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Biomedical subjects

H S Chang

Publications and source records attributed to H S Chang.

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

Environmental measurements of total dust and fiber concentration in manufacturer and user of man-made mineral fibers.

Man-made mineral fibers (MMMF), most of which are referred to as man-made vitreous fibers (MMVF), are mostly amorphous silicates manufactured from glass, rock, or other minerals. Analysis for MMMF have been restricted largely to the measurement of total airborne mass concentrations, but more recently to the determination of airborne fiber levels by phase contrast optical microscopy. In Korea, many small factories are related with manufacturing and using MMMF without any special evaluation of environmental measurements. Though MMMF are known as the substitute of asbestos and their toxicity are regarded as very low, MMMF do not totally excluded from the respiratory and/or skin diseases now. Therefore, we evaluated the environments of many workplaces with total dust and fiber concentration. Most dust and fiber concentrations were below threshold limit value (TLV) at various industries and working processes. However, these data showed a slight relationship between total dust and fiber concentration.

Air Pollutants, Occupational↗
PubMed1999

Theoretical comparison of surgery and radiosurgery in cerebral arteriovenous malformations.

OBJECT: Management of patients with cerebral arteriovenous malformations (AVMs) is controversial. Excellent surgical results are obtained in patients with low Spetzler-Martin grades, whereas radiosurgery offers a good alternative with its high obliteration rate. In the absence of randomized studies, physicians must choose a treatment plan based on the currently available data. To support this decision-making process, a mathematical model designed to describe patient survival rates after each treatment option was developed. METHODS: The theoretical survival curve in patients undergoing conventional surgery, radiosurgery, or observation was calculated. Theoretical life expectancies in patients with AVMs who presented at various initial ages were calculated for each treatment strategy. A systematic method was also developed to compare the estimated risks of various treatment combinations. CONCLUSIONS: Conventional surgery and radiosurgery definitely produced better survival rates than observation. In the comparison of surgery with radiosurgery, radiosurgery was equivalent to surgery with a combined morbidity and mortality rate of approximately 7% for a 20-year-old patient with an unruptured cerebral AVM. Data for other patient ages and treatment combinations are tabulated for use in determining the best treatment strategy. The authors believe that their analysis will provide logical support for the decision-making process involved in the treatment of patients with cerebral AVMs.

Adult↗
PubMed1999

The effect of orthodontic treatment on salivary flow, pH, buffer capacity, and levels of mutans streptococci and lactobacilli.

Fixed orthodontic treatment has been shown to cause an increased incidence of enamel demineralisation. The purpose of this study was to investigate the changes in stimulated salivary flow rate, pH, buffer capacity, and the levels of mutans streptococci (MS) and lactobacilli in patients undergoing therapy with fixed orthodontic appliances. Saliva samples, plaque index scores and dietary histories were taken from 21 sequential patients before the start of treatment, and one month and three months after placement of brackets and bands. There was a statistically significant increase in stimulated salivary flow rate, pH, buffer capacity, plaque index scores, and in the levels of MS and lactobacilli after three months of active treatment. It is postulated that the balance between the cariogenic challenge posed by high levels of MS and lactobacilli, and the reparative effects of concurrent increases in salivary flow rate, pH and buffer capacity, determines the likelihood of mineral loss or gain over time. A failure to follow basic preventive measures may increase the risk for some patients of enamel decalcification during orthodontic treatment with fixed appliances.

Adolescent↗
PubMed1998

Effects of basic fibroblast growth factor on irradiated porcine skin flaps.

