Biomedical subjects

Y Yamada

Publications and source records attributed to Y Yamada.

At least 379 records · Page 21Linked to original sources

PubMed2000

M-S vibrational study in three-coordinate thiolato compounds (NEt4)2[M(SC6H4-p-X)3] and (NEt4).

By using p-substituted benzenethiolate ligands, the novel three-coordinate copper(I) and silver(I) thiolato complexes (NEt4)2[Cu(SC6H4-p-X)3] (X=Cl (1) and Br (2)), (NEt4)2[Ag(SC6H4-p-X)3] (X=Cl (3) and Br (4)) and novel clusters (NEt4)2[M4(mu-SC6H4-p-Cl)6] (M=Cu (5) and Ag(6)) have been prepared and structurally characterized by single crystal X-ray diffraction. All the complexes have three-coordinate sites having point-group D3h symmetry. The three-coordinate mononuclear silver(I) complexes 3 and 4 are the first examples. The M-S stretching bands were determined by far-IR and FT-Raman spectroscopies; nu(Cu-S) 363-372 cm(-1) and nu(Ag-S) 353-363 cm(-1). These results indicate that M-S stretching vibration energy in the three-coordinate metal(I) site of the mononuclear compounds or clusters is around 340-380 cm(-1), and it is a useful tool for determining their coordination modes.

Benzene Derivatives↗

PubMed2000

Characterization of functional endothelin receptors in the porcine myometrium.

To characterize the endothelin (ET) receptor that mediates the contraction induced by ET-1 in the porcine myometrium, we carried out a contraction study, radioligand binding study and molecular study (reverse transcription polymerase chain reaction) for detection of ET receptor-coding genes (mRNA). ET-1 (1 nM-1 microM) caused a tetrodotoxin-insensitive contraction in both longitudinal and circular muscles, but the longitudinal muscle was more sensitive to ET-1 than was the circular muscle. On the other hand, ET-3 and sarafotoxin S6c were less effective to cause a contractile response. The contraction induced by ET-1 was markedly inhibited by BQ123 and FR139317, but BQ788 only slightly inhibited the response induced by ET-1. The radioligand binding study indicated the presence of a single class of 125I-ET-1 binding sites with the same Kd value in both muscle layers. However, Bmax in the longitudinal muscle (3252 fmol/mg protein) was significantly higher than that in the circular muscle (1883 fmol/mg protein). ET-1 and FR139317 inhibited the specific 125I-ET-1 binding completely, but ET-3, sarafotoxin S6c and BQ3020 only slightly inhibited the specific binding (inhibition, 10-20%), suggesting that ET(A) is the dominant ET receptor subtype in the porcine myometrium. The results of the molecular study indicated the expression of both ET(A) and ET(B) receptor-coding genes in the porcine myometrium. In conclusion, ET-1 causes contraction of the porcine myometrium through activation of the ET(A) receptor present on smooth muscle cells. There is a marked muscle layer-related difference (longitudinal muscle > circular muscle) in the ET-1-induced contraction and the ET(A) receptor concentration.

Animals↗

PubMed2000

Changes in chewing pattern after surgically induced disc displacement in the rabbit temporomandibular joint.

PURPOSE: This study investigated whether surgically induced disc displacement (DD) in the rabbit temporomandibular joint leads to joint dysfunction. MATERIALS AND METHODS: Fourteen adult Japanese white rabbits were divided into two groups. Eight animals had surgically induced DD, and 6 were used as a sham operation group. Jaw movement trajectories during chewing were recorded preoperatively and 2 weeks after induction of DD. Postoperative recordings after administration of a nonsteroidal anti-inflammatory drug (NSAID) were also performed to eliminate any influence of joint pain on chewing. Vertical and horizontal ranges of chewing movement, duration of the opening and closing phase, and total cycle of chewing were analyzed. Thereafter, the presence of induced DD was confirmed histologically. RESULTS: In the sham group, the rhythm and pattern of chewing were almost the same as preoperatively. In the experimental group, increase in the cycle duration and decrease in the vertical and horizontal ranges of movement were observed. When the sham and experimental groups were compared, there was a decreased ratio of vertical movement in the experimental animals. There was no effect of preadministration of the NSAID in either the DD or sham group. All of the experimental animals had total anterior DD histologically. CONCLUSION: Changes in the chewing pattern of the experimental animals occurred from mechanical interference of the displaced disc. This animal model can be used as a model for human internal derangement.

