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Biomedical subjects

K Hamada

Publications and source records attributed to K Hamada.

At least 271 records · Page 15Linked to original sources
PubMed1996

[Allergic granulomatous angiitis in a patient with positive reactions on serological tests for parasite antigens].

A 68-year-old woman with bronchial asthma complained of fever, right thigh pain, sensory disturbance at the tips of the upper and lower limbs, and abdominal pain. She had severe eosinophilia and radiologic examination showed a mass-like shadow in the left lower lobe of the lung. Allergic granulomatous angiitis was diagnosed on the basis of findings from a muscle biopsy (gangrenous vasculitis with eosinophilia). This patient also had positive results of serological tests (Ouchterlony method) for various parasite antigens, despite the fact that no eggs of parasites were found in her feces. After steroid administration, the serological reactivity to parasite antigens had decreased. The positive reactions to parasite antigens was probably related to the cause of the vasculitis.

Aged↗
PubMed1996

Expression of tissue factor in glioma.

Tissue factor (TF) is a cell surface glycoprotein that initiates the extrinsic coagulation protease cascade and it is expressed in some tumor cells. TF belongs to the interferon receptor family, and it is one of the early immediate genes, suggesting that TF has a biological function other than hemostasis. We investigated the expression of TF in gliomas. Immunocytochemistry showed the expression of TF in 3 glioma cell lines. Immunohistochemical analysis of 44 surgical specimens revealed that all gliomas were positive for TF, and 19 (95%) of 20 glioblastomas, 12 (86%) of 14 anaplastic astrocytomas and 1 (10%) of 10 benign gliomas were moderately or strongly positive for TF. Our study showed that TF is expressed in gliomas, and that the level of TF expression is correlated with the grade of malignancy of the glioma, suggesting that TF may participate in cell growth.

Brain Neoplasms↗
PubMed1996

Changes of expression of complement 3bi receptors on granulocytes after physical exercise in rats.

OBJECTIVE: The purpose of this study was to examine the effects of physical exercise on the expression of clusters of differentiation (CD)11b, CD18 and CD 54 on granulocytes and complement 3bi (C3bi)-dependent functions in rats. EXPERIMENTAL DESIGN: The rats were separated into two groups: the control group (n = 21) and the training group (n = 14). The rats in the training group were subjected to a program that consisted of swimming 6 days in a week for 7 weeks. MEASURES: The phagocytic and hydrogen peroxide (H2O2) generating activities and the expression of receptors on granulocytes were measured using flow cytometric techniques. RESULTS: The acute swimming and the 7 weeks of swim training caused high C3bi-dependent phagocytic activity of granulocytes. Swim training led to an increase of H2O2 generating activity together with C3bi-dependent phagocytosis both immediately after and 24 hrs after the 120 min swimming. The 24 hrs recovery from the 120 min swimming in trained and untrained rats caused an increase of H2O2 generating activity of granulocytes. In the training group, an increase in this activity could be observed immediately after the 120 min swimming exercise. The upregulation of the CI1b on granulocytes was induced by the 120 min of swimming regardless of swim training. CONCLUSIONS: These results suggest that the increase of C3bi receptor-dependent phagocytosis and H2O2 generating activities induced by the physical exercise might depend on the upregulation of the CD11b that is the component of C3bi receptor.

Animals↗
PubMed1995

The DRE sequence TATCGATA, a putative promoter-activating element for Drosophila melanogaster cell-proliferation-related genes.

We have confirmed that the DNA replication-related element (DRE) consisting of an 8-bp palindrome, TATCGATA, and not neighboring sequences, are responsible for activating promoters of the Drosophila melanogaster (Dm) PCNA (proliferating cell nuclear antigen)- and DNA polymerase alpha-encoding genes in both cultured cell and transgenic fly systems. We have so far found 153 copies of DRE in the Dm gene database. 73 of them are concentrated within the 600-bp upstream regions from the transcription start points of 61 genes. Interestingly, many of these genes are involved in either DNA replication, transcription, translation, signal transduction, cell cycle or other putative regulatory functions, and are possibly related to cell proliferation. It seems likely that DRE is an element common to the regulation of cell-proliferation-related genes, although their expression patterns may be different depending on which of regulatory elements other than the DRE are combined.

Animals↗
PubMed1995

Polysynaptic neural pathways from low threshold trunk cutaneous afferents to tail motoneurons in the spinalized cat.

