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D Rainey

Publications and source records attributed to D Rainey.

9 recordsLinked to original sources
PubMed2000

The transport of group 2 capsular polysaccharides across the periplasmic space in Escherichia coli. Roles for the KpsE and KpsD proteins.

The cell surface expression of group 2 capsular polysaccharides involves the translocation of the polysaccharide from its site of synthesis on the inner face of the cytoplasmic membrane onto the cell surface. The transport process is independent of the repeat structure of the polysaccharide, and translocation across the periplasm requires the cytoplasmic membrane-anchored protein KpsE and the periplasmic protein KpsD. In this paper we establish the topology of the KpsE protein and demonstrate that the C terminus interacts with the periplasmic face of the cytoplasmic membrane. By chemical cross-linking we show that KpsE is likely to exist as a dimer and that dimerization is independent of the other Kps proteins or the synthesis of capsular polysaccharide. No interaction between KpsD and KpsE could be demonstrated by chemical cross-linking, although in the presence of both KpsE and Lpp, KpsD could be cross-linked to a 7-kDa protein of unknown identity. In addition, we demonstrate that KpsD is present not only within the periplasm but is also in both the cytoplasmic and outer membrane fractions and that the correct membrane association of KpsD was dependent on KpsE, Lpp, and the secreted polysaccharide molecule. Both KpsD and KpsE showed increased proteinase K sensitivity in the different mutant backgrounds, reflecting conformational changes in the KpsD and KpsE proteins as a result of the disruption of the transport process. Collectively the data suggest that the trans-periplasmic export involves KpsD acting as the link between the cytoplasmic membrane transporter and the outer membrane with KpsE acting to facilitate this transport process.

Bacterial Proteins↗
PubMed1997

Masking by modulated and unmodulated noise: effects of bandwidth, modulation rate, signal frequency, and masker level.

The threshold for a sinusoidal signal masked by a band of noise is often times lower when the masking noise is modulated than when it is unmodulated. The difference in masked thresholds is referred to as the modulated-unmodulated difference, or MUD. These present experiments examined the effects of masker bandwidth, masker rate, and masker level on the MUD at several different signal frequencies. The MUD generally increased with increasing masker bandwidth; for masker bandwidths wider than a critical band (or an equivalent rectangular bandwidth-ERB), the results may be influenced by across-channel processes underlying comodulation masking release. The MUD for an ERB masker (MUDERB) was influenced less by masker rate than was the MUD for a broadband (BB) masker (MUDBB). The MUDERB and especially the MUDBB increased significantly with increasing masker level when the modulated masker was modulated at a depth (m) of 1.0, but not when it was modulated at a depth of 0.75. These results have significant implications for extending the MUD paradigm to hearing-impaired subjects. Finally, the MUDERB and the MUDBB increased with increasing signal frequency. This effect for the ERB masker is largely (if not completely) due to the wider absolute bandwidths at higher frequencies. The effect with the BB masker may be influenced by differences in the magnitude of suppression across frequency.

Adult↗
PubMed1997

Speech intelligibility as a function of the number of channels of stimulation for signal processors using sine-wave and noise-band outputs.

Vowels, consonants, and sentences were processed through software emulations of cochlear-implant signal processors with 2-9 output channels. The signals were then presented, as either the sum of sine waves at the center of the channels or as the sum of noise bands the width of the channels, to normal-hearing listeners for identification. The results indicate, as previous investigations have suggested, that high levels of speech understanding can be obtained using signal processors with a small number of channels. The number of channels needed for high levels of performance varied with the nature of the test material. For the most difficult material--vowels produced by men, women, and girls--no statistically significant differences in performance were observed when the number of channels was increased beyond 8. For the least difficult material--sentences--no statistically significant differences in performance were observed when the number of channels was increased beyond 5. The nature of the output signal, noise bands or sine waves, made only a small difference in performance. The mechanism mediating the high levels of speech recognition achieved with only few channels of stimulation may be the same one that mediates the recognition of signals produced by speakers with a high fundamental frequency, i.e., the levels of adjacent channels are used to determine the frequency of the input signal. The results of an experiment in which frequency information was altered but temporal information was not altered indicates that vowel recognition is based on information in the frequency domain even when the number of channels of stimulation is small.

Adult↗
PubMed1997

Simulating the effect of cochlear-implant electrode insertion depth on speech understanding.

Normally hearing listeners were presented with vowels, consonants, and sentences for identification through an acoustic simulation of a five-channel cochlear implant with electrodes separated by 4 mm (as in the Ineraid implant). The aim of the experiment was to simulate the effect of depth of electrode insertion on identification accuracy. Insertion depth was simulated by outputting sine waves from each channel of the processor at a frequency determined by the cochlear place of electrodes inserted 22-25 mm into the cochlea. The results indicate that simulated insertion depth had a significant effect on performance. Performance at 22- and 23-mm simulated insertion depths was always poorer than normal, and performance at 25 mm simulated insertion depth was, most generally, the same as normal. It is inferred from these results that, if insertion depth could be unconfounded from other coexisting factors in implant patients, then insertion depth would be found to affect speech identification performance significantly.

Cochlear Implantation↗
PubMed1995

Magnitude of stress reported by basketball referees.

723 basketball referees responded to a survey that assessed stress related to officiating. Mean reported ratings were between "very little" and "moderate amount"; only 4% reported high stress. Results are consistent with other accounts, suggesting that most sport officials experience low occupational stress.

Age Factors↗
PubMed1994

Mental imagery, relaxation, and accuracy of basketball foul shooting.

18 female college basketball players were pretested on foul shooting, alternately assigned to relaxation or mental imagery training, and posttested after 4 training sessions over 3 weeks. Analysis of covariance indicated that the predicted improvement of the imagery group did not occur. The relaxation group was marginally superior at posttest.

Adolescent↗
PubMed1989

Recognizing faces in bright and dim light.

32 undergraduates viewed 10 photographs of faces for 3 sec. each in a brightly or dimly illuminated room. Then they viewed 40 photographs in the same light, including the original 10, and identified each photograph as new or old. Subjects recognized significantly more photographs in the bright illumination condition, possibly because that condition allowed for more processing of information.

Adult↗
PubMedDate not supplied

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