Design of a self-cleaning thermoresponsive nanocomposite hydrogel membrane for implantable biosensors.

Following implantation of a biosensor, adhesion of proteins and cells and eventual fibrous encapsulation will limit analyte diffusion and impair sensor performance. A thermoresponsive nanocomposite hydrogel was developed as a self-cleaning biosensor membrane to minimize the effect of the host response and its utility for an optical glucose sensor, demonstrated here. It was previously reported that thermoresponsive nanocomposite hydrogels prepared from photopolymerization of an aqueous solution of N-isopropylacrylamide (NIPAAm) and polysiloxane colloidal nanoparticles released adhered cells with thermal cycling. However, poly(N-isopropylacrylamide) hydrogels exhibit a volume phase transition temperature (VPTT) of approximately 33-34 degrees C, which is below body temperature. Thus, the hydrogel would be in a collapsed state in vivo, which would ultimately limit diffusion of the target analyte (e.g., glucose) to the encapsulated sensor. In this study, the VPTT of the nanocomposite hydrogel was increased by introducing N-vinylpyrrolidone (NVP) as a comonomer, so that the hydrogel was in the swollen state in vivo. This thermoresponsive nanocomposite hydrogel was prepared by the photopolymerization of an aqueous solution of NIPAAm, NVP, and polysiloxane colloidal nanoparticles. In addition to a VPTT a few degrees above body temperature, the hydrogel also exhibited good mechanical strength, glucose diffusion, and in vitro cell release upon thermal cycling. Thus, this nanocomposite hydrogel may be useful as a biosensor membrane to minimize biofouling and extend the lifetime and efficiency of implantable glucose sensors and other biosensors.

Surgical experience with an implanted artificial cervical joint.

OBJECT: To assess the effectiveness of Cummins' artificial cervical joint, the authors reviewed the cases of 20 patients in whom the joint had been placed. METHODS: A review of patients' medical records and reexamination of 18 patients were performed. The review of the surgical experience with the implantation of movable stainless-steel joints in 20 patients treated for cervical myelopathy (16 patients), cervical radiculopathy (three patients), and severe pain (one patient) indicated that the procedure is safe and well tolerated and does preserve cervical joint motion in most patients over an extended period of observation. To date, adjacent segmental symptomatic degenerative changes leading to further surgical treatment have been avoided. The joint has been placed in patients with advanced congenital and acquired cervical fusion and has been demonstrated to be stable, mobile, and biomechanically and biochemically compatible; it has shown no subsidence into adjacent bone. Wear debris has not occurred. CONCLUSIONS: The use of stainless steel in the cervical spine appears to be suitable for this joint replacement design.

Event-related potentials--neurophysiological tools for predicting emergence and early outcome from traumatic coma.

OBJECTIVE: To determine the prognostic value of multimodal evoked potentials (EPs) and event-related (ERPs) potentials in coma (Glasgow Coma Score <8), after severe traumatic brain injury (TBI). DESIGN: Prospective, longitudinal study of neurophysiological responses recorded during traumatic coma. SETTING: Intensive Care Unit, Frenchay Hospital, Bristol, UK. PARTICIPANTS: Fifty-four comatose TBI patients (age range 1-80 years, mean 36.4). METHODS: Neurophysiological responses were recorded from 11 scalp electrodes with earlobe reference. Conduction times were measured for brainstem auditory, flash visual and somatosensory, short-latency EPs. Peak latencies and amplitudes were determined for long-latency components of visual and auditory ERPs, generated by passive "oddball" paradigms. These neurophysiological and various clinical parameters were correlated with patient outcome using Pearson's coefficient. MAIN OUTCOME MEASURE: Three month Glasgow Outcome Scale (GOS). RESULTS AND CONCLUSION: Highly significant (P <0.001) correlations exist between long-latency ERP components and 3-month outcome. Short-latency EPs, brainstem (wave I-V) and somatosensory conduction times also correlate significantly with the GOS (P <0.01). Of the clinical measurements, pupillary response patterns, APACHE II and Glasgow Coma Scores (GCS) correlate significantly with outcome, as do the retrospective measures of duration of coma and post-traumatic amnesia (PTA) in survivors. Unfortunately, due to variance of long-latency responses, even in controls, absolute values cannot be relied upon as prognosticators. The presence of "mismatch negativity" predicted the return of consciousness (89.7% sensitivity and 100% specificity) and preceded changes in GCS. Its latency was the single best indicator of 90-day outcome from coma (r = -0.641).

The ISG viewing wand: an application to atlanto-axial cervical surgery using the Le Fort I maxillary osteotomy.

