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Biomedical subjects

T Uchida

Publications and source records attributed to T Uchida.

At least 289 records · Page 16Linked to original sources
PubMed1997

Influence of retinoic acid on the differentiation pathway of T cells in the thymus.

This study investigated the ability of retinoic acid (RA) to influence T cell differentiation. All-trans-RA had marked effects on T cell differentiation in murine fetal thymic organ cultures (FTOCs). The time course of the effect of all-trans-RA in FTOC of day 14 C57BL/6 embryos revealed a twofold increase in the frequency of CD4 single-positive (SP) cells and a high level of CD3-bearing cells (CD3high cells) at a later stage of T cell development. At an earlier stage, all-trans-RA induced a twofold increase in the frequency of CD4 SP cells, but significantly suppressed the upregulation of CD3 and TCR. Reverse transcription-PCR using RA receptor (RAR) subtype-specific primers showed that RAR alpha but not beta and gamma is expressed during T cell development in the thymus and that its expression was associated with the generation of CD4/CD8 double-positive (DP) cells. In FTOC of day 16 BALB/c embryos, the level of V beta 3high cells was greatly reduced (1.4% of the CD3high cells) in response to the mouse mammary tumor virus-6-encoded superantigen, but V beta 3-bearing cells were rescued from the deletion in the presence of all-trans-RA (5.6% of the CD3high cells). Further, the inhibitory effect of all-trans-RA on thymocyte deletion was observed when the deletion was induced by a low concentration of staphylococcal enterotoxin B in FTOC. Taken together, these data suggest that RA increases the frequency of mature and self-reactive T cells in the thymus, possibly by inhibiting the process of negative selection at the DP stage of T cell differentiation.

Animals↗
PubMed1997

Importance of location and timing of electrical stimuli in terminating sustained functional reentry in isolated swine ventricular tissues: evidence in support of a small reentrant circuit.

BACKGROUND: In excitable chemical media, a spiral wave is formed by reentrant excitation around a core and normal propagation away from the core. Whether or not this applies to cardiac muscle is unknown. METHODS AND RESULTS: In six isolated swine ventricular slices, we induced sustained episodes of functional reentry with a stationary core. A train of stimuli applied away from the core (7- to 8-mm distance) and near the core (within 1.6 mm) terminated 5 of 24 and 14 of 17 episodes of reentry, respectively (P<.001). When the stimulus was applied away from the core, successful terminations occurred when the line connecting the stimulus and the core was along the myocardial fiber orientation and when the coupling interval was 54+/-11% of the reentrant cycle length. Stimulation near the core terminated reentry primarily by propagation of the stimulus-induced wave fronts that closed up the excitable gap. However, in two episodes, the application of a stimulus near the core changed the electrogram morphology in only four bipolar pairs. This was sufficient to cause abrupt termination of reentry. CONCLUSIONS: (1) A thin layer of activation near the core is responsible for the maintenance of functional reentry. (2) Access to the tissue near the core is essential for the termination of functional reentry by a point stimulus. (3) To terminate reentry with a stimulus away from the core, the stimulus must occur at certain critical coupling intervals, and the line connecting the stimulus and the core must be roughly parallel to the fiber orientation.

Animals↗
PubMed1997

Hypermethylation of the p15INK4B gene in myelodysplastic syndromes.

Previous studies have shown that the cyclin-dependent kinase inhibitor (CDKI) genes p15INK4B and p16INK4A are frequently inactivated by genetic alterations in many malignant tumors and that they are candidate tumor-suppressor genes. Although genetic alterations in these genes may be limited to lymphoid malignancies, it has been reported that their inactivation by aberrant methylation of 5' CpG islands may be involved in various hematologic malignancies. In this study, we investigated the p15INK4B and p16INK4A genes to clarify their roles in the pathogenesis of myelodysplastic syndrome (MDS). Southern blotting analysis showed no gross genetic alterations in either of these genes. However, hypermethylation of the 5' CpG island of the p15INK4B gene occurred frequently in patients with MDS (16/32 [50%]). Interestingly, the p15INK4B gene was frequently methylated in patients with high-risk MDS (refractory anemia with excess blasts [RAEB], RAEB in transformation [RAEB-t], and overt leukemia evolved from MDS; 14/18 [78%]) compared with patients with low-risk MDS (refractory anemia [RA] and refractory anemia with ring sideroblast [RARS]; 1/12 [8%]). Furthermore, methylation status of the p15INK4B gene was progressed with the development of MDS in most patients examined. In contrast, none of the MDS patients showed apparent hypermethylation of the p16INK4A gene. These results suggest that hypermethylation of the p15INK4B gene is involved in the pathogenesis of MDS and is one of the important late events during the development of MDS.

