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Biomedical subjects

M Ng

Publications and source records attributed to M Ng.

At least 55 records · Page 3Linked to original sources
PubMed1999

Delayed facial paralysis after stapedotomy using KTP laser.

OBJECTIVE: Delayed facial paralysis after stapes surgery is uncommon and has been reported after traditional, nonlaser techniques for stapedotomy. The purpose of this paper is to inform the reader of the potential risk of delayed facial nerve paralysis associated with the use of the potassium titanyl phosphate (KTP) laser for stapedotomy. Etiologic mechanisms are discussed. STUDY DESIGN: The study was a descriptive study-case report. SETTING: The study was conducted at a university-based otologic practice. PATIENTS: Two patients with otosclerosis and delayed onset facial palsy 5 to 7 days after uncomplicated stapedotomy using the KTP laser were included in the study. INTERVENTION: Potassium titanyl phosphate laser stapedotomy was performed. Patients received treatment of facial palsy with a tapering course of oral steroids. MAIN OUTCOME MEASURE: House-Brackmann facial nerve grade scores were used. RESULTS: Improvement of House-Brackmann facial nerve scores from Grade VI to Grade I-II in one patient, and improvement from Grade IV to Grade I-II in the other was seen. CONCLUSION: The probable etiology of delayed facial palsy is viral neuritis from reactivation of dormant virus within the facial nerve, initiated by thermal stress of the KTP laser. Presentation and resolution of the facial palsy is similar to other types of delayed facial palsy resulting from nonlaser techniques of stapes surgery and other types of middle ear and neurotologic surgeries previously reported.

Facial Nerve↗
PubMed1999

Safety of endoscopic sinus surgery in a residency training program.

Over the past decade, endoscopic sinus surgery has become one of the most frequently performed operations in otolaryngology. Nevertheless, concerns have been raised about the safety of this procedure in a residency training program. To address this issue, we carried out a retrospective review to assess the complications of endoscopic sinus surgery performed by otolaryngology residents under close supervision. We reviewed the medical records of 597 patients who had undergone 719 operations performed by residents in the Department of Otolaryngology-Head and Neck Surgery of the University of Southern California-Los Angeles County Medical Center and at the University Hospital between June 1988 and December 1995. Most of these procedures were performed by junior residents under the supervision of either a senior resident or faculty member. We found that the incidence of minor and major complications was 12.2 and 0.4%, respectively. The most common minor complications were vascular. The only major complication was excessive bleeding that required transfusion. There were no cases of blindness, cerebrospinal fluid rhinorrhea, or death. We conclude that endoscopic sinus surgery in an otolaryngology residency training program is a relatively safe procedure, especially when performed under faculty supervision.

Adolescent↗
PubMed1998

Expression of P-glycoprotein, a multidrug-resistance gene product, is induced by radiotherapy in patients with oral squamous cell carcinoma.

BACKGROUND: It has been observed that patients who have previously undergone radiotherapy have a lower rate of response to chemotherapy. METHODS: The authors investigated the effects of radiation on the expression of P-glycoprotein (Pgp), a multidrug-resistance gene product, in 56 patients with primary oral cancer. No patients received prior or concurrent chemotherapy. The 56 patients consisted of 3 groups: 1) 20 patients with preradiation or pretreatment specimens only, 2) 18 patients with both pre- and postradiation specimens, and 3) 18 patients with postradiation specimens only. Pgp expression was determined by immunohistochemistry with two monoclonal antibodies, C219 and C494. RESULTS: Among patients in Groups 1 and 2, only 1 (2.6%) and 2 (5.3%) patients had Pgp expression in their tumors before treatment with C219 and C494, respectively. For Group 2 patients, 66.7% and 72.2% had tumors that expressed Pgp with the two antibodies, respectively, only after and not prior to radiation. When patients in Groups 2 and 3 were combined, 63.9% and 72.2% had Pgp expression with the two antibodies, respectively, after radiation. Pgp expression was significantly induced after radiation compared with expression before treatment (P < 0.001). Overexpression of p53 protein, detected by immunohistochemistry with DO-7 antibody, was seen in the tumors of 40 patients (71.4%), and the status was quite consistent throughout radiotherapy. Pgp expression had no significant association with p53 protein expression. CONCLUSIONS: Pgp expression was significantly induced by radiation in human oral cancers. This induction of Pgp expression likely confers multidrug resistance to the cancer cells and may affect the efficacy of subsequent or concurrent chemotherapy. It may explain the lower rate of response to chemotherapy among patients who have previously had radiotherapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

p21/WAF1, p53 and PCNA expression and p53 mutation status in hepatocellular carcinoma.

