Biomedical subjects

S Nagasawa

Publications and source records attributed to S Nagasawa.

At least 19 recordsLinked to original sources

PubMed2005

Effects of coupling methods on galvanic corrosion behavior of commercially pure titanium with dental precious alloys.

BACKGROUND: When a dissimilar couple is exposed to corrosive environment, it will normally exhibit a galvanic corrosion. The galvanic corrosion might be influenced by various factors, including type and concentration of electrolyte, surface area ratio between anode and cathode, type of coupling material, and coupling manner. PURPOSE: The purpose of this study was to investigate and compare the galvanic corrosion behavior of commercially pure titanium when coupled with type IV Au alloy, Au-Ag-Pt alloy, and Ag-Au-Pd alloy by different coupling methods. MATERIALS AND METHODS: Couples were prepared by a laser welding or a mechanical adhering method. Electrochemical corrosion studies were conducted in a Ringer's solution at a scanning rate of 0.1 mV/sec in a range from -250 mV to +250 mV with respect to E(OCP). Corrosion parameters (E(OCP), I(CORR), E(CORR)) were obtained. RESULTS: It was found that (i) there was a significant difference between LWC and AJC for three couples (p<0.05), (ii) the crevice line caused all three couples more corrosive than weld joint line, (iii) for both joint, it was found that type (IV) Au alloy exhibited discoloration to some extent. CONCLUSIONS: It is concluded that among the three couples with two different coupling methods, Ti/Ag-Au-Pd couple exhibited best corrosion resistance in a room temperature Ringer's solution.

Corrosion↗

PubMed2002

Effectiveness of preoperative chemotherapy using carboplatin (CBDCA) and surgery against an esophageal small cell carcinoma.

A 63-year-old man presented to our hospital with persistent dysphagia. Radiologic and endoscopic examination disclosed a 2.0-cm exophytic tumor in the middle third of the esophagus. An endscopically obtained biopsy specimen was found to represent undifferentiated small cell carcinoma. Computed tomography of the chest, abdomen, and cervical region was performed, as were gallium and bone scintigraphy. Metastasis to an adjacent lymph node was detected, without metastasis to distant organs. After neoadjuvant chemotherapy with carboplatin (CBDCA) (400 mg/m2) and etoposide (VP-16) (100 mg/m2), endoscopy and barium-swallow esophagography showed regression. Thoracic esophagectomy then was performed with mediastinal, abdominal and cervical lymph node dissection. The resected tumor was polypoid, measuring 0.5 x 0.5 cm. The lesion consisted mainly of small anaplastic cells, but included a small focus of squamous cell carcinoma. The patient has survived for more than 7 months with no further treatment and no evidence of recurrent disease.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2002

Maintenance of bone mass and mechanical properties after short-term cessation of high impact exercise in rats.

Abstract. The effects of cessation of high-impact exercise on bone mass in female Wistar rats was assessed. Fifty 10-week old rats were randomly divided into five groups (n = 10): 4 weeks jump-exercise (4JEX), 4 weeks sedentary control (4S), 8 weeks jump-exercise (8JEX), 4 weeks jump-exercise followed by 4 weeks sedentary (4JEX4S) and 8 weeks sedentary control (8S). The rats were jumped trained 40 times/session, 5 days/week. After 4 weeks or 8 weeks the mass and breaking force in tibia and cross-sectional areas of the tibia were measured. The tibia in the 4JEX and 8JEX groups had significantly greater fat-free dry weight and maximum loads at the fracture tests than those in the 4S and 8S groups. The tibia of 4JEX and 8JEX also had significantly larger cortical area without a significant change in the medullary area at the cross-sectional analysis. Bone mass acquired in 4JEX4S group was retained after cessation of exercise. The results indicate that high-impact jump-exercise, which is osteotropic, leads to an increased cortical bone with enhanced periosteal bone formation, which is also, however, maintained after cessation of exercise. It is therefore suggested that high-impact jump-exercise may provide greater safety margin against disuse-related or/and age-related bone loss and skeletal fragility later in life.

Analysis of Variance↗

PubMed2001

Cyclin D1 overexpression as a prognostic factor in patients with esophageal carcinoma.

