Motility mechanisms Dotaz Zobrazit nápovědu
- MeSH
- kuřecí embryo růst a vývoj MeSH
- nervový přenos MeSH
- pohyb analýza MeSH
- Check Tag
- kuřecí embryo růst a vývoj MeSH
Acta physiologica Scandinavica, ISSN 0302-2994 vol. 125, suppl. 546, 1985
39 s. : grafy ; 24 cm
As opposed to pathogens passively circulating in the body fluids of their host, pathogenic species within the Spirochetes phylum are able to actively coordinate their movement in the host to cause systemic infections. Based on the unique morphology and high motility of spirochetes, we hypothesized that their surface adhesive molecules might be suitably adapted to aid in their dissemination strategies. Designing a system that mimics natural environmental signals, which many spirochetes face during their infectious cycle, we observed that a subset of their surface proteins, particularly Decorin binding protein (Dbp) A/B, can strongly enhance the motility of spirochetes in the extracellular matrix of the host. Using single-molecule force spectroscopy, we disentangled the mechanistic details of DbpA/B and decorin/laminin interactions. Our results show that spirochetes are able to leverage a wide variety of adhesion strategies through force-tuning transient molecular binding to extracellular matrix components, which concertedly enhance spirochetal dissemination through the host.
- MeSH
- bakteriální adheze * MeSH
- bakteriální adheziny genetika metabolismus MeSH
- Borrelia burgdorferi genetika metabolismus patogenita MeSH
- dekorin metabolismus MeSH
- extracelulární matrix metabolismus mikrobiologie MeSH
- interakce hostitele a patogenu MeSH
- kinetika MeSH
- klíště mikrobiologie MeSH
- králíci MeSH
- laminin metabolismus MeSH
- lymeská nemoc metabolismus mikrobiologie MeSH
- pohyb MeSH
- vazba proteinů MeSH
- zobrazení jednotlivé molekuly MeSH
- zvířata MeSH
- Check Tag
- králíci MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Electric stimulation (ES) could induce contraction of intestinal smooth muscle. The aim of this study was to analyze the effects of ES on esophageal motility and the underlying mechanism in vivo. Twenty-eight rabbits were equipped with a pair of subserosa electrodes (connected to an electrical stimulator) in the lower segment of the esophagus. The ES signal consisted of bipolar rectangular pulse trains, lasting for 3 s, with different amplitudes (1 mA, 3 mA, 5 mA and 10 mA), and frequencies (10 Hz, 20 Hz and 50 Hz). The amplitude of the contraction was recognized by high-resolution manometry. The effect of ES was tested under anesthesia and following administration of atropine, phentolamine or L-NAME. ES induced esophageal contraction at the stimulated site. A statistically significant increase in esophageal pressure was observed when the stimulation amplitude was above 3 mA. The increase in esophageal pressure was associated with the amplitude of stimulus as well as the frequency. During stimulation, atropine, phentolamine and L-NAME had no effect on the increase of esophageal pressure induced by ES. These findings implied that ES induced esophageal contraction were not mediated via the NANC, adrenergic or cholinergic pathway. The amplitude of esophageal contraction was current and frequency dependent.
- MeSH
- alfa blokátory farmakologie MeSH
- antagonisté muskarinových receptorů farmakologie MeSH
- atropin farmakologie MeSH
- elektrická stimulace * MeSH
- ezofágus účinky léků fyziologie MeSH
- fentolamin farmakologie MeSH
- gastrointestinální motilita účinky léků fyziologie MeSH
- králíci MeSH
- manometrie MeSH
- NG-nitroargininmethylester farmakologie MeSH
- poruchy motility jícnu patofyziologie MeSH
- svalová kontrakce MeSH
- zvířata MeSH
- Check Tag
- králíci MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Príjem jedla môže u niektorých ľudí vyvolať pokles krvného tlaku prechodného charakteru. Ak pokles systolického tlaku krvi dosiahne 20 mm Hg alebo viac, hovoríme o postprandiálnej hypotenzii. Tento jav prebieha asymptomaticky, alebo podmieňuje klinické príznaky zo strany centrálnej nervovej sústavy alebo kardiovaskulárneho systému. Postprandiálna hypotenzia sa častejšie vyskytuje u starých ľudí, hypertonikov, diabetikov alebo pacientov so zlyhaním autonómneho nervového systému. Patogenéza postprandiálnej hypotenzie nie je dostatočne objasnená. Uvažuje sa o vplyve starnutia, artériovej hypertenzie, nedostatočnosti autonómneho nervového systému, o účasti inzulínu, vazoaktívnych gastrointestinálnych hormónov, nadmernej krvnej náplni splanchnika a zmenenej motilite žalúdka. Dôležitým faktorom je tiež zloženie a teplota potravy. Naše pozorovania výskytu potsprandiálnej hypotenzie v skupine 89 pacientov s artériovou hypertenziou (41 žien, 48 mužov, priemerný vek = 67±12 rokov) ukázali 45% incidenciu tohto fenoménu. Maximálny pokles systolického tlaku krvi u pacientov s identifikovanou postprandiálnou hypotenziou sme najčastejšie zaznamenali pol hodinu po príjme štandardného jedla. Užívanie antihypertenzív nebolo spojené s vyšším postprandiálnym poklesom krvného tlaku. U pacientov liečených benzodiazepínmi sme na hraničnej úrovni štatistickej významnosti (p=0,05) pozorovali nižšie postprandiálne hodnoty TK. V súhlase s literárnymi údajmi konštatujeme, že postprandiálna hypotenzia je častý jav, ktorý môže interferovať s meraním krvného tlaku po príjme jedla, čo je potrebné zohľadniť v každodennej praxi pri posudzovaní efektu antihypertenzívnej liečby.
