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Biomedical subjects

J Kim

Publications and source records attributed to J Kim.

At least 19 recordsLinked to original sources
PubMed2025

HLA-E and NKG2A Mediate Resistance to BCG Immunotherapy in Non-Muscle-Invasive Bladder Cancer.

Bacillus Calmette-Guérin (BCG) is the first-line therapy for high-grade non-muscle-invasive bladder cancer (NMIBC), yet many patients experience recurrence due to immune evasion. We identify HLA-E and NKG2A as mediators of adaptive resistance involving chronic activation of NK and T cells in BCG-unresponsive tumors. Prolonged IFN-γ exposure enhances HLA-E and PD-L1 expression on recurrent tumors, accompanied by the accumulation of NKG2A+ NK and CD8 T cells. HLA-Ehigh tumor cells preferentially cluster near CXCL12-rich stromal regions with dense effector cell presence, underscoring a spatially segregated tumor architecture. Although cytotoxic lymphocytes retain effector potential, their activity is restrained by HLA-E/NKG2A and PD-L1/PD-1 pathways located in their immediate neighborhood within the bladder tumor microenvironment. These data reveal a spatially organized immune escape program that limits anti-tumor immunity. Our findings support dually targeting NKG2A and PD-L1 checkpoint blockade as a rational, bladder-sparing strategy for patients with BCG-unresponsive NMIBC.

BCG-unresponsive↗
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↗
PubMed1992

Expression of carcinoembryonic antigen and related genes in lung and gastrointestinal cancers.

Carcinoembryonic antigen (CEA), a tumor marker for lung cancers of small cell (SCLC) and non-small cell (NSCLC) types, belongs in a multigene family which includes non-specific cross-reacting antigen (NCA) and biliary glycoprotein 1 (BGP). We used specific cDNA probes and a CEA immunoassay to determine the pattern of expression in normal and malignant lung and gastrointestinal (GI) tissues. Normal lung contained high amounts of NCA and a low concentration of CEA. All 3 genes were expressed discordantly in lung tumors and cell lines. In contrast, all three genes were expressed in most G1 tumor cell lines. In both lung and colorectal cell lines expression of NCA RNA was relatively high, while BGP RNA was relatively low, and the median concentrations of CEA were greater than in corresponding non-malignant tissues. While CEA protein concentrations in lung cell lines were similar to those present in G1 cell lines, the ratio of NCA:CEA RNA was significantly higher in lung cancer lines than in colorectal lines. Thus, NCA constitutes most of the "CEA-like" immunoreactivity previously described in lung cancers. There was excellent concordance between expression of CEA RNA and CEA protein, as well as between concentrations of CEA protein in cell line pellets and supernatant fluids. Of interest, significantly higher rates of CEA expression were present in lung cancers expressing neuroendocrine (NE) markers. The association between CEA expression and NE cell properties is intriguing and may prove to be of clinical interest.

Antigens, CD↗
PubMed1992

Allosteric changes in the cAMP receptor protein of Escherichia coli: hinge reorientation.

The cAMP receptor protein (CRP) of Escherichia coli is a dimer of a two-domain subunit. It requires binding of cAMP for a conformational change in order to function as a site-specific DNA-binding protein that regulates gene activity. The hinge region connecting the cAMP-binding domain to the DNA-binding domain is involved in the cAMP-induced allosteric change. We studied the structural changes in CRP that are required for gene regulation by making a large number of single and double amino acid substitutions at four different positions in or near the hinge. To achieve cAMP-independent transcription by CRP, amino acid residues 138 (located within the hinge region) and 141 (located in the D alpha-helix adjacent to the hinge) must be polar. This need for polar residues at positions 138 and 141 suggests an interaction that causes the C and D alpha-helices to come together. As a consequence, the F alpha-helix is released from the D alpha-helix and can interact with DNA. At position 144 in the D alpha-helix and within interacting distances of the F alpha-helix, replacement of alanine by an amino acid with a larger side chain, regardless of its nature, allows cAMP independence. This result indicates that pushing against the F alpha-helix may be a way of making the helix available for DNA binding. We believe that the cAMP-induced allosteric change involves similar hinge reorientation to adjust the C and D alpha-helices, allowing outward movement of the F alpha-helix.