Surgical access to the clivus and upper cervical spine may be facilitated by a number of approaches. The Le Fort I maxillary osteotomy has been described to give improved access to the skull base for removal of tumours and treating vertebrobasilar aneurysms. We describe a case in which the combination of a particularly high translocation of the body of C2 and poor mouth opening had precluded a standard transoral approach by restricting access to the operative field. Anterior decompression of the body of C2 was therefore performed via a maxillary down-fracture with the aid of an interactive image guidance system, the ISG Viewing Wand. The ISG Viewing Wand is a new intra-operative 3 dimensional (3D) image guidance system which has now been used in over three hundred neurosurgical cases at Frenchay Hospital, Bristol. We briefly discuss the principles of the viewing wand and describe its unique application providing anatomical navigation in upper cervical spine surgery.

Intracranial large vessel vasculopathy and anaplastic meningioma 19 years after cranial irradiation for acute lymphoblastic leukaemia.

A child was diagnosed in 1969 as having acute lymphoblastic leukaemia (ALL) and received chemotherapy. On bone marrow relapse in 1973, he was treated with cranial irradiation (20 Gy) in addition to chemotherapy. He continues in complete remission 19 years after his relapse. At age 25 years, he presented with headaches and left hemiparesis. Computerised tomograph demonstrated a large, enhancing right-sided intracranial tumour. Angiography was performed and showed the right internal carotid artery was occluded. Most of the right hemisphere was supplied from the external carotid via the middle meningeal artery. The left posterior cerebral artery and the left anterior cerebral artery were absent presumably as a result of radiation-induced arteritis. A resection of an anaplastic meningioma arising from the right sphenoidal ridge was achieved. There was a rapid improvement in function and he returned to work. Vasculopathy of the large intracranial arteries has been described after high dose radiation. It may occur as in this case after moderate dose radiation. There is a correlation with meningioma. There is a possibility that large artery vasculopathy will be present in a proportion of patients irradiated for ALL. The long lag time between irradiation and the development of meningioma may mean that, as survivors of childhood ALL enter their third decade since cure, this tumour may be seen increasingly.

Initial assessment and management of the severely head-injured patient.

Head injuries account for a significant proportion of acute hospital admissions. The first few hours after a serious head injury are extremely important, particularly in terms of reducing possible secondary injuries. This article addresses the management problems in this group of patients during this initial critical period.

Intracranial meningiomas following irradiation--a growing problem?

We present 10 cases of meningiomas occurring after high-dose irradiation for other brain tumours. These constitute 3.7% of 272 patients with meningiomas treated in our unit over 10 years. The clinical and pathological features of the 10 cases were added to those of 69 previous cases documented in the literature and compared with the features of our 262 spontaneous meningiomas. The literature on 119 cases of low-dose radiation-induced meningiomas was also reviewed. Malignant histological features and multiplicity were more common in the radiation-induced meningiomas (p < 0.01). Increasing long-term survival rates following radiotherapy for primary intracranial tumours, particularly in childhood, may lead to an increased incidence of postirradiation meningiomas.

Revisional lumbar microdiscectomy: an analysis of operative findings and clinical outcome.

Forty-one consecutive patients who underwent a revision microlumbar exploration for recurrent or persistent sciatica were reviewed retrospectively to analyse the operative findings and assess the clinical outcome following surgery. Thirty-three (80%) patients were found to have a recurrent intervertebral disc protrusion at the previous site, two patients had a disc herniation at a new site, one had severe perineural scarring, two had lateral recess stenosis, one patient had undergone previous exploration at an incorrect site and in two patients no cause for ongoing symptoms was found. Nineteen of the 33 patients with a re-prolapse presented with persistent or recurrent sciatica within 1 year of their first operation. The other 14 patients presented with a late re-prolapse (after 1 year) and their clinical outcome was better than for those patients with an early re-prolapse (12/14 vs 11/19 satisfactory result, respectively). The result of operating on patients with a late re-prolapse was comparable to the 80-95% satisfactory outcomes following primary lumbar microdiscectomy reported by other authors.

Clinical characteristics of traumatic extradural hematoma: a comparison between children and adults.

In this study of 43 children who had surgery for traumatic extradural hematoma (EDH) at Frenchay Hospital, England, between 1975 and 1987, the authors attempt to outline the various clinical characteristics of EDH which are different in children (age range 1-15 years) and adults (age range 16-84 years). The results confirm that children with traumatic EDH are less likely to have injury be caused by an RTA, are less likely to remain unconscious from the time of injury to the time of the operation, and are less likely to require immediate surgery (less than 6 hours after injury). In addition, the CT scan is less likely to show in associated intradural injury, and the outcome is significantly better.

Tophaceous gout of the spine causing spinal cord compression.

