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Biomedical subjects

C Ahn

Publications and source records attributed to C Ahn.

At least 199 records · Page 11Linked to original sources
PubMed1994

Quantitative immunohistochemical assay for hormonal receptors: technical aspects and biological significance.

Over 250 breast carcinomas were studied in order to establish whether or not quantitative immunohistochemical assays (ICA) for estrogen and progesterone receptors (ER and PR) with computer-assisted image analysis could favorably compare with standard cytosolic assays. Initially, variable antigenic preservation secondary to improper tissue fixation and processing led to irregular receptor preservation and unevenly stained areas indistinguishable from true intratumor antigenic heterogeneity. As a direct consequence of the field selections chosen for analysis, assay reproducibility was less than optimal. Proper tissue fixation and handling eliminated most of the irregular staining; selection of fields to analyze became less cumbersome and more reproducible. Differences in staining intensity due to minimal variations in the ICA also resulted in difficult reproducibility. Standardizing the technique and using an automatic stainer notably eliminated that problem. The second and equally important question was to establish if quantitative ER-ICA had relevance as a predictor for prognosis. The Kaplan-Meier product limit estimator for quantitated ER values and Cox regression for risk of mortality and disease progression were performed. The results obtained discriminated high- and low-risk groups for overall survival (p = 0.016) better than the dextran-coated charcoal assay. Elimination of two major obstacles and proof of the predictive value of quantitative ICA has transformed the assay into a valid alternative to cytosolic methods; however, before that takes place it is critical to establish standard procedures for both ICA and quantitation so interlaboratory variability is reduced to a minimum.

Adult↗
PubMed1994

[Expression of p53 in gastric carcinoma. Prognostic value].

P53 gene mutation has been described with variable frequency in gastric cancer and its biological significance remains unclear. We studied 101 gastric carcinomas to evaluate the association between this genetic alteration and the evolution of gastric cancer. Of these, 67 patients were men and 34 were women. The median age at diagnosis was 68 years. The tumors were obtained from gastrectomies. The p53 gene mutation was determined with the monoclonal antibody DO7 (Novocastra). The neoplasms were classified as tumors with high or low level p53 expression according to the intensity and distribution of the nuclear staining. Forty eight tumors showed high level of p53 immunoreactivity. The association of p53 expression with age, sex, tumor size, histologic type, histologic grade, depth of invasion, localization, lymph node metastases, type of surgery and 5 year survival rate was investigated. The results did not demonstrate any significant association between p53 expression and the factors mentioned above.

Adenocarcinoma↗
PubMed1994

Predictive value of estrogen receptors evaluated by quantitative immunohistochemical analysis in breast cancer.

To establish the reliability and biologic importance of quantitative immunohistochemical assays for estrogen receptors, more than 200 stage I and II breast cancers were studied. Immunohistochemical analysis was performed using antibody ER 1D5 (AMAC Westbrook, ME) in an automatic stainer (Tech Mate, Biotek, Santa Barbara, CA). Nuclear stain was quantitated by image analysis (SAMBA 4000; IPI, Chantilly, VA). Statistical analyses were performed using Kaplan-Meier product limit estimator for quantitated values and Cox regression for risk for death and disease progression. Estrogen receptor values obtained using the dextran-coated charcoal method were available for comparison. Quantitated immunohistochemical values, expressed as mean optical density of stained nuclei, could discriminate groups of patients that had as much as 3 times higher risk for death and 2.5 times higher risk for disease relapse (P = .006 and P = .018, respectively). Patients could be divided into three risk groups, based on their overall and disease-free survival, that were statistically significant (P = .018). The same analysis was performed using biochemically assayed estrogen receptors values showing that at a cutoff value of 20 fmol/mg, estrogen status predicted overall survival, albeit with lesser probability values (P = .032). These results show that quantitative immunohistochemistry of estrogen receptors provides results that have better predictive value than the biochemically procured ones. This approach not only obviates many pitfalls of the methods requiring tissue homogenates but also allows simultaneous correlation with histopathologic tumor features and expression of other relevant markers.

