bluuebunny/crossref_metadata_2025 huggingface dataset:
Possible mechanisms of action in quercetin reversal of morphine tolerance and dependence
Authors: NAIDU PATTIPATI , SINGH AMANPREET , JOSHI DIPESH , KULKARNI SHRINIVAS
Published: November 2003

In an earlier study, we reported the ability of quercetin to reverse the development of morphine tolerance and dependence in mice. In the present study we have attempted to explore the possible involvement of nitric oxide (NO) system in quercetin reversal of morphine tolerance and dependence in mice. Co‐administration of L ‐N G ‐nitro arginine methyl ester (L ‐NAME) or quercetin with morphine during the induction phase (days 1–9) delayed the development of tolerance to the antinociceptive action of morphine and also reversed naloxone precipitated withdrawal jumps. L ‐Arginine administration during the induction phase enhanced the development of tolerance to the antinociceptive effect of morphine but had no effect on the naloxone‐precipitated withdrawal jumps. During the expression phase (day 10) acute administration of quercetin or L ‐NAME reversed, whereas L ‐arginine facilitated naloxone‐ precipitated withdrawal jumps in morphine‐tolerant mice, but none of these drugs affected the nociceptive threshold in morphine‐tolerant mice. Further, co‐administration of quercetin or L ‐NAME with L ‐arginine during the induction phase antagonized the latter effects on the development of morphine tolerance. Also, prior administration of quercetin or L ‐NAME reversed the L ‐arginine potentiation of naloxone‐precipitated withdrawal jumps in morphine‐tolerant mice. The results of the present study suggest that quercetin reversal of morphine tolerance and dependence may involve its ability to suppress nitric oxide synthase (NOS) activity.
Predicting treatment time with the Lidcombe Program: replication and meta‐analysis
Authors: Kingston Mary , Huber Anna , Onslow Mark , Jones Mark , Packman Ann
Published: November 2003

Background: The benefits of treating stuttering close to onset have become obvious in recent years, and the Lidcombe Program has emerged as an effective and safe treatment method for children in their preschool years. The benefits of implementing the programme with young children, however, need to be weighed against the knowledge that many children recover from stuttering without treatment. In light of this, speech‐language therapists need to know how long treatment is likely to take and whether treatment time can be predicted. In particular, they need to know if adopting a ‘watchful waiting’ approach—to see if natural recovery occurs—jeopardizes responsiveness to treatment. A recent Australian study of 250 preschool‐age children found that stuttering rate was the only significant predictor of treatment time with the Lidcombe Program. In other words, children whose stuttering was more severe took longer to pass through the programme. There were other trends in the data but they did not reach significance.

Aims: The present study, conducted independently in the UK, was designed to replicate the Australian study. Direct replication enabled pooling of the data from the two studies in a meta‐analysis.

Methods & Procedures: The study included 66 children who began treatment before 6 years of age. They were treated with the Lidcombe Program at a specialist stuttering clinic in Norwich. Logistic regression analyses were conducted on the data. The data from both the British and Australian cohorts were pooled in a meta‐analysis.

Outcomes & Results: Results indicated that Stage 1 of the Lidcombe Program was completed in a median of 11 clinic visits, which is in line with the findings of the Australian study. Stuttering rate at first clinic visit was again found to be a significant predictor of treatment time. The remaining data trends were similar to those in the Australian data. In the meta‐analysis, stuttering rate was once more found to be a predictor of treatment time. Of particular interest, however, was that the increased power provided by the meta‐analysis identified an additional predictor, namely onset‐to‐treatment interval. Contrary to what is known about the responsiveness of children to the Starkweather and Gottwald treatment, and contrary to what might be expected given what we know about natural recovery, children who had been stuttering for more than 12 months took less time to progress through the programme than children who had been stuttering for less than 12 months.

Conclusions: These findings indicate that delaying intervention with the Lidcombe Program for 1 year after onset, within the preschool years, is unlikely to jeopardize responsiveness to treatment. The clinical implications of these findings are discussed.
Autism and autism risk in siblings of children with specific language impairment
Authors: Tomblin J. Bruce , Hafeman Laura L. , O'Brien Marlea
Published: November 2003

Background: Several studies have shown that family members of children with autism have elevated rates of spoken and written speech and language problems. Aims: This study asked whether there was also a greater rate of siblings with autism among probands with specific language impairment.

Methods & Procedures: The probands in this study were 158 children with specific language impairment and 132 children with normal language status. These probands had 522 siblings who were examined for risk of autism using the Autism Behavior Checklist. Siblings found to be at risk were then examined using the Autism Diagnostic Interview—Revised and the Autism Diagnostic Observation Schedule‐G.

Outcomes & Results: A concentration of siblings with risk for a diagnosis of autism was found in association with probands who had poor spoken language skills. Four siblings of the 522 (0.8%) met the diagnostic standards for autism. All the probands of these siblings had spoken language scores below − 1 SD and three had diagnoses of spoken language impairment.

