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Biomedical subjects

J Kim

Publications and source records attributed to J Kim.

At least 1,009 records · Page 56Linked to original sources
PubMed1993

[Procedures in color Doppler ultrasound--comparison of methods].

Various colour flow imaging techniques for diagnostic ultrasound have been reported in the literature, each claiming distinctive performance characteristics for the benefit of the user. The following is a review of the principles of autocorrelation, autoregression (or maximum entropy), and of cross-correlation methods. All three approaches are based on the same principle of physics, i.e. the analysis of echoes backscattered from red blood cells of fluctuating density due to motion, but differ in their sampling requirements and in signal processing. A comparison of major performance features and challenges is given.

Algorithms↗
PubMed1993

Epidermal growth factor stimulates vascular endothelial growth factor production by human malignant glioma cells: a model of glioblastoma multiforme pathophysiology.

Hypervascularity, focal necrosis, persistent cerebral edema, and rapid cellular proliferation are key histopathologic features of glioblastoma multiforme (GBM), the most common and malignant of human brain tumors. By immunoperoxidase and immunofluorescence, we definitively have demonstrated the presence of vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFr) in five out of five human glioma cell lines (U-251MG, U-105MG, D-65MG, D-54MG, and CH-235MG) and in eight human GBM tumor surgical specimens. In vitro experiments with glioma cell lines revealed a consistent and reliable relation between EGFr activation and VEGF production; namely, EGF (1-20 ng/ml) stimulation of glioma cells resulted in a 25-125% increase in secretion of bioactive VEGF. Conditioned media (CM) prepared from EGF-stimulated glioma cell lines produced significant increases in cytosolic free intracellular concentrations of Ca2+ ([Ca2+]i) in human umbilical vein endothelial cells (HUVECs). Neither EGF alone or CM from glioma cultures prepared in the absence of EGF induced [Ca2+]i increases in HUVECs. Preincubation of glioma CM with A4.6.1, a monoclonal antibody to VEGF, completely abolished VEGF-mediated [Ca2+]i transients in HUVECs. Likewise, induction by glioma-derived CM of von Willebrand factor release from HUVECs was completely blocked by A4.6.1 pretreatment. These observations provide a key link in understanding the basic cellular pathophysiology of GBM tumor angiogenesis, increased vascular permeability, and cellular proliferation. Specifically, EGF activation of EGFr expressed on glioma cells leads to enhanced secretion of VEGF by glioma cells. VEGF released by glioma cells in situ most likely accounts for pathognomonic histopathologic and clinical features of GBM tumors in patients, including striking tumor angiogenesis, increased cerebral edema and hypercoagulability manifesting as focal tumor necrosis, deep vein thrombosis, or pulmonary embolism.

Brain Neoplasms↗
PubMed1993

The Drosophila melanogaster suppressor of Hairy-wing zinc finger protein has minimal effects on gene expression in Saccharomyces cerevisiae.

Many mutations in Drosophila melanogaster are gypsy retrotransposon insertions. Gypsy binds the protein (SUHW) encoded by the suppressor of Hairy-wing [su(Hw)] gene, and SUHW alters expression of surrounding genes. When gypsy is between an enhancer and promoter, SUHW blocks activation of transcription by the enhancer. Additionally, when gypsy is downstream of a promoter in a parallel orientation, SUHW increases truncation of transcripts at the poly(A) site in the gypsy 5' long terminal repeat, thereby decreasing the gene transcript levels. The effects of SUHW appear to involve fundamental and general mechanisms controlling gene expression because SUHW potentiates other poly(A) sites and blocks several enhancers in Drosophila. To investigate these mechanisms, SUHW was expressed in Saccharomyces cerevisiae. Although SUHW enters the nucleus and binds DNA in yeast, it has surprisingly minor effects on utilization of the CYC1 poly(A) site and transcription activation by a GAL upstream activation sequence. These observations indicate that the observed effects of SUHW on gene expression in Drosophila require specific interactions with other factors that are absent or unrecognizable in yeast.

Animals↗
PubMed1993

Refined localization and yeast artificial chromosome (YAC) contig--mapping of genes and DNA segments in the 7q21-q32 region.

