Biomedical subjects

T Fryer

Publications and source records attributed to T Fryer.

3 recordsLinked to original sources

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↗