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Y Hui

Publications and source records attributed to Y Hui.

103 records · Page 6Linked to original sources
PubMed1993

Photoperiod regulates the LH response to central glutamatergic stimulation in the male Syrian hamster.

This study investigated central glutamatergic function in relation to photoperiodically-induced changes in the secretion of luteinizing hormone (LH). The experimental approach was to compare the central effects of glutamate agonists on LH secretion in reproductively active hamsters kept in long days (LD) with those in photoinhibited hamsters kept in short days (SD) for 6 weeks and having regressed testes. Agonists were delivered via a cannula into the III ventricle of freely moving hamsters, and blood samples collected 10 to 15 min after the start of the infusion. A high dose (3.0 nmole) of N-methyl-D-L-aspartate (NMDA) induced significant (P<0.01) increases in serum concentrations of LH in hamsters in both photoperiods, though the NMDA-induced increase relative to endogenous LH concentrations was greater in SD than in LD. However, a lower dose of NMDA (0.3 nmole revealed a difference in sensitivity. This dose significantly increased serum LH (P<0.05) in hamsters in SD but had no effect in those in LD. The seasonal difference in response to NMDA was compared with the response to an equimolar dose of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), a non-NMDA agonist. This dose of AMPA (0.3 nmole) induced a two-fold increase (P<0.05) in serum concentrations of LH in hamsters in both photoperiods, relative to vehicle-treated controls. In a third experiment the dose-response effects of central AMPA on LH secretion were examined more closely. The sensitivity of LH secretion to stimulation with AMPA did not differ between SD- and LD-housed hamsters. Thus the photoperiod-related difference in sensitivity to stimulation with glutamate agonists is specific for NMDA receptor-mediated activation, rather than a passive reflection of differences in the capacity to secrete GnRH/LH in SD and LD photoperiods. To investigate the site of action of NMDA, the expression of the c-fos immediate-early gene, as assessed by immunocytochemistry for its protein product Fos, was used as a marker of neuronal activation, because previous studies in rodents indicate that a high proportion of GnRH neurons express c-fos at the time of the mid-cycle LH surge. NMDA induced widespread expression of c-fos in many periventricular regions including the medial preoptic area (POA) and ventromedial hypothalamic nucleus. However, dual ICC revealed that in neither photoperiod was Fos present in GnRH-positive neurons 1 h after infusion of 3 nmole of NMDA, despite the increases in LH secretion induced by the infusion. AMPA injected icv at doses which released LH did not enhance expression of c-fos in the hypothalamus. Thus, in the male, enhanced expression of c-fos cannot be detected in GnRH neurons at the time of increased secretion of this hormone induced by glutamate agonists. In conclusion, these results show that both NMDA and non-NMDA glutamatergic pathways potentially regulated LH secretion in the Syrian hamster. The increased sensitivity to NMDA but unaltered sensitivity to AMPA in photoinhibited hamsters in SD is consistent with the view that changes in photoperiod might induce specific alterations in NMDA-mediated pathways that ultimately regulate GnRH neurosecretory activity.

Animals↗
PubMed1992

Early changes of auditory brain stem evoked response after radiotherapy for nasopharyngeal carcinoma--a prospective study.

A prospective study of the effect of radiotherapy for nasopharyngeal carcinoma on hearing was carried out on 49 patients who had pure tone, impedance audiometry and auditory brain stem evoked response (ABR) recordings before, immediately, three, six and 12 months after radiotherapy. Fourteen patients complained of intermittent tinnitus after radiotherapy. We found that 11 initially normal ears of nine patients developed a middle ear effusion, three to six months after radiotherapy. There was mixed sensorineural and conductive hearing impairment after radiotherapy. Persistent impairment of ABR was detected immediately after completion of radiotherapy. The waves I-III and I-V interpeak latency intervals were significantly prolonged one year after radiotherapy. The study shows that radiotherapy for nasopharyngeal carcinoma impairs hearing by acting on the middle ear, the cochlea and the brain stem auditory pathway.

Adult↗
PubMed1992

Additional bioactive compounds and trilobacin, a novel highly cytotoxic acetogenin, from the bark of Asimina triloba.