Carrier Proteins↗
PubMed1997

Expression of a neutrophil chemotactic protein LECT2 in human hepatocytes revealed by immunochemical studies using polyclonal and monoclonal antibodies to a recombinant LECT2.

A recombinant human neutrophil chemotactic protein LECT2 (rhLECT2) was purified as a 16-kDa protein from the culture fluids of stable transfectants derived from CHO cells (clone C1D8-1) and L929 cells (clone L2E4-1). The N-terminal amino acid sequence of the protein secreted by both clones were homologous to the previously described bovine LECT2. We produced polyclonal and monoclonal antibodies against rhLECT2 and investigated secretion of LECT2 protein in six human hepatoma cell lines, which express LECT2 mRNA, and in hepatocytes of normal human livers by a sandwich enzyme-linked immunosorbent assay and by immunostaining using the antibodies, respectively. We revealed that five of six hepatoma cell lines secreted LECT2 into culture fluids at concentrations of 30-135 ng/mg. We also demonstrated that the cytoplasm of human hepatocytes was diffusely stained, although periportal hepatocytes tended to be weakly and granularly stained by immunostaining. These results indicated that the novel protein was expressed in hepatocytes and suggested an important role of LECT2 in the cells in addition to the activation of neutrophils.

Animals↗
PubMed1997

The extent of lymph node dissection for colon carcinoma: the potential impact on laparoscopic surgery.

BACKGROUND: The surgeon is no longer able to palpate the mesocolon for lymph node metastases during laparoscopic colectomy. The extent of lymph node dissection should be determined beforehand for cancer control. METHODS: The distribution of lymph node metastases was obtained by the clearing method on colon carcinomas for 164 patients. RESULTS: For pericolic spread: for pT1 tumors, the distance from the primary tumor to a metastatic lymph node was 2.5 cm; for pT2, the distance was within 5 cm; for 97.0 % of pT3 tumors with lymph node metastases, the distance was within 7 cm; for 93.3 % of pT4 tumors with lymph node metastases, the distance was within 7 cm. For central spread: for pT1 tumors, the rate of metastasis to central lymph nodes was 0 %; for pT2, the rate of metastasis was 20.0 % to intermediate lymph nodes; for pT3, the rate of metastasis was 30.6 % to intermediate lymph nodes and 15.3 % to main lymph nodes; for pT4, the rate of metastasis was 44.4 % to intermediate lymph nodes and 22.2 % to main lymph nodes. CONCLUSIONS: Central lymph node dissection is not required for patients with T1 carcinomas, but proximal and distal 3-cm margins of resection are required. For T2, central lymph node dissection that includes the intermediate lymph node should be performed, as well as 5-cm proximal and distal margins of resection. For T3 and T4, central lymph node dissection including the main lymph node should be performed, as well as 7-cm proximal and distal margins of resection. [See editorial on pages 177-8, this issue.]

Colectomy↗
PubMed1997

Cellular graded responses and ventricular vulnerability to reentry by a premature stimulus in isolated canine ventricle.

