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Biomedical subjects

W Kim

Publications and source records attributed to W Kim.

At least 145 records · Page 8Linked to original sources

Pancreatoblastoma.

BACKGROUND: Pancreatoblastoma is a rare pancreatic tumor with distinct acinar and squamoid cell differentiation that generally affects infants and young children. Just over 50 cases have been reported in the literature. METHODS: Five cases of pathologically proven pancreatoblastoma treated at Seoul National University Hospital from 1984 to 1994 were reviewed. There were three girls and two boys who were 2 years to 5 years of age. All cases came to medical attention because of an abdominal mass. RESULTS: Abdominal pain was observed in one case and anorexia, vomiting, and weight loss in one case. There was marked elevation of serum alpha-fetoprotein (27,000 ng/mL) in one case of liver metastases. Complete excision was performed in two cases in which the tumors were located in the tail of the pancreas. Partial excision was performed in two patients who had unresectable tumors of the head of the pancreas. One patient had an unresectable tumor at diagnosis and needle aspiration biopsy was carried out under ultrasound guidance. Electron microscopy was performed on pathological specimens of three cases and showed zymogen granules but not neuroendocrine granules. Immunocytochemical studies for alpha-fetoprotein, insulin, glucagon and somatostatin were performed in one patient, and results were all negative. Of two patients who underwent complete excision, one patient presented with liver metastases 4 months after operation and received chemotherapy, but died of tumor 6 months after operation. The other patient had local recurrence 1 year after operation. Reoperation and chemotherapy were performed, and the child is now alive without evidence of disease for 32 months. All three patients who had unresectable tumor died of tumor despite adjuvant radiotherapy and chemotherapy. CONCLUSIONS: The authors emphasize that the diagnosis of pancreatoblastoma in childhood should be suspected with palpation of an abdominal mass, and the chance for cure may be determined by complete excision of the tumor.

Child, Preschool↗

Evidence for thiol-dependent production of oxygen radicals by 4-methyl-5-pyrazinyl-3H-1,2-dithiole-3-thione (oltipraz) and 3H-1,2-dithiole-3-thione: possible relevance to the anticarcinogenic properties of 1,2-dithiole-3-thiones.

1,2-Dithiole-3-thiones are an important class of anticarcinogens that selectively induce cellular production of chemoprotective phase II detoxification enzymes. It is important to identify chemical properties of anticarcinogens that are responsible for this enzyme induction. Previously, the ability of 1,2-dithiole-3-thiones to induce phase II enzymes has been attributed to their electrophilic character. We report here that the anticarcinogenic 1,2-dithiole-3-thiones, oltipraz (4-methyl-5-pyrazinyl-3H-1,2-dithiole-3-thione, 1) and 3H-1,2-dithiole-3-thione (2), in conjunction with thiols, including the biological thiol glutathione, mediate the conversion of molecular oxygen to reactive oxygen radicals. Using a plasmid-based assay that monitors DNA cleavage, we find that 1 and 2, at micromolar concentrations, efficiently cleave DNA and that this cleavage can be suppressed by removal of molecular oxygen, addition of radical scavenging agents (mannitol, methanol, ethanol, and dimethyl sulfoxide), chelators of adventitious trace metals, and the peroxide-destroying enzyme catalase. Taken together, our data suggest that, in these reactions, molecular oxygen is converted to a peroxide species that undergoes a trace metal-catalyzed, Fenton-type reaction to generate oxygen radicals that cleave DNA. Reactive oxygen species are known to be capable of modulating gene expression in mammalian cells; thus, our studies indicate that oxygen radical production by 1,2-dithiole-3-thiones should be considered as a second chemical property, in addition to electrophilicity, that may play a role in the induction of protective phase II enzymes by this promising class of anticarcinogens.

Anaerobiosis↗

Testing transposable elements as genetic drive mechanisms using Drosophila P element constructs as a model system.

