Does sedation offer better outcomes than local anaesthesia for thyroid FNA in adult patients?

OBJECTIVE: To examine the potential benefits of sedation in adults undergoing fine needle aspiration (FNA) of thyroid nodules. METHODS: This retrospective study compared the outcomes of sedated and non-sedated FNA patients. RESULTS: A total of 860 patients underwent 1698 FNAs of thyroid nodules. The mean patient age was 52.4±14.4 years, and 80.2% of patients were women. The non-sedated group consisted of 782 patients with 1543 (93.5%) FNA procedures. The sedated group consisted of 66 patients who underwent 107 (6.5%) FNAs. There was no statistical difference between these groups with respect to age, gender, nodule size, nodule vascularity, non-diagnostic sample rate and post FNA hematoma (P > .05). CONCLUSIONS: Performing FNA of thyroid nodules in adult patients under sedation is not associated with a higher diagnostic yield or lower bleeding rate when compared to local anesthesia. Sedation should be judiciously used on only very anxious patients due to the increased overall cost.

Psychiatrists' views on clozapine prescribing in Ireland.

INTRODUCTION: Despite proven effectiveness in refractory schizophrenia, clozapine remains underutilised, and it is important to understand potential reasons for this. This study's aim was to examine in a National sample of Consultant Psychiatrists their knowledge of, attitudes and perceived barriers to clozapine use. METHODS: A novel questionnaire was designed and distributed by email to 275 Consultant Psychiatrists in Republic of Ireland. RESULTS: Twenty-eight percent (n = 77) completed the survey, with 55% of respondents practicing for 15 or more years. Clinicians expressed confidence in managing clozapine treatment and side effects and were well aware of clozapine's clinical effectiveness and guideline-based use. A majority indicated insufficient experience managing rechallenge and half expressed insufficient experience managing adverse events. Perceived patient factors were highlighted as barriers with 69% of respondents reporting patients' concern about effectiveness and 50% regarding tolerability. Sixty-four percent (n = 40) indicated that a specialised/tertiary clozapine service would facilitate initiation, with 57% (n = 36) reporting less frequent blood monitoring would aid clozapine prescribing. A majority identified that access to dedicated staff (81%, n = 51) and dedicated day hospital services (84%, n = 53) would facilitate community initiation. CONCLUSION: Consultants are familiar with clozapine use and related guidelines. Dedicated staff and facilities for clozapine use is one identified structural change to enhance clozapine prescribing in Ireland. Tertiary service or clinical advice service would assist in clozapine rechallenge cases or in managing significant adverse events. More structured patient education regarding clozapine effectiveness and professional development programmes focused on managing side effects and rechallenge may promote clozapine use.

Closed-Loop Bowel Obstruction Induced by Ventriculoperitoneal Shunt Catheter Coiling at the Sigmoid Colon: A Case Report.

Intestinal obstruction is a rarely encountered complication in patients with ventriculoperitoneal (VP) shunt. The most common causes of bowel obstruction in this subset of patients include volvulus, formation of a spontaneous knot, and adhesions. Herein, we report a 21-year-old bedridden male with a history of congenital hydrocephalus on VP shunt, spina bifida, neurogenic bladder, and paraplegia who presented with a seven-day history of abdominal discomfort, distention, constipation, vomiting, and intolerance to oral intake. Abdominal x-ray showed dilated bowel loops. Computed tomography (CT) of the abdomen demonstrated a closed-loop bowel obstruction at the level of the sigmoid colon caused by the coiling of the VP shunt catheter. Diagnostic laparoscopy revealed the VP shunt tube coiling around a segment of the sigmoid colon with no signs of bands, ischemia, or perforation. Pulling and shortening of the tube was done. The procedure went uneventfully, and the patient was discharged home in stable condition. Maintaining a high index of suspicion for knotting the peritoneal catheter around the bowel is crucial when a patient on a VP shunt presents with a picture suggestive of intestinal obstruction. Early surgical intervention might be required to prevent further progression and complications.

