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Biomedical subjects

M Nasu

Publications and source records attributed to M Nasu.

At least 181 records · Page 10Linked to original sources
PubMed1997

Sequential analyses of the mutations in the core upstream and precore regions of hepatitis B virus genome in anti-HBe positive-carriers developing acute exacerbation.

The nucleotide sequences of the core upstream and precore regions (371 nucleotide length, nt. 1604-1974) of hepatitis B virus (HBV) were analysed sequentially in three subjects who were positive serologically for anti-HBe and had acute clinical exacerbation after immunosuppressive treatment. These patients were asymptomatic HBV carriers before therapy. The results revealed that the mutant with an 8-bp deletion (nt. 1768-1775) located in the basic core promoter region was dominant in the asymptomatic HBV carrier phase in two of three subjects. After exacerbation, however, such mutant clones possessing 8-bp deletion disappeared or decreased in number and were replaced by the clones possessing a precore stop codon mutation G to A (nt. 1896) or by the clones possessing additional contiguous point mutations A to T (nt. 1762) and G to A (nt. 1764) and a new point mutation C to T (nt. 1653). Possible relationships between acute exacerbation of liver function accompanied by mutation and the transition of the dominant clones were discussed.

Acute Disease↗
PubMed1997

Clinical usefulness of the effective regurgitant orifice area determined by transesophageal echocardiography in patients with eccentric aortic regurgitation.

BACKGROUND AND AIMS OF THE STUDY: The aortic regurgitant jet is frequently eccentric, and Doppler color flow mapping techniques of the distal jet is influenced by this eccentricity. The aim of the present study was to determine whether the effective regurgitant orifice area (EROA), determined by the proximal isovelocity surface area (PISA) method using multiplane transesophageal echocardiography (m-TEE), could be used to evaluate the severity of aortic regurgitation (AR) in patients with an eccentric jet. METHODS: Forty-eight patients with eccentric AR were studied. Values of EROA determined by the PISA method were compared with results from cross-sectional area (CSA), vena contracta (VC) width, aortic angiography, and regurgitant fraction. RESULTS: Values of EROA correlated well with results from CSA (r = 0.73, p < 0.001), VC (r = 0.74, p < 0.001), angiographic grade (rs = 0.90 p < 0.001), and regurgitant fraction (r = 0.84, p < 0.001) in patients with eccentric aortic regurgitation. Values of EROA > 0.27 cm2 were always associated with a regurgitant fraction > 0.4, while EROA values < 0.27 cm2 were always associated with a regurgitant fraction < 0.4. CONCLUSIONS: We conclude that, in patients with an eccentric jet, measurement of EROA values by the PISA method using m-TEE is a reliable method of assessing the severity of AR.

Aorta, Thoracic↗
PubMed1996

Optical imaging of spatiotemporal patterns of glutamatergic excitation and GABAergic inhibition in the guinea-pig auditory cortex in vivo.

1. Glutamatergic excitation and gamma-aminobutyric acid (GABA)-ergic inhibition in layers II and III of the auditory cortex of anaesthetized guinea-pigs were recorded optically using a voltage-sensitive dye RH795 and a 12 x 12 photodiode array. 2. After contralateral ear stimulation with pure tones, transient excitatory responses followed by inhibitory responses were observed in fields A (primary) and DC of the auditory cortex. The area of the excitatory responses was sandwiched or surrounded by the areas of the inhibitory responses. 3. Optically recorded excitatory responses to pure tones had two components: a component sensitive to 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), a non-N-methyl-D-aspartate (non-NMDA) receptor antagonist, and a component sensitive to 2-amino-5-phosphono-valerate (APV), an NMDA receptor antagonist. Application of CNQX (5 microM) to the auditory cortex suppressed an early, but not a late, phase of the excitation; application of APV (100 microM) had the opposite effect. Concomitant application of CNQX and bicuculline methiodide (BMI, 4 microM), a GABAA receptor antagonist, increased the amplitude of the late phase 4-fold. This enhanced response was suppressed by APV. 4. These results indicate that (i) auditory cortical excitatory responses are mediated by both non-NMDA and NMDA receptors, (ii) inhibition is mediated by GABAA receptors, (ii) the excitatory bands are sandwiched or surrounded by GABAA receptor-mediated inhibitory areas and (iv) GABAA receptors effectively inhibit the NMDA, but not the non-NMDA, receptor-mediated excitation.