The use of transposable elements (TEs) as genetic drive mechanisms was explored using Drosophila melanogaster as a model system. Alternative strategies, employing autonomous and nonautonomous P element constructs were compared for their efficiency in driving the ry+ allele into populations homozygous for a ry- allele at the genomic rosy locus. Transformed flies were introduced at 1%, 5%, and 10% starting frequencies to establish a series of populations that were monitored over the course of 40 generations, using both phenotypic and molecular assays. The transposon-borne ry+ marker allele spread rapidly in almost all populations when introduced at 5% and 10% seed frequencies, but 1% introductions frequently failed to become established. A similar initial rapid increase in frequency of the ry+ transposon occurred in several control populations lacking a source of transposase. Constructs carrying ry+ markers also increased to moderate frequencies in the absence of selection on the marker. The results of Southern and in situ hybridization studies indicated a strong inverse relationship between the degree of conservation of construct integrity and transposition frequency. These finding have relevance to possible future applications of transposons as genetic drive mechanisms.

Animals↗

Renal tubule regeneration after ischemic injury is coupled to the up-regulation and activation of cyclins and cyclin dependent kinases.

Proliferation of renal tubules after acute injury is a reactive process of renal regeneration for recovery of renal function. Molecular and cellular mechanisms of the re-entrance of renal cells into the cell cycle after injury remain largely unknown. We have measured the correlations among the extent of proliferative activity and expression of cyclins and CDKs, and activity of each CDK during the regeneration period in the outer medullae of kidneys after ischemic injury in rats. The ratio of proliferating cell nuclear antigen (PCNA) positively immuno-stained nuclei to total nuclei per each section of the outer medulla of kidney indicated the proliferative index (PI) for this study. PI in the control period was 0.1%. The PI was increased at day 1 (13.4%), remained at a plateau at days 3 and 5 (30.5 and 32.3%), and decreased at day 7 and day 14 (17.3 and 12.2%) after ischemic injury. Proliferative activity was readily detectable in renal tubules, but was hardly detectable in glomeruli or blood vessels. As the PI increased, the mRNA and protein levels of cyclins D1, D3 and B, the mRNA levels of cyclin A, the protein levels of CDK4 and CDK2, and the activities of CDKs (CDK4, CDK2 and cdc2) increased in the outer medullae of kidneys after ischemic injury. These findings suggest that the temporal induction of proliferative activity in outer medullary tubules was closely linked with the cyclin/CDK system for regeneration of kidney after ischemic injury.

Animals↗

Effect of cutting the plantar fascia on mechanical properties of the foot.

A biomechanical model was used to calculate the loadbearing characteristics of the plantar fascia and to determine the effect of cutting the plantar fascia on the stiffness of the foot. With a load of 683 N applied to the foot, the model predicted a 17% increase in vertical displacement and a 15% increase in horizontal elongation when the plantar fascia was cut, compared with the corresponding value when the plantar fascia was intact. Plantar fasciotomy, although clinically satisfactory in cases of recalcitrant heel pain, decreases the stiffness of the foot and creates a less rigid and more deformable arch. The biomechanical model described can help to evaluate the possible outcome of such a procedure.

Elasticity↗

Angiotensin-converting enzyme gene polymorphism in patients with minimal-change nephrotic syndrome and focal segmental glomerulosclerosis.

To evaluate angiotensin-converting enzyme (ACE) gene insertion/deletion polymorphism in nephrotic syndrome, 85 patients (minimal-change nephrotic syndrome, MCNS: 55 cases; focal segmental glomerulosclerosis, FSGS: 30 cases) and 61 control subjects were examined. The distribution of ACE genotype in the control group was II 44%, ID 41% and DD 15%. The distribution of ACE genotypes in MCNS was similar to that in controls. However, the distribution of ACE genotypes in FSGS was markedly different from those of MCNS. The DD genotype was more frequent (p < 0.05) in FSGS than in MCNS. Patients with the DD genotype tended to present clinical symptoms at an earlier age. They also showed a lower responsiveness to corticosteroid therapy and a higher incidence of chronic renal failure than those with other genotypes. Our results indicate that the ACE DD genotype in FSGS may be a risk factor for the poor responsiveness to steroid therapy and the development of chronic renal failure.

Adolescent↗

Racial differences in surgically staged patients with endometrial cancer.