Food intake may cause a temporary but significant decline of blood pressure in susceptible people. If the systolic blood pressure falls by 20 mm Hg or more after food ingestion this indicates postprandial hypotension. This phenomenon can be asymptomatic or accompanied by a variety of neurological or cardiovascular symptoms. Postprandial hypotension occurs more commonly in elderly people, patients with hypertension, diabetes or autonomic nervous system failure. The mechanism of postprandial hypotension is not completely understood. It may be associated with ageing, arterial hypertension, impairment of the autonomic nervous system, insulin, vasoactive gastrointestinal hormones, disproportionate splanchnic blood pooling, and altered gastric motility. Food composition and its temperature are also significant. We found a 45% incidence of postprandial hypotension in a group of hypertensive patients (41 females, 48 males, mean age 67±12 years). The maximal decrease in systolic blood pressure in subjects with identified postprandial hypotension occurred most frequently 30 minutes after a standardized meal. The use of antihypertensives was not associated with a higher postprandial blood pressure decline. However this association was noted at the borderline level of statistical significance (p=0.05) with benzodiazepine treatment. In accordance with the literature we affirm that postprandial hypotension is a common disorder of blood pressure regulation, which may interfere with blood pressure measurements. Consequently, this phenomenon should be considered when evaluating the effects of antihypertensive medications in everyday routine.
5th ed. xviii, 605 s. : ill.
- Konspekt
- Ortopedie. Chirurgie. Oftalmologie
- NLK Obory
- oftalmologie
Though bivalve mollusks are keystone species and major species groups in aquaculture production worldwide, gamete biology is still largely unknown. This review aims to provide a synthesis of current knowledge in the field of sperm biology, including spermatozoa motility, flagellar beating, and energy metabolism; and to illustrate cellular signaling controlling spermatozoa motility initiation in bivalves. Serotonin (5-HT) induces hyper-motility in spermatozoa via a 5-HT receptor, suggesting a serotoninergic system in the male reproductive tract that might regulate sperm physiology. Acidic pH and high concentration of K+ are inhibitory factors of spermatozoa motility in the testis. Motility is initiated at spawning by a Na+-dependent alkalization of intracellular pH mediated by a Na+/H+ exchanger. Increase of 5-HT in the testis and decrease of extracellular K+ when sperm is released in seawater induce hyperpolarization of spermatozoa membrane potential mediated by K+ efflux and associated with an increase in intracellular Ca2+ via opening of voltage-dependent Ca2+ channels under alkaline conditions. These events activate dynein ATPases and Ca2+/calmodulin-dependent proteins resulting in flagellar beating. It may be possible that 5-HT is also involved in intracellular cAMP rise controlling cAMP-dependent protein kinase phosphorylation in the flagellum. Once motility is triggered, flagellum beats in asymmetric wave pattern leading to circular trajectories of spermatozoa. Three different flagellar wave characteristics are reported, including "full", "twitching", and "declining" propagation of wave, which are described and illustrated in the present review. Mitochondrial respiration, ATP content, and metabolic pathways producing ATP in bivalve spermatozoa are discussed. Energy metabolism of Pacific oyster spermatozoa differs from previously studied marine species since oxidative phosphorylation synthetizes a stable level of ATP throughout 24-h motility period and the end of movement is not explained by a low intracellular ATP content, revealing different strategy to improve oocyte fertilization success. Finally, our review highlights physiological mechanisms that require further researches and points out some advantages of bivalve spermatozoa to extend knowledge on mechanisms of motility.
- MeSH
- druhová specificita MeSH
- energetický metabolismus MeSH
- flagella fyziologie MeSH
- mlži fyziologie MeSH
- motilita spermií fyziologie MeSH
- spermie cytologie fyziologie MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Motility is a characteristic function of the male gamete, which allows spermatozoa to actively reach and penetrate the female gamete in organisms with internal and external fertilization. Sperm motility is acquired under the control of many extrinsic and intrinsic factors and is based on a specialized structure of the sperm flagellum called "axoneme". An overview of how the sperm flagellum is organized, and it operates to support cell motility is presented, with special focus on the molecular mechanisms and factors involved in the development, maintenance and control of motility. Data obtained in aquatic organisms with external fertilization, such as sea urchins, ascidians or fishes are critically analyzed because they constitute model species on which most of the present day understanding of sperm motility function is based. In most animal species, sperm motility is dependent on a long appendage called flagellum. Flagella are essential organelles found in most eukaryotic cells; their basic structure is the axoneme, which consists of a scaffold of microtubules and is responsible for movement in an autonomous manner if ATP-energy is present. Flagellar beat propels the cell through the medium which surrounds sperm cells and is responsible of the translational drive of spermatozoa. The present paper includes: (1) an introduction to typical sperm morphology and ultrastructure in most aquatic species, (2) the motility apparatus or axoneme of the spermatozoa: the axoneme, (3) the structural and biochemical composition of the axoneme, (4) the axonemal motor or dynein, and its operation, (5) the regulation of motility at axoneme and cell membrane levels, including several effectors such as Ca2+ ions, (6) biophysical features of the wave propagation mechanism in motile spermatozoa, (7) the energy production and consumption, and (8) the building of a flagellum. Flagellar beating in aquatic animals is illustrated using several examples in figures and video-clips. These types of data are also used for computer simulation of various aspects of the modulation of sperm motility of marine animals.
