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Biomedical subjects

Hideyuki Hayashi

Publications and source records attributed to Hideyuki Hayashi.

69 records · Page 4Linked to original sources
PubMed2002

Reaction mechanism of alanine racemase from Bacillus stearothermophilus: x-ray crystallographic studies of the enzyme bound with N-(5'-phosphopyridoxyl)alanine.

The crystal structures of alanine racemase bound with reaction intermediate analogs, N-(5'-phosphopyridoxyl)-L-alanine (PLP-L-Ala) and N-(5'-phosphopyridoxyl)-D-alanine (PLP-D-Ala), were determined at 2.0-A resolution with the crystallographic R factor of 17.2 for PLP-L-Ala and 16.9 for PLP-D-Ala complexes. They were quite similar not only to each other but also to the structure of the native pyridoxal 5'-phosphate (PLP)-form enzyme; root mean square deviations at Calpha among the three structures were less than 0.28 A. The side chains of the amino acid residues around the PLP-L-Ala and PLP-D-Ala were virtually superimposable on each other as well as on those around PLP of the native holoenzyme. The alpha-hydrogen of the alanine moiety of PLP-L-Ala was located near the OH of Tyr(265)', whereas that of PLP-D-Ala was near the NZ of Lys(39). These support the previous findings that Tyr(265)' and Lys(39) are the catalytic bases removing alpha-hydrogen from L- and D-alanine, respectively. The prerequisite for this two-base mechanism is that the alpha-proton abstracted from the substrate is transferred (directly or indirectly) between the NZ of Lys(39) and the OH of Tyr(265'); otherwise the enzyme reaction stops after a single turnover. Only the carboxylate oxygen atom of either PLP-Ala enantiomer occurred at a reasonable position that can mediate the proton transfer; neither the amino acid side chains nor the water molecules were located in the vicinity. Therefore, we propose a mechanism of alanine racemase reaction in which the substrate carboxyl group directly participates in the catalysis by mediating the proton transfer between the two catalytic bases, Lys(39) and Tyr(265)'. The results of molecular orbital calculation also support this mechanism.

Alanine↗
PubMed2002

Estrogenic and anti-estrogenic activities of two types of diesel exhaust particles.

In an earlier study using a recombinant yeast screen we found that a suspension of diesel exhaust particles (DEP) and some extracts of DEP are not estrogenic but possess anti-estrogenic activity. In the present study, estrogenic and anti-estrogenic activities of two types of DEP, type-1 (old type) and type-2 (new type) were compared. Whole DEP of both types were found to possess estrogenic and anti-estrogenic activities. The DEP were serially extracted with organic solvents and then with 1 M ammonia and 1 M HCl. In type-2 DEP, the ratio of dry weight of a hexane extract was higher than those of methanol and ammonia extracts, which were lower than those in type-1 DEP. In the hexane extract, estrogenic activity was found in both types of DEP. In the benzene and dichloromethane extracts, estrogenic and anti-estrogenic activities were found in both types of DEP. In the methanol extract, estrogenic activity was found in type-2 DEP, and extracts of both types decreased the activity of estrogen. Anti-estrogenic activity was found in extracts of ammonia and HCl from both types of DEP. It was found that both type-1 and type-2 DEP possess estrogenic and anti-estrogenic activities.

Air Pollutants↗
PubMed2002

Posterior capsule opacification after cataract surgery in patients with diabetes mellitus.

PURPOSE: To examine the degree of posterior capsule opacification (PCO) after cataract surgery in patients with diabetes and in nondiabetic age-matched control patients. DESIGN: Case-control study. METHODS: The PCO density value in 100 consecutive diabetic patients and in 100 nondiabetic age-matched control patients who underwent cataract surgery was measured using a Scheimpflug videophotography system at 1 week and at 3, 6, 12, 18, 24, 30, and 36 months after surgery. The incidence of neodymium:yttrium-aluminum-garnet (Nd:YAG) laser posterior capsulotomy was also evaluated. Furthermore, the stage of diabetic retinopathy and systemic condition of the diabetes were correlated with the degree of PCO. RESULTS: No significant difference between the two groups was observed in the mean value of the PCO for up to 12 months after cataract surgery. However, at 18 months and later, the PCO value in the diabetic group increased significantly and was significantly greater than in the control group. Kaplan-Meier survival curves showed that diabetic patients were significantly more likely to require Nd:YAG capsulotomy than control patients (P =.0139, Mantel-Cox log rank test). Among the diabetic patients, there was no significant correlation of PCO value with the stage of retinopathy. Furthermore, type of treatment, duration of diabetes, and hemoglobin A(1C) did not correlate with the PCO value. CONCLUSIONS: Diabetic patients developed significantly greater PCO after cataract surgery than did nondiabetic patients, but among the diabetics, the stage of diabetic retinopathy and systemic status of the diabetes did not correlate with the degree of PCO.

