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Biomedical subjects

A Shafik

Publications and source records attributed to A Shafik.

At least 109 records · Page 6Linked to original sources
PubMed1998

Electrocholecystogram: a study of the electromechanical activity of the gall bladder in a canine model.

To characterize an 'electrocholecystogram' (EChG) for the normal gall bladder (GB) that might act as a standard for the evaluation of pathological electrocholecystograms of the diseased GB, ten mongrel dogs (14.4+/-3.2 kg) were studied. Under anaesthesia, the abdomen was opened and three silver-silver chloride electrodes were sutured to the GB serosa. The GB pressure was measured by a perfused catheter introduced through the fundus. The response of the myoelectrical activity of the GB to balloon distension was tested and the direction of electrical waves was defined by GB myotomies. Pacesetter potentials (PPs) were recorded exhibiting the same frequency, amplitude and velocity of conduction from the three electrodes of each dog on all test days. Action potentials (APs) followed the PPs randomly and were associated with a rise of the GB pressure. Balloon distension of the GB caused increased PP and AP frequency. The electrical waves showed proximally but not distally to GB myotomy, indicating that they propagate proximo-distally towards the cystic duct. To conclude, the GB possesses electrical waves which are probably initiated from a 'pacemaker' at the GB fundus. A normal EChG could be characterized in the canine model. It is suggested that this EChG might show changes in gall bladder diseases and might thus act as an investigative tool, provided it can be developed to be performed percutaneously.

Animals↗
PubMed1998

Effect of magnetic stimulation on the contractile activity of the rectum in the dog.

PURPOSE: Magnetic stimulation (MS) produces its effect, according to Faraday's law, by creating an electric field which can stimulate the neuromuscular tissues. The current study investigates, to our knowledge for the first time, the effect of MS on rectal pressure and evacuation with a view on its possible application in emptying the inertic or neuropathic rectum. METHODS: The rectal, rectal neck and vesical pressures as well as the EMG activity of the two rectus abdominis muscles were recorded during sacral MS with a magnetic coil while the rectum was empty and while filled. Stimulation parameters were set at 70% intensity, 20 Hz frequency and 1- to 5-second burst length. RESULTS: Sacral MS of both the filled and empty rectum effected a significant increase in rectal (p<0.01) and vesical (p<0.01) pressures and a decrease in rectal neck pressure (p<0.01). Rectal evacuation of the filled rectum using intermittent stimulation was achieved in all animals. CONCLUSION: Sacral MS resulted in a rectal evacuation. It is a simple, easy and noninvasive method that might prove applicable in the treatment of inertic constipation and neuropathic rectum.

Animals↗
PubMed1998

Electro-oophorogram: A preliminary study of the electric activity of the ovary.

The electric activity of the ovary was studied in 13 female mongrel dogs aiming at characterizing a normal electro-oophorogram (EOOG). Two monopolar silver-silver chloride electrodes were sutured under anesthesia to the ovary of the bitches which were in the anestrus phase of the estrous cycle. A daily recording session of 60 min was performed for 10 days. Furthermore, the effect of ovarian vessels' clamping, of oophorectomy and of ovarian insult by irradiation on the electric activity, was studied. Electric waves were recorded from the two electrodes. Each wave consisted of a negative followed by a positive deflection with a mean amplitude of 52.6 +/- 10.7 microV and frequency of 9.2 +/- 1.6 cycles per second. The waves showed the same amplitude and frequency from the two electrodes and were reproducible when the test was repeated in the same animal. Fast activity spikes were not encountered. Temporary clamping of the ovarian vessels caused diminution of the normal ovarian electric activity which returned to the preclamping state after clamp release. A 'silent' EOOG was obtained after oophorectomy. Two EOOG patterns were recorded from the irradiated ovary: silent and dysrhythmic. To conclude, an EOOG could be characterized for the bitches in the anestrus phase which is a quiescent phase of the estrous cycle. Further studies are required to record the EOOG in the other phases of the estrous cycle and in the various pathologic conditions of the ovary.

