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Biomedical subjects

T Yamane

Publications and source records attributed to T Yamane.

At least 217 records · Page 12Linked to original sources
PubMed1998

Inhibitory effects of rebamipide on ENNG-induced duodenal carcinogenesis in mice: a possible strategy for chemoprevention of gastrointestinal cancers.

Rebamipide is a potent antioxidative agent; it increases gastric mucosal PGE2 production and thus protects the gastric mucosa. We hypothesized that the mechanisms of ulcer formation could be extended to carcinogenesis and that an increase in gastric mucosal protection may result in a decrease in gastric carcinogenesis. Therefore, we assessed the inhibitory effects of rebamipide on N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) -induced carcinogenesis in mice. The percentage of tumor-bearing mice in three treatment groups--ENNG + rebamipide 20 mg, ENNG + rebamipide 50 mg, and ENNG alone--was 55%, 42%, and 67%, respectively. The incidence of tumorigenesis tended to decrease with increasing doses of rebamipide. The difference between ENNG + rebamipide 50 mg and ENNG alone was statistically significant (P < 0.05). These results suggest that rebamipide may strengthen the host defense mechanisms related to carcinogenesis in the digestive tract.

Alanine↗
PubMed1998

Problems with assays based on fibrin clot formation principle: analysis of multilaboratory data.

In order to investigate the inter-laboratory differences of coagulation assays, three different control plasmas were distributed for coagulation assays to 162 institutes. Three types of coagulation tests, that is, prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen (Fbg) assay were carried out by routine methods in each institute. In our laboratory, the Fbg concentrations were measured in two different plasmas using one instrument and nine reagents, and the Fbg concentrations were measured in ten control plasmas using three instruments and one reagent. Results were obtained as follows: (1) The coefficient of variance (CV) for control plasma with the highest value was significant in the PT assay and APTT assay. (2) Inter and intra-institute differences in PT and APTT assays were observed when the reagent or the instrument used was changed. (3) Inter and intra-institute differences in PT and APTT assays were also observed when both the reagent and the instrument were changed. (4) Inter and intra-institute differences in the PT and APTT assays were observed between the manual and the mechanical methods. (5) The CVs for the Fbg assays were the largest in the plasma at the lowest concentration of the three plasmas. (6) When control plasmas of three different Fbg concentrations were assayed, the number of the institutes which obtained a value greater than 3 standard deviations (SDs) was highest for the control plasma with the lowest concentrations of Fbg, and some of the instruments were not able to measure such a low Fbg concentration. (7) When the fibrinogen concentration was measured in various kinds of commercially-available control plasmas with a calibrated instrument, the values determined were different from the assigned ones and varied significantly from instrument to instrument. From the results, we concluded that standardization of the quality of control plasma, and its value assignment to the plasma should be established as soon as possible, and that a reliable standard fibrinogen assay should be developed.

Blood Coagulation↗
PubMed1997

Development of osteoclasts from embryonic stem cells through a pathway that is c-fms but not c-kit dependent.

Osteoclasts are hematopoietic cells essential for bone resorption. To study the derivation of these interesting cells, we developed a stepwise culture system where stromal cells promote embryonic stem (ES) cells to differentiate into mature osteoclasts. Three phases to this differentiation process include (1) induction of hematopoiesis, along with the generation of osteoclast precursors, (2) expansion of these precursors, and (3) terminal differentiation into mature osteoclasts in the presence of 1alpha,25-dihydroxyvitamine D3 . Although the transition of ES cells to the hematopoietic lineage was not blocked by an antibody to c-fms, later phases were dependent on a signaling through this transmembrane receptor as indicated by the finding that anti-c-fms treatment of cells in the second and third phases reduced the number of osteoclasts produced by 75% and more than 99%, respectively. Blockade of signaling through another tyrosine kinase-type receptor, c-kit, did not affect any stages of osteoclastogenesis, although generation of other hemopoietic lineages was reduced to less than 10% of untreated. When small numbers of ES cells were directly cultured under conditions that promote osteoclast differentiation, tartrate-resistant acid phosphatase-positive multinucleated cells were observed at the edge but not inside of colonies. This suggests that some types of cell-cell interactions may inhibit development of mature osteoclasts. The culture system developed here provides an important tool for osteoclast biology.

Animals↗
PubMed1997

Cloning and sequence analysis of a Bothrops jararaca cDNA encoding a precursor of seven bradykinin-potentiating peptides and a C-type natriuretic peptide.

