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N Yamamoto

Publications and source records attributed to N Yamamoto.

At least 181 records · Page 10Linked to original sources
PubMed2000

DNA binding mode of the Fab fragment of a monoclonal antibody specific for cyclobutane pyrimidine dimer.

Monoclonal antibodies specific for the cyclobutane pyrimidine dimer (CPD) are widely used for detection and quantification of DNA photolesions. However, the mechanisms of antigen binding by anti-CPD antibodies are little understood. Here we report NMR analyses of antigen recognition by TDM-2, which is a mouse monoclonal antibody specific for the cis - syn -cyclobutane thymine dimer (T[ c, s ]T). (31)P NMR and surface plasmon resonance data indicated that the epitope recognized by TDM-2 comprises hexadeoxynucleotides centered on the CPD. Chemical shift perturbations observed for TDM-2 Fab upon binding to d(T[ c, s ]T) and d(TAT[ c, s ]TAT) were examined in order to identify the binding sites for these antigen analogs. It was revealed that d(T[ c, s ]T) binds to the central part of the antibody-combining site, while the CPD-flanking nucleotides bind to the positively charged area of the V(H)domain via electrostatic interactions. By applying a novel NMR method utilizing a pair of spin-labeled DNA analogs, the orientation of DNA with respect to the antigen-binding site was determined: CPD-containing oligonucleotides bind to TDM-2 in a crooked form, draping the 3'-side of the nucleotides onto the H1 and H3 segments, with the 5'-side on the H2 and L3 segments. These data provide valuable information for antibody engineering of TDM-2.

Animals↗
PubMed2000

Stromal cell-derived factor-1 (SDF-1) acts together with thrombopoietin to enhance the development of megakaryocytic progenitor cells (CFU-MK).

Stromal cell-derived factor-1 (SDF-1) is a CXC chemokine that acts as a stimulator of pre-B lymphocyte cell growth and as a chemoattractant for T cells, monocytes, and hematopoietic stem cells. More recent studies also suggest that megakaryocytes migrate in response to SDF-1. Because genetic elimination of SDF-1 or its receptor lead to marrow aplasia, we investigated the effect of SDF-1 on megakaryocyte progenitors (colony-forming units-megakaryocyte [CFU-MK]). We report that SDF-1 augments the growth of CFU-MK from whole murine bone marrow cells when combined with thrombopoietin (TPO). The addition of SDF-1 to interleukin-3 (IL-3) or stem cell factor (SCF) had no effect. Specific antagonists for CXCR4 (the sole receptor for SDF-1), T22, and 1-9 (P2G) SDF-1 reduced megakaryocyte colony growth induced by TPO alone, suggesting that many culture systems contain endogenous levels of the chemokine that contributes to the TPO effect. To examine whether SDF-1 has direct effects on CFU-MK, we developed a new protocol to purify megakaryocyte progenitors. CFU-MK were highly enriched in CD41(high) c-kit(high) cells generated from lineage-depleted TPO-primed marrow cells. Because the growth-promoting effects of SDF-1 were also observed when highly purified populations of CFU-MK were tested in serum-free cultures, these results suggest that SDF-1 directly promotes the proliferation of megakaryocytic progenitors in the presence of TPO, and in this way contributes to the favorable effects of the bone marrow microenvironment on megakaryocyte development.

Animals↗
PubMed2000

Identification of the promoter region of human placental 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase gene.

The placenta-type isozyme of human 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (HP2K) is expressed in several tissues such as placenta, brain, testis, liver, kidney, skeletal muscle, and primary blood mononuclear cells. To better understand the regulation of HP2K gene expression, we isolated and characterized its genomic DNA, which includes the promoter region. The results of oligo-capping analysis indicate that the transcription start point (tsp) is an adenine residue 329 bp upstream of the translational start codon. DNA sequence analysis of this gene shows that the promoter region that contains the TATA box sequence and the 5'-UTR is different from the other known PFK-2/F2, 6BPase genes. In addition, its 5'-flanking and 5'-UTR both have G + C-rich sequences containing Sp1 binding sites. To identify the promoter/enhancer region of HP2K gene, we performed transfection analyses of human choriocarcinoma BeWo cells with HP2K promoter-luciferase constructs. These experiments identified a promoter region 164 bp upstream from the tsp and an enhancer region between -1265 and -1329 on the 5'-flanking sequences. We also showed that Sp1 sites were not essential for HP2K transcription. Following transfection, stimulation experiments with serum, progesterone and phorbol 12-myristate 13-acetate showed that only the construct with the enhancer containing putative early growth response-1 binding motif was responsive to serum. We propose that the transcription of HP2K is strictly controlled by tissue-specific factors even though its genomic DNA contains several transcriptional elements.