Animals↗

PubMed2000

Maternal program of apoptosis activated shortly after midblastula transition by overexpression of S-adenosylmethionine decarboxylase in Xenopus early embryos.

When we studied polyamine metabolism in Xenopus embryos, we cloned the cDNA for Xenopus S-adenosylmethionine decarboxylase (SAMDC), which converts SAM (S-adenosylmethionine), the methyl donor, into decarboxylated SAM (dcSAM), the aminopropyl donor, and microinjected its in vitro transcribed mRNA into Xenopus fertilized eggs. We found here that the mRNA injection induces a SAM deficient state in early embryos due to over-function of the overexpressed SAMDC, which in turn induces inhibition of protein synthesis. Such embryos developed quite normally until blastula stage, but stopped development at the early gastrula stage, due to induction of massive cell dissociation and cell autolysis, irrespective of the dosage and stage of the mRNA injection. We found that the dissociated cells were TUNEL-positive, contained fragmented nuclei with ladder-forming DNA, and furthermore, rescued completely by coinjection of Bcl-2 mRNA. Thus, overexpression of SAMDC in Xenopus embryos appeared to switch on apoptotic program, probably via inhibition of protein synthesis. Here, we briefly review our results together with those reported from other laboratories. After discussing the general importance of this newly discovered apoptotic program, we propose that the maternal program of apoptosis serves as a surveillance mechanism to eliminate metabolically severely-damaged cells and functions as a 'fail-safe' mechanism for normal development in Xenopus embryos.

Adenosylmethionine Decarboxylase↗

PubMed2000

Are nitrite/nitrate (NOx) levels elevated by inhalation injury?

The relationship between airway burn and nitric oxide (NO) levels in the early burn stage was investigated by quantifying nitrite/nitrate (NOx), which are the final metabolites of NO, in 22 burn patients. Although total body surface area (TBSA) and burn index (BI) were significantly higher in patients with airway-burn than in patients without airway burn (P=0.0347 and 0.0422, respectively), no significant difference in NOx levels was observed between the two groups (P=0.6196). The NOx levels were found to correlate significantly with TBSA (r=0.4775, P=0.0246). A significant correlation was also noted between the NOx levels and BI (r=0.4391, P=0.0409). These results suggest that NO reflects the intensity of inflammation in the early burn stage, but that excessive NO formation is unlikely to be induced by stress, such as that caused by airway burn.

Adult↗

PubMed2000

Bound and soluble adhesion molecule and cytokine levels in patients with severe burns.

We measured endotoxins, inflammatory cytokines and soluble adhesion molecules in the blood of 17 severe burn patients to determine the involvement of these factors in the pathophysiology of severe burns. All seventeen patients had burns with a total burn surface area of 20% or more and a burn index of 15% or more. Endotoxin was measured by an endotoxin-specific assay and tumor necrosis factor-alpha, interleukin 6 and interleukin 8 and soluble adhesion molecules were measured by enzyme-linked immunosorbent assay. CD11a, CD11b and CD18, measured by flow cytometry, were elevated in the non-surviving group, the septic shock group and the multiple organ dysfunction syndrome group, suggesting a close connection between these adhesion molecules and burns complicated by infection. Soluble adhesion molecules were found to indirectly reflect the level of endothelial cell adhesion molecules, suggesting that inflammatory cytokines may also be involved in their production.

Adult↗

PubMed2000

Tumor necrosis factor-alpha and tumor necrosis factor receptor I, II levels in patients with severe burns.

Tumor necrosis factor alpha (TNF-alpha) and tumor necrosis factor receptor I and II (TNFRI and TNFRII) were studied in 24 burn patients who had a total burn surface area (TBSA) of 50.2 +/- 20.4%. Immediately after the injury, both the TNFRI and TNFRII levels correlated significantly with TBSA (r = 0.7344, P < 0.0001; r = 0.6074, P = 0.0012). The TNFRI and TNFRII levels immediately after the injury were significantly higher in the 11 patients who later died of their burns than in the 13 patients who survived (0.8 +/- 0.4 ng/ml vs. 1.8 +/- 0.7 ng/ml, P = 0.0002; 2.3 +/- 1.1 ng/ml vs. 4.5 +/- 1.6 ng/ml, P = 0.0009). The TNF-alpha levels immediately after the injury did not differ significantly between the group that survived and the group that died. The TNFRI and TNFRII values for the entire follow-up period also correlated significantly with TBSA. Peak TNFRI and TNFRII levels were significantly higher in the group that died than in the group that survived (6.0 +/- 4.7 ng/ml vs. 14.1 +/- 7.8 ng/ml, P = 0.0009; 7.0 +/- 5.1 ng/ml vs. 16.7 +/- 5.2 ng/ml, P = 0.0003). The TNF-alpha levels correlated significantly with both the TNFRI and the TNFRII levels. The TNFRI and TNFRII levels thus closely reflected the severity of the burns in both the acute postburn period and the subsequent follow-up period. In other words, these parameters well reflected the severity and outcome of the burns, irrespective of the presence or absence of accompanying infection.

