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Biomedical subjects

S S Choi

Publications and source records attributed to S S Choi.

At least 19 recordsLinked to original sources
PubMed1999

Clinical applications of transiently evoked otoacoustic emissions in the pediatric population.

Our objectives were 1) to determine whether transiently evoked otoacoustic emissions (TEOAEs) are affected by the status of the tympanic membrane (TM) and middle ear (ME) as determined by clinical examinations and tympanograms; 2) to determine the efficacy of TEOAEs in detecting hearing loss; and 3) to determine the relative effects of the ME status and hearing loss on TEOAEs. In a prospective observational study in a tertiary care children's hospital, 89 patients (169 ears; 9 ears eliminated from analyses) were examined by 2 attending pediatric otolaryngologists for otologic conditions and underwent audiologic evaluations including TEOAEs from August 1994 through May 1995. The main outcome measures were presence or absence of TEOAE whole reproducibility (WR) and reproducibility (R) at 2 kHz. Statistical analyses showed that of the 8 ME and TM conditions evaluated (normal, TM perforation, pressure equalization [PE] tube, TM retraction, tympanosclerosis, TM atrophy, ME effusion, surgery other than PE tube insertion), only the presence of ME effusion and normal examination findings had a significant effect on the results of WR and R at 2 kHz. Of the 6 different types of tympanograms evaluated (A, B, C, AD, As, B with large volume), type A, B, and C tympanograms had a significant effect on WR and types A and B had a significant effect on R at 2 kHz. Hearing losses > or = 25 dB hearing level (HL) at any of the 5 frequencies (0.25, 0.5, 1, 2, and 4 kHz) were well predicted by the absence of WR and R at 2 kHz. When clinical examination and impedance data were evaluated simultaneously with hearing status, hearing status had a greater effect on WR and R at 2 kHz. We conclude that type B and C tympanograms and the presence of ME effusion (which reflect abnormal ME status) have an adverse effect on TEOAEs. However, the presence of hearing loss is the most significant predictor of TEOAE results. The TEOAE WR and R at 2 kHz are effective in identifying patients with normal hearing and with hearing losses > or = 25 dB HL.

Acoustic Impedance Tests↗
PubMed1998

Expression of Bfl-1 in normal and tumor tissues: Bfl-1 overexpression in cancer is attributable to its preferential expression in infiltrating inflammatory cells.

Bfl-1, a member of the Bcl-2 gene family, blocks p53-mediated apoptosis and has oncogenic transforming activity. In normal tissues, the transcript of Bfl-1 is expressed abundantly in bone marrow and at a low level in several other tissues. In previous experiments, elevated expression of Bfl-1 was observed by Northern analysis of stomach cancer samples. To study the role of Bfl-1 in normal cell development and in tumorigenesis, we have analyzed the expression of Bfl-1 in normal and tumor tissues by the in situ hybridization technique. The Bfl-1 transcript was detected in the white pulp of the spleen and in the germinal center of lymphatic tissues. In tumor tissues, its expression was preferentially detected in infiltrating inflammatory cells rather than in cancer cells, suggesting that Bfl-1 is not involved in tumorigenesis.

Colonic Neoplasms↗
PubMed1997

Ideal timing of pediatric laryngotracheal reconstruction.

OBJECTIVE: To determine whether there is an ideal age at which to perform a laryngotracheal reconstruction (LTR) in the pediatric population. DESIGN: Prospective observational study. SETTING: Tertiary care children's hospital. PATIENTS: Forty-eight patients aged 48 months or younger with laryngotracheal stenosis who underwent 50 LTRs from October 1, 1986, to June 30, 1995. Patients were divided into 2 groups: group 1, aged 8 through 24 months (22 patients); group 2, aged 25 through 48 months (26 patients). INTERVENTION: Endoscopy and LTR. MAIN OUTCOME MEASURES: Successful decannulation. RESULTS: Statistical analysis showed that (1) patients in group 2 had more severe degree of laryngotracheal stenosis as determined by duration of stenting with no difference in multiple sites of stenosis or type of repair required to correct laryngotracheal stenosis and (2) patients in group 2 were more likely to have successful decannulation. CONCLUSION: Laryngotracheal reconstruction at a younger age (< 25 months) is important for a child's speech and language development as well as for eliminating the morbidity and mortality associated with a tracheotomy. However, LTR at a younger age is associated with a higher risk of failure despite lesser degree of pathology. Therefore, although we still recommend LTR at a younger age since it may be beneficial for a child's speech and language development and avoidance of tracheotomy complications, this recommendation may be at the price of LTR failure and requirement for revision procedures.

