Voltage-dependent sodium channels have a decisive role in the generation of action potentials (AP) in many types of cells. In addition to the fast inactivating Na-current, associated with AP generation, the Na-channel can give rise to a noninactivating or persistent Na-current. The latter current generally comprises up to 5% of the transient current having important physiological consequences. It was established that persistent Na-currents have functional significance in setting the membrane potential in a subthreshold range regulating by this way dendritic depolarisations, repetitive firing and enhancing synaptic transmission. Voltage dependent sodium channel genes have been identified in a variety of invertebrates, as well as mammalian and nonmammalian vertebrates. It has been established that the biophysical properties, pharmacology and gene organization of invertebrate sodium channels are largely similar to the vertebrate ones, supporting the view that the ancestral sodium channel was established before the evolutionary separation of the invertebrates from the vertebrates. Although different isoforms of voltage sensitive Na-channels have now been identified the mechanism for persistent current remains controversial. An important yet unanswered question is whether persistent and fast inactivating Na-currents arise from different sets of sodium channels or whether the persistent Na-current results from different gating of the same channel type. The aim of the present review is to discuss the origin and the function of the persistent current, focusing on data derived from an invertebrate animal.
The mature mRNA always carries nucleotide sequences that faithfully mirror the protein product according to the rules of the genetic code. However, in the chromosome, the nucleotide sequence that represents a certain protein is interrupted by additional sequences. Therefore, most eukaryotic genes are longer than their final mRNA products. The human genome project revealed that only a tiny portion of sequences serves as protein-coding region and almost one quarter of the genome is occupied by non-coding intervening sequences. The elimination of these non-coding regions from the precursor RNA in a process termed splicing must be extremely precise, because even a single nucleotide mistake may cause a fatal error. At present, two types of intervening sequences have been identified in protein-coding genes. One of them, the U2-dependent or major-class is prevalent and represents 99% of known sequences. The other one, the so-called U12-dependent or minor-class of introns, occurs in much lesser amounts in the genome. The basic problem of nuclear splicing concerns i/ the molecular mechanisms, which ensure that the coding regions are correctly recognized and spliced together; ii/ the principles and mechanisms that guarantee the high fidelity of the splicing system; iii/ the differences in the excision mechanisms of the two classes of introns. We are going to present models explaining how intervening sequences are accurately removed and the coding regions correctly juxtaposed. The two splicing mechanisms will also be compared.
Energy efficiency measures and the enhancement of investments in renewable energy play important role in sustainable development and lead to advancement of competitiveness of national economies. The increase of renewable energy consumption and the reduction of greenhouse gas emissions are significant stages of the process to achieve the main purposes of sustainable development at global and national levels.
In this paper the change in the share of renewable energy in gross final energy consumption and in the greenhouse gas emissions intensity in Hungary between 2004 and 2011 is investigated.
It is demonstrated that the share of the renewable energy in gross inland energy consumption increased during the examined period. The measure and the tendency of the change in Hungary show similarity to the EU 27 average.
The greenhouse gas emissions intensity of energy consumption decreased in Hungary between 2004 and 2011. According to the data, the decrease is the second largest among the European Member States.
In this paper we analyse the trends and developments of energy imports as a percentage of gross inland energy consumption including bunkers in Hungary and the European Union countries between 2000 and 2011. Data show that the average of the energy dependence increased in the EU27 Member States (7.1 percentage points) and in Hungary, too (3.4 percentage points). The energy intensity in Member States is examined as well. According to the data the energy intensity decreased in the majority of the Member States, the average decreased by 16 percent.