Biomedical subjects

C E Constantinou

Publications and source records attributed to C E Constantinou.

At least 19 recordsLinked to original sources

PubMed1997

Comparative analysis of bladder wall compliance based on cystometry and biosensor measurements during the micturition cycle of the rat.

The stiffness characteristics of the empty and filling bladder and the modulating influence of oxybutynin were investigated using a new biosensor system. Studies were done comparing the stiffness measured using the pressure/volume relationship with direct biosensor monitoring on male and female rats during isovolumetric contractions elicited during the cystometrogram (CMG). Bladder stiffness at zero volume, measured in vitro using the biosensor, was evaluated and compared with the stiffness of the prostate, seminal vesicles, testicles, and uterus. In 5 small anesthetized male rats, in vivo isovolumetric studies were performed and bladder stiffness was measured during the storage and contraction phase of the CMG. In 6 mature female rats, change in bladder stiffness during isovolumetric contractions was investigated following intraarterial (i.a.) administration of 0.1 and 1.0 mg/kg of oxybutynin. After the in vivo CMG was completed, an in vitro CMG was done measuring bladder stiffness. The results show that bladder stiffness, measured during the storage phase of the CMG, increased in accordance with the stretched length of bladder wall. During the in vivo CMG, bladder stiffness increased consequent to a spontaneous contraction from 10.0 +/- 1.9 g/cm to 29.9 +/- 3.0 g/cm (P < 0.005). Oxybutynin produced a significant decrease in bladder stiffness during the storage phase of the CMG, as measured using the biosensor, which was concomitant with an increase in bladder compliance derived from pressure/volume data. The incremental change in stiffness, delta K, during isovolumetric contraction decreased due to i.a. oxybutynin in accordance with a decrease of maximum detrusor pressure. These results indicate that delta K is related to the active change of viscoelastic properties of bladder smooth muscle. These findings imply that direct measurement of the stiffness of the bladder wall possesses the potential to be an objective assessment of bladder biomechanical properties and of their functional response to obstruction and pharmacological intervention.

Animals↗

PubMed1997

Modulation of detrusor contraction strength and micturition characteristics by intrathecal baclofen in anesthetized rats.

PURPOSE: The effect of intrathecal (i.t.) baclofen in modulating the micturition reflexes, detrusor contraction strength, and micturition efficiency was evaluated in anesthetized rats. MATERIAL AND METHODS: Female Wistar rats (n = 14, 337 +/- 8 gm.) were anesthetized with urethane (1.2 gm./kg. s.c.). Cystometrograms were done through a lower midline incision made to expose the bladder and a catheter was inserted through the bladder dome to record pressure during filling with saline at the rate of 0.038 ml./min. During the micturition phase of cystometrogram, the measurement of voided volume was made synchronously with the intravesical pressure. Baclofen was given intrathecally at the increasing doses of 0.05, 0.10, 0.5 microgram. and pressure/flow parameters were measured. RESULTS: The measured urodynamic parameters show that baclofen produced a significant dose dependent increase in bladder capacity and a decreases in voiding efficiency, detrusor pressure and maximum and average flow rate. Baclofen (0.1 microgram.) significantly decreased detrusor contractility reducing both Wmax from 3.7 +/- 0.1 (control) to 2.0 +/- 0.1 W/m2 and Wisv,max from 5.9 +/- 0.3 to 5.5 +/- 0.4 W/m2 respectively. Baclofen altered the characteristic pattern of the micturition reflex by suppressing high frequency pressure oscillations during voiding which was completely abolished after 0.1 microgram. in 75% of the rats. Furthermore, urinary dribbling incontinence was evident at a dose of 0.5 microgram. in 58% of all rats. CONCLUSIONS: These results demonstrate that i.t. baclofen has a significant inhibitory effect on the micturition reflex, depressing detrusor contraction strength and micturition efficiency, while increasing bladder capacity.

Anesthesia↗

PubMed1996

Influence of hormone treatment on prostate growth and micturition characteristics of the rat.

