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Biomedical subjects

P H Powell

Publications and source records attributed to P H Powell.

At least 19 recordsLinked to original sources
PubMed1995

The use of duplex ultrasound in the assessment of arterial supply to the penis in vasculogenic impotence.

Impotence may be caused by arterial disease affecting the vessels supplying the corpora cavernosa. Color duplex ultrasound was used to measure the peak systolic velocity and systolic rise time in the deep penile arteries in 22 impotent men following papaverine stimulation. The results were compared with the findings of selective internal pudendal pharmaco-arteriography. A further comparison was made using color duplex ultrasound with 37 impotent men who all responded well to papaverine. A systolic rise time of 110 msec. or more was found to be the best discriminant of disease in the arteries supplying the corpora giving a positive predictive value of 0.92. A long systolic rise time in a papaverine responder may indicate that the arterial supply is borderline or that the arterial flow is maximal and that the problem lies on the sinusoidal-venous side. It appears that in the absence of a pathological condition there is a large surplus arterial supply.

Adult↗
PubMed1995

Nitric oxide and cyclic GMP formation following relaxant nerve stimulation in isolated human corpus cavernosum.

OBJECTIVE: To investigate further the role of the nitric oxide (NO)-cyclic GMP pathway as the mediator of relaxant neurotransmission in human corpus cavernosum and to establish whether impaired activity of this pathway contributes to the pathophysiology of impotence. PATIENTS AND METHODS: Samples of cavernosal tissue were obtained from 59 men undergoing penile operations. The controls comprised four men with penile carcinoma and 17 with Peyronie's disease. Of the impotent men, 35 had clinical evidence of penile vascular disease on pre-operative investigation, whilst three had non-vascular impotence. Each biopsy was divided into two strips which were then suspended under tension in organ bath chambers. The relaxant innervation of one strip of each pair was stimulated electrically whilst the other strip was left unstimulated. The formation of NO and cyclic GMP was calculated by comparing their respective tissue content in the stimulated and unstimulated strips. RESULTS: Overall, stimulation of the relaxant innervation produced significant increases in the tissue content of both NO and cyclic GMP. Incubation with an inhibitor of NO biosynthesis abolished the mechanical relaxant response and the formation of both NO and cyclic GMP. The magnitude of relaxant response and the formation of NO was diminished in tissue from men with vascular impotence compared to controls. The increase in cyclic GMP content was similar in both these groups. Relaxant response, NO formation and cyclic GMP formation in tissue from men with non-vascular impotence was similar to controls. CONCLUSIONS: This study provides further evidence that the NO-cyclic GMP pathway acts as the mediator of nerve-evoked smooth muscle relaxation in human corpus cavernosum. Diminished NO formation following relaxant nerve stimulation may account for impaired relaxant responses found in tissue from men with vascular impotence and may contribute to the cause of their erectile dysfunction.

Adult↗
PubMed1994

Corpus cavernosal relaxation in impotent men.

OBJECTIVE: To investigate smooth muscle responsiveness in isolated preparations of corpus cavernosum from men with vasculogenic impotence. PATIENTS AND METHODS: Biopsies of corpus cavernosum were obtained from 63 men undergoing penile surgery. These included a control group of eight men (mean age 59 years, range 38-82) undergoing penile amputation for carcinoma, 47 men with vasculogenic impotence (mean age 58, range 36-72) who were further sub-divided into arterial (n = 9), venous (n = 24) or mixed arterial/venous (n = 14) impotence according to the results of pre-operative haemodynamic investigation, and eight men with non-vasculogenic impotence (mean age 49 years, range 34-66). Smooth muscle contractile responses to alpha-adrenoceptor activation and relaxant responses to stimulation of intrinsic nerves and exposure to papaverine and sodium nitroprusside were recorded in tissue strips prepared from the biopsies. Morphology was assessed histologically using haematoxylin and eosin staining of tissue sections together with immunocytochemical labelling of intrinsic nerves. RESULTS: Nerve-evoked relaxation was markedly impaired in tissue from men with venous or mixed arterial/venous impotence. A lesser degree of impairment was found in tissue from men with arterial impotence alone. Tissue from men with all types of vasculogenic impotence also showed a decreased contractile response to alpha-adrenoceptor stimulation. The magnitude of relaxant responses to papaverine and sodium nitroprusside in the vasculogenic group was similar to that of the control. There were no differences in smooth muscle content or nerve density between the vasculogenic group and the control. In the non-vasculogenic group responses to relaxant nerve stimulation, alpha-adrenoceptor activation and relaxant drugs were similar to those of the control. Nerve density in this group was similar to the control but smooth muscle content was reduced. CONCLUSIONS: The results of this study demonstrate a functional impairment of smooth muscle contractility and neurogenic relaxation in corpus cavernosum from impotent men with abnormal penile haemodynamics. Altered smooth muscle responsiveness is likely to be a factor in the aetiology of impotence in such men and may contribute to the relatively poor results of vascular surgery for impotence.

