Biomedical subjects

W P Ng

Publications and source records attributed to W P Ng.

7 recordsLinked to original sources

PubMed1999

Neuronal age influences the response to neurite outgrowth inhibitory activity in the central and peripheral nervous systems.

Axonal regeneration is abortive in the central nervous system (CNS) of adult mammals, but readily occurs in the injured peripheral nervous system (PNS). Recent experiments indicate an important role for both intrinsic neuronal features and extrinsic substrate properties in determining the propensity for axonal regrowth. In particular, certain components of adult mammalian CNS myelin have been shown to exert a strong inhibitory influence on neurite outgrowth. To determine whether the potent neurite outgrowth inhibitory activity found in CNS myelin may also be present in PNS myelin and to study the influence of neuronal age on neurite outgrowth, we used a cryoculture assay in which dissociated rat dorsal root ganglion (DRG) neurons of different ages were challenged to extend neurites on fractionated myelin and cryostat sections from the PNS (sciatic nerve and myelin-free degenerated sciatic nerve) and CNS (optic nerve) of adult rats. The CNS environment of the optic nerve did not support E17 to P8 DRG neurite adhesion or outgrowth. E17 DRG neurons, unlike their older counterparts, however, were able to attach and extend neurites onto normal sciatic nerve and onto purified PNS myelin. In contrast, a vigorous neurite outgrowth response from all the ages tested was observed on the myelin-free degenerated sciatic nerve. These results indicate that PNS myelin is a potent inhibitor of neurite outgrowth and that DRG neuronal age plays an important role in determining the propensity for neurite outgrowth and regenerative response on inhibitory PNS and CNS substrata.

Animals↗

PubMed1999

Surgical treatment for acute spinal cord injury study pilot study #2: evaluation of protocol for decompressive surgery within 8 hours of injury.

Acute spinal cord injury (SCI) is a major public health problem for which there is still only limited treatment available. The National Acute Spinal Cord Injury Study-2 (NASCIS-2) and -3 clinical trials demonstrated that the use of acute pharmacotherapy with methylprednisolone can attenuate the secondary injury cascade if administered within 8 hours of acute SCI. However, no trial has been performed to examine whether acute surgical decompressive procedures within this critical 8-hour time window can improve patients' neurological outcome. The purpose of the current prospective Surgical Treatment for Acute Spinal Cord Injury Study (STASCIS) pilot study was to determine the feasibility of obtaining a radiological diagnosis of spinal canal compromise of 25% or more and to perform spinal cord (C3-T1) decompressive procedures by 8 hours postinjury. One of the following three decompressive methods was used: 1) traction alone; 2) traction and surgery; or 3) surgery alone. Twenty-six patients from eight North American centers were entered into the study between 1996 and 1997. Significant difficulties were encountered in many centers in performing immediate magnetic resonance imaging examination in patients with acute SCI. Fewer than 10% of acute cervical SCI patients could be enrolled into this protocol mainly because the combination of the required time for rescue, resuscitation, transport, imaging study, and surgical preparation exceeded the 8-hour injury-to-decompressive surgery window. Eleven patients underwent decompressive procedures initially by being placed in traction at a mean time of 10.9 hours postinjury. Those patients not undergoing this procedure underwent decompressive surgery at a mean time of 40.1 hours. However, the surgical decompressive procedure was completed within 12 hours in seven patients. As a result of these findings, several major changes have been made to the STASCIS protocol for early decompressive therapy.

Journal Article↗

PubMed1998

Emergency defibrillation performed by coronary nursing staff: A pilot report.

The time taken to initiate defibrillation is a key factor in determining survival after cardiac arrest; all first-responding medical or paramedical personnel are thus recommended to receive training in defibrillation skills. We have recently established a working programme that allows trained coronary care nurses to defibrillate in emergencies. Prospective data collected from 1 October 1996 to 31 January 1997 showed that a total of 11 witnessed episodes of ventricular fibrillation or pulseless ventricular tachycardia occurred in nine patients, and were defibrillated by nurses. All the defibrillations were started within 1 minute of cardiac arrest. In five patients, defibrillation was commenced before the arrival of the crash team of doctors; three of the five patients survived. There were no violations of the resuscitation protocol or complications relating to defibrillation. Through programmed training in advanced cardiac life-support, coronary care nurses are capable of providing safe and prompt defibrillation. The importance of training and re-certification is also stressed.

