Showing papers by "Hunter C. Champion published in 2001"

Report of the Council on Scientific Affairs: methadone maintenance and needle-exchange programs to reduce the medical and public health consequences of drug abuse.

Abstract: Extensive evaluation studies show that methadone maintenance therapy (MMT) reduces heroin use and associated problems in a cost-effective manner, without negative public health impact. MMT is limited by inadequate funding and understanding of relevant research, extensive regulation, and limits on the freedom of physicians to provide methadone in a variety of medical settings. Broad-based medical, public health, and scientific support exists for expansion of MMT with greater emphasis on consistency and quality, and provision of ancillary services. Programs for the exchange, free distribution, and legal pharmacy sale of needles and syringes reduce injection drug use and prevent the spread of bloodborne pathogens; drug abuse treatment and other services are important components. Neither strategy increases existing drug use nor leads to drug use initiation. The scientific literature supports assertions that drug abuse issues should be treated primarily as medical and public health rather than crimina...

Gene transfer of prepro-calcitonin gene-related peptide restores erectile function in the aged rat.

Abstract: Erectile dysfunction in the aging male is caused, in part, by inadequate relaxation of the corpora cavernosal smooth musculature. Calcitonin gene-related peptide (CGRP), a peptide neurotrasmitter localized in the corpora cavernosa, is down-regulated in the aging rat penis. We examined the hypothesis that this reduction in CGRP may contribute to decreased cavernosal smooth muscle relaxation. Therefore, we sought to determine whether adenoviral-mediated gene transfer of prepro-CGRP (AdRSVCGRP) could enhance erectile responses in aged rats. We found a significant decrease in CGRP concentrations and in cAMP and cGMP levels in aged rat cavernosal tissue compared to younger rats. Aged rats also had significantly lower erectile function as determined by cavernosal nerve stimulation compared to younger rats. Five days after transfection with AdRSVCGRP, these aged rats had an approximately threefold increase in cavernosal CGRP levels compared to animals transfected with adenoviruses encoding nuclear-targeted beta-galactosidase (AdRSV beta gal). The AdRSVCGRP-transfected animals also demonstrated an increase in CGRP mRNA and immunohistochemical localization of CGRP in the smooth muscle of the corpora cavernosa. In addition, cAMP levels in the corpora cavernosa were significantly increased, whereas cGMP levels remained unchanged. Adenoviral transduction efficiency of beta-galactosidase reporter gene was measured by chemiluminescence and was observed in cavernosal tissue 5 days after transfection with AdRSV beta gal. More importantly, 5 days after administration of AdRSVCGRP, a significant increase was observed in the erectile response to cavernosal nerve stimulation in the aged rat, similar to the response observed in younger rats. These data suggest that in vivo adenoviral gene transfer of CGRP can physiologically improve erectile function in the aged rat.

Evaluation of nitric oxide synthase and arginase in the induction of a Peyronie's-like condition in the rat.

Abstract: Peyronie's disease is an idiopathic, localized connective tissue disorder of the penis, involving the tunica albuginea of the corpus cavernosum and adjacent areolar space. Current proposals as to the origin of Peyronie's disease suggest that fibrosis and collagen changes of the tunica are the result of an inflammatory process following vascular trauma. Our laboratory and other investigators have recently proposed an animal model for the study of Peyronie's disease. When transforming growth factor-beta1 (TGF-beta1) was injected into the rat tunica albuginea, tissue fibrosis was observed at 6 weeks. Therefore, our aim was to assess arginase II, endothelial and inducible nitric oxide synthase isoforms, and nitrotyrosine levels--all factors involved in inflammatory reactions--in the cavernosal tissue of saline-injected and TGF-beta1-injected rats after 6 weeks in order to evaluate the roles these enzymes may play in the induction of a Peyronie's-like condition in the rat. To examine the expression of endothelial nitric oxide synthase (eNOS), iNOS, and arginase II protein, and mRNA in the corpus cavernosum, immunoblot analysis, and reverse transcriptase-polymerase chain reaction were performed. We also determined immunohistochemically the expression of nitrotyrosine, a marker of peroxynitrite formation, in the rat penis. After 6 weeks, iNOS protein and gene expression was up-regulated and eNOS protein and gene expression was down-regulated in the corpora cavernosa of the TGF-beta1-injected penises. Furthermore, arginase II protein expression as well as immunohistochemical localization of nitrotyrosine was significantly higher in the TGF-beta1-injected corpora cavernosa. These results suggest that iNOS is the key control element for peroxynitrite formation, arginase II expression, and eNOS down-regulation in the induction of a Peyronie's-like condition in the rat.

