Biomedical subjects

W P Gray

Publications and source records attributed to W P Gray.

9 recordsLinked to original sources

PubMed2005

Persistent and intractable ventriculitis due to retained ventricular catheters.

It is generally recommended that, in cases of difficulty in removing a ventricular catheter during a shunt revision, it is best left alone to avoid intraventricular haemorrhage. Retained ventricular catheters (RVCs) are usually safe, although in the presence of ventriculitis they may become colonized by organisms and become a source of persistent or recurrent infection. The authors present a case of persistent and intractable ventriculitis due to an old retained ventricular catheter. A 23-year-old female, who had a RVC and a functioning shunt, was admitted for a suspected blocked shunt. At surgery the shunt was found to be infected and external drainage was instituted. Over the next 4 months, she developed intractable and persistent staphylococcal ventriculitis, despite undergoing 10 further surgical procedures, and appropriate intravenous and intrathecal antibiotic therapy. She responded rapidly only after surgical removal of the old RVC via a craniotomy. The staphylococcus cultured from the RVC had an identical antibiogram to the organism responsible for the intractable ventriculitis. This case emphasizes the point that, although RVC are generally considered safe, removal becomes imperative in the presence of concurrent CSF infection that fails to respond quickly to intrathecal antibiotic therapy.

Adult↗

PubMed2002

Seizure induced dentate neurogenesis does not diminish with age in rats.

Neurogenesis in the mammalian dentate gyrus occurs throughout life, is believed to be important for the laying down of episodic memory and diminishes significantly with increasing age. Pathological insults such as seizures, hypoxia and traumatic brain injury increase dentate neurogenesis compared to age matched controls. Using unilateral intracerebroventricular kainate we show that although baseline neurogenesis is significantly lower in 3 month old rats compared to 1 month old rats, kainate increases neurogenesis to reach similar levels in both age groups. Additionally, this effect is bilateral after a unilateral intracerebroventricular kainate injection. We conclude that the potential for dentate neurogenesis is maintained despite diminishing baseline levels with increasing age and that injury signals override the age related suppression of neurogenesis.

Aging↗

PubMed1998

Kainic acid increases the proliferation of granule cell progenitors in the dentate gyrus of the adult rat.

Granule cell progenitors in the dentate gyrus of the hippocampal formation have the unusual capacity to be able to divide in the brains of adult rats and primates. The basal proliferation rate of granule cell progenitors in the adult rat is low compared with development, however, it is possible that this rate may become significantly altered under pathological conditions such as epilepsy. We have investigated whether the proliferation of granule cell progenitors is increased in adult rats in a model of temporal lobe epilepsy, by using systemic bromodeoxyuridine injections to label dividing cells. We report here for the first time that granule cell neurogenesis is increased bilaterally 1 week after a single unilateral intracerebroventricular injection of kainic acid. Bromodeoxyuridine labeled neurons increased at least 6-fold on the side ipsilateral to the kainic acid injection compared to controls, but significantly, were also increased, by at least 3-fold on the side contralateral to the injection. The dividing cells in the subgranular zone were identified as neurons since they expressed Class III beta tubulin but not glial fibrillary acidic protein.

Animals↗

PubMed1998

Chemopreventive agents: selenium.

The element selenium (Se) was recognized only 40 years ago as being essential in the nutrition of animals and humans. It is recognized as being an essential component of a number of enzymes, in which it is present as the amino acid selenocysteine. Se compounds have also been found to inhibit tumorigenesis in a variety of animal models, and recent studies indicate that supplemental Se in human diets may reduce cancer risk. The antitumorigenic activities have been associated with Se intakes that correct nutritionally deficient status in animals, as well as higher intakes that are substantially greater than those associated with maximal expression of the selenocysteine-containing enzymes. Therefore, it is proposed that while some cancer protection, particularly that involving antioxidant protection, involves selenoenzymes, specific Se metabolites, which are produced in significant amounts at relatively high Se intakes, also discharge antitumorigenic functions. According to this two-stage model of the roles of Se in cancer prevention, individuals with nutritionally adequate Se intakes may benefit from Se supplementation. Evidence for chemoprevention by Se and for the apparent mechanisms underlying these effects is reviewed to the end of facilitating the development of the potential of Se compounds as cancer chemopreventive agents.

Anticarcinogenic Agents↗

PubMed1998

Report of a national neurosurgical emergency teleconsulting system.

OBJECTIVE: The goal was to develop a low-cost, national, neurosurgical emergency teleconsulting system that is independent of vendor computed tomographic (CT) or magnetic resonance imaging (MRI) scanner type. METHODS: Charge-coupled device scanners are used to digitize hard copies of CT and MRI scans. An enhanced optical density range is achieved by using an algorithm to fuse data from multiple exposures at different integration periods. The system is based on personal computers using Microsoft Windows 3.11. Data are transmitted on a wide-area network at 128 kilobits/s, over Integrated Systems Digital Network lines. The network connects both neurosurgical departments in Ireland to all major hospitals with CT/MRI scanners. RESULTS: The scanner optical density is 0.05 to 3.0, with 2.24 to 2.5 line pairs/mm. Five-megabyte images are transmitted uncompressed in 6 minutes. To date, more than 750 CT and MRI scans have been transmitted. The system is completely automated, and operator acceptance has been very high. Images are automatically stored and displayed at the receiving workstation, where the images can be viewed and manipulated on-screen. This system has significantly enhanced acute neurosurgical patient care. CONCLUSION: The system is cost effective and simple to use, has gained widespread physician acceptance, and delivers an image quality superior to that of many commercially available systems.

