Ceskoslovenska fysiologie最新文献

Proteins are the basic material of tissue structure. They are the most important component of striated skeletal muscle. Their classification is correlated with the histological structure of muscle tissue. The muscle proteins can be divided in to contratile, regulatory, sarcoplasmic and extracellular forms. The most important are the contractile proteins actin and myosin. Among the regulatory proteins, troponin, tropomyosin, M-protein, beta-actin, gamma-actin and C-protein are great importance. Sarcolemma is also a protein component. Proteins such as myoglobin, myogen, myoalbumin and x-globulin are found in the sarcoplasm and proteins such as elastin, collagen and reticulin are also found in the muscle. The remaining of proteins includes myofibrillar proteins of the Z-disc as well as small quantities of other proteins. This work is a short review of some properties of the muscular proteins.

Drug abuse is still a serious problem of nowadays. One of the most abused drugs in the Czech Republic is methamphetamine (MA). MA is strongly addictive substance with high disposition to abuse. It belongs to the group of synthetic amphetamines that together with cocaine and caffeine are classified as psychomotor stimulant drugs. Lately, the growing problem is drug abuse of pregnant women. MA is popular drug in pregnant women dependent on addictive substances. Drugs abused during pregnancy are risky not only for the mother, but may induce changes in developing organism that may have permanent consequences. Prenatal exposure to MA may have teratogenic effects by inducing malformations or impair postnatal functional development of offspring. The impairing effects may last until adulthood and may affect even next generation. Mechanism of these long-term consequences is not fully explained yet. The present review summarizes the existing information.

Addiction is a still an acute problem of nowadays. Drug addiction does not develop within the first taste of the drug and does not progress in each individual, who abuse drugs. Several factors play a role in this process, such as: factor of environment, stress and also genetic dispositions. This review summarizes all available findings about: what is addiction; how it develops; what brain structures and neurotransmitter systems play a role in it and what are the possibilities of its treatment in nowadays.

In present time, to classify the healthy as potencional possibility of the organism to accept variable environment influences without the break of the biological important functions is not satisfactory. Examples from the different field of the clinical medicine refer to importance of the knowledge's of the circadian rhythmicity concerning many diseases, symptoms or significant remissions. Therefore, clinical trials considering the biological variability differ from the convectional studies by assumption that biology of patient is dynamic, that time of the diagnostic test running is significant and that drugs can influence safety and therapeutic effect in the dependence on the day-time. In paper, it is showed on some examples from the clinical practice that respection of the chronobiological principles may play the important role in the medical diagnostics as well as in therapy and may improve accuracy of the whatever functional examination. For terms, which are often used in the chronobiological texts, no suitable terms were available and therefore it was necessary to introduce the descriptive phrases, which would be accepted by specialists in the field. Many of the introduced terms are still unknown to many investigators and physicians who might benefit from the application of chronobiologic principles to their work.

Vascular system is a large complex of tubes with different diameters which are able to perceive changes of endogenous milieu, to integrate and modulate signals of intercellular communication and to respond and adapt by a local production of different kinds of mediators affecting vascular structure and function. For a long time, it has been assumed that the main determinant of vasomotor function was the nervous system and the monolayer of endothelial cells was only a physical barrier between the vessel wall and blood. However, the first publications in 1960s and 70s indicated that endothelium is not only a passive barrier. Endothelium features autocrine, paracrine and endocrine activities. Vascular endothelium plays an important role in the regulation of vascular tone, blood pressure and blood flow beside central regulation of nervous system. The existence of endothelium-derived relaxing factor (EDRF) was found out by Furchgott and Zawadzki (1980) who showed that acetylcholine induced relaxation of the rabbit aorta only in the presence of intact endothelium. Nowadays, nitric oxide (NO), previously known as EDRF, is considered one of the crucial endothelium-derived vasorelaxing substances participating in the regulation of basal vascular tone, vascular resistance and thus in the regulation of blood pressure. Arterial bed is dilated continuously as a consequence of constant production of NO. Any damage of endothelium modifies regulatory functions of endothelial cells. These conditions are characterised as endothelial dysfunction associated with imbalance between vasodilating and vasoconstricting factors, pro- and anticoagulation factors and factors stimulating and inhibiting growth and proliferation of cells. However, cellular mechanisms which are involved in the development of endothelial dysfunction, are still not well-known.

The purpose of this report is to describe regulatory mechanisms of the NQR, its role during development and maintenance of the peripheral synapse and to stress functional roles of this type of release in denervation, hibernation and surplus hyperpolarization at the muscle endplate zone.

The purpose of this report is to describe what progress was made in defining and explaining the phenomenon of NQR and to stress some functional roles of this type of release, as based on our own data and other observations.

Experimental model of 5/6 nephrectomy or the remnant kidney model represents one of the most used animal models of progressive renal failure by reduced nephron number, best-characterized in rats. The reduction of renal mass is achieved by either infarction or surgical excision of both poles, with removal of the contralateral kidney. It enables to investigate the influence of pharmacological, nutritive and other factors on functional and morphological renal parameters. 5/6 nephrectomy produced by infarction is characterised by high plasma renin levels. By contrast, reduction of an equivalent amount of renal parenchyma by surgical excision does not result in the development of hypertension and plasma renin activity is normal to low. The initially normal remnant nephrons undergo compensatory functional and structural adaptations. Simultaneous glomerular hypertension is one of the main factors responsible for the development of renal injury. Morphologicaly progressive focal segmental to global glomerulosclerosis is present, accompanied clinically by increasing proteinuria and deteriorating renal function.

Testosterone (C19H28O2), the main testicular hormone, is 19-carbonic steroid substance with -OH group in position 17. Precursor for its synthesis is cholesterol, or possibly androstendione released by adrenal cortex. Testosterone is produced in smooth endoplasmatic reticulum of Leydig cells of testes. Apart from testes it is also produced in adrenal cortex, liver, kidneys, in fat and muscle tissue, even though in smaller extent--around 5% (Bidlingmaier, F. et al., 1986). Approximately 4-9 mg (13.9-31.2 nmol/l) of testosterone is daily produced in healthy men. Absolute majority, around 99% from overall plasmatic testosterone is bound to albumin, erythrocytes, but mainly to sex hormone binding globulin (SHBG) (Diver, M.J. et al., 2003). Only small proportion (1-2%) of testosterone circulates as free fraction (Ostatníková, D., 2003). Production and secretion of the main androgen in testes is regulated by well known and accepted axis of hypothalamus, hypophysis and testes. Testosterone and its metabolite dihydrotestosterone can influence the expression of genes, development of masculine type of habitus and behavior, acting via androgen receptor (AR) (Zitzmann, M. and Nieschlag, E., 2003). Testosterone can affect also via its metabolites, whose production is conditioned by enzymes. In peripheral tissues is testosterone converted via aromatase to estradiol and via 5alpha-reductase to dihydrotestosterone (Weber, K.S. et al., 1999).