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Biomedical subjects

R B Moreland

Publications and source records attributed to R B Moreland.

At least 19 recordsLinked to original sources
PubMed2002

Rationale for combination therapy of intraurethral prostaglandin E(1) and sildenafil in the salvage of erectile dysfunction patients desiring noninvasive therapy.

Corpus cavernosum smooth muscle relaxation and hence penile erection are regulated in part by increases in smooth muscle synthesis of the second messengers cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). The object of this study was to determine 30-month follow-up results in motivated patients desiring noninvasive medical therapy using sildenafil citrate (Viagra) in combination with intraurethral prostaglandin E(1) (PGE(1)) (Medicated Urethral System for Erection [MUSE]). Twenty-eight patients (mean +/- s.d. age, 59 +/-7.3 y; 17 who had undergone radical prostatectomy and 11 who had a diagnosis of organic erectile dysfunction) were included in this study. Detailed history taking and physical examinations were performed and vascular risk factors noted. In these patients, treatment with either 100 mg of sildenafil citrate and/or 1000 microg of MUSE had failed. None of these patients desired intracavernosal injection. Duplex Doppler ultrasonography after redosing was carried out on all patients. Dynamic infusion corpus cavernosography/cavernosometry was obtained in 17 of 28 patients, and combination therapy was initiated using 100 mg of sildenafil citrate orally 60 min before intercourse and 500 microg of MUSE intraurethrally immediately before intercourse. Independently, either 100 mg of sildenafil citrate or 1000 microg of MUSE was not efficacious in inducing an erection sufficient for vaginal penetration in any of the 28 patients. After initiating a combination therapy, at 30 months, all 28 patients were reporting erections sufficient for vaginal penetration, with 3.6 intercourse episodes per month. None of the patients crossed over to intracavernosal therapy or penile prosthesis. During therapy, eight of 28 patients reduced the dose of sildenafil citrate to 50 mg. Combination therapy with MUSE and sildenafil may be more efficacious in the salvage of patients who desire noninvasive therapy but in whom single-treatment modalities fail. Although both cAMP- and cGMP-mediated vasodilation can lead to penile erection, combining therapies that incorporate both pathways may succeed when single therapies fail.

Aged↗
PubMed2002

Activators of soluble guanylate cyclase for the treatment of male erectile dysfunction.

Soluble guanylate cyclase (sGC) is an important enzyme in corpus cavernosum smooth muscle cells as it is one of the regulators of the synthesis of cGMP. The efficacy of sildenafil (Viagra) in the treatment of male erectile dysfunction indicates the importance of the cGMP system in the erectile response as the increased levels of cGMP induce relaxation of the corpus cavernosum. sGC is physiologically activated by nitric oxide (NO) during sexual stimulation, and its activity can be pharmacologically enhanced by several NO-donors. Agents like YC-1 can also activate sGC after binding to a novel allosteric site in the enzyme, a site different from the NO binding site. YC-1 can relax rabbit cavernosal tissue and it facilitates penile erection in vivo. This review summarizes the enzymology, biochemistry and pharmacology of this novel allosteric site and its relevance for the regulation of penile function. This type of sGC activators represent a new class of compounds with a different pharmacological profile in comparison to the classical NO-donors and they could be beneficial for the treatment of male erectile dysfunction.

Allosteric Site↗
PubMed2002

Activation of soluble guanylate cyclase causes relaxation of corpus cavernosum tissue: synergism of nitric oxide and YC-1.

