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8783. Role a využití plazmatu při laserovém svařování

Creator:
Mrňa, Libor and Šarbort, Martin
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
fyzika, plazma (fyzika), svařování laserem, physics, plasma (ionized gases), 6, and 53
Language:
Czech and English
Description:
Článek se zabývá principy laserového penetračního svařování a souvisejícími kmity svarové lázně obklopující dutinu, tzv. keyhole, absorbující dopadající laserový svazek. Svařování doprovází vznik plazmatu uvnitř keyhole, které expanduje v podobě obláčku nad materiál. Záření obláčku má impulzivní charakter s časově náhodným průběhem. Jsou uvedeny možné metody analýzy záření plazmatu pomocí Fourierovy transformace a nově pomocí autokorelační funkce. V článku je popsán nový mechanismus generace plazmatu vysvětlující jeho impulzní charakter. Na absorpci záření v plazmatu lze pohlížet jako na systém s pozitivní zpětnou vazbou, koeficient absorpce totiž pozitivně závisí na teplotě. V prostředí Matlab/Simulink byl sestaven jednoduchý model s pozitivní zpětnou vazbou, který pomocí variace vstupních parametrů umožňuje studovat impulzní chování laserem indukovaného plazmatu. Vzhledem k lavinovitému nárůstu teploty elektronů v plazmatu byl navržen název jevu: plazmový burst. Vzhledem k citlivosti časování procesu na počáteční teplotu lze tímto mechanismem vysvětlit náhodný charakter a impulzní chování záření, ale také souvislost s kmity keyhole., The article deals with the principles of deep penetration laser welding and the associated oscillations of the weld pool that surrounds the cavity calles a "keyhole" where and incident laser beam is absorbed. The welding prcess is accompanied by the formation of the plasma inside the keyhole which expands above the welded material in the form of a plume. The light emissions from the plasma plume have a pulsing character with random timing. We discuss possible methods for the analysis of the plasma plume light emissions using Fourier transform and a new approach using an autocorrelation function. We also describe a new mechanism of the plasma formation which explains its pulsing character. The absorption of the laser radiation in the plasma can be considered as a system with positive feedback, the absorption coefficient has positive temperature dependence. To study the pulsing character of the laser induced plasma for various input parameters we compiled a simple model with positive feedback using Matlab - Simulink. With respect to the rapidly increasing electron temperature in the plasma we proposed a new name for the phenomenon: plasma burst. Due to the sensitivity of this mechanism to the intial temperature, it can be used to explain the random pulsing character of the light emissions as well as the relationship with the keyhole oscillation., Libor Mrňa, Martin Šarbort., and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

8784. Role of brain angiotensin AT1 receptor in the carbachol-induced natriuresis and expression of nNOS in the locus coeruleus and proximal convoluted tubule

Creator:
Wang, M., Jiang, C. L., Wang, C. Y., and Yao, Q. Y.
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, fyziologie, biochemie, physiology, biochemistry, AT1 receptor, neuronová syntáza oxidu dusnatého, karbachol, locus coeruleus, neuronal nitrix oxide synthase, carbachol, proximal convoluted tubule, 14, and 612
Language:
English
Description:
Central administration of losartan effectively blocked the increase of blood pressure and drinking response induced by angiotensin II (Ang II) or carbachol. However, the relationship between angiotensin AT1 receptors and the natriuresis induced by brain cholinergic stimuli is still not clear. The purpose of the study is to reveal the role of brain angiotensin AT1 receptor in the carbachol-induced natriuresis and expression of neuronal nitric oxide synthase (nNOS) in the locus coeruleus (LC) and proximal co nvoluted tubule (PCT). Our results indicated that 40 min after in tracerebroventricular (ICV) injection of carbachol (0.5 μg), urinary sodium excretion was significantly increased to 0.548±0.049 μmol·min-1·100 g-1. Immunohistochemistry showed that carbachol induced an increase of neuronal nitric oxide synthase immunoreactivity (nNOS-IR) in the LC and renal proximal tubular cells. After pretreatment with losartan (20 μg), carbachol-induced urinary sodium excretion was reduced to 0.249±0.067 μmol·min-1·100 g-1. The same was true for carbachol-induced increase of nNOS-IR in the LC and PCT. The present data suggest that ICV cholinergic stimulation could induce a natriuresis and upregulate the activity of nNOS in the LC and PCT. The blockade of AT1 receptors might downregulate the effects induced by carbachol in the LC and PCT. Consequently, we provide a new evidence that brain angiotensinergic pathway and NO-dependent neural pathway contribute to the natriuresis following brain cholinergic stimulation and thus play an important role in the regulation of fluid homeostasis. Furthermore, the final effect of nitric oxide on proximal tubular sodium reabsorption participated in the natriuresis induced by brain cholinergic stimulation., M. Wang, C. L. Jiang, C. Y. Wang, Q. Y. Yao., and Obsahuje bibliografii a bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

8785. Role of endothelin and nitric oxide in the pathogenesis of arterial hypertension in autosomal dominant polycystic kidney disease