A 1.8-kb cDNA clone was isolated from a Bothrops jararaca venom gland cDNA library that encodes a 256-aa precursor for bradykinin-potentiating peptides (angiotensin-converting enzyme inhibitors) and a C-type natriuretic peptide (CNP). The seven bradykinin-potentiating peptides are aligned tandemly after the hydrophobic signal peptide sequence, followed by a putative intervening sequence and a CNP at the C terminus. Northern blot analysis indicated the predominant expression of a 1.8-kb mRNA in the venom glands as well as in the spleen and the brain. Two lower intensity mRNA bands of 3.5 kb and 5.7 kb also hybridized to the cDNA clone. Radioimmunoassay for the CNP was performed using the antiserum against rat CNP. The presence of CNP immunoreactivity was detected in the low molecular weight fraction of the Bothrops jararaca venom.

Amino Acid Sequence↗
PubMed1997

Osteoclast precursors in bone marrow and peritoneal cavity.

Osteoclasts differentiate from cells that share some phenotypes with mature macrophages and monocytes, but early precursors for osteoclasts still remain obscure. To characterize osteoclast precursors, using monoclonal anti-c-Fms and anti-c-Kit antibodies, bone marrow cells were separated and the frequency of clonogenic progenitors were measured. Osteoclast precursors in the bone marrow mainly expressed c-Kit and diminished in frequency when they expressed c-Fms. In contrast to bone marrow, the precursors in the peritoneal cavity were enriched with a population of c-Fms+. Injection of these antibodies into mice demonstrated that peritoneal osteoclast precursors were sensitive to anti-c-Fms but not to anti-c-Kit antibodies, whereas those in bone marrow only declined in the presence of both antibodies. Meanwhile, c-Fms as opposed to c-Kit played an essential role in the generation of osteoclasts in cultures. We also compared osteoclast precursors with colony forming cells (CFU-M) by a macrophage colony stimulating factor. CFU-M in bone marrow decreased when anti-c-Kit antibody was administered and no CFU-M was detected in peritoneum. In this study, we show differences between proliferative potential osteoclast precursors maintained in bone marrow and peritoneum and between CFU-M and osteoclast precursors.

Animals↗
PubMed1997

Distribution of serotonin-immunoreactive nerve cells and fibers in the rat gastrointestinal tract.

The distribution of serotonin-immunoreactive (5HT-IR) nerve cells and fibers was thoroughly investigated immunohistochemically in the rat stomach, duodenum, jejunum, ileum, and colon. The immunoreactivity of the 5HT neurons was compared between non-treated controls and animals treated with colchicine, colchicine plus 5-hydroxytryptophan (5HTP), colchicine plus pargyline, and reserpine. The intensity of immunoreactivity in nerve fibers as well as nerve cell bodies was enhanced mostly in colchicine plus pargyline treated animals, therefore these animals were used for an observation of precise localization of 5HT in the rat gastrointestinal (GI) tract. Immunoreactivity in the nerve cell bodies and fibers was completely abolished in the GI tract of reserpine treated animals. The pattern of localization and projection of 5HT-IR neurons was similar in all segments of the rat GI tract: 5HT-IR nerve cell bodies were located in the myenteric plexus and showed the distinctive features of Dogiel type I neurons. Prominent bundles of varicose fibers traversed the myenteric ganglia and some of them surrounded the cell bodies of immunopositive and immunonegative neurons. 5HT-IR nerve fibers were located in the submucous plexus, densely entwined about the submucosal blood vessels. Most characteristically, 5HT-IR nerve fibers invaded the lamina propria of mucosa where they underlay the crypt epithelium. In conclusion, the present study showed that 5HT-IR neurons located in the myenteric plexus projected fibers widely in the rat GI tract. The localization of fibers in the lamina propria of mucosa implies that this neuron may exert an important role in the epithelial function of the GI tract.

5-Hydroxytryptophan↗
PubMed1997

Cloning and characterization of a repetitive 1.9 Kb HindIII DNA fragment from Crotalus durissus terrificus genome.

Eukaryote genomes are endowed with varying quantities of repeated DNA families. These families show different patterns of conservation among species, copy numbers, chromosomal distribution, and transcription. Characterization of repeated DNA sequences could help to understand the genome anatomy and organization or be used in molecular systematics and molecular evolution studies. We describe here a repetitive DNA sequence of the HindIII family present in the genome of the rattlesnake Crotalus durissus terrificus. In Brazil, the family Crotalus is comprised only by one species durissus, which include several subspecies. The number and distribution of these subspecies are controversial. In the present study, the genomic DNA of a female rattlesnake was digested with HindIII resulting in a strong 1.9 Kb band. A partial genomic library was constructed from the 1.9 Kb DNAs rescued from the agarose gel after HindIII digestion and ligated to the vector pGEM3Zf(+) (Promega). Analysis of 69 clones, 44 hybridized with the 1.9 Kb probe isolated from one of the clones-clone 76, indicating that the DNA isolated from this clone should represent the 1.9 Kb HindIII fragment. This 1.9 Kb HindIII DNA was completely characterized by sequencing.