The influence of dihydrotestosterone propionate (DHT) and estradiol (E) on prostate growth and micturition was evaluated. Complete studies were carried out on 49 Sprague-Dawley rats over a 14-day period. Rats were divided into three groups: (1) controls, (2) DHT, and (3) DHT + E. All groups were injected daily with 0.1 ml of sesame oil, together with 1.25 mg/kg of DHT for group 2 and 1.25 DHT + 0.125 mg/kg E for group 3. Physiological measurements of micturition were done weekly by subcutaneously administering a fluid loading dose consisting of 10 mg/kg furosemide + 5 ml saline. Parameters of micturition frequency, volume, and prostate weight were calculated. Prostate weight values for controls were 0.89 +/- 0.06 g while those treated with DHT increased significantly to 1.26 +/- 0.10 g (P < 0.05) and those treated with DHT + E also increased significantly to 1.24 +/- 0.09 g (P < 0.05). There was no significant difference in prostate weight between the DHT and DHT + E groups. Analysis of micturition data shows that the mean volume voided per micturition decreases in both the DHT and DHT + E treated rats. At between 7 and 14 days of DHT and DHT + E treatment, rats micturated at significantly reduced mean volumes. The lowest mean volume per micturition was detected on the 14th day of DHT treatment, showing a significant reduction from control values of 3.05 +/- 0.27 to 1.68 +/- 0.05 ml. The corresponding value of the mean micturated volume in the DHT + E groups was 1.86 +/- 0.31 ml. Control values for frequency of micturition was 3.25 +/- 0.52/hr, while for rats treated with DHT it was 3.62 +/- 0.38/hr and for DHT + E it was 4.0 +/- 0.54/hr. Evidence is provided to demonstrate that 14 day DHT, and particularly DHT + E, stimulation produces significant alterations in prostate weight and micturition characteristics of unanesthetized rats. On the basis of these observations it is proposed that the hormonally enlarged prostate promotes stimuli to trigger the spinal micturition reflex, thereby producing increased frequency of micturition.

Animals↗

PubMed1996

Analysis of the relative biomechanical effects of alpha 1 and alpha 2 antagonists in modifying the compliance of the prostate and micturition parameters of the hormonally manipulated male rat.

The potential of the alpha 1 and alpha 2 antagonists to modify prostate compliance, and micturition characteristics of rats with hormonally enlarged prostates was studied. Prostate growth was induced in Sprague-Dawley rats using dihydrotestosterone (DHT) and estradiol (E) by daily subcutaneous injections of DHT 1.25 mg/kg and E 0.25 mg/kg together with 0.1ml of sesame oil, as a vehicle, for a period of 3 weeks. A control group of six rats was used wherein the vehicle alone was administered. Dose levels of 3, 10, 30, and 300 micrograms/kg of alpha 1 or alpha 2 antagonist were given at weekly intervals to each of the groups defined above. Voiding characteristics, in terms of micturition frequency and volume per micturition, were measured and correlated with the pharmacological and hormonal stimulus. Prostate compliance and weight was evaluated in each of the groups after rats were terminated and the ventral prostate was dissected and removed in in toto. Compliance measurements were made using a new biosensor system which is based on the principle of detecting the shift in the resonance frequency of the biosensor produced by the hormones on the acoustic impedance of prostate. The results show that DHT and [DHT+E] significantly increased prostate weight and decreased prostate compliance. The alpha 2 antagonist atipamezole significantly increased the compliance of all prostates, including controls, while the alpha 1 antagonist did not alter the compliance. It is concluded that this alpha 2 antagonist is more effective than the prazosin in reversing the hardening effect of hormones on the prostate.

Adrenergic alpha-Antagonists↗

PubMed1996

Analysis of pressure/flow characteristics in the female rat and their pharmacologic modulation.

