Long-term followup and selection criteria for penile revascularization in erectile failure

PURPOSE

We report the long-term results of penile revascularization surgery for erectile failure and suggest possible selection criteria for this controversial surgical procedure.

MATERIALS AND METHODS

In 7 years 62 impotent men who did not respond to pharmacotherapy underwent microsurgical penile revascularization and completed long-term followup evaluation in 41 months (range 18 to greater than 62) consisting of a detailed questionnaire, duplex sonography and optional pharmacotherapy or angiography. The Virag procedure was chosen for the first 7 patients, the original Hauri technique for the next 13 and the modified Mannheim triple anastomosis for 42.

RESULTS

Of all patients 34% achieved spontaneous and another 20% pharmacologically induced erections. Success in diabetics and older patients was lower (43% for diabetics, 39% for those older than 50 years at surgery), while it was high in men with less than 2 risk factors (58%) as well as in younger patients (69% for those up to 50 years old). Shunt patency was 92%. Complications such as glans hyperemia developed in 13% of patients, shunt thrombosis in 8% and inguinal hernias in 6.5%.

CONCLUSIONS

Patient selection is vital for the successful outcome of penile revascularization surgery. We adhere to strict selection criteria, such as patient age maximum of 50 years, less than 2 risk factors, no recent diabetes and termination of nicotine abuse. Penile revascularization surgery is highly indicated in this group of patients, especially since it is the only causal therapy for erectile failure.

Discovery of novel selective hypotensive vasopressin peptides that exhibit little or no functional interactions with known oxytocin/vasopressin receptors

1. Arginine-vasopressin (VP) has both vasoconstricting and vasodilating action. We report here the discovery of four novel selective hypotensive VP analogues: d(CH2)5[D-Tyr(Et)2,Arg3,Val4]AVP; d(CH2)5[D-Tyr(Et)2,Lys3,Val4]AVP and their iodinatable Tyr-NH2(9) analogues. 2. Bioassays in rats for activities characteristic of neurohypophysial peptides showed that the four VP peptides possessed little or no V1a, V2 or oxytocin (OT) receptor agonistic or antagonistic activities. 3. In anaesthetized rats, these peptides (0.05-0.10 mg kg(-1) i.v.) elicited a marked fall in arterial blood pressure. 4. Blockade of cholinoceptors, adrenoceptors and bradykinin B2 receptors, and inhibition of prostaglandin synthesis had little effect on their vasodepressor action. 5. Classical V1a, V2 and OT receptor antagonists did not block the vasodepressor response. 6. L-NAME, 0.2 mg kg(-1) min(-1), markedly suppressed the hypotensive response to ACh but not the vasodepressor response to the hypotensive VP peptides. However, the duration of the vasodepressor response was shortened. Very high doses of L-NAME attenuated both the vasodepressor response and the duration of action. 7. These findings indicate that the vasodepressor action of these VP peptides is independent of the peripheral autonomic, bradykinin and PG systems and is not mediated by the known classical OT/VP receptors. NO does not appear to have an important role in their vasodepressor action. 8. The discovery of these novel VP peptides could lead to the development of new tools for the investigation of the complex cardiovascular actions of VP and the introduction of a new class of hypotensive agents. The two iodinatable hypotensive VP peptides could be radiolabelled as potential markers for the localization of the receptor system involved.

[Vascular surgery, implant surgery and vacuum erectile aids. Review-overview-prospects of 3 therapy options in erectile dysfunction]

Vascular surgery or penile prosthesis implantation are the main surgical options for erectile dysfunction. In this category, penile revascularization is the only causal therapy for selected patients: males younger than 50 years of age at time of surgery, maximum of two risk factors, exclusion of diabetes mellitus. Long-term success decreased to 53% to 55% in comparison to first encouraging reports of 80% success. Venous surgery resulted in an even more distinct decline of success the longer the elapse of time after surgery. Long-term success dropped under 40%, leaving only a few indications for penile venous ligation. In contrast, penile prosthesis implantation results in high satisfaction rates. Despite this, it is not generally recommended as first choice surgical management as it is linked to irreversible damage of the cavernosal bodies. Among numerous types of penile implants, preference is nowadays mostly given to the three-piece hydraulic models. However, such complications as defective or perforated cylinders in up to 35% after 5 years have arisen, depending on the type of implant. In a selected patient group, vacuum constriction devices with a mean patient acceptance of 75% (50% to 90%) seldom result in complications and are thus considered to be a well-established therapeutical option.

