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Biomedical subjects

M Ozaki

Publications and source records attributed to M Ozaki.

At least 55 records · Page 3Linked to original sources
PubMed2001

An artificial sweetener stimulates the sweet taste in insect: dual effects of glycyrrhizin in Phormia regina.

Glycyrrhizin, found in the root of licorice (Glycyrrhizia glabra), has been used extensively as a non-sugar sweetener for humans and also as a medicine. As far as we know, the present work is the first report describing that a non-sugar sweetener for humans induces a sweet taste in insects. In behavioural experiments, we found that glycyrrhizin induced the feeding response, including full proboscis extension in the blowfly, Phormia regina. Glycyrrhizin also induced impulses of the sugar receptor cell in the labellar chemosensillum, which is highly specialized for the tastes of sugars and nucleotides. The optimum concentration of glycyrrhizin was 3.0 mM, which is much lower than that of sucrose. It has been established that multiple receptor sites, the pyranose receptor site (P site) and the furanose receptor site (F site), are present in the sugar receptor cell of the blowfly and the fleshfly. The inhibitors specific to the P site, starch and PCMB (p-chloromercuribenzoate), partially inhibited glycyrrhizin-induced responses but not levan (an inhibitor to the F site), indicating that the P site on the sugar receptor cell is involved in the glycyrrhizin action but not the F site. When 30 s stimulation with 3.0 mM glycyrrhizin was repeated with an interval of 3--10 min, the impulse frequency to the second stimulus was higher than that to the first one and doubled within 6 min. The first stimulus lasting longer than 10 s potentiated the impulse generation and reduced the adaptation rate during the second stimulus. These results suggest that, in addition to the action via the P site, an additional mechanism, possibly in the signal transduction cascade of the sugar receptor cell, may be involved in the action of glycyrrhizin.

Adaptation, Physiological↗
PubMed2001

Taste-enhancing effects of glycine on the sweetness of glucose: a gustatory aspect of symbiosis between the ant, Camponotus japonicus, and the larvae of the lycaenid butterfly, Niphanda fusca.

The lycaenid butterfly, Niphanda fusca, has a parasitic relationship with its host ant, Camponotus japonicus: the caterpillars may use chemical mimicry to enter the ant nest where they are fed mouth-to-mouth by the adult ants until pupation. Nevertheless, larvae offer their host ants a nutritious secretion that contains 160 mM glucose and 43 mM glycine. Using glucose and glycine mixture as artificial secretions, we investigated the gustatory effect of glucose and/or glycine on the ants. Glycine induced neither feeding behavior nor gustatory response in the ants if its concentration was <500 mM. In the presence of glycine at the concentration in the secretion, however, the ants improved their preference to glucose, and the sugar receptor cell exhibited electrophysiological enhancement of response to glucose in a glycine-concentration-dependent manner. By adding glycine to glucose in their secretions, therefore, the butterfly larvae can manipulate the gustatory sense of the ants. The alluring taste of 'glycine-flavored glucose' could motivate the host ants to feed the larvae and thereby receive the secretions as a reward. The taste enhancement created by the combination of sugar and amino acid may play a role in the evolution of the parasitic relationships of these insects. The taste-enhancing effect appears to be analogous to taste enhancement by 'umami' substances in humans.

Amino Acids↗
PubMed2001

Opioids inhibit febrile responses in humans, whereas epidural analgesia does not: an explanation for hyperthermia during epidural analgesia.

BACKGROUND: Epidural analgesia is frequently associated with hyperthermia during labor and in the postoperative period. The conventional assumption is that hyperthermia is caused by the technique, although no convincing mechanism has been proposed. However, pain in the "control" patients is inevitably treated with opioids, which themselves attenuate fever. Fever associated with infection or tissue injury may then be suppressed by opioids in the "control" patients while being expressed normally in patients given epidural analgesia. The authors therefore tested the hypothesis that fever in humans is manifested normally during epidural analgesia, but is suppressed by low-dose intravenous opioid. METHODS: The authors studied eight volunteers, each on four study days. Fever was induced each day by 150 IU/g intravenous interleukin 2. Volunteers were randomly assigned to: (1) a control day when no opioid or epidural analgesia was given; (2) epidural analgesia using ropivacaine alone; (3) epidural analgesia using ropivacaine in combination with 2 microg/ml fentanyl; or (4) intravenous fentanyl at a target plasma concentration of 2.5 ng/ml. RESULTS: Fentanyl halved the febrile response to pyrogen, decreasing integrated core temperature from 7.0 +/- 3.2 degrees C. h on the control day, to 3.8 +/- 3.0 degrees C. h on the intravenous fentanyl day. In contrast, epidural ropivacaine and epidural ropivacaine-fentanyl did not inhibit fever. The fraction of core-temperature measurements that exceeded 38 degrees C was halved by intravenous fentanyl, and the fraction exceeding 38.5 degrees C was reduced more than fivefold. CONCLUSIONS: These data support the authors' proposed mechanism for hyperthermia during epidural analgesia. Fever during epidural analgesia should thus not be considered a complication of the anesthetic technique per se.