Animals↗
PubMed1997

Follicular dendritic cell tumor of the mesentery.

Follicular dendritic cell (FDC) tumor is an exceedingly rare malignant neoplasm and occurs mainly in the cervical lymph nodes. We report a mesenteric FDC tumor occurring in a 66-year-old female, that manifested with intraabdominal multifocal recurrence 7 years after resection of the primary tumor. Histologically, both primary and recurrent tumors were composed of oval to spindle cells with paley eosinophilic cytoplasms, indistinct cell borders, round to elongated nuclei with clear or finely dispersed chromatin, and medium to large nucleoli. Characteristically, the tumor cells were growing in sheets, fascicles, and sometimes in whorls and a storiform pattern. In addition, focal necrosis, nuclear pleomorphism and abnormal mitoses were also observed. The neoplastic cells were intimately admixed with small lymphocytes. The diagnosis was confirmed by positive immunoreactivity with CD21 and CD35 antibodies and by ultrastructural demonstration of convoluted interdigitating cell processes connected by scattered desmosome-like junctions. Although our case showed a low proliferative activity evaluated by MIB-1, multifocal recurrence has occurred. The clinicopathologic features and differential diagnosis of FDC tumors are discussed with the review of the literature.

Aged↗
PubMed1997

Moderately controlled transport of ascorbate into aortic endothelial cells against slowdown of the cell cycle, decreasing of the concentration or increasing of coexistent glucose as compared with dehydroascorbate.

Uptake of L-[1-(14)C]ascorbic acid (Asc) of 12.5-200 microM for 1 h into bovine aortic endothelial BAE-2 cells grown to confluence was as low as 43-64% (per cell) of uptake into the cells grown to nearly one-fourth confluence. [14C]Asc undergoing transmembrane uptake was concentrated and accumulated in the cell less efficiently ([Asc]in/ex = 8-13) at confluence than at subconfluence ([Asc]in/ex = 15-24). The declined Asc uptake at confluence is attributable to slowdown of the cell cycle, because a similar decrease in [Asc]in/ex was shown by subconfluent cells precultured in serum-insufficient medium, resulting in an increase in G1 phase and concurrent decreases in S and G2 + M phase distributions as determined by flow cytometry. [1-(14)C]Dehydroascorbic acid (DehAsc) was taken up and accumulated as Asc, after metabolic reduction, without detectable DehAsc. The [Asc]in/ex values for DehAsc at confluence were as low as 15-69% of those at subconfluence in contrast to the values as retentive as 62-75% for Asc, suggesting the moderate control of Asc uptake against slowdown of the cell cycle. At either confluence or subconfluence, dose-dependence for DehAsc uptake was more marked than for Asc uptake as shown by an uphill slope in a curve of doses versus [Asc]in/ex for DehAsc in contrast to a downhill slope for Asc, suggesting the moderate control for Asc uptake against fluctuation of the dose. Increasing of coexistent glucose of 5 mM to 20-40 mM, plasma concentrations in diabetic patients, declined DehAsc uptake to 46-48%, which was less moderately controlled than Asc uptake retained to 59-73%. Asc uptake did not compete with DehAsc uptake, suggesting different transporter proteins for Asc and DehAsc. Thus, Asc uptake into the aortic endothelial cells is more moderately controlled against slowdown of the cell cycle, decreasing of the extracellular concentrations or increasing of coexistent glucose than DehAsc uptake, suggesting a homeostatic advantage of Asc over DehAsc in terms of retention of intracellular Asc contents within a definite range.

Animals↗
PubMed1997

Crystallization and preliminary X-ray analysis of a truncated family A alkaline endoglucanase isolated from Bacillus sp. KSM-635.

The catalytic domain of an alkaline endo-1,4-beta-glucanase (family A) isolated from Bacillus sp. KSM-635 (Mr = 40.2 kDa) was crystallized using the hanging drop vapor diffusion method. Two different crystal forms were obtained. Form 2 crystals (trigonal space group R3 with cell dimensions of a = b = 111.9 and c = 207.1 angstroms in a hexagonal lattice) were found to be more stable than form 1 ones upon X-ray irradiation. A full data set for form 2 crystals has been collected up to 3.3 angstroms resolution.

Amino Acid Sequence↗
PubMed1997

High-resolution crystal structure of M-protease: phylogeny aided analysis of the high-alkaline adaptation mechanism.

