Characterization and chromosomal localization of PTP-NP-2, a new isoform of protein tyrosine phosphatase-like receptor, expressed on synaptic boutons.

Recently, there have been several reports describing the cloning and characterization of the novel family of protein tyrosine phosphatase-like receptor molecules (known as IA-2 and PTP-NP/PTP-IAR/IA-2beta/phogrin), which may act as autoantigens in diabetes. Here, we report the molecular characterization and chromosomal localization of a new isoform of this family in brain termed PTP-NP-2 (for PTP-NP tyrosine phosphatase isoform), and its function in rat primary hippocampal neurons. PTP-NP-2 has 48% identity to IA-2. The principal difference between PTP-NP-2 and PTP-NP is a 17-amino-acid insert near the N-terminus of PTP-NP that is absent in PTP-NP-2. Genomic DNA analysis indicates that the 17-amino-acid insert is coded by a separate exon, suggesting that both IA-2beta and PTP-NP-2 are isoforms arising by alternate splicing of the same gene. Reverse transcriptase-PCR revealed that both isoforms are present in human SH-SY5Y neuroblastoma cells. PTP-NP-2 mRNA expression is highly restricted, with a 5.5-kb specific transcript in human fetal and adult brain and 5.5 and 3. 8 kb in human adult pancreas. SH-SY5Y neuroblastoma and U87-MG glioblastoma cells showed specific transcripts of 5.5 and 3.8kb, respectively, indicating the existence of several isoforms of this molecule in the nervous system. The human gene encoding PTP-NP-2 was assigned to human chromosome 7q22-qter using Southern blot analysis of genomic DNAs from rodent/human somatic hybrid cell lines. Confocal microscopy analyses of rat primary hippocampal neurons revealed that PTP-NP-2 is abundantly expressed on synaptic boutons in primary neurons. Wild-type PTP-NP-2 showed no measurable tyrosine phosphatase activity using an in-vitro pNPP assay. Examination of the PTP-NP-2 catalytic consensus sequence revealed that this sequence differed from the typical tyrosine phosphatase-domain consensus sequence by an alanine to aspartate change (amino acid 930). Mutation of aspartate 930 to alanine produced a catalytically active enzyme, suggesting that native PTP-NP and its isoform PTP-NP-2 are catalytically inactive receptor protein tyrosine phosphatase homologues. Taken together, these results indicate that the tyrosine phosphatase PTP-NP-2 is a new isoform of PTP-NP tyrosine phosphatase, is expressed on synaptic boutons and may participate in the regulation of synaptic bouton endocytosis.

Smooth muscle phosphatases: structure, regulation, and function.

Smooth muscle contraction is regulated primarily by the reversible phosphorylation of myosin by myosin light chain kinase. Secondary mechanisms that might modulate contractility are phosphorylation-dephosphorylation of myosin light chain kinase and thin-filament proteins, caldesmon and calponin. Purification of several protein phosphatases that are active toward myosin light chains and (or) myosin and heavy meromyosin from smooth muscles has been reported. All the cytosolic turkey gizzard smooth muscle phosphatases, termed SMP-I, -II, -III, and -IV, dephosphorylate myosin light chains rapidly, but only SMP-III and -IV are active toward myosin and heavy meromyosin, suggesting that SMP-III and -IV might be directly involved in the relaxation of smooth muscle. SMP-III and -IV exhibit properties typical of type 1 protein phosphatases following tryptic digestion. These enzymes appear to share structural similarity with myofibrillar phosphatase PP1M. Purified calponin phosphatase and caldesmon phosphatase from chicken gizzards are structurally and immunologically identical with SMP-I, a type 2A protein phosphatase. SMP-I dephosphorylates calponin faster than it does caldesmon, and has much higher activity toward these substrates than SMP-II, -III, and -IV. Thus, one role for SMP-I might be to regulate the activities of caldesmon and calponin. Since SMP-I is active toward myosin light chain kinase, it might also modulate this enzyme.

The role of intracavernosal vasoactive agents to overcome impotence due to spinal cord injury.

Twenty-two spinal cord injured men (mean age 35.2 years) referred because of impotence were treated with intracavernosal vasoactive agents. Papaverine 2-20 mg, papaverine 40 mg plus phentolamine 0.5 mg or prostaglandin E1 (1-20 micrograms) were used. Nineteen responded and were taught to self administer the medication with varying degrees of assistance from their partners. Fourteen men participated in a postal survey; 12 (86%) continued to use the drugs every 1 to 4 weeks and reported satisfaction with the method. Partner responses were positive in half of the group and when not so it influenced the patients to abandon or reduce the frequency of treatment. Counselling was essential to allay anxiety. Clinical management was not compromised and side effects were minimal. Overall we found this treatment effective, safe and worthwhile.

Turkey gizzard smooth muscle myosin phosphatase-III is a novel protein phosphatase.

