Search results for "POLARIZATION"
showing 10 items of 1884 documents
Clinicopathological and Immunohistochemical Study of Oral Amalgam Pigmentation
2012
Amalgam tattoo, the most common exogenous oral pigmentation, can sometimes be confused with melanotic lesions, being then biopsied. We present the clinicopathological characteristics of 6 biopsied cases (5 females and 1 male) of oral amalgam pigmentation. The most common location was the gingival mucosa, followed by the buccal and palatal mucosa. Morphology and distribution (stromal, perivascular, perineural, endomysial) of pigmentation was variable; there was only 1 case with fibrous capsular reaction and likewise only a single case of granulomatous foreign body reaction. Morphological variability is conditioned by the timing and amount of the pigment deposit, which is often associated wit…
Subthreshold oscillation of the membrane potential in magnocellular neurones of the rat supraoptic nucleus
2000
The hypothalamic supraoptic nucleus (SON) contains two major populations of magnocellular neurosecretory neurones, producing and secreting vasopressin and oxytocin, respectively (for review see Poulain & Wakerley 1982). Neurones of a subpopulation of supraoptic neurosecretory cells share the capability of generating phasic bursts of action potentials. In these neurones, action potentials are succeeded by a depolarizing afterpotential (DAP; Andrew, 1987; Armstrong et al. 1994; Li et al. 1995). Depending on the discharge frequency, DAPs summate, eventually resulting in the generation of a plateau potential that gives rise to the discharge of a long-lasting train of action potentials. Thus, DA…
Switching between persistent firing and depolarization block in individual rat CA1 pyramidal neurons
2018
The hippocampal formation plays a role in mnemonic tasks and epileptic discharges in vivo. In vitro, these functions and malfunctions may relate to persistent firing (PF) and depolarization block (DB), respectively. Pyramidal neurons of the CA1 field have previously been reported to engage in either PF or DB during cholinergic stimulation. However, it is unknown whether these cells constitute disparate populations of neurons. Furthermore, it is unclear which cell-specific peculiarities may mediate their diverse response properties. However, it has not been shown whether individual CA1 pyramidal neurons can switch between PF and DB states. Here, we used whole cell patch clamp in the current …
Use of QT intervals for a more accurate diagnose of syncope and evaluation of syncope severity.
2014
Abstract BACKGROUND: This study aimed to evaluate the use of QT intervals, their diagnostic predictive value in patients with syncope and their relationship with syncope severity. METHODS: One hundred and forty nine patients with a diagnosis of syncope were admitted to Internal Medicine departments at the University of Palermo, Italy, between 2006 and 2012, and 140 control subjects hospitalised for other causes were enrolled. QT maximum, QT minimum, QTpeak, QT corrected, QT dispersion and Tpeak-to-Tend interval were compared between two groups. The paper medical records were used for scoring with San Francisco Syncope Rule (SFSR), Evaluation of Guidelines in SYncope Study (EGSYS) score and …
L-type calcium channel activity in human atrial myocytes as influenced by 5-HT.
