Biomedical subjects

M Tsunoda

Publications and source records attributed to M Tsunoda.

At least 19 recordsLinked to original sources

PubMed2002

Differential expression of VAMP2/synaptobrevin-2 after antidepressant and electroconvulsive treatment in rat frontal cortex.

The biological basis for the therapeutic mechanisms of depression is still unknown. We have previously performed expressed-sequence tag (EST) analysis to identify some molecular machinery responsible for antidepressant effect. Then, we developed our original cDNA microarray, on which cDNA fragments identified as antidepressant-related genes/ESTs were spotted. In this study, with this microarray followed by Western blot analysis, we have demonstrated the induction of vesicle-associated membrane protein 2(VAMP2/synaptobrevin-2) in rat frontal cortex not only after chronic antidepressant treatment, but also after repeated electroconvulsive treatment. On the other hand, expression of SNAP-25 and syntaxin-1 was not changed by these treatments. These components make a soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor complex with VAMP2 and mediate the synaptic vesicle docking/fusion machinery. In conclusion, it is suggested that VAMP2/synaptobrevin-2 plays important roles in the antidepressant effects. Our results may contribute to a novel model for the therapeutic mechanism of depression and new molecular targets for the development of therapeutic agents.

Animals↗

PubMed2001

Crystallographic studies on damaged DNAs IV. N( 4)-methoxycytosine shows a second face for Watson-Crick base-pairing, leading to purine transition mutagenesis.

To investigate the mutation mechanism of purine transitions in DNA damaged with methoxyamine, a DNA dodecamer with the sequence d(CGCAAATTmo(4)CGCG), where mo(4)C is 2'-deoxy-N(4)-methoxycytidine, has been synthesized and the crystal structure determined by X-ray analysis. The duplex structure is similar to that of the original undamaged B-form dodecamer, indicating that the methoxylation does not affect the overall DNA conformation. Electron density maps clearly show that the two mo(4)C residues form Watson-Crick-type base pairs with the adenine residues of the opposite strand and that the methoxy groups of mo(4)C adopt the anti conformation to N(3) around the C(4)-N(4) bond. For the pair formation through hydrogen bonds the mo(4)C residues are in the imino tautomeric state. Together with previous work, the present work establishes that the methoxylated cytosine residue can present two alternate faces for Watson-Crick base-pairing, thanks to the amino<-->imino tautomerism allowed by methoxylation. Based on this property, two gene transition routes are proposed.

Adenine↗

PubMed2001

Determination of catecholamines and their 3-O-methyl metabolites in mouse plasma.

The determination of catecholamines and their 3-O-methyl metabolites in a single mouse plasma is necessary to understand the role of the sympathetic nervous activity, while the inactivation of catecholamines by catechol-O-methyltransferase indicates the activity of blood pressure regulation in animals. Here we report the basal catecholamines and their 3-O-methyl metabolite concentrations obtained from 15 microL of mouse plasma utilizing semi-microcolumn high-performance liquid chromatography (HPLC)-peroxyoxalate chemiluminescence detection system. The concentrations were 6.63 +/- 1.37 pmol/mL plasma, 0.49 +/- 0.10 pmol/mL plasma, 5.25 +/- 2.30 pmol/mL plasma, 3.23 +/- 0.84 pmol/mL plasma, 0.44 +/- 0.11 pmol/mL plasma, and 3.39 +/- 1.67 pmol/mL plasma for norepinephrine, epinephrine, dopamine, normetanephrine, metanephrine and 3-methoxytyramine, respectively (n = 5-7). Further, when blood pressure was reduced by minoxidil, plasma catecholamines were found to be significantly increased by the baroreflex-mediated response in mouse.

Animals↗

PubMed2001

Effect of tributyltin on the N-methyl-D-aspartate (NMDA) receptors in the mouse brain.

The purpose of this study was to determine the effect of tributyltin chloride (TBTCI) on the NMDA receptor by in vitro and in vivo experiments. In the first in vitro experiment, the binding of [3H]MK-801 and of [3H]-CGP39653 were studied in membrane preparations from the cerebral cortex of intact mice to obtain control values. Saturation experiments for [3H]MK-801 and [3H]CGP39653 revealed single binding sites with Kd values of 10.27 and 37.8 nM, and receptor densities of 1.75 and 2.20 pmol/mg of protein, respectively. In the second in vitro experiment, displacement studies were carried out with TBTCI over a concentration range of 0.1 microM to 2 mM. TBTCI inhibited [3H]MK-801 binding but did not affect [3H]CGP39653 binding. In the in vivo experiments, the mice received 1-125 ppm TBTCI in the diet ad libitum for 30 days. Ligand binding to cortical membrane preparations from each mouse was measured by a one-concentration point (2 nM) binding assay. [3H]MK-801 binding was significantly lowered (P < 0.05) in the 5 and 125 ppm TBTCl-exposed animals compared with the controls. [3H]CGP39653 binding was also significantly lowered (P<0.05) in the 1 and 125 ppm TBTCI-exposed animals compared with the controls. These results suggest that the NMDA receptors in the mouse brain are sensitive to relatively low level exposure to TBTCl.

