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J Y Koo

Publications and source records attributed to J Y Koo.

At least 19 recordsLinked to original sources
PubMed2001

Structure of the Ba-induced Si(111)- (3 x 2) reconstruction.

The Ba/Si(111) surface, previously known as a 3 x 1 phase, is found to have a 3 x 2 periodicity and a semiconducting band gap. The substrate reconstructs into the honeycomb chain-channel (HCC) structure with Ba atoms in the channel, as in the alkali-metal-induced Si(111)-(3 x 1). However, the metal coverage is determined to be 1/6 monolayers, half the alkali-metal coverage. We propose that the structure and the metal coverage determined for the Ba adsorbate is universal for other alkaline-earth-metal adsorbates. With the alkali-metal-induced 3 x 1 case, our results lead to a rule that one donated electron per 3 x 1 surface unit is necessary to stabilize the HCC reconstruction of Si.

Journal Article↗
PubMed2001

Image reconstruction using the wavelet transform for positron emission tomography.

We conducted positron emission tomography (PET) image reconstruction experiments using the wavelet transform. The Wavelet-Vaguelette decomposition was used as a framework from which expressions for the necessary wavelet coefficients might be derived, and then the wavelet shrinkage was applied to the wavelet coefficients for the reconstruction (WVS). The performances of WVS were evaluated and compared with those of the filtered back-projection (FBP) using software phantoms, physical phantoms, and human PET studies. The results demonstrated that WVS gave stable reconstruction over the range of shrinkage parameters and provided better noise and spatial resolution characteristics than FBP.

Algorithms↗
PubMed2000

Tazarotene plus UVB phototherapy in the treatment of psoriasis.

BACKGROUND: The addition of oral retinoids to phototherapy may accelerate and enhance antipsoriatic efficacy, but can result in systemic adverse events and additional laboratory monitoring costs. OBJECTIVE: Our purpose was to determine whether the topical addition of tazarotene to UVB phototherapy improves efficacy without problems related to photosensitivity. METHODS: Bilateral target plaques were randomized to receive two of the following, one on each plaque once daily for 14 days: tazarotene 0.1% gel, vehicle gel, or no treatment. Thereafter, the same treatments were continued 3 times per week, plus UVB phototherapy 3 times per week, for an additional 67 days. RESULTS: Tazarotene plus UVB phototherapy achieved faster and significantly greater reductions in plaque elevation and scaling throughout treatment and achieved at least 50% improvement from the pretreatment baseline with a significantly lower median cumulative UVB exposure than vehicle gel plus UVB light or UVB phototherapy alone. No case of unusual photosensitivity was noted in the tazarotene plus UVB treatment group. CONCLUSION: The addition of tazarotene to UVB phototherapy improves and accelerates efficacy and maintains acceptable safety and tolerability.

Administration, Topical↗
PubMed2000

Concomitant administration of vitamin E does not change the side effects of isotretinoin as used in acne vulgaris: a randomized trial.

BACKGROUND: Isotretinoin treatment is frequently associated with reversible, dose-related side effects. Recent studies claimed that combining vitamin E with high-dose isotretinoin ameliorated isotretinoin-induced side effects. OBJECTIVE: The purpose of this double-blind, randomized study was to determine the effects of a fixed dose of vitamin E on the side effects of isotretinoin for treatment-resistant acne vulgaris. METHODS: One hundred forty subjects were randomly assigned to one of two treatment programs with isotretinoin (1 mg/kg) together with either vitamin E (800 IU/day) or a vitamin E placebo for 20 weeks. The incidence, severity, and duration of the side effects (eg, dry eyes, dry lips) were assessed. RESULTS: A fixed 800 IU/day dose of vitamin E did not improve the incidence, severity, or duration of side effects associated with isotretinoin (1 mg/kg per day). CONCLUSION: Vitamin E did not significantly ameliorate retinoid side effects when combined with 1 mg/kg of isotretinoin in the treatment of acne.

Acne Vulgaris↗
PubMed2000

Malignant gastroduodenal obstructions: treatment by means of a covered expandable metallic stent-initial experience.

