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Biomedical subjects

C Lathan

Publications and source records attributed to C Lathan.

8 recordsLinked to original sources
PubMed2000

Changes in the vertical size of a three-dimensional object drawn in weightlessness by astronauts.

The purpose of this study was to investigate the effects of weightlessness on mental representation of spatial cues. Two astronauts drew two groups of three-dimensional cubes with their eyes closed, one on Earth (preflight) and the other under weightless conditions during a 7-day orbital flight (inflight). Differences in the average height of the two groups of cubes were observed. The ratio of average length of the horizontal vs. the vertical lines of the inflight cubes increased significantly compared to that of the preflight cubes. The disappearance of the gravitational reference system, which determines on Earth the vertical direction, seems to influence the internal representation of the vertical dimension, (i. e. the height) of a three-dimensional object.

Analysis of Variance↗
PubMed2000

Announcements

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Journal Article↗
PubMed2000

Announcements

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Journal Article↗
PubMed1998

Postural reactions induced by vertical motion of visual scenes and the effects of weightlessness.

Postural reactions induced by vertical optokinetic stimulation were recorded for 5 subjects in a ground-based study, and for one astronaut before, during, and after a 25-day spaceflight. On the ground, the amplitude of visually-induced postural reactions generally increased with stimulus velocity and saturated around 60 degrees/s, with an angle of body tilt which never exceeded 2-3 degrees. For velocities higher than 20 degrees/s, backward body tilt during upgoing optokinetic stimulation was larger than forward body tilt during downgoing stimulation. In weightlessness, the angle of body tilt was reduced compared to ground values, but after the flight the postural reactions were larger than before the flight. If the limited angle of body tilt on Earth is due to an inhibition from the graviceptive inputs which do not confirm the visual inputs, the larger angle of tilt might reflect that this inhibition was less effective after spaceflight. This ineffectiveness might reflect a confusion between body tilt and translation as the result of adaptation to weightlessness.

Adult↗
PubMed1998

Development and evaluation of a spine biopsy simulator.

A spine biopsy simulator is being developed to 1) train surgeons on the current method for CT-directed needle biopsy and 2) provide a testbed for developing new image-guided and robot-assist methodologies. A task analysis and function allocation assessment provide the needed information for the first stage of the simulator development and evaluation.

Biopsy, Needle↗
PubMed1995

Design, biochemical, biophysical and biological properties of cooperative antisense oligonucleotides.

Short oligonucleotides that can bind to adjacent sites on target mRNA sequences are designed and evaluated for their binding affinity and biological activity. Sequence-specific binding of short tandem oligonucleotides is compared with a full-length single oligonucleotide (21mer) that binds to the same target sequence. Two short oligonucleotides that bind without a base separation between their binding sites on the target bind cooperatively, while oligonucleotides that have a one or two base separation between the binding oligonucleotides do not. The binding affinity of the tandem oligonucleotides is improved by extending the ends of the two oligonucleotides with complementary sequences. These extended sequences form a duplex stem when both oligonucleotides bind to the target, resulting in a stable ternary complex. RNase H studies reveal that the cooperative oligonucleotides bind to the target RNA with sequence specificity. A short oligonucleotide (9mer) with one or two mismatches does not bind at the intended site, while longer oligonucleotides (21mers) with one or two mismatches still bind to the same site, as does a perfectly matched 21mer, and evoke RNase H activity. HIV-1 inhibition studies reveal an increase in activity of the cooperative oligonucleotide combinations as the length of the dimerization domain increases.

Antiviral Agents↗