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Biomedical subjects

A Melman

Publications and source records attributed to A Melman.

At least 73 records · Page 4Linked to original sources
PubMed1995

A nonimaging scintillation probe to measure penile hemodynamics.

UNLABELLED: We have developed a penile nonimaging scintillation (PNIS) probe consisting of a plastic well-type scintillation crystal interfaced to a portable computer and acquisition board. This report describes the design of the PNIS probe, performance characteristics, mode of usage and illustrative results which demonstrate its capabilities. METHODS: With the PNIS probe, penile blood-pool studies were performed in nine patients utilizing 3.7 MBq (100 microCi) autologous 99mTc-labeled red blood cells (RBCs). Venous blood standards were assayed to enable conversion of the count rate to volummetric measurements. Washin of peripherally administered 99mTc-RBCs was mathematically analyzed to estimate penile blood volume and cavernosal flow rate in the flaccid state. The rate of change of penile blood volume after intracavernosal vasodilators was used to generate measures of stimulated flow. RESULTS: A major advantage of this device over the gamma-camera is a 3300-fold increase in count rate sensitivity, which allows for markedly improved temporal resolution while significantly reducing the radiopharmaceutical dosage. Additionally, the PNIS probe is portable, economical and is not dependent on operator-defined regions of interest. Count rate sensitivity is relatively constant within the bore, with the exception of the proximal region adjacent to the opening, where geometric efficiency is reduced. CONCLUSION: The PNIS probe is an effective device for measuring penile activity in radionuclide studies, allowing for acquisition of time-activity curves of the penis during flaccid washin of peripherally labeled red blood cells and after pharmacologic stimulation to induce erection.

Adult↗
PubMed1994

Combined laparoscopic pelvic lymph node dissection and modified belt radical perineal prostatectomy for localized prostatic adenocarcinoma.

OBJECTIVE: Despite many known advantages, the radical perineal prostatectomy (RPP) had fallen out of favor because of the need for a second incision for the regional lymph node dissection. Laparoscopic lymphadenectomy, however, provides an accurate and minimally invasive alternative to open lymph node dissection. Herein are reported the practical advantages of combining laparoscopic lymph node dissection (LPLND) with RPP. METHODS: Forty-nine patients with clinically localized carcinoma of the prostate were considered candidates for RPP using a modified Belt technique. Thirty-five patients underwent attempted LPLND and 31 of these patients subsequently underwent RPP; 14 patients underwent RPP alone. Variables examined included total operative time, transfusion requirement, length of hospital stay, continence, and potency. RESULTS: The mean operative time for LPLND combined with RPP in 31 patients, including time for repositioning, was 4.5 hours (range 3.0 to 7.0 hours). Only 26 percent of the patients who underwent the combined approach required blood transfusions of which 75 percent received autologous units. Mean length of stay was six days, and laparoscopy did not contribute significantly to postoperative morbidity. Eighty-four percent of the patients are completely continent. Of 27 potent patients who underwent nerve-sparing surgery, 22 percent are potent and an additional 30 percent are sexually active with intracavernous pharmacotherapy. There were no perioperative deaths, 2 major complications, and 5 minor complications. CONCLUSIONS: Laparoscopic techniques now permit the urologist to utilize the perineal approach, and its many advantages, to radical prostatic extirpation without the need for a formal abdominal incision. The minimal blood loss and low morbidity associated with laparoscopic pelvic lymphadenectomy combined with the radical perineal prostatectomy make this procedure an attractive alternative to the open retropubic approach for clinically localized prostatic adenocarcinoma.

Adenocarcinoma↗
PubMed1994

Characterization of cyclic AMP accumulation in cultured human corpus cavernosum smooth muscle cells.

Intracavernous pharmacotherapy relies heavily on the use of vasoactive agents which act by increasing intracellular cAMP levels in human corpus cavernosum smooth muscle. Yet little is known about the cAMP generating system in this tissue, and how it may affect observed patient variability. Thus, the goal of these studies was to better characterize the biochemistry of cAMP formation in human corpus cavernosum smooth muscle, and thus provide more insight into the mechanisms of corporal smooth muscle relaxation in vivo. We studied both receptor and nonreceptor mediated increases in cAMP formation in short-term cultures of human corpus cavernosum smooth muscle cells. Both isoproterenol (ISO) and prostaglandin E1 (PGE1) produced concentration-dependent increases in cAMP, but histamine, serotonin and vasoactive intestinal polypeptide did not. Forskolin, a relatively specific activator of adenylate cyclase, was also a potent stimulant of cAMP formation in these cells. Moreover, there was a direct correlation between the degree of forskolin-induced cAMP accumulation in cultured corporal smooth muscle cells and the magnitude of the forskolin-induced relaxation response of precontracted isolated corporal smooth muscle strips. Prostaglandin E1 and ISO concentration response curves (CRCs) were then assayed in the absence and presence of subthreshold forskolin (0.1 microM.). In the presence of forskolin, the calculated maximal PGE1-induced cAMP accumulation (Emax) was significantly greater than that elicited by PGE1 alone, ISO alone, or ISO + forskolin (p < or = 0.02). In addition, a fixed molar ratio (FMR) (PGE1:ISO) protocol was used to demonstrate that both 80:20 and 70:30 FMRs (but not 95:5 or 90:10), were associated with significantly greater cAMP Emax values than that observed for PGE1 alone (p < or = 0.01). These data provide direct evidence that the degree of cAMP formation in cultured corporal smooth muscle cells is strongly correlated with the magnitude of relaxation of isolated corporal smooth muscle strips. In addition, since simultaneous activation of distinct components of the cAMP generating system produces significant increases in maximal intracellular cAMP accumulation, this suggests that such drug combinations may also augment corporal smooth muscle relaxation in vitro and in vivo.

