Biomedical subjects

W S Choi

Publications and source records attributed to W S Choi.

114 records · Page 7Linked to original sources

PubMedDate not supplied

Nontraumatic prolapse of the orbital contents into the ethmoid sinus: evaluation with screening sinus CT.

PURPOSE: The purpose of this study is to evaluate the incidence and CT features of nontraumatic prolapse of the orbital content into the ethmoid sinus, which may be a cause of orbital complication of ethmoidectomy. MATERIALS AND METHODS: CT of 1,024 consecutive patients with subjective sinonasal symptoms who underwent screening sinus CT were reviewed and analyzed. The 573 men and 451 women were between the ages of 5 and 79 years old. The patients with a history of sinus surgery of facial trauma were excluded from this study. The incidence and CT features of dehiscence and/or bowing of the lamina papyracea with prolapse of the orbital content in each age group and differences between the age groups were analyzed. RESULTS: Ethmoidal prolapse of the orbital content was found in 67 patients (6.5%). There was a tendency of increasing incidence with increasing age. The incidence in the juvenile age group was significantly low (1.9%) as compared with that of adult. Four patients (0.4%) had bilateral lesions. Twenty-nine lesions showed prolapse of moderate to severe degree, and deformity of the medial rectus muscle on coronal CT image was associated in 21 lesions. Inflammatory change of adjacent ethmoid sinus was indicated in 19 lesions, and there was no statistical difference in incidence from that of the opposite side. CONCLUSIONS: The incidence of nontraumatic prolapse of the orbital content is far beyond general expectations, and detailed structural information with CT for this anatomic alteration may be important before endoscopic sinus surgery to avoid possible complication. The higher incidence in adult may suggest age-related acquired etiologic factors besides congenital dehiscence or weakness of the lamina papyracea.

Adolescent↗

PubMedDate not supplied

Spinal involvement of hematopoietic malignancies and metastasis: differentiation using MR imaging.

The purpose of this study was to determine the usefulness of magnetic resonance imaging (MRI) for distinguishing spinal involvement of hematopoietic malignancies (lymphoma, leukemia, and multiple myeloma) from metastasis. 62 spinal MRIs were obtained in 60 patients with hematopoietic malignancies (n = 24) and metastasis (n = 36) in clinically and pathologically proven cases. MRI findings were evaluated in each group of patients for the pattern of involvement, signal change of vertebral body, location of paraspinal mass formation, location of epidural mass formation, cortical destruction, contour change, and compression fracture. Diffuse involvements were more commonly seen in hematopoietic malignancies than in metastasis (p < 0.05). Signal change confined to anterior element was seen in 9 metastasis but was not seen in hematopoietic malignancies. Cortical destructions were more commonly seen in metastasis than in hematopoietic malignancies (p < 0.05). Other findings did not show any statistical significance in both groups. MRI findings such as diffuse involvement, posterior epidural mass formation, and cortical destruction were useful to distinguish spinal involvement of hematopoietic malignancies and metastasis.

Adolescent↗

PubMedDate not supplied

Melatonin receptors and signal transduction mechanisms.

The ovine pars tuberalis (PT) still offers the best model for the study of signal transduction pathways regulated by the melatonin receptor. From the evidence accumulated so far, it seems likely that the cAMP signal transduction pathway will be a major effector of a stimulatory signal to the PT which can be regulated by melatonin. Thus a principal action of melatonin in the PT may be the repression of biochemical processes driven by cAMP. However, through the phenomenon of sensitization, melatonin may also act to amplify a stimulatory input to the cAMP signal transduction pathway in the PT. These events are mediated via the melatonin receptor, which is itself a target for regulation by the melatonin signal. Studies using the PT have identified several signalling pathways that may serve to positively or negatively regulate the expression of the melatonin receptor. These and other studies in the PT have alluded to cAMP-independent pathways regulated by the melatonin receptor.

Animals↗

PubMedDate not supplied

Insulin-stimulated glycogen synthesis in cultured hepatoma cells: differential effects of inhibitors of insulin signaling molecules.

In rat HTC hepatoma cells overexpressing human insulin receptors, insulin stimulated glycogen synthesis by 55-70%. To study postreceptor signaling events leading to insulin-stimulated glycogen synthesis in these cells, we have employed pathway-specific chemical inhibitors such as LY294002, rapamycin and PD98059 to inhibit phosphatidylinositol-3-kinase (PI3K), p70 ribosomal S6 kinase and mitogen-activated protein kinase (MAPK) kinase/MAPK, respectively. LY294002 (50 microM) completely abolished insulin-stimulated glycogen synthesis whereas rapamycin (2-20 nM) partially inhibited it. Neither LY294002 nor rapamycin significantly affected the basal glycogen synthesis. However, PD98059 (100 microM) significantly inhibited the basal glycogen synthesis without affecting insulin-stimulated glycogen synthesis. In these cells, insulin at 100 nM decreased glycogen synthase kinase 3 alpha (GSK3 alpha) activity by 30-35%. LY294002, but neither rapamycin nor PD98059, abolished insulin-induced inactivation of GSK3 alpha. These data suggest that insulin-stimulated glycogen synthesis in rat HTC hepatoma cells is mediated mainly by PI3K-dependent mechanism. In these cells, inactivation of GSK3 alpha, downstream of PI3K, may play a role in insulin-stimulated glycogen synthesis.

Amino Acid Sequence↗

PubMedDate not supplied

Restricting minors' access to tobacco: a review of state legislation, 1991.

Currently, 46 states and the District of Columbia prohibit the sale of tobacco products to minors, and the minimum age requirement differs by state. In general, these laws are poorly enforced and inadequately prevent youth from obtaining tobacco. According to a four-part classification scheme used in this article, no states have comprehensive laws banning access to tobacco, four states have moderate laws, 37 states and the District of Columbia have basic laws, five states have nominal laws, and the remaining four states have no regulations. We recommend 11 important elements for laws that would adequately restrict minors' access to tobacco products.

Adolescent↗

PubMedDate not supplied

Which adolescent experimenters progress to established smoking in the United States.

INTRODUCTION: This study examined the adolescent smoking uptake process, specifically, the progression from experimentation to established smoking. Although adolescent smoking uptake has been described as consisting of five stages (preparation, initial trying, experimentation, regular smoking, and addiction), there is no accepted method of identifying which experimenters will proceed to become addicted. METHODS: Using a nationally representative sample of adolescents between the ages of 12 and 18 at baseline, we examined their transition from experimentation (had at least a puff but has not smoked 100 cigarettes) to established smoking (smoked at least 100 cigarettes in lifetime) four years later. RESULTS: At follow-up, 31% of the experimenters at baseline had progressed to established smoking. Baseline level of smoking experience was the strongest independent predictor of established smoking, with current experimenters (smoked in the past 30 days but less than 100 cigarettes in lifetime) having the greatest risk of progressing to established smoking compared to puffers (puffed but have not smoked a whole cigarette). Furthermore, this effect was modified by age; older current experimenters at baseline had more than double the risk of younger current experimenters of progressing to established smoking at follow-up. Absence of a firm commitment not to smoke was a significant predictor among older experimenters but not in younger experimenters. Other important predictors of the transition from experimentation to established smoking were exposure to other smokers and perceived school performance. CONCLUSIONS: We found that, even among experimenters, there is an identifiable group of adolescents who are at higher risk of progressing to established smoking that can be targeted for intervention.

Adolescent↗