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Biomedical subjects

G D Chen

Publications and source records attributed to G D Chen.

At least 37 records · Page 2Linked to original sources
PubMed1999

Effects of interaural time differences on the responses of chinchilla inferior colliculus neurons to consonant-vowel syllables.

The responses of 100 inferior colliculus neurons to syllables differing in voice onset time (VOT) presented binaurally were studied. As in a previous study of monaural responses (Chen et al., 1996), the responses consisted of 1-3 response 'components', referred to as release responses, VOT responses or vowel responses. The discharge rate of all response components could vary cyclically with the interaural time difference (ITD). The maximal rate often occurred at an ITD around +0.2 ms (contralateral ear leading). Response frequencies (RF) based on the periodicity of the delay curves varied with the characteristic frequency (CF) and VOT. RF also varied across response components. Overall, RF was correlated with the 'most effective frequency', the spectral component with the highest amplitude, relative to the tuning curve. VOT response latency for a given syllable could change by a few ms with ITD, but those changes were small, relative to the range of latencies observed over the entire range of VOTs. Changes in ITD produced large changes in the overall shape of the peristimulus time histogram. There was no relation between the histogram shape and perceptual consonant categories.

Animals↗
PubMed1999

Intermittent noise-induced hearing loss and the influence of carbon monoxide.

Intermittent noise causes less hearing loss than continuous noise of equal intensity. The reduction in damage observed with intermittent noise may be explained by the fact that the auditory system has time to recover between the noise phases. Simultaneous carbon monoxide (CO) exposure produces greater noise-induced hearing loss than does noise alone (Chen and Fechter, 1999). In the present study, intermittent noise (octave-band with a center frequency of 13.6 kHz, 100 dB) of a 2 h total duration but with a different duty cycle (% of noise during exposure) was used. The intermittent exposure that had a shorter noise duty cycle induced a less permanent threshold shift (PTS) than those that had a longer noise duty cycle (or less rest periods). This relation between the loss in compound action potential (CAP) sensitivity and the noise duty cycle (or rest period) was abolished by the presence of CO. The cochlear microphonic (CM) amplitude revealed similar results to those seen using the CAP. While intermittent noise that had a short noise duty cycle did not cause hair cell loss by itself, the combined exposure to noise and CO (1200 ppm) caused remarkable OHC loss in the basal turn.

Action Potentials↗
PubMed1999

Serum anti-p53 antibodies in gastric adenocarcinoma patients are associated with poor prognosis, lymph node metastasis and poorly differentiated nuclear grade.

Mutation of the p53 tumour suppressor gene often leads to the accumulation of mutant p53 protein in tumour cells. Many cancer patients develop antibodies that recognize the overexpressed p53 protein. The presence of these antibodies is, in some tumour types, associated with poor prognosis. Gastric cancer is a highly prevalent disease associated with a high rate of mortality, there is a need for improved clinical and biological markers for disease behaviour. To investigate the clinical relevance of serum anti-p53 antibodies in patients with gastric adenocarcinoma, we have examined the sera of 501 gastric cancer patients for the presence of serum antibodies against the p53 protein. By immunoblotting analysis using a cell lysate containing overexpressed p53 protein as well as affinity-purified recombinant p53 protein as antigens, we have detected anti-p53 antibodies in 11.2% (61 of 501) of gastric cancer patients, but in none of 46 cancer-free individuals. The presence of anti-p53 antibodies was tightly associated with tumours of higher nuclear grade and lymph node metastasis, and a negative association was found between the presence of anti-p53 antibodies and survival. These results suggest that a preoperative test of serum anti-p53 antibodies in gastric cancer patients can be useful to identify subset of patients who may need gastrectomy with lymph node dissection and post-operative adjuvant therapy.

Adenocarcinoma↗
PubMed1999

STR HUMARA locus gene and genotype frequencies in Han and Bei populations in China.

