Biomedical subjects

J H Yoon

Publications and source records attributed to J H Yoon.

At least 19 recordsLinked to original sources

PubMed2002

Geobacillus toebii sp. nov., a novel thermophilic bacterium isolated from hay compost.

A thermophilic, spore-forming rod isolated from hay compost in Korea was subjected to a taxonomic study. The micro-organism, designated strain SK-1(T), was identified as being aerobic, Gram-positive, motile and rod-shaped. Growth of the isolate was observed at 45-70 degrees C (optimum 60 degrees C) and pH 6.0-9.0 (optimum pH 7.5). The G+C content of the genomic DNA was 43.9 mol%. Chemotaxonomic characteristics of the isolate included the presence of mesodiaminopimelic acid in the cell wall and iso-C15:0 and iso-C17:0 as the major cellular fatty acids. The predominant isoprenoid quinone was MK-7. The chemotaxonomic characteristics of strain SK-1(T) were the same as those of the genus Geobacillus. Phylogenetic analysis based on 16S rDNA sequences showed that strain SK-1(T) is most closely related to Geobacillus thermoglucosidasius. However, the phenotypic properties of strain SK-1(T) were clearly different from those of G. thermoglucosidasius. The level of DNA-DNA relatedness between strain SK-1(T) and the type strain of G. thermoglucosidasius was 27%. On the basis of the phenotypic traits and molecular systematic data, strain SK-1(T) represents a novel species within the genus Geobacillus, for which the name Geobacillus toebii sp. nov. is proposed. The type strain is strain SK-1(T) (= KCTC 0306BP(T) - DSM 14590(T)).

Base Composition↗

PubMed2002

Mutation analysis of the PIG-A gene in Korean patients with paroxysmal nocturnal haemoglobinuria.

AIM: Paroxysmal nocturnal haemoglobinuria (PNH) is caused by deficient biosynthesis of the glycosylphosphatidylinositol (GPI) anchor in haemopoietic stem cells. Mutation of the phosphatidylinositol glycan class A (PIG-A) gene, an X linked gene that participates in the first step of GPI anchor biosynthesis, is responsible for PNH. The characteristics of somatic mutation of the PIG-A gene in Korean patients with PNH were studied. METHODS: Twenty four patients with PNH were selected. Ham tests and sucrose haemolysis tests were carried out on all patients. The expression of CD59 in erythrocytes and granulocytes was investigated in 14 and five patients, respectively, to confirm the diagnosis. Dideoxy fingerprinting (ddF) was used to screen mutations, and direct sequencing of DNA was performed to characterise the mutations. RESULTS: Gene mutation was detected in 12 of the 24 patients. The other 12 patients were negative in ddF screening. Ten new mutations and two known mutations were detected. The mutations consisted of five deletions, six substitutions, and one insertion. These mutations resulted in six premature terminations, three abnormal splicings, one missense mutation in exon 2, and two nonsense mutations. Two patients with venous thrombosis showed mutations in exon 3 only. Substitution mutations were seen in six patients and frameshift mutations in the other six. CONCLUSIONS: There were 10 new mutations among the 12 mutations in the Korean patients with PNH and the characteristics of the mutations varied, with no significant hot spots in sites or types.

Adult↗

PubMed2002

DNA-directed magnetic network formations with ferromagnetic nanoparticles.

We formed a DNA network embedding ferromagnetic cobalt nanoparticles with a 12-nm diameter through a nanoscale self-assembly of DNA molecules on large-scale mica surfaces (12 mm x 12 mm); we then confirmed its structural characteristics with an atomic force microscope. Moreover, noncontact magnetic force microscope measurement revealed that some embedded cobalt nanoparticles have different directions of magnetization, similar to "bits" in magnetic data storage devices.

Aluminum Silicates↗

PubMed2001

UV-induced DNA damage and mutations in Hupki (human p53 knock-in) mice recapitulate p53 hotspot alterations in sun-exposed human skin.