Intra-cardiac pressure drop and flow distribution of bicuspid aortic valve disease in preserved ejection fraction.

Background: Bicuspid aortic valve (BAV) is more than a congenital defect since it is accompanied by several secondary complications that intensify induced impairments. Hence, BAV patients need lifelong evaluations to prevent severe clinical sequelae. We applied 4D-flow magnetic resonance imaging (MRI) for in detail visualization and quantification of in vivo blood flow to verify the reliability of the left ventricular (LV) flow components and pressure drops in the silent BAV subjects with mild regurgitation and preserved ejection fraction (pEF). Materials and methods: A total of 51 BAV patients with mild regurgitation and 24 healthy controls were recruited to undergo routine cardiac MRI followed by 4D-flow MRI using 3T MRI scanners. A dedicated 4D-flow module was utilized to pre-process and then analyze the LV flow components (direct flow, retained inflow, delayed ejection, and residual volume) and left-sided [left atrium (LA) and LV] local pressure drop. To elucidate significant diastolic dysfunction in our population, transmitral early and late diastolic 4D flow peak velocity (E-wave and A-wave, respectively), as well as E/A ratio variable, were acquired. Results: The significant means differences of each LV flow component (global measurement) were not observed between the two groups (p > 0.05). In terms of pressure analysis (local measurement), maximum and mean as well as pressure at E-wave and A-wave timepoints at the mitral valve (MV) plane were significantly different between BAV and control groups (p: 0.005, p: 0.02, and p: 0.04 and p: <0.001; respectively). Furthermore, maximum pressure and pressure difference at the A-wave timepoint at left ventricle mid and left ventricle apex planes were significant. Although we could not find any correlation between LV diastolic function and flow components, Low but statistically significant correlations were observed with local pressure at LA mid, MV and LV apex planes at E-wave timepoint (R: -0.324, p: 0.005, R: -0.327, p: 0.004, and R: -0.306, p: 0.008, respectively). Conclusion: In BAV patients with pEF, flow components analysis is not sensitive to differentiate BAV patients with mild regurgitation and healthy control because flow components and EF are global parameters. Inversely, pressure (local measurement) can be a more reliable biomarker to reveal the early stage of diastolic dysfunction.

Ketamine administration for acute painful sickle cell crisis: A randomized controlled trial.

OBJECTIVE: The objective was to evaluate the efficacy and safety of single-dose ketamine infusion in adults with sickle cell disease (SCD) who presented with acute sickle vasoocclusive crisis (VOC). METHODS: This study was a parallel-group, prospective, randomized, double-blind, pragmatic trial. Participants were randomized to receive a single dose of either ketamine or morphine, infused over 30 min. Primary outcome was mean difference in the numerical pain rating scale (NPRS) score over 2 h. NPRS was recorded every 30 min for a maximum of 180 min and secondary outcomes were cumulative dose of opioids, emergency department (ED) length of stay, hospital admission, change in vital signs, and drug-related side effects. Authors performed the analysis using intention-to-treat principle. RESULT: A total of 278 adults with SCD and who presented with acute sickle VOC participated in this trial. A total of 138 were allocated to the ketamine group. Mean (±standard deviation [SD]) NPRS scores over 2 h were 5.7 (±2.13) and 5.6 (±1.90) in the ketamine and morphine groups. The ketamine group received significantly lower cumulative doses of morphine during their ED stay (mean ± SD = 4.5 ± 4.6 mg) than of the morphine group (mean ± SD = 8.5 ± 7.55 mg). Both groups had similar rates of hospital admission: 6.3% in the ketamine group had drug-related side effects compared to 2.2% in the morphine group. CONCLUSION: Early use of ketamine in adults with VOC resulted in a meaningful reduction in pain scores over a 2-h period and reduced the cumulative morphine dose in the ED with no significant drug-related side effects in the ketamine-treated group.

