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Biomedical subjects

Y Yoshida

Publications and source records attributed to Y Yoshida.

At least 73 records · Page 4Linked to original sources
PubMed2003

Four-year water degradation of total-etch adhesives bonded to dentin.

Resin-dentin bonds degrade over time. The objective of this study was to evaluate the influence of variables like hybridization effectiveness and diffusion/elution of interface components on degradation. Hypotheses tested were: (1) There is no difference in degradation over time between two- and three-step total-etch adhesives; and (2) a composite-enamel bond protects the adjacent composite-dentin bond against degradation. The micro-tensile bond strength (microTBS) to dentin of 2 three-step total-etch adhesives was compared with that of 2 two-step total-etch adhesives after 4 years of storage in water. Quantitative and qualitative failure analyses were conducted correlating Fe-SEM and TEM. Indirect exposure to water did not significantly reduce the microTBS of any adhesive, while direct exposure resulted in a significantly reduced microTBS of both two-step adhesives. It is concluded that resin bonded to enamel protected the resin-dentin bond against degradation, while direct exposure to water for 4 years affected bonds produced by two-step total-etch adhesives.

Acid Etching, Dental↗
PubMed2003

Surgical management of malignant soft tissue tumours in patients aged 65 years or older.

OBJECTIVE: With the aim to determine the most effective treatment for primary malignant musculoskeletal tumours in patients aged 65 years or older, we reviewed cases of low- and high-grade neoplasms, surgical margins, surgical methods, and the prognoses of elderly and aged patients at our institution. METHODS: Records of 25 patients aged 65 years or older who had malignant soft tissue tumours from December 1986 to February 1997 were reviewed. Low- and high-grade neoplasms accounted for 8 and 17 patients, respectively. 11 patients were aged 65 to 69 years, while 14 were 70 years or older. Surgical margins were wide in 19 cases, marginal in 4, and intralesional in 2. Reconstruction was done using 6 musculocutaneous flaps and/or 4 vessel grafts. As adjuvant therapy, radiotherapy was used in 5 cases and chemotherapy in 3. There was no recurrence in patients with wide surgical margins (determined on the basis of gross inspection of the excised tumour and the cut surface); but there was recurrence in 4 patients with marginal margins, and one patient with intralesional margin. Two patients with intralesional, 4 with marginal, and 2 with wide margins, died from recurrence at the primary site and metastasis, or from metastasis without recurrence at the primary site. RESULTS: Follow-up periods ranged from 4 months to 180 months (mean, 91.6 months). The overall 5-year survival rate was 79.6%; for low- and high-grade neoplasms, the figures were 100% and 69.7%, respectively; for those aged 65 to 69 years and in their 70's or older, the figures were 90.9% and 70.1%, respectively. CONCLUSION: For geriatric patients, wide surgical margins are required to manage both low- and high-grade neoplasms, in order to avoid multiple surgeries.

Age Factors↗
PubMed2003

Comparison of gastric histology among Swedish and Japanese patients with peptic ulcer and Helicobacter pylori infection.

BACKGROUND: The natural course of Helicobacter pylori gastritis may vary between different ethnic groups. Gastric histopathology and the occurrence of H. pylori organisms in the stomach were investigated in healed duodenal (DU) and gastric (GU) ulcer patients recruited in Sweden (S) and Japan (J) in an identical trial. METHODS: In 203 patients (JGU = 39, JDU = 55, SDU = 109), various morphological gastritis variables and H. pylori were assessed from biopsy specimens obtained using a specific sampling protocol and interpreted according to guidelines of the updated Sydney grading system. RESULTS: The ratio of GU:DU was observed to be very different between the recruited Japanese (39:55) and Swedish (0:109) patients. A comparison of data from SDU and JDU showed that the prevalence of H. pylori infection and the antral predominant gastritis demonstrated by both SDU and JDU were essentially identical. A comparison of data from JDU and JGU demonstrated a greater prevalence of H. pylori infection in the antrum, but not corpus, of JDU compared to JGU patients. The prevalence of atrophy and intestinal metaplasia was higher in both the antrum and corpus of JGU compared to JDU in all patients. CONCLUSIONS: The site specified biopsy methodology and standardized interpretation criteria utilized in this study clearly show that the histotopographic profile of Swedish and Japanese DU patients is essentially the same.

Adult↗
PubMed2003

Expression of cyclooxygenase-2 in human hyperplastic gastric polyps.