2-Amino-5-phosphonovalerate↗

PubMed2001

A method for the measurement of catechol-O-methyltransferase activity using norepinephrine, an endogenous substrate.

We propose a highly sensitive method for the measurement of catechol-O-methyltransferase (COMT) activity with norepinephrine (NE), an endogenous native substrate. The product, normetanephrine, was determined by high-performance liquid chromatography (HPLC)-peroxyoxalate chemiluminescence reaction detection or, if required, less sensitive fluorescence detection. For the measurement of membrane-bound (MB)-COMT activity in the rat erythrocyte, the HPLC-peroxyoxalate chemiluminescence reaction detection was employed. Soluble (S)- and MB-COMT activities in the rat erythrocyte were 22.9 +/- 2.5 and 4.62 +/- 1.23 pmol min-1 (mg protein)-1, respectively (n = 5). The Km values obtained for S- and MB-COMT were 366 +/- 31 mumol l-1 and 12.0 +/- 1.1 mumol l-1, respectively (n = 5), suggesting that the use of NE as a substrate would give more precise information on the role of both isoenzymes. However, with dihydroxybenzoic acid as an artificial substrate, the Km values for S- and MB-COMT were similar, with values of 69.2 +/- 11.4 mumol l-1 and 72.2 +/- 9.2 mumol l-1, respectively. The proposed method is thought to be useful for the measurement of both S-COMT and MB-COMT activities, and would give us critical information on the role of metabolism of catecholamines in rat tissues.

Animals↗

PubMed2001

Effects of light and sleep stages on heart rate variability in humans.

Effects of light intensity and sleep stages on heart rate variability (HRV) were investigated in young healthy subjects. The low-frequency (LF)/high-frequency (HF) ratio was significantly increased by exposing either to bright lights of 10 000 lx or to extreme darkness (< 0.01 lx), while HF and LF components of HRV were not changed, when compared with those under dim light (100 lx). However, LF was significantly increased at REM sleep, when compared with that at the pre-sleep wake. In contrast, HF was increased at all stages of sleep, and the LF/HF ratio was decreased at slow wave sleep during the baseline night.

Adult↗

PubMed2001

Histologic analysis of the implanted cartilage in an exact-fit osteochondral transplantation model.

PURPOSE: Osteochondral transplantation is one of the useful treatments for articular cartilage defect. However, the histologic change of the implanted cartilage has not been reported in detail. We investigated the histology of exact-fit osteochondral transplants used to repair articular cartilage defects in an animal model. TYPE OF STUDY: This was a nonrandomized control study using an animal model. METHODS: Sixteen skeletally mature female Japanese white rabbits were used in the study. The region of the femoral groove was selected as the site for the osteochondral defect. A full-thickness cylindrical defect (7 mm in diameter and 7 mm in depth) through the articular cartilage and into the subchondral bone was made using the Osteochondral Autograft Transfer System (Arthrex, Naples, FL). The entire osteochondral fragment was removed and then returned to its original site in the femoral condyle precisely. Thus, the defect was repaired with an autogenous osteochondral transplantation of exactly the same size and configuration as the defect. Specimens were obtained 2, 4, 12, and 24 weeks postoperatively and were analyzed both macroscopically and histologically. RESULTS: Macroscopically, there was smooth continuity of the articular surface and the integration of the graft to the normal host cartilage. However, histologic examination showed that the layer of the grafted cartilage was thicker than that of the normal host cartilage and the extracellular matrix of the implanted cartilage exhibited a stronger staining pattern with safranin-O fast green than the normal cartilage. Cell density was higher in the grafted cartilage, particularly in the middle and the deep zones. Round and polygonal hypertrophic clusters of chondrocytes were observed in the middle and deep zones of the grafted cartilage. CONCLUSIONS: The histologic properties of the exact-fit implanted cartilage were different from that of normal articular cartilage. Further investigation of mechanical and structural properties of grafted cartilage is necessary to verify the long-term effects of osteochondral transplantation.

