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Biomedical subjects

K Kohno

Publications and source records attributed to K Kohno.

At least 181 records · Page 10Linked to original sources
PubMed1997

[Molecular mechanism of the stress induction of MDR1 gene].

MDR1 promoter activity increases in response to various environmental stimuli, including anticancer drugs and in a manner that is dependent on the inverted CCAAT box. The binding activity of a nuclear factor MDR-NF1 that interacts with this promoter region was augmented when the nuclear extract was prepared from cells that had been treated with either UV or anticancer drugs. In an attempt to understand the molecular basis for the stress-dependent induction of MDR1 promoter activity, the cDNA for MDR-NF1 have been cloned. The amino acid sequence encoded by the cloned cDNA was identical to that of YB-1. The human Y-Box binding protein (YB-1) is a member of a DNA-binding protein family with a structurally and functionally conserved cold shock domain. YB-1 was found to be much higher in all cisplatin-resistant cell lines than that in the respective drug-sensitive parental counterparts. Two transfectants with a YB-1 antisense construct showed increased sensitivity to cisplatin, mitomycin C and UV irradiation, but not to vincristine, doxorubicin, camptothecin or etoposide. Thus, YB-1 may protect cells from the cytotoxic effects of agents that induce cross-linking of DNA, suggesting a novel function of this ancestor DNA binding protein. Regulatory mechanism of the YB-1 gene expression and the cellular functions of YB-1 are currently under investigation in relation to drug resistance.

Antineoplastic Agents↗
PubMed1997

[Postgadolinium MR angiography of normal intradural veins of the thoracolumbar spine].

To evaluate the normal intradural spinal veins, we used postgadolinium three-dimensional time-of-flight MR angiography (MRA) at 1.5T in 7 subjects. MR images and MR angiograms[32/6/1 (TR/TE/NEX)] were obtained after a bolus injection of Gd-DTPA (0.15-0.2 mmol/kg). We reconstructed images using an equipped function, so-called multiplanar reconstruction. The anterior median veins in 2 patients and the posterior median veins were shown in 2. The great medullary veins were demonstrated in 2. We successed in obtaining venous angiograms by postgadolinium MRA. Disseminated tumors and abnormal enhanced cauda equina are often indistinguishable from normal intradural veins. This study suggests that it is useful to know the MR angiographic features of normal intradural veins in order to evaluate enhanced intradural components.

Adult↗
PubMed1997

Sequential analyses of the mutations in the core upstream and precore regions of hepatitis B virus genome in anti-HBe positive-carriers developing acute exacerbation.

The nucleotide sequences of the core upstream and precore regions (371 nucleotide length, nt. 1604-1974) of hepatitis B virus (HBV) were analysed sequentially in three subjects who were positive serologically for anti-HBe and had acute clinical exacerbation after immunosuppressive treatment. These patients were asymptomatic HBV carriers before therapy. The results revealed that the mutant with an 8-bp deletion (nt. 1768-1775) located in the basic core promoter region was dominant in the asymptomatic HBV carrier phase in two of three subjects. After exacerbation, however, such mutant clones possessing 8-bp deletion disappeared or decreased in number and were replaced by the clones possessing a precore stop codon mutation G to A (nt. 1896) or by the clones possessing additional contiguous point mutations A to T (nt. 1762) and G to A (nt. 1764) and a new point mutation C to T (nt. 1653). Possible relationships between acute exacerbation of liver function accompanied by mutation and the transition of the dominant clones were discussed.

Acute Disease↗
PubMed1997

[Treatment strategies for lung cancer brain metastases].

Forty-one patients suffered initial relapses with brain metastasis after surgery for non-small lung cancer at our hospital between 1978 and 1995. These patients were a total of 8.4% of all cases of surgical removal, and had an average relapse period of 8.6 months +/- 8.0 months after surgery on the primary lesions. Of these, surgical removal of metastasized lesions was performed on 18 patients (43%), in which the 5-year post-operative survival rate was 35.7%, and the median survival time was good at 28 months. It was found that the survival period was significantly extended in the group whose relapse period was less than one year after surgery on the primary lesions, and in the group who received cranial irradiation post-operatively on the metastasized brain lesion. Following surgery on the metastasized lesion, second relapses occurred in nine patients, and six patients suffered from second relapses in the brain, of which four did not receive cranial irradiation post-operatively. Cases of radiotherapy in patients of 70 years of age or more frequently manifested post-radiotherapy subacute neuropathy. From the above, it is thought that the following procedures should be adopted: 1. Periodic examination for brain metastasis during the 24 months following surgery for non-small cell lung carcinoma for purposes of early detection; 2. in cases where brain metastasis is detected, if no metastasis is identified in other organs, a policy of surgical removal should be adopted where possible; and, 3. in cases of 70 years of age or less following surgery on the metastasized lesion, cranial irradiation should be considered.