Conclusions: These data provide additional support for a familial association between autism and spoken language impairment.
Cellular levels of p120 catenin function as a set point for cadherin expression levels in microvascular endothelial cells
Authors: Xiao Kanyan , Allison David F. , Buckley Kathleen M. , Kottke Margaret D. , Vincent Peter A. , Faundez Victor , Kowalczyk Andrew P.
Published: November 2003

The mechanisms by which catenins regulate cadherin function are not fully understood, and the precise function of p120 catenin (p120ctn) has remained particularly elusive. In microvascular endothelial cells, p120ctn colocalized extensively with cell surface VE-cadherin, but failed to colocalize with VE-cadherin that had entered intracellular degradative compartments. To test the possibility that p120ctn binding to VE-cadherin regulates VE-cadherin internalization, a series of approaches were undertaken to manipulate p120ctn availability to endogenous VE-cadherin. Expression of VE-cadherin mutants that competed for p120ctn binding triggered the degradation of endogenous VE-cadherin. Similarly, reducing levels of p120ctn using siRNA caused a dramatic and dose-related reduction in cellular levels of VE-cadherin. In contrast, overexpression of p120ctn increased VE-cadherin cell surface levels and inhibited entry of cell surface VE-cadherin into degradative compartments. These results demonstrate that cellular levels of p120ctn function as a set point mechanism that regulates cadherin expression levels, and that a major function of p120ctn is to control cadherin internalization and degradation.
A core function for p120-catenin in cadherin turnover
Authors: Davis Michael A. , Ireton Renee C. , Reynolds Albert B.
Published: November 2003

p120-catenin stabilizes epithelial cadherin (E-cadherin) in SW48 cells, but the mechanism has not been established. Here, we show that p120 acts at the cell surface to control cadherin turnover, thereby regulating cadherin levels. p120 knockdown by siRNA expression resulted in dose-dependent elimination of epithelial, placental, neuronal, and vascular endothelial cadherins, and complete loss of cell–cell adhesion. ARVCF and δ-catenin were functionally redundant, suggesting that proper cadherin-dependent adhesion requires the presence of at least one p120 family member. The data reveal a core function of p120 in cadherin complexes, and strongly predict a dose-dependent loss of E-cadherin in tumors that partially or completely down-regulate p120.
p190RhoGAP is cell cycle regulated and affects cytokinesis
Authors: Su Ling , Agati Joyce M. , Parsons Sarah J.
Published: November 2003

p190RhoGAP (p190), a Rho family GTPase-activating protein, regulates actin stress fiber dynamics via hydrolysis of Rho-GTP. Recent data suggest that p190 also regulates cell proliferation. To gain insights into the cellular process(es) affected by p190, we altered its levels by conditional or transient overexpression. Overexpression of p190 resulted in a multinucleated phenotype that was dependent on the GTPase-activating protein domain. Confocal immunofluorescence microscopy revealed that both endogenous and exogenous p190 localized to the newly forming and contracting cleavage furrow of dividing cells. However, overexpression of p190 resulted in abnormal positioning of the furrow specification site and unequal daughter cell partitioning, as well as faulty furrow contraction and multinucleation. Furthermore, levels of endogenous p190 protein were transiently decreased in late mitosis via an ubiquitin-mediated degradation process that required the NH2-terminal GTP-binding region of p190. These results suggest that a cell cycle–regulated reduction in endogenous p190 levels is linked to completion of cytokinesis and generation of viable cell progeny.
Myosin V motor proteins
Authors: Vale Ronald D.
Published: November 2003

Mammalian myosin V motors transport cargo processively along actin filaments. Recent biophysical and structural studies have led to a detailed understanding of the mechanism of myosin V, making it perhaps the best understood cytoskeletal motor. In addition to describing the mechanism, this review will illustrate how “dynamic” single molecule measurements can synergize with “static” protein structural studies to produce amazingly clear information on the workings of a nanometer-scale machine.
LIME, a Novel Transmembrane Adaptor Protein, Associates with p56lck and Mediates T Cell Activation
Authors: Hur Eun Mi , Son Myoungsun , Lee Ok-Hee , Choi Young Bong , Park Changwon , Lee Hyunsook , Yun Yungdae
Published: November 2003

In this study, we identify and characterize a novel transmembrane adaptor protein, designated Lck-interacting membrane protein (LIME), as a binding partner of the Lck Src homology (SH)2 domain. LIME possesses a short extracellular domain, a transmembrane domain, and a cytoplasmic tail containing five tyrosine-based motifs. The protein is primarily expressed in hematopoietic cells and lung. Interestingly, LIME expression is up-regulated by TCR stimulation and sustained up to 24 h, suggesting that LIME acts throughout the early to late stages of T cell activation. LIME is localized to membrane rafts and distributed within the T cell–APC contact site. Upon TCR stimulation of Jurkat T cells, LIME associates with Lck as a tyrosine-phosphorylated protein. Experiments using Jurkat T cells expressing CD8–LIME chimera reveal that the protein associates with phosphatidylinositol 3-kinase, Grb2, Gads, and SHP2, and activates ERK1/2 and JNK but not p38. Moreover, overexpression of LIME in Jurkat T cells induces transcriptional activation of the IL-2 promoter. Our data collectively show that LIME is a raft-associated transmembrane adaptor protein linking TCR stimuli to downstream signaling pathways via associations with Lck.
Molecular Movement of the Voltage Sensor in a K Channel
Authors: Broomand Amir , Männikkö Roope , Larsson H. Peter , Elinder Fredrik
Published: November 2003

