Responses Of Strips Research Articles

Aging differentially modifies agonist-evoked mouse detrusor contraction and calcium signals

Although aging-induced changes in urinary bladder neurotransmission have been studied in some detail, information regarding alterations in detrusor muscle is scanty and addresses only partial aspects of the myogenic response of detrusor. Rodent bladder aging shows several features similar to those reported in humans. The aim of this study was to characterize in aged mouse the alterations of detrusor muscle contraction and the putative underlying changes in Ca(2+) signals. We studied in vitro the myogenic contraction induced by agonists in detrusor strips from adult (3months old) or aged (23-25months old) mice. In addition, we determined the agonist-induced [Ca(2+)](i) signals by epifluorescence microscopy in fura-2 loaded isolated detrusor cells. Aging impaired the contractile response of bladder strips to cholinergic stimulation with bethanechol and to chemical depolarization with KCl-containing solutions. On the contrary, the response to purinergic stimulation (ATP) was enhanced. Aging also diminished the transient Ca(2+) signal evoked by bethanechol and the Ca(2+) influx induced by KCl in bladder strips. Treatments aimed to release calcium from intracellular stores (caffeine and a low level of ionomycin in Ca(2+)-free medium) showed that aging reduces the size of agonist-releasable stores. Similar to contraction, the mobilization of Ca(2+) by ATP was increased in aged cells. Therefore, the differential effects of aging on detrusor contraction are associated to alterations of [Ca(2+)](i) signals: the cholinergic inhibition is due to inhibition of voltage-operated Ca(2+) influx and reduction of the size of intracellular Ca(2+) stores, while the age-induced ATP response is accompanied by an enhanced Ca(2+) mobilization.

Changes in caveolin-1 expression and vasoreactivity in the aorta and corpus cavernosum of fructose and streptozotocin-induced diabetic rats

Hyperglycemia is a common defining feature in the development of endothelial dysfunction which plays a key role in the pathogenesis of both type 1 and type 2 diabetes. Caveolin-1 is the main structural component of caveolae which might be involved in the pathophysiology of macrovascular complications of diabetes. In this study we aimed to observe the effect of caveolin-1 on functional responses of aorta and corpus cavernosum in the streptozotocin and fructose-induced diabetes groups. Type 1 diabetes was induced by intraperitoneal administration of streptozotocin (60 mg/kg),. Type 2 diabetes by adding fructose in the rat's drinking water (10% (w/v)) for 8 weeks. For insulin treatment; rats were treated with insulin (6 U/kg) for 8 weeks. In Type I and Type II diabetic groups the contractile responses of corpus cavernosum strips to phenylephrine (EC 50:1.82 × 10 − 5 M;1.47 × 10 − 5 M, respectively)and relaxation responses to acetylcholine (EC 50:7.5 × 10 − 5 M;4.48 × 10 − 5 M, respectively)were significantly impaired. Contractile responses of aorticstrips to phenylephrine in diabetic groups were markedly decreased (EC 50:3.7 · 10 − 7 M;2.61 · 10 − 7 M respectively) and dose-dependent relaxation responses to acetylcholine were also attenuated (EC 50:3.23 · 10 − 6 M; 2.0 · 10 − 6 M respectively). Treatment with insulin improved the functional responses in the aorta and corpus cavernosum. Protein expression of caveolin-1 was increased in the aorta and corpus cavernosum of the diabetic groups, but this increase seen in the streptozotocin group was more significant than the fructose group. Our findings indicate that an attenuation of the functional responses in both diabetes groups were probably associated with an enhanced expression of caveolin-1, and therefore a decrease in the eNOS activity with a concomitant decrease in NO synthesis.

REGULATION OF CONTRACTILE ACTIVITY OF SMOOTH MUSCLE CELLS BY REACTIVE OXYGEN SPECIES: EVIDENCE FOR CYTOSKELETON-MEDIATED SIGNALING: PP.21.344