Aged↗
PubMed2002

Elapsed time for capsular apposition to intraocular lens after cataract surgery.

OBJECTIVE: To examine when the anterior and posterior lens capsule completely become apposed to optics of silicone and acrylic intraocular lenses (IOLs) implanted after cataract surgery and to determine whether the different IOL materials influence the timing of completion of capsular contact. DESIGN: Randomized controlled clinical trial. PARTICIPANTS: Seventy eyes of 70 patients who were scheduled to undergo cataract surgery were randomly assigned to two groups using random number tables based on the type of IOL implanted: silicone or acrylic. Thirty-two patients in each group completed the follow-up. INTERVENTION: All eyes underwent phacoemulsification surgery with implantation of either a silicone or acrylic IOL. All IOLs were accurately placed into the capsular bag. MAIN OUTCOME MEASURES: Contact of the anterior and posterior lens capsule with the IOL optic surface was evaluated using the Scheimpflug videophotography system at 3, 5, 7, 9, 11, 14, 21, and 28 days after surgery. The postoperative day at which each capsule was completely apposed to the IOL optic was determined. In addition, anterior chamber depth was also measured. RESULTS: The anterior capsule was in contact with the IOL optic on the same day or earlier than the posterior capsule in all patients. Complete apposition of the IOL was observed significantly earlier with silicone IOLs than with acrylic IOLs with both the anterior capsule (6.2 versus 3.6 postoperative days; P < 0.0001) and the posterior capsule (11.1 versus 7.4 postoperative days; P = 0.0339). No significant change in mean anterior chamber depth was observed with the silicone IOL, whereas there was significant anterior shift after implantation of the acrylic IOL. CONCLUSIONS: Capsular contact with the IOL optic is completed within approximately 8 days after cataract surgery with silicone IOLs and 11 days with acrylic IOLs. Complete apposition to both the anterior and posterior capsule was significantly earlier with silicone IOLs than with acrylic IOLs.

Acrylic Resins↗
PubMed2002

Effect of diesel exhaust particle extracts on collagen-induced arthritis in mice.

We investigated the effect of diesel exhaust particles (DEP) extracts on collagen-induced arthritis (CIA) in mice. For this study, a single DEP sample was consecutively extracted with hexane (HEX-DEP), benzene (BEN-DEP), dichloromethane (DIC-DEP), methanol (MET-DEP), and 1 M ammonia (AMM-DEP) in that order. Residues unextracted with the last extraction solvent 1 M ammonia (UNE-DEP) were also used for experiments. To induce CIA, mice were immunized with type II collagen (CII) and 21 days later given a booster injection. DEP, each DEP extract, and UNE-DEP were intranasally administered every two days over a period of 20 days, commencing on the day of immunization. The results showed that treatment of mice with DEP, DIC-DEP, and UNE-DEP augmented both the incidence and the severity of CIA. DEP and DIC-DEP increased production of anti-CII IgG, IgG2a, and IgG1 antibodies as well as secretion of JFN-gamma and IL-4. Treatment with UNE-DEP resulted in an increase in antigen-specific IgG, IgG2a, and IFN-gamma but neither IgG1 nor IL-4. AMM-DEP failed to affect CIA as well as production of IgG2a and IFN-gamma, although significant increases in anti-CII IgGI and IL-4 were observed in the treatment group. HEX-DEP, BEN-DEP, and MET-DEP had no effects on CIA and production of antibodies and cytokines examined. Thus, DEP and DIC-DEP appear to contain compounds, which enhance both Th1 and Th2 responses, while UNE-DEP and AMM-DEP to contain chemicals, which augment Th1 and Th2 alone, respectively. Th1- but not Th2-modulating compounds from DEP, DIC-DEP, and UNE-DEP seem to influence CIA.

Animals↗
PubMed2002

Spectroscopic analysis of recombinant rat histidine decarboxylase.