Nitric oxide (NO) activates corpus cavernosum smooth muscle soluble guanylate cyclase (sGC) and increases the synthesis of cGMP that results in smooth muscle relaxation and ultimately, penile erection. To characterize sGC and define the potential synergy between NO and the allosteric activator YC-1 in corpus cavernosum, rat sGC was activated by either sodium nitroprusside (SNP) or YC-1, and YC-1 potentiated the effects of SNP with a 200-fold activation of sGC. Both SNP and YC-1 decreased the Km and increased the Vmax. ODQ significantly inhibited sGC activated by SNP with IC50 of 0.5 nM, but did not affect the sGC activated by YC-1 as well as basal sGC activity. SNP and YC-1 synergistically increased intracellular cGMP levels in rabbit corpus cavernosum smooth muscle cell cultures. YC-1 significantly relaxed rabbit cavernosum tissue strips in organ baths with an EC50 of 8.4 microM. In the presence of L-nitroarginine methyl ester to block endogenous NO production, co-administration of SNP shifted the dose response of YC-1 to the left, showing the synergism of SNP and YC-1 in tissue strips. In view of the clinical efficacy of phosphodiesterase-5 inhibitors, activation of sGC may provide an alternative means for enhancing the activity of neurally derived NO during sexual stimulation in the corpus cavernosum, representing a novel approach for the treatment of erectile dysfunction.

Animals↗
PubMed2002

Pathophysiology of Peyronie's disease.

Peyronie's disease is an inflammatory condition characterized by the formation of fibrous, noncompliant nodules in the tunica albuginea which can impede tunical expansion during penile erection, leading to deformity and bending. While the cause of this disease is thought to be due to microvascular trauma and abnormal wound healing, other hypotheses include genetic predisposition. In this review the pathophysiology of Peyronie's disease is discussed as well as current hypotheses regarding its origin.

Blood Vessels↗
PubMed2002

Expression of functional prostaglandin D (DP) receptors in human corpus cavernosum smooth muscle.

Prostaglandin D(2) (PGD(2)) binds to specific G-protein coupled receptors (DP) and induces smooth muscle relaxation by stimulating the synthesis of intracellular cAMP. In this study, we examined the role of PGD(2) and DP receptors in regulating human penile smooth muscle contractility. We determined that human corpus cavernosum tissue and smooth muscle cells in culture expressed functional DP receptor and lipocalin-like prostaglandin D synthase by reverse-transcribed polymerase chain reaction (RT-PCR). Functional PGD synthase activity was confirmed by the synthesis of PGD(2) in human corpus cavernosum smooth muscle cells upon addition of exogenous arachidonic acid. Organ bath preparations of human corpus cavernosum tissue strips, contracted with phenylephrine, relaxed in a dose-dependent fashion to either PGD(2) or the DP selective agonist BW245C. Cultures of human corpus cavernosum smooth muscle cells treated with BW245C showed a two-fold increase in cAMP synthesis. These data are consistent with the expression of functional DP receptors in human corpus cavernosum. This suggests the presence of an intact prostanoid autocrine system that may play a role in regulating penile erectile function.

Bridged Bicyclo Compounds, Heterocyclic↗
PubMed2001

Immunodetection of nmt55/p54nrb isoforms in human breast cancer.

BACKGROUND: We previously identified and characterized a novel 55 kDa nuclear protein, termed nmt55/p54nrb, whose expression was decreased in a subset of human breast tumors. The objective of this study was to determine if this reduced expression in human breast tumors was attributed to the regulation of mRNA transcription or the presence of altered forms of this protein. RESULTS: Northern blot analysis and ribonuclease protection assay indicated that nmt55/p54nrb mRNA is expressed at varying levels in estrogen receptor positive (ER+) and estrogen receptor negative (ER-) human breast tumors suggesting that reduced expression of nmt55/p54nrb protein in ER- tumors was not due to transcriptional regulation. To determine if multiple protein isoforms are expressed in breast cancer, we utilized Western blot and immunohistochemical analyses, which revealed the expression of an nmt55/p54nrb protein isoform in a subset of ER+ tumors. This subset of ER+ human breast tumors expressed an altered form of nmt55/p54nrb that was undetectable with an amino-terminal specific antibody suggesting that this isoform contains alterations or modifications within the amino terminal domain. CONCLUSIONS: Our study indicates that nmt55/p54nrb protein is post-transcriptionally regulated in human breast tumors leading to reduced expression in ER- tumors and the expression of an amino terminal altered isoform in a subset of ER+ tumors. The potential involvement of nmt55/p54nrb in RNA binding and pre-mRNA splicing may be important for normal cell growth and function; thus, loss or alteration of protein structure may contribute to tumor growth and progression.