For the purpose of the population genetics study of the HUMARA locus, the allele, and genotype frequencies were determined in two Chinese population samples (Han-101, Bei-113) using PCR, PAGE, and silver staining. Fourteen alleles were found. The size of amplified fragments were 258 bp-315 bp. The observed heterozygosities were 0.83 in the Han population and 0.73 in the Bei population respectively. The expected heterozygosities were 0.91 in the Han population and 0.97 in the Bei population respectively. Both populations meet Hardy-Weinberg expectation, Han population x2 = 17.7206, df = 11, p > 0.05; Bei population x2 = 7.4268, df = 10, p > 0.05. The discrimination power were 0.95 in females and 0.89 in males in the Han population, 0.94 in females and 0.88 in males in the Bei population. Thus, the allelic frequency data can be used in the personal identification and parentage testing in the forensic science practice. The PCR test established in this study is robust and reproducible.

Alleles↗
PubMed1999

Frequencies of D8S384 alleles and genotypes in European, African-American, Chinese, and Japanese populations.

D8S384 is a tetranucleotide tandem repeat locus. In order to evaluate the forensic validation of D8S384, the genotype distributions and allele frequencies in ten populations from three main ethnic groups were investigated, including Germans, Slovakians, African Americans, Japanese, and Chinese (Jilin, Guangzhou, Nanning, Hailaer, Dali, and Chengdu). A total of 1011 unrelated individuals, 41 pedigrees, 30 disputed paternity trios and three personal identification cases were analyzed for D8S384 by Amp-FLP technique. Many kinds of tissues, body fluids, secreta and stains have been tested. The alleles were determined by comparison with a human allele ladder. The results showed that D8S384 typing was both precise and reliable. There were eight alleles in these populations. The genotype distributions conformed to Hardy-Weinberg equilibrium predictions. No mutation events were observed. With a maximum likelihood method, the mutation rate was indirectly estimated as 2.14 x 10(-5). The heterozygosity was 0.704 +/- 0.014 at D8S384 locus. All these results suggest that D8S384 locus is a useful marker for forensic identification and paternity analysis.

Adult↗
PubMed1999

[MBP content in serum after closed diffuse cranial injury in rats].

The MBP content change in serum was observed by ELISA in rats with experimental closed diffuse cranial injury. The MBP content was 6.1633 +/- 1.5301 ng/ml (X +/- S) in the normal group, 11.3818 +/- 2.6574 ng/ml in the first group died immediately after injury, 10.8319 +/- 2.3135 ng/ml in the second group of 15 min after injury. This increased level of MBP was lasting in the following 3 days and returned to normal at the 4th and 5th day after injury. The difference of the MBP levels between the groups after injury and that in the normal group is significant (P < 0.01).

Animals↗
PubMed1999

[Allele and genotype frequency distribution of D19S400 locus in several populations].

Using polymerase chain reaction and PAG electrophoresis, D19S400 Locus was investigated in the populations of Chinese, Germany, Slovakian, and American Black Population. 620 samples collected from the four populations were tested and a total of 11 alleles (*7 to *17) and 47 genotypes were found. The heterozygosity was observed between 0.78 and 0.88, and the discriminating power was between 0.9385 and 0.9664. The distributions of genotypes in the four populations were in accordance with Hardy-Weinberg equilibrium. Significant differences were observed in the distribution of allele frequencies among the three major racial populations (Mongoloid, Caucasian, Negroid). According to the results obtained in this study, D19S400 locus is a robust STR for forensic and genetic purposes.

Alleles↗
PubMed1998

Effects of stimulus duration on responses of neurons in the chinchilla inferior colliculus.