Adult↗
PubMed1991

The role of colour duplex ultrasonography in the diagnosis of vasculogenic impotence.

Colour duplex ultrasonography was used to obtain peak systolic velocity (PSV) readings from cavernosal arteries at rest and during papaverine-induced tumescence. Results from 31 men with vasculogenic impotence were compared with those from 17 men with non-vasculogenic impotence and a control group of 6 potent men. In the flaccid state no significant differences in PSV readings were found between the vasculogenic and control groups. Following the injection of papaverine, men from the vasculogenic group without venous leakage were alone in having significantly lower PSV readings compared with the potent controls. All 23 men with normal penile haemodynamics had a mean PSV greater than or equal to 20 cm/s during tumescence. This was also the case for 19 (61%) of the vasculogenic group, including 9 (69%) of the 13 patients with venous leakage. The remaining 12 men in the vasculogenic group (39%) had a mean PSV less than 20 cm/s, this being diagnostic of an inadequate arterial inflow. Colour duplex ultrasonography can identify patients who have marked arterial insufficiency as the major cause of their impotence and hence allows more rational selection for angiography and revascularisation. Lesser degrees of arterial deficit are difficult to characterise using mean PSV readings alone.

Adult↗
PubMed1991

The effect of inhibitors of nitric oxide biosynthesis and cyclic GMP formation on nerve-evoked relaxation of human cavernosal smooth muscle.

1. The inhibitory transmission in isolated preparations of cavernosal smooth muscle from human penis has been studied. 2. Electrical field stimulation (EFS; 2-64 pulses/train, 0.8 ms pulse duration, 10 Hz) evoked relaxation of preparations treated with guanethidine (50 microM). The EFS-evoked relaxations were atropine-resistant and tetrodotoxin-sensitive indicating their origin to be non-adrenergic, non-cholinergic (NANC) nerve stimulation. 3. EFS-evoked relaxation was attenuated dose-dependently by the nitric oxide (NO)-synthase inhibitor, L-NG-nitro arginine (L-NOARG; 0.3-100 microM) but not by D-NG-nitro arginine. The inhibitory effect of L-NOARG on transmission was antagonized by L-arginine (100 microM), a NO precursor, but not by D-arginine. 4. Incubation with methylene blue (10-50 microM), a known inhibitor of guanylate cyclase activation by NO, caused a concentration-related inhibition of EFS-evoked relaxation. 5. It is concluded that NANC nerve-evoked relaxation of human cavernosal smooth muscle is mediated by NO or a NO-like substance.

Arginine↗
PubMed1989

Outcome of elective prostatectomy.

OBJECTIVES: To determine the symptomatic and urodynamic outcome of elective prostatectomy and to establish whether the outcome is influenced or can be predicted by preoperative urodynamic measurements. DESIGN: Prospective non-randomised study with follow up at a mean of 11 months after operation. Most men were assessed jointly by a urologist and a general practitioner. SETTING: Department of urology in a teaching hospital serving a large district population. PATIENTS: 253 Men listed for elective prostatectomy because of symptoms and low urinary flow rates (less than 15 ml/s) and excluding those already on a waiting list or with acute urinary retention, clinically apparent prostatic cancer, and neurological or cerebrovascular disease; 217 (86%) were followed up. INTERVENTION: Elective prostatectomy. MAIN OUTCOME MEASURE: Classification on the basis of relief of symptoms assessed by patients and urologist and general practitioner and of symptom scores obtained by questionnaire. RESULTS: Of the 217 men followed up, 171 (79%) had a satisfactory subjective review and 155 (72%) had a satisfactory review and also low symptom scores. An unsatisfactory outcome was associated with preoperative symptoms of urge incontinence, small prostatic size and resected weight, low voiding pressures, and low urethral resistance. Preoperative maximum urinary flow rates did not predict outcome. Men with poor outcome could be classified into two groups: those with irritative symptoms who were more likely before operation to have had urge incontinence and detrusor instability and men with symptoms of poor urinary flow who were more likely before operation to have had a small prostate, low voiding pressures, and low urethral resistance. In patients in the second group flow rates or voiding pressures improved little after operation. Men with stable detrusors and either low urethral resistance or low voiding pressures were less likely to do well after prostatectomy, but despite these associations preoperative urodynamic measurements were unable to predict outcome accurately. CONCLUSIONS: Prostatectomy was satisfactory in relieving symptoms and improving urodynamic measurements in most men, but even in those with classic symptoms and low urinary flow rates a substantial minority experienced little improvement afterwards and urodynamic measurements did not accurately predict outcome in individual patients.