Adult↗
PubMed2001

A calcium channel blocker, benidipine, inhibits intimal thickening in the carotid artery of mice by increasing nitric oxide production.

OBJECTIVE: Recent studies suggest that several calcium channel blockers exert their protective effects against vascular disorders by increasing nitric oxide (NO) production from the endothelium. The purpose of this study was to clarify the effects of a long-lasting calcium channel blocker, benidipine, on vascular remodeling. METHODS: The left common carotid arteries of mice were completely ligated just proximal to the carotid bifurcation. Treatment with benidipine (3 mg/kg per day) or vehicle was started 1 week before the carotid ligation, and continued throughout the experiments. Four weeks after the carotid ligation, these mice were killed and vascular remodeling was analyzed. Moreover, NO production and endothelial NO synthase (eNOS) expression were assessed. RESULTS: At 4 weeks after ligation, the neointimal area in the vehicle-treated mice was 39,400 +/- 4,900 microm2 (n = 8), whereas that in the drug-treated mice was reduced to 18,300 +/- 3,800 microm2 (n = 10). Consequently, the luminal area was 35% larger in the drug-treated mice. Benidipine increased the basal as well as agonist-induced NO production from the endothelium, detected by Griess method or NOx analyzer. Endothelial NOS expression in vessels of the drug-treated mice was increased compared with that of the vehicle-treated mice. CONCLUSION: Our data provide evidence that benidipine increases NO production via increment of eNOS protein in vessels and prevents intimal thickening in mice. These results show the possibility of benidipine as a protective tool against vascular remodeling independent of its effect on blood pressure.

Animals↗
PubMed2001

Further reduction of radiation dose in helical CT for lung cancer screening using small tube current and a newly designed filter.

A new aluminum filter, 5.8 mm thick at the center, was designed. The effective energy, exposure dose, absorbed dose, and noise were measured by using low-dose technique, very low-dose technique with a conventional filter, and very low-dose technique with a new filter on a chest phantom. Accuracy of very low-dose computed tomography (CT) with a new filter was compared against standard helical CT in 40 patients and against chest radiography in 35 patients. Effective energies were 42.6 keV and 51.6 keV at a conventional filter and the new filter, respectively. Compared against 20mA with a conventional filter, exposure dose was reduced by 17%, and absorbed dose was equivalent, at 30 mA with the new filter. Noise was improved by 9%. Compared with standard helical CT, the sensitivity, specificity, and accuracy of very-low-dose helical CT were 100%, 88%, and 95%, respectively. Very-low-dose helical CT was found to be significantly superior to chest radiography in the detection of lung cancers. Using a smaller tube current and an appropriate filter allows a further reduction in radiation dose in helical CT for lung cancer screening.

Adult↗
PubMed2001

Endothelial NO synthase overexpression inhibits lesion formation in mouse model of vascular remodeling.

NO produced by endothelial NO synthase (eNOS) plays important roles in the regulation of vascular tone and structure. The purpose of this study was to clarify the role of eNOS-derived NO on vascular remodeling by use of eNOS-transgenic (eNOS-Tg) mice. The common carotid artery was ligated just proximal to the carotid bifurcation. Four weeks later, the proximal carotid artery of the ligation site was histologically examined. In this vascular remodeling model, the endothelium remains uninjured, but neointimal and medial thickening occurs in combination with a reduction in vascular diameter at the proximal portion of the ligation. At 4 weeks after ligation, the respective neointimal and medial areas in wild-type mice were 17 200+/-1100 and 24 300+/-1500 microm(2), whereas both were reduced to 8000+/-1900 (P:<0.01) and 18 400+/-700 microm(2) (P:<0.01) in eNOS-Tg mice (n=8). Total vascular area was not different between the 2 genotypes. N:(G)-Nitro-L-arginine methyl ester treatment increased neointimal and medial areas to the same extent in both genotypes. Leukocyte infiltration was observed in the luminal side of the vessel, but the number of infiltrating cells was significantly attenuated in eNOS-Tg mice compared with wild-type mice. This reduction of leukocyte infiltration in eNOS-Tg mice was associated with reduced expressions of intracellular adhesion molecule-1 and vascular cellular adhesion molecule-1 on the endothelium. In conclusion, chronic eNOS overexpression in the endothelium reduced leukocyte infiltration and inhibited neointimal formation and medial thickening. Our data provide the evidence for the regulatory role of NO from the endothelium on vascular structure integrity.

