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  • 1
    Electronic Resource
    Electronic Resource
    TEMPERATURE-DEPENDENT INOTROPIC EFFECTS OF LIGNOCAINE AND ETHANOL ON RAT HEART PAPILLARY MUSCLES (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 25 (1998), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The main objective of the present study was to investigate the temperature dependence of the cardiac inotropic effects of lignocaine and ethanol (EtOH). 2. We studied the in vitro inotropic actions and interactions of EtOH (2.4 g/L) and lignocaine (25 mg/L) on rat papillary muscles superfused with Tyrode's solution and stimulated at 1 Hz at either 37 or 30°C. Peak tension developed (PTD), maximum velocity of development of tension (VmaxT) and time to peak tension (TPT) were measured. 3. At 37°C, EtOH depressed PTD, while VmaxT and TPT remained unchanged. At 37°C, lignocaine alone or in combination with EtOH depressed all three parameters. 4. At 30°C, EtOH did not modify PTD or VmaxT, whereas TPT decreased. At 30°C, lignocaine decreased TPT, but VmaxT did not change and the effect of lignocaine on PTD was smaller at 30°C than at 37°C. Ethanol and lignocaine in combination decreased all three parameters at 30°C. However, the depression of VmaxT by the combination of lignocaine and EtOH was less at 30°C than at 37°C. 5. Hypothermia (30°C) protected the myocardium against the depressant actions of EtOH and lignocaine, alone or in combination. With EtOH alone, the protection resulted in no change in PTD. When lignocaine was involved, the protection resulted in a weaker action on PTD and VmaxT. The temperature dependence of the action of lignocaine may explain, at least in part, the development of ventricular failure in cardiac surgical patients exposed to lignocaine during hypothermia and rewarming.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1998.tb02343.x
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  • 2
    Electronic Resource
    Electronic Resource
    Adaptability of tomato and pepper leaves to changes in photoperiod: Effects on the composition and function of the thylakoid membrane (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 94 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The adaptability of the thylakoid membrane to extended photoperiod (from natural to 24 h) was studied using a photoperiod-sensitive species (Lycopersicon esculentum Mill. cv. Trend) and a non-photoperiod-sensitive species (Capsicum annuum L. cv. Delphin). Our results have shown that thylakoid membranes of both species adapt to an extended photoperiod by increasing their photosystem II to photosystem I ratio (PSII/PSI) in order to provide a more balanced energy distribution between both photosystems to improve quantum yield. In tomato plants, these results correspond with a lower chlorophyll (Chl) a/b ratio, a decrease in Chl associated with PSI light-harvesting chlorophyll a/b protein complexes and with an increase in Chl associated with PSII light-harvesting chlorophyll a/b protein complexes. In spite of these changes, the electron transport capacity through PSII and PSI per unit of Chl and the light saturation point of PSII remained unchanged. The inability of tomato plants to use supplemental light for an extended photoperiod is not the result of photoinhibitory conditions. In pepper plants a significant increase in electron transport capacity and in the light saturation point of PSII was found. There was a significant increase in CO2 assimilation when the light period was increased from 12 to 24 h. In contrast to tomato, pepper plants adapt to a 24-h photoperiod by increasing their carboxylation capacity which is accompanied by an increase in electron transport capacity and the light saturation point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00986.x
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  • 3
    Electronic Resource
    Electronic Resource
    The efficiency of electron transfer from QA − to the donor side of Photosystem II decreases during induction of photosynthesis: Evidences from chlorophyll fluorescence and photoacoustic techniques (1996)
    Springer
    Photosynthesis research 47 (1996), S. 13-20 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence ; photoacoustics ; Photosystems I and II ; photosynthetic induction ; reaction centers (active, inactive) ; quinone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The amplitudes ratio of the fast and slow phases (Afast/Aslow) in the kinetics of the dark relaxation of variable chlorophyll fluorescence (FV) was studied after various periods of illumination of dark-adapted primary barley leaves. Simultaneously, photosynthetic activity was monitored using the photoacoustic technique and the photochemical and non-photochemical fluorescence quenching parameters. The ratio Afast/Aslow changed with the preceding illumination time in a two-step manner. During the first stage of