Search Results - (Author, Cooperation:R. G. Moore)

2014-11-14

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

2011-03-26

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2014-03-08

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

1572-879X

ethylbenzene ; styrene ; iron oxide ; potassium promotion

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Abstract The dehydrogenation of ethylbenzene to styrene over unpromoted and potassium-promoted model iron oxide catalysts has been studied using ultrahigh vacuum techniques in conjunction with elevated pressure reaction kinetics. Model iron oxide catalysts were prepared by oxidizing a polycrystalline Fe sample that was subsequently dosed with metallic potassium. At 875 K the unpromoted catalyst exhibited a turnover frequency of 5×10−4 molecules/ site s and an activation energy of 39 kcal/mol, both in excellent agreement with the results found for an analogous iron oxide powder catalyst. Potassium promotion increased the turnover frequency to 1.0×10−3 molecules/site s and lowered the activation energy to 36 kcal/mol for the dehydrogenation reaction. Similarities between the activation energies on the unpromoted and promoted catalysts indicate that the active site is the same on both catalysts. Creation of the active site was dependent upon the formation of an Fe3+ metastable species, consistent with the formation of a KFeO2 phase, upon the addition of potassium.

Electronic Resource

1433-0563

Key words Urethral strictive ; Balloon dilatation ; Laser urethrotomy ; Endoscopic urethroplasty ; Stent ; ”cut to the light” ; Schlüsselwörter Harnröhrenstriktur ; Ballondilatation ; Laserurethrotomie ; Endourethralplastik ; „cut to the light“

Springer Online Journal Archives 1860-2000

Medicine

Zusammenfassung Verbesserungen beim endourologischen Instrumentarium und Fortschritte bei den Behandlungsmethoden ermöglichen neue Alternativen bei der Behandlung der Harnröhrenstriktur. Die Urethrotomie unter Sicht als Standardbehandlungsverfahren ist mit einer erhöhten Strikturrezidivrate verbunden. Diese Erfahrungen führten zur Entwicklung von alternativen Methoden, die dieses Problem verhindern oder verringern sollen. In diesem Artikel wird die aktuelle Literatur aufgearbeitet. Neuere Methoden wie Ballondilatation, Laserurethrotomie, endoskopische Harnröhrenplastik, „Cut-to-the-light“- und „Core-through-Verfahren“ sowie Harnröhrenstentimplantation werden diskutiert.

Summary Advances in endoscopic instrumentation and techniques offer new alternatives for safe and effective treatment of urethral strictures. Visual internal urethrotomy, the standard treatment modality, is associated with new scar formation with stricture recurrence. This experience has led to the investigation of alternative techniques which would avoid or ameliorate this result. This article reviews the current literature and discusses these newer approaches, including balloon dilatation, laser urethrotomy, endoscopic urethroplasty, ”cut to the light” and ”core through” procedures, and urethral wallstent implantation.

Electronic Resource

1432-1041

Chlormethiazole ; pharmacokinetics ; man ; plasma levels ; gas-liquid chromatography

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Medicine

Summary The pharmacokinetics of chlormethiazole have been studied in six healthy volunteers following an intravenous infusion of the drug. The log. plasma concentration-time curve of chlormethiazole after cessation of the infusion was found to be curvilinear and was fitted therefore, by a bi-exponential equation computed by non-linear least squares regression analysis. Half-lives for the inital α-phase (0.54±0.05 h) and the terminal β-phase (4.05 ±0.60 h) were calculated together with other pharmacokinetic parameters of the two compartment open model. An explanation for the discrepancy between the presently reported plasma half-lives and those appearing in the literature has been presented. The pharmacokinetic treatment of the plasma concentration-time data obtained following intravenous infusion also enabled the prediction that the maximal systemic availability of an orally administered dose of chlormethiazole would be of the order of 15%.

Electronic Resource

1432-1041

Diazepam ; pharmacokinetics ; pregnant women ; plasma clearance ; blood/plasma concentration ratio ; placental transfer