Tophaceous gout of the spine rarely causes spinal cord compression. Only eight cases have been reported previously. We report a further case presenting with progressive quadriparesis caused by gouty tophi at C1, treated successfully by decompressive laminectomy and internal fixation. This case and the previously reported cases are reviewed.

The outcome of surgery of aneurysmal subarachnoid haemorrhage.

Aneurysmal subarachnoid haemorrhage is a challenging pathology which remains a cause of considerable mortality and morbidity. To demonstrate to general practitioners the results of surgery for this condition a retrospective study of 160 consecutive cases who had undergone aneurysmal surgery was carried out. On admission 57% of cases had a good Hunt and Hess grade (grades I and II) and 43% a poor grade (grades III, IV and V). Twelve per cent of cases had a pre-existing hypertension and 73% of cases were treated with nimodipine. Angiography was performed from 0 to 73 days (median 3 days) after the bleed. Early surgery (within the first three days after the bleed) was performed in 41% of cases. Twenty-two per cent of cases rebled before surgery from 1 to 69 days after initial presentation (median seven days). Delayed cerebral ischaemia was diagnosed in 38% of cases, but only 15% of cases had evidence of low density on the CT scan. The outcome was determined at six months using the 'Glasgow outcome scale'. Fifty-five per cent of cases made a good recovery (back to normality), 15% a fair recovery (moderately disabled but independent), 15% a poor recovery (severely disabled and dependent), and 15% died. The significant poor prognostic factors were: a poor pre-operative Hunt and Hess grade, the presence of an intracerebral haematoma or angiographic spasm, evidence of rebleeding and early surgery without treatment with nimodipine. Other factors which did not reach a statistical significance include: age, presence of subarachnoid and intraventricular blood on CT, timing of surgery, history of long-standing hypertension, intraoperative rupture, and the development of hydrocephalus or delayed ischaemia.

Outcome following surgical evacuation of traumatic intracranial haematomas in the elderly.

In order to determine the factors influencing outcome following craniotomy for trauma in patients over the age of 65 and to establish criteria for surgical intervention, the authors carried out a retrospective analysis of the hospital and general practice records of all head injury patients over the age of 65 who underwent a craniotomy for evacuation of a post-traumatic haematoma within 7 days of injury at Frenchay Hospital during a 10-year period (1980-89). Outcome was measured using the Glasgow Outcome Scale and patients were allotted to a good outcome group (good recovery or moderate disability but independent) or a poor outcome group (severe disability, vegetative state of death). There were 35 men and 31 women with a mean age of 72.5 years (range 65-85 years). The mortality rate was 61% and 9% of patients survived in a severely disabled or vegetative state. All 20 (30%) patients with a good outcome had a Glasgow Coma Score (GCS) of 5 or more immediately before surgery. All 18 (27%) patients with a GCS of 4 or less and all 22 (33%) patients with unilateral or bilateral pupillary dilatation had a poor outcome. Outcome was significantly worse in the older patients (75-85 years) compared with the younger patients (65-74 years) and in those patients requiring craniotomy within 24 hours of injury, but the mechanism of injury (fall or road traffic accident), the presence or absence of skull fractures and limb fractures and the pre-operative CT scan appearances did not influence outcome. This study confirms the high probability of poor outcome following surgical evacuation of traumatic intracranial haematomas for elderly head-injured patients with pupillary dilatation or extensor motor responses. Craniotomy under these circumstances is not justified.

Paraplegia following a rivet gun injury: the use of magnetic resonance imaging in the management.

We describe the case of a 39-year-old man who was accidentally shot in the back by a rivet gun. This resulted in paraplegia and partial sensory loss. Magnetic resonance imaging (MRI) was helpful in the accurate localization of the foreign body and in the assessment of the spinal cord damage. MRI enabled accurate pre-operative localization of the rivet and provided information on the degree of damage to the spinal cord. The artefact produced on computed tomography plus the limited anatomical detail of the spinal cord in the absence of intrathecal contrast makes this technique unhelpful.

Cyclohexanedione modification of arginine at the active site of Aspergillus ficuum phytase.

Reaction of Aspergillus ficuum phytase with the arginine specific modifier 1,2-cyclohexanedione causes a rapid loss of activity. The inactivation can be partially reversed by 0.2 M hydroxylamine and exhibits pseudo-first order kinetics. The reaction order and second order rate constant of inactivation were 0.87 and 6.72 M-1 Min-1, respectively. Amino acid analysis of modified phytase indicates that about 7 arginine of the total 19 were modified. While the chymotryptic maps of treated and untreated phytase wer virtually identical, the tryptic maps had 4 peaks of altered mobility. An Arg containing tripeptide was identified in the phytase which is also present in other phosphohydrolases and may represent one of the labile Arg involved in the formation of the active site.