Mammalian histidine decarboxylases have not been characterized well owing to their low amounts in tissues and instability. We describe here the first spectroscopic characterization of a mammalian histidine decarboxylase, i.e. a recombinant version of the rat enzyme purified from transformed Escherichia coli cultures, with similar kinetic constants to those reported for mammalian histidine decarboxylases purified from native sources. We analyzed the absorption, fluorescence and circular dichroism spectra of the enzyme and its complexes with the substrate and substrate analogues. The pyridoxal-5'-phosphate-enzyme internal Schiff base is mainly in an enolimine tautomeric form, suggesting an apolar environment around the coenzyme. Michaelis complex formation leads to a polarized, ketoenamine form of the Schiff base. After transaldimination, the coenzyme-substrate Schiff base exists mainly as an unprotonated aldimine, like that observed for dopa decarboxylase. However, the coenzyme-substrate Schiff base suffers greater torsion than that observed in other L-amino acid decarboxylases, which may explain the relatively low catalytic efficiency of this enzyme. The active center is more resistant to the formation of substituted aldamines than the prokaryotic homologous enzyme and other L-amino acid decarboxylases. Characterization of the similarities and differences of mammalian histidine decarboxylase with respect to other homologous enzymes would open new perspectives for the development of new and more specific inhibitors with pharmacological potential.

Animals↗
PubMed2002

Structure of imidazole glycerol phosphate synthase from Thermus thermophilus HB8: open-closed conformational change and ammonia tunneling.

Imidazole glycerol phosphate synthase (IGPs) catalyzes the fifth step in the histidine biosynthetic pathway located at the branch point to de novo purine biosynthesis. IGPs is a multienzyme comprising glutaminase and synthase subunits. The glutaminase activity, which hydrolyzes glutamine to give ammonia, is coupled with substrate binding to the synthase subunit. The three-dimensional structure of the IGPs from Thermus thermophilus HB8 has been determined at 2.3 A resolution, and compared with the previously determined structures for the yeast and Thermotoga maritima enzymes. The structure of each subunit is similar to that of the corresponding domain in the yeast enzyme or subunit in the T. maritima enzyme. However, the overall structure is significantly different from the yeast and T. maritima enzymes, indicating that IGPs may change the relative orientation between the two subunits and close the glutaminase site upon glutamine binding. The putative ammonia tunnel, which carries nascent ammonia from glutaminase to the synthase site, has a closed gate comprising a cyclic salt bridge formed by four charged residues of the synthase subunit. The side chain of Lys100 in the cyclic salt bridge might change its side chain direction to form new interactions with the main chain carbonyl group of glutamine from the synthase subunit and the hydoxyl group of tyrosine from the glutaminase subunit, resulting in the opening of the gate for ammonia transfer.

Aminohydrolases↗
PubMed2002

Effect of diesel exhaust particle extracts on induction of oral tolerance in mice.

We examined the effect of diesel exhaust particle (DEP) extracts on oral tolerance in mice. For this examination, a single DEP sample was consecutively extracted with hexane (HEX-DEP), benzene (BEN-DEP), dichloromethane (DIC-DEP), methanol (MET-DEP), and 1 M ammonia (AMM-DEP). Residues unextracted (UNE-DEP) with the last extraction solvent 1 M ammonia were also used to test their ability to induce oral tolerance. To immunize mice, hen egg lysozyme (HEL) emulsified with an equal volume of CFA was injected sc (day 0). Oral tolerance was induced by feeding 10 mg HEL on days -5, -4, -3, -2, and -1. DEP, each DEP extract, and UNE-DEP were intranasally administered immediately after each feeding of HEL. The results showed that oral administration of HEL markedly suppressed production of anti-HEL IgG antibodies as well as proliferative responses of spleen cells to HEL. The suppression of anti-HEL IgG antibody production and the cell proliferation by the oral antigen was significantly blocked by DEP, DIC-, AMM-, and UNE-DEP. Neither HEX-, BEN-, nor MET-DEP modulated the orally induced suppression of these immune responses. When the levels of anti-HEL IgG2a antibodies and IFN-gamma (Th1 responses) and anti-HEL IgG1 antibodies and IL-4 (Th2 responses) were determined, DEP and DIC-DEP diminished the suppression of both Th1 and Th2 responses observed following oral administration of HEL. In contrast, UNE- and AMM-DEP prevented the reduction of Th1 but not Th2, and Th2 but not Th1 oral tolerance, respectively. Thus, UNE-DEP appears to contain compounds that block induction of Th1 but not Th2 oral tolerance, whereas AMM-DEP have compounds that abrogate induction of Th2 but not Th1 oral tolerance. DIC-DEP, as well as DEP, appear to contain components that block induction of both Th1 and Th2 oral tolerance. As oral tolerance is thought to play a critical role in preventing Th1 as well as Th2 food allergy, the blockade of oral tolerance by these DEP extracts suggests that DEP may contain compounds different in hydrophobicity associated with the cause of such adverse immunologic responses to food proteins.