2-Amino-5-phosphonovalerate↗
PubMed1996

Molecular typing of Helicobacter pylori: differences in pathogenicity among diverse strains.

Helicobacter pylori appears to be a species with strain diversity, according to studies carried out using various molecular biological techniques. Differences in pathogenicity caused by the strain diversity of H. pylori were therefore investigated. Two hundred and thirty strains were divided into four types by polymerase chain reaction-restriction fragment length polymorphism, and their relationship to endoscopic diagnosis, ammonia concentration of gastric juice, and urease activity were assessed. With regard to incidence by type, patients infected with type 1, type 2, and type 3 exhibited the highest incidences of gastric ulcer, duodenal ulcer, and gastritis, respectively. The urease activity of type 2 was significantly lower than that of types 1 and 3 (P < 0.05). These observations suggest differences in pathogenicity due to the strain diversity of H. pylori. However, the diversity of diseases related to H. pylori is also presumed to be caused by both the diversity of H. pylori strains and differences in the host immunological reaction. Future studies should be directed toward clarifying the entire pathogenic mechanism of H. pylori infection.

Bacterial Typing Techniques↗
PubMed1996

Diverse inotropic effects of 5-hydroxytryptamine in heart muscles of various mammalian species.

The inotropic effects of 5-hydroxytryptamine (5-HT) on mammalian heart muscles were investigated. 5-HT (10(-8)-10(-3)M) produced increases in the contractile tension of atrial and ventricular muscles isolated from guinea pigs, Japanese monkeys, and humans, but not in rat heart preparations. The maximum percent increase of contraction was largest in guinea pig ventricular muscles (142.0 percent), followed by monkey atrium (86.3 percent), human atrium (71.7 percent), guinea pig atrium (48.7 percent), and monkey ventricle (30.1 percent). The sensitivity to 5-HT, measured as the negative logarithm of the half-maximal inotropic molar contractions of 5-HT, i.e., -logEC(50), was highest in the human atrium (6.65 +/- 0.20), followed by guinea pig atrium (5.53 +/- 0.36), monkey ventricle (4.83 +/- 0.28), guinea pig ventricle (4.56 +/- 0.11), and monkey atrium (4.46 +/- 0.16). The inotropic effects of 5-HT seen in the atrial and ventricular muscles of guinea pigs were abolished in the presence of the beta-receptor blocker, pindolol (8 mu M), while these effects in human atrial muscles and monkey atrial and ventricular muscles were abolished only in the presence of both pindolol (8 mu M) and of prazosin (1 mu M), an alpha(1)-receptor blocker. 5-HT increased the V(max) of the slow response recorded from guinea pig ventricular muscles exposed to high K+ (27 mM) media, whereas this agent did not alter the calcium current of isolated guinea pig ventricular myocytes devoid of sympathetic nerve terminals. In reserpinized guinea pig hearts, 5-HT exerted no inotropic effect on ventricular muscle, yet it had an inotropic effect in the atrial muscle, although the latter effect was considerably depressed, compared to that seen in non-reserpinized atrial muscles. We conclude that the positive inotropic effects of 5-HT observed in the ventricular muscle of the guinea pig and in the atrial and ventricular muscles of the Japanese monkey can be attributed to the release of noradrenaline from sympathetic nerve terminals (indirect effect). In contrast, in human atrial muscles, the positive inotropic effect of 5-HT was apparently the result of stimulation of a specific membrane receptor for 5-HT (direct effect). In guinea pig atrial muscles, both direct and indirect effects of 5-HT were involved in the positive inotropism. An explanation for the lack of sensitivity of rat atrial and ventricular muscles to 5-HT awaits further studies.

Adrenergic Fibers↗
PubMed1996

Flow reserve capacity of left internal thoracic artery 23 years after Vineberg procedure.

Graft flow volume and flow reserve were assessed by Doppler echocardiography 23 years after Vineberg left internal thoracic artery implantation. Angiography showed good patency of the left internal thoracic artery, and the flow velocity profile was as biphasic as that of the coronary circulation. Drug-stressed test showed a physiologic reactivity of the Vineberg left internal thoracic artery but less response than that of a directly anastomosed left internal thoracic artery.