Objective: Recent studies showed that the cytoskeleton is the primary target of reactive oxygen species (ROS). This study examines the role of cytoskeleton network in regulation of vascular smooth muscle cell contractions by ROS. Design and Methods: Contractile responses of rat aorta strips triggered by depolarization and activation of α1-adrenergic receptors with high K+-medium and phenylephrine, respectively, were measured as increments of isometric tension. Cytoskeleton elements were modified with colchicines (10 μM), cytochalasin D (0,5 μM) and nocodazole (10 μM). Production of ROS was evoked by hydrogen peroxide (500 μM). Results: Hydrogen peroxide increased contractions triggered by high-K+ -medium by 25,2 ± 2,9% (p < 0,05) and reduced the amplitude of phenylephrine-induced contractile responses by 51,7 ± 2,9% (p < 0,05). Colchicine and cytochalasin D, but not nocodazole increased the relaxing effect of hydrogen peroxide in the reduction of phenylephrine-induced contractions by 83,5 ± 4,1% (p < 0,05) and 89,4 ± 2,9% (p < 0,05), respectively, but did not affect modulation by ROS of contractions triggered by depolarization. Conclusion: Our data demonstrate the involvement of cytoskeleton-mediated signaling in regulation by ROS of vascular smooth muscle cell contractions caused by activation of - α1-adrenergic receptors.

Impaired Bladder Function in Aging Male Rats

The prevalence of bladder dysfunctions increases with age. In humans it is difficult to separate changes related to exogenous factors from those directly related to the aging process. Some confounding variables can be avoided by studying age related changes in an animal model. We evaluated the impact of age on bladder function in vivo and in vitro, and characterized the corresponding morphological changes. Young (4 to 6 months old) and old (older than 28 to 30 months) male Fischer/Brown Norway rats were used in the study. Cystometric studies were done in conscious, freely moving rats. After cystometry tissue strips from the bladder body were used in in vitro studies of muscarinic receptor activation and electrical field stimulation, and histological examination. Old rats had higher bladder weight than young rats but the bladder-to-body weight ratio did not change. We noted significant age related differences in 8 of 10 cystometric parameters. Old rats had increased bladder capacity, post-void residual volume, micturition volume and frequency, baseline and intermicturition pressure, and spontaneous activity but decreased micturition pressure. Bladder strip responses to carbachol and electrical field stimulation were significantly lower in old than in young rats. Histological examination revealed urothelial thinning, lower muscle mass and higher collagen content in the bladders of old vs young rats. Physiological aging alters bladder function in male rats even when external factors remain constant. Thus, in old rats bladder capacity, post-void residual urine and spontaneous activity are higher, and responses to muscarinic receptor stimulation and electrical field stimulation are lower than in young rats. Such changes correspond to findings in aging human bladders, supporting the view that the Fischer/Brown Norway rat is a useful model in which to study age related bladder function changes.

Dc magnetoelectric sensor based on direct coupling of Lorentz force effect in aluminum strip with transverse piezoelectric effect in 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 single-crystal plate

We report theoretically and experimentally a dc magnetoelectric sensor consisting of a thickness-polarized 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN-PT) piezoelectric single-crystal plate arranged along the longitudinal direction and sandwiched between a pair of electrically connected aluminum strips. The operation of the sensor is based on the direct coupling of the Lorentz force effect in the aluminum strips in response to an applied dc magnetic field under a reference ac electric current with the transverse piezoelectric effect in the PMN-PT single-crystal plate. The sensor shows a good linear ac electric voltage response to broad ranges of applied dc magnetic field of 0–180 mT and reference ac electric current of 1–100 mA, giving a high and linear current-controlled dc magnetic field sensitivity of 0.23 V/T/A. It also provides the direction information of the applied dc magnetic field.

Effectiveness of trimebutine maleate on modulating intestinal hypercontractility in a mouse model of postinfectious irritable bowel syndrome

Trimebutine maleate, which modulates the calcium and potassium channels, relieves abdominal pain in patients with irritable bowel syndrome. However, its effect on postinfectious irritable bowel syndrome is not clarified. The aim of this study was to investigate the effectiveness of trimebutine maleate on modulating colonic hypercontractility in a mouse model of postinfectious irritable bowel syndrome. Mice infected up to 8 weeks with T. spiralis underwent abdominal withdrawal reflex to colorectal distention to evaluate the visceral sensitivity at different time points. Tissues were examined for histopathology scores. Colonic longitudinal muscle strips were prepared in the organ bath under basal condition or to be stimulated by acetylcholine and potassium chloride, and consecutive concentrations of trimebutine maleate were added to the bath to record the strip responses. Significant inflammation was observed in the intestines of the mice infected 2 weeks, and it resolved in 8 weeks after infection. Visceral hyperalgesia and colonic muscle hypercontractility emerged after infection, and trimebutine maleate could effectively reduce the colonic hyperreactivity. Hypercontractility of the colonic muscle stimulated by acetylcholine and high K(+) could be inhibited by trimebutine maleate in solution with Ca(2+), but not in Ca(2+) free solution. Compared with 8-week postinfectious irritable bowel syndrome group, 2-week acute infected strips were much more sensitive to the stimulators and the drug trimebutine maleate. Trimebutine maleate was effective in reducing the colonic muscle hypercontractility of postinfectious irritable bowel syndrome mice. The findings may provide evidence for trimebutine maleate to treat postinfectious irritable bowel syndrome patients effectively.