Age Factors↗
PubMed1997

Management of oropharyngeal trauma in children.

OBJECTIVE: To determine the indications for admission, requisite imaging studies, and urgent medical or surgical intervention. DESIGN: We retrospectively reviewed the charts of 26 children (age range, 5 months to 14 years) who were seen by the otolaryngology service in the emergency department at the Children's National Medical Center, Washington, DC, from 1985 to 1993 and who were diagnosed as having oropharyngeal trauma. We specifically looked for common findings in the history and physical examination on initial presentation to predict the necessary steps in evaluation and management. SETTING: Tertiary care pediatric referral center. RESULTS: Indications for admission were (1) concern about neurologic injury, (2) concern about vascular injury, (3) radiographic evidence of retropharyngeal free air or abscess, (4) pneumomediastinum, and (5) unreliable adult supervision at home. Six patients required surgery; 3 underwent retropharyngeal aspiration or incision and drainage procedures; 2 required neck explorations; and 1, who had an impaled foreign body in the parapharyngeal space, underwent surgical extraction. There were no vascular, neurologic, or other permanent injuries. CONCLUSIONS: Oropharyngeal trauma may result in palatal and posterior pharyngeal wall injury requiring closure of lacerations and management of retropharyngeal free air. Rarely does an injury lead to retropharyngeal abscess or significant pneumomediastinum. Lateral oropharyngeal injuries require increased concern about potential neurovascular impairment. However, neither the mechanism of injury nor the degree of injury correlates with the potential for neurovascular sequelae. Since neurovascular involvement may not become clinically apparent until days or weeks after the incident, admission for observation alone should be based on the distance from the patient's home to the hospital and on the level of reliable adult supervision. Indications for medical and surgical treatment of internal carotid artery thrombosis remain controversial.

Adolescent↗
PubMed1997

Relative incidence and alternative approaches for surgical drainage of different types of deep neck abscesses in children.

OBJECTIVES: To determine the relative frequency of retropharyngeal abscesses (RPAs) vs lateral pharyngeal abscesses (LPAs) and to analyze alternative approaches for surgical drainage. DESIGN: Retrospective chart review. SETTING: Tertiary care children's hospital. PATIENTS: Seventy pediatric patients who were evaluated, admitted, and treated for presumed deep neck abscesses (RPAs and LPAs) between January 1, 1986, and December 31, 1996. INTERVENTION: Intravenous antibiotic therapy and surgical drainage. MAIN OUTCOME MEASURE: Clinical resolution of the abscess. RESULTS: Fifty-eight patients were evaluated with computed tomographic scan. Thirteen of these patients did not have surgical intervention. Of 12 patients diagnosed as having an isolated RPA, all had intraoral surgical drainage and 9 had evidence of pus at surgery. Twenty-one patients had an isolated LPA. Sixteen of these underwent intraoral drainage and 5 underwent external drainage. Purulence was found at surgery in 14 and 2 patients, respectively. The remaining 12 patients had a combination of RPA and LPA. Eight patients underwent intraoral drainage, and 4 patients required both intraoral and external approaches. Purulence was found at surgery in 5 and 4 patients, respectively. Of the 12 patients who were not evaluated with computed tomographic scan, two thirds were treated prior to 1987. Six of these 12 patients underwent surgical drainage via an intraoral approach, and 4 of the 6 patients had pus. The remaining 6 improved without surgery. CONCLUSIONS: Most deep neck abscesses in children are located in the retropharyngeal or in the lateral pharyngeal space medial to the great vessels. Therefore, most can be managed successfully with intraoral rather than external drainage. External approaches are better reserved for those abscesses that are lateral to the great vessels or that involve multiple spaces. In this patient population, LPAs were more commonly seen than RPAs.

Abscess↗
PubMed1997

Pneumomediastinum and pneumothorax from blunt cervical trauma in children.

