Search PubMed⌕ Search

Biomedical subjects

J Yoo

Publications and source records attributed to J Yoo.

At least 55 records · Page 3Linked to original sources
PubMed2000

Glycation impairs high-density lipoprotein function.

AIMS/HYPOTHESIS: To examine the effects of incubation of high-density lipoprotein (HDL) under hyperglycaemic conditions on several functions of HDL in vitro. METHODS: Human HDL (5 mg protein) was incubated for 1 week at 37 degrees C in the presence or absence of 25 mmol/l glucose. Additional samples of human HDL were incubated in butylated hydroxytoluene to control for oxidation. RESULTS: High-density lipoprotein incubated for 1 week in 25 mmol/l glucose had significant increases in the glycation product, fructoselysine and in the advanced glycation end product, N epsilon-(carboxymethyl)-lysine. High-density lipoprotein apolipoprotein AI and AII concentrations were not altered but glycated HDL had a 65% reduction in paraoxonase enzymatic activity. Glycated HDL did not inhibit monocyte adhesion to human aortic endothelial cells in response to oxidised low-density lipoprotein in vitro (43 +/- 4 monocytes bound vs 21 +/- 2 monocytes for control HDL, p < 0.0001). Hepatic lipase-mediated non-esterified fatty acid release from HDL lipids was enhanced in glycated HDL compared with control HDL (25 +/- 1 vs 16 +/- 1 nmol non-esterified fatty acid hydrolysed/min, respectively, p < 0.0001). Direct glycation of purified paraoxonase protein by incubation in 25 mmol/l glucose caused a 40% reduction in enzymatic activity. This glycated paraoxonase did not inhibit monocyte adhesion to human aortic endothelial cells in vitro (68 +/- 3 monocytes vs 49 +/- 2 monocytes bound for control paraoxonase, respectively, p < 0.001). We also measured a 40% reduction in paraoxonase activity in patients with Type II (non-insulin-dependent) diabetes mellitus and documented coronary artery disease compared with non-diabetic subjects, p < 0.0001. CONCLUSIONS/INTERPRETATION: Alterations in function of HDL caused by exposure to hyperglycaemic conditions could contribute to the accelerated atherosclerosis observed in Type II diabetes.

Aorta↗
PubMed2000

Frey's syndrome and parotidectomy flaps: A retrospective cohort study.

Gustatory sweating, also known as Frey's syndrome, is a recognized phenomenon after parotidectomy. The incidence of clinically significant gustatory sweating may be dependent on the thickness of the skin flap that is elevated at the time of surgery. Dissection in the subcutaneous level or the deeper sub-superficial musculoaponeurotic system level are 2 commonly used techniques in the operation. Twenty-eight patients were prospectively evaluated for Frey's syndrome after superficial parotidectomy. Thirteen patients underwent subcutaneous and 15 patients sub-superficial musculoaponeurotic system flap elevation. The overall incidence of gustatory sweating was determined, and a comparison of the two surgical techniques was assessed subjectively by patient interview-questionnaire and objectively evaluated with starch-iodine testing.

Cohort Studies↗
PubMed2000

Bacteriophage SP6 RNA polymerase mutants with altered termination efficiency and elongation processivity.

An Escherichia coli strain containing two plasmids was developed for in vivo isolation of the phage SP6 RNA polymerase mutants. It was developed to isolate mutants with increased proficiency of termination at the SP6 terminator and/or with reduced elongation processivity. Mutations were randomly introduced into an N-terminal third of the polymerase gene that was placed under a lac promoter in one plasmid. In the other plasmid, a promoter-lacking lacZ gene modified for reduced translation efficiency was placed downstream of a tandem pair of the SP6 terminator located downstream of an SP6 promoter-chloramphenicol acetyltransferase gene. Termination-up mutants were selected in vivo as they rendered LacZ activity level lower than the wild-type, without reducing chloramphenicol resistance substantially. Three such mutants (M15L, M15S, and D117G) were purified, and their termination efficiencies were measured in vitro at two different intrinsic termination signals in the E. coli rrnB terminator t1 that are different in requiring RNA hairpin formation. All three mutations enhanced termination efficiencies in vitro at the SP6 terminator and the upstream signal of rrnB t1, but reduced the efficiency at the downstream signal of it. All the mutations reduced elongation processivity, as the mutants produced much less amounts of large transcripts (2.1 kb) than the wild-type but the similar amounts of small transcripts (up to 670 nt). Thus, the mutations, all reducing elongation processivity of the polymerase, exhibited opposite effects on the two types of intrinsic termination signals, suggesting that the two mechanisms involve different interactions with the phage RNA polymerase.