OBJECTIVE: To determine the vascular and collagen effects of supplemental basic fibroblast growth factor (bFGF) in irradiated porcine skin flaps. INTERVENTION: Animals were subjected to 2 fractions of 650 cGy orthovoltage radiation. Following this, the skin flaps were administered bFGF intracuticularly for 6 days before and after surgery. The animals were sacrificed 3 weeks after the start of bFGF administration. Tissues were analyzed for vascularity, collagen content, wound-breaking strength, and histopathological analysis. RESULTS: The bFGF-treated flaps showed a 62% increase in vascularity compared with controls (10.4%+/-2.4% vs 6.43%+/-2.27%; P<.05). The bFGF flaps had a significantly lower collagen concentration compared with control flaps when measured by hydroxyproline content (0.0619+/-0.0211 nm/microg vs 0.0784+/-0.0150 nm/microg). Wound-breaking strength was not significantly different, although the bFGF flaps had a trend toward lower breaking strength. Histologically, the bFGF-treated flaps showed increased cellularity, fibroblasts, and extracellular mucopolysaccharides compared with controls. CONCLUSIONS: This study provides evidence that supplemental bFGF can increase vascularity to skin flaps in previously irradiated porcine skin tissue. Histologically, radiation did not prevent the angiogenic effect of bFGF.

Animals↗
PubMed1998

Sclerotherapy with OK-432 for recurrent cystic thyroid nodule.

We have adopted OK-432 as a sclerosing agent in the treatment of cystic predominant thyroid nodules and have analyzed our findings to assess the efficacy of intralesional instillation of OK-432. From 1992 through 1993, 48 patients with recurrent or progressive cystic thyroid nodules after 2 or 3 aspirations alone, and whom were cytologically negative for malignancy, were used for this study. The OK-432 solution was prepared by dissolving 0.1 mg of OK-432 in 2 ml of physiologic saline and it was instilled in the amount of 1/10-to-1/5 of the aspirated cystic fluid. A repeated course of therapy was given up to 3 times when sufficient resolution was not obtained 4-to-6 weeks after treatment. The mean number of treatment sessions per patient was 1.5. Throughout the follow-up period from 30-to-45 months (mean, 38 months), 32 (66.7%) patients experienced an almost complete disappearance (< 0.05 cm in diameter) of the cystic lesion, and 12 (25%) patients responded partially by having it decrease by more than half (> 0.5 cm in diameter) of the initial cyst size, and none of these patients required further treatment. The remaining 4 (8.3%) patients showed insufficient resolution despite 3 courses of therapy and 2 of these patients underwent thyroidectomy, in which the lesion proved benign in both cases. All of the patients tolerated the sclerotherapy well. No significant local complications attributed to this treatment were observed. However, a low-grade fever was observed in 26 (54.2%) patients for 2 to 5 days after instillation, which subsided with symptomatic treatment. On the basis of our experience, OK-432 sclerotherapy appears to be safe, simple and effective, and can be a useful alternative treatment for cystic thyroid nodules.

Adolescent↗
PubMed1997

Myasthenia gravis and Charcot-Marie-Tooth disease type 1A: an unusual combination of diseases.

Concurrence of myasthenia gravis (MG) and Charcot-Marie-Tooth type 1 (CMT1A) neuropathy is rare. We describe a 60-year-old woman with MG and genetically proved CMT1A. The fluctuating ocular symptoms and proximal limb weakness were markedly improved by pyridostigmine treatment. Recognition of the possible association of MG and CMT1A in the same patient is important because the therapeutic result is rewarding.

Charcot-Marie-Tooth Disease↗
PubMed1997

Enamel demineralization during orthodontic treatment. Aetiology and prevention.

The aetiology of enamel demineralization during fixed orthodontic treatment and its sequelae are discussed. A summary is given of the various methods available to assess the risk of demineralization prior to active treatment. The best preventive strategy would appear to be an assessment of risk factors prior to banding, coupled with fluoride rinses, regular reinforcement of oral hygiene, and dietary advice throughout the course of treatment.

Cariostatic Agents↗
PubMed1996

Local application of anti-NGF blocks the collateral sprouting in rats following chronic constriction injury of the sciatic nerve.

Systemic administration of anti-nerve growth factor (NGF) antibodies can block nociceptive fiber sprouting into denervated adult rat skin. However, the effect of local application of anti-NGF on collateral sprouting in rats caused by chronic constriction injury (CCI) has not been well studied. We investigated the influence of local anti-NGF on collateral sprouting caused by CCI of the rat's sciatic nerve. Using a dye-labeled plasma extravasation technique, we can easily evaluate the extent of collateral sprouting by the clearly defined blue coloration area. Our results showed that local application of anti-NGF either in a high or low dose significantly prevented the spread of collateral sprouting from the saphenous nerve into the sciatic innervation territory. In contrast, distilled water did not show a significant block of the saphenous nerve collateral sprouting. Our study suggests that collateral sprouting is dependent on the local availability of NGF by the nearby intact cutaneous nerve fibers.

