Biomedical subjects

Y C Chiang

Publications and source records attributed to Y C Chiang.

At least 73 records · Page 4Linked to original sources

PubMed1997

Onset dominance in lateralization.

Saberi and Perrott [Acustica 81, 272-275 (1995)] found that the in-head lateralization of a relatively long-duration pulse train could be controlled by the interaural delay of the single pulse pair that occurs at onset. The present study examined this further, using an acoustic pointer measure of lateralization, with stimulus manipulations designed to determine conditions under which lateralization was consistent with the interaural onset delay. The present stimuli were wideband pulse trains, noise-burst trains, and inharmonic complexes, 250 ms in duration, chosen for the ease with which interaural delays and correlations of select temporal segments of the stimulus could be manipulated. The stimulus factors studied were the periodicity of the ongoing part of the signal as well as the multiplicity and ambiguity of interaural delays. The results, in general, showed that the interaural onset delay controlled lateralization when the steady state binaural cues were relatively weak, either because the spectral components were only sparsely distributed across frequency or because the interaural time delays were ambiguous. Onset dominance can be disrupted by sudden stimulus changes within the train, and several examples of such changes are described. Individual subjects showed strong left-right asymmetries in onset effectiveness. The results have implications for understanding how onset and ongoing interaural delay cues contribute to the location estimates formed by the binaural auditory system.

Auditory Perception↗

PubMed1996

ADR1 activation domains contact the histone acetyltransferase GCN5 and the core transcriptional factor TFIIB.

The yeast transcriptional activator ADR1, which is required for ADH2 and peroxisomal gene expression, contains four separable and partially redundant activation domains (TADs). Mutations in ADA2 or GCN5, encoding components of the ADA coactivator complex involved in histone acetylation, severely reduced LexA-ADR1-TAD activation of a LexA-lacZ reporter gene. Similarly, the ability of the wild-type ADR1 gene to activate an ADH2-driven promoter was compromised in strains deleted for ADA2 or GCN5. In contrast, defects in other general transcription cofactors such as CCR4, CAF1/POP2, and SNF/SWI displayed much less or no effect on LexA-ADR1-TAD activation. Using an in vitro protein binding assay, ADA2 and GCN5 were found to specifically contact individual ADR1 TADs. ADA2 could bind TAD II, and GCN5 physically interacted with all four TADs. Both TADs I and IV were also shown to make specific contacts to the C-terminal segment of TFIIB. In contrast, no significant binding to TBP was observed. TAD IV deletion analysis indicated that its ability to bind GCN5 and TFIIB was directly correlated with its ability to activate transcription in vivo. ADR1 TADs appear to make several contacts, which may help explain both their partial redundancy and their varying requirements at different promoters. The contact to and dependence on GCN5, a histone acetyltransferase, suggests that rearrangement of nucleosomes may be one important means by which ADR1 activates transcription.

Acetyltransferases↗

PubMed1996

Paediatric liver transplantation: a 10 year experience in Taiwan.

Between March 1984 and August 1994, 13 orthotopic liver transplantations were performed in 13 patients < or = 25 years of age. The indications included Wilson's disease (n = 7), biliary atresia (n = 4), choledochal cyst (n = 1) and hepatitis C cirrhosis (n = 1). Technical variants included full-size (n = 11), reduced-size (n = 1) and living-related (n = 1) liver transplantation. These recent technical innovations have offered an expanded donor pool for earlier transplantation, shorter waiting times and excellent quality grafts. Surgical complications occurred in six patients; all required additional surgery. Biliary complications were encountered more commonly in our earlier patients. Our actuarial patient and graft survival rate is 92% at 2 years. The long-term follow-up of our liver-transplanted Wilson's disease patients provides confirmatory evidence that orthotopic liver transplantation cures the underlying metabolic defect with complete normalization of biochemical abnormalities of copper metabolism, reversal of neurological impairments and the disappearance of Kayser-Fleischer corneal rings. The high rate of patient survival and excellent rehabilitation indicate that with prudent clinical judgement, liver transplantation can be achieved with an acceptable rate of morbidity, mortality and cost in a setting where manpower and donor organs are very limited.

Adolescent↗

PubMed1996

Consonant recognition for spectrally degraded speech as a function of consonant-vowel intensity ratio.

Normal-hearing subjects' recognition of spectrally degraded speech was evaluated under conditions in which the consonant-vowel (C-V) intensity ratio was modified. Subjects identified 22 consonants presented in an /a-Consonant-a/ format at suprathreshold and near threshold conditions. Prior to C-V ratio modification, the stimuli were processed to limit spectral information. In the suprathreshold experiment, stimuli were presented at the natural C-V ratio and at six modified C-V ratios. C-V ratio manipulations had dramatic effects on recognition scores for some groups of consonants. Scores for glides and sibilant fricatives increased with increasing C-V ratio, while scores for nasals and weak fricatives were best at low C-V ratios. Recognition scores for the stops and affricates were generally independent of C-V ratio. For nearly all consonants, changes in recognition scores as a function of C-V ratio were associated with changes in a general response bias toward those sounds. Performance was poor when the spectrally smeared VCVs were presented at low SN ratios in a second experiment. The influence of C-V ratio on percent correct scores was generally similar to the suprathreshold results, but consonant audibility, which was not a factor in the suprathreshold experiment, appeared to alter the effect of C-V ratio modification for some consonants.

Humans↗

PubMed1996