Aged↗
PubMed1997

[A case report of multiple aneurysms of pancreaticoduodenal region with celiac obstruction].

We treated a 53-year-old man who had a dorsal pancreatic aneurysm and three pancreaticoduodenal aneurysms with celiac obstruction. Resection of the dorsal pancreatic aneurysm and bypass grafting from abdominal aorta to common hepatic artery with his saphenous vein were performed. A diagnosis of the aneurysm caused by arteriosclerotic changes was confirmed by the pathohistological findings. The postoperative clinical course was uneventful and angiography revealed disappearance of the left pancreaticoduodenal aneurysms. These findings suggest that not arterioscrelotic changes but also circulatory disturbance caused by celiac obstruction are reasonable as a part of etiology in growth of aneurysms.

Aneurysm↗
PubMed1996

Enhanced coexpression of thioredoxin and high mobility group protein 1 genes in human hepatocellular carcinoma and the possible association with decreased sensitivity to cisplatin.

Thioredoxin (TRX), a disulfide-reducing intracellular protein, functions as a cellular defense mechanism against oxidative stress. In this study, we asked whether expression of TRX, glutathione-thiol transferase pi, and high mobility group protein 1 (HMG-1) genes is enhanced in human hepatocellular carcinoma and whether expression of these genes is associated with sensitivity to cisplatin. Both TRX and HMG-1 were co-overexpressed in almost all cancerous lesions in comparison to normal tissue in surgically resected hepatocellular carcinomas of 20 patients. Tumor sensitivity to cisplatin [cis-diamminedichloroplatinum (II)], but not to mitomycin C or doxorubicin, correlated with mRNA levels of TRX in cancer tissue. TRX and HMG-1 may be useful tumor markers, and TRX might be also a useful marker for sensitivity to cisplatin in human hepatocellular carcinomas.

Adult↗
PubMed1996

Induction of vascular endothelial growth factor by tumor necrosis factor alpha in human glioma cells. Possible roles of SP-1.

The expression of vascular endothelial growth factor (VEGF) has been implicated in brain tumor angiogenesis, and the promoter region for the VEGF gene contains several SP-1 and AP-1 (c-Fos and c-Jun) binding motifs. Among eight human glioma cell lines, cellular mRNA levels of transcription factors SP-1 and AP-1 (c-Fos and c-Jun) were found to be closely correlated with those of VEGF. VEGF expression appears to be highly susceptible to hypoxia or exogenous cytokines and growth factors. Of various cytokines and growth factors, basic fibroblast growth factor (bFGF), tumor necrosis factor alpha (TNF-alpha), and interleukin 1 most potently enhanced VEGF mRNA levels of a glioma cell line, U251. Incubation of the glioma cells with bFGF or TNF-alpha increased both VEGF and SP-1 mRNA at 30 min and c-Fos mRNA at 1-3 h, over 5-fold. Nuclear run-on assays showed an apparent increase of the transcription of the VEGF gene as well as the SP-1 gene by bFGF or TNF-alpha. Gel mobility shift assays demonstrated that only SP-1 binding activity was increased 1 h after exposure to bFGF or TNF-alpha, and also that AP-1, but not SP-1, activity was significantly activated by hypoxia. Mithramycin, an inhibitor of SP-1, at 1-10 nM inhibited activation of the VEGF gene by bFGF or TNF-alpha but not that by hypoxia. Western blot analysis also demonstrated an increase in cellular amounts of VEGF by TNF-alpha and a decrease by co-administration with mithramycin. The promoter activity of the VEGF gene, which contains five SP-1 binding sites and one AP-1 binding site but not hypoxia regulatory elements, was enhanced by bFGF or TNF-alpha but not by hypoxia. The chloramphenicol acetyltransferase assay with VEGF promoter deletion constructs demonstrated that four clusterized SP-1 binding sites in the proximal promoter were essential for the basal transcription and the TNF-alpha-dependent activation. These data indicated that the expression of the VEGF gene enhanced by bFGF or TNF-alpha appeared to be mediated in part through the transcription factor SP-1, suggesting a different mechanism from that for hypoxia-induced activation of the VEGF gene.

