Biomedical subjects

M Longo

Publications and source records attributed to M Longo.

At least 19 recordsLinked to original sources

PubMed2004

Magnetic resonance angiography virtual endoscopy in the assessment of pulmonary veins before radiofrequency ablation procedures for atrial fibrillation.

Magnetic resonance angiography (MRA) is a safe and non-invasive imaging method that can readily depict the pulmonary veins (PV), whose imaging has acquired momentum with the advent of new techniques for radiofrequency ablation of atrial fibrillation (AF). We evaluated whether virtual endoscopy from 3D MRA images (MRA-VE) is feasible in studying the morphology of PV. Fifty patients with AF underwent pre-ablative MRA (1.5 T). Images were acquired with axial T-2 weighted and 3D-SPGR sequences after intravenous administration of Gd-DTPA and automatic triggering. Postprocessing was performed by an experienced radiologist with maximum intensity projection (MIP) and virtual endoscopy software (Navigator, GEMS). The venoatrial junction was visualized with MRA-VE in 49 of 50 patients (98.0%). Twenty-seven patients (55.1%) had two ostia on both sides, 13 patients (26.5%) had two ostia on the right and a single common ostium on the left, 5 patients (10.2%) had accessory PV and 4 patients (8.2%) had both an accessory right PV and a single common ostium on the left. Flythrough navigation showed the number and spatial disposition of second-order PV branches in 48 out of 49 patients (98.0%). MRA-VE is an excellent tool for at-a-glance visualization of ostia morphology, navigation of second-generation PV branches and easy endoluminal assessment of left atrial structures in pre-ablative imaging.

Adult↗

PubMed2004

Effective treatment and control of biting lice, Felicola subrostratus (Nitzsch in Burmeister, 1838), on cats using fipronil formulations.

The efficacy of 0.25% fipronil spray (Frontline Spray, Merial), 10% fipronil spot-on (Frontline Spot-on for Cats, Merial) and 10% fipronil/12% (S)-methoprene (Frontline Plus for Cats, Merial) against the biting louse Felicola subrostratus on cats was assessed and confirmed under laboratory conditions. A field study evaluated the efficacy of a single topical application of Frontline Spray, and spot-on against the parasite on cats. In the laboratory studies, animals were allocated based on pre-treatment louse counts to the treatment groups: (1) untreated control and (2) 10% fipronil spot-on in the exploratory study or (1) untreated control, (2) 0.25% fipronil spray, at 6 ml/kg; (3) 10% fipronil spot-on as per label and (4) 10% fipronil/12% (S)-methoprene as per label in the confirmation study. Cats in treatment groups 2-4 were treated twice topically on Days 0 and 28. No live F. subrostratus were found on cats treated with fipronil formulations at any post-treatment examination. The difference from controls was significant (P < 0.01) for each product at each examination. Based on whole body counts at Day 42, the efficacy of each product was determined to be 100%. In the field study, cats were allocated in strict order of presentation. Cats were randomly allocated to one of the three treatment groups: (1) propoxur collar (Bolfo, Bayer); (2) 0.25% fipronil spray, at 6 ml/kg and (3) 10% fipronil spot-on as per label. Cats were treated once topically on Day 0. Louse counts of cats treated with fipronil formulations were not different than those of cats receiving the propoxur collar. The efficacy was determined to be > 98% on Day 2 and 100% on Days 28 and 42 in all treatment groups. The results of these studies demonstrate that fipronil in topical formulations is effective for treatment and control of biting lice (F. subrostratus) infestations on cats.

Administration, Topical↗

PubMed2003

Volcanogenic fluorine in rainwater around active degassing volcanoes: Mt. Etna and Stromboli Island, Italy.