Anestrus↗
PubMed1998

Role of the calices in urine flow with characterization of a caliceopelvic sphincter and reflex.

AIM: To study the role of the caliceal system in urine flow. METHODS: Eight patients (6 men, 2 women; mean age 42.6 +/- 7.6 years) with an upper polar renal mass (6 renal cysts; 2 hypernephromas) which did not encroach on the pelvicaliceal system were studied. After mass removal, a manometric catheter was introduced into one of the intact calices. Another catheter was introduced through the same calix, and the calix was filled with saline in increments of 0.1 ml, and the caliceal, caliceopelvic junction (CPJ), and renal pelvis pressures were recorded. The catheter was moved to the renal pelvis, and the pressure response of the aforementioned sites to renal pelvic filling with saline in increments of 1 ml was registered. The effect of filling of the locally anesthetized calix on the pelvicaliceal pressure was also determined. RESULTS: Caliceal filling resulted in a rise of the caliceal (p < 0.01) and a drop of the CPJ (p < 0.01) pressures with no pressure response in the renal pelvis. Renal pelvic filling produced a rise of renal pelvic (p < 0.01) and CPJ (p < 0.05) pressures; the caliceal pressure showed no change (p > 0.05). Filling of the anesthetized calix or renal pelvis produced no significant pressure changes in calix, CPJ, or renal pelvis (p > 0. 05). CONCLUSIONS: The CPJ dilatation upon caliceal contraction suggests a reflex relationship which we named 'caliceopelvic inhibitory reflex'. The reflex is suggested to effect caliceal evacuation. On the other hand, CPJ closure upon renal pelvic contraction postulates another reflex relationship which we designated 'pelvicaliceal excitatory reflex'. This reflex seems to prevent pelvicaliceal reflux. It is suggested that a 'functional' sphincter exists at the CPJ.

Adult↗
PubMed1998

Botulin toxin in the treatment of nonrelaxing puborectalis syndrome.

PURPOSE: To evaluate the results of botulin toxin injection in the external anal sphincter for the treatment of nonrelaxing puborectalis syndrome. METHOD: 15 patients (13 women, 2 men; aged 36-48 years) were treated with botulinum A toxin injection, using a dose of 25 IU diluted in 1 ml normal saline injected into the top loop of the external anal sphincter at the 3 and 9 o'clock positions. The mean follow-up period was 14.6 +/- 3.3 (SD) months. RESULTS: Two patients did not respond to the treatment while improvement occurred in 13. Straining at defecation disappeared and stool frequency was normalized. Improvement was maintained for a mean of 4. 8 +/- 1.4 SD months, after which time reinjection needed to be done. No adverse side effects were encountered. CONCLUSIONS: Botulin toxin injection is a simple, easy and safe method for the treatment of nonrelaxing puborectalis syndrome. It is to be considered after biofeedback has failed.

Adult↗
PubMed1997

Deflation reflex: description and clinical significance.

BACKGROUND: During our study of the defecation mechanism, we found that the external anal sphincter contracted not only upon rectal inflation but also upon deflation. As this reflex relationship was reproducible, it was studied to elucidate its clinical significance in the light of its function. METHODS: A catheter with a condom at its end was introduced into the rectum of 16 healthy volunteers (mean age 45.2 years). The EMG response of the external anal sphincter to rapid rectal inflation and deflation was studied by means of a concentric needle electrode inserted into the muscle. The procedure was repeated in eight subjects after sphincter infiltration with xylocaine or saline. RESULTS: The external sphincter contracted twice on rectal distension: once on inflation and another time on deflation. The amplitude increased and latency decreased with increasing rectal inflation, while neither was affected on deflation. The anesthetized sphincter did not respond, while the saline-infiltrated sphincter responded to rectal distension. CONCLUSIONS: The deflation reflex functions to interrupt or terminate the act of defecation. It may prove of diagnostic significance in defecation disorders.