5' Untranslated Regions↗
PubMed2000

Epstein-Barr virus-specific antibodies in Epstein-Barr virus-positive and -negative gastric carcinoma cases in Japan.

We examined Epstein-Barr virus (EBV)-specific antibodies in serum samples from 64 and 59 patients with EBV-positive and -negative gastric carcinomas, respectively, and 73 healthy controls using immunofluorescence assays. EBV capsid antigen (VCA) IgG and EBV-determined nuclear antigen (EBNA) IgG were detected in all 196 subjects. The geometric mean titer (GMT) of VCA-IgG, but not EBNA-IgG, was higher in EBV-positive carcinoma cases than in EBV-negative carcinoma cases (P < 0.001). The seroprevalence rates of VCA-IgA and EBV early antigen (EA) IgG were higher in EBV-positive carcinoma cases than in EBV-negative carcinoma cases. Odds ratios (ORs) comparing seroprevalence rates between EBV-positive and -negative carcinoma cases were 3.4 (95% confidence interval [CI] = 1.3-8.8) and 6.6 (95% CI = 2.7-16.3) for VCA-IgA and EA-IgG, respectively. These results suggest that EBV reactivation occurs in vivo, since more than 90% of Japanese are infected with EBV in early childhood. The GMT of VCA-IgG in EBV-negative carcinoma cases was higher than that of healthy controls (P = 0.028). The seroprevalence rates of EA-IgG were greater in EBV-negative carcinoma cases than in healthy controls (OR = 4.9, 95% CI = 1.2-19. 7). VCA-IgA was the only antibody that showed a significantly high seroprevalence and GMT in EBV-positive carcinoma cases, but not in EBV-negative carcinoma cases. Thus, VCA-IgA can be a marker of immune response to EBV in EBV-positive carcinoma cases. Our findings support the hypothesis that if EBV is involved in the development of EBV-positive gastric carcinoma, the EBV reactivation occurs in vivo.

Adult↗
PubMed2000

Characterization of factors regulating lamina-specific growth of thalamocortical axons.

During development, most thalamocortical axons extend through the deep layers to terminate in layer 4 of neocortex. To elucidate the molecular mechanisms that underlie the formation of layer-specific thalamocortical projections, axon outgrowth from embryonic rat thalamus onto postnatal neocortical slices which had been fixed chemically was used as an experimental model system. When the thalamic explant was juxtaposed to the lateral edge of fixed cortical slice, thalamic axons extended farther in the deep layers than the upper layers. Correspondingly, thalamic axons entering from the ventricular side extended farther than those from the pial side. In contrast, axons from cortical explants cultured next to fixed cortical slices tended to grow nearly as well in the upper as in the deep layers. Biochemical aspects of lamina-specific thalamic axon growth were studied by applying several enzymatic treatments to the cortical slices prior to culturing. Phosphatidylinositol phospholipase C treatment increased elongation of thalamic axons in the upper layers without influencing growth in the deep layers. Neither chondroitinase, heparitinase, nor neuraminidase treatment influenced the overall projection pattern, although neuraminidase slightly decreased axonal elongation in the deep layers. These findings suggest that glycosylphosphatidylinositol-linked molecules in the cortex may contribute to the laminar specificity of thalamocortical projections by suppressing thalamic axon growth in the upper cortical layers.

Animals↗
PubMed2000

Radio frequency transmyocardial revascularization enhances angiogenesis and causes myocardial denervation in canine model.

BACKGROUND AND OBJECTIVE: Transmyocardial revascularization (TMR) relieves angina and improves exercise tolerance in patients. Angiogenesis and myocardial denervation have been proposed as factors contributing to these benefits. To test whether radio frequency transmyocardial revascularization (RF-TMR) enhances angiogenesis and causes myocardial denervation. STUDY DESIGN/MATERIALS AND METHODS: RF-TMR channels were created in 12 dogs which survived up to 4 weeks. Bromodeoxyuridine was administered subcutaneously to mark proliferating cells as an assay of angiogenesis. Western blot analysis of tyrosine hydroxylase and blood pressure response to topical bradykinin were used as indices of myocardial denervation. RESULTS: RF-TMR increased local vascularity by an average of 50%, whereas the rate of vascular cell proliferation was tripled over that of the untreated region. Changes in mean arterial pressure with bradykinin and tyrosine hydroxylase content were significantly decreased in RF-TMR regions as compared with normal myocardium in the same hearts. CONCLUSION: RF-TMR enhances angiogenesis and causes myocardial denervation in canine myocardium as with laser TMR.

