Biomedical subjects

M Nakata

Publications and source records attributed to M Nakata.

At least 91 records · Page 5Linked to original sources

PubMed2000

Occlusal contacts during lateral excursions in children with primary dentition.

The presence of non-working occlusal contacts in adults is considered abnormal and may initiate parafunctional activity. Few studies have looked for non-working occlusal contacts in children with primary dentition. The purposes of this study were (1) to prove the existence of non-working-side occlusal contacts, and (2) to quantify their area during lateral excursion in children with primary dentition. To achieve this purpose, we developed a measurement system that combined a tracking system for mandibular movements with a three-dimensional digitizer for tooth shape. Ten children were selected for this study. Estimated occlusal contact area of the primary second molar on the non-working side was 0.8 mm2, in contrast to 2.0 mm2 on the working side, at 3.0 mm of movement of the lower incisor. All children examined had some occlusal contacts on the non-working side during the first part of lateral excursion.

Child↗

PubMed2000

Pharmacokinetics of propranolol and its metabolites in horses after intravenous or oral administration.

The pharmacokinetics characteristics of propranolol (PPL) in horses was studied by administering the drug intravenously or orally to the animals. The predominant primary pathway was ring oxidation, and 4-hydroxypropranolol glucuronide (4-OHPG) was the major metabolite in both plasma and urine. Side-chain glucuronidation and oxidation were not significant. A two-compartment model was employed for PPL followed by a one-compartment model for 4-OHPG. After oral administration, one-step absorption and two-step first pass metabolism were employed. The fraction absorbed of PPL was approximately 70% after oral administration, and the bioavailability varied among individual horses from 1 to 79% depending on the first pass metabolism. The biologic half-life (T1/2) of PPL obeys the allometric equation in some animal species including rats and horses, except for human. T 1/2 of PPL in horses was approximately 2 h.

Administration, Oral↗

PubMed2000

Inhibition of caspase-3 activation by SB 203580, p38 mitogen-activated protein kinase inhibitor in nitric oxide-induced apoptosis of PC-12 cells.

Mitogen-activated protein kinase (MAPK) p38 plays pivotal role in cell proliferation, differentiation, and apoptosis when cysteine protease caspase induces apoptosis in different cell systems. SB 203580 (4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1 H-imidazole) is widely used as a specific inhibitor of p38 MAPK, and prevents apoptosis induced by various agents. The effect of SB 203580 on nitric oxide(NO)- or peroxynitrite-induced cell death is not known. Western blotting results indicate that p38 MAPK was activated significantly in NO- or peroxynitrite-induced cell death in a time-dependent manner, and subsequently this cell death was markedly inhibited by SB 203580, as determined by fluorescence-activated cell sorting (FACS)-can analyzer. Furthermore, NO/peroxynitrite-induced caspase-3 activation was notably inhibited by SB 203580, however, phosphorylation of either p38 MAPK or p44/42 was not influenced by SB 203580. Thus, it is likely that SB 203580 prevents NO/peroxynitrite-induced cell death by inhibiting caspase-3 activation in PC-12 cells.

Animals↗

PubMed2000

Two cases of atypical carcinoid of the thymus.

We describe two cases of atypical carcinoid of the thymus. One was an 82-year-old woman with complaints of nonproductive cough and back pain, and the other a 64-year-old woman with no symptoms. Computed tomography scans of the chest in both cases revealed a large mass in the anterior mediastinum. Multiple metastases to bone and liver were also noted in the former case. Histological examination of their tumors revealed that the tumor cells were arranged in a nested, trabecular, or pseudorosette pattern, with increased numbers of mitoses, nuclear pleomorphism, and presence of necrosis. In addition, immunohistochemically, the cells stained for neuron-specific enolase, synaptophysin and chromogranin A. Combination chemotherapy consisting of carboplatin and etoposide was performed as initial chemotherapy in the former case and as adjuvant therapy in the latter. The former patient achieved a short-term partial response. It is important to differentiate atypical carcinoid from other thymic tumors, since such tumors including thymoma have a much better prognosis than does atypical carcinoid.

Aged↗

PubMed2000

[Definition and classification of cardiomyopathies and specific cardiomyopathies].