Animals↗

PubMed2001

X-ray analyses of DNA dodecamers containing 2'-deoxy-5-formyluridine.

It is known that formylation of thymine base induces purine transition in DNA replication. In order to establish the structural basis for such mutagenesis, crystal structures of two kinds of DNA dodecamers d(CGCGRATf5UCGCG) with f5U = 2'-deoxy-5-formyluridine and R = A or G have been determined. The f5U residues form a Watson-Crick-type pair with A and two types of pairs (wobble and reversed wobble) with G, the latter being the first example. Structural modeling suggests that the DNA polymerase can accept the reversed wobble pair with G, as well as the Watson-Crick pair with A.

Base Pairing↗

PubMed2001

Crystallographic studies on damaged DNAs: III. N(4)-methoxycytosine can form both Watson-Crick type and wobbled base pairs in a B-form duplex.

To investigate the mutation mechanism of purine transition in DNA damaged with methoxyamine, a DNA dodecamer with the sequence d(CGCGAATTmo(4)CGCG), where mo(4)C is 2'-deoxy-N(4)-methoxycytidine, has been synthesized and its crystal structure determined. Two dodecamers form a B-form duplex. Electron density maps clearly show that one of the two mo(4)C residues forms a pair with a guanine residue of the opposite strand, the geometry being the canonical Watson-Crick type, and that the other mo(4)C residue forms a wobble pair with the opposite guanine residue. These two pairings are ascribed to the tautomerization of the methoxylated cytosine moieties between the amino and imino forms.

Base Pairing↗

PubMed2001

Crystallization and preliminary X-ray analysis of a DNA dodecamer containing 2'-deoxy-5-formyluridine; what is the role of magnesium cation in crystallization of Dickerson-type DNA dodecamers?

To investigate the role of divalent cations in crystal packing, four different crystals of a Dickerson-type dodecamer with the sequence d(CGCGAATXCGCG), containing 2'-deoxy-5-formyluridine at X, were obtained under several conditions with and without divalent cations. The crystal structures are all isomorphous. The octahedrally hydrated magnesium cations found in the major groove cement the two neighbouring duplexes along the b axis. In the Mg(2+)-free crystals, a five-membered ring of water molecules occupies the same position as the magnesium site and connects the two duplexes similarly to the hydrated Mg(2+) ion. It has been concluded that water molecules can take the place of the hydrated magnesium cation in crystallization, but the magnesium cation is more effective and gives X-ray diffraction at slightly higher resolution. In all four crystals, the 5-formyluracil residues form the canonical Watson-Crick pair with adenine residues.

Base Sequence↗

PubMed2001

Kinematic magnetic resonance imaging (MRI) of the normal shoulder: assessment of the shapes and signals of the superior and inferior labra with abductive movement using an open-type imager.

A preliminary study was conducted to evaluate the superior and inferior glenoid labra with abductive movement using an open-type MR unit in asymptomatic healthy volunteers. Both fast low angle shot (FLASH) and turbo spin echo (TSE) images were obtained to evaluate the shapes of both the superior and inferior labra, as well as to assess changes in signal at these sites. As the abduction angle was increased, the shape of the superior labrum changed from round or triangular to crescentic and a higher signal was frequently seen. At an abduction angle of 150 degrees, an increase in signal was seen in one-half of the superior labra; this increase was noted more frequently in volunteers over 40 years of age. In some of the superior labra, the increase in signal seen at 150 degrees abduction disappeared on subsequent images obtained at 0 degrees abduction. Hence, the increase in signal was considered to be a reversible change. The shape of the inferior labrum tended to change from crescentic to triangular or round. An increase in signal in the inferior labrum was unrelated to the abduction angle. Abductive kinematic studies using an open-type MR unit provides information about the morphology of the superior and inferior labra, as well as information about signal changes occurring at these sites.

Adult↗

PubMed2001

Experimental study of fast and ultrafast T2-weighted imaging sequences using AMI-25 superparamagnetic iron oxide (SPIO).