Creator:
Miroslav Merta, Jana Reiterová, Romana Ryšavá, Vladimír Tesař, Závada, J., Marie Jáchymová, and Tomáš Zima
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, oxid dusnatý, arteriální hypertenze, nitric oxide, arterial hypertension, endothelin, autosomal dominant polycystic kidney disease, chronic renal failure, 14, and 612
Language:
English
Description:
The pathogenesis of arterial hypertension in autosomal dominant polycystic kidney disease (ADPKD) is complex and likely dependent on interaction of hemodynamic, endocrine and neurogenic factors. We decided to evaluate the role of endothelin (ET1) and nitric oxide (NO) in the regulation of arterial blood pressure (BP) and to determine plasma levels of ET1 and NO in the group of patients with ADPKD. The ADPKD group (18 patients, 6 men + 12 women, mean age 44.611.7 years, with creatinine clearancecorrig > 1.1 ml/s) was compared with a control group of 27 healthy volunteers of comparable age. Plasma levels of ET1 assessed by direct RIA determination in the group of ADPKD patients (11.03±1.8 fmol/ml) were significantly increased (p<0.001) in comparison with the control group (2.660.58 fmol/ml), while no significant differences were observed between normotensive and hypertensive patients in the ADPKD group. Serum levels of NO were evaluated according to the determination of serum levels of their metabolites - nitrites/nitrates. Serum levels of NO in the group of ADPKD patients (39.85±6.38 μmol/l) were significantly higher (p<0.05) in comparison with the control group (22.7±1.20 μmol/l), whereas in the ADPKD group no significant differences were observed between normotensive and hypertensive patients. Thus, our study supports the concept of complex alteration of both vasoconstrictor and vasodilator systems in the pathogenesis of arterial hypertension in ADPKD., M. Merta, J. Reiterová, R. Ryšavá, V. Tesař, M. Jáchymová., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

8786. Role of endothelium and nitric oxide in experimental hypertension

Creator:
Vapaatalo, H., Mervaala, E., and Nurminen, M.-L.
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, endotel, endoteliální dysfunkce, oxid dusnatý, hypertenze, endothelium, endothelial dysfunction, nitric oxide, hypertension, antihypertensive drugs, 14, and 612
Language:
English
Description:
A short review on the role of endothelium and nitric oxide (NO) in experimental hypertension is presented in the light of the literature and our own recent findings. Based on these data, it is concluded that even though there is a lot of evidence in favor of the primary and causal association of endothelial dysfunction and NO in experimental hypertension, it seems still more plausible that they are causative in some types of hypertension only. Our own experience rather speaks for a secondary but still an important participation of endothelium in the maintenance and further elevation of high blood pressure. Endothelium plays a key role in the development of organ damages in hypertension., H. Vapaatalo, E. Mervaala, M.-L. Nurminen., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

8787. Role of ghrelin in the regulation of gastric acid secretion involving nitrergic mechanisms in rats

Creator:
Bilgin, H. M., Tumer, C., Diken, H., Kelle, M., and Sermet, A.
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
fyziologie, oxid dusnatý, potkan, physiology, nitric oxide, Rattus norvegicus, ghrelin, and acid secretion
Language:
English
Description:
Ghrelin, an endogenous ligand for growth hormone secretagogue receptor (GHS-R), has been id entified in the rat and human gastrointestinal tract. Ghrelin has been proposed to play a role in gastric acid secretion. Nitric oxide (NO) was shown as a mediator in the mechanism of ghrelin action on gastric acid secretory function. However, there is a little knowledge about this topic. We have investigated the role of ghrelin in gastric acid secretion and the role of NO as a mediator. Wistar albino rats were used in this study. The pyloric sphincter was ligated through a small midline incision. By the time, saline (0.5 ml, iv) was injected to the control group, ghrelin (20 μg/kg, iv) was injected to the first experimental group, ghrelin (20 μg/kg, iv) +L-NAME (70 mg/kg, sc) was injected to the second group and L-NAME (70 mg/kg, sc) was administered to the third group. The rats were killed 3 h after pylorus ligation; gastric acid secretion, mucus content and plasma nitrite levels were measured. Exogenous ghrelin administration increased gastric acid output, mucus content and total plasma nitrite levels, while these effects of ghrelin were inhibited by applying L-NAME. We can conclude that ghrelin participates in the regulation of gastric acid secretion through NO as a mediator., H. M. Bilgin, C. Tumer, H. Diken, M. Kelle, A. Sermet., and Obsahuje bibliografii a bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