Postsynaptic potentials (PSPs) after stimulating the cutaneous nerves of the trunk, dorsal cutaneous nerve (DC) and ventral cutaneous nerve (VC) were recorded from alpha-motoneurons innervating two tail muscles, the m. extensor caudae lateralis (ECL) and m. flexor caudae longus (FCL) in 22 spinalized (T10) cats. Stable recordings were obtained from 33 ECL and 42 FCL motoneurons. Stimulation of cutaneous nerves at 1.5-5 times threshold typically produced three types of synaptic effects in ECL and FCL motoneurons: predominant excitation (EPSP), or predominant inhibition (IPSP), or mixed effects characterized chiefly by early excitation followed by inhibition (EPSP/IPSP). The average central latencies of PSPs were distributed over a wide range (4.5-15.6 ms). Latency measurements indicated that most neural circuits from the trunk cutaneous afferents to the tail muscle motoneurons were oligosynaptic pathways via intraspinal slow-conducting fibers or polysynaptic pathways.

Afferent Pathways↗
PubMed1995

Ultrastructural effects of pressure stress to the nucleus in Saccharomyces cerevisiae: a study by immunoelectron microscopy using frozen thin sections.

The effects of hydrostatic pressure on subcellular structures, particularly the nucleus, of Saccharomyces cerevisiae were investigated by immunoelectron microscopy. Cells were treated with hydrostatic pressure from 0.1 to 400 MPa for 10 min at room temperature. Frozen thin sections of the cells revealed that spindle pole bodies disappeared at 100 MPa. At 150 MPa, the deposition of gold particles for anti alpha-tubulin was noticed in the nucleus, although the filamentous structure of microtubules was lost. At 200 MPa, fewer gold particles were scattered in the nucleus and the nuclear membrane in several portions was also observed to be open at 300 MPa. These results show that elements of the nuclear division apparatus were susceptible to pressure stress, particularly spindle pole bodies and microtubules. The damage to spindle pole bodies, microtubules, and nuclear membrane caused by pressure stress was followed by the inhibition of nuclear division. After the release of pressure, the spindle pole bodies and microtubules of pressurized cells at below 200 MPa regained their normal appearance at 24 h.

Cell Division↗
PubMed1995

Selective inhibition of gastrulation in the starfish embryo by albuside B, an inosine analogue.

External application of 0.2-100 micrograms/ml albuside B inhibits gastrulation of the starfish (Asterina pectinifera) embryo. Treated embryos retain the late blastula morphology with the vegetal plate. However, the vegetal plate is unreactive to soybean agglutinin, a probe for observing the progenitor cells of the archenteron (mesendoderm) in a normal embryo. The effective period of the treatment is limited from 4 to 6 h after fertilization, a period immediately before the onset of blastulation. RNA synthesis is unaffected during the period of sensitivity. The selectivity of the inhibition shows that albuside B may be a useful tool for studying the mechanisms of mesendoderm differentiation.

Animals↗
PubMed1995

Mutation and allelic loss of the p53 gene in endometrial carcinoma. Incidence and outcome in 92 surgical patients.

BACKGROUND: Alterations of the p53 gene are involved in the development of diverse human malignancies, but their incidence and clinicopathologic features are still not well characterized for endometrial carcinoma. METHODS: To investigate the clinicopathologic significance of p53, mutations and loss of heterozygosity (LOH) in endometrial carcinoma in 92 patients with this disease were examined. RESULTS: Mutations of p53 were detected in 20 (22%) of the 92 patients with carcinoma, and LOH was detected in 23 (32%) of the 72 patients in whom heterozygosity of the gene was available. There was a significant correlation between the occurrence of mutation and LOH. Mutations and LOH were more frequent in patients with Grade 3 tumors than in those with Grades 1 and 2 tumors (P = 0.0498, P = 0.0051, respectively). Patients with LOH had a poorer postoperative survival than those without LOH (P = 0.0022, log-rank test), and patients with both LOH and mutation showed the worst prognosis (P < 0.0001, log rank test). Loss of heterozygosity of the p53 gene showed a significant relation to prognosis that was independent of tumor stage, histologic grade, and muscular invasion. CONCLUSIONS: Mutation and LOH of the p53 gene are prognostic indicators in patients with endometrial carcinoma, suggesting that alterations of p53 may play an important role in the development of this cancer.

Alleles↗
PubMed1995

Mucosa-preferential DNA adduct formation by 2-amino-3-methylimidazo-[4,5-f]quinoline in the rat colonic wall.

