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Biomedical subjects

M Taki

Publications and source records attributed to M Taki.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Laboratory tests for detection of antiphospholipid antibodies].

Antiphospholipid antibodies(APA) have been reported to be a heterogeneous family of immunoglobulins. Some APA can be detected via phospholipid dependent coagulation assays when they present as an aspecific coagulation inhibitor, lupus anticoagulant(LA), other antibodies can be measured via immunological assays mostly via their capability to bind to immobilized cardiolipin (anticardiolipin antibody; aCL). Despite their name, APA associated with antiphospholipid syndrome(APS) do not bind phospholipids, but are directed at plasma proteins bound with anionic phospholipids. The antigenic targets of these antibodies include beta 2 glycoprotein I(beta 2 GP I), prothrombin, high- and low-molecular-weight kininogens, annexin V, protein C and protein S. In this article, the current knowledge on the methods of detection and their functional properties are reviewed, and the interaction of these antibodies and acquired activated protein C resistance are discussed.

Antibodies, Antiphospholipid↗
PubMed2000

Influence of walkoff on pattern formation in nondegenerate optical parametric oscillators.

Convective and absolute nature of instabilities in nondegenerate optical parametric oscillators with large transverse section, for negative detunings and in the presence of walkoff, is examined. The asymptotic response of the signal and idler fields to a transverse localized two-dimensional perturbation is evaluated. The presence of walkoff breaks the rotational symmetry in the transverse plane, and the system, at the absolute instability threshold, selects traveling waves propagating in the walkoff direction among an infinity of unstable spatiotemporal modes. We show that in optical parametric oscillators (OPO's) with negative detunings, contrary to the case of positive detunings, the walkoff shrinks the region of convective instabilities, and even may suppress the convective/absolute transition. Hence, in a certain range of parameters, signal field envelopes in the form of wave packets of zero group velocity are found where the instability is absolute at the onset, although the walkoff is present. We also show that nonlinear pattern selection is ruled by the cross-coupling terms appearing in the asymmetric coupled Ginzburg-Landau equations derived near-threshold of the signal and idler generation. The numerical solutions of the original OPO equations confirm the analytical predictions for the values of the instability thresholds and the corresponding selected patterns.

Journal Article↗
PubMed2000

Hydrogen atom abstraction by Cu(II)- and Zn(II)-phenoxyl radical complexes, models for the active form of galactose oxidase.

The Cu(II) and Zn(II) complexes of phenoxyl radical species [M(II)(L1*)(NO3)]+ (M=Cu or Zn, L1H: 2-methylthio-4-tert-butyl-6-[[bis[2-(2-pyridyl)ethyl]amino]methyl]phenol ) and [M(II)(L2*)(NO3)]+ (M=Cu or Zn, L2H: 2,4-di-tert-butyl-6-[[bis[2-(2-pyridyl)ethyl]amino]methyl]phenol) are prepared as model complexes of the active form of galactose oxidase (GAO). Hydrogen atom abstraction of 1,4-cyclohexadiene and tert-butyl substituted phenols by the GAO model complexes proceeds very efficiently to give benzene and the corresponding phenoxyl radical or its C-C coupling dimer as the oxidation products, respectively. Kinetic analyses on the oxidation reactions have shown that the hydrogen atom abstraction of the phenol substrates is significantly enhanced by the coordinative interaction of the OH group to the metal ion center of the complex, providing valuable insight into the enzymatic mechanism of the alcohol oxidation. Details of the substrate-activation process have been discussed based on the activation parameters (deltaH* and deltaS*) of the reactions.

Copper↗
PubMed2000

Aliphatic Hydroxylation by a Bis(µ-oxo)dicopper(III) Complex.

By using molecular oxygen bis(µ-oxo)dicopper(III) complexes can be produced from Cu(I) complexes with ligand L(X) (L(X)=p-substituted N-ethyl-N-[2-(2-pyridyl)ethyl]-2-phenylethylamine; X=OMe, Me, H, Cl, NO(2)) in which the benzylic position of the ligand is activated and hydroxylated by the Cu(2)O(2) core (see reaction scheme). Detailed characterization of this new C-H bond activation reaction by the bis(µ-oxo)dicopper(III) core reveals important information on the fundamental chemistry underlying copper monooxygenase reactivity.

