Selective reduction of neurotransmitter release by cAMP-dependent pathways in mouse detrusor

Parasympathetic nerve-mediated contractions of detrusor smooth muscle are generated by ATP and acetylcholine (ACh) release from efferent nerve terminals. In humans, ACh is responsible for detrusor contractions in normal human bladders, whereas ATP has an additional role in overactive bladder pathologies. The ATP metabolite, adenosine, relaxes nerve-mediated contractions, with a potential action via presynaptic adenosine A1 receptor activation and subsequent suppression of neuronal ATP release. We investigated the effect of A1 receptor activation and downstream cAMP-dependent pathways on nerve-mediated ATP and ACh release, and detrusor contraction in mouse detrusor. Bladders from male C57BL/6 mice (12 wk) were used for in vitro experiments. Upon electrical field stimulation of intact preparations (detrusor and mucosal layers), ATP or ACh release was measured simultaneously with tension recordings. Activation of A1 receptors by adenosine or exogenous agonists reduced the lower frequency component of nerve-mediated contractions and neuronal ATP release. The A1 receptor antagonist abolished these effects. A1 receptor activation inhibits adenylyl cyclase (AC) activity and cAMP generation. The effect of A1 receptor activation was mimicked by a PKA antagonist but not by modulators of exchange proteins activated by cAMP, demonstrating that modulation of nerve-mediated ATP release is via PKA. Adenosine had no effect on ACh release or the higher frequency component of nerve-mediated contractions. Differential regulation of neurotransmitter release is possible at the detrusor nerve-muscle junction, as demonstrated by A1 receptor activation, and downstream inhibition of AC, cAMP generation, and PKA. The ability to specifically attenuate ATP release offers a potential to target purinergic motor pathways enhanced in overactive bladder pathologies

Emphasizing Task-Specific Hypertrophy to Enhance Sequential Strength and Power Performance

While strength is indeed a skill, most discussions have primarily considered structural adaptations rather than ultrastructural augmentation to improve performance. Altering the structural component of the muscle is often the aim of hypertrophic training, yet not all hypertrophy is equal; such alterations are dependent upon how the muscle adapts to the training stimuli and overall training stress. When comparing bodybuilders to strength and power athletes such as powerlifters, weightlifters, and throwers, while muscle size may be similar, the ability to produce force and power is often inequivalent. Thus, performance differences go beyond structural changes and may be due to the muscle’s ultrastructural constituents and training induced adaptations. Relative to potentiating strength and power performances, eliciting specific ultrastructural changes should be a variable of interest during hypertrophic training phases. By focusing on task-specific hypertrophy, it may be possible to achieve an optimal amount of hypertrophy while deemphasizing metabolic and aerobic components that are often associated with high-volume training. Therefore, the purpose of this article is to briefly address different types of hypertrophy and provide directions for practitioners who are aiming to achieve optimal rather than maximal hypertrophy, as it relates to altering ultrastructural muscular components, to potentiate strength and power performance

Estimation of bladder contractility from intravesical pressure–volume measurements

© 2016 Wiley Periodicals, Inc. Aims: To describe parameters from urodynamic pressure recordings that describe urinary bladder contractility through the use of principles of muscle mechanics. Methods: Subtracted detrusor pressure and voided flow were recorded from patients undergoing filling cystometry. The isovolumetric increase of detrusor pressure, P, of a voluntary bladder contraction before voiding was used to generate a plot of (dP/dt)/P versus P. Extrapolation of the plot to the y-axis and the x-axis generated a contractility parameter, vCE (the maximum rate of pressure development) and the maximum isovolumetric pressure, P0, respectively. Similar curves were obtained in ex vivo pig bladders with different concentrations of the inotropic agent carbachol and shown in a supplement. Results: Values of vCE, but not P0, diminished with age in female subjects. vCE was most significantly associated with the 20–80% duration of isovolumetric contraction t20–80; and a weaker association with maximum flow rate and BCI in women. P0 was not associated with any urodynamic variable in women, but in men was with t20–80 and isovolumetric pressure indices. Conclusions: The rate of isovolumetric subtracted detrusor pressure (t20–80) increase shows a very significant association with indices of bladder contractility as derived from a derived force–velocity curve. We propose that t20–80 is a detrusor contractility parameter (DCP). Neurourol. Urodynam. 36:1009–1014, 2017. © 2016 Wiley Periodicals, Inc

Contractile function of detrusor smooth muscle from children with posterior urethral valves – the role of fibrosis

