Biomedical subjects

M A Bazeed

Publications and source records attributed to M A Bazeed.

28 records · Page 2Linked to original sources

PubMed1983

Chronic stimulation of the sacral roots in dogs.

To investigate the feasibility of chronic stimulation of the sacral nerves for control of sphincter and bladder function, we implanted bipolar electrodes in 10 dogs. These electrodes, of conventional cuff (4 dogs), as well as innovative spiral designs (6 dogs) were placed around the S2 roots of the 10 dogs and in 3 of them around the S1 root additionally. The electrodes were connected to subcutaneous radiofrequency receivers for external activation. Microsurgical techniques were employed to perform dorsal rhizotomy and ganglionectomy. 5 dogs, 3 kept as long as 8 months, were chronically stimulated to a cumulated time of 100-150 h each. Functional and histological results reveal that sacral root nerves can be stimulated safely on a chronic basis for effective control of the lower urinary tract.

Animals↗

PubMed1982

Partial flap ureteroneocystostomy for bilharzial strictures of lower ureter.

Partial flap ureteroneocystostomy was applied for the management of bilharzial strictures of the lower ureter for 30 ureters (24 patients). Follow-up excretory urography (IVP) showed improvement or stabilization in 83.3 per cent of renoureteral units. Creatinine clearance improved or remained stable in 79 per cent of cases. Postoperative reflux occurred in 30 per cent of renoureteral units. We recommend partial flap ureteroneocystostomy for the management of bilharzial strictures if submucosal tunnel ureteroneocystostomy is not applicable.

Adult↗

PubMed1982

Histochemical study of urethral striated musculature in the dog.

The striated musculature of the dog urethra was studied histochemically. Two main groups of muscle fibers could be identified: 1 with slow twitch oxidative fibers, which are fatigue resistant (type 1), and 1 with fast twitch fibers (type 2). The fast twitch fibers were subdivided into glycolytic (fatiguable) and oxidative glycolytic (fatigue resistant) fibers: the latter constitute 20 per cent of all fast twitch fibers. Type 1 constitutes of 35 per cent of the whole musculature and its proportion tends to decrease toward the distal end of the external urethral sphincter. From these observations we infer that type 1 fibers are likely responsible for continence at rest and that type 2 fibers are recruited in stress conditions, for example, during coughing or sneezing. Additional studies are needed to confirm this conjecture. The clinical implications of these studies for the control of incontinence, urinary retention and dyssynergic urethral sphincter are presented.

Adenosine Triphosphatases↗

PubMed1982

Effect of chronic electrostimulation of the sacral roots on the striated urethral sphincter.

Chronic electrostimulation of the sacral roots induces an increase in urethral resistance due to activation of muscles of the striated urethral sphincter. Histochemical study of the urethral striated musculature (nonstimulated) revealed 3 main varieties of fibers: 1) Slow twitch fibers (35 per cent of the whole muscle); 2) Fast twitch fatiguable fibers (52 per cent); and 3) An intermediate type, fast twitch fatigue resistant (13 per cent). Ten dogs with chronically implanted electrodes at the 2nd sacral root were subjected to a program of prolonged stimulation under anesthesia. After prolonged electrostimulation, we detected hypertrophy of the striated muscle fibers of the urethra, anal sphincter and stimulated side of the tail. The stimulated muscle fibers showed a higher overall oxidative activity than the controls. This occurred both in intact and spinalized animals. We thus expect the urethral striated musculature to be more resistant to fatigue because of the increased oxidative activity. Stimulated fibers also had increased glycolytic activity as shown by the enhanced intermyofibrillar deposition, especially in the fast twitch fibers. The increased glycolytic activity may also increase fatigue resistance by producing energy during periods of low oxygen supply at the peak of muscular contraction. As a consequence of increase in oxidative and glycolytic capacities and muscular hypertrophy, we expect that the striated musculature of the urethra will be not only more resistant to fatigue but also capable of generating higher tension. Both are important in achieving continence via electrostimulation of sacral nerve roots. Approximately 3 months after conclusion of the stimulation program these changes had gradually reverted to the normal prestimulation level.

Animals↗

PubMed1982

Functional pattern of sacral root stimulation in dogs. I. Micturition.

Prior to this study, electrostimulation of the ventral sacral roots had only limited success in evacuation of the bladder because dyssynergic sphincter contraction simultaneously increased urethral resistance. Thus, pudendal nerve blockade, pudendal neurotomy, selective peripheral neurotomy, or external sphincterotomy for reduction of sphincteric resistance seemed inevitable. To avoid those procedures we used electrical sphincter fatigue to induce effective micturition with stimulation of the ventral sacral roots. Stimuli of 200 Hz frequency rapidly fatigue the dyssynergic sphincteric response but not the desired detrusor contraction, eliminating the need of interference with the sphincteric activity.

Animals↗

PubMed1982

Functional pattern of sacral root stimulation in dogs. II. Urethral closure.

