Biomedical subjects

James I Gillespie

Publications and source records attributed to James I Gillespie.

14 recordsLinked to original sources

PubMed2006

Bladder volume alters cholinergic responses of the isolated whole mouse bladder.

PURPOSE: The isolated bladder expresses autonomous activity, which may contribute to the generation of lower urinary tract sensation or pathophysiology. We evaluated how the effect of a cholinergic agonist on autonomous activity alters with increasing volume and in the presence of substances known to modulate functional bladder capacity. MATERIALS AND METHODS: The bladder of 22 adult female C57 black mice were mounted in whole organ tissue baths. Recordings of intravesical pressure were performed under standardized conditions at different bladder volumes. RESULTS: At low volume the muscarinic agonist arecaidine elicited an initial peak response, which subsided to a sustained steady state pressure. At high volume phasic pressure fluctuations were also apparent. An M2-receptor antagonist caused a significantly greater decrease in peak and steady state responses than in pressure fluctuations. An M3-receptor antagonist decreased all 3 components. Alpha, beta-methylene adenosine triphosphate markedly decreased fluctuations, in contrast to norepinephrine, which eliminated the steady state response while preserving fluctuations. CONCLUSIONS: The response to cholinergic stimulation of the isolated bladder has 3 components. The initial tonic peak response increases with bladder distention and it is inhibited by M2 and M3 muscarinic receptor antagonists. The tonic steady state response does not vary with bladder volume and it is inhibited by M2 and M3-receptor antagonists, and by beta3-adrenergic receptor agonists. Phasic fluctuations are minimal at low bladder volume, and with alpha, beta-methylene adenosine triphosphate or an M3-receptor antagonist. Thus, the response to cholinergic stimulation varies with bladder volume. It can be differentially modulated by muscarinic antagonists and also by agents acting through nonmuscarinic receptors.

Animals↗

PubMed2006

Interstitial cells and cholinergic signalling in the outer muscle layers of the guinea-pig bladder.

OBJECTIVES: To explore the relationship between cholinergic mechanisms and interstitial cells (ICs) in the outer muscle layer of the bladder. MATERIALS AND METHODS: In bladder tissue from male guinea-pigs, ICs were identified by their response to nitric oxide (NO) with a rise in cGMP. Sections of the lateral bladder wall were incubated in Krebs' solution containing 1 mm of the nonspecific phosphodiesterase inhibitor isobutyl-methyl-xanthene. Tissues were then exposed to 100 microm of the NO donor NONOate for 10 min, control tissues remained in Krebs' solution. Tissues were then processed for immunohistochemistry for cGMP, choline acetyltransferase (ChAT), neurofilament protein, and the nonspecific neuronal marker protein gene product (PGP) 9.5. RESULTS: cGMP-positive ICs were found mainly in the outer muscle layers of the bladder wall. Three types were identified based on location; on the outer surface of the bladder wall, on the surface of the muscle bundles, and within the muscle bundles. Some of the intramuscular ICs stained for ChAT, but they did not stain with PGP 9.5. Nerve fibres were seen in close contact with the ChAT-positive intramuscular ICs, and these nerves expressed ChAT and neurofilament protein. CONCLUSIONS: A subpopulation of intramuscular ICs can synthesise acetylcholine, and might release acetylcholine onto the underlying muscle. These cells are in close contact with nerves, suggesting that they might be activated by neural inputs. Thus there may be a system in the detrusor involving cholinergic nerves acting on ICs which can activate the smooth muscle via a complex cholinergic input.

Animals↗

PubMed2006

Phasic non-micturition contractions in the bladder of the anaesthetized and awake rat.