Antineoplastic Agents↗
PubMed1996

Nitric oxide synthase inhibitor reduces delayed neuronal death in gerbil hippocampal CA1 neurons after transient global ischemia without reduction of brain temperature or extracellular glutamate concentration.

We planned a study to determine whether or not the mechanism of nitric oxide (NO) neurotoxicity involves the elevation of extracellular glutamate or changes of brain temperature in the pathogenesis of delayed neuronal death of gerbil hippocampal CA1 neurons following 5-min transient forebrain ischemia. Intraventricular injection of 5 microliters of 5.0 mg/ml N omega-nitro-L-arginine (LNNA) significantly preserved neuronal density in the central part of the CA1 region examined 7 days after 5-min ischemia [188.5 +/- 8.5/mm: 90.0% of the 209.5 +/- 11.1/mm density in the sham-operated controls vs. 16.7 +/- 6.4/mm in those injected with artificial cerebrospinal fluid (CSF) only]. There was no difference between these two groups in hippocampal temperature before, during or after 5-min ischemia. The glutamate concentration ([Glu]) during 5-min ischemia measured by a microdialysis technique was similar in the two groups (peak [Glu.] = 2.76 +/- 0.62 pmol/microliters dialysate in the artificial CSF group and = 2.93 +/- 0.64 pmol/microliters dialysate in the LNNA group). It was found that the neuronal toxicity of NO does not involve hyperthermia or the increase of extracellular glutamate concentration in the hippocampal CA1 region during 5-min ischemia.

Analysis of Variance↗
PubMed1996

The loss of recombinant human granulocyte colony-stimulating factor and recombinant human TNF-alpha priming effects on the superoxide-generating response in exudated neutrophils is associated with a decrease in their receptor affinities.

Several cytokines are known to enhance FMLP-stimulated superoxide generation in human circulating blood neutrophils through binding to their specific receptors, a process referred to as the priming effect. The priming effects produced by recombinant human granulocyte CSF (rhGCSF) and TNF-alpha (rhTNF-alpha) on FMLP-stimulated superoxide production in human and rabbit blood neutrophils were compared with their effects in their respective tissue neutrophils, i.e., human salivary and rabbit peritoneal neutrophils. The receptor binding characteristics of rhGCSF and rhTNF-alpha were also compared between the two types of neutrophils. Both rhGCSF and rhTNF-alpha produced dose-dependent priming effects on FMLP-stimulated superoxide production in human blood neutrophils, whereas they failed to produce any priming effects in human salivary neutrophils. Similar results were obtained for the priming effects by rhGCSF in rabbit blood and peritoneal neutrophils. A decrease in receptor binding affinity, but not in receptor density, in tissue neutrophils was demonstrated by analyzing the binding of [125I]rhGCSF and [125I]rhTNF-alpha. These findings suggest that tissue neutrophils are less responsive to rhGCSF and rhTNF-alpha in the modulation of FMLP-stimulated superoxide generation. This is due at least in part to the lower affinities of GCSF and TNF-alpha to their receptors in tissue neutrophils. This marked difference in priming effects by cytokines between blood and tissue neutrophils may represent an early step in the defensive responses against invading microorganisms or Ags.

Animals↗
PubMed1996

A human canalicular multispecific organic anion transporter (cMOAT) gene is overexpressed in cisplatin-resistant human cancer cell lines with decreased drug accumulation.

By targeting the ATP binding conserved domain in three ATP binding cassette superfamily proteins (P-glycoprotein, multidrug resistance protein, and cystic fibrosis transmembrane regulator), we isolated the cDNA of a new ATP binding cassette superfamily that was specifically enhanced in a cisplatin-resistant human head and neck cancer KB cell line. A human clone homologous to rat canalicular multispecific organic anion transporter (cMOAT) was found and designated human cMOAT. Fluorescence in situ hybridization demonstrated the chromosomal locus of the gene on chromosome 10q24. The human cMOAT cDNA hybridized a 6.5-kb mRNA that was expressed 4- to 6-fold higher by three cisplatin-resistant cell lines derived from various human tumors exhibiting decreased drug accumulation. Human cMOAT may function as a cellular cisplatin transporter.

Adenosine Triphosphate↗
PubMed1996

Role of the human Y box-binding protein YB-1 in cellular sensitivity to the DNA-damaging agents cisplatin, mitomycin C, and ultraviolet light.