The challenges with NOTES retroperitoneal access in humans.

BACKGROUND: Animal studies have supported natural orifice transluminal endoscopic surgery (NOTES) retroperitoneal access. NOTES also may offer unique retroperitoneal access in humans. OBJECTIVES: This study was designed to assess the feasibility of endoscopic transgastric and transrectal retroperitoneal access in a cadaver model using prone and supine positioning, and to compare NOTES retroperitoneal examination with endoscopic ultrasound. METHODS: Using a multidisciplinary team, this institutional review board-approved study evaluated transgastric and transrectal retroperitoneal examination in six cadavers (3 male, 3 female; body mass index range, 25-37 kg/m(2)). Endoscopic ultrasound retroperitoneal examination preceded NOTES access. Transgastric Access: Using a prototype dual channel endoscope, a needle knife gastrotomy was created on the preantral posterior gastric wall. Retroperitoneal examination specifically targeted the pancreas and surrounding structures with the cadaver supine and prone. Transrectal Access: Using the same endoscope, a posterior needle knife rectotomy distal to the upper valve of Houston provided extraluminal access. Retroperitoneal examination proceeded with the cadaver prone and supine. Open dissection followed procedure completion. RESULTS: Access into the retroperitoneum succeeded at all sites. Significant challenges locating identifiable landmarks were faced-mostly transrectal and improved transgastric prone. All cadavers, despite body mass index or sex, had significant retroperitoneal adipose tissue limiting the endoscopic view. CONCLUSIONS: Although porcine studies have highlighted successful NOTES retroperitoneal procedures, the abundant human retroperitoneal adipose tissue challenged the translation of porcine research to humans. Additionally, although access to the retroperitoneal space and dissection within this space were accomplished easily, the appearance of cadaveric tissue and lack of blood flow made confident landmark identification impossible. Further study should continue in this area and focus on confident landmark identification for directed dissection. In a cadaveric model, this would best be improved by pre-NOTES anatomic marking or active perfusion of vasculature along with consideration of direct entry into the retroperitoneum from a targeted intraperitoneal site in clinical patients.

A common antigenic determinant found in two functionally unrelated toxins.

The heat-stable enterotoxin ST Ib produced by enterotoxigenic E. coli strains shares a sequence homology with the sea snail neurotoxin, conotoxin GI. Rabbit antisera were raised against synthetic analogs of these toxins and to a six-residue peptide representing the region common to both toxins. Results from enzyme-linked immunosorbent assays indicate that the homologous region of both toxins represents part of their antigenic site. The lack of cross-reactivity exhibited by the six-residue common domain with serum directed against either toxin suggests that this region probably retains a similar conformation in the intact toxins but not in the isolated fragment.

Cigarette smoke activates guanylate cyclase and increases guanosine 3',5'-monophosphate in tissues.

The gaseous phase of cigarette smoke induced a 2- to 36-fold increase in the activity of guanylate cyclase in supernatant and particulate fractions from various rat and bovine tissues over basal activity. The characteristics of this phenomenon paralleled those of the activation of guanylate cyclase by nitric oxide, which is a component of tobacco smoke.

Insulin secretion from pancreatic B cells caused by L-arginine-derived nitrogen oxides.

L-arginine causes insulin release from pancreatic B cells. Data from three model systems support the hypothesis that L-arginine-derived nitrogen oxides (NOs) mediate insulin release stimulated by L-arginine in the presence of D-glucose and by the hypoglycemic drug tolbutamide. The formation of NO in pancreatic B cells was detected both chemically and by the NO-induced accumulation of guanosine 3',5'-monophosphate. NG-substituted L-arginine analogs inhibited the release of both insulin and NO. Protein immunoblot and histochemical analysis with antiserum to type I NO synthase suggest that the formation of NO in pancreatic B cells is catalyzed by an NADPH- (reduced form of nicotinamide adenine dinucleotide phosphate), Ca2+/calmodulin-dependent type I NO synthase of about 150 kilodaltons.