The major etiological agent contributing to human nonmelanoma skin cancer is sunlight. The p53 tumor suppressor gene is usually mutated in these tumors, and the mutations are "UV signature" single or tandem transitions at dipyrimidine sequences in the DNA-binding domain (DBD). Cells that harbor these characteristic mutations are already present in sun-exposed skin areas of healthy individuals, and small epidermal patches that are immunoreactive to anti-p53 antibody accrue as exposure increases. To explore carcinogen-specific human p53 mutation patterns experimentally, we generated a knock-in (Hupki) mouse in which the murine DBD of the p53 gene has been replaced by the homologous human p53 DBD segment; thus, the precise base sequence context frequently targeted by mutagens or endogenous mutagenic processes in human carcinogenesis is present in this strain (J. L. Luo et al., Oncogene, 20: 320-328, 2001). Here we show that when epidermal cells of Hupki mice (p53(ki/ki)) are irradiated in vivo with a single acute dose of UVB light, they accumulate UV photoproducts at the same locations of the p53 gene as human cells. Chronic exposure of Hupki mice (4.5 kJ/m(2) 5x/week for 4 weeks) results in the appearance of cell patches that stain intensely with the anti-p53 antiserum CM1. DNA preparations from 2 cm(2) sections of chronically irradiated Hupki epidermis harbor C to T and CC to TT mutations at two mutation hotspots identified in human skin cancer, one at codons 278-279, and one at codons 247-248; the latter is the most frequent UVB-associated mutation site in humans but not in p53 wild-type mice. Thus, Hupki keratinocytes with these p53 mutations encode an aberrant DBD identical in amino acid sequence to the mutant p53 molecules in human UV-induced tumors. The Hupki mouse model offers a new experimental tool in molecular epidemiology and biomedical research.

Amino Acid Sequence↗

PubMed2001

Characterization of inwardly rectifying K(+) conductance across the basolateral membrane of rat tracheal epithelia.

The rat primary cultured-airway monolayer has been an excellent model for deciphering the ion channel after nystatin permeabilization of its basolateral or apical membrane. Inwardly rectifying K(+) currents were characterized across the basolateral membrane in symmetrical HCO(-)(3)-free high K(+) Ringer's solution (125 mM) in this study. The potency of K(+) channel inhibitors against K(+) conductance was Ba(2+) (IC(50) = 5 microM) > Cs(+) (IC(50) = 2 mM) >> glybenclamide (IC(50) > 5 mM) >> TEA (IC(50) >> 100 mM). The application of basolateral Cs(+) changed K(+) conductance into an oscillating current, and its frequency (holding voltage = -100 mV) increased with increase in concentration of basolateral Cs(+) (0.05-5 mM) and in degree of hyperpolarization. Addition of basolateral Cs(+) blocked inward current strongly at -100 mV and hardly at all at -60 mV, giving a sharp curvature to the I-V relation of the IRK current. RT-PCR, Western blotting, and immunohistochemical analyses showed that Kir2.1 might be present in basolateral membrane of tracheal epithelia and plasma membrane of pulmonary alveolar cells.

Amino Acid Sequence↗

PubMed2001

Hypermethylation of the CpG island of the RASSF1A gene in ovarian and renal cell carcinomas.

Homozygous deletion and loss of heterozygosity (LOH) at chromosome 3p21 have been observed in several types of human cancer including lung cancer and breast cancer. In previous work, we cloned and identified the human RAS association domain family 1A gene (RASSF1A) from the lung tumor suppressor locus 3p21.3. The CpG island and promoter region of RASSF1A is highly methylated in primary lung and breast tumors. In this study, we analyzed the methylation status of the promoter region of RASSF1A in 3 different tumor types: colon, ovarian and renal cell carcinoma. In colon cancers, 3 out of 26 tumor tissues (12%) were methylated at the CpG island of the RASSF1A gene. Renal and ovarian cancers showed a much higher frequency of methylation. For ovarian tumors, 8 out of 20 tumors (40%) were methylated. In renal cell carcinomas, 18 out of 32 cases (56%) were methylated. For all tumor types, none of the available normal tissues was methylated. This data suggests that methylation of the CpG island and promoter of the RASSF1A gene is common not only in lung and breast tumors but also in renal cell carcinoma and ovarian cancer.