A New Perfusion Model for Studying Erectile Function

The present study introduces a newly devised in vitro penile perfusion model, which allows the measurement of changes in intracavernosum pressure (ICP), tension, and cyclic nucleotides in penile tissue in a one-step procedure. We compared the penile perfusion model with the classical penile strip chamber model to develop the new model. We investigated the role of nitric oxide-cyclic guanosine monophosphate pathway in both systems activated by acetylcholine or electrical field stimulation (EFS). We measured cGMP (cyclic guanosine monophosphate) in the penile corpus cavernosum smooth muscle in both systems and perfusates in the penile perfusion model. We determined ICP, tension, and cGMP simultaneously in penile perfusion model during the experiments. Changes of tension and cGMP in both models, and of cGMP in perfusates and of ICP in penile perfusion model. In both systems, acetylcholine relaxed the phenylephrine-precontracted penile corpus cavernosum smooth muscle in a concentration-dependent manner. EFS decreased the tension in both models and ICP in the penile perfusion model in a frequency-dependent manner. Pretreatment with atropine, Nomega nitro-L-arginine-methyl ester (L-NAME), and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) blocked the acetylcholine-induced decrease in the tension in both models and ICP in penile perfusion model. Acetylcholine increased cGMP levels in the perfusate of penile perfusion model and the changes were attenuated by tetrodotoxin (TTX), atropine, L-NAME and ODQ. EFS increased cGMP levels of the penile corpus cavernosum smooth muscle of both models and the changes were attenuated by TTX, atropine, L-NAME, and ODQ. The results indicated that the responses of penile strip and perfused penile tissue to acetylcholine and EFS were very similar in both models in terms of tension and cGMP levels. Furthermore, the new model has more advantages over the classical penile strip chamber model in measuring intracavernosum metabolic changes and ICP without interruption of the procedure.

1688 THE INHIBITORY ROLE OF MELATONIN ON ISOLATED RAT URINARY BLADDER CONTRACTION: THE NOVEL PATHWAY FOR THE PHARMACOLOGICAL MANAGEMENT OF NOCTURIA

You have accessJournal of UrologyUrodynamics/Incontinence/Female Urology: Non-Neurogenic Voiding Dysfunction II1 Apr 20101688 THE INHIBITORY ROLE OF MELATONIN ON ISOLATED RAT URINARY BLADDER CONTRACTION: THE NOVEL PATHWAY FOR THE PHARMACOLOGICAL MANAGEMENT OF NOCTURIA In Ho Chang, Yong Wook Kwon, Moon Soo Ha, Byung Hoon Chi, Moo Yeol Lee, and Soon Chul Myung In Ho ChangIn Ho Chang More articles by this author , Yong Wook KwonYong Wook Kwon More articles by this author , Moon Soo HaMoon Soo Ha More articles by this author , Byung Hoon ChiByung Hoon Chi More articles by this author , Moo Yeol LeeMoo Yeol Lee More articles by this author , and Soon Chul MyungSoon Chul Myung More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2010.02.1513AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Nocturnal melatonin levels may affect bladder activity. Here, we tested the effects of melatonin on detrusor muscle contraction of isolated rat bladder METHODS We evaluated the effects of melatonin on the contractions induced by phenylephrine (PE), acetylcholine (ACh), betanechol (BCh), KCl, and electrical field stimulation (EFS) in 20 detrusor smooth muscles of Sprague-Dawley rats. To determine the mechanisms of the inhibitory responses after melatonin, melatonin pretreated muscle strips were reacted with the calcium channel antagonist (verapamil), the potassium channel blockers [tetraethyl ammonium (TEA), 4-aminopyridine (4-AP), and glibenclamide], direct voltage dependent calcium channel opener (Bay K 8644), and KN-93 [ specific calcium/calmodulin-dependent kinase II (CaMKII) inhibitor] RESULTS Melatonin pretreatment (10-8∼10-6 M) dose-dependently decreased the contractile responses of PE (10-9 ∼ 10-4 M) and Ach (10-9 ∼ 10-4 M). Melatonin (10-7 M) also blocked contraction induced by high KCl ([KCl]ECF; 35 mM, 70 mM, 105 mM and 140 mM) and EFS. Verapamil potentiated the relaxation response of melatonin-treated strips (10-7 M), but other potassium channel blockers did not. Melatonin pretreatment significantly decreased the contractile responses of Bay K 8644 (10-11 ∼ 10-7 M). KN-93 enhanced melatonin-induced relaxation. CONCLUSIONS The present results suggest that melatonin can inhibit bladder smooth muscles as a voltage dependent calcium antagonistic effect and calmodulin/CaMKII system inhibition. Clinical significance will be studied in the future. Seoul, Republic of Korea© 2010 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 183Issue 4SApril 2010Page: e652 Advertisement Copyright & Permissions© 2010 by American Urological Association Education and Research, Inc.MetricsAuthor Information In Ho Chang More articles by this author Yong Wook Kwon More articles by this author Moon Soo Ha More articles by this author Byung Hoon Chi More articles by this author Moo Yeol Lee More articles by this author Soon Chul Myung More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Effect of low concentrations of hydrogen peroxide on the contractile responses of rat detrusor smooth muscle strips