A new in vivo urodynamic animal model was developed to analyze the micturition characteristics of the rat. This model was used to study the modulating effect of pharmacological agents on vesicourethral function, using cystometry and uroflowmetry. Pressure-flow studies were done in 25 female rats anesthetized with urethane. Filling cystometry was recorded using a physiological rate of bladder filling through transvesical infusion. Micturition characterization was done by identifying the time course and amount of voided volume. Voided volume was measured by a novel application of a mechanotransducer, which provided the data to measure flow rate and compute the voided volume-time curve. Flow rate was calculated by differentiating the curve produced by the mechanotransducer. Using this system, comparative tests of pharmacological stimulus were done using anticholinergic stimulation, alpha 1, and a new N-methyl-D aspartate (NMDA) receptor antagonist. The effects of the intravenous use of these drugs in the lower urinary tract were evaluated at various dose levels. The results showed that anticholinergic stimulation produced an increase of bladder capacity and decreases of detrusor pressure and maximum flow rate. Although the alpha 1 blocker decreased detrusor pressure, flow rate did not change significantly. By contrast, NMDA receptor antagonism produced a depressant effect on bladder reflex contraction, and increased bladder capacity in a dose-dependent way. However, maximum flow rate increased at a dose of 10 mg/kg and decreased at 30 mg/kg significantly. These results suggest that a decrease in flow resistance through the outlet region was due to the effects of NMDA receptor inhibition at lower doses. In conclusion, this model enables the evaluation of drugs regarding lower urinary tract function and provides in small animals the possibility of evaluating the relationships between pressure and flow in various experimental models.

Animals↗

PubMed1996

Videomicroscopic imaging of ureteral peristaltic function in rats during cystometry.

Videomicroscopic imaging of the upper urinary tract was performed in 26 female anesthetized rats during bladder filling and micturition. Recordings were made of the pressure of the renal pelvis through a nephrostomy and visualization of the dynamics of the ureteral bolus. Peristaltic velocity, frequency, bolus length, and direction urine bolus propagation were derived on the basis of image processing using indigo carmine for contrast. In addition, nonstop cystometrograms were performed at an infusion rate of 0.22 ml/min characterizing bladder filling and micturition reflexes. Using this setup the pharmacological response of the upper and lower urinary tract dynamics to intravenous oxybutynin and LY274614 was evaluated and compared to observations made with placebo time controls. The data, obtained from the time controls, indicate that there is a significant time-dependent influence on the upper urinary function caused by the experimental methodology in the frequency of ureteral peristalsis and length of the bolus. Oxybutynin produced a significant increase in the length of the but not in the velocity of the bolus. LY274614 depressed pelvic pressure and ureteral frequency and increased bolus length. It is concluded that videomicroscopic imaging, in association with nonstop cystometry, provides a unique method to investigate the pharmacological effects of centrally and peripherally acting drugs on the upper and lower urinary tract function without mechanical manipulation of the ureter.

Animals↗

PubMed1995

Imaging of pelvic floor contractions using MRI.

Magnetic resonance was used to visualize the effect of voluntary pelvic floor contractions on the abdominal structures with particular emphasis in determining the dynamic relationship between the bladder and surrounding organs. The pelvic floor was imaged in 6 asymptomatic female volunteers using MRI viewed in seven coronal and seven sagittal planes. The relative displacement of the bladder resulting from voluntary pelvic floor contraction was measured and the changes from the relaxed to the contracted stage were identified. Measurements from sagittal images show superior bladder wall movement of 3.8 +/- 1.3 mm, posterior of 7.0 +/- 2.8 mm, while maximum movement in the gluteal region was 3.5 +/- 4.0 mm. The results show that voluntary contractions of the pelvic floor measured and visualized using this technique can be identified and displayed using image processing techniques. Anatomical displacement of the bladder in the superior direction is illustrated, demonstrating that pelvic floor contraction provides increased levator muscle support. There is no significant displacement of the anterior aspect of the bladder, while the posterior wall demonstrates maximum movement.

Adult↗

PubMed1995

Modeling of micturition characteristics based on prostatic stiffness modulation induced using hormones and adrenergic antagonists.

