the extracellular pH to 7.5, while the potential of the H-region is slightly depolarized. This seems to be an all-or-none type response. However, the electric profile is always homogenized with the pH of 6.8. Thus, the pH around 7.5 may be a threshold level to open/close putative OH- (or H+) channels of the D-region.     

Inhibition of Electrogenesis by Aluminum in Characean Cells

The effects of aluminum (AI) on electrogenesis at the plasmamembrane were examined in internodal cells of Chara corallina.After treating cells with 0.1 mM A1C1₃ (pH 4.5), we measuredboth the membrane potential and the membrane resistance in artificialpond water (pH 5.6). Electrogenesis at the membrane was significantlyinhibited by the treatment with A1C1₃ A decrease in the pumpcurrent of the electrogenic proton pump and/or a decrease inthe electrical resistance (an increase in conductance) of thepassive diffusion channel were considered to be responsiblefor the inhibition of electrogenesis. CaCI₃ had a partial amelioratingeffect. Both malic acid and citric acid were very effectivein reversing the effects of A1C1₃. In addition, these organicacids restored electrogenesis in cells that had been treatedwith A1CI₃. It is suggested that Al affects electrogenesis fromthe exterior of the membrane, at least during the initial stagesof treatment (4-24 h). ¹Present Address: Graduate School of Agriculture, Kyoto University,Sakyo-ku, Kyoto, 606-01 Japan     

A model of evolutionary appearance of dissipative structure in ecosystems

The interrelation between autonomous oscillations in local systems and stable dissipative structures in spatially distributed systems is analyzed. Darwinian evolution in populations comprising the ecosystem is shown to be able to cause the qualitative rearrangements of dynamic modes and smooth appearance of oscillations in local systems. The same evolutionary mechanisms analyzed within bilocal systems, may lead to appearance of dissipative structures (both smooth and sharp).     

The metrical structure of aging (dissipative) systems

A quantification of the aging of a system is achieved by establishing a metric algebra based upon the dissipation function associated with the system. The phenomenological coefficient, L_ij, of irreversible thermodynamics is shown to be a dynamical analogue of the metric tensor, g_ij, of geometry. Given this metric for aging systems, it then becomes possible to compare the aging of two similar systems exposed to different environmental forces and to use the concept of age-preserving transformations to determine under what conditions two different systems will age at the same rate.     

Immunotherapy of cervical cancer as a biological dissipative structure

Cervical cancer can be not only prevented, but also effectively treated. Decreased efficiency of biochemical, neurohormonal and/or immunological mechanisms leads to infectious states which, irrespective of their bacterial, viral or parasitic aetiology, are only the necessary, but not the sufficient causes of neogenesis. The cause of cancer is the natural and common phenomenon of the self-organization of systems, endangered by ending of their existence, into more efficient time-space structures at the expense of their surrounding. Infected cells or infectiously changed tissues in their final phase of existence are often recognized as a precancerous state, but their genome does not differ from other organism cells, and that is why the carcinogenesis can still be prevented by direct fighting of pathogenic microorganisms, and indirectly by strengthening the body by neurohormonal therapy or vaccine immunopotentialization. Primary prophylaxis of neoplasms requires that not only the dissipathogenic state of cells be prevented, but also their tissue surrounding be normalized to head off the risk of the self-organization of neoplastic forms of life, differing in their genetic identity from the surrounding cells. Lactovaginal immunopotentialization complements the conservative and operative methods of oncological treatment, as well as has prophylactic application in women with the history of miscarriages, premature deliveries, lack of or significantly shortened lactation, neurohormonal menstruating disorders, chronic and recurrent inflammations of the reproductive organs, long-term hormonal contraception and hormone replacement therapy during menopause, or only deficiency of Lactobacillus vaginalis, as indicators of risk of cervical cancer.     

