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Biomedical subjects

H Dai

Publications and source records attributed to H Dai.

At least 127 records · Page 7Linked to original sources
PubMed1994

A new method to quantify behavioral attention to a stimulus object in a modified open-field.

A new method was developed to measure locomotion and attention to a stimulus object in a typical open-field environment using a video image-analyzer system. A computer-generated central zone (CZ) composing 1/9 of the open-field floor area was monitored independently from the rest of the area. Intermittently, a 4 x 4 x 2 cm object was placed in the CZ. In 10 min test sessions, the presence of the object repeatedly and consistently increased the animal's time spent in the CZ as compared with tests when the object was absent. The presence of the object, however, did not increase either the number of entries to the CZ or overall locomotor activity. The object reliably elicited an investigatory response when the animal enter the CZ but otherwise was behaviorally neutral. Thus, by incorporating a stimulus object in a conventional open-field test environment, the present methodology extends the open-field test beyond the measurement of overall spontaneous activity to include an assessment of behavioral processes linked to attention mechanisms.

Animals↗
PubMed1994

Detection of unexpected tones with short and long durations.

The detectability of short and long unexpected tones masked by a continuous wideband noise was assessed using a probe-signal method. This method leads the listener to expect a target frequency by presenting the signal most often at that frequency, and only occasionally at other unexpected probe frequencies. The probe-signal contour (percent correct as a function of probe frequency) was considerably broader with 5-ms than with 295-ms signals. However, auditory filter shapes measured using the notched-noise technique were very similar for those two signal durations, indicating that the results obtained in the probe-signal conditions do not simply reflect peripheral frequency selectivity. Further supporting this interpretation, probe tones having the same frequency but a different duration from the target were poorly detected. It is proposed that the subject listens through a time-frequency window whose location and shape in the time-frequency plane is determined by the duration and frequency of the target.

Acoustic Stimulation↗
PubMed1994

Detection of unexpected tones in gated and continuous maskers.

The effect of gating a wideband masker on the detectability of tones having unexpected frequencies was assessed using a probe-signal method. This method leads the listener to expect a target frequency by presenting the signal most often at that frequency, and measures sensitivity to other unexpected frequencies via occasionally presented probe tones. For 295-ms signals, the probe-signal contours (percent correct as a function of probe frequency) of two of four subjects were considerably broader for a 295-ms masker than for a continuous masker. For 5-ms signals, the probe-signal contours of four of five subjects were quite broad and similar for both gated and continuous maskers. When the probe-signal contours were expressed as the attenuation in decibels of the probes, the resulting "probe-signal filters" were frequently broader than auditory filters measured using notched noise in the same subjects. This suggests that subjects may monitor multiple auditory filters under some conditions in the probe-signal task. Signal threshold tended to be higher for conditions showing wider probe-signal filters, indicating a potential link between changes in signal threshold due to masker gating and the number of frequency channels that are monitored.

Acoustic Stimulation↗
PubMed1994

Signal-frequency uncertainty in spectral-shape discrimination: psychometric functions.

Psychometric functions were measured for spectral-shape discrimination (profile analysis) with the signal frequency either fixed, what we call the signal-known condition, or randomly varied, what we call the signal-unknown condition. The functions were obtained using an adaptive, up-down procedure. In the signal-unknown condition, independent tracks for each signal frequency were interleaved within the same block of trials. The mean slope of the psychometric function [k in log d' = k log delta L+C, where delta L = 20 log(1 + delta p/p)] was 1.13 for the signal-known conditions and 1.19 for the signal-unknown condition. The mean signal-to-standard ratio at threshold (Pc = 79.4%) obtained in the signal-unknown condition was 3 to 4 dB higher than that obtained in the signal-known conditions. The psychometric functions of the ideal observer were derived for both the signal-known and signal-unknown conditions. A comparison of the measured and derived psychometric functions suggests that the internal noise component that is statistically independent across frequency channels contributes minimally to the total (internal and external) noise sources that are involved in the decision process.

Auditory Perception↗
PubMed1994

[Treatment of macular hole retinal detachment with vitrectomy].

Pars plana vitrectomies were performed on 64 eyes with macular hole retinal detachment of which 20 with severe proliferative vitreoretinopathy (PVR C-D) and 18 with definite vitreoretinal traction on the maculae were found. Retinal reattachment occurred in 57 eyes in the follow-up (89.1%) of which the visual acuities improved in 43 (74.5%), unchanged in 13 and decreased in 1. The points for attention in the operation were discussed. The key factors influencing the success of the operation are severe PVR, the course of the retinal detachment.