OBJECTIVE: To characterize the contractile activity that occurs in the bladder during the filling phase of the micturition cycle (non-micturition contractions, NMCs), which generate transient rises in intravesical pressure not associated with urine flow. MATERIALS AND METHODS: The experiments were conducted using anaesthetized (chloral hydrate) and un-anaesthetized rats. In un-anaesthetized rats bladder contractile activity was measured using an intravesical cannula implanted under full surgical anaesthesia 3 days previously. In the anaesthetized rats the bladder was exteriorized and a cannula inserted through the dome. In these experiments electrical activity within the detrusor was also measured with a suction electrode on the bladder surface. For each rat, the experimental protocol involved filling the bladder at a constant rate (10 mL/h) to evoke micturition cycles, or infusion of a fixed volume and recording made under effective isovolumetric conditions. RESULTS: In both anaesthetized and un-anaesthetized rats there were transient rises in bladder pressure (0.5-3 cmH2O). In the anaesthetized rats the amplitude of the transients increased throughout the filling phase, with little change in frequency. The phasic NMCs generating these pressure transients were accompanied by electrical changes in the detrusor. In the middle phase of bladder filling the slow pressure changes were accompanied by slow waves of electrical activity which changed in the pressure cycles immediately before micturition to high-frequency low-amplitude signals. In the un-anaesthetized rats there was a period immediately after voiding where there was no activity. As filling proceeded, low-amplitude low-frequency NMCs appeared that gradually increased in frequency and amplitude during the filling phase. However, the frequency of the transients decreased immediately before micturition despite an increase in amplitude. Similar responses were seen during isovolumetric recording. CONCLUSION: The present results show the presence of NMCs in the rat bladder, identify volume-dependent changes in the pattern of this activity during the micturition cycle, and show that NMCs are accompanied by electrical changes in the detrusor. The physiological significance of NMCs is not known but it might be linked to the generation of afferent discharge from mechanoreceptors in the wall, so contributing to sensations related to bladder volume.

Analysis of Variance↗

PubMed2006

Location of interstitial cells and neurotransmitters in the mouse bladder.

INTRODUCTION: To investigate whether interstitial cells (ICs) are present in the adult mouse bladder, and what transmitters characterize adjacent nerve fibres, as ICs in human and guinea-pig bladder lie close to nerve fibres but transmitters present in these nerves have not yet been reported. MATERIALS AND METHODS: Sections of the bladder wall from 12 adult male mice (six each, aged 3-4 or 18-24 months) were incubated in carboxygenated Krebs' solution containing isobutyl-methyl-xanthene (1 mm), followed by the nitric oxide (NO) donor diethylamino-NONOate; control tissues remained in Krebs' solution. Samples were fixed in 4% paraformaldehyde and processed for immunofluorescence histochemistry for cGMP, neuronal NO synthase (nNOS), vesicular acetylcholine transferase (VAChT), calcitonin gene-related polypeptide (CGRP) and protein gene product (PGP) 9.5. ICs were identified as non-neuronal cells of appropriate morphology manifesting an increase in cGMP after exposure to the NO donor. RESULTS: ICs were apparent in the outer muscle, but not the inner muscle or suburothelial region. nNOS- and CGRP-immunoreactive fibres were close to and alongside IC processes. In contrast, nerve fibres containing VAChT were only occasionally found close to ICs and rarely running alongside them. ICs showed no immunoreactivity to c-kit. There was no overt difference in IC cell distribution between young and aged adult specimens. Older mice showed patchy denervation of the detrusor, but ICs were not specifically affected. CONCLUSIONS: ICs are confined to the outer part of the bladder wall in the mouse and may receive peptidergic and nitrergic innervation, which might serve to modulate their putative functional role. Alterations in the overall IC population do not appear to underlie ageing-related changes in lower urinary tract function.

Animals↗

PubMed2006

Interstitial cells and phasic activity in the isolated mouse bladder.

