Biomedical subjects

Tim Schneider

Publications and source records attributed to Tim Schneider.

12 recordsLinked to original sources

PubMed2006

Effects of gender, age and hypertension on beta-adrenergic receptor function in rat urinary bladder.

beta-Adrenoceptors mediate urinary bladder relaxation, and gender, age and hypertension have been linked to bladder dysfunction. Therefore, we have studied whether any of these factors affects the ability of beta-adrenoceptor agonists to relax rat bladder detrusor muscle in vitro. For this purpose we have compared male and female Wistar rats, young and old male Wistar rats, and male normotensive and spontaneously hypertensive rats (SHR). Comparisons were done using KCl-precontracted bladder strips (length about 15-20 mm) and the endogenous agonist noradrenaline, the synthetic non-subtype-selective agonist isoprenaline, and the prototypical beta(3)-adrenoceptor agonists BRL 37,344 and CGP 12,177. While all agonists yielded numerically weaker relaxation in female as compared to male rats (for example for noradrenaline E(max) 40+/-4% vs 53+/-6% relaxation, pEC(50) 5.41+/-0.13 vs 5.60+/-0.14), this difference reached statistical significance only for the weak partial agonist CGP 12,177. Responses to all agonists were attenuated in old as compared to young rats, largely due to a reduced maximum effect, although the difference did not reach statistical significance for isoprenaline. The maximum relaxation responses to noradrenaline and isoprenaline were significantly lower in SHR than in normotensive rats, but both strains exhibited similar responses to the partial agonist BRL 37,344. We conclude that factors associated with bladder dysfunction, such as gender, age and hypertension, can be associated with impaired beta-adrenoceptor-mediated bladder relaxation. However, these alterations are not always consistent across various agonists, and the extent of the differences can be small. Therefore, we propose that beta-adrenoceptor dysfunction may contribute to the pathophysiology of such conditions, but is unlikely to be the only or even the major factor in this regard. We speculate that beta-adrenoceptor agonists may be effective in the treatment of bladder dysfunction under all of these conditions.

Adrenergic beta-3 Receptor Agonists↗

PubMed2005

Effects of ageing on muscarinic receptor subtypes and function in rat urinary bladder.

We compared the density and function of M2 and M3 muscarinic acetylcholine receptor subtypes in the urinary bladder of young adult (3 months) and old (23 months) male Wistar rats. Old rats had a reduced density of muscarinic receptors (96+/-10 vs. 156+/-21 fmol/mg protein), but competition experiments with the M3-selective darifenacin did not indicate alterations in the relative roles of M2 and M3 receptors, with the former being more abundant. The amount of immunodetectable alpha-subunits of various G-proteins potentially linked to muscarinic receptor function was unchanged. The potency of carbachol to contract bladder strips was also unaltered; its maximum effects as well as those of a single KCl concentration were unchanged if raw data or those corrected for strip length were analysed, but somewhat reduced when those corrected for strip weight were analysed. Antagonistic effects of atropine, the M2-selective Ro 320-6206 and the M3-selective darifenacin were unchanged. Agonistic effects of the M3-sparing agonist 4-(2-oxo-2,3-dihydro-benzoimidazol-1-yl)-[1,4']bipiperidinyl-1'-carboxylic acid ethyl ester were similarly poor in young and old rats. Additional experiments were concomitantly performed in submandibular glands from the same animals. While total muscarinic receptor density in submandibular glands was not significantly affected by age (56+/-5 vs. 61+/-4 fmol/mg protein), the relative contribution of M3 receptors significantly declined from 68+/-3% to 57+/-2% based upon darifenacin competition curves. We conclude that aged Wistar rats express fewer muscarinic receptors in their urinary bladder, but there is no change in the relative abundance of M2 and M3 receptors; this is accompanied by only minor if any alterations in receptor responsiveness. In contrast, submandibular gland expresses similar receptor numbers in young and old rats, but slightly fewer M3 receptors in old animals.

Aging↗

PubMed2005

A role for muscarinic receptors or rho-kinase in hypertension associated rat bladder dysfunction?

