JooHun Lee

Comparison of propofol and fentanyl administered at the end of anaesthesia for prevention of emergence agitation after sevoflurane anaesthesia in children

BACKGROUND Propofol and fentanyl can be administered at the end of sevoflurane anaesthesia to decrease the incidence and severity of emergence agitation (EA), although it has not been determined which agent has superior efficacy. The purpose of this study was to compare the effects of propofol and fentanyl on EA. METHODS In this prospective, randomized, double-blind study, 222 children, 18-72 months of age, undergoing sevoflurane anaesthesia were randomly assigned to one of the three groups receiving either propofol 1 mg kg(-1) (Group P), fentanyl 1 µg kg(-1) (Group F), or saline (Group S) at the end of anaesthesia. The incidence and severity of EA were evaluated with the paediatric anaesthesia emergence delirium (PAED) scale. Time to recovery and incidence of nausea/vomiting were assessed. RESULTS The mean PAED score was 4.3 in Group P and 4.9 in Group F (P=0.682), which were lower than 9.0 in Group S (P<0.001). Nausea and vomiting were significantly more frequent in Group F than Groups P and S (adjusted P=0.003 and adjusted P<0.001). Group F had also longer stay in the post-anaesthesia care unit (PACU) than Group S (P<0.001), while Group P did not. However, the differences in PACU stays between the P and F groups were considered clinically insignificant. CONCLUSION Small doses of propofol or fentanyl at the end of sevoflurane anaesthesia comparably reduced EA. Propofol was better than fentanyl due to a lower incidence of nausea and vomiting.

O-GlcNAcylation of tubulin inhibits its polymerization

The attachment of O-linked β-N-acetylglucosamine (O-GlcNAc) to proteins is an abundant and reversible modification that involves many cellular processes including transcription, translation, cell proliferation, apoptosis, and signal transduction. Here, we found that the O-GlcNAc modification pattern was altered during all-trans retinoic acid (tRA)-induced neurite outgrowth in the MN9D neuronal cell line. We identified several O-GlcNAcylated proteins using mass spectrometric analysis, including α- and β-tubulin. Further analysis of α- and β-tubulin revealed that O-GlcNAcylated peptides mapped between residues 173 and 185 of α-tubulin and between residues 216 and 238 of β-tubulin, respectively. We found that an increase in α-tubulin O-GlcNAcylation reduced heterodimerization and that O-GlcNAcylated tubulin did not polymerize into microtubules. Consequently, when O-GlcNAcase inhibitors were co-incubated with tRA, the extent of neurite outgrowth was decreased by 20% compared to control. Thus, our data indicate that the O-GlcNAcylation of tubulin negatively regulates microtubule formation.

De novo formation of basal bodies in Naegleria gruberi : regulation by phosphorylation

The de novo formation of basal bodies in Naegleria gruberi was preceded by the transient formation of a microtubule (MT)-nucleating complex containing γ-tubulin, pericentrin, and myosin II complex (GPM complex). The MT-nucleating activity of GPM complexes was maximal just before the formation of visible basal bodies and then rapidly decreased. The regulation of MT-nucleating activity of GPM complexes was accomplished by a transient phosphorylation of the complex. Inhibition of dephosphorylation after the formation of basal bodies resulted in the formation of multiple flagella. 2D-gel electrophoresis and Western blotting showed a parallel relationship between the MT-nucleating activity of GPM complexes and the presence of hyperphosphorylated γ-tubulin in the complexes. These data suggest that the nucleation of MTs by GPM complexes precedes the de novo formation of basal bodies and that the regulation of MT-nucleating activity of GPM complexes is essential to the regulation of basal body number.

