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Biomedical subjects

T F Lue

Publications and source records attributed to T F Lue.

At least 163 records · Page 9Linked to original sources
PubMed1991

The sympathetic role as an antagonist of erection.

The effects of the lumbar and pelvic sympathetic system on penile erection were studied in a canine model. Erection was induced by cavernous nerve stimulation and detumescence by sympathetic trunk stimulation. Erection induced by cavernous nerve stimulation normally subsides slowly. After discontinuation of electrical stimulation the intracavernous pressure drops within a mean of 291 s to 50% and after a mean of 372 s to 10% of the highest level. However, stimulation of the sympathetic trunk at the level of L4-S1 applied directly after discontinuation of cavernous nerve stimulation accelerated this drop of intracavernous pressure significantly: to 50% after a mean of 19 s and to 10% after a mean of 36 s. If stimulation of the sympathetic trunk was initiated 20 s before cavernous nerve stimulation, the pressure rise was aborted completely. Neurostimulation of the hypogastric nerves alone or in combination with cavernous nerve stimulation did not change the intracavernous pressure. These results were not altered after neurotomy of the pudendal or hypogastric nerves. The main pathway of the fibers from the sympathetic trunk to the penis seems to run via the pelvic plexus. The stimulation voltage and frequency to induce erection or detumescence were equivalent. Our results suggest that an elevated central sympathetic tone may be one of the causes of psychogenic impotence.

Animals↗
PubMed1991

Extravaginal torsion of spermatic cord in adult.

A twenty-six-year-old man with no history of testicular trauma presented with both extra- and intravaginal torsion of the spermatic cord. This phenomenon is extremely rare in the adult, having been reported only twice before.

Adult↗
PubMed1991

Sympathetic inhibition of papaverine induced erection.

We studied the effect of neurostimulation of the lumbar sympathetic trunks on papaverine-induced penile erection in dogs and monkeys. The mean of 124 cm. H2O intracavernous pressure after papaverine injection was reduced under sympathetic trunk stimulation to 40.6 cm. H2O within a mean of 39 sec. In addition the flow of the internal pudendal artery was reduced indicating a decrease of the inflow to the penis. After the sympathetic stimulation was terminated, the intracavernous pressure increased again to the same level as before. This pressure recovery time was delayed after several sympathetic stimulations from 134 sec. (5 min. after papaverine injection) to at least 362 sec. (45 minutes after papaverine injection). Stimulation of the inferior hypogastric plexus had no effect on the intracavernous pressure. The neurostimulation range (3-4V; 20 Hz) was most effective in reducing the papaverine action on penile smooth muscles. The effect of sympathetic trunk stimulation seems to antagonize the relaxing action of papaverine on the cavernous smooth muscles and the cavernous arterioles. Our results imply that high sympathetic tone in some patients with psychogenic impotence may explain their poor response to intracavernous injection of papaverine.

Animals↗
PubMed1991

Penile detumescence: characterization of three phases.

In 22 dogs in which erection was induced by cavernous nerve stimulation, we analyzed the intracavernous pressure changes during detumescence without and with acute clamping of the aorta or electrostimulation of the lumbar sympathetic chains. Additionally, the degree of venous outflow obstruction was assessed by saline perfusion of the cavernous body during aortic occlusion. Detumescence had three distinct phases: an initial phase exhibiting a small pressure increase; a second phase showing a slow pressure decrease; and a third phase in which a fast decrease occurred. The first phase was abolished by aortic clamping, whereas the other phases were not significantly affected. Sympathetic stimulation abolished or prevented the second phase. Perfusion of the cavernous body during the second phase resulted in a pressure rise to off-scale values; however, when initiated during the terminal phase or in the nonstimulated penis, the pressure increase was slight. Our study indicates that the arterial flow rate influences the duration of the first phase of detumescence and that venous drainage is completely restored in the third phase. Furthermore, sympathetic stimulation causes an almost immediate full restoration of venous drainage, as cavernous perfusion initiated with an intracavernous pressure about twice as high as without sympathetic stimulation failed to increase pressure to off-scale values.

Animals↗
PubMed1991

Ultrastructural changes in impotent penile tissue: a comparison of 65 patients.

To determine whether impotence is caused by specific and consistent changes in erectile tissue, we compared the ultrastructure of the corpora cavernosa in 6 controls with that in 59 patients undergoing implantation of a penile prosthesis. The impotent patients were divided into groups based on a medical history of hypertension (10), pelvic surgery (9), alcoholic smokers (8), hypertensive alcoholics (3), hypertensive alcoholic smokers (3), smokers (3), diabetics (8), diabetic smokers (3), Peyronie's disease (3), spinal cord injury (3) and isolated causes (6). Our data demonstrate that different behavioral and/or medical conditions produce similar degenerative tissue responses. There is no single or specific cause of impotence that is manifest by consistent changes in erectile tissue.