Alprostadil↗
PubMed1994

Laparoscopic treatment of small-bowel obstruction following laparoscopic lymphadenectomy.

Laparoscopic pelvic lymph node dissection followed by radical perineal prostatectomy has become the treatment of choice for selected patients at our institution with clinically localized adenocarcinoma of the prostate. We describe 2 cases in which bowel obstruction caused by incarceration of a loop of small bowel into a trocar site was managed with laparoscopic techniques.

Adenocarcinoma↗
PubMed1994

Male erectile dysfunction assessment and treatment options.

Until the early 1970s impotence was believed to be primarily a psychological disorder. The treatment usually consisted of empiric testosterone administration and psychotherapy, that were often ineffective. The introduction in the early 1970s of penile implants changed the treatment options and at the same time ushered in the modern era of male sexual medicine. Clinical as well as laboratory research improved significantly the diagnosis and treatment options of the impotent man. Today the man with a sexual problem has a much better chance of proper diagnosis and effective treatment.

Adult↗
PubMed1993

Relationship between contraction and relaxation in human and rabbit corpus cavernosum.

Although alterations in corporeal smooth muscle tone undoubtedly play an important role in the etiology of erectile dysfunction, the relationship between the degree of corporeal smooth muscle contraction and the magnitude of the observed relaxation response has never been quantitated. Thus, in vitro studies were conducted to examine the relationship between alpha 1-adrenergic contractility, and relaxations elicited by the clinically and physiologically relevant vasorelaxants, nitroglycerin, nitroprusside, and prostaglandin E1. Corporeal tissues strips were isolated from impotent and potent men, as well as sexually mature rabbits, and precontracted over a wide range of phenylephrine doses, prior to exposure of each tissue to the same dose of vasorelaxant. Plots of percent contraction versus percent relaxation revealed that the relationship between contraction and relaxation was accurately described by a first order linear equation, and characterized by an inverse relationship in all tissues studied, for all vasorelaxants examined. Statistical analysis indicated that the slope of the regression line was significantly greater than unity in all corporeal tissues obtained from patients with organic impotence; however, corporeal tissues obtained from patients with documented erections and from sexually mature rabbits had significantly lower slopes that were indistinguishable from unity. The existence of an inverse relationship between contraction and relaxation, even in the absence of organic disease, emphasizes the importance of the level of basal corporeal smooth muscle tone per se. These studies provide further evidence implicating heightened adrenergic tone as a significant etiologic factor in erectile dysfunction.

Alprostadil↗
PubMed1993

Dorsal vein sclerosis as a predictor of outcome in penile venous ligation surgery.

We studied the pathological specimens obtained from 24 impotent men who underwent proximal penile vein ligation and 6 potent men who underwent total penectomy as part of male-to-female transsexual surgery to determine if a correlation exists between venous pathology and surgical outcome. Pathology specimens, consisting of cavernosal tissue and penile veins, were independently reviewed by a single uropathologist (V. A.). The degree of vein wall thickness was carefully quantified for each patient. Venous leakage was documented by cavernosometry and cavernosography. Followup ranged from 7 to 19 months (mean 11 months). Within 6 months of the procedure 10 patients (41%) achieved rigid erections while 14 (59%) did not. Although no preoperative index could predict operative success, in the 10 patients with successful outcome histological examination of the excised vein segments revealed normal venous architecture with minimal vein wall thickness (calculated mean per cent vein wall thickness 39.4, range 17.5 to 51.7). In contrast, in the 14 patients in whom ligation failed there was marked vein wall thickness and sclerosis (calculated mean per cent vein wall thickness 68.0, range 55.3 to 85.6). In comparison, the vein segments obtained from the 6 potent patients had a wall thickness of 32.8% (range 8 to 39), which was equivalent to the 10 patients with postoperative erections. These findings suggest that there may be a correlation between vein wall thickness and the prognosis of patients who undergo venous ligation surgery for erectile dysfunction secondary to presumed corporeal venous incompetence.