Breast Neoplasms↗
PubMed1993

The use of cryopreserved venous allografts in microvascular surgery without immunosuppression: an experimental study.

Excellent patency rates are currently established in the use of autogenous veins as interposition vein grafts in microsurgical practice. Allografts may be a viable alternative source of vein grafts. Recent advances in cryobiology have enabled the controlled freezing of tissues with preservation of vital cellular elements. Although several reports have shown the successful use of cryopreserved large-vessel allografts, few have addressed cryopreservation of microvessels (1 to 2 mm in diameter). In this study, the authors have successfully cryopreserved femoral veins in a rat model and transplanted them as interposition vein grafts into arterial defects across major histocompatibility barriers (ACI to Lewis). Short-term patencies (21 days) were determined, and histologic and scanning electron microscopic analysis were performed. Patency of 100 percent was achieved in both fresh control veins and in cryopreserved veins at 21 days.

Animals↗
PubMed1993

Molecular analysis of the lactacin F operon.

Lactacin F is a nonlantibiotic, heat-stable, peptide bacteriocin produced by Lactobacillus johnsonii VPI11088. Molecular analysis of the lactacin F DNA region characterized a small operon that codes for three open reading frames, designated lafA, lafX, and ORFZ. The peptide encoded by lafA, the lactacin F structural gene, was compared with various peptide bacteriocins from lactic acid bacteria, and similarities were identified in the amino and carboxy termini of the propeptides. Site-directed mutagenesis of the LafA precursor at the two glycine residues in positions -1 and -2 defined an essential motif for processing of mature lactacin F. The involvement of the peptides encoded by lafX and ORFZ in bacteriocin expression was investigated by subcloning various fragments from the lactacin F region into the shuttle vector pGKV210. In addition to lafA, expression of lafX is essential to lactacin F activity. The lactacin F operon resembles the genetic organization of lactococcin M. Although no function has been assigned to ORFZ by genetic analysis, both peptide Z and the lactococcin M immunity protein are predicted to be integral membrane proteins with four putative transmembrane segments. Lactacin F activity, defined by bactericidal action on Lactobacillus delbrueckii, is dependent on the expression of two genes, lafA and lafX.

Amino Acid Sequence↗
PubMed1993

Alterations in erythrocyte glutathione metabolism associated with cervical dysplasias and carcinoma in situ.

The study was designed to test the hypothesis whether cervical dysplasias of the more severe grades are associated with elevated erythrocyte glutathione levels. Subjects were women who obtained Pap tests and were subsequently found (1) not to have any cervical lesions or (2) to have colposcopically visualized, biopsy-confirmed cervical abnormalities histopathologically diagnosed as mild, moderate, severe dysplasias, or carcinoma in situ (CIS). The erythrocyte levels of reduced glutathione (GSH), oxidized glutathione (GSSG), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PD), and 6-phosphogluconate dehydrogenase (6PGD) were analyzed from coded peripheral venous blood samples. GSH and GR concentrations increased with increasing severity of dysplasia. Exploratory data analysis and multiple pairwise comparisons suggested comparable levels of the glutathione-related variables between these histopathological pairs: (1) mild and moderate dysplasias or (2) severe dysplasia and CIS. We suggest that the changes in erythrocyte glutathione-related indices in conjunction with histopathological diagnosis may have the potential to distinguish between low- and high-grade cervical dysplastic lesions.

Carcinoma in Situ↗
PubMed1993

Cellular localization of type 1 plasminogen activator inhibitor messenger RNA and protein in murine renal tissue.