Ten dogs were used for electrostimulation of the sacral roots to improve urethral sphincter closure. To induce and maintain urethral closure in longstanding stimulation, a variety of stimulation patterns was investigated systematically. With continuous stimulation, the induced sphincteric response faded corresponding with the increase in frequency of stimulation applied, but in phasic stimulation with a stimulation/rest ratio of 1:2, strong sphincteric contractions were reproducible after each rest interval. If the stimulation bursts were shortened to 30-60 msec., interrupted by an off-time of again twice the duration of the stimulation, unfused sphincteric tetani were induced, resulting in a sinusoidal oscillating closure pressure that did not drop in the prestimulus baseline during the off-time. A sufficient sphincteric closure pressure could thus be sustained over 1 hour of uninterrupted stimulation.

Animals↗

PubMed1982

Mechanisms of urinary continence: an animal model to study urethral responses to stress conditions.

Under conditions of stress, the urethral sphincteric mechanism has to compensate a passive bladder pressure rise induced by increase in intraabdominal pressure. To evaluate the various closure mechanisms contributing to urethral response to stress, we subjected a female dog model to the physiologic stress condition triggered by sneezing. Vesical, rectal and 4 urethral pressures during sneezing were recorded simultaneously under various experimental situations: in the intact animal, after transection of the bladder and urethra, and with the abdomen open. The effects of the Credé maneuver and of manual squeezing of the surgically exposed bladder were also recorded. The data obtained support the existence of a 2-component urethral closure mechanism under stress: the proximal closure mechanism of the smooth muscular, intrapelvic urethra is from passive transmission of abdominal pressure. It is apt to balance a passive increase in bladder pressure and thus maintain proximal closure pressure during stress. The distal closure pressure mechanism reflects active reflex contraction of the intrinsic external sphincter and pelvic floor muscles, which is capable of exceeding passive increase in bladder pressure and thus augments closure pressure during stress.

Abdomen↗

PubMed1982

Management of bilharzial strictures of the lower ureter.

Ureteral strictures are serious and frequent complications of chronic bilharziasis of the urinary tract are seen. To determine which corrective surgical procedures are most successful, we compared the results of those most commonly done. We retrospectively analyzed our experience with mucosa to mucosa ureterovesical anastomosis (68 ureters), transvesical ureteral meatotomy (30 ureters) are submucosal tunnel ureteroneocystostomy, (UNC; 10 ureters). Complete follow-up data are available for 102 patients (108 ureters); half of these cases were followed for 4 years or even more. It is to be noted that, in our series, only 10 ureters were suitable for submucosal tunnel anastomosis: bilharzial ureters are usually fibrotic, noncompressible, and the vesical mucosa is adherent to the muscular layer - which renders creation of a tunnel difficult or impossible. However, this procedure produced the best results. The conclusion was reached that, whenever possible, antireflux procedures suitable for the bilharzial bladder and ureter should be attempted. Based on this analysis, a prospective clinical trial was carried out, which compared Boari flap UNC (30 ureters), triangular flap ureterovesicoplasty of Girgis et al. (30 ureters), and ileal loop replacement of the pathologic segment (30 ureters). The average period of follow-up was 20 months. Triangular flap and Boari flap were found to be superior to ileal replacement. Ileal replacement is consistently followed by vesicoileal reflux and commonly by persistent urinary tract infection. In consequence, the latter operation must be reserved for cases with extensive ureteral loss or destruction. Antireflux procedures still remain the most desirable methods whenever technically possible.

Adult↗

PubMed1982

Regional topography of spinal cord neurons innervating pelvic floor muscles and bladder neck in the dog: a study by combined horseradish peroxidase histochemistry and autoradiography.

To identify the spinal origin of the innervation of the bladder neck and pelvic floor muscles retrograde axonal transport of horseradish peroxidase and tritiated horseradish peroxidase was used in a technique combining histochemistry and autoradiography. This technique proved to be suitable for differential labeling of spinal cord neurons innervating two different targets, thus extension as well as overlap of different nuclei could be judged. The parasympathetic outflow was concentrated in the intermediolateral and intermediomedial gray matter of S2, the somatic innervation was derived mostly from Onuf's motor nucleus in S1 and S2. Onuf's nucleus proved to be the main somatic motonucleus for pelvic floor muscles; there was no evidence of an autonomic share. The innervation of the striated urethral sphincter also originated in this nucleus; there was no basic difference when it was compared to the innervation of other pelvic floor muscles.

Animals↗

PubMed1981

Acquired urethral diverticula in the male.

Male urethral diverticula are rare. In our review of the literature between 1928 and 1980 we found only about 250 cases. Acquired diverticula are only slightly more frequent than congenital ones. The 13 cases we present (1965-1980) are all acquired. In 50% of these cases periurethral suppuration was the promoting etiology. Urinary tract infection complicated 12 cases. Retrograde urethrography was diagnostic in all instances. We recommend urethral diverticulectomy as the treatment of choice whenever possible. We stress prophylaxis via gentle manipulation of the urethra and proper drainage of periurethral suppuration.

Abscess↗