Adenocarcinoma↗
PubMed2001

Neurologic erectile dysfunction.

Neurologic erectile dysfunction presents a diagnostic and treatment challenge to the internist and urologist. Multiple chronic disease modalities and traumatic etiologies exist. Education regarding these conditions and a detailed and thorough history and office work-up are the best resources for the clinician. Treatment can follow the model of proceeding from the least to most invasive procedure (process of care), taking into account patient and partner satisfaction. Because the psychology of grief and loss may enter into treatment of some neurologic conditions (e.g., erectile dysfunction after radical retropubic prostatectomy, spinal cord injury, or chronic diseases), a whole-patient approach encompassing psychotherapy is warranted.

Chronic Disease↗
PubMed2001

Hypoxia-activated ligand HAL-1/13 is lupus autoantigen Ku80 and mediates lymphoid cell adhesion in vitro.

Hypoxia is known to induce extravasation of lymphocytes and leukocytes during ischemic injury and increase the metastatic potential of malignant lymphoid cells. We have recently identified a new adhesion molecule, hypoxia-activated ligand-1/13 (HAL-1/13), that mediates the hypoxia-induced increases in lymphocyte and neutrophil adhesion to endothelium and hypoxia-mediated invasion of endothelial cell monolayers by tumor cells. In this report, we used expression cloning to identify this molecule as the lupus antigen and DNA-dependent protein kinase-associated nuclear protein, Ku80. The HAL-1/13-Ku80 antigen is present on the surface of leukemic and solid tumor cell lines, including T and B lymphomas, myeloid leukemias, neuroblastoma, rhabdomyosarcoma, and breast carcinoma cells. Transfection and ectopic expression of HAL-1/13-Ku80 on (murine) NIH/3T3 fibroblasts confers the ability of these normally nonadhesive cells to bind to a variety of human lymphoid cell lines. This adhesion can be specifically blocked by HAL-1/13 or Ku80-neutralizing antibodies. Loss of expression variants of these transfectants simultaneously lost their adhesive properties toward human lymphoid cells. Hypoxic exposure of tumor cell lines resulted in upregulation of HAL-1/13-Ku80 expression at the cell surface, mediated by redistribution of the antigen from the nucleus. These studies indicate that the HAL-1/13-Ku80 molecule may mediate, in part, the hypoxia-induced adhesion of lymphocytes, leukocytes, and tumor cells.

3T3 Cells↗
PubMed2001

O2-dependent prostanoid synthesis activates functional PGE receptors on corpus cavernosum smooth muscle.

We have previously demonstrated that decreased O2 tension inhibits prostaglandin synthesis from human corpus cavernosum smooth muscle cells in static culture over 8-18 h (R. B. Moreland et al., Molecular Urology 2: 41-47, 1998). In this report, an experimental system was designed that allowed determination of the effects of O2 tension changes over the time frame of physiological penile erection. Human corpus cavernosum smooth muscle cells were cultured on microcarrier beads in enclosed stirrer flasks so that rapid changes of O2 tension could be modulated. After 18 h of equilibration at 30-40 mmHg to simulate blood PO2 at penile flaccidity, O2 tension was increased to 100 mmHg for 1 h and then returned to 30-40 mmHg. Media samples were withdrawn for prostanoid synthesis and cell samples were taken for cAMP determinations. After 18 h of 30-40 mmHg PO2 values, prostanoid synthesis by human corpus cavernosum smooth muscle cells was low (0.1-0.7 pmol/10(6) cells). When PO2 was increased to 100 mmHg, a rapid increase in PGE2 >> PGF2alpha > PGD2 was observed (thromboxane A2 was undetectable), which peaked at 5.7 pmol PGE2/10(6) cells. Increased O2 tension correlated with increased PGE2 and increased intracellular synthesis of cAMP. The prostaglandin G/H synthase inhibitor indomethacin or the E prostanoid (EP2)-selective antagonist AH-6809 each inhibited the O2-tension-dependent increases in cAMP. These data support a role of differential O2 tension in the penis in the smooth muscle synthesis of PGE2, which in turn increases cAMP synthesis via EP2 receptors.