Minor blunt cervical injuries in children are relatively common occurrences leading to serious sequelae in only rare circumstances, yet sufficient impact of even a seemingly minor event may lead to a significant posterior tracheal wall laceration, resulting in pneumomediastinum with or without pneumothorax. Three cases demonstrate how the mechanism of injury does not always match either the severity of initial presentation or the consequent necessary level of emergent management. Pneumomediastinum without pneumothorax often can be treated conservatively; however, the onset of massive pneumomediastinum and pneumothorax may necessitate both tracheotomy and tube thoracostomy as initial treatment.

Adolescent↗
PubMed1997

Role of mRNA termination in regulation of ermK.

To study the role of mRNA termination in the regulation of ermK, we introduced mismatches into terminators by in vitro mutagenesis. In wild-type ermK, only truncated transcription products were detected in the absence of induction. In contrast, only the full-length transcript was synthesized in the terminator 1 and terminator 2 double mutants, even in the absence of erythromycin. These results indicate that the expression of ermK is primarily regulated by transcriptional attenuation rather than translational attenuation. We also tested the possible contribution of translational attenuation control to the regulation of ermK by constructing a triple mutant (terminator 1 plus terminator 2 plus the methylase Shine-Dalgarno region). A higher level of beta-galactosidase synthesis was seen in the triple mutant. Therefore, unlike with previously described attenuators, it can be concluded that both transcriptional and translational attenuation contribute to the regulation of ermK, although transcriptional attenuation plays a larger role.

Bacillus subtilis↗
PubMed1997

Cytotoxicity and multinucleate giant cell formation in Chinese hamster lung fibroblast caused by crocidolite and chrysotile.

The mechanism of carcinogenic action of asbestos remains unclear but the physical properties of the fiber appear to be important in this process. Asbestos may cause multinucleate giant cell formation primarily by interfering with the normal course of mitosis. We evaluated the cytotoxicity and multinucleate giant cell formation induced by crocidolite and chrysotile in Chinese hamster lung fibroblast (V79 cell) with observation of phagocytic activities. Asbestos fibers were rapidly ingested by V79 cells and most fibers were inside the cells. Cytotoxicity was evaluated by observing inhibition of V79 cell proliferation with trypan blue exclusion test. For determination of frequency of multinucleate giant cells, the cells were treated with different doses of crocidolite or chrysotile for 72 hours. Crocidolite and chrysotile induced cytotoxicity in V79 cells in a dose-dependent manner. The pattern of inhibition of cell proliferation is similar for both types of fibers, but chrysotile was more potent at the highest level (20.0 micrograms/ml) of fiber concentration. There was a good relationship (regression coefficientcrocidolite = 0.02, P < 0.01; regression coefficientchrysotile = 0.04, P < 0.01) between the dose of both asbestos fibers and the frequency of multinucleate giant cells. Chrysotile was again more potent at inducing multinucleate giant cells in higher levels of fiber concentrations. We found that asbestos fibers were cytotoxic after phagocytosis and induced multinucleate giant cells by interfering mitosis.

Animals↗
PubMed1996

A bacterial artificial chromosome-based framework contig map of human chromosome 22q.

We have constructed a physical map of human chromosome 22q using bacterial artificial chromosome (BAC) clones. The map consists of 613 chromosome 22-specific BAC clones that have been localized and assembled into contigs using 452 landmarks, 346 of which were previously ordered and mapped to specific regions of the q arm of the chromosome by means of chromosome 22-specific yeast artificial chromosome clones. The BAC-based map provides immediate access to clones that are stable and convenient for direct genome analysis. The approach to rapidly developing marker-specific BAC contigs is relatively straightforward and can be extended to generate scaffold BAC contig maps of the rest of the chromosomes. These contigs will provide substrates for sequencing the entire human genome. We discuss how to efficiently close contig gaps using the end sequences of BAC clone inserts.

Cell Line↗
PubMed1996

Prostaglandin-E2 regulation of tumor necrosis factor receptor release in human monocytic THP-1 cells.