We present a biosensor intended to evaluate prostatic stiffness. The stiffness of the prostate was modulated using hormonal induction and adrenergic stimulation. The results show that the sensor can be sufficiently accurate to discriminate between soft prostates used as controls and those stiffened with hormones. The modulation produced by an adrenergic agent on prostatic stiffness was detected using this system. An electrical model was constructed embodying the parameters of prostatic stiffness, micturition frequency, and volume, demonstrating that prostatic stiffness correlates with micturition frequency.

Adrenergic alpha-Antagonists↗

PubMed1995

New method for direct stiffness measurement of the corpora cavernosa.

We describe a new methodology for direct ex vivo measurements of corporal stiffness. Using a new biosensor, stiffness of the corpora cavernosa was measured in 32 mature male Spraque Dawley rats. Mean stiffness (+/- se) value of the corpora was 8.186 +/- 0.318 gm/cm. The corpora was numerically the stiffest organ, when compared to the bladder and the prostate. Values measured at different points from both corpora showed a quite uniform stiffness (range 7.576-8.835 gm/cm). Hormonal stimulation with DHT was shown to significantly increase prostatic stiffness but not corpora stiffness. Similarly alpha-adrenergic antagonists did not affect corporal stiffness in a statistically significant manner. These results suggest that the influence of hormones and adrenergic stimulation on the passive properties of the corpora is negligible. It is concluded that this new method provides a reproducible new parameter for the measurement of corporal stiffness. It is anticipated that in the future this kind of stiffness measurement may be of use for the evaluation of the biomechanical properties of the corpora and its response to pharmacologic manipulation of the trabecular smooth muscle tone in vivo.

Adrenergic alpha-Antagonists↗

PubMed1994

Prostate specific antigen as a predictor of an abnormal digital rectal examination.

OBJECTIVE: To assess the ability of serum prostate specific antigen (PSA) to predict and differentiate patients with normal and abnormal digital rectal findings. SUBJECTS AND METHODS: A prospective analysis of 1374 participants in a prostate cancer screening programme was performed. After completion of a questionnaire including age and voiding symptoms as well as phlebotomy for PSA analysis, digital rectal examination was performed and the findings were categorized with respect to size, consistency, symmetry and nodularity. RESULTS: In men less than 50 years of age the mean serum PSA level failed to discriminate any of the digital rectal examination categories. In men over 50 there was a statistically significant difference in mean PSA levels between symmetrical, normal sized prostates and symmetrically enlarged glands as well as between symmetrical, normal sized and abnormal prostates (P < 0.05). No statistically significant difference was found in mean serum PSA levels between symmetrically enlarged prostate glands and those with palpable nodules. PSA levels < or = 2.5 ng/ml (normal range for the Yang polyclonal assay) and < 7.4 ng/ml (corresponding to the normal range of < 4.0 ng/ml for the Hybritech monoclonal assay) demonstrated a probability of an abnormal digital rectal examination of 11% and 14% respectively. PSA levels > 18.4 ng/ml (corresponding to monoclonal levels of > 10 ng/ml) had a 67% probability of an abnormal digital rectal examination. However, moderate elevations in PSA could not be used to predict digital examination abnormalities due to the high incidence of moderate PSA elevations associated with symmetrical enlargement of the prostate. CONCLUSIONS: Serial annual PSA measurements may provide an alternative means of screening men over 50 years of age. Contamination of results with PSA elevation due to benign prostatic hyperplasia remains, however, a problem.

Adult↗

PubMed1993

The effect of alpha 2 agonists and antagonists on the lower urinary tract of the rat.