Base Sequence↗

PubMed2001

Methylated CpG dinucleotides are the preferential targets for G-to-T transversion mutations induced by benzo[a]pyrene diol epoxide in mammalian cells: similarities with the p53 mutation spectrum in smoking-associated lung cancers.

A large fraction of the p53 mutations in lung cancers from smokers are G-to-T transversions, a type of mutation that is infrequent in lung cancers from nonsmokers and in most other tumors. Previous studies have indicated that there is an association between G-to-T transversion hotspots in lung cancers and sites of preferential formation of polycyclic aromatic hydrocarbon adducts along the p53 gene. p53 codons containing methylated CpG sequences are preferential targets for formation of adducts by (+/-) anti-7beta,8alpha-dihydroxy-9alpha,10alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE). To assess the role of CpG methylation in induction of mutations by BPDE, we analyzed BPDE mutagenesis in three CpG methylated target genes: a supF shuttle vector and the cII and lacI transgenes in embryonic mouse fibroblasts. After methylation of the shuttle vector at all CpG sequences, 42% of all G-to-T transversions were at CpG sites compared with 23% in unmethylated DNA. In the cII transgene, which is methylated at CpG sequences in vivo, 83 of 147 (56%) of the BPDE-induced mutations were G-to-T transversions, and 58% (48 of 83) of all G-to-T transversions occurred at methylated CpG sequences. In the lacI gene, 68% (75 of 111) of the BPDE-induced mutations were G-to-T events, and 58 of 75 (77%) of these occurred at methylated CpG sequences. The occurrence of transversion hotspots at methylated CpGs correlated with high levels of BPDE adducts formed at such sites. This situation mirrors the one in the p53 gene in lung cancers from smokers where 236 of 465 (51%) of the G-to-T transversions occurred at methylated CpG sites. These findings further strengthen a link between polycyclic aromatic hydrocarbons present in cigarette smoke and lung cancer mutations and provide evidence that mutational processes other than C-to-T transition mutations can occur selectively at methylated CpG sequences.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed2001

Cyclobutane pyrimidine dimers are responsible for the vast majority of mutations induced by UVB irradiation in mammalian cells.

The most prevalent DNA lesions induced by UVB are the cyclobutane pyrimidine dimers (CPDs) and the pyrimidine (6-4) pyrimidone photoproducts ((6-4)PPs). It has been a long standing controversy as to which of these photoproduct is responsible for mutations in mammalian cells. Here we have introduced photoproduct-specific DNA photolyases into a mouse cell line carrying the transgenic mutation reporter genes lacI and cII. Exposure of the photolyase-expressing cell lines to photoreactivating light resulted in almost complete repair of either CPDs or (6-4)PPs within less than 3 h. The mutations produced by the remaining, nonrepaired photoproducts were scored. The mutant frequency in the cII gene after photoreactivation by CPD photolyase was reduced from 127 x 10(-5) to 34 x 10(-5) (background, 8-10 x 10(-5)). Photoreactivation with (6-4) photolyase did not lower the mutant frequency appreciably. In the lacI gene the mutant frequency after photoreactivation repair of CPDs was reduced from 148 x 10(-5) to 28 x 10(-5) (background, 6-10 x 10(-5)). Mutation spectra obtained with and without photoreactivation by CPD photolyase indicated that the remaining mutations were derived from background mutations, unrepaired CPDs, and other DNA photopoducts including perhaps a small contribution from (6-4)PPs. We conclude that CPDs are responsible for at least 80% of the UVB-induced mutations in this mammalian cell model.

Animals↗

PubMed2001

Fatal submassive hepatic necrosis associated with tyrosine-methionine-aspartate-aspartate-motif mutation of hepatitis B virus after long-term lamivudine therapy.