The X-ray crystallographic structure of KvAP, a voltage-gated bacterial K channel, was recently published. However, the position and the molecular movement of the voltage sensor, S4, are still controversial. For example, in the crystallographic structure, S4 is located far away (>30 Å) from the pore domain, whereas electrostatic experiments have suggested that S4 is located close (<8 Å) to the pore domain in open channels. To test the proposed location and motion of S4 relative to the pore domain, we induced disulphide bonds between pairs of introduced cysteines: one in S4 and one in the pore domain. Several residues in S4 formed a state-dependent disulphide bond with a residue in the pore domain. Our data suggest that S4 is located close to the pore domain in a neighboring subunit. Our data also place constraints on possible models for S4 movement and are not compatible with a recently proposed KvAP model.
Preanesthetic Medication with Intranasal Midazolam for Brief Pediatric Surgical Procedures
Authors: Davis Peter J. , Tome Julie A. , McGowan Francis X. , Cohen Ira Todd , Latta Karen , Felder Herman
Published: November 2003

Background

The perfect preanesthesia medication and its ideal route of administration are still debated, but for pediatric surgical patients undergoing brief procedures, preanesthesia medication is frequently omitted because of the concern that it will prolong the child's recovery from anesthesia. The effects of nasally administered midazolam on anesthetic recovery and hospital discharge times were determined in 88 ASA physical status 1 and 2 ambulatory surgical patients undergoing a brief surgical procedure.

Methods

Using a randomized, double-blind, placebo-controlled design, 88 ambulatory surgical patients 10-36 months of age undergoing myringotomy and tube insertion were entered into the study. All patients were randomly assigned to one of three medication groups. One group received 0.2 mg/kg intranasal midazolam; a second group received 0.3 mg/kg intranasal midazolam; and the third group received intranasal saline drops. All patients were anesthetized with nitrous oxide, oxygen, and halothane administered via mask. The duration of anesthesia lasted between 9 and 10 min. After preanesthetic medication, the children were evaluated for ease of separation and induction of anesthesia. In addition, the time from when the anesthetic was discontinued until the child recovered from anesthesia and the time the child was discharged home were recorded by a nurse observer blinded to the patient grouping.

Results

Children receiving midazolam had smoother, calmer parent-child separation and anesthesia induction scores, and their anesthesia recovery times and hospital discharge times were the same as those receiving placebo.

Conclusions

For children undergoing brief surgical procedures, nasal midazolam provides satisfactory anxiolysis without delaying anesthesia recovery and hospital discharge.
Parturients Infected with Human Immunodeficiency Virus and Regional Anesthesia
Authors: Hughes Samuel C. , Dailey Patricia A. , Landers Daniel , Dattel B. J. , Crombleholme William R. , Johnson Judy L.
Published: November 2003

Background

It is estimated that 1.5 million Americans are infected with the human immunodeficiency virus (HIV-1), and the consequences of HIV infection are a leading cause of death in women aged 15-44 yr. Thus, HIV-1 disease, or acquired immunodeficiency syndrome, occurs with increasing frequency in the parturient, and there is little information concerning the risks of regional anesthesia. Fear of spreading infection to the central nervous system or adverse neurologic sequelae have led some clinicians to advise against regional anesthesia. Thus, this study was undertaken to evaluate the possible problems or risks associated with regional anesthesia in parturients infected with HIV-1 and to determine whether anesthesia affected the clinical course of the disease.

Methods

The clinical course and immunologic function of 30 parturients infected with HIV-1 were evaluated prospectively. Extensive medical and laboratory evaluation before delivery and 4-6 months postpartum was undertaken. Medical problems related to HIV-1 disease and use of antiviral drugs also were monitored. The anesthetic management was dictated by the clinical situation and the patient's wishes were careful postpartum follow-up to evaluate possible neurologic changes or infection.

Results

Regional anesthesia was administered in 18 parturients, and 12 received small doses of opioids or no analgesia. There were no changes in the immunologic parameters studied (CD4+, p24, beta 2 microglobulins), and HIV-1 disease remained stable in the peripartum period. There were no infections, complications, or neurologic changes in the peripartum period. Sixty-eight percent of the infants were HIV-1-negative and, in 21% of infants, the HIV-1 status was indeterminate (probably negative).

Conclusions

This prospective study of parturients infected with HIV-1 demonstrated that regional anesthesia can be performed without adverse sequelae. There were no neurologic or infectious complications related to the obstetric or anesthetic course. The immune function of the parturient was stable in the peripartum period. Although the number of patients studied was small, with careful medical evaluation, regional anesthesia is an acceptable choice in the parturient infected with HIV-1.
Volumetric Capnography in Children
Authors: Ream Robert S. , Schreiner Mark S. , Neff Joseph D. , McRae Karen M. , Jawad Abbas F. , Scherer Peter W. , Neufeld Gordon R.
Published: November 2003

Background

Lung growth in children is associated with dramatic increases in the number and surface area of alveolated airways. Modelling studies have shown the slope of the alveolar plateau (phase III) is sensitive to the total cross-sectional area of these airways. Therefore, the influence of age and body size on the phase III slope of the volumetric capnogram was investigated.

Methods

Phase III slope (alveolar dcCO2/dv) and airway deadspace (VDaw) were derived from repeated single-breath carbon dioxide expirograms collected on 44 healthy mechanically ventilated children (aged 5 months-18 yr) undergoing minor surgery. Ventilatory support was standardized (VT = 8.5 and 12.5 ml/kg, f = 8-15 breaths/min, inspiratory time = 1 s, end-tidal partial pressure of carbon dioxide = 30-45 mmHg), and measurements were recorded by computerized integration of output from a heated pneumotachometer and mainstream infrared carbon dioxide analyzer inserted between the endotracheal tube and anesthesia circuit. Experimental data were compared to simulated breath data generated from a numeric pediatric lung model.