Type 1 plasminogen activator inhibitor (PAI-1) may be markedly increased in the plasma of patients with endotoxemia and/or renal disease. To investigate renal PAI-1 production during acute endotoxemia, a murine model system was used. Mice were injected with either saline alone or saline containing 50 micrograms endotoxin, and sacrificed 3 hours later and their tissues analyzed for PAI-1 messenger RNA (mRNA) and antigen. Northern blot analysis confirmed that the level of renal PAI-1 mRNA was greatly increased in the endotoxemic mice relative to the saline controls. In situ hybridization was then performed to determine the cellular localization of PAI-1 mRNA within the renal tissues. In the control kidneys, low levels of PAI-1 mRNA were detected in the renal papilla and in the muscular walls of renal arteries. However, in the endotoxemic mice, an intense hybridization signal for PAI-1 mRNA was observed in glomerular and peritubular cells. These cells also stained positively for von Willebrand factor antigen, an endothelial cell-specific marker. The PAI-1 mRNA hybridization signal could further be observed in peritubular endothelial cells in the medulla and in endothelial cells of veins and arteries throughout the kidney. Immunochemical analysis revealed that PAI-1 antigen co-localized to the cytoplasm of cells expressing PAI-1 mRNA. This study provides the first direct evidence that PAI-1 is induced in endothelial cells of the kidney during endotoxemia in vivo and suggests a role for PAI-1 in the pathogenesis of renal disease.

Adipose Tissue↗
PubMed1992

Tumor-associated antigen 43-9F is of prognostic value in squamous cell carcinoma of the lung. A retrospective immunohistochemical study.

BACKGROUND: Squamous cell lung carcinoma (SLC), the most frequent type of lung cancer, generally is treated surgically and its prognosis is poor. The only current clinically useful prognostic criterion is lymph node staging (TNM classification). Expression of a novel tumor-associated carbohydrate epitope Gal beta 1-3[Fuc alpha 1-4]GlcNAc beta 1-4[Fuc alpha 1-3]GlcNAc beta 1-3 Gal beta 1-4Glc identified by the 43-9F monoclonal antibody (MoAb) is associated with the growth pattern of SLC cell lines in athymic mice and in vitro. This implies that the 43-9F epitope may be related to tumor progression in patients with SLC and that, as such, it could be of prognostic value. METHODS: Primary tumor specimens from 231 patients with lung carcinoma (130 with SLC, 64 with adenocarcinoma, 10 with small cell carcinoma, 16 with large cell carcinoma, and 11 with adenosquamous carcinoma) were examined by immunohistochemical studies on formalin-fixed, paraffin-embedded tissue samples for immunoreactivity with an MoAb to the 43-9F antigen. Univariate and step-wise Cox regression analyses were used to compare survival time by histopathologic diagnosis, smoker status, TNM classification, and type of surgical treatment. RESULTS AND CONCLUSIONS: Patients with 43-9F epitope-positive SLC tumors had a significantly (P less than 0.01) better prognosis than patients with epitope-negative tumors. In contrast, no association was seen between 43-9F epitope expression and survival time for patients with lung adenocarcinomas. Further, the prognostic value of 43-9F expression in SLC was found to be superior to the N-classification with the added advantage that it requires access only to primary tumor tissue and thus is available before therapy.

Adult↗
PubMed1992

Two subsets of epithelial cells in the thymic medulla.

Information was sought on the features of epithelial cells in the murine thymic medulla. The expression of major histocompatibility complex (MHC) molecules on medullary epithelium was defined by light microscopy with the aid of bone marrow chimeras and MHC-transgenic mice. A proportion of medullary epithelial cells was found to show conspicuously high expression of conventional MHC (H-2) class I (K, D, L) and class II (I-A, I-E) molecules. These cells express a high density of the Y-Ae epitope, a complex of an E alpha peptide and I-Ab molecules found on typical bone marrow-derived cells. MHC+ medullary epithelial cells show limited expression of I-O molecules, a class of atypical nonpolymorphic MHC-encoded class II molecules present on B cells. Other medullary epithelial cells express a high density of I-O molecules but show little or no expression of typical MHC class I or II molecules. MHC and I-O expression thus appear to subdivide medullary epithelial cells into two phenotypically distinct subsets. This applies in adults. In the embryonic thymus most medullary epithelial cells express both types of molecules.

