bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Halothane on the Guanosine 5′ Triphosphate Binding Activity of G-Protein αiSubunits
Authors: Streiff John , Jones Kristofer , Perkins William J. , Warner David O. , Jones Keith A. 
Published: November 2003

Background
Receptor-mediated increases in the force produced by airway smooth muscle are attenuated by anesthetics such as halothane. Guanosine 5'-triphosphate (GTP) binding protein alpha subunits (Galpha(i)) are known to participate in the regulation of force in airway smooth muscle. The authors hypothesized that halothane would inhibit the ability of Galpha(i) subunits to bind a nonhydrolyzable analog of GTP (GTPgammaS).

Methods
The effect of halothane on both GTPase-specific activity and [35S]GTPgammaS binding were assayed using purified, recombinant Galpha(i1). In separate experiments, [35S]GTPgammaS binding to Galpha(i) in crude airway smooth muscle membrane preparations was assayed using an immunoprecipitation technique in the presence and absence of halothane.

Results
The steady state GTPase-specific activity of the recombinant Galpha(i1) was 0.033 +/- 0.018 (mean +/- SD) mole P(i) mole Galpha(i1)-1 min-1 under control conditions and 0.035 +/- 0.015 mole P(i) mole Galpha(i1)-1 min-1 in the presence of 1.1 +/- 0.2 mm halothane, a difference that is not significant. The mole fractions of recombinant Galpha(i1) bound to [35S]GTPgammaS were 0.49 +/- 0.02 and 0.60 +/- 0.02 at 10 and 20 min, respectively. The addition of halothane (1.26 +/- 0.07 mm) did not significantly change these values. Halothane did not affect the binding of [35S]GTPgammaS to Galpha(i) subunits in membrane fractions of airway smooth muscle as measured using immunoprecipitation. Validity of the assays was confirmed using suramin, an inhibitor of GTP binding.

Conclusion
These results suggest that halothane, which inhibits receptor-activated Galpha(i)-coupled pathways in intact airway smooth muscle, must functionally target a component of the G protein-coupled receptor complex other than Galpha(i).
Role of Protein Kinase C, Ca2+/Calmodulin-dependent Protein Kinase II, and Mitogen-activated Protein Kinases in Volatile Anesthetic–induced Relaxation in Newborn Rabbit Pulmonary Artery
Authors: Su Judy Y. , Vo Anhkiet C. 
Published: November 2003

Background
This study examined the responsiveness of skinned pulmonary arteries from newborn rabbit to volatile anesthetics and the role of protein kinase C (PKC), Ca2+/calmodulin-dependent protein kinase II (CaMKII), and the downstream effectors, mitogen-activated protein kinases (ERK1/2 and p38).

Methods
Pulmonary arterial strips from 9- to 12-day-old rabbits were mounted on force transducers and treated with saponin ("skinned" strips). The skinned strips were activated by pCa 6.3 until force reached a steady state (control). Isoflurane or halothane was then administered. The result (test) was expressed as a percentage of the control. Inhibitors included bisindolylmaleimide (Ca2+-dependent and -independent PKC), Gö6976 (Ca2+-dependent PKC), CKIINtide (CaMKII), KN-93 (CaMKII), PD98059 (MEK/ERK1/2), and SB203580 (p38).

Results
The anesthetics dose-dependently decreased pCa-induced force (4-32% for 1-5% isoflurane; 17-76% for 1-3% halothane). The inhibitors of PKC (bisindolylmaleimide and Gö6976) and MEK/ERK1/2 (PD98059) completely prevented the relaxation induced by 3% isoflurane and partially prevented that induced by 2% and 3% halothane with the same effective inhibitor concentrations. In contrast, the effective concentration of CaMKII inhibitors was a direct function of the anesthetic concentration for different inhibitors (KN-93 for isoflurane and CKIINtide for halothane), and that of the p38 inhibitor (SB20358) was a direct function of both anesthetics.