The chromosome localizations for 159 gene and DNA segments have been refined to one of five intervals in the 7q21-132 region through hybridization analysis with a panel of somatic cell hybrid lines. Seventy-two of these chromosome 7 markers are also mapped on common or overlapping yeast artificial chromosome (YAC) clones. In addition, the breakpoints of chromosome rearrangement contained in five of the somatic cell hybrid lines have been defined by flanking probes within YAC contigs. To provide a framework for further mapping of the 7q21-q32 region, we have established the physical order of a set of reference markers: cen-(COL1A2-D7S15-CYP3A4-PON)-D7S456-(brea kpoint contained in cell hybrid 1EF2/3/K017)-GUSB-D7S186-ASL-(PGY1-PGY3 -GNB2-EPO-ACHE)-D7S238-(proximal breakpoint in GM1059-Rag5)-D7S240-(CUTL1-PLANH1)-(breakp oints in 1CF2/5/K016 and 2068Rag22-2)-(PRKAR2B-D7S13)-LAMB1-(breakpoint in JSR-17S)-DLD-D7S16-MET-WNT2-CFTR-D7S8-tel.

Base Sequence↗
PubMed1993

Surface quality of excimer laser corneal ablation with different frequencies.

To test the effects of different frequencies of a 193-nm excimer laser on the surface smoothness of the ablated materials and the damage to the adjacent structure, four different frequencies (5, 10, 15, and 20 Hz) of a 193-nm excimer laser were used to perform ablations on 20 rabbit corneas and four polymethylmethacrylate blocks at a fluence of 160 mJ/cm2. Each frequency was tested five times on five corneas. The ablated materials were processed and examined with scanning electron microscopy (SEM) and light and transmission electron microscopy (TEM) and a Zygo interference microscope, which quantitatively evaluates the surface smoothness. The results from the Zygo microscope show that there is no statistically significant difference in surface smoothness between any two different frequencies. The SEM reveals similar regularity and uniformity on the ablated surfaces, with no relationship between the laser frequencies and the amount of surface deposits. The TEM demonstrates no correlation between the various frequencies and the thickness of the superficial pseudomembrane and the amount of collateral damage in the adjacent stroma. It appears that the higher frequencies are comparable to the lower one (5 Hz) as to ablation quality, with the benefit of curtailing surgical time and decreasing the chances of eye movement.

Animals↗
PubMed1993

Islet allograft, islet xenograft, and skin allograft survival in CD8+ T lymphocyte-deficient mice.

Despite extensive study, the immunologic mechanisms mediating allograft rejection have not been completely defined. In the current study, we evaluated the T cell subsets important in islet allograft, skin allograft, and islet xenograft rejection using a genetically engineered line of mice deficient in beta 2-microglobulin expression. Because these mice lack cell surface MHC class I expression, they are deficient in T cells of the CD8 subset (class I-restricted cytotoxic T cells). Pancreatic islet allografts transplanted to CD8+ T cell-deficient recipients showed prolonged survival compared with controls. No prolongation was observed in the survival of pancreatic islet xenografts or in the survival of skin allografts transplanted to the CD8+ T cell--deficient hosts. We conclude that CD8+ T cells play a prominent role in islet allograft, but not islet xenograft or skin allograft, rejection in mice.

Animals↗
PubMed1993

The presence of a novel type of surface polysaccharide in Rhizobium meliloti requires a new fatty acid synthase-like gene cluster involved in symbiotic nodule development.

Bacterial exopolysaccharide (EPS) and lipopolysaccharide (LPS) molecules have been shown to play important roles in plant-bacterium interactions. Here we have demonstrated that the fix-23 loci, which compensate for exo mutations during symbiotic nodule development, are involved in the production of a novel polysaccharide that is rich in 3-deoxy-D-manno-2-octulosonic acid (Kdo) but is not the classical LPS. This molecule is likely to be a surface antigen since antiserum to whole Rhizobium meliloti cells reacts strongly with it, and since mutations in fix-23 result in an inability to produce this polysaccharide and to bind bacteriophage 16-3. It is likely that this Kdo-rich polysaccharide is analogous to certain Escherichia coli K-antigens which are anchored to the membrane via a phospholipid moiety. DNA sequence analysis of one gene cluster of this region revealed that the predicted protein products of six genes exhibit a high degree of homology and similar organization to those of the rat fatty acid synthase multifunctional enzyme domains.

Amino Acid Sequence↗
PubMed1993

A myogenic regulatory gene, qmf1, is expressed by adult myonuclei after injury.