The cardiomyopathies were previously defined as "heart muscle diseases of unknown cause" and were differentiated from specific heart muscle disease with known cause. With increasing understanding of etiology and pathogenesis, the difference between cardiomyopathy and specific heart muscle disease has become indistinct. Accordingly in 1995 WHO/ISFC task force, the definition and classification of cardiomyopathies were revised as cardiomyopathies are defined as disease of the myocardium associated with cardiac dysfunction. On the other hand, since the classification has become established clinical entities, the terminology is preserved as follows: dilated cardiomyopathy, hypertrophic cardiomyopathy, restrictive cardiomyopathy. While arrhythmogenic right ventricular cardiomyopathy is additionally included. The term specific cardiomyopathies is used to describe heart diseases that are associated with specific cardiac or systemic disorders. These were previously defined as specific heart muscle diseases. They included ischemic cardiomyopathy, valvular cardiomyopathy, hypertensive cardiomyopathy, inflammatory cardiomyopathy, metabolic cardiomyopathy, general system disease, muscular dystrophies, sensitivity and toxic reactions and peripartal cardiomyopathy. The cardiomyopathies are therefore classified by the dominant pathophysiology or, if possible, by etiological/pathogenetic factors.

Cardiomyopathies↗

PubMed2000

[A case report of pulmonary nocardiosis successfully treated with a combination of sulfamethoxazole-trimethoprim (ST) and sparfloxacin].

We encountered a case of pulmonary nocardiosis that responded dramatically to combined ST and sparfloxacin treatment. A 55-year-old woman presented with fever, cough and yellowish sputum. She had been under treatment with oral prednisolone (15 mg per day) since July 1997 after a diagnosis of Evans syndrome. A high fever of 39.8 degrees C was noted on January 30, 1998. The patient was hospitalized for bloody sputum, bilateral hypochondriac pain and evidence of infiltrative opacities in the left lower lobe on chest radiography. Bacterial pneumonia was suspected, and she was treated with piperacillin, but her clinical symptoms did not improve. Sputum culture and serologic examination failed to lead to a definitive diagnosis. Nocardia farcinica was isolated by culturing tissue obtained by CT-guided transcutaneous pulmonary biopsy, leading to a diagnosis of pulmonary nocardiosis. The results of an MIC test for antimicrobial agents led to treatment with a combination of ST and sparfloxacin, and the clinical symptoms improved. These clinical observations suggest that, when pneumonia is diagnosed in patients who have been receiving oral steroids for a prolonged period, pulmonary nocardiosis should be considered in the differential diagnosis to enable selection of appropriate antimicrobial agents.

Anti-Infective Agents↗

PubMed1999

Hypernuclear acetylation in atherosclerotic lesions and activated vascular smooth muscle cells.

Recent studies have implicated acetylation of several nuclear proteins such as histones and p53 on their epsilon-portion of lysine residues in eukaryotic transcription. Here we raised a specific polyclonal antibody against epsilon-acetylated lysine. Using the antibody, we detected hypernuclear acetylation (HNA) in atherosclerotic vascular smooth muscle cells (VSMCs). Thrombin, a humoral factor known to cause activation and proliferation of VSMCs, strongly potentiated HNA in cultured VSMCs. MAP kinase pathway and a signal coactivator CREB binding protein (CBP) were involved in thrombin-induced HNA of VSMCs. Our results suggest that coactivators cooperating with signal-dependent transcription activators play an important role in atherosclerogenesis via HNA in VSMCs.

Acetylation↗

PubMed1999

Exposure of rat thymocytes to hydrogen peroxide increases annexin V binding to membranes: inhibitory actions of deferoxamine and quercetin.