Studies on Mechanoperception in Characean Cells: Pharmacological Analysis

The mechanisms for generating receptor potentials and actionpotentials upon mechanical stimulation were studied in internodalcells of Chara. Receptor potentials and the subsequent actionpotentials could be generated even when the electrogenic protonpump was inhibited, indicating that the proton pump does notplay a central role in generating receptor potentials and actionpotentials. The involvement of Ca²⁺ and/or Cl^– channelsin both receptor and action potentials was suggested, basedon the equilibrium potentials of these ions across the plasmamembrane. Inhibitors of the Ca²⁺ channel, Cl^– channeland stretch-activated channel could not inhibit generation ofthe receptor potential. These findings suggested that the channelsinvolved in generating the receptor potential are insensitiveto these channel inhibitors, although all inhibitors significantlyinhibited the action potential. (Received July 26, 1996; Accepted November 19, 1996)     

Sulphate Influx in Characean Cells: I. GENERAL CHARACTERISTICS

There is a significant sulphate influx in Chara australis, Nitellatranslucens, and Tolypella intricata but not in Nitellopsisobtusa. The uptake is active in Chara, the ions moving intothe vacuole against an electrochemical potential gradient. Influxrate in the light remains constant whereas a transient increasein rate occurs upon transfer to the dark. Both the light andthe dark influx rate respond similarly to temperature, and toexternal sulphate ion concentration. It is proposed that sulphateis pumped actively across the plasmalemma and that the increasein influx rate following transfer to the dark reflects a transientincrease in the rate at which the pump operates. There is anapparent light stimulation of the tonoplast flux.     

Methodological aspects of pressure loading of Fura-2 into Characean cells

Four different fura-2 compounds were tested for the applicationin Characean cells (fura-AM; fura-C₁₈; fura- K₅; fura-dextran;MW = 10 kDa). It is demonstrated that Characean cells imposespecial problems when cytosolic pCa has to be measured withfluorescent ratio dyes. Fluorescence (_ex=340 nm) from the dyewhich had diffused from the cytosol to the huge central vacuolewith milimolar Ca²⁺ concentrations overrides the signal fromthe cytosol and makes Ca²⁺ -quantification difficult. This canbe avoided by pressure injection of fura-dextran. Because ofinhomogeneities in dye concentration or in thickness of thecytoplasmic layer, cytoplasmic streaming causes high noise orpretend oscillations in pCa if data are obtained by subsequentimage grabbing. In addition, vesicles filled with high 'concentrationsof dye may sometimes be expelled into the vacuole during theloading procedure enhance this effect. These sources of inhomogeneitiescan be minimized by loading fura-dextran via the neighbouringcell. The slow loading procedure through the plasmodesmata takes1–10 h. It results in a more homogeneous distributionof the dye. The operation of the new method is illustrated bythe measurement of Ca²⁺ -transients during action potentials,the temperature dependence of the fluorescence signal in vivoand in vitro and the butyrate-induced elevation of [Ca²⁺]_c.Fura-AM was found not to be well suited for use in algal cells.Fura-C₁₈ has toxic effects and induces clotting of the cytoplasm.In addition, some aspects of the properties of dextran-derivatesare discussed. Key words: Manual pressure microinjection, fura-2, characean cells, fluorescence ratio imaging, temperature dependence     

Roles of electric field and fiber structure in cardiac electric stimulation.

This study investigated roles of the variation of extracellular voltage gradient (VG) over space and cardiac fibers in production of transmembrane voltage changes (DeltaV(m)) during shocks. Eleven isolated rabbit hearts were arterially perfused with solution containing V(m)-sensitive fluorescent dye (di-4-ANEPPS). The epicardium received shocks from symmetrical or asymmetrical electrodes to produce nominally uniform or nonuniform VGs. Extracellular electric field and DeltaV(m) produced by shocks in the absolute refractory period were measured with electrodes and a laser scanner and were simulated with a bidomain computer model that incorporated the anterior left ventricular epicardial fiber field. Measurements and simulations showed that fibers distorted extracellular voltages and influenced the DeltaV(m). For both uniform and nonuniform shocks, DeltaV(m) depended primarily on second spatial derivatives of extracellular voltages, whereas the VGs played a smaller role. Thus, 1) fiber structure influences the extracellular electric field and the distribution of DeltaV(m); 2) the DeltaV(m) depend on second spatial derivatives of extracellular voltage.     

