Ceskoslovenska fysiologie最新文献

Baroreflex regulation of blood pressure primarily moderates its fluctuations and also affects mean blood pressure. Heart rate baroreflex sensitivity is described as changes of the inter-beat interval induced by a change of blood pressure of 1 mmHg (BRS). BRS is decreased in many cardiovascular diseases (hypertension, diabetes mellitus, obesity, cardiac failure, etc.). Decreased BRS in disposed individuals, especially after myocardial infarction, increases the risk of sudden cardiac death. Therefore, early diagnosis of BRS decrease gains in importance. This article describes different methods of determination of baroreflex sensitivity. The methods are based on evaluation of the spontaneous fluctuation of heart rate and blood pressure (spectral, sequential or nonlinear methods), or of primary changes of blood pressure induced by a vasoactive substance or a physiological manoeuvre and corresponding changes of cardiac intervals (Valsalva manoeuvre, phenylephrine administration). Each method has its advantages and disadvantages resulting from a different difficulty of calculation or from inclusion of different deviations in the results, which are not directly linked with baroreflex. Baroreflex regulating total peripheral resistance is less described. A mathematical model of baroreflex blood pressure regulation by fluctuation of heart rate and peripheral resistance is presented in this paper.

The treatise "De structura nervorum" by Jirí Procháska was published in 1779 after his appointment as a professor in Prague. This work is remarkable not only for its anatomical and histological findings, but also for its historical introduction, which contains a very detailed bibliographical review of previous knowledge about the structure of the nervous tissue. The treatise "De structura nervorum" has never been translated from the Latin language, but as a historical document about the level of neuroscience research conducted by a famous Czech researcher, it deserves further analysis. The present article includes a historical overview of knowledge about the structure of nervous tissue up to the late 18th century from the perspective of today, a translation of the historical introduction about the medieval knowledge of the structure of the nervous tissue and documenting the way in which Jirí Procháska processed his bibliography, a translation and interpretation of his neurohistological observations and an analysis of the results in the light of current knowledge.

Brain development is determined by neuronal differentiation including changes of cell polarity and asymetric growth of neuronal processes. Although, there are many unkown factors contributing to changes of lenght of neuronal cones, mounting experimental and review papers focus on changes of growth conus and role of axonal transport. In particular, mechanisms of actin/microtubule polymerisation and depolymerisation are important. Role of intracellular calcium is also significant. Normal and properly timed changes of lenght of axons and dendrites are dependent on interaction of neurons and glia. Moreover, regeneration of injured axons is dependent on growth factors secreted from glial cells. The aim of the present study is characterisation of the most important mechanisms underlying changes of lenght of neurites.

Pulmonary circulation is completely different compared to systemic circulation. Chronic hypoxia damages peripheral pulmonary arterioles and causes hypoxic pulmonary hypertension (HPH) which consists of vasoconstriction and remodelling of the arterioles. The release of reactive oxygen species (ROS)--mainly superoxide and nitric oxide (NO) contribute to the pathogenesis of HPH. During exposition to chronic hypoxia, the NO production is markedly elevated and it has two effects: the first, direct vasodilatory effect caused by NO, the second, contribution to remodelling of the peripheral pulmonary vessels by interaction with ROS. The interaction of superoxid and NO releases peroxynitrite which plays a role in the onset of collagen cleavage. A typical low molecular weight of collagen fragments induces remodelling of the peripheral pulmonary arterioles. These changes are typical for the first week of exposure to the chronic hypoxia which also correlates with sudden elevation of the mean pulmonary artery pressure. Continual exposition to the chronic hypoxia after first week does not cause progressive worsening of HPH.

Bone remodeling is determined by function of two basic cell forms--bone resorbing osteoclasts and bone formation activating osteoblasts. Both cells are under control of a variety of endogenic and environmental factors, which ensure balance between bone resorption and bone formation. This article reviews the neuro-hormonal factors with osteoanabolic (central isoform of serotonin, melatonin, cannabinoids, beta 1 adrenergic system, oxytocin, ACTH and TSH) or osteocatabolic effects (neuropeptide Y, neuromedin U, beta2 adrenergic system). The dual effects of the beta-adrenergic system, serotonin and leptin are also discussed. The goal of studies focused on neuro-skeletal interaction is to synthesize new molecules, which can modify osteo-anabolic or osteo-catabolic pathways.

The peripheral nerve's degeneration and regeneration after its injury was described by Waller in 1850. The distal stump and small part of the proximal part of the transected fibre disintegrate. Proliferating Schwann cells create the band of Büngner for the guiding of the regrowing axon. Even if the suture of the nerve is quickly and well performed, the reinervation is never absolute. Regrowing axons can grow into wrong endoneurial tubes or outside the area of the suture and long-lasting denervation leads to progressive atrophy of the target organs. In the future, the neurotrophic factors might improve the outcome of the reinervation.

Acute pulmonary embolism (PE) is the life-threatening condition with high incidence and mortality where the death is the result of pulmonary hypertension followed by right side heart failure. There are two important mechanisms concerned in the development of pulmonary embolism--induced pulmonary hypertension--mechanic obstruction of pulmonary vessels by the embolus and vasoconstriction. The effect of mechanic obstruction is quite clear, in contrast to the role of vasoconstriction. Activation of endothelial cells, thrombocytes and leucocytes, which release vasoconstricting substances (ET-1, 5-HT etc.) and production of reactive oxygen species (ROS) are the most important factors causing the vasoconstriction after PE. ROS are produced as a result of hypoxia, increased (and decreased) shear stress and are released from activated leukocytes. Vasoconstriction after PE is caused by change of conformation voltage-gated potassium channels, the decrease of vasodilatation effect of NO and activation of matrix metalloproteinases.. Most of the current therapeutic protocols in PE are focused on mechanic obstruction of pulmonary vessels. Thus, the research of the role of vasoconstriction in PE and potentially protective factors in vasocostriction--induced injury represent clinically highly important field.

Regulation of G protein coupled receptors (GPCRs) looks to be not only classically lineary regulated but it is now discovered to be a complex network of interconnected proteins. Taking these in mind it is highly probable that there is multilevel system of regulation that is able to maintain control of signaling. We review here main mechanisms of GPCRs regulation.

Changes in experimental animals' behavior as well as humans' behavior reflect even mild alterations in function of central nervous system. In order to detect those changes variety of tests' batteries were developed. With help of such unified tests it is possible to determine and differentiate individual behavioral parameters and establish their relation to specific CNS alterations. Behavioral tests results from animal studies thereafter can be linked to certain type of behavioral changes in humans, because biochemical composites and reactions of the brain are significantly alike in all of mammals. The advantages of behavioral tests include its non-invasive methods of detection and possibility to determine changes of function even before there are any morphological or biochemical representations. The following work overviews specific aspects of behavioral testing, e.g., animals' preparation to the test, behavioral categories, possibility of tests' measurements and their limitations.