Effects of hydrogen peroxide (H(2)O(2)) on rat thymocytes were examined, using a flow cytometer and three fluorescent probes, annexin V-fluorescein isothiocyanate (annexin V-FITC) for detecting phosphatidylserine expressed on the membrane surface, ethidium bromide for estimating dead cells, and fluo-3-acetoxymethyl ester (fluo-3-AM) for monitoring changes in intracellular Ca(2+) concentration ([Ca(2+)](i)), to characterize H(2)O(2)-induced cytotoxicity. Exposure to H(2)O(2) (30 microM or more) increased the number of annexin V-positive live cells dose- and time-dependently while the number of dead cells increased at concentrations of 1 mM or more. H(2)O(2) (30 microM or more) increased [Ca(2+)](i) in a dose-dependent manner. Threshold concentration of H(2)O(2) to increase [Ca(2+)](i) was similar to that to increase annexin V binding to membranes. The H(2)O(2)-induced change in cell membranes was attenuated under Ca(2+)-free conditions. Therefore, it is likely that Ca(2+) is involved in the H(2)O(2)-induced cytotoxicity. Deferoxamine was effective to protect the cells suffering from H(2)O(2)-induced oxidative stress, suggesting a contribution of hydroxyl radicals generated by the Fenton reaction. Quercetin also exerted a potent protective action on cells suffering from H(2)O(2)-induced oxidative stress. The results indicate that the exposure of rat thymocytes to H(2)O(2) at micromolar concentrations increases annexin V binding to cell membranes in a Ca(2+)-dependent manner, suggesting the possibility that the oxidative stress caused by H(2)O(2) (and/or hydroxyl radicals) induces apoptosis via increasing [Ca(2+)](i).

Animals↗

PubMed1999

Cholesterol-dependent generation of a seeding amyloid beta-protein in cell culture.

Deposition of aggregated amyloid beta-protein (Abeta), a proteolytic cleavage product of the amyloid precursor protein (Abeta ), is a critical step in the development of Alzheimer's disease(Abeta++). However, we are far from understanding the molecular mechanisms underlying the initiation of Abeta polymerization in vivo. Here, we report that a seeding Abeta, which catalyzes the fibrillogenesis of soluble Abeta, is generated from the apically missorted amyloid precursor protein in cultured epithelial cells. Furthermore, the generation of this Abeta depends exclusively on the presence of cholesterol in the cells. Taken together with mass spectrometric analysis of this novel Abeta and our recent study (3), it is suggested that a conformationally altered form of Abeta, which acts as a "seed" for amyloid fibril formation, is generated in intracellular cholesterol-rich microdomains.

Amyloid beta-Peptides↗

PubMed1999

Clinical investigation of atypical adenomatous hyperplasia of the lung.

The clinicopathologic characteristics of atypical adenomatous hyperplasia (AAH) remain unclear. A total of 137 patients underwent resection for adenocarcinoma of the lung at our institution. Examination of resected lung tissue showed that in addition to adenocarcinoma AAH was present in 26 cases and was not present in 111 cases. All nonsmokers with AAH (n = 13) had earlier-stage disease (stage IA, IB, IIA, and IIB) and no history of respiratory disease. Among patients with stage IA disease, the relapse-free and overall survival curves for those with AAH (n = 14) tended to be better than for those without AAH (n = 40), but the difference was not statistically significant (P = 0.056 and 0.087, respectively). Concurrent presence of AAH may be a favorable prognostic indicator in patients with stage IA adenocarcinoma.

Adenocarcinoma↗

PubMed1999

Insulinotropin PACAP potentiates insulin-stimulated glucose uptake in 3T3 L1 cells.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is localized in pancreatic nerve fibers and islets and potently augments glucose-induced insulin secretion. The present study explored a possible extra-pancreatic action of PACAP. The specific PACAP receptor (PAC1 receptor) was expressed in the rat fat tissue and 3T3-LI adipocytes. PACAP-38 (10 nM) significantly enhanced insulin-induced 2-deoxyglucose uptake by 3T3-L1 adipocytes. Insulin-stimulated phosphatidylinositol 3-kinase activity was further increased by PACAP-38, whereas the tyrosine-phosphorylation of insulin receptor beta-subunit and insulin receptor substrate-1 was unaltered by PACAP-38. These results reveal that PACAP-38 enhances insulin-induced glucose uptake, an effect probably mediated by insulin-stimulated phosphatidyl-inositol 3-kinase, and that PACAP potentiates not only insulin secretion, but also insulin action in adipocytes.

3T3 Cells↗

PubMed1999

Evaluation of the antioxidant activity of environmental plants: activity of the leaf extracts from seashore plants.