Fractionation of the EtOH extract of the bark of Asimina triloba, monitoring by brine shrimp lethality, has led to the isolation and structural elucidation of a novel highly cytotoxic Annonaceous acetogenin, trilobacin [1], in addition to six known compounds: asimicin 2], bullatacin [3], bullatacinone [4], N-p-coumaroyltyramine [5], N-trans-feruloyltyramine [6], and (+)-syringaresinol [7]. Acetogenin 1 was identified as a diastereomer of asimicin [2] by spectral and chemical methods, and both 1 and 2 showed potent and selective cytotoxicities in the NCI human tumor cell line screen.

Antineoplastic Agents, Phytogenic↗
PubMed1992

Effect of irradiation on middle ear effusion due to nasopharyngeal carcinoma.

The management of middle ear effusion by myringotomy and insertion of ventilation tubes in 75 adult patients was evaluated. In Group 1 the middle ear effusion was not related to nasopharyngeal carcinoma. The patients with nasopharyngeal carcinoma were subdivided into pre and post-radiotherapy groups (Group 2 and Group 3) according to the time of insertion of the ventilation tubes. Myringotomy and insertion of ventilation tubes achieved significant hearing gain in all three groups. The pre and post-radiotherapy groups had a higher post-operative infection rate than Group 1 (P greater than 0.01). The duration of a persistent tympanic membrane defect in the post-radiotherapy group was significantly longer than Group 1 (P = 0.03). The post-radiotherapy group had more perforations than Group 1 (P = 0.02). A total of 28% of ears in the post-radiotherapy group were discharging at the last visit. In view of the higher complication rate in the post-radiotherapy group, the role of myringotomy and insertion of ventilation tube is reassessed.

Adolescent↗
PubMed1992

Photoperiodic regulation of glutamatergic stimulation of secretion of luteinizing hormone in male Syrian hamsters.

It has been suggested that changes in endogenous glutamatergic stimulation of secretion of luteinizing hormone (LH) induced by photoperiod play a role in regulating seasonal cycles of reproductive activity. The aim of this study was to test the hypothesis that the glutamatergic control of the secretion of LH in the male Syrian hamster is sensitive to photoperiod, by determining whether the glutamate agonist N-methyl-D-aspartate (NMDA) could stimulate LH secretion in this species and, if so, to determine whether the response varied among animals exposed to different daylengths. In the first experiment, adult male hamsters were housed in either short day (8 h light: 16 h dark) for 6 weeks to induce testicular regression, or long days (16 h light: 8 h dark) to maintain testicular function, and the effects of systemic administration of NMDA on serum LH concentrations were determined. In the short-day hamsters, all s.c. doses of NMDA (25-75 mg kg-1 body weight) produced a robust rise in serum LH concentrations within 15 min. In the long-day hamsters, basal LH concentrations were higher than in short-day hamsters, but only the highest dose of NMDA produced a significant increase in LH concentrations, and the magnitude of this increment was less than those observed in short days. In hamsters in long days, the low doses of NMDA that did not significantly alter LH concentrations nevertheless significantly suppressed serum prolactin concentrations, demonstrating the efficacy of the drug. In hamsters in short days, serum prolactin concentrations were at the limit of detection of the assay, so no inhibitory effect of NMDA on prolactin secretion could be determined on this photoperiod. In the second experiment, the effects of a fixed dose of NMDA (50 mg kg-1 body weight) was tested at intervals in hamsters exposed to short days for a prolonged period such that their testes initially regressed, but then became scotorefractory and testicular recrudescence occurred. After 6 and 12 weeks in short days, NMDA stimulated LH secretion. However, after 24 weeks in short days when testicular recrudescence was complete, the response to NMDA was lost. A third experiment determined whether the reduced response to NMDA in hamsters on long days relative to those in short days might result from higher concentrations of circulating testosterone. Hamsters in long days were castrated to remove the influence of gonadal feedback, and the response to NMDA tested 3 weeks later when endogenous LH concentrations had risen to levels characteristic of the chronically castrated condition.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Design and testing of a functional group-specific DNA probe for the study of natural populations of acetogenic bacteria.

The acetogens, although phylogenetically diverse, can be characterized by their possession of the acetyl coenzyme A (acetyl-CoA) pathway for autotrophic CO2 fixation. The gene encoding formyltetrahydrofolate synthetase, a key enzyme of the acetyl-CoA pathway, was previously cloned from the thermophilic acetogen Clostridium thermoaceticum and has now been tested as a group-specific probe for acetogens. Stable hybrids were formed between the probe and single DNA fragments from eight known acetogens representing six genera. A hybrid was also formed between the probe and a DNA fragment from one sulfate reducer known to be capable of both autotrophic CO2 fixation and acetate catabolism. No such hybrid was formed between the probe and DNA from a homoacetate fermenter not known to use the acetyl-CoA pathway, with two known formyltetrahydrofolate synthetase-producing purine fermenters, or with DNA from 27 other species representing 16 genera of organisms that do not use the acetyl-CoA pathway. DNA purified from cells extracted from horse manure was also screened with the acetogen probe. Six hybrids, indicating at least six detectable acetogen "strains," were observed.