Blood Flow Velocity↗
PubMed1996

Cloning and sequencing of the spore germination gene of Bacillus megaterium ATCC 12872: similarities to the NaH-antiporter gene of Enterococcus hirae.

The germination mutant TM-31 of Bacillus megaterium ATCC 12872, was isolated by transposon Tn917 insertional mutagenesis. Glucose, L-proline, L-leucine and KNO3 germinated TM-31 poorly. The DNA in the region of the Tn917 insertion was cloned, and its nucleotide sequence determined. One major open reading frame was present on the cloned DNA. The hydrophobic protein encoded is presumably membrane-associated. A homology search revealed that the gene encoded in the region of the Tn917 insertion is homologous to napA of Enterococcus hirae. napA codes for the NaH-antiporter. It is hypothesized that transport of cations must play an important role in spore germination in B. megaterium ATCC 12872.

Amino Acid Sequence↗
PubMed1996

Helicobacter pylori infection delays the healing of acetic acid-induced gastric ulcer in Japanese monkeys.

To clarify the relationship between Helicobacter pylori and the healing of gastric ulcers, we investigated the healing of acetic acid-induced gastric ulcers in the antral mucosa of Japanese monkeys (n = 5) infected with H. pylori and in control monkeys without H. pylori infection (n = 6). Using H. pylori-infected Japanese monkeys as an experimental model, gastric ulcers were induced endoscopically with acetic acid. Healing of ulcers and factors that influenced healing were studied. Continuous colonization with H. pylori was confirmed in the infected group throughout the observation period; no H. pylori were isolated from the gastric mucosa of the control group. White scarring was not observed in any infected monkeys 4 weeks after ulcer formation, but was observed in one (20%) of five monkeys at 6 weeks and in all five monkeys eight weeks after ulcer formation. In the control group, white scarring was observed in one (16.7%) of six monkeys at 4 weeks and in six monkeys at 6 (P < 0.01 vs infected group) and 8 weeks. The ammonia concentration of the gastric secretions and the grade of inflammation were significantly increased in the H. pylori-infected group compared with the control group (P < 0.01 and P < 0.001, respectively). The volume of intracellular PAS-positive substance was decreased (P < 0.025-0.01) at the ulcer margin in the infected group compared with the ulcer margin in the control group. The proliferation of gastric epithelial cells was markedly accelerated at the ulcer margin in the infected group compared with the ulcer margin in control group (P < 0.025-0.01). Our results strongly suggest that H. pylori infection delays the healing of gastric ulcers.

Acetic Acid↗
PubMed1996

[Detection of DNA specific for Aspergillus species in serum samples from two patients with invasive pulmonary aspergillosis].

We investigated the possible presence of DNA specific for Aspergillus species in serum samples of two patients who were strongly suspected for invasive pulmonary aspergillosis (IPA) by a nested polymerase chain reaction (PCR) method. Both patients were diagnosed as having acute myelogenous leukemia and treated with induction chemotherapy. During chemotherapy-induced granulocytopenia, they complained of high fever, and the chest X-rays indicated infiltration shadows in their lungs. They were treated with antibiotics intravenously, but no clinical improvement was observed. As the results of the nested PCR were positive at the acute stage of infection, amphotericin B i.v. and granulocyte colony stimulating factor s.c. administrations were started in both cases. In case 1, the infectious disease improved and the nested PCR results turned negative after treatment. In case 2, in spite of the progression of the disease, the nested PCR results turned negative during treatment. Although we consider this method very useful for the diagnosis of IPA, further prospective evaluation with a large clinical population sample is required.

Aged↗
PubMed1996

[Prevention of infections in a case with myelodysplastic syndrome by an intermittent subcutaneous administration of G-CSF].