The effects of the stimulus duration (10 to 300 ms) on the responses of chinchilla inferior colliculus neurons to pure tones were studied in 41 units. The responses of the majority of the neurons (90%) were classified as sustained, onset, pause with onset peak and pause without onset peak response patterns. Three neurons were found to have response to the stimulus offset (offset response pattern). One neuron responded to the sound with the decrease of the spontaneous discharge rate (inhibitory response pattern). The responses restricted within the stimulus duration could be simply predicted from the peristimulus time histogram (PSTH) to the longer duration. The leading part of the PSTH to the longer stimulus duration resembled that to the shorter stimulus duration. The function of the spike number versus duration was correlated with the PSTH patterns. The response following the stimulus offset (including inhibitory response) could vary with the stimulus duration nonmonotonically and show a band-pass or band-reject property. Overall, four (about 10%) of the neurons could be regarded as duration-tuned units. The duration selectivity could be understood by the interaction between the ongoing and the offset process of the neurons.

Acoustic Stimulation↗
PubMed1998

High frequency of rearrangement of the RET protooncogene (RET/PTC) in Chinese papillary thyroid carcinomas.

The activation of RET protooncogene, through chromosomal translocation, is unique to papillary thyroid carcinomas. Rearrangement of the RET kinase domain to 3 partner genes has been described, of which the RET/PTC1 is the most common. To investigate the frequency of RET rearrangement in Chinese papillary thyroid carcinomas, we have performed RT-PCR to amplify specific RET/PTC transcripts. Among the papillary thyroid carcinomas of 11 patients examined, we have identified 2 containing RET/PTC1, 3 containing RET/PTC2, and 1 containing RET/PTC3 oncogenes. Although the cause of the high frequency of RET/PTC oncogenes in Chinese papillary thyroid carcinomas is unknown, our study suggests that RET rearrangement is an important genetic lesion underlying the development of thyroid papillary carcinoma in Taiwan.

Adult↗
PubMed1998

Dynamic displacement changes of the bladder neck with the patient supine and standing.

PURPOSE: With the patient standing and supine we determine the differences in dynamic changes of the bladder neck and directions of dynamic bladder neck displacement. MATERIALS AND METHODS: To evaluate the dynamic movement of the bladder neck we recruited into the study 78 consecutive women 27 to 69 years old with various urogynecological complaints. The anatomical changes of the bladder neck from rest to maximal straining and from rest to holding were evaluated and compared with the patients supine and standing. RESULTS: Except for bladder neck rotational angle with the patient standing, all parameters were significantly different from corresponding measurements with the patient supine. Mean rotational angle of rest to maximal straining plus or minus standard deviation was 39.4 +/- 18.9 degrees when standing versus 39.8 +/- 23.4 degrees when supine (p > 0.05). The distances between the bladder neck and symphysis pubis at rest, and during maximal straining and holding the bladder neck in the supine position were significantly longer than those in the standing position. The direction of bladder neck displacement from rest to maximal straining was more caudad and ventral when standing. The bladder neck moved cephalad and ventral when the patient was standing, and cephalad and dorsal with the patient supine and holding the bladder neck. CONCLUSIONS: The anatomical locations and dynamic displacements of the bladder neck at rest, and during maximal straining and holding were significantly different in the supine and standing positions. While evaluating the dynamic motion of the bladder neck to determine bladder neck mobility, patient position must be considered and specified in accordance with diagnostic standards.

Adult↗
PubMed1997

Applicability of perineal sonography in anatomical evaluation of bladder neck in women with and without genuine stress incontinence.

Thirty-seven patients with proven genuine stress incontinence (GSI) underwent ultrasound study to evaluate the bladder neck position relative to the symphysis pubis. Sixty-five continent women including 40 parous and 25 nulliparous women were recruited as a control group. Several parameters were found to be statistically different between incontinent and control groups (P < 0.01). If 28 degrees or 13 mm were used as the cut-off point for rotational angle (RA) and descent of bladder neck (DBN), the sensitivity, specificity, and positive and negative predictive values were 78.0%, 76.9%, 64.3%, and 33.3%, respectively. The specificity and positive predictive value for GSI increased to 83.1% and 67.6% if these two parameters were used together. Perineal sonography is valuable in assessing anatomic change of the bladder neck, but it is not a sensitive tool for predicting GSI.