OBJECTIVE: To describe the distribution of interstitial cells (ICs, defined as cells which show an increase in cGMP in response to nitric oxide, NO) in the isolated mouse bladder, and changes in phasic contractile activity after exposure to a NO donor. MATERIALS AND METHODS: The whole bladder was removed from 17 female mice, killed by cervical dislocation. For immunohistochemistry (six mice) the bladder was incubated in carboxygenated Krebs' solution at 36 degrees C, containing 1 mm of the phosphodiesterase inhibitor isobutyl-methyl-xanthine. Individual pieces of tissue were exposed to 100 microm of the NO donor diethylamine NONOate for 10 min; control tissues remained in Krebs' solution. Tissues were then fixed in 4% paraformaldehyde and processed for cGMP immunohistochemistry. Bladder pressure was measured in bladders from 11 mice; the bladders were cannulated via the urethra and suspended in a heated chamber containing carboxygenated Tyrode solution at 33-35 degrees C and intravesical pressure recorded. All drugs were added to the solution bathing the abluminal surface. RESULTS: NO induced an increase in cGMP in cells in the outer layers of the bladder wall, forming two distinct types based on their location; cells lying on the surface of the muscle bundles (surface muscle ICs) and cells within the muscle bundles (intramuscular ICs). Cholinergic nerve fibres were identified by the expression of vesicular acetylcholine transporter and neuronal NO synthase (nNOS). Choline acetyltransferase- and nNOS-positive nerves also had high cGMP levels in response to 100 microm diethylamine NONOate. In vitro exposure of an isolated whole unstimulated bladder to 100 microm diethylamine NONOate had no effect on resting bladder pressure. When whole bladders were exposed to muscarinic stimulation (30-100 nm arecaidine) there was an initial large transient rise in pressure followed by complex phasic changes in pressure. Adding 100 microm diethylamine NONOate abolished this phasic activity. Interestingly, the phasic activity was inhibited midway between the peak and trough of a phasic cycle. Such a pattern of inhibition might reflect the complexity of the phasic activity involving both excitatory and inhibitory components. CONCLUSIONS: These data show the presence of NO/cGMP-sensitive ICs in the outer muscle layers of the mouse bladder. Activating these cells alters the pattern of muscarinic-induced phasic activity. We suggest that the role of the ICs in the outer muscle layers is to generate and modulate phasic activity. If so, then this is the first report of a functional role for ICs in the bladder.

Animals↗

PubMed2006

Antimuscarinic drugs in detrusor overactivity and the overactive bladder syndrome: motor or sensory actions?

Antimuscarinic drugs are generally thought to exert their therapeutic action on detrusor overactivity by reducing the ability of the detrusor muscle to contract. We review currently available published data to establish whether there is any evidence to support this contention. Using a PubMed data search, only 14 original articles (including two abstracts) were found that contained cystometric data for both filling and voiding phases and where the actions of antimuscarinic drugs have been reported in detail. These articles were separated into three groups dealing with neuropathic patients (three papers), patients with idiopathic overactive bladder (four papers) and a group whose aetiology was unclear (seven papers). Variables relating to bladder function during the filling phase (time of first desire to void, time to first unstable contraction, and bladder capacity) were identified. Similarly, variables relating to voiding were identified and compared (e.g. maximum detrusor pressure and detrusor pressure at maximum flow rate). The antimuscarinic drugs have a clearly significant effect on sensations of urge, time to first sensation to void, maximum bladder capacity, decrease in voiding frequency and reduction in incontinence episodes. However, only one article (studying neuropaths) reported a significant reduction of the variables associated with detrusor contraction. The remaining four studies (idiopaths/not stated), reported no change in bladder contractility with antimuscarinic drugs. Thus the available data do not support the conclusion that antimuscarinic drugs at doses used in current clinical practice exert their therapeutic action by inhibiting detrusor contractility, but they suggest effects on variables associated with sensation.

Humans↗

PubMed2005

Inhibitory actions of calcitonin gene-related peptide and capsaicin: evidence for local axonal reflexes in the bladder wall.