This study was designed to determine how the contractility of rat detrusor smooth muscle strips changes in the presence of low concentrations of hydrogen peroxide (H 2O 2). The strips were dissected from the base of Sprague–Dawley rat bladders and their contractile responses to a cumulative increase in H 2O 2 concentration (3 × 10 − 6 –3 × 10 − 2 g%) were measured. How the duration of exposure to the fixed concentration of 3 × 10 − 4 g% H 2O 2 affected contractility was also examined. Moreover, the effect of 3 × 10 − 4 g% H 2O 2 pretreatment on the response to cumulative increases in the concentrations of phenylephrine or acetylcholine (10 − 8 –10 − 4 M) was assessed. To elucidate the mechanism by which H 2O 2 induced contraction, we examined the effect of pretreatment with 10 nM Y-27632, 10 μM indomethacin, 10 μM SQ29548, 10 μM verapamil, 10 μM vitamin E, or 1 μM Bay-K 8644 on the contractile responses generated by cumulatively increasing the concentration of H 2O 2. H 2O 2-induced contractile responses in Ca 2+-free physiological solution were also examined. Low concentrations of H 2O 2 increased the contractile responses of the strips in a dose-dependent manner but increasing treatment duration decreased these responses. H 2O 2-pretreatment significantly augmented the contraction induced by phenylephrine ( P < 0.05) but had no effect on the response to acetylcholine. Pretreatment with Y-27632, indomethacin, vitamin E, verapamil, and Bay-K 8644 significantly inhibited the H 2O 2-induced contraction ( P < 0.05). SQ 29548-pretreatment had no effect. H 2O 2 could not increase the contractile responses in Ca 2+-free physiological solution. Thus, low concentrations of H 2O 2 may directly affect detrusor smooth muscles and thereby induce detrusor overactivity.

Preparation of a novel colorimetric luminescence sensor strip for the detection of indole-3-acetic acid

A novel colorimetric luminescence sensor strip for the detection of indole-3-acetic acid (IAA) has been fabricated by using green emissive quantum dots of cadmium telluride (CdTe QDs) as a background layer and a red emissive europium chelate, [4′-(9-anthryl)-2,2′:6′,2″-terpyridine-6,6″-diyl]bis(methylenenitrilo) tetrakis(acetate)-Eu 3+ (ATTA-Eu 3+), as a specific sensing layer coated on the surface of glass slide, respectively. The luminescence response of the sensor strip is given by the dramatic changes in emission colors from green to red at different IAA concentrations. This approach provides a simple, rapid, sensitive and accurate method for the detection of IAA without using any special scientific instruments.

