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Biomedical subjects

Y Hamada

Publications and source records attributed to Y Hamada.

At least 145 records · Page 8Linked to original sources
PubMed2000

MRI and arthroscopic findings in the temporomandibular joint after mandibulectomy including the unilateral condyle. Report of two cases.

In this report, the MRI and arthroscopic findings in the temporomandibular joint (TMJ) of two patients who underwent partial mandibulectomy including the condyle are presented. The disc and superior joint compartment of the affected TMJs were preserved in both patients. MRI of the affected TMJs without condyle demonstrated that the intermediate zone of the discs was located anteriorly to the summit of the articular eminence. Joint effusion was detected in the superior joint compartment of one patient. Fibrous adhesions were observed arthroscopically in the superior joint compartment of both affected TMJs. In contrast, no specific findings were demonstrated in the contralateral TMJs connected with the residual mandibular fragment.

Adult↗
PubMed2000

Na+/H+ exchange inhibitor reduces vascular injury caused by ischemia-reperfusion in the rat hind limb.

This study was designed to evaluate the effects of an Na+/H+ exchange inhibitor, SM-20550, on ischemia-reperfusion injury in the skeletal muscle. Male Sprague-Dawley rats were exposed to ischemia and reperfusion by clamping and releasing clamps both at the abdominal aorta and the bilateral femoral arteries. Rats were divided into three groups; the sham, the SM-20550 treated (SM), and the untreated control (Control) groups. In the SM and control groups, rats were exposed to 5-hr ischemia and 5-hr reperfusion. In the sham group, vessel isolation only was performed. SM-20550 (2.8 mg/kg/hr) in the SM group or vehicle in the sham and control group was continuously administered during ischemia and reperfusion periods. The wall thickness of the vessels were significantly (p<0.01) decreased in the control group than any other group. The internal diameter was significantly (p<0.01) higher in the control and SM group than in the sham group. The wall thickness/internal diameter ratio was significantly (p<0.05) lower in the control group than in the SM group. Thus, an Na+/H+ exchange inhibitor, SM-20550, ameliorated the morphological change due to ischemia reperfusion. These findings provide a clue into the mechanism of ischemia reperfusion injury.

Animals↗
PubMed1999

Mouse jagged1 physically interacts with notch2 and other notch receptors. Assessment by quantitative methods.

The Delta/Serrate/LAG-2 (DSL) domain containing proteins are considered to be ligands for Notch receptors. However, the physical interaction between DSL proteins and Notch receptors is poorly understood. In this study, we cloned a cDNA for mouse Jagged1 (mJagged1). To identify the receptor interacting with mJagged1 and to gain insight into its binding characteristics, we established two experimental systems using fusion proteins comprising various extracellular parts of mJagged1, a "cell" binding assay and a "solid-phase" binding assay. mJagged1 physically bound to mouse Notch2 (mNotch2) on the cell surface and to a purified extracellular portion of mNotch2, respectively, in a Ca(2+)-dependent manner. Scatchard analysis of mJagged1 binding to BaF3 cells and to the soluble Notch2 protein demonstrated dissociation constants of 0.4 and 0.7 nM, respectively, and that the number of mJagged1-binding sites on BaF3 is 5,548 per cell. Furthermore, deletion mutant analyses showed that the DSL domain of mJagged1 is a minimal binding unit and is indispensable for binding to mNotch2. The epidermal growth factor-like repeats of mJagged1 modulate the affinity of the interaction, with the first and second repeats playing a major role. Finally, solid-phase binding assay showed that Jagged1 binds to Notch1 and Notch3 in addition to Notch2, suggesting that mJagged1 is a ligand for multiple Notch receptors.

Amino Acid Sequence↗
PubMed1999

Steric restrictions on the binding of large metal ions to serum transferrin.