Increased urinary excretion of cyclic guanosine monophosphate in rats bearing Morris hepatoma 3924A.

Urinary excretion of cyclic guanosine monophosphate (GMP) increased in rats bearing Morris hepatoma 3924A, and a correlation coefficient of .842 was observed comparing nucleotide excretion and tumor size. Irradiation of tumor or 5-fluorouracil administration delayed the increases in urinary cyclic GMP and tumor size. Surgical removal of tumors resulted in a rapid decline in cyclic GMP excretion to baseline levels. Cyclic adenosine monophosphate excretion was not altered by implantation, irradiation, or excision of tumor.

Crohn's disease: A retrospective analysis between computed tomography enterography, colonoscopy, and histopathology.

INTRODUCTION: To investigate the spectrum of computed tomography enterography (CTE) findings of active Crohn's disease (CD) in comparison to endoscopic, histopathologic and inflammatory markers. METHODS: Hospital records of 197 patients with known or suspected CD who underwent CTE over a period of 5 years were reviewed. Eighty-nine patients fulfilled the inclusion criteria. Three-point severity scores for endoscopy, pathology, and haematologic inflammatory markers were recorded. The findings on CTE were identified by three readers and correlated with endoscopic, pathologic, and haematologic severity scores. Statistical analysis was carried out employing a Pearson Chi square test and Fisher exact test. Receiver operating characteristic (ROC), visual grading characteristic (VGC) and Cohens' kappa analyses were performed. RESULTS: The CTE findings which were significantly correlated with the severity of active disease on endoscopy include bowel wall thickening, mucosal hyperenhancement, bilaminar stratified wall enhancement, transmural wall enhancement, and mesenteric fluid adjacent to diseased bowel (p < 0.05). Only bowel wall thickening and bilaminar stratified wall enhancement correlated with the pathological severity of active CD. ROC and VGC analysis demonstrated significantly higher areas under the curve (p < 0.0001) together with excellent inter-reader agreement (k = 0.86). CONCLUSION: CTE is a reliable tool for evaluating the severity of active disease and helps in the clinical decision pathway.

Study protocol for a randomized, blinded, controlled trial of ketamine for acute painful crisis of sickle cell disease.

BACKGROUND: Sickle cell disease (SCD) is an inherited hematological disorder where the shape of red blood cells is altered, resulting in the destruction of red blood cells, anemia, and other complications. SCD is prevalent in the southern and eastern provinces of the Arabian peninsula. The most common complications for individuals with SCD are acute painful episodes that require several doses of intravenous opioids, making pain control for these individuals challenging. Instead of opioids, some studies have suggested that ketamine might be used for pain control in acute pain episodes of individuals with SCD. This study aims to evaluate whether the addition of ketamine to morphine can achieve better pain control, decreasing the number of repeated doses of opiates. We hypothesize that early administration of ketamine would lead to a more rapid improvement in pain score and lower opioid requirements. METHODS AND ANALYSIS: This study will be a prospective, randomized, concealed, blinded, pragmatic parallel group, controlled trial enrolling adult patients with SCD and acute vaso-occlusive crisis pain. All patients will receive standard analgesic therapy during evaluation. Patients randomized to the treatment arm will receive low-dose ketamine (0.3 mg/kg in 0.9% sodium chloride, 100 ml bag) in addition to standard intravenous hydration, while those in the control group will receive a standard dose of morphine (0.1 mg/kg in 0.9% sodium chloride, 100 ml bag) in addition to the standard intravenous hydration. All healthcare providers will be blinded to the treatment arm. Data will be analyzed according to the intention-to-treat principle. The primary outcome is improvement in pain severity using the Numerical Pain Rating Score. TRIAL REGISTRATION: Clinicaltrials.gov, NCT03431285 . Registered on 13 February 2018.

Interaction of polymorphonuclear neutrophils with Escherichia coli. Effect of enterotoxin on phagocytosis, killing, chemotaxis, and cyclic AMP.