BACKGROUND: The cellular mechanism by which a point strong premature stimulus (S2) induces reentry is unknown. We hypothesized that cellular graded responses induced by an S2 mediate and control tissue vulnerability to reentry. METHODS AND RESULTS: Reentry is induced in normal canine ventricular epicardial slices (30x38x2 mm, n=30) by an S2 at intervals shorter than the effective refractory period. The S1 is applied at the edge and the S2 at the center of the tissue. The line connecting the S1-S2 sites is parallel to the long axis of the fiber orientation. Isochronal activation maps were constructed with 56 to 480 bipolar electrodes, and the activation pattern was visualized dynamically. Reentry induced by an S2 is mediated by the graded responses as follows: The induced graded responses propagate with decrement toward recovered cells. When the amplitude of the propagated depolarizing graded responses reaches threshold relative to the recovering cells, an action potential is initiated along the fiber 2 to 3 mm away from the cathode of the S2. The distally initiated activation wave front blocks near the S2 site because the same S2-induced graded response prolongs the refractory period. The "broken" wave front then circulates around both sides of the block and reenters when the site of block recovers its excitability, completing the first figure-eight reentry cycle. Reentry cannot be induced when the S2 strength is >72+/-21 mA (upper limit of vulnerability) because these strong S2-induced graded responses convert the unidirectional block to bidirectional block by excess prolongation of the refractoriness. CONCLUSIONS: We conclude that the magnitude and the propagation of S2-induced cellular graded responses mediate and control vulnerability to reentry in the ventricular epicardium.

Action Potentials↗
PubMed1997

Nitric oxide is an effector molecule in inhibition of tumor cell growth by rIFN-gamma-activated rat neutrophils.

This study was designed to determine the effector molecule responsible for the tumor-inhibitory activity of rat neutrophils treated with rat recombinant interferon gamma (rIFN-gamma) in vitro. The results show that nitric oxide (NO) production by neutrophils is dependent on rIFN-gamma concentration, and that neutrophil-mediated tumor cytostasis is in turn dependent on the amount of NO. NO production and tumor cytostasis by rIFN-gamma-activated neutrophils were inhibited completely by N(G) monomethyl-L-arginine (NGMMA), a specific competitive NO production inhibitor. Tumor cytostasis was also inhibited by oxyhemoglobin (HbO(2)), an NO scavenger. An extracellular oxygen radical scavenger, superoxide dismutase (SOD), was found to increase tumor cell inhibition by rIFN-gamma-activated neutrophils by a factor of 4. This SOD-enhanced cytostasis was not even inhibited by catalase. Tumor cytostasis was slightly increased by a hydroxyl radical-(.OH) scavenger, dimethylthiourea (DMTU), which did not affect NO production by rIFN-gamma-activated neutrophils. Our findings suggest that tumor cytostasis of neutrophils activated by rIFN-gamma is mediated by L-arginine-derived nitrogen oxidation products, and that O(2)- produced by these neutrophils reduces NO-mediated tumor cytostasis at low NO concentrations.

Animals↗
PubMed1997

rIFN-gamma-activated rat neutrophils induce tumor cell apoptosis by nitric oxide.

We have previously shown that 1) neutrophils activated with various cytokines, including rat recombinant interferon gamma (rIFN-gamma), inhibit tumor cell growth and that 2) nitric oxide (NO) is the effector molecule in tumor inhibition by rIFN-gamma-stimulated rat peritoneal exudate neutrophils. In this study, we examined the nature of tumor cell death induced by rat peritoneal neutrophils activated by rIFN-gamma in order to clarify the mechanism of apoptosis in neoplastic tumor cell death. DNA of 3 syngeneic rat tumor cell lines was significantly fragmented within 3 hr of incubation in the presence of rIFN-gamma-activated neutrophils, and this effect was dependent on both the concentration of rIFN-gamma and the number of neutrophils. This DNA fragmentation was inhibited by L-N-(I-iminoethyl)-ornithine (L-NIO), a NO synthase inhibitor, but not by superoxide dismutase (SOD). Tumor cells treated with the activated neutrophils were shown by electron microscopy to be apoptotic, exhibiting necrotic features with a longer incubation. On the other hand, cytolysis of tumor cells, as determined by a [3H]-uridine release assay, was first observed only at 24 hr of incubation with the rIFN- gamma-activated neutrophils. Taken together, our results suggest that tumor cell apoptosis by activated neutrophils is NO-dependent and that apoptotic tumor cells undergo necrosis as a secondary process. We suggest that tumor cell apoptosis induced by activated neutrophils plays an important role in regulation of neoplastic tumor cell growth and death in vivo.