PURPOSE: Essential arterial hypertension is a frequent condition. Spontaneously hypertensive rats (SHRs) show bladder dysfunction similar to that seen in patients with overactive bladder. Since muscarinic receptors and rho-kinase have a key role in the regulation of bladder contractility, we determined whether alterations of either one might contribute to hypertension associated bladder dysfunction. MATERIALS AND METHODS: The bladders of SHRs and normotensive Wistar Kyoto rats (WKYs) were compared in in vitro radioligand binding and contractility studies. RESULTS: The mean total number of muscarinic receptors +/- SEM (181 +/- 14 vs 191 +/- 22 fmol/mg protein) and the relative roles of their subtypes were similar in SHRs and WKYs. Contractile responses to the muscarinic agonist carbachol (maximum effect 2.04 +/- 0.24 vs 2.05 +/- 0.14 mN/mm strip length and -log EC50 5.61 +/- 0.07 vs 5.64 +/- 0.04) and to KCl in a receptor independent manner were similar in the 2 strains. The M3 selective antagonist darifenacin inhibited carbachol responses much more potently than the M2 selective antagonist methoctramine but the potency of the 2 drugs was similar in each strain. The rho-kinase inhibitor Y27,632 attenuated carbachol induced contraction in a quantitatively similar manner in SHRs and WKYs. CONCLUSIONS: An altered function of muscarinic receptor subtypes or rho-kinase does not appear to contribute to bladder dysfunction in SHRs.

Animals↗

PubMed2004

Comparison of symptom severity and treatment response in patients with incontinent and continent overactive bladder.

PURPOSE: Two thirds of patients with overactive bladder (OAB) are continent, but our knowledge on the treatment of the syndrome is largely based on studies with incontinent patients. Therefore, we have explored baseline symptoms and treatment responses to tolterodine in continent relative to incontinent OAB patients. MATERIALS AND METHODS: Data from an open-label, observational study involving 3824 patients with OAB symptoms were analyzed for baseline symptoms and alterations thereof upon a 9 months treatment with 4 mg q.d. tolterodine ER. RESULTS: Baseline symptoms (number of urgency episodes, total urination frequency, daytime frequency, nocturia, and three scales of OAB severity) were similar in 1147 continent and 2571 incontinent patients, the latter having 4.8+/-3.7 incontinence episodes per 24 h. Tolterodine ER-induced reduction of OAB symptoms was very similar in both groups of patients. CONCLUSIONS: The severity of OAB in continent patients can be similar to that in incontinent ones. Symptom improvement upon treatment with tolterodine ER is very similar in both groups. We propose that continent patients may similarly deserve treatment with a muscarinic receptor antagonist as incontinent ones.

Aged↗

PubMed2004

Signal transduction underlying carbachol-induced contraction of human urinary bladder.

The present study was designed to reexamine the muscarinic acetylcholine receptor subtype mediating carbachol-induced contraction of human urinary bladder and to investigate the underlying signal transduction. Based upon the nonselective tolterodine, the highly M(2)-selective (R)-4-[2-[3-(4-methoxy-benzoylamino)-benzyl]-piperidin-1-ylmethyl]piperidine-1-carboxylic acid amide (Ro-320-6206), and the highly M(3)-selective darifenacin and 3-(1-carbamoyl-1,1-diphenylmethyl)-1-(4-methoxyphenylethyl)pyrrolidine (APP), contraction occurs via M(3) receptors. The phospholipase C inhibitor 1-(6-[([17beta]-3-methoxyestra-1,3,5[10]-trien-17-yl)amino]hexyl)-1H-pyrrole-2,5-dione (U 73,122) (1-10 microM) did not significantly affect carbachol-stimulated bladder contraction. The phospholipase D inhibitor butan-1-ol relative to its negative control butan-2-ol (0.3% each) caused small but detectable inhibition of carbachol-induced bladder contraction. The Ca(2+) entry blocker nifedipine (10-100 nM) strongly inhibited carbachol-induced bladder contraction. In contrast, 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole HCl (SK&F 96,365) (1-10 microM), an inhibitor of store-operated Ca(2+) channels, caused little inhibition. The protein kinase C inhibitor bisindolylmaleimide I (1-10 microM) did not significantly affected carbachol-induced bladder contraction. In contrast, trans-4-[(1R)-1-aminoethyl]-N-4-pyridinylcyclohexanecarboxamide (Y 27,632) (1-10 microM), an inhibitor of rho-associated kinases, concentration dependently and effectively attenuated the carbachol responses. We conclude that carbachol-induced contraction of human urinary bladder via M(3) receptors largely depends on Ca(2+) entry through nifedipine-sensitive channels and activation of a rho kinase, whereas phospholipase D and store-operated Ca(2+) channels contribute only in a minor way. Surprisingly, phospholipase C or protein kinase C do not seem to be involved to a relevant extent.