Animals↗
PubMed1996

Positive elements in the laminin gamma 1 gene synergize to activate high level transcription during cellular differentiation.

Transcription of the murine laminin gamma 1 gene is activated during retinoic acid/cAMP induced differentiation of F9 embryonal carcinoma cells. Positive transcription control elements associated with two DNase I hypersensitive regions in the large first intron of the gene have been identified which confer a differentiation response on the laminin gamma 1 promoter. However, the kinetics of transcriptional activation suggest each DNA region interacts with transcription factors appearing at different times during differentiation. Synergy between the two regions in cis causes high level activation.

Animals↗
PubMed1996

Osteoradionecrosis of the anterior cranium.

Osteoradionecrosis occurs in approximately 10% to 15% of patients following radiation therapy for head and neck cancer. In these patients, it is most commonly reported in sites involving the mandible, but it has also been reported in the maxilla, sphenoid, and temporal bones. The majority of these cases are related to some type of trauma such as dental extraction or intraoral biopsies. However, approximately 40% of these entities occur spontaneously and are felt to be secondary to cell kill in intermediate tissues such as bone and periosteum. Our literature review yielded no previously reported cases of osteoradionecrosis involving the anterior cranium. The following two cases present patients who experienced osteoradionecrosis of their frontal bone flaps following subcranial approaches for tumor resection. Both patients suffered from carcinomas involving the ethmoid sinuses; one tumor was a moderately well-differentiated squamous cell carcinoma, the other a mucinous adenocarcinoma. One patient's radiation therapy consisted of external beam photons; the other patient received external beam neutrons. Treatment for these patients, as well as possible causative factors regarding their osteoradionecrosis, are discussed.

Case Reports↗
PubMed1996

Tuberculous meningitis in patients with nasopharyngeal carcinoma.

Mycobacterial infection has been recognized as a complication in patients with malignancy. Tuberculous (TB) meningitis has not been reported in patients with nasopharyngeal carcinoma (NPC); it may have been overlooked or confused with the underlying malignancy or meningitis caused by other microorganisms. We describe the occurrence of culture-proven TB meningitis in 2 NPC patients. The time lag between the diagnosis of NPC and the occurrence of TB meningitis was 4 years in 1 patient and 6 years in the other. In both patients, the diagnosis of TB meningitis was delayed; they were initially treated for bacterial meningitis. Subsequent antituberculous chemotherapy was successful in 1 patient but failed in the other. Recognition of the infection is important for early diagnosis and proper treatment of this potentially fatal condition in patients with NPC.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1995

Cervical central cord syndrome involving the spinal trigeminal nucleus: a case report.

BACKGROUND: Central cord syndrome is a commonly encountered disease entity. Its underlying pathophysiology, however, is not well understood. METHODS: A 20-year-old patient with cervical injury with an atypical symptom of burning sensation in the face and neck area is reported. RESULTS: The initial burning sensation in the face retreated from the center towards the periphery according to the "onionskin" segmentation of facial dermatomes, which suggested some pathologic condition residing in the spinal trigeminal nucleus. CONCLUSIONS: The findings of this case suggest that the main locus of pathologic process of the central cord syndrome is in the gray matter rather than the white matter.

Adult↗
PubMed1995

Quantification of operative benefit for unruptured cerebral aneurysms: a theoretical approach.