Adult↗

PubMed2000

Visuospatial imagery is a fruitful strategy for the digit span backward task: a study with near-infrared optical tomography.

Our newly developed 64-channel time-resolved optical tomographic imaging system using near-infrared light enables us to obtain a quantitative image of hemoglobin concentration changes associated with neuronal activation in the human brain ¿H. Eda, I. Oda, Y. Ito, Y. Wada, Y. Oikawa, Y. Tsunazawa, M. Takada, Y. Tsuchiya, Y. Yamashita, M. Oda, A. Sassaroll, Y. Yamada, M. Tamura, Multi-channel time-resolved optical tomographic imaging system, Rev. Sci. Instrum., 70 (1999) 3595-3602. Here, we used this optical imaging system to demonstrate that the backward digit span (DB) task activated the dorsolateral prefrontal cortex (DLPFC) of each hemisphere more than the forward digit span (DF) task in healthy adult volunteers, and higher performance of the DB task was closely related to the activation of the right DLPFC. These results suggest that visuospatial imagery is a useful strategy for the DB task. Optical tomography described here is a new modality of neuropsychological studies.

Adult↗

PubMed2000

Differential expression of laminin alpha chains during proliferative and differentiation stages in a model for skin morphogenesis.

The purpose of this study was to determine the mRNA and protein expression of laminin alpha chains at various stages of in vitro skin morphogenesis. Fibroblasts in mono-cultures express low levels of the mRNA of laminin alpha1,alpha2, alpha3 and alpha4 chains. When co-cultured with keratinocytes for 28 days, they expressed the mRNA for all these chains. Keratinocytes in monolayer expressed the laminin alpha3 chain mRNA and very low levels of the mRNA of the alpha1 and alpha2 chains, although, when recombined with fibroblasts they also expressed laminin alpha1and alpha2 mRNA, but not the laminin alpha4 mRNA. Immunocytochemistry of cells in co-culture showed that laminin alpha1, alpha3 and alpha5 chains were expressed in the epidermis, while the laminin alpha2, beta1, and gamma1 chains were noted in the dermis and at the epidermo-dermal interface. The laminin alpha1chain was first expressed during the proliferative stage (14-21 days) and the laminin alpha2 and alpha5 chains appeared later, during the differentiation stage (28-42 days). The above results suggest that epithelial-mesenchymal interactions are involved in the expression of laminin alpha chain mRNA during in vitro skin morphogenesis. In addition, there is distinct temporal and spatial expression of these chains during proliferative and differentiation stages, possibly reflecting different functions.

Cell Differentiation↗

PubMed2000

Mössbauer studies on laser evaporated iron atoms and their reactions with oxygen in argon matrices.

Laser-evaporated iron atoms were isolated in low-temperature Ar matrices and their chemical reactions with oxygen were investigated by means of Mössbauer spectroscopy. Reactions of iron atoms with oxygen produce FeO, Fe(O2), FeO3, (O2)FeO2 and OFeO isolated in the Ar matrices and their yields vary depending on the concentration of oxygen. Similarly, FeO and Fe(O2) were obtained by the reaction of iron atoms with N2O. Infrared spectroscopy and molecular orbital calculations were applied to support their assignments.

Calorimetry↗

PubMed2000

A new method for qualitative and quantitative evaluation of tooth displacement under the application of orthodontic forces using magnetic sensors.