Calcium Channels, L-Type↗

PubMed2003

Signal transduction underlying carbachol-induced contraction of rat urinary bladder. I. Phospholipases and Ca2+ sources.

We have reexamined the muscarinic receptor subtype mediating carbachol-induced contraction of rat urinary bladder and investigated the role of phospholipase (PL)C, D, and A2 and of intra- and extracellular Ca2+ sources in this effect. Based on the nonsubtype-selective tolterodine, the highly M2 receptor-selective (R)-4-[2-[3-(4-methoxy-benzoylamino)-benzyl]-piperidin-1-ylmethyl]-piperidine-1-carboxylic acid amide (Ro-320-6206), and the highly M3 receptor-selective darifenacin and 3-(1-carbamoyl-1,1-diphenylmethyl)-1-(4-methoxyphenylethyl)pyrrolidine (APP), contraction occurs via M3 receptors. Carbachol stimulated inositol phosphate formation in rat bladder slices, and this was abolished by the phospholipase C inhibitor 1-(6-[([17beta]-3-methoxyestra-1,3,5[10]-trien-17-yl)-amino]hexyl)-1H-pyrrole-2,5-dione (U 73,122; 10 microM). Nevertheless, U 73,122 (1-10 microM) did not significantly affect carbachol-stimulated bladder contraction. Carbachol had only little effect on PLD activity in bladder slices, but the PLD inhibitor butan-1-ol, relative to its negative control butan-2-ol (0.3% each), caused detectable inhibition of carbachol-induced bladder contraction. The cytosolic PLA2 inhibitor arachidonyltrifluoromethyl ketone weakly inhibited carbachol-induced contraction at a concentration of 300 microM, but the cyclooxygenase inhibitor indomethacin (1-10 microM) remained without effect. The Ca2+ entry blocker nifedipine (10-100 nM) almost completely inhibited carbachol-induced bladder contraction. In contrast, 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole HCl (SKF 96,365; 10 microM), an inhibitor of store-operated Ca2+ channels, caused little inhibition. We conclude that carbachol-induced contraction of rat bladder largely depends on Ca2+ entry through nifedipine-sensitive channels and, perhaps, PLD, PLA2, and store-operated Ca2+ channels, whereas cyclooxygenase and, surprisingly, also PLC are not involved to a relevant extent.

Animals↗

PubMed2003

Signal transduction underlying carbachol-induced contraction of rat urinary bladder. II. Protein kinases.

We have investigated the role of several protein kinases in carbachol-stimulated, M(3) muscarinic receptor-mediated contraction of rat urinary bladder. Concentration-response curves for the muscarinic receptor agonist carbachol were generated in the presence of multiple concentrations of inhibitors of various protein kinases, their inactive controls, or their vehicles. Bladder contraction was not significantly inhibited by three protein kinase C inhibitors (chelerythrine, 1-10 microM; calphostin C, 0.1-1 microM; and 2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)-maleimide (Gö 6850), 1-10 microM), by the tyrosine kinase inhibitor genistein or its inactive control daidzein (3-30 microM each), or by two inhibitors of activation of mitogen-activated protein kinase [10-100 microM 2'-amino-3'-methoxyflavone (PD 98,059) and 3-30 microM 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene (U 124)] or their negative control 1,4-diamino-2,3-dicyano-1,4-bis(methylthio)butadiene (U 126) (3-30 microM). Although high concentrations of wortmannin (3-30 microM) inhibited bladder contraction, this was not mimicked by another inhibitor of phosphatidylinositol-3-kinase, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY 294,002) (3-30 microM) and, hence, was more likely due to direct inhibition of myosin light chain kinase by wortmannin than to an involvement of phosphatidylinositol-3-kinase. In contrast, trans-4-[(1R)-1-aminoethyl]-N-4-pyridinylcyclohexanecarboxamide (Y 27,632) (1-10 microM), an inhibitor of rho-associated kinases, concentration-dependently and effectively attenuated the carbachol responses. We conclude that carbachol-induced contraction of rat urinary bladder does not involve protein kinase C, phosphatidylinositol-3-kinase, tyrosine kinases, or extracellular signal-regulated kinases; in contrast, rho-associated kinases appear to play an important role in the regulation of bladder contraction.