Cyclooxygenase (COX)-2, an inducible isoform of prostaglandin synthetase, has been reported to be a key molecular target of colon cancer prevention by nonsteroidal anti-inflammatory drugs. Recently, it has been shown that Helicobacter pylori (H. pylori) could induce COX-2 together with inflammatory cytokines. Although human hyperplastic gastric polyps disappeared or decreased in number and size after eradication of H. pylori, the mechanisms in this step, especially the roles of COX-2, have not been yet elucidated. The aims of the present study were to examine the expression and localization of COX-2 in human hyperplastic gastric polyps immunohistochemically. Twelve specimens of human hyperplastic gastric polyps were obtained from endoscopic polypectomy. The expression of the COX-2 protein was immunohistochemically examined on formalin-fixed and paraffin-embedded tissue sections using an anti-COX-2 antibody and an avidin-biotin complex method. Cells expressing COX-2 were further immunohistochemically identified using a specific antibody against macrophages (CD68), and myofibroblasts (alpha-smooth muscle actin). Immunoreactive COX-2 was predominantly and strongly expressed in interstitial cells in the sub-epithelial layer of 10 hyperplastic polyps. Semi-quantitative analysis revealed a significant increase in COX-2 expression in interstitial cells. The staining pattern of macrophages and myofibroblasts partly corresponded to that observed for COX-2 in hyperplastic gastric polyps. These results suggest that COX-2 in mesenchymal cells induced by H. pylori may play an important role in the tumorigenesis of human hyperplastic gastric polyps.

Aged↗
PubMed2002

Hypocretin stimulates [(35)S]GTP gamma S binding in Hcrtr 2-transfected cell lines and in brain homogenate.

In vitro functional analyses of hypocretin/orexin receptor systems were performed using [(125)I]hypocretin radioreceptor and hypocretin-stimulated [(35)S]GTP gamma S binding assay in cell lines expressing human or canine (wild-type and narcoleptic-mutation) hypocretin receptor 2 (Hcrtr 2). Hypocretin-2 stimulated [(35)S]GTP gamma S binding in human and canine Hcrtr 2 expressing cell lines, while cell lines expressing the mutated canine Hcrtr 2 did not exhibit specific binding for [(125)I]hypocretin or hypocretin-stimulated [(35)S]GTP gamma S. In rat brain homogenates, regional specific hypocretin-stimulated [(35)S]GTP gamma S binding was also observed. Hypocretin-stimulated [(35)S]GTP gamma S binding, may thus be a useful functional assay for hypocretin receptors in both cell lines and brain tissue homogenates.

Animals↗
PubMed2002

Thermal analysis of dental resins cured with blue light-emitting diodes (LEDs).

Thermal analysis was used to measure the characteristics of dental resins cured with the use of a new light-activation unit equipped with high illuminant blue light-emitting diodes (LEDs). The characteristics were compared with those of resins cured with the use of two conventional halogen lamp units. The prepared base monomer consisted of a mixture of Bis-GMA and TEGDMA (60:40 by weight), with 0.5 wt% CQ/DMPT or CQ/DMAEMA. The two experimental visible-light-cured resins were polymerized for 40 s. Differential scanning calorimetry (DSC) was used to examine the thermal characteristics of the cured resins. The activation energy for the decomposition of the dental resin was calculated from the peaks of the endothermic curves obtained when the specimens were heated at three different rates (5, 10, and 15 C/min) during DSC. The activation energies calculated for the LED-cured specimens were more than 220 kJ/mol; specimens cured with the use of the halogen units had activation energies of less than 192 kJ/mol. The Knoop hardness number (KHN) of the same specimens was measured, and was higher with the blue LED units than with halogen lamp units. Therefore, dental resins cured using blue LEDs have a higher degree of polymerization and more stable three-dimensional structures than those cured with halogen lamps.

Calorimetry, Differential Scanning↗
PubMed2002

Synthesis of functionally graded MgCO3 apatite accelerating osteoblast adhesion.