Many studies have assessed the strong influence of volcanic activity on the surrounding environment. This is particularly true for strong gas emitters such as Mt. Etna and Stromboli volcanoes. Among volcanic gases, fluorine compounds are potentially very harmful. Fluorine cycling through rainwater in the above volcanic areas was studied analysing more than 400 monthly bulk samples. Data indicate that only approximately 1% of fluorine emission through the plume is deposited on the two volcanic areas by meteoric precipitations. Although measured bulk rainwater fluorine fluxes are comparable to and sometimes higher than in heavily polluted areas, their influence on the surrounding vegetation is limited. Only annual crops, in fact, show some damage that could be an effect of fluorine deposition, indicating that long-living endemic plant species or varieties have developed some kind of resistance.

Air Pollutants↗

PubMed2003

Pyrrolopyrimidine c-Src inhibitors reduce growth, adhesion, motility and invasion of prostate cancer cells in vitro.

Two bona fide c-Src inhibitors, denominated CGP77675 and CGP76030, reduced in a time- and concentration-dependent manner (i) the proliferation of the PC3 prostate carcinoma cell line, as assessed by the [3H]-thymidine incorporation test, (ii) the capacity of PC3 cells to adhere and spread on Matrigel substrate, as determined by crystal violet staining, (iii) the ability of PC3 cells to migrate through a gelatine boundary and invade a Matrigel substrate. The latter effect was not due to a decrease of urokinase-type plasminogen activator (uPA), nor of metalloproteinase-2 (MMP-2) activities. The MMP-9 activity, along with the expression of the Tissue Inhibitor of Metalloproteinases (TIMP)-1 and TIMP-2, were reduced by the two inhibitors, consistent with the ability of c-Src to enhance MMP-9 and TIMP expression levels. Collectively, these data demonstrate that the pyrrolopyrimidine-derived c-Src inhibitors significantly reduced PC3 cell activities associated with their malignant phenotype.

Antineoplastic Agents↗

PubMed2003

Effects of L-type Ca(2+)-channel blockade, K(+)(ATP)-channel opening and nitric oxide on human uterine contractility in relation to gestational age and labour.

Relative uterine inactivity during pregnancy changes to vigorous rhythmic contractility during labour. We hypothesized that mechanisms involved in the regulation of uterine quiescence and contractility differ between term and preterm myometrium and in labour and non-labour states. Myometrial strips, prepared from biopsies taken at Caesarean section from labouring and non-labouring women preterm and at term, were mounted in organ chambers for isometric tension recording. Oxytocin (10(-9) mol/l) was added to maintain stable contractions, and effects of various inhibitors of uterine contractility were studied. The inhibitory effects of L-type Ca(2+)-channel blocker nifedipine and ATP-sensitive K(+)-channel opener pinacidil were greater in myometrium from the non-labour versus the labour group, both preterm and at term. In addition, pinacidil's effect was greater at term compared with preterm in the non-labour group. Mg(2+) and the nitric oxide donor sodium nitroprusside significantly inhibited contractility in all groups without significant differences with regard to labour or gestational age. Decreased inhibition of human uterine contractility by L-type Ca(2+)-channel blockers and K(+)(ATP)-channel openers in preterm and term labour may reflect changes in expression and activity of these channels. Effects of nitric oxide and Mg(2+) are not affected by gestational age or labour.

Adult↗

PubMed2003

Nitric oxide and its role during pregnancy: from ovulation to delivery.

Nitric oxide (NO) is a major paracrine mediator and important regulatory agent in various female reproductive processes, such as ovulation, implantation, pregnancy maintenance, labor and delivery. Ovulation: Circulating NO-products are increased during follicle development and decreased right after ovulation. INOS-inhibition results in a 50% reduction of ovulation, an effect completely reversed by an NO. Endometrium/Implantation: NO also regulates endometrial functions such as endometrial receptivity, implantation and menstruation. NO-donors may be useful for promoting fertility, while NO-inhibitors might be used for contraception. Uterine contractility: Throughout gestation myometrial NO-production is upregulated thus contributing to achieve uterine quiescence. Close to term, NO-production decreases promoting effective contractions resulting in labor. Clinical trials have demonstrated that NO-donors are effective tocolytics. Cervical ripening: In contrast to the myometrium, NO-production in the cervix is low during gestation and becomes upregulated once pregnancy advances to term. NO-donors are effective and safe cervical ripening agents. This finding from animal studies has been confirmed by several clinical trials. Vasoreactivity: In blood vessels, NO is a potent vasodilator and platelet-aggregation-inhibitor. Lack of NO during gestation was related to the development of pregnancy-induced hypertension and preeclampsia. In conclusion, NO-donors and NOS-inhibitors may provide novel, effective, safe, and inexpensive drugs to regulate and steer various functions in female reproductive life. The benefits reach from contraception to preventing possibly lethal pregnancy complications such as preeclampsia. Introducing NO-donors as tocolytics and cervical ripening agents may contribute to a reduction of fetal and maternal perinatal morbidity and mortality.