Analgesic efficacy of caudal dexamethasone combined with ropivacaine in children undergoing orchiopexy

BACKGROUND Epidural administration of dexamethasone might reduce postoperative pain in adults. We evaluated whether a caudal block of 0.1 mg kg(-1) dexamethasone combined with ropivacaine improves analgesic efficacy in children undergoing day-case orchiopexy. METHODS This randomized, double-blind study included 80 children aged 6 months to 5 yr who underwent day-case, unilateral orchiopexy. Patients received either 1.5 ml kg(-1) of 0.15% ropivacaine (Group C) or 1.5 ml kg(-1) of 0.15% ropivacaine in which dexamethasone of 0.1 mg kg(-1) was mixed (Group D) for caudal analgesia. Postoperative pain scores, rescue analgesic consumption, and side-effects were evaluated 48 h after operation. RESULTS Postoperative pain scores at 6 and 24 h post-surgery were significantly lower in Group D than in Group C. Furthermore, the number of subjects who remained pain free up to 48 h after operation was significantly greater in Group D [19 of 38 (50%)] than in Group C [four of 37 (10.8%); P<0.001]. The number of subjects who received oral analgesic was significantly lower in Group D [11 of 38 (28.9%)] than in Group C [20 of 37 (54.1%); P=0.027]. Time to first oral analgesic administration after surgery was also significantly longer in Group D than in Group C (P=0.014). Adverse events after surgery including vomiting, fever, wound infection, and wound dehiscence were comparable between the two groups. CONCLUSIONS The addition of dexamethasone 0.1 mg kg(-1) to ropivacaine for caudal block can significantly improve analgesic efficacy in children undergoing orchiopexy. Clinical trial registration NCT01604915.

Cloning and characterization of a divergent α-tubulin that is expressed specifically in dividing amebae of Naegleria gruberi

A novel alpha-tubulin gene (alpha6) was cloned from a genomic library of Naegleria gruberi strain NB-1 and characterized. The open reading frame of alpha6 contained 1359 nucleotides encoding a protein of 452 amino acids (aa) with a calculated molecular weight of 50.5 kDa. The nucleotide sequence of the open reading frame of alpha6 showed considerable divergence (68.4% identity) when compared with previously cloned N. gruberi alpha-tubulin genes, which share about 97% identity in DNA sequences. The deduced aa sequence of alpha6-tubulin was 61.9% identical to that of alpha13-tubulin, which was cloned from the same strain, and showed similar identities to those of alpha-tubulins from other species (54 approximately 62%). These data showed that alpha6-tubulin is one of the most divergent alpha-tubulins so far known. Alpha6-tubulin was found to be expressed in actively growing cells and repressed quickly when these cells were induced to differentiate. Immunostaining with an antibody against alpha6-tubulin showed that alpha6-tubulin is present in the nuclei and mitotic spindle-fibers but absent in flagellar axonemes or cytoskeletal microtubules. These data finally established the presence of an alpha-tubulin that is specifically utilized for spindle-fiber microtubules and distinct from the flagellar axonemal alpha-tubulins in N. gruberi, hence confirmed the multi-tubulin hypothesis in this organism.

De novo formation of basal bodies during cellular differentiation of Naegleria gruberi: progress and hypotheses.

Under defined laboratory conditions, Naegleria gruberi undergo an amoeba-to-flagellate differentiation. During this differentiation, N. gruberi changes its shape from an amorphous amoeba to a regular shaped flagellate and forms de novo a flagellar apparatus, which is composed of two basal bodies, two flagella, a flagellar rootlet, and cytoplasmic microtubules. The entire process is accomplished within 2h after initiation of differentiation and more than 95% of cells in the population undergo this differentiation. This rapid and synchronous differentiation of N. gruberi provides us with a unique system in which we can study the process of de novo basal body assembly. In this review, I summarize recent findings associated with de novo basal body assembly and propose a hypothesis to explain how N. gruberi assemble two basal bodies per cell, which is what happens in the majority of cells.

Mad1p, a component of the spindle assembly checkpoint in fission yeast, suppresses a novel septation-defective mutant, sun1, in a cell-division cycle.

To enhance our understanding of the cytokinesis, we have carried out a genetic screen for temperature-sensitive Schizosaccharomyces pombe mutants that show defects in septum formation and cell division. Here we present the isolation and characterization of a new temperature-sensitive mutant, sun1 (septum uncontrolled), which undergoes uncontrolled septation during cell-division cycle at restrictive temperature (37 degrees C). In sun1 mutant, the actin ring and septum are positioned at random locations and angles, and the nuclear division cycle continues. These observations suggest that the sun1 gene product is required for the proper placement of the actin ring as well as precise septation. In a screen for the sun1(+) gene to complement the sun1 mutant, we have isolated a mad1(+) (mitotic arrest deficient) gene, which encodes a component of the spindle checkpoint in the cell-division cycle. Analysis of crossing the sun1 cell with the mad1(+) null mutant indicates that mad1(+) suppresses the sun1 mutant defective in controlled septation in a cell-division cycle.