Adult↗
PubMed1997

The results of laparoscopic adhesiolysis for intractable urinary frequency.

PURPOSE: We evaluated urinary frequency related to pelvic adhesions around the bladder serosa and the result of laparoscopic adhesiolysis on intractable urinary frequency caused by adhesions that did not respond to conservative treatment. MATERIALS AND METHODS: Laparoscopic adhesiolysis was performed for the diagnosis and treatment of 10 referred patients with a history of pelvic surgery in whom conservative treatment had failed. Urinary symptoms and signs, a urinary diary and cystometry were followed before and after surgery. RESULTS: In all cases there were various degrees of pelvic adhesion, mainly around the bladder. Frequency and urgency were improved in 9 of 10 patients. Urinary diary and cystometry parameters showed improvement at followup. CONCLUSIONS: Adhesions involving the bladder wall may restrict bladder distension in most of these patients. Laparoscopic adhesiolysis is beneficial in the diagnosis and treatment of this subgroup of patients.

Adult↗
PubMed1995

Salicylate-induced abnormal activity in the inferior colliculus of rats.

The evaluation of the spontaneous activity of 471 units from the external nucleus of the IC revealed that salicylate induces an increase of the spontaneous activity and the emergence of a bursting type of activity longer than 4 spikes. For sharply tuned units, the affected cells were from the frequency range of 10-16 kHz, which corresponds to the behaviorally measured pitch of salicylate-induced tinnitus in rats. An exogenous calcium supplement, provided under the conditions shown to attenuate the behavioral manifestation of salicylate-induced tinnitus, abolished the modification of the spontaneous activity induced by salicylate. Finally, profound changes of activity were observed for cells not responding to contralateral sound. We propose that the observed long bursts of discharges represent tinnitus-related neuronal activity. The results are consistent with the hypothesis that GABA-mediated disinhibition is involved in the processing of tinnitus-related neuronal activity.

Acoustic Stimulation↗
PubMed1994

Diagnosis of interstitial pregnancy with sonography.

Interstitial pregnancy is a rare and extremely dangerous form of ectopic pregnancy. Preoperative diagnosis of this condition prior to rupture is difficult, and early detection is essential to avoid a fatal outcome. Six cases in our series were diagnosed as interstitial pregnancy. Their clinical features were missed period, positive pregnancy test, and sudden onset of lower abdominal pain with or without vaginal spotting. The sonographic images showed an endometrial echo in uterine cavity, eccentric sac, protruding mass over the cornual area, and/or the presence of free fluid in the cul-de-sac. Five of 6 patients had sacs found in the cornual area or a protruding cornual mass. We termed the sonographic findings of interstitial pregnancy as "pregnancy in cornus." High resolution transvaginal sonography permits determination of the exact location of the gestational sac and increases the diagnosis rate of interstitial pregnancy.

Adult↗
PubMed1989

[Synthesis and antimalarial as well as antitumor activities of 2,4-diamino-6-(N-methyl-substituted benzylamino) quinazolines].

Sixteen 2,4-diamino-6-(N-methyl-substituted benzylamino) quinazolines (I) were synthesized by two different methods. 2-Nitro-5-chloro-benzonitrile was treated with the appropriate N-methyl-substituted benzylamines and I was formed after reduction and cyclization. Another method was reductive methylation, i.e., 2,4-diamino-6-substituted benzylaminoquinazolines reacted with formaldehyde and sodium cyanoborohydride at pH 6.3. Suppressive therapeutic tests in mice infected with Plasmodium berghei showed that four (I6,7,10,16) out of these compounds suppressed all the parasites when administered orally at the dose of 5 mg/kg and produced more than 99% suppression at 2.5 mg/kg. Eight compounds (I1,2,4,5,8-10,15) were found to have antitumor effects against Leukemia cells in culture comparable with or superior to those of the positive control methotrexate.

Animals↗