Role of genitourinary inflammation in infertility: Synergistic effect of lipopolysaccharide and interferon-γ on human spermatozoa

Abstract: Pro-inflammatory cytokines are elevated in the semen of patients with genitourinary inflammation (GUI). Whether this increase in cytokines in GUI patients plays any critical role in male factor infertility is not clear. The present study investigated the in vitro effects of two important pro-inflammatory cytokines, lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma), on sperm motility, viability, membrane integrity and motion parameters. Washed spermatozoa from healthy donors were incubated with LPS (0.1 mg/mL) or IFN-gamma (0.1 mg/mL) alone or in combination. Sperm motility, viability, membrane integrity and computer-assisted motion were evaluated at various time intervals (0, 30, 60 and 180 min) after treatment. Sperm membrane integrity was analysed using the hypo-osmotic swelling test (HOST). LPS and IFN-gamma individually did not alter sperm viability or motility, but their combination showed a significant time-dependent decrease (p < 0.05) in sperm motility, viability and membrane integrity. Sperm motion parameters (straight-line velocity, curvilinear velocity, mean linearity, or amplitude of lateral head displacement) were not affected by LPS or IFN-gamma at the concentrations used in this study. These data suggest that the combination of LPS and IFN-gamma is detrimental to human spermatozoa and may contribute to male factor infertility in patients with chronic GUI.

Analysis of vasodilator responses to novel nitric oxide donors in the hindquarters vascular bed of the cat.

Abstract: Controlled release of nitric oxide (NO*) may be useful in the treatment of a variety of vascular disorders. NO* donors of the diazeniumdiolate family with different rates of spontaneous NO* release have been synthesized. In the current study responses to seven diazeniumdiolate NO* donors (DEA/NO*, DETA/NO*, OXI/NO*, PIPERAZI/NO*, PROLI/NO*, SPER/NO*, and SULFI/NO*) were investigated in the hindquarters vascular bed of the cat. Intravenous injections of all NO* donors caused dose-dependent decreases in systemic arterial pressure and the rank order of potency was SNP > DEA/NO* > PIPERAZI/NO* > SPER/NO* > PROLI/NO* > OXI/NO*. Injections of all NO* donors into the hindlimb perfusion circuit caused dose-related decreases in hindquarters perfusion pressure that were similar to the order of potency in decreasing systemic arterial pressure. The rank order of the time required for the response to return to 50% of the maximal decrease in pressure (T(1/2)) and total duration of action of the NO* donors was SPER/NO* > PIPERAZI/NO* > DEA/NO* > OXI/NO* > DETA/NO* > PROLI/NO* > SULFI/NO*. After treatment with the NO* synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (100 mg/kg, i.v.), hindlimb vasodilator responses to the NO* donors were not significantly different, but vasodilator responses to acetylcholine were significantly reduced. After treatment with zaprinast (2 mg/kg, i.v.), a type V cyclic 3',5'-guanosine monophosphate-specific phosphodiesterase inhibitor, the duration of vasodilator responses to the NO* donors, as measured by T(1/2), was increased significantly, whereas the duration of the response to the beta2-adrenergic receptor agonist albuterol was unchanged. These data suggest that diazeniumdiolate NO* donors are endothelium-independent, directly stimulate soluble guanylate cyclase, and decrease vascular resistance by increasing cyclic 3',5'-guanosine monophosphate levels in the hindquarters vascular bed of the cat.

In vivo Adenoviral Gene Transfer of CGRP and Related Peptides to the Rat and Mouse