Light inhibition of internode elongation in green plants

The clongation of the first internode of fully greenVigna sinensis L. is inhibited by white light (W). This inhibition is fluence-rate dependent between 0 and 70 Wm^–2. The kinetics of elongation rate in the light after darkness were investigated with linear displacement transducers. The internode elongation rate does not exhibit any endogenous rhythm. A rapid inhibition occurs during the first 2 or 3 h after the onset of light, and a second type of inhibition (slow reaction) increases from the beginning to the 8th hour of light. The rapid inhibition is not fluence-rate dependent between 20 and 70 Wm^–2, but the slow reaction is. There is no rapid inhibition in a low fluence rate white light to high fluence rate white light transition, only the slow reaction is observed. The responses to different wavebands, i.e., blue light (B), yellow and green light (YG), and red light (R), are the same for the two inhibition reactions. Each waveband used separately does not reproduce the full effect observed in W. Results show a stimulation with B, a greater inhibition activity with YG than with R, and a synergistic action of B and R which when given together lead to an inhibition similar to that obtained in W. Plants returned from the light to darkness progressively recover a high elongation rate without any latent period. The W light regulating internode elongation rate is mainly perceived by the growing internode itself.Abbreviations B blue light - D darkness - F far-red light - HW high fluence rate white light - LW low fluence rate white light - R red light - W white light - YG yellow and green light     

Role of polyamines in gibberellin-induced internode growth in peas

To determine the requirement for polyamines in gibberellin (GA) induced internode growth polyamine content was measured in internodes of peas of various internode phenotypes (slender, tall, dwarf, nana) with and without applied gibberellin (GA₃) and polyamine synthesis inhibitors. Polyamines were assayed as dansyl derivatives which were separated by reverse phase high performance liquid chromatography and detected by fluorescence spectrophotometry. The amounts of polyamines in the different genetic lines of peas, which differed in internode lengths and extractable GA content, correlated with the extent of internode elongation. High polyamine concentrations were associated with young internodes and decreased with internode expansion. Extremely short internodes of nana plants without GA exhibited equal or higher amine concentrations relative to internodes of other lines of peas and GA-stimulated nana seedlings. The polyamine synthesis inhibitors, α-difluoromethylornithine and α-difluoromethylarginine, independently or in combination, inhibited polyamine accumulation and internode elongation of tall peas and GA-stimulated nana plants. Agmatine and putrescine restored growth and endogenous polyamine content to variable degrees. However, exogenous polyamines were not effective in promoting growth unless intracellular amines were partially depleted.

These results suggest that polyamines do not have a role in cell elongation, but may be required to support cell proliferation. Polyamines do not mediate the entire action of GA in internode growth of peas since GA induction of growth involves both cell division and cell elongation, whereas polyamines appear to affect cell division only.

     

Inheritance of internode and culm length in hexaploid Triticale

Summary A diallel cross of twelve cultivars of hexaploid Triticale was made in order to study genie action types for total culm length and for the length of its different segments. Culm length, and four partial lengths of the culm were studied in the F₁ and F₂ generations. The analysis was made according to the Griffing, Hayman and Jinks models. Heterosis in culm length is mainly due to its upper half. Spanish cultivars have, in general, positive GCA and transmit greater height in crosses, whereas the Mexican ones show a negative GCA effect and have a tendency to decrease in height when crossed. Additivity greatly influences the inheritance of culm length, this influence being lower at the first plant internodes. The environmental component has also a large influence in the phenotypic expression of Triticale height. Dominance is only partial for the five traits studied. The predominant kind of interaction seems to be of the duplicate type. All correlations between culm length and its components are high and positive, especially the genetic ones.     

The Use of Membrane Electrical Noise in the Study of Characean Electrophysiology

The technique of examining membrane properties through the useof endogenous electrical noise is applied to the study of Characeanelectrophysiology. The frequency band between 0·1 and1·0 Hz is particularly sensitive to the metabolic stateof the cell. It is concluded that measurements of the powerspectral density function and the low frequency excess noisewill prove a useful adjunct to the normal measurements of restingpotential and membrane resistivity.     