Recent in vitro studies indicate that tumor necrosis factor (TNF) production in human monocytic THP-1 cells is suppressed by action of arachidonic acid metabolite prostaglandin-E2 (PGE2). PGE2 stimulation of human monocytic cell line THP-1 demonstrates that PGE2 not only regulates TNF activity at production levels, but does so through the release of two soluble TNF receptors (BP-55, BP-75) as well. PGE2 can thus exert a regulatory effect on TNF biologic activity by interfering with its ability to reach cell membrane receptors. THP-1 cells were activated with PGE2 for either 2- or 6-hr time periods, and the supernatants subsequently tested by ELISA to quantitate the levels of soluble receptor released. In addition, we examined mechanisms of receptor shedding by investigating the rate of membrane internalization and the role of serine proteases. PGE2-stimulated THP-1 cells showed soluble 55- and 75-kDa TNF receptor release levels which exceeded that of spontaneous release at both 2- and 6-hr activation periods. The numbers of both membrane TNF receptors were significantly upregulated as well in PGE2-activated cells, whereas the levels of 55- and 75-kDa TNF receptor mRNA levels remained unchanged. Thus, PGE2 induces TNF receptor release primarily at posttranscriptional levels. Inhibition of serine proteases with Pefabloc, a phenylmethylsulfonyl fluoride analog, resulted in the inhibition of both spontaneous and PGE2-stimulated release. Treatment of THP-1 cells with N-ethylmaleimide and low-temperature incubation, both known to block membrane internalization, also blocked spontaneous and PGE2-induced release. Internalization and cleavage by protease are therefore critical factors in PGE2-induced release of soluble TNF receptor shedding.

Animals↗
PubMed1996

The effect of gastroesophageal reflux on laryngotracheal reconstruction.

OBJECTIVES: To determine the need for preoperative evaluation for gastroesophageal reflux disease (GERD) in all children undergoing laryngotracheal reconstruction (LTR) and to assess the effect of GERD on the outcome of LTR. DESIGN: Prospective, single-blind observational study. SETTING: Tertiary care children's hospital. PATIENTS: Seventy-four pediatric patients with laryngotracheal stenosis who underwent LTR at the Children's National Medical Center, Washington, DC, from October 1, 1986, through August 31, 1994. INTERVENTION: Evaluation for and treatment of GERD, LTR, endoscopy, and removal of granulation tissue. MAIN OUTCOME MEASURES: Successful decannulation and number of endoscopies required to remove laryngeal and tracheal granulation tissue. RESULTS: Seventy-four patients underwent 82 LTRs. The senior surgeon was blinded to the status of GERD evaluation and treatment. Four groups were identified: 37 patients (40 LTRs) with no preoperative evaluation for GERD; 10 patients (11 LTRs) with normal findings on preoperative evaluation for GERD; seven patients (nine LTRs) with abnormal findings on preoperative evaluation for GERD but who failed to receive appropriate treatment; and 20 patients (22 LTRs) with abnormal findings on preoperative evaluation for GERD who received appropriate therapy. Severity and extent of stenosis as determined by multicentricity of stenosis, type of repair, and duration of stent were similar in the four groups. The effect of GERD and its treatment on the outcome of LTR was measured by the number of endoscopies necessary for removal of granulation tissue following reconstruction and successful decannulation. Statistical analyses indicate that (1) all children do not require preoperative evaluation for GERD; (2) neither the presence of GERD nor its treatment are major factors in determining the outcome of LTR. CONCLUSION: Preoperative evaluation for GERD and its treatment do not favorably affect the outcome of LTR.

Analysis of Variance↗
PubMed1996

Laryngomalacia. The search for the second lesion.

OBJECTIVES: To determine the necessity of rigid endoscopy in the diagnosis and management of laryngomalacia and its associated synchronous airway lesions (SALs), to analyze the incidence of SALs associated with laryngomalacia and their significance, and to determine the need for epiglottoplasty in management of laryngomalacia. DESIGN: Retrospective medical chart review. SETTING: Tertiary care children's hospital. PATIENTS: Two hundred thirty-three patients with a primary diagnosis of laryngomalacia on flexible fiberoptic laryngoscopy treated at the Children's National Medical Center, Washington, DC, from January 1, 1984, to June 30, 1994. INTERVENTION: Evaluation and treatment of laryngomalacia and associated SAL by flexible fiberoptic laryngoscopy, radiographic studies, rigid endoscopy, and other surgical procedures. MAIN OUTCOME MEASURES: Resolution of airway symptoms from laryngomalacia and associated SAL. RESULTS: Ninety patients (38.6%) underwent rigid endoscopy, and 12 patients (5.2%) required epiglottoplasty. Synchronous airway lesions were discovered in 44 patients (18.9%). Eleven patients (4.7%) had SALs that wre considered clinically significant; nine (3.9%) of these required surgical intervention. CONCLUSIONS: Rigid endoscopy in evaluation of an infant with laryngomalacia is rarely necessary. Clinically significant SALs requiring surgical intervention are uncommon. Surgical intervention for laryngomalacia also is rarely necessary.