Results

An increased VDaw, a smaller VDaw/VT, and flatter phase III slope were found at the larger tidal volume (P < 0.01). Strong relationships were seen at VT = 12.5 ml/kg between airway deadspace and age (R2 = 0.77), weight (R2 = 0.93), height (R2 = 0.78), and body surface area (R2 = 0.89). The normalized phase III slopes of infants were markedly steeper than that of adolescents and were reduced at both tidal volumes with increasing age, weight, height, and body surface area. Phase III slopes and VDaw generated from modelled carbon dioxide washout simulations closely matched the experimental data collected in children.

Conclusions

Morphometric increases in the alveolated airway cross-section with lung growth is associated with a decrease of the phase III slope. During adolescence, normalized phase III slopes approximate those of healthy adults. The change in slope with lung growth may reflect a decrease in diffusional resistance for carbon dioxide transport within the alveolated airway resulting in diminished acinar carbon dioxide gradients.
Cerebral Oxygenation during Pediatric Cardiac Surgery Using Deep Hypothermic Circulatory Arrest
Authors: Kurth Dean C. , Steven James M. , Nicolson Susan C.
Published: November 2003

Background

Deep hypothermic circulatory arrest is a widely used technique in pediatric cardiac surgery that carries a risk of neurologic injury. Previous work in neonates identified distinct changes in cerebral oxygenation during surgery. This study sought to determine whether the intraoperative changes in cerebral oxygenation vary between neonates, infants, and children and whether the oxygenation changes are associated with postoperative cerebral dysfunction.

Methods

The study included eight neonates, ten infants, and eight children without preexisting neurologic disease. Cerebrovascular hemoglobin oxygen saturation (SCO2), an index of brain oxygenation, was monitored intraoperatively by near-infrared spectroscopy. Body temperature was reduced to 15 degrees C during cardiopulmonary bypass (CPB) before commencing circulatory arrest. Postoperative neurologic status was judged as normal or abnormal (seizures, stroke, coma).

Results

Relative to preoperative levels, the age groups experienced similar changes in SCO2 during surgery: SCO2 increased 30 +/- 4% during deep hypothermic CPB, it decreased 62 +/- 5% by the end of arrest, and it increased 20 +/- 5% during CPB recirculation (all P < 0.001); after rewarming and removal of CPB, SCO2 returned to preoperative levels. During arrest, the half-life of SCO2 was 9 +/- 1 min in neonates, 6 +/- 1 min in infants, and 4 +/- 1 min in children (P < 0.001). Postoperative neurologic status was abnormal in three (12%) patients. The SCO2 increase during deep hypothermic CPB was less in these patients than in the remaining study population (3 +/- 2% versus 33 +/- 4%, P < 0.001). There were no other significant SCO2 differences between outcome groups.

Conclusions

Brain oxygenation changed at distinct points during surgery in all ages, reflecting fundamental cerebral responses to hypothermic CPB, ischemia, and reperfusion. However, the changes in SCO2 half-life with age reflect developmental differences in the rate of cerebral oxygen utilization during arrest, consistent with experimental work in animals. Certain intraoperative cerebral oxygenation patterns may be associated with postoperative cerebral dysfunction and require further study.
Thoracic Epidural Anesthesia Attenuates Halothane-induced Myocardial Sensitization to Dysrhythmogenic Effect of Epinephrine in Dogs
Authors: Kamibayashi Takahiko , Hayashi Yukio , Mammoto Tadanori , Yamatodani Atsushi , Taenaka Nobuyuki , Yoshiya Ikuto
Published: November 2003

Background

The autonomic nervous system plays a critical role in the central modulation of cardiac dysrhythmias. Because sympathetic blockade by thoracic epidural anesthesia has been documented to protect patients from various stress responses, the authors speculate that epidural anesthesia can attenuate the dysrhythmogenic interaction between halothane and epinephrine.

Methods

In adult mongrel dogs anesthetized with halothane, the dysrhythmogenic dose (DD) of epinephrine, defined as the smallest dose producing four or more premature ventricular contractions within a 15-s period, was determined in the presence of thoracic epidural mepivacaine or saline. To address the effect of circulating mepivacaine after epidural administration, the authors examined the DD of epinephrine in the presence of intravenous mepivacaine. They also investigated the effect of thoracic epidural anesthesia in bilaterally vagotomized dogs.

Results

Epidural mepivacaine significantly increased the DD of epinephrine compared with epidural saline. However, intravenous mepivacaine did not affect the DD of epinephrine, even when the plasma concentration of mepivacaine during the dysrhythmias was twice that in the epidural mepivacaine group. The beneficial effect of epidural mepivacaine was not seen in bilaterally vagotomized dogs.

Conclusions

Thoracic epidural anesthesia attenuated the myocardial sensitization by halothane, and vagal activity had an essential role in this action.
Local Anesthetics Inhibit Substance P Binding and Evoked Increases in Intracellular Calcium sup 2+
Authors: Li Yue-Ming , Wingrove Douglas E. , Too Phon H. , Marnerakis Margarita , Stimson Evelyn R. , Strichartz Gary R. , Maggio John E.
Published: November 2003

Background

During spinal and epidural anesthesia, local anesthetics reach concentrations in cerebrospinal fluid and spinal cord tissues at which their actions may extend beyond the classic blockade of sodium channels. This study examines the effects of several clinical and experimental local anesthetics on the binding and actions of a peptide neurotransmitter, substance P, known to be important in nociceptive transmission in the dorsal horn.

