Contribution of nitric oxide to beta2-adrenoceptor mediated vasodilatation in human forearm arterial vasculature.
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AIMS: beta2-adrenoceptor agonists are generally considered to produce endothelium independent vasodilatation through adenylate cyclase. We determined whether nitric oxide contributes to beta2-adrenoceptor vasodilatation in human arterial vasculature. METHODS: Forearm blood flow responses to brachial intra-arterial infusions of ritodrine (2.5-50 microg min(-1)), a selective beta2-adrenoceptor agonist, were determined in 24 healthy, normotensive subjects (mean age 22 years, 5F) on two occasions with initial and concomitant administration of L-NMMA (800 microg min(-1)), an NO synthase inhibitor, or noradrenaline (5-30 ng min(-1)), a control constrictor not affecting basal NO activity. Responses to the endothelium dependent vasodilator scrotonin (n = 6) and an endothelium independent vasodilator GTN (n = 9) were also determined. RESULTS: Maximal dilatation to ritodrine during L-NMMA infusion (310+/-32%; mean+/-s.e.mean) was reduced compared to that during noradrenaline infusion (417+/-41%, P<0.05), as were summary responses (1023+/-101 vs 1415+/-130; P<0.05). Responses to GTN were unaffected by L-NMMA compared to noradrenaline; max 177+/-26 vs 169+/-20%, 95% CI for difference -33,48; P=0.68; summary response 361+/-51 vs 396+/-37, 95% CI -142,71; P=0.46. Dilator responses to serotonin were reduced by L-NMMA; max 64+/-20 vs 163+/-26%, P<0.01; summary response 129+/-36 vs 293+/-60; P<0.05) and to a greater extent than ritodrine (58+/-7 vs 25+/-14%, P<0.05). CONCLUSIONS: beta2-adrenoceptor mediated vasodilatation in the human forearm has an NO mediated component. The underlying mechanism for this effect is unclear, but flow mediated vasodilatation is unlikely to be responsible. (+info)
Fimbrial capture of the ovum and tubal transport of the ovum in the rabbit, with emphasis on the effects of beta 2-adrenoreceptor stimulant and prostaglandin F2 alpha on the intraluminal pressures of the tubal ampullae.
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PURPOSE: Our purpose was to elucidate the roles of the ampullar and isthmic portions of the oviduct and the effects of drugs on oviductal contractility. METHODS: Prostaglandin F2 alpha (PGF2 alpha; Ono Pharmaceuticals, Osaka) and oxytocin (Atonin-O; Teikoku Hormone Manufacturing Co. Ltd., Tokyo) were used to stimulate oviductal contractility, and ritodrine hydrochloride (Utemerin; Solvay-Duphar Corp., Denmark) to inhibit the contractility. RESULTS: Both PGF2 alpha and Atonin-O were involved in ovum capture by the ampullar oviduct by stimulating contractility, thus altering the intraductal pressures. Utemerin is effective in inhibiting the enhanced contractility induced by PGF2 alpha and Atonin-O. CONCLUSIONS: Variations in pressure of the ampullar portion of the oviduct seem necessary for the capture of ova expelled from the ovary. Once in the isthmic portion of the oviduct, transport appears to be under the influence of ciliary activity rather than variations in contractility. (+info)
Effect of maternal tocolysis on the incidence of severe periventricular/intraventricular haemorrhage in very low birthweight infants.
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AIM: To examine the relation between grade III-IV periventricular/intraventricular haemorrhage (PVH/IVH) and antenatal exposure to tocolytic treatment in very low birthweight (VLBW) premature infants. STUDY DESIGN: The study population consisted of 2794 infants from the Israel National VLBW Infant Database, of gestational age 24-32 weeks, who had a cranial ultrasound examination during the first 28 days of life. Infants of mothers with pregnancy induced hypertension or those exposed to more than one tocolytic drug were excluded. Of the 2794 infants, 2013 (72%) had not been exposed to tocolysis and 781 (28%) had been exposed to a single tocolytic agent. To evaluate the effect of tocolysis and confounding variables on grade III-IV PVH/IVH, the chi(2) test, univariate analysis, and a logistic regression model were used. RESULTS: Of the 781 infants (28%) exposed to tocolysis, 341 (12.2%) were exposed to magnesium sulphate, 263 (9.4%) to ritodrine, and 177 (6.3%) to indomethacin. The overall incidence of grade III-IV PVH/IVH was 13.4%. In the multivariate logistic regression analysis, the following factors were related significantly and independently to grade III-IV PVH/IVH: no prenatal steroid treatment, low gestational age, one minute Apgar score 0-3, respiratory distress syndrome, patent ductus arteriosus, mechanical ventilation, and pneumothorax. Infants exposed to ritodrine tocolysis (but not to the other tocolytic drugs) were at significantly lower risk of grade III-IV PVH/IVH after adjustment for other variables (odds ratio = 0.3; 95% confidence interval 0.2 to 0.6). CONCLUSION: This study suggests that antenatal exposure of VLBW infants to ritodrine tocolysis, in contrast with tocolysis induced by magnesium sulphate or indomethacin, was associated with a lower incidence of grade III-IV PVH/IVH. (+info)
Changes in fetal hemodynamics with ritodrine tocolysis.