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Medicine

Summary The disposition of diazepam has been studied in pregnant women at parturition. The plasma concentration of diazepam was monitored for at least 3 days in 18 women who received a single intravenous injection of 10 mg during the 10 h-period prior to delivery. Fourteen mothers had uneventful puerperia (Group I) and in 13 of these cases there was a pronounced postnatal increase in the plasma concentration of diazepam. The terminal phase half-life (t1/2) was significantly greater for Group I (mean = 65 h; range = 24–114 h) than for age-matched non-pregnant patients (mean = 29 h; range = 18–44 h from literature). The prolonged t1/2 appeared to be related to changes in the distribution of diazepam and not to a reduction in hepatic elimination since the total plasma clearance (Cltp) in these 14 pregnant patients (mean = 28 ml/min; range = 18–43 ml/min) was not reduced compared to that reported for non-pregnant controls (mean = 30 ml/min; range = 22–45 ml/min). Four mothers underwent postnatal surgery for tubal ligation (Group II) and the plasma concentration-time profiles for this group did not show the same postnatal phenomenon as did the profiles obtained for Group I. The t1/2 for Group II was shorter (mean = 31 h; range = 24–37 h) than for Group I and similar to that for the non-pregnant controls. The Cltp for Group II was greater (mean = 56 ml/min; range = 48–63 ml/min) than for both Group I and non-pregnant controls. These results suggest that delivery alters the disposition of diazepam and is generally associated with a postnatal re-distribution of diazepam into the systemic circulation. The blood/plasma concentration ratio was determined in 9 patients (mean = 0.62; range = 0.54–0.77). There was no difference in the total blood clearance between the pregnant patients of Group I and the non-pregnant controls. In most cases the umbilical venous plasma concentration (Cpuv) of diazepam was greater than the peripheral maternal venous plasma concentration (Cpmv) at delivery. The foetus appears to constitute a slowly equilibrating tissue-group in which diazepam does not reach equilibrium with the maternal systemic circulation for at least 5–10 h at which time the diazepam concentration in maternal and foetal plasma is similar.

Electronic Resource

1432-1041

Mepivacaine ; pharmacokinetics ; neonates ; healthy adults ; metabolism ; renal excretion ; lignocaine

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Medicine

Summary The pharmacokinetics and metabolism of mepivacaine has been studied in premature neonates dosed subcutaneously and in healthy adults dosed intravenously. The pharmacokinetics of mepivacaine in four neonates (N) was compared with that in six adults (A). Newborns had a significantly longer terminal phase half-life than adults (N mean 8.69 h; A mean 3.17 h). Total plasma clearance normalized on body weight was significantly smaller in neonates (mean 2.34 ml/min/kg) than in adults (mean 5.47 ml/min/kg), as was the hepatic blood clearance (N mean 1.37 ml/min/kg; A mean 5.10 ml/min/kg). The renal plasma clearance, however, was significantly greater in neonates (mean 0.76 ml/min/kg) than adults (mean 0.20 ml/min/kg). There was an average six-fold increase in the fraction of the dose excreted unchanged in newborns (mean 43.3%) compared to adults (mean 7.1%) with acidified urine (pH 5.5–6.0). There was significantly more of the mono-N-demethylated metabolite of mepivacaine excreted by newborns (mean 11.4%) than by adults (mean 2.2%), but their capacity to carry out aromatic hydroxylation of mepivacaine was negligible. These results for mepivacaine were compared with those previously reported for lignocaine in premature infants. The immaturity of hepatic function appears to have diminished more profoundly the ability of premature infants to metabolize mepivacaine than lignocaine. These findings are discussed in terms of perfusion theory of hepatic drug elimination.

Electronic Resource

1432-1041

diazepam ; perinatal period ; plasma NEFA concentration ; regression analyses ; alpha-1-acid glycoprotein concentrations

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Medicine

Summary The plasma binding of diazepam was determined serially in 24 women undergoing either elective induction of labour (vaginal or emergency caesarean delivery) or elective caesarean section at term and in 5 nonpregnant women requiring abdominal surgery. In the majority of pregnant patients, a marked increase in diazepam percentage free was observed during labour or prior to caesarean section, reaching a maximum, 1.6 to 3.2 fold increase at delivery or within 4 h postpartum; by the fifth day postpartum, diazepam percentage free was lower than on admission to hospital. In contrast, little change in diazepam percentage free was observed during the perisurgical period in nonpregnant patients. In parturient and surgical patients, the time courses of diazepam percentage free and plasma nonesterified fatty acid (NEFA) concentration were parallel. Bivariate regression analyses of pooled data demonstrated a strong correlation (r=0.642, p=〈0.01) between diazepam percentage free and corresponding NEFA concentration and a weaker correlation between diazepam percentage free and both albumin (r=−0.319, p〈0.02) or total protein (r=−0.438, p〈0.01). From multiple linear regression it was demonstrated that 54% of the variability in diazepam percentage free could be attributed to plasma NEFA and albumin concentrations. NEFA displacement of plasma bound diazepam was substantiated using crystalline human serum albumin. An approximate 65% increase in plasma α1acid glycoprotein levels was observed posttrauma in both parturient and surgical patients but was unrelated to diazepam binding events. A relationship between diazepam plasma binding changes and concurrently altered disposition of diazepam during parturition is postulated.

