Role of extracellular Ca2+ in diaphragmatic contraction: effects of ouabain, monensin, and ryanodine

1992 ◽  
Vol 73 (1) ◽  
pp. 30-35 ◽  
Author(s):  
J. H. Zavecz ◽  
W. M. Anderson
Keyword(s):  
Relaxation Time ◽  
Free Solution ◽  
Pharmacological Agents ◽  
Resting Tension ◽  
High K ◽  
Before And After ◽  
Small Muscle ◽  
Ionophore Monensin

The effects of zero extracellular Ca2+ on the contractility of rat diaphragmatic strips in vitro were studied in conjunction with various pharmacological agents known to influence the intracellular Ca2+ concentration: the Na+ ionophore, monensin, and the Na(+)-K+ pump inhibitor, ouabain, which enhance [Ca2+]i, caffeine, which induces Ca2+ release from the sarcoplasmic reticulum (SR), and ryanodine, which prevents Ca2+ retention by the SR. The effect of increasing [Ca2+]i on diaphragmatic contraction was assessed by comparing contractions induced by 120 mM K+ in the small muscle strips before and after the addition of ouabain or monensin. Monensin (20 microM) and ouabain (1–100 microM) augmented contractions up to threefold. Treatment of diaphragm strips with 3 nM ryanodine increased baseline tension 360% above the original resting tension but only if the diaphragm was electrically stimulated concurrently; 100 microM ryanodine induced contracture in quiescent tissue. High K+ contractures were of greater magnitude in the presence of ryanodine compared with control, and relaxation time was prolonged by greater than 200%. Ca(2+)-free conditions ameliorated these actions of ryanodine. Ryanodine reduced contractions induced by 10 mM caffeine and nearly abolished them in Ca(2+)-free solution. The data demonstrate that extracellular Ca2+ is important in certain types of contractile responses of the diaphragm and suggest that the processes necessary to utilize extracellular Ca2+ are present in the diaphragm.

scholarly journals Role of Na+/Ca2+ exchanger in Ca2+ homeostasis in rat suprachiasmatic nucleus neurons

2015 ◽  
Vol 113 (7) ◽  
pp. 2114-2126 ◽  
Author(s):  
Yi-Chi Wang ◽  
Ya-Shuan Chen ◽  
Ruo-Ciao Cheng ◽  
Rong-Chi Huang
Keyword(s):  
Suprachiasmatic Nucleus ◽  
Signal Amplitude ◽  
Free Solution ◽  
Fast Decay ◽  
Plasmic Reticulum ◽  
High K ◽  
Intracellular Ca ◽  
Kinetics Of ◽  
Ionophore Monensin

Intracellular Ca2+ is critical to the central clock of the suprachiasmatic nucleus (SCN). However, the role of Na+/Ca2+ exchanger (NCX) in intracellular Ca2+ concentration ([Ca2+]i) homeostasis in the SCN is unknown. Here we show that NCX is an important mechanism for somatic Ca2+ clearance in SCN neurons. In control conditions Na+-free solution lowered [Ca2+]i by inhibiting TTX-sensitive as well as nimodipine-sensitive Ca2+ influx. With use of the Na+ ionophore monensin to raise intracellular Na+ concentration ([Na+]i), Na+-free solution provoked rapid Ca2+ uptake via reverse NCX. The peak amplitude of 0 Na+-induced [Ca2+]i increase was larger during the day than at night, with no difference between dorsal and ventral SCN neurons. Ca2+ extrusion via forward NCX was studied by determining the effect of Na+ removal on Ca2+ clearance after high-K+-induced Ca2+ loads. The clearance of Ca2+ proceeded with two exponential decay phases, with the fast decay having total signal amplitude of ∼85% and a time constant of ∼7 s. Na+-free solution slowed the fast decay rate threefold, whereas mitochondrial protonophore prolonged mostly the slow decay. In contrast, blockade of plasmalemmal and sarco(endo)plasmic reticulum Ca2+ pumps had little effect on the kinetics of Ca2+ clearance. RT-PCR indicated the expression of NCX1 and NCX2 mRNAs. Immunohistochemical staining showed the presence of NCX1 immunoreactivity in the whole SCN but restricted distribution of NCX2 immunoreactivity in the ventrolateral SCN. Together our results demonstrate an important role of NCX, most likely NCX1, as well as mitochondrial Ca2+ uptake in clearing somatic Ca2+ after depolarization-induced Ca2+ influx in SCN neurons.

