Ceskoslovenska fysiologie最新文献

The growth is inseparable part of ontogenesis and simply is characterised as a biological process, which is outcome of internal and external changes and interaction of all organ systems. The striated skeletal muscles are developed during a prenatal period from mesoderm and individual development is finished in time of birth and also post partum. The basic sign of the last stage is a nuclei periphery movement from the centre under sarcolemma whereas myofibriles fill interior. Every individual muscular system consists of the specific particular type of muscle fibres, which were formed during embryogenesis. The nuclei of muscle fibres are postmitotic and it is evident, that only one way of muscle growth consists of coarsing and lengthening of existing muscle fibres. The muscle fibres growth and development is followed by various effects, which can be classified as genetic or other effects. By intensive studies of genetic effects was recognised that in muscles are presented not only tissular specific gene but also ubiquitous genes, which regulate processes of protein muscles and fat synthesis. The latest research exposed the existence of genes in muscles, which have influence to structural component of skeletal muscles. In present contribution we describe genetic factors effects to genesis and growth of the striated skeletal muscles.

The hypertensive rat strain transgenic for the mouse Ren-2 renin gene (TGR) strain name TGR [mRen 2] 27 is a valuable monogenic model of renin-dependent and thus angiotensin II dependent hypertension. It carries a salt -sensitive component. Homozygous animals exhibit clinically and morphologically typical sings of fulminant hypertension. Glomerular changes in accelerated (malignant) hypertension are acute or chronic. The acute changes have focal character; the most obvious change is segmental fibrinoid necrosis. Fibrinoid necrosis may extend from a similar lesion in the afferent arteriole and may be associated with crescent. Chronic changes are of two different types. The first is similar to that seen in benign hypertension, in that there is collapse of the capillary tuft with wrinkling of the glomerular basement membrane accompanied by collagenization of Bowmann's space. In the second type, glomeruli are also collapsed but seem almost acellular. Male heterozygous TGR are more suitable for experiments because their hypertension is lower and this model is much more similar to clinical situation. Morphologically prominent hyalinosis and segmental sclerotisation of capillary tuft of some glomeruli is present. These features correspond to secondary form of focal segmental glomerulosclerosis (FSGS). High salt diet in heterozygous animals induces a transition from benign to malignant phase of hypertension. In such case ischemic changes are superimposed on the pre-existing renal parenchymal disease (secondary FSGS). Selective blockade of endothelin receptors ET(A) is superior to non-selective ET(A)/ET(B) blockade in attenuating of hypertension and also morphology. ET receptor blockade in homozygous and heterozygous TGR has similar effect on morphological structure of renal parenchyma applied in rats with established hypertension as in young animals. Podocyte injury is crucial also in experimental hypertensive glomerulopathy. Podocytes showed degenerative changes and thickening of glomerular basement membrane was also present. Degree of morphological podocyte injury rather than hypertension correlated with mortality in homozygous TGR.

The actual level of factual individual ageing of organism is characterized by biological age. By means of measuring function ability of physiological systems it is possible to evaluate the biological age and use it as an indicator of premature ageing and therefore as an indicator of the risk of getting ill. The article brings an overview of contemporary used, non-standard markers for the measurement of biological age and uncovers the possibility of measurement of biological age (BA) of skeleton and its use in osteoporosis precaution. Inclusion of BA measurement of skeleton into basic screening of precaution should bring another perspective how to measure objectively the changes in organism that correspond with ageing.

The effect of atropine and diazepam on the mammalian neuromuscular junction. Nicotinolytic effect of atropine on the neuromuscular junction is discussed as a main mechanism of the beneficial effect of this drug during war and agriculture poisoning by anticholinesterases. Atropine is beneficial as it reduces the amplitude of intracellularly recorded endplate potentials and, first of all, causes a marked shortening of their time course (Beránek, Vyskocil 1968, Magazanik, Vyskocil 1969). Diazepam effectively blocks trains of action potentials in individual rat diaphragm muscle fibers, apparently by elevating the chloride permeability. It is suggested that similar increase in Cl- permeability may occur in brain excitable structures and can counteract the anticholinesterase-induced prolongation of ACh-depolarization that evokes repetitive firing.