Animals↗
PubMed1997

Quasiperiodicity and chaos in cardiac fibrillation.

In cardiac fibrillation, disorganized waves of electrical activity meander through the heart, and coherent contractile function is lost. We studied fibrillation in three stationary forms: in human chronic atrial fibrillation, in a stabilized form of canine ventricular fibrillation, and in fibrillation-like activity in thin sheets of canine and human ventricular tissue in vitro. We also created a computer model of fibrillation. In all four studies, evidence indicated that fibrillation arose through a quasiperiodic stage of period and amplitude modulation, thus exemplifying the "quasiperiodic transition to chaos" first suggested by Ruelle and Takens. This suggests that fibrillation is a form of spatio-temporal chaos, a finding that implies new therapeutic approaches.

Action Potentials↗
PubMed1997

Effects of the intramolecular disulfide bond on ligand binding dynamics in myoglobin.

In order to investigate the effects of an intramolecular disulfide bond on protein structure and ligand binding dynamics in myoglobin, we prepared a mutant myoglobin having a disulfide bond at the EF corner by introducing two cysteine at the position of Ile 75 and Glu 85. On the basis of the spectral features of the mutant, the formation of the disulfide bond only affected minor structural deviations of the heme environmental structure in the carbonmonoxy form, whereas more substantial structural alterations were induced in the deoxygenated form. Laser photolysis experiments for carbon monoxide rebinding clearly showed that the artificial S-S bond accelerates the bimolecular rebinding rate from 1.0 to 1.8 microM-1 s-1 and increases the geminate yield from 0.072 to 0.092. The ligand migration rate from the solvent to the heme pocket and the bond formation rate from the heme pocket to the heme iron also increased. The free energy diagram for the mutants indicates that the energy barrier for the bond formation was raised as well as that for the ligand migration by introduction of the disulfide bond. However, the effects of the disulfide linkage at the EF corner on the kinetic parameter is much smaller than those of the amino acid substitutions located in the heme cavity. We can conclude that the perturbation of the protein fluctuations by formation of the disulfide bond would be localized at the mutation site or the contributions from other regions and motions might be more important for the ligand binding dynamics.

Binding Sites↗
PubMed1997

The ratio of free to total serum prostate specific antigen and its use in differential diagnosis of prostate carcinoma in Japan.

BACKGROUND: To improve the clinical usefulness of prostate specific antigen (PSA), unique methods have been proposed. The percentage of free PSA in serum facilitates the distinction between benign histologic conditions and prostate carcinoma while retaining high sensitivity. METHODS: Using monoclonal antibodies, an AIA total PSA assay system was established that recognized PSA equally in free or complex form. The clinical usefulness of the ratio of two different molecular forms of PSA was investigated using 268 archival serum samples. RESULTS: Men with prostate carcinoma had significantly lower ratios of free to total PSA than those with benign prostatic hyperplasia (BPH) (P = 0.0001). At total PSA levels between 2.1 and 10 ng/mL, medians of total PSA were not significantly different between men with prostate carcinoma and men with BPH. Differences in median percentages of free PSA for these two groups were statistically significant (P = 0.0001). The ratio of free to total PSA was useful for identifying prostate carcinoma in palpably benign glands with total PSA of 2.1-10 ng/mL (P = 0.0001), whereas total PSA was not useful for such identification. When calculated for low total PSA levels between 2.1 and 4 ng/mL, sensitivity and specificity were 91.7% and 72.2%, respectively, with a cutoff value of 17%. This ratio of free to total PSA was as useful as PSA density in receiver-operating curve analysis. CONCLUSIONS: The use of the ratio of free to total PSA renders total PSA of greater use of distinguishing prostate carcinoma and is applicable to patients with low total PSA. Elderly men with a clinical diagnosis of BPH who are scheduled for surgery may benefit from the determination of this ratio.

Aged↗
PubMed1997

Hepatitis C virus is frequently coinfected with serum marker-negative hepatitis B virus: probable replication promotion of the former by the latter as demonstrated by in vitro cotransfection.