Amino Acid Substitution↗
PubMed2000

Hemostatic effect of glue-lipiodol mixture plugged in the needle tract after renal biopsies in a high-risk, anticoagulated rabbit model.

RATIONALE AND OBJECTIVES: To investigate the hemostatic effect of a glue-lipiodol mixture plugged immediately into the needle tract after renal biopsy of high-risk, anticoagulated rabbits by use of a large-core gun biopsy needle and the subsequent pathological changes of the biopsy tract. METHODS: Twenty-five rabbits weighing 2 kg were divided into five groups (five rabbits each) according to time of sacrifice at 0, 2, 4, 6, and 8 days after biopsy. After anesthesia was induced, both kidneys were exposed and a bolus of 100 U/kg heparin was administered intravenously. Blood sampling was done twice, once before and once after heparinization, and activated partial thromboplastin times were measured for each. Then renal biopsies were performed in 25 pairs of kidneys by using an 18-gauge automated biopsy gun. The glue-lipiodol mixture was not injected into the first biopsy sites (control). Immediately after the second biopsies were done, 0.5 mL of the glue-lipiodol mixture at a 1:3 ratio was plugged into the needle tract through the outer cannula while withdrawing it slowly. Bleeding times of the two biopsies of each pair of kidneys were measured. All rabbits were humanely killed at their previously scheduled times, and histopathological findings were evaluated for the presence of inflammation, necrosis, foreign body reaction, and fibrosis around the biopsy tract. All parameters were classified into four categories according to the degree of severity, from 0 to + + +. RESULTS: Twenty-five cases (100%) of the controls bled after the biopsies were performed. Four of them (16%) showed immediate, massive, pulsatile bleeding. In contrast, only 11 of 25 cases (44%) bled at the second biopsy (plugged) sites and only two of them (8%) showed pulsatile bleeding. Mean bleeding times were 228 seconds in controls and 26 seconds in the glue-lipiodol mixture-plugged sites (P < 0.000). Histopathological examination of the needle tract in the plugged group revealed mild inflammation in the 0- to 2-day groups and moderate inflammation and mild necrosis in the 4- and 6-day groups. In the 8-day group, inflammation was diminished and only mild fibrosis was noted. There was no foreign body reaction in any of the specimens of the plugged group. CONCLUSIONS: We conclude that a glue-lipiodol mixture, when used as a plug material for the renal biopsy tract, is an efficacious method of bleeding control that is associated with a low incidence of pathological alterations in an anticoagulated rabbit model, thus demonstrating its future potential for clinical application.

Animals↗
PubMed2000

Expression of telomerase activity and telomerase RNA in human soft tissue sarcomas.

OBJECTIVE: To investigate whether telomerase is reactivated in soft tissue tumor and whether telomerase activity is regulated at the transcriptional level. DESIGN: Fresh tissue samples of 24 soft tissue sarcomas were analyzed for telomerase activity by a radioactive polymerase chain reaction-based telomeric repeat amplification protocol assay and for human telomerase RNA (hTR) by an in situ hybridization assay. SETTING: Tertiary care teaching hospital. PATIENTS: Twenty-four patients with soft tissue tumor were surgically treated. Twelve patients had malignant fibrous histiocytoma, 5 had liposarcoma, 6 had leiomyosarcoma, and 1 had rhabdomyosarcoma. RESULTS: Telomerase activity was detected in 4 sarcoma samples (17%), all of which were positive for hTR. Expression of hTR was demonstrated in 13 sarcomas (54%), 4 of which were positive for telomerase and 9 of which were negative for telomerase. One (50%) of 2 grade 1 tumors, 9 (50%) of 18 grade 2 tumors, and 3 (75%) of 4 grade 3 tumors showed hTR expression. CONCLUSIONS: The relatively low frequency of telomerase activity in soft tissue sarcomas suggests that telomerase may not play an important role in tumorigenesis in these tumors. Telomerase ladders were demonstrated only in association with tumors expressing hTR. It is noteworthy that half of the patients with grade 1 and 2 tumors expressed hTR, suggesting that telomerase RNA may be useful as a marker for identifying tumor aggressiveness earlier than the conventional histopathologic grading scale.