BACKGROUND AND OBJECTIVES: Cyclin D1 is known to play important roles in the G1/S check-point of the cell cycle. We investigated the correlation between cyclin D1 overexpression and clinical characteristics to clarify its prognostic significance in patients with esophageal cancer. METHODS: From 1991 to 1998, cyclin D1 was investigated in esophageal cancers from 86 patients who underwent esophagectomy. Overexpression of cyclin D1 was demonstrated using an immunohistochemical method. RESULTS: Overexpression of cyclin D1 was found in 23 (26.7%) of 86 cases. Overexpression of cyclin D1 correlated with lymph node metastasis (P = 0.0083) and lymphatic vessel invasion (P = 0.018). Cyclin D1 overexpression may indicate resistance to chemotherapy. The patients with cyclin D1 overexpression had a significantly lower survival rate than those without overexpression (P = 0.013). The multivariate analysis revealed cyclin D1 overexpression to be an important prognostic factor in patients with esophageal cancer. CONCLUSIONS: Immunohistochemical examination of cyclin D1 expression may provide important prognostic information in univariate and multivariate analysis and may be necessary for determining therapeutic strategies for esophageal cancer.

Carcinoma, Squamous Cell↗

PubMed2001

Bactericidal/permeability-increasing protein promotes complement activation for neutrophil-mediated phagocytosis on bacterial surface.

The neutrophil bactericidal/permeability-increasing protein (BPI) has both bactericidal and lipopolysaccharide-neutralizing activities. The present study suggests that BPI also plays an important role in phagocytosis of Escherichia coli by neutrophils through promotion of complement activation on the bacterial surface. Flow cytometric analysis indicated that fluorescein-labelled E. coli treated with BPI were phagocytosed in the presence of serum at two- to five-fold higher levels than phagocytosis of the bacteria without the treatment. In contrast, phagocytosis of the fluoresceined bacteria with or without treatment by BPI did not occur at all in the absence of serum. The phagocytosis stimulated by BPI and serum was dose-dependent. The effect of BPI on phagocytosis in the presence of serum was not observed on Gram-positive bacteria (Staphylococcus aureus). Interestingly, the complement C3b/iC3b fragments were deposited onto the bacterial surface also as a function of the BPI concentration under conditions similar to those for phagocytosis. Furthermore, the BPI-promoted phagocytosis was blocked completely by anti-C3 F(ab')(2) and partially by anti-complement receptor (CR) type 1 and/or anti-CR type 3. These findings suggest that BPI accelerates complement activation to opsonize bacteria with complement-derived fragments, leading to stimulation of phagocytosis by neutrophils via CR(s).

Antimicrobial Cationic Peptides↗

PubMed2001

Detergent-resistant membrane domains are required for mast cell activation but dispensable for tyrosine phosphorylation upon aggregation of the high affinity receptor for IgE.

Aggregation of the high affinity receptor for IgE (FceRI) on mast cells results in the rapid phosphorylation of tyrosines on the beta and gamma chains of the receptor by the Src family kinase Lyn, which initiates the signaling cascades leading to secretion of inflammatory mediators. The detergent-resistant membranes (DRMs) have been implicated in FcepsilonRI signaling because aggregated receptors emigrate to DRMs that are enriched in certain signaling components. We evaluated the role of DRMs in FcepsilonRI signaling by disruption of DRMs using a cholesterol-binding agent, methyl-beta-cyclodextrin (MBCD). While treatment of rat basophilic leukemia cells with MBCD inhibits degranulation and Ca(2+) mobilization upon aggregation of FcepsilonRI, MBCD hardly affects the aggregation-induced tyrosine phosphorylation of FcepsilonRI as well as other signaling molecules such as phospholipase C-gamma1 (PLC-gamma1). MBCD delocalizes phosphatidylinositol 4,5-bisphosphate from DRMs, which may prevent MBCD-treated cells from producing inositol 1,4,5-trisphosphate by means of activated PLC-gamma1. These data suggest an indispensable role for DRMs in the Ca(2+) response rather than tyrosine phosphorylation, and support a model of receptor phosphorylation in which aggregated FcepsilonRI is tyrosine phosphorylated outside DRMs by constitutively associated Src family kinase Lyn via a transphosphorylation mechanism.