Enterotoxigenic Escherichia coli are associated with noninflammatory diarrhea and stimulate adenylate cyclase activity of mammalian cells, thereby increasing intracellular cyclic adenosine 3',5'-monophosphate (cyclic AMP). Increased concentrations of cyclic AMP in polymorphonuclear neutrophils (PMN) inhibit phagocytosis, candidacidal activity, granule discharge, and chemotactic responsiveness. We examined the effect of enterotoxin on the interaction of human PMN with E. coli. Enterotoxigenic and nonenterotoxigenic strains, including serotypes of E. coli identical except for the presence or absence of the plasmid coding for enterotoxin production, were utilized. Enterotoxigenic and nonenterotoxigenic E. coli, tumbled with PMN, were phagocytized and killed (>97%) equally well, and these strains stimulated PMN hexose monophosphate shunt activity equivalently.However, a chemotaxis assay under agarose demonstrated that filtrates of 10 enterotoxigenic strains were less chemotactic for PMN by 15+/-2% total migration or 46+/-1% directed migration, when compared with 6 non-enterotoxigenic strains (P < 0.001). Inactivation of the enterotoxin by heat (65 degrees C for 30 min) or antibodies formed to E. coli enterotoxin eliminated the inhibitory effect of the enterotoxic filtrates for PMN chemotaxis. Addition of purified E. coli enterotoxin directly to the PMN decreased chemotaxis to E. coli filtrates by 32+/-2% (P < 0.001). These data suggest that the effect was due to the heat-labile enterotoxin. The phosphodiesterase inhibitor, 1-methyl-3-isobutylxanthine (0.1 mM), which potentiates effects due to an increase in intracellular cyclic AMP, further decreased total PMN migration (random plus directed) toward enterotoxic filtrates to 46% of that to nonenterotoxic filtrates (P < 0.001). Addition of cholera toxin (1 mug/ml), which is similar to E. coli enterotoxin, to the PMN inhibited total migration toward nonenterotoxic filtrates by 16+/-2% (P < 0.001). Exogenous dibutyryl cyclic AMP (2 mM) inhibited total PMN migration toward E. coli filtrates by 32% (P < 0.001). PMN intracellular cyclic AMP levels increased by 220% after 2 h of incubation with purified E. coli enterotoxin. The decreased chemotactic attractiveness of enterotoxic E. coli filtrates appears to be related to the ability of enterotoxin to increase cyclic AMP in PMN. Enterotoxin production by E. coli may be advantageous to the microbe by decreasing its chemotactic appeal for PMN.

Urinary excretion of cyclic guanosine 3':5'-monophosphate and cyclic adenosine 3':5'-monophosphate in rats bearing transplantable liver and kidney tumors.

Cyclic guanosine 3':5'-monophosphate (cyclic GMP) and cyclic adenosine 3':5-monophosphate were measured in the urine of normal rats and those bearing transplantable liver and kidney tumors. The level of cyclic GMP ranged from 1.4 to 1.6 mumoles/g urinary creatinine in several strains of rats without tumors. Rats bearing Morris hepatomas 20, 21, 9618A and 9633F and kidney tumor MK2 had urine levels of cyclic GMP from 1.3 to 3.6 mumoles/g creatinine. Rats bearing the fast growing hepatomas 9618A2 and 3924A and Morris kidney tumor MK3 had urinary values of 5.6. 41.9, and 32.7 mumoles cyclic GMP per g creatinine, respectively. Urine levels of cyclic adenosine 3':5'-monophosphate ranged from 10.1 to 19.7 mumoles/g creatinine in all normal and tumor-bearing rats and were not significantly different in any of the groups examined.

The Endothelium-Dependent Nitric Oxide-cGMP Pathway.

