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Biomedical subjects

R Bevan

Publications and source records attributed to R Bevan.

9 recordsLinked to original sources
PubMed1991

Viewer-centred and object-centred coding of heads in the macaque temporal cortex.

An investigation was made into the sensitivity of cells in the macaque superior temporal sulcus (STS) to the sight of different perspective views of the head. This allowed assessment of (a) whether coding was 'viewer-centred' (view specific) or 'object-centred' (view invariant) and (b) whether viewer-centred cells were preferentially tuned to 'characteristic' views of the head. The majority of cells (110) were found to be viewer-centred and exhibited unimodal tuning to one view. 5 cells displayed object-centred coding responding equally to all views of the head. A further 5 cells showed 'mixed' properties, responding to all views of the head but also discriminating between views. 6 out of 56 viewer and object-centred cells exhibited selectivity for face identity or species. Tuning to view varied in sharpness. For most (54/73) cells the angle of perspective rotation reducing response to half maximal was 45-70 degrees but for 19/73 it was greater than 90 degrees. More cells were optimally tuned to characteristic views of the head (the full face or profile) than to other views. Some cells were, however, found tuned to intermediate views throughout the full 360 degree range. This coding of many distinct head views may have a role in the analysis of social signals based on the interpretation of the direction of other individuals' attention.

Animals↗
PubMed1989

Frameworks of analysis for the neural representation of animate objects and actions.

A variety of cell types exist in the temporal cortex providing high-level visual descriptions of bodies and their movements. We have investigated the sensitivity of such cells to different viewing conditions to determine the frame(s) of reference utilized in processing. The responses of the majority of cells in the upper bank of the superior temporal sulcus (areas TPO and PGa) found to be sensitive to static and dynamic information about the body were selective for one perspective view (e.g. right profile, reaching right or walking left). These cells can be considered to provide viewer-centred descriptions because they depend on the observer's vantage point. Viewer-centred descriptions could be used in guiding behaviour. They could also be used as an intermediate step for establishing view-independent responses of other cell types which responded to many or all perspective views selectively of the same object (e.g. head) or movement. These cells have the properties of object-centred descriptions, where the object viewed provides the frame of reference for describing the disposition of object parts and movements (e.g. head on top of shoulders, reaching across the body, walking forward 'following the nose'). For some cells in the lower bank of the superior temporal sulcus (area TEa) the responses to body movements were related to the object or goal of the movements (e.g. reaching for or walking towards a specific place). This goal-centred sensitivity to interaction allowed the cells to be selectively activated in situations where human subjects would attribute causal and intentional relationships.

Animals↗
PubMed1976

The psychiatric resident as an ex-officio community board member.

The authors describe a program in which third-year psychiatric residents participate as ex-officio members on the boards of community service agencies. Experience as board members gives residents a broad understanding of issues related to the delivery of community mental health services and encourages them to continue community involvment after their training is completed.

Attitude of Health Personnel↗
PubMedDate not supplied

Clinical pharmacokinetics of ganciclovir in patients with normal and impaired renal function.

The pharmacokinetics of ganciclovir was evaluated in 21 patients with life- or sight-threatening cytomegalovirus infections. Thirteen patients had normal renal function and eight patients had various degrees of renal insufficiency. Most patients received 5 mg of ganciclovir/kg as a 1-hour intravenous infusion twice daily for periods of up to 2 weeks. Quantification of ganciclovir was assessed by high-performance liquid chromatography and radioimmunoassay. In patients with normal renal function, a biexponential decay of ganciclovir from plasma was observed, with an initial distribution half-life (t1/2) of 0.76 +/- 0.67 hour and a terminal elimination t1/2 of 3.60 +/- 1.40 hours. A large fraction of the administered dose was excreted in urine, and total clearance of ganciclovir correlated well with creatinine clearance. In patients with renal insufficiency who were receiving 5 mg of ganciclovir/kg, the terminal elimination t1/2 of ganciclovir was markedly increased (11.50 +/- 3.90 hours), as compared with values obtained in patients with normal renal function. Hemodialysis efficiently reduced levels of ganciclovir in plasma by approximately 53.0% +/- 11.5%, a finding that indicates this drug should be administered after dialysis.

Acyclovir↗
PubMedDate not supplied

Glucuronidation of 3'-azido-3'-deoxythymidine by rat and human liver microsomes.

The glucuronidation of 3'-azido-3'-deoxythymidine (AZT) by rat and human liver microsomes has been studied in vitro. The AZT-glucuronide was preliminarily identified through specific hydrolysis by beta-glucuronidase and rigorous product identification was performed by high-field proton nuclear magnetic resonance and fast-atom-bombardment mass spectrometry. A beta-linked 5'-O-glucuronide was the exclusive product formed in liver microsomes. Rat and human liver microsomal uridine 5'-diphosphoglucuronyltransferase activities toward AZT were investigated. These studies revealed that AZT had a lower Km and a 5-6-fold higher relative catalytic efficiency for uridine 5'-diphosphoglucuronyltransferase in human as compared to rat liver microsomes which may play a role in the quantitative differences observed in the degree of AZT glucuronidation between rat and human.

Animals↗