Autocrine Communication↗
PubMed2001

Corporeal structural and vascular micro architecture with X-ray micro computerized tomography in normal and diabetic rabbits: histopathological correlation.

PURPOSE: The pathophysiology of diabetes mellitus induced erectile dysfunction is poorly understood. In patients with diffuse venous leakage structural changes in the corpora cavernosa have correlated with failure of the veno-occlusive mechanism. Three-dimensional (D) micro computerized tomography (CT) has proved to be an important imaging technique for the intact kidney, heart, liver and bone. We examined control and diabetic rabbit penises by 3-D micro CT and quantified any structural changes. MATERIALS AND METHODS: Male white New Zealand rabbits were treated with alloxan to induce diabetes or used as normal controls. Via aortic access at laparotomy the penile vascular tree was vasodilated with papaverine and perfused with radiopaque silicone rubber. X-ray micro CT was then performed at 21 microm. resolution and images were analyzed in 3-D using custom software. RESULTS: Nine diabetic rabbits with blood glucose greater than 400 mg./dl. and 9 control animals were used for micro CT analysis. Significant decreases (p <0.05) were observed in the mean sinusoidal and vascular volume fraction plus or minus standard error of mean of the corpus cavernosum in the diabetic (323.7 +/- 43.1 mm.3 and 37.9 +/- 2.0%, respectively) and control (510.1 +/- 47.4 mm.3 and 53.1 +/- 3.80%, respectively) groups. Also, the mean left and right cavernous artery luminal cross-sectional area in diabetics (0.15 +/- 0.02 and 0.16 +/- 0.01 mm.2, respectively) versus controls (0.2 +/- 0.01 and 0.2 +/- 0.01 mm.2, respectively) was significantly decreased (p <0.05). Furthermore, the mean left and right total cavernous artery luminal volume in diabetics (0.4 +/- 0.07 and 0.4 +/- 0.09 mm.3, respectively) versus controls (1.0 +/- 0.13 and 0.9 +/- 0.11 mm.3, respectively) was significantly decreased (p <0.05). CONCLUSIONS: Diabetic rabbit penises showed a significant decrease in corporeal vascular volume as well as decreased cavernous artery diameter and luminal volume compared to controls. This finding correlated well with the mean decrease in trabecular smooth muscle in control and severely diabetic rabbits on histopathological studies (42.2% +/- 1.5% versus 35.8% +/- 1.5%). This combination of potential arterial insufficiency as well as an increase in diffuse connective tissue may contribute to the overall pathophysiology of diabetic erectile dysfunction. These results suggest that 3-D x-ray micro CT with molecular analysis may be a powerful tool for examining the pathophysiology of diabetic erectile dysfunction.

Angiography↗
PubMed2000

Cross-regulation of intracellular cGMP and cAMP in cultured human corpus cavernosum smooth muscle cells.