Journal Article↗

PubMed1996

Human central nervous system myelin inhibits neurite outgrowth.

In vitro and animal studies have identified molecules in mammalian CNS myelin which inhibit neuritic extension and which may be responsible, at least in part, for the lack of axonal regeneration after injury in the injured brain, optic nerve and spinal cord. To determine whether such inhibitory activity may be present in human CNS myelin, we used a bioassay to characterize neurite outgrowth on this substrate. Human CNS myelin strongly inhibited neuritic outgrowth from newborn rat dorsal root ganglion neurons and NG-108-15 cells, a neuroblastoma-glioma hybrid cell line. Similar but less potent inhibitory activity was identified in human gray matter. The CNS myelin inhibition of neuritic outgrowth appeared to be dependent on direct contact between the myelin substrate and neurites. The inhibitory activity in human CNS myelin closely resembled that described in adult rodents. Inhibition of neurite growth by human CNS myelin in this in vitro bioassay mirrors the lack of regeneration in vivo and can be used as a model to develop strategies designed to enhance axonal regeneration and neural recovery.

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PubMed1996

Myelin from MAG-deficient mice is a strong inhibitor of neurite outgrowth.

Myelin-associated glycoprotein (MAG) has potent neurite outgrowth inhibitory activity in vitro. To assess the importance of MAG in the neurite outgrowth inhibitory activity in CNS myelin, we used an in vitro bioassay to characterize neurite growth on CNS myelin derived from mice carrying a null mutation of the MAG gene. Myelin proteins from MAG-deficient mice inhibited neurite outgrowth to a similar degree to the wild-type CNS myelin. These results suggest that CNS myelin molecules other than MAG exert strong inhibitory effects on the growth of neurites.

Animals↗

PubMed1996

Abscess within a brain metastasis.

BACKGROUND: Neoplastic metastases to the cerebellum are a frequent complication in patients with carcinoma. However, the co-existence of an abscess within a CNS metastasis is a rare event. METHODS: We report the case of a 79-year-old woman with two cerebellar abscesses within metastatic lesions in the cerebellum. She presented with a rapidly progressing syndrome characterized by elevated intracranial pressure and cerebellar findings. RESULTS: At surgery, a purulent exudate within discrete metastatic tumours was identified. Pathological and microbiological examinations confirmed the coexistence of an abscess within a metastatic carcinoma. SIGNIFICANCE AND CONCLUSION: The radiological diagnosis o f intracranial abscesses and metastases can be non-specific and brain imaging may not reliably identify both processes when they coexist. Furthermore, brain metastases often contain liquefied material which can be mistaken for tissue necrosis rather than an infectious process. It is important to be aware that a brain metastasis can also be infected. Therefore, acquisition of lesional tissue for both pathological and microbiological examinations is essential for accurate diagnosis and to direct optimal therapy in situations where the intracranial lesion could be either an abscess or a metastatic deposit.

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PubMed1995

Intradural metastasis mimicking nerve sheath tumor.

STUDY DESIGN: This is a case report. OBJECTIVE: This is an unusual case of a 69 year-old man with metastatic carcinoma to the C8 and T1 intradural roots, with extension through the intervertebral foramen of C7-T1 mimicking a nerve sheath tumor clinically and radiologically. This report reviews the clinical features, radiology, pathology, and pathogenesis of these metastatic lesions. SUMMARY OF BACKGROUND DATA: Nerve sheath tumors are the most common primary spinal tumors. In contrast, metastasis to the spinal nerve roots is very rare. Metastatic tumors may clinically simulate other diseases and, as in this case, a nerve sheath tumor. METHODS: A review and discussion of the case facts are presented. RESULTS: Metastatic carcinoma to C8 and T1 nerve roots was diagnosed intraoperatively during C7-T1 laminectomy and partial tumor debulking. The patient had a satisfactory recovery, with symptomatic relief of painful radiculopathy, but with no improvement in motor strength. CONCLUSION: Metastasis to spinal nerve roots can clinically mimic other diseases. As in this case, the proper diagnosis may be possible only at surgery.

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