Animals↗

PubMed2001

Wide-spread distribution of sentinel lymph nodes in esophageal cancer.

Sentinel lymph nodes are the first draining nodes that contain tumor cells. Identification of sentinel nodes may help to determine the suitable extent of lymphadenectoy. To assess the location of sentinel lymph nodes, a series of 41 patients with single and two metastatic lymph nodes who underwent esophagectomy and 3-field lymphadenectomy between 1991 and 1999 were investigated retrospectively. Only 29 (47.5%) of 61 metastatic nodes showed correspondence between the tumor site and the regional metastatic lymph nodes by routine histologic examination. In the patients with tumors in the upper and middle thoracic esophagus, metastatic lymph nodes were distributed in the cervix, mediastinum and abdomen. Although sentinel nodes were limited to the regional and adjusting compartments in 82%, nodes were found beyond the adjusting compartments in 18%. The sentinel nodes were broadly distributed depending on the location of the tumor in esophageal cancer.

Adult↗

PubMed2001

Effect of high-impact and low-repetition training on bones in ovariectomized rats.

This study was designed to investigate the effect of high-impact and low-repetition jump training on bones in ovariectomized (OVX) rats. Forty female Wistar rats were sham-operated (sham) or OVX at the age of 11 weeks. The rats were divided randomly into the following four groups: sham-sedentary (SS; n = 10), sham-exercised (SE; n = 10), OVX-sedentary (OS; n = 10), and OVX-exercised (OE; n = 10). The rats started the jump training at the age of 12 weeks. The jump-training protocol was 10 times/day, 5 days/week and the jumping-height was 40 cm. After 8 weeks of training, the mass and breaking force in the tibia and ulna, cross-sectional areas of diaphysis in the tibia, and serum bone turnover markers were measured. The jump training significantly increased the fat-free dry weight, ash weight, and ultimate breaking force in the tibia. The rate of increase in these parameters was similar in both the sham and the OVX groups. On the other hand, in the ulna, there were no significant changes in the ultimate breaking force. The jump training significantly increased the periosteal perimeter and cortical area, although the increase in these parameters in OE compared with OS was lower than that in SE compared with SS. The jump training significantly increased serum osteocalcin in the OVX groups, as well as in the sham groups. These results suggest that high-impact and low-repetition training had beneficial effects on bone formation and bone biomechanical properties in OVX rats, as well as in sham rats.

Animals↗

PubMed2001

Porcelain-metal bonding: part I. Effects of repeated baking process.

A plurality of repeated porcelain-baking procedures are normally practiced in order to achieve the final adjustment metal-porcelain restorations. By increasing the number of baking cycles, the undesired internal strain would be built-up, causing the reduction of mechanical properties and deterioration of color characteristics. However the extensive studies on such deterioration have not been done. In this study, effects of numbers (up to 10 times) of repeated baking cycles on baking shrinkage, surface roughness, bend strength, color changes and internal microstructure were investigated when opaque, body and enamel was individually applied or when a triple-player comprising of these three porcelains was repeatedly applied. It was concluded that (1) the bend strengths increased by increasing baking cycles, (2) the average surface roughness decreased by increasing number of baking procedures, (3) changes in color characteristics was very small in the Vintage halo porcelain system, and (4) since the pores entrapped in the porcelain remained even by increasing baking cycles, it is recommended to remove the surface pores before forming the next layer when handling the high viscous opaque porcelain.

Biomechanical Phenomena↗

PubMed2000

Enhancement of Fc gamma R- and CR3-mediated neutrophil phagocytosis by cerebrosides.

