bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Volatile Anesthetics on Store-operated Ca2+Influx in Airway Smooth Muscle
Authors: Pabelick Christina M. , Ay Binnaz , Prakash Yedatore S. , Sieck Gary C. 
Published: July 2004

Background
In airway smooth muscle (ASM), volatile anesthetics deplete sarcoplasmic reticulum (SR) Ca(2+) stores by increasing Ca(2+) "leak." Accordingly, SR replenishment becomes dependent on Ca(2+) influx. Depletion of SR Ca(2+) stores triggers Ca(2+) influx via specific plasma membrane channels, store-operated Ca(2+) channels (SOCC). We hypothesized that anesthetics inhibit SOCC triggered by increased SR Ca(2+) "leak," preventing SR replenishment and enhancing ASM relaxation.

Methods
In porcine ASM cells, SR Ca was depleted by cyclopiazonic acid or caffeine in 0 extracellular Ca(2+), nifedipine and KCl (preventing Ca(2+) influx through L-type and SOCC channels). Extracellular Ca(2+) was rapidly introduced to selectively activate SOCC. After SOCC activation, SR was replenished and the protocol repeated in the presence of 1 or 2 minimum alveolar concentration halothane, isoflurane, or sevoflurane. In other cells, characteristics of SOCC and interactions between acetylcholine (Ach) and volatile anesthetics were examined.

Results
Cyclopiazonic acid produced slow SR leak, whereas the caffeine response was transient in ASM cells. Reintroduction of extracellular Ca(2+) rapidly increased [Ca(2+)]i. This influx was insensitive to nifedipine, SKF-96365, and KBR-7943, inhibited by Ni and blockade of inositol 1,4,5-triphosphate-induced SR Ca(2+) release, and enhanced by ACh. Preexposure to 1 or 2 minimum alveolar concentration halothane completely inhibited Ca(2+) influx when extracellular Ca(2+) was reintroduced, whereas isoflurane and sevoflurane produced less inhibition. Only halothane and isoflurane inhibited ACh-induced augmentation of Ca(2+) influx.

Conclusion
Volatile anesthetics inhibit a Ni/La-sensitive store-operated Ca(2+) influx mechanism in porcine ASM cells, which likely helps maintain anesthetic-induced bronchodilation.
Protein Kinase C-ε Primes the Cardiac Sarcolemmal Adenosine Triphosphate–sensitive Potassium Channel to Modulation by Isoflurane
Authors: Aizawa Kei , Turner Lawrence A. , Weihrauch Dorothee , Bosnjak Zeljko J. , Kwok Wai-Meng 
Published: July 2004

Background
Cardioprotection by volatile anesthetic-induced preconditioning is known to involve intracellular signaling pathways. Recent studies have shown that protein kinase C (PKC) plays an important role in anesthetic-induced preconditioning. In this study, the effects of the activation of specific isozymes of PKC, specifically PKC-epsilon and -delta, on the modulation of the sarcolemmal adenosine triphosphate-sensitive potassium (sarcKATP) channel by isoflurane were investigated.

Methods
The sarcKATP current was measured in ventricular myocytes isolated from guinea pig hearts using the whole cell configuration of the patch clamp technique. Peptides that induced the translocation of specific PKC isozymes were used to activate PKC-epsilon and PKC-delta.

Results
Under whole cell conditions, isoflurane alone was unable to elicit the opening of the sarcKATP channel. Pretreatment with the specific PKC-epsilon activator, PP106, primed the sarcKATP channel to open in the presence of isoflurane. The resulting sarcKATP current densities in the presence of 0.88 mm isoflurane were 6.5 +/- 6.0 pA/pF (n = 7) and 40.4 +/- 18.2 pA/pF (n = 7) after pretreatment with 100 and 200 nm PP106, respectively. The PKC-epsilon antagonist PP93 abolished this effect. A scrambled peptide of the PKC-epsilon activator PP105 did not prime the sarcKATP channel. The PKC-delta activator PP114 was significantly less effective in priming the sarcKATP channel. 5-Hydroxydecanoate significantly attenuated the effect of the PKC-epdsilon activator on the sarcKATP channel. In addition, immunohistochemical analysis showed that the PKC-epsilon isoform translocated to both the mitochondria and sarcolemma after anesthetic-induced preconditioning, whereas the PKC-delta isoform translocated to the mitochondria.

Conclusion
The PKC-epsilon isozyme primed the sarcKATP channel to open in the presence of isoflurane. The PKC-delta isozyme was significantly less effective in modulating the isoflurane effect on this channel.
Molecular Mechanisms of the Inhibitory Effects of Bupivacaine, Levobupivacaine, and Ropivacaine on Sarcolemmal Adenosine Triphosphate–sensitive Potassium Channels in the Cardiovascular System
Authors: Kawano Takashi , Oshita Shuzo , Takahashi Akira , Tsutsumi Yasuo , Tomiyama Yoshinobu , Kitahata Hiroshi , Kuroda Yasuhiro , Nakaya Yutaka 
Published: July 2004

Background
Sarcolemmal adenosine triphosphate-sensitive potassium (KATP) channels in the cardiovascular system may be involved in bupivacaine-induced cardiovascular toxicity. The authors investigated the effects of local anesthetics on the activity of reconstituted KATP channels encoded by inwardly rectifying potassium channel (Kir6.0) and sulfonylurea receptor (SUR) subunits.

Methods
The authors used an inside-out patch clamp configuration to investigate the effects of bupivacaine, levobupivacaine, and ropivacaine on the activity of reconstituted KATP channels expressed in COS-7 cells and containing wild-type, mutant, or chimeric SURs.

Results
Bupivacaine inhibited the activities of cardiac KATP channels (IC50 = 52 microm) stereoselectively (levobupivacaine, IC50 = 168 microm; ropivacaine, IC50 = 249 microm). Local anesthetics also inhibited the activities of channels formed by the truncated isoform of Kir6.2 (Kir6.2 delta C36) stereoselectively. Mutations in the cytosolic end of the second transmembrane domain of Kir6.2 markedly decreased both the local anesthetics' affinity and stereoselectivity. The local anesthetics blocked cardiac KATP channels with approximately eightfold higher potency than vascular KATP channels; the potency depended on the SUR subtype. The 42 amino acid residues at the C-terminal tail of SUR2A, but not SUR1 or SUR2B, enhanced the inhibitory effect of bupivacaine on the Kir6.0 subunit.

Conclusions
Inhibitory effects of local anesthetics on KATP channels in the cardiovascular system are (1) stereoselective: bupivacaine was more potent than levobupivacaine and ropivacaine; and (2) tissue specific: local anesthetics blocked cardiac KATP channels more potently than vascular KATP channels, via the intracellular pore mouth of the Kir6.0 subunit and the 42 amino acids at the C-terminal tail of the SUR2A subunit, respectively.
Hemorrhagic Shock in Swine: Nitric Oxide and Potassium Sensitive Adenosine Triphosphate Channel Activation
Authors: Musser Jeffrey B. , Bentley Timothy B. , Griffith Scott , Sharma Pushpa , Karaian John E. , Mongan Paul D. 
Published: July 2004

Background
To determine the role of nitric oxide and adenosine triphosphate-sensitive potassium (KATP) vascular channels in vascular decompensation during controlled hemorrhagic shock in swine.

Methods
Thirty instrumented, anesthetized adolescent Yorkshire swine were subjected to controlled isobaric hemorrhage to a mean arterial pressure of 40 mmHg for 2 h (n = 6) or 4 h (n = 10) or 50 mmHg for 4 h (n = 8). An additional six animals were used as anesthetized instrumented time controls. During controlled hemorrhage, plasma and tissue samples were obtained every 30 to 60 min. Before euthanasia, tissue (carotid artery, lung, liver, and aorta) was obtained for analysis of nitrate concentrations and nitric oxide synthase activity. Isolated carotid artery ring reactivity to norepinephrine was also determined with and without glibenclamide.

Results
Animals hemorrhaged to 40 mmHg decompensated earlier than animals hemorrhaged to 50 mmHg. Plasma nitrate concentrations and nitric oxide synthase activity rose consistently throughout hemorrhage in both groups. However, they were substantially higher in the mean arterial pressure 40 group. Constitutive nitric oxide synthase activity was the major contributor to total nitric oxide synthase activity throughout the protocol with only the animals maintained at 40 mmHg for 4 h showing evidence of inducible nitric oxide synthase activity. Profound KATP channel activation and hyporeactivity of isolated vessel rings to norepinephrine was not observed until 4 h after the initiation of hemorrhagic shock. Only those animals with inducible nitric oxide synthase activity showed a decreased response to norepinephrine, and this hyporeactivity was reversed with the KATP channel inhibitor, glibenclamide.

Conclusions
The data indicate that profound KATP activation associated with increased nitric oxide concentrations and inducible nitric oxide synthase induction is a key factor in vascular smooth muscle hyporeactivity characteristic of the late decompensatory phase of hemorrhagic shock in swine.
Temperature-independent Inhibition of L-Type Calcium Currents by Halothane and Sevoflurane in Human Atrial Cardiomyocytes
Authors: Hüneke Rocco , Zitzelsberger Daniela , Fassl Jens , Jüngling Eberhard , Brose Stefan , Buhre Wolfgang , Rossaint Rolf , Lückhoff Andreas 
Published: July 2004

Background
Cardiac L-type calcium currents (ICa,L) are affected by volatile anesthetics, possibly contributing to their side effects. Actions of anesthetics on ion channels are usually studied in vitro at room temperature. However, the solubility of anesthetic gases as well as ICa,L are markedly sensitive to the study temperature. Therefore, temperature-dependent effects of halothane and sevoflurane on cardiac ICa,L were analyzed.

Methods
ICa,L were studied at 21 degrees C and 36 degrees C with the patch clamp technique in isolated human atrial cardiomyocytes. Concentrations of anesthetics brought into solution by gassing at both temperatures were determined with gas chromatography.

Results
The aqueous concentrations of halothane and sevoflurane were linearly related to their concentration in the gas phase (1 to 3 minimum alveolar concentration [MAC]). At 21 degrees C, the slope of this relation was 0.52 and 0.12 mm/vol % for halothane and sevoflurane, respectively, and decreased at 36 degrees C to 0.29 and 0.09 mm/vol %, respectively. ICa,L displayed significantly higher current amplitudes at 36 degrees C than at 21 degrees C and significantly accelerated time-dependent inactivation. Halothane (1-2 MAC) and sevoflurane (1-3 MAC) evoked stronger inhibitions of ICa,L at 21 degrees C than at 36 degrees C. In spite of different temperature-dependent current amplitudes, the fractional (percent) inhibition of ICa,L showed the same linear relationship to the concentrations of halothane and sevoflurane in the bath medium at both temperatures, as revealed from present and previous experiments.

Conclusions
Inhibition of ICa,L by halothane and sevoflurane is determined by the aqueous concentration of the anesthetics, independently of the temperature. Increased solubility may explain the stronger effects of the anesthetics at lower temperatures.
Retigabine Stimulates Human KCNQ2/Q3 Channels in the Presence of Bupivacaine
Authors: Punke Mark A. , Friederich Patrick 
Published: July 2004

Background
Inhibition of KCNQ2/Q3 channels may cause convulsion in humans. The interaction of bupivacaine with these channels is unknown. The anticonvulsant retigabine activates KCNQ2/Q3 channels and may reverse inhibitory actions of bupivacaine. Potassium channel stimulation may thus constitute a novel approach to treat local anesthetic-induced seizures. The aim of this study was to characterize bupivacaine effects on KCNQ2/Q3 channels and to investigate whether retigabine reverses the effects of the local anesthetic.

Methods
KCNQ2/Q3 channels were transiently expressed in Chinese hamster ovary cells. The effects of bupivacaine and retigabine were studied with the patch-clamp technique.

Results
Bupivacaine inhibited KCNQ2/Q3 channels in a concentration-dependent and reversible manner. The concentration-response curve was described by a Hill equation (IC50 = 173 +/- 7 microm, Hill coefficient = 1.4 +/- 0.1, mean +/- SEM, n = 37). The inhibitory effect did not differ between bupivacaine and levobupivacaine (42 +/- 4%, n = 7, versus 42 +/- 5%, n = 10; P > 0.05). Ropivacaine was four times less potent than bupivacaine. The inhibition of KCNQ2/Q3 channels by bupivacaine resulted in a significant and reversible depolarization of the membrane potential. Retigabine (300 nm-10 microm) reversed the inhibitory action of bupivacaine on KCNQ2/Q3 channels as well as the depolarization of the membrane potential.

Conclusions
The anticonvulsant retigabine at nanomolar concentrations reverses the inhibitory effect of micromolar concentrations of bupivacaine. Our results allow the hypothesis that activation of KCNQ2/Q3 channels by retigabine may offer a novel therapeutic approach for the treatment of bupivacaine-induced seizures.
Lumbar Plexus in Children
Authors: Kirchmair Lukas , Enna Birgit , Mitterschiffthaler Gottfried , Moriggl Bernhard , Greher Manfred , Marhofer Peter , Kapral Stephan , Gassner Ingmar 
Published: July 2004

Background
Pediatric regional anesthesia has gained increasing interest over the past decades. The current study was conducted to investigate the lumbar paravertebral region and the lumbar plexus at L3-L4 and L4-L5 by means of sonography to obtain fundamentals for the performance of ultrasound-guided posterior lumbar plexus blocks.

Methods
Thirty-two children (12 boys, 20 girls) with American Society of Anesthesiologists physical status I or II were enrolled in the current study. The lumbar paravertebral region was visualized at L3-L4 and L4-L5 on two corresponding posterior sonograms (longitudinal, transverse). The lumbar plexus had to be delineated, and skin-plexus distances were measured. In a series of five pediatric patients undergoing inguinal herniotomy, ultrasound-guided posterior lumbar plexus blocks at L4-L5 were performed.

Results
The children were stratified into three age groups (group 1: > 3 yr and </= 5 yr; group 2: > 5 yr and </= 8 yr; group 3: > 8 yr and </= 12 yr). The lumbar plexus could be delineated at L3-L4 and L4-L5 in 19 of 20 cases in group 1, in 17 of 20 cases in group 2, in 22 of 24 cases at L3-L4 in group 3, and in 16 of 24 cases at L4-L5 in group 3. In all patients, the lumbar plexus was situated within the posterior part of the psoas major muscle. Skin-plexus distances showed statistical significant differences between groups 1 and 3 and between groups 2 and 3. The strongest positive correlation existed between skin-plexus distances and the children's weight. Ultrasound guidance enabled safe und successful posterior approaches to the lumbar plexus, thus resulting in effective anesthesia and analgesia of the inguinal region.

Conclusions
Sonography of the lumbar plexus in children proved to be feasible. Skin-plexus distances correlated with the children's weight rather than with their age. The sonographic findings were fundamental for the performance of successful ultrasound-guided posterior approaches in a small group of pediatric patients.
Changes in Tissue pH and Temperature after Incision Indicate Acidosis May Contribute to Postoperative Pain
Authors: Woo Young Cheol , Park Soo Seog , Subieta Alberto R. , Brennan Timothy J. 
Published: July 2004

Background
Incisional pain is a common form of acute pain. Previously, the authors studied persistent pain behaviors caused by incisions, using animal models for postoperative pain. In this study, the authors measured tissue pH and hind paw temperature before and after incision to understand factors that may activate and sensitize nociceptors in the incision.

Methods
Rats underwent a plantar incision, a gastrocnemius muscle incision, or a cutaneous paraspinal incision. For the hind paw incision, pain behaviors were measured. Tissue pH was measured using a pH-sensitive needle electrode in halothane-anesthetized rats. The pH in the incision was compared to a corresponding control site on the contralateral side of the rat or to the sham-operated group.

Results
Plantar tissue pH was 7.16 +/- 0.04 in sham-operated rats. Ten minutes after plantar incision, tissue pH was decreased to 6.91 +/- 0.20 (P < 0.05), and this decrease was sustained through 60 min after incision, when pH was 6.99 +/- 0.06 (P < 0.05). Tissue pH values were 6.95, 6.90, 6.89, and 6.95 (P < 0.05 vs. sham) 4 h and 1, 2, and 4 days after incision, respectively. On postoperative day 7, when plantar pH was same as for the control side (7.13 +/- 0.05), guarding behavior, heat responses, and responses to mechanical stimuli recovered. Outside the incised area in the hind paw, tissue pH was normal. Tissue pH was significantly correlated with all pain behaviors. In the gastrocnemius muscle, tissue pH was 7.14 +/- 0.7 in the sham-operated side. Ten minutes after incision, tissue pH was 6.54 +/- 0.12 (P < 0.05), and muscle pH remained decreased through 60 min after gastrocnemius incision when pH was 6.76 +/- 0.17 (P < 0.05). Tissue pH was also significantly decreased (P < 0.05) on day 1 (6.96 vs. 7.20) and day 4 (7.06 vs. 7.18) after gastrocnemius incision but was not reduced on postoperative day 8 (7.11 vs. 7.15). A paraspinal incision also decreased tissue pH in the hairy skin of the rat compared with the preincision value. Hind paw skin temperature did not change after incision.

Conclusion
A decrease in pH occurs immediately after incision and is sustained for at least 4 days. During the period of decreased tissue pH, pain behaviors are evident. When the tissue pH returns to normal, pain behaviors are diminished. The decreased pH is localized at the incision site and not to areas surrounding the incision. Decreased pH likely contributes to nociceptor sensitization and pain related behaviors after incision. The magnitude of the pH change varies among tissues. An increase in hind paw skin temperature does not play a role in these pain-related behaviors.
Global analysis of three‐state protein unfolding data
Authors: Harder Mark E. , Deinzer Max L. , Leid Mark E. , Schimerlik Michael I. 
Published: July 2004

AbstractA new method for analyzing three‐state protein unfolding equilibria is described that overcomes the difficulties created by direct effects of denaturants on circular dichroism (CD) and fluorescence spectra of the intermediate state. The procedure begins with a singular value analysis of the data matrix to determine the number of contributing species and perturbations. This result is used to choose a fitting model and remove all spectra from the fitting equation. Because the fitting model is a product of a matrix function which is nonlinear in the thermodynamic parameters and a matrix that is linear in the parameters that specify component spectra, the problem is solved with a variable projection algorithm. Advantages of this procedure are perturbation spectra do not have to be estimated before fitting, arbitrary assumptions about magnitudes of parameters that describe the intermediate state are not required, and multiple experiments involving different spectroscopic techniques can be simultaneously analyzed. Two tests of this method were performed: First, simulated three‐state data were analyzed, and the original and recovered thermodynamic parameters agreed within one standard error, whereas recovered and original component spectra agreed within 0.5%. Second, guanidine‐induced unfolding titrations of the human retinoid‐X‐receptor ligand‐binding domain were analyzed according to a three‐state model. The standard unfolding free energy changes in the absence of guanidine and the guanidine concentrations at zero free‐energy change for both transitions were determined from a joint analysis of fluorescence and CD spectra. Realistic spectra of the three protein states were also obtained.
Probing folding and fluorescence quenching in human γD crystallin Greek key domains using triple tryptophan mutant proteins
Authors: Kosinski‐Collins Melissa S. , Flaugh Shannon L. , King Jonathan 
Published: July 2004

AbstractHuman γD crystallin (HγD‐Crys), a major component of the human eye lens, is a 173‐residue, primarily β‐sheet protein, associated with juvenile and mature‐onset cataracts. HγD‐Crys has four tryptophans, with two in each of the homologous Greek key domains, which are conserved throughout the γ‐crystallin family. HγD‐Crys exhibits native‐state fluorescence quenching, despite the absence of ligands or cofactors. The tryptophan absorption and fluorescence quenching may influence the lens response to ultraviolet light or the protection of the retina from ambient ultraviolet damage. To provide fluorescence reporters for each quadrant of the protein, triple mutants, each containing three tryptophan‐to‐phenylalanine substitutions and one native tryptophan, have been constructed and expressed. Trp 42‐only and Trp 130‐only exhibited fluorescence quenching between the native and denatured states typical of globular proteins, whereas Trp 68‐only and Trp 156‐only retained the anomalous quenching pattern of wild‐type HγD‐Crys. The three‐dimensional structure of HγD‐Crys shows Tyr/Tyr/His aromatic cages surrounding Trp 68 and Trp 156 that may be the source of the native‐state quenching. During equilibrium refolding/unfolding at 37°C, the tryptophan fluorescence signals indicated that domain I (W42‐only and W68‐only) unfolded at lower concentrations of GdnHCl than domain II (W130‐only and W156‐only). Kinetic analysis of both the unfolding and refolding of the triple‐mutant tryptophan proteins identified an intermediate along the HγD‐Crys folding pathway with domain I unfolded and domain II intact. This species is a candidate for the partially folded intermediate in the in vitro aggregation pathway of HγD‐Crys.
Evolutionary constraints associated with functional specificity of the CMGC protein kinases MAPK, CDK, GSK, SRPK, DYRK, and CK2α
Authors: Kannan Natarajan , Neuwald Andrew F. 
Published: July 2004

AbstractAmino acid residues associated with functional specificity of cyclin‐dependent kinases (CDKs), mitogen‐activated protein kinases (MAPKs), glycogen synthase kinases (GSKs), and CDK‐like kinases (CLKs), which are collectively termed the CMGC group, were identified by categorizing and quantifying the selective constraints acting upon these proteins during evolution. Many constraints specific to CMGC kinases correspond to residues between the N‐terminal end of the activation segment and a CMGC‐conserved insert segment associated with coprotein binding. The strongest such constraint is imposed on a “CMGC‐arginine” near the substrate phosphorylation site with a side chain that plays a role both in substrate recognition and in kinase activation. Two nearby buried waters, which are also present in non‐CMGC kinases, typically position the main chain of this arginine relative to the catalytic loop. These and other CMGC‐specific features suggest a structural linkage between coprotein binding, substrate recognition, and kinase activation. Constraints specific to individual subfamilies point to mechanisms for CMGC kinase specialization. Within casein kinase 2α (CK2α), for example, the binding of one of the buried waters appears prohibited by the side chain of a leucine that is highly conserved within CK2α and that, along with substitution of lysine for the CMGC‐arginine, may contribute to the broad substrate specificity of CK2α by relaxing characteristically conserved, precise interactions near the active site. This leucine is replaced by a conserved isoleucine or valine in other CMGC kinases, thereby illustrating the potential functional significance of subtle amino acid substitutions. Analysis of other CMGC kinases similarly suggests candidate family‐specific residues for experimental follow‐up.