All ahead stop! How intestinal motility adapts to cope with inflammation induced ulceration

All ahead stop! How intestinal motility adapts to cope with inflammation induced ulceration

Effect of phenoxybenzamine on the contractile responses of rabbit aortic and pulmonary arterial strips with various vasoconstrictors (author's transl)

Effect of phenoxybenzamine on the contractile responses of rabbit aortic and pulmonary arterial strips with various vasoconstrictors (author's transl)

Montelukast reduces ischaemia/reperfusion-induced bladder dysfunction and oxidant damage in the rat

The present study aimed to investigate the possible beneficial effects of the cysteinyl leukotriene-1 receptor antagonist montelukast on contractility and oxidant damage after ischaemia/reperfusion (I/R) of rat urinary bladder. The abdominal aorta of Sprague-Dawley rats was occluded to induce I/R. Montelukast (10 mg kg(-1)) or saline was administered intraperitoneally before I/R. In the sham-operated group, the abdominal aorta was left intact and the animals were treated with montelukast or saline. After decapitation, the bladder was removed and the tissue was either used for functional studies or stored for biochemical assays. In the I/R group, the isometric contractile responses of the bladder strips to carbachol (10(-8)-10(-4) M) were lower than those of the control group and were reversed by treatment with montelukast. Lipid peroxidation and myeloperoxidase activity of the bladder tissues in the I/R group were greater than in the sham-operated group. Montelukast treatment in the I/R group decreased these parameters compared with I/R alone. Similarly, the significant decrease in tissue glutathione level in the I/R group compared with controls was also prevented by montelukast. Treatment with montelukast almost completely reversed the low contractile responses of rat urinary bladder to carbachol and prevented oxidative tissue damage following I/R.

Flavonoid galangin prevents smooth muscle fatigue of pig urinary bladder

There is increasing evidence that the generation of free radicals plays a role in the development of bladder dysfunction. Flavonoids are a group of polyphenolic compounds with broad pharmacological activity. In the present study, the protective effects of the flavonoid galangin on the progressive decrease of bladder smooth muscle contractile responses during repetitive field stimulation (RFS; a model for muscular fatigue) were demonstrated. Pig detrusor strips were mounted for tension recording in organ baths aand were subjected to RFS for 90 min at 32 Hz for 15 s every 5 min. The strips were then washed four times with fresh buffer and allowed a period of recovery for 90 min. The 90 min of RFS caused a progressive decrease in maximal contractile response to electrical field stimulation and to muscarinic agonist-induced contractions (34% and 46% decrease, respectively). Galangin (10(-7) M) prevented the decrease in contractile smooth muscle response of strips to electrical field stimulation during RFS compared with untreated tissues. The antioxidant activity of galangin was assessed by measuring its ability to inhibit the lipid peroxidation induced by iron and ascorbate in rat liver microsomes (IC50 1.7+0.12x10(-6) M). If the data are confirmed in-vivo, exogenously administered galangin may be a new approach in the prevention and/or treatment of bladder dysfunction.

Cellular Phone-Based Image Acquisition and Quantitative Ratiometric Method for Detecting Cocaine and Benzoylecgonine for Biological and Forensic Applications

Here we describe the first report of using low-cost cellular or web-based digital cameras to image and quantify standardized rapid immunoassay strips as a new point-of-care diagnostic and forensics tool with health applications. Quantitative ratiometric pixel density analysis (QRPDA) is an automated method requiring end-users to utilize inexpensive (∼ $1 USD/each) immunotest strips, a commonly available web or mobile phone camera or scanner, and internet or cellular service. A model is described whereby a central computer server and freely available IMAGEJ image analysis software records and analyzes the incoming image data with time-stamp and geo-tag information and performs the QRPDA using custom JAVA based macros (http://www.neurocloud.org). To demonstrate QRPDA we developed a standardized method using rapid immunotest strips directed against cocaine and its major metabolite, benzoylecgonine. Images from standardized samples were acquired using several devices, including a mobile phone camera, web cam, and scanner. We performed image analysis of three brands of commercially available dye-conjugated anti-cocaine/benzoylecgonine (COC/BE) antibody test strips in response to three different series of cocaine concentrations ranging from 0.1 to 300 ng/ml and BE concentrations ranging from 0.003 to 0.1 ng/ml. This data was then used to create standard curves to allow quantification of COC/BE in biological samples. Across all devices, QRPDA quantification of COC and BE proved to be a sensitive, economical, and faster alternative to more costly methods, such as gas chromatography-mass spectrometry, tandem mass spectrometry, or high pressure liquid chromatography. The limit of detection was determined to be between 0.1 and 5 ng/ml. To simulate conditions in the field, QRPDA was found to be robust under a variety of image acquisition and testing conditions that varied temperature, lighting, resolution, magnification and concentrations of biological fluid in a sample. To determine the effectiveness of the QRPDA method for quantifying cocaine in biological samples, mice were injected with a sub-locomotor activating dose of cocaine (5 mg/kg; i.p.) and were found to have detectable levels of COC/BE in their urine (160.6 ng/ml) and blood plasma (8.1 ng/ml) after 15-30 minutes. By comparison rats self-administering cocaine in a 4 hour session obtained a final BE blood plasma level of 910 ng/ml with an average of 62.5 infusions. It is concluded that automated QRPDA is a low-cost, rapid and highly sensitive method for the detection of COC/BE with health, forensics, and bioinformatics application and the potential to be used with other rapid immunotest strips directed at several other targets. Thus, this report serves as a general reference and method describing the use of image analysis of lateral flow rapid test strips.