Adult↗
PubMed2000

ras gene mutations in salivary gland tumors.

OBJECTIVE: To assess the prevalence of activating mutations in K-ras and H-ras genes in salivary gland tumors with ductal or acinar differentiation and to evaluate their potential correlation with clinical parameters. DESIGN: Paraffin-embedded tissue samples of salivary gland carcinomas were investigated by the application of a direct sequence analysis procedure with automated DNA sequencing of polymerase chain reaction-amplified ras sequences. SETTING: Tertiary care teaching hospital. PATIENTS: Twenty-four patients with salivary gland carcinoma were surgically treated. Nine had adenocarcinoma, 1 had adenosquamous carcinoma, 11 had mucoepidermoid carcinoma, and 3 had acinic cell carcinoma. RESULTS: Point mutations were detected in 7 (29%) of the 24 carcinomas examined. The K-ras gene was mutated in only 2 samples (8%): a GGC-to-ATC mutation at codon 13 in an adenocarcinoma and a GGC-to-GTC transversion mutation at codon 13 in a mucoepidermoid carcinoma. Five (21%) harbored H-ras mutations: 4 contained a GGC-to-GTC transversion mutation at codon 12 and 1 had 2 distinct mutations, the same G-to-T at codon 12 as was shown in the other cases and a GGT-to-GGA heterozygous mutation at codon 13. All the H-ras mutations were in the group of mucoepidermoid carcinoma lesions (45%; 5/11). CONCLUSION: Our data suggest that K-ras gene alteration is probably not an important factor in the oncogenesis of human salivary gland tumors. However, mutational activation of the H-ras gene appears to play a role in the development and/or progression of salivary gland mucoepidermoid carcinomas.

Adenocarcinoma↗
PubMed1999

H-ras and K-ras mutations in soft tissue sarcoma: comparative studies of sarcomas from Korean and American patients.

BACKGROUND: The authors' recent investigation of Korean patients with sarcoma has suggested that ras gene activation may play a role in oncogenesis. The authors attempted to extend the mutation analysis to sarcomas in American patients to determine whether there were racial or geographic factors relevant to the initiation or progression of sarcoma. METHODS: H-ras and K-ras genes were examined in sarcomas obtained from patients in the midwestern U. S. using the polymerase chain reaction technique and direct automated sequencing analysis. Tumors studied included 29 malignant fibrous histiocytomas, 7 liposarcomas, 5 rhabdomyosarcomas, and 9 leiomyosarcomas. RESULTS: Of the 50 sarcomas evaluated, only 1 (2%) definable mutation was found; a GGC to AGC transition at codon 12 of H-ras was found in a rhabdomyosarcoma. None of the patients had a K-ras mutation. The rates of incidence of ras point mutations in these samples were much lower (H-ras: 2%; 95% confidence interval [95% CI], 0-11.5% and K-ras: 0%) than described for both genes in Korean studies (H-ras: 16%; 95% CI, 5.2-26.8% and K-ras: 44%; 95% CI, 29.5-58.5%). CONCLUSIONS: Although the reason for this discrepancy is not clear, there were no major differences found in histology or clinical stages. Based on this study of 50 sarcoma samples from American patients and the authors' previous study of 45 Korean tumor samples, the authors conclude that differing genetic and/or environmental mechanisms can affect sarcoma development or progression. Mutation of the H-ras and K-ras genes appears to be uncommon in sarcomas occurring in American patients, suggesting that the activation by point mutations of the H-ras and K-ras genes does not play a significant role in the pathogenesis or progression of sarcoma in these patients.