The pharmacologic potential of selective alpha 2 adrenergic agents in modulating vesicourethral function was evaluated in urethane-anesthetized and conscious rats. The bladder was exposed through a midline incision and intubated via a cystostomy to measure pressure. The bladder was filled with saline at 0.05 ml./min. In six animals intravenous dexmedetomidine 0.6 micrograms./kg. followed by 2 micrograms./kg. was given. In another six rats the infusion was made with atipamezole at the same concentration. The parameters obtained were pressure/volume during cystometry, detrusor voiding pressures, and evidence of urine leakage. Conscious rats were placed in a restrainer outfitted with a voided volume sensor and a data recorder. The animals were divided in three groups. In controls, group I (n = 8), the animals were injected with a subcutaneous (SC) load of 5 ml. saline in which furosemide 10.0 mg./kg. was added. In group II (n = 6), dexmedetomidine was added in group III (n = 6), atipamezole was added. Parameters obtained were volume per micturition, latency, frequency of micturition, and patterns of micturition (such as dribbling), and total volume produced after a three hour recording. Values are expressed as mean +/- standard deviation. The results show that in an anesthetized preparation, the alpha 2 agonist dexmedetomidine produced inhibitory effects on the volume evoked micturition reflex (VEMR) at a dose level of 2.0 micrograms./kg. There was a significant decrease in peak pressure from 26.4 +/- 3.6 to 6.8 +/- 2.1 cm. H2O (p < 0.01). Urine leakage was observed at the external meatus. Atipamezole, the alpha 2 agonist, gradually increased bladder baseline pressure and inhibited VEMR. At a critical pressure there was continuous leakage from the external meatus. There was a significant elevation of baseline bladder pressure by atipamezole from 6.3 +/- 1.7 to 29.8 +/- 4.6 cm. H2O (p < 0.005). In conscious rats, the alpha 2 agonist produced urinary dribbling at approximately 20 minutes after SC injection, while the antagonists produced delayed dribbling 70 minutes after SC injection. Leakage occurred in 3 of 6 rats at a dose of 10 micrograms./kg. of atipamezole and in 5 of 6 rats at a dose of 30 micrograms./kg. The alpha 2 agonist caused a diuretic effect and a dose-dependent increase in the frequency of voiding (p < 0.05), while the antagonist decreased the frequency of voiding. Bladder capacity was decreased with the alpha 2 agonist while the antagonist increased capacity.

Adrenergic alpha-Agonists↗

PubMed1992

Rapid evaluation of the efficacy of pharmacologic agents and their analogs in enhancing bladder capacity and reducing the voiding frequency.

We report here the results of a simplified screening method to rapidly compare the pharmacologic action of drugs relevant to the urinary tract. This method avoids the use of anesthesia and of external infusion into the bladder relying on the physiological stimulation of the volume-evoked micturition reflex (VEMR) by diuresis. Mature female rats weighing 240-310 g were placed in restrainer cages that afforded access to food and water but limited movement. Under the rear of the rat, a collecting funnel and weight measuring device was secured. For each VEMR, the weight of the volume voided was recorded on a polygraph which also provided a record of the time of voiding. To evaluate the relative pharmacologic efficacy of the drug under study, 1 mg/kg furosemide along with the drug to be evaluated was diluted in 5 ml of saline and injected subcutaneously. Rats received approximately equimolar concentrations of thiphenamil and 15 other analogs, Ca2+ channel blockers, and K+ channel openers. The furosemide was given to obtain a controlled level of diuresis and avoid the effects of circadian variations in urine flow. Parameters considered were 1) mean volume voided per VEMR, 2) frequency, 3) output, and 4) latency. This model allows the rapid evaluation of drugs designed to increase bladder capacity and decrease the frequency of voiding, and it is particularly useful in evaluating the relative efficacy of drugs that are chemical analogs.

Analysis of Variance↗

PubMed1992

The effect of bacteriuria on bladder and renal pelvic pressures in the rat.

We investigated the effect of urinary tract infection on bladder and renal pelvic urodynamics in a rat model to examine the role of pressure during infection. Either an antibiotic solution (control group) or Escherichia coli with type 1 pili (infected group) was instilled into the bladder. After 2 to 6 days simultaneous continuous bladder and renal pelvic pressures were measured during urinary flows from less than 2 to greater than 20 ml./kg. per hour while the bladder filled and emptied. Bladder pressures from 50 to 100% of maximum capacity and maximum voiding pressures were significantly higher in the infected group than the control group (36.7 +/- 6.79 cm. water versus 25.5 +/- 5.21 cm. water, respectively, p less than 0.0001). Renal pelvic pressures were significantly higher in the infected group during bladder filling at all urinary flows examined and actually exceeded bladder pressure for the highest flows. We conclude that elevated renal pelvic pressures may contribute to renal changes observed during urinary tract infection.