Animals↗

PubMed2003

Gender comparison of muscarinic receptor expression and function in rat and human urinary bladder: differential regulation of M2 and M3 receptors?

Since symptoms of bladder dysfunction occur more frequently in women than in men and since muscarinic receptors are the physiologically most important system to mediate bladder contraction, we have compared the number, subtype distribution and function of muscarinic receptors in bladders from male and female rats. Muscarinic receptor function was also assessed in bladder strips from male and female human bladder. Male and female rats expressed a similar number of muscarinic receptors (144+/-5 vs. 140+/-6 fmol/mg protein in saturation radioligand binding). While competition binding curves for the moderately M(2)-selective methoctramine were not consistently better fitted by a two-site model, most competition curves for the M(3)-selective darifenacin were biphasic and yielded 29+/-10% and 31+/-7% high affinity sites (corresponding to M(3) receptors) in male and females, respectively. Immunoreactivity of alpha-subunits of the G-proteins G(q/11), G(i1/2), G(i3) and G(s) did not significantly differ between both genders. The muscarinic receptor agonist carbachol similarly stimulated inositol phosphate accumulation in bladder slices from male and female rats with calculated maximum responses of 69+/-17 and 77+/-18% over basal and pEC(50) values of 4.90+/-0.45 and 4.40+/-0.46, respectively. While darifenacin inhibited carbachol-stimulated inositol phosphate formation approximately 100-fold more potently than methoctramine, each antagonist was similarly potent in both genders. Carbachol concentration-dependently contracted bladder strips with a pEC(50) of 5.66+/-0.05 and 5.72+/-0.06 and maximum effects of 4.3+/-0.1 and 4.2+/-0.2 mN/mg wet weight in male and female rats, respectively. The contractile effect of carbachol was concentration-dependently antagonised by the non-selective atropine (1-30 nM), the M(1)-selective pirenzepine (1-30 M), the M(2)-selective methoctramine (1-10 microM) and the M(3)-selective darifenacin (10-100 nM), with the latter exhibiting a partly unsurmountable antagonism. The overall potency of all four antagonists suggested that contraction was mediated predominantly if not exclusively by M(3) receptors with no appreciable differences between both male and female rats. Similarly, the maximum effects (4.4+/-0.6 vs. 4.4+/-2.4 mN/mg) and pEC(50) (6.07+/-0.05 vs. 6.32+/-0.14) of carbachol did not differ between genders in bladder samples from 25 consecutive patients. We conclude that number und function of muscarinic receptors and the relative roles of their M(2) and M(3) subtypes do not differ between urinary bladders of male and female rats; at least with regard to overall muscarinic responsiveness this situation appears to be similar in humans.

Animals↗

PubMed2003

[New treatment options for erectile dysfunction. Pharmacologic and nonpharmacologic options].