Efficacy, safety, and effects on quality of life of salmeterol versus albuterol in patients with mild to moderate persistent asthma

BACKGROUND

Salmeterol xinafoate is a long-acting, highly selective, beta2-adrenergic agonist that produces bronchodilation and clinically significant improvement in pulmonary function for up to 12 hours in patients with asthma.

OBJECTIVE

To evaluate the impact on asthma-specific quality of life, efficacy, and safety of salmeterol versus albuterol in adult patients with mild-to-moderate persistent asthma.

METHODS

A randomized, double-blind, double-dummy, parallel-group, multicenter study was conducted in 539 adult asthma patients over 12 weeks. Patients were randomized to receive either salmeterol 42 microg via metered-dose inhaler twice daily or albuterol 180 microg four times daily. Upon entry into the study, 46% of patients were being treated with an inhaled corticosteroid and were allowed to continue treatment throughout the study. Pulmonary function and asthma symptoms were monitored daily, and patients completed the Asthma Quality of Life Questionnaire (AQLQ) at baseline and after 4, 8, and 12 weeks of treatment.

RESULTS

Treatment with salmeterol twice daily produced significantly greater improvements from baseline in all quality of life domain ("Activity Limitation," "Asthma Symptoms," "Emotional Function," "Environmental Exposure") scores and in the global AQLQ score at 12 weeks (P < or = .038) compared with albuterol treatment four times daily. Pulmonary function and asthma symptoms were also significantly improved with salmeterol compared with albuterol.

CONCLUSIONS

Salmeterol 42 microg administered twice daily is significantly more effective than albuterol 180 microg four times daily for improving asthma-specific quality of life, controlling asthma symptoms, and improving pulmonary function in patients with mild-to-moderate persistent asthma. Furthermore, those improvements were maintained over a 12-week period.

Inhibition of erythroid progenitor cells by anti-Kell antibodies in fetal alloimmune anemia

BACKGROUND

In alloimmune anemia of the newborn, the level of hemolysis caused by the presence of antibodies to antigens of the Kell blood-group system is less than that caused by antibodies to the D antigen of the Rh blood-group system, and the numbers of reticulocytes and normoblasts in the baby's circulation are inappropriately low for the degree of anemia. These findings suggest that sensitization to Kell antigens results in suppression of fetal erythropoiesis as well as hemolysis.

METHODS

We compared the growth in vitro of Kell-positive and Kell-negative hematopoietic progenitor cells from cord blood in the presence of human monoclonal anti-Kell antibodies and anti-D antibodies and serum from women with anti-Kell antibodies.

RESULTS

The growth of Kell-positive erythroid progenitor cells (erythroid burst-forming units and colony-forming units) from cord blood was markedly inhibited by monoclonal IgG and IgM anti-Kell antibodies in a dose-dependent fashion (range of concentrations, 0.2 to 20 percent), but monoclonal anti-D antibodies had no effect. The growth of these types of cells from Kell-negative cord blood was not affected by either type of antibody. Neither monoclonal anti-Kell antibodies nor monoclonal anti-D antibodies inhibited the growth of granulocyte or megakaryocyte progenitor cells from cord blood. Serum from 22 women with anti-Kell antibodies inhibited the growth of Kell-positive erythroid burst-forming units and colony-forming units but not of Kell-negative erythroid burst-forming units and colony-forming units (P<0.001 for the difference between groups). The maternal anti-Kell antibodies had no inhibitory effects on granulocyte-macrophage or mega-karyocyte progenitor cells from cord blood.

CONCLUSIONS

Anti-Kell antibodies specifically inhibit the growth of Kell-positive erythroid burst-forming units and colony-forming units, a finding that supports the hypothesis that these antibodies cause fetal anemia by suppressing erythropoiesis at the progenitor-cell level.