Apotransferrin in 0.1 M N-(2-hydroxyethyl)piperazine-N'-2-ethanesulfonic acid at 25 degrees C and pH 7.4 was titrated with acidic solutions of Lu3+, Tb3+, and Eu3+. Metal binding at the two specific metal-binding sites of transferrin was followed from changes in the difference UV spectra at 245 nm. The binding of Tb3+ was also followed from changes in the fluorescence emission spectrum at 549 nm. Apotransferrin was titrated with solutions containing varying ratios of the metal ion and the competitive chelating agent nitrilotriacetic acid, and metal-transferrin binding constants were calculated by nonlinear least-squares fits of the absorbance as a function of titrant added. The sequential carbonate-independent equilibrium constants for the binding of two metal ions are log KM1 = 11.08 and log KM2 = 7.93 for Lu3+, log KM1 = 11.20 and log KM2 = 7.61 for Tb3+, and log KM1 = 9.66 and log KM2 = 7.27 for Eu3+. Titrations of both C-terminal and N-terminal monoferric transferrins indicate that all of these metal ions bind more strongly to the C-terminal binding site. The trend in log K values as a function of the lanthanide ionic radius has been evaluated both by plots of log K versus the metal ion charge/radius ratio and by linear free-energy relationships in which binding constants for complexes of the larger lanthanides are plotted versus the binding constants for complexes with the smallest lanthanide, Lu3+. Both methods indicate that there is a sharp drop in the binding constants for the C-terminal binding site for metals larger than Tb3+. This decrease is attributed to a steric hindrance to the binding of the larger cations. The steric effect is not as strong for metal binding at the N-terminal site. As a result, the selectivity for binding to the C-terminal site, which is quite high for the smaller lanthanides, drops sharply on going from Tb3+ to Nd3+.

Allosteric Site↗
PubMed1999

Inhibition of advanced protein glycation by a Schiff base between aminoguanidine and pyridoxal.

Aminoguanidine is a well-known inhibitor of the formation of advanced glycation end products and is considered to be promising for the treatment of diabetic complications. We recently reported, however, that administration of aminoguanidine caused the formation of a Schiff base adduct between aminoguanidine and pyridoxal phosphate in the liver and kidney of mice and a concomitant decrease in the amount of liver pyridoxal phosphate. Our study led us to hypothesize that the Schiff base adduct and/or another Schiff base adduct formed from aminoguanidine and pyridoxal might be a better compound than aminoguanidine. In the present study, we examined the in vitro inhibitory potency of the latter adduct against advanced glycation end product formation and its effect on the tissue contents of pyridoxal and its phosphate. Aminoguanidine-pyridoxal phosphate adduct was not employed in this study because of its poor solubility in water. Aminoguanidine-pyridoxal adduct was hydrolyzed by only about 15% during 10 days at pH 7.4 and 37 degrees C. The adduct at 1 mM did not inhibit Amadori product formation induced by incubation of albumin with 100 mM mannose for 10 days. The adduct, when tested at 1 and 2 mM, dose-dependently inhibited advanced glycation end product formation induced by incubation of albumin with mannose; and the inhibitory potency of the adduct was similar to or higher than that of aminoguanidine. The presence of an appreciable amount of aminoguanidine-pyridoxal adduct in the kidney of mice given the adduct suggested that at least part of the adduct administered was absorbed from the gastrointestinal duct. The amounts of pyridoxal and its phosphate in tissues were not at all decreased by administration of the aminoguanidine-pyridoxal Schiff base. We conclude that the Schiff base may be a more promising inhibitor of advanced protein glycation than aminoguanidine.

Animals↗
PubMed1999

An aldose reductase inhibitor prevents the glucose-induced increase in PDGF-beta receptor in cultured rat aortic smooth muscle cells.

To examine the role of platelet-derived growth factor (PDGF) and the polyol pathway in the growth activity of smooth muscle cells (SMCs), [(3)H]-thymidine incorporation, [(125)I]-PDGF-BB binding and expression of PDGF-beta receptor protein were measured in rat aortic SMCs cultured with 5.5 or 20 mM glucose with or without anti-PDGF antibody or an aldose reductase inhibitor, epalrestat. SMCs cultured with 20 mM glucose demonstrated an accelerated thymidine incorporation compared with SMCs cultured with 5.5 mM glucose, which was prevented by anti-PDGF antibody. This acceleration of growth activity by 20 mM glucose was accompanied by an increase in PDGF-BB binding, which was due to the increased number of PDGF-beta receptors and the overexpression of PDGF-beta receptor protein. Epalrestat prevented all these abnormalities. These observations suggest that polyol pathway hyperactivity plays an important role in the proliferation of SMCs which may be mediated through the accelerated expression of PDGF-beta receptor protein.

Aldehyde Reductase↗
PubMed1999

The interaction between human and bovine serum albumin and zinc studied by a competitive spectrophotometry.