OBJECTIVES: To explore the actions of capsaicin and the neurotransmitters released by capsaicin (substance P and calcitonin gene-related peptide, CGRP) on the phasic contractile activity generated in the whole isolated guinea pig bladder by muscarinic stimulation, and to examine the hypothesis that collateral fibres of sensory axons contribute to a local reflex in the bladder wall. MATERIALS AND METHODS: All experiments used whole isolated bladders from female guinea pigs (270-300 g). Bladders were cannulated via the urethra to measure intravesical pressure and suspended in a heated chamber containing oxygenated Tyrode's solution at 33-35 degrees C. All drugs were added to the solution bathing the abluminal surface. RESULTS: Application of capsaicin (10 micromol/L) to the whole isolated bladder resulted in complex changes in the frequency and amplitude of phasic activity generated by muscarinic stimulation; an initial burst of activity involving a rise in frequency, a second phase of reduced amplitude and frequency and a third phase where the amplitude of the transients recovered and the frequency increased. Capsaicin had no effect on the phasic activity generated by the nicotinic ligand lobeline (30 micromol/L). As capsaicin releases the neurotransmitter content of the sensory nerves, experiments explored the actions of CGRP and substance P on the muscarinic-induced activity. CGRP (3-30 nmol/L) reduced the amplitude and slowed the frequency of the phasic activity. On washing off CGRP the amplitude and frequency of the transient activity recovered and there was a transient increase in frequency above the levels before stimulation. There was also evidence of a desensitization to CGRP on repeated application. In contrast, substance P (100-300 nmol/L) increased the frequency of the transients, while on removing it there was an inhibition of both amplitude and frequency. CONCLUSIONS: These results suggest that neurotransmitters released from sensory nerve endings in the guinea pig bladder wall affect phasic activity. The direct application of CGRP inhibited phasic activity while substance P was excitatory, indicating the specific contributions of these neurotransmitters. The excitation after stimulation with CGRP and inhibition with substance P may indicate that these neurotransmitters feed back on the sensory nerves to induce transmitter release. Taken together, these observations suggest the presence of a local reflex in the bladder wall, where axon collaterals of afferent sensory fibres innervate the pacemaker mechanism in the bladder wall responsible for generating phasic activity. The possible importance of this reflex in the physiology and pathophysiology of the bladder is discussed.

Action Potentials↗

PubMed2005

Localized contractions in the normal human bladder and in urinary urgency.

OBJECTIVE: To describe an observational study to establish whether localized activity arises in the normal human bladder, and whether there is any correspondence between changes in such activity and reported sensation. PATIENTS, SUBJECTS AND METHODS: The generation of sensory information by the bladder depends on afferent stimulation by increased tension within the bladder wall. Autonomous bladder activity is apparent in several species, which is often localized and multifocal, giving rise to localized areas of stretch. Thus afferent activity may partly result from localized distortions of the bladder wall. Fourteen women patients presenting with increased bladder sensation during filling-phase cystometry were compared with six asymptomatic women volunteers. Localized bladder activity was assessed by the micromotion detection (MMD) method, using eight electrodes mounted on a Silastic balloon; local displacements of the electrodes were recorded as changes in electrical resistance, which were used to compute changes in the distance between each pair of electrodes. RESULTS: In two of the six volunteers, micromotions were seen in the extraperitoneal (ventral) portion of the bladder. Women with increased sensation on filling cystometry had a significantly higher prevalence of localized activity than the control group during MMD recording. The localized activity was more sustained and at a higher frequency than in asymptomatic women. All nine women reporting urinary urgency during MMD recording had localized contractile activity, while only four had phasic increases in detrusor pressure during the episodes of urgency. CONCLUSIONS: By measuring localized contractions within the bladder wall, we established a significant difference in the prevalence of localized activity between the groups studied, but there was no objective difference with conventional urodynamic studies. There was also a difference in the character of the localized contractions, with the exaggerated activity in the symptomatic group corresponding with the reported sensations. These findings suggest that localized distortion of the bladder wall stimulates afferent activity, and that the human detrusor may be functionally modular.

Adult↗

PubMed2005

A developing view of the origins of urgency: the importance of animal models.