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OBJECTIVE: To evaluate the effect of ritodrine on the fetal cardiovascular system. METHODS: Cardiac and extracardiac Doppler waveforms were recorded in 12 fetuses prior to and during ritodrine therapy used for preterm labor. Maternal and fetal heart rates, the Doppler pulsatility indices of the umbilical artery, middle cerebral artery, descending thoracic aorta and renal artery, and time velocity integrals of the atrioventricular valves and the ductus arteriosus, were measured. RESULTS: Ritodrine infusion caused an increase in maternal and fetal heart rates, the left cardiac output as measured by the product of time velocity integral and heart rate, and the pulsatility index of the middle cerebral artery, and a decrease in the pulsatility index of the umbilical artery. CONCLUSIONS: Ritodrine infusion may alter placental and cerebral blood flow and may have a selective effect on the left side of the heart. (+info)
Invasive pulmonary aspergillosis in a puerperant with drug-induced agranulocytosis.
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Invasive pulmonary aspergillosis (IPA) is an acute infection of Aspergillus species to the lungs. It generally occurs in immunocompromised hosts, especially with neutropenia. We report a 30-year-old puerperant, who developed IPA from agranulocytosis. She had been treated for threatened labor with ritodrine and cefepime, one of which induced agranulocytosis. After vaginal delivery of twins, pneumonia emerged in the right lower lobe. She was diagnosed to have IPA according to the halo sign on computed tomography (CT) and positive circulating antibody against Aspergillus, and was treated successfully with oral itraconazole followed by surgical resection. It is important to note that IPA might arise in otherwise immunocompetent hosts when neutropenia is long-standing. (+info)
The importance of oxytocin mechanisms in the control of mouse parturition.
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The role of oxytocin in parturition in mice was investigated. Pup birth profiles, blood samples and brains were collected from parturient mice observed under red light conditions in a reversed light:dark photoperiod. Peripheral administration of an oxytocin antagonist in a dose-dependent manner delayed the birth of subsequent pups, indicating that oxytocin is required for a normal pup birth profile. Oxytocin neurones were activated during birth as shown by both increased immediate early gene ( Fos) expression in oxytocin neurones in the supraoptic nucleus and increased plasma oxytocin concentrations during birth. In addition, the nucleus of the tractus solitarius and the olfactory bulbs, sites that process inputs to oxytocin neurones, become activated during parturition. Exposure to stress during parturition halted subsequent deliveries; at this stage plasma oxytocin concentrations were not higher than those of virgin mice, and birth was restored by administration of oxytocin. Administration of beta-adrenergic antagonist (propranolol) also restored stress-delayed birth, whereas administration of ritrodrine (beta-agonist) delayed birth in non-stressed mice, indicating that adrenergic mechanisms contribute to stress-delayed births in mice. Administration of morphine (mu-opioid agonist) delayed births transiently, but naloxone (opioid antagonist) did not prevent stress-delayed birth, indicating that endogenous opioids do not appear to contribute to neuroendocrine or uterine mechanisms that promote birth in mice. Therefore, despite evidence in oxytocin knockout mice that oxytocin is not essential for parturition in this species, the results of the present study indicate that oxytocin neurone activity and secretion contribute to the birth process in normal mice. (+info)
Effects of meluadrine tartrate and ritodrine hydrochloride on oxytocin-induced uterine contraction, uterine arterial blood flow and maternal cardiovascular function in pregnant goats.
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This study was designed to elucidate the effects of meluadrine tartrate on oxytocin-induced uterine contraction and maternal hemodynamics in unanesthetized, chronically instrumented pregnant goats. After the administration of meluadrine tartrate or ritodrine hydrochloride to pregnant goats, changes in heart rate (HR), arterial blood pressure (AOP), and arterial blood pH and gasses (P(O2) and P(CO2)) in the mother, as well as changes in intrauterine pressure (IUP) and uterine arterial blood flow (UBF), were measured. The escalating administration of meluadrine tartrate (0.03, 0.1, 0.3 and 1 micro g. kg(-)(1). min(-)(1)) or ritodrine hydrochloride (1, 3, 10 and 30 microg. kg(-)(1). min(-)(1)) to the maternal femoral vein caused a marked and similar inhibition in oxytocin-induced uterine contraction (a rise in IUP). By these escalating dosings, maternal HR was increased dose-dependently in both treatment groups; however, the degree of the HR increase in the meluadrine tartrate-treatment group was significantly less than that in the ritodrine hydrochloride-treatment group. Furthermore, the degree of the UBF decrease in the meluadrine tartrate-treatment group was significantly less than that in the ritodrine hydrochloride-treatment group. The present study suggests that meluadrine tartrate has a mild influence on the maternal cardiovascular function relative to the effects of ritodrine taking the potent efficacy on oxytocin-induced uterine contraction into account. (+info)
Effects of meluadrine tartrate on maternal metabolic responses and fetal hemodynamics in pregnant goats.
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This study was designed to elucidate the effects of meluadrine tartrate on maternal metabolic responses and fetal hemodynamics in unanesthetized, chronically instrumented pregnant goats. After the administration of meluadrine tartrate to pregnant goats or directly to fetuses, changes in heart rate (HR), arterial blood pressure and arterial blood pH, gasses, electrolytes and metabolic responses were measured. The constant administration of meluadrine tartrate (0.1 microg. kg(-)(1). min(-)(1)) to pregnant goats resulted in the increases of maternal HR, glucose and free fatty acid and the decrease of maternal blood K(+) concentration. The direct escalating administration of meluadrine tartrate (0.01, 0.03 and 0.1 microg. kg(-)(1). min(-)(1)) did not increase the fetal HR, while ritodrine hydrochloride (0.3, 1 and 3 microg. kg(-)(1). min(-)(1)) to fetuses increased the fetal HR dose-dependently. The present study suggests that meluadrine tartrate has a mild influence relative to the effects of ritodrine to the maternal metabolic responses and fetal cardiovascular function. (+info)