We present a case of infection with lamivudine-resistant mutant hepatitis B virus (HBV) that fatally exacerbated hepatitis following the emergence of HBV with mutations in the tyrosine-methionine-aspartate-aspartate (YMDD) motif in an immunocompetent patient who was receiving long-term lamivudine therapy. Restriction fragment length polymorphism analysis showed that the YMDD-motif mutant was the predominant form of circulating HBV at the time of the fatal exacerbation, and a necropsy specimen of the liver revealed submassive hepatic necrosis without steatosis.

Amino Acid Motifs↗

PubMed2001

The significance of granzyme B expression in patients with angiocentric lymphoma of the head and neck.

BACKGROUND: The objectives of this study were to establish a correlation between granzyme B expression and the clinicopathologic characteristics of patients with angiocentric lymphomas of the head and neck and to determine whether the expression of granzyme B had any influence on the treatment outcomes of such patients. METHODS: Fifty-seven patients with angiocentric lymphoma of the head and neck who were treated between 1987 and 1996 were divided into two groups according to whether their tumors were immunoreactive for granzyme B: the granzyme B negative group (n = 22 patients) and the granzyme B positive group (n = 35 patients). The clinicopathologic features, immunohistochemical findings, patterns of disease failure, and survival data for the granzyme B positive group were compared with those for the granzyme B negative group. RESULTS: Greater than 60% of patients with angiocentric lymphoma of the head and neck were shown to have granzyme B positive tumors. All tumors that expressed granzyme B also consistently coexpressed CD56, indicating that they probably are the neoplastic equivalent of either natural killer (NK) cells or activated cytotoxic T cells. Although there were no significant differences in histopathologic features or expression of CD45RO and polyclonal CD3-epsilon between the groups, the Epstein-Barr virus genomes were detected more frequently in the granzyme B positive group compared with the granzyme B negative group. Despite a similar rate of complete remission after initial treatment, the locoregional recurrence rate of patients in the granzyme B positive group was much higher compared with patients in the granzyme B negative group. In addition, compared with patients in the granzyme B negative group, patients in the granzyme B positive group also had an increased risk of systemic disease recurrence and a decreased overall survival rate. CONCLUSIONS: The data indicate that the cytotoxic granule-associated protein, granzyme B, may be used as an additional marker for identifying NK/T-cell lymphoma and as a prognostic indicator for risk assessment in patients with angiocentric lymphoma of the head and neck.

Adult↗

PubMed2001

Cyclooxygenase-2 protein and prostaglandin E(2) production are up-regulated in a rat bladder inflammation model.

Cyclooxygenase-1 and cyclooxygenase-2 mRNAs and proteins and prostaglandin E(2) production are evaluated in a rat model of inflammation in which Escherichia coli lipopolysaccharide is intraperitoneally injected or intravesically instilled into the bladder. While cyclooxygenase-1 mRNA and protein and cyclooxygenase-2 mRNA do not change in bladders treated with lipopolysaccharide, cyclooxygenase-2 protein is elevated in bladders from rats intravesically instilled with lipopolysaccharide or phosphate buffered saline (PBS) or intraperitoneally injected with lipopolysaccharide. Urinary prostaglandin E(2) levels and prostaglandin E(2) synthesis in bladder particulates are elevated by intravesical instillation and intraperitoneal injection of lipopolysaccharide. The nitric oxide donor, S-nitroso-N-acetyl-D,L-penicillamine, increases prostaglandin E(2) synthesis in bladders from lipopolysaccharide intravesically instilled and intraperitoneally injected rats. Lipopolysaccharide increases prostaglandin E(2) synthesis by increasing cyclooxygenase-2 protein levels in rat bladder and prostaglandin E(2) synthesis may be further elevated by increases in nitric oxide caused by an up-regulation of inducible nitric oxide synthase (iNOS).

Administration, Intravesical↗

PubMed2001

Effects of simultaneous kidney-pancreaticoduodenal transplantation on diabetes-induced renal insufficiency in rats.

