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Y Yoon

Publications and source records attributed to Y Yoon.

At least 55 records · Page 3Linked to original sources
PubMed1995

Purification and characterization of assembly-competent tubulin from Aspergillus nidulans.

We have developed a procedure for purifying assembly-competent tubulin from Aspergillus nidulans. To our knowledge, this is the first report of the purification of assembly-competent tubulin from a filamentous fungus, and the procedure should be of great value in analyzing the large number of alpha- and beta-tubulin mutations that have been isolated and characterized in A. nidulans. Our procedure consists of overproduction of alpha- and beta-tubulin, partial purification by ion-exchange chromatography, and final purification by rounds of assembly and disassembly. We have found that taxol promotes the assembly of A. nidulans tubulin into microtubules, but a higher concentration of taxol is required for maximal assembly of A. nidulans tubulin than is required for brain tubulin. The critical concentration for assembly in the presence of taxol is also significantly higher for A. nidulans tubulin than for brain tubulin. In addition, A. nidulans microtubules that were assembled and maintained in the presence of taxol depolymerized in conditions in which taxol-stabilized mammalian microtubules remain intact. These results suggest that A. nidulans tubulin has a lower affinity for taxol than mammalian tubulin.

Amino Acid Sequence↗
PubMed1995

Mapping of replication initiation sites in human ribosomal DNA by nascent-strand abundance analysis.

New techniques for mapping mammalian DNA replication origins are needed. We have modified the existing nascent-strand size analysis technique (L. Vassilev and E.M. Johnson, Nucleic Acids Res. 17:7693-7705, 1989) to provide an independent means of studying replication initiation sites. We call the new method nascent-strand abundance analysis. We confirmed the validity of this method with replicating simian virus 40 DNA as a model. We then applied nascent-strand abundance and nascent-strand size analyses to mapping of initiation sites in human (HeLa) ribosomal DNA (rDNA), a region previously examined exclusively by two-dimensional gel electrophoresis methods (R.D. Little, T.H.K. Platt, and C.L. Schildkraut, Mol. Cell. Biol. 13:6600-6613, 1993). Our results partly confirm those obtained by two-dimensional gel electrophoresis techniques. Both studies suggest that replication initiates at relatively high frequency a few kilobase pairs upstream of the transcribed region and that many additional low-frequency initiation sites are distributed through most of the remainder of the ribosomal DNA repeat unit.

Animals↗
PubMed1995

Percutaneous drainage of splenic abscess in typhoid fever--a case report.

Salmonella typhi splenic abscesses are a very rare complication of typhoid fever. Splenectomy is the standard surgical treatment for these lesions. But these days, with improvements in imaging techniques, percutaneous drainage of splenic abscesses has been demonstrated to be one of the alternative treatment in selected cases. We report the case of a 7 year-old male, who presented with Salmonella typhi in blood and urine cultures, and a 1: 320 in O titer of Widal test. Ultrasound and computed tomography showed a single splenic abscess, 3 cm in diameter. He was treated with antibiotics, but the symptoms were not relieved. Thus we performed the percutaneous drainage of the splenic abscess under ultrasound guidance. A culture of the aspirated material was positive for Salmonella typhi, and the boy's condition improved. We think that percutaneous drainage of a single lesion was an excellent alternative to surgery, particularly because our patient was young and spleen conservation was desirable.

Abscess↗
PubMed1994

Sonography and color Doppler imaging of Budd-Chiari syndrome of membranous obstruction of the inferior vena cava.

We examined 18 patients with Budd-Chiari syndrome (membranous obstruction of the hepatic IVC). IVC obstruction was detected by sonography in 17 cases (94%). The causes were a web in 10 cases and a fibrous cord in four cases. In three cases, the cause was unspecified. Obliteration of the hepatic veins or intrahepatic collateral vessels or both was delineated in 16 cases (89%). With seven cases of color Doppler imaging, there was no detectable color or Doppler signal within the IVC, and the direction of hepatic venous blood flow through intravenous communications was fairly well demonstrated in all cases. In four cases of follow-up color Doppler imaging, the patency of the IVC was well demonstrated. Sonography is useful in detecting obstruction of the hepatic IVC and in demonstrating the hepatic venous obstruction and intrahepatic collateral vessels. Color Doppler sonography is useful in demonstrating the direction of blood flow through interconnecting vessels and in evaluating the patency of the IVC after treatment.

Adolescent↗
PubMed1994

Spinal cholinergic alpha-2 adrenergic interactions in analgesia and hemodynamic control: role of muscarinic receptor subtypes and nitric oxide.