A number of diverse extracellular signals are at the cell surface specifically recognized by different types of membrane-bound receptors, which subsequently activate the relevant signalling cascades. The most plentiful group of these receptors is formed by heptahelical (or serpentine) receptors coupled to trimeric G-proteins. Trimeric G-proteins (composed of alpha and betagamma subunits) function as molecular switches that directly regulate activity of various effector molecules, such as adenylylcyclase, phospholipase C and some ionic channels. G-proteins thus play a crucial role in regulating cellular responses. Transmembrane signalling mediated by trimeric G-proteins may be seriously deranged in various pathophysiological conditions and, therefore, a great attention is currently being paid to investigation of these signalling systems. The practical significance of this research is well documented by the fact that substantial portion of medicinal drugs produced by pharmaceutical industry is oriented to amend functioning of these signalling systems. The present review is intended to provide a brief up-to-date characterization of all major components of transmembrane signaling systems regulated by G-proteins, i.e., heptahelical receptors, G-proteins and some crucial effector molecules.

The history of the renin-angiotensin system goes back to the 19th century. ANG II is still considered to be the most effective component of the RAS. This octapeptide plays an important role in the control of body fluid volume, in blood pressure regulation and in cardiovascular remodeling through the mediation of the direct effects on protein synthesis, on the cell growth and the cell differentiation, on the induction of growth-promoting genes and on the suppression of synthesis of oxygen species, prostanoids and cytokines.

Peroxisome proliferator activated receptors (PPARs) belong to the nuclear receptor superfamily, which act as transcription factors. PPARs affect expression of many genes, which products are involved in lipid and carbohydrates metabolism, cell proliferation and differentiation and numerous other processes. Three different subtypes (isoforms) of PPARs have been identified: PPAR-alpha, PPAR-gamma, PPAR-delta. PPAR-alpha receptors play an important role in the regulation of lipid metabolism: they decrease circulating fatty acids and triglyceride levels. Recently, the ability of PPAR-alpha receptors to improve insulin sensitivity in rodent model of insulin resistance have been documented and numerous studies have focused on this topic. One of the possible mechanisms of its action on the insulin sensitivity is lowering of ectopic lipids in liver and muscle tissues with subsequent heightening of insulin signalling cascade. Here we summarize the experimental studies focusing on the role of PPAR-alpha in the regulation of insulin sensitivity and discuss possible mechanisms involved.

The liver is a common target of toxic effect of a number of xenobiotics, which is in particular a result of its central role in intermediary and energetic metabolism and in biotransformation processes. Ethical, economic, legislative, research and other reasons do not allow testing all of newly-synthesized compounds in in vivo conditions. Hence new methods and approaches for hepatotoxicity testing in vitro have been developing. The most important systems for study of toxicity and metabolic activity in vitro are isolated perfused liver, liver slices, isolated liver cells in suspensions or in primary cultures including co-culture methods and special 3D techniques, various subcellular fractions and stabilised cell lines. These models can be used for cytotoxicity and genotoxicity screening, evaluation of potential hepatoprotective capacity of different compounds, study of toxic injury and characterization of hepatotoxicity mechanisms. Currently there is no an ideal in vitro liver model system for testing of hepatotoxic substances in vitro, nevertheless use of these model systems reduces economic costs and ethic and legislative problems. Model systems in vitro afford opportunity to study in detail mechanisms of hepatotoxicity in comparison with in vivo conditions. Definition of their actual advantages and disadvantages allows choosing a suitable model system for study of particular problem. We cannot imagine current research of liver toxicity without using these model sytems.

Functional state of extremities of players is important for performance of complex movements. We tested subsequent hypothesis: The technique of the overhead passing depends on the functional state of the upper extremities of volleyball players. We tested 10 young (15 - 16 year old) female players. All of them were from the same team. The players underwent physical medical examination. Special attention was paid to manual examination of upper extremities. Then we performed computer assisted 3-dimensional kinematic analysis of the overhead passing of the ball. The medical examination showed that 80 % of players exhibited some functional derangements of joints of upper extremities. Surprisingly these findings did not correlate with 3D kinematic analysis of the overhead passing. Our hypothesis was not confirmed. The results of medical examination depict the importance of systematic medical care.