Methods

The binding of radiolabeled (Bolton-Hunter modified) substance P was studied in chick brain membranes in the presence of local anesthetics. The increase in intracellular calcium [Ca2+]in evoked by substance P was measured by the fluorescent indicator fura-2 loaded in a murine cell line expressing substance P (NK1) receptors. Cells were preincubated with bupivacaine before and during the transient addition of substance P.

Results

Both substance P binding and Ca2+ increase were inhibited half-maximally by approximately 1 mM bupivacaine at pH 7.5, whereas tetracaine, lidocaine, and benzocaine were slightly less potent at inhibiting binding. Concentration-dependent substance P-binding studies showed that bupivacaine's inhibition was not competitive. Inhibition of substance P binding by bupivacaine increased with increasing pH, but the protonated species appears to have some inhibitory activity, and quaternary lidocaine also inhibited binding. There was no stereoselectively to the binding inhibition.

Conclusions

Because millimolar concentrations of local anesthetics are within the range measured in spinal cord during intrathecal and epidural procedures, these results are consistent with a direct action of local anesthetics on tachykinin-mediated neurotransmission during regional anesthesia.
Ketamine Inhibits Glutamate-, N-Methyl-D-Aspartate-, and Quisqualate-stimulated cGMP Production in Cultured Cerebral Neurons
Authors: Gonzales Jerry M. , Loeb Alex L. , Reichard Peter S. , Irvine Steven
Published: November 2003

Background

Glutamatergic signaling has been linked to the recently discovered neurotransmitter/neuromodulator nitric oxide (NO), and several classes of anesthetics block some step in glutamatergic signaling. This study was designed to determine whether or not ketamine would prevent NO-dependent cGMP production stimulated by glutamate (GLU) and the GLU analogs NMDA, quisqualate (QUIS), and kainate (KAIN).

Methods

Primary cultures of cortical neurons and glia (prepared from 16-day gestational rat fetuses) were used after 12-16 days in culture. Reactions were carried out in magnesium-free buffer containing 100 microM 3-isobutyl-1-methylxanthine, and cGMP content of cultures was used as a bioassay of NO production.

Results

Cyclic GMP production stimulated by sodium nitroprusside (100 microM) occurred predominately in neurons and not in glia. Neurons were spontaneously active in these cultures; basal cGMP production was decreased by 50% in the presence of 1 microM tetrodotoxin (TTX). Glutamate (100 microM), NMDA (100 microM), QUIS (300 microM), and KAIN (100 microM) each increased cGMP content of neuronal cultures. L-NMMA (100 microM), a NO synthase inhibitor, prevented the stimulation of cGMP production by GLU or its analogs. Pretreatment with MK-801 (1 microM) or ketamine (10-100 microM) inhibited GLU-, NMDA-, and QUIS-stimulated cGMP production. Quisqualate-stimulated responses were the most sensitive to inhibition by ketamine and NMDA-stimulated responses were the least sensitive to inhibition. MK-801 and ketamine did not significantly inhibit KAIN-stimulated cGMP production. CNQX (10 microns) blocked KAIN-stimulated cGMP production only.

Conclusions

The authors' data demonstrate that ketamine inhibited NO synthesis stimulated by NMDA- and non-NMDA-receptor specific analogs. Our findings indicate that blockade of QUIS- as well as NMDA-subtypes of GLU- receptor may be important in the development of ketamine-induced anesthesia.
Metabolism of a New Local Anesthetic, Ropivacaine, by Human Hepatic Cytochrome P450
Authors: Oda Yutaka , Furuichi Katsuji , Tanaka Kazuo , Hiroi Toyoko , Imaoka Susumu , Asada Akira , Fujimori Mitsugu , Funae Yoshihiko
Published: November 2003

Background

Ropivacaine is a local anesthetic with a long duration of action. Although it is less toxic than bupivacaine, local anesthetic toxicity is possible when the plasma concentration is increased. Because ropivacaine is an amide-type local anesthetic, it is metabolized by cytochrome P450 (P450) in the liver, and its elimination and plasma concentration can be dependent on the level of P450. The purpose of this investigation was to elucidate the metabolism of ropivacaine by human hepatic P450.

Methods

The metabolism of ropivacaine was compared using recombinant human and purified rat hepatic P450 isozymes. An inhibition study using antibodies against rat P450 was performed using hepatic microsomes from human and rat to identify which P450s are involved in ropivacaine metabolism.

Results

Ropivacaine was metabolized to 2',6'-pipecoloxylidide (PPX), 3'-hydroxyropivacaine (3'-OH Rop), and 4'-hydroxyropivacaine (4'-OH Rop) by hepatic microsomes from human and rat. PPX was a major metabolite of both human and rat hepatic microsomes. In a reconstituted system with rat P450. PPX was produced by CYP2C11 and 3A2, 4'-OH Rop by CYP1A2, and 3'-OH Rop by CYP1A2 and 2D1. Formation of PPX in rat hepatic microsomes was inhibited by anti CYP3A2, but not by CYP2C11 antibody, and formation of 3'-OH Rop was inhibited by CYP1A2 and 2D1 antibodies. Anti CYP3A2 and 1A2 antibodies inhibited the formation of PPX and 3'-OH Rop in human hepatic microsomes, respectively. Recombinant human P450s expressed in lymphoblast cells were used for further study. CYP3A4 and 1A2 formed the most PPX and 3'-OH Rop, respectively. Ropivacaine N-dealkylation and 3'-hydroxylation activities correlated well with the level of CYP3A4 and 1A2 in human hepatic microsomes, respectively.

