Biodiversity and ecology of epilithic diatoms in the Agnéby River,Ivory Coast

The ecology and taxonomy of the epilithic diatom flora of the Agnéby River, Ivory Coast were studied in 2012. Ten sites were investigated and diatoms were sampled on glass slides immersed for a period of 30 days during the wet and dry seasons. Physico-chemical parameters were measured at each site while sampling diatoms. Five taxa were largely dominant: Planothidium comperei CE Wetzel, N’Guessan and Tison-Rosebery, Eolimna minima (Grunow) Lange-Bertalot, Planothidium piaficum (JR Carter and Denny) CE Wetzel and Ector, Cocconeis schroederi Foged and Cocconeis scutellum var. parva (Grunow in Van Heurck) Cleve. Electrical conductivity, temperature, dissolved oxygen, nitrite and phosphorus were found to influence the distribution of taxa.     

Absence of harmful effects of protracted negative air ionisation

The absence of harmful effects of protracted negative air ionisation was studied in 5 weather-sensitive women and 5 normal men chosen at random. Negative ions were generated by the Modulion of Amcor-Amron (Herzliya, Israel). The patients were exposed separately during 8 sleeping hours and 8 working hours to the apparatus at 1–2 m distance in a 4 × 4 m room, for 2 months. Thus they were exposed to a daily uptake of 1 × 10⁴ negative ions/cm³ for 16 h/day during 2 months. Urinary 17-KS, 17-OH, adrenaline and noradrenaline excretion was not affected by the negative ionisation. However serotonin, 5-HIAA, histamine and thyroxine excretion — if increased before — diminished by 50% on an average. There were no changes in body weight, blood pressure, pulse, respiratory rate, oral morning temperature, dynamometer grip strength, routine liver function tests, urinary pH, albumen, glucose, ketones, bilirubin, or occult blood, red and white blood count and ECG records. The EEG revealed the typical changes due to negative air ionisation: stabilising of frequency, increased amplitudes, spreading of brainwaves from the perceptive occipital area to the conceptive frontal area and synchronisation of both hemisphere tracings.     

Cooperativity in mechano-calcium feedbacks in the myocardium: Some conceptual discrepancies and overcoming inconsistency within the framework of a mathematical model

Mechano-calcium feedbacks that provide fine tuning of electrical and calcium activation of the heart muscle to mechanical conditions of contractions are an important element of electromechanical coupling as a key mechanism of the autoregulation of the contractile activity of the myocardium. A large quantity of experimental and theoretical evidence supports the cooperative dependence of the calcium-troponin complex kinetics on the cross-bridge concentration as a principal mechanism that underlies the mechano-calcium feedback in the intact myocardium. At the same time, experiments performed using skinned myocardial preparations have demonstrated that mechanical conditions significantly affected only the calcium sensitivity of the Ca²⁺–force relationship rather than its Hill coefficient of cooperativity. These data make some investigators doubt the contribution of cooperativity to the mechano-calcium feedbacks. To overcome these arising discrepancies, we propose an improved conception of cooperativity that reveals the extent of intensity differently in the steady state and in transitional processes. The proposed conception enables us to reproduce and explain both the mechanodependence of calcium activation in the intact myocardium and the results with skinned muscle within the framework of a mathematical model.     

Contribution of mechanical factors to arrhythmogenesis in calcium overloaded cardiomyocytes: model predictions and experiments

It is well-known that Ca²⁺ overload in cardiomyocytes may underlie arrhythmias. However, the possible contribution of mechanical factors to rhythm disturbances in Ca²⁺ overloaded myocytes has not been sufficiently investigated. We used a mathematical model of the electrical and mechanical activity of cardiomyocytes to reveal an essential role of the mechanisms of cardiac mechano-electric feedback in arrhythmogenesis in Ca²⁺ overloaded myocardium. In the model, the following mechanical factors increased Ca²⁺ overload in contracting cardiomyocytes and promoted rhythm disturbances: i) a decrease in the mechanical load for afterloaded contractions; and ii) a decrease in the initial length of sarcomeres for isometric twitches. In exact accordance with the model predictions, in experiments on papillary muscles from the right ventricle of guinea pigs with Ca²⁺ overloaded cardiomyocytes (using 0.5-1 μM of ouabain), we found that emergence of rhythm disturbances and extrasystoles depends on the mechanical conditions of muscle contraction.