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Biomedical subjects

J Ahn

Publications and source records attributed to J Ahn.

104 records · Page 6Linked to original sources
PubMed1993

Pulmonary tuberculosis: CT findings--early active disease and sequential change with antituberculous therapy.

To evaluate findings of active pulmonary tuberculosis on computed tomographic (CT) scans and their sequential changes before and after antituberculous chemotherapy, 29 patients with newly diagnosed pulmonary tuberculosis and 12 patients with recent reactivation were studied prospectively. The diagnosis of active pulmonary tuberculosis was based on positive acid-fast bacilli in sputum (n = 29) and changes on serial radiographs obtained during treatment (n = 12). Twenty-six patients were followed up with CT during treatment for 1-20 months. Lungs from the cadavers of nine other patients, who died of pulmonary tuberculosis, were studied to provide a pathologic basis for diagnosis. At examination with CT, centrilobular lesions (nodules or branching linear structures 2-4 mm in diameter) were most commonly seen (n = 39 [95%]); in the 26 patients with follow-up, most of these lesions disappeared within 5 months after the start of treatment. In 11 of 12 patients with recent reactivation, CT clearly differentiated old fibrotic lesions from new active lesions. Lesions in and around the small airways appear to be the most characteristic CT feature of early active tuberculosis and may be a reliable criterion for disease activity.

Adult↗
PubMed1992

Dietary soluble fiber and cholesterol affect serum cholesterol concentration, hepatic portal venous short-chain fatty acid concentrations and fecal sterol excretion in rats.

Sprague-Dawley rats were fed diets containing 7.5% dietary fiber as cellulose (control), pectin, psyllium or oat bran with or without 0.3% added cholesterol for 3 wk. Among rats fed cholesterol, liver total lipid and cholesterol concentrations were significantly lower in groups fed pectin, psyllium and oat bran compared with cellulose-fed controls. Cholesterol feeding resulted in significantly greater liver cholesterol in rats fed cellulose, psyllium and oat bran but not in those fed pectin. Among rats fed cholesterol, total serum cholesterol levels were significantly lower in those fed pectin than in those fed psyllium, oat bran or cellulose. When cholesterol was fed, the oat bran-fed group had significantly higher butyrate and the pectin-fed group had significantly higher propionate concentrations in the hepatic portal vein than did cellulose-fed controls. The groups fed psyllium, oat bran and pectin all had significantly higher fecal neutral sterols than did the cellulose-fed group when cholesterol was fed. Without dietary cholesterol only pectin-fed rats had significantly higher fecal excretion of neutral sterols than those fed cellulose. Dietary fiber did not influence fecal acidic sterol excretion. However, the addition of cholesterol to these fiber diets was accompanied by a significantly higher bile acid excretion than that of animals fed cellulose without cholesterol. The results of this study indicate that soluble dietary fibers may exert their hypocholesterolemic effect by increasing excretion of fecal neutral sterols.

Animals↗
PubMed1992

Growth factors, receptor kinases, and protein tyrosine phosphatases in normal and malignant melanocytes.

Normal human melanocyte proliferation and differentiation is dependent on stimulation of one of three growth factor/receptor systems. They are fibroblast growth factor (FGF), hepatocyte growth factor (HGF), and mast cell growth factor (MGF), which activate the FGF receptor, c-Met, and c-Kit, respectively, known to be receptor tyrosine kinases. In contrast, human melanoma cells from primary nodular and metastatic lesions grow autonomously partially because of inappropriate production of basic FGF (bFGF) and continuous activation of the bFGF-receptor kinase. Activation of transmembrane receptor tyrosine kinases in melanocytes stimulates not only proliferation but also the expression of pigmentation. Melanoma cells constitutively express several tyrosyl-phosphorylated proteins that in normal melanocytes are stimulated in response to growth factors. This high level of phosphorylation was not due to either the presence of constitutively active Kit kinase and Met kinase nor to the absence of any of several known protein tyrosine phosphatases. Because bFGF by itself does not transform melanocytes to melanomas, there must be additional cooperating factors that confer the malignant phenotype to pigment cells.

Animals↗
PubMed1990

A common mechanism may be involved in the selective loss of plasma membrane functions during reticulocyte maturation.

During the maturation of the mammalian reticulocyte to the erythrocyte, 50nm bodies (called exosomes) are released from the cell. These exosomes carry the transferrin receptor (TFR) as well as other plasma membrane and lysosomal activities which the cells are known to lose during maturation. Using an antibody attached to an iron core bead, we have shown that other plasma membrane activities (nucleoside transporter and acetylcholine esterase) are packaged in the same exosome as the transferrin receptor. This population of exosomes is devoid of lysosomal enzymes. Exosomes were detected in the circulation of several species of phlebotomized animals, suggesting that exosome formation is a natural phenomenon, and probably a route by which the red cell decreases in size and sheds specific plasma membrane activities during maturation.

