Christos E. Constantinou

Treatment of urinary incontinence by the periurethral implantation of glutaraldehyde cross-linked collagen.

Injectable materials have been used to augment the urethral sphincter and improve urinary continence with some success. However, none of these materials has received widespread use because they are difficult to inject and have been reported to migrate. We investigated the efficacy of transurethral implantation of glutaraldehyde cross-linked collagen, a highly purified bovine collagen. A total of 17 patients (16 men and 1 woman) with urinary incontinence resulting from a previous operation was selected for glutaraldehyde cross-linked collagen injection into the region of the urethral sphincter. Before and after implantation patients underwent urodynamic evaluation. Glutaraldehyde cross-linked collagen was injected into the area of the bladder neck or urinary sphincter under direct endoscopic vision. If no improvement occurred reinjection to increase the implant volume was performed at least 3 months after a previous injection. Of the 17 patients 9 were cured or improved. No complications have been reported. This investigation shows that glutaraldehyde cross-linked collagen can be injected into the urinary tract to correct urinary incontinence without observable or measurable morbidity.

Spatial Distribution and Timing of Transmitted and Reflexly Generated Urethral Pressures in Healthy Women

We localized the temporal and spatial distribution of pressures in the urethra to identify their contribution to continence. With the data obtained we resolved the timing between the passively transmitted and actively generated urethral pressures. Data were obtained from 11 healthy female volunteers, with a mean age of 22 years. Simultaneous measurements of bladder and urethral pressures were taken from subjects during the Valsalva maneuver and coughing, and then holding with the subject in the supine, standing and sitting positions. The ratio of urethral to bladder pressure increase and the latency between these pressure increases were analyzed. A biphasic pressure distribution results from coughing with subjects in all positions. The first phase occurs at the normalized distance of 10 to 15 per cent from the bladder neck, where the ratio of urethral to bladder pressure increase is 0.8. The second phase occurs at 60 to 70 per cent of the urethral length and has a 1.5 to 1.7 ratio of urethral to bladder pressure increase, indicating the presence of pressure magnification. Simultaneous latency measurements indicate that the pressure increase in the urethra precedes that of the bladder by 240 plus or minus 30 msec. in the region that exhibits maximum pressure magnification. These results indicate that a fast-acting contraction occurs in the distal third of the urethra, which contributes reflexly to the compressive forces of the proximal urethra, thereby preventing urine loss during stress.

Micro-mechanical sensing platform for the characterization of the elastic properties of the ovum via uniaxial measurement

Stiffness is an important parameter in determining the physical properties of living tissue. Recently, considerable biomedical attention has centered on the mechanical properties of living tissues at the single cell level. In the present paper, the Youngs modulus of zona pellucida of bovine ovum was calculated using Micro Tactile Sensor (MTS) fabricated using piezoelectric (PZT) material. The sensor consists of a needle-shaped 20-microm transduction point made using a micro-electrode puller and mounted on a micro-manipulator platform. Measurements were made under microscopic control, using a suction pipette to support the ovum in the same horizontal axis as the MTS. Youngs modulus of ovum was found to be 25.3+/-7.94 kPa (n=28). This value was indirectly determined based on calibration curves relating change in resonance frequency (Deltaf(0)) of the sensor with tip displacement for gelatin at concentrations of 4%, 6%, and 8%. The regression equation between the rate of change in resonance frequency (versus sensor tip displacement), Deltaf(0)/x and Youngs modulus is Deltaf(0)/x (Hz/microm)=0.2992 x Youngs modulus (kPa)-1.0363. It is concluded that a reason that the stiffness of ovum measured in the present study is approximately six times larger than previously reported, may be due to the absence of large deformation present in of existing methodologies.

International continence society guidelines on urodynamic equipment performance

These guidelines provide benchmarks for the performance of urodynamic equipment, and have been developed by the International Continence Society to assist purchasing decisions, design requirements, and performance checks. The guidelines suggest ranges of specification for uroflowmetry, volume, pressure, and EMG measurement, along with recommendations for user interfaces and performance tests. Factors affecting measurement relating to the different technologies used are also described. Summary tables of essential and desirable features are included for ease of reference. It is emphasized that these guidelines can only contribute to good urodynamics if equipment is used properly, in accordance with good practice. Neurourol. Urodynam. 33:370–379, 2014.

The Impact of Bladder Neck Suspension on the Resting and Stress Urethral Pressure Profile: A Prospective Study Comparing Controls with Incontinent Patients Preoperatively and Postoperatively

Abstract For further understanding of the urodynamics of urinary stress incontinence 20 female patients with this condition were evaluated using resting and stress urethral pressure profiles before and after endoscopic suspension of the bladder neck. The results were compared to those in 13 normal volunteers who were evaluated similarly. In addition, the effect of posture on the urethral pressure profile was studied with the patients in the supine, standing and sitting positions. The results show that the mean maximum urethral closure pressure and functional profile length were significantly lower (p equals 0.005) in patients with stress urinary incontinence when compared to the normal volunteers. Posture did not significantly affect the maximum urethral closure pressure and functional profile length in either group (p greater than 0.1). Successful endoscopic suspension of the bladder neck did not significantly alter the maximum urethral closure pressure, while it significantly increased the functional profile length with the patient in the standing position only (p less than 0.05). The stress urethral pressure profile separated objectively the stress urinary incontinent patients and the continent volunteers. In continent women the transmitted abdominal pressure in the urethra during a cough or Valsalva’s maneuver was significantly higher than that in the bladder over most of the urethral length in all 3 positions. In the group with stress urinary incontinence the transmitted abdominal pressure in the urethra during the same maneuvers was less than that in the bladder. The data also showed that the stress urethral pressure profile curves in patients with stress urinary incontinence who were cured surgically reverted to the normal control pattern with higher abdominal pressure transmission in the urethra than in the bladder during a cough or Valsalva’s maneuver. The anatomical and physiological implications of these findings with their clinical application in the understanding of the mechanisms of continence in normal and stress incontinent women are discussed.