Haemostatic Platelet Plug Formation in the Isolated Rabbit Mesenteric Preparation - An Analysis of Red Blood Cell Participation

1980 ◽  
Vol 44 (01) ◽  
pp. 006-008 ◽  
Author(s):  
D Bergqvist ◽  
K-E Arfors
Keyword(s):  
Whole Blood ◽  
Platelet Rich Plasma ◽  
Adenosine Diphosphate ◽  
In Vitro Test ◽  
Pharmacological Agents ◽  
Vitro Test ◽  
Releasing Effect ◽  
Plug Formation

SummaryIn a model using an isolated rabbit mesenteric preparation microvessels were transected and the time until haemostatic plugs formed was registered. Perfusion of platelet rich plasma gave no haemostasis whereas whole blood did. Addition of chlorpromazine or adenosine to the whole blood significantly prolonged the time for haemostasis, and addition of ADP to the platelet rich plasma significantly shortened it. It is concluded that red cells are necessary for a normal haemostasis in this model, probably by a combination of a haemodynamic and ADP releasing effect.The fundamental role of platelets in haemostatic plug formation is unquestionable but there are still problems concerning the stimulus for this process to start. Three platelet aggregating substances have been discussed – thrombin, adenosine diphosphate (ADP) and collagen. Evidence speaking in favour of thrombin is, however, very minimal, and the discussion has to be focused on collagen and ADP. In an in vitro system using polyethylene tubings we have shown that "haemostasis" can be obtained without the presence of collagen but against these results can be argued that it is only another in vitro test for platelet aggregation (1).To be able to induce haemostasis in this model, however, the presence of red blood cells is necessary. To further study this problem we have developed a model where haemostatic plug formation can be studied in the isolated rabbit mesentery and we have briefly reported on this (2).Thus, it is possible to perfuse the vessels with whole blood as well as with platelet rich plasma (PRP) and different pharmacological agents of importance.

Sensory regulation of quadrupedal locomotion: a top-down or bottom-up control system?

2012 ◽  
Vol 108 (3) ◽  
pp. 709-711 ◽  
Author(s):  
Yann Thibaudier ◽  
Marie-France Hurteau
Keyword(s):  
Control System ◽  
Central Pattern Generators ◽  
Top Down ◽  
Bottom Up ◽  
Sensory Inputs ◽  
Sensory Regulation ◽  
Before And After ◽  
Pattern Generators

Propriospinal pathways are thought to be critical for quadrupedal coordination by coupling cervical and lumbar central pattern generators (CPGs). However, the mechanisms involved in relaying information between girdles remain largely unexplored. Using an in vitro spinal cord preparation in neonatal rats, Juvin and colleagues ( Juvin et al. 2012 ) have recently shown sensory inputs from the hindlimbs have greater influence on forelimb CPGs than forelimb sensory inputs on hindlimb CPGs, in other words, a bottom-up control system. However, results from decerebrate cats suggest a top-down control system. It may be that both bottom-up and top-down control systems exist and that the dominance of one over the other is task or context dependent. As such, the role of sensory inputs in controlling quadrupedal coordination before and after injury requires further investigation.

Evidence against local neural mechanism for intestinal postprandial hyperemia

1983 ◽  
Vol 245 (3) ◽  
pp. H437-H446 ◽  
Author(s):  
R. A. Nyhof ◽  
C. C. Chou
Keyword(s):  
Oxygen Consumption ◽  
Oleic Acid ◽  
Neural Mechanism ◽  
Jejunal Mucosa ◽  
Vasoactive Substances ◽  
Before And After ◽  
Anesthetized Dogs ◽  
Postprandial Hyperemia