Tissue response to biomaterials used for staple-line reinforcement in lung resection: a comparison between expanded polytetrafluoroethylene and bovine pericardium

OBJECTIVE

A study in a canine model of lung-reduction surgery evaluated the tissue response to polytetrafluoroethylene (ePTFE) and bovine pericardium (BP) used for staple-line reinforcement.

METHODS

In each of ten dogs, BP was placed in one lung and ePTFE in the other. The implants were retrieved at 30, 95, or 167 days after implantation and studied histologically. The connective tissue covering the implants was measured and analysis of variance was used to compare results with the two materials.

RESULTS

At 30 days, the BP specimens showed focal chronic inflammation and thin tissue coverage, whereas the ePTFE specimens had no focal inflammation and thick tissue coverage. At 95 and 167 days, the inflammation in the BP specimens had resolved, but tissue coverage remained minimal, and there was no resorption of the BP. In the ePTFE specimens, tissue coverage had increased. Analysis of variance comparing representative tissue specimens showed that the tissue encapsulating the ePTFE was significantly thicker than that surrounding the BP (P < 0.0001). No air leaks, staple-line disruptions, or infections occurred in the study.

CONCLUSIONS

Neither ePTFE nor BP is resorbable. Both materials have been used successfully, without resultant infections, for clinical staple-line reinforcement. The more favorable tissue response to ePTFE observed in this study may have clinical ramifications. Comparative clinical studies of the two materials are needed.

Properties of a new radioiodinated antagonist for human vasopressin V2 and V1a receptors

A vasopressin receptor antagonist, [1-(beta-mercapto-beta,beta-pentamethylenepropionic acid), 2-o-ethyl-D-tyrosine, 4-valine, 9-tyrosylamide] arginine vasopressin (d(CH2)5[o-ethyl-D-Tyr2,Val4,Tyr-NH9(2)]AVP), has been prepared. This antagonist is a potent antiantidiuretic, antivasopressor and antioxytocic peptide with pA2 values of 7.69-7.94 and affinities of 1.12-11.0 nM. When radioiodinated at the phenyl moiety of the tyrosylamide residue at position 9, this peptide was demonstrated to bind to vasopressin V2 and V1a receptors with a dissociation constant of 0.22-0.75 nM. This ligand is a good tool for further studies on human vasopressin V2 receptor localization and characterization, when used in combination with a selective vasopressin V1a ligand.

Nosocomial infections in neonates receiving extracorporeal membrane oxygenation

OBJECTIVE

To determine the incidence of, and risk factors for, nosocomial infections in neonates during and after treatment with extracorporeal membrane oxygenation (ECMO).

DESIGN

A retrospective cohort study of all infants treated with ECMO during a 4-year period.

PATIENTS

26 neonates experiencing 32 nosocomial infections, and 54 neonates with no nosocomial infections.

SETTING

A large, urban children's hospital.

RESULTS

30% of neonates treated with ECMO experienced at least one nosocomial infection. The rate of nosocomial infections was 10.3 per 1,000 patient-days. Risk factors significantly associated with nosocomial infection included duration of ECMO > 7 days (mean, 12 vs 7 days; odds ratio [OR], 2.84; 95% confidence interval [CI95], 0.96-8.56); neonatal intensive care-unit stay > 21 days (mean, 44 vs 19 days; OR, 8.73; CI95, 2.49-31.94); hospitalization > 50 days (mean, 63 vs 29 days; OR, 5.44; CI95, 1.47-20.87); and surgical procedure before or during ECMO (46% vs 22%; OR, 4.58 CI95, 1.25 to 17.38).

CONCLUSIONS

Nosocomial infections occurred in 30% of patients undergoing ECMO. Although nosocomial infections were not associated with an increase in mortality, hospitalization was prolonged.