An 83-year-old male was admitted to our hospital because of pancytopenia and low grade fever on April 19, 1993. On admission, hematological data were as follows: WBC 1,000/microliters with 19% neutrophils, RBC 367 x 10(4)/microliters, Hb 9.5 g/dl and platelets 6.7 x 10(4)/microliters. Bone marrow examination revealed 6.6% myeloblasts and 33.5% erythroblasts. Morphological abnormalities included hypersegmentation, degranulation and pseudo-Pelger's nuclear anomaly in neutrophils. Based on these findings the diagnosis of refractory anemia with excess of blasts (RAEB) of the myelodysplastic syndrome (MDS) was made and therapy with low dose Cytarabine (Ara-C) was initiated in April 1993. The patient had two episodes of severe pneumonia in June and July. Therefore, 75 micrograms/day of G-CSF was given in addition to antibiotic therapy for the second episode of infection in July. Thereafter the severe infection subsided, and G-CSF administration was switched to an intermittent schedule (75 micrograms twice a week) since September. Cytarabine ocfosfate (100 mg/day) was added for 10-14 days at interval 1-2 months from October,1993. He has been well with no episode of infection for more than two year. One major concern regarding the clinical application of G-CSF in MDS patients is related to the possible stimulation of leukemic cell proliferation. Frequent hematological monitoring is necessary in patients with RAEB who are prone to develop acute myeloid leukemia. However, we administered G-CSF at a relatively low dose twice a week for over two year and could successfully prevent infections without inducing the leukemic changes.

Aged↗
PubMed1996

Detection of specific bacterial cells with 2-hydroxy-3-naphthoic acid-2'-phenylanilide phosphate and fast red TR in situ hybridization.

An in situ hybridization technique with HNPP (2-hydroxy-3-naphthoic acid-2'-phenylanilide phosphate) and Fast Red TR was used to detect specific bacterial cells at the single-cell level. By this technique, the fluorescent signals of target bacterial cells were up to eight times more intense than those of standard fluorescence in situ hybridization with mono-fluorescein isothiocyanate-labeled oligonucleotide probes. This novel HNPP-Fast Red TR whole-cell hybridization technique is available for the identification of small or low-rRNA-content bacterial cells in the natural environment.

Bacteria↗
PubMed1996

PCR detection of DNA specific for Aspergillus species in serum of patients with invasive aspergillosis.

We investigated the possible presence of DNA specific for Aspergillus species in serum samples of patients with invasive aspergillosis (IA) by the nested PCR method. Fourteen strains of fungi including 5 strains of Aspergillus species and 10 strains of common bacteria were used for examination of specificity and sensitivity of the nested PCR. Two sets of oligonucleotide primers were derived from the sequence of the variable regions V7 to V9 of the 18S rRNA genes of Aspergillus fumigatus. The specific fragment was amplified from five strains of Aspergillus species in the single and nested PCR but not from other microorganisms. Target DNA was detected by the nested PCR with as little as 50 fg of the extracted DNA of A. fumigatus. We investigated the detection of DNA specific for Aspergillus species in serum samples of a murine model of aspergillosis and 20 patients with IA. The specific fragment was detected by the nested PCR in 71% of serum samples of infected mice and 70% of serum samples of patients with IA, while galactomannan antigen was detected in 43 and 60% of samples, respectively. The high sensitivity and specificity of the nested PCR indicate that the assay can provide early diagnosis with sufficient accuracy to be clinically useful for immunocompromised patients with IA.

Animals↗
PubMed1996

In vitro susceptibility of Trichosporon beigelii to antifungal agents.

The minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) of amphotericin B, flucytosine, miconazole, fluconazole and itraconazole against 21 isolates of Trichosporon beigelii in RPMI-1640 medium were determined using National Committee for Clinical Laboratory Standards (NCCLS) methodology in microdilution method. Most isolates were sensitive to miconazole (MIC90 0.78 microgram/ml), fluconazole (MIC90 6.25 micrograms/ml), and itraconazole (MIC90 0.19 microgram/ml), with the former being the most active agent tested (MFC90 3.12 mu/ml). Although amphotericin B inhibited most strains (MIC range, 0.78-3.12 micrograms/ml), poor fungicidal activity was observed (MFC range, 1.56-12.5 micrograms/ml) showing a pattern of relative resistance in vitro. Flucytosine showed generally poor activity against most isolates tested. These in vitro findings confirm the resistance of T.beigelii to amphotericin B and suggest that azoles may be an alternative to the former for the treatment of disseminated trichosporonosis. However, in vivo studies would better validate these in vitro findings.