Erectile Dysfunction↗
PubMed1993

Delayed high flow priapism: pathophysiology and management.

Two cases of the management and pathophysiology of high flow arterial priapism are presented. Both cases were post-traumatic with delayed onset of priapism and both had angiographically diagnosed arteriocorporeal fistulas. Case 1 was managed with selective cavernous artery ligation and case 2 resolved spontaneously, both with excellent return of premorbid levels of erectile function. We propose that the pathophysiological mechanism involves injury to the intracavernous artery, causing ischemic necrosis. After a delay the arterial segment blows out, leading to unregulated blood flow into the corpus cavernosum. Management with surgical ligation is highly selective and nondisruptive to unaffected vessels, offering precise control of the bleeding vessel.

Adult↗
PubMed1993

A single center experience with renal transplantation in young children.

Results of pediatric renal transplantation have been variable. We evaluated our experience with renal transplantation in children less than 5 years old to determine its safety and efficacy. Of the 428 renal transplants done at our institution from August 1983 to December 1989, 14 were performed in 13 children 13 to 50 months old (mean age 34 months). All of the patients were small for age with height standard deviation scores ranging from -1.7 to -4.5. Patient survival, allograft survival and statural growth were used as determinants of successful outcome. Followup was complete in all patients, including renal function studies and serial height measurements. Growth velocity standard deviation scores were calculated. Patient survival was 100%. Allograft survival was 100% 2 to 7.3 years after transplantation for living related donor recipients whereas 1-year graft survival was poor (40%) for cadaveric graft recipients. Of 10 patients with good graft function at 1 year 9 demonstrated improvement in the height standard deviation score. Seven of 10 patients demonstrated significant catch-up growth (growth velocity standard deviation score greater than 0, p = 0.04). Our study supports the safety and efficacy of renal transplantation in young children. Early transplantation using living-related donor organs is the optimal therapy to prevent growth retardation and allow the young child with end stage renal disease to have a normal life.

Body Height↗
PubMed1993

Gap junctions formed of connexin43 are found between smooth muscle cells of human corpus cavernosum.

Despite sparse autonomic innervation, the smooth muscle cells of the corpus cavernosum relax and contract synchronously to achieve penile erection and flaccidity. As with other smooth muscle cell types, the excitation process in the corpora is presumably propagated through gap junctions to allow the diffusion of current-carrying ions and second messenger molecules from cell to cell. Using both molecular and immunocytochemical techniques, we have identified gap junctions between human corporal smooth muscle cells in situ and in culture. Northern analyses demonstrated that corporal smooth muscle cells express the gap junction protein connexin43, but not connexin26 mRNA. Immunoblots showed the presence of connexin43 isoforms, whereas connexin32 was not detected. Immunocytochemical studies in cultured cells identified prominent connexin43 immunoreactive puncta between cells, as well as within the cytoplasm. In addition, gap junction membranes both in situ and in culture were labelled in thin section by anti-connexin43 antibodies using the immunogold technique. We conclude that the presence and distribution of gap junctions in this sparsely innervated tissue may provide an important mechanism of intercellular communication among the smooth muscle cells, and thus play a major role in coordinating tissue contraction and relaxation.

Blotting, Northern↗
PubMed1993

Sacral root stimulation for controlled micturition: prevention of detrusor-external sphincter dyssynergia by intraoperative identification and selective section of sacral nerve branches.

Electrical stimulation of the S2 nerve root can be used to produce detrusor contraction and voiding in patients with spinal cord injury, but concurrent stimulation of the external urethral sphincter causes detrusor-sphincter dyssynergia. This has been managed with a second surgical procedure, peripheral transection of the pudendal nerve. In this study, performed in dogs after spinal cord transection, laminectomy and ventral foraminotomy permitted tracing of the S2 root into the pelvis, where its branches were identified by electrical stimulation and urodynamic recording. The pudendal (somatic) branch was sectioned; the autonomic branch innervating the detrusor was preserved. Electrical stimulation of the proximal S2 root then produced detrusor contraction without contraction of the external urethral sphincter. This approach, which requires a single operation and spares pudendal nerve functions mediated by nerve roots other than S2, may enable a neurostimulator to provide effective voiding, without detrusor-external sphincter dyssynergia, in man.

Animals↗
PubMed1993

Gap junctions between human corpus cavernosum smooth muscle cells: gating properties and unitary conductance.