PURPOSE: To investigate the technical feasibility and clinical effectiveness of a polyurethane-covered expandable nitinol stent in the treatment of malignant gastroduodenal obstructions. MATERIALS AND METHODS: The stent was constructed in-house by weaving a single thread of 0.2-mm nitinol wire in a tubular configuration and was covered with polyurethane solution by means of a dipping method. With fluoroscopic guidance, the stent was placed in 19 consecutive patients with malignant gastric outlet obstruction (n = 15) or duodenal obstruction (n = 4). All patients had severe nausea and recurrent vomiting, and their obstructions were inoperable. RESULTS: Stent placement was technically successful in all but one patient. After stent placement, symptoms improved in all but one patient, who had another stenosis at the proximal jejunum. One patient with stent placement in the second portion of the duodenum became jaundiced. During the mean follow-up of 11 weeks, stent migration occurred in five patients 1-4 days after the procedure. All patients with stent migration were treated by means of placing a second, uncovered nitinol stent. Two of these five patients showed recurrence of stricture because of tumor ingrowth; they underwent coaxial placement of a third, covered nitinol stent with good results. CONCLUSION: Placement of a polyurethane-covered expandable nitinol stent seems to be technically feasible and effective for palliative treatment of inoperable malignant gastroduodenal obstructions. Stent migration, however, is problematic and requires further investigation.

Adult↗
PubMed1999

Current consensus and update on psoriasis therapy: a perspective from the U.S.

Psoriasis is one of the more common forms of chronic dermatitis in the world. The latest U.S.-wide epidemiological study conducted by the author revealed a prevalence rate of 2.6% of the population, which translates to over 6 million Americans (1). Psoriasis comes in many different degrees of severity and responsiveness to treatment modalities. Some cases are very mild and quite responsive to treatment, while others are so severe, chronic and recalcitrant that they test the skill and ingenuity of the best clinicians. Fortunately, there are also many different treatment options. Topical therapies include crude coal tar, anthralin, corticosteroids, calcipotriol, and tazarotene. Phototherapy may be a better choice in patients with more extensive psoriasis; UVB or psoralen plus subsequest UVA (PUVA) can be used. There are also a host of systemic therapies (cyclosporine, methotrexate, acitretin), which can be chosen in recalcitrant cases, or when topical or phototherapy is impractical. Importantly, significant increases in efficacy can be obtained by combining multiple therapies (Re-PUVA, topical calcipotriol plus topical halobetasol) and significant decreases in side effects can be obtained by transitioning through or rotating between therapies (cyclosporine transitioning into acitretin).

Administration, Oral↗
PubMed1999

Early rehabilitation program in postmastectomy patients: a prospective clinical trial.

The purpose of this study was to determine whether 20 patients who received an early postmastectomy rehabilitation treatment program showed more improvement in range of shoulder motion and functional activities than 13 patients who received instruction for exercise only. Data were obtained at preoperatively, three days after operation, at discharge and at postdischarge one month for each patient on parameters such as range of motion of the ipsilateral shoulder joint, upper extremity circumferential measurements, as well as 10 elements of shoulder function. Postoperatively, both groups showed an increased range of motion of the shoulder joint and improved functional activities, but the group that received postoperative rehabilitation management had a better range of shoulder motion and less difficulty in five items for functional assessment. This study also showed that an early rehabilitation program did not increase postoperative complications. We concluded that an early rehabilitation program or intensive instruction program only by a well-trained physical therapist or physiatrist was beneficial to postmastectomy patients in regaining the function and range of shoulder motion, and significantly better in a rehabilitation group.

Adult↗
PubMed1998

Tazarotene in combination with phototherapy.

