Biomedical subjects
A F Carpenter
Publications and source records attributed to A F Carpenter.
The departure of Jerome P. Kassirer.
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Motor cortical encoding of serial order in a context-recall task.
The neural encoding of serial order was studied in the motor cortex of monkeys performing a context-recall memory scanning task. Up to five visual stimuli were presented successively on a circle (list presentation phase), and then one of them (test stimulus) changed color; the monkeys had to make a single motor response toward the stimulus that immediately followed the test stimulus in the list. Correct performance in this task depends on memorization of the serial order of the stimuli during their presentation. It was found that changes in neural activity during the list presentation phase reflected the serial order of the stimuli; the effect on cell activity of the serial order of stimuli during their presentation was at least as strong as the effect of motor direction on cell activity during the execution of the motor response. This establishes the serial order of stimuli in a motor task as an important determinant of motor cortical activity during stimulus presentation and in the absence of changes in peripheral motor events, in contrast to the commonly held view of the motor cortex as just an "upper motor neuron."
Clinical problem-solving: if at first you don't succeed.
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Morphometric analysis of microglia in Alzheimer's disease.
HLA-DR-immunoreactive microglia were quantitated in the middle temporal gyrus of five late-stage patients with Alzheimer's disease (AD) and five age-matched control subjects using LN3 immunocytochemistry and computerized morphometric image analysis. The grand mean numerical density of HLA-DR-immunoreactive microglia in AD (403.86/mm2) was significantly larger than in the five control subjects (193.33/mm2) (p < 0.0001). The grand mean cross-sectional area of HLA-DR-immunoreactive microglia in AD subjects (222.90 microns2) was significantly larger than in control subjects (121.59 microns2) (p < 0.0001). The percentage of total microglia that were large activated microglia was much greater in AD (47.9%) than in control subjects (15.2%). The grand mean percent of the cortical area occupied by HLA-DR-immunoreactive microglia in AD (9.02%) was significantly greater than in controls (2.35%) (p < 0.0001). Microglia were present in greater numbers in the outer three cortical laminae in both AD and controls. The striking increase in activated microglia in the neocortex and their role in the inflammatory response and possible secretion of neurotoxins could be important in neuron degeneration in AD.
Midtrimester genetic amniocentesis. Use of ultrasound direction vs. blind needle insertion.
A prospective comparison of ultrasound-directed second-trimester genetic amniocentesis to blind amniocentesis showed a significant reduction in the incidence of both bloody taps and failed amniocentesis. The incidence of other parameters, such as fetal outcome, failed culture of amniotic fluid fibroblasts and spontaneous abortion, was similar. These data support the use of amniocentesis under ultrasound control as a routine component of prenatal genetic diagnosis.