Electronic Resource

1432-1041

betamethasone ; pharmacokinetics ; cortisol ; high-performance liquid chromatography

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Medicine

Summary The pharmacokinetics of betamethasone and its phosphate ester are described in 8 healthy adults after i. v. bolus injection of 10.6 mg betamethasone phosphate. Both compounds were measured by high-performance liquid chromatography with ultraviolet detection using sample handling methods which prevented hydrolysis of the ester in vitro. Betamethasone phosphate disappeared rapidly from plasma (mean half-life=4.7 min) as betamethasone levels rose. Betamethasone plasma levels reached a peak 10–36 min after administration of the phosphate before declining in a biexponential manner. The terminal slow disposition phase had a mean half-life of 6.5 h. Only about 5% of the dose was recovered from urine as betamethasone, indicating extensive extrarenal clearance of betamethasone. Protein binding and blood/plasma concentration ratio were also determined. In comparison with its stereoisomer, dexamethasone, betamethasone is also cleared mainly by metabolism but has a lower plasma clearance, is less plasma bound, has a higher blood/plasma concentration ratio, and a higher volume of distribution. Endogenous cortisol levels were measured in the subjects who received betamethasone phosphate and in a matched control group of 4 subjects who did not. Betamethasone abolished the normal episodic secretion of cortisol and rapidly reduced its plasma concentration to a basal level. Cortisol plasma levels were not restored at 24 h but had returned to normal by 48 h after dosing.

Electronic Resource

1432-1041

zimelidine ; norzimelidine ; antidepressant ; pharmacokinetics ; bioavailability ; urinary excretion

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Medicine

Summary Five healthy adults were administered zimelidine orally (150 mg) and by intravenous infusion (20 mg) in a crossover design. Blood and urine samples were collected for a period of 28 hours after dosing and the concentrations of zimelidine and norzimelidine determined. There was no significant difference in terminal phase half-life of zimelidine after oral (4.7 h±1.3 SD) or intravenous dosing (5.1 h±0.7 SD). An average of 50% of the ingested oral dose reached the systemic circulation. Excretion of unchanged zimelidine in urine was on average 1.26% of the intravenous dose. In appears that zimelidine is completely absorbed from the gastrointestinal tract and “first-pass metabolism” in the liver reduces the bioavailability to 50%. The mean plasma half-life for norzimelidine was 22.8 h. The area under the plasma concentration time curve for norzimelidine after oral administration was 92% of that after intravenous administration. The plasma concentration of both zimelidine and norzimelidine are predicted to approach steady-state within 3–5 days.

Electronic Resource

1432-1041

Atenolol ; metoprolol CR ; elderly subjects ; subjective symptoms ; pharmacokinetics ; pharmacodynamics

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Medicine

Summary In a double-blind, randomised, cross-over study, the pharmacokinetic/dynamic effects and subjective symptoms of a new controlled-release (CR) formulation of metoprolol (50 and 100 mg) have been compared with atenolol (50 mg) and placebo in 20 elderly healthy subjects. The metoprolol CR formulation displayed an even plasma concentration-time profile over the dosage interval while atenolol produced a peak at 2–4 h. All three active treatments produced significant β1-blockade at 24 h compared to placebo. Four hours after dose intake, the degree of β1-blockade was significantly greater with conventional atenolol 50 mg than with either dose of metoprolol CR. Subjective well-being was examined with a self-administered questionnaire (MSE-profile), including three dimensions: Contentment, Vitality and Sleep. No significant differences were detected between placebo and either dose of metoprolol CR. At 2 h, following atenolol, a deterioration in Vitality was observed compared to placebo and metoprolol CR 100 mg. At the end of the dosage interval there was no longer any significant difference between the treatments. Perceived leg fatigue during exercise, evaluated 4 h after dosing, was more pronounced during treatment with atenolol than metoprolol CR 50 mg. The results suggest that the metoprolol CR formulation was not associated with significant effects on subjective well-being, whereas atenolol caused a deterioration at the time of the peak plasma concentration of the drug.

Electronic Resource

1432-2218

Laparoscopy ; Telemedicine ; Telementoring

Springer Online Journal Archives 1860-2000

Medicine

Abstract Background: To assess the feasibility of telementoring, a clinical telepresence system was developed. Methods: Telementoring was attempted in 14 advanced and 9 basic urologic laparoscopic procedures. The remote surgeon located in a control room (〉1,000 feet from operating room) supervised an inexperienced surgeon. Mentoring was accomplished with real-time video images, two-way audio communication, a robotic arm used to control the videoendoscope, and a telestrator. The patient outcome, complications, and operative time were assessed and compared to patients undergoing matched procedures in which the experienced surgeon was working side by side with the primary surgeon. Results: The overall telementoring success rate was 95.6% (22/23 cases) with no increase in complications. Telementoring of a laparoscopic radical nephrectomy failed secondary to improper positioning of the robotic arm. Operative times compared between telementored and traditionally mentored procedures were not statistically different for basic procedures but were longer for advanced cases. Conclusions: Telementoring of laparoscopic procedures is safe and feasible. Further clinical studies are needed prior to implementing telementoring in surgical training.