Conclusions

Ropivacaine was metabolized to PPX, 3'-OH Rop, and 4'-OH Rop by hepatic P450. PPX was a major metabolite in human hepatic microsomes. CYP3A4 was involved in producing PPX. CYP1A2 was involved in the formation of 3'-OH Rop in human hepatic microsomes.
Prevention of Kinking of a Percutaneous Transtracheal Intravenous Catheter
Authors: Sdrales Lorraine , Benumof Jonathan L.
Published: November 2003

Background

Transtracheal jet ventilation (TTJV) through a percutaneously inserted intravenous/TTJV catheter, using a high-pressure oxygen source and noncompliant tubing is a simple and quick method of effective ventilation, especially in a patient in whom the lungs cannot be ventilated via mask and/or whose trachea cannot be intubated. TTJV becomes impossible if any part of the plastic portion of the TTJV catheter kinks; although the incidence of this problem is not known, kinking of the catheter is most likely to occur as the catheter turns from a predominantly posterior to a predominantly caudad direction. These experiments tested the hypothesis that a small-angle bend in the tip of the TTJV catheter would reduce the requirement to aim the entire TTJV catheter in a caudad-directed orientation.

Methods

A model of the trachea was designed using polyvinylchloride tubing to observe TTJV catheter insertion and plastic catheter kinking. The TTJV catheters were inserted at 0, 5 degrees, 10 degrees, 15 degrees, 20 degrees, 25 degrees, and 30 degrees angles in trials of 15 times each. Small-angle bends, placed at 2.5 cm from the distal end of the TTJV catheter, of 0, 5 degrees, 10 degrees, 15 degrees, and 20 degrees were used, and each bent TTJV catheter was inserted at each of the above insertion angles 15 times.

Results

Increasing the angle of insertion decreased the incidence of kinking of the TTJV catheter at every small-angle bend in the tip of the TTJV catheter. Increasing the small-angle bend in the tip of the TTJV catheter decreased the incidence of kinking with every angle of insertion. A small-angle bend in the tip of the TTJV catheter and the angle of insertion often were complementary in their ability to decrease the incidence of kinking. With a cumulative angle of 10 degrees, 98% of the plastic catheters kinked, compared to 0 in trials involving a cumulative angle of 30 degrees or more. Analysis via the chi-squared test yielded a P value of < 0.0001 when comparing incidence of kinking for cumulative angles of 10-30 degrees.

Conclusions

A modest bend in the tip of the TTJV catheter greatly reduces the sharpness of the angle of insertion required to eliminate kinking of the plastic catheter. Because the risk/benefit ratio is so low, we suggest that a small-angle bend of 15 degrees should always be created and, combined with a 15 degrees angle of insertion, should result in a rare incidence of kinking.
Epidural and Intravenous Fentanyl Produce Equivalent Effects during Major Surgery
Authors: Guinard Jean-Phillipe , Carpenter Randall L. , Chassot Pierre-Guy
Published: November 2003

Background

The benefit of epidural versus intravenous fentanyl administration for postoperative analgesia is controversial. In the current study, the intraoperative effects of epidural versus intravenous fentanyl administration were compared during major surgery.

Methods

Twenty elective patients scheduled for thoracoabdominal esophagectomy under general anesthesia with propofol infusion were randomly allocated to receive either intravenous or epidural boluses of 50-100 micrograms fentanyl in a double-blind fashion to maintain hemodynamic stability. Plasma cortisol and fentanyl, as well as total urinary catecholamines, were obtained at the end of the operations.

Results

Hemodynamic variations were similar except that patients receiving epidural fentanyl had a lower incidence of heart rate reduction (> 20% reduction from baseline, P < 0.05). There were no differences in mean intraoperative fentanyl (1,115 +/- 430 and 1,010 +/- 377 micrograms, epidural and intravenous, respectively) or propofol (2,281 +/- 645 and 2,452 +/- 1,169 mg) doses, number of boluses of fentanyl (nine in both groups), plasma fentanyl concentration (1.13 +/- 0.4 and 1.02 +/- 0.46 ng/ml), or number of anesthesiologists correctly identifying the site of fentanyl administration. Similarly, there were no differences in plasma glucose (8.9 +/- 1.8 and 9.3 +/- 1.8 mM) and cortisol (696 +/- 446 and 846 +/- 257 mM), or urinary epinephrine (12 +/- 3.7 and 13.1 +/- 9.2, micrograms/sample) and norepinephrine (42.7 +/- 26.7 and 39.1 +/- 27.6, micrograms/sample).

Conclusions

There appears to be no clinical advantage to epidural administration of fentanyl over intravenous administration during anesthesia for major surgery.
Cardiorespiratory and Spinal Cord Blood Flow Effects of Intrathecal Neostigmine Methylsulfate, Clonidine, and Their Combination in Sheep
Authors: Hood David D. , Eisenach James C. , Tong Chuanyao , Tommasi Ellen , Yaksh Tony L.
Published: November 2003

Background

Intrathecal neostigmine may produce analgesia by itself and may enhance analgesia from spinal clonidine. Before clinical trials, the spinal cord blood flow effects of these drugs alone and in combination should be examined in animals.