Animals↗
PubMed2000

Dendritic cells are associated with augmentation of antigen sensitization by influenza A virus infection in mice.

To study the mechanisms responsible for enhanced sensitization of inhaled antigen in respiratory viral infections, we examined the contribution of dendritic cells (DC) and T lymphocytes to the development of inhalation sensitization during infection with influenza A virus in mice. BALB/c mice were sensitized by inhalation of ovalbumin (OA) from 3 to 7 days after the inoculation with influenza A virus, and were challenged with OA 3 weeks later. Airway responsiveness and serum OA-specific IgE were increased. The numbers of eosinophils and CD4(+) and CD8(+) T cells in bronchoalveolar lavage fluid were also increased. These changes were not observed in animals only sensitized with OA or only inoculated with the virus. In animals only inoculated with the virus, DC were immunohistochemically detected on the bronchial epithelium on days 2-5. With OA inhalation after virus inoculation, DC with high expression of MHC class II were retained for 5 weeks. These results show that influenza virus infection induces the migration of DC to the bronchial epithelium, and that simultaneous inhalation of antigen causes the loading of antigen-peptide / class II molecule complex on DC. Thus, the migration of DC in viral infection may play some role in the augmentation of antigen sensitization.

Animals↗
PubMed2000

Transcriptional regulation of HIV-1 LTR during antigen-dependent activation of primary T cells by dendritic cells.

Numerous factors are known to bind human immunodeficiency virus (HIV) long terminal repeat (LTR) and activate viral transcription, but little is known as to how they function in naturally activated T cells and to what extent their binding is relevant to HIV replication in vivo. To characterize the HIV LTR-binding factors responsible for antigen-dependent activation of HIV, we examined replication of LTR mutant viruses in CD4+ T cells activated by different stimuli. NF-kappaB or Sp1 mutant virus replicated well in CD4+ T cells activated by phorbol ester and calcium ionophore. When they were activated by antigen-pulsed dendritic cells, the replication of the Sp1-deleted virus was severely impaired in CD45RA+, but not in CD45RO+ T cell subsets that dominantly produce interleukin-2 (IL-2). Stimulation via CD3/CD28 induced a high level of IL-2 production in both T cell subsets, but Sp1-deleted virus poorly replicated in CD45RA+ subset. The level of NF-kappaB and Sp1-binding factors did not differ between these subsets. Our results suggest that additional cofactors distinct from IL-2-inducing signaling molecules are important for LTR activation during antigen-dependent T cell activation.

Antigen Presentation↗
PubMed2000

Investigation of menstruation recovery after LH-RH agonist therapy for premenopausal patients with breast cancer.

BACKGROUND: Recently Luteinizing hormone-releasing hormone (LH-RH) agonist has been used for premenopausal patients with breast cancer as endocrine therapy. However, there is no consensus regarding recovery of menstruation after long-term treatment with LH-RH agonist. We investigated recovery of menstruation after this treatment. METHODS: We investigated 28 premenopausal patients with breast cancer who underwent operation at Chiba Cancer Center Hospital in 1995 or 1996. The patients were treated with LH-RH agonist (goserelin) for 24 months as an adjuvant therapy, and were observed for more than 6 months after the last goserelin depot. Ages ranged 31-55 years old from at the time of last treatment. We defined recovery of menstruation as regular menstruation occurring more than three times. RESULTS: There were 22 patients in the recovery group (range: 31-53 years, mean 45.1 years). There were 6 patients in the non-recovery group (range: 50-55 years, mean 52.2 years). The overall recovery rate was 78.6%. Recovery rate was 81.8% for the patients under 50 years, and 66.7% for over 51 years. We separated all patients into groups by age at 5 years intervals, and investigated the distribution of the recovery time. In the recovery group (22 patients), there were 15 patients (68.2%) who confirmed recovery of menstruation within 6 months. CONCLUSION: Our investigation suggested that the recovery of menstruation after this therapy would occur in those less than 50 years old, within 6 months from the last treatment.

Adult↗
PubMed2000

Histologic evidence that basic fibroblast growth factor enhances the angiogenic effects of transmyocardial laser revascularization.