The antioxidant activity of the methanolic extracts of the leaves of 39 plant species was examined. These leaves were collected from the plants growing on subtropical seashores. The activity was evaluated by three kinds of assay methods, which included the DPPH radical scavenging assay, linoleic acid oxidation assay, and oxidative cell death assay. Two extracts from Excoecaria agallocha and Terminalia catappa showed remarkably potent activity in all assay systems. The HPLC analysis of the extracts indicated the presence of the same antioxidant and isolation work for the compound identified ellagic acid. The isolated ellagic acid showed strong antioxidant activity in the assay systems used.

Antioxidants↗

PubMed1999

Inhibition by simvastatin, but not pravastatin, of glucose-induced cytosolic Ca2+ signalling and insulin secretion due to blockade of L-type Ca2+ channels in rat islet beta-cells.

1. Hypercholesterolaemia often occurs in patients with type 2 diabetes, who therefore encounter administration of HMG-CoA reductase inhibitors. Alteration of pancreatic beta-cell function leading to an impaired insulin secretory response to glucose plays a crucial role in the pathogenesis of type 2 diabetes. Therefore, it is important to examine the effects of HMG-CoA reductase inhibitors on beta-cell function. 2. Cytosolic Ca2+ concentration ([Ca2+]i) plays a central role in the regulation of beta-cell function. The present study examined the effects of HMG-CoA reductase inhibitors on the glucose-induced [Ca2+]i signalling and insulin secretion in rat islet beta-cells. 3. Simvastatin, a lipophilic HMG-CoA reductase inhibitor, at 0.1-3 microg ml(-1) concentration-dependently inhibited the first phase increase and oscillation of [Ca2+]i induced by 8.3 mM glucose in single beta-cells. The less lipophilic inhibitor, simvastatin-acid, inhibited the first phase [Ca2+]i increase but was two orders of magnitude less potent. The hydrophilic inhibitor, pravastatin (100 microg ml(-1), was without effect on [Ca2+]i. 4. Simvastatin (0.3 microg ml(-1)), more potently than simvastatin-acid (30 microg ml(-1)), inhibited glucose-induced insulin secretion from islets, whereas pravastatin (100 microg ml(-1)) had no effect. 5. Whole-cell patch clamp recordings demonstrated a reversible inhibition of the beta-cell L-type Ca2+ channels by simvastatin, but not by pravastatin. Simvastatin also inhibited the [Ca2+]i increases by L-arginine and KCl, agents that act via opening of L-type Ca2+ channels. 6. In conclusion, lipophilic HMG-CoA reductase inhibitors can inhibit glucose-induced [Ca2+]i signalling and insulin secretion by blocking L-type Ca2+ channels in beta-cells, and their inhibitory potencies parallel their lipophilicities. Precaution should be paid to these findings when HMG-CoA reductase inhibitors are used clinically, particularly in patients with type 2 diabetes.

Animals↗

PubMed1999

Expression of vascular endothelial growth factor in sera and lymph nodes of the plasma cell type of Castleman's disease.

To evaluate the possible involvement of vascular endothelial growth factor (VEGF) in the pathogenesis of Castleman's disease, we studied VEGF levels in sera and supernatants of cultured lymph nodes from two patients with the plasma cell type of Castleman's disease, and analysed the expression of VEGF immunohistochemically in the lymph nodes. Clinically, one patient was classified as the localized type and the other as the multicentric type. Histologically, mature plasma cells and hyalinized vessels were prominent in the interfollicular region. The VEGF levels of the sera and the supernatants of cultured lymph nodes of both patients were higher than those of normal controls. VEGF was strongly expressed in plasma cells in the interfollicular region of the lymph nodes of both patients, but rarely in normal lymph nodes. Our results suggest that VEGF may be involved in the marked vascular proliferation in the interfollicular region of the lymph nodes of the plasma cell type of Castleman's disease.

Adult↗

PubMed1999

A calculation method for the range of occluding phase at the lower incisal point during chewing movements using the curved mesh diagram of mandibular excursion (CMDME).