Despite the vast array of available therapies for treating psoriasis, there remains a need for safer, more effective treatments. Topical tazarotene has been shown to be effective in treating mild-to-moderate psoriasis without causing the adverse effects, such as mucocutaneous toxicity, hyperostosis, and elevation in serum lipids, often associated with orally administered retinoids. A 2-week pretreatment with tazarotene 0.1% gel once daily, followed by tazarotene plus UVB therapy (tazarotene-UVB) 3 times per week for 10 weeks, was more effective than UVB therapy alone or in combination with vehicle gel in reducing plaque elevation, scaling, and erythema. The tazarotene-UVB treatment was well tolerated, and no phototoxicity was observed. Treatment success, defined as a moderate response or better in psoriatic lesions (ie, > or = 50% improvement in psoriatic lesions compared with baseline), was achieved within 32 days with the tazarotene-UVB treatment, compared with 67 days with UVB alone or UVB plus vehicle gel.

Administration, Cutaneous↗
PubMed1998

How and where tazarotene might fit into the current therapeutic armamentarium: an expert opinion.

When a new class of topical medication becomes available to treat psoriasis, its optimal usage may not be fully defined for years. This is because even the "experts" who tested the medication in clinical research and reviewed the scientific literature may have limited experience with its use in actual clinical practice. Eventually, the optimal usage will probably be defined by the sum total of the practitioner's experience with it, rather than by the researchers who investigated the agent initially. However, with that limitation in mind, and based on available information, one can start to define where this agent is likely to show its greatest advantage. Three areas of possible strength, and one situation where tazarotene might not show its best advantage, will be discussed in detail.

Administration, Topical↗
PubMed1997

Breast conserving therapy in stage I & II breast cancer in Korea.

A randomized clinical study of 187 patients with T1, T2 breast cancer was performed, in order to compare the effects of modified radical mastectomy (MRM) and breast conserving therapy (BCT) on breast recurrence, overall survival, and disease-free survival. One hundred eighty seven patients with T1, T2 breast cancer, admitted at Yongdong Severance Hospital from April 1991 to August 1994, were randomized into two different treatment groups. Of the 187 patients, 111 patients had received MRM and 76 had received BCT. In any of the variables considered with the exceptions of age and menopausal status, patient characteristics such as tumor size, incidence of axillary lymph node metastasis, histologic grading, and estrogen and progesterone receptor positive rate were not significantly different between the two groups (p < 0.05). Using the Kaplan-Meier Product-limit method and log-rank test, the difference of locoregional recurrence, and overall and disease-free survival, between these comparable groups was analyzed. Average follow-up period was 37.6 months. Two out of 111 MRM patients and two out of 76 BCT patients had locoregional recurrence. Only one patient who had MRM was found to have a recurrence in her opposite breast. The overall survival rates in MRM and BCT patients were, respectively 93.7% and 94.1%. Furthermore, the disease-free survival rates were, respectively, 89.2% and 93.9%. This result indicates that there were no significant differences between two groups in locoregional recurrence, and overall and disease-free survival. Having gained a better cosmetic appearance, the conservative treatment group was satisfied with the BCT. In this study, we conclude that BCT is a good alternative surgical treatment modality for T1, T2 Korean breast cancer patients, which could substitute for the more traditional MRM. However, further follow-up will be needed for long-term results.

Adult↗
PubMed1997

Correlations of bcl-2 expression with clinicopathological features in breast cancer.

To evaluate the prognostic significance of bcl-2, we investigated the correlation of bcl-2 expression with the established indicators of prognosis and tumor behavior in breast cancer. This study included a patient group of 91 histologically diagnosed female breast carcinomas. To determine the bcl-2 immunoreactivity, we used a monoclonal antibody directed against the bcl-2 protein by immunohistochemistry from paraffin-embedded tissue in a series of 91 women with breast cancer. Interpretable DNA histograms were obtained from 84 patients. The median age at diagnosis was 45.5 years and the median follow-up time was 30.5 months. Forty-eight (52.7%) cancers showed the bcl-2 immunoreactivity in the cytoplasm. The nonneoplastic portion of ductal epithelial cells and normal lymphocytes were usually stained with bcl-2 antibody. Estrogen receptors (ER)(p < 0.001) and progesterone receptors (PR)(p < 0.001) showed strong positive correlation with bcl-2 immunoreactivity. The histologic grade (p < 0.05) and nuclear grade (p < 0.01) also showed positive relationships with bcl-2 positivity but tumor size (p > 0.05) and DNA ploidy (p > 0.05) were not related with it. The bcl-2 positive patients showed longer survival (p < 0.05) compared to bcl-2 negative tumors in univariate analysis (Kaplan-Meier life table analysis). Using multivariate analysis with Cox regression, bcl-2 (p > 0.05), nuclear grade (p > 0.05), ER status (p > 0.1) and PR status(p > 0.1) were not reliable indicators for overall survival except histologic grade (p < 0.05). Our results suggest that bcl-2 expression may be related to hormonal regulation and tumor differentiation in breast carcinoma. Larger patient study groups with a longer follow-up period will be helpful to clarify the prognostic significance of bcl-2.