OBJECTIVES: To determine whether addition of basic fibroblast growth factor (bFGF), an angiogenic growth factor, enhances the angiogenic effects of transmyocardial laser revascularization (TMR). BACKGROUND: TMR is an investigational therapy for treating patients with medically refractory angina not amenable to traditional therapies. Histologic and blood flow studies in animals have suggested that TMR enhances angiogenesis above that normally seen in ischemic myocardium. We tested the hypothesis that bFGF administered into TMR channels further enhance the angiogenic effects of TMR. METHODS: Chronic ischemia was created in 3 groups of dogs using an ameroid constrictor on the proximal LAD. In the bFGF group (n = 5) non-transmyocardial channels were created in the LAD territory and bFGF, (100 ng/ml) dissolved in pluronic gel was injected into the each channel. In the TMR group (n = 7), transmyocardial channels were created without bFGF. A control group (n = 7) had ischemia without TMR of bFGF. 5-bromo-2'-deoxyuridine (BrdU) was administered to mark proliferating cells. After 8 weeks survival, colored microspheres were injected to assess the regional myocardial blood flow. RESULTS: TMR and TMR+bFGF increased total vascular density by approximately 40% over that observed in the control group. However, the number of large vessels (internal diameter > or = 50 microm) was doubled by the addition of bFGF, and this correlated with a 50% increase in the density of proliferating vascular cells and a tripling of the total estimated vascular cross sectional area. Blood flow to the LAD territory was increased by TMR compared to controls, with no further benefit observed in the bFGF group. CONCLUSIONS: On a histologic basis, basic fibroblast growth factor further enhances angiogenesis following TMR in ischemic myocardium mainly by increasing the size but not the total number of vessels.

Animals↗
PubMed2000

True exfoliation of the lens capsule following uveitis.

PURPOSE: To report a rare case of true exfoliation of the lens capsule following panuveitis, with slit-lamp photographs before and following the development of the true exfoliation. METHODS: Case report. Review of the history and clinical features of a 70-year-old woman who developed true exfoliation during the treatment for panuveitis. RESULTS: After 7 months of treatment for bilateral panuveitis with topical steroid and tropicamide, the patient developed a thin, transparent membrane arising on the lens surface in the right eye. A diagnosis of true exfoliation of the lens capsule was made. CONCLUSIONS: True exfoliation of the lens capsule following uveitis may occur due to the weakening of the anterior capsule by metabolic disorder caused by uveitis and precipitated by repeated mydriasis.

Acetazolamide↗
PubMed2000

Influence of Helicobacter pylori infection on development of stress-induced gastric mucosal injury.

Immediately after the Great Hanshin Earthquake in Kobe in 1995, the recurrence rate of peptic ulcer in patients infected with Helicobacter pylori was higher than that in patients in whom H. pylori had been eradicated. We evaluated the influence of H. pylori infection on stress-induced gastric mucosal injury in Mongolian gerbils and C57BL/6 mice. These animals were immersed in water for 30, 120, and 720 min 12 weeks after inoculation with H. pylori, and then killed to assess gastric mucosal damage, and to measure cytokine production (interleukin [IL]-1beta, IL-4, IL-6, and IL-10; interferon [IFN]-gamma; and tumor necrosis factor [TNF]-alpha) in the gastric tissue of the mice. The stress treatment for 30 min resulted in a significantly higher bleeding rate and bleeding index among infected gerbils and mice compared with results in uninfected animals. Conversely, the bleeding and ulcer indexes were significantly higher in uninfected gerbils after 720 min of the stress treatment than in infected gerbils. Prior to the stress treatment, gastric IL-1beta and IFN-gamma production was significantly higher in the infected group than in the uninfected group. After 120 min of the stress treatment, TNF-alpha production was increased in the infected group, and IL-1beta and IL-10 production was increased in the uninfected group. However, the production of these cytokines showed no change at 30 min of the stress treatment. These results suggest that H. pylori infection influences the development of gastric mucosal injury in the early phase of stress exposure; cytokines do not play a major role in this process.

Animals↗
PubMed2000

Cystic adventitial disease of the popliteal artery: elongation into the media of the popliteal artery and communication with the knee joint capsule: report of a case.

Cystic disease of the popliteal artery is a rare disorder in which most cases involve the formation of an adventitial cyst that disturbs the popliteal artery blood flow. We present herein the case of a patient presenting with popliteal artery occlusion due to compression by a cyst which formed at the media of the popliteal artery. The onset occurred during a baseball game in which he played catcher. Preoperative magnetic resonance imaging demonstrated a communication of the cyst with the adjacent knee joint. This unusual case could provide important clues to help identify the pathogenesis of this disease.