Animals↗

PubMed2002

Cerebral angiography in the rat with mammographic equipment: a simple, cost-effective method for assessing vasospasm in experimental subarachnoid haemorrhage.

We report quantification of vasospasm following subarachnoid haemorrhage (SAH) and the effect of a new antivasospastic free radical scavenger (AVS) in rats, using an angiographic technique developed in our laboratory. We acquired single-exposure angiograms with mammographic equipment, using a 0.1 mm diameter focal spot and single-emulsion mammographic films. Contrast medium was injected through a PE50 catheter in the common carotid artery, after the external carotid artery had been ligated to divert flow towards the internal carotid artery territory. Measurements of the M1 and A1 segments and of the middle third of the basilar artery were made by projecting the angiograms directly as slides and using the endovascular catheter as an internal reference. We tested the technique on 40 male albino Sprague-Dawley rats divided into four groups: sham-operated+saline, SAH+saline, sham-operated+AVS and SAH+AVS. We were able to measure the diameter of the principal intracranial arteries in all the animals. With our technique, which is cost-effective when compared to many of those reported recently, we could detect intracranial vasospasm in all untreated rats with SAH, and confirm antivasospastic effects of AVS.

Animals↗

PubMed2002

Contrast-enhanced MR imaging with fat suppression in adult-onset septic spondylodiscitis.

Spinal infections typically involve vertebrae as well as discs, and for this reason they are called septic spondylodiscitis. Magnetic resonance imaging is the most sensitive imaging method for the evaluation of this group of spinal diseases. The use of contrast-enhanced T1-weighted sequences with fat suppression, if correctly applied, may increase information provided by MRI. Firstly, this technique allows the primary vertebral focus, which often precedes disc involvement, to be identified at a very early stage. When the disease spreads, T1-weighted fat-suppressed gadolinium dimeglumine (Gd-DTPA) enhanced images provide macroscopic details of the primary vertebral focus, disc involvement patterns, and pathways of infection diffusion. All this information, when correlated with laboratory tests, may be useful in identifying the infectious agents (tuberculous vs piogenic forms), thus enabling a suitable therapy to be started. This technique is also useful in the assessment of the real extension of the disease, providing a clear depiction of paravertebral space involvement and of psoas muscle abscesses. Dangerous complications, such as meningitis, myelitis, and epidural abscesses, may be more promptly diagnosed and fully evaluated with fat-suppressed post-contrast T1-weighted images. Finally, this imaging technique may help to differentiate infectious processes from degenerative disorders, extradural neoplastic processes, and rheumatic diseases.

Adipose Tissue↗

PubMed2002

Structure analysis of polymerized phospholipid bilayer by TED and direct methods.

This paper describes the use of elastic energy filtered transmission electron diffraction combined with Direct Methods in order to study the structure of thin Langmuir-Blodgett films of a radiation sensitive diacetylene polymer (DC8.9PC). We obtain a potential map for one projection by direct phasing of zone axis patterns, and discuss experimental problems and possible solutions.

Lipid Bilayers↗

PubMed2002

Hyperlipidaemic state and cardiovascular risk in primary biliary cirrhosis.