Acetyl Coenzyme A↗
PubMed1987

The role of the fibreoptic bronchoscope in otorhinolaryngological practice.

Flexible fibreoptic bronchoscope has been employed in the examination of the nasopharynx, pharynx, larynx, trachea, bronchus and intrathoracic oesophagus under local anaesthesia. It is used either for diagnostic or therapeutic purposes. A total of 1690 procedures have been performed with no complication. The indications and findings in these procedures are listed. The advantages and limitations of the use of flexible fibreoptic bronchoscope as a 'panendoscopic examination' instrument are discussed.

Adolescent↗
PubMedDate not supplied

Comprehensive analysis of pharyngeal recurrence of laryngeal carcinoma after total laryngectomy.

PURPOSE: This study analyzes the incidence, risk factors, treatment results, and prognosis of local recurrence at the pharynx after total laryngectomy for laryngeal carcinoma. PATIENTS AND METHODS: The records of 292 patients who underwent total laryngectomy for the treatment of laryngeal carcinoma between January 1978 and December 1990 were reviewed. RESULTS: Of these 292 patients, there were 24 patients who developed local recurrence at the pharynx. The 5-year actuarial cumulative local recurrence rate was 10%. There were 17 cases of pharyngeal recurrence alone, five cases of pharyngeal and nodal recurrence, one case of pharyngeal and tracheostomal recurrence, and one case of pharyngeal and distant metastasis. Ten (42%) patients were salvaged surgically; the 5-year actuarial survival rate after surgical salvage was 53%. The other 14 patients were treated with palliative treatment, and all died of tumor, with the longest period of survival being 28 months. CONCLUSION: Surgical salvage of pharyngeal recurrence has acceptable results. Close monitoring of patients is important to have an early diagnosis of salvageable recurrence.

Adult↗
PubMedDate not supplied

Otorrhea after grommet insertion for middle ear effusion in patients with nasopharyngeal carcinoma.

PURPOSE: To document the incidence of complications after myringotomy and grommet insertion in patients with nasopharyngeal carcinoma. The focus is on the incidence of otorrhea and perforation. The possible risk factors for these conditions and treatment response were studied. MATERIALS AND METHODS: We reviewed the records on 206 ears of 163 patients who suffered from nasopharyngeal carcinoma and underwent myringotomy and grommet insertion in a 7-year period. The follow-up period ranged from 4 weeks to 78 months (median, 9 months). RESULTS: The overall incidence of otorrhea in these ears was 38%. Patients with nasopharyngeal carcinoma (NPC) had a significantly high incidence of postoperative discharge (chi2 test, P<.0001) compared with other patients who underwent myringotomy and grommet insertion. The mean interval between myringotomy and otorrhea was 19.8 weeks. Forty-seven per cent of the ears with a discharge developed otorrhea within 1 month. In 42%, the otorrhea responded to treatment and the ears became dry. After extrusion of the grommet, 29% of those ears with otorrhea ended with an eardrum perforation, and 24% of the ears showed recurrent effusion. CONCLUSIONS: For patients with NPC who underwent myringotomy, there was a significant risk of otorrhea (49%) and persistent perforation (29%), and these complications were difficult to manage. We conclude that myringotomy and grommet insertion should not be routinely offered to NPC patients with middle ear effusion.

Case-Control Studies↗
PubMedDate not supplied

Glomangiomyoma of the nasal cavity.

Glomus tumor is a rare neoplasm that typically occurs in soft tissue of the extremity, particularly the subungual region of the finger tip. It rarely occurs in the nasal septum. Glomangiomyoma is a rare histologic variant of glomus tumor. The authors describe a case of glomangiomyoma of the nasal septum that presented as nasal obstruction. The histologic, immunohistochemical, and electronmicroscopic findings are described. The otolaryngologist and surgical pathologist should be aware of such an entity, and should not confuse it with the totally unrelated glomus jugulare tumor, or paraganglioma of the middle ear.

Adult↗