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Biomedical subjects

C Choi

Publications and source records attributed to C Choi.

At least 109 records · Page 6Linked to original sources
PubMed1997

Ca(2+)-independent autophosphorylation of postsynaptic density-associated Ca2+/calmodulin-dependent protein kinase.

A major protein in the postsynaptic density fraction is alpha-CAM kinase II, the alpha-subunit of the Ca2+/calmodulin-dependent protein kinase. Autophosphorylation of the postsynaptic density-associated CaM kinase II is likely to be a crucial event in the induction of activity-dependent synaptic modification. This study focuses on the regulation and consequences of Ca(2+)-independent autophosphorylation of the enzyme. In isolated postsynaptic densities, a sub-stochiometric level of autophosphorylation in the presence of Ca2+ is sufficient to trigger maximal Ca(2+)-independent autophosphorylation of alpha-CaM Kinase II. A major fraction of the sites phosphorylated in the absence of Ca2+ can be dephosphorylated by the endogenous phosphatase activity in the preparation. Ca(2+)-independent autophosphorylation is correlated with a drastic decrease in calmodulin binding to postsynaptic densities. This may represent a physiological mechanism that lower the calmodulin trapping capacity of the organelle, thus increasing the availability of calmodulin to other elements within a spine.

Animals↗
PubMed1997

Analysis of clonality by X chromosome inactivation in uterine cervix cancer.

The determination of a unicellular or a multicellular origin of a tumor is an important due for understanding its etiology. To investigate this issue, we performed clonality assay of cervix cancer using polymerase chain reaction based on highly polymorphic locus of the androgen receptor gene, in which methylation of DNA correlates with inactivation of X chromosome. DNA samples were obtained from formalin-fixed, paraffin-embedded tissue of 20 invasive epidermoid carcinomas and 10 carcinoma in situ. Seven of ten carcinoma in situ, heterozygous for the androgen receptor locus, were monoclonal pattern. Among twenty invasive epidermoid carcinomas, eighteen of which showed heterozygous, twelve were monoclonal pattern and six were polyclonal pattern. We conclude that carcinoma in situ arises from a single cell. In invasive epidermoid carcinoma, most cases were monoclonal, although some cases were polyclonal. These suggest that invasive carcinoma of the cervix does not always arise from a single cell, but may arise from several cells with different mechanisms.

Carcinoma in Situ↗
PubMed1997

Microsatellite instability in Korean patients with gastric adenocarcinoma.

OBJECTIVES: Microsatellites are short repeated oligonucleotide sequences found throughout the human genome. High mutation rates in microsatellite sequences have been found in tumors from patients with hereditary non-polyposis colorectal carcinoma and some sporadic carcinomas. However, little information is available regarding RER-positive phenotype in gastric carcinomas, particularly in terms of age of onset and other pathologic features, such as histologic types, degree of differentiation, location or stage of the carcinoma. METHODS: To obtain a better understanding of the molecular mechanism of gastric carcinogenesis, microsatellite instability was examined at 6 gene loci (D2S71, D2S119, D3S1067, D6S87, D8S87, D11S905) in 77 gastric carcinomas (40 cases of young patients and 37 cases of elderly patients). RESULTS: RER-positive phenotypes were found in 17 (22.1%) of 77 cases. In young patients (under 40 years) RER-positive phenotype was found in 9 (22.5%) of 40 cases, and in elderly patients 8 (21.6%) of 37 cases. Moderately differentiated carcinoma revealed a significantly high frequency of RER-positive phenotype than well differentiated carcinoma(p < 0.001). Tumors arising from the middle third (p < 0.001) or lower third (p < 0.001) revealed higher frequency of RER-positive phenotype than the tumors arising from the upper third of the stomach. The RER-positive phenotype was not significantly affected by the sex, histologic type or stage of carcinoma. CONCLUSION: RER-positive phenotype occurs frequently in gastric carcinoma, although the frequency of RER-positive phenotype between young and elderly patient was not significantly different. Thus, the acquisition of RER-positive phenotype might be an early event in gastric carcinogenesis.

Adenocarcinoma↗
PubMed1997

Tuberculosis: a strategy to detect and treat new and reactivated infections.

Adults age 65 and older are among those most likely to develop active tuberculosis (TB). Classic symptoms include fatigue, anorexia, weight loss, and a persistent low-grade fever. Older patients may have atypical symptoms, and studies show they have significantly more weight loss and more crackles in the lung fields than younger patients. Skin testing is a useful screening tool and is indicated in individuals suspected of active TB, those in whom prophylaxis would be considered, and nursing home residents. Definitive diagnosis is based on a positive sputum culture. Combination therapy with first-line antituberculous drugs is usually effective and well-tolerated in older patients. Preventive therapy is indicated in tuberculin reactors who have been recently infected.