photosynthetic induction (0–20 s of illumination), characterized by a drop in O2-dependent photoacoustic signal following an initial spike and by a relatively stable small value of photochemical FV quenching, the ratio Afast/Aslow remained practically unaltered. During the second stage (20–60 s of illumination), when both the rate of O2 evolution and the photochemical FV quenching were found to be sharply developed, a marked increase in the above ratio was also observed. A linear correlation was found between the value of the photochemical quenching and the ratio Afast/Aslow during the second phase of photosynthetic induction. It is concluded that the slow phase appearing in the kinetics of FV dark relaxation is not due to the existence of Photosystem II reaction centres lacking the ability to reduce P700+ with high rates, but is instead related to the limitation of electron release from Photosystem I during the initial stage of the induction period of photosynthesis. This limitation keeps the intersystem electron carriers in the reduced state and thus increases the probability of back electron transfer from QA − to the donor side of Photosystem II.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00017749
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  • 4
    Electronic Resource
    Electronic Resource
    Hg2+, Cu2+, and Pb2+ -induced changes in Photosystem II photochemical yield and energy storage in isolated thylakoid membranes: A study using simultaneous fluorescence and photoacoustic measurements (1999)
    Springer
    Photosynthesis research 59 (1999), S. 167-174 
    Details
    ISSN: 1573-5079
    Keywords: cyclic electron transport ; fluorescence ; metal ions ; Photosystem II ; thermal dissipation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Simultaneous fluorescence and photoacoustic measurements have been used to study the effects of metal ions (copper, lead, and mercury) during dark incubation of thylakoid membranes. The values of the chlorophyll fluorescence parameters Fo (initial fluorescence yield with the reaction centers in the open state), Fm (maximal fluorescence yield), Ft (steady state fluorescence yield) and the calculated parameters, Φo (maximal quantum yield of Photosystem II photochemistry) and Φt (actual quantum yield of Photosystem II photochemistry), strongly decreased in the presence of the metal ions coinciding with an increase in the non-photochemical deexcitation rate constant k(N). It was observed that photosynthetic energy storage measured by photoacoustic spectroscopy also decreased but a large portion of energy storage remained unaffected even at the highest metal ion concentrations used. A maximal inhibition of photosyntheti c energy storage of 80% and 50% was obtained with Hg2+ and Cu2+-treated thylakoids, respectively, while energy storage was insensitive to Pb2+. The results are consistent with the known predominant inhibition of the donor side of Photosystem II by the metal ions. The insensitive portion of energy storage is attributed to the possible recurrence of cyclic electron transport around Photosystem II that would depend on the extent of inhibition produced on the acceptor side by the metal ion used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006194621553
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  • 5
    Electronic Resource
    Electronic Resource
    Potential for use of a cyanobacterium Synechocystis sp. immobilized in poly(vinylalcohol): Application to the detection of pollutants (1999)
    Springer
    Biotechnology techniques 13 (1999), S. 559-562 
    Details
    ISSN: 1573-6784
    Keywords: cyanobacterium ; immobilization ; photoelectrochemical cell ; poly(vinylalcohol) ; pollutant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A cyanobacterium, Synechocystis sp. PCC 6803, was immobilized by entrapment in poly(vinylalcohol) bearing styrylpyridinium groups. Its properties in a single-compartment micro-photoelectrochemical cell using platinum electrodes in potentiosatic mode were compared with the native material. The operational activity was measured in the presence of an electrolytic solution containing 20 mM sodium phosphate, 0.15 mM NaCl and 1 mM MgCl2. The best conditions of use are pH 7.0, 38 °C and a 2,5-dichlorobenzoquinone concentration equal to 350 μM with native cyanobacteria or pH 6.5, 25 °C and 500 μM 2,5-dichlorobenzoquinone after entrapment. Using this procedure, the photocurrent could be inhibited by pollutants such as Diuron or HgCl2. After entrapment, the detection limits (corresponding to a 10% inhibition) were respectively 0.5 μM and 50 μM for Diuron and HgCl2 after five minutes of incubation. A permeabilization technique was used to increase sensitivity of the procedure to the detection of HgCl2 (25% inhibition with 50 μM after five minutes of incubation).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008991531206
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