Oscillations of membrane potential during inhibition of cytoplasmic streaming in Characean internodes

Oscillatory changes in electrical parameters of cells of Nitellopsis obtusa (Desv. in Lois) J. Gr. and Nitella flexilis f. Atkahensis R. D. W., particularly in the membrane potential, were investigated with external Ag/AgCl electrodes. Three main types of oscillations were observed. The measurements were carried out on 30 cells with the application of an inhibitor of cytoplasmic streaming (procaine) and revealed that there was no direct correlation between cytoplasmic streaming and oscillations in the membrane potential.     

Temporal Relationship between Action Potential and Ca2+ Transient in Characean Cells

Temporal relationship between the action potential and the changein cytosolic Ca²⁺ concentration was investigated in cells offour species of Characeae, Chara corallina, Nitellopsis obtusa,Nitella flexilis and Nitella axilliformis. The Ca²⁺ transientwas detected by light emission from Ca²⁺-sensitive photoproteinaequorin injected into the cytoplasm. Action potential was triggeredby an outward or sometimes inward electric current pulse of20–50 ms in most cases. In all species the action potentialstarted at almost the same time as the time at which the lightemission from aequorin began to increase. Also the peak of actionpotential almost coincided with that of light emission, whichis in contrast with the slower Ca²⁺ transient in Chara reportedby Thiel et al. [(1997) J. Exp. Bot. 48: 609]. A discussionwas made on the origin of Ca²⁺ transient and the ionic processesduring membrane excitation. (Received July 2, 1998; Accepted October 5, 1998)     

Analogue Inhibition of the Active HCO-3 Transport Site in the Characean Plasma Membrane

Competitive inhibition of the HCO^–₃ transport site, atthe plasmalemma of Chara coraUina, by the CO^2–₃ ion isdemonstrated. This CO^2–₃ inhibition was used to demonstratethat HCO^–₃ ions enter the cell by facilitated ‘diffusion’when the HCO^–₃ transport system has been inactivated bytreatment with 10 mM K⁺. Use of CO^2–₃ as a HCO^–₃analogue is limited, however, because of the necessity to employsolutions of high pH. Inhibition was not observed in the presenceof a range of organic and inorganic acid anions. These resultsdemonstrate the stereo-specific nature of the HCO^–₃ bindingsite. A variety of amino compounds were found to inhibit H¹⁴CO^–₃influx. Inhibition appeared to be competitive, being completelyrelieved at higher substrate (HCO^–₃) concentrations. Asimple correlation was not found between the degree of inhibitionand the concentration of neutral base. A combination of thepresence of neutral base and experimental pH values of at least8·0 was required to produce the reactive species thatinhibited HCO^–₃ transport. This species is consideredto be the amino carbamate. These results are discussed withrespect to further HCO^–₃ analogue experiments.     

Light-Induced Membrane Hyperpolarization and Adenine Nucleotide Levels in Perfused Characean Cells

This study examines the relationship between light-induced membranehyperpolarization and changes in adenine nucleotide levels intonoplast-free characean cells. When cells were perfused witha medium containing 1 mM ATP in the dark, the plasma membranedepolarized, the cytosolic ATP level decreased, and the ADPand AMP levels increased. Under light, the membrane hyperpolarized,the ATP level increased, and the ADP and AMP levels decreased.These changes in the adenine-nucleotide levels could partiallyexplain the membrane hyperpolarization. When cells were perfusedwith a medium containing an ATP-regenerating system consistingof phosphoenolpyruvate and pyruvate kinase, the membrane potentialremained in the hyperpolarized state, the ATP level remainedat a high level and no light-induced hyperpolarization was observed.The intracellular adenine nucleotide levels were also controlledby continuous perfusion. The membrane potential was determinedonly by the adenine nucleotide levels of perfusion media, irrespectiveof the light condition. Chloroplast-free Nitellopsis cells into which isolated Pisumchloroplasts were introduced also showed light-induced membranehyperpolarization. Pretreatment of chloroplasts with dicyclohexylcarbodiimide(DCCD) completely abolished the hyperpolarization with parallelinhibition of photophosphorylation. These results strongly suggestthat changes in adenine nucleotide levels caused by photophosphorylationare responsible for light-induced membrane hyperpolarizationin perfused cells. (Received August 17, 1985; Accepted December 13, 1985)