The role of local intestinal nerves in the nutrient-induced intestinal hyperemia was investigated in jejunal segments of anesthetized dogs by comparing the hyperemic effect of intraluminal glucose and oleic acid solutions before and after mucosal anesthesia and infusions of methysergide, hexamethonium, and tetrodotoxin. Methysergide, hexamethonium, and tetrodotoxin all failed to alter either the vascular or metabolic responses to luminal placement of glucose or oleic acid. The increases in blood flow and oxygen uptake produced by glucose or oleic acid, however, were blocked or attenuated after exposing the mucosa to dibucaine. The effect was norepinephrine due to an altered vascular response to vasoactive substances as dibucaine did not alter vascular responses to isoproterenol or norepinephrine. Dibucaine, however, inhibited active transport and increased passive transport of glucose across rat intestinal sacs in vitro. Oxygen consumption of the canine jejunal mucosa was also inhibited by dibucaine in vitro. It seems that inhibition of the nutrient-induced intestinal hyperemia by dibucaine is due, at least in part, to its effect on oxygen consumption and glucose transport of the mucosal epithelial cells. Nutrient-induced hyperemia appears not to be neurally mediated but more closely related to metabolism.

Neuroprotective Effects of Increased Extracellular Ca2+ During Aglycemia in White Matter

2002 ◽  
Vol 88 (3) ◽  
pp. 1302-1307 ◽  
Author(s):  
Angus M. Brown ◽  
Bruce R. Ransom
Keyword(s):  
Action Potentials ◽  
Divalent Cations ◽  
Neuroprotective Effects ◽  
Adult Rat ◽  
Artificial Cerebrospinal Fluid ◽  
Before And After ◽  
Compound Action Potentials ◽  
Compound Action

We investigated the effects of extracellular [Ca2+] ([Ca2+]o) on aglycemia-induced dysfunction and injury in adult rat optic nerves. Compound action potentials (CAPs) from adult rat optic nerve were recorded in vitro, and the area under the CAP was used to monitor nerve function before and after 1 h periods of aglycemia. In control artificial cerebrospinal fluid (ACSF) containing 2 mM Ca2+, CAP function fell after 29.9 ± 1.5 (SE) min and recovered to 48.8 ± 3.9% following aglycemia. Reducing bath [Ca2+] during aglycemia progressively improved recovery. For example, in Ca2+-free ACSF, the CAP recovered to 99.1 ± 3.8%. Paradoxically, increasing bath [Ca2+] also improved recovery from aglycemia. In 5 or 10 mM bath [Ca2+], CAP recovered to 78.8 ± 9.2 or 91.6 ± 5.2%, respectively. The latency to CAP failure during aglycemia increased as a function of bath [Ca2+] from 0 to 10 mM. Increasing bath [Mg2+] from 2 to 5 or 10 mM, with bath [Ca2+] held at 2 mM, increased latency to CAP failure with aglycemia and improved recovery from this insult. [Ca2+]o recorded with calcium-sensitive microelectrodes in control ACSF, dropped reversibly during aglycemia from 1.54 ± 0.03 to 0.45 ± 0.04 mM. In the presence of higher ambient levels of bath [Ca2+] (i.e., 5 or 10 mM), the aglycemia-induced decrease in [Ca2+]o declined, indicating that less Ca2+ left the extracellular space to enter an intracellular compartment. These results indicate that the role of [Ca2+], and divalent cations in general, during aglycemia is complex. While extracellular Ca2+ was required for irreversible aglycemic injury to occur, higher levels of [Ca2+] or [Mg2+] increased the latency to CAP failure and improved the extent of recovery, apparently by limiting Ca2+ influx. These effects are theorized to be mediated by divalent cation screening.

Endothelium-dependent arterial wall tone elasticity modulated by blood viscosity

2002 ◽  
Vol 282 (2) ◽  
pp. H389-H394 ◽  
Author(s):  
Edmundo I. Cabrera Fischer ◽  
Ricardo L. Armentano ◽  
Franco M. Pessana ◽  
Sebastián Graf ◽  
Luis Romero ◽  
...  
Keyword(s):  
Blood Viscosity ◽  
Muscle Activation ◽  
Arterial Wall ◽  
Mock Circulation ◽  
Significant Difference ◽  
Before And After ◽  
Strain Relationship ◽  
Instantaneous Pressure

The role of blood viscosity on arterial wall elasticity before and after deendothelization (DE) was studied. Seven ovine brachiocephalic arteries were studied in vitro under physiological pulsatile flow conditions achieved by a mock circulation loop. Instantaneous pressure and diameter signals were assessed in each arterial segment. Incremental elastic modulus ( E inc) was calculated using the slope of the pure elastic stress-strain relationship. There was no significant difference between E inc values before and after DE (3.11 vs. 3.16 107 dyn/cm2) at a blood viscosity of 2.00 mPa · s. Increases in blood viscosity (2.50, 3.00, 3.50, and 4.00 mPa · s) always resulted in decreases of E inc before DE; inversely, increases in blood viscosity resulted in increases of E inc after DE. These values of E inc, for identical levels of blood viscosity, were always significantly lower ( P< 0.05) before DE than those obtained after DE. Arterial wall elasticity assessed through E inc was strongly influenced by blood viscosity, probably due to presence or absence of endothelium relaxing factors or to direct shear smooth muscle activation when endothelial cells are removed.