The binding of zinc to human serum albumin (HSA) and bovine serum albumin (BSA) has been studied by a competitive spectrophotometry. The indictor ligand, 5-Br-PAPS, as well as its metal complexes, ML and ML2, having intense colors with sufficient separate absorption peaks permits the analysis of the interaction between zinc and HSA or BSA. The results show that zinc binds to both albumins in the molar ratio of 1:1 at pH 6-8. The apparent association constants of Zn-HSA and Zn-BSA decrease with decreasing pH. The pH dependence of the constants for both Zn-HSA and Zn-BSA indicates the 1:1 competition between metal ions and hydrogen ions for the binding site. The intrinsic association constants of the metal and the proton are found to be log KZn-HSA = 7.1 +/- 0.2 and log KH-HSA = 8.2 +/- 0.3 for HSA and log KZn-BSA = 7.6 +/- 0.2 and log KH-BSA = 8.2 +/- 0.3 for BSA, respectively.

Animals↗
PubMed1999

Regional difference in correlation of 5-HT4 receptor distribution with cholinergic transmission in the guinea pig stomach.

Localization and function of 5-HT4 receptors in the stomach were examined in mucosa-free preparations of antrum, corpus and fundus from guinea pig stomach by determination of acetylcholine release and in vitro receptor autoradiography. Specific [125I]SB207710, (1-n-butyl-4-piperidinyl) methyl-8-amino-7-iodo-1,4-benzodioxane-5-carboxylate, binding sites were detected in 3 regions of the stomach. High densities of binding were observed in the myenteric plexus of antrum and corpus, but not fundus. In mucosa-free preparations treated with 5-HT1, 5-HT2 and 5-HT3 receptor antagonists, 5-HT (10(-8)-10(-6) M) potentiated the electrically stimulated (0.5 Hz, 1 ms) outflow of [3H]acetylcholine from antrum and corpus strips preloaded with [3H]choline, but not from fundus strips, and the potentiation was antagonized by SB204070, (1-n-butyl-4-piperidinyl) methyl-8-amino-7-chloro-1,4-benzodioxane-5-carboxylate. Thus, 5-HT4 receptors are located on myenteric cholinergic neurons in the antrum and corpus of guinea pig stomach and their activation evokes the release of acetylcholine.

Acetylcholine↗
PubMed1999

Establishment of a human hemangiosarcoma cell line (ISO-HAS).

A cell line (ISO-HAS) has been established from tumor tissue of a human hemangiosarcoma arising on the scalp by the use of conditioned medium from a murine-phenotypic angiosarcoma cell line (ISOS-1). Cells have been cultured for more than 2 years with up to 100 passages. The cells retained endothelial-cell properties, such as a characteristic cobblestone appearance at confluency, contact-inhibited growth, active uptake of acetylated low-density lipoprotein labeled with 1,1-dioctadecyl 1,3,3,3,3-tetramethyl-indocarbocyanine perchlorate (DiI-Ac-LDL) and CD31 expression. However, they were weakly positive for von-Willebrand-factor (vWf) antigen and for binding of Ulex europaeus agglutinin-I (UEA-I) lectin, and lacked tube-formation activity. These findings indicate that ISO-HAS is a poorly differentiated endothelial cell line. ISO-HAS cells showed accumulation of p53 protein in the nuclei, and a new-typed p53-gene point mutation was found in exon 7 at codon 240. When inoculated s.c. into severe-combined-immunodeficiency (SCID) mice, the cells showed solid-tumor growth that caused death. These properties suggest that ISO-HAS is a malignant endothelial cell line with high tumorigenicity.

Animals↗
PubMed1999

Conformational change of ascidiacyclamide caused by asymmetric modification for an isoleucine residue: structural analyses of [Gly], [Leu], and [Phe]ascidiacyclamides by x-ray diffraction and NMR spectroscopy.