Amphotericin B↗
PubMed1996

Estrogen blocks parathyroid hormone (PTH)-stimulated osteoclast-like cell formation by selectively affecting PTH-responsive cyclic adenosine monophosphate pathway.

Several lines of evidence have previously indicated that estrogen inhibits PTH-induced bone resorption in vivo and in vitro. However, its mechanism remains unknown. Therefore, the present study was performed to investigate the effect of estrogen on PTH-stimulated osteoclast-like cell formation and clarify its mechanism. 17 beta-estradiol (17 beta-E2) significantly antagonized osteoclast-like cell formation stimulated by 10(-8) M human (h) PTH-(1-34) as well as 10(-8) M hPTH-related peptide (PTHrP)-(1-34)in osteoblast-containing mouse bone cell cultures. The conditioned medium derived from osteoblastic SaOS-2 cells or MC3T3-E1 cells pretreated with both PTH-(1-34) (10(-8)M) and 17 beta-E2(10(-8)M) stimulated osteoclast-like cell formation from hemopoietic blast cells more weakly than conditioned medium from cells pretreated with PTH-(1-34) alone. Moreover, 10(-8) M 17 beta-E2 significantly blocked the formation of osteoclast-like cells stimulated by 10(-8) M hPTH-(1-34) in spleen cell cultures derived from 5-fluorouracil-pretreated mice. On the other hand, 10(-8) M 17 beta-E2 significantly inhibited osteoclast-like cell formation stimulated by dbcAMP (10(-4)M) and Sp-cAMPS (10(-4)M), as well as forskolin (10(-5)M) in mouse bone cell cultures. In contrast, 10(-8)M 17 beta-E2 did not affect PMA (10(-7)M)-, A23187 (10(-7)M)-, or BAYK-8644 (5 x 10(-6) M)-stimulated osteoclast-like cell formation. In conclusion, the present study demonstrated that estrogen inhibits PTH-stimulated osteoclast-like cell formation by directly acting on hemopoietic blast cells as well as by indirectly acting on them via osteoblasts. The inhibitory effects of estrogen on PTH-stimulated osteoclast-like cell formation seemed to be mediated through blocking the cAMP-dependent protein kinase pathway but not by blocking calcium/protein kinase C.

Animals↗
PubMed1996

[Effect of (-)-N-[(S)-hexahydro-l-methyl-2, 6-dioxo-4-pyrimidinylcarbonyl]-L-histidyl-L-prolinamide (TA-0910), a new TRH analog, on plasma levels of TSH and thyroid hormones in rats].

The stimulatory effect of TA-0910 on the secretions of thyroid-stimulating hormone (TSH) and thyroid hormones was investigated in male and female rats. Single intravenous administration of TA-0910 at 8.3 nmol/body acutely elevated the plasma TSH level, with delayed and moderate increases of T3 and T4 in plasma. Similar increments of plasma TSH and thyroid hormones were observed when TRH was injected at the dose of 0.83 nmol/body. Oral administration of TA-0910 at 2.75 mumol/body was equally potent or slightly more potent to secrete TSH than TRH at 0.275 mumol/body. The elevated TSH by TA-0910 decreased to the control level within 2 hr after intravenous injection or within 6 hr after oral administration; on the other hand, the higher levels of the thyroid hormones were retained for up to 4 and 6 hr after intravenous and oral administration, respectively. These findings indicate that TA-0910 and TRH stimulate the secretion of TSH and thyroid hormones by a similar manner and that the TSH-secreting activity of TA-0910 is lower by an order of magnitude compared with that of TRH.

Administration, Oral↗
PubMed1996

Electrocardiographic diagnosis of left circumflex artery occlusion and the occlusion site.

In patients with a posteroinferior acute myocardial infarction and both ST depression (in lead V1 or V2) and ST elevation in the inferior leads, it is difficult to differentiate a left circumflex artery occlusion from a right coronary artery occlusion. Furthermore, there is no useful method to identify the obstruction site in the left circumflex artery. In a study of 52 patients with single-vessel left circumflex artery disease, ST elevation in V6 was found to be a useful indicator for left circumflex artery occlusion in such patients. Furthermore, the sum of the ST changes in leads a VF and V2 is useful for identifying the occluded site in the left circumflex artery.

Aged↗