CGRP and ANF cause relaxation of opossum internal anal sphincter via different mechanisms

1991 ◽  
Vol 260 (5) ◽  
pp. G764-G769 ◽  
Author(s):  
S. Rattan ◽  
C. Moummi ◽  
S. Chakder
Keyword(s):  
Smooth Muscle ◽  
Anal Sphincter ◽  
Cyclic Nucleotides ◽  
Internal Anal Sphincter ◽  
Camp Content ◽  
Calcitonin Gene ◽  
Before And After ◽  
Camp And Cgmp

This investigation examined and compared the role of cyclic nucleotides in the mediation of internal anal sphincter (IAS) relaxation caused by the addition of neuropeptide calcitonin gene-related peptide (CGRP) and atrial natriuretic factor (ANF). The studies were performed in vitro on smooth muscle strips of opossum IAS. The relaxation produced by CGRP and ANF was examined before and after the addition of tetrodotoxin (TTX) (1 x 10(-6)M). At this concentration, TTX did not have any significant effect on the relaxation produced by either CGRP or ANF, suggesting that these peptides act directly on the smooth muscle. Addition of CGRP (3 x 10(-6) M) produced the maximal relaxation and significantly increased cAMP content without changing cGMP. On the other hand, addition of ANF (3 x 10(-6) M) caused a similar fall in IAS tension that was accompanied by a significant elevation in cGMP without any change in cAMP content. The rises in the levels of cyclic nucleotides preceded the onset of fall in the resting tension of IAS. Our results demonstrate that CGRP and ANF relax isolated strips of opossum IAS by their action directly at the smooth muscle and that this relaxation is associated with an increase in cAMP and cGMP, respectively. The studies suggest the presence of both cAMP and cGMP pathways in the IAS and that the relaxation of IAS smooth muscle in response to different peptides may occur via a specific intracellular biochemical pathway.

scholarly journals Reassessing the Role of Intra-Arterial Drug Delivery for Glioblastoma Multiforme Treatment

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Jason A. Ellis ◽  
Matei Banu ◽  
Shaolie S. Hossain ◽  
Rajinder Singh-Moon ◽  
Sean D. Lavine ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Targeted Delivery ◽  
Optical Measurements ◽  
Pharmacological Agents ◽  
Cellular Targets ◽  
Therapeutic Landscape ◽  
Rational Drug

Effective treatment for glioblastoma (GBM) will likely require targeted delivery of several specific pharmacological agents simultaneously. Intra-arterial (IA) delivery is one technique for targeting the tumor site with multiple agents. Although IA chemotherapy for glioblastoma (GBM) has been attempted since the 1950s, the predicted benefits remain unproven in clinical practice. This review focuses on innovative approaches to IA drug delivery in treating GBM. Guided by novel in vitro and in vivo optical measurements, newer pharmacokinetic models promise to better define the complex relationship between background cerebral blood flow and drug injection parameters. Advanced optical technologies and tracers, unique nanoparticles designs, new cellular targets, and rational drug formulations are continuously modifying the therapeutic landscape for GBM. Personalized treatment approaches are emerging; however, such tailored approaches will largely depend on effective drug delivery techniques and on the ability to simultaneously deliver multidrug regimens. These new paradigms for tumor-selective drug delivery herald dramatic improvements in the effectiveness of IA chemotherapy for GBM. Therefore, within this context of so-called “precision medicine,” the role of IA delivery for GBM is thoroughly reassessed.

scholarly journals The role of the cyclooxygenase products in evoking sympathetic activation in exercise