Animals↗

PubMed1992

Impact of radical prostatectomy on the characteristics of bladder and urethra.

A prospective study was done to evaluate the long-term effects of radical prostatectomy on the function of the bladder in filling and voiding. Preoperative urodynamic studies were done on 29 patients with a mean age of 62.9 +/- 5.2 years. The preoperative results show that 16 of the 29 patients demonstrated detrusor instability with maximum contractile pressures of 59 +/- 28 cm. water. Followup urodynamic assessment was done in 13 of these patients 22.9 +/- 1.1 months after surgery. Postoperatively, the maximum detrusor instability pressure did not decrease significantly (49 +/- 17 cm. water). Comparison of the operative and postoperative urodynamic characteristics of bladder filling shows that radical prostatectomy produced no significant change in the filling characteristics of the bladder in terms of bladder capacity, or volume at which sensations of fullness or urgency are reported. Voiding pressure-flow studies show a significant increase in maximum flow rate (8 +/- 1 to 13 +/- 2 ml., per second, p = 0.007), and significant decreases in maximum detrusor pressure (61 +/- 5.4 to 39 +/- 4 cm. water, p = 0.002), urethral opening pressure (45 +/- 7 to 25 +/- 4 cm. water, p = 0.004) and residual volume (150 +/- 37 to 62 +/- 43 ml., p = 0.019). Urethral profile measurements show that there was no significant change in either the maximum urethral closure pressure (94 +/- 9 to 83 +/- 9 cm. water) or external sphincter length (3.6 +/- 0.8 to 3.2 +/- 0.8 cm.). Preoperatively, the bladder neck pressures were 25 +/- 4.4 cm. water and were abolished after prostatectomy, indicating that the decrease in obstructive characteristics is due to removal of the prostate.

Aged↗

PubMed1992

Relaxant effect of thiphenamil HCl on upper urinary tract frequency of contraction of healthy asymptomatic volunteers.

The pharmacologic effect of thiphenamil HCl on the upper urinary tract as a relaxant of renal pelvic contractions was studied. A total of 17 subjects with no known upper urinary tract abnormalities were scanned. A Diasonics ultrasound scanner at 3.5 MHz was used to visualize the kidney and renal pelvis with the subject in the supine position. Control recordings of renal pelvic and calyceal contractility were made on videotape for approximately 30 min. The subject was then given a single dose of 400 mg thiphenamil HCl and visualization of contractility continued for approximately 60-90 min. Criteria for the evaluation of the data were the mean frequency of pelvic contraction cross-section of the pelvis, and velocity and direction contraction. Ultrasonic images were filtered by a video filtering process and averaged using the digital conversion and summation in real time. The results show that under control conditions renal pelvic contractions are at a frequency of 2 +/- 1.8 min-1. Contractions are initiated with the intrarenal pelvis and continue towards the ureter at a rate of 1.3 +/- 0.8 cm/s. Following thiphenamil HCl, there is a significant reduction in pelvic contraction frequency, 0.6 +/- 0.6 min-1, and the opposing walls of the renal pelvis do not completely close in the formation of a bolus. The results obtained from this study demonstrate that thiphenamil suppresses upper urinary tract contractility. As a consequence of this observation, it is postulated that this agent may be of use in the acute relaxation of the upper urinary tract for renal colic and stone management.

Diphenylacetic Acids↗

PubMed1992

Pharmacologic treatment of detrusor incontinence with thiphenamil HCl.