Allosteric Regulation↗
PubMed1992

Structural models for the metal centers in the nitrogenase molybdenum-iron protein.

Structural models for the nitrogenase FeMo-cofactor and P-clusters are proposed based on crystallographic analysis of the nitrogenase molybdenum-iron (MoFe)-protein from Azotobacter vinelandii at 2.7 angstrom resolution. Each center consists of two bridged clusters; the FeMo-cofactor has 4Fe:3S and 1Mo:3Fe:3S clusters bridged by three non-protein ligands, and the P-clusters contain two 4Fe:4S clusters bridged by two cysteine thiol ligands. Six of the seven Fe sites in the FeMo-cofactor appear to have trigonal coordination geometry, including one ligand provided by a bridging group. The remaining Fe site has tetrahedral geometry and is liganded to the side chain of Cys alpha 275. The Mo site exhibits approximate octahedral coordination geometry and is liganded by three sulfurs in the cofactor, two oxygens from homocitrate, and the imidazole side chain of His alpha 442. The P-clusters are liganded by six cysteine thiol groups, two which bridge the two clusters, alpha 88 and beta 95, and four which singly coordinate the remaining Fe sites, alpha 62, alpha 154, beta 70, and beta 153. The side chain of Ser beta 188 may also coordinate one iron. The polypeptide folds of the homologous alpha and beta subunits surrounding the P-clusters are approximately related by a twofold rotation that may be utilized in the binding interactions between the MoFe-protein and the nitrogenase Fe-protein. Neither the FeMo-cofactor nor the P-clusters are exposed to the surface, suggesting that substrate entry, electron transfer, and product release must involve a carefully regulated sequence of interactions between the MoFe-protein and Fe-protein of nitrogenase.

Azotobacter vinelandii↗
PubMed1992

Analyzing multivariate flow cytometric data in aquatic sciences.

Flow cytometry has recently been introduced in aquatic ecology. Its unique feature is to measure several optical characteristics simultaneously on a large number of cells. Until now, these data have generally been analyzed in simple ways, e.g., frequency histograms and bivariate scatter diagrams, so that the multivariate potential of the data has not been fully exploited. This paper presents a way of answering ecologically meaningful questions, using the multivariate characteristics of the data. In order to do so, the multivariate data are reduced to a small number of classes by clustering, which reduces the data to a categorical variable. Multivariate pairwise comparisons can then be performed among samples using these new data vectors. The test case presented in the paper forms a time series of observations from which the new method enables us to study on the temporal evolution of cell types.

Data Interpretation, Statistical↗
PubMed1992

Topical and intravenous gentamicin in traumatically lacerated eyes.

Intravenous or topical gentamicin may be the initial mode of treatment for lacerated or ruptured eyes by emergency room physicians while awaiting ophthalmic consultation and surgical repair. The purpose of this study was to determine the possibility of having retinotoxic intravitreal gentamicin concentrations in experimentally lacerated rabbit eyes treated with either intravenous or topical gentamicin separately or in combination with each other. Nontoxic concentrations of gentamicin were found in the vitreous bodies by all routes of drug administration. After 3 h intravitreal concentrations of gentamicin were: 0.20-0.30 microgram/ml when treated intravenously, 0-2.9 micrograms/ml when treated topically, and 0.20-0.51 microgram/ml when treated both intravenously and topically. While the upper range of topically applied gentamicin concentrations (2.9 micrograms/ml) is therapeutic for some pathogens, the wide range of intravitreal concentrations (0-2.9 micrograms/ml) achieved does not indicate that topically applied gentamicin with or without intravenously administered gentamicin can reliably achieve therapeutic concentrations.

Administration, Topical↗
PubMed1992

Ictal spikes: a marker of specific hippocampal cell loss.