Animals↗
PubMed1992

Prognosis in ischemic heart disease. Can you tell as much at the bedside as in the nuclear laboratory?

BACKGROUND--While the resting left ventricular ejection fraction (LVEF) predicts prognosis in ischemic heart disease, clinical evaluation is also useful. METHODS--To compare the prognostic value of LVEF by resting radionuclide ventriculography with that of clinical signs and symptoms of congestive heart failure (CHF), 170 patients with suspected ischemic heart disease were followed up in this prospective study. Patients had a standardized history and physical examination performed by a study cardiologist immediately before the nuclear scan. Chest roentgenography and radionuclide ventriculography were performed in a standard manner. The diagnosis of CHF was made by validated clinicoradiographic criteria based on the Framingham study. Mortality was determined by means of the National Death Index; median follow-up time was 3 years. RESULTS--There was CHF at baseline in 70 patients, and baseline LVEF was low (< or = 0.4) in 63 patients. Low LVEF was significantly associated with CHF. During follow-up, 55 of the subjects died (overall mortality, 32%). Subjects with CHF had a significantly higher risk of death than those without CHF, and subjects with low LVEF had a higher mortality than those with preserved LVEF. Both CHF and LVEF were independent predictors of mortality. In a Cox model, each percentage increase in LVEF was associated with a 2% decreased mortality, while subjects with CHF had a mortality 2.5 times higher than that of those without CHF. Also, CHF with preserved LVEF had a better prognosis than CHF with depressed LVEF, but this prognosis was worse than that in subjects without CHF. CONCLUSIONS--The clinical diagnosis of CHF, based on clinical evaluation and chest roentgenogram, is a valid predictor of mortality and provides information independent of the radionuclide LVEF in determining prognosis in patients with ischemic heart disease.

Aged↗
PubMed1992

Mobilization and location of the genetic determinant of chloramphenicol resistance from Lactobacillus plantarum caTC2R.

The mobilization of a nonconjugative plasmid (pCaT) that mediates chloramphenicol resistance in Lactobacillus plantarum caTC2R was achieved by comobilization with the conjugative plasmid pAM beta 1. The conjugation studies confirmed that the 8.5-kb pCaT in L. plantarum caTC2R contains the gene responsible for chloramphenicol resistance and that the plasmid has several unique restriction sites which make it useful for genetic studies in Carnobacterium spp. Cloning studies showed that the gene responsible for chloramphenicol resistance is located in the 2.6-kb EcoRV-SalI region of pCaT. This was confirmed by probing the 3.0-kb BglII fragment of pCaT with a biotin-labeled 1.6-kb BstEII-HpaII fragment from the streptococcal-derived plasmid pVA797(Cmr). Expression of chloramphenicol resistance in Carnobacterium as well as in other Lactobacillus species was achieved by electrotransformation using donor DNA from pCaT.

Bacterial Proteins↗
PubMed1992

Depressive symptoms and mortality in elderly persons.

Studies on the relationship between depression and mortality in elderly community populations have yielded contradictory findings, although an association frequently is found in studies of elderly psychiatric patients. These different results may be due to differences in the measures of depression, the populations under study, the covariates in the analysis, or to sample attrition. In this study of elderly residents of an urban neighborhood, depressive symptoms are measured at two time points. People are classified as consistently nonsymptomatic (N-N), with emergent symptoms (N-D), in remission (D-N), or persistently symptomatic (D-D). Symptoms of depression, sociodemographic characteristics, and measures of changes in health, functional status, number of chronic medical conditions, and social support are examined in relation to mortality in multivariate Cox regression models. Although symptoms of depression are not found to be related to time-to-death, older people, those with declines in health and functional status, and men have greater relative risks of mortality over a three-year follow-up.

Aged↗