The purpose of this study was to develop a new method for the quantitative and qualitative measurement of tooth displacement under load and to clarify the relationship between the force system acting on a tooth and a resultant movement. A combination of eight magnetic sensors and a magnet was employed to measure three-dimensional displacement. Two sets of sensors and a magnet were placed in front and at the back of a front tooth subjected to orthodontic forces. Magnets and sensors were fixed to the subject tooth and posterior teeth, respectively. Sensors detected displacements of two magnets extended from the subject tooth separately in real time. The tooth trajectories projected on the sagittal plane were studied. From displacements of two magnets, angle of tooth rotation, the position of center of rotation and the amount and direction of displacement of an arbitrary point on the tooth could be calculated with high accuracy. Also, the location of center of resistance could be determined. It was found that the center of rotation is moving substantially even with a small difference in the level of force application. Furthermore, a small amount of displacement of the center of resistance was observed with varying the force magnitude.

Biomechanical Phenomena↗

PubMed2000

A null mutant of the Streptomyces virginiae barA gene encoding a butyrolactone autoregulator receptor and its phenotypic and transcriptional analysis.

The Streptomyces virginiae barA gene encodes a specific receptor protein for virginiae butanolide (VB), one of the gamma-butyrolactone autoregulators of Streptomyces species. By homologous recombination, a barA null strain was constructed to clarify the in vivo function of BarA protein in S. virginiae. The deltabarA mutant showed no difference in terms of growth, but lost VB production and produced virginiamycin 7 h earlier than the wild-type strain. These results indicated that, phenotypically, BarA protein acts negatively in virginiamycin biosynthesis and positively in VB biosynthesis. Furthermore, Northern (RNA) blot analysis of the DeltabarA mutant revealed that transcription of the BarA target gene (barB) was derepressed, confirming that BarA acts as a transcriptional repressor in S. virginiae.

Journal Article↗

PubMed2000

In vivo antioxidative activity of propolis evaluated by the interaction with vitamins C and E and the level of lipid hydroperoxides in rats.

In vivo antioxidative activity of propolis was evaluated on the basis of ameliorative effects on the oxidative stress induced by vitamin E deficiency in rats. The control group was fed vitamin E-deficient diet, and the propolis group was fed vitamin E-deficient diet supplemented with 1% of propolis for 4 and 8 weeks. Comparisons were made in tissue concentrations of vitamin C, vitamin E, and lipid hydroperoxides between these groups. No significant difference was observed in tissue vitamin E concentration between these groups after both 4 and 8 weeks. After 4 weeks, the plasma vitamin C concentration of the propolis group was significantly higher than that of the control group. After 8 weeks, the tissue concentrations of vitamin C in the kidney, stomach, small intestine, and large intestine of the propolis group were significantly higher than those of the control group. These results suggest that some components of propolis are absorbed to circulate in the blood and behave as a hydrophilic antioxidant that saves vitamin C. The concentration of lipid hydroperoxides in the large intestine of the propolis group was significantly lower than that of the control group after 8 weeks. These results suggest that propolis exerts its antioxidative effect where it is assumed to accumulate, such as on the kidney, where it is excreted, and on the gastrointestinal tract, where propolis influences these tissues even from the outside of the cell.

Animals↗

PubMed2000

Three new scalarane sesterterpenoids from the Okinawan sponge Hyrtios erectus.

Three new scalarane sesterterpenoids-hyrtiolide (1), 16-hydroxyscalarolide (2), and 12-deacetyl-Delta(17)-hyrtial (3), were isolated from Okinawan sponge Hyrtios erectus, along with scalarolide (4) and 12-deacetylhyrtial (5). The structures of new compounds 1-3 were determined by spectroscopic analysis and chemical conversions. Compounds 3 and 5 showed antiproliferative activity toward KB cells.

Animals↗

PubMed2000

Induction of choline acetyltransferase activity in cholinergic neurons by stolonidiol: structure-activity relationship.

The effect of stolonidiol (1), a bioactive marine diterpenoid from the Japanese soft coral Clavularia sp., on choline acetyltransferase (ChAT) activity was examined using cultured cholinergic neurons. Stolonidiol (1) showed potent ChAT inducible activity in primary cultured basal forebrain cells and clonal septal SN49 cells, suggesting that it may act as a potent neurotrophic factor-like agent on the cholinergic nervous system. Further expansion of the structure-activity relationship to include stolonidiol (1) and its derivatives demonstrated that the exo-methylene group and the epoxide group are essential for ChAT-inducing activity. Stolonidiol (1) showed the highest activity among the test samples.

Animals↗

PubMed2000

Up-regulation of urokinase-type plasminogen activator and its receptor correlates with enhanced invasion activity of human glioma cells mediated by transforming growth factor-alpha or basic fibroblast growth factor.