The cyclin-dependent kinase inhibitor p21/WAF1 is regulated by p5S3-dependent and p53-independent pathways. In addition, p21/WAF1 binds with proliferating cell nuclear antigen (PCNA) and inhibits the action of PCNA. To investigate the possible role of p21/WAF1 in human hepatocellular carcinomas (HCCs), we examined the expression of p21/WAF1 and its relation with PCNA and p53 expression in 97 surgically resected HCCs by immunohistochemistry and with the mutation status of p53 in 26 HCCs. p53 mutation status was examined by direct DNA sequencing using 3 sets of primers covering exons 5-9. Six of the 26 tumors showed p53 point mutations and only 33% of these HCCs demonstrated p21/WAF1 expression. In contrast, 75% of HCCs without p53 mutations showed p21/WAF1 expression. Of all 97 HCCs, p21/WAF1 expression was significantly higher in the tumors than in corresponding non-tumorous liver. When the tumors were stratified into 2 groups by the median tumor p21/WAF1 score, those with higher expression were found to have a lower incidence of multiple tumor nodules (p = 0.008) and tumor microsatellite formation (p = 0.050). The tumor p21/WAF1 score was positively associated with tumor PCNA expression (p = 0.036) but not with tumor p53 expression. Thus, in HCC, expression of p21/WAF1 is in part dependent on p53 status, but a p53-independent pathway also plays a significant role in the regulation of p21/WAF1 expression. High p21/WAF1 expression is significantly associated with solitary tumor nodules and, to a lesser extent, tumor microsatellites but may not be enough to suppress tumor progression.

Adult↗
PubMed1998

FADD: essential for embryo development and signaling from some, but not all, inducers of apoptosis.

FADD (also known as Mort-1) is a signal transducer downstream of cell death receptor CD95 (also called Fas). CD95, tumor necrosis factor receptor type 1 (TNFR-1), and death receptor 3 (DR3) did not induce apoptosis in FADD-deficient embryonic fibroblasts, whereas DR4, oncogenes E1A and c-myc, and chemotherapeutic agent adriamycin did. Mice with a deletion in the FADD gene did not survive beyond day 11.5 of embryogenesis; these mice showed signs of cardiac failure and abdominal hemorrhage. Chimeric embryos showing a high contribution of FADD null mutant cells to the heart reproduce the phenotype of FADD-deficient mutants. Thus, not only death receptors, but also receptors that couple to developmental programs, may use FADD for signaling.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Extracranial repair of pediatric traumatic cerebrospinal fluid rhinorrhea.

OBJECTIVE: To examine the methods of extracranial repair of traumatic defects in the cribriform plate and ethmoid roof resulting in persistent cerebrospinal fluid (CSF) rhinorrhea in pediatric patients. DESIGN: Retrospective case series. SETTING: A single-institution, tertiary care, pediatric hospital. PATIENTS: Four children, ranging in age from 3 1/2 to 9 years, who sustained fractures in the cribriform plate or ethmoid roof. INTERVENTION: Transnasal endoscopic repair in 4 patients, with 2 patients also undergoing external ethmoidectomy because of the large bony defect and the need for further exposure for repair. MAIN OUTCOME MEASURES: Time free from CSF leaks or recurrence, meningitis, and other postoperative complications. RESULTS: All patients except 1 have been free of recurrent CSF leaks, meningitis, and other postoperative complications. The 3 patients who solely underwent the extracranial approach did not experience the complications of the traditional intracranial approach. CONCLUSIONS: In a select group of pediatric patients, the extracranial approach for the repair of CSF leaks is appropriate. Successful use of an extracranial approach in 3 of 4 patients supports this method.

Accidental Falls↗
PubMed1998

Ultrastructure of the nucleus of the Iodamoeba bütschlii cyst.

The ultrastructure of the Iodamoeba bütschlii cyst from human feces was studied. The glycogen mass appears as a compact dense body in the cytoplasm without any surrounding membrane. The cytoplasm has no mitochondrion. The nucleus shows a distinct nucleolus filled with electron-dense particles. On one side of the nucleolus are electron-dense cytoplasmic masses measuring 200-400 nm. The nuclear membrane is two-layered and shows pores.

Amebiasis↗
PubMed1998

Scanning electron microscopy of Blastocystis hominis cysts.

