Biomedical subjects

T Fryer

Publications and source records attributed to T Fryer.

6 recordsLinked to original sources

PubMed2005

Monitoring emergence from coma following severe brain injury in an octogenarian using behavioural indicators, electrophysiological measures and metabolic studies: a demonstration of the potential for good recovery in older adults.

This case study describes a multi-disciplinary investigation of the emergence from coma of an 80-year old female (KE) following severe traumatic brain injury. The relationship between cognitive/behavioural ability and the integrity of cerebral function was assessed using neuropsychological measures, positron emission tomography, electroencephalography, somatosensory evoked potentials and trans-cranial magnetic stimulation. These investigations were performed as KE was beginning to emerge from coma (4 weeks) and, again, approximately 1 year following brain injury, when she was judged to have achieved her maximum level of recovery. Neuropsychological measures revealed improvement during the first year post-injury in KE's speed of information processing, memory and executive abilities. Electrophysiological and metabolic studies indicated a restoration of functional integrity that was consistent with the gradual recovery in higher brain function documented using behavioural procedures. This case study demonstrates the rehabilitation potential of pre-morbidly healthy older adults following severe traumatic brain injury.

Accidents, Traffic↗

PubMed2004

Cerebral neutrophil recruitment, histology, and outcome in acute ischemic stroke: an imaging-based study.

BACKGROUND AND PURPOSE: Evidence now exists for a pathogenic role for neutrophils in acute cerebral ischemia. We have studied the patterns and temporal profile of cerebral neutrophil recruitment to areas of acute ischemic stroke (IS) and have attempted to correlate this with neurological status and outcome. METHODS: Patients with cortical middle cerebral artery (MCA) IS were recruited within 24 hours of clinical onset. Neutrophil recruitment was studied using indium-111 (111In) troponolate-labeled neutrophils, planar imaging, and single-photon emission computed tomography (SPECT). Volume of brain infarction was calculated from concurrent computed tomography (CT). Hematoxylin and eosin sections were obtained postmortem (n=2). Outcome was measured using Barthel, Rankin, and National Institute of Health Stroke (NIHSS) scales. RESULTS: Fifteen patients were studied. Significant 111In-neutrophil recruitment to ipsilateral hemisphere, as measured by asymmetry index (AI), was demonstrated within 24 hours of onset in 9 patients; this response was heterogenous between patients and on repeated measurement attenuated over time. Histologically, recruitment was confirmed within intravascular, intramural, and intraparenchymal compartments. Interindividual heterogeneity in neutrophil response did not correlate with infarct volume or outcome. In an exploratory analysis, neutrophil accumulation appeared to correlate significantly with infarct expansion (Spearman rho=0.66; P=0.03, n=12). CONCLUSIONS: Neutrophils recruit to areas of ischemic brain within 24 hours of symptom onset. This recruitment attenuates over time and is confirmed histologically. While neutrophil accumulation may be associated with either the magnitude or the rate of infarct growth, these results require confirmation in future studies.

Brain Ischemia↗

PubMed2003

Evaluation of an MRI-based protocol for cell implantation in four patients with Huntington's disease.

The purpose of this study was to evaluate our surgical protocol for the preparation and delivery of suspensions of fetal tissue into the diseased human brain. We implanted suspensions of human fetal striatal anlage into the right caudate and putamen of four patients with Huntington's disease. Postoperative 3 tesla MR imaging confirmed accurate graft placement. Variability in graft survival was noted and the MR signal changes over 6 months revealed persistent hyperintense signal on T2-weighted images. Our results are consistent with those described by other groups and indicate that our surgical protocol is safe, accurate, and reproducible.

Brain↗

PubMed2000

Potential role of NovoSeven in the prevention of rebleeding following aneurysmal subarachnoid haemorrhage.

Rebleeding following aneurysmal subarachnoid haemorrhage is a major factor contributing to unfavourable outcome. Antifibrinolytic agents reduce the rate of rebleeding but increase the risk of cerebral ischaemia and infarction and hence provide no overall benefit. To address the theoretical concern that recombinant activated factor VII (NovoSeven, Novo Nordisk A/S, Bagsvaerd, Denmark) might increase the risk of cerebral ischaemia while stabilizing the clot at the site of aneurysmal rupture, an open-label, dose-escalation safety study has been developed in collaboration with the UK Spontaneous Intracranial Haemorrhage Group. The trial design includes the recruitment of 15 patients (aged 18 years or over) in good grade with subarachnoid haemorrhage verified by computerized tomography scan or lumbar puncture. Safety evaluation includes clinical observation, monitoring of laboratory variables, positron emission tomography (PET) scanning (rCBF, rOEF, rCMRO2) and transcranial Doppler ultrasound. To date, ten patients have been recruited [NovoSeven 80 microg/kg single bolus (n = 2), NovoSeven 80 microg/kg single bolus followed by continuous infusion at 3.5 microg/kg per h (n = 2) or 7 microg/kg per h (n = 1), or control (n = 5)]. Clinical observation, transcranial Doppler ultrasound and PET studies revealed no evidence of cerebral ischaemia in the first nine patients treated with NovoSeven. The last patient developed middle cerebral artery branch thrombosis contralateral to the aneurysm. The study is currently suspended pending further investigation.

Adult↗

PubMed1999

Sperm competition. II-post-copulatory guarding

A two round sperm competition model is analysed to determine which male strategy is advantageous for fertilization of a given set of eggs; guarding a particular female or searching for another copulation. A guarding male is one who would guard if he mates in the first round (which may not occur) whilst a non-guarding male decides on how much sperm to allocate if given the opportunity to inseminate a female in round one. Guarding behaviour is defined in terms of a probability of preventing a further insemination if challenged by a rival male. Sperm success with a single female obeys the "raffle principle". An evolutionarily stable strategy (ESS) approach is used to ascertain the best non-guarding ejaculation strategy. We show that for each fixed proportion of guarders in the population the strategies are ordered and that only a single guarding strategy need be considered. The model predicts that there will be evolution to either the guarding strategy or a single non-guarding strategy or a polymorphic combination of guarding and some (or all) of the non-guarding strategies. The conditions for coexistence to occur were shown to be rare in comparison to those necessary for a monomorphism. Copyright 1999 Academic Press.

Journal Article↗

PubMed1999

Sperm competition I: basic model, ESS and dynamics.

We examine models of sperm competition to determine which strategies are evolutionarily stable according to game theory. Games are considered in which the males of a species must divide a fixed amount of sperm between a fixed number of rounds in competition over fertilization of a given set of eggs. Sperm success with a single female is allocated using the raffle principle". A two round model is formulated and we show that the evolutionarily stable strategy (ESS) is a pure strategy in which a male should use at least half his sperm in the first round if given the opportunity to mate. The ESS is unique and globally stable, in contrast to most classical ESSs which are only locally stable. The model is extended to include the effects of sperm replenishment and egg oviposition between rounds. Both serve to increase the ESS amount of sperm inseminated in round one.

Animals↗