Action Potentials↗
PubMed1997

Pelviureteral inhibitory reflex and ureteropelvic excitatory reflex: role of the two reflexes in regulation of urine flow from the renal pelvis to the ureter.

The mechanism by which the ureteropelvic junction (UPJ) regulates the passage of urine from the renal pelvis to the ureter, and prevents urinary backflow from the the ureter to the renal pelvis, is not completely understood. The current communication studies this mechanism in 18 dogs. With the dogs under anesthesia, nephrostomy was done through which two catheters (one pressure and one balloon-tipped) were introduced into the UPJ and the renal pelvis, respectively. Renal pelvis distension with a balloon filled with 1 ml of saline effected a rise of renal pelvic pressure from a mean basal pressure of 4.8 +/- 1.2 cm H2O to 6.9 +/- 2.3 cm H2O (P < 0.05). The basal UPJ pressure of 12.6 +/- 2.7 cm H2O showed no significant change with 1 ml distention of the renal pelvic balloon (P > 0.05). Renal pelvic distension with 2, 3, and 4 ml caused a significant rise of renal pelvic pressure to 8.4 +/- 2.7 (P < 0.05), 10.6 +/- 2.2 (P < 0.01), and 11.8 +/- 1.9 (P < 0.01) cm H2O, respectively, and a significant drop of UPJ pressure to 4.8 +/- 1.2, 4.7 +/- 1.1, and 4.6 +/- 1.2 cm H2O (P < 0.01), respectively. Ureteric distension with a balloon filled with 0.5 ml of saline significantly raised the ureteric pressure from a mean basal value of 4.3 +/- 1.4 cm H2O to 14.7 +/- 3.3 cm H2O (P < 0.01) and the UPJ pressure to a mean of 20.8 +/- 3.8 (P < 0.05). Ureteric distension with 1 and 1.5 ml of saline led to an elevation of ureteric and UPJ pressure which was not significantly different from that observed with distension with 0.5 ml (P > 0.05). In contrast, the UPJ showed no significant pressure change upon distension of the locally anesthetized renal pelvis or ureter, respectively. Likewise, the locally anesthetized UPJ exhibited no significant pressure response to renal pelvic or ureteric distension. The study demonstrates that urine might have to accumulate in the renal pelvis up to a certain volume and pressure so as to effect UPJ opening, which occurs at its maximum irrespective of the distending volume. UPJ opening upon renal pelvic distension postulates a reflex relationship which we call "pelviureteral inhibitory reflex." This reflex is believed to regulate the passage of urine from the renal pelvis to the ureter. Ureteric distension closes the UPJ; we call this reflex action the "ureteropelvic excitatory reflex" as it seems to prevent reflux of urine through the UPJ and thus protects the kidney. The concept that the UPJ acts as a physiologic sphincter is put forward.

Anesthesia↗
PubMed1997

Mucosal plication in the treatment of partial rectal prolapse.

A technique used for the treatment of 34 patients with partial rectal prolapse [20 children (mean age 4.2 +/- 1.4 years), 10 women, and 4 men (mean age 44.6 years)] is presented. The prolapsed mucosa protruded outside the anus in 26 patients and was inside the rectal neck in 8. Mucosal plication was performed; the prolapsed mucosa was reefed by multiple vertical pursestring sutures. Associated hemorrhoids and anal fissures were also corrected. The patients were followed up for a mean of 31.6 months. No straining at stool or recurrence of the mucosal prolapse occurred. The technique is simple, cost-effective, had no complications, and was performed on an outpatient basis.

Adult↗
PubMed1997

Study on the origin of the external anal, urethral, vaginal and prostatic sphincters.