BACKGROUND: Primary biliary cirrhosis (PBC), a chronic cholestatic liver disease, is frequently associated with severe hypercholesterolaemia but the clinical significance of this finding is unclear. AIMS: To characterise changes in serum lipid profile over time and to assess the risk of cardiovascular disease in PBC. SUBJECTS AND METHODS: We studied a cohort of 400 PBC patients for 6.2 years (range 4 months to 24 years) by serial determinations of serum lipid levels and registration of all cardiovascular events. Subjects included in an Italian prospective population based study served as controls. RESULTS: At presentation, 76% of patients had serum cholesterol levels >5.2 mmol/l. Hyperbilirubinaemic patients had higher total cholesterol and lower high density lipoprotein (HDL) cholesterol levels (p<0.001). With time, disease progression was associated with a reduction in total (p<0.001) and HDL (p<0.05) cholesterol. The incidence of cardiovascular events was similar to that of the general population (cerebrovascular events: standardised ratio 1.4; 95% confidence interval 0.5-3.7; coronary events: 2.2; 0.9-4.3). Hypertension was associated with an increased risk of cardiovascular events (3.8; 1.6-8.9). Association with moderate hypercholesterolaemia was of borderline significance (3.8; 0.9-17) whereas severe hypercholesterolaemia was not associated with increased risk (2.4, 0.5-11). CONCLUSIONS: In PBC, serum cholesterol levels markedly increase with worsening of cholestasis, and decrease in the late disease stages, despite a severe reduction in biliary secretion. Marked hypercholesterolaemia, typical of severe longstanding cholestasis, is not associated with an excess risk of cardiovascular disease while less advanced patients with moderate hypercholesterolaemia are exposed to an increased cardiovascular risk. Putative protective factors in PBC patients with severe hypercholesterolaemia should be assessed.

Adult↗

PubMed2001

Endothelium dependence and gestational regulation of inhibition of vascular tone by magnesium sulfate in rat aorta.

OBJECTIVE: The aim of this study was to investigate the role of nitric oxide in the vasorelaxant effect of magnesium sulfate during pregnancy. STUDY DESIGN: Segments of 3 mm of the aorta, with or without intact endothelium, from 16- or 22-day-pregnant rats were mounted in organ chambers with standard Krebs solution or low-magnesium Krebs solution for measurement of isometric tension. The rings were contracted with phenylephrine, and cumulative concentration-response curves for magnesium were determined after incubation with various inhibitors. RESULTS: Magnesium relaxed the aortic rings from pregnant rats in a concentration-dependent manner. The relaxation was significantly lower on day 22 of gestation than on day 16 of gestation. Removal of the endothelium or incubation with 10(-4)-mol/L N omega-nitro-L -arginine methyl ester (a nitric oxide synthase inhibitor), 10(-5)-mol/L 6-anilino-5,8-quinolinedione (a guanylate cyclase inhibitor), or 10(-5)-mol/L indomethacin (a cyclooxygenase inhibitor) significantly decreased the relaxant effect of magnesium on aortic rings from 16-day-pregnant but not 22-day-pregnant rats. Treatment with minimally effective concentrations of a nitric oxide donor (3 x 10(-10)-mol/L sodium nitroprusside) or a cyclic guanosine monophosphate analog (10(-6)-mol/L 8-bromo-cyclic guanosine monophosphate) restored the response to magnesium. CONCLUSIONS: The relaxant effect of magnesium on rat aortic rings was dependent on both endothelium and gestational age and was lower at term than during late pregnancy. The endothelium appears to potentiate the vasorelaxant effects of magnesium through the nitric oxide-cyclic guanosine monophosphate and cyclooxygenase systems.

Aminoquinolines↗

PubMed2001

Pragmatic randomised trial to evaluate the use of patient held records for the continuing care of patients with cancer.