Adult↗
PubMed1994

[A new species of Pseudomonas].

A strain No. 9191 isolated from fruit juice mineral drink is gram-negative short-rod. It differs from reported species of Pseudomonas in morphological, physiological and biochemical characteristics. Main characteristics of No. 9191 are single polar flagelled, oxidase and catalase positive, no acid from glucose but producing alkali, nitrate reduced to nitrite, inability to hydrolize gelatin and starch, arginine dihydrolase absent, no growth in presence of 0.85% NaCl. The G+C mol% of DNA is 65.15. It is named Pseudomonas halosensibilis Zou & Cai nov. sp. by the sensibility property for salt.

Beverages↗
PubMed1993

Discrimination of spectral shape as a function of stimulus duration.

Thresholds for discriminating the changes in the spectral shape of simultaneously presented components (profile analysis) are measured as a function of stimulus duration for various complex stimuli. For all stimuli, the threshold decreases with increasing duration until a transition time is reached, and thereafter the threshold remains constant. The amount of change in threshold and the value of transition time appear to be greater for complexes having narrower frequency spacing of the components. The results can be accounted for, at least qualitatively, by assuming that the bandwidth of the auditory filters decreases after the onset of the stimulus.

Acoustic Stimulation↗
PubMed1993

On the pitch of two-tone complexes.

The predictions of two models for the pitch of two-tone complexes were compared to pitch matching results obtained in a previous study [Feth, O'Malley, and Ramsey, J. Acoust. Soc. Am. 72, 1403-1412 (1982)] and the present study. In one model, the pitch value of a waveform was calculated from the envelope-weighted average of instantaneous frequency of the waveform (the EWAIF model). In the other model, the pitch value was calculated from the squared-envelope-weighted average of instantaneous frequency (the SEWAIF model). The SEWAIF model better predicts the data.

Acoustics↗
PubMed1993

A composite randomization procedure for measuring spectral shape discrimination.

In studies of auditory profile analysis [D. M. Green, Profile Analysis: Auditory Intensity Discrimination (Oxford U. P., New York, 1988)], the sounds are presented at random levels to discourage the listener from basing the discrimination on a difference in absolute level rather than on a difference in the shape of the spectrum. A difference in absolute level, however, can still provide an effective discrimination cue if the difference is comparable to the range of randomization. Using enormous ranges of random levels is not desirable, because it is distracting to normal listeners and may exceed the dynamic range of hearing for listeners with hearing loss. This article describes a new experimental procedure which permits the experimenter to greatly reduce the range of level randomization in roving-level tasks.

Acoustic Stimulation↗
PubMed1992

Auditory intensity perception: successive versus simultaneous, across-channel discriminations.

This study measures the ability of observers to compare the intensities of two stimuli occupying different frequency regions. It includes three experiments, each experiment having two conditions. In one condition, the two stimuli to be compared were presented simultaneously within each interval; this condition has been called profile analysis. In the other condition, the two stimuli were presented successively within each interval. Because the overall level of the stimuli was randomized between intervals, the observers were encouraged to compare the intensities of the two stimuli within each observation interval rather than between intervals. The stimuli were two simple tones in experiment 1 and two tonal complexes in both experiments 2 and 3. The stimuli used in experiments 2 and 3 differed in frequency. The results show that simultaneous comparisons are superior to successive comparisons. For simple tones, the difference in threshold is about 8 dB; for complexes with 10 to 11 components, the difference in threshold is about 15 dB. These differences can be explained by assuming that internal noises in different channels were partially correlated when stimuli in those channels were presented simultaneously and were independent when the stimuli were presented successively. Cancellation of the correlated noise is therefore possible with simultaneous comparisons, making such discrimination better than that achievable with successive comparisons.

Acoustic Stimulation↗
PubMed1992

Spectral and temporal weights in spectral-shape discrimination.

The COSS analysis [B. G. Berg, J. Acoust. Soc. Am. 86, 1743-1746 (1989)] was used to estimate spectral and temporal weights of a three-component, amplitude-modulated stimulus in a spectral-shape discrimination task. In all experiments, the task of the observer was to detect an increment in the level of the center component. A spectral-temporal weight quantifies the relative influence of a spectral component on the decisions of an observer during a specified segment of the total stimulus duration. In the first two experiments, the signal was added to all three temporal segments of the center component. The ideal weights for each component should be the same across temporal segments. Spectral-temporal weights were obtained for four conditions with different stimulus durations. In general, the estimated weights for each component were not equal at different temporal segments. In the third experiment, the signal was added to only one of three segments of the center component. Ideally, weight patterns should have changed when the temporal position of the signal segment was altered. Two stimulus durations, 300 and 15 ms, were used. For the 300-ms condition, the signal was added to only the end segment, and for all three observers the weight patterns are different from that obtained in experiment 1 with the signal added to all segments. For the 15-ms conditions, altering the signal position changed the estimated weights for only one observer.