Nitric oxide (NO)-cyclic 3'-5' guanosine monophosphate (cGMP) signaling plays a critical role on smooth muscle tone, platelet activity, cardiac contractility, renal function and fluid balance, and cell growth. Studies of the 1990s established endothelium dysfunction as one of the major causes of cardiovascular diseases. Therapeutic strategies that benefit NO bioavailability have been applied in clinical medicine extensively. Basic and clinical studies of cGMP regulation through activation of soluble guanylyl cyclase (sGC) or inhibition of cyclic nucleotide phosphodiesterase type 5 (PDE5) have resulted in effective therapies for pulmonary hypertension, erectile dysfunction, and more recently benign prostatic hyperplasia. This section reviews (1) how endothelial dysfunction and NO deficiency lead to cardiovascular diseases, (2) how soluble cGMP regulation leads to beneficial effects on disorders of the circulation system, and (3) the epigenetic regulation of NO-sGC pathway components in the cardiovascular system. In conclusion, the discovery of the NO-cGMP pathway revolutionized the comprehension of pathophysiological mechanisms involved in cardiovascular and other diseases. However, considering the expression "from bench to bedside" the therapeutic alternatives targeting NO-cGMP did not immediately follow the marked biochemical and pathophysiological revolution. Some therapeutic options have been effective and released on the market for pulmonary hypertension and erectile dysfunction such as inhaled NO, PDE5 inhibitors, and recently sGC stimulators. The therapeutic armamentarium for many other disorders is expected in the near future. There are currently numerous active basic and clinical research programs in universities and industries attempting to develop novel therapies for many diseases and medical applications.

Association of PKC delta and active Src in PMA-treated MCF-7 human breast cancer cells.

Phorbol ester treatment of MCF-7 cells led to the tyrosine phosphorylation and activation of PKC delta. However, through Western blot analysis and in vitro immunecomplex kinase assays, we detected a differential localization of tyrosine-phosphorylated PKC delta and catalytically active PKC delta. Catalytically active PKC delta was concentrated in Triton X-100 solubilized-membrane fractions while tyrosine-phosphorylated PKC delta was localized to the cytosol fraction. Phorbol ester treatment of MCF-7 cells stimulated both the time-dependent in vivo association of Src with PKC delta, evidenced in Src immunoprecipitates by the co-immunoprecipitation of PKC delta, and activation of Src, evidenced in Src immunoprecipitates as an increase in reactivity with a Src antibody (clone 28) reactive only with active Src (dephosphorylated on residue 530) and in Src and PKC delta immunoprecipitates by an increase in Src kinase activity. While our data are consistent with reports in the literature showing the activator/stimulus-dependent tyrosine phosphorylation of PKC delta, our data show that the tyrosine phosphorylation of PKC delta is not essential for kinase activity. These results are the first to demonstrate an in vivo association between PKC delta and active Src in the absence of over-expression of either PKC delta or Src, and support the association of Src and PKC delta towards a physiological function.

Purification of guanylyl cyclase from rod outer segments.

The particulate form of guanylyl cyclase from bovine rod outer segments has been solubilized and purified to near homogeneity by a combination of liquid chromatography and native gel electrophoresis. The procedure enriches enzyme activity 6700-fold from rod outer segment extracts to a final specific activity of 17.5 mumol/min per mg (when assayed with Mn-GTP as substrate). Purified preparations of guanylyl cyclase contain a single glycoprotein with an apparent molecular mass of 60,000 Da and a native isoelectric point of 7.6. Although crude or partially purified enzyme activity is modulated by sub-micromolar concentrations of Ca2+, the fully purified enzyme is insensitive to this cation. However, the purified enzyme remains sensitive to nitrovasodilators, being stimulated over 10-fold by sodium nitroprusside. These data suggest that retinal rods contain a unique isoform of guanylyl cyclase.

Effects of pyruvate and other metabolites on cyclic GMP levels in incubations of rat hepatocytes and kidney cortex.