Adult↗
PubMed1991

Reduction of sympathetic influences on penile erection by phentolamine.

The lumbosacral sympathetic trunks seem to play a major role in penile detumescence. In animal experiments an erection induced by cavernous nerve stimulation can be abolished by neurostimulation of the canine sympathetic trunks. This canine experiment was designed to study the possible reduction of the sympathetic effect by intravenous injection of phentolamine. The aborted erection by sympathetic trunks stimulation was partially antagonized by phentolamine. The arterial flow to the penis as well as the intracavernous pressure were elevated by this drug. As an expected side effect the systemic arterial blood pressure decreased by 4-14 cm H2O after phentolamine injection.

Animals↗
PubMed1991

Impotence after radical pelvic surgery: physiology and management.

Impotence has been a common problem after radical surgery of the colon, rectum, prostate, bladder, and seminal vesicle. However, a better understanding of the neuroanatomy of erection has resulted in its decline. When impotence does result, in cases where the extent of tumor involvement renders preservation of the neurovascular bundle impossible, the variety of treatments available is now improved: these include intracavernous injection of vasodilators, vacuum constriction devices, penile arterial and venous surgery, and penile prostheses. The improved understanding and management of impotence has greatly enhanced the quality of life of patients after radical pelvic surgery.

Erectile Dysfunction↗
PubMed1991

Hypertension and impotence.

In a group of 472 impotent patients who were evaluated with pharmacologic duplex sonography, 117 patient (24.8%) had a history of hypertension, 26 of them (22.2%) for more than 10 years. Objective data about the changes in pulsation, diameter and blood flow velocity of the penile arteries after papaverine injection and the resulting erectile response allowed indirect assessment of the penile venous function. Varying degrees of impaired arterial function were diagnosed in 85% of the patients. The duration of hypertension had less deteriorating effects on the penile arterial system than second risk factors such as diabetes mellitus (n = 31) or smoking (n = 26). Patients on antihypertensive medication (n = 88, 75.2%) demonstrated a worse arterial response to papaverine than those without medication (n = 29, 24.8%). The best vascular response to papaverine injection was found in patients taking a combination of beta-blockers and vasodilators (n = 6), whereas thiazides either taken alone or in combination (n = 51, 60%) seem to have a deteriorating effect on arterial function. However, the arterial response did not correlate with the ability to achieve 'full erection' after intracavernous papaverine injection. Clinical experience confirms that certain antihypertensive drugs affect not only the blood pressure, but also compliance of the erectile tissue resulting in a functional venous leak. This may impair erectile function as much as arteriosclerotic changes of the vascular system secondary to hypertension.

Antihypertensive Agents↗
PubMed1991

Loss of penile erectile response to intracavernous injection of acetylcholine in castrated dog.

Castrated dogs showed a slightly weak erectile response to cavernous nerve stimulation compared with normal dogs. Intracavernous injection of acetylcholine induced a dose-dependent increase of intracavernous pressure in normal dogs, however, there was almost no penile response in castrated dogs. Histological study showed a significant higher ratio of collagen tissue/smooth muscle in the corpus cavernosum of castrated dogs, but no difference in acetylcholine-esterase staining and the number of endothelial cells lining the sinusoidal spaces between castrated and normal dogs. These results indicate that the corpus cavernosum of castrated dogs nearly lost responsiveness to acetylcholine probably due to a high ratio of collagen/smooth muscle fibers and that there are different mechanisms for erectile response to nerve stimulation and intracavernous injection of acetylcholine.

Acetylcholine↗
PubMed1991

Pharmacological effects of adenosine on canine penile erection.

We investigated the pharmacological effects of adenosine on canine penile erection in vivo. Intracavernous injection of adenosine induced a full erection, which was unaffected by hexamethonium and atropine. The erectile response induced by adenosine was augmented by intracavernous pretreatment with dipyridamole and markedly depressed by theophylline. The erectile response induced by cavernous nerve stimulation was also enhanced by dipyridamole and reduced by theophylline. The combination of acetylcholine and adenosine, when injected intracavernously, induced a full erection, and the effect of these drugs was not additive but synergistic. These results suggest that penile erection induced by adenosine is due to a direct relaxing effect on cavernous smooth muscle. We propose that adenosine plays a cooperative role with acetylcholine and also has a physiological role as a neuromodulator in canine penile erection.

Acetylcholine↗
PubMed1990

Cavernous vein arterialization for vasculogenic impotence. An animal model.