M-protease is a subtilisin-family serine protease produced by an alkaliphilic Bacillus sp. strain. Optimal enzymatic activity of the protein occurs at pH 12.3. The crystal structure of M-protease (space group P2(1)2(1)2(1), a = 62.3, b = 75.5, c = 47.2 A) has been refined to a crystallographic R-factor of 17.2% at 1.5 A resolution. The alkaline adaptation mechanism of the enzyme was analyzed. Molecular phylogeny construction was used to determine the amino acid substitutions that occurred during the high-alkaline adaptation process. This analysis revealed a decrease in the number of negatively charged amino acids (aspartic acid and glutamic acid) and lysine residues and an increase in arginine and neutral hydrophilic amino acids (histidine, asparagine and glutamine) residues during the course of adaptation. These substitutions increased the isoelectric point of M-protease. Some of the acquired arginine residues form hydrogen bonds or ion pairs to combine both N- and C-terminal regions of M-protease. The substituted residues are localized to a hemisphere of the globular protein molecule where positional shifts of peptide segments, relative to those of the less alkaliphilic subtilisin Carlsberg, are observed. The biased distribution and interactions caused by the substituted residues seem to be responsible for stabilization of the conformation in a high-alkaline condition.

Adaptation, Physiological↗
PubMed1997

Histopathologic study of islets of Langerhans in patients after gastrectomy.

In autopsy specimens removed after gastrectomy from patients who had survived for 2.5 to 40 years after surgery, we found hyalinization of the islets of Langerhans in 9 of 15 cases (60%) with Billroth's I anastomosis (B-I) and in 8 of 16 cases (50%) with Billroth's II anastomosis (B-II). The hyalinization in the postgastrectomy patients was significantly increased compared with that in controls (p < 0.01). The percentage of hyalinized islets of Langerhans in the 17 cases showing hyalinization ranged from 0.2% to 14.3%. The percentage increased relative to the period after gastrectomy in the B-I patients but not in those with B-II. The blood glucose level was mildly elevated in three B-I patients, whereas it was increased in only one patient with B-II. Hyalinization of the islets of Langerhans may be due to vagotomy or to excessive stimulus and hyperactivation of the islets. In any event, the islets of Langerhans in patients after gastrectomy were frequently replaced by hyalinization, which might cause impaired glucose tolerance.

Aged↗
PubMed1997

New mechanism to reduce the size of the monopivot magnetic suspension blood pump: direct drive mechanism.

Size reduction of the monopivot magnetic suspension blood pump has been achieved by reducing the size of the magnetic suspension and employing a direct drive mechanism in place of a brushless DC motor and a magnetic coupling. The flow has also been improved using a closed hollow impeller to remove flow obstruction at the inlet and using radial straight vanes to reduce the impeller speed by 30%. Hemolysis testing was conducted for the new models. Results showed that model DD1 presented only a slightly higher level of hemolysis than a regular extracorporeal centrifugal pump.

Centrifugation↗
PubMed1997

Quantitative visualization of flow through a centrifugal blood pump: effect of washout holes.

To clarify the effect of washout holes on the flow in a centrifugal blood pump to prevent blood stagnation, a quantitative flow visualization technique was applied to compare flows in models with and without washout holes. A scaled-up model of a prototype pump and a high speed video camera were used for the flow visualization, and images were processed by particle tracking velocimetry. Particular attention was paid to the flow through the gaps behind and in front of the impeller. The results showed that in the gap behind the impeller, washout holes caused not only an inward flow, but also an increase in the tangential velocities. In the gap in front of the impeller, washout holes caused an outward flow and a decrease in the tangential velocities. Head flow characteristics were little affected by the washout holes in this initial design for which the flow through the washout holes was set to be approximately 10% of the flow in the external circuit. These results suggest that the flow through washout holes is significant in the prevention of blood stagnation in 2 ways. First, the inward radial velocity behind the impeller and outward velocity in front of the impeller result in fluid exchange, and second, a tangential velocity increase reduces fluid stagnation behind the impeller.

Blood Flow Velocity↗
PubMed1997

Magnetically levitated motor for rotary blood pumps.

The noncontact rotary pumps under development for use as artificial heart pumps are highly efficient and can prevent thrombus formation. In these pumps magnetic bearings have been widely used to support the rotors to avoid any physical contact. The use of magnetic bearings, however, has led to requirements for the control of a large degree of freedom and for a separate driving motor. This paper introduces 2 types of levitated motors, each of which uses a combination of a rotary motor and a magnetic bearing. These motors are suitable for use in artificial blood pumps because they are small in size and can replace contact components. The radial type levitated motor has the merit of being small in size and capable of controlling the 2 degrees of freedom in the x and y directions. The axial type motor controls only one degree of freedom in the z direction. This paper also introduces the theoretical background of the functions of the motor and magnetic bearing. Experimental results of tests of the proposed motor show a great potential for its application in rotary blood pumps.

Algorithms↗