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A Nehra

Publications and source records attributed to A Nehra.

51 records · Page 3Linked to original sources
PubMed1998

Engineering analysis of penile hemodynamic and structural-dynamic relationships: Part I--Clinical implications of penile tissue mechanical properties.

PURPOSE: The least investigated physical determinant of penile rigidity has been penile tissue material properties. The goals in this study (Part I) were to define two penile mechanical parameters, cavernosal expandability X and tunical distensibility VE/VF, determine their magnitudes in humans and develop an analytical expression for penile volume as a function of these two tissue characteristics and intracavernosal pressure. METHODS: Dynamic infusion pharmacocavernosometry was performed in 21 impotent patients (age 43 +/- 19 y) to provide human geometric, hemodynamic and structural data. A mathematically derived model of hemodynamic and structural-dynamic characteristics of penile erection was developed (Parts I, II, III) incorporating penile tissue mechanical qualities. RESULTS: Cavernosal expandability X provided a measure of the ability to approach maximum volume at relatively low intracavernosal pressures. Tunical distensibility VE/VF denoted the maximal erect to flaccid penile volume ratio. The magnitudes of X and VE/VF in the study population were 0.04-0.17 mmHg-1 and 1.7-5.0 respectively. CONCLUSIONS: Enabling penile volume to be derived as a function of tissue mechanical characteristics and pressure, allows for penile rigidity to be expressed (in Part II) as a function of pressure, geometry and tissue qualities.

Adult↗
PubMed1998

Engineering analysis of penile hemodynamic and structural-dynamic relationships: Part II--Clinical implications of penile buckling.

PURPOSE: Penile buckling force was analytically described in terms of its constituents. In addition, theoretically-derived buckling force data were compared to clinically measured data and the influence of each constituent on penile buckling force data was assessed. METHODS: Using engineering buckling theory for a column, a mathematically-derived penile buckling model was developed which incorporated geometric and hemodynamic data obtained by dynamic infusion pharmacocavernosometry studies in 21 impotent patients (age 43, range 24-62 y) as well as penile tissue mechanical characteristics previously developed (Part I). RESULTS: In 17 of 21 patients the mean difference between theoretically derived and clinically measured buckling force data was 0.33 +/- 0.25 kg (r = 0.96). Factors which increased penile buckling forces were: (1) high intracavernosal pressure values (rigidity was related to pressure in an exponential-like fashion); (2) high penile aspect ratio (D/L) values (relatively large diameter/short length penile geometry) and high flaccid diameter; and (3) high cavernosal expandability values (a measure of the ability of the corpora to approach its erect volume with relatively low intracavernosal pressures). CONCLUSIONS: Pressure-volume data (pressure, geometry and tissue characteristics) obtained during erectile function testing have been shown, for the first time, to theoretically predict the magnitude of clinically-measured penile buckling forces.

Adult↗
PubMed1998

Engineering analysis of penile hemodynamic and structural-dynamic relationships: Part III--Clinical considerations of penile hemodynamic and rigidity erectile responses.

PURPOSE: The extent to which hemodynamic erectile responses predict penile buckling forces has not previously been analytically investigated. An engineering study was performed to compare hemodynamic data with penile buckling force values. METHODS: Dynamic infusion pharmacocavernosometry studies in 21 impotent patients (age 43, range 24-62 y) were accomplished to obtain information during penile erection concerning hemodynamic values, penile buckling forces and their determinants: intracavernosal pressure, erectile tissue mechanical properties and penile geometry. RESULTS: In the 21 patients, discrepancies existed in several patients who demonstrated normal hemodynamic values (low flow-to-maintain and high equilibrium intracavernosal pressures) but elevated cavernosal compliance values and diminished penile buckling forces. There was poor correlation between cavernosal compliance and equilibrium intracavernosal pressure (r = -0.36); better correlation between compliance and expandability (r = -0.72) and best correlation between dimensionless compliance and the dimensionless product of expandability with equilibrium pressure (r = -0.88). These data implied that cavernosal compliance was dependent on multiple factors, not only equilibrium intracavernosal pressure. CONCLUSIONS: Hemodynamic indices which correlate with intracavernosal pressure alone do not predict penile buckling forces since the latter are dependent not only on intracavernosal pressure but also on penile geometry and erectile tissue properties. The most relevant tissue property in predicting adequate penile buckling forces is cavernosal expandability. A new impotence classification system and diagnostic algorithm based on the determinants of penile rigidity and not exclusively on hemodynamic responses in proposed.