Spontaneous seizures recorded from mesial temporal depth electrodes in the human are commonly manifested by one of two onset patterns: a high frequency discharge or a periodic spike discharge morphologically similar but clearly distinguished from ongoing interictal activity. We categorized medial temporal lobe seizure onset for the presence of periodic ictal spikes at a frequency of less than 2 Hz lasting for more than 5 sec to investigate the relationship of this ictal pattern to anatomical changes in the resected temporal lobe tissue. Fifty-one patients had hippocampal depth electrode recordings of spontaneous seizures, subsequent hippocampal resection, and quantitative cell counts of hippocampal subfields. Thirty-two of these patients had ictal spikes lasting at least 5 sec in more than 50% of their seizures. The presence of ictal spikes was significantly correlated with decreased cells in CA1 only (P = 0.015). The correlation of a common ictal pattern with focal cell loss in the hippocampus suggests that electrophysiological manifestations of seizures provide a clue to the underlying pathological substrate. Ictal spikes may be a cause or result of the cell loss. These observations should be correlated with independent investigations in humans and animal models that reflect the CA1 cell loss associated with temporal lobe epilepsy.

Electroencephalography↗
PubMed1992

Prophylactic and therapeutic carboprost tromethamine bladder irrigation in rats with cyclophosphamide-induced hemorrhagic cystitis.

Recently, prostaglandins have been shown to be effective agents for the treatment of cyclophosphamide-induced hemorrhagic cystitis. Among the prostaglandins studied is carboprost tromethamine, a PGF2a analog. To determine the effectiveness of carboprost tromethamine therapy on the urothelium, we induced hemorrhagic cystitis in 81 rats. These were divided into two treatment arms. One arm was treated prophylactically at the time of cyclophosphamide injection, and the other started treatment only after hemorrhagic cystitis was established. Animals were divided equally into groups receiving 0, 0.4, 0.8, and 1.6 mg.% carboprost tromethamine in 0.9% normal saline by continuous bladder irrigation. All bladders were examined grossly for edema and hemorrhage, then histologically for mucosal ulceration, congestion, and perivascular hemorrhage. Results from the prophylactic arm, as compared to those for controls, revealed that all groups except those treated only with 0.9% normal saline had a lower incidence of hemorrhagic cystitis (p less than 0.05). In the established hemorrhagic cystitis arm, the group treated with 1.6 mg.% carboprost tromethamine showed the best response (p less than 0.05), whereas the group treated with 0.9% normal saline showed the poorest response. This study reveals that hemorrhagic cystitis in the rat model may be prevented by prophylactic continuous bladder irrigation with carboprost tromethamine, whereas established hemorrhagic cystitis may be treated effectively with intravesical instillation of carboprost tromethamine. Although the mechanism of action of this prostaglandin on the urothelium is unknown, it appears grossly and histologically to decrease ulceration, perivascular hemorrhage, and congestion in the mucosa and submucosa.

Animals↗
PubMed1992

Mitral valve endocarditis caused by a serum-resistant strain of Escherichia coli.

Endocarditis due to Escherichia coli is rare. The case of a 79-year-old woman with E. coli bacteremia and multiple hemorrhagic cerebral infarcts is reported. A two-dimensional echocardiogram showed no evidence of a vegetation. While she was receiving antimicrobial therapy, bacteremia, hematuria, conjunctival petechiae, and a mitral regurgitant murmur occurred. The patient died, and at autopsy a large (2.2 x 2.0 x 0.7 cm) necrotic vegetation on the anterior leaflet of the mitral valve and several hemorrhagic infarcts of the brain were noted. An in vitro study with use of pooled human serum was performed and demonstrated that the patient's infecting strain of E. coli was serum resistant, in contrast to a serum-sensitive control strain of E. coli that was isolated from the cultures of blood from a patient with pyelonephritis. Including our case, 19 well-described cases of E. coli endocarditis from 1945 to 1990 have been reported. E. coli can cause endocarditis of both sides of the heart. More cases of endocarditis of host valves than of prosthetic valves have been documented.

Aged↗
PubMed1992

Streptococcal toxic shock syndrome due to noninvasive pharyngitis.

Serious infections due to group A beta-hemolytic streptococcus (GABHS) have been reported with increasing frequency in recent years. We report a case of toxic shock syndrome (TSS) due to GABHS pharyngitis in an otherwise healthy 14-year-old boy. The organism was found to produce toxin A. To our knowledge, this is the second reported case of streptococcal TSS associated with the production of toxin A that is not associated with an invasive disease and the first case associated with a documented rise in the level of antibody to the streptococcal toxin itself. Clinicians must be especially vigilant for this entity in patients who have streptococcal pharyngitis because early recognition and institution of aggressive supportive therapy can be lifesaving.