Pyruvate increased cyclic GMP levels in rat hepatocytes. The effects were observed without or with 1-methyl-3-isobutylxanthine. Lactate, acetate, oxaloacetate, alpha-ketoglutarate, succinate, acetoacetate and beta-hydroxybutyrate also increased cyclic GMP levels. Some compounds increased cyclic GMP in kidney cortex slices. The effects were dependent upon Ca2+ in the medium. Cyclic AMP was increased 30-50% by some of these substances with 2.6 mM Ca2+. Rotenone, oligomycin, antimycin, dinitrophenol, KCN, and arsenate decreased GTP and ATP, basal cyclic GMP and the pyruvate effect, but did not alter cyclic AMP. Although fluoroacetate alone had no effect on cyclic nucleotides, GTP, or ATP, it potentiated the pyruvate effect on cyclic GMP. Adenosine and guanosine increased cyclic GMP and GTP to a similar extent of 30-50%. Aminooxyacetate, cycloserine, pentenoic acid and mepacrine decreased the pyruvate effect while cycloserine or mepacrine alone increased cyclic GMP. Citrate and mepacrine inhibited soluble and particulate guanylate cyclase from rat liver while cycloserine and acetoacetate increased guanylate cyclase activity. None of the other compounds altered guanylate cyclase activity. These results indicate that various metabolites and inhibitors can alter cyclic GMP accumulation in hepatocytes and renal cortex slices. Several mechanisms may be involved in these effects.

Comparison of binding and cyclic GMP accumulation by atrial natriuretic peptides in endothelial cells.

Rat 125I-labeled atrial natriuretic factor (ANF (8-33)) was used to identify ANF receptors on cultured bovine aortic endothelial cells. Specific binding of 125I-ANF at 37 degrees C to confluent endothelial cells was saturable and of high affinity. Scatchard analysis of the equilibrium binding data indicated that endothelial cells contain a single class of binding sites with a Kd of 0.1 +/- 0.01 nM. This particular clone of endothelial cells had 16000 +/- 1300 receptors per cell. The order of potency for competing with 125I-ANF binding was human atrial natriuretic peptide (hANP) = atrial natriuretic factor (ANF (8-33)) greater than atriopeptin II greater than atriopeptin III greater than atriopeptin. The weakest competitor, atriopeptin I, had a K1 of 0.45 nM, which was only 6-fold higher than the K1 for hANP and ANF (8-33). ANF (8-33) and hANP in the presence of 0.5 mM isobutylmethyl-xanthine produced a 15-20-fold increase in cyclic GMP content at 10 pM and a maximal 500-fold elevation of cyclic GMP at 10 nM. The concentrations required to elicit a half-maximal increase in cyclic GMP for hANP, ANF (8-33), atriopeptin I, atriopeptin II and atriopeptin III were 0.30, 0.35, greater than 500, 4.0 and 5.0 nM, respectively. Although atriopeptin I acted as a partial agonist, it was unable to antagonize the effect of ANF (8-33) on cyclic GMP formation. These findings suggest that endothelial cells have multiple and functionally distinct ANF-binding sites.

Separation of soluble adenylate and guanylate cyclases from the mature rat testis.

The mature rat testis contains both a soluble guanylate cyclase and a soluble adenylate cyclase. Both these soluble enzymes prefer manganous ion for activity. It is known that guanylate cyclase can, when activated by a variety of agents, catalyze the formation of cyclic AMP. The following experiments were performed to determine whether the testicular soluble adenylate and guanylate cyclase activities were carried on the same molecule. Analysis of supernatants from homogenized rat testis by gel filtration and sucrose density gradient centrifugation showed that the two activities were clearly separable. The molecular weight of guanylate cyclase is 143 000, while that of adenylate cyclase is 58 000. Treatment of the column fractions with 0.1 mM sodium nitroprusside allowed guanylate cyclase activity to be expressed with Mg(2+) as well as with Mn(2+). Sodium nitroprusside did not affect the metal ion or substrate specificity of adenylate cyclase. These experiments show that adenylate and guanylate cyclase activities are physically separable.