As a means of improving the biological properties of materials for use as bone substitutes, functionally graded carbonate apatite containing Mg, FGMgCO3Ap, was synthesized at 60 degrees C and pH 7.4 using a gradient magnesium supply system. X-ray diffraction analysis of FGMgCO3Ap showed a poorly crystallized apatitic pattern, similar to that of human bone. ESCA analysis clearly showed the negative gradient distribution in Mg1s intensity (atomic concentration) of magnesium from the crystal surface toward the inner core. When the FGMgCO3Ap crystals were mixed with collagen, the resulting FGMgCO3Ap-collagen composite, irradiated with UV light for 4 h, retained their features in the saline solution. After washing away the nonadhesive cells, a cell adhesion assay showed that the optical density of the FGMgCO3Ap-collagen composite was higher than that of the CO3Ap-collagen composite. SEM observation showed that the osteoblast-like cells adhered well to the surface of the FGMgCO3Ap-collagen composite. Staining with hematoxylin-eosin and alizarin red confirmed the existence of a great many more cells and a thicker extracellular matrix layer on the FGMgCO3Ap-collagen composite than on the CO3Ap-collagen composite. This result demonstrated the acceleration effect of magnesium ions on osteoblast adhesion on the FGMgCO3Ap-collagen composite.

Animals↗
PubMed2002

Adhesion/decalcification mechanisms of acid interactions with human hard tissues.

In order to study adhesion/decalcification mechanisms of acid interactions with human hard tissues such as bones and teeth, the chemical interaction of five carboxylic acids (acetic, citric, lactic, maleic, and oxalic) and two inorganic acids (hydrochloric and nitric) with enamel and two synthetic hydroxyapatite (HAp) powders with, respectively, a high and a low crystallinity were analyzed using X-ray photoelectron spectroscopy (XPS), atomic absorption spectrophotometry (AAS), and spectrophotometry (S). X-ray diffraction revealed that the crystallinity of the highly crystallized HAp was considerably higher than that of enamel while the crystallinity of the poorly crystallized HAp was similar to that of dentin and bone. XPS of acid-treated enamel demonstrated for all carboxylic acids ionic bonding to calcium of HAp. AAS and S showed for both HAps that all carboxylic and inorganic acids except oxalic acid extracted Ca significantly more than P, leading to a Ca/P ratio close to that of synthetic HAp (2.16 w/w). Oxalic acid extracted hardly any Ca, but substantially more P, leading to a significantly smaller Ca/P ratio than that of HAp. AAS showed that the calcium salt of oxalic acid hardly could be dissolved, whereas the calcium salts of all the other acids were very soluble in their respective acid solution. These results confirm the adhesion/decalcification concept (AD-concept) previously advanced. Depending on the dissolution rate of the respective calcium salts, acids either adhere to or decalcify apatitic substrates. It is concluded that the AD-concept that originally dictated the interaction of carboxylic acids with human hard tissues can be extended to inorganic acids, such as hydrochloric and nitric acid. Furthermore, HAp crystallinity was found not to affect the adhesion/decalcification behavior of acids when interacting with apatitic substrates, so that the AD-concept can be applied to all human hard tissues with varying HAp crystallinity.

Acids↗
PubMed2002

Review article: COX-2, prostanoids and colon cancer.

Epidemiological, experimental, and clinical studies have demonstrated that colon carcinogenesis may be prevented by nonsteroidal anti-inflammatory drugs (NSAIDs). Although controversy remains, recent studies, including ours, have revealed that NSAIDs suppress colon carcinogenesis at the adenoma stage where cyclooxygenase-2 (COX-2), a major molecular target in this action, is mainly expressed in interstitial cells but not in tumour cells. Therefore, it is unlikely that NSAIDs prevent colon cancer formation through modulating the functions of tumour cells. A more possible assumption is that NSAIDs suppress colon carcinogenesis through the inhibition of prostaglandin formation. However, the mechanisms by which prostanoids promote colon carcinogenesis have not been elucidated to date. A prostanoids act through both membrane receptors and nuclear receptors such as peroxisome proliferator receptor (PPAR) gamma or delta, one focus in this area is to investigate their roles in colon carcinogenesis, including the induction of growth factors.

Animals↗
PubMed2002

Ventricular activation and recovery measured in electrocardiographic limb leads correlate with measurements from specific areas in body surface mapping.