Adult↗
PubMed1998

Preliminary report on the development and characterization of rabbit clitoral smooth muscle cell culture.

PURPOSE: Scientific model systems for physiological evaluation and investigation of pathophysiologies in clitoral function have been limited. The aim was to develop a New Zealand White rabbit clitoral corpus cavernosum smooth muscle cell culture. METHODS: Clitoral corpus cavernosum erectile tissue was harvested and placed in culture. Clitoral smooth muscle cells which migrated out from explants were grown to confluence and subcultured. Characterizations were performed by morphological and biochemical analyses. RESULTS: The cells exhibited typical morphologic characteristics of smooth muscle cells. Indirect immunofluorescence studies confirmed the presence of a-smooth muscle cell actin. Androgen and estrogen receptors were detected by specific antibodies and binding studies. The cells expressed subtypes of TGF-beta receptors. Treatment with 80 pM TGF-beta 1 24 h resulted in induction and/or increased availability of TGF-beta receptors. CONCLUSIONS: An in-vitro cell culture system using rabbit clitoral smooth muscle cells was developed. These smooth muscle cells retain their biochemical and functional integrity. This in-vitro cell culture system may facilitate studies aimed at understanding the molecular basis of female sexual function.

Animals↗
PubMed1997

Priapism: diagnosis and management.

Recent advances in the understanding of erectile physiology have improved the prompt diagnosis and treatment of priapism. During the initial assessment, the physician must distinguish between the two basic types of priapism--low and high flow--because their associated treatment and prognosis differ. To illustrate the diverse manifestation of priapism, we describe the management of four patients with a history of priapism due to varying causes. In addition, we propose an algorithm that provides a systematic and timely approach to treatment. Resumption of erectile function after a prolonged episode of priapism has traditionally been poor but has improved. Patients must be informed that the long-term sequelae of priapism can be avoided with prompt medical or surgical treatment.

Adolescent↗
PubMed1996

Mechanisms of venous leakage: a prospective clinicopathological correlation of corporeal function and structure.

PURPOSE: We investigated the pathophysiology of structurally based corporeal veno-occlusive dysfunction. MATERIALS AND METHODS: We prospectively evaluated 24 impotent patients (mean age plus or minus standard error 46 +/- 3 years) who had exposure to vascular risk factors and/or disorders inducing diffuse trabecular structure alterations and who underwent penile prosthesis insertion. Preoperative indexes of veno-occlusive function (flow to maintain, venous outflow resistance and pressure decay measurements using repeat dosing pharmacocavernosometry) were correlated with postoperative erectile tissue computer assisted color histomorphometry (percent trabecular smooth muscle to total erectile tissue area). To develop further study findings and correlate histomorphometric findings with molecular biological properties molecular biological studies (ribonuclease protection analysis, reverse transcription-polymerase chain reaction assay for expression of transforming growth factor-beta 1 messenger [m] ribonucleic acid [RNA] and protein affinity labeling techniques for specific transforming growth factor-beta receptors) were performed in representative patients with high (39 to 43%), intermediate (30 to 37%) and low (13 to 29%) trabecular smooth muscle content (normal 42 to 50%). RESULTS: Flow to maintain, venous outflow resistance and pressure decay values significantly correlated with trabecular smooth muscle cell content (r = -0.89, 0.82 and -0.85, respectively). In the high, intermediate and low smooth muscle content subgroups flow to maintain, venous outflow resistance and pressure decay values were 1 to 5, 9 to 30 and 50 to 120 ml. per minute, 17 to 84, 3 to 9 and 1 to 2 mm. Hg/ml. per minute, and 40 to 60, 48 to 80 and 110 to 120 mm. Hg decrease in 30 seconds from 150 mm. Hg, respectively. There were no significant differences in patient age or prevalence of risk factors among the 3 subgroups. Patients representative of all 3 subgroups had transforming growth factor-beta 1 mRNA, auto-induction of transforming growth factor-beta 1 mRNA and induction and/or increased availability of all 3 types of transforming growth factor-beta receptors. CONCLUSIONS: The pathophysiology of structurally based corporeal veno-occlusive dysfunction is related to elevated corporeal connective tissue content. Based on our data and those in the literature corporeal fibrosis is hypothesized to develop secondary to abnormalities in the regulation of normal collagen synthesis and degradation, most likely associated with adverse influences of chronic ischemia.

