Asystole in Orthognathic Surgery: A Case Report.

A previously healthy 26-year-old man presented for elective Le Fort I osteotomy, bilateral mandibular osteotomy, and genioplasty. During the intraoperative course, the patient developed sudden bradycardia and asystole on placement of a bite block. Asystole is an extremely rare consequence of the trigeminocardiac reflex, and awareness of this potentially life-threatening complication is pivotal in its management.

Design of matching layers for high-frequency ultrasonic transducers.

Matching the acoustic impedance of high-frequency (≥100 MHz) ultrasound transducers to an aqueous loading medium remains a challenge for fabricating high-frequency transducers. The traditional matching layer design has been problematic to establish high matching performance given requirements on both specific acoustic impedance and precise thickness. Based on both mass-spring scheme and microwave matching network analysis, we interfaced metal-polymer layers for the matching effects. Both methods hold promises for guiding the metal-polymer matching layer design. A 100 MHz LiNbO3 transducer was fabricated to validate the performance of the both matching layer designs. In the pulse-echo experiment, the transducer echo amplitude increased by 84.4% and its -6dB bandwidth increased from 30.2% to 58.3% comparing to the non-matched condition, demonstrating that the matching layer design method is effective for developing high-frequency ultrasonic transducers.

Modification of microstructure on PZT films for ultrahigh frequency transducer.

Porous Lead zirconate titanate (PZT) films may have promising applications in high frequency ultrasonic transducers for their capability to modify electrical properties for better electrical and acoustic matching. In this work, porous PZT films in range of several micrometers were fabricated using a chemical solution deposition (CSD) method modified with polyvinylpyrrolidone (PVP) as a pore-foaming agent. The crystalline phase, microstructure and electrical properties of the porous films were investigated as a function of PVP contents, molecular weights and annealing temperatures. It was found that the electrical properties were closely associated with the porosity.

Propofol induces MAPK/ERK cascade dependant expression of cFos and Egr-1 in rat hippocampal slices.

BACKGROUND: Propofol is a commonly used intravenous anesthetic agent, which produce rapid induction of and recovery from general anesthesia. Numerous clinical studies reported that propofol can potentially cause amnesia and memory loss in human subjects. The underlying mechanism for this memory loss is unclear but may potentially be related to the induction of memory-associated genes such as c-Fos and Egr-1 by propofol. This study explored the effects of propofol on c-Fos and Egr-1 expression in rat hippocampal slices. FINDINGS: Hippocampal brain slices were exposed to varying concentrations of propofol at multiple time intervals. The transcription of the immediate early genes, c-Fos and Egr-1, was quantified using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). MAPK/ERK inhibitors were used to investigate the mechanism of action. We demonstrate that propofol induced the expression of c-Fos and Egr-1 within 30 and 60 min of exposure time. At 16.8 muM concentration, propofol induced a 110% increase in c-Fos transcription and 90% decrease in the transcription of Egr-1. However, at concentrations above 100 muM, propofol failed to induce expression of c-Fos but did completely inhibit the transcription of Egr-1. Propofol-induced c-Fos and Egr-1 transcription was abolished by inhibitors of RAS, RAF, MEK, ERK and p38-MAPK in the MAPK/ERK cascade. CONCLUSIONS: Our study shows that clinically relevant concentrations of propofol induce c-Fos and down regulated Egr-1 expression via an MAPK/ERK mediated pathway. We demonstrated that propofol induces a time and dose dependant transcription of IEGs c-Fos and Egr-1 in rat hippocampal slices. We further demonstrate for the first time that propofol induced IEG expression was mediated via a MAPK/ERK dependant pathway. These novel findings provide a new avenue to investigate transcription-dependant mechanisms and suggest a parallel pathway of action with an unclear role in the activity of general anesthetics.

Propofol induces ERK-dependant expression of c-Fos and Egr-1 in neuronal cells.

This study explored the effects of propofol on c-Fos and Egr-1 in neuroblastoma (N2A) cells. We demonstrate that propofol induced the expression of c-Fos and Egr-1 within 30 and 60 min of exposure time. At 16.8 microM concentration, propofol induced a 6 and 2.5-fold expression of c-Fos and Egr-1, respectively. However, at concentrations above 100 microM, propofol failed to induce expression of c-Fos or Egr-1. Propofol-induced c-Fos and Egr-1 transcription was unaffected by bicuculline, a gamma-aminobutyric acid-A receptor antagonist, but was abolished by PD98059, a mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitor. Our study shows that clinically relevant concentrations of propofol induce c-Fos and Egr-1 expression through an extracellular signal-regulated kinase mediated and gamma-aminobutyric acid-A independent pathway.