The goal of this study was to assess the potential cross-regulation of cyclic nucleotides in human corpus cavernosum (HCC). Incubation of primary cultures of HCC smooth muscle cells with either the NO donor sodium nitroprusside (SNP, 10 microM) or the phosphodiesterase type 5 (PDE 5) inhibitor sildenafil (50 nM) produced little or no changes in the intracellular cGMP levels. Incubation with both SNP and sildenafil produced marked increases in cGMP. Interestingly, incubation of cells with 10 microM of forskolin or PGE(1) produced significant enhancement of cGMP accumulation. These increases were not further enhanced by the addition of SNP and sildenafil. Kinetic analyses of cGMP hydrolysis by PDE 5 showed that high concentrations of cAMP reversibly inhibited the enzyme with a K(i) of 258 +/- 54 microM. The increase in cGMP levels in response to cAMP generating agents is not due to assay artifact since cAMP did not cross-react with cGMP antibody. Our data suggest that cAMP up-regulates intracellular levels of cGMP, in part, by inhibition of PDE 5. We also noted that cGMP down-regulates cAMP synthesis via a mechanism requiring G-protein coupling of adenylyl cyclase. These observations may have important implications in the utility of pharmacotherapeutic agents targeting cyclic nucleotide metabolism for the treatment of erectile dysfunction.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2000

Misoprostol induces relaxation of human corpus cavernosum smooth muscle: comparison to prostaglandin E1.

Prostaglandin E1 (PGE1) relaxes trabecular smooth muscle by interacting with specific G-protein coupled receptors on human corpus cavernosum smooth muscle and increasing intracellular synthesis of cAMP. Misoprostol (Cytotec), is an oral prostaglandin E analogue. The purpose of this study was to compare the functional activity of misoprostol with PGE1 in human corpus cavernosum and cultured human corpus cavernosum smooth muscle cells. Misoprostol, misoprostol free acid or PGE1 induced dose-dependent relaxations in strips of human corpus cavernosum. At concentrations greater than 10(-6) M, tissue recontraction was observed with all three agents. This was abrogated by pretreatment with the thromboxane A2 receptor antagonist SQ29,548. From these observations, we conclude that misoprostol is activated by human corpus cavernosum in situ and relaxes phenylephrine-precontrated tissue strips in vitro. This relaxation response is mediated by the increased cAMP synthesis by these agents.

Alprostadil↗
PubMed2000

Alpha-adrenergic receptor blockade by phentolamine increases the efficacy of vasodilators in penile corpus cavernosum.

Penile trabecular smooth muscle tone, a major determinant of erectile function, is highly regulated by numerous inter- and intracellular pathways. The interaction between pathways mediating contraction and relaxation has not been studied in detail. To this end, we investigated the functional effects of alpha adrenergic receptor blockade with phentolamine and its interaction with vasodilators (sildenafil, vasoactive intestinal polypeptide (VIP) and PGE1) that elevate cyclic nucleotides on penile cavernosal smooth muscle contractility. In organ bath preparations of cavernosal tissue strips contracted with phenylephrine, phentolamine significantly enhanced relaxation induced by sildenafil, VIP and PGE1. Sildenafil, VIP or PGE1 also significantly enhanced relaxation induced by phentolamine in cavernosal tissue strips contracted with phenylephrine. To study the effects of alpha adrenergic receptor blockade and modification of cyclic nucleotide metabolism during active neurogenic input, cavernosal tissue strips in organ bath preparations were contracted with the non-adrenergic agonist endothelin-1 and subjected to electrical field stimulation (EFS) in the absence or presence of phentolamine and/or sildenafil. EFS (5-40Hz) typically caused biphasic relaxation and contraction responses. Phentolamine alone enhanced relaxation and reduced or prevented contraction to EFS. Sildenafil enhanced relaxation to EFS at lower frequencies (< or = 5 Hz). The combination of phentolamine and sildenafil enhanced EFS-induced relaxation at all frequencies tested. EFS, in the presence of 10 nM phentolamine and 30 nM sildenafil, produced enhanced relaxation responses which were quantitatively similar to those obtained in the presence of 50 nM sildenafil alone. Thus, blockade of alpha-adrenergic receptors with phentolamine increases the efficacy of cyclic nucleotide-dependent vasodilators. Furthermore, phentolamine potentiates relaxation and attenuates contraction in response to endogenous neurotransmitters which are released during EFS. These findings suggest that antagonism of alpha-adrenergic signaling enables other independent relaxatory pathways to predominate within penile trabecular smooth muscle.