An investigation of the functional and histological changes was done after en-bloc kidney-pancreaticoduodenal transplantation (kpdt) in the diabetes-induced, renal insufficient Lewis rats. For donor preparation, an end-to-side portocaval shunt was performed, and the aortic, vena caval segments, and ureter-bladder patch were obtained. They were anastomosed microsurgically to recipient's aorta, vena cava, and bladder in end-to-side fashion. Of 15 diabetes-induced kpdt rats, 14 survived. Two of the 14 surviving rats showed ischemic necrosis. The remaining 12 transplants showed well-preserved glomeruli and Langerhans islets for 5 months postoperatively. Biochemical data comparing diabetic and sham-operated rats (six rats each), six diabetic controls, and 12 kpdt rats showed no significant statistical difference at said observation period. The diabetes-induced kpdt rats showed improvement of following biochemical data: within 1 week postoperatively, the glucose level fell from 300 to 115 mg/dL; BUN level from >20 to <20 mg/dL; the creatinine level from 1.5 to <1.2 mg/dL. The insulin level returned to normal, 1.1 ng/mL, in 2 weeks. The results demonstrate that the kpdt model is an effective and successful operative technique in diabetic rats and may provide effective therapeutic methods for diabetes-induced renal insufficiency.

Animals↗

PubMed2001

Rate-adaptive pacemaker controlled by motion and respiratory rate using neuro-fuzzy algorithm.

Rate-adaptive pacemakers use information from sensors to change the rate of heart stimulation. Until now, fuzzy-pacemaker algorithms have been used to combine inputs from sensors to improve heart rate control, but they have been difficult to implement. In this paper, a pacemaker algorithm which controlled heart rate adaptively by motion and respiratory rate was studied. After chronotropic assessment exercise protocol (CAEP) tests were performed to collect activity and respiratory rate signals, the intrinsic heart rate was inferred from these two signals by a neuro-fuzzy method. For 10 subjects the heart rate inference, using the neuro-fuzzy algorithm, gave 52.4% improved accuracy in comparison with the normal fuzzy table look-up method. The neuro-fuzzy method was applied to a real pacemaker by reduced mapping of the neuro-fuzzy look-up table.

Adaptation, Physiological↗

PubMed2001

Evaluation of premalignant potential in oral lichen planus using interphase cytogenetics.

This study attempted to evaluate whether oral lichen planus (OLP) has the potential to progress to oral squamous cell carcinoma (OSCC) by comparing the degree of genetic instability between clinically-curable OLP and lesions that progressed to OSCC. Fifteen cases of steroid-responsive OLP and two cases of lichenoid dysplasia (LD) that progressed to OSCC were used for this study. Chromosome in situ hybridization (CISH) was performed for chromosomes 9 and 17. The fraction of polysomic and monosomic cells for chromosome 9 increased in mucosal epithelium compared to those of lymphocytes in OLP. This difference was statistically significant (P=0.0017, 0.0054, respectively). Two LD patients showed 15.38% and 22.58% of PI for chromosome 9. In OSCC that developed from LD, the fraction of monosomic cells for chromosome 9 increased by more than 70%. We concluded that LD should be treated as a high-risk premalignant lesion and strongly suggest that the monosomy of chromosome 9 may have a critical role in progress to malignancy from LD.

Adult↗

PubMed2001

Transcolumellar approach in transsphenoidal pituitary surgery for patients with small nostril.

OBJECTIVE: Sublabial approach has been widely used as the standard technique for transsphenoidal pituitary surgery. But it has several possible drawbacks, such as; postoperative flat nose deformity, hypesthesia of upper gum, and feeding difficulty until 2 to 3 weeks after surgery. As an alternative, an endonasal approach was adopted for patients who had large nostrils, such as white or acromegalic patients. In patients with small nostrils, especially oriental people, it requires an additional tension release incision that leaves a definitely visible scar at the base of nose. STUDY DESIGN: We applied the transcolumellar approach, which modified the external rhinoplasty approach on the 136 cases of transsphenoidal pituitary surgery that were performed from 1994 to June 1999. RESULTS: In all patients, we found we could reach the anterior portion of nasal septum in 7 to 8 mm in depth from the skin surface and eliminate the disadvantages of sublabial and endonasal approach. Also, this method can markedly reduce the surgical dissection time and blood loss. CONCLUSIONS: We concluded that this technique was relatively simple and more than adequate in most transsphenoidal pituitary surgery, even in patients with small nostrils.