Adult↗
PubMed1996

Vacuum erection associated impotence and Peyronie's disease.

PURPOSE: Use of a nonmedical, catalogue type vacuum erection device resulted in a case of vacuum induced vasculogenic impotence and Peyronie's disease. MATERIALS AND METHODS: A 66-year-old potent man used a nonmedical vacuum erection device (cylinder plus a hand pump without a pressure-release valve and a doughnut-shaped ring at the base without tension bands) after having achieved a spontaneous rigid erection. The resultant excessive overinflation of the penis was followed by dorsal curvature, diminished rigidity and decreased erectile maintenance. RESULTS: Physical examination revealed a dorsal mid shaft Peyronie's plaque. Nocturnal penile tumescence testing and office injection testing were abnormal and demonstrated partial, short-lived, dorsally curved erections. Dynamic pharmaco-cavernosometry and pharmaco-cavernosography established vasculogenic impotence with site-specific crural (unrelated to the Peyronie's plaque) veno-occlusive dysfunction and dorsal penile curvature. CONCLUSIONS: Vacuum erection devices create pulling forces on the penis. We estimate that the pulling forces in this case were prohibitively high (approximately 29 pounds) due to absence of a pressure-release valve and to the preexistent erection at vacuum application. These intense pulling forces are hypothesized to have damaged the tunica in the mid shaft (Peyronie's disease) and the crus (veno-occlusive dysfunction), the latter being the site of attachment of the corpora to the ischiopubic ramus and a most likely location for high magnitude pulling forces to exert an abnormal injury effect. The patient underwent a Nesbit plication procedure and presently performs self-injection for satisfactory sexual activity.

Aged↗
PubMed1996

Vibratory stimulation and rectal probe electroejaculation as therapy for patients with spinal cord injury: semen parameters and pregnancy rates.

PURPOSE: The conception rate of patients with spinal cord injuries following penile vibratory stimulation and rectal probe electroejaculation in conjunction with self-insemination, intrauterine insemination or assisted reproductive technique is poorly documented. We reviewed our success rates with penile vibratory stimulation and rectal probe electroejaculation, and the pregnancy rates achieved with self-insemination, intrauterine insemination and assisted reproductive techniques. MATERIALS AND METHODS: A total of 78 consecutive patients with spinal cord injuries had a complete neurological examination and was treated initially with penile vibratory stimulation. If unsuccessful, rectal probe electroejaculation was performed to obtain an ejaculate. The ejaculate was then used with self-insemination, intrauterine insemination or assisted reproductive techniques and pregnancies were monitored. RESULTS: Vibratory stimulation was successful in 20 of 37 patients (54%) with a cervical lesion, 14 of 26 (54%) with a lesion at or above T10 and none of 15 when the lesion was below T10. All patients except 2 who elected followup rectal probe electroejaculation had antegrade or retrograde ejaculate. Six patients (7.7%) with extremely poor semen quality were not candidates for assisted fertilization. Of 27 couples who attempted conception 17 were successful (5 self-insemination, 5 intrauterine insemination and 7 assisted reproductive techniques). CONCLUSIONS: Penile vibratory stimulation should be used as first line therapy in patients with lesions above T10 while rectal probe electroejaculation should be considered as a second option. Motivated patients can achieve success with self-insemination, intrauterine insemination and assisted reproductive techniques.

Adult↗
PubMed1995

Systemic sclerosis and impotence: a clinicopathological correlation.