Adult↗
PubMed1992

Spectral shape discrimination of narrow-band sounds.

Measurements are reported on the detectability of signals added to narrow-band sounds. The narrow-band sounds had a bandwidth of 20 Hz and were either Gaussian noise with flat amplitude spectra or sets of equal-amplitude sinusoidal components whose phases were chosen at random. Four different kinds of sinusoidal signals were used. Two signals produced symmetric changes in the audio spectrum adding a component either at the center of the spectrum or at both ends. The other two signals produced asymmetric changes adding a component at either end of the spectrum. The overall level of the sound was randomly varied on each presentation, so that the presence of a signal was largely unrelated to the absolute level of the signal component(s). A model is proposed that assumes the detection of the symmetric signals is based on changes in the shape of the power spectrum of the envelope. Such changes in the envelope power spectrum are probably heard as changes in the "roughness" or "smoothness" of the narrow-band sound. The predictions of this model were obtained from computer simulations. For the asymmetric signals, the most probable detection cues were changes in the pitch of the narrow-band sound. Results from a variety of different experiments using three listeners support these conjectures.

Adult↗
PubMed1992

[RFLPs study of parental origin and mechanism of 3 cases with X chromosome structural abnormality].

In this study, we analysed the parental origin and mechanism of X chromosome abnormalities in 3 cases by using RFLPs on short or long arm of X chromosome as genetic markers. Their karyotypes were 46,X,dup(X)(p21); 46,X,del(X)(p11); 46,X,i(Xq). The results demonstrated that the dup(X)(p21) and the del(X)(p11) were of paternal origin and i(Xq) was of maternal origin. The dup(X)(p21) arose from an unequal sister chromatid exchange. The del(X) (p11) occurred through X chromosome breakage and deletion mechanism. The i(Xq) resulted from X chromosome centromere misdivision in oocyte.

Adolescent↗
PubMed1991

Protein Synthesis in Isolated Mitochondria of Rice (Oryza sativa L.) Seedlings.

For studies of in organello mitochondrial protein synthesis in rice, Oryza sativa L., conventional surface-sterilization procedures were demonstrated to be ineffective. Because of the over-whelmingly efficient [(35)S]methionine utilization by contaminating bacteria, even "essentially bacteria-free" rice mitochondria were shown to be unsuitable for the study of in organello protein synthesis. We developed a procedure to obtain a bacteria-free preparation of rice mitochondria. Such mitochondria favored a membrane-dependent ATP-generating system over an external ATP-generating system as the energy supplement for in organello protein synthesis. Two distinct classes of [(35)S]methionine-labeled, cycloheximide-insensitive products were detected: an electrophoretically unresolved population and a set of some 22 to 27 discrete polypeptide species, each with a characteristic electrophoretic mobility and relative abundance.

Journal Article↗
PubMed1991

Assignment of a Chinese xeroderma pigmentosum patient from Taiwan to complementation group C.

A 2 years and 7 months-old Chinese boy with severe skin symptoms was diagnosed as xeroderma pigmentosum (XP) at Chang Gung Memorial Hospital in Taipei, Taiwan. Skin fibroblasts derived from the patient (patient identification number, XP1CTA) were used for genetic complementation analysis by the conventional cell-fusion technique followed by measurement of ultraviolet light (UV)-induced unscheduled DNA synthesis (UDS). The level of UDS in XP1CTA cells measured by autoradiography was about 20% of that in normal cells. When XP1CTA cells were fused with cells of a representative strain from each of the complementation groups A, D, E, F, G, and H, binuclear cells showed UDS levels in the range of normal cells, demonstrating a clear complementation between XP1CTA strain and either one of these strains. XP1CTA cells failed to complement with all the five reference strains belonging to group C. From these results, the XP1CTA was unambiguously assigned to complementation group C. Sensitivity of XP1CTA cells to UV, as measured by colony-forming ability, also fell within a range of variation in UV sensitivities of these group C XP cell strains.

Asian People↗