Age Distribution↗
PubMed1997

Meningitis in older patients: how to diagnose and treat a deadly infection.

Studies of bacterial meningitis have documented a peak of incidence among persons age 60 and older. The most common bacterial pathogens in these patients differ from those seen in children. Presentation of meningitis in older patients may be atypical; fever is not a consistent finding, and nonspecific symptoms such as confusion are often seen. Nuchal rigidity is not as sensitive nor as specific a sign as in younger patients. Definitive diagnosis relies on interpretation of CSF studies. Ampicillin plus a third-generation cephalosporin should be administered for community-acquired meningitis until Gram's stain and culture results return. Cases of S pneumoniae meningitis may require varying strategies, based upon the degree of penicillin resistance.

Aged↗
PubMed1997

Loss of heterozygosity at chromosome segment Xq25-26.1 in advanced human ovarian carcinomas.

To determine whether a tumor suppressor gene of importance to epithelial ovarian cancer resides on the X chromosome, we examined loss of heterozygosity (LOH) in 123 epithelial ovarian cancer cases. In 54 such cases, we examined LOH at 26 loci on the human X chromosome. In eight cases, we examined LOH in 14 loci and in 61 cases we examined LOH in 13 loci. Matched DNA samples from tumors and corresponding normal tissues were analyzed by polymerase chain reaction (PCR) amplification of microsatellite markers. Frequent losses were found in epithelial carcinomas at the Xq25-26.l region, including DXS1206 (34.5% loss in informative cases), DXS1047 (27.7%), HPRT (24.1%), and DXS1062 (33.3%). The minimum overlapping region of LOH was approximately 5 megabases (Mb), flanked by DXS1206 (Xq25) and HPRT (Xq26.1). The methylation status of the remaining allele of the androgen receptor gene in the tumors exhibiting LOH at the Xq25-26.1 region suggested that the loss was exclusively in the inactive X chromosome. We next determined whether a significant relationship exists between Xq LOH and other parameters, including histologic grade and/or clinical stage of the tumors and LOH at TP53. The Xq LOH had a significant association with grade 2 to 3 tumors at stages II to IV. Sixteen of 18 cases that showed Xq LOH revealed LOH at the TP53 locus, and 45% of tumors exhibiting LOH at TP53 showed Xq LOH. These results suggest that there may be a tumor suppressor gene or genes which escape inactivation of the X chromosome at Xq25-26.1, and that the loss of the gene(s) at Xq25-26.1 is frequently accompanied by loss of the TP53 or loss of another gene on chromosome 17. These losses may contribute to the progression from a well-differentiated to a more poorly differentiated state or to metastatic aggressiveness.

Carcinoma↗
PubMed1997

A clinical trial of all-ceramic crown restorations: status, fall 1995.

Although porcelain-fused-to-metal (PFM) restorations are the most widely used full-coverage crown restoration systems, their inherent properties make the achievement of natural aesthetic restorations an elusive task. In contrast, the all-ceramic system (IPS Empress, Ivoclar North America, Amherst, NY) offers excellent translucency and vitality, without the opacity associated with PFM restorations. Its vitality is further enhanced by an adhesive resin cementation method that conducts the color of the underlying tooth structure. This article reports the status of a 5-year investigation, initiated in 1992, of the clinical performance of the IPS Empress all-ceramic system and the resin cementation system used with it.

Adolescent↗
PubMed1996

A clinical trial of all-ceramic crown restorations: status, fall 1995.

Although porcelain-fused-to-metal (PFM) restorations are the most widely used full-coverage crown restoration systems, their inherent properties make the achievement of natural aesthetic restorations an elusive task. In contrast, the all-ceramic system (IPS Empress, Ivoclar North America, Amherst, NY) offers excellent translucency and vitality, without the opacity associated with PFM restorations. Its vitality is further enhanced by an adhesive resin cementation method that conducts the color of the underlying tooth structure. This article reports the status of a 5-year investigation, initiated in 1992, of the clinical performance of the IPS Empress all-ceramic system and the resin cementation system used with it.

Adolescent↗
PubMed1995

The changing availability of residential aged care in Australia.

Australian aged care services have undergone a series of substantial reforms in recent years under the rubric of the Aged Care Reform Strategy. Overall, there has been a progressive refinement of the targeting of available services on those most in need, defined in terms of both disability levels and financial resources. A key component of this process has been a deliberate reduction in the relative emphasis accorded to nursing home care within the aged care system. This has been accompanied by increases in the resources directed toward less intensive forms of residential care (hostels) and community based services. This paper explores the actual consequences of these intentional policy changes in terms of the availability of nursing home and hostel care, and the changing characteristics of nursing home residents. The results suggest that a more substantial reduction has occurred in the availability of nursing home care than has hitherto been suggested, with consequent decreases in the proportion of aged persons in nursing homes. The effect has been particularly marked amongst women and the very old. These findings raise policy questions about the appropriateness of current and planned future levels of provision.

