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Biomedical subjects

Y Choi

Publications and source records attributed to Y Choi.

At least 325 records · Page 18Linked to original sources
PubMed1992

The application of positron emission tomographic imaging with fluorodeoxyglucose to the evaluation of breast disease.

Positron emission tomography (PET) is a computer-aided tomographic imaging technique that uses positron-emitting compounds to trace biochemical processes of tissue, and construct images based on them. The authors applied a whole-body PET imaging technique to patients with breast masses or mammographic abnormalities using the isotope 2-[F-18]-fluoro-2-deoxy-D-glucose (FDG), in a clinical trial to evaluate the feasibility of using PET to identify primary breast cancer, axillary lymph node involvement, and systemic metastases, before surgical resection. Fourteen patients have been entered on this study, 10 of whom proved to have breast cancer. Positron emission tomography correctly predicted the nature of 12 of the 14 primary breast lesions, and correctly determined the lymph node status of 11 of the 14 patients. The authors conclude that PET with FDG has potential as a diagnostic modality for detection of primary breast cancer, particularly in the patient with radiodense breasts by conventional mammography, and that it has potential for the preoperative identification of axillary lymph node metastases.

Adolescent↗
PubMed1992

Identification of T-cell epitopes on E2 protein of rubella virus, as recognized by human T-cell lines and clones.

T-cell epitopes on the E2 protein of rubella virus were studied by using 15 overlapping synthetic peptides covering the E2 protein sequence. The most frequently recognized epitopes on E2 were E2-4 (residues 54 to 74), with 5 of 10 tested T-cell lines responding to it. Two CD4+ cytotoxic T-cell cloned isolated from one T-cell line responded strongly in proliferation assays with peptide E2-4 and were cytotoxic to target cells presenting the E2-4 determinant. Truncated peptides contained within the E2-4 peptide sequence were used to define the T-cell determinants. Results indicated that amino acid residues 54 to 65 were directly involved. Human cell lines with different HLA phenotypes were tested for the capacity to present the antigenic determinants. The results suggested that recognition of peptide E2-4 by T-cell clones was associated with HLA DR7.

Amino Acid Sequence↗
PubMed1992

Evaluation of the skeletal kinetics of fluorine-18-fluoride ion with PET.

To evaluate the feasibility of quantitatively assessing regional skeletal fluoride uptake in humans in focal and generalized bone disease, we investigated the skeletal kinetics of [18F]fluoride ion with dynamic PET imaging. Dynamic image sets were acquired over a 60-min interval in a multiplane PET device, and input functions (plasma 18F time-activity curves) were measured directly from arterialized blood and, in some cases, determined from image-derived left ventricular cavity activity measurements. Our results indicate: 1. A steady-state ratio of [18F]fluoride ion concentration in plasma to whole blood greater than unity (1.23 for plasma to directly assayed whole blood and 1.44 for plasma to left ventricular cavity imaged concentrations. This concentration difference produces a scaling factor that must be considered when using image derived or directly measured input functions. 2. The preferred tracer kinetic model configuration for [18F]fluoride ion skeletal kinetics is a three compartment model that includes a "bound" and "unbound" bone [18F]fluoride ion compartment. 3. The rate constant for forward transport of [18F]fluoride ion from plasma to the extravascular space of bone (K1) and the regional blood volume parameter generate estimates of bone blood flow and vascular volume, respectively, that are in the physiologic range of reported for mammals. Estimates of the uptake constant for fluoride in bone, using nonlinear regression (KNLR = 0.0360 +/- 0.0064 ml/min/ml), are in very good agreement with an estimate of the same parameter obtained with Patlak graphical analysis (KPAT = 0.0355 +/- 0.0061 ml/min/ml). 4. Generating parametric images of KPAT facilitates quantification of regional bone [18F]fluoride ion kinetics. The method is computationally practical, and, with either the parametric imaging approach or with standard region of interest analysis, can be used to generate quantitative estimates of fluoride uptake (a "bone metabolic index") in focal skeletal regions or in more generalized distributions.

Adult↗
PubMed1991

A superantigen encoded in the open reading frame of the 3' long terminal repeat of mouse mammary tumour virus.

Mice express a collection of superantigens, which bind to class II major histocompatibility proteins and interact with T cells bearing particular V beta chains as part of their alpha beta receptors. These superantigens have been suggested to be encoded by exogenous or endogenous mouse mammary tumour viruses. One such superantigen is now shown to be encoded in the open reading frame of the long terminal repeat of a mammary tumour virus, a gene of previously unknown function.

Amino Acid Sequence↗
PubMed1991

Transforming growth factor alpha induces collagen degradation and cell migration in differentiating human epidermal raft cultures.