Adolescent↗
PubMed1992

Oxygen binding and other physical properties of human hemoglobin made in yeast.

Wagenbach et al. (1991, BioTechnology, 9, 57-61) have recently developed a system for producing soluble recombinant tetrameric hemoglobin in yeast: hemoglobin begins to appear 4-5 h after induction with galactose, alpha- and beta-globin chains fold in vivo and endogeneously produced heme is incorporated into hemoglobin tetramers. We have further characterized the oxygen-binding properties, as well as the tetramer stability, of recombinant human Hb A made in yeast. After purification by ion-exchange chromatography, a single band at the same position as normal human Hb A was obtained using cellulose acetate electrophoresis. Although the oxy and deoxy forms of purified recombinant Hb A made in yeast were spectrophotometrically identical to native human Hb A, the oxygen-binding curve was shifted slightly left of that for native human Hb A. Further purification of recombinant hemoglobin by FPLC revealed two fractions: one (fraction B) with low cooperativity and high oxygen affinity, and the other (fraction A) with almost identical cooperativity and oxygen affinity compared with native human Hb A. The Bohr effect of fraction A was also identical to native human Hb A. Hemoglobin in fraction B with lowered cooperativity precipitated approximately 1.5 times faster than normal human Hb A during mechanical agitation, while hemoglobin in fraction A with normal cooperativity precipitated with kinetics identical to native human Hb A. These results suggest that some of the recombinant molecules made in yeast fold improperly, and that these molecules may exhibit decreased cooperativity for oxygen binding and decreased stability.(ABSTRACT TRUNCATED AT 250 WORDS)

Allosteric Regulation↗
PubMed1992

Involvement of SecB, a chaperone, in the export of ribose-binding protein.

Ribose-binding protein (RBP) is an exported protein of Escherichia coli that functions in the periplasm. The export of RBP involves the secretion machinery of the cell, consisting of a cytoplasmic protein, SecA, and the integral membrane translocation complex, including SecE and SecY. SecB protein, a chaperone known to mediate the export of some periplasmic and outer membrane proteins, was previously reported not to be involved in RBP translocation even though small amounts of in vitro complexes between SecB and RBP have been detected. In our investigation, it was shown that a dependence on SecB could be demonstrated under conditions in which export was compromised. Species of RBP which carry two mutations, one in the leader that blocks export and a second in the mature protein which partially suppresses the export defect, were shown to be affected by SecB for efficient translocation. Five different changes which suppress the effect of the signal sequence mutation -17LP are all located in the N domain of the tertiary structure of RBP. All species of RBP show similar interaction with SecB. Furthermore, a leaky mutation, -14AE, generated by site-specific mutagenesis causes reduced export in the absence of SecB. These results indicate that SecB can interact with RBP during secretion, although it is not absolutely required under normal circumstances.

Bacterial Proteins↗
PubMed1992

Alternate use of divergent forms of an ancient exon in the fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster.

The fructose-1,6-bisphosphate aldolase gene of Drosophila melanogaster contains three divergent copies of an evolutionarily conserved 3' exon. Two mRNAs encoding aldolase contain three exons and differ only in the poly(A) site. The first exon is small and noncoding. The second encodes the first 332 amino acids, which form the catalytic domain, and is homologous to exons 2 through 8 of vertebrates. The third exon encodes the last 29 amino acids, thought to control substrate specificity, and is homologous to vertebrate exon 9. A third mRNA substitutes a different 3' exon (4a) for exon 3 and encodes a protein very similar to aldolase. A fourth mRNA begins at a different promoter and shares the second exon with the aldolase messages. However, two exons, 3a and 4a, together substitute for exon 3. Like exon 4a, exon 3a is homologous to terminal aldolase exons. The exon 3a-4a junction is such that exon 4a would be translated in a frame different from that which would produce a protein with similarity to aldolase. The putative proteins encoded by the third and fourth mRNAs are likely to be aldolases with altered substrate specificities, illustrating alternate use of duplicated and diverged exons as an evolutionary mechanism for adaptation of enzymatic activities.

Amino Acid Sequence↗
PubMed1992

The thermostable direct hemolysin of Vibrio parahaemolyticus is a pore-forming toxin.