Aged↗
PubMed1994

Summary of first round cluster analysis: complete antibody panel.

The reactivities of 141 monoclonal antibodies (mAbs) with 60 target cell types or lines were analysed by flow cytometry and the data subjected to statistical clustering. mAbs were assigned to 23 clusters by statistical similarity and information on specificity supplied by the contributor. Clustered mAbs were examined in more detail in the second round of workshop analyses.

Animals↗
PubMed1994

Establishment of the formalin-free surgical pathology laboratory. Utility of an alcohol-based fixative.

Concerns about the toxicity of formalin dictate the need for alternative methods of tissue fixation. Alcohol-based fixatives have been proposed as optimal for immunohistochemical and nucleic acid methods and may be useful for diagnostic light microscopy. We recently converted our surgical pathology laboratory from 10% neutral buffered formalin to an alcoholic fixative (56% ethanol and 20% polyethylene glycol) and compared 100 consecutive cases after conversion with 100 formalin-fixed cases prior to conversion. One representative slide from each case was reviewed independently by four pathologists without knowledge of the fixative employed. The quality of fixation of each case was graded (0, very poor; 1, below average; 2, average; and 3, above average) based on the subjective composite evaluation of seven morphological features: tissue architecture, cell borders, cytoplasm, nuclear contours, chromatin texture, red blood cell membranes, and uniformity of staining. No significant difference in the quality of fixation was observed, although the average score of the alcoholic fixative was slightly lower than that of the formalin (2.59 vs 2.74). Interobserver concordance was 74%. Advantages of the alcoholic fixative included elimination of carcinogenic vapors, more rapid fixation, greater stain avidity, elimination of enzyme predigestion in immunohistochemical studies, and simple and rapid disposal. Disadvantages included slightly increased viscosity, increased variability of tissue staining and nuclear shrinkage, artifactual pigment deposition in bloody specimens, and increased flammability risk. Alcohol-polyethylene glycol appears to be a satisfactory alternative to formalin in routine diagnostic surgical pathology.

Ethanol↗
PubMed1992

Bacterial meningitis.

Meningitis remains a significant health problem for the older adult population. Although the overall incidence of this disease has decreased in the United States, the incidence of meningitis in the elderly population is increasing. Additionally, the recognition of meningitis in the older adult may be more difficult because the usual symptoms and signs are neither as specific nor as sensitive as they are in a younger population. Newer antibiotics have provided better therapeutic approaches to some of the organisms responsible for this disease, and newer methods of therapy beyond antibiotics hold the promise of altering the unacceptably high morbidity and mortality.

Aged↗
PubMed1991

The impact of hospital closures on travel time to hospitals.

In this paper, we investigate the impact of closures on local access to hospital care. We measured the incremental travel time to alternate hospitals. The results show that even in rural markets, closures nearly always occur near open hospitals, which by itself may imply a minimal effect in terms of human welfare. These results support the view that hospital closures rarely directly limit general access to hospital care.

Health Facility Closure↗
PubMed1988

Fissure sealant knowledge and characteristics of parents as a function of their child's sealant status.

A survey was conducted to identify and compare sealant knowledge and sources of sealant information of parents whose children had and had not received fissure sealants. The socioeconomic characteristics of these individuals were also compared. The sealant group was composed of the parents of children found to have a sealant on at least one permanent tooth during dental examinations of 2,036 elementary schoolchildren in southwestern Michigan. Another group of children was selected from the same population and matched to the children with sealants by child's age, sex, school location, and community. Surveys were returned by 210 of 260 sets of parents (81% response rate). Significant differences were found between the two groups with regard to parents' ages and levels of income. Parents of children with sealants had more correct information about the procedure and 74 percent of these individuals reported that the dental office was their primary source of information. For the group without sealants, 48 percent of respondents reported no source of sealant information. Findings suggest that dental personnel may strongly influence dissemination of information about sealants and utilization of this preventive procedure.

Adolescent↗
PubMed1984

A stretcher that facilitates the radiographic evaluation and closed reduction of spinal fractures.

A rigid and exceptionally radiolucent stretcher with an attachment for cervical traction has been constructed. A patient is able to remain on this stretcher in the same position during the entire radiographic examination of a spinal fracture, including plain x-ray and computed tomographic and myelographic studies. Two advantages are obtained if this stretcher is used: 1) A patient's spine is well supported and does not need to be moved at any time during these radiographic studies, and 2) the application of traction during the myelography or closed reduction of a cervical fracture is facilitated.

Equipment and Supplies↗