The objective of this study was to evaluate fast and ultrafast T2-weighted images (T2WI), including echo planar imaging (EPI), using an AMI-25 agar phantom. Image quality for conventional spin echo (CSE) and turbo spin echo (TSE) was almost equivalent. In high-resolution TSE, image quality was highest due to the use of a 512 x 256 matrix. Half-Fourier single-shot turbo SE (HASTE) was associated with blurring of images, and turbo-gradient SE (TGSE) showed a deterioration of image quality. EPI also suffered from poor image quality because this method is very sensitive to magnetic field inhomogeneity. CSE showed good signal-to-noise ratio (S/N) and contrast ratio (CR), but also required the longest imaging times. Among the TSE sequences, TSE with a short echo train length (ETL) was superior in terms of S/N. The CR of EPI and fast low angle shot (FLASH) images were improved in proportion to the effective echo time (TE). At present, TSE is inferior to CSE in terms of S/N and CR. However, taking into consideration scanning time, TSE with a short ETL is thought to be suitable for routine examinations. Effective TE is an important factor in gradient echo (GRE) examinations.

Contrast Media↗

PubMed2001

Low-intensity pulsed ultrasound initiates bone healing in rat nonunion fracture model.

Low-intensity pulsed ultrasound exposure has been shown clinically to shorten the fracture repair process and to induce healing of nonunions in humans, but its mechanism of action remains unclear. In this study we investigated the effect and mechanism of low-intensity pulsed ultrasound on nonunion fracture healing in rat tibias. A consistently reproducible nonunion was produced in rat tibias by muscle interposition without osteotomy. This model was produced by creating a closed tibial fracture with only the distal end of the tibialis anterior muscle interposed into the fracture site. One limb was noninvasively exposed to low-intensity pulsed ultrasound (a 200-millisecond burst of sine waves of 1.5 MHz, repeating at 1.0 kHz) for 20 minutes daily. The incident intensity was approximately 30 mW/cm2. Rats were killed at intervals between 2 and 6 weeks. The events were assessed by radiographs, microfocus X-ray computed tomograms, and histologic examination. After 6 weeks of exposure, 7 of 14 nonunion fractures showed healing on radiologic assessment. The results of three-dimensional microfocus X-ray computed tomographic reconstruction and histologic examination also supported this finding. On the other hand, all control tibias remained in a state of nonunion during the same period. These results indicate that low-intensity pulsed ultrasound promotes healing in the rat nonunion fracture model.

Animals↗

PubMed2001

[Grading of light perception and hand movement utilizing a novel device called the low vision evaluator].

PURPOSE: There has been no device for grading very low visual function expressed as light perception or hand movement up to the present. It is necessary to evaluate even slight effects of modern and classical therapies during the follow-up period. The goal of this study was to invent a novel device for grading such low visual function. METHODS: Sixty-two patients with a visual acuity of counting fingers or worse due to various diseases were examined. The device, which we call the Low Vision Evaluator, has a pair of goggles equipped with two white light-emitting diodes. Nine variations of stimulus for light intensity (1, 10, 100 cd/m2 or 10, 100, 1,000 cd/m2) and duration (0.1, 0.3, 1 second) can be delivered in a random sequence. Patients were asked to push a button whenever they saw a stimulus. Response of patients to the stimuli was recorded. RESULTS AND CONCLUSIONS: The visual function of light perception and hand movement could be reproducibly assessed by this method. The method represents a valuable new tool for evaluating low visual function.

Adult↗

PubMed2000

An automatic analyzer for catecholamines and their 3-O-methyl metabolites using a micro coulometric flow cell as a postcolumn reactor for fluorogenic reaction.

A coulometric flow cell for a miniaturized LC system was developed. The cell was examined, as 3-O-methyl catecholamines were converted to their relative omicron-quinones for subsequent fluorometric and chemiluminescence detection. Its performance was evaluated in comparison with commercially available amperometric and coulometric detectors in terms of specification of the low dead volume and high conversion efficiency. The fully automated small-bore LC analyzer for simultaneous determination of catecholamines and their 3-O-methyl metabolites included precolumn pretreatment, column switching, column separation, postcolumn oxidative conversion, fluorometric derivatization, and chemiluminescence detection. The detection limits were 0.3-2.0 fmol for catecholamines and their 3-O-methyl metabolites. Because of the high sensitivity, the required volume of rat plasma sample was only 15 microL.

Animals↗

PubMed2000

Fumonisin toxicity in a transgenic mouse model lacking the mdr1a/1b P-glycoprotein genes.