Scanning electron microscopy of Blastocystis hominis cysts reveals that some cysts have an outer coat, whereas others are naked. If intact, the outer coat forms a fan-like structure around the cyst and its surface is granular. The fragmented outer coat adheres to other cysts and bacteria, forming irregular clumps.

Animals↗
PubMed1998

Morphology of the developing human endolymphatic sac.

The adult human endolymphatic sac (ES) has been described as a complex network of interconnected tubules. Embryologic examination describes the human ES as a single-lumen, pouch-like structure. Transition from saccular shape to tubules during the entire fetal period has not been previously reported. Tubular ES structure is thought to be unique to humans. Animal investigations describe similar saccular appearance, but without tubules in mature sacs. The authors examined 45 human fetal temporal bones to trace ES development and reviewed six types of animal sacs. Results in humans reveal tubular structure as early as 26 weeks' gestation. Maturation variably occurred in the fetal period and postnatally. For the first time, the tubular system is noted in the animal, the rhesus monkey. These findings suggest that the tubular system may represent more advanced specialized function.

Adolescent↗
PubMed1998

Mastoid size and otitis media with effusion: question of correlation.

OBJECTIVES/HYPOTHESIS: To determine the incidence of otitis media (OME) with effusion on histologic examination in temporal bones with mastoid cavities reduced by the fenestration procedure for otosclerosis. STUDY DESIGN: Temporal bone histologic study. METHODS: Light-microscopic examination of serially sectioned temporal bones. RESULTS: The incidence of otitis media with effusion in temporal bones with prior fenestration operation was not any more frequent than the control group of temporal bones with surgically unaltered mastoid cavity. CONCLUSIONS: There is no increased incidence of otitis media with effusion in temporal bones with prior fenestration operation.

Aged↗
PubMed1998

Expression of insulin-like growth factor II mRNA in hepatocellular carcinoma.

Insulin-like growth factor II (IGF-II) is a mitogenic polypeptide closely related to insulin. Its gene has complex regulation of transcription, resulting in multiple mRNA initiated by different promoters. To study its role in hepatocarcinogenesis, we examined the expression of IGF-II mRNA in hepatocellular carcinomas (HCC) and correlated it with the pathological features of the tumours. Using northern blot analysis, transcription of the normal adult promoter was repressed in all but two of the 30 HCC. Instead, there was re-expression of two foetal transcripts (6 and 5 kb) in 12 tumours. In contrast, most (93.3%) of the non-tumorous livers showed expression of adult transcript only, and there were three livers demonstrating expression of foetal transcripts in addition to the adult one. There was a significant association of IGF-II expression with direct tumour invasion into the adjacent liver parenchyma but foetal expression did not influence other parameters directly related to tumour invasiveness, including venous permeation, formation of tumour microsatellites and positive resection margin. Besides, IGF-II expression was significantly more frequently seen in tumours from older patients. To conclude, repression of normal adult promoter and re-expression of foetal promoters of IGF-II are common events in HCC. The observation that foetal IGF-II expression was significantly more frequent in older patients suggests that spontaneous foetal expression of IGF-II late in life may promote the growth of tumours which have already arisen through other mechanisms, but foetal re-expression itself is not enough to contribute to tumour progression.

Blotting, Northern↗
PubMed1998

Correlation of medical dosimetry quality indicators to the local tumor control in patients with prostate cancer treated with iodine-125 interstitial implants.

The treatment of prostate cancer by 125I interstitial implants has been extensively studied with mixed results by one institution or another. A recent study from Hahnemann [Int. J. Radiat. Oncol., Biol., Phys. 21,955-960 (1991)] reported results that were extremely poor compared to those reported in an earlier study at Yale [Int. J. Radiat. Oncol., Biol., Phys. 14, 1153-1157 (1988)] or those in an Eastern Virginia Study [Cancer 63, 2415-2420 (1989)]; differences in 5-yr survival rates being more than a factor of 2. Such large discrepancies from institution to institution led us to a reexamination of the dosimetry. This study analyzed quantitatively three-dimensional dosimetric parameters of 110 prostate cancer patients treated with 125I interstitial implants. The study searched for "cutoff" values in each parameter that divided the patients into two groups with statistically significant differences in the local recurrence-free survival rates. A comparison of the three-dimensional isodose surfaces of patients with favorable values in all of the parameters to those patients with all unfavorable parameters show how these characteristics translated into poor dose coverage and much inhomogeneity within the implant even for cases that met the traditional criteria for adequacy (160 Gy to the tumor volume). Patients in the favorable group had 10-yr survival rates higher by a factor of up to 2 compared to those in the unfavorable group. The strong correlation of three-dimensional volume-dose parameters to the local control rate observed in this study further emphasizes how important it is to assess the three-dimensional dosimetric adequacy of interstitial implants before deciding on their clinical efficacy. If implants are performed with appropriate attention to dosimetry parameters, excellent clinical results are obtained. On the other hand, if dosimetry parameters are not correct, the implant results can be poor.