8788. Role of hereditary factors in weight loss and its maintenance

Creator:
Vojtěch Hainer, Hana Zamrazilová, Spálová, Jana, Irena Aldhoon Hainerová, Marie Kunešová, Bashar Aldhoon, and Běla Bendlová
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, endokrinologie, obezita, genetické aspekty, environmentální aspekty, redukce tělesné hmotnosti, endocrinology, obesity, genetic aspects, environmental aspects, weight loss, weight maintenance, obesity candidate genes, gene polymorphisms, 14, and 612
Language:
English
Description:
The prevalence of obesity is increasing worldwide at an alarming rate in both developed and developing countries. Obesity is a chronic complex disease of multifactorial origin resulting from a long-term positive energy balance, in which both genetic and environmental factors are involved. Genetically prone individuals are the first to accumulate fat in the present obesogenic environment. Obesity increases the risks of type 2 diabetes, hypertension, cardiovascular disease, dyslipidemia, arthritis, and several cancers and reduces the average life expectancy. Implementation of effective strategies in prevention and management of obesity should be come an important target in health care systems. Weight changes throughout life depend on the interaction of behavioral, genetic and environmental factors. Weight loss in response to weight management shows a wide range of interindividual variation which is largely influenced by genetic determinants. The strong control of weight loss by genotype was confirmed by twin and family studies. Recently, special attention has been paid to nutritional, hormonal, psychobehavioral and genetic factors which can predict the response to weight reduction programme. In this article currently available data on the role of obesity candidate gene polymorphisms in weight loss and maintenance are reviewed. It is believed that an elucidation of the genetic component in the prognosis of weight management could assist in the development of more effective and individually tailored therapeutic strategies., V. Hainer, H. Zamrazilová, J. Spálová, I. Hainerová, M. Kunešová, B. Aldhoon, B. Bendlová., and Obsahuje bibliografii a bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

8789. Role of mucus in ischemia/reperfusion-induced gastric mucosal injury in rats

Creator:
Ján Mojžiš, Renáta Hegedüšová, and Ladislav Mirossay
Format:
print, bez média, and svazek
Type:
article, články, journal articles, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, ischemie, ischemia, ischemia/reperfusion, gastric mucus, sucralfate, malotilate, n-acetylcysteine, 14, and 612
Language:
English
Description:
Gastric mucus plays an important role in gastric mucosal protection. Apart from its “barrier” function, it has been demonstrated that mucus protects gastric epithelial cells against toxic oxygen metabolites derived from the xanthine/xanthine oxidase system. In this study, we investigated the effect of malotilate and sucralfate (mucus production stimulators) and N-acetylcysteine (mucolytic agent) on ischemia/reperfusion-induced gastric mucosal injury. Gastric ischemia was induced by 30 min clamping of the coeliac artery followed by 30 min of reperfusion. The mucus content was determined by the Alcian blue method. Sucralfate (100 mg/kg), malotilate (100 mg/kg), and N-acetylcysteine (100 mg/kg) were given orally 30 min before surgery. Both sucralfate and malotilate increased the mucus production in control rats. On the other hand, N-acetylcysteine significantly decreased mucus content in control (sham) group. A significant decrease of mucus content was found in the control and the N-acetylcysteine pretreated group during the period of ischemia. On the other hand, sucralfate and malotilate prevented the decrease the content of mucus during ischemia. A similar result can be seen after ischemia/reperfusion. In the control group and N-acetylcysteine pretreated group a significant decrease of adherent mucus content was found. However, sucralfate and malotilate increased mucus production (sucralfate significantly). Sucralfate and malotilate also significantly protected the gastric mucosa against ischemia/reperfusion-induced injury. However, N-acetylcysteine significantly increased gastric mucosal injury after ischemia/reperfusion. These results suggest that gastric mucus may be involved in the protection of gastric mucosa after ischemia/reperfusion., J. Mojžiš, R. Hegedüšová, L. Mirossay., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

8790. Role of nitric oxide in adaptation to hypoxia and adaptive defense

Creator:
Manukhina, E. B., Mashina, S. Yu., Smirin, B. V., Lyamina, N. P., Senchikhin, V. N., Vanin, A. F., and Malyshev, I. Yu.
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Fyziologie člověka a srovnávací fyziologie, oxid dusnatý, hypoxie, adaptace (biologie), infarkt myokardu, nitric oxide, hypoxia, adaptation (biology), myocardial infarction, spontaneously hypertensive rats, 14, and 612
Language:
English
Description:
Adaptation to hypoxia is beneficial in cardiovascular pathology related to NO shortage or overproduction. However, the question about the influence of adaptation to hypoxia on NO metabolism has remained open. The present work was aimed at the relationship between processes of NO production and storage during adaptation to hypoxia and the possible protective significance of these processes. Rats were adapted to intermittent hypobaric hypoxia in an altitude chamber. NO production was determined by plasma nitrite/nitrate level. Vascular NO stores were evaluated by relaxation of the isolated aorta to diethyldithiocarbamate. Experimental myocardial infarction was used as a model of NO overproduction; stroke-prone spontaneously hypertensive rats (SHR-SP) were used as a model of NO shortage. During adaptation to hypoxia, the plasma nitrite/nitrate level progressively increased and was correlated with the increase in NO stores. Adaptation to hypoxia prevented the excessive endothelium-dependent relaxation and hypotension characteristic for myocardial infarction. At the same time, the adaptation attenuated the increase in blood pressure and prevented the impairment of endothelium-dependent relaxation in SHR-SP. The data suggest that NO stores induced by adaptation to hypoxia can either bind excessive NO to protect the organism against NO overproduction or provide a NO reserve to be used in NO deficiency., E. B. Manukhina, S. Yu. Mashina, B. V. Smirin, N. P. Lyamina, V. N. Senchikhin, A. F. Vanin, I. Yu. Malyshev., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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