Myogenic regulatory factors (MRFs) induce differentiation in developing muscle. We examined the role of MRFs in the repair of adult muscle using a model of stretch-induced injury in 5-wk-old chickens. The anterior latissimus dorsi muscle was stretched by loading the wing with 10% of body weight, while the contralateral muscle served as a control. At various intervals (0.5-72 h), chickens were killed by CO2 asphyxiation and the muscles were frozen. Slot hybridizations showed that the onset of high qmf1 expression occurred as early as 0.5 h, which was before regenerative processes involving satellite cell proliferation were observed. Maximal qmf1 expression varied among animals from 3 to 16 h and returned to control levels by 72 h. Within a muscle, in situ hybridization showed that maximal qmf1 expression varied spatially with > 60% of the nuclei within active fascicles being positive. We interpret this high percentage to mean that many of the nuclei of preexisting muscle fibers must be expressing qmf1. The expression of the protooncogene c-myc (presumably by proliferating cells such as satellite cells, fibroblasts, and capillary epithelial cells) and the MRF qmf1 (by myoblasts and adult muscle nuclei) are among the early molecular responses of injured muscle. We conclude that myogenic regulatory factors are not permanently repressed after embryonic development and that derepression plays a role in the repair of terminally differentiated myofibers.

Animals↗
PubMed1993

Immunohistochemical mapping of cellular and subcellular distribution of 5-HT1A receptors in rat and human kidneys.

Northern blotting studies have demonstrated mRNA for the serotonin 5-HT1A receptor in human neonatal kidney (B. K. Kobilka, T. Frielle, S. Collins, T. Yang-Feng, T. S. Kobilka, U. Francke, R. J. Lefkowitz, and M. G. Caron. Nature Lond. 329: 75-79, 1987). To confirm expression of receptor protein in kidney, we raised antibodies to two peptides derived from the third intracellular loop of the human 5-HT1A receptor. Specific immunoglobulin G (IgG) was purified sequentially on protein A-Sepharose and peptide-Affigel 10 columns. Each IgG was able to: 1) quantitatively immunoprecipitate [3H]8-OH-2-(di-n-propylamino)1,2,3,4-tetrahydronaphthalene ([3H]8-OH-DPAT)-labeled human and rat receptors; 2) immunoblot a new protein in cells transfected with human 5-HT1A receptor DNA; and 3) immunoautoradiographically label areas of rat brain (frontal cortex, hippocampus, and lateral septum) in a highly characteristic pattern similar to that labeled by 125I-Bolton-Hunter-8-methoxy-2-(N-propyl-N-propylamino)Tetralin, a specific 5-HT1A receptor autoradiography ligand. By use of a light microscopic immunoperoxidase labeling technique, incubation of each IgG antibody with sections of rat and human kidney demonstrated an identical pattern of immunoreactivity. Specific labeling of basolateral plasma membranes was detected throughout medullary and cortical thick ascending limbs (TAL), in distal convoluted tubules (DCT), in connecting tubule cells of the connecting tubule, and in principal cells of the initial collecting tubule. There was no labeling in the inner medulla, glomeruli, or blood vessels. The labeling was blocked by preincubation with the corresponding peptide, but not with noncorresponding peptide or carrier protein. There was no labeling with preimmune IgG. Electron microscopic immunoperoxidase labeling confirmed the specific localization of the IgG antibody along the basolateral plasma membrane in all positively staining cells in rat kidney. Radioligand binding studies with the specific 5-HT1A receptor ligand [3H]8-OH-DPAT confirmed the presence of 5-HT1A receptor binding sites in bulk-isolated rat medullary TAL. These studies provide the first evidence that the 5-HT1A receptor is expressed on the basolateral surface of TAL and DCT cells of human and rat kidney. The specific localization to these cells suggests a possible role for the 5-HT1A receptor in the regulation of salt and water transport in mammalian kidney.

Amino Acid Sequence↗
PubMed1993

Photografting of albumin onto dimethyldichlorosilane-coated glass.

4-Azido-2-nitrophenyl albumin (ANP-albumin) was prepared by displacing the fluoro group of 4-fluoro-3-nitrophenyl azide (FNPA) by an amino group of albumin. Photolysis of phenyl azides of ANP-albumin was studied by Fourier-transform infrared (FTIR) spectroscopy. The band of phenyl azide disappeared completely after a 12-min exposure to long wave UV light (366 nm), and the photolysis was first-order. Albumin was grafted onto dimethyldichlorosilane-coated glass (DDS-glass) by photolysis of the azido groups of ANP-albumin without any premodification of the surface. The albumin-grafted DDS-glass was characterized by determining the relative amount of nitrogen resulting from the grafted albumin on the surface using electron spectroscopy for chemical analysis (ESCA). The amount of nitrogen increased when the concentration of ANP-albumin in the adsorption solution increased up to 0.1 mg/ml. As the solution concentration increased above this value, the amount of nitrogen decreased. The platelet resistance of the albumin-grafted surfaces was evaluated by measuring the number of adherent platelets and the extent of activation that was quantitated by the area of platelets spread on the surfaces. The maximum platelet-resistant effect was observed when the ANP-albumin was adsorbed for more than 50 min at the solution concentration ranging from 0.05 to 10 mg/ml.