Animals↗
PubMed1989

Maturation-associated loss and incomplete de novo synthesis of the transferrin receptor in peripheral sheep reticulocytes: response to heme and iron.

Hemin, but not iron, in the culture medium stimulates the maturation-associated loss of the transferrin receptor from sheep reticulocytes (t1/2 for loss approximately 6 hr) and its appearance in a population of externalized vesicles. A similar pattern is seen with nucleoside binding (a measure of the nucleoside transporter), where hemin increases the loss of binding activity from the cells during culture, concomitant with an increase in nucleoside binding in the externalized vesicles. Sheep reticulocytes retain the ability to synthesize the transferrin receptor, but the 35S-labeled receptors are not detected in released vesicles. Whereas hemin stimulates the loss of 35S-labeled transferrin receptors from the cell (t1/2 for loss approximately 20 hr), nonheme iron is more effective than heme. This difference in response of native and 35S-labeled receptor to hemin and iron supplements appears to be related to the differences in the two classes of receptors. Although the 35S-labeled receptor binds transferrin and both native and 35S-labeled peptides comigrate after chemical deglycosylation, the 35S-receptor is approximately 2 kD smaller than the native receptor and fails to acquire its complete size even when chased for up to 24 hr. Moreover, the 35S-labeled receptor is not expressed at the cell surface, but is retained in a nonrecycling compartment, where it is insensitive to digestion by trypsin at both 0 degrees C and 37 degrees C.

Animals↗
PubMed1989

Pretarsal fixation of gold weights in facial nerve palsy.

Implantation of a gold weight in the pretarsal space was performed on 17 patients with poor eyelid closure secondary to facial nerve weakness. Successful results were obtained in 14 (82%) of 17 patients. Postmortem histopathology of such a case demonstrated firm fibrous encapsulation of the weight. Although some authors advocate fixation of lid weights to the orbital septum, fixation in the pretarsal space is preferred for the following reasons: (a) "cheesewiring" is less likely to occur, (b) a limited levator recession may be more easily performed, (c) greater mechanical benefits are obtained, and (d) the potential for inferior migration is less.

Adult↗
PubMed1985

Phorbol ester inhibition of Na-H exchange in rabbit proximal colon.

In rabbit proximal colon, in vitro addition of phorbol 12,13-dibutyrate (PDB, 10(-7) M) to the serosal bathing medium inhibits mucosal (m)-to-serosal (s) unidirectional Na flux (JsmNa) without altering JsmNa or unidirectional Cl fluxes. Similar results were obtained when amiloride (2 X 10(-4) M) was added to the mucosal bathing medium. No additivity of effect was seen when tissues were exposed to both agents. Measurements with carboxyfluorescein reveal that the two agents cause equal decreases of intracellular pH (pHi), an effect that is dependent on the presence of extracellular Na (Na replacement also decreases pHi). No additivity of pHi effects is seen when both agents are added together. To determine the membrane site of this PDB-inhibitable Na-H exchange, Na influx across the luminal border of proximal colon was measured and was found to be inhibited equally by PDB and amiloride. We conclude that PDB, by activation of protein kinase C, inhibits electro-neutral amiloride-sensitive Na-H exchange in the luminal membrane of proximal colon.

Animals↗
PubMedDate not supplied

Enhancement of gene transfer efficiency into human cancer cells by modification of retroviral vectors and addition of chemicals.

Retroviral vectors have recently experienced limited use in cancer gene therapy mainly due to poor transduction efficiency. To overcome this drawback, we attempted to enhance the transduction efficiency by employing different retroviral packaging cell lines and chemical additives. The retrovirus from the PG13 packaging cell line gave mostly higher or similar transduction efficiencies in a variety of human cancer cell lines compared to the retrovirus from the PA317, Bing, or FLYRD18 packaging cell line. A cationic liposome, especially Lipofectamine, significantly enhanced the transduction efficiency of a retrovirus. However, the retrovirus derived from the PG13 cell line could not infect the murine cell line efficiently even after Lipofectamine treatment. Furthermore, chloroquine did not improve the transduction efficiency regardless of the presence of chemical additives. These results, therefore, suggested that the transduction efficiency of a retrovirus in human cancer cells can certainly be improved when a proper packaging cell line is chosen. In addition, this study implied that Lipofectamine is a superb additive to enhance the transduction efficiency of a retrovirus via a specific virus envelope protein-receptor interaction for virus entry, and that receptor-mediated endocytosis does not seem to be the leading route of virus delivery to liberate a virus genome.

3T3 Cells↗