Abstract: Calcitonin gene-related peptide (CGRP) and adrenomedullin (ADM) play an important role in maintaining low pulmonary vascular resistance (PVR) and may be involved in modulating the pulmonary vascular response to chronic hypoxia. Adenoviral vectors encoding prepro-CGRP (AdRSVCGRP) and ADM (AdRSVADM) were used to examine the effects of in vivo gene transfer of the peptides to the lung on increases in PVR, right ventricular mass, and pulmonary vascular remodelling that occurs in chronic hypoxia in the mouse. Intratracheal administration of AdRSVCGRP or AdRSVADM, followed by 16 days of chronic hypoxia (FIO2 0.10), increased lung CGRP and ADM levels, respectively. The increase in pulmonary arterial pressure (PAP), PVR, right ventricular mass, and pulmonary vascular remodeling in response to chronic hypoxia was attenuated in animals overexpressing prepro-CGRP or ADM whereas systemic arterial pressure was not altered. In chronically hypoxic mice, increases in PAP in response to i.v. injections of angiotensin II and endothelin-1 were attenuated following in vivo gene transfer. These data show that in vivo transfer of the CGRP or ADM gene to the lung attenuates the increase in PVR and right ventricular mass, pulmonary vascular remodeling, and responsiveness in chronically hypoxic mice with little effect on the systemic circulation. In order to study the roles of RAMP 1, 2, and 3 in mediating responses to CGRP and related peptides in the pulmonary and systemic vascular beds, gene transfer of adenovirus vectors encoding CRLR and RAMP 1, 2, or 3 were delivered to the lung and/or hindlimb of the mouse. Transfection of CRLR and RAMP 2 to the pulmonary and hindlimb vascular beds of the mouse resulted in enhanced vasodilator responses to ADM, but not CGRP.

Analysis of responses to angiotensin II in the mouse.

Abstract: Responses to angiotensin II (Ang II) were investigated in anaesthetised CD1 mice. Injections of Ang II caused dose-related increases in systemic arterial pressure that were antagonised by candesartan. Responses to Ang II were not altered by PD 123319. At the lowest dose studied (20 µg/kg i.v.), the inhibitory effects of candesartan were competitive, whereas at the highest dose (100 µg/kg i.v.), the dose-response curve for Ang II was shifted to the right in a non-parallel manner. The inhibitory effects of candesartan were selective and were similar in animals pretreated with enalaprilat to reduce endogenous Ang II production. Pressor responses to Ang II were not altered by propranolol, phentolamine or atropine, but were enhanced by hexamethonium. Increases in total peripheral resistance were inhibited by the AT1-receptor antagonist (ARB) but were not altered by AT2-receptor, alpha- or beta-receptor antagonists. These results suggest that pressor responses to Ang II are mediated by AT 1-receptors, are buffered by the baroreceptors, are not modulated by effects on AT2receptors, and that activation of the sympathetic nervous system plays little role in mediating rapid haemodynamic responses to the peptide in anaesthetised mice.

Emerging therapeutic targets in nitric oxide-dependent cardiac disease.

Abstract: Nitric oxide (NO) is a free radical gas that plays paracrine/autocrine and intracrine roles in maintaining physiological cardiovascular performance. In the coronary circulation, NO mediates endothelium-dependent vasodilator responses to shear stress and agonist-induced responses to neurohumoral stimulation. In the heart, NO modulates myocardial relaxation, β-adrenergic responses, mitochondrial respiration and substrate metabolism and excitation-contraction coupling. Endothelial dysfunction and the resulting decrease in the production, bioavailability and/or second messenger response-coupling has been implicated in coronary artery disease and complications associated with restenosis following coronary angioplasty, stent placement and coronary artery bypass grafting (CABG). However, there are a number of pathophysiological conditions (ischaemia-reperfusion, cardiac transplant rejection, myocarditis, sepsis) in which unregulated overproduction of NO and other reactive oxygen species (ROS) results in deleteri...

Vasodilator Responses to ATP and UTP are cAMP Dependent in the Mesenteric Vascular Bed of the Cat

Abstract: Background: This study was designed to examine the responses to and the mechanism by which purinergic agonists decrease vascular resistance in the mesenteric vascular bed of the cat.Methods and Results: Injections of ATP, UTP, and 2-MethylThioATP (2-MetSATP) into the mesenteric perfusion circuit elicited dose-dependent decreases in perfusion pressure while injections of P,y-MethylATP (f3,y-MetATP) produced a biphasic response with an initial vasopressor response followed by a vasodilator response. The order of potency of the vasodilator response was 2-MetSATP > ATP > UTP > P,y-MetATP. The vasodilator responses to ATP, UTP, 2-MetSATP, and P,y-MetATP were increased in duration by the cAMP phosphodiesterase inhibitor, rolipram. However, vasodilator responses were not altered by the adminstration of a nitric oxide synthase inhibitor, a cGMP phosphodiesterase inhibitor, or a cyclooxygenase inhibitor. Treatment with PPADS, a P2X,, P2Y, and P2Y4 receptor antagonist, did not alter vasodilator responses to the pur...