The response of the external anal, urethral, prostatic and vaginal sphincters to stimulation of the puborectalis muscle was studied aiming at the physiological validation of their origin from the PRM. Twenty-eight healthy volunteers were examined (16 men, 12 women: mean age 40.6 +/- 8.3 SD years). The PRM was stimulated by a needle electrode and the response of the EAS and EUS recorded. The PS and VS were monitored by manometric measuring of the urethral and vaginal pressures. Upon stimulation, the EMG activity of the EAS (P < 0.001) and EUS (P < 0.001), as well as of the prostatic urethral (P < 0.05) and vaginal (P < 0.0001) pressures, increased. There was no response to stimulation of the anesthetized PRM; this might indicate that the sphincters contract in response to PRM stimulation. The EMG recorded no latency, suggesting that the motor units of the EAS and EUS were simultaneously activated with those of the PRM, and also that their muscle fibers seem to be directly derived from the PRM. However, proof of PS and VS continuity with PRM could not be supplied by the study.

Adult↗
PubMed1997

Effect of esophageal distention on pressure and electromyographic activity of the pharyngoesophageal sphincter, with identification of the esophagopharyngeal reflex.

PURPOSE: My purpose was to study the effect of balloon-produced esophageal distention on the pharyngoesophageal sphincter to shed light on the mechanism by which esophagopharyngeal reflux is prevented. METHOD: Nine dogs (mean weight 15.7 +/- 4.3 kg) were used for the study. A balloon-tipped catheter was introduced into the esophagus and a manometric catheter into the pharyngoesophageal sphincter. The pressure response of the pharyngoesophageal sphincter to esophageal distention was recorded. The response was also tested while the esophagus and the pharyngoesophageal sphincter were anesthetized, each separately. In six of nine dogs the electromyographic response of the pharyngoesophageal sphincter to esophageal distention was studied before and after the esophagus was anesthetized. RESULTS: Lower and midesophageal distention produced no pressure changes in the pharyngoesophageal sphincter (p = 0.082). Upper esophageal distention effected an elevation in pharyngoesophageal sphincter pressure (p = 0.024), which showed no further rise when the distending volume was increased. The anesthetized pharyngoesophageal sphincter did not respond to esophageal distention. Likewise, the pharyngoesophageal sphincter did not respond to distention of the anesthetized upper esophagus. Esophageal distention produced increased electromyographic activity of the pharyngoesophageal sphincter, but no activity was recorded in response to distention of the anesthetized esophagus. CONCLUSION: This study has demonstrated contraction of the pharyngoesophageal sphincter on distention of the upper esophagus. This response seems to prevent esophagopharyngeal reflux and choking and is postulated to be evoked by means of an "esophagopharyngeal reflex."

Animals↗
PubMed1997

Study of the effect of external urethral sphincter contraction on the mechanical activity of the ureterovesical junction and urinary bladder: recognition of the sphinctero-ureterovesical reflex.

OBJECTIVES: To study the effect of external urethral sphincter (EUS) contraction on the urinary bladder and ureterovesical junction (UVJ). METHODS: The study was comprised of 9 healthy volunteers (7 men, 2 women; mean age 40.8 +/- 6.6 years). A manometric catheter was introduced into each of the two UVJs and urinary bladder. The EUS was made to contract by voluntary squeezing and by electromyographic stimulation with a needle electrode inserted into the sphincter. The response of the bladder and the UVJs to EUS contraction was determined before and after anesthetization of the EUS, bladder, and the two UVJs, each at a different time. RESULTS: On voluntary squeezing or electromyographic needle stimulation of the EUS, the pressure in both the UVJs and the urinary bladder showed a significant drop (P < 0.05 in both instances). There was no pressure response in the UVJs or in the urinary bladder 10 minutes after separate anesthetization of either the EUS or the UVJs and the bladder; however, 2 hours later, the pressure response was similar to that before anesthesia (P > 0.05). CONCLUSIONS: Bladder and UVJ relaxation on EUS contraction postulate a reflex relationship that was reproducible and absent on anesthetization of either of the suggested two arms of the reflex: the EUS on one end and the bladder and UVJs on the other end. We call this reflex the "sphinctero-ureterovesical reflex." Further studies are needed to evaluate the possible role of this reflex in the micturition mechanism and disorders.