Chromatography of turkey gizzard extract on Sephacryl S-300 has been shown to fractionate the various smooth muscle phosphatases. We have previously reported the purification and characterization of three of these enzymes, termed smooth muscle phosphatase (SMP)-I, -II, and -IV. Recently, we have purified SMP-III to near homogeneity. Although all of the smooth muscle phosphatases dephosphorylate the isolated myosin light chains, only SMP-III and -IV are active toward intact myosin and, therefore, are most likely to play a direct role in the muscle contraction-relaxation process. SMP-III has a higher molecular weight (390,000), as determined by gel filtration, than the other smooth muscle phosphatases and migrates as single band with a molecular weight of 40,000 in a sodium dodecyl sulfate-polyacrylamide gel. SMP-III is immunologically distinct from SMP-I and -II. It dephosphorylates heavy meromyosin and the isolated myosin light chains at a rapid rate but has low activity toward phosphorylase alpha. The activity of SMP-III is not affected by Ca2+ but is activated by Mn2+.Mg2+ stimulates the activity toward heavy meromyosin but inhibits the myosin light chain phosphatase activity. Attempts to classify SMP-III according to the scheme proposed by Ingebritsen and Cohen (Ingebritsen T. S., and Cohen, P. (1983) Science 221, 331-338) revealed that it is resistant to the heat stable inhibitor-2, suggesting that it is a Type 2 protein phosphatase. However, SMP-III is inhibited by concentrations of okadaic acid which are characteristic of Type 1 protein phosphatases and it binds to heparin-Sepharose like other Type 1 phosphatases. But most interestingly, SMP-III does not dephosphorylate the alpha- or beta-subunits of phosphorylase kinase, a property not reported for any Ser/Thr protein phosphatase.

Effects of a sclerosant, ethanolamine, on the venous drainage system of the dog penis.

To explore the possibility of using venous sclerosant therapy to overcome venogenic impotence we studied the effects of ethanolamine on the veins draining the dog penis. Following injection of the sclerosant into the deep dorsal vein radiological and histological evidence of occlusion was obtained but by one month recanalization of thrombi had occurred and collateral venous channels had formed. These findings cast doubt on the effectiveness of this sclerosant as a means of treating impotence.

Effects of acute alcohol on penile tumescence in normal young men and dogs.

To determine the cause of the inhibition of sexual function observed in normal subjects with elevated blood alcohol concentrations (BAC), nocturnal penile tumescence (NPT) was monitored in 11 subjects over three consecutive nights. On the third night alcohol was administered (BAC = 0.154 g/100 mL). We observed no effect of alcohol on the size, duration, or number of erections. These results were confirmed in dogs. The latent period, magnitude, and duration of corpus cavernosal pressure changes produced by pelvic nerve stimulation were not affected by mean blood alcohol levels of 0.327 g/100 mL in three dogs. These results suggest that the inhibition of sexual response caused in conscious subjects by the ingestion of alcohol is not due to a suppression of the underlying spinal reflex but may be the result of its effect on perceptual or cognitive sexual mechanisms.

Prostaglandin E1 therapy for impotence, comparison with papaverine.

The efficacy of prostaglandin E1 as a pharmacological treatment of erectile dysfunction (impotence) was compared with the standard treatment, papaverine, in a single blind, crossover trial. A total of 129 impotent men received intracavernous injections of either prostaglandin E1 (5 micrograms) or papaverine (18 mg.) 1 month apart. Observations by 1 observer recorded 10 to 20 minutes after injection demonstrated that prostaglandin E1 generated a better erection in 72 men (55.8%) compared to papaverine. Papaverine was more effective than prostaglandin E1 in 23 men (17.8%, chi-square 6.26, p less than 0.025). Subjective assessment by the patients who detected a difference showed that 71 (55%) preferred prostaglandin E1 and 35 (27%) preferred papaverine (chi-square 11.56, p less than 0.001). A total of 34 men achieved full erections with prostaglandin E1 compared to 17 who used papaverine.

Complications associated with penile implants used to treat impotence.

The complications associated with a variety of penile prostheses used in the treatment of 302 men with erectile dysfunction are described. Infection of the prostheses resulted in their removal from 11 patients (3.6%), antibiotic therapy and replacement in five men. Mechanical failures required reoperation in 43 men (14.2%); however, recent advances in prosthesis design have reduced this type of malfunction. Adverse psychological reactions prompted removal of the prostheses from two men. Despite these complications, this surgery is remarkably effective.

The role of dynamic corpora cavernosography in the management of impotence.

Sixty eight impotent men underwent corpora cavernosography and corpora cavernosal pressure measurements during saline infusion. Nineteen of the men had internal pudendal arteriograms. Correlation between the cavernosograms and saline infusion induced pressure measurements was "good" in 56/66(84%), "approximate" in 5/66(8%) and there was no correlation in 5/66(8%). Two patients were excluded for technical reasons. The spread of results and the good correlation of the two tests speaks for the accuracy of the method. It was of value in diagnosis and will be of paramount importance if veno occlusive surgery becomes a reliable method of treatment.

Treatment of impotence by intrapenile injections of papaverine and phenoxybenzamine: a double blind, controlled trial.