Position three in vasopressin antagonist tolerates conformationally restricted and aromatic amino acid substitutions: a striking contrast with vasopressin agonists

We report the solid-phase synthesis and some pharmacological properties of 12 position three modified analogues (peptides 1-12) of the potent non-selective antagonist of the antidiuretic (V2-receptor), vasopressor (V1a-receptor) responses to arginine vasopressin (AVP) and of the uterine contracting (OT-receptor) responses to oxytocin (OT), [1(-beta mercapto-beta,beta-pentamethylenepropionic acid)-2-O-ethyl-D-tyrosine 4-valine] arginine vasopressin [d(CH2)5D-Tyr(Et)2VAVP] (A) and two analogues of (B) (peptides 13,14), the 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid3 (Tic3) analogue of (A). Peptides 1-12 have the following substituents at position three in (A): (1) Pro; (2) Oic; (3) Atc; (4) D-Atc; (6) D-Phe; (7) Ile; (8) Leu; (9) Tyr; (10) Trp; (11) Hphe; (12) [HO]Tic; Peptide (13) is the Tyr-NH2(9) analogue of (B): Peptide (14) is the D-Cys(6) analogue of (B). All 14 new peptides were evaluated for agonistic and antagonistic activities in in vivo V2 and V1a assays and in vitro (no Mg2+)n oxytocic assays. With the exception of the D-Phe3 peptide (No. 6), which exhibits very weak V2 agonism (approximately 0.0017 U/mg), none of the remaining 13 peptides exhibit any agonistic activities in these assays. In striking contrast to their deleterious effects on agonistic activities in AVP, the Pro3, Oic3, Tyr3 and Hphe3 substitutions in (A) are very well tolerated, leading to excellent retention of V2, V1a and OT antagonistic potencies. All are more potent as V2 antagonists than the Ile3 and Leu3 analogues of (A). The Tyr-NH2(9) and D-Cys(6) substitutions in (B) are also well tolerated. The anti-V2 pA2 values of peptides 1-5 and 7-14 are as follows (1) 7.77 +/- 0.03; (2) 7.41 +/- 0.05; (3) 6.86 +/- 0.02; (4) 5.66 +/- 0.09; (5) approximately 5.2; (7) 7.25 +/- 0.08; (8) 6.82 +/- 0.06; (9) 7.58 +/- 0.05; (10) 7.61 +/- 0.08; (11) 7.59 +/- 0.07; (12) 7.20 +/- 0.05; (13) 7.57 +/- 0.1; (14) 7.52 +/- 0.06. All analogues antagonize the vasopressor responses to AVP, with anti-V1a pA2 values ranging from 5.62 to 7.64, and the in vitro responses to OT, with anti-OT pA2 values ranging from 5.79 to 7.94. With an anti-V2 potency of 7.77 +/- 0.03, the Pro3 analogue of (A) is surprisingly equipotent with (A), (anti-V2 pA2 = 7.81 +/- 0.07). These findings clearly indicate that position three in AVP V2/V1a antagonists, in contrast to position three in AVP agonists, is much more amenable to structural modification than had heretofore been anticipated. Furthermore, the surprising retention of V2 antagonism exhibited by the Pro3, Oic3, Tyr3, Trp3 and Hphe3 analogues of (A), together with the excellent retention of V2 antagonism by the Tyr-NH2(9) and D-Cys6 analogues of (B) are promising new leads to the design of potent and possibly orally active V2 antagonists for use as pharmacological tools and/or as radioiodinatable ligands and for development as potential therapeutic agents for the treatment of the hyponatremia caused by the syndrome of the inappropriate secretion of the antidiuretic hormone (SIADH).

The Genome Sequence DataBase version 1.0 (GSDB): from low pass sequences to complete genomes

The Genome Sequence DataBase (GSDB) has completed its conversion to an improved relational database. The new database, GSDB 1.0, is fully operational and publicly available. Data contributions, including both original sequence submissions and community annotation, are being accomplished through the use of a graphical client-server interface tool, the GSDB Annotator, and via GIO (GSDB Input/Output) files. Data retrieval services are being provided through a new Web Query Tool and direct SQL. All methods of data contribution and data retrieval fully support the new data types that have been incorporated into GSDB, including discontiguous sequences, multiple sequence alignments, and community annotation.