Intrathecal injection of neostigmine enhances antinociception from clonidine while it counteracts clonidine-induced hypotension. This study further examined the pharmacology of neostigmine-clonidine interactions in the spinal cord and focused on the roles of muscarinic receptor subtypes and local nitric oxide synthesis. Spinal neostigmine counteracted clonidine-induced decreases in blood pressure and heart rate in conscious sheep and this effect was blocked by spinal injection of the M2 muscarinic antagonist, AFDX-116, but not by the M1 muscarinic antagonist, pirenzepine. Carbamylcholine injected spinally alone increased blood pressure and heart rate and these effects and neostigmine's hemodynamic interaction with clonidine were blocked by spinal injection of the nitric oxide synthase inhibitor, N-methyl-L-arginine. The authors also investigated antinociceptive interactions by using a mechanical pressure stimulus on the forelimb of conscious sheep. Spinal clonidine produced dose-dependent antinociception, which was enhanced by neostigmine and antagonized by N-methyl-L-arginine. NADPH diaphorase staining of sheep spinal cord revealed dense localization to the superficial dorsal horn and the intermediolateral cell column. These results suggest that counteraction of spinal clonidine-induced hypotension by neostigmine is due to stimulation of spinal M2 muscarinic receptors and synthesis of nitric oxide. Nitric oxide synthesis is also necessary for clonidine-induced antinociception in sheep.

Analgesia↗
PubMed1993

Carcinoma of the ampulla of Vater: sonographic and CT diagnosis.

Twenty patients with carcinoma of the ampulla of Vater were studied with sonography (N = 9) or both sonography and CT (N = 11). The tumor was shown by sonography in 16 patients (80%) as a small, round or oval, fairly well delineated mass in between the dilated distal common bile duct and duodenum which was delineated owing to luminal fluid or gas (N = 13); or as a polypoid mass within the dilated distal common bile duct resulting in abrupt obstruction (N = 3). In the remaining four patients, the mass was not delineated. Bile ducts were dilated down to the level of mass or ampullary region in all cases (100%), while the pancreatic duct was dilated in five cases (45%). We believe that sonography is the technique of initial choice in the diagnosis of carcinoma of the ampulla of Vater by identifying the mass at the distal end of the dilated common bile duct and/or pancreatic duct.

Adenocarcinoma↗
PubMed1993

Small intestinal phytobezoars: sonographic detection.

Three cases of small intestinal phytobezoar, suggested by sonography and later confirmed at surgery, are reported. Sonographic findings of bezoar were intraluminal mass presenting as an arc-like surface echo casting clear posterior acoustic shadow within the lumen of the dilated small bowel. Compression of the mass with a transducer induced fluid shift around the mass. We propose that diagnosis of bezoars can be suggested on the basis of sonographic findings.

Aged↗
PubMed1993

Primary breast lymphoma.

We report the case of a 20-year-old female with lymphoma of the breast. Mammography showed an asymmetric pattern of confluent densities without any discrete mass. Sonography revealed diffuse heterogenous echoic mass intermingled with low-and medium level echoes. We present the clinical, radiographic and histologic features of primary breast lymphoma with a brief review of the literatures.

Adult↗
PubMed1993

Sonographic findings of intestinal tuberculosis.

Sonograms in 41 patients with intestinal tuberculosis were analyzed. The sonographic findings of intestinal tuberculosis were thickening of the wall in the ileum, cecum, or ascending colon (or in more than one of these). We detected the wall thickening in 38 cases by sonography (detection rate, 93%). The ileum was the most frequent site of involvement. The patterns of bowel wall thickening were diffuse in 30 cases and focal in eight cases and were concentric in 28 cases and eccentric in six cases. The associated findings were ascites, lymphadenopathy, omental cake, and cecal spasm in order of decreasing frequency. The sonographic findings are not specific for the diagnosis of intestinal tuberculosis, but when noted in the appropriate clinical situation would be of great help in the diagnosis of intestinal tuberculosis.

Adult↗
PubMed1991

Sonographic findings in tuberculous peritonitis of wet-ascitic type.

Sonograms in 46 patients with tuberculous peritonitis of the wet-ascitic type were analysed retrospectively. The ascites was clear in 24 patients (52%). There were fixed membranes, septa and debris in eight patients (17%), floating debris in six patients (13%), mobile strands or membranes in four patients (9%), and fixed septa in four patients (9%). The patients were divided into two groups depending on the amount of ascites: small amount of ascites with clear fluid in eight patients (17%), and moderate or large amount of ascites with clear or complex fluid in 38 patients (83%). Associated findings were omental 'cake' (26%), hepatomegaly (24%), thickened mesentery with adherent small bowel loop (22%), splenomegaly (20%), pleural effusion (17%), lymphadenopathy (13%), and thickening of the ileal wall (7%). The sonographic findings are not specific for tuberculous peritonitis, but may give valuable information to prevent unnecessary laparotomy.

Abdomen↗
PubMed1990

Gamma-tubulin is a component of the spindle pole body that is essential for microtubule function in Aspergillus nidulans.