Although caution should be used when applying animal data to human physiology, if care is taken to differentiate between general principles and complications of detail, particular to the species being examined, then experimentation on animal models can reveal basic phenomena in the bladder that offer clues to the origin of urgency. Recent data from the whole isolated bladder of guinea pigs showed unexpected complexities in autonomous activity during the filling phase of the micturition cycle: small, transient increases in intravesical pressure were associated with propagating waves of contractile activity and localized stretches of bladder wall. This complex, coordinated activity suggests that there are mechanisms within the bladder wall devoted specifically to generating phasic activity. Thus, there appear to be two systems controlling detrusor contractions: one associated with overall contractions similar to the micturition contraction and the other generating phasic activity. The mechanisms generating the phasic activity appear to be the point of complex integration of both excitatory and inhibitory inputs. There is evidence that local activity in the bladder wall generates afferent discharge, which probably contributes to bladder sensations. Animal data suggest a novel motor/sensory system incorporating contractile (motor) events, which cause stretches resulting in activation of afferent nerves (sensory). The motor element of this system appears to be controlled in a highly complex fashion such that the amplitude and frequency of the motor activity can be modulated by a variety of inputs. This raises the possibility that the sensitivity of the system informing the central nervous system, and thus awareness of the bladder's state during the micturition cycle, can be manipulated, possibly via novel drugs targeted at areas involved in overactive bladder, including urgency incontinence.

Animals↗

PubMed2004

Smooth muscle alpha-actin expression in endothelial cells derived from CD34+ human cord blood cells.

Human fetal cord blood contains subsets of mononuclear cells with the potential to form both hematological and endothelial cells. Vascular progenitor cells, which can produce all three elements of mature blood vessels, including smooth muscle, have been identified in animals. We hypothesized that similar multipotential progenitor cells exist in humans and used the expression of alpha-smooth muscle actin (alpha-SMA) to identify such cells in fetal cord blood. Mononuclear cell preparations were isolated from human umbilical cord blood and CD34(+) and CD133(+) cells obtained by magnetic bead separation. Isolated cells were cultured on fibronectin-coated dishes with medium containing vascular endothelial growth factor, basic fibroblast growth factor, and insulin-like growth factor. mRNA was extracted, and the expression of alpha-SMA and a number of endothelial cell markers (VEGFR-2, vWF, eNOS, VE-Cadhein, PECAM-1 and Tie-2) was determined by reverse transcriptase-PCR techniques. Human umbilical vein endothelial cells (HUVECs) were used as positive controls. Freshly isolated CD34(+) and CD133(+) cells expressed all endothelial cell markers, but did not express alpha-SMA. HUVECs expressed alpha-SMA. Following 4 weeks of culture, CD34(+) isolates produced morphologically endothelial-like cells that expressed both endothelial cell markers and alpha-SMA. CD133(+) cells failed to produce morphological endothelial-like cells but expressed a range of endothelial markers. However, they did not express alpha-SMA. Following culture in an endothelial cell-promoting environment, CD34(+), but not CD133(+), isolates produced endothelial-like cells that expressed alpha-SMA. Human fetal cord blood contains a population of cells that may differentiate toward both an endothelial and a smooth muscle phenotype in culture.

AC133 Antigen↗

PubMed2004

Volume-induced effects on the isolated bladder: a possible local reflex.