Electronic Resource

1432-2218

Key words: Robot — Laparoscopic surgery — Voice — Foot — Interface

Springer Online Journal Archives 1860-2000

Medicine

Abstract Background: In order for robotic devices to be introduced successfully into surgical practice, the development of transparent surgeon/machine interfaces is critical. Methods: This study evaluated the standard foot pedal for the AESOP robot compared to a voice control interface. Speed, accuracy, learning curves, durability of learning at 2 weeks, and operator-interface failures were analyzed in an ex vivo model. Results: Foot control was faster and had less operator-interface failures. Voice control was more accurate as measured by ``pass points.'' The foot control learning curve reached a plateau at the third trial, while the voice control did not fully plateau. Durability of learning favored the foot control but was not significantly different. Conclusions: Currently, the voice control is more accurate and has the advantage of not requiring the surgeon to look away from the operative field. However, it is slower and may require more attention as an interface. As voice recognition software continues to advance, speed and transparency are anticipated to improve.

Electronic Resource

1432-2218

Key words: Laparoscopy — Renal function — Oliguria — N-acetyl-β-D-glucosaminidase — Kidney

Springer Online Journal Archives 1860-2000

Medicine

Abstract Background: Oliguria during laparoscopy is a well-documented phenomenon of unknown etiology. Experimental evidence suggests that renal perfusion is reduced during pneumoperitoneum. N-acetyl-β-D-glucosaminidase (NAG), which is present in renal tubular cells, is released into the urine in response to tubular insults. In this study, urinary NAG was measured before and after procedures to assess for ischemic renal injury. Methods: A total of 31 patients underwent laparoscopic procedures while 28 patients had conventional surgery. Urine was obtained first at the time of preoperative Foley catheter placement and later during the recovery room stay. NAG levels were measured and indexed to urinary creatinine. Results: Operative time for the laparoscopy group was 105 min (range, 15–255); for the conventional group, it was 179 min (range, 75–385) (P 〈 0.05). No differences were noted between pre- and postoperative NAG levels or between the groups. There was no correlation between urinary NAG levels and operative time. Conclusion: Pneumoperitoneum is not associated with a change in the urinary concentration of NAG. This finding suggests that there is no significant renal tubular injury associated with laparoscopic surgery.

Electronic Resource

1432-2218

Key words: Telesurgery—Laparoscopy—Telemedicine

Springer Online Journal Archives 1860-2000

Medicine

Abstract Background: Minimally invasive surgical techniques yield significant individual, economic, and social benefits when performed by experienced surgeons. Unfortunately, many of these techniques, such as laparoscopy, are associated with steep learning curves, and the incidence of complications has clearly been shown to be inversely related to experience. The initial high complication rate and the dearth of experienced endoscopic surgeons have raised concerns over training, granting of hospital privileges, and most importantly patient safety. The goal of this study was to employ current telecommunications technology in a system for the mentoring of relatively inexperienced surgeons. Therefore, we created a telesurgical system that would allow an endoscopic specialist at a central site to offer guidance and assistance to a surgeon during a laparoscopic procedure. Methods: We developed a system that connected a central site and an operative site, a distance of approximately 3.5 miles, via a single T1 (1.54 Mbs) point-to-point communications link. The system provided real-time video display from either the laparoscope or an externally mounted camera located in the operating room, full duplex audio, telestration over live video, control of a robotic arm that manipulated the laparoscope, and access to electrocautery for tissue cutting or hemostasis. Results: Seven patients underwent laparoscopic procedures using the telesurgical consultation system over the communications link. In all cases, the primary surgeon had limited experience with the laparoscopic approach but still had the basic skills required to obtain intraperitoneal access. All seven cases were completed successfully without complications. Conclusion: These initial studies have demonstrated the feasibility, effectiveness, and safety of telementoring. Telesurgical applications have the potential to greatly improve surgical education, credentialing, and patient care by offering patients and their surgeons global access to surgical specialists.

Electronic Resource

0001-1541

Chemistry ; Chemical Engineering

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Process Engineering, Biotechnology, Nutrition Technology

Multiresponse kinetic models are established for the low-temperature oxidation (LTO) reactions of Athabasca oil sands bitumen. The models provide adequate description of the overall rate of oxygen consumption and of the reactions of the liquid phase bitumen components. The LTO models are suitable for use in the in situ combustion numerical simulators of the oil sands.

10 Ill.

Electronic Resource