IntroductionPosterior urethral valves (PUV) is the most common cause of congenital bladder outflow obstruction with persistent lower urinary tract and renal morbidities. There is a spectrum of functional bladder disorders ranging from hypertonia to bladder underactivity, but the aetiology of these clinical conditions remains unclear.Aims and objectivesWe tested the hypothesis that replacement of detrusor muscle with non-muscle cells and excessive deposition of connective tissue is an important factor in bladder dysfunction with PUV. We used isolated detrusor samples from children with PUV and undergoing primary or secondary procedures in comparison to age-matched data from children with functionally normal bladders. In vitro contractile properties, as well as passive stiffness, were measured and matched to histological assessment of muscle and connective tissue. We examined if a major pathway for fibrosis was altered in PUV tissue samples.MethodsIsometric contractions were measured in vitro in response to either stimulation of motor nerves to detrusor or exposure to cholinergic and purinergic receptor agonists. Passive mechanical stiffness was measured by rapid stretching of the tissue and recording changes to muscle tension. Histology measured the relative amounts of detrusor muscle and connective tissue. Multiplex quantitative immunofluorescence labelling using five epitope markers was designed to determine cellular pathways, in particular the Wnt-signalling pathway, responsible for any changes to excessive deposition of connective tissue.Results and DiscussionPUV tissue showed equally reduced contractile function to efferent nerve stimulation or exposure to contractile agonists. Passive muscle stiffness was increased in PUV tissue samples. The smooth muscle:connective tissue ratio was also diminished and mirrored the reduction of contractile function and the increase of passive stiffness. Immunofluorescence labelling showed in PUV samples increased expression of the matrix metalloproteinase, MMP-7; as well as cyclin-D1 expression suggesting cellular remodelling. However, elements of a fibrosis pathway associated with Wnt-signalling were either reduced (β-catenin) or unchanged (c-Myc). The accumulation of extracellular matrix, containing collagen, will contribute to the reduced contractile performance of the bladder wall. It will also increase tissue stiffness that in vivo would lead to reduced filling compliance.ConclusionsReplacement of smooth muscle with fibrosis is a major contributory factor in contractile dysfunction in the hypertonic PUV bladder. This suggests that a potential strategy to restore normal contractile and filling properties is development of the effective use of antifibrotic agents

Meta-analysis of changes in the levels of catecholamines and blood pressure with continuous positive airway pressure therapy in obstructive sleep apnea

Stress from obstructive sleep apnea (OSA) stimulates catecholamine release consequently exacerbating hypertension. However, different studies have shown a conflicting impact of continuous positive airway pressure (CPAP) treatment in patients with OSA on catecholamine levels and blood pressure. We aimed to examine changes to catecholamine levels and blood pressure in response to CPAP treatment. We conducted a meta‐analysis of data published up to May 2020. The quality of the studies was evaluated using standard tools for assessing the risk of bias. Meta‐analysis was conducted using RevMan (v5.3) and expressed in standardized mean difference (SMD) for catecholamines and mean difference (MD) for systolic (SBP) and diastolic blood pressure (DBP). A total of 38 studies met our search criteria; they consisted of 14 randomized control trials (RCT) totaling 576 participants and 24 prospective cohort studies (PCS) of 547 participants. Mean age ranged between 41 and 62 year and body mass index between 27.2 and 35.1 kg/m(2). CPAP treatment reduced 24‐hour urinary noradrenaline levels both in RCT (SMD = −1.1; 95% confidence interval (CI): −1.63 to − 0.56) and in PCS (SMD = 0.38 (CI: 0.24 to 0.53). SBP was also reduced by CPAP treatment in RCT (4.8 mmHg; CI: 2.0‐7.7) and in PCS (7.5 mmHg; CI: 3.3‐11.7). DBP was similarly reduced (3.0 mmHg; CI: 1.4‐4.6) and in PCS (5.1 mmHg; CI: 2.3‐8.0). In conclusion, CPAP treatment in patients with OSA reduces catecholamine levels and blood pressure. This suggests that sympathetic activity plays an intermediary role in hypertension associated with OSA‐related stress

Accurate quantification of apoptosis progression and toxicity using a dielectrophoretic approach

A loss of ability of cells to undergo apoptosis (programmed cell death, whereby the cell ceases to function and destroys itself) is commonly associated with cancer, and many anti-cancer interventions aim to restart the process. Consequently, the accurate quantification of apoptosis is essential in understanding the function and performance of new anti-cancer drugs. Dielectrophoresis has previously been demonstrated to detect apoptosis more rapidly than other methods, and is low-cost, label-free and rapid, but has previously been unable to accurately quantify cells through the apoptotic process because cells in late apoptosis disintegrate, making cell tracking impossible. In this paper we use a novel method based on light absorbance and multi-population tracking to quantify the progress of apoptosis, benchmarking against conventional assays including MTT, trypan blue and Annexin-V. Analyses are performed on suspension and adherent cells, and using two apoptosis-inducing agents. IC50 measurements compared favourably to MTT and were superior to trypan blue, whilst also detecting apoptotic progression faster than Annexin-V

The Validation of a Functional, Isolated Pig Bladder Model for Physiological Experimentation

