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  • Author: Jozef Kováčik x
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Antioxidative Responses of Microalgae to Heavy Metals

Abstract

Microalgae are unicellular free living entities and therefore their responses to excess of heavy metals must be faster and more efficient than those in vascular plants protected by various types of tissues. Up to date, numerous studies reported metal bioaccumulation potential of algae but metabolic responses have relatively rarely been monitored. Here I provide basic overview of quantitative changes of ascorbic acid (AA), reduced glutathione (GSH), phytochelatins (PCs) and selected related enzymes (ascorbate peroxidase and glutathione reductase) in some common microalgae exposed to various metals (cadmium mainly). Despite various culture and exposure conditions, some common signs of metal toxicity (including e.g. enhancement of phytochelatin biosynthesis) are clearly identifiable in algae. Other metal chelators such as organic acids are also briefly mentioned. Comparison with macroalgae, mosses and vascular plants is discussed in terms of basal values and evolutionary similarities.

Open access
Controlled Switching of the T402 Transformer in the Križovany 400kV Substation

Controlled Switching of the T402 Transformer in the Križovany 400kV Substation

The paper deals with simulating the circumstances of switching surge and trigger current at switching-in of the T402 autotransformer recently installed in Križovany, with the tests conducted by means of ATP (Alternative Transient Program) simulation software for simulating transient electromagnetic phenomena. The target has been to determine temporal curves for the most critical surge instances against earth and between the phases and the curves for trigger current with and without surge limiters connected, and to determine by means of simulations the size and statistical frequency of switching surges and based on a controlled switching simulation, to describe the elimination of transient phenomena during the process and in reference to the simulations and to operating manual for the PSD02 Siemens control unit, suggest the required configuration settings for the unit.

Open access
Human Urine Alterations Caused by Apricot Seeds Consumption

Abstract

Amygdalin is a cyanogenic glucoside derived from various plants seeds. It is a natural product that owns antitumor activity, it has also been used for the treatment of asthma, bronchitis, emphysema, leprosy and diabetes and produces antitussive and antiasthmatic effects. The present in vivo study was designed to reveal whether amygdalin in apricot seeds has got an effect on human urine composition, pH value and urine associated health status after twelve weeks of oral administration. The study group finally consisted of 12 healthy adult volunteers. All participants consumed 60 mg/kg of body weight of bitter apricot seeds daily (approximately 3.0 mg/kg of amygdalin) during 12 weeks. Two urine collections were carried out (at the beginning of the experiment and after 84 days). Quantification of urine calcium, magnesium, phosphorus, sodium, potassium, chlorides, urea and pH value after apricot seeds supplementation was performed. Paired t-test showed, that consumption of bitter apricot seeds during 84 days had a significant (P < 0.01) effect on amount of calcium excreted in urine, though this decrease shifted its level from elevated mean value in control collection into normal physiological range. No significant changes were observed in other parameters after apricot seed ingestion.

Open access