The Y box-binding protein (YB-1) binds to DNA sequences, present in the control regions of many genes, that contain an inverted CCAAT box. The binding activity of a nuclear factor, designated MDR-NF1, to an inverted CCAAT box in the promoter of the multidrug resistance 1 (MDR1) gene has previously been shown to be increased in nuclear extracts of cells exposed to UV radiation or various anticancer agents. The MDR-NF1 cDNA has now been cloned by screening a human colon library with an active fragment of the MDR1 promoter. The amino acid sequence encoded by the cloned cDNA was identical to that of YB-1. Northern blot analysis revealed that YB-1 mRNA was present in all human tissues examined. Rabbit antibodies were generated against synthetic peptides corresponding to YB-1, and indirect immunofluorescence microscopy with these antibodies showed that the concentration of YB-1 in all cisplatin-resistant cell lines examined was higher than that in the respective drug-sensitive parental cells. Transfection of human epidermoid cancer KB cells with a YB-1 antisense construct established two cell lines with reduced concentrations of YB-1. These transfectants showed increased sensitivity to cisplatin, mitomycin C, and UV radiation but not to vincristine, doxorubicin, camptothecin, or etoposide. Thus, YB-1 may protect cells from the cytotoxic effects of agents that induce cross-linking of DNA, suggesting a novel function of this ancestor DNA-binding protein.

Amino Acid Sequence↗
PubMed1996

Cloning and expression of cDNA for O-acetylation of GD3 ganglioside.

O-acetylated sialic acids of glycoproteins and gangliosides show cell type-specific and developmentally regulated expression in various systems and sometimes reappear as oncofetal antigens. O-acetylation of sialic acids may influence cell-cell interactions mediated by the sialic acid-binding lectins. Here we describe the molecular cloning and sequencing of a gene that produces O-acetyl disialoganglioside (O-acetyl GD3). Expression analysis showed that this gene product participates the O-acetylation of GD3 ganglioside sialic acid. The deduced amino acid sequence of the product was found to be similar to the milk fat globule membrane glycoprotein.

Acetylation↗
PubMed1996

Detection of molecular gas in the quasar BR1202 - 0725 at redshift z = 4.69.

Although great efforts have been made to locate molecular gas--the material out of which stars form--in the early Universe, there have been only two firm detections at high redshift. Both are gravitationally lensed objects at redshift z approximately = 2.5 (refs 9-14). Here we report the detection of CO emission from the radio-quiet quasar BR1202 - 0725, which is at redshift z = 4.69. From the observed CO luminosity, we estimate that almost 10(11) solar masses of molecular hydrogen are associated with the quasar; this is comparable to the stellar mass of a present-day luminous galaxy. Our results suggest that BR1202 - 0725 is a massive galaxy, in which the gas is largely concentrated in the central region, and that is currently undergoing a large burst of star formation.

Astronomical Phenomena↗
PubMed1996

Preferential replication-dependent mutagenesis in the lagging DNA strand in Escherichia coli.

The mutation frequencies attributable to -1 frameshift or one-base substitution in the structural genes coding for resistance to chloramphenicol (Cm) and tetracycline (Tc) were followed over several cycles of DNA replication, and found to differ several-fold, depending on the orientation of the gene on the plasmid with respect to the direction of (unidirectional ColE1-type) replication. The mutation frequency was higher when the reporter gene was present in the plasmid in the same orientation as the direction of the origin, i.e., when the transcription template is the lagging daughter strand, than when the gene was inserted in the opposite orientation. This significant difference in reversion frequencies of genes with different polarities was demonstrated only for a brief period of cell growth (several cycles of replication) after induction of the dnaQ49 mutator, but was not observed when an increased number of replication cycles, was permitted, most probably due to fixation of the mutation into both strands. The mutated intermediate DNA which possesses a misaligned basepair in the Cm gene was demonstrated to be replicated into two progeny DNA molecules; one is the chloramphenicol-resistant (CmR) DNA synthesized from the template strand having the mutation and the other is the CmS DNA from the template strand without mutation. Our results suggest that replication-dependent mutagenesis may occur preferentially in the lagging strand.

Bacteriocin Plasmids↗
PubMed1996

Conformational changes of smooth endoplasmic reticulum induced by brief anoxia in rat Purkinje cells.