The role of oxytocin receptors and vasopressin V1a receptors in uterine contractions in rats: implications for tocolytic therapy with oxytocin antagonists

OBJECTIVE

The objective of the study was to determine in the rat model whether the uterotonic action of vasopressin is mediated by the vasopressin V1a receptor in the uterus, by the oxytocin receptor, or by both. The purpose is to assess whether the anti-V1a activity of oxytocin antagonists is a desirable pharmacologic property in tocolytic therapy for preterm labor.

STUDY DESIGN

Dose-response characteristics of the uterotonic action of oxytocin and arginine vasopressin were compared and analyzed by the in vitro cumulative dose-response curve technique. A nonselective oxytocin-V1a receptor antagonist, a selective oxytocin receptor antagonist, and a selective V1a receptor antagonist were selected for this study. Their relative effectiveness in inhibiting the uterine contractile responses induced by oxytocin and by arginine vasopressin in the isolated rat uterus was examined.

RESULTS

The uterotonic dose-response curves for oxytocin and arginine vasopressin were parallel and had the same maximal response. The nonselective oxytocin/V1a receptor antagonist and the selective oxytocin receptor antagonist were equally potent in inhibiting the uterine contractions induced by either oxytocin or arginine vasopressin, whereas the selective V1a receptor antagonist had no antiuterotonic activity. Inhibition by the selective oxytocin antagonist caused a similar parallel shift to the right of the dose-response curves for oxytocin and arginine vasopressin.

CONCLUSIONS

The parallel dose-response curves for oxytocin and arginine vasopressin suggest that the uterotonic action of vasopressin is also mediated by the oxytocin receptor. Arginine vasopressin binds to both oxytocin and V1a receptors in the uterus, but the activation of V1a receptors appears not to be a mechanism involved in the uterine-stimulating action of vasopressin. The anti-V1a activity of oxytocin antagonists does not contribute to tocolytic efficacy and may represent an undesirable side effect. By blocking the vascular V1a receptors, it may compromise the patient's ability to maintain arterial blood pressure during hemorrhage.

Isosteric substitution of Asn5 in antagonists of oxytocin and vasopressin leads to highly selective and potent oxytocin and V1a receptor antagonists: new approaches for the design of potential tocolytics for preterm labor

Substitution of Asn5 in oxytocin (OT) or vasopressin (VP) invariably leads to a dramatic loss of the biological activities of the peptides. Because of this observation, few structure-activity-relationship studies of OT and VP peptides have involved modifications in the 5 position. It is now recognized that peptide agonists and antagonists may use different structural and conformational features in their interactions with the receptors. Our prior studies showed that OT and VP antagonists, unlike the agonists, tolerate amino acid substitutions in the 5 position. This opens new approaches for the design of antagonists. We describe the effects of isosteric replacement of Asn5 by diaminopropionic acid (Dap) or diaminobutyric acid (Dab) in three OT and VP antagonists: (1) the V1a (vasopressor receptor) antagonist d(CH2)5[Tyr(Me)2]AVP; (2) the OT (uterine OT receptor) antagonist d(CH2)5[Tyr(Me)2, Thr4, Tyr-NH29] OVT and (3) three selective OT antagonists, desGly-NH2,d(CH2)5[D-Tyr2, Thr4]OVT, desGly-NH2, d(CH2)5[D-Phe2, Thr4]OVT and desGly-NH2, d(CH2)5- [D-Trp2, Thr4]OVT. The Dap5 and Dab5 substitutions were tolerated remarkably well, with the less isosteric Dap5 substitution leading to a greater retention of anti-OT potency than the Dab5 substitution. Furthermore, the Dap5 and Dab5 and OT and VP antagonist analogues were surprisingly shown to be much more selective than their respective parent compounds. The Dab5 analogue of (1) was devoid of anti-OT activity. The three Dap5 analogues of (3) were devoid of anti-V1a activities. These appear to be the first single-receptor-type-selective OT and VP antagonists discovered to date. These findings could provide new leads for the development of single-receptor-type-selective receptor probes for the localization and characterization of OT and VP receptors and potential selective tocolytics for the treatment of premature labor.