The purpose of this study was to develop a method for calculating the range of the occluding phase in chewing movements. In this study, we defined 'range' as the distance of the movement at the lower incisal point while the mandible moves with tooth contact. First, mandibular excursions were measured using an opto-electronic movement analysis system, which can measure mandibular movement with six degrees-of-freedom at a sampling frequency of 100 Hz. With use of this measurement data, the curved mesh diagram of mandibular excursion (CMDME) previously reported was made. Then, chewing movements were measured using the same analysis system. The movements were separated into their component chewing cycles. Finally, we calculated the distance between each cycle and the CMDME. The occluding range of our subject was 0.4 mm at the closing phase and 3.4 mm at the opening phase. These results suggest that tooth contact occurs during chewing movement and demonstrate that the range of the occluding phase for the opening and closing phases of a subject can be calculated without morphological data from a dental cast.

Adult↗

PubMed1999

Regulated expression of the Shiga toxin B gene induces apoptosis in mammalian fibroblastic cells.

Shiga toxins (Stxs) produced by enterohaemorrhagic Escherichia coli may induce colonic ulceration, bloody diarrhoea and acute renal failure. The A subunit (StxA) is known to inhibit protein synthesis, whereas the B subunits (StxB) bind to Gb3 on the cell surface. However, the mechanisms by which Stxs kill target cells remain unclear. Stx1A or Stx1B genes were introduced into pcDNA3.1 vectors and transfected into NIH3T3 and HeLa cells. The Stx1B gene-transfected cells became apoptotic with accompanying DNA fragmentation, whereas the Stx1A gene-transfected cells were found to be necrotic and no DNA fragmentation occurred. The HeLa/C4 cells integrated with the Stx1B gene with a tetracycline-inducible promoter eventually produced cytoplasmic Stx1B, leading to DNA fragmentation on the addition of doxycycline. These apoptotic changes were abrogated by pretreatment with Z-VAD-fmk. These results suggest that the transfected Stx1B gene induces apoptosis by activating the caspase cascade after Stx1B expression in the cytoplasm.

3T3 Cells↗

PubMed1999

In vivo evaluation of the national cardiovascular center electrohydraulic total artificial heart.

We have been developing an electrohydraulic total artificial heart system. The system comprises an intrathoracic pumping unit composed of diaphragm type ellipsoidal blood pumps and an energy converter in addition to an electronics unit. The in vivo performance of the pumping unit was evaluated in a series of animal implantations with 3 calves weighing 62-85 kg. An interatrial shunt 4.5 mm in diameter was made in the atrial septum to compensate left-right imbalance. Two calves died early postoperatively, one of external controller power failure and the other of interatrial shunt stenosis due to thrombus formation. One calf, however, survived over 10 days under stable circulatory conditions. No abnormality was found in the oxygen metabolic condition or in major organ functions. The generation and dissipation of heat from the device was acceptable. This animal died of device malfunction caused by energy converter bearing breakdown. The device demonstrated a good anatomic fit without compromising the great vessels and adjacent tissues. It is concluded that the pumping unit has a sufficient in vivo basic performance although appropriate countermeasures are to be implemented against the detected problems concerning mechanical durability and interatrial shunt patency.

Animals↗

PubMed1999

Cardiac autonomic nervous function during long-term nonpulsatile left heart bypass.

We investigated the changes in cardiac autonomic nervous activities during long-term nonpulsatile left heart bypass (NLHB) by analyzing heart rate variability. A pulsatile ventricular assist device was installed in 3 goats, and pulsatile left heart bypass (PLHB) was conducted for 2 weeks. Then, NLHB was maintained for the following 4 weeks. The segmental data of the R-R intervals (R-Rs) was analyzed by maximum entropy spectral analysis. Changes in evaluated parameters from the last week of PLHB to the 4th week of NLHB were as follows: the mean R-Rs increased from 511 ms to 692 ms; the coefficient of variation of R-R increased from 10.2 to 14.1%; the power of the low frequency band (LF) increased from 747 ms2 to 2,855 ms2; the power of the high frequency band (HF) increased from 512 ms2 to 1,270 ms2; and the ratio of LF to HF increased from 2.6 to 6.5. These results indicated that the cardiac autonomic nervous activity, both sympathetic and parasympathetic, increased during long-term NLHB.

Analysis of Variance↗