Morphological changes of the smooth endoplasmic reticulum (SER) in rat cerebellar Purkinje cell dendrites were examined under apneic conditions for 1-5 minutes, induced by an incision of the diaphragm and the collapse of the lungs. The dendrites obtained from control rats contained a tubular network of the SER and hypolemmal cisterns adjacent to the plasma membrane. After a 3-5-minute apnea, the cytoplasm was occupied by many flattened cisterns stacked into lamellae, referred to as "lamellar bodies." A quantitative analysis revealed that the number of lamellar bodies became maximum after 3 minutes of apnea. After the treatment time, they increased in size by adding new cisterns to the previous core lamellae. This analysis also showed that the total amount of the SER membranes contained in a dendrite did not change during anoxia. Conformational changes from the tubular or hypolemmal SER to lamellar bodies during brief anoxia might occur through a transient and intermediate form of "fenestrated cisterns," flat across the transverse plane and penetrated by many longitudinally arranged microtubules. We suggest that these morphological changes of the SER during brief anoxia are not fixation artifacts but represent a biological reaction for protecting against intracellular abnormalities during anoxia.

Animals↗
PubMed1996

Structural and functional analysis of the human Y-box binding protein (YB-1) gene promoter.

We have isolated three overlapping genomic clones containing the 5'portion of the human YB-1 gene. These clones span approximately 25 kb of contiguous DNA containing 10 kb of 5' flanking sequence and 15 kb of the gene. The nucleotide sequence of the first exon and of 2000 upstream base pairs (bp) was determined. The first axon is unusually large and contains a 166 bp coding sequence and a 331 bp untranslated region. CpG sequences cover the 5'-end of the YB-1 gene including its first axon and intron as well as the upstream regions. The GC content around the first exon is approximately 70% and a CpG-free region was located in the untranslated sequence. The segment preceding the major transcription initiation site does not contain a TATA box, CCAAT box and the binding sequence for known transcription factors. A transient expression assay using the chloramphenicol acetyltransferase (CAT) gene showed that the sequence from +24 to +281 was critical for CAT expression. Fluorescence in situ hybridization demonstrated the chromosomal locus of YB-1 gene on chromosome 1p34. Polymerase chain reaction analysis on other genomic phage DNAs showed that several clones were derived from pseudogenes.

Base Composition↗
PubMed1996

Drug-induced down-regulation of topoisomerase I in human epidermoid cancer cells resistant to saintopin and camptothecins.

The anticancer agent saintopin induces DNA cleavage mediated by both topoisomerase (topo) I and topo II in vitro through stabilization of the reversible enzyme-DNA cleavable complex. We established saintopin-resistant cell lines (KB/STP-1 and KB/STP-2) from human epidermoid cancer KB cells by stepwise exposure to increasing doses of the drug. KB/STP-1 and KB/STP-2 cells showed 12- and 44-fold increases, respectively, in resistance to saintopin relative to that of KB cells. Both saintopin-resistant cell lines showed only small reductions in sensitivity to the topo II inhibitor etoposide but developed marked cross-resistance to the topo I-targeting camptothecin derivative CPT-11 [(4s)-4,11-diethyl-4-hydroxy-9-[(4-piperidinopiperidino)carbony loxy] dione hydrochloride trihydrate] and its active form, SN-38 (7-ethyl-10-hydroxycamptothecin). In contrast, both KB/STP-1 and KB/STP-2 cells showed increased collateral sensitivity to cisplatin, a nitrosourea derivative, mitomycin C, and UV light. The protein concentration, activity, and mRNA abundance of both topo I and topo II were similar in KB/STP-1, KB/STP-2, and the parental KB cells. There were no significant changes in the drug-stabilized topo-DNA cleavable complex formation in KB and KB/STP-2 cells. Two point mutations were detected in topo I cDNA from KB/STP-2 cells, but these were also present in KB cells. Topo I mRNA abundance decreased markedly immediately after exposure of KB/STP-2 cells to saintopin; no such effects were apparent in KB cells. In contrast, topo II mRNA was not markedly affected by saintopin in either KB or KB/STP-2 cells. Treatment with CPT-11 or SN-38 also induced a markedly greater and more persistent reduction in topo I mRNA abundance in KB/STP-2 cells than in KB cells. Etoposide had no marked effect on topo I mRNA abundance in either KB/STP-2 or KB cells. Topo I mRNA was highly unstable in KB/STP-2 cells in comparison to KB cells when incubated with saintopin. This novel regulation of topo I mRNA by topo I-targeting agents could be associated with acquirement of drug resistance to saintopin or SN-38/CPT-11 in KB/STP-2 cells.

Antibiotics, Antineoplastic↗