Animals↗
PubMed2001

Reduced hypoxic pulmonary vascular remodeling by nitric oxide from the endothelium.

We examined whether overproduction of endogenous nitric oxide (NO) can prevent hypoxia-induced pulmonary hypertension and vascular remodeling by using endothelial NO-overexpressing (eNOS-Tg) mice. Male eNOS-Tg mice and their littermates (wild-type, WT) were maintained in normoxic or 10% hypoxic condition for 3 weeks. In normoxia, eNOS protein levels, Ca(2+)-dependent NOS activity, and cGMP levels in the lung of eNOS-Tg mice were higher than those of WT mice. Activity of eNOS and cGMP production in the lung did not change significantly by hypoxic exposure in either genotype. Chronic hypoxia did not induce iNOS expression nor increase its activity in either genotype. Plasma and lung endothelin-1 levels were increased by chronic hypoxia, but these levels were not significantly different between the 2 genotypes. In hemodynamic analysis, right ventricular systolic pressure (RVSP) in eNOS-Tg mice was similar to that in WT mice in normoxia. Chronic hypoxia increased RVSP and induced right ventricular hypertrophy in both genotypes; however, the degrees of these increases were significantly smaller in eNOS-Tg mice. Histological examination revealed that hypoxic mice showed medial wall thickening in pulmonary arteries. However, the increase of the wall thickening in small arteries (diameter <80 microm) by chronic hypoxia was inhibited in eNOS-Tg mice. Furthermore, muscularization of small arterioles was significantly attenuated in eNOS-Tg mice. Thus, we demonstrated directly that overproduction of eNOS-derived NO can inhibit not only the increase in RVSP associated with pulmonary hypertension but also remodeling of the pulmonary vasculature and right ventricular hypertrophy induced by chronic hypoxia.

Animals↗
PubMed2001

Neuregulins and the shaping of synapses.

In developing and mature neural circuits, neural electrical activity controls the correct formation of connections and their state. Neuregulins (NRGs) mediate between the electrical neural activity and molecular components by regulating the expression of ion channel receptors or transmitter release in synapses. Furthermore, NRGs may be signaling factors involved in tuning locomotion or other higher functions by coordinating excitatory and inhibitory neurons.

Animals↗
PubMed2001

Level of plasma tissue factor pathway inhibitor is inversely correlated with intraarterial diastolic pressure in subjects who underwent coronary angiography.

There are only a few studies of the relationship between hemostatic abnormalities and intraarterial pressure, so the present study investigated the association of various newer lipid and hemostatic variables with intraarterial pressure levels. Levels of total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol, triglyceride, lipoprotein-(a), remnant-like particle cholesterol, cholesteryl ester transfer protein, uric acid, blood glucose, fibrinogen, free form of tissue factor pathway inhibitor (TFPI), C-reactive protein, serum amyloid A protein, anti-Chlamydia pneumoniae immunoglobulin G and immunoglobulin A, and apolipoproteins (apo) A-I, B, and E were measured in 176 patients who underwent diagnostic coronary angiography. Intraarterial blood pressure was determined from central aortic pressure using a standard fluid-filled catheter-external transducer system. Multivariate regression analyses showed that TFPI level was the only independent factor associated with aortic diastolic pressure. The linear regression equation demonstrated a significant negative correlation of TFPI level with aortic diastolic pressure (r=-0.395, p=0.0011). With respect to the association with other parameters, the TFPI level showed significant correlations between the HDL-C level and the apo A-I level, both in the overall patients and in the patients with coronary artery stenosis. This is the first evidence that the level of the plasma free form of TFPI is inversely correlated to aortic diastolic pressure.

Adult↗
PubMed2001

Isolation and characterization of two genes encoding ubiquitin fused to a ribosomal protein of 53 amino acids in rice.

We isolated and determined the nucleotide sequences of two genes encoding ubiquitin fused to a ribosomal protein, Ub-CEP52, from rice (Oryza sativa L.). The deduced amino-acid sequences of the two genes were found to be completely identical. The N-terminal region of 76 residues corresponds to ubiquitin, and the C-terminal region of 53 residues corresponds to ribosomal protein L40. A putative TATA-like sequence, a polypyrimidine sequence, and a similar sequence to telo-box were found in the promoter regions of the two genes. Furthermore, the putative tRNA(Pro) gene was found in the 5'-upstream region of one of them.