Angiography↗

PubMed1997

Report of a national neurosurgical teleradiology system.

An emergency neurosurgical teleradiology system was initially installed in two referring hospitals in ireland to transmit images to the neurosurgical department in Cork. It was subsequently expanded to six major referring hospitals transmitting to both neurosurgical departments in ireland serving the entire population of 3.5 million people, effectively becoming a national teleradiology system. The system was based on PCs interconnected by leased data circuits and ISDN. The network was operational 24 hours a day. Over 750 emergency computerized tomography scans were transmitted and transmission failures occurred in only 6% of cases. We conclude that current PC technology can be used to form a peer-to-peer wide-area network upon which a robust emergency teleradiology system can be based.

Emergencies↗

PubMed1997

Motor nerve transplantation.

The motor nerve transplantation (MNT) technique is used to transfer an intact nerve into a denervated muscle by harvesting a neurovascular pedicle of muscle containing motor endplates from the motor endplate zone of a donor muscle and implanting it into a denervated muscle. Thirty-six adult New Zealand White rabbits underwent reinnervation of the left long peroneal (LP) muscle (fast twitch) with a motor nerve graft from the soleus muscle (slow twitch). The right LP muscle served as a control. Reinnervation was assessed using microstimulatory single-fiber electromyography (SFEMG), alterations in muscle fiber typing and grouping, and isometric response curves. Neurofilament antibody was used for axon staining. The neurofilament studies provided direct evidence of nerve growth from the motor nerve graft into the adjacent denervated muscle. Median motor endplate jitter was 13 microsec preoperatively, and 26 microsec at 2 months, 29.5 microsec at 4 months, and 14 microsec at 6 months postoperatively (p < 0.001). Isometric tetanic tension studies showed a progressive functional recovery in the reinnervated muscle over 6 months. There was no histological evidence of aberrant reinnervation from any source outside the nerve pedicle. Isometric twitch responses and adenosine triphosphatase studies confirmed the conversion of the reinnervated LP muscle to a slow-type muscle. Acetylcholinesterase studies confirmed the presence of functioning motor endplates beneath the insertion of the motor nerve graft. It is concluded that the MNT technique achieves motor reinnervation by growth of new nerve fibers across the pedicle graft into the recipient muscle.

Acetylcholinesterase↗

PubMed1996

A clinical study of parenchymal and subdural miniature strain-gauge transducers for monitoring intracranial pressure.

OBJECTIVE: Previous studies have shown that a new strain-gauge MicroSensor (Codman/Johnson & Johnson Professional, Inc., Randolph, MA) for measuring intracranial pressure (ICP) performs well in the intraventricular space. We hoped to evaluate the MicroSensor in the subdural space and the brain parenchyma, because ICP is often measured in these compartments when the ventricles are difficult to cannulate. METHODS: Fifteen patients had simultaneous recordings of ICP from an externally transduced fluid-filled subdural catheter, a MicroSensor placed within the subdural catheter, and a nearby MicroSensor placed intraparenchymally in the right frontal lobe. RESULTS: The total number of valid simultaneous recordings of ICP was 95,946. A highly significant correlation was found between the tissue MicroSensor ICP (TMICP) and the subdural MicroSensor ICP (SMICP) (n = 95,946; r = 0.89; P < 0.00005), the TMICP and the fluid-transduced subdural catheter ICP (r = 0.86, P < 0.00005), and the fluid-transduced subdural catheter ICP and SMICP (r = 0.88, P < 0.00005). The mean simultaneous difference between the TMICP and the SMICP was 0.1 +/- 3.8 mm Hg with no obvious bias. The fluid-transduced subdural catheter ICP was 2.8 +/- 3.9 mm Hg lower than the TMICP and 2.7 +/- 3.9 mm Hg lower than the SMICP (P < 0.0005). The mean zero drifts of the tissue and subdural MicroSensors were 0.312 and 0.475 mm Hg/d, respectively. The tissue MicroSensor recordings showed the best quality wave form with the least damping. CONCLUSION: The strain-gauge MicroSensor is highly accurate and stable in the tissue and subdural spaces.

Brain↗

PubMed1990

Extradural haematoma in the Irish Republic: an analysis of 82 cases with emphasis on 'delay'.

Eighty-two cases of extradural haematoma were analysed to elucidate the factors contributing to delay in treatment and poor outcome. The majority of cases occurred in the first three decades of life with falls being the commonest aetiological factor. Five distinct modes of presentation are described. Excessive delay occurred in recognizing the condition and in subsequent transfer of patients. This resulted in many patients being operated on while in coma. Associated intracranial and extracranial injury occurred in a significant number of cases. Recommendations for the management of these patients are outlined.

Adolescent↗