Asian People↗

PubMed2001

Malignant lymphoma of the maxillary sinus manifesting as a persistent toothache.

Many teeth have been mistakenly extracted or endodontically treated because of an incorrect diagnosis of orofacial pain, including toothache. A case of persistent toothache originating from a malignant lymphoma of the left maxillary sinus is presented. Root canal therapy and extraction of the upper left quadrant teeth from the canine to the second molar did not resolve the chief complaint. The patient was referred to a neurologist and received a diagnosis of a malignant lymphoma, a rare lesion of the maxillary sinus. This case stresses the importance of considering malignant neoplasm of the maxillary sinus as a potential etiologic factor in the differential diagnosis of orofacial pain.

Aged↗

PubMed2001

Computed tomographic and anatomical analysis of the basal lamellas in the ethmoid sinus.

OBJECTIVES: To investigate the exact anatomical structure of the lamellas in the ethmoid sinus by computed tomography (CT) and anatomical analysis. STUDY DESIGN: Cadaver dissections and CT scans were used to compare lamellar structures and their radiological images. METHODS: Anatomical microdissection of 100 midsagittal sections from adult cadaver head specimens were examined and compared with those of sagittal CT scans at 1-mm intervals. RESULTS: The posteroinferior end of the uncinate process attaching to the inferior turbinate divided the fontanelle into the anterior and posterior portions in the majority of cases. The basal lamellas of the bulla ethmoidalis were subdivided into three major types. The posteroinferior portion of its basal lamella was connected to the lower horizontal portion of the third basal lamella in all cases. The anterior indentation of the third lamella was identified in nine cases, but there was no indentation in the posterior direction. The basal lamella of the superior turbinate was attached to the skull base superiorly either separately or fused to the third lamella, and its posteroinferior portion was attached to the lowest portion of the anterior wall of the sphenoid sinus. The supreme turbinate existed in 50 cases; however, its basal lamella was identified in only 15 cases. CONCLUSIONS: Our results indicate that the lamellas of the ethmoid sinus have relatively uniform patterns, although there is variability in shape. It is hoped that this study will provide surgeons with a more detailed structure of the basal lamellas for better surgical results and lower complication rates.

Adult↗

PubMed2001

Surgical anatomy of the nasofrontal duct: anatomical and computed tomographic analysis.

OBJECTIVES: Although complete anatomical knowledge of the nasofrontal duct has been of great importance, little is known about it. The aim of this study is to examine the drainage site of the nasofrontal duct and to investigate the anatomical boundaries of the nasofrontal duct according to the drainage site. STUDY DESIGN: One hundred sagittally divided adult head specimens were analyzed by computed tomography and dissection under the surgical microscope. METHODS: Computed tomography scans of 50 adult cadaver heads were taken sagittally at 1-mm intervals and coronally at 3-mm intervals to find the nasofrontal duct. One hundred specimens, made up of sagittally divided adult cadaver heads, were dissected under the microscope to study the structure of the nasofrontal duct. RESULTS: We identified the anterior, posterior, medial, and lateral boundaries of the nasofrontal duct. In the most common type, the superior portion of the uncinate process formed the anterior border and the superior portion of the bulla ethmoidalis formed the posterior border of the nasofrontal duct. The conchal plate formed the medial border and the suprainfundibular plate formed the lateral border of the nasofrontal duct. Other variations are described in detail. CONCLUSIONS: To widen the nasofrontal communication, removing the upper portion of the ground lamella of the ethmoid bulla, which is the posterior boundary of the nasofrontal duct, with cutting forceps seems to be a safe and easy method.

Adult↗