Breast Neoplasms↗
PubMed1994

Bombesin inhibits growth of pancreatic ductal adenocarcinoma (H2T) in nude mice.

Bombesin (BBS), a tetradecapeptide, stimulates growth of various types of cells, including fibroblasts and human small cell lung cancer, and has been termed the universal "on-switch" due to its ability to stimulate the release of numerous hormones. In addition, BBS receptors have been identified in normal and neoplastic pancreatic tissue. A pancreatic ductal adenocarcinoma cell line (H2T), established in our laboratory, possesses specific binding sites for BBS. The purpose of this study was to examine the effect of BBS on the growth of H2T tumors transplanted into athymic nude mice. H2T cells (5 x 10(6) cells/mouse) were injected s.c. into the interscapular region of the nude mice and then the mice were randomized into two groups (n = 10/group). Mice received either 0.1 ml of saline with 0.1% bovine serum albumin (BSA) (control) or 0.1 ml BBS (5 micrograms/kg) intraperitoneally, three times/day. Tumor area was measured twice weekly until the mice were killed (day 32), when tumor and normal pancreas were removed, weighted, and assayed for DNA and protein content. Administration of BBS significantly inhibited H2T tumor area, weight, and DNA and protein content. Conversely, growth of normal pancreas, removed as an in vivo bioassay so as to ensure the efficacy of BBS, was stimulated. We conclude that BBS is a growth inhibitory factor for H2T tumors and that different mechanisms may be responsible for the differential growth effects elicited by normal and neoplastic pancreas in response to BBS.

Animals↗
PubMed1994

Alopecia areata and increased prevalence of psychiatric disorders.

BACKGROUND: The relationship between psychiatric disorders and alopecia areata has not been well studied. Although previous reports have been unable to correlate psychiatric illness with hair loss, a recent study determined that 74% of patients with alopecia areata (AA) under evaluation had one or more lifetime psychiatric diagnoses. METHODS: Two hundred and ninety-four community-based patients with alopecia areata responded to a detailed questionnaire distributed by Help Alopecia International Research, Inc. The prevalence of psychiatric disorders was determined using diagnostic criteria from the Diagnostic and Statistical Manual of Mental Disorders (DSM-IIIR). RESULTS: Major depression, generalized anxiety disorder, social phobia, and paranoid disorder were all present in patients with alopecia areata at rates significantly higher than in the general population. CONCLUSIONS: Alopecia areata patients are at a higher risk of developing psychiatric comorbidity during their clinical course.

Alopecia Areata↗
PubMed1994

Angiodysplastic syndrome with capillary and venous malformation associated with soft tissue hypotrophy.

Angiodysplastic syndromes include a vascular malformation which may often be associated with secondary changes such as further vascular abnormalities, soft tissue and bone hypertrophy. One of the best known is the syndrome triad originally described by Klippel and Trenaunay, which includes a unilateral capillary malformation, ectatic veins and osseous and soft tissue hypertrophy. A female patient is reported who had an extensive capillary malformation, discrete ectatic veins overlying an extensive venous malformation and soft tissue hypotrophy without bone involvement. Our patient and cases from the literature illustrate the occurrence of 'atypical', hypotrophic variants of angiodysplastic syndromes. Discrete superficial angiodysplasias may overlie deep, extensive malformations, and identification of such cases is important with regard to management and prognosis. The current classification of angiodysplasias is based on the primary vascular malformation. The use of eponyms should be avoided, because they do not contribute to the diagnosis and management of such cases.

Adolescent↗