The Genome Sequence DataBase (GSDB): meeting the challenge of genomic sequencing

The genome sequence database (GSDB) is a complete, publicly available relational database of DNA sequences and annotation maintained by the National Center for Genome Resources (NCGR) under a Cooperative Agreement with the US Department of Energy (DOE). GSDB provides direct, client- server access to the database for data contributions, community annotation and SQL queries. The GSDB Annotator, a multi-platform graphic user interface, is freely available. Automatically updated relational replicates of GSDB are also freely available.

Evidence for cell-specific differences in transformation by N-, H- and K-ras

Although Ras plays a fundamental role in cellular proliferation, differentiation and transformation, clear functional differences between the three major Ras proteins (N-, H- and K-Ras) have not as yet been demonstrated. In this study, chimeric constructs were used to compare directly transformation by N-, H- and K-ras oncogenes. In Rat-2 and NIH3T3 fibroblasts, transformation assays (anchorage independence, focus-formation and growth in 1% FCS) showed that H12-Ras was more transforming than N12-Ras or K12-Ras. By contrast, in the human multipotent haemopoietic cell line, TF-1, N12-Ras exhibited greater biological activity. Northern blotting and protein analyses indicated that these findings were not the result of differences in expression or stability of p21Ras. Using further H-ras/N-ras chimeric constructs, we found that the greater transforming activity of H12-Ras in fibroblasts was not due to the hypervariable-CAAX region, but rather to unique sequences between amino acids 84 and 143. These data demonstrate cell specific differences in the intrinsic transforming potential of N-ras, H-ras and K-ras oncogenes.

Design and synthesis of highly selective in vitro and in vivo uterine receptor antagonists of oxytocin: comparisons with Atosiban

We report the solid phase synthesis and some pharmacological properties of seven position two analogues (peptides 1-7) of one of our lead oxytocin antagonists, des-9-glycinamide[1-(beta-mercapto-beta,beta-pentamethylenepropionic+ ++ acid),2-O-methyltyrosine,4-threonine]ornithinevasotocin(desGly+ ++-NH2, d(CH2)5-[Tyr(Me)2,Thr4]OVT) (A). Peptides 1-7 have the following substituents at position two (1) D-Tyr(Me); (2) L-Tyr(Et); (3) D-Tyr(Et); (4) L-Tyr; (5) D-Tyr; (6) D-Phe and (7) D-Trp. These were evaluated for agonistic and antagonistic activities in in vitro and in vivo OT assays, in vivo vasopressor (V1a-receptor) assays and in vivo antidiuretic (V2-receptor) assays. None of the seven peptides exhibits oxytocic or vasopressor agonism. Peptides 1, 2, 4, 6 and 7 are extremely weak V2 agonists (V2 activities range from 0.001 to 0.02 U/mg). Peptides 3 and 5 exhibit weak V2 antagonism (pA2 < 6.0 and < 5.5, respectively). Peptides 1-7 exhibit potent in vitro (no Mg2+) OT antagonism (anti-OT pA2 values range from 7.66 to 8.03). Peptides 1 and 4-7 exhibit potent in vivo OT antagonism. Estimated in vivo anti-OT pA2 values range from 7.06 to 7.79 (peptides 2 and 3 were not tested). With anti-V1a pA2 values of 5.17-6.25 all seven peptides exhibit reduced anti-V1a potencies relative to the parent peptide (A) (anti-V1a pA2 = 6.46). Four of these peptides (4-7) exhibit striking gains in in vitro and in vivo anti-OT/anti-V1a selectivities compared to (A) which has an in vitro selectivity of 30 and an in vivo selectivity of 18. The D-Tyr2 (5), D-Trp2 (7), D-Phe2 (6) and L-Tyr2 (4) analogues of (A) exhibit anti-OT (in vitro)/anti-V1a selectivities = 240, 390, 404 and 540, respectively. The L-Tyr2 (4), D-Trp2 (7), D-Phe2 (6) and D-Tyr2 (5) analogues exhibited anti-OT (in vivo)/anti-V1a selectivities of 72, 80, 88 and 95, respectively. Peptides 4-7 appear to be the most selective peptide OT antagonists reported to date. In this regard it may be noted that they appear to be as or more potent and much more selective than the closely related OT antagonist 1-deamino[D-Tyr(Et)2,Thr4]OVT (Atosiban) which is currently undergoing clinical trial as a potential therapeutic agent for the prevention of premature labor. Atosiban (peptide 8) was resynthesized and pharmacologically evaluated in our laboratories. Atosiban exhibits the following antagonistic potencies. Anti-OT (in vitro, no Mg2+) pA2 = 7.71; anti-OT in vivo pA2 = 7.05; anti-V1a pA2 = 6.14 and anti-V2 pA2 approximately 5.9. Its anti-OT (in vivo)/anti-V1a selectivity is 8. Some of these antagonists may be suitable candidates for evaluation as potential tocolytic agents for use in the treatment of pre-term labor. They could also serve as useful new pharmacological tools for studies on the physiological roles of oxytocin. Finally, the findings presented here provide useful clues for the design of more potent and more selective OT antagonists.