There is increasing evidence that the ligation of adhesion molecules such as L-selectin can activate phagocytes to their full inflammatory potential. Sulfatide has been established as ligand for L-selectin and shown to trigger intracellular signals in human neutrophils. However, it remains unclear whether the ligation of L-selectin with sulfatide affects neutrophil phagocytosis. We studied the effects of sulfatide upon Fc gamma R- and CR3-mediated human neutrophil phagocytosis. Adhesion of the cells to a sulfatide-coated surface resulted in a dose-dependent enhancement of phagocytosis mediated via Fc gamma R or CR3, or both receptors. Galactocerebroside, but not glucocerebroside, also enhanced phagocytosis by neutrophils; therefore, galactose residue is thought to be required on ceramide molecules for the activation. Chymotrypsin-treated neutrophils, from which most L-selectin had been removed, reacted with sulfatide and galactocerebroside to enhance phagocytosis. These results suggest that an unidentified receptor for these cerebrosides exists on neutrophils and participates in the enhancement of phagocytosis.

Cell Adhesion↗

PubMed2000

Phase II trial of combination intraperitoneal cisplatin and 5-fluorouracil in previously treated patients with advanced ovarian cancer: long-term follow-up.

OBJECTIVES: This trial was performed to determine the response rate and progression-free and overall survivals of patients with advanced recurrent ovarian cancer who were treated with intraperitoneal cisplatin and 5-fluorouracil. METHODS: Twenty-four patients with ovarian cancer were entered on this trial and treated with intraperitoneal (ip) cisplatin (DDP) and ip 5-fluorouracil, every 3 weeks for eight cycles. Following iv hydration, the cisplatin and 5-fluorouracil were administered through an ip catheter in 2 liters of 0.9% normal saline with a 4-h dwell. RESULTS: All patients were evaluable for progression-free and overall survival and toxicity analysis, and 22 patients for response. The median age was 59 (range, 35-71); initial disease status included 9 patients with residual disease following chemotherapy prior to entry on this study; 5 patients had progressed, and 10 patients had recurrent disease more than 6 months following initial chemotherapy. Of the 9 patients with residual disease, 1 complete response and 3 partial responses were observed; of 10 patients with recurrent disease, 1 complete and 1 partial response were observed for an overall response rate of 27%. No objective responses were seen in the 7 patients who were platinum-refractory on protocol entry. The median progression-free and overall survivals are 7.0 (range, 0.5-137) and 15.5 (range, 3-147) months, respectively. Toxicity included hypomagnesemia, vomiting, abdominal pain, and mild anemia. Only one patient required a dosage adjustment of cisplatin for a serum creatinine elevation >2.0 mg/dl. CONCLUSIONS: We conclude that the combination of ip cisplatin and 5-FU is an effective regimen for patients with residual or relapsed epithelial ovarian cancer with survival durations, response rates, and toxicity profiles that compare favorably with those of other second-line ovarian cancer regimens. Patients who are primarily platinum-refractory are unlikely to benefit from these agents administered into the peritoneal cavity.

Adult↗

PubMed2000

Exercise and mechanical loading increase periosteal bone formation and whole bone strength in C57BL/6J mice but not in C3H/Hej mice.

To identify the genes, and the mechanisms that account for the 53% higher peak bone density in C3H/HeJ (C3H) mice compared with C57BL/6J (B6) mice, we are performing quantitative trait locus and phenotypic analyses. The phenotypic studies revealed differences in bone formation and resorption, and showed that hindlimb immobilization (by sciatic neurectomy) caused a greater increase in endosteal resorption in the tibiae of B6 compared with C3H mice. The current studies were intended to examine the hypothesis that the bones of C3H mice are less sensitive to mechanical loading than the bones of B6 mice. To increase mechanical loading, 9-week-old female B6 and C3H mice (n = 10-13 mice/group) were subjected to a jumping exercise (20 jumps/day, 5 days/week, to heights of 20-30 cm) for a total of 4 weeks. Control mice did not jump. Osteocalcin, alkaline phosphatase (ALP) activity, and IGF-I were measured in serum. The left tibiae were used for histomorphometry (ground cross-sections prepared at the tibiofibular junction) and the right tibiae and femora were used for determinations of bone breaking strength (3-point bending). The results of these studies revealed (1) significant effects of both mouse strain (B6 and C3H) and the jumping exercise on tibial strength; (2) an exercise-dependent increase in serum IGF-I in C3H, but not B6 mice; and (3) no effects on serum ALP or osteocalcin. The histomorphometric analyses showed no effect of exercise on C3H tibiae, but significant exercise-dependent increases in total bone area, periosteal perimeter, periosteal mineral apposition rate (MAR), and periosteal bone formation (P < 0.02 for each) in B6 tibiae. There were no effects of exercise on periosteal resorption or any endosteal measurement in either C3H or B6 mice. Since the jumping exercise was designed to cause a two-three fold increase in muscular-skeletal loading at the tibio-fibular junction, and the calculated stress (g/mm2) at this sampling site was only 16% greater for B6 compared with C3H mice, we had anticipated that both strains of mice would show exercise-dependent increases in periosteal bone formation, with a greater response in the B6 mice. The lack of a response in the C3H tibiae demonstrates that the bones of C3H mice are less sensitive to mechanical loading (and unloading) than the bones of B6 mice.