Adolescent↗
PubMed1999

Synthesis, structures and antitumor activity of the first crown ester-linked bipyridyl platinum complexes.

Three new crown ester-linked bipyridine homologs with three, four or five ethylene glycol units, which are bulky and soluble in both hydrophilic and lipophilic media, were synthesized. The reaction of the appropriate macrocycles with K2PtCl4 in water gave yellow cisplatin analogs in good yield. These complexes were converted to carboplatin analogs by exchange of the leaving group. All the compounds were characterized by elemental analysis and various spectroscopic methods. Carboplatin analogs showed good solubility in both hydrophilic and lipophilic media. The crystal structure of 2c, the carboplatin analog with macrocycles containing five ethylene glycol units, was determined by X-ray diffraction: space group P1, a = 9.798(1), b = 12.580(3), c = 13.945(2) A, alpha = 108.61(2), beta = 94.59(1), gamma = 97.42(2) degrees, Z = 2, R = 0.0618. Some of platinum complexes showed a moderate cytotoxic effect on both murine leukemia L1210 and P388 even though they do not have any NH proton.

2,2'-Dipyridyl↗
PubMed1999

Acute post streptococcal interstitial nephritis in an adult and review of the literature.

While glomerular lesions are a recognized sequel to infection with group A beta haemolytic streptococci, literature on primary tubular lesions, as remote effects of streptococcal infection, is scanty. A case of interstitial nephritis in a 29-year-old woman following streptococcal sore throat is described. This adult admitted with tonsillitis developed acute renal failure from acute interstitial nephritis and subsequently had full recovery of renal function. Acute interstitial nephritis should be included in the differential diagnosis of patients with streptococcal infections who develop acute renal failure.

Adult↗
PubMed1999

Engineering of osteochondral tissue with bone marrow mesenchymal progenitor cells in a derivatized hyaluronan-gelatin composite sponge.

The aim of this study was to investigate the potential of a composite matrix, containing esterified hyaluronic acid and gelatin, to facilitate the osteochondral differentiation of culture-expanded, bone marrow-derived mesenchymal progenitor cells. The cell loading characteristics and the effects of the matrix on cell differentiation were examined in vitro and in vivo. Empty and cell-loaded composites were cultivated for up to 28 days in a chemically defined medium with or without transforming growth factor-beta1 (TGF-beta1). A type II collagen-rich extracellular matrix was produced by cells loaded in the matrix and cultured in the presence of TGF-beta1. Empty and cell-loaded matrices were also implanted subcutaneously in immunodeficient mice. Three types of implant were used: empty (group I), cell-loaded matrices (Group II), and cell-loaded matrices cultured for 14 days in vitro in defined medium with TGF-beta1 (group III). No osteochondral differentiation was found in implanted empty matrices; however, the matrix supported osteochondrogenic cell differentiation in the cell-loaded implants. Preculture in vitro in a chondrogenic medium increased the percentage of osteochondral tissue found in the constructs after 3 weeks. These results indicate the potential use of this composite matrix for delivery of bone marrow-derived mesenchymal progenitor cells for the repair of chondral and osseous defects. The results also indicate that this composite matrix is useful for in vitro tissue engineering.

Animals↗
PubMed1999

Motivational-behavioral correlates of goal orientation and perceived motivational climate in physical education contexts.

The purpose of this study was to investigate how goal orientation (task and ego) and perceived motivational climate (mastery and performance) related to intrinsic motivation, self-esteem, adherence, and evaluated skill within Korean physical education contexts, 218 men attending physical education classes completed the Korean versions of the Perception of Success Questionnaire and the Perceived Motivational Climate in Sport Questionnaire, including a battery of motivational and behavioral assessments. Confirmatory factor analyses suggested that over-all fit for the modified versions of the questionnaires were reasonably acceptable. The results of canonical correlation analyses indicated that the task goal orientation was positively associated with intrinsic motivation and self-esteem, while the climate of perceived mastery was positively related to intrinsic motivation, adherence, and evaluated skill. These results were discussed within the frame of goal perspective theory in physical education contexts.

