Biomedical subjects

David Chapman

Publications and source records attributed to David Chapman.

4 recordsLinked to original sources

PubMed2006

The role of CA3 hippocampal NMDA receptors in paired associate learning.

The hippocampus is necessary for declarative memory in humans and episodic memory in rodents. Considerable current research is focused on the role of plasticity within specific subfields of the hippocampus. Here, using a viral vector to temporally control a focal deletion of the NR1 gene, we show that learning novel paired associations between specific cues and their context is dependent on CA3 NMDA receptors. Deletion of CA3 NR1 genes in <30% of the dorsal hippocampus was sufficient to disrupt new learning, whereas the same treatment does not prevent expression of previously acquired paired associates and does not affect the ability to discriminate contexts or paired associate learning when either the cues or the context is familiar. The findings suggest that CA3 NMDA receptors specifically support the encoding of new experiences to involve incidental and contingent associations.

Animals↗

PubMed2006

An environmental decision framework applied to marine engine control technologies.

This paper develops a decision framework for considering emission control technologies on marine engines, informed by standard decision theory, with an open structure that may be adapted by operators with specific vessel and technology attributes different from those provided here. Attributes relate objectives important to choosing control technologies with specific alternatives that may meet several of the objectives differently. The transparent framework enables multiple stakeholders to understand how different subjective judgments and varying attribute properties may result in different technology choices. Standard scoring techniques ensure that attributes are not biased by subjective scoring and that weights are the primary quantitative input where subjective preferences are exercised. An expected value decision structure is adopted that considers probabilities (likelihood) that a given alternative can meet its claims; alternative decision criteria are discussed. Capital and annual costs are combined using a net present value approach. An iterative approach is advocated that allows for screening and disqualifying alternatives that do not meet minimum conditions for acceptance, such as engine warranty or U.S. Coast Guard requirements. This decision framework assists vessel operators in considering explicitly important attributes and in representing choices clearly to other stakeholders concerned about reducing air pollution from vessels. This general decision structure may also be applied similarly to other environmental controls in marine applications.

Air Pollutants↗

PubMed2005

Adenosine mediation of presynaptic feedback inhibition of glutamate release.

Conditions of increased metabolic demand relative to metabolite availability are associated with increased extracellular adenosine in CNS tissue. Synaptic activation of postsynaptic NMDA receptors on neurons of the cholinergic brainstem arousal center can increase sufficient extracellular adenosine to act on presynaptic A1 adenosine receptors (A1ADRs) of glutamate terminals, reducing release from the readily releasable pool. The time course of the adenosine response to an increase in glutamate release is slow (tau > 10 min), consistent with the role of adenosine as a fatigue factor that inhibits the activity of cholinergic arousal centers to reduce arousal.

Adenosine↗

PubMed2002

Context effects on the spontaneous leg movements of infants with spina bifida.

PURPOSE: Our understanding of the developmental profiles of infants with spina bifida (SB) is limited. Therefore, the purpose of this study was to examine over four months the impact of the movement context on the spontaneously produced leg movements of infants with spina bifida (SB). METHOD: Six infants with lumbar or sacral SB and six infants who were developing typically were videotaped while they were supine and seated in two different infant seats. RESULTS: Infants with SB moved their legs less often than did the infants who are developing typically. Both groups produced the slowest, smallest leg movements when they were in a conventional infant seat, moved their legs with the greatest velocities when they were supine and in a specially designed infant seat, and with the greatest amplitudes when they were supine. CONCLUSIONS: These results suggest that the leg movements of infants with SB emerge from the cooperative interactions of their intrinsic characteristics and their movement context.

Journal Article↗