Commonly used intravenous anesthetics decrease bladder contractility: An in vitro study of the effects of propofol, ketamine, and midazolam on the rat bladder

Aim:This study was designed to test the hypothesis that propofol, ketamine, and midazolam could alter the contractile activity of detrusor smooth muscle.Materials and Methods:Four detrusor muscle strips isolated from each rat bladder (n = 12) were placed in 4 tissue baths containing Krebs-Henseleit solution. The carbachol (10 −8to 10−4mol/L)-induced contractile responses as well as 5, 10, 20, 30, 40, 50 Hz electrical field stimulation (EFS)-evoked contractile responses of the detrusor muscles were recorded using isometric contraction measurements. After obtaining basal responses, the in vitro effects of propofol, ketamine, midazolam (10−5 to 10−3 mol/L), and saline on the contractile responses of the detrusor muscle strips were recorded and evaluated.Results:All the 3 drugs reduced the carbachol-induced and/or EFS-evoked contractile responses of rat detrusor smooth muscles in different degrees. Midazolam (10−4 to 10−3 mol/L) caused a significant decrease in the contractile responses elicited by either EFS or carbachol (P=0.000−0.013). Propofol (10−3mol/L) caused a decrease only in EFS-evoked contractile responses (P=0.001−0.004) and ketamine (10−3mol/L) caused a decrease only in carbachol-induced contractile responses (P=0.001−0.034).Conclusion:We evaluated the effects of the 3 different intravenous anesthetics on detrusor contractile responses in vitro and found that there are possible interactions between anesthetic agents and detrusor contractile activity. The depressant effects of midazolam on the contractile activity were found to be more significant than ketamine and propofol. Despite the necessity of further studies, it could be a piece of wise advice to clinicians to keep the probable alterations due to intravenous anesthetics in mind, while evaluating the results of urodynamic studies in children under sedation.

Mechanisms mediating CCK-8S-induced contraction of proximal colon in guinea pigs

To investigate the effects of sulfated cholecystokinin octapeptide (CCK-8S) on the contractile activity of guinea-pig proximal colon. Proximal colonic smooth muscle (PCSM) strips were obtained from adult female guinea pigs and contractile response of PCSM strips was recorded using a polyphysiograph. PCSM cells were isolated by enzymatic digestion. Resting potential (RP), action potential (AP), large conductance potassium channel currents (I(BKCa)) and L-type calcium currents (I(Ca-L)) were recorded by patch-clamp techniques. (1) CCK-8S (10(-7) mol/L) enhanced the mean contractile amplitude of colonic circular muscle and longitudinal muscle (LM) strips by 56.53% + or - 11.92% (P = 0.038) and 65.93% + or - 12.98% (P = 0.019), respectively, as well as the mean frequency of LM by 31.69% + or - 13.58% (P = 0.023), which were significantly attenuated by pretreating strips with devazepide, nifedipine, iberiotoxin, thapsigargin (TG) and BAPTA-AM (BA) respectively; (2) CCK-8S (10(-7) mol/L) increased the AP amplitude by 38.6% + or - 3.2% (P = 0.015), decreased AP duration by 36.9% + or - 8.7% (P = 0.026), and depolarized the RP from -61.3 + or - 2.7 mV to -29.8 + or - 5.9 mV (P = 0.032); and (3) Compared with the normal control group, CCK-8S (10(-7) mol/L) enhanced the peak current of I(BKCa) by 18.7% + or - 2.1% (from 916 + or - 183 pA to 1088 + or - 226 pA; at +60 mV; P = 0.029), which was inhibited by respective pretreatment with iberiotoxin and devazepide. Additionally, CCK-8S (10(-7) mol/L) intensified the peak current of I(Ca-L) by 40% (from 60 + or - 8 pA to 84 + or - 11 pA; at +10 mV; P = 0.012), compared to the normal control group, which was apparently suppressed by respective pretreatment with nifedipine, devazepide, TG and BA. In the respective presence of heparin and staurosporine, CCK-8S did not significantly enhance I(BKCa) and I(Ca-L). The results suggest that CCK-8S promotes guinea-pig proximal colon contraction by CCK1 receptors, following activation of the inositol triphosphate-protein kinase C signal transduction pathway.