The mechanism of mucosa-specific formation of DNA adducts, which was found recently in human intestines, was studied in male F344 rats treated with 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). There are three conceivable pathways for p.o. administered IQ to reach the target colonic mucosal cells: pathway 1, through the digestive canal which exposes from the lumenal direction; pathway 2, following enterohepatic circulation re-expose from the lumenal direction; and pathway 3, exposure via blood circulation. To investigate these possible pathways, the following surgical procedures were performed: (a) portal catheterization for IQ administration to eliminate pathway 1 and (b) choledochal catheterization for bile drainage to eliminate pathway 2. When both procedures are combined, only pathway 3 is active. Four types of IQ-DNA adducts were commonly observed in the colons of all experimental groups, with no qualitative difference between the mucosal and muscular layers. When IQ-HCl was administered by p.o. gavage at a dose of 100 mumol/kg body weight, approximately 70% of the IQ-DNA adducts in the colonic mucosa (13.1 +/- 4.3 adducts/10(7) nucleotides) was induced through pathway 1. Pathway 3 induced the remaining 30% of mucosal adducts, producing equal adduct levels in both layers. Pathway 2 did not work for adduct formation. The DNA adduct formation was unaffected in the presence of intestinal flora, indicating that detoxified IQ does not reactivate by floral enzymes. In conclusion, mucosa-specific DNA adduct formation in the colon is caused most likely by the absorption of carcinogens through the lumen.

Animals↗
PubMed1995

Refined structure of cytochrome b562 from Escherichia coli at 1.4 A resolution.

The structure of cytochrome b562 from Escherichia coli has been refined at 1.4 A resolution against X-ray data collected on a Picker four-circle diffractometer. The triclinic unit cell parameters are a = 33.68 A, b = 50.48 A, c = 32.67 A, alpha = 102.51 degrees, beta = 86.56 degrees and gamma = 107.01 degrees and there are two molecules in the asymmetric unit. A total of 138 cycles of restrained crystallographic refinement using the program PROLSQ were augmented at intermediate stages by two cycles of simulated annealing refinement using X-PLOR. The final crystallographic R-factor is 16.4% for data in the resolution range 6.0 A to 1.4 A for a model containing 1650 protein atoms, 86 heme atoms, 165 water molecules and four sulfate anions. The root-mean-square deviations from ideal bond lengths and angles are 0.012 A and 2.0 degrees, respectively. Each molecule consists of a bundle of four alpha-helices arranged in a simple up-down-up-down manner with a non-covalently bound heme group inserted between the first and fourth helices. In addition, there is a very short 3(10) helix in the 15-residue loop connecting the first and second pairs of helices. The two independent molecules show r.m.s. differences of 0.30 A for main-chain atoms and 0.88 A for all atoms. A detailed comparison with the structurally similar cytochrome c' from Rhodospirulum molishianum is presented. In addition, the titration behavior of cytochrome b562 in solution is discussed in terms of its molecular structure.

Biological Evolution↗
PubMed1995

CNS myelinogenesis in vitro: time course and pattern of rat oligodendrocyte development.

Oligodendrocyte precursor cells that develop into myelin-forming cells of the central nervous system (CNS) were cultured from newborn rat brain to study how they proliferate and differentiate in normal conditioning medium, and their cell development was characterized by scanning electron microscopy (SEM) observation and immunocytochemical studies. We have identified A2B5-negative pre-O2A progenitor cells (so-called "type-1" oligodendrocytes) in the secondary cultures on the astrocyte feeder layer. These cells are very small (diameter: 3.5 microns), round, and glossy, and develop into the process-bearing O2A progenitor cells (called "type-2" oligodendrocytes), which also express myelin basic protein (MBP) both in the cell body and in their cell processes. Finally, they develop into mature oligodendrocytes (called "type-3" oligodendrocytes). After MBP expression is elicited in these cells and MBP accumulates in the cell process in the area in contact with the axon, these cells are capable of forming the myelin sheath. Therefore, we examined the mechanism of myelin-sheath formation of "type-3" oligodendrocytes using video time-lapse movies, and demonstrated that these cells initially sent out processes to search for axons several times before the onset of myelination. Then thick filopodia extended towards the axon, and at the same time, the axonal part of neuron moved forward. Finally the ruffling lamellipodial parts wrapped up the axon similarly to a transverse wave with the secured thick filopodial process on the axon acting as scaffolding. These results suggest that our experimental systems are useful in studying normal oligodendrocyte development and their cellular biochemistry, as well as investigating the mechanism of myelin formation by oligodendrocytes.

Animals↗
PubMed1995

The detection of the mRNAs of procollagen types I, II and III in human fetal fingers by in situ hybridization using digoxigenin-labelled oligonucleotide probes.