AIMS: Dispersion of ventricular depolarization-repolarization in 12-lead electrocardiograms (ECGs) has been reported to provide noninvasive information on arrhythmogenicity. However, there are two methods to calculate the dispersion from ECGs including and excluding limb leads. The aim of this study was to examine whether temporal parameters from limb leads represent activation and repolarization of a particular part of the body surface. METHODS AND RESULTS: We compared the temporal parameters of activation time (AT), activation-recovery interval (ARI), and recovery time (RT) from limb leads of ECGs with those from an 87-lead body surface maps. The study population consisted of 50 normal subjects (25 men and 25 women, 19.4 +/- 1.6 years). The temporal parameters in leads I, II, and III were highly (r > 0.9) correlated with those in unipolar leads over the left lateral, left lower, and right lower chest, respectively. The temporal parameters in leads aVR, aVL, and aVF showed a significant correlation (r > 0.8) with those in unipolar leads over the right upper, left upper, and lower anterior chest, respectively. The mean AT, ARI, and RT from each limb lead of ECG were almost the same as those of unipolar leads over the corresponding areas of the body surface. CONCLUSIONS: These findings suggest that ATs, ARIs, and RTs from limb leads may represent those from unipolar leads of particular areas over the body surface in normal subjects. The temporal parameters from limb leads of ECGs may provide information on activation and repolarization as well as the precordial leads of ECGs.

Adolescent↗
PubMed2002

Establishment of FSH-responsive cell lines by transfection of pre-ovulatory human granulosa cells with mutated p53 (p53val135) and Ha-ras genes.

Human granulosa cells were immortalized by transfection of the primary cells with a mutated p53 gene in combination with the Harvey-ras oncogene, yielding established cell lines designated HGP53. Here we report that forskolin, 8-Br-cAMP and FSH modulate cell growth and steroidogenesis in HGP53 cells. Low concentrations of 8-Br-cAMP or FSH stimulated cell proliferation, while higher doses attenuated cell proliferation. Progesterone production was already evident at an FSH concentration of 0.3 mIU/ml and was maximally stimulated (50-135-fold) at 50 mIU/ml of FSH. Expression levels of steroidogenic acute regulatory protein (StAR), adrenodoxin and cytochrome P450scc were enhanced 64-, 48- and 3.1-fold respectively by FSH stimulation. Dexamethasone enhanced FSH/cAMP-induced steroidogenesis and this effect involved a marked elevation in the intracellular level of adrenodoxin and P450scc, concomitantly with a marked decrease in StAR. Conversely, basic fibroblast growth factor attenuated FSH-stimulated progesterone production, and this effect involved reductions in adrenodoxin, P450scc and StAR levels. These data suggest that the rate of steroidogenesis may be determined by the ratio of StAR and P450scc, rather than by the level of each protein alone. Whereas FSH at a low dose slightly reduced apoptosis induced by serum withdrawal from HGP53 cells, higher doses enhanced it. Dexamethasone dramatically attenuated FSH- or forskolin-enhanced apoptosis. In conclusion, FSH-dependent mechanisms of differentiation, luteinization and apoptosis can be preserved in human granulosa cells immortalized by mutated p53. Moreover, this system lends itself to studies on cross-talk between the endocrine and paracrine factors that control these processes.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2002

A new delivery system for 5-fluorouracil using prodrug and converting enzyme.

AIMS: To evaluate a new delivery system of 5-fluorouracil (5-FU) using 5-fluorocytosine (5-FC) as a prodrug and cytosine deaminase induced in vitro and in vivo. METHODS: Fibroblastic cells from rabbit Tenon's capsule were cultured. The cells were exposed to 5-FU and 5-FC with or without cytosine deaminase induced by recombinant adenovirus. In the in vitro study, cell proliferation and DNA synthesis were assessed by MTS, BrdU assay. The effect of 5-FC removal after the treatment of 5-FC and cytosine deaminase induction was also assayed. In the in vivo study cells with or without cytosine deaminase induction were transplanted into the subconjunctival space of mice, followed by eye drops of 1000 microg/ml of 5-FC three times a day. The mice were sacrificed at days 1, 5, and 10, then the cells transplanted were evaluated. RESULTS: Cell proliferation was inhibited by exposure to 5-FU in a dose dependent manner; however, up to 1000 microg/ml of 5-FC did not affect cell proliferation. Cell proliferation was inhibited by exposure to 5-FC in a time dependent manner with induction of cytosine deaminase following infection of recombinant adenovirus. When 5-FC was removed 3 or 6 days after the treatment, the cells grew again. The effect was reproduced in the in vivo model of subconjunctival cellular proliferation although 5-FC was administrated as eye drops. There were no cases with corneal erosion. CONCLUSION: Cell proliferation was inhibited by co-exposure of 5-FC and cytosine deaminase. This new delivery system may merit controlled delivery of 5-FU after filtering surgery.

Animals↗
PubMed2002

Improved filler-matrix coupling in resin composites.