Conclusions
In Ca2+-clamped skinned pulmonary arterial strips from newborn rabbits, the anesthetics induce relaxation, which is prevented by the PKC inhibitors MEK/ERK/12, CaMKII, and p38. It is proposed that the anesthetic-induced relaxation is via cPKC/MEK/ERK1/2 and CaMKII/p38 pathways and, in addition, via CaMKII-p/MLCK-p(-)/MLC-p(-) for halothane.
Effect of Combining Naloxone and Morphine for Intravenous Patient-controlled Analgesia
Authors: Sartain James B. , Barry John J. , Richardson Christopher A. , Branagan Helen C. 
Published: November 2003

Background
An early study showed that a naloxone infusion decreased the incidence of morphine-related side effects from intravenous patient-controlled analgesia. The authors tested the hypothesis that a more convenient combination of morphine and naloxone via patient-controlled analgesia would decrease the incidence of side effects compared to morphine alone.

Methods
Patients scheduled for hysterectomy under general anaesthesia were enrolled in a double-blind, randomized, placebo-controlled trial. Patients received a standardized general anesthetic and postoperative patient-controlled analgesia. They were randomized to receive 60 mg patient-controlled analgesia morphine in 30 ml saline or 60 mg morphine in 30 ml saline with naloxone 0.8 mg. Parameters for patient-controlled analgesia were a 1-mg bolus of morphine with a 5-min lockout and no background infusion. Patient recall of nausea, vomiting, itching, and pain (at rest and with movement) were assessed at 6 and 24 h postoperatively by verbal rating score. Pain was also assessed by a 0- to 100-mm visual analog score, and sedation was assessed by an observer. The amount of morphine used and the requirements for symptomatic treatment were also recorded.

Results
Ninety-two patients completed the study, with no significant differences in outcomes between groups. At 24 h, the incidence of nausea was 84.8% in each group; the incidence of pruritus was 56.5% in the naloxone group and 58.7% in the placebo group. There were also no differences in symptomatic treatment requirements, pain scores, morphine use, or sedation between groups. The median dose of naloxone received equated to 0.38 microg x kg-1 x h-1 over 24 h.

Conclusions
There was no benefit from administering naloxone combined with morphine via patient-controlled analgesia.
Differential Modulation of Remifentanil-induced Analgesia and Postinfusion Hyperalgesia by S -Ketamine and Clonidine in Humans
Authors: Koppert Wolfgang , Sittl Reinhard , Scheuber Karin , Alsheimer Monika , Schmelz Martin , Schüttler Jürgen 
Published: November 2003

Background
Experimental studies and clinical observations suggest a possible role for opioids to induce pain and hyperalgesia on withdrawal. The authors used a new experimental pain model in human skin to determine the time course of analgesic and hyperalgesic effects of the mu-receptor agonist remifentanil alone or in combination with the N-methyl-D-aspartate-receptor antagonist S-ketamine or the alpha(2)-receptor agonist clonidine.

Methods
Thirteen volunteers were enrolled in this randomized, double-blind, placebo-controlled study. Transcutaneous electrical stimulation at a high current density (2 Hz, 67.3 +/- 16.8 mA, mean +/- SD) induced acute pain (numerical 11-point rating scale: 5-6 out of 10) and stable areas of mechanical hyperalgesia to punctate stimuli and touch (allodynia). The magnitude of pain and area of hyperalgesia were assessed before, during, and after drug infusion (remifentanil at 0.1 microg x kg-1 x min-1 and S-ketamine at 5 microg x kg-1 x min-1 over a period of 30 min, respectively; clonidine infusion at 2 microg/kg for 5 min).

Results
Remifentanil reduced pain and areas of punctate hyperalgesia during infusion. In contrast, postinfusion pain and hyperalgesia were significantly higher than control. During infusion of S-ketamine, pain and hyperalgesia decreased and gradually normalized after infusion. When given in combination, S-ketamine abolished postinfusion increase of punctate hyperalgesia but did not reduce increased pain ratings. Clonidine alone did not significantly attenuate pain or areas of hyperalgesia. However, when given in combination with remifentanil, clonidine attenuated postinfusion increase of pain ratings.

Conclusions
Opioid-induced postinfusion hyperalgesia could be abolished by S-ketamine, suggesting an N-methyl-d-aspartate-receptor mechanism. In contrast, elevated pain ratings after infusion were not reduced by ketamine but were alleviated by the alpha(2)-receptor agonist clonidine. The results of this study suggest different mechanisms of opioid-induced postinfusion antianalgesia and secondary hyperalgesia.
Chronically Infused Intrathecal Morphine in Dogs
Authors: Yaksh Tony L. , Horais Kjersti A. , Tozier Nicolle A. , Allen Jeffrey W. , Rathbun Michael , Rossi Steven S. , Sommer Claudia , Meschter Carol , Richter Philip J. , Hildebrand Keith R. 
Published: November 2003

Background
Despite the extensive use of intrathecal morphine infusion for pain, no systematic safety studies exist on its effects in high concentrations. The authors assessed the effects of morphine and clonidine given 28 days intrathecally in dogs.