Ego↗
PubMed1999

H-ras and K-ras gene mutations in primary human soft tissue sarcoma: concomitant mutations of the ras genes.

ras gene mutations have been described with varying frequency in several types of human malignancies. To determine the incidence and type of ras mutations in human soft tissue tumors, we studied 45 sarcomas, including 27 malignant fibrous histiocytomas (MFHs), 10 liposarcomas, 2 rhabdomyosarcomas, and 6 leiomyosarcomas. Al of the tumors were investigated by direct sequence analysis with the automated DNA sequencing of polymerase chain reaction-amplified ras sequences. Twenty (44%) of the sarcomas examined harbored K-ras mutations, 18 (90%) of which were MFHs. All of the K-ras mutations were G-to-A transition mutations in the second position of codon 13 (glycine --> aspartic acid). Of the samples with K-ras activation, 7 (16% of the total of 45 tumors), including 6 MFHs and 1 leiomyosarcoma, also contained H-ras mutation. All of the tumors that showed H-ras alteration had G-to-T transversion mutations in the second base of codon 12 (glycine --> valine). These data possibly implicate that ras gene activation may be a relatively uncommon event in soft tissue tumors, with the exception of MFH. It is suggested that the oncogenic process underlying the development of tumors between these groups may be different and that ras gene mutations may play a role in the etiology and/or progression of MFH. It is noteworthy that when ras gene activation occurs in sarcoma, it predominantly affects the K-ras gene, particularly codon 13. Moreover, H-ras mutations in our samples were detected only in association with tumors that also displayed K-ras-mutated genes. This study demonstrates for the first time concomitant mutations in two different members of the ras gene family in sarcoma

Adolescent↗
PubMed1998

Selective conservation of an E-protein gene promoter during vertebrate evolution.

The murine E-protein gene ME1 encodes a non-tissue-specific, helix-loop-helix transcription factor that is associated with morphological development. ME1 gene expression is regulated by a TATA-less promoter that contains multiple Sp1 consensus elements, E-boxes, and a novel transcription initiation site. In this study, we compared DNA homologous to the ME1 promoter from vertebrate species ranging from frog to human. A region of striking sequence similarity was identified in a region corresponding to the ME1 transcription initiation site (ME1 Inr). Within this region, a poly d(A) tract and a 9-bp inverted repeat (5'-GTCCGCCTG) were highly conserved in all species that were examined. Protein complexes that recognized these DNA elements were present among distant vertebrates (frog, chick, monkey and human), and were able to bend the ME1 Inr to a similar extent (approximately 60 degrees) as the previously described murine MBP alpha and MBP beta proteins. Collectively, these results suggest that an ME1 Inr-like element and its associated proteins functioned in an ancestral vertebrate more than 350 million years ago.

Animals↗
PubMed1998

A biomechanical evaluation of graft loading characteristics for anterior cervical discectomy and fusion. A comparison of traditional and reverse grafting techniques.

STUDY DESIGN: A biomechanical study of graft loading characteristics for anterior cervical discectomy and fusion comparing the amount and location of transmitted forces. OBJECTIVES: To evaluate the difference between traditional iliac grafting and reverse iliac grafting used for anterior cervical discectomy and fusion in the amount and location of forces applied to the grafts. SUMMARY OF BACKGROUND DATA: Traditional fusion after anterior cervical discectomy involves placing a tricortical iliac crest strut into the disc space with the cortical portion facing anteriorly and the cancellous portion posteriorly. Recently, reverse iliac grafting has been introduced in which the cortical portion is placed in the posterior disc space and the cancellous portion in the anterior disc space. There is no biomechanical or clinical study showing an advantage of using one technique over the other. This study is the first to produce data supporting one technique as biomechanically superior. METHODS: Five fresh cadaveric cervical spines were tested using pressure-sensitive film placed between the bone graft and the vertebral endplate after an anterior discectomy was performed. A 10-pound load was applied to the cervical spine at predetermined sagittal positions. Recordings were made at neutral, 10 degrees of flexion, and 10 degrees and 20 degrees of extension after traditional and reverse iliac grafting. RESULTS: Graft forces were identical in both traditional and reverse grafting in the location and amount of force applied. Total force increased to the maximum in flexion and gradually decreased in more extended positions. The location of the forces was completely anterior with flexion, moving to the posterior portion of the graft with positions of extension. With 10 degrees of flexion, the load applied to the grafts was 20.4 N. In the neutral position, the load was 12 N. The loads decreased further with extension with forces of 11 N in 10 degrees extension, and 4 N in 20 degrees of extension. CONCLUSIONS: The optimal position of the tricortical iliac graft for an anterior cervical fusion is with the stronger cortical portion placed in the anterior disc space and the weaker cancellous portion placed in the posterior disc space. In this traditional position, the graft will best resist the loads applied to the cervical spine, preventing graft collapse.