Adrenergic alpha-Antagonists↗
PubMed2000

Pathophysiology of erectile dysfunction: the contributions of trabecular structure to function and the role of functional antagonism.

Erectile dysfunction (ED) is estimated to impact more than 150 million men this year worldwide. An understanding of the pathophysiology of ED both furthers the basic scientific knowledge of disease processes and provides a rational design of pharmacotherapy. At present, there are two major views regarding the pathophysiology of ED. In the first hypothesis, the oxygen tension-dependent changes in the penis during erection are proposed to impact corpus cavernosum structure by inducing various cytokines, vasoactive factors and growth factors at the two different oxygen tensions (flaccidity and erection) which, in turn, alter smooth muscle metabolism and connective tissue synthesis. Decreases in the corpus cavernosum smooth muscle/connective tissue ratio have been correlated with an increased likelihood of diffuse venous leak and a failure of the veno-occlusive mechanism in prospective patient studies. Evidence for such a hypothesis incorporates nocturnal penile tumescence and circadian changes in oxygenation as important in maintaining erectile health. The alternate hypothesis proposes that ED is the result of a metabolic imbalance between relaxatory and contractile processes within the trabecular smooth muscle such that contractile processes predominate. Based on this hypothesis, therapy can be accomplished via drugs which shift this balance towards vasodilatation, or by gene therapy approaches to supplement the deficient components favoring smooth muscle relaxation. Both of these hypotheses predict a management strategy for ED that impacts pharmacotherapeutics. In this review of the pathophysiology of ED, each hypothesis will be examined and a synthesis devised incorporating both views. The future of research in this area as well as pharmacotherapy in ED in terms of pathophysiology is discussed including the merits and drawbacks of prophylaxis and prevention of ED. International Journal of Impotence Research (2000) 12, Suppl 4, S39-S46.

Animals↗
PubMed2000

Cyclic AMP regulates mRNA expression of alpha-1d and alpha-2a adrenergic receptors in cultured human corpus cavernosum smooth muscle cells.

While the physiological effects of contractile (e.g. norepinephrine) and relaxatory (e.g. PGE1, forskolin) agents on corpus cavernosum smooth muscle tone have been characterized, the regulation of alpha adrenergic receptor mRNA expression in erectile tissue remains to be investigated. The goal of this study was to investigate the modulation of alpha-1 and alpha-2 adrenergic receptor mRNA expression in cultured human corpus cavernosum smooth muscle cells in response to increased intracellular cAMP induced by prostaglandin E1 and forskolin. Human corpus cavernosum smooth muscle cells were incubated for 24 h with or without PGE1 (5.7 microM), forskolin (10 microM) or an admixture of both. Total RNA was prepared from the cultures. Expression of alpha-1d adrenergic receptor, alpha-2a adrenergic receptor and m2 muscarinic acetylcholine receptor was determined by RNase protection assays. Loading was normalized by RNase protection of the housekeeping gene, cyclophilin A. The relative abundance of mRNAs was quantitated by scanning densitometry. Treatment of human corpus cavernosum smooth muscle cells with PGE1 or forskolin resulted in decreased mRNA expression of alpha-1d and alpha-2a adrenergic receptors and m2 muscarinic acetylcholine receptor when compared to untreated cells. Combinations of PGE1 and forskolin produced a more pronounced decrease in mRNA than either agent alone. PGE1 and forskolin increased intracellular levels of cAMP in human corpus cavernosum smooth muscle cells and combinations of both agents produced a more pronounced increase in cAMP synthesis. These results suggest that cAMP modulates the expression of alpha adrenergic receptors, one of the principal contractile receptor systems in the corpora cavernosa. These observations further support the concept that erectile function is a balance between contractile and relaxatory processes, which in turn regulate structure and function of the corpora cavernosa.

Alprostadil↗