Search results for "Calcium"
showing 10 items of 1740 documents
Biochemical characteristics of the soluble organic matrix from the shell of three recent terebratulid brachiopod species.
2008
7 pages; International audience; To build their shells, brachiopods secrete a mixture of proteins and polysaccharides, collectively called the organic matrix. This matrix mediates the calcification process by allowing crystal nucleation followed by elongation and finally by stopping the crystal growth. Ultimately, the matrix controls the different microstructures formed. Brachiopod shells are composites with both organic and inorganic constituents intimately associated. This work represents an attempt to characterize the matrices using two combined approaches: (1) scanning electron microscopy for localization within the shell, (2) analysing extracted matrices at the molecular level to deter…
Understanding altered contractile properties in advanced age : insights from a systematic muscle modelling approach
2023
Age-related alterations of skeletal muscle are numerous and present inconsistently, and the effect of their interaction on contractile performance can be nonintuitive. Hill-type muscle models predict muscle force according to well-characterised contractile phenomena. Coupled with simple, yet reasonably realistic activation dynamics, such models consist of parameters that are meaningfully linked to fundamental aspects of muscle excitation and contraction. We aimed to illustrate the utility of a muscle model for elucidating relevant mechanisms and predicting changes in output by simulating the individual and combined effects on isometric force of several known ageing-related adaptations. Simu…
Alteration of loosely bound calcium in the guinea pig organ of Corti after treatment with diltiazem as calcium channel blocker
1997
After oral administration of the organic calcium channel blocker diltiazem to guinea pigs for 7 days, calcium ions were precipitated with potassium antimonate in the cochleae. The spatial distribution of the precipitates was studied by energy-filtering transmission electron microscopy and the amount of the ultrastructural reaction products formed was determined semiquantitatively by an image processing system. Compared with untreated control ears, the number of the formed precipitates was reduced drastically in the inner hair cells after diltiazem treatment. In addition, electron microscopic analysis revealed that the number of calcium precipitates attached at the basolateral membrane of th…
Food consumption and nutrient intakes with a special focus on milk product consumption in early pubertal girls in Central Finland
2005
AbstractObjectiveTo evaluate the current status of dietary intakes in early pubertal girls with a special focus on milk products.DesignCross-sectional data using 3-day food records.SubjectsEight hundred and sixty girls, aged 10–12 years, at Tanner maturation stage I-III.ResultsThe mean consumption of milk products (620 g day−1) was similar to that of a Finnish study in the 1980s, while the consumption of non-milk drinks (403 gday−1) had increased. Twelve per cent of the girls had a dairy-restricted diet and consumed significantly less milk products than girls with a non-restricted diet (465 vs. 644 g day−1, P<0.001). Girls with low milk product consumption had the highest non-milk drinks…
Is diabetes the cost to pay for a greater cardiovascular prevention?
2010
The recent JUPITER (Justification for the Use of statins in Primary prevention: an Intervention Trial Evaluating Rosuvastatin) trial is another study providing evidence about the effectiveness of statin therapy in reducing cardiovascular risk. Yet, in this study significantly higher glycated hemoglobin levels and incidence rates of diabetes were observed in persons treated with rosuvastatin than the placebo group. It should be noted that adverse effects on glucose metabolism have already been reported, albeit rarely, in previous trials with statins. Although the exact mechanisms involved are unknown, it seems that statins may deteriorate glycemic control by decreasing different metabolites,…
Characterization of adenosine receptors in guinea-pig isolated left atria
1989
1. The effects of purinergic stimulation on action potential, force of contraction, 86Rb efflux and 45Ca uptake were investigated in guinea-pig left atria. 2. Adenosine exerted a negative inotropic effect which was antagonized by adenosine deaminase but enhanced by dipyridamole. 3. The negative inotropic effect of adenosine was mimicked by 5'-(N-ethyl)-carboxamido-adenosine (NECA) and the isomers of N6-(phenyl-isopropyl)-adenosine, R-PIA and S-PIA. NECA and R-PIA were about 100 times more potent than adenosine, whereas R-PIA was about 100 times more potent than S-PIA. 4. The inotropic effects of adenosine (in the presence of dipyridamole), NECA, R-PIA and S-PIA were competitively antagonize…
Adrenoceptor-mediated effects on calcium channel currents are antagonized by 5?-(N-ethyl)-carboxamido-adenosine in guinea-pig atrial cells
1992
In guinea-pig atrial myocytes, the effects of the adenosine analogue 5′-(N-ethyl)-carboxamido-adenosine (NECA) in the presence of isoprenaline (ISO) on Ca2+ channel activity were analyzed. Single Ca2+ channel currents were recorded from cell-attached patches by application of several hundred 100 ms depolarizing steps. Under control conditions, burstlike activity of channel openings during some depolarizing steps were followed by variably long periods of quiescence (blank sweeps). During superfusion with ISO (100 nmol/l), ensemble-averaged (mean) current was increased by about 150%. The underlying mechanism was found to be a significant increase in the channel availability, defined as the ra…
Parathyroid hormone serum concentration kinetic profile in critically ill patients undergoing continuous renal replacement therapies: a prospective o…
2021
Introduction: Elevated serum parathormone (PTH) levels have been observed in acute kidney injury and are related to calcium-phosphate metabolism disturbance, decreased renal production of 1,25 dihydroxyvitamin D3, impaired renal PTH excretion, and other renal-independent factors. There are no data regarding PTH concentration kinetics in critically ill patients undergoing continuous renal replacement therapies (CRRT) in an intensive care setting. The primary objective of this study was to investigate trends in PTH serum levels in critically ill patients with multiorgan failure undergoing CRRT, by performing periodic PTH measurements in the acute phase of critical illness. Material and method…
Inhibition of Delta-like 4 mediated signaling induces abortion in mice due to deregulation of decidual angiogenesis.
2013
Objective: To explore whether the Dll4/Notch1 pathway plays a key role in regulating the vascular endothelial growth factor (VEGF)/VEGF receptor 2 (VEGFR2) driven decidual angiogenesis and related pregnancy through induction of a tip/stalk phenotype. Methods: Progesterone-replaced ovariectomized pregnant mice received a single injection of YW152F (Dll4 blocking antibody, BAb) or placebo at embryonic day (E) 4.5. Animals were sacrificed at different time points; blood and uterus were collected for further analysis. Number of embryos and implantation site, uteri weight, and serum progesterone levels were assessed. Alterations in the tip/stalk phenotype were determined by quantitative immunofl…
Magnesium and Alzheimer’s Disease
2015
Environmental factors, including nutrition and metal elements, are implicated in the pathophysiology of Alzheimer’s disease (AD). Several in vitro and in vivo data indicate a role for magnesium (Mg) in many biological and clinical aspects of AD. Mg deficiency, aside from having a negative impact on the energy production pathways required by the mitochondria to generate adenosine triphosphate, also affects many biochemical mechanisms vital for neuronal properties and synaptic plasticity, including the response of N-methyl- d -aspartate receptors to excitatory amino acids, stability, and viscosity of the cell membrane. Mg also has an action as a mild calcium antagonist, and as an antioxidant …