長さの異なる二個の平行き裂を有する圧電厚板の非定常電気熱弾性応答

長さの異なる二個の平行き裂を有する圧電厚板の非定常電気熱弾性応答

Contribution of endogenous nitrergic and peptidergic influences to the altered neurally-induced gastric contractile responses in strips from dystrophic (mdx) mice

Gastrointestinal motor disorders have been reported to occur in dystrophic (mdx) mice. The aim of the present study was to investigate the contribution of endogenous nitrergic and peptidergic components to the gastric contractile responses in strips from wild type (WT) and mdx mice. In both preparations, electrical field stimulation (EFS) induced frequency-dependent excitatory responses that were abolished by atropine or tetrodotoxin. The amplitude of the neurally-induced contractile responses was greater in strips from mdx mice in respect to the WT ones. In both preparations, at the end of the stimulation period strip tension decayed below the pre-stimulus level (off-relaxations). The nitric oxide (NO) synthesis inhibitor L-NNA increased the amplitude of the EFS-induced contractile responses without influencing off-relaxations. α-chymotrypsin and PACAP 6–38 abolished off-relaxations and also caused a reduction in amplitude of the contractile responses, whereas VIP receptor antagonists were ineffective. The efficacy of L-NNA, α-chymotrypsin or PACAP 6–38 on the excitatory responses was lower in strips from mdx mice in respect to the WT ones. α-chymotrypsin, in the presence of L-NNA, was no longer able to decrease the amplitude of the neurally-induced contractile responses but still abolished off-relaxations in both preparations. Direct muscular responses to methacholine were similar in amplitude in the two preparations and were not influenced by L-NNA or α-chymotrypsin. The results indicate that both endogenous NO and peptides influence the EFS-induced cholinergic responses: a stronger peptidergic modulatory action on a weaker nitrergic neurotransmission is suggested to occur in strips from mdx mice in respect to the WT ones and to contribute to the altered gastric contractile responses.

Selenium restores defective beta-adrenergic receptor response of thoracic aorta in diabetic rats

Increased oxidative stress is one of the basic contributors to the development of the cardiovascular complications in diabetes. Both endothelial and vascular smooth muscle cell dysfunctions are the main sign involved in the pathogenesis of diabetic cardiovascular dysfunction. Matrix metalloproteinases (MMPs) are expressed in the vasculature, and participate in tissue remodeling under pathological conditions such as increased oxidative stress, whereas little is known about effect of hyperglycemia on regulation of MMPs in vascular system. Therefore, we aimed to evaluate the effect of an antioxidant, sodium selenate treatment (0.3 mg/kg for 4 weeks) on function of streptozotocin-diabetic rat aorta. Sodium selenate treatment improved significantly impaired isoproterenol-induced relaxation responses and contraction responses of the aortic strips, and exhibited marked protection against diabetes-induced degenerative changes in the smooth muscle cell morphology. Biochemical data showed that sodium selenate treatment induced a significant regulation of MMP-2 activity and protein loss as well as normalization of increased levels of tissue nitrite and protein thiol oxidation. In addition, this treatment restored diabetes-induced increased levels of endothelin-1, PKC, and cAMP production in the aortic tissue. Taken together, our data demonstrate that these beneficial effects of sodium selenate treatment in diabetics are related to be not only inhibition of increased oxidative stress but also prevention of both receptor- and smooth muscle-mediated dysfunction of vasculature, in part, via regulation of MMP-2. Such an observation provides evidence for potential therapeutic usage of selenium compounds for the amelioration of vascular disorders in diabetes.