Adsorption↗
PubMed1993

Purification and characterization of a lectin-like substance from silkworm faeces.

To obtain biologically active substances that are useful in the study of cell structures and functions, we examined several biological activities of an extract of silkworm faeces with hot buffer. We detected a lectin-like substance in the extract and purified it. When the extract of silkworm faeces was added to a culture of quail myoblasts transformed with temperature-sensitive Rous sarcoma virus (QM-RSV cells), the plated cells which were cultured at 35.5 degrees C (the permissive temperature for RSV that suppresses myogenic differentiation) became detached from the dishes and the cells in suspension aggregated. However, when the same amount of extract was added to plated QM-RSV cells cultured at 41 degrees C, which is a nonpermissive temperature for RSV, the cells did not become detached. Other kinds of plated cells examined also did not become detached. Unlike plated cells, nonplated cells of all kinds aggregate in suspension upon the addition of the extract. This active substance was purified by monitoring its induction of cell aggregation. The purified substance was found to be a lectin-like glycoprotein with an apparent molecular mass of about 60 kDa. Further studies showed that the binding sites of this glycoprotein are sugar chains on the cell surface and that mannose is an epitope.

Animals↗
PubMed1993

Preparation of a monoclonal antibody and expression of its antigen associated with myogenic differentiation on spontaneous and artificial myotubes derived from avian myoblasts.

Quail myoblasts transformed with a temperature-sensitive mutant of Rous sarcoma virus (ts-RSV) proliferate and do not differentiate at 35.5 degrees C, the permissive temperature for the virus, whereas their myoblast differentiation proceeds at 41.0 degrees C, a non-permissive temperature. In this experimental system, myogenic differentiation is controlled by src gene products. Using QM-RSV cells as an antigen, a monoclonal antibody, Mb-N3, was prepared. Expression of Mb-N3 antigen was found to increase during differentiation. Therefore, in studies on the mechanism of myogenic differentiation, we examined the expression of Mb-N3 antigen on spontaneously forming myotubes formed at 41.0 degrees C and fused myoblasts with hemagglutinating virus of Japan (HVJ, Sendai virus) disregarding programmed processes for myogenic differentiation. When the myoblasts cultured at 35.5 degrees C were treated with HVJ, they fused with each other. These fused myoblasts were elongated and were morphologically similar to spontaneously forming myotubes. Thus, we called fused myoblasts with HVJ "artificial myotubes." During culture at 35.5 degrees C, the artificial myotubes did not show increased expression of Mb-N3 antigen and increase of creatine kinase activity, which are markers of normal biochemical differentiation. When artificial myotubes were cultured at 41.0 degrees C, expression of Mb-N3 antigen and creatine kinase activity increased. These results suggest that the expression of the antigen is regulated by kinase activity derived from src gene products even after compulsory cell fusion. Moreover, compulsory fusion does not cause myogenic differentiation and expression of Mb-N3 antigen. Thus it seems that the differentiation program must proceed in order for myogenic differentiation and expression of Mb-N3 antigen to take place.

Animals↗
PubMed1993

Differential expression of GAD65 and GAD67 in human, rat, and mouse pancreatic islets.

The smaller form of the autoantigen glutamic acid decarboxylase, GAD65 (formerly the 64,000 M(r) autoantigen), is a major target of humoral autoimmunity in type I diabetes. Human autoantisera have been used extensively to characterize the GAD65 antigen in both rat and human islets, but the protein has escaped detection in mouse islets. We have now analyzed the expression of GAD65 and GAD67, the larger glutamic acid decarboxylase protein, in human, rat, and mouse islets of Langerhans and brain, using human monoclonal islet cell autoantibodies, human autoantisera, and experimentally raised antibodies to glutamic acid decarboxylase. Human monoclonal autoantibodies and experimentally raised antibodies reacted with mouse GAD65 produced in a baculovirus expression system by Western blotting and immunoprecipitation and with GAD65 in mouse brain by immunohistochemistry but failed to detect GAD65 in mouse islets by the latter two methods. However, analysis of mouse islets by Western blotting technique, using the most sensitive experimentally raised antibody, showed that mouse islets express both GAD65 and GAD67 but at levels that are severalfold lower than those in mouse brain or in human and rat islets. Furthermore, both human and rat islets predominantly express GAD65, whereas GAD67 is the major glutamic acid decarboxylase protein in mouse islets. Human islets are significantly distinct from mouse and rat islets and from brain because they only express GAD65, which is consistent with the predominant role of this form as a target of autoantibodies associated with beta-cell destruction in humans. Human as well as rat islet GAD65 are found in both membrane-bound and soluble forms. The low level of glutamic acid decarboxylase expression in mouse islets compared with human and rat islets is likely to have implications for both the development of tolerance to glutamic acid decarboxylase as well as the homing of glutamic acid decarboxylase-specific lymphocytes to the mouse beta-cell. In this context, the results suggest 1) that the mouse is ideal for studies of the consequences of an expression of high levels of glutamic acid decarboxylase in the beta-cell from a transgene and 2) that the rat may be better suited than the mouse for development of nontransgenic animal models of glutamic acid decarboxylase autoimmunity by immunization.