This study examined whether differences in survival for endometrial cancer attributed to race are primarily associated with socioeconomic status, comorbid illnesses, molecular genetic alterations, and other disease-related characteristics identified as poor prognostic factors. One hundred fifty-two surgically staged patients with endometrial cancer (37 African-American and 115 European-American women) treated from 1990 to 1994 were analyzed for differences in demographics, disease-related characteristics, and survival. Survival was poorer for African-American women than for European-American women. African-American women had lower socioeconomic status and a higher prevalence of poor prognostic factors. Surgical stage, positive peritoneal cytology, angiolymphatic invasion, cervical stromal involvement, and a history of other malignancies were similar between the two groups. The most important predictors of survival were age at diagnosis, surgical stage, myometrial invasion, positive peritoneal cytology, cervical stromal involvement, tumor grade, aneuploidy, histology, S-phase fraction, number of poor prognostic factors, and race. Racial differences in survival were not explained by socioeconomic status, comorbid illnesses, or estrogen use. When incorporating the number of poor prognostic factors in a survival model with race and surgical stage, race ceased to be of significant prognostic value. In an analysis restricted to women with poor prognostic factors, this phenomena also occurred after adjusting for the number of poor prognostic factors. These findings suggest that the cumulative number of poor prognostic factors, not race, is a more important predictor of survival in endometrial cancer.

Aged↗

1,2-Dithiolan-3-one 1-oxides: a class of thiol-activated DNA-cleaving agents that are structurally related to the natural product leinamycin.

Leinamycin is a recently discovered, thiol-dependent DNA-cleaving natural product. The mechanism of DNA cleavage by leinamycin is unknown. Inspired by this intriguing natural product, we have investigated the DNA-cleaving properties of three 1,2-dithiolan-3-one 1-oxides (1-3) that are structurally related to the suspected DNA-cleaving "core" of leinamycin. It was found that, similar to leinamycin, these three 1,2-dithiolan-3-one 1-oxides are thiol-dependent DNA-cleaving agents. At the concentrations of 1-3 used in these experiments (approximately 100 microM), efficient DNA cleavage is absolutely dependent on added thiol, with optimum cleavage occurring at 5-10 equiv (500 microM-1 mM) of added thiol. 2-Mercaptoethanol, glutathione, dithiothreitol, and thiophenol function with approximately equal efficiency as triggering agents for the cleavage reaction. DNA cleavage by 1-3 is not highly pH-dependent. Cleavage of DNA by these sulfur heterocycles is diminished by the removal of molecular oxygen from the reaction medium, by the radical scavengers methanol, ethanol, and mannitol, and by the enzyme catalase. Superoxide dismutase does not suppress DNA cleavage by these compounds. When diethylenetriaminepentaacetic acid is employed in these reactions as a chelator of adventitious trace metal ions, DNA cleavage is efficiently inhibited. The S-deoxy analog of 1 does not cleave DNA under conditions where 1 effects efficient thiol-mediated cleavage of DNA. These experiments indicate that, in concert with thiols, 1,2-dithiolan-3-one 1-oxides convert molecular oxygen to DNA-cleaving oxygen radicals. The marked effect of catalase further suggests that molecular oxygen is converted to hydrogen peroxide which ultimately cleaves DNA via a trace metal-dependent Fenton reaction. This work demonstrates that 1,2-dithiolan-3-one 1-oxides represent a general class of thiol-potentiated DNA-cleaving molecules.

Antibiotics, Antineoplastic↗

Phylogenetic relationships of annelids, molluscs, and arthropods evidenced from molecules and morphology.

Annelids and arthropods have long been considered each other's closest relatives, as evidenced by similarities in their segmented body plans. An alternative view, more recently advocated by investigators who have examined partial 18S ribosomal RNA data, proposes that annelids, molluscs, and certain other minor phyla with trochophore larva stages share a more recent common ancestor with one another than any do with arthropods. The two hypotheses are mutually exclusive in explaining spiralian relationships. Cladistic analysis of morphological data does not reveal phylogentic relationships among major spiralian taxa but does suggest monophyly for both the annelids and molluscs. Distance and maximum-likelihood analyses of 18S rRNA gene sequences from major spiralian taxa suggest a sister relationship between annelids and molluscs and provide a clear resolution within the major groups of the spiralians. The parsimonious tree based on molecular data, however, indicates a sister relationship of the Annelida and Bivalvia, and an earlier divergence of the Gastropoda than the Annelida-Bivalvia clade. To test further hypotheses on the phylogenetic relationships among annelids, molluscs, and arthropods, and the ingroup relationships within the major spiralian taxa, we combine the molecular and morphological data sets and subject the combined data matrix to parsimony analysis. The resulting tree suggests that the molluscs and annelids form a monophyletic lineage and unites the molluscan taxa to a monophyletic group. Therefore, the result supports the Eutrochozoa hypothesis and the monophyly of molluscs, and indicates early acquisition of segmented body plans in arthropods.