Methods
Beagles with lumbar intrathecal catheters received solutions delivered by a vest-mounted infusion pump. Six groups (n = 3 each) received infusions (40 microl/h) of saline or 1.5, 3, 6, 9, or 12 mg/day of morphine for 28 days. Additional groups received morphine at 40 microl/h (1.5 mg/day) plus clonidine (0.25-1.0 mg/day) or clonidine alone at 100 microg/h (4.8 mg/day).

Results
In animals receiving 9 or 12 mg/day morphine, allodynia was observed shortly after initiation of infusion. A concentration-dependent increase in hind limb dysfunction evolved over the infusion interval. Necropsy revealed minimal reactions in saline animals. At the higher morphine concentrations (all dogs receiving 12 mg/day), there was a local inflammatory mass at the catheter tip that produced significant local tissue compression. All animals with motor dysfunction displayed masses, although all animals with masses did not show motor dysfunction. The mass, arising from the dura-arachnoid layer, consisted of multifocal accumulations of neutrophils, monocytes, macrophages, and plasma cells. Inflammatory cells and endothelial cells displayed significant IL1beta, TNFalpha, iNOS, and eNOS immunoreactivity. No evidence of bacterial or fungal involvement was detected. There were no other changes in spinal morphologic characteristics. In four other groups of dogs, clonidine alone had no effect and in combination with morphine reduced the morphine reaction.

Conclusions
The authors found that high intrathecal morphine concentrations lead to aseptic intrathecal inflammatory masses. The lack of effect of clonidine and the possible suppressive effects of clonidine on the local reaction suggest the utility of such coadministration.
Safety of Chronic Intrathecal Morphine Infusion in a Sheep Model
Authors: Gradert Tamara Lee , Baze Wallace B. , Satterfield William C. , Hildebrand Keith R. , Johansen Mary J. , Hassenbusch Samuel J. 
Published: November 2003

Background
The safety of chronically administered intrathecal morphine has been questioned. Therefore, the authors examined the behavioral and neurologic effects and neurotoxicity of continuous intrathecal morphine administration in sheep.

Methods
Groups of three sheep were implanted with intrathecal infusion systems for the continuous administration of morphine (3, 6, 9, 12, or 18 mg/day) or saline at a fixed infusion rate of 1.92 ml/day beginning approximately 7 days after implantation. Sheep were examined daily for any changes in behavior or neurologic function. After 28-30 days, the animals were humanely killed. Cerebrospinal fluid samples were collected and analyzed for protein, erythrocytes and leukocytes, and morphine content. The spinal cord and meninges with the catheter in situ was removed en bloc and fixed in formalin for histologic analysis.

Results
Unilateral hind-leg gait deficits were observed in two of three animals in each of the 12- and 18-mg/day dose groups. Gross and microscopic evaluation of spinal cord tissue from these animals revealed intradural-extramedullary inflammatory masses that compressed the spinal cord at the catheter-tip and mid-catheter areas. This inflammation was ipsilateral to extremities that exhibited gait deficits and had acute and chronic cellular components.

Conclusions
The toxicity of intrathecal morphine seems to be dependent on the amount of morphine infused, although the effects of dose versus concentration cannot be clearly distinguished in this study. Intrathecal morphine doses of 12- 18 mg/day produced inflammatory masses extending from the catheter tip down the length of the catheter within the subarachnoid space. Doses of 6-9 mg/day produced mild-to-moderate inflammation 5 cm cranial to the catheter tip. A dose of 3 mg/day produced no neurotoxicity and spinal histopathologic changes that were equivalent to those observed in the saline-treated animals.
Plasticity in Action of Intrathecal Clonidine to Mechanical but Not Thermal Nociception after Peripheral Nerve Injury
Authors: Paqueron Xavier , Conklin Dawn , Eisenach James C. 
Published: November 2003

Background
Intrathecal clonidine reduces tactile allodynia in animal models of neuropathic pain, and this effect is blocked by atropine. However, the role of tonic spinal cholinergic activity and its interaction with alpha2-adrenergic systems in normal and neuropathic conditions and to different sensory methods has not been systematically examined. The authors examined cholinergic receptor involvement in thermal and mechanical sensitivity in normal and neuropathic animals and its interaction with intrathecal clonidine.