Ascidiacyclamide, a cytotoxic cyclic peptide from tunicate, is composed of unusual amino acids and has a repeated sequence, c[-thiazole-D-Val-oxazoline-L-Ile-]2 ([Ile]ASC). The symmetric chemical structure has been assumed to be correlated with the cytotoxicity, and it is reasonable to consider that the disturbance of its structure from the C2 symmetry results in the changes of conformation and activity. In order to quantitatively estimate the molecular conformation-activity relationship, an isoleucine residue was substituted by Gly, Leu, or Phe to disturb the C2 symmetry. The conformations of three derivatives were examined by nmr spectroscopy and the crystal structure of [Leu]ASC was also analyzed by x-ray diffraction method. The 1H-nmr experiments and the constrained molecular dynamics simulations showed the twisted "figure 8" conformers for [Gly] and [Phe]ASCs and the "square" conformer for [Leu]ASC in the DMSO solution. The x-ray crystal analysis of [Leu]ASC also revealed the square form similar to the solution structure. On the other hand, their cytotoxic activities were measured using L1210 leukemia cells and were related with the bulkiness and/or hydrophobicity of the side chain of the substituted amino acid; [Phe] > or = [Ile] > [Leu] >> [Gly]ASCs. As an attempt to consider the correlation between the activity and conformer, the accessible surface area (ASA) was calculated for each derivative to estimate the size or bulkiness of its conformation. Although the ASAs of nmr structures were not directly related to the type of conformer (figure 8 or square form), it was an important probe to consider the cytotoxicity of each derivative.

Amino Acid Substitution↗
PubMed1999

The wear of a polyethylene socket articulating with a zirconia ceramic femoral head in canine total hip arthroplasty.

Wear of yttria-zirconia (zirconia) in the femoral head was investigated in mature mongrel dogs weighing 10 to 13 kg. Two dogs, which were used as a control group, were sacrificed 18 months after implantation of the uncemented modular hip system with an alumina ceramic (alumina) femoral head. A zirconia femoral head was implanted in five dogs: one was sacrificed 12 months after implantation, two at 18 months, and two at 24 months. In each femoral head and polyethylene (PE) socket, the surface was observed by means of scanning electron microscopy (SEM); the mean articulation surface roughness on the femoral head and PE socket and the thickness of the PE socket were measured. Wear was not seen on the surface of either the zirconia or the alumina heads. In both groups, minute white spots on the smooth surface of the PE socket were visible by SEM. In the alumina and zirconia groups the mean roughness was 0.1 microm. The mean thickness of the PE socket was reduced by 0.2 mm in the alumina group. In the zirconia group it was reduced by 0.2 to 0.3 mm. However, the mechanical strength of zirconia is known to be greater than that of alumina and it may be possible to reduce the diameter of the femoral head. The smaller zirconia head may contribute to the reduction of the wear of the PE socket in an uncemented modular total hip system.

Animals↗
PubMed1999

Accelerating bone formation and earlier healing after using demineralized bone matrix for limb lengthening in rabbits.

We studied the effects of grafting with demineralized bone matrix during lengthening of the tibia in young Japanese White rabbits. The demineralized bone matrix was made from frozen cortical bone harvested from other rabbits. A 5-mm gap was created in the tibial diaphysis by a subperiosteal osteotomy; a maximum of 20 mm (2-3 mm/day) of tibial lengthening was reached in a week with use of an external fixator. The control group of 20 rabbits did not receive an implant; the group of 21 experimental rabbits received an implant of demineralized bone matrix in the surgical gap. The control group failed to demonstrate radiographic callus 5 weeks after surgery, and nonunion was persistent after 1 year. In the group with demineralized bone matrix, new radiodensity was demonstrated within the lengthening gap at 3 weeks, with a gradual increase in bone density to 85% that of the intact tibia after 12 weeks. Bone union was seen within 1 year for all experimental animals for whom the external fixator was removed 8 weeks after the procedure. These bones showed normal bone structure histologically. The lengthening was carried out at a rapid distraction rate of 2-3 mm/day; therefore, this method allows for satisfactory bone formation at a faster rate than normal.

Absorptiometry, Photon↗
PubMed1999

An aldose redutase inhibitor prevents the intimal thickening in coronary arteries of galactose-fed beagle dogs.