Alkaline Phosphatase↗

PubMed2000

Molecular remodelling of human CD46 for xenotransplantation: designing a potent complement regulator without measles virus receptor activity.

In pig-to-human discordant xenotransplantation, human complement (C) is a major barrier to long survival of xenografts. The current idea on how to cope with this barrier is that human complement regulatory proteins are forcibly expressed on xenografts to serve as safeguards against host C-induced hyperacute rejection of xenografts. Co-expression of decay-accelerating factor (DAF) (CD55) and membrane cofactor protein (MCP) (CD46) would be the first choice for this trial, because most of the human cells are protected from C-mediated damage by two different modes with these two kinds of C-regulators. Many problems have arisen, however, for MCP expression on grafts. (i) MCP acts as a measles virus receptor, which may function to render donor pigs measles virus (MV) sensitive. (ii) MCP signals immune suppression which causes devastation of the recipient's immune responses. (iii) MCP exerts relatively low self-protective activity against C compared with other cofactors; development of more efficient forms is desirable. (iv) Grafts with a high expression level of MCP are difficult to produce. In this study, we made a number of cDNA constructs of MCP, expressed them on swine endothelial cell lines, and tested cell-protective potency and MV susceptibility. The short consensus repeat 1 (SCR1)-deleted MCP with glycosyl phosphatidylinositol (GPI)-anchored form (Delta1MCP-PI) of MCP was found to be most suitable for the purpose of overcoming these problems. However, it was also found that MV induces two modes of cytopathic effect (CPE) on swine endothelial cells, either MCP-dependent or -independent. Here, we discuss these two points which will be raised through study of MCP-transgenic animals.

Animals↗

PubMed2000

Multiple primary malignant neoplasms in patients with esophageal cancer.

This study aims to elucidate the incidence and the therapeutic and prognostic implications of co-existent non-esophageal primary malignant neoplasms in patients with esophageal cancer. Between 1974 and 1997, 33 patients with esophageal cancer treated at the Nippon Medical School Hospital were documented as having multiple primary malignant neoplasms (MPN). The therapeutic strategies and post-therapeutic survival of these patients were retrospectively investigated. Among 291 patients with esophageal cancer, 33 patients (11.3%) were also found to have non-esophageal primary malignant neoplasms. Twenty patients (60.6%) had synchronous MPN and 13 (39.4%) had metachronous MPN. Among the MPN, apart from esophageal cancer, gastric (32.6%) and head and neck cancer (32.6%) were the most common. The incidence of esophageal cancer occuring in association with cancers of the head and neck or gastric cancer was high. Frequent examination in these cancer patients, using fiberoptic esophagogastric endoscopy for example, may be helpful in the early diagnosis of esophageal cancer.

Aged↗

PubMed2000

Intra-operative measurement of cortical arterial flow volumes in posterior circulation using Doppler sonography.

