Detachment of Chain-Forming Neuroblasts by Fyn-Mediated Control of cell-cell Adhesion in the Postnatal Brain.

In the rodent olfactory system, neuroblasts produced in the ventricular-subventricular zone of the postnatal brain migrate tangentially in chain-like cell aggregates toward the olfactory bulb (OB) through the rostral migratory stream (RMS). After reaching the OB, the chains are dissociated and the neuroblasts migrate individually and radially toward their final destination. The cellular and molecular mechanisms controlling cell-cell adhesion during this detachment remain unclear. Here we report that Fyn, a nonreceptor tyrosine kinase, regulates the detachment of neuroblasts from chains in the male and female mouse OB. By performing chemical screening and in vivo loss-of-function and gain-of-function experiments, we found that Fyn promotes somal disengagement from the chains and is involved in neuronal migration from the RMS into the granule cell layer of the OB. Fyn knockdown or Dab1 (disabled-1) deficiency caused p120-catenin to accumulate and adherens junction-like structures to be sustained at the contact sites between neuroblasts. Moreover, a Fyn and N-cadherin double-knockdown experiment indicated that Fyn regulates the N-cadherin-mediated cell adhesion between neuroblasts. These results suggest that the Fyn-mediated control of cell-cell adhesion is critical for the detachment of chain-forming neuroblasts in the postnatal OB.SIGNIFICANCE STATEMENT In the postnatal brain, newly born neurons (neuroblasts) migrate in chain-like cell aggregates toward their destination, where they are dissociated into individual cells and mature. The cellular and molecular mechanisms controlling the detachment of neuroblasts from chains are not understood. Here we show that Fyn, a nonreceptor tyrosine kinase, promotes the somal detachment of neuroblasts from chains, and that this regulation is critical for the efficient migration of neuroblasts to their destination. We further show that Fyn and Dab1 (disabled-1) decrease the cell-cell adhesion between chain-forming neuroblasts, which involves adherens junction-like structures. Our results suggest that Fyn-mediated regulation of the cell-cell adhesion of neuroblasts is critical for their detachment from chains in the postnatal brain.

[A case-control study of airway management for 68 patients with cervical spine injury: comparison of the direct laryngoscope with a Macintosh blade and the fiberoptic bronchoscope].

BACKGROUND: As for cervical spine injury, special consideration for airway management is required but the optimal strategy remains controversial. Direct laryngoscopy (DL) creates some degree of cervical extension leading to secondary neurologic deterioration. Fiberoptic bronchoscopy (FOB) may facilitate tracheal intubation with little cervical motion, but has several inherent limitations. A few objective data prompted us to compare the neurologic outcome relating to the orotracheal intubation using the different types of technique, the DL with a Macintosh blade or the FOB. METHODS: To identify the effect of different methods on the intubation time, neurologic disability, and adverse effects, 68 cervical spine-injured patients with the use of DL (group L; 36 patients) or FOB (group F; 32 patients) were retrospectively reviewed using hospital records. Following the induction of general anesthesia, the trachea was intubated with no immobilizing forces in group L, while awake intubation was accomplished in group F after judicious application of local anesthesia to the larynx and trachea. RESULTS: No significant differences were observed between the groups in age, BMI, intubation time, postoperative neurologic outcome or incidence of aspiration pneumonia. Moreover, no neurologic deterioration was shown after DL and orotracheal intubation. CONCLUSIONS: We found no evidence to support the routine practice of the bronchoscope-assisted awake intubation in patients with cervical spine injury. The clinical value of this technique in offering some neurologic advantage remains limited.

[Anesthetic considerations for spine surgery in 71 patients with infectious spondylitis: effects of different pathogen either pyogenic or tuberculous on intraoperative blood loss].

BACKGROUND: Little information is available about anesthetic management in spine surgery for infectious spondylitis, in which major bleeding can be expected. The amount of blood loss may vary somewhat with pyogenic or tuberculous spondylitis. Limited data prompted us to get a clue to determine how best to care for these patients. METHODS: To examine the amount of intraoperative bleeding, 71 patients with either pyogenic (group A; 44 patients) or tuberculous spondylitis (group B; 27 patients) were retrospectively reviewed using hospital records. They underwent posterior fusion with instrumentation and anterior radical resection of the lesion. RESULTS: No significant differences were observed between the groups in age, gender, comorbidity or length of hospital stay. Operative time was longer in patients with group B (A: 126 +/- 41 vs B: 197 +/- 76 min, P<0.01). There was a trend toward greater blood loss in group B, especially massive bleeding (>1.5 l) occurred at a higher rate (13.6 vs 33.3%, P=0.05). The number of involved vertebrae was more in group B (1.8 +/- 0.9 vs 2.9 +/- 1.3, P<0.01). Both operative time and blood loss volume showed a good correlation with the number of vertebrae infected, suggesting that extensive eradication over several spinal segments may be indicated for tuberculous spondylitis. CONCLUSIONS: Spine surgery for tuberculous spondylitis is more likely to carry risks of longer operative time and higher rate of blood loss.

[Case of obstructive sleep apnea possibly having led to postoperative appearance of generalized convulsion].

Adverse surgical outcomes appear to be more frequent in patients with known obstructive sleep apnea (OSA). However, OSA patients may present for surgery without a prior diagnosis. A 37-year-old man underwent craniotomy for surgical direct neck clipping of the right ruptured internal carotid aneurysm. His intraoperative and early postoperative courses were uneventful. At night, about 48 hr after surgery, he developed sudden generalized tonic-clonic convulsion and temporary depressed consciousness resulting in marked hypercapnea (Pa(CO2)>100 mmHg). His respiration was transiently supported by PSV mode via LMA. He soon got well without neurologic deficits. At night, about 74 hr postoperatively, a generalized convulsion was again observed with hypercapnea. Aside from the respiratory support, percutaneous cricothyroidotomy was performed using Minitrach II system for his airway control, leading to no further recurrence of seizure. He was suspected to have unrecognized OSA due to such characteristic findings of sleep apnea as obesity (BMI>30) and witnessed apneas by his family. Postoperative rapid eye movement (REM) sleep rebound has been suggested to contribute to two consecutive night appearance of seizure. Clinical suspicion for OSA should be required preoperatively and perioperative heightened awareness is recommended.

[Cardiac arrest induced by dexmedetomidine].

A 64-year-old woman with hypertension, diabetes mellitus and asymptomatic first degree AV block underwent low anterior resection of the rectum. Anesthesia was induced with propofol, vecuronium bromide and remifentanil and maintained with nitrous oxide in oxygen, propofol and remifentanil. We did not use epidural anesthesia. After the operation, the patient was admitted to the intensive care unit under general anesthesia with propofol and remifentanil. In addition, dexmedetomidine was given without loading dose. The EKG changed from first degree AV block to second degree AV block followed by complete AV block and finally cardiac arrest. As soon as we performed heart massage, sinus rhythm appeared. We should be careful in giving dexmedetomidine to a patient with AV block.