Amino Acid Sequence↗
PubMed2001

Rainwater drainage management for urban development based on public-private partnership.

The Urban Development Corporation (UDC) is one of the biggest implementation bodies for urban development in Japan. UDC has developed rainwater infiltration technology since 1975. This technology has effectively reduced runoff to a river and sewer system in the new town project areas. Recently, UDC has developed a new system which is defined as a "Rainwater Recycle Sewer System", which is supported by "Rainwater Storage and Infiltration Technology (RSIT)" applicable to new town creation and urban renewal. The new system consists of two elements: RSIT components based on Public-Private Partnership (PPP) and a stormwater drainage system. Herein, the private sector is responsible for the main part of RSIT, and the public sector is responsible for the stormwater drainage from the development area. As a result, the capacity of public facilities, such as rainwater sewers and stormwater reservoirs, can be reduced effectively. In parallel, the initial/running cost of public facilities is expected to be reduced. In conclusion, the authors would stress the importance of a co-maintenance system also based on PPP, which will be required especially in order to properly operate the whole system for the long term.

Cities↗
PubMed2000

Attenuation of expression of gamma-glutamylcysteine synthetase by ribozyme transfection enhance insulin secretion by pancreatic beta cell line, MIN6.

Low levels of intracellular antioxidant enzyme activities as well as glutathione (GSH) concentrations have been described in pancreatic beta cells. We examined the effects of intracellular GSH depletion on insulin secretion and the role of intracellular GSH in signal transduction in beta cell line, MIN6 cells. Anti-gamma-glutamylcysteine synthetase (gamma-GCS) heavy subunit ribozyme was stably transfected to MIN6 cells to reduce intracellular GSH concentration. In the presence of 10 mM glucose, ribozyme-transfected cells (RTC) increased insulin secretion from 0.58 microg/10(6) cells/h in control cells (CC) to 1.48 microg/10(6) cells/h. This was associated with increased intracellular Ca(2+) concentration in RTC, detected by fluo-3 staining. Our results demonstrated that intracellular GSH concentration might influence insulin secretion by MIN6 cells, and suggest that enhanced insulin secretion by beta cells conditioned by chronic depletion of GSH is mediated by increased intracellular Ca(2+) concentration.

Adenosine Triphosphate↗
PubMed2000

Rac1 regulates stress-induced, redox-dependent heat shock factor activation.

The signaling pathway by which environmental stresses activate heat shock factors (HSFs) is not completely understood. We show that the small GTPase rac1, and Rac1-regulated reactive oxygen species (ROS) play an important role in stress-stimulated heat shock response. A dominant-negative allele of Rac1 (Rac1N17) inhibits the hypoxia/reoxygenation and sodium arsenite-induced transcriptional activity of HSF-1 and the transcription of heat shock protein 70. Rac1N17 also suppresses the production of intracellular ROS induced by hypoxia/reoxygenation or sodium arsenite. Moreover, direct suppression of intracellular ROS levels by antioxidants decreases stress-stimulated HSF activity. However, expression of a constitutively active mutant of Rac1 (Rac1V12) in the absence of extracellular stresses does not increase intracellular ROS levels or induce the heat shock response. These results show that Rac1 is a necessary but insufficient component of the stress-induced signaling pathway that leads to ROS production, activation of HSFs, and transcription of heat shock proteins.

Adenoviridae↗
PubMed2000

Roles of neuregulin in synaptogenesis between mossy fibers and cerebellar granule cells.

Neuregulins (NRGs), a large group of structurally related signaling proteins, are likely to have important roles in the development, maintenance and repair of the nervous system and other selected tissues. We have demonstrated, by using the major form of NRG cloned from the mouse cerebellum that both the soluble form and the membrane anchored form of NRG may serve different functions in synaptogenesis. The soluble form of NRG was produced by proteolytic cleavage of the membrane anchored form of NRG. The proteolytic cleavage was promoted by protein kinase activation. The cleaved form of NRG trans-synaptically regulated the expression of the NMDA (N-methyl-D-aspartate) receptor subunit NR2C as neurally-derived factors, whereas the membrane anchored form of NRG showed a homophilic binding activity between NRGbeta1s. In adult mice the membrane anchored form of NRG was concentrated in neuro-terminals of both granule cells and pontocerebellar mossy fibers. The fact that NRG can be functionally viewed as cell recognition molecules as well as neurotrophic agents suggests new possibilities for the important class of molecules.

Amino Acid Sequence↗