When cultured on plastic and treated with transforming growth factor alpha (TGF alpha), human keratinocytes exhibit an increase in proliferation at the colony periphery, apparently as a consequence of enhanced cell migration (Barrandon and Green, 1987). To investigate the effects of TGF alpha on a differentiating stratified squamous epithelium and to begin to examine the molecular basis mediating this influence, we cultured human epidermal cells on a gelled lattice of collagen and fibroblasts, floating on the air-liquid interface. Under these conditions, raft cultures differentiate and exhibit morphological and biochemical features of human skin in vivo (Asselineau et al., 1986; Kopan et al., 1987). When 3-wk-old raft cultures were treated with TGF alpha, basal cells showed a marked increase in cell proliferation. At elevated concentrations of TGF alpha, the organization of cells within the artificial tissue changed and islands of basal cells entered the collagen matrix. Biochemical analysis of the response revealed that type I collagenase and gelatinase were induced by keratinocytes within 12 h after TGF alpha treatment. In contrast, invasion of basal cells into the collagen matrix was not significant until 48-72 h post-treatment, suggesting that collagenase and gelatinase production may be a prerequisite to this phenomenon. These results have important implications for the possible role of TGF alpha in squamous cell carcinoma and tumor invasion.

Cell Differentiation↗
PubMed1991

Parametric images of myocardial metabolic rate of glucose generated from dynamic cardiac PET and 2-[18F]fluoro-2-deoxy-d-glucose studies.

We describe a method for generating parametric images of the myocardial metabolic rate of glucose (MMRGlc) with positron emission tomography (PET). The method employs serially acquired images of 2-[18F]fluoro-2-deoxy-D-glucose (FDG) uptake and a Patlak graphical analysis of the image data. The arterial input function is derived from images of the left ventricular blood pool calibrated with 18F-plasma measurements. The approach is computationally fast enough to be used in a clinical environment. The MMRGlc parametric images improve myocardial contrast relative to non-parametric images, especially in studies with poor myocardial uptake of FDG. In addition, MMRGlc parametric images consolidate the large amount of data in a dynamic PET study into a clinically usable image set.

Adult↗
PubMed1990

Selective expansion of T cells expressing V beta 2 in toxic shock syndrome.

Infection with Staphylococcus aureus and the production of toxic shock syndrome toxin-1 (TSST-1) have been implicated in the pathogenesis of toxic shock syndrome. Previous in vitro studies have demonstrated that TSST-1 is a powerful but selective stimulator of human T cells, and that the majority of activated cells express the TCR V beta 2 gene segment. We therefore studied patients with toxic shock syndrome using a modification of the PCR to determine if expansion of V beta 2+ T cells is a marker of the in vivo disease process. Five of eight patients studied demonstrated markedly elevated levels of circulating V beta 2+ T cells, whereas none showed significantly elevated levels of T cells expressing other V beta gene segments. The results suggest that toxin-mediated T cell activation, which involves a large fraction of the human T cell repertoire, may be critical in the pathogenesis of this disease.

Antigens, CD↗
PubMed1990

TGF-beta and retinoic acid: regulators of growth and modifiers of differentiation in human epidermal cells.

In the epidermis of skin, a fine balance exists between proliferating progenitor cells and terminally differentiating cells. We examined the effects of TGF-beta s and retinoic acid (RA) on controlling this balance in normal and malignant human epidermal keratinocytes cultured under conditions where most morphological and biochemical features of epidermis in vivo are retained. Our results revealed marked and pleiotropic effects of both TGF-beta and RA on keratinocytes. In contrast to retinoids, TGF-beta s acted on mitotically active basal cells to retard cell proliferation. Although withdrawal from the cell cycle is a necessary prerequisite for commitment to terminal differentiation, TGF-beta s inhibited normal keratinization in suprabasal cells and promoted the type of differentiation commonly associated with wound-healing and epidermal hyperproliferation. The actions of TGF-beta s and RA on normal keratinization were synergistic, whereas those on abnormal differentiation associated with hyperproliferation were antagonistic. These observations underscore the notion that environmental changes can act separately on proliferating and differentiating cells within the population. Under the conditions used here, the action of TGF-beta s on human keratinocytes was dominant over RA, and TGF-beta s did not seem to be induced as a consequence of RA treatment. This finding is consistent with the fact that RA accelerated, rather than inhibited, proliferation in raft cultures. Collectively, our data suggest that the effects of both factors on epidermal growth and differentiation are multifaceted and the extent to which their action is coupled in keratinocytes may vary under different conditions and/or in different species.

Carcinoma, Squamous Cell↗
PubMed1990

Negative regulation in correct tissue-specific expression of mouse mammary tumor virus in transgenic mice.