OBJECTIVE: To evaluate the use of a multidisciplinary record held by patients with cancer in the community. DESIGN: Pragmatic randomised controlled trial. SETTING: The environs of Swansea in south west Wales. PARTICIPANTS: 501 patients under the care of the Department of Oncology, Singleton Hospital, Swansea. INTERVENTION: A patient held record used by the patient and healthcare professionals. Main outcome measures-Health related quality of life (EORTC QLQ-C30) measured at entry into the study and at 6 months; patients' views at 6 months; healthcare professionals' views collected after the completion of patient follow up; NHS resource and booklet use. RESULTS: 1148 patients were eligible for the study; 501 were recruited (44%) and 344 completed the study (172 in each group). There was no significant difference between the two groups in change in quality of life or NHS resource use. The patient held record did not have an impact on communication but was significantly helpful to patients in preparing for appointments, reducing difficulties in monitoring their own progress, and helping them to feel more in control (p<0.05). Fifty three percent of patients would have preferred not to have a patient held record. There was a low level of use of the record by healthcare professionals but most of those who remembered using it indicated that they would prefer patients to have it. CONCLUSIONS: The patient held record is valued by some patients and professionals but has no significant impact on the quality of life of patients or NHS resource use. It has a positive impact on quality by helping patients feel more in control and prepare for meetings with healthcare staff. Patients who find it useful tend to be younger and have more professionals involved in their care. It is recommended that it should be made available to patients on request and used by them according to need.

Adolescent↗

PubMed2000

Evolution of aortic dissection after surgical repair.

Patients after aortic dissection repair still have long-term unfavorable prognosis and need careful monitoring. The purpose of this study was to analyze the evolution of aortic dissection after surgical repair in correlation to anatomic changes emerging from systematic magnetic resonance imaging (MRI) follow-up. Between January 1992 and June 1998, 70 patients underwent surgery for type A aortic dissection. Fifty-eight patients were discharged from the hospital (17% operative mortality) and were followed by serial MRI for 12 to 90 months after surgery. In all, 436 postoperative MRI examinations were analyzed. In 13 patients (22.5%) no residual intimal flap was identified, whereas 45 patients (77.5%) presented with distal dissection, with a partial thrombosis of the false lumen in 24. The yearly aortic growth rate was maximum in the descending aortic segment (0.37 +/- 0.43 cm) and was significantly higher in the absence of thrombus in the false lumen (0.56 +/- 0.57 cm) (p <0.05). There were 4 sudden deaths, with documented aortic rupture in 2. Sixteen patients underwent reoperation for expanding aortic diameter. In all but 1 patient, a residual dissection was present (in 13 without any thrombosis of the false lumen). Close MRI follow-up in patients after dissection surgical repair can identify the progression of aortic pathology, providing effective prevention of aortic rupture and timely reoperation. Thrombosis of the false lumen appears to be a protective factor against aortic dilation.

Adult↗

PubMed2000

Open access follow up for inflammatory bowel disease: pragmatic randomised trial and cost effectiveness study.

OBJECTIVE: To evaluate whether follow up of patients with inflammatory bowel disease is better through open access than by routine booked appointments. DESIGN: Pragmatic randomised controlled trial. SETTING: Two district general hospitals in Swansea and Neath, Wales. PARTICIPANTS: 180 adults (78 with Crohn's disease, 77 ulcerative or indeterminate colitis, 25 ulcerative or idiopathic proctitis) recruited from outpatient clinics during October 1995 to November 1996. INTERVENTION: Open access follow up according to patient need. MAIN OUTCOME MEASURES: Generic (SF-36) and disease specific (UK inflammatory bowel disease questionnaire UKIBDQ) quality of life, number of primary and secondary care contacts, total resource use, and views of patients and general practitioners. RESULTS: There were no differences in generic or disease specific quality of life. Open access patients had fewer day visits (0.21 v 0. 42, P<0.05) and fewer outpatient visits ( 4.12 v 4.64, P<0.01), but some patients had difficulty obtaining an urgent appointment. There were no significant differences in specific investigations undertaken, inpatient days, general practitioner surgery or home visits, drugs prescribed, or total patient borne costs. Mean total cost in secondary care was lower for open access patients (P<0.05), but when primary care and patient borne costs were added there were no significant differences in total costs to the NHS or to society. General practitioners and patients preferred open access. CONCLUSIONS: Open access follow up delivers the same quality of care as routine outpatient care and is preferred by patients and general practitioners. It uses fewer resources in secondary care but total resource use is similar. Better methods of ensuring urgent access to outpatient clinics are needed.