Animals↗
PubMed2002

Estrogenic activities of chemicals in diesel exhaust particles.

In a previous study, we focused on estrogenic activity of the hexane extract of diesel exhaust particles (DEP). The extract of hexane was first fractionated to acidic, phenolic and neutral portions according to their chemical properties, of which the neutral fraction was fractionated by column chromatography on silica gel. The chemical structures of compounds in these fractions were then analyzed. It was found that the neutral fraction of the hexane extract of DEP contains dibenzothiophene derivatives, one of which, 4,6-dimethyldibenzothiophene, possesses estrogenic activity.

Estrogens, Non-Steroidal↗
PubMed2002

Depicting cerebral veins by three-dimensional CT angiography before surgical clipping of aneurysms.

BACKGROUND AND PURPOSE: Cerebral veins show wide variation, and unexpected veins occasionally limit surgical procedures for clipping of cerebral aneurysms. This study was undertaken to assess the utility of three-dimensional CT angiography (3D-CTA) in the evaluation of venous anatomy before surgical clipping of cerebral aneurysms. METHODS: 3D-CTA was performed in 19 patients before pterional craniotomy. The venous anatomy visualized by use of 3D-CTA was compared retrospectively with intraoperative findings. RESULTS: 3D-CTA clearly depicted the superficial sylvian veins (SSVs) in 17 of 19 cases. In three of these 17 cases, 3D-CTA failed to reveal the additional connecting veins from SSVs to the midportion of the sphenoid wing. 3D-CTA also depicted bridging veins from: 1) the basal vein of Rosenthal to the sphenoparietal sinus (SPS) (three cases); 2) a junction of the anterior cerebral vein and the deep middle cerebral vein to the SPS (two cases); 3) the anterior cerebral vein into the cavernous sinus (one case); and 4) the deep middle cerebral vein to the cavernous sinus in one case. Surgical findings corresponded well with the angiographic findings. 3D-CTA depicted bridging veins from the frontal base into the SPS in two cases; retraction of the frontal lobe was severely limited in these cases. 3D-CTA also exhibited anatomic variation of deep cerebral veins, which suggests the utility of 3D-CTA in evaluating the risks carried by sacrifice of some bridging veins. In two patients, aneurysmal dissection was restricted because of adhering veins. 3D-CTA depicted these cerebral veins to be lying in contact with the aneurysm. In one case, the contiguous vein was hidden behind a large middle cerebral artery aneurysm; 3D-CTA was helpful for visualization of this vein. CONCLUSION: 3D-CTA can clearly depict the venous anatomy of the brain and is useful for surgical planning of a pterional or temporopolar approach for cerebral aneurysms.

Adult↗
PubMedDate not supplied

Enhanced detection of malignant glioma xenograft by fluorescein-human serum albumin conjugate.

OBJECT: During the surgical resection of malignant gliomas, it is important to make clear the border zone between the tumor tissue and normal brain tissue. For this purpose, we conjugated fluorescein and human serum albumin (FLS-HSA) and compared its effectiveness against that of fluorescein-sodium (FLS-Na) alone in detecting human glioma xenografts in SCID mice through a fluorescence microscope. METHODS: We made FLS-HSA conjugate using carbodiimide as a linking reagent. SCID mice, with U251MG cells transplanted subcutaneously, were prepared as tumor models. The animals were sacrificed 15, 30, 60, 180, 360, or 720 min after the intravenous administration of either the FLS-HSA conjugate or FLS-Na alone (n = 3). Fluorescence images were taken with a digital camera, and the brightness of the tumor and that of the peripheral tissue in each image were quantified. In the group of tumor-bearing mice that received FLS-Na, the fluorescence of tumor tissue disappeared 60 min after the reagent was administered, and there was no significant difference in brightness between the tumor and peripheral tissue at any time point. On the other hand, injection of FLS-HSA revealed relative tumor-selective brightness and sufficient contrast between the tumor and surrounding tissue 60 and 360 min after administration. CONCLUSION: FLS-HSA has the advantages of specificity and persistence of fluorescence over FLS-Na for the purpose of identifying glioma nodules in xenogenic subcutaneous tumor transplantation models.

Animals↗
PubMedDate not supplied

Non-paralleled increase of hepatocyte growth factor and vascular endothelial growth factor in the eyes with angiogenic and nonangiogenic fibroproliferation.