A controlled double-blind crossover study is reported in which quantitative urodynamic data and qualitative information are combined to evaluate the treatment of detrusor incontinence using thiphenamil HCl in patients with detrusor instability. Patients placed on the treatment protocol were randomized to placebo or thiphenamil 400 mg q.i.d. Two weeks of thiphenamil HCl or placebo administration were followed by 1 week of washout followed by a cross-over to an additional 2 weeks of placebo or thiphenamil HCl administration. Of the 23 patients 7 dropped out at various stages of the study. The mean age of patients studied was 44 +/- 14 years old. Throughout the study, patients were asked to complete a formalized diary card of the amount and time of voiding and the incidence of incontinence. Three urodynamics studies were done in the following sequence: pretreatment, postwashout, and posttreatment. Parameters of bladder capacity, sensations, stability and pressure/flow were obtained. In addition, resting urethral closure pressures were recorded. The results show that the frequency of incontinence, which was based on the patients' responses, decreased significantly (0.01 less than p less than 0.025). There was an insignificant decrease in the number of voidings and increase in the amount voided each time. Patients on thiphenamil reported that their pads were significantly drier from baseline (p = 0.01). In response to questions comparing problems caused by urine loss during baseline and thiphenamil treatment, analysis shows a significant decrease of problems due to loss of urine (p = 0.01) when the patient was taking the drug compared to the placebo.(ABSTRACT TRUNCATED AT 250 WORDS)

Diphenylacetic Acids↗

PubMed1992

Topological localization of the frequency and amplitude characteristics of the whole and segmented renal pelvis.

The contractile characteristics of pacemaker regions in the unicalyceal renal pelvis of the rabbit were examined in vitro. The amplitude and frequency spectra of spontaneous contractions of whole and separated circular and longitudinal renal pelvic strips were identified. The effect of stretch on these parameters were examined in order to establish whether the pacemaker region that generates contractions in the renal pelvis was sensitive to distention. The results show that the frequency of spontaneous contractions in the whole pelvis (65 +/- 18 mHz) was significantly higher than any part of the circularly (41 x 8 mHz) or longitudinally cut (43 +/- 8 mHz) pelvis. The amplitude of longitudinal strips, 52 +/- 11 mg, was significantly smaller than that of the circular strips, 267 +/- 52 mg. In the circularly separated pelvis the frequency of spontaneous contractions was highest in the proximal part (41 +/- 8 mHz) and lowest in the pelviureteral junction (8 +/- 1 mHz). No significant increase in frequency was seen upon stretch in the whole or separated pelvis although there was a decrease in the amplitude of both the whole and separated pelvis. These results show that the frequency of contraction of the whole or the segmented renal pelvis is not sensitive to stretch.

Animals↗

PubMed1992

Renal pelvic pressure isolation from active and passive bladder pressures in the rat: the facilitating effect of urine flow rate.

The circumstances facilitating hydrostatic pressure communication between the bladder and renal pelvis were evaluated. In particular, we compared active detrusor contractions occurring spontaneously during voiding and evoked contractions produced during electrical pelvic nerve stimulation with passive abdominal compression. These variables were evaluated with respect to urine flow rate and bladder capacity. Waveform analysis of the pacemaker characteristics of the renal pelvis shows that the rat pelvis has a narrow frequency band of spontaneous contraction at 0.5 +/- 0.06 Hz. The baseline waveform and pressure of the pelvis is effected by urine flow and bladder capacity. Significant elevations in pelvic pressure of 25.8 +/- 7.9 and 28.7 +/- 5.8 cm H2O were observed for bladder pressures of 30 cm H2O (n = 8) at flow rates in the range of 2.5-5.0 and over 5.0 ml/kg/h respectively (p less than 0.05). At flow rates between 2.5 and 5.0 ml/kg/h, spontaneous contractions produced an increase in pelvic pressure in all rats, while electrical stimulation produced an increase in pelvic pressure in 63%. At flow rates above 5 ml/kg/h, abdominal compression produced sharp elevations in pelvic pressure in 75%. At the same flow rate, electrical stimulation produced a slow increase in 75% and spontaneous contraction produced a slow increase in 86%. These results suggest that the exposure of the upper urinary tract to vesical pressures occurring during active and passive contractions is facilitated by flow.

Animals↗