Determining the displacement of the pelvic floor and pelvic organs during voluntary contractions using magnetic resonance imaging in younger and older women

Objectives  To: (i) visualize the effect of sustained voluntary contractions on the anatomical configuration of the pelvic floor (PF) muscles using magnetic resonance imaging (MRI); (ii) examine the effect of ageing on the range of displacement of the PF contents secondary to contraction and simulating incontinence exercises; and (iii) introduce the concept of contractile change in volume (ΔPF‐V) using three‐dimensional (3D) reconstruction from axial, sagittal and coronal MRI.

Age dependent response to exogenous estrogen on micturition, contractility and cholinergic receptors of the rat bladder

The age related effects of 17beta-estradiol (E) supplementation on micturition and contractility of ovariectomized rats (OVX) were evaluated. Studies were carried out in young, 2 month, and mature, 10 month old rats which were distributed into three groups: Sham-operated (SHAM), (OVX), and (OVX+E). Following treatment, urodynamic studies were performed followed by an in vitro bladder tissue evaluation. Urodynamic studies show age and time related changes in bladder function. The in vitro results show that the hormone deprived tissues of 2 months old rats had a decreased responsiveness to cholinergic stimulation; maximum contractile force occurred at 78% and 187% for the SHAM. The response from the OVX+E tissues was evident at 113%. E supplementation of the mature rats increased bladder contractile force to the same levels as SHAM (156% and 176%). The response of the mature OVX rats remained significantly below that of SHAM or OVX+E rats. Findings suggest that the impact of E on bladder function depends on age at which it is given. Differential response between young and mature to exogenous E indicates that endogenous estrogen plays a major role in the neuromuscular development of normal bladder function and micturition reflexes. Contractility data show that OVX in young rats irreversibly decreases the response of the bladder to cholinergic stimulation, suggesting that exogenous E partially restores function while in mature rats, exogenous E was able to reverse the effects of OVX.

Mechanisms of Pelvic Floor Muscle Function and the Effect on the Urethra during a Cough

BACKGROUND Current measurement tools have difficulty identifying the automatic physiologic processes maintaining continence, and many questions still remain about pelvic floor muscle (PFM) function during automatic events. OBJECTIVE To perform a feasibility study to characterise the displacement, velocity, and acceleration of the PFM and the urethra during a cough. DESIGN, SETTING, AND PARTICIPANTS A volunteer convenience sample of 23 continent women and 9 women with stress urinary incontinence (SUI) from the general community of San Francisco Bay Area was studied. MEASUREMENTS Methods included perineal ultrasound imaging, motion tracking of the urogenital structures, and digital vaginal examination. Statistical analysis used one-tailed unpaired student t tests, and Welchs correction was applied when variances were unequal. RESULTS AND LIMITATIONS The cough reflex activated the PFM of continent women to compress the urogenital structures towards the pubic symphysis, which was absent in women with SUI. The maximum accelerations that acted on the PFM during a cough were generally more similar than the velocities and displacements. The urethras of women with SUI were exposed to uncontrolled transverse acceleration and were displaced more than twice as far (p=0.0002), with almost twice the velocity (p=0.0015) of the urethras of continent women. Caution regarding the generalisability of this study is warranted due to the small number of women in the SUI group and the significant difference in parity between groups. CONCLUSIONS During a cough, normal PFM function produces timely compression of the pelvic floor and additional external support to the urethra, reducing displacement, velocity, and acceleration. In women with SUI, who have weaker urethral attachments, this shortening contraction does not occur; consequently, the urethras of women with SUI move further and faster for a longer duration.

Tactile resonance sensors in medicine.

Tactile sensors in general are used for measuring the physical parameters associated with contact between sensor and object. Tactile resonance sensors in particular are based on the principle of measuring the frequency shift, Δf, defined as the difference between a freely vibrating sensor resonance frequency and the resonance frequency measured when the sensor makes contact to an object. Δf is therefore related to the acoustic impedance of the object and can be used to characterize its material properties. In medicine, tactile resonance sensor systems have been developed for the detection of cancer, human ovum fertility, eye pressure and oedema. In 1992 a Japanese research group published a paper presenting a unique phase shift circuit to facilitate resonance measurements. In this review we summarize the current state-of-the-art of tactile resonance sensors in medicine based on the phase shift circuit and discuss the relevance of the measured parameters for clinical diagnosis. Future trends and applications enabled by this technology are also predicted.

Endothelium Dependent Relaxation of Human Corpus Cavernosum by Bradykinin

Abstract The release of endothelium-derived relaxing factor (EDRF) from human corpus cavernosum (CC) tissue was confirmed by demonstrating that bradykinin produces endothelium dependent relaxation of human CC tissue. Human CC strips were set in a tissue bath and isometric tension changes were recorded. All strips showed spontaneous contractions and produced tonic contractions by both high potassium solution and noradrenaline (NA) (10 −9 to 10 −4 M) in a dose dependent manner. In preparations precontracted with NA, relaxation was produced by bradykinin (10 −7 to 2 × 10 −6 M). Strips lacking endothelium were contracted by NA but no relaxation was observed with the addition of bradykinin. More direct evidence of the release of EDRF from human CC was demonstrated by a “sandwich” mount. We conclude that bradykinin relaxes human CC by releasing EDRF and that this EDRF may be a factor in erectile function. ( J. Urol., 144: 1015–1017, 1990 )