The hemolytic mechanism of thermostable direct hemolysin (TDH), a possible virulence factor of Vibrio parahaemolyticus, was studied. We demonstrated that TDH acts as a "pore-forming toxin" in temperature-dependent and -independent steps. The first temperature-dependent step requires only about 1-2 min incubation at 37 degrees C and makes a "pore" with a functional diameter of approximately 2 nm. The pore size was deduced from the molecular diameter of the colloidal inhibitory polysaccharides. The formation of the pores on TDH-treated erythrocyte membranes was also demonstrated by electron microscopic examination. The second step, which is a temperature-independent lytic step, causes the erythrocytes to swell owing to a colloidal osmotic influx of water via the "pores" into cells, resulting in erythrocyte lysis (or rupture) owing to increased intracellular pressure.

Erythrocytes↗
PubMed1992

Immunocytochemical response of type A and type B intercalated cells to increased sodium chloride delivery.

Two populations of intercalated cells, type A and type B, are present in the rat cortical collecting duct (CCD). Type A cells are involved in proton secretion and contain an apical H(+)-adenosinetriphosphatase (ATPase) and a basolateral Cl(-)-HCO3- exchanger. Type B cells are believed to be involved in HCO3- secretion, which is mediated by a Cl(-)-HCO3- exchange process and is Cl- dependent. The aim of this study was to examine the morphological and immunocytochemical response of type B intercalated cells in the rat to increased delivery of Cl- to the CCD. This was accomplished by chronic infusion of a loop diuretic, bumetanide (30 mg.kg body wt-1.day-1), via an osmotic minipump, and simultaneous administration of 0.9% sodium chloride in the drinking water for 6 days. The kidneys were preserved by in vivo perfusion with a periodate-lysine-paraformaldehyde fixative and processed for horseradish peroxidase and protein A gold immunocytochemistry, using rabbit polyclonal antibodies against carbonic anhydrase II, proton ATPase, and band 3 protein. Chronic infusion of bumetanide in combination with a high salt intake was associated with significant changes in the intercalated cells. Type B cells were increased in size and exhibited numerous apical microvilli, increased basolateral membrane area, and marked cytoplasmic and basolateral labeling for H(+)-ATPase. In contrast, type A cells were small and had sparse apical microprojections. H(+)-ATPase immunolabeling was observed primarily over apical tubulovesicles, and there was decreased basolateral immunolabeling for band 3 protein and occasional labeling for band 3 in lysosome-like structures. These observations support the hypothesis that increased delivery of Cl- to the CCD is associated with stimulation of type B intercalated cells to secrete HCO3-. The observations in type A cells are consistent with the cells being in a resting or inactivated state.

Adenosine Triphosphatases↗
PubMed1992

Intracellular band 3 immunostaining in type A intercalated cells of rabbit kidney.

Intercalated cells (ICs) in the collecting duct and the connecting tubule (CNT) are involved in H+ secretion and HCO3- reabsorption. H+ secretion is mediated by an H(+)-adenosinetriphosphatase in the apical plasma membrane, whereas a band 3-like Cl(-)-HCO3- exchanger in the basolateral membrane is responsible for HCO3- reabsorption. Recent studies have reported that a band 3-like protein is also present in mitochondria in rabbit ICs. The purpose of this study was to establish the subcellular location of the band 3-like Cl(-)-HCO3- exchanger in rabbit ICs by electron microscopic immunocytochemistry using a monoclonal antibody, IVF12, against erythrocyte band 3 protein. Rabbit kidneys were preserved by in vivo perfusion with a paraformaldehyde-lysine-periodate solution and processed for immunocytochemistry using a horseradish peroxidase preembedding technique. Band 3 immunostaining was observed on the basolateral plasma membrane of ICs in the outer medullary collecting duct and type A cells in the cortical collecting duct (CCD) and CNT. In addition, distinct staining for band 3 was present in numerous small vesicles and in multivesicular bodies in type A ICs in the CCD and CNT. However, there was no evidence of band 3 immunostaining of mitochondria or of the apical plasma membrane in any cells of the collecting duct. These observations suggest that basolateral Cl(-)-HCO3- exchangers in type A ICs in the rabbit kidney are stored in intracellular vesicles and possibly degraded in the vascular-lysosomal system when these cells are in a resting state. The previously reported band 3 immunolabeling of mitochondria could not be confirmed.

Animals↗