The indications for surgery on unruptured asymptomatic cerebral aneurysms are still unclear. In this report, the authors use mathematical methods to attempt to quantify the benefit of surgery for unruptured aneurysms. Theoretical survival curves for either operative or conservative treatment were obtained by solving differential equations on the survival rate of a patient harboring an unruptured aneurysm. Patients' life expectancies were calculated as areas under these curves, and operative benefit was quantified as a gain in average life expectancy. To analyze morbidity, two concepts were introduced: premorbid survival rate and average premorbid survival period, and the operative gain of average premorbid survival period was calculated under certain assumptions. Larger operative benefit was observed in younger patients, with increasingly less benefit in the elderly. The operative gain of average life expectancy was 3.9 years for a 40-year-old patient, 2.4 years for 50, 1.3 years for 60, and 0.6 years for a 70-year-old. Quantified operative benefit is presented in a table for various patient ages, yearly rupture rates, and expected operative morbidity and mortality. This mathematical method would be useful to both surgeons and patients in making their decisions on surgery.

Actuarial Analysis↗
PubMed1995

Preoperative chemoradiotherapy for locoregional esophageal cancer: preliminary report.

Conventional treatment of esophageal cancer with surgery or radiation alone has afforded few long-term survivors. In order to improve outcome and determine the efficacy of a combined modality approach, this prospective study was performed. Between May 1993 and August 1994, 27 patients with loco-regional squamous cell carcinoma of the esophagus were treated with 2 courses of combined fluorouracil(1000mg per square meter of body-surface area daily for 5 days) and cisplatin(60mg per square meter on the first day)(D1 and D29) plus 48Gy of radiation therapy(RT) over 4 weeks. A transhiatal esophagectomy was planned 3-4 weeks after chemoradiotherapy. Twenty-seven patients completed a full course of therapy. Clinical response was evaluable in 26 patients: 22 patients showed improvement and relief from dysphagia, 2 patients stable disease, and 2 patients progression. One patient died of sepsis 1 week after completion of chemoradiotherapy and was excluded from the analysis. Ten patients underwent operation after chemoradiation. Of them, 5 showed complete histologic response. One of the complete responders died of recurred disease 8.5months after operation, the other 2 patients died of sudden death, and sepsis from wound deheiscence 7 days after operation, respectively. Nine patients refused operation because of excellent relief of their dysphagia and 6 patients were denied because of disease progression(2), fear of operations(2), old age and family member's disapprovement(1), and underlying liver cirrhosis(1). The last one patient was awaiting for operation. Of 13 patients who refused or denied operation, 6 patients finished further chemotherapy and radiatherapy(external radiation 1200 cGy+intracavitary radiation 900 cGy, 2 cycles of 5FU+cisplatin). This intensive preoperative chemoradiotherapy is feasible, and allows for a high rate of resectability and a high rate of complete pathologic response in a locoregional esophageal cancer. Toxicity is considerable but manageable. This study warrants further investigation.

Adult↗
PubMed1995

Fabry's disease: report of a case.

Fabry's disease is a rare hereditary disorder of glycosphingolipid metabolism. Its clinical features have not been adequately described in Taiwan. This paper reports on a 32-year-old man who had painful acroparesthesia, disseminated skin angiokeratomas, whorled corneal opacity, mitral valve prolapse and renal insufficiency. There was also involvement of the central motor pathways and the autonomic nervous system. A sural nerve biopsy showed loss of small myelinated and unmyelinated fibers. A reduced serum activity of alpha-galactosidase A and a large amount of urinary globotriaosylceramide confirmed the diagnosis of Fabry's disease.

Adult↗
PubMed1992

Chlorination of cellulose with N-chlorosuccinimide-triphenylphosphine under homogeneous conditions in lithium chloride-N,N-dimethylacetamide.

Microcrystalline cellulose was chlorinated with N-chlorosuccinimide-triphenylphosphine under homogeneous conditions in LiCl-N,N-dimethylacetamide. At the early stage of the reaction only replacement of the 6-hydroxyl groups with chlorine was observed, and 3-hydroxyl groups were replaced at a lower rate with Walden inversion. The effects of reaction conditions on the extent of chlorination were studied in detail. More than two equivalents of chlorination reagents per glucose residue were necessary to attain a high degree of substitution (ds) by chlorine, and the maximum ds attained was 1.86. Chlorinated disaccharides were found in the hydrolyzates of chlorodeoxycelluloses hydrolyzed under mild conditions, and their structures were studied by mass spectrometry.

Acetamides↗