Journal Article↗
PubMed2000

Isolation of 10-hydroxycoronaridine from Tabernaemontana penduliflora and its estrogen-like activity.

The methanol extract of Tabernaemontana penduliflora was found to appreciably inhibit [3H]-estradiol binding to estrogen receptors. Activity-guided fractionation led to the isolation of two known alkaloids, 10-hydroxycoronaridine (1) and its 10-O-methyl ether, voacangine (2). These alkaloids together with other related alkaloids were tested for their estrogenic activities. Among these molecules, 1 was found to be the most potent estrogen agonist and is distinctly more active than genistein.

Cell Division↗
PubMed2000

Order parameter description of walk-off effect on pattern selection in degenerate optical parametric oscillators

Degenerate optical parametric oscillators can exhibit both uniformly translating fronts and nonuniformly translating envelope fronts under the walk-off effect. The nonlinear dynamics near threshold is shown to be described by a real convective Swift-Hohenberg equation, which provides the main characteristics of the walk-off effect on pattern selection. The predictions of the selected wave vector and the absolute instability threshold are in very good quantitative agreement with numerical solutions found from the equations describing the optical parametric oscillator.

Journal Article↗
PubMed2000

Stereochemistry of cis- and trans-hinokiresinol and their estrogen-like activity.

Naturally occurring phenylpropanoids, hinokiresinol (trans-hinokiresinol) and nyasol (cis-hinokiresinol) were found to possess appreciable estrogen receptor binding activity. Strong differences in activity were observed between the geometrical isomers and enantiomers. Among these, (3S)-cis-hinokiresinol displayed the highest activity, one order of magnitude greater than the activity of genistein. Furthermore, cis- and trans-hinokiresinol stimulated the proliferation of estrogen-dependent T47D breast cancer cells, and their stimulatory effects were blocked by an estrogen antagonist, indicating that the compounds are estrogen agonists. In addition, the absolute configuration of C-3 in (+)-cis-hinokiresinol has been assigned as S by comparison with the circular dichroism spectra of the hydrogenated products prepared from cis and trans ((3S)-trans-hinokiresinol: previously assigned) isomers. These results incidentally provide us with an unambiguous answer to contradictory reports regarding the assignment of the full stereochemisry of cis- and trans-hinokiresinol that have existed in the literature for more than two decades.

Animals↗
PubMed2000

Structures of 4-aryl-coumarin (neoflavone) dimers isolated from Pistacia chinensis BUNGE and their estrogen-like activity.

Activity-guided fractionation of twigs of Pistacia chinensis resulted in the isolation and characterization of two novel ingredients as potent estrogen agonists. On the basis of spectral analysis and comparison with a related compound their structures were elucidated as 3,3''-dimers of 4-aryldihydrocoumarins (3,4-dihydro-4-(4'-hydroxyphenyl)-7-hydroxycoumarin) differing only in the stereochemical disposition of the linkage between the two 4-arylcoumarin moieties. These compounds are the first examples of bis-flavonoids which have been proven to possess estrogen-like activity.

Animals↗
PubMed2000

Normal and abnormal day-to-day variability of urinary albumin excretion in control and diabetic subjects.

Urinary albumin excretion (UAE) is very variable from day to day. This variability, more or less potent, might by itself have a patho-physiological significance. We analyzed day-to-day UAE in 207 elderly (60-75 years) inpatients (134 with and 73 without diabetes mellitus) attending the department of internal medicine of the Angers University hospital. Twenty-four-hour urine was collected 3 times during a 5-10 day hospitalization period. One-hundred-fifty-one patients (73%) displayed normoalbuminuria (UAE<30 mg/24 h in 2 or 3 measures) while 56 patients (27%) had microalbuminuria (UAE within 30-300 mg/24 h in 2 or 3 measures). As the raw data of UAE was not normally distributed, we transformed UAE into the variable z=log (log (k + UAE)) where k is an integer and looked for a k value for which z might be normally distributed. We found that z was actually normally distributed for k=2. Mean value and coefficient of variation of z in the 3 measurements were used to define the level and the temporal intra-individual variability of UAE. Expressed in term of z, the day-to-day intra-individual variability of UAE showed a potent change (from large variability to small variability) at the particular level z=1.25, corresponding to UAE=30.8 mg/24 h. This value is precisely the level currently used to define microalbuminuria