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Biomedical subjects

D Comfort

Publications and source records attributed to D Comfort.

7 recordsLinked to original sources
PubMed2001

NMR studies of the sporulation protein SpoIIAA: implications for the regulation of the transcription factor sigmaF in Bacillus subtilis.

SpoIIAA participates in a four-component mechanism for phosphorylation-dependent transcription control at the outset of sporulation. We report the refinement of the solution structure of SpoIIAA by using the automated iterative NOE assignment method ARIA. To complement the structural data, the protein dynamics were determined by measuring the T1, T2 and NOE of the backbone 15N-nuclei. The refined structure permits a discussion of the structural features that are important for the function of SpoIIAA in the regulation of the sporulation sigma factor sigmaF, and for homologous regulatory pathways present in B. subtilis and in other bacilli.

Bacillus subtilis↗
PubMed2001

Human sensorimotor coordination during spaceflight: an analysis of pointing and tracking responses during the "Neurolab" Space Shuttle mission.

BACKGROUND: It has been shown that pointing movements are slowed during microgravity, however there is a paucity of corresponding data for other movement types. METHODS: In our study, subjects pointed at visual targets without seeing their hand, and tracked targets moving around a circular path with and without hand vision, with and without a secondary reaction-time task. RESULTS: Pointing responses were slowed distinctly in microgravity, but the speed of tracking movements was not affected. The secondary task had comparable effects on tracking performance in space and on Earth. CONCLUSIONS: Response slowing in space is not due to an increased dependence on visual feedback, since it persists without hand vision. Differential effects of microgravity on pointing and tracking could be due to subjects' strategic decisions.

Adult↗
PubMed2000

Is dual-task performance necessarily impaired in space?

Recent single-subject experiments in space have reported impaired dual-task performance that could result from either a direct effect of microgravity on the central nervous system or from the multistressor environment. We sought to distinguish between these hypotheses using 6 astronauts in the 16-day NASA Neurolab mission, testing them at intervals with a dual task consisting of primary pursuit tracking without vision of the hand and secondary reaction time (RT). The participants were highly trained, instructed to maintain a fixed attention strategy, and restrained in the apparatus. The results showed that absolute and variable tracking error, as well as correct RT and the standard deviation of RT, were unimpaired. However, RT errors became more variable, an effect attributed to a decrease in strategic control. We conclude that the impairments observed in previous dual-task space experiments can be attributed to stressors rather than to microgravity and that performance deficits are probably not a necessary concomitant of space flight if attention is paid to task design and astronaut training.

Adult↗
PubMed2000

A review of cognitive and perceptual-motor performance in space.

Although a consensus developed early in the space program that complex operations could be performed successfully in space, it appears that humans are slower there than on Earth. Recent experiments aimed at determining the cause of this slowing suggest that central cognitive operations are unaffected but that perceptual-motor performance is degraded under certain circumstances. Two hypotheses have been proposed to account for this degradation-the direct effects of microgravity on the central nervous system and the non-specific effects of multiple stressors. Present evidence can be interpreted as supporting either hypothesis and further experiments are required to settle the question. This issue has practical implications since the countermeasures needed to ameliorate or prevent performance deficits will differ according to which hypothesis is correct. Understanding and ameliorating performance deficits will help ensure safe operations aboard the International Space Station and during a mission to Mars.

Cognition Disorders↗
PubMed1998

Solution structure of SpoIIAA, a phosphorylatable component of the system that regulates transcription factor sigmaF of Bacillus subtilis.

The establishment of differential gene expression in sporulating Bacillus subtilis involves four protein components, one of which, SpoIIAA, undergoes phosphorylation and dephosphorylation. We have used NMR spectroscopy to determine the solution structure of the nonphosphorylated form of SpoIIAA. The structure shows a fold consisting of a four-stranded beta-sheet and four alpha-helices. Knowledge of the structure helps to account for the phenotype of several strains of B. subtilis that carry known spoIIAA mutations and should facilitate investigations of the conformational consequences of phosphorylation.

Amino Acid Sequence↗