We previously showed that corpus cavernosum smooth muscle cells are connected via gap junctions in situ and in culture and that a major protein component of these gap junctions is connexin43. To characterize the physiological properties of the gap junctions between corpus cavernosum smooth muscle cells, we now demonstrate that the cells are dye and electrically coupled and describe some of the gating properties of these gap junctional channels at macroscopic and single-channel levels. Junctional conductance (gj) between corporal smooth muscle cells was moderately voltage sensitive; was reduced rapidly, reversibly, and completely by halothane; and was increased by treatment with a tumor-promoting phorbol ester [12-O-tetradecanoylphorbol-13-acetate (TPA)] and decreased by isoproterenol. Histograms of unitary junctional currents revealed multiple conductance peaks with events of approximately 90 pS being the most abundant. TPA and phenylephrine produced large increases in relative frequencies of the smaller events, whereas isoproterenol and 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) slightly increased the relative frequencies of the larger events. None of the tested drugs substantially affected the steady-state voltage dependence of gj. These second messenger systems also affected expression of connexin43 by corpus cavernosum smooth muscle cells, as judged by immunoblots. At 6 h of treatment, both TPA- and 8-BrcAMP-treated cultures showed markedly elevated levels of connexin43, whereas at 24 h, the level of connexin43 in TPA-treated cultures had returned to control levels. Together, these data indicate that second messenger molecules involved in penile erection produce changes in gap junction expression and function; it is plausible that these changes could be physiologically relevant in altering and propagating changes in vasomotor tone.

Cell Communication↗
PubMed1993

In pursuit of the best candidates and procedures for penile revascularization.

Coronary bypass surgery to provide better blood flow to deficient areas of the heart is commonplace; the arteries of the heart in which blockage occurs are relatively large, and rerouting of blood is readily accomplished. In the penis, the internal pudendal system that provides arterial inflow can be easily bypassed when injury to a large vessel is the cause of erectile dysfunction. In the great majority of cases of penile arterial disruption, however, large-vessel disease cannot be demonstrated; the problem of low arterial flow originates within the corpora cavernosa, in the so-called helicine arteries. These arteries are very small, and are inaccessible unless the spongy erectile tissue of the corpora cavernosa is violated. In recent years, modest success has been reported in revascularizing the smaller arteries of the penis. The expert panelists in this symposium discuss the indications for such revascularization procedures, compare their techniques, and review the success rate in their work.

Adult↗
PubMed1993

The role of gap junctions and ion channels in the modulation of electrical and chemical signals in human corpus cavernosum smooth muscle.

Intercellular communication through aqueous intercellular channels, known as gap junctions, has been postulated to provide an important mechanism for coordinating the rapid and synchronous responses of corporal smooth muscle during human penile erection and detumescence. Mathematical modeling analyses of drug diffusion were utilized to examine the potential physiological importance of the intercellular pathway to the regulation of smooth muscle tone in the human corpus cavernosum. In addition, patch clamp analyses and optical imaging studies were conducted to assess the ionic basis for cellular excitability and homeostasis in cultured corporal smooth muscle cells. In short, the computer modeling studies demonstrated that intercellular communication through gap junctions is likely to be the 'preferred' pathway for coordination of cellular activation and syncytial smooth muscle responses in this tissue. Moreover, the observed ion channel diversity reveals even further complexities to the modulation of corporal smooth muscle tone.

Calcium Channels↗
PubMed1993

The success of microsurgical penile revascularization in treating arteriogenic impotence.

The treatment of arteriogenic erectile dysfunction with revascularization techniques has been controversial both in terms of its use and the type of surgical repair. Success rates reported in the literature are based almost exclusively on patient testimonial, without the use of objective post-operative criteria. At our institution from 7/88 through 8/91, 18 patients were treated for arteriogenic impotence using microsurgical penile revascularization. The patient population ranged in age from 23 to 64 years, and each patient underwent a complete history and physical examination, serum hormone testing, psychological evaluation of patient and partner, biothesiometry, penile plethysmography, nocturnal penile tumescence/rigidity testing with a Rigiscan device, and selective pudendal arteriography. One patient was status post a pelvic fracture, 2 lacked identifiable risk factors, 2 had diabetes, 6 were heavy smokers, and 7 had hypertension. Pre-operatively each patient had a suspicious medical history, abnormal plethysmography, abnormal Rigiscan testing, and a hemodynamically significant lesion on angiography. Revascularization was done by anastomosing the inferior epigastric artery to the deep dorsal veing and dorsal artery, or the deep dorsal vein alone if both arteries were atretic. Postoperatively, all 18 patients underwent a personal interview, repeat penile plethysmography, and repeat Rigiscan testing. Six patients reports successful coitus and an additional four were having coitus with the aid of intracavernous pharmacotherapy. Seventy-eight percent (14/18) had improved tracings on penile plethysmography, and 56% (10/18) had normal erectile capability by Rigiscan testing.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