Adult↗
PubMed1998

Sequential changes of sonographic and computed tomography findings in the normal rabbit liver after percutaneous ethanol injection. Correlation with pathologic findings.

RATIONALE AND OBJECTIVES: The authors assessed the sequential sonographic and computed tomographic (CT) findings and their correlations with pathologic findings of the normal rabbit liver after percutaneous ethanol injection (PEI). METHODS: In 30 anesthetized rabbits, 1 mL of ethanol was injected percutaneously under sonographic guidance. The animals were divided into five groups of six rabbits each according to the times of sonography and CT examinations after PEI: day 1 (immediately after), day 3, week 1, week 2, and week 4. The radiologic findings were analyzed regarding echogenicity (sonography) and density patterns before and after contrast administration (CT). The relations between radiologic findings and pathologic findings were examined using statistical analysis. The lesion size was measured using sonography and CT and compared with the actual size of the pathologic specimen. RESULTS: Sonography and CT showed various radiologic findings according to the time elapsed after PEI. The livers were hyperechoic in 100% (6/6) of the rabbits on day 1; this changed to isoechoic (67%, 12/18) or slightly hypoechoic (22%, 4/18) after week 1 through week 4 after PEI on sonography. CT scanning showed well-defined, hypodense lesions with no contrast enhancement in 100% (6/6) of the rabbits on day 1, and the lesions were slightly hypodense and relatively poorly defined in 88% (21/24) after day 3. Peripheral enhancement was noted in 83% (15/18) after week 1. Histopathologic examination revealed thrombosis and atrophic hepatic cell cords correlating well with hyperechogenicity on sonography and very low density on CT immediately after PEI. Coagulation necrosis was a main pathologic finding in the central portion of the lesions after day 3 and correlated with the CT findings of central low density without contrast enhancement. After week 1, peripheral granulation tissue and fibrosis were correlated with peripheral contrast enhancement on CT. Lesion size was largest in the week 1 group, and the size difference was statistically significant between the week 1 group and the day 1 group. CONCLUSIONS: Sonographic and CT findings of the PEI-treated normal rabbit liver varied with time in a predictable manner and correlated with pathologic findings. After a week, the PEI-treated normal liver shows perilesional enhancement that is nodular and irregular (particularly until 2 weeks); this must be taken into account when evaluating the therapeutic effect after PEI using conventional CT studies. Although long-term data are missing, control CT scans for residual tumor should not be performed before the second week after PEI because of the difficulty discerning enhancing tumor from enhancing fibrosis.

Analysis of Variance↗
PubMed1998

Desmoplastic cerebral astrocytoma of infancy: a case report.

We present a case of desmoplastic cerebral astrocytoma of infancy (DCAI) in a 9-month-old boy including immunohistochemical and proliferative activity studies. It was mainly composed of glial fibrillary acidic protein (GFAP)-positive astrocytes and desmoplastic stroma. Studies with Ki-67 and synthetic phase fraction disclosed a low proliferative activity. Flow cytometric study revealed diploidy pattern. These findings suggest a positive correlation with the favorable prognosis.

Astrocytoma↗