The efficacy of papaverine and phenoxybenzamine as a pharmacological treatment of impotence was compared in a double blind, crossover, placebo controlled trial. Thirty-four impotent men received intra-cavernosal injections of papaverine (60 mg), phenoxybenzamine (6 mg) or normal saline (10 ml) at monthly intervals. Observations by EJK up to 45 minutes after injection demonstrated that papaverine caused full erections in 35% of men and partial erections in 62%. Phenoxybenzamine injection resulted in full erections in 20% of men and 62% had partial erections. The differences were not significant. Despite 82-97% of patients attaining some degree of erection in the clinical setting only six of the patients decided to use this mode of treatment for more than three months. Sexual function during the month after injection was better with either drug when compared with placebo.

Experience in the management of erectile dysfunction using the intracavernosal self-injection of vasoactive drugs.

We report the results of a survey of 75 patients with erectile dysfunction, all of whom were treated by self-injection of the corpora cavernosa with vasoactive agents. At the time of the survey each patient had been self-injecting at home for at least 3 months. Of the patients 62 were followed for 3 to 21 months. Patients used this form of treatment with minimal assistance from our clinic staff. It was acceptable to them with few complications except for prolonged erections in 11 per cent of the men. Fifteen patients (24 per cent) with psychogenic impotence reported spontaneous improvement in erections during treatment and 4 discontinued treatment for this reason. Another 26 patients (42 per cent) continue to use self-injection as the definitive mode of treatment for erectile dysfunction.

Prolonged erections following intracorporeal injection of medications to overcome impotence.

We describe the management of 17 men who developed prolonged erections following the intracorporeal injection of vasoactive drugs (e.g. papaverine) for the treatment of erectile dysfunction. Twelve men who had psychogenic impotence developed prolonged erections following injection compared with 5 who had an organic aetiology. The aspiration of 20 to 50 ml of blood from the penis together with the intracorporeal injection of 1 to 2 mg metaraminol is an effective treatment of this complication.

Experience with the Nesbit procedure in the treatment of penile curvature.

Thirteen men who had undergone Nesbit's operation for penile curvature were assessed to determine the efficacy of the procedure. Ten patients had Peyronie's disease and three had a congenital curvature. Follow-up ranged from 8 months to 28 months. The degree of penile curvature was improved in twelve patients at the time of follow-up. The three men with a congenital curvature were all satisfied, whereas only seven of the 10 with Peyronie's disease were satisfied with the results of surgery. Two men believed that the operation had reduced their erectile function and a third man felt that the operation had not improved his penile deformity. Patients with a penile curvature associated with deteriorating erectile function should be counselled that a Nesbit's procedure will not improve their potency and that the insertion of a malleable penile prosthesis may be necessary.

The assessment of catheter-induced urethritis using an experimental dog model.

A new experimental model for the assessment of urethral catheters is described. Fifty catheters, comprising brands of latex, silicone, teflon-coated latex and polyvinylchloride (PVC) were assessed. The silicone, teflon-coated latex and PVC catheters were shown to cause minimal inflammatory change of the urethral mucosa, whereas the latex catheters showed variable and more marked changes. The model was simple to establish, and gave reproducible results.

Catheter-induced urethritis: a comparison between latex and silicone catheters in a prospective clinical trial.

A controlled randomised prospective study has been carried out on 100 male patients to compare the incidence of urethritis following catheterisation with either latex or silicone catheters. All patients underwent elective cardiac surgery and were catheterised for 48 h with antibiotic cover, and were followed up for 6 months post-operatively. Of those with latex catheters 22% developed urethritis, compared with 2% of those in the silicone catheter group. This difference is statistically significant (P less than 0.01). Two of the former patients developed a decreased urinary flow and both had tight anterior urethral strictures.

Primary linitis plastica carcinoma of urinary bladder.

Primary linitis plastica type carcinoma of the urinary bladder in a sixty-one-year-old man is described. Only 2 other cases have been reported in the English medical literature.

Impotence--the team approach to investigation and surgical treatment.

A multidisciplinary study group was established to assess impotent patients. One hundred and forty-eight patients were fully assessed and 25 potent volunteers underwent measurement of nocturnal penile tumescence (NPT). This report describes the selection process and results of surgical implantation of the American Medical Systems (AMS) inflatable and the Jonas silver-silicone prostheses.

The action of imipramine on the lower urinary tract of the dog.

Imipramine at 1 mg/kg body weight reduced contractions of the urethra and bladder produced in response to pelvic nerve stimulation by 58 and 56% in female anaesthetised dogs. Responses to injection into the internal iliac artery of acetylcholine, histamine and 5 hydroxytryptamine (5HT) were also reduced but those to ATP and noradrenaline were not altered. Atropine (0.1 mg/kg) blocked responses to acetylcholine and pelvic nerve stimulation but was without action on responses to ATP, histamine or 5HT. Mepyramine (1 mg/kg) but not metiamide (0.5 mg/kg) selectively blocked responses to histamine. The responses to pelvic nerve stimulation or acetylcholine were not altered. It was concluded that imipramine does not have significant anticholinergic action and is unlikely to block uptake of biogenic amines. The powerful inhibitory action on histamine responses could reduce the effects of circulating histamine but cannot explain the reduction of the nerve-induced response.