Characterization of a novel, linear radioiodinated vasopressin antagonist: an excellent radioligand for vasopressin V1a receptors

We report on the pharmacological properties of a potent and selective linear vasopressin (AVP) V1a receptor antagonist HO-Phenylacetyl1-D-Tyr(Me)2-Phe3-Gln4-Asn5-Arg6-Pro7-Arg8-NH2 (HO-LVA). Iodinated on the phenolic substituent at position 1, [125I]-HO-LVA displayed the highest affinity for rat liver V1a receptors (8 pM) ever reported. Furthermore, affinities of HO-LVA and I-HO-LVA for V1b, V2 and oxytocin (OT) receptors was 400- to 1,000-fold lower than for V1a receptors, rendering it a highly selective ligand. Both HO-LVA and its iodinated derivative are V1 antagonists, they potently inhibited AVP-induced inositol-phosphate accumulation in WRK1 cells, and also, although with a much lower potency, the AVP-induced ACTH release from freshly prepared pituitary cells. Using autoradiography [125I]-HO-LVA appeared to be the first radioligand to successfully identify and localize the presence of V1a receptors in rat liver and blood vessel walls. Moreover, several new brain regions expressing V1a receptors could be identified, in addition to those brain regions that were previously identified with other radiolabelled AVP analogues.

Tyr115 is the key residue for determining agonist selectivity in the V1a vasopressin receptor

Using a three-dimensional model of G protein-coupled receptors (GPCR), we have previously succeeded in docking the neurohypophysial hormone arginine-vasopressin (AVP) into the V1a receptor. According to this model, the hormone is completely embedded in the transmembrane part of the receptor. Only the side chain of the Arg residue at position 8 projects outside the transmembrane core of the receptor and possibly interacts with a Tyr residue located in the first extracellular loop at position 115. Residue 8 varies in the two natural neurohypophysial hormones, AVP and oxytocin (OT); similarly, different residues are present at position 115 in the different members of the AVP/OT receptor family. Here we show that Arg8 is crucial for high affinity binding of AVP to the rat V1a receptor. Moreover, when Tyr115 is replaced by an Asp and a Phe, the amino acids naturally occurring in the V2 and in the OT receptor subtypes, the agonist selectivity of the V1a receptor switches accordingly. Our results indicate that the interaction between peptide residue 8 and the receptor residue at position 115 is not only crucial for agonist high affinity binding but also for receptor selectivity.

Effects of a D-Cys6/L-Cys6 interchange in nonselective and selective vasopressin and oxytocin antagonists