Follow-Up Studies↗
PubMed1988

Deferred treatment for prostate cancer.

The clinical outcome of 278 prostate cancer patients managed by a deferred treatment policy was analysed retrospectively. Following TURP or biopsy, all patients were asymptomatic and deemed suitable for management by a deferred treatment policy, i.e. hormone therapy or other forms of treatment were only initiated if and when symptomatic progression occurred. The overall 5-year survival rate was 30%; 18% of patients died from other causes without needing treatment for their prostate cancer; 11% were alive and untreated after 5 years' follow-up; 17% died from prostate cancer without further treatment. Poor tumour grade, anaemia, metastatic disease, a short history, presentation with retention, and a raised serum creatinine at presentation were associated with a poor prognosis.

Aged↗
PubMed1988

Reproducibility of measurement of prostatic volume by ultrasound. Comparison of transrectal and transabdominal methods.

88 men undergoing elective prostatectomy were investigated by transrectal and transabdominal ultrasound. A repeat examination was performed by a second observer in 28 patients. The aims were to determine the correlation between transrectal and transabdominal ultrasonic estimation of prostatic volume and the degree of observer error. Transabdominal estimation of prostatic volume correlated well with the transrectal method (p less than 0.001) and good agreement between the two observers was found with both methods (p less than 0.001). In the individual patient, however, a wide variation in prostatic volume was found between the two observers and the two methods.

Aged↗
PubMed1987

Detection of blood group antigens in frozen sections of prostatic epithelium.

The detection of blood group antigens (BGA) in non-malignant prostates by previous workers has been at best inconsistent. BGA have not before been detected in prostatic carcinomas. In this preliminary study, a variety of anti-BGA reagents, with known specificities that involve the carbohydrate backbone in addition to the BGA specific terminal monosaccharides, were used to study the expression of the A and H (O) BGA in cryostat sections of 16 patients with benign prostatic disease and nine with prostatic cancer. Positive staining, appropriate to the patients' blood group, was seen in all of the benign tissues when anti-BGA reagents that included specificity against type 2 backbone structures were used. Staining was absent, however, if the reagent had only type 1 specificity. The anti-A and anti-H (O) reagents which gave the best staining patterns in benign tissues were used in malignant tissues. No cancer was found to express A antigen but eight of the nine prostatic cancers were positive for the H (O) antigen irrespective of blood group. Using fresh frozen material and appropriate reagents, BGA may be reproducibly detected in the epithelium of all non-malignant prostates, suggesting that a significant component of BGA is probably lipid-based on type 2 carbohydrate backbone chains. Further studies of changes in BGA expression in prostatic cancer are warranted.

ABO Blood-Group System↗
PubMed1987

Relationship between voiding pressures, symptoms and urodynamic findings in 253 men undergoing prostatectomy.

Two hundred and fifty-three men (age 69.2 +/- 7 years) undergoing prostatectomy for bladder outflow obstruction were studied. The aims were to determine the distribution of voiding pressures and their relationship to presenting symptoms and urodynamic findings. Symptoms were scored by means of a standardised questionnaire and urodynamic studies were performed. Within this study group, high obstructive symptom scores were associated with low flow rates and high urethral resistance. However, high voiding pressures were not associated statistically with low flow rates or obstructive symptoms. Voiding pressures followed a unimodal, parametric distribution and a significant number of men had voiding pressures within the normal range: 9.1% had voiding pressures less than 55 cm H2O and 27.7% less than 75 cm H2O. Irritative symptoms, on the other hand, correlated significantly with obstructive symptoms, high voiding pressures and urethral resistance. Furthermore, high voiding pressures were associated with small cystometric bladder capacities, low compliance and detrusor instability. Whilst these clinical and urodynamic parameters were associated statistically with voiding pressures, none proved specific in being able to identify men with voiding pressures in the high or low end of the range.

Aged↗
PubMed1987

Relationship between detrusor function and residual urine in men undergoing prostatectomy.

Two hundred and fifty-three men undergoing prostatectomy were studied by means of urodynamic investigation to determine the relationship between the volume of residual urine and detrusor function. Increased volumes of residual urine were associated significantly with increasing age, low peak flow rate and high urethral resistance. However, weak voiding pressures were uncommon and did not correlate with increased residual volumes. Increased residual volumes also correlated significantly with a high resting detrusor pressure and a high detrusor pressure rise during the filling phase, but there was a wide scatter of the results for pressure rise and patients could not be classified into groups on the basis of this parameter. Whilst detrusor decompensation was not manifest by weak voiding pressures in patients with increased residual volumes, impairment of the ability of the detrusor to empty the infused cystometric capacity during the subsequent voiding study correlated with increased residual volumes. These data are consistent with theories relating bladder outflow obstruction to the development of increased volumes of residual urine in men undergoing prostatectomy.

Aged↗