Glioblastoma multiforme is a highly malignant tumor that is extremely refractory to therapy. One reason is its highly invasive nature into brain tissue. Metalloproteinases and their inhibitors, plasminogen activators (PA) and their inhibitors and cathepsins are thought to be involved in invasion by tumor cells. In this study, we determined if the urokinase-type plasminogen activator (uPA) and/or the urokinase-type plasminogen activator receptor (uPAR) were responsible for the invasion activity of a human glioma cell line. We determined the invasion activity of a human glioma U251 cell line using an in vitro invasion assay system. A 2.4- to 5.8-fold increase in invasion activity was observed in the presence of basic fibroblast growth factor (bFGF) or transforming growth factor (TGF)-alpha. Northern blot analysis showed that bFCF and TGF-alpha treatment was associated with increases in cellular mRNA levels of uPA and uPAR. Zymographic activity correlated to mRNA levels of uPA and uPAR. Addition of an anti-uPAR monoclonal antibody significantly inhibited the invasion activity induced by bFGF- and TGF-alpha. Irsogladine, an inhibitor of uPA synthesis, also blocked the invasion activity. These observations suggest that uPA and its receptor have a role in the invasion process of human gliomas.

Fibroblast Growth Factor 2↗

PubMed2000

Basement membrane laminin-5 is deposited in colorectal adenomas and carcinomas and serves as a ligand for alpha3beta1 integrin.

Interplay between laminin-5 (Ln-5) and its integrin (Int) receptors alpha2beta1, alpha3beta1 and alpha6beta4 has been implicated in the progression and invasion of carcinomas. In this study we found abundant immunoreactivity for chains of Ln-5 (alpha3-beta3-gamma2) and Ln-10 (alpha5-beta1-gamma1), as well as for type VII collagen, in basement membranes (BM) of colorectal adenomas. In carcinomas of all differentiation grades, Lns were seen in tumor BMs, whereas type VII collagen was almost absent. Ln-5 appeared to accumulate along the invading edges of carcinomas, while Ln-10 was mostly absent. Immunoreactivity for Ln al chain, a component of Lns-1 and -3, was not seen in adenomas or carcinomas. Immunoreactivity for alpha2, alpha6, beta1 and beta4 Ints was found in all tumors and that for alpha3 Int in all adenomas and most of the carcinomas, often in colocalization with Ln-5. Immunoblotting of carcinoma tissues showed that the gamma2 chain of Ln-5 was present as typical Mr 105000 and 155000 isoforms. Immunoprecipitation experiments showed production of Ln-5 by cultured colon carcinoma cells. In quantitative cell adhesion experiments, function-blocking MAbs to alpha3 and beta1 Int subunits, but not those to Int alpha2 or alpha6 subunits, significantly inhibited the adhesion of cells to Ln-5. Our results suggest that BM composition in colorectal adenomas reflects the properties of surface epithelial BM of colorectal mucosa. In invading carcinomas, trimeric Ln-5, produced by carcinoma cells, is a major BM component and the cells use the alpha3beta1 Int complex for adhesion to Ln-5.

Adenoma↗

PubMed2000

Lactacystin activates FLICE (caspase 8) protease and induces apoptosis in Fas-resistant adult T-cell leukemia cell lines.

Lactacystin (LC) is a specific inhibitor of the proteasome, and has recently been shown to induce apoptosis in certain cell lines. In the present study, we established Fas-resistant adult T-cell leukemia (ATL) cell subclones RSO4 and RST1 from their parental Fas-sensitive cell lines SO4 and ST1, and examined whether LC can overcome Fas resistance. LC completely inhibited proteasome function as determined by a peptidyl-MCA substrate (LLVY-MCA and LLE-MCA), and induced apoptosis in these cell lines irrespective of Fas sensitivity at low concentrations (approximately 10 microM). LC induced the activation of caspase 3 (CPP32/Yama) and caspase 6 proteases in an identical manner to Fas-mediated apoptosis. Moreover, LC induced the activation of caspase 8 (FLICE) protease, which is the initiator of the Fas-mediated apoptotic cascade. Synthesized proteasome inhibitory peptide MG-115 (ZLLnV-CHO) also induced apoptosis in these cell lines. These results indicated that proteasome inhibitors overcome Fas-resistance by bypassing the proximal part of the Fas signal. Inhibition of the proteasome function may be a new strategy for the treatment of ATL.

Acetylcysteine↗