Mouse mammary tumor virus (MMTV) is an endogenous murine retrovirus that is expressed in the epithelial cells of the mammary and salivary glands, lungs, kidneys, and seminal vesicles and in the lymphoid cells of the spleen and thymus. Several studies have shown that the long terminal repeat (LTR) of this virus can direct the expression of reporter genes to the same tissues in transgenic mice. To determine whether multiple regulatory elements within the LTR are involved in this tissue-specific expression, we have established lines of transgenic mice containing transgenes that have deletions in the MMTV LTR. Deletions of all LTR sequences upstream of -364 or of LTR sequences from -165 to -665 both result in the expression of linked reporter genes such as the simian virus 40 early region or the bacterial enzyme chloramphenicol acetyltransferase in novel sites, such as the heart, brain, and skeletal muscle; expression of endogenous MMTV and transgenes containing the full-length LTR is not detected in these organs. Negative regulation appears to involve more than one region, since deletion of sequences between either -201 and -471 or -201 and -344, as well as sequences upstream of -364, results in inappropriate expression in heart, brain, and skeletal muscle. Therefore, a negative regulatory element(s) in the MMTV LTR can suppress transcription from the viral promoter in several different organs. This represents the first example of generalized negative regulatory elements that act in many different tissues in transgenic mice to prevent inappropriate expression of a gene.

Animals↗
PubMed1990

Abnormalities of glomerular basement membrane in acute postinfectious glomerulonephritis.

The segmental abnormalities of glomerular basement membrane (GBM) were studied by electron microscopy in 69 renal biopsies with acute postinfectious glomerulonephritis (APGN) and correlated with the general morphologic features and clinical findings. Thirty-six were children and 33 were adults. Biopsies were grouped into three stages by light microscopy: exudative stage (25 patients), exudative-proliferative stage (26) and proliferative stage (18). Subepithelial deposits or "humps" were present in 59 patients (86%). The frequency of humps was significantly lower at the proliferative stage than that noted in the earlier biopsies (p less than 0.01). Intramembranous, subendothelial and mesangial deposits were shown in 83% to 88% of the patients. The overall frequency of GBM abnormalities was 45%, showing significantly higher frequency in children than in adults (p less than 0.01). Dissolving subepithelial deposits were often present in the foci with GBM abnormalities. The GBM lesions were not related to more severe clinical manifestations or outcomes, but tended to occur more frequently in later biopsies (p less than 0.01). These results suggest that abnormalities of GBM in APGN are more often present than formerly assumed, especially in children, and could be a normal response to subepithelial deposits. The occurrence of these lesions in other types of immune-related glomerulonephritis may be considered along the same lines.

Acute Disease↗
PubMed1990

Primary intimal fibroplasia with multiple aneurysms of renal artery in childhood.

Although fibromuscular dysplasia (FMD) rarely occurs, it is the most common cause of renal artery disease in children. Aneurysm formation in FMD is well documented in adults. However, it was rarely described in children, partly because medial fibroplasia with a tendency to aneurysm formation is relatively rare. This report describes a 7-year-old girl with very unusual sets of abnormalities involving the left renal artery. Intimal fibroplasia with multiple small saccular aneurysms was seen. She presented with recent-onset renovascular hypertension, headache and intermittent severe colicky abdominal pain. Angiography revealed multifocal stenosis with multiple aneurysms of the left renal artery. Renal vein renin was twice as high on the involved side than on the contralateral side. After nephrectomy, the hypertension was under control without medication.

Aneurysm↗
PubMed1989

V beta-specific stimulation of human T cells by staphylococcal toxins.

The staphylococcal toxins are responsible for a number of diseases in man and other animals. Many of them have also long been known to be powerful T cell stimulants. They do not, however, stimulate all T cells. On the contrary, each toxin reacts with human T cells bearing particular V beta sequences as part of their receptors for major histocompatibility complex protein-associated antigen. The specificity of these toxins for V beta s puts them in the recently described class of superantigens and may account for the differential sensitivity of different individuals to the toxic effects of these proteins.

Antibodies↗
PubMed1989

Ultrastructural changes in IgA nephropathy in relation to histologic and clinical data.

In order to evaluate the ultrastructural changes in IgA nephropathy (IgAN) and their relationship with light microscopic and clinical features, renal biopsy material from 239 Korean patients with IgAN was studied by light, electron and immunofluorescence microscopy. Forty-one were children and 198 were adults. Modified classification of Meadow et al (1972) for Henoch-Schönlein nephritis was used for the histologic grading of glomerular lesions. Forty-three adults (18%) exhibited histologic grades IV and V lesions in association with more severe clinical findings, when compared to the remaining 196 patients with histologic grades I to III. A significant difference was noted between children and adults in the severity of the glomerular lesions (P less than 0.01). Mesangial deposits were observed in all (100%), subendothelial deposits in 37%, subepithelial deposits in 18%, abnormalities in glomerular basement membrane (GBM) in 20%, mesangiolysis in 44%, and mesangial interposition in 25%. The frequency of GBM abnormalities and subepithelial deposits in children was significantly higher than that seen in adults (P less than 0.01). The abnormalities of GBM were not related to more severe clinical manifestations when our analysis was restricted to grade III histologic lesions. All of the above ultrastructural changes except for mesangial deposits were associated with more severe histologic grading in adults (P less than 0.025 or P less than 0.01). Yet a correlation between these ultrastructural changes and histologic grading could not be studied in children due to confinement of their histology within a more benign group. These results suggest that the five ultrastructural parameters described here appear to bear important prognostic value in adults with IgAN.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