Patients with hepatitis C have been reported occasionally to be coinfected with serum marker-negative (silent) hepatitis B virus (HBV). The frequency and significance of such coinfection were investigated. Thirty patients with hepatitis C virus (HCV) infections (10 acute, 10 chronic, 10 cirrhotic) were selected randomly; the acute cases were without serum hepatitis B surface antigen (HBsAg) and anti-hepatitis B core IgM, and the chronic cases were without HBsAg. A nested polymerase chain reaction for the X open reading frame was used to amplify HBV DNA in serum, and immunoperoxidase staining was carried out on liver biopsy specimens. Nucleotide sequencing was carried out to characterize the amplified HBV DNAs. In order to clarify the possibility that the silent HBV mutant promotes HCV replication in the liver, the full-length HCV RNA and the cloned silent HBV DNA dimer were cotransfected into an established cell line, HuH-7, and the amount of secreted HCV RNA was quantified serially. The target HBV DNA was amplified in 26 (86.7%) of the 30 patients. Subsequent direct nucleotide sequencing in 9 selected patients revealed an 8-nucleotide deletion, characteristic of a silent HBV mutant. Immunostaining revealed hepatitis B surface antigen in 15 (50.0%). Cotransfected silent HBV DNA augmented the secretion of HCV RNA by up to 5-fold in comparison with HCV RNA transfection alone. In conclusion, HCV is coinfected frequently with the silent HBV mutant and the latter probably promotes the replication of the former in the liver.

Adult↗
PubMed1997

The McCoy levering laryngoscope in patients with limited neck extension.

PURPOSE: The McCoy levering laryngoscope is a modified Macintosh laryngoscope, which has a hinged tip controlled by a lever on the handle. The purpose of this study was to investigate whether the tip elevation of this laryngoscope results in better laryngeal visualization than using the Macintosh laryngoscope when the patient's neck is fixed in the neutral position. METHODS: Fifty female patients (ASA physical status I-II) undergoing elective surgery during general anaesthesia were investigated. The patient's neck was manually fixed in the neutral position by an assistant, and laryngeal visualization was attempted first with a size #3 Macintosh laryngoscope (Macintosh trial), and then with a size #3 McCoy levering laryngoscope with blade tip elevation (McCoy trial), and tracheal intubation was attempted. Trials of laryngeal visualization were evaluated with the Cormack score. RESULTS: In the Macintosh trial, 36 of 50 (72%) patients were evaluated grade 3, and two grade 4. In most of the patients graded 2 and 3 in the Macintosh trial (70% of the grade 2 and 83% of the grade 3 cases), the laryngeal view was improved by using the McCoy levering laryngoscope. The Cormack grade in the McCoy trial was less than that in the Macintosh trial (P < 0.01). No complications were observed during the study. CONCLUSION: The McCoy levering laryngoscope improved laryngeal visualization in patients whose neck cannot be extended.

Female↗
PubMed1997

Pharmacokinetic properties of YM17E, an inhibitor of acyl coenzyme A: cholesterol acyl transferase, and serum cholesterol levels in healthy volunteers.

We conducted a single and repeat oral dose study of YM17E, a novel inhibitor of acyl coenzyme A (CoA): cholesterol acyltransferase, in healthy male volunteers to evaluate the pharmacokinetic profile, tolerability and effect of the drug on serum cholesterol. In the single administration study, YM17E was administered after a meal to two groups of subjects (each containing six subjects taking the drug and three taking placebo) receiving 3, 60 and 300 mg or 15, 60 and 450 mg YM17E, respectively. Plasma concentrations of unchanged drug following single oral administration at 3-300 mg after a meal increased with increasing dose. In contrast, plasma concentrations after administration of 450 mg were almost the same as after 300 mg. Unchanged YM17E was not detected in urine after single administration, suggesting that it was excreted via the bile or urine after metabolism. Five active metabolites (M1, M2-a, M2-b, M3 and M4) were observed in plasma at concentrations comparable to those of unchanged YM17E. Their plasma concentrations increased in a slightly greater than dose-dependent manner from 3 to 300 mg. The effect of food was studied in an open crossover design with a 1-week washout period. Twelve subjects received 150 mg YM17E in both the fasted and post-prandial states. The AUC and Cmax after fasting were closely similar to those after a meal, showing that bioavailability was not affected by food intake. In the repeated oral dose study, the subjects received test drug at 150 mg or 300 mg (n = 6 each) or placebo (n = 3) twice a day (after breakfast and after dinner) for 7 days. On days 1 and 7, the subjects received YM17E once a day (after breakfast) for evaluation of pharmacokinetic properties. After repeated oral administration of 150 mg b.d., plasma concentrations reached steady state by day 5 (mean Cmin 48.6 ng.ml-1). After repeated administration of 300 mg b.d., plasma concentrations prior to each daily morning dose increased up to the 5th day (mean Cmin 166.6 ng.ml-1) and then tended to decrease until the 7th day. No significant signs, symptoms or changes in serum cholesterol levels were observed during the single and repeated oral dose studies at 150 mg b.d. Although statistical analysis was not conducted because of the small number of subjects, all subjects receiving repeated oral administration of 300 mg twice daily showed a 25% decrease in serum cholesterol level on day 7, but also the simultaneous occurrence of diarrhoea.