Methods

Conscious, nonpregnant ewes with indwelling vascular and thoracic spinal catheters received intrathecal injection of 0.2 or 2 mg neostigmine, 0.2 mg clonidine, or 2 mg neostigmine plus 0.2 mg clonidine. Mean systemic and pulmonary arterial and central venous pressures, heart rate, and cardiac output were monitored, arterial blood was sampled for blood gas tensions and pH, and spinal cord blood flow was determined by colored microsphere injection before and at 15, 60, and 240 min after spinal study drug injection.

Results

Neostigmine alone did not affect cardiorespiratory variables or spinal cord blood flow. Intrathecal clonidine alone decreased systemic arterial and central venous pressures, whereas these effects were not observed with addition of neostigmine. Clonidine or neostigmine alone or the combination of clonidine and neostigmine did not affect spinal cord blood flow.

Conclusions

Intrathecal neostigmine alone or in combination with clonidine does not reduce spinal cord blood flow, an important preclinical toxicity issue. These results provide additional support for initial clinical trials of intrathecal neostigmine for analgesia.
Glutamate Release from the Ovine Fetal Brain during Maternal Hemorrhage
Authors: Penning Donald H. , Chestnut David H. , Dexter Franklin , Hrdy James , Poduska Dan , Atkins Barry
Published: November 2003

Background

Glutamate has been implicated in the pathophysiology of neuronal injury associated with cerebral hypoxia-ischemia. A model using chronic in utero microdialysis was developed to sample the extracellular space of the fetal brain. Using this model, we tested the hypothesis that glutamate efflux from the parasagittal parietal cortex of near-term fetuses would increase during maternal hemorrhage.

Methods

Twelve near-term fetal sheep were instrumented with vascular catheters, and a microdialysis probe(s) was implanted into the parasagittal parietal cortex. After a 3-day recovery period, the animals were subjected to maternal hemorrhage until either the fetal pH was < 7.00 or the fetus died. The extracellular glutamate concentration in the collected dialysate was determined by high pressure liquid chromatography (HPLC).

Results

Maternal hemorrhage resulted in an 80-90% decrease in uterine blood flow, a decrease fetal po2, and a mixed metabolic and respiratory fetal acidosis. There were two groups of fetuses, survivors (n = 5) and nonsurvivors (n = 7). The nonsurvivor group showed a large increase (10-30-fold) in peak glutamate release (P = 0.0015). Survivors demonstrated a small (threefold) increase that was not statistically significant (P = 0.065), unless one animal with very low probe recovery was excluded (P = 0.0048).

Conclusions

Extracellular glutamate release from the fetal brain can occur during maternal hemorrhage with fetal acidemia. The pathophysiologic role (if any) of glutamate release in the survivors remains to be elucidated. Our results are consistent with the hypothesis that in utero release of glutamate occurs during periods of fetal asphyxia. This experimental preparation of chronic fetal brain microdialysis can be used to monitor the brain extracellular concentration of any dialyzable substance in response to stress, including maternal hemorrhage.
Hypoxic Contraction of Isolated Rabbit Mesenteric Veins
Authors: Stadnicka Anna , Stekiel Thomas A. , Hogan Quinn H. , Bosnjak Zeljko J. , Kampine John P.
Published: November 2003

Background

Acute systemic hypoxia induces mesenteric venoconstriction in intact rabbits in part because of an increase in chemoreflex-mediated sympathetic efferent nerve activity. Inhaled anesthetics attenuate this reflex response. The direct effects of hypoxia on mesenteric veins are unknown. The purpose of the current study was to examine the effects of hypoxia on isolated rabbit mesenteric capacitance veins and to determine the effects of halothane, isoflurane, and enflurane on the responses to hypoxia.

Methods

Isometric tension was measured before, during, and after 10 min of hypoxia in the rings of either quiescent or norepinephrine contracted veins, with or without endothelium. Effects of various pharmacologic agents and volatile anesthetics on the responses to hypoxia were examined.

Results

Hypoxia augmented contractions to norepinephrine and phenylephrine only in endothelium-intact veins. The hypoxic response was inhibited by phentolamine (alpha-adrenoceptor antagonist) and abolished in the absence of extracellular Ca2+. There were no effects of propranolol (beta-adrenoceptor antagonist), ryanodine (a sarcoplasmic reticulum Ca2+ depleter), indomethacin (cyclooxygenase inhibitor), or nordihydroguaiaretic acid (lipoxygenase inhibitor). L-NAME (an inhibitor of nitric oxide synthase) enhanced basal sensitivity of veins to norepinephrine but had no effect on the response to hypoxia. Nicardipine (a blocker of voltage-gated calcium channels) depressed the hypoxic contraction by 86 +/- 5%, phosphoramidon (an inhibitor of endothelin-converting enzyme) by 82 +/- 8%, and BQ-123 (a specific endothelin-1 receptor antagonist) by 47 +/- 10%. Volatile anesthetics (1.0 MAC) inhibited responses to hypoxia in the absence as well as presence of L-NAME.