1993
5-Hydroxytryptamine (10 mumol/l; 5-HT) exerted a positive inotropic effect associated with an increase in the Ca2+ current (ICa) in the human right atrium. For detailed analysis, L-type Ca2+ channel currents were recorded from cell-attached patches using 100 mmol/l Ba2+ as charge carrier. Ca2+ channel activity was identified, first, by burst-like inwardly directed currents and, second, by the appearance of long channel openings promoted by Bay K 8644 (1 mumol/l) upon repetitive depolarizations from -80 to 0 mV. The unitary conductance of the Ca2+ channel amounted to 25.8 pS. During superfusion with 5-HT, ensemble averaged (mean) current was enhanced by about 60%. The increase in mean curren…
Characterization of 5-hydroxytryptamine release from isolated rabbit and rat trachea: the role of neuroendocrine epithelial cells and mast cells
1995
Rabbit or rat isolated tracheae were incubated in vitro, and the release of 5-hydroxytryptamine (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) was determined by HPLC with electrochemical detection. Release of 5-HT from rabbit tracheae could be evoked by the calcium ionophore A 23187 and, in a calcium-dependent manner, by depolarizing concentrations of potassium (45 mmol/l), but not by the mast cell degranulating drug compound 48/80. High potassium- and A 23187-evoked release of 5-HT was markedly higher from tracheae of newborn compared to adult rabbits. In rabbit tracheae, mechanical removal of the mucosa resulted in 80-90% reduction in tissue 5-HT and in a similar reduction …
Presynaptic effects of anandamide and WIN55,212-2 on glutamatergic nerve endings isolated from rat hippocampus
2006
We examined the effects of the endocannabinoide-anandamide (AEA), the synthetic cannabinoid, WIN55,212-2, and the active phorbol ester, 4-beta-phorbol 12-myristate 13-acetate (4-beta-PMA), on the release of [(3)H]d-Aspartate ([(3)H]d-ASP) from rat hippocampal synaptosomes. Release was evoked with three different stimuli: (1) KCl-induced membrane depolarization, which activates voltage-dependent Ca(2+) channels and causes limited neurotransmitter exocytosis, presumably from ready-releasable vesicles docked in the active zone; (2) exposure to the Ca(2+) ionophore-A23187, which causes more extensive transmitter release, presumably from intracellular reserve vesicles; and (3) K(+) channel block…
Global electrical heterogeneity as a predictor of cardiovascular mortality in men and women
2018
Aims The aim of this study was to investigate the contribution of depolarization and repolarization abnormalities, specially abnormalities in global electrical heterogeneity of heart in cardiovascular disease (CVD) and all-cause mortality. Methods and results Eight hundred and forty men and 911 women, average age of 63 years participated in this study with average follow-up was 14 years. Six electrocardiogram/vector electrocardiogram (ECG/VECG) markers QRS-duration, QTc-interval, QRST-angle, sum of absolute QRST integral (SAI QRST), T-wave roundness, and TV1-amplitude were estimated from VECG measurements. Hazard ratios (HRs) for CVD events (164 deaths) and all-cause mortality (383 deaths) …
Role of K+ and Ca2+ fluxes in the cerebroarterial vasoactive effects of sildenafil
2007
The aim of this study was to assess the role of K(+) and Ca(2+) fluxes in the cerebroarterial vasoactive effects of the phosphodiesterase-5 inhibitor sildenafil. We used isolated rabbit basilar arteries to assess the effects of extracellular K(+) raising on sildenafil-induced vasodilatation, and studied the pharmacological interaction of sildenafil with selective modulators of membrane K(+) and Ca(2+) channels. Expression of Kv1 subunits of K(+) channels was assessed at messenger and protein levels. Parallel experiments were carried out with zaprinast for comparison. Sildenafil (10 nM-0.1 mM) induced concentration-dependent relaxation of endothelin-1 (10 nM)-precontracted arteries, which wa…
Modulation of cytosolic free calcium concentration by ?1-adrenoceptors in rat atrial cells
1992
The effects of α1-adrenoceptor stimulation by phenylephrine (PE) and β-adrenoceptor stimulation by isoprenaline (ISO) on Ca2+ current (ICa) and free intracellular Ca2+ concentration ([Ca2+]i) were studied in isolated atrial myocytes from rat hearts. PE did not significantly affect the magnitude of ICa, whereas large increases of peak ICa were observed in response to ISO. In electrically driven cells, PE evoked a concentration-dependent, gradual increase in diastolic [Ca2+]i and, initially, an increase in the height of peak [Ca2+]i transients. When the diastolic [Ca2+]i was increased to a greater extent, the amplitude of [Ca2+]i transients was decreased. Simultaneous measurements of [Ca2+]i …