OBJECTIVES: To: (i) determine the effects of changing intravesical volume on autonomous activity in the isolated whole bladder of the guinea pig; (ii) identify the mechanisms which might contribute to induced changes; and (iii) explore the idea that changes in bladder volume which affect phasic activity are part of a local reflex operating within the bladder wall. MATERIALS AND METHODS: Bladders were isolated from female guinea pigs, cannulated via the urethra and maintained in vitro in Tyrode's solution. The intravesical pressure (IVP) was monitored and drugs added to the bathing solution. RESULTS: The isolated unstimulated bladder containing 500-600 microL of fluid generates small (1-2 cm H2O) phasic rises in IVP, i.e. autonomous activity. When the bladder volume was increased, autonomous activity increased. In the presence of muscarinic agonists (100 nmol/L arecaidine and carbachol 100 nmol/L) autonomous activity is augmented, giving rise to large (>10 cm H2O) phasic rises in IVP. When the volume was increased, both the amplitude and frequency of the transients increased. When the bladder volume was reduced there was a period of marked inhibition of phasic activity. To explore the mechanisms underlying these changes the possible involvement of local neural reflexes was explored. The neurotoxin tetrodotoxin had no effect on the volume-induced changes. Sensory nerves are insensitive to tetrodotoxin and thus to assess their possible contribution bladders were exposed to capsaicin (10 micromol/L) to stimulate and eliminate sensory fibres; capsaicin caused complex changes in phasic activity, i.e. an initial increase, a secondary slowing and decrease, followed by a period of recovering amplitude and increased frequency. These changes suggest actions of the sensory nerves on the phasic mechanism indicative of a local axonal reflex. Once the phasic activity had returned to levels before capsaicin, changes in bladder volume still produced increases in activity and inhibition after the volume decrease. Interstitial cells (cells capable of increasing cGMP) are found in the bladder wall; to assess their possible role in the volume-induced changes, bladders were treated with 30 micromol/L ODQ, an inhibitor of guanyl cyclase, for 30-60 min. The volume-induced rise in frequency was little affected but the inhibition seen on volume reduction was reduced. CONCLUSIONS: These results show that there are components in the bladder wall which respond to distension by affecting phasic activity. This stimulus/response may reflect a volume 'reflex' within the bladder wall, consisting of excitatory and inhibitory components. This local reflex does not appear to involve directly motor or sensory nerves, although the latter can affect phasic activity, and their actions may represent a further reflex mechanism in the bladder wall. The possible involvement of guanyl cyclase in the volume-induced inhibition may indicate a role for interstitial cells. The physiological role of these mechanisms as a component of a motor/sensor system in the bladder wall is discussed.

Animals↗

PubMed2004

cGMP-generating cells in the bladder wall: identification of distinct networks of interstitial cells.

OBJECTIVE: To identify cells which might contribute to the complex physiological responses of the guinea-pig bladder, and specifically to describe the distribution and types of cell in the bladder wall of the guinea pig which respond to nitric oxide (NO) with an increase in intracellular cGMP, i.e. putative interstitial cells (ICs). MATERIALS AND METHODS: The whole bladder was removed from 11 male guinea pigs killed by cervical dislocation. Sections of the bladder wall, from the dome lateral wall and base, were isolated and incubated separately in Krebs' solution at 36 degrees C, gassed with 95% O(2) and 5% CO(2), and containing 1 mmol/L of the nonspecific phosphodiesterase inhibitor isobutyl-methyl-xanthene. Individual pieces of tissue were then exposed to 100 micromol/L of the NO donor NONOate for 10 min; control tissues remained in Krebs' solution. Tissues were then fixed in 4% paraformaldehyde and processed for immunohistochemistry. cGMP and neuronal NO synthase (nNOS) were subsequently visualized using appropriate primary and secondary antibodies. RESULTS: Cells responding to NO with an increase in cGMP were detected in the dome, lateral wall and base, with positive cells in the thin outer surface of the wall (muscle coat), associated with muscle bundles in an outer layer of muscle, and in a region immediately beneath the urothelium. These cells (not urothelium, smooth muscle or vascular) are described as interstitial cells. Superficial urothelial umbrella cells were apparent and were strongly cGMP-positive. A high density of interstitial cells was associated with muscle bundles on the outer aspects of the wall, while few cells were detected on inner bundles. Thus there appeared to be two distinct types of muscle, inner and outer, with no obvious orientation of the fibres in each layer. Both muscle groups contained fibres expressing nNOS. In the outer muscle layer most of these fibres co-localized with cGMP, suggesting that different populations of nerves innervate each layer. There were more nNOS-positive fibres in the base of the bladder than in the dome. Three populations of cGMP-positive interstitial cells were associated with the outer muscle layer; cells in the outer surface (muscle coat interstitial cells, MC-ICs), cells on the surface of the bundles (superficial, SM-ICs) and cells within the muscle bundles (intramuscular, IM-ICs). The IM-ICs form a network in close apposition to the smooth muscle cells while the SM-ICs may connect adjacent muscle bundles and connect to the MC-ICs. Thus, there is a network linking potentially the muscle cells in the outer muscle bundles. cGMP-positive cells were also detected in the suburothelial layer (suburothelial, SU-ICs) which had a different structure to the cells associated with muscle, had a oval cell bodies with bifurcating processes and appeared to form a complex network; they were prevalent in the base and virtually absent in the dome. CONCLUSIONS: There are structures within the bladder wall that can be identified and categorized by the ability of the constituent cells to increase intracellular cGMP in response to NO; these cells have been defined as ICs. Two distinct networks were identified, one associated with the outer muscle layers and another lying immediately beneath the urothelium, predominantly in the base of the bladder. The functions of these cells and networks are unknown; their possible roles in complex motor activity, urothelial signalling and bladder pathophysiology are discussed.