AIMS/HYPOTHESIS: Although increased polyol pathway activity has been implicated in the pathogenesis of diabetic microangiopathy, the relation with diabetic macroangiopathy remains unclear. Galactose feeding is known to stimulate the polyol pathway and to develop abnormalities similar to those in diabetic microangiopathy. Our study was conducted to investigate whether an activation of polyol pathway by long-term treatment with galactose produced morphological changes in coronary arteries of dogs and the effect of an aldose reductase inhibitor, epalrestat, was also studied. METHODS: Dogs received either normal chow or chow containing 30% galactose with or without epalrestat given orally (20 or 50 mg x kg(-1)). After 44 months, morphometric analyses of coronary arteries were carried out and the galactitol contents in aortas were measured. RESULTS: The ratio of areas of the intimal layer to those of the medial layer, an indicator of intimal thickening, was statistically significantly increased in galactose-fed dogs compared with control dogs. Galactose-fed dogs had a remarkable accumulation of galactitol in their aortas. These morphological and biochemical deficits were reduced by treatment with epalrestat. CONCLUSION/INTERPRETATION: This report morphologically shows diabetes-like macrovascular abnormalities in galactosaemic animals, suggesting that polyol pathway hyperactivity is closely related to the development of diabetic macroangiopathy, which could be prevented by aldose reductase inhibition.

Aldehyde Reductase↗
PubMed1999

Prenatally diagnosed cystic neuroblastoma.

An exceedingly rare case of prenatally diagnosed cystic neuroblastoma (NB) is described. Prenatal ultrasonography at 28 weeks' gestation revealed a cystic right suprarenal mass that measured 15 x 17 mm in diameter. The mass increased parallel to fetal size until it was 41 x 44 mm in diameter at 39 weeks' gestation. Magnetic resonance imaging performed prenatally and after delivery showed two different intracystic intensities with fluid levels, suggesting intracystic hemorrhage. The patient underwent a right adrenalectomy at 20 days of age, and the resected tumor was diagnosed as a poorly-differentiated ganglioneuroblastoma. Eight months after surgery, the patient is generally healthy with no evidence of recurrence. We reviewed 25 additional cases of prenatally diagnosed adrenal cystic NB and examined the clinical features of this rare entity.

Adrenal Gland Neoplasms↗
PubMed1999

A case of old trapezoid fracture.

We studied a rare case of old dorsal displacement fracture of the trapezoid. Favorable results were obtained with sugical reduction, despite the fracture being old.

Adult↗
PubMed1999

Intraluminal duodenal diverticulum in a child: incidental onset possibly associated with the ingestion of a foreign body.

UNLABELLED: Funnel-type intraluminal duodenal diverticulum (windsock web) is a rare congenital malformation. A 4-year-old boy with vomiting and abdominal pain for several weeks was referred to the hospital. A plain abdominal X-ray on admission disclosed a double bubble sign. Abdominal echography and CT disclosed a foreign body lodged in the alimentary tract. After the foreign body was removed with a fibrescope, endoscopy showed a stenotic descending portion where the foreign body was located. An upper gastro-intestinal contrast study demonstrated a post-bulbar duodenal stenosis with a barium-filled pear-shaped sac in the descending portion of the duodenum. Surgical exploration was done under the diagnosis of windsock web of the duodenum. A simple excision of the web at its base was carried out. A hole 7 mm in diameter was found at the edge of the web. The microscopic appearance of the resected specimen was characterized by the duodenal mucosa with an extensive chronic inflammation lining both sides of the diverticulum and the lack of muscular layer of mucosa. CONCLUSION: If an ingested material is not excreted in the stool, possible clogging in the intestinal tract should always be considered and a further intensive examination is warranted.

Child, Preschool↗
PubMed1999

Fibroxanthoma arising from the cranial dura mater.

A primary xanthomatous tumor is very rare in the central nervous system (CNS). Here we report the case of a fibroxanthoma arising from the dura mater of the cerebrum that demonstrated no systemic disease or metabolic abnormalities. A 19-month-old, otherwise healthy boy was found to have an enlarged head. Magnetic resonance imaging demonstrated a left occipital dural mass lesion and an enlarged left cerebral hemisphere with ipsilateral ventricular enlargement. Subtotal removal of the tumor was performed through the left parieto-occipital craniotomy. The tumor was composed of a central fibrous portion, a peripheral xanthomatous area, and a boundary. The peripheral area of the tumor showed abundant uniform xanthomatous cells with a thin fibrous stroma and the mass was diagnosed as fibroxanthoma involving the dura. This may represent a distinct category of tumor, which is different from the previously reported cases of fibrous xanthoma and fibrous histiocytoma. Intracranial xanthomatous tumors may be heterogeneous in their origin and histological features. However, further studies are needed to elucidate their clinical features, biological behavior, and optimal treatment strategies.

Brain Neoplasms↗