Little has been reported on the flow volume of cortical arteries in the posterior circulation. During craniotomy in 28 patients, we measured the flow velocity of the arteries using microvascular Doppler sonography and recorded their arterial radii and the insonation angle. The flow velocities and radii were 25.7 cm sec-1 and 0.11 cm for the posterior cerebral artery (PCA), 19.5 cm sec-1 and 0.07 cm for the superior cerebellar artery (SCA), 19.6 cm sec-1 and 0.04 cm for the anterior inferior cerebellar artery (AICA), 14.9 cm sec-1 and 0.05 cm for the posterior inferior cerebellar artery (PICA), 28.3 cm sec-1 and 0.18 cm for the basilar artery, and 18.5 cm sec-1 and 0.16 cm for the vertebral artery, respectively. Since the flow velocities of these arteries were confined in a narrow range compared to the cross-sectional areas, the latter was considered to be the primary determinant for flow volume in these arteries. Based on certain assumptions, we estimated the flow volume of the PCA, SCA, AICA and ICA to be 60, 20, 10 and 10 ml min-1, respectively, which could be regarded as the current reference values for the arterial flow volumes.

Adult↗

PubMed2000

Regulation of mast cell signaling through high-affinity IgE receptor by CD45 protein tyrosine phosphatase.

The transmembrane tyrosine phosphatase CD45 regulates the activity of src family protein tyrosine kinases (PTK) and thereby influences the signaling via such receptors as T and B cell antigen receptors associated with these PTK. However, its implication in signaling through the mast cell receptor with high affinity for IgE (FcepsilonRI) is less clear, although Lyn, a member of the src family, plays an important role in FcepsilonRI-mediated signaling. To define a role for CD45 in FcepsilonRI signal transduction, we established CD45 high expressing rat basophilic leukemia cell lines (RBL-CD45H) and cell lines expressing trace amounts of CD45 (RBL-CD45L). We demonstrate that although all RBL-CD45L cell lines degranulate following IgE- and antigen-induced FcepsilonRI aggregation, the response is significantly reduced at a low dose of antigen. The cells show a delayed and slowed Ca(2+) mobilization even though at a higher dose where the cells degranulate to a similar extent as RBL-CD45H. This diminished Ca(2+) response is restored by reconstitution of RBL-CD45L with a chimeric molecule containing the cytoplasmic phosphatase domains of rat CD45. Furthermore, tyrosine phosphorylation of FcepsilonRI, association of FcepsilonRI with Lyn and PTK activity associated with FcepsilonRI, all of which are enhanced upon FcepsilonRI aggregation in RBL-CD45H, are impaired in RBL-CD45L. Finally, we show that FcepsilonRI is physically associated with CD45 in RBL-CD45H prior to receptor aggregation. Thus, we propose that, although not indispensable in mast cell degranulation, CD45 positively regulates the signaling through FcepsilonRI by promoting the activation of FcepsilonRI-associated Lyn.

Animals↗

PubMed2000

VIP- and PACAP-induced salivary chromogranin A secretion in the isolated perfused submandibular gland of rats.

In the study reported in this paper, sensitive ELISA for rat CgA was developed using synthetic rat CgA(359-389) as antigen, N alpha-biotinylated glycylglycyl rat CgA(359-389), and antirat CgA(359-389) serum for the measurement of CgA-LI in rat saliva. CgA-LI in rat submandibular tissues and saliva was characterized by both immunohistochemical and immunochemical methods. Using isolated perfused rat submandibular gland. VIP at 0.1-1.0 nM in the presence of 0.1 microM ACh was found to cause CgA-LI secretion, whereas neither PACAP-27 nor PACAP-38 showed any effect on CgA secretion.

Amino Acid Sequence↗

PubMed2000

Surgical strategy for meningioma extension into the optic canal.

Neuroimaging of the extension of meningioma into the optic canal was evaluated for planning the surgical strategy. Intracanalicular extension and localization were retrospectively analyzed in 13 patients with frontal base meningioma near the optic canal, based on the findings of visual field defects, magnetic resonance (MR) imaging, and surgical observations. MR imaging confirmed intracanalicular localization in one of three patients with tumors extending into the optic canals, and indicated the tumor in the others. The visual field defect did not precisely correspond to the tumor localization. Unroofing of the optic canal was performed in four patients and no adverse effects were observed. The interhemispheric approach was employed for tumors localized medially in the canal, and the pterional approach for tumors localized laterally. MR imaging is useful to evaluate the intracanalicular extension, but aggressive confirmation during surgery is essential. Tailored unroofing of the optic canal and removal of the intracanalicular tumor can be performed with few adverse effects and results in good tumor control.

Adult↗