Airway Obstruction↗
PubMed1996

Transaxillary minithoracotomy versus video-assisted thoracic surgery for spontaneous pneumothorax.

BACKGROUND: Although management of spontaneous pneumothorax by video-assisted thoracic surgery (VATS) has generally shown superior clinical results to thoracotomy, management of spontaneous pneumothorax by transaxillary minithoracotomy (TAMT) has also shown good clinical results. The objective of this study was to compare the clinical results of VATS and TAMT in treating spontaneous pneumothorax. METHODS: Sixty-six patients, aged 13 to 81 years, with recurrent, persistent or contralateral spontaneous pneumothorax were involved in this study. Thirty-six patients were treated by VATS and 30 by TAMT. The operating time, the amount of analgesics used on the first postoperative day, the duration of the indwelling chest tube, and the number of recurrences after operation were compared. The follow-up periods of both procedures were from 6 to 24 months. RESULTS: Of the 66 patients, 64 were male and 2 were female. The duration of operation, from start of skin incision to insertion of chest tube, was 91.2 +/- 36.8 minutes in VATS and 86.3 +/- 40.9 minutes in TAMT (p = 0.6061). The amount of analgesics (keptoprofen) used was 1.9 +/- 2.3 ampules in VATS and 2.1 +/- 2.9 ampules in TAMT (p = 0.0883). The duration of indwelling chest tube was 5.0 +/- 4.0 days in VATS and 4.3 +/- 2.1 days in TAMT (p = 0.3707). The number of recurrences after operation was 4 in VATS and none in TAMT. CONCLUSIONS: There were no advantages of VATS over TAMT for management of recurrent, persistent, or contralateral spontaneous pneumothorax in regard to the operating time, the amount of analgesics used on the first postoperative day, the duration of the indwelling chest tube, and the number of postoperative recurrences in patients with apical bullae.

Adolescent↗
PubMed1996

Speaking clearly for the hard of hearing IV: Further studies of the role of speaking rate.

The contribution of reduced speaking rate to the intelligibility of "clear" speech (Picheny, Durlach, & Braida, 1985) was evaluated by adjusting the durations of speech segments (a) via nonuniform signal time-scaling, (b) by deleting and inserting pauses, and (c) by eliciting materials from a professional speaker at a wide range of speaking rates. Key words in clearly spoken nonsense sentences were substantially more intelligible than those spoken conversationally (15 points) when presented in quiet for listeners with sensorineural impairments and when presented in a noise background to listeners with normal hearing. Repeated presentation of conversational materials also improved scores (6 points). However, degradations introduced by segment-by-segment time-scaling rendered this time-scaling technique problematic as a means of converting speaking styles. Scores for key words excised from these materials and presented in isolation generally exhibited the same trends as in sentence contexts. Manipulation of pause structure reduced scores both when additional pauses were introduced into conversational sentences and when pauses were deleted from clear sentences. Key-word scores for materials produced by a professional talker were inversely correlated with speaking rate, but conversational rate scores did not approach those of clear speech for other talkers. In all experiments, listeners with normal hearing exposed to flat-spectrum background noise performed similarly to listeners with hearing loss.

Adult↗
PubMed1995

A novel Bcl-2 related gene, Bfl-1, is overexpressed in stomach cancer and preferentially expressed in bone marrow.