The toxicity of fumonisin B(1) (FB(1)) was investigated in male mdr1a/1b double knockout (MDRK) mice, lacking the drug-transporting P-glycoproteins. These transgenic animals are deficient in their blood:brain barrier and accumulate different drugs in brain and other tissues. The MDRK and their wild-type counterparts, FVB mice, were injected subcutaneously with 2.25 mg/kg per day of FB(1) for 5 days and sampled one day after the last treatment in a protocol that has resulted in marked hepatic and renal damage in other strains. FB(1) caused liver enlargement in both FVB and MDRK. Hematological parameters were not affected in either strain. Plasma levels of alanine aminotransferase and aspartate aminotransferase, measures of liver damage, were increased by FB(1) in both FVB and MDRK mice. Histopathological evaluation of liver corroborated this finding. Kidney lesions were induced by FB(1) in both types of mice. Concentrations of free sphingosine and sphinganine increased in liver and kidney of both strains after the FB(1) treatment, although the increase in liver sphingoid bases was half as much in MDRK as compared to FVB. The levels of sphinganine-containing complex sphingolipids were increased in kidney. The levels of sphingosine-containing complex sphingolipids in kidney were unaffected by FB(1) treatment but were significantly lower in control MDRK than in FVB mice. The levels of neurotransmitters and their metabolites were similarly affected in both strains by FB(1), suggesting no influence of disrupted blood:brain barrier on FB(1)-induced neurotoxicity. In both strains, the liver mRNA for tumor necrosis factor alpha was increased; however, the increase was statistically significant only in FVB. It was apparent that mice deficient in P-glycoprotein do not exhibit greater sensitivity to FB(1), the cellular or brain transport of FB(1) appears to be independent of this multidrug transporting system.

Journal Article↗

PubMed2000

Nontumorous decrease in Tc-99m GSA accumulation.

Nontutimorous decrease in 99mTc-GSA accumulation has not been well covered in the literature. Understanding of this phenomenon is, however, essential for accurate evaluation of regional hepatic function. Scintigrams (transaxial SPECT) of 269 patients who underwent 99mTc-GSA liver scintigraphy were reviewed for the presence of nontumorous decreases in 99mTc-GSA accumulation. Nontumorous decreases in 99mTc-GSA accumulation were seen in 32 of 269 patients (12%). In 16 of the 32 patients (6%), nontumorous decreases in 99mTc-GSA accumulation corresponded to regional decrease in portal venous flow. The causes of such decrease in portal venous flow were portal thrombus of hepatocellular carcinomas in eight patients, portal venous stenosis or occlusion by hilar cholangiocarcinomas in five patients, inter alia. In eight patients (3%), the regions with decreased 99mTc-GSA accumulation correlated with massive hepatic necrosis in fulminant hepatitis, scar in hepatitis, or confleuent in portal venous flow, lobar biliary stasis, or both. In four patients (1.5%), the exact causes of nontumorous decrease in 99mTc-GSA accumulation could not be determined.

Adult↗

PubMed2000

Fumonisin hepatotoxicity is reduced in mice carrying the human tumour necrosis factor alpha transgene.

Our previous studies have indicated that tumour necrosis factor alpha (TNFalpha) is involved in fumonisin B1 (FB1)-induced toxic responses. To investigate the role of TNFalpha in FB1 toxicity further we employed male transgenic mice expressing human TNFalpha gene (TG) and their wild-type equivalent C57BL/6 (WT). It was hypothesized that TG animals would have enhanced response to FB1. Repeated subcutaneous treatment of animals with 2.25 mg/kg per day of FB1 for 5 days caused minimal changes in body weight, organ weights, blood cell counts, and TNFalpha levels in plasma 1 day after the last injection. The mRNA for TNFalpha in liver increased in both TG and WT after FB1 treatment, providing evidence that FB1 induces hepatic TNFalpha expression. Liver and kidney lesions were found in TG after FB1 treatment; however, liver lesions seen in FB1-treated TG were considerably less than those observed in WT. The decreased hepatotoxicity in TG after FB1 treatment correlated with plasma concentrations of alanine aminotransferase and aspartate aminotransferase. Free sphinganine levels increased significantly in both the liver and kidney of WT and TG mice treated with FB1. The increase of free sphinganine in the liver from TG mice was 40% less than in WT mice and paralleled the changes in serum liver enzymes. Regional brain neurotransmitters and their metabolites were increased to a similar extent by FB1 in both WT and TG mice. Since the data did not support the original hypothesis, we investigated the levels of NFkappaB in liver. The cytosolic NFkappaB was significantly higher in TG compared with WT. Induction of NFkappaB, caused by increased endogenous production of TNFalpha, is a possible explanation of decreased FB1 hepatotoxicity in TG. The results suggest a protective role for NFkappaB in FB1-induced liver damage.

Alanine Transaminase↗