Conclusions

These results suggest that in mesenteric capacitance veins of rabbits an intrinsic vascular mechanism contributes to endothelium-dependent hypoxic augmentation of contraction to alpha-adrenergic agonists that involve activation of endothelin-1, an endothelium-derived constricting factor. Inhibition of hypoxic contraction by volatile anesthetics is not mediated by endothelium relaxing factor.
Additive Interactions between Propofol and Ketamine When Used for Anesthesia Induction in Female Patients
Authors: Hui T. W. , Short T. G. , Hong W. , Suen T. , Gin T. , Plummer J.
Published: November 2003

Background

Propofol and ketamine may be paired for anesthesia induction and for total intravenous anesthesia. The nature of any sedative interactions occurring between propofol and ketamine are unknown. The combination when used for anesthesia induction in female patients was studied.

Methods

Quantal dose-response curves were determined in 180 female patients to whom the drugs were administered individually and in combination. Two minutes after administering the drugs, two endpoints were assessed. First, loss of response to verbal command (hypnosis) and then, in those who failed to respond to this endpoint, loss of response to a 5-s transcutaneous tetanus (anesthesia). Interactions were analyzed by fitting the data to a mathematical model in which response was analyzed in terms of the doses of the two drugs and an additional term included to describe nonadditive interactions. The incidences of apnea, arterial pressure, and heart rate changes during the first 5 min were recorded.

Results

At the hypnotic endpoint, the ED50s were 1.10 mg/kg propofol (95% CIs 0.93-1.27), 0.39 mg/kg ketamine (95% CIs 0.27-0.46), and the combination of 0.63 mg/kg propofol and 0.21 mg/kg ketamine (95% CIs 0.53/0.18-0.73/0.24). At the anesthetic endpoint, the ED50s were 1.85 mg/kg propofol (95% CIs 1.58-2.36) 0.66 mg/kg ketamine (95% CIs 0.58-0.77), and the combination of 1.05 mg/kg propofol and 0.35 mg/kg ketamine (95% CIs 0.88/0.29-1.27/0.42). The effects were additive at both endpoints; there was no evidence of an interaction. The ED50s for apnea were 1.61 mg/kg propofol (95% CIs 1.39-1.94), greater than 0.85 mg/kg ketamine and for the combination 1.50 mg/kg propofol and 0.50 mg/kg ketamine (95% CIs 1.15/0.38-3.09/1.03). The addition of ketamine did not significantly alter the ED50 for apnea of propofol. There was a significant difference in the arterial pressures among the three groups (P < 0.001). Using the combination, the cardiostimulant effects of ketamine balanced the cardiodepressant effects of propofol. There was no change in arterial pressure or heart rate after the noxious stimulus.

Conclusions

When using the combination, doses were additive at hypnotic and anesthetic endpoints. Ketamine had no influence on the incidence of apnea after propofol, and the net hemodynamic effects were minimal.
Human Kidney Methoxyflurane and Sevoflurane Metabolism
Authors: Kharasch Evan D. , Hankins Douglas C. , Thummel Kenneth E.
Published: November 2003

Background

Methoxyflurane nephrotoxicity is mediated by cytochrome P450-catalyzed metabolism to toxic metabolites. It is historically accepted that one of the metabolites, fluoride, is the nephrotoxin, and that methoxyflurane nephrotoxicity is caused by plasma fluoride concentrations in excess of 50 microM. Sevoflurane also is metabolized to fluoride ion, and plasma concentrations may exceed 50 microM, yet sevoflurane nephrotoxicity has not been observed. It is possible that in situ renal metabolism of methoxyflurane, rather than hepatic metabolism, is a critical event leading to nephrotoxicity. We tested whether there was a metabolic basis for this hypothesis by examining the relative rates of methoxyflurane and sevoflurane defluorination by human kidney microsomes.

Methods

Microsomes and cytosol were prepared from kidneys of organ donors. Methoxyflurane and sevoflurane metabolism were measured with a fluoride-selective electrode. Human cytochrome P450 isoforms contributing to renal anesthetic metabolism were identified by using isoform-selective inhibitors and by Western blot analysis of renal P450s in conjunction with metabolism by individual P450s expressed from a human hepatic complementary deoxyribonucleic acid library.

Results

Sevoflurane and methoxyflurane did undergo defluorination by human kidney microsomes. Fluoride production was dependent on time, reduced nicotinamide adenine dinucleotide phosphate, protein concentration, and anesthetic concentration. In seven human kidneys studied, enzymatic sevoflurane defluorination was minima, whereas methoxyflurane defluorination rates were substantially greater and exhibited large interindividual variability. Kidney cytosol did not catalyze anesthetic defluorination. Chemical inhibitors of the P450 isoforms 2E1, 2A6, and 3A diminished methoxyflurane and sevoflurane defluorination. Complementary deoxyribonucleic acid-expressed P450s 2E1, 2A6, and 3A4 catalyzed methoxyflurane and sevoflurane metabolism, in diminishing order of activity. These three P450s catalyzed the defluorination of methoxyflurane three to ten times faster than they did that of sevoflurane. Expressed P450 2B6 also catalyzed methoxyflurane defluorination, but 2B6 appeared not to contribute to renal microsomal methoxyflurane defluorination because the P450 2B6-selective inhibitor had no effect.

Conclusions

Human kidney microsomes metabolize methoxyflurane, and to a much lesser extent sevoflurane, to fluoride ion. P450s 2E1 and/or 2A6 and P450 3A are implicated in the defluorination. If intrarenally generated fluoride or other metabolites are nephrotoxic, then renal metabolism may contribute to methoxyflurane nephrotoxicity. The relative paucity of renal sevoflurane defluorination may explain the absence of clinical sevoflurane nephrotoxicity to date, despite plasma fluoride concentrations that may exceed 50 microM.