Erectile dysfunction is a medical condition that influences the sexual life of millions of men and women worldwide. Due to a large number of currently available drugs, the therapy of erectile dysfunction has changed profoundly during the last decades. The pharmacologic options are divided into initiators versus conditioners and central- or peripheral-acting drugs. Besides intraurethral and intracavernous application of prostaglandin E(1) (PGE(1), peripheral initiator)--a transdermal application is still in clinical testing--there are drugs for oral application. PGE(1), the vasoactive drug mainly used, was replaced by sildenafil in first-line-therapy. PGE(1), administered intracavernosally or intraurethrally, is highly effective with success rates up to 90%, but the attrition rate due to personal inconvenience remains significant. Yohimbine is known as a central amplifier of erection and is useful in psychogenic and mild organic erectile dysfunction. Apomorphine, a central initiator of erection, amplifies erectile response as a central dopamine agonist in mild and moderate erectile dysfunction and starts acting 15-20 min after sublingual application. The phosphodiesterase type 5 (PDE-5) inhibitors sildenafil, vardenafil, and taldalafil are peripheral conditioners. Sildenafil, the most distributed oral agent worldwide, should be taken orally 60 min before sexual intercourse in combination with sexual stimulation. Sildenafil shows a high efficacy-safety profile with success rates for all etiologies between 50-80%. Paralleling nitrate-containing medication is an absolute contraindication. Vardenafil, another selective PDE-5 inhibitor with potentially higher selectivity and efficacy compared to sildenafil was just approved. The data from the clinical trials show the same adverse events and success rates as sildenafil. Tadalafil, just launched as well, amplifies erectile function for up to 24 h, allowing the patient to engage in sexual activity for this period. Adverse events and success rates resemble those of the other two substances. If medical treatment fails, there are nonpharmacologic options such as the vacuum constriction device and penile implants. The vacuum device is a safe and effective option for well-selected patients. Penile implants, especially the inflatable ones, completely imitate the physiologic erection. Due to recent research, infection rates and mechanical failures were minimized. Therefore penile implant surgery is well accepted by the patients and their partners. Despite this wide variety of options, therapy of erectile dysfunction should be performed in an individually adapted way. The patient's exact history, physical examination, collaboration of medical disciplines and choice of therapy will offer all patients the possibility to achieve or regain a satisfying sexual life.

Alprostadil↗

PubMed2003

Posterior tibiotalar ligament injury resulting in posteromedial impingement.

OBJECTIVE: To describe the imaging features of the normal anatomy and injury of the posterior tibiotalar ligament (PTTL) of the ankle in a group of patients presenting with posteromedial impingement. MATERIALS AND METHODS: Twenty-five consecutive patients underwent imaging for posteromedial ankle pain following injury. All 25 patients were investigated with MR imaging, 17 with ultrasound and 5 with radionuclide bone scanning. Clinical data and surgical findings were correlated with the results of radiological investigation. RESULTS: The PTTL demonstrated scar formation and a hypertrophic response consistent with previous injury in all 25 patients. Displacement or encasement of the surrounding tendons and their sheaths was often encountered (12/25). Bony avulsion was demonstrated in 5/25 occasions with ultrasound and 2/25 with MR imaging. Twelve patients underwent surgery, confirming the radiological findings. CONCLUSION: Imaging can effectively evaluate the integrity of the PTTL in the context of ongoing posteromedial ankle pain.

Adult↗

PubMed2003

Snow skiing injuries.

BACKGROUND: Skiing is a sport that has exploded in popularity over the past 20 years. There are estimated to be 200 million skiers worldwide. OBJECTIVE: This article outlines the type and prevalence of ski injuries, and measures that have been made to reduce the incidence of injuries to skiers. DISCUSSION: The incidence of injury has decreased with the development of improved equipment, resort management and skier preparation. This decrease has been reflected in a lower rate of foot, ankle and tibial injuries. The overall incidence of knee injuries has increased and in particular an increase in more serious knee injuries. Snowboard injuries now account for approximately half the presentations to ski resort medical centres.

Ankle Injuries↗

PubMed2002

Does gender or age affect the efficacy and safety of tolterodine?

PURPOSE: We compared the importance of patient age and gender relative to the intensity of baseline symptoms of overactive bladder in the therapeutic response to the muscarinic receptor antagonist tolterodine. MATERIALS AND METHODS: Data from an open label, observational study of 2,250 patients with overactive bladder treated for 12 weeks with tolterodine were analyzed for alterations in frequency, urgency and urge incontinence, and for global efficacy and tolerability using logistic regression analysis, stratifying for gender, age, baseline symptom intensity and tolterodine dose. RESULTS: Gender or tolterodine dose were not consistently associated with altered treatment efficacy. Greater age was associated with a slight but statistically significant decrease in treatment efficacy. Patients with great baseline symptom intensity had greater treatment associated improvement but a lesser chance to become symptom-free. Even with a large number of patients no statistically significant gender or age associated alterations in the tolerability of tolterodine treatment were detected. CONCLUSIONS: The extent of the therapeutic response to tolterodine is largely determined by the extent of baseline symptoms. While gender does not affect the efficacy or tolerability of tolterodine in a clinically relevant manner, advanced age is associated with a slight decrease in efficacy but not in tolerability.

Age Factors↗