Administration, Oral↗
PubMed1997

Immunochemical and immunohistochemical study of the 27- and 29-kDa calcium-binding proteins and related proteins in the porcine tooth germ.

Our previous report identified 27- and 29-kDa calcium-binding proteins in porcine immature dental enamel. In this study we revealed that the N-terminal amino acid sequences of the two proteins were identical: LLANPXGXIPNLARGPAGRSRGPPG. The sequence matches a portion of the amino acid sequence of the porcine sheath protein, sheathlin. Porcine tooth germs were investigated immunochemically and immunohistochemically using specific antibodies raised against synthetic peptide that included residues 13-25 of this sequence. The affinity-purified antibodies reacted with several proteins extracted from newly formed immature enamel in immunochemical analyses, especially protein bands migrating at 62, 35-45, 29, and 27 kDa in SDS-polyacrylamide gels. The largest protein detected was a weak band near 70 kDa. In immunochemical analyses of proteins extracted from the inner (old) immature enamel, the antibody reacted faintly with the 27- and 29-kDa proteins. In immunohistochemical preparations, the Golgi apparatus and secretory granules of the secretory ameloblast, and the surface layer of immature enamel showed immunoreactivity. The immunoreactivity of immature enamel just beneath the secretory face of the Tomes' process was intense. No immunoreactivity was found in the Golgi apparatus of the maturation ameloblast. These results suggest that the 70-kDa protein, whose degradation might be very fast, is the parent protein of the 27- and 29-kDa proteins.

Ameloblasts↗
PubMed1997

Regional perfusion abnormalities with phenylephrine during normothermic bypass.

BACKGROUND: Hypotension and vasopressors during cardiopulmonary bypass may contribute to splanchnic ischemia. The effect of restoring aortic pressure on visceral organ, brain, and femoral muscle perfusion during cardiopulmonary bypass by increasing pump flow or infusing phenylephrine was examined. METHODS: Twelve anesthetized swine were stabilized on normothermic cardiopulmonary bypass. After baseline measurements, including regional blood flow (radioactive microspheres), aortic pressure was reduced to 40 mm Hg by decreasing the pump flow. Next, aortic pressure was restored to 65 mm Hg either by increasing the pump flow or by titrating phenylephrine. The animals had both interventions in random order. RESULTS: At 40 mm Hg aortic pressure, perfusion to all visceral organs and femoral muscle, but not to the brain, was significantly reduced. Increasing pump flow improved perfusion to the pancreas, colon, and kidneys. In contrast, infusing phenylephrine (2.4 +/- 0.6 micrograms.kg-1.min-1) increased aortic pressure but failed to improve splanchnic perfusion, so that significant perfusion differences existed between the pump flow and phenylephrine intervals. CONCLUSIONS: Increasing systemic pressure during cardiopulmonary bypass with phenylephrine causes significantly lower values of splanchnic blood flow than does increasing the pump flow. Administering vasoconstrictors during normothermic cardiopulmonary bypass may mask substantial hypoperfusion of splanchnic organs despite restoration of perfusion pressure.

Animals↗