A hypothesis of the mechanism of systemic sclerosis associated impotence was developed by making a clinicopathological correlation between the results of preoperative erectile function testing and those of pathological examination of excised erectile tissue in an impotent man with systemic sclerosis. Preoperative examination revealed firm corporeal tissue with diminished penile stretch capability. Pharmacocavernosometry/pharmacocavernosography under conditions consistent with trabecular smooth muscle relaxation revealed severe diffuse corporeal veno-occlusive dysfunction. During penile implantation surgery the compact erectile tissue was unable to be dilated and required sharp corporeal tissue excision under direct vision to achieve cylinder insertion. Histological investigation of the excised corporeal tissue demonstrated severe corporeal fibrosis. Computer assisted color histomorphometry revealed that the mean percentage of trabecular smooth muscle area to total erectile tissue area was 18.2 +/- 13.9% (normal 40 to 52). Immunohistochemical staining with desmin, a protein found in smooth muscle, verified prolific corporeal fibrosis. In situ hybridization of the corporeal tissue demonstrated messenger ribonucleic acid collagen and fibronectin messenger ribonucleic acid expression. Strong hybridization signals were found in mesenchymal cell types, including trabecular smooth muscle cells. In summary, clinicopathological correlation revealed that veno-occlusive dysfunction and loss of penile length were secondary to the excessive accumulation of extracellular matrix, partially due to trabecular smooth muscle cells undergoing synthetic as opposed to contractile phenotypic activity.

Adult↗
PubMed1994

Penile ultrasound.

Explore the source record for details and available documents.

Erectile Dysfunction↗
PubMed1992

Effect of spinal cord ischemia on vesicourethral function.

We studied 9 patients with clinical evidence of spinal cord ischemia or infarction who had altered vesicourethral function. Of the patients 6 had some preservation of bladder and lower extremity sensation, a clinical pattern consistent with the anterior spinal artery syndrome. A total of 3 patients had a clinical picture more consistent with complete transverse myelopathy, since they had no preservation of bladder or lower extremity sensation. Despite sensory levels well above the sacral spinal cord segments, 6 patients had detrusor areflexia (4 with bethanechol supersensitivity and 4 with neuropathic changes in the perineal electromyograph) indicating longitudinal spinal cord involvement. Three patients had detrusor hyperreflexia with vesicosphincter dyssynergia, indicating some preservation of the sacral spinal cord. In 6 patients appreciation of pinprick in the lower extremities was absent or decreased but light touch or position sense was preserved. Bladder sensation was dissociated in 4 of these 6 patients, since they had perception of bladder distention but loss of urge to void. These findings indicate that bladder distention is a sensory modality probably mediated via the posterior spinal cord, while the sense of urgency is probably conveyed by the anterior spinal cord.

Adolescent↗
PubMed1990

Pemoline-associated hepatic injury.

Among 100 cases of hepatic injury attributed to the administration of pemoline, 43 had sufficient accompanying information to permit analysis. All but two patients were less than 20 years old, and 80% were less than 12 years old. Males predominated the study. Injury appeared as early as 1 week or as late as greater than 1 year of taking the drug. The injury was uniformly hepatocellular as judged by the high values for aminotransferases and by death in massive necrosis in one patient. Mechanism was judged to be idiosyncratic, and the idiosyncrasy was probably metabolic rather than immunologic.

Adolescent↗
PubMedDate not supplied

Intracavernosal pharmacotherapeutic advances toward a new millennium.

The National Institutes of Health Consensus Statement on impotence estimates that the number of men with erectile dysfunction in the United States is approximately 20 million, presenting with varying degrees of erectile dysfunction (1). Prevalence of erectile dysfunction varies with age; the estimated probability of impotence is 5% at the age of 40 years, increasing to 15-25% at the age of 70 years and older (2). Significant improvements in the pathophysiology have resulted in newer treatment modalities of erectile dysfunction. One of the most significant developments has been the use of intracavernosal vasoactive agents as a successful method of management. This method and the use of injection pharmacotherapy account for approximately 40% of all treatment options for patients with sexual dysfunction.

Journal Article↗