Characterizing the integrative physiology of the bladder requires whole organ preparations. The purpose of this study was to validate an isolated large animal (pig) bladder preparation, through arterial and intravesical drug administration, intravesical pressure recording, and filming of surface micromotions. Female pig bladders were obtained from the local abattoir and arterially perfused in vitro. Arterial and intravesical pressures were recorded at varying volumes. Bladder viability was assessed histologically and by monitoring inflow and outflow pH. Arterial drug administration employed boluses introduced into the perfusate. Intravesical administration involved slow instillation and a prolonged dwell-time. Surface micromotions were recorded by filming the separation of surface markers concurrently with intravesical pressure measurement. Adequate perfusion to all bladder layers was achieved for up to 8 h; there was no structural deterioration nor alteration in inflow and effluent perfusate pH. Arterial drug administration (carbachol and potassium chloride) showed consistent dose-dependent responses. Localized movements (micromotions) occurred over the bladder surface, with variable correlation with fluctuations of intravesical pressure. The isolated pig bladder is a valid approach to study integrative bladder physiology. It remains viable when perfused in vitro, responds to different routes of drug administration and provides a model to correlate movements of the bladder wall directly to variation of intravesical pressure

Characterisation of nerve‐mediated ATP release from bladder detrusor muscle and its pathological implications

Background and Purpose. To characterise the molecular mechanisms that determine variability of atropine‐resistance of nerve‐mediated contractions in human and guinea‐pig detrusor smooth muscle Experimental Approach. Atropine‐resistance of nerve‐mediated contractions, and the role of P2X1 receptors, was measured in isolated preparations from guinea‐pigs and also humans with or without overactive bladder syndrome, from which the mucosa was removed. Nerve‐mediated ATP release was measured directly with amperometric ATP‐sensitive electrodes. Ecto‐ATPase activity of guinea‐pig and human detrusor samples was measured in vitro by measuring the concentration‐dependent rate of ATP breakdown. The transcription of ecto‐ATPase subtypes in human samples was measured by qPCR. Key Results Atropine resistance was greatest in guinea‐pig detrusor, absent in human tissue from normally‐functioning bladders and intermediate in human overactive bladder. Greater atropine resistance correlated with reduction of contractions by the ATP‐diphospho‐hydrolase apyrase, directly implicating ATP in their generation. E‐NTPDase‐1 was the most abundantly transcribed ecto‐ATPase of those tested and transcription was reduced in tissue from human overactive, compared to normal, bladders. E‐NTPDase‐1 enzymatic activity was inversely related to the magnitude of atropine resistance. Nerve‐mediated ATP release was continually measured and varied with stimulation frequency over the range 1‐16 Hz. Conclusion and Implications Atropine‐resistance in nerve‐mediated detrusor contractions is due to ATP release and its magnitude is inversely related to E‐NTPDase‐1 activity. ATP is released under different stimulation conditions compared to acetylcholine that implies different routes for their release</p

Disparity in the risk of exposure to respirable crystalline silica dust among non- manual and manual employees in the construction industry

Construction workers are at increased health risk due to exposure to respirable crystalline silica (RCS) dust. We examined differences in health risk among non-manual and manual employees in the construction industry. Online survey of construction industry employees using a questionnaire consisted of 17 items to obtain information on demographic data, employment history and health risk exposure. Chi-squared tests were used to explore differences in health risk between manual and non-manual employees, and logistic regression to determine the risk of adverse events in manual workers. Of the 47 employees invited, 45 completed the questionnaire (95% response rate). Seventeen were non-manual (professional, project managers and managers) and 28 were manual employees (tradesmen and construction workers). There was a significantly higher percentage of non-manual employees below 45 years than older group (70.6% vs 39.3%; 2 = 4.2, p = 0.039) and they worked less than 20 years than those working longer (82.4% vs 32.1%; 2 = 10.7, p = 0.001). Compared to non-manual workers, manual workers were more likely to work >20 years: OR = 2.2 (95% CI = 1.3-3.6); be exposed to RCS dust and smoke: unadjusted OR = 1.8 (1.1-3.1), age and length of time working in construction industry adjusted OR = 2.2(1.2-4.2); and have breathing problems: unadjusted OR = 3.9 (1.5-10.4), age, smoking and length of time working in construction industry adjusted OR = 3.7 (1.1-12.5). The risk of breathing problems was increased among individuals working more than 20 years: OR = 4.8 (1.2-18.6), exposed to dust and smoking: unadjusted OR = 3.8 (1.0-14.1), age and length of time working in construction industry adjusted OR = 5.4 (1.2-24.4), whilst those with adequate information on health hazards were associated with lower risk of breathing problems. There is an increased risk of exposure to RCS dust and pulmonary symptoms among manual employees in the construction industry. Further efforts are required to provide greater protection for this group of workers to reduce their health risk