Programmed cell death (apoptosis) is an active process which is genetically encoded and plays an important role in several cellular activities such as embryonic development, deletion of autoreactive T-cells and homeostasis. Several genes regulating apoptosis have been reported, including p53, one of the tumor suppressor genes, c-myc, one of the proto-oncogenes, and various kinds of Bcl-2 related genes. A new cDNA clone which is homologous to Bcl-2, named as Bfl-1 were isolated from a human fetal liver at 22 week of gestation. This clone was identified by computer analysis of random cDNA sequences that were obtained in an effort to expand the expressed sequence tag (EST) databases to be used for human genome analysis. The homology was recognized by 72% amino acid identity to the murine A1 gene, a member of the Bcl-2-related genes. The homology to the BH1 and BH2 domains of Bcl-2 was especially significant, suggesting that Bfl-1 is a new member of the Bcl-2-related genes. Bfl-1 is abundantly expressed in the bone marrow and at a low level in some other tissues. Interestingly, a correlation was noted between the expression level of Bfl-1 gene and the development of stomach cancer in eight sets of clinical samples. It is conceivable that Bfl-1 is involved in the promotion of the cell survival in the stomach cancer development or progression.

Amino Acid Sequence↗
PubMed1995

Invasive Aspergillus sinusitis in pediatric bone marrow transplant patients. Evaluation and management.

OBJECTIVES: To evaluate the following: the incidence of invasive Aspergillus sinusitis (AS); the value of surveillance nasal cultures and screening radiologic studies in predicting AS; the clinical criteria used to decide on surgical biopsy in patients suspected of having AS; the surgical and medical management of AS; and the outcome of AS in the peritransplantation period of children who underwent bone marrow transplantation. DESIGN: Retrospective medical chart review. SETTING: Tertiary care children's hospital. PATIENTS: Eighty pediatric patients who underwent bone marrow transplantation for a variety of refractory malignant neoplasms or lymphohematopoietic disorders at the Children's National Medical Center, Washington, DC, from April 1, 1988, to September 30, 1993. INTERVENTION: Diagnostic surgical biopsies, surgical débridement, and treatment with amphotericin B. MAIN OUTCOME MEASURE: Resolution of AS and discharge from the hospital. RESULTS: Seventy-two patients had screening sinus radiographs, 27 of which showed abnormalities. Aspergillus sinusitis developed in three of the patients with abnormal screening radiographs. Fifty-eight patients had screening nasal cultures. One culture was positive for Aspergillus, and histopathologically proved AS developed in this patient. Twelve diagnostic biopsies were done in nine patients. Three biopsy specimens showed histopathologic evidence of AS. The three patients with AS were successfully treated with aggressive surgical and medical therapy and were discharged from the hospital. CONCLUSION: The incidence of AS was 4% (3/80) in the patients who underwent bone marrow transplantation. Screening radiographs, while not a good predictor of AS, have a role in evaluation of patients undergoing bone marrow transplantation to define preexisting sinus disease. Screening nasal cultures do not reliably predict AS. When AS is suspected and diagnostic biopsy is considered, the seven clinical criteria outlined in this article should be used. Survival of immunocompromised patients with AS requires early diagnosis and aggressive surgical and medical therapy.

Adolescent↗
PubMed1995

Construction of a gene expression profile of a human fetal liver by single-pass cDNA sequencing.

We have obtained an overall gene expression profile of a human fetal liver by sequencing the 5' ends of random cDNA clones from an unbiased cDNA library. As a result, many novel genes that might be related to liver growth and hemopoiesis have been identified. Poly (A)+ RNA was purified from the liver of a human fetus obtained at the 22nd week of gestation, and a directional library was constructed with oligo d(T)-primed cDNAs synthesized without any normalizing procedures. The 5' end of each randomly chosen clone was sequenced by the dideoxy-chain termination methods, and each sequence was used for homology search in the public databases such as GenBank, SWISS-PROT, and PIR. Of 1231 random cDNA clones analyzed, 697 clones representing 204 different transcripts (57%), were identical to previously known human genes. The spectrum of the genes in this category reflected well the physiological characteristics of the fetal liver, a combination of hepatic and hemopoietic functions. About 4% of the clones represented novel gene transcripts with significant homologies to known genes of human or other organisms. These included several genes that are known to be involved in cellular differentiation and/or proliferation. About 25% of the clones had no statistically significant match to any known genes. In summary, we have identified 546 different gene transcripts consisting of 204 known human genes, 42 homologous genes, and 300 unknown genes. Thus, this approach appears to be a highly efficient way to identify novel genes of biological interest.

Base Sequence↗