2007 ◽  
Vol 293 (3) ◽  
pp. H1861-H1868 ◽  
Author(s):  
Jian Cui ◽  
Patrick McQuillan ◽  
Afsana Momen ◽  
Cheryl Blaha ◽  
Raman Moradkhan ◽  
...  
Keyword(s):  
Animal Studies ◽  
Muscle Sympathetic Nerve Activity ◽  
Prostaglandin Synthesis ◽  
Pharmacological Agents ◽  
Exercise Pressor Reflex ◽  
Exercise Blood Pressure ◽  
Before And After ◽  
Pressor Reflex ◽  
Bier Block

Animal studies suggest that prostaglandins in skeletal muscles stimulate afferents and contribute to the exercise pressor reflex. However, human data regarding a role for prostaglandins in this reflex are varied, in part because of systemic effects of pharmacological agents used to block prostaglandin synthesis. We hypothesized that local blockade of prostaglandin synthesis in exercising muscles could attenuate muscle sympathetic nerve activity (MSNA) responses to fatiguing exercise. Blood pressure (Finapres), heart rate, and MSNA (microneurography) were assessed in 12 young healthy subjects during static handgrip and postexercise muscle ischemia (PEMI) before and after local infusion of 6 mg of ketorolac tromethamine in saline via Bier block (regional intravenous anesthesia). In the second experiment ( n = 10), the same amount of saline was infused via the Bier block. Ketorolac Bier block decreased the prostaglandins synthesis to ∼33% of the baseline. After ketorolac Bier block, the increases in MSNA from the baseline during the fatiguing handgrip was significantly lower than that before the Bier block (before ketorolac: Δ502 ± 111; post ketorolac: Δ348 ± 62%, P = 0.016). Moreover, the increase in total MSNA during PEMI after ketorolac was significantly lower than that before the Bier block ( P = 0.014). Saline Bier block had no similar effect. The observations indicate that blockade of prostaglandin synthesis attenuates MSNA responses seen during fatiguing handgrip and suggest that prostaglandins contribute to the exercise pressor reflex.

scholarly journals GENE SILENCING

2018 ◽  
Vol 25 (12) ◽  
pp. 1954-1960
Author(s):  
Farah Deeba Khan ◽  
Ghazala Irshad ◽  
Samra Hafiz
Keyword(s):  
Cell Proliferation ◽  
Hela Cells ◽  
Mapk Pathway ◽  
In Vitro Study ◽  
Small Gtpase ◽  
Molecular Medicine ◽  
Tumor Growth Inhibition ◽  
Before And After

Objectives: Cancer, the most complex group of genetic disorders results due to over expression or mutation of oncogenes/molecules involved in cell signaling pathways. KRAS is an oncogene that encodes a small GTPase protein with two isoforms KRasA & KRasB and is involved in the regulation of cell division. KRas is frequently found mutated in lung, pancreas, colorectal and many other cancers. Various studies have found that KRasB promotes cell proliferation and inhibits apoptosis whereas KRasA has negligible role in cell proliferation or rather is involved in apoptosis at times. Several experiments have shown tumor growth inhibition by silencing KRas in various tumor models having a differential allelic expression.The goal of our study was to determine the possible differential role of KRas A and B on MAPK Pathway. To examine the disparity in role of various isoforms of KRas on apoptosis, we evaluated the expression of these isoforms through different modalities in HeLa cells before and after silencing KRas through RNA interference. Study Design: In vitro study for isolation of protein molecules (Proteomics) and to study various genes (Genomics) through Polymerase chain reaction. Study Duration: December, 2011-September, 2014. Setting: Center for Research in Molecular Medicine, University of Lahore. Material & Methods: In present study, we studied the expression level and behavior of many sets of molecules such as KRasA, KrasB, Bad, Bcl2, BclxL and Mcl-1 through gene quantitation by Real Time PCR. We also analyzed the protein expression through Western blot immune-precipitation. All the tests were done before and after 48-hours of silencing of HeLa cells with shRNA designed for KRas. Results: We successfully downregulated KRasB (80%) but found upregulation of KRasA with continued cell proliferation. We also found overexpression of antiapoptotic genes, BclxL and Mcl1 and downregulation of proapoptotic molecule-Bad. Differences were considered significant at p< 0.01. Values were expressed as mean ± SEM from six separate experiments. Conclusion: We were able to show that in the absence of one proliferative gene, another sister gene upregulates and takes over the role of uncontrolled cell proliferation. This usually leads to failure of most cancer controltherapies. 

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