Amino Acid Sequence↗
PubMed1993

Effects of visualization and Danjeon breathing on target shooting with an air pistol.

This investigation was conducted to assess which technique, visualization, Danjeon breathing, or a combination of these, would be most effective in enhancing target shooting with an air pistol. 48 college students (28 men, 20 women) were selected and randomly assigned to one of four groups (ns = 12): control, visualization, Danjeon breathing, and visualization plus Danjeon breathing. Data were analyzed by a 4 x 5 (groups x days) analysis of variance with repeated measures on days. Both the combination of visualization plus Danjeon breathing and the Danjeon breathing alone were significantly better than the control on most of the measures of shooting performance.

Adolescent↗
PubMed1993

Hb Shelby [beta 131(H9)Gln-->Lys] in association with Hb S [beta 6(A3)Glu-->Val]: characterization, stability, and effects on Hb S polymerization.

When first tested for abnormal hemoglobins, a 2-year-old boy, appeared to have Hb F, Hb S and Hb A2. Confirmatory testing revealed a beta chain variant inherited from his father and beta S from his mother. Analysis of tryptic peptides in conjunction with automated DNA sequence analysis showed that the variant hemoglobin was Hb Shelby [beta 131(H9)Gln-->Lys (CAG-->AAG)]. Heat and mechanical stabilities of various liganded Hb Shelby tetramers were compared to those of Hb A and Hb S. Oxy-Hb Shelby precipitated more readily than oxy-Hb A, but was much more stable than oxy-Hb S during mechanical agitation. In contrast, oxy-Hb Shelby was much less stable than oxy-Hb A and oxy-Hb S following heat treatment. Met-Hb Shelby was most unstable compared to other liganded forms of Hb Shelby, while deoxy- and carbonmonoxy-forms of Hb Shelby showed similar heat-induced precipitation rates. These data indicate that heat instability of Hb Shelby is accompanied by heme oxidation, and that denaturation by mechanical agitation occurs in the absence of heme oxidation. Hb Shelby, like Hb A, can form hybrids with Hb S which participate in polymer formation in vitro. However, Hb S/Hb Shelby hybrids copolymerized with Hb S less than A/S hybrids. Since the patient's MCHC value is normal, this finding coupled with the elevated Hb A2 and Hb F levels, both of which are known to inhibit polymerization of Hb S, may contribute to the patient's mild clinical presentation.

Base Sequence↗
PubMed1993

Estimating heterogeneity in the probabilities of enumeration for dual-system estimation.

"We show how conditional logistic regression can be used to estimate the probability of being enumerated in a census and apply the model to the 1990 Post-Enumeration Survey (PES) in the United States.... We discuss some special problems caused by the fact that the PES sample area is open to migration between the captures. We also consider the effect of data errors in estimation. We characterize hard-to-enumerate populations and give some tentative estimates of correlation bias."

Americas↗
PubMed1992

Cloning and characterization of cDNAs coding for heavy and light chains of a monoclonal antibody specific for pre-S2 antigen of hepatitis B virus.

Binding specificity of a monoclonal antibody (mAb) (kappa, gamma 2b) H8 which can react with the pre-S2 peptide of hepatitis B virus (HBV) was determined by Western blot analyses. From the hybridoma cell line secreting mAb H8, poly(A)+ RNA was prepared and used as a template for cDNA synthesis and cloning. Full-length cDNAs coding for the heavy and kappa light chains of the mAb were cloned from the cDNA library and characterized by nucleotide (nt) sequence analyses and N-terminal amino acid sequencing. The sequence analyses revealed that both heavy and light chain-specific cDNAs are functional, and the variable regions of the heavy and light chains are members of mouse heavy chain subgroup III(c) and light chain group I, respectively. Comparison of the nt sequences with mouse immunoglobulin genes listed in the GenBank data base show that the cDNAs have not been previously reported. The cDNAs will be used for the construction of a therapeutic antibody for HBV infection.

Amino Acid Sequence↗