We designed acute and chronic animal models to evaluate a new procedure of arterialization of the cavernous vein. In the acute study, arteriogenic impotence was induced in 6 dogs by bilateral ligation of the penile arteries just proximal to the crus of the penis. The cavernous vein and penile artery were anastomosed proximal to the site of ligation, and the pudendal vein was ligated proximally to prevent the diversion of arterial blood away from the penis. Erection was induced either by electrostimulation of the cavernous nerves or by intracavernous injection of papaverine, and the erectile response was studied before and after cavernous vein arterialization. Four dogs were followed up for two months to evaluate the long-term effects of the procedure. Shortly after arterialization of the cavernous vein, the basal flow rate in the internal pudendal artery increased dramatically to almost six times the control rate, and the erectile response to neurostimulation was approximately 85 percent of control. Selective pudendal arteriography at two months confirmed the patency of all arteriovenous anastomoses. However, scanning electron microscopy and histologic examination revealed sinusoidal damage most probably consequent to the chronically elevated arterial flow.

Animals↗
PubMed1990

The effect of venous incompetence and arterial insufficiency on erectile function: an animal model.

We designed an animal model to elucidate the effect of venous leakage and arterial insufficiency on erectile function. In 10 dogs, electrodes were implanted around the cavernous nerves for electroerection and blood flow in the internal pudendal artery was recorded. Venous leakage was mimicked by inserting needles of varying gauges (30 to 16G) into the corpus cavernosum and the erectile response to neurostimulation was recorded before and after the creation of the leak. The relationship between the size and the amount of the venous leakage, the changes in the intracavernous pressure (peak and drop), and the changes in the peak and maintenance arterial blood flow were documented. Arterial blood flow was then reduced by 25 and 50 per cent by means of a screw clamp on the terminal aorta. The erectile response to neurostimulation was again determined, with the same electrical parameters, first with reduced blood flow alone, then in combination with leakage of varying size. Our results showed that minor cavernous vein leakage in the presence of normal arterial flow and a healthy sinusoidal system had a minimal effect on erectile function owing to a compensatory increase in penile blood flow. However, when reduction of arterial blood flow was superimposed on venous leakage, even of a minor degree, the erectile response to neurostimulation was markedly impaired.

Animals↗
PubMed1990

A possible role for calcitonin-gene-related peptide in the regulation of the smooth muscle tone of the bladder and penis.

We investigated the effect of calcitonin-gene-related peptide (CGRP) on bladder contractions and penile erection in 12 dogs. In a system in which the arteries were tied bilaterally to ensure delivery of high drug levels to the bladder, arterial injections of CGRP significantly reduced the peak intravesical pressure of bladder contractions induced by pelvic nerve stimulation or arterial injection of carbachol. When given intravenously, CGRP had no effect on bladder contractions consequent to neural stimulation. Intravesical instillation of CGRP, however, reduced the bladder contractions significantly. Histologic staining showed CGRP-immunoreactive nerve fibers within the smooth muscle layers of the bladder wall. Intracavernous CGRP increased cavernous arterial flow and induced cavernous smooth muscle relaxation and venous outflow occlusion. Muscarinic blockade had no effect on the canine intracavernous pressure response to intracavernous injection of CGRP. Histologic staining for CGRP-immunoreactivity showed nerve-fiber-like staining within the cavernous arterial wall, the nerves running near the cavernous arteries, and the cavernous smooth muscles. Our results suggest a possible role for CGRP in the regulation of the smooth muscle tone of the bladder and penis.

Animals↗
PubMed1990

Norepinephrine involvement in penile detumescence.

Adrenergic neurotransmission was studied in dogs. Blood samples for catecholamine assay were collected from the flaccid penis, the erect penis after cavernous nerve stimulation and during detumescence induced by sympathetic trunk stimulation. Epinephrine concentration was not significantly different in these three stages. However, norepinephrine concentration increased significantly (p less than 0.005) during induced detumescence from 505 +/- 311 [pg./ml.] to 747 +/- 489 [pg./ml.]. Intracavernous application of norepinephrine abolished cavernous nerve induced erection in a dose dependent manner. Sympathetic trunk stimulation reduced or abolished erection induced by acetylcholine or by vasoactive intestinal polypeptide. We conclude that norepinephrine is an important neurotransmitter in the control of penile detumescence.

Acetylcholine↗
PubMed1990

Self-administration in the pharmacological treatment of impotence.

Recent innovative research into the physiology and pharmacology of erection and the introduction of intracavernous injection of vasoactive agents have revolutionised our approach to the diagnosis and treatment of impotence. A thorough understanding of the rationale, indications, precautions and potential complications of intracavernous self-injection is essential for successful management. The commonly used drugs for injection are papaverine, either alone or in combination with phentolamine, and alprostadil (prostaglandin E1). The major adverse effects include priapism, prolonged erection, and fibrosis of the erectile tissue. With the proper technique and appropriate dosage, this is a safe, minimally invasive, and highly effective treatment.

Animals↗
PubMed1990

Impotence after prostatectomy.

Reportedly, 4 to 30 per cent of patients suffer impotence after prostatectomy. Some cases of neurovascular impotence can be attributed to the surgical technique. The author examines the incidence and mechanisms of such impotence and outlines the evaluation and treatment options.

Erectile Dysfunction↗