Adult↗

PubMed2000

Role of nucleotide cyclases in the inhibition of pregnant rat uterine contractions by the openers of potassium channels.

OBJECTIVE: Our objective was to study the involvement of adenylate and guanylate cylases in spontaneous uterine contractions and inhibition induced by the opening of potassium channels. STUDY DESIGN: Uterine rings from rats at mid and term gestation and from rats at term gestation in labor were suspended in organ chambers for isometric tension recording. Concentration-response relationships to an opener of adenosine triphosphate-dependent potassium channels, levcromakalim, or to an opener of calcium-dependent potassium channels, NS 1619, were studied in the absence and presence of inhibitors of adenylate cyclase (MDL 12330 A, 2 x 10(-5) mol/L; SQ 22536, 10(-4) mol/L) or guanylate cyclase (LY 83583,3 x 10(-6) mol/L). RESULTS: MDL 12330 A and SQ 22536 accentuated contractions in rings from rats at mid gestation but not at term gestation or at term gestation in labor. LY 83583 inhibited contractions in the rings from all 3 groups. Levcromakalim was equally effective in inhibiting contractions of rings from all 3 groups. MDL 12330 A, but not SQ 22536, decreased sensitivity and maximal inhibition induced by levcromakalim (term gestation greater than mid gestation greater than term gestation in labor). LY 83583 decreased the sensitivity to and maximal inhibition induced by levcromakalim in rings from pregnant rats at mid gestation. NS 1619 attenuated contraction of rings from rats at mid gestation and, to a lesser extent, at term gestation but accentuated contractions in rings from animals at term gestation in labor. MDL 12330 A, but not SQ 22536 or LY 83583, attenuated the changes induced by NS 1619 in rings from all 3 groups. CONCLUSIONS: (1) The influence of nucleotide cyclases on basal uterine contractility depends on gestational age. (2) The inhibition of uterine contractions that results from the opening of calcium-dependent potassium channels depends on adenylate cyclase, whereas that of adenosine triphosphate-dependent potassium channels depends on both adenylate and guanylate cyclases. 3. Activation of adenosine triphosphate-dependent potassium channels is more efficient than activation of calcium-dependent potassium channels. 4. The inhibition induced by calcium-dependent potassium channel openers, but not adenosine triphosphate-dependent potassium channel openers, decreases as pregnancy progresses, and at delivery the activation of spontaneous contractile activity is evident.

Adenine↗

PubMed2000

Usefulness of transesophageal echocardiography during open heart surgery of mitral stenosis.

BACKGROUND: The aim of this study was to verify if the use of intraoperative transesophageal echocardiography (TEE), by detecting mitral insufficiency or residual stenosis during surgery, may improve medium term results in patients with severe mitral stenosis who undergo open heart valvuloplasty. METHODS: This prospective study included twenty-two patients (20 women and 2 men) with a mean age of 49+/-13 years with severe mitral stenosis. Mean follow-up was 32 months (range 12-55 months). All the patients underwent transthoracic echocardiography (TrE) before surgery and intraoperative TEE. Before surgery the mean transmitral gradient was 11+/-6.8 mmHg, the mean pressure half time (PHT) area was 0.89+/-0.19 cm2, the mean echo score was 8.9+/-2.2. Intraoperative TEE before the repair showed a mean echo score of 7.9+/-1.8. RESULTS: Two patients with unsatisfactory repair at TEE underwent immediate valve replacement. In the remaining patients, mean transmitral gradient and PHT valve area before discharge was 5.2+/-3 mmHg and 2.5 cm2. No patients had more than trivial mitral regurgitation. During the follow-up two patients had to be reoperated. Patients with poor immediate (2 patients) or medium term results (2 patients), had a mean echocardiographic score of 12.24, while patients with a satisfactory medium term outcome had a mean score of 7.27 (p<0.001). CONCLUSIONS: Intraoperative TEE may guide the surgeon in the assessment of valvuloplasty. However the absence of mitral regurgitation after repair and at discharge cannot predict the medium term results, which are related to the degree of the disease of the mitral valve.