Animals↗

Purification and characterization of a fibrinolytic enzyme produced from Bacillus sp. strain CK 11-4 screened from Chungkook-Jang.

Bacillus sp. strain CK 11-4, which produces a strongly fibrinolytic enzyme, was screened from Chungkook-Jang, a traditional Korean fermented-soybean sauce. The fibrinolytic enzyme (CK) was purified from supernatant of Bacillus sp. strain CK 11-4 culture broth and showed thermophilic, hydrophilic, and strong fibrinolytic activity. The optimum temperature and pH were 70 degrees C and 10.5, respectively, and the molecular weight was 28,200 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The first 14 amino acids of the N-terminal sequence of CK are Ala-Gin-Thr-Val-Pro-Tyr-Gly-Ile-Pro-Leu-Ile-Lys-Ala-Asp. This sequence is identical to that of subtilisin Carlsberg and different from that of nattokinase, but CK showed a level of fibrinolytic activity that was about eight times higher than that of subtilisin Carlsberg. The amidolytic activity of CK increased about twofold at the initial state of the reaction when CK enzyme was added to a mixture of plasminogen and substrate (H-D-Val-Leu-Lys-pNA). A similar result was also obtained from fibrin plate analysis.

Amino Acid Sequence↗

Sequences of the 18S rDNAs from two Collembolan insects: shorter sequences in the V4 and V7 regions.

The complete 18S rDNA sequences were determined for Hypogastrura sp. and Crossodonthina koreana (Insecta: Collembola) using PCR cloning and Taq dideoxy sequencing. These two wingless insects show high sequence similarity to each other, without large insertions and/or deletions, and are clearly distinguished from the two dipteran insects Drosophila melanogaster and Aedes albopictus by shorter sequences in the V4 (61-76 bp) and in the V7 (89-104 bp). regions.

Animals↗

Role of plantar fascia in the load bearing capacity of the human foot.

Plantar fascia release is an accepted and widely used surgical way to reduce heel pain, however its effect of the load bearing characteristics of the foot is not well studied. A simple biomechanical model is developed here to analyze load bearing mechanism of the foot during the stance phase of the gait cycle. Quasilinearization is used for the system identification, and all model's parameters are determined from the in vivo tests. The model is used to compare the load bearing mechanism of different pathological situations. The results of the study suggest that the plantar fascia carries as much as 14% of the total load on the foot. Its surgical release decreases dynamic loading on the ankle by only 10%. It is also found that the lowering of the arch degenerates the load bearing capacity of the foot. Thus, the plantar fascia plays an important part in the load bearing by the foot and its surgical release should be carefully considered.

Adolescent↗

Comparison of the mechanical performance of three types of external fixators: linear, circular and hybrid.

Different configurations of the Monticelli-Spinelli and Ilizarov external fixation systems were tested to define their mechanical properties. In five configurations the external fixator consisted of rings with tensioned wires (circular), while in one configuration two pairs of the tensioned wires and their correspondent ring were replaced by threaded pins (hybrid). Testing was performed in axial compression, bending and torsion. The results were compared to the characteristics of a selected linear fixator group. Both the circular and the hybrid configurations were non-linear in compression. In bending, circular fixators had a similar pattern in both anteroposterior and oblique loading directions. The bending load-displacement pattern for the hybrid fixators was similar to the linear fixators, higher stiffness in the plane of the pins. Torsion was linear for both circular and hybrid fixators, as for the linear fixators. By combination of wires and pins (hybrid configuration), the mechanical behaviour had characteristics from both linear and circular fixators. It is concluded that the three studied groups own different mechanical performance and can be considered as different types of fixators. While it has been demonstrated that osteogenesis can be achieved independently of the mechanical behaviour of the fixator, this study supports the suggestion that some complications can be related to the mechanical behaviour of the fixator.

Journal Article↗