Ineffective silane coupling between filler and matrix within dental composites is prone to accelerated in vivo degradation. In this study, we examined to what degree a procedure involving chemical decontamination of filler prior to silanization could improve the filler-matrix bonding, and thus the physico-mechanical properties, of composites. X-ray photoelectron spectroscopy revealed that filler-matrix coupling largely depended upon siloxane bridge (Si-O-Si) formation between the silica surface and the silane molecule, rather than on intermolecular bonding between adjacent silane molecules. Pre-silanization decontamination based upon boiling silica in 0.05-5% sodium peroxodisulfate, followed by ultrasonic rinsing in acetone, most effectively decontaminated filler. Consequently, it significantly improved the bonding of silane molecules to silanol groups at the silica surface. Experimental composites produced following pre-silanization decontamination of filler revealed a diametral tensile strength that was resistant to degradation by thermocycling.

Composite Resins↗
PubMed2001

Effects of psychological stress on monoamine systems in subregions of the frontal cortex and nucleus accumbens of the rat.

We investigated the effects of two types of psychological stress, novelty stress and psychological stress using the communication box, on dopamine and serotonin systems in subregions of the frontal cortex and nucleus accumbens of rats. Placement of rats into a compartment of the communication box (novelty stress) increased both dopamine and serotonin metabolism in medial precentral, anterior cingulate, and prelimbic subregions of the frontal cortex as evaluated by the levels of 3,4-dihydroxyphenylacetic acid and homovanillic acid for dopamine, and 5-hydroxyindoleacetic acid for serotonin. In contrast, novelty stress had no effect on these monoamine systems in infralimbic and sulcal subregions of the frontal cortex. In the nucleus accumbens, novelty stress increased both dopamine and serotonin metabolism in the shell, but decreased dopamine metabolism in the core. On the other hand, psychological stress using the communication box augmented dopamine metabolism in the anterior cingulate and prelimbic subregions. This stress, however, failed to affect the dopamine system in the medial precentral, infralimbic and sulcal subregions. In the nucleus accumbens, the stress selectively decreased dopamine metabolism in the shell but showed no effect in the core. The serotonin system showed little change due to the stress. These results demonstrate that psychological stress causes distinct changes in both the dopamine and serotonin systems in the frontal cortex and the nucleus accumbens. These changes vary with the subregions of these areas, suggesting that the region-specific responsiveness to psychological stress reflects the functional differences among these subregions. In addition, our results also suggest that changes in brain monoamine systems induced by psychological stress are quite different from those induced by physical stress.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2001

Cloning of a new aquaporin (AQP10) abundantly expressed in duodenum and jejunum.

A new aquaporin (AQP10) was identified in human small intestine. This gene encoded a 264-amino-acid protein with high sequence identity with AQP3 (53%), 9 (52%), and 7 (43%). These AQPs constitute one subfamily of AQP family that is differentiated from the other subfamily of AQP (AQP0, 1, 2, 4, 5, 6, and 8) by sequence homology. Ribonuclease protection assay and Northern blotting demonstrated almost exclusive expression of AQP10 mRNA in the duodenum and jejunum. In situ hybridization localized it in absorptive jejunal epithelial cells. Xenopus oocytes expressing AQP10 exhibited an increased osmotic water permeability in a mercury-sensitive manner. Although AQP10 belongs to the AQP subfamily, which has been characterized by permeability to water and neutral solutes such as urea and glycerol, it was not permeable to urea nor glycerol. The specific expression of AQP10 suggests its contribution to the water transport in the upper portion of small intestine.

Amino Acid Sequence↗
PubMed2001

Hypothalamic 11,12-epoxyeicosatrienoic acid attenuates fever induced by central interleukin-1beta in the rat.

Inhibitors of cytochrome P-450 augment fever in rats and mice, indicating that the metabolite of the enzyme is candidate of endogenous antipyretic. Cytochrome P-450 of arachidonic acid cascade leads to the formation of regioisomeric 5,6-, 8,9- 11,12- and 14,15-epoxyeicosatrienoic acid (EET). Various isomers of EET were administrated into the preoptic area and anterior hypothalamus (PO/AH) to test their influence on fever induced by interleukin-1beta (IL-1beta) administrated into the PO/AH in conscious rats. The IL-beta-induced fever was attenuated in the 11,12-EET-pretreated rats, although 5,6-, 8,9- and 14,15-EET did not affect the fever. Intra-PO/AH injection of 11,12-EET did not alter normal body temperature. The results suggest that 11,12-EET acts in the hypothalamus as an endogenous antipyretic.

8,11,14-Eicosatrienoic Acid↗