We have recently discovered that the mipA gene of A. nidulans encodes gamma-tubulin, a new member of the tubulin superfamily. To determine the function of gamma-tubulin in vivo, we have created a mutation in the mipA gene by integrative transformation, maintained the mutation in a heterokaryon, and determined the phenotype of the mutation in spores produced by the heterokaryon. The mutation is lethal and recessive. It strongly inhibits nuclear division, less strongly inhibits nuclear migration, and, as judged by immunofluorescence microscopy, causes a reduction in the number and length of cytoplasmic microtubules and virtually a complete absence of mitotic apparatus. We conclude that gamma-tubulin is essential for microtubule function in general and nuclear division in particular. Immunofluorescence microscopy of wild-type hyphae with affinity-purified, gamma-tubulin-specific antibodies reveals that gamma-tubulin is a component of interphase and mitotic spindle pole bodies. We propose that gamma-tubulin attaches microtubules to the spindle pole body, nucleates microtubule assembly, and establishes microtubule polarity in vivo.

Alleles↗
PubMed1990

Medial extent of the posterior renal fascia. An anatomic and computed tomography study.

To study the medial extent of the posterior renal fascia and the perirenal space, the authors dissected two cadavers and reviewed 50 computed tomographic (CT) abdominal scans. The results demonstrated that the medial extent of the posterior renal fascia depends on the level in a vertical direction and its relationship to the kidney which varies at different levels. At the renal hilus, the fascia inserts posteromedially to the fascia of the quadratus lumborum along its lateral margin; more cranially, the line of insertion is more lateral, onto the diaphragmatic fascia; more caudally, the line of insertion is more medial, inserting onto the anterior surface of the quadratus lumborum. Therefore the posteromedial insertion of the posterior renal fascia extends medially, from the more laterally placed diaphragmatic fascia, to the lateral margin of the quadratus lumborum and then to the anterior surface of the quadratus lumborum, depending on the anatomic level. The clinical implication of these findings are discussed.

Cadaver↗
PubMed1990

Lobar bronchioloalveolar carcinoma: "angiogram sign" on CT scans.

The authors reviewed computed tomographic (CT) scans of 12 patients with lobar bronchioloalveolar carcinoma. Seven patients had consolidation of the entire lobe, and five patients had segmental consolidation. After contrast material was administered intravenously, the consolidated lung typically appeared on the scan as an area of homogeneous low attenuation, within which were enhanced branching pulmonary vessels (the CT angiogram sign). To evaluate the specificity of this sign in the discrimination of bronchioloalveolar carcinoma, CT scans of 26 patients who had lobar consolidation from other diseases were randomly mixed with the CT scans of 11 patients with bronchioloalveolar carcinoma. Two independent observers who were unfamiliar with the cases classified 10 and nine of the 11 patients with bronchioloalveolar carcinoma, respectively, as positive for bronchioloalveolar carcinoma by applying the CT angiogram sign, and classified as negative 25 and 23 of the 26 patients without bronchioloalveolar carcinoma, respectively, for an overall specificity of 92.3%. The angiogram sign appeared on the CT scan because of the low-attenuating consolidation, which was caused by the production of mucin or other fluid and the intact bronchovascular framework within the tumor.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed1990

Sonographic detection of pneumoperitoneum in patients with acute abdomen.

We describe five patients who presented with an acute abdomen in whom pneumoperitoneum was first detected by sonography. All five subsequently were proved to have a perforated viscus. In all cases, the pneumoperitoneum was seen as an echogenic line with a posterior ring-down or reverberation artifact between the anterior abdominal wall and the anterior surface of the liver. The finding was shown best in the right upper quadrant with the patient in the left lateral decubitus position. The echoes caused by the pneumoperitoneum overlapped the echoes of the lung during inspiration, but the echoes were separate during expiration. The probable cause of pneumoperitoneum was determined with sonography in four of the five patients: three had perforation of duodenal ulcer and one had perforation of gastric cancer. The fifth patient had a perforated ileum, which was not evident on the sonogram. Our experience with these patients suggests that the detection of pneumoperitoneum on sonography in patients with an acute abdomen is an important sign of a perforated viscus.

Abdomen, Acute↗
PubMed1988

Superior aspect of the perirenal space: anatomy and pathological correlation.

To study the anatomy of the superior aspect of the perirenal space, we analysed 50 computed tomographic (CT) scans with reference to the anatomy of Gerota's fascia, and dissected five cadavers laying special emphasis on the ascent of Gerota's fascia. We also reviewed 10 scans of patients with a large lesion in the right upper abdomen regarding localisation of the lesion. We conclude that Gerota's fascia does not cover the upper portion of the kidney and adrenal gland so that the superior aspect of the perirenal space is open towards the upper abdominal extraperitoneal space. Thus, a large lesion arising from the right adrenal gland or kidney easily invaginates the liver through the bare area mimicking a hepatic lesion, and vice versa. This explains the difficulty in localising a large lesion in the right upper abdomen.

Humans↗