Adult↗
PubMed2000

The fate of small aneurysms of the internal iliac artery following proximal ligation in abdominal aortic aneurysm repair.

To assess the natural history of small internal iliac artery aneurysms (IIAA) measuring 2.0-3.0 cm in diameter, proximally ligated in association with abdominal aortic aneurysm (AAA) repair, we examined 9 of 12 patients who underwent this type of surgery. Postoperative computed tomography scanning demonstrated that three IIAAs were still patent and the other six were thrombosed. An increase in the maximum diameter from that at the time of surgery was seen in four IIAAs. One patient suffered serious complications in that a dilated IIAA caused right ureteral obstruction and subsequent hydronephrosis accompanied by unilateral renal dysfunction. This was successfully treated by resection of the IIAA. The findings of this analysis led us to conclude that small IIAAs associated with AAA repair should be treated by either endoaneurysmorrhaphy or resection of the aneurysm after both proximal and distal ligation.

Aged↗
PubMed2000

Mechanical properties of collagen fascicles from in situ frozen and stress-shielded rabbit patellar tendons.

OBJECTIVE: To know the effects of stress shielding on the biomechanical properties of collagen fascicles obtained from in situ frozen patellar tendons (an autograft model). DESIGN: Collagen fascicles of approximately 300 microm in diameter were obtained from in situ frozen rabbit patellar tendons and also from in situ frozen and stress-shielded ones, and their mechanical properties and fibroblast density were determined. BACKGROUND: Stress shielding changes the mechanical properties of in situ frozen patellar tendons in which there exist no fibroblasts. The mechanisms of this phenomenon have not been studied well. METHOD: Patellar tendons of both in situ frozen group and in situ frozen and stress-shielded group were frozen in situ by liquid nitrogen to kill fibroblasts. Then, in the in situ frozen and stress-shielded group, no tension was applied to the tendons for 2, 3, and 6 weeks, while normal tension was applied to the tendons of the in situ frozen group. Tensile properties of the collagen fascicles obtained from these tendons were determined using a microtensile tester, and were compared to the collagen fascicles from non-frozen, stress-shielded patellar tendons. RESULTS: Tangent modulus and tensile strength of collagen fascicles from the in situ frozen and stress-shielded group progressively decreased with the time of stress shielding; however, these decreases were much smaller than those of the fascicles obtained from non-frozen, stress-shielded tendons. Although there were few fibroblasts in the patellar tendon of the in situ frozen and stress-shielded group at 2 weeks, the modulus and strength of the fascicles from the posterior portion were significantly lower than those in the in situ frozen group. In addition, the reduction of strength caused by stress shielding was much smaller in collagen fascicles than in bulk patellar tendons. CONCLUSION: The mechanical properties of collagen fascicles in in situ frozen tendons (an autograft model) are affected by stress shielding even under acellular condition. RelevanceThe in situ frozen, stress-shielded patellar tendon is a model of augmented autografts which are clinically used for the reconstruction of injured anterior cruciate ligaments. The sub-macroscopic studies of the tendon are useful to understand the mechanisms of the reduction of graft strength and its gradual recovery observed after reconstruction.

Animals↗
PubMed2000

Effects of growth on the response of the rabbit patellar tendon to stress shielding: a biomechanical study.

OBJECTIVE: To know the effect of stress deprivation on the dimensions and mechanical properties of the patellar tendon during growth. DESIGN: The dimensions and tensile properties of stress-shielded patellar tendons were studied in growing rabbits and compared to those in mature animals. BACKGROUND: Although the effects of stress deprivation on the remodeling of ligaments and tendons have been studied in various animal models, the effect of growth on the remodeling has not been studied well. METHOD: A stress shielding technique was applied to 1-, 2-, and 3-month-old Japanese white rabbits to completely remove stress in the patellar tendons for 4, 7, and 14 days. Changes in the dimensions and mechanical properties as well as fibroblast density of the tendon were determined. RESULTS: The tensile strength and tangent modulus of the patellar tendons were markedly decreased by stress shielding, while the cross-sectional area was significantly increased, with the largest changes in 1-month-old rabbits. Fibroblast density also increased; however, the degree of increase was highest in 3-month-old rabbits. CONCLUSION: The changes in the dimensions and mechanical properties of the patellar tendons induced by stress shielding were greater in younger animals. RELEVANCE: The biomechanical response of tendons and ligaments to stress deprivation induced by, for example, limb immobilization is greater and occurs earlier in younger subjects, which is important for the surgical treatment and rehabilitation protocol of joint diseases in young subjects.

Age Factors↗