Methods
Normal rats and rats that received L5/L6 spinal nerve ligation were tested with acute radiant heat, paw pressure, and punctate mechanical stimulation before and after the intrathecal administration of saline, the muscarinic receptor antagonist, atropine, or a toxin to destroy cholinergic neurons, and then after intrathecal clonidine.

Results
Atropine, the cholinergic neuronal toxin, and saline did not alter baseline withdrawal thresholds. In nerve-injured rats, neither saline nor atropine altered antinociception from clonidine to a thermal stimulus, but atropine reduced the effect of clonidine to von Frey filament withdrawal threshold (34 +/- 5.6 vs. 14 +/- 5.8 g [mean +/- SEM], saline vs. atropine; P < 0.05) and to withdrawal threshold to paw pressure after clonidine (174 +/- 18 g vs. 137 +/- 16 g, saline vs. atropine; P < 0.05).

Conclusions
These data suggest that after nerve injury, mechanical but not thermal antinociception from intrathecal clonidine relies on a muscarinic interaction, because only mechanical antinociception was antagonized by atropine. These results do not favor a regulation of nociceptive transmission by a tonic release of acetylcholine in nerve-injured rats.
Protocol for the Sequence Analysis of Ryanodine Receptor Subtype 1 Gene Transcripts from Human Leukocytes
Authors: Kraev Natasha , Loke Julian C. P. , Kraev Alexander , MacLennan David H. 
Published: November 2003

Background
The search for novel mutations in the ryanodine receptor subtype 1 (RYR1) gene causing malignant hyperthermia and central core disease is hampered by the fact that the gene contains 106 exons. Searching for novel mutations in complementary DNA (cDNA) requires an invasive muscle biopsy. Accordingly, an alternate source of RYR1 cDNA was sought for sequence analysis.

Methods
Leukocytes were isolated from human blood and used for extraction of RNA and reverse transcription of messenger RNA into cDNA. A detailed protocol was developed in which overlapping fragments of RYR1 cDNA were amplified by polymerase chain reaction in a series of steps and used for double-strand sequencing.

Results
The sequences of full-length leukocyte RYR1 cDNA obtained from four human blood samples were shown to be identical to the sequence of a human muscle RYR1 cDNA. The incidence of aberrant splicing was more pronounced in the blood-derived cDNAs, but this could be minimized by adequate sample preparation. Protocols to sequence alternatively spliced products were also developed. Several silent nucleotide polymorphisms were detected, and minor revisions were made to the RYR1 sequence.

Conclusions
Because there are no differences in RYR1 transcript structure between muscle and leukocytes, aside from those that may be ascribed to RNA splicing aberrations during processing, leukocytes seem to be an adequate substitute tissue for screening the RYR1 gene for previously undiscovered mutations in families with malignant hyperthermia or central core disease.
Detection of a Novel Ryanodine Receptor Subtype 1 Mutation (R328W) in a Malignant Hyperthermia Family by Sequencing of a Leukocyte Transcript
Authors: Loke Julian C. P. , Kraev Natasha , Sharma Parveen , Du GuoGuang , Patel Leena , Kraev Alexander , MacLennan David H. 
Published: November 2003

Background
To determine whether malignant hyperthermia (MH) susceptibility in a Canadian pedigree is associated with a mutation in the ryanodine receptor subtype 1 (RYR1) gene, the complete RYR1 transcript obtained from the leukocytes of one MH-susceptible family member was sequenced, using a newly developed protocol.

Methods
RNA was extracted from leukocytes and converted into complementary DNA. Overlapping fragments of RYR1 complementary DNA were amplified by the polymerase chain reaction and used for double-strand sequencing to find a single mutation likely to be causal of MH susceptibility. Inheritance of the mutation in the family was studied by restriction endonuclease analysis and/or sequencing of genomic DNA and compared to available caffeine halothane contracture test data. The mutation was introduced into rabbit RYR1 complementary DNA, the complementary DNA was expressed in human embryonic kidney line 293 cells, and Ca2+ release by the mutant Ca2+ release channel was measured following the addition of caffeine and halothane.