Adult↗
PubMed1997

Electrohysterogram: study of the electromechanical activity of the uterus in humans.

The electromechanical activity of the uterus was studied in 18 healthy women (mean age 38.3+/-14.2 SD years; 8 were nulliparous, 10 multiparous) aiming at characterizing a normal electrohysterogram. Two monopolar silver-silver chloride electrodes were applied to the uterine and one to the cervical mucosa. The uterine pressure was measured by a water-perfused tube connected to a pressure transducer. Monophasic, negatively deflected slow waves or pacesetter potentials (PPs) were recorded from the 2 uterine electrodes. They had regular rhythm and exhibited the same frequency, amplitude and velocity of conduction by the 2 electrodes. The PPs were followed randomly by bursts of action potentials (APs). The APs and not the PPs were associated with uterine pressure rise. PPs from the cervix were registered only occasionally. The occurrence of the electric activity is believed to depend on the smooth muscle fibers content which is high in the uterine body and meagre in the cervix. The APs seem to have contractile activity which might act to sweep away the uterine secretions. According to the uterocervical reflex, the cervix dilates upon uterine contractions. A normal electrohysterogram could be characterized. It might show a different pattern in the various uterine pathologic conditions and may thus represent an investigative tool in the diagnosis of such disorders.

Action Potentials↗
PubMed1997

Perineal nerve stimulation: role in penile erection.

The effect of perineal nerve stimulation on penile erection was studied in ten dogs. Through a paraanal incision, the nerve was exposed in the ischiorectal fossa and a bipolar electrode was applied to it. A radiofrequency receiver was implanted subcutaneously in the abdomen. Upon perineal nerve stimulation, the corporeal pressure and EMG activity of the bulbo- and ischiocavernosus muscles increased; penile erection occurred. With increased stimulus frequency up to 80 Hz, the pressure and muscles' response augmented while the latency and duration of response diminished. No further changes occurred above a frequency of 80 Hz (P > 0.05). Response was reproducible indefinitely after an off-time of double the time of the stimulation phase. Penile erection upon perineal nerve stimulation is suggested to be an effect of corporeal pressure elevation resulting from cavernosus muscles' contraction. In terms of force and speed of contraction, a stimulus frequency of 80 Hz evokes the most adequate cavernosus muscles' contraction.

Action Potentials↗
PubMed1997

Reinnervation of the rectum with a somatic nerve: a canine study.

The purpose of this communication was to evaluate the possibility of rectal stimulation through nerve autografting. Eleven mongrel dogs were studied. The abdomen was opened under anesthesia. The obturator nerve was cut at its entrance into the obturator foramen and was embedded in a tunnel within the musculature of the rectal wall. Six months later, the abdomen was re-opened and bilateral pelvic ganglionectomy was done to denervate the rectum. As the urinary bladder was also denervated subsequent to the pelvic ganglionectomy, cystostomy was performed. Two bipolar electrodes were applied to the obturator nerve. The effects of electrostimulation were evaluated under basic conditions after urecholine and atropine administration and after xylocaine topical application to the obturator nerve. After bilateral pelvic neurectomy, the basic rectal pressure dropped (P < 0.05) and there was no response to urecholine or to atropine injection. Obturator nerve electrostimulation induced evoked potentials within the nerve as well as rectal pressure rise (P < 0.001); the former was abolished with xylocaine topical application to the nerve and the latter with atropine administration. Microscopic examination revealed that the Schwann cells and axons grew in the connective tissue between the rectal muscle bundles. In conclusion, reinnervation of the denervated rectum using a somatic nerve implant is possible. To our knowledge this study is the first to show "smooth' muscle excitability by stimulation of a somatic nerve implant.

Anesthetics, Intravenous↗