Adenocarcinoma↗
PubMed1998

Managing the emergency airway in Le Fort fractures.

Le Fort fractures are a part of the facial fracture spectrum, sustained from significant forces of impact to the midface. The mechanism of airway obstruction in Le Fort fractures is attributed to midface instability with posterior inferior displacement into the oropharyngeal airway. Otolaryngologists often participate in the evaluation and management of such patients, securing the airway, if necessary. It is important, therefore, to understand the mechanisms responsible for acute airway obstruction in these types of fractures. A retrospective review of 64 cases of Le Fort fractures, representing a 3-year period, was performed to determine the factors responsible for acute airway obstruction. The review disclosed that airway obstruction is due most often to hemorrhage into the upper airway from multiple sources, with inability to handle blood and the oral secretions. An emergency airway was required by one third of the patients with Le Fort fractures in this review.

Adolescent↗
PubMed1997

Variation in the cyst morphology of Blastocystis hominis.

Two types of Blastocystis hominis cyst are passed in human feces, one with an outer fibrillar coat and the other without it. The outer fibrillar coat is shed as the cyst matures, but another fibrillar coat forms that is closely attached to the cyst wall and is clearly visible at high magnification in the electron microscope. The internal structure of the two cyst form is similar.

Animals↗
PubMed1997

Observations on the surface coat of Blastocystis hominis.

The surface coat of Blastocystis hominis was studied in the electron microscope. In some cells the surface coat was seen in two layers; the external layer was more electron-dense and fragmented than the internal layer. It appears that the surface coat is being continuously formed by the parasite and shed in the environment. The fibrillar material of the surface coat attaches to the bacteria, in some cases, completely surrounding them, possibly causing cytoplasmic damage to the bacterial cell as indicated by loss of electron density.

Animals↗
PubMed1997

The spectrum of chronic lymphoproliferative disorders in Hong Kong. A prospective study.

We report the incidence of the chronic lymphoproliferative disorders evolving with leukaemia in Hong Kong. Our findings demonstrate that B cell malignancies are significantly more frequent than mature T cell neoplasms, a picture similar to that seen in Western countries but different from other Eastern countries, eg Japan, where T cell malignancies are more frequent. In contrast to the West, where chronic lymphocytic leukaemia (CLL) is the most common disorder, in Hong Kong there is a clear predominance of B cell lymphomas in leukaemic phase accounting for two-thirds of the cases and particularly those displaying lymphoplasmacytic features or with villous lymphocytes. CLL in Hong Kong has similar clinical and laboratory features to the disease in patients from the West. Distinct disease categories, rare in the West such as the variant form of hairy cell leukaemia and T cell prolymphocytic leukaemia, are also documented. It is unclear whether the differences in prevalence of disease subtypes between Hong Kong and the West relate to different genetic background or environmental factors determinant of the development or progression of the leukaemia. Further studies investigating the genetic/molecular lesions may help to clarify whether the aetiopathogenesis of the lymphoid disorders in Hong Kong is similar to that of Western countries.

Adult↗
PubMed1997

The use of endoscopy in liver diseases.

The use of fibre-optic endoscopy has greatly facilitated the management of some patients with chronic liver disease. Upper endoscopy plays a pivotal role in the diagnosis and management of oesophageal and gastric varices. With the use of reflectance septrophotometry, gastroduodenal mucosal haemoglobin concentration and oxygen saturation can be more precisely measured. Recently, it has been shown that acute gastroduodenitis is associated with a lower pre-treatment mucosal oxygen concentration in the antrum and the first part of the duodenum. Endoscopic ultrasound is increasingly being used to detect varices and in the staging of gastrointestinal tumours. Endoscopic retrograde cholangiopancreatography plays an important role in the diagnosis of recurrent pyogenic cholangitis and endoscopic sphincterotomy is a useful form of treatment. Laparoscopy, with the aid of ultrasound and biopsy is helpful in staging chronic liver disease, identifying focal lesions, and diagnosing peritoneal disease.

Journal Article↗