We report the solid-phase synthesis of the D-Cys6 analogues of arginine-vasopressin (AVP), peptide 1, of the selective AVP vasopressor (V1a receptor) antagonist [1-(beta-mercapto-beta,beta-pentamethylenepropionic acid),2-O-methyltyrosine]arginine-vasopressin (d(CH2)5[Tyr(Me)2]-AVP, (A)), peptide 2, of the three nonselective antidiuretic/vasopressor (V2/V1a receptor) AVP antagonists d(CH2)5[Tyr(Et)2]VAVP (B), d(CH2)5[D-Tyr(Et)2]VAVP (C), and d(CH2)5[D-Phe2]VAVP (D) (where V = Val4), peptides 3-5, of the nonselective oxytocin (OT) antagonists d(CH2)5-[Tyr(Me)2]OVT (E) and d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]OVT (F) (where OVT = ornithine-vasotocin), peptides 6 and 7, and of the selective OT antagonists desGly-NH2,d(CH2)5[Tyr(Me)2,Thr4]OVT (G) and d(CH2)5]D-Trp2,Thr4]OVT (H), peptides 8 and 9. We also present the repeat syntheses of the previously reported d(CH2)5[D-Trp2]AVT (peptide 10) and its D-Cys6 analogue (peptide 11) (where AVT = arginine-vasotocin). Peptides 1-11 were assayed for agonistic and antagonistic activities in in vivo V1a, V2, and oxytocic assays and in in vitro oxytocic assays without and with 0.5 mM Mg2+. With V2 and V1a agonistic potencies of 0.82 and 0.41 units/mg, [D-Cys6]AVP has retained less than 0.3% of the V2 and V1a potencies of AVP. It exhibits no oxytocic activity and is an in vitro OT antagonist. pA2 = 6.67 (no Mg2+); pA2 = 5.24 (0.5 mM Mg2+). By contrast, with one or two exceptions, a D-Cys6/L-Cys6 interchange in antagonists 2-9, although resulting in reductions of antagonistic potencies in all assays for virtually all peptides 2-9 relative to A-H, has been well tolerated. For peptides 2-5, the anti-V2 and anti-V1a pA2 values range from approximately 5.54 to 7.33 and from 7.19 to 8.06, respectively; the range of in vitro anti-OT pA2 values (no Mg2+) is 7.35-7.87; with 0.5 mM Mg2+, the range is 7.24-8.21. Peptides 2 and 4 have in vivo anti-OT pA2s = 6.60 and 7.16, respectively. For peptides 6-9, the range of in vitro anti-OT pA2 values (no Mg2+) is 7.65-7.96; with 0.5 mM Mg2+, the range is 7.41-7.65, and the in vivo anti-OT pA2 values range from 6.85 to 7.33. With an in vivo anti-OT pA2 = 7.33, peptide 6 is equipotent with its parent E. The in vivo anti-OT potencies of peptides 7-9 are significantly reduced relative to those of F-H. The in vitro anti-OT (0.5 mM Mg2+) pA2 values of 10 and 11 are 7.54 and 7.50, both significantly lower than those previously reported.(ABSTRACT TRUNCATED AT 400 WORDS)

The clinical introduction of a third generation lithotriptor: Modulith SL 20

The Modulith SL 20* was designed as a third generation lithotriptor with outstanding disintegrative efficacy in vitro, and equipped with a combined fluoroscopic and ultrasound localization system integrated in a multifunctional table. Its introduction to clinical extracorporeal shock wave lithotripsy took place in 3 phases. In phase 1 (49 patients) only in line ultrasound localization was possible. The many caliceal stones were adequately disintegrated with restricted generator voltage. In phase 2 (81 patients) fluoroscopic localization with the virtual focus of an adapted x-ray C-arm unit enabled in situ lithotripsy of ureteral stones in 33% of all patients. Phase 3 (549 patients) was characterized by additionally increasing the generator voltage to 20 kv. This development of the lithotriptor by improving the localization system and shock wave energy resulted in the possibility for successful disintegration of stones in the entire upper urinary tract (including the complete ureter), decreased treatment time (52 to 39 minutes) and an improved efficiency quotient (0.45 to 0.67). During phase 3 auxiliary measures were performed before lithotripsy in 24% of the cases. After 1.8% of the treatments minor or moderate perirenal fluid collection or bleeding was detected by routine followup sonography. A 91% stone-free rate was achieved with only 9.3% curative auxiliary measures after extracorporeal shock wave lithotripsy, including a 23% retreatment rate. Thus, the Modulith device had a high efficacy quotient compared with other lithotriptors.