Results
A novel arginine 328 to tryptophan mutation in RYR1 was detected by direct sequencing of the RYR1 transcript from leukocytes of one MH-susceptible individual. A causal role for this mutation in MH is indicated by cosegregation of the mutation with the MH-susceptible phenotype within the family and by the demonstration that the mutant channel has increased sensitivity to both caffeine and halothane.

Conclusions
The feasibility of using complete RYR1 transcripts from leukocytes for sequence analysis offers an efficient and noninvasive method for scanning RYR1 for novel mutations.
Propofol Reduces Perioperative Remifentanil Requirements in a Synergistic Manner
Authors: Mertens Martijn J. , Olofsen Erik , Engbers Frank H. M. , Burm Anton G. L. , Bovill James G. , Vuyk Jaap 
Published: November 2003

Background
Remifentanil is often combined with propofol for induction and maintenance of total intravenous anesthesia. The authors studied the effect of propofol on remifentanil requirements for suppression of responses to clinically relevant stimuli and evaluated this in relation to previously published data on propofol and alfentanil.

Methods
With ethics committee approval and informed consent, 30 unpremedicated female patients with American Society of Anesthesiologists physical status class I or II, aged 18-65 yr, scheduled to undergo lower abdominal surgery, were randomly assigned to receive a target-controlled infusion of propofol with constant target concentrations of 2, 4, or 6 microg/ml. The target concentration of remifentanil was changed in response to signs of inadequate anesthesia. Arterial blood samples for the determination of remifentanil and propofol concentrations were collected after blood-effect site equilibration. The presence or absence of responses to various perioperative stimuli were related to the propofol and remifentanil concentrations by response surface modeling or logistic regression, followed by regression analysis. Both additive and nonadditive interaction models were explored.

Results
With blood propofol concentrations increasing from 2 to 7.3 microg/ml, the C(50) of remifentanil decreased from 3.8 ng/ml to 0 ng/ml for laryngoscopy, from 4.4 ng/ml to 1.2 ng/ml for intubation, and from 6.3 ng/ml to 0.4 ng/ml for intraabdominal surgery. With blood remifentanil concentrations increasing from 0 to 7 ng/ml, the C(50) of propofol for the return to consciousness decreased from 3.5 microg/ml to 0.6 microg/ml.

Conclusions
Propofol reduces remifentanil requirements for suppression of responses to laryngoscopy, intubation, and intraabdominal surgical stimulation in a synergistic manner. In addition, remifentanil decreases propofol concentrations associated with the return of consciousness in a synergistic manner.
Spontaneous Breathing Improves Lung Aeration in Oleic Acid–induced Lung Injury
Authors: Wrigge Hermann , Zinserling Jörg , Neumann Peter , Defosse Jerome , Magnusson Anders , Putensen Christian , Hedenstierna Göran 
Published: November 2003

Background
Experimental and clinical studies have shown reduction in intrapulmonary shunt with improved oxygenation by spontaneous breathing with airway pressure release ventilation (APRV) in acute lung injury. The mechanisms of these findings are not clear. The authors hypothesized that spontaneous breathing results in better aeration of lung tissue and that improvement in oxygenation can be explained by these changes. This hypothesis was studied in a porcine model of oleic acid-induced lung injury.

Methods
Two hours after induction of lung injury, 24 pigs were randomly assigned to APRV with or without spontaneous breathing at a positive end-expiratory pressure of 5 cm H(2)O. Hemodynamics, spirometry, and end-expiratory lung volume by nitrogen washout were measured at baseline, after 2 h of lung injury, and after 2 and 4 h of mechanical ventilation in the specific mode. Finally, spiral computed tomography of the chest was performed at end-expiratory lung volume in 22 pigs.

Results
Arterial carbon dioxide tension and mean and end-inspiratory airway pressures were comparable between settings. Four hours of APRV with spontaneous breathing resulted in improved oxygenation compared with APRV without spontaneous breathing (arterial oxygen tension, 144 +/- 65 vs. 91 +/- 50 mmHg, P < 0.01 for interaction time x mode), higher end-expiratory lung volume (786 +/- 320 vs. 384 +/- 148 ml, P < 0.001), and better aeration. End-expiratory lung volume and venous admixture were both correlated with the amount of lung reaeration (r(2) = 0.62 and r(2) = 0.61, respectively).

Conclusions
The results support the hypothesis that spontaneous breathing during APRV improves oxygenation mainly by recruitment of nonaerated lung and improved aeration of the lungs.