Animals↗

PubMed2003

Partial outlet obstruction enhances modular autonomous activity in the isolated rat bladder.

PURPOSE: Autonomous bladder activity can take the form of localized micromotions (MMs), suggesting that the detrusor may be arranged into component modules, of which each is capable of contracting autonomously. We examined MMs in isolated whole rat bladder and the effects of partial bladder outlet obstruction as a model of detrusor overactivity (DO) to ascertain whether altered modular activity could be an etiological factor in DO. MATERIALS AND METHODS: A total of 12 adult female Sprague-Dawley rats underwent obstruction or sham operation for 1 or 4 weeks. Bladders were microsurgically removed and mounted in whole organ tissue baths. Recordings of intravesical pressure and simultaneous registration of intramural contractions were performed under standardized conditions. RESULTS: Prior to filling MMs took the form of localized contractions near the vesicoureteral junction in sham operated animals and multifocal microcontractions in obstructed animals. Intravesical volume increases were associated with a change in localized MMs to propagated contraction waves. In sham operated animals stretch resulted in increased MM frequency but decreased amplitude. After obstruction stretch elicited highly coordinated MMs and enhanced intravesical pressure transmission. The time since surgery did not alter observations in the sham or obstructed group. CONCLUSIONS: Detrusor muscle in isolated bladders under conditions modeling urine storage may have a functional modular arrangement with the basolateral region most active prior to filling. Peripheral factors determining intravesical pressure include the number of modules active, coordination and intramural tension at other sites. After bladder outlet obstruction more modules are active at baseline and their coordination is enhanced by stretch, leading to increased pressure fluctuations. Such changes may contribute to the development of DO.

Animals↗

PubMed2002

Mechanical stretch regulates cell survival in human bladder smooth muscle cells in vitro.

Our understanding of the pathophysiology of the overactive bladder is poor. It has been proposed that localized contractions result in the abnormal stretching of bladder smooth muscle. We hypothesize that stretch regulates the cellular processes that determine tissue size. The purpose of this study was to investigate the effect of stretch on apoptosis, proliferation, cell hypertrophy, and growth factor production in human bladder smooth muscle cells in vitro. Normal human detrusor muscle was obtained from patients undergoing radical cystectomy for invasive bladder cancer, and primary cultures were established. Cells were mechanically stretched on flexible plates at a range of pressures and times. Apoptosis was assessed by propidium iodide incorporation and flow cytometry. Radiolabeled thymidine and amino acid incorporation were used to assess proliferation and cell hypertrophy. ELISA and RT-PCR were used to assess growth factor production. Mechanical stretch inhibits apoptosis in a time- and dose-dependent manner and was associated with increases in the antiapoptotic proteins heat shock protein-70 and cIAP-1. Stretch also increases smooth muscle cell proliferation and hypertrophy, but hypertrophy is the more dominant response. These changes were associated with increases in IGF-1 and basic FGF and a decrease in transforming growth factor-beta1. Mechanical stretch regulates apoptosis, proliferation, and cell hypertrophy in human bladder smooth muscle cells.

Cell Division↗