Messenger RNAs (mRNAs) encoding procollagen alpha 1 type I,alpha 1 type II and alpha 1 type III have been localized in paraffin sections of human fetal fingers using digoxigenin-labelled synthetic oligonucleotide probes. The probe-mRNA hybrids were visualized using an anti-digoxin antibody amplified with sandwich techniques. These protocols provided an excellent hybridization signal with minimal background noise. The sensitivity of the protocols was nearly equivalent to that seen when using isotopic cDNA probes. In human fetal fingers, intense hybridization signals for procollagen alpha 1 type I mRNA were detected in the osteoblasts and the fibroblasts of periosteum and perichondrium, the tenocytes of tendons, fibroblasts of ligaments, the synovial membrane and deeper layers of the dermis. In contrast, positive hybridization signals for procollagen alpha 1 type II mRNA were visualized in chondrocytes and the cambial layer of perichondrium. The signals for procollagen alpha 1 type III mRNA were detected in the fibroblasts of the dermis and perichondrium. The probes which have lower melting temperatures (Tm) could not detect the corresponding mRNAs.

Base Sequence↗
PubMed1995

Blocking of DNA synthesis in vitro by a guanosine 2',3'-cyclic phosphate: a possible mechanism of chromosome aberrations induced by U5 snRNA.

U5 snRNA can induce both transformation and chromosome aberrations of cells. The polypurine tract, GGAGAGGAA, of the RNA has been suggested to participate in both phenomena. In vitro transcription expected to give this polypurine oligoribonucleotide was associated with cleavage of transcripts, generating 5'-terminal hydroxyl and 3'-terminal 2',3'-cyclic phosphate groups. The cleavage was further studied by making use of a Mg(2+)-catalyzed reaction and RNase T1 and RNase U2 digestion. The cleavage was found to generate highly reactive RNA molecules, participating in subsequent ligation of RNAs. Such a reactive molecule, guanosine-2',3'-cyclic phosphate, was capable of blocking DNA synthesis in vitro. The results may provide a possible mechanism of the chromosome aberrations induced by U5.

Base Sequence↗
PubMed1995

Renal aging change of alpha 1-adrenoceptor in Wistar rats.

1. The aging changes of density of the alpha 1-adrenoceptors in the kidney were evaluated with Wistar rats of several ages (8, 52 and 104 weeks old). 2. [3H]prazosin and [3H]YM617 (newly synthesized alpha 1-blocker) were used for the ligand. The Bmax of [3H]prazosin was 74.0 +/- 9.5 fmol/mg/protein in 8 week, 52.1 +/- 7.3 fmol/mg protein in 52 week, and 31.3 +/- 4.2 fmol/mg protein in 104 week rats, and that of [3H]YM617 was 45.0 +/- 6.6 fmol/mg/protein in 8 week, 32.4 +/- 5.7 fmol/mg/protein in 52 week, and 19.3 +/- 5.5 fmol/mg/protein in 104 week rats. 3. The Bmax of both ligands for 104 week rats was significantly decreased compared to 8 week rats, however, 52 week rats showed no decrease of Bmax for both ligands. 4. The Kd values showed no difference in these three age groups for both ligands. 5. Autoradiographic study supported the result above mentioned. Furthermore, the binding sites of alpha 1-adrenoceptors were mainly in the cortex (vascular wall and peritubular area) and that alpha 1-adrenoceptors were chiefly chlorethylclonidine dihydrochloride (CEC) insensitive.

Adrenergic alpha-Antagonists↗
PubMed1995

Crystal structure of the unliganded alkaline protease from Pseudomonas aeruginosa IFO3080 and its conformational changes on ligand binding.

The crystal structure of the unliganded alkaline protease from Pseudomonas aeruginosa IFO3080 has been determined at 2.0 A resolution by the X-ray method. The enzyme consists of N-terminal catalytic and C-terminal beta-helix domains. On structural comparison between the present unliganded enzyme and structurally- known liganded enzyme, some structural changes were observed around the active site. In the unliganded enzyme, Y216 serves as the fifth ligand for the active site zinc ion. On ligand binding, Y216 may move to form a hydrogen-bond with the carbonyl oxygen of the P1 residue of a ligand peptide. D191 in the flexible loop, Y190 to D196, over the active site cleft forms hydrogen-bonds with the backbone atoms of the P1 and P2 residues of the ligand to close the entrance to the cleft. The water molecule which is the fourth ligand for the zinc ion is replaced by the carbonyl oxygen of the P1 residue. These structural changes around the active site may reflect the substrate-binding mode during the enzymatic reaction.

Bacterial Proteins↗