Adult↗

PubMed1999

Effect of nitric oxide and carbon monoxide on uterine contractility during human and rat pregnancy.

OBJECTIVE: We sought to study the effects of authentic nitric oxide and carbon monoxide on the contractile activity of pregnant human and rat myometrium. STUDY DESIGN: Strips were prepared from uterine biopsy specimens of 10 pregnant, nonlaboring women at term gestation undergoing cesarean delivery. In addition, rings were prepared from the uteri of pregnant rats at midterm (day 14) and at term (day 22) gestation (n = 10-12). The tissues were mounted in organ chambers filled with Krebs-Henseleit solution continuously aerated with 5% carbon dioxide in air (37 degrees C, pH approximately 7.4) for isometric tension recording. The effects of nitric oxide and carbon monoxide gases on spontaneous contractile activity were studied. Responses to hemin (hemoxygenase substrate), which produces endogenous carbon monoxide, were also examined. Responses to nitric oxide and carbon monoxide were also studied in aortic and tail artery rings from pregnant rats after contraction with phenylephrine. RESULTS: Nitric oxide significantly inhibited contractility of human myometrium at term (area under the concentration-response curve, 145.36 +/- 30.02 vs 40.56 +/- 22.81 in controls; P <.05) and rat myometrium at midterm gestation (264.23 +/- 47.86 vs 121.82 +/- 23.50; P <.05) but not at term. No statistically significant inhibition was induced in human or rat myometrium by carbon monoxide, whereas hemin significantly attenuated contractility in human myometrium at term and in rat myometrium at midterm gestation (P <. 05). Nitric oxide, carbon monoxide, and hemin relaxed aortic and tail artery rings. CONCLUSIONS: Authentic nitric oxide inhibits rat uterine contractile activity at midterm gestation but not at term. However, nitric oxide inhibits human myometrium activity at term. Authentic carbon monoxide does not appear to modulate uterine contractility, whereas hemin may have some inhibitory properties.

Adult↗

PubMed1999

Roles of potassium channels and nitric oxide in modulation of uterine contractions in rat pregnancy.

OBJECTIVE: We sought to study the involvement of potassium channels in the inhibition by nitric oxide of spontaneous contractions in isolated uterine rings from midterm and term pregnant rats. STUDY DESIGN: Uterine rings from Sprague-Dawley rats at midterm and term gestation were used for isometric tension recording. The inhibition of spontaneous contractile activity by potassium channel openers and nitric oxide was studied in the absence and presence of potassium channel inhibitors. RESULTS: The adenosine triphosphate-dependent potassium channel opener levcromakalim inhibited spontaneous contractions in rings from both midterm and term pregnant rats in a concentration-dependent manner, and the effects were significantly attenuated by pretreatment with selective inhibitor of the adenosine triphosphate-dependent potassium channel inhibitor glibenclamide. The opener of calcium-dependent potassium channel NS 1619 inhibited spontaneous contractions in rings from midterm but significantly less so in rings from term pregnant rats in a concentration-dependent manner, and the effect was significantly attenuated by pretreatment with potassium channel inhibitors tetraethylammonium and tetrabutylammonium but not with glibenclamide. Rings from midterm and term pregnant rats were more sensitive to the inhibitory effect of levcromakalim compared with NS 1619. Nitric oxide donor diethylamine-nitric oxide inhibited spontaneous contractions in rings from midterm but significantly less in rings from term pregnant rats in a concentration-dependent manner, and the effect was attenuated by tetraethylammonium and tetrabutylammonium but not by glibenclamide. CONCLUSIONS: There is gestational age-dependent refractoriness to calcium-dependent potassium but not adenosine triphosphate-dependent potassium channel opener-induced inhibition of spontaneous contractile activity of isolated rat uterine rings. Nitric oxide inhibits uterine contractions by opening of calcium-dependent potassium channels in pregnant rat myometrium. Refractoriness to nitric oxide toward term may result from decreased probability to open or number of calcium-dependent potassium channels.

Adenosine Triphosphate↗