Vascular endothelial growth factor (VEGF) has been known as principal angiogenic factor in vasculogenesis, tumor angiogenesis and ocular angiogenesis. Currently, hepatocyte growth factor (HGF) has been reported to play a major role in ocular angiogenesis. We studied distribution of both growth factors in angiogenic and non-angiogenic fibroproliferation to determine the correlation of VEGF and HGF in retinal angiogenesis. Concentrations of VEGF and HGF molecules in vitreous samples from 27 eyes with angiogenic proliferative diabetic retinopathy (PDR) and 9 eyes with non-angiogenic proliferative vitreoretinopathy (PVR) were measured by enzyme-linked immunosorbent assay (ELISA). Vitreous samples with idiopathic macular role (IMH) served as a control. Concentrations of VEGF in the angiogenic PDR were 4.3 +/- 5.8 ng/ml (mean +/- SD), and were significantly higher than in non-angiogenic PVR (0.5 +/- 0.1 ng/ml). No significant differences were observed on VEGF concentrations between PVR to control. On the contrary, HGF concentrations were significantly higher in PVR (22.5 +/- 21.8 ng/ml) than in control (6.9 +/- 5.2 ng/ml), those of PDR (24.0 +/- 16.3 ng/ml) were also significantly higher than control. Among PDR samples, VEGF concentration was significantly higher than in the subgroup with higher angiogenic activity represented by iris neovascularization, although there were no significant differences on HGF concentration between the subgroups. Focal increases in HGF on fibroproliferation in the eye regardless of the involvement of angiogenesis were not in remarkable relation with angiogenic activity, unlike VEGF. These data suggested a more extensive role of HGF than VEGF strictly related to angiogenesis.

Diabetic Retinopathy↗
PubMedDate not supplied

Colocalization of Tie2, angiopoietin 2 and vascular endothelial growth factor in fibrovascular membrane from patients with retinopathy of prematurity.

PURPOSE: The tyrosine kinase receptor Tie2 and its ligands, the angiopoietins (Angs), play important roles in vascular integrity and neovascularization, modulating vascular endothelial growth factor (VEGF) activity. To elucidate the potential role of Angs and the Tie2 system in retinopathy of prematurity (ROP), we have investigated the expression of Angs, Tie2 and VEGF within fibroproliferative membranes in ROP. METHODS: Fibroproliferative membranes were obtained from 38 cases with stage 5 ROP at the time of vitrectomy. Membranes were fixed in formalin and embedded in paraffin. Each specimen was serially sectioned for immunohistochemistry. Polyclonal antibodies specific for Ang1, Ang2, Tie2 and VEGF were used for immunostaining. Immunoreactivity for von Willebrand factor (factor VIII) was also assessed to confirm the identity of vascular endothelial cells. RESULTS: Positive staining for Tie2 was observed in 23 of 38 specimens (60.5%). Tie2 was localized in vascularized regions of fibrovascular membranes and was co- expressed with VEGF and factor VIII. Ang2 stained positively in 18 of 38 (47.3%) serial sections where Tie2 was present, and was also co-expressed with VEGF and factor VIII. Ang1 was not generally observed in these specimens (3/38). CONCLUSIONS: VEGF and Ang2-Tie2 interactions may play an important role in the pathogenesis of ROP.

Angiogenesis Inducing Agents↗
PubMedDate not supplied

Increased intraocular pressure and corneal endothelial cell loss following phacoemulsification surgery.

BACKGROUND AND OBJECTIVE: To compare the influence of low-molecular-weight viscoelastics on postoperative intraocular pressure (IOP) and corneal endothelial cell loss after phacoemulsification PATIENTS AND METHODS: Sixty-nine eyes undergoing phacoemulsification surgery were randomized to have either Opegan (Santen Pharmaceuticals, Osaka, Japan) alone or the soft-shell technique using Viscoat (Alcon Surgical, Fort Worth, TX) during phacoemulsification. The IOP was measured preoperatively and at 5 and 24 hours postoperatively. Intraoperative factors and corneal endothelial cell loss were also examined. RESULTS: Mean IOP was increased at 5 hours after surgery but returned to preoperative levels at 24 hours in the Opegan group, whereas it remained higher at 24 hours than at preoperative levels in the soft-shell group. When comparing groups, IOP at 5 and 24 hours postoperatively in the Opegan group was significantly less than that in the soft-shell group. Corneal endothelial cell loss was approximately the same in the two groups. CONCLUSION: The increase in IOP following phacoemulsification surgery with the use of Opegan was less than that with the soft-shell technique using Viscoat, although endothelial injury was almost the same.

Aged↗