Comparison of propofol and fentanyl for preventing emergence agitation in children

Editor—We read with interest the article by Lee and colleagues comparing propofol and fentanyl for prevention of emergence agitation after sevoflurane anaesthesia in children. We thank the authors for their work in this very common and often very distressing scenario. We would like to raise a few important questions regarding this study. Pain is one of the important causes for emergence agitation particularly in children, and although the authors excluded the children in whom caudal analgesia had not worked, we think assessment of pain by appropriate scales would have been very helpful in addressing this confounding factor. Also considering the authors have used lidocaine for caudal analgesia and the patients had at least 60 min duration of anaesthesia and a further 40 min in Post Anaesthesia Care Unit (PACU), we consider assessment of pain in PACU would have been invaluable data in this study. Propofol was used as the rescue agent for severe agitation in PACU. Considering that propofol was one of the study drugs, we think that it introduces bias into the study. The starvation times used in this study were very long compared with the common clinical practice in the UK (where it is 6 h for solids and 2 h for clear fluids). We appreciate this could have been the standard protocol of the institution, but longer starvation periods would lead to more distress before induction, which possibly could have led to some exclusions from the study. Preoperative anxiety and distress is another significant contributing factor for emergence agitation in children. 3 Parental stay during recovery of anaesthesia is another factor influencing emergence agitation in children. We understand the policy of the institution of not having parental presence in PACU influencing the study protocol, and we would like to commend the authors in acknowledging this factor for higher incidence of emergence agitation in Group S.

Effects of retinoic acid and cAMP on the differentiation of Naegleria gruberi amoebas into flagellates

During the differentiation of Naegleria gruberi amoebas into flagellates, the amoebas undergo sequential changes in cell shape and form new cellular organelles. To understand the nature of the signal which initiates this differentiation and the signal transduction pathway, we treated cells with four agents, PMA, retinoic acid (RA), okadaic acid, and cAMP. Retinoic acid and cAMP had specific effects on the differentiation of N. gruberi depending on the time of the drug treatment. Addition of (100 μM) retinoic acid at the initiation of differentiation inhibited differentiation by blocking the transcription of differentiation specific genes (e.g., (β‐tubulin). This inhibition of differentiation by retinoic acid was overcome by co‐treatment with cAMP (or dbcAMP, 20 μM). Addition of retinoic acid at later stages (30 and 70 min) had no effect on the transcriptional regulation of the β‐tubulin gene, however the differentiation was inhibited by different degrees. Co‐treatment of cAMP at these stages did not overc...

Coordinate Synthesis but Discrete Localization of Homologous N-Glycosylated Proteins, CLP and CLB, in Naegleria pringsheimi Flagellates

The synchronous amoebae‐to‐flagellates differentiation of Naegleria pringsheimi has been used as a model system to study the formation of eukaryotic flagella. We cloned two novel genes, Clp, Class I on plasma membrane and Clb, Class I at basal bodies, which are transiently expressed during differentiation and characterized their respective protein products. CLP (2,087 amino acids) and CLB (1,952 amino acids) have 82.9% identity in their amino acid sequences and are heavily N‐glycosylated, leading to an ~ 100 × 103 increase in the relative molecular mass of the native proteins. In spite of these similarities, CLP and CLB were localized to distinct regions: CLP was present on the outer surface of the plasma membrane, whereas CLB was concentrated at a site where the basal bodies are assembled and remained associated with the basal bodies. Oryzalin, a microtubule toxin, inhibited the appearance of CLP on the plasma membrane, but had no effect on the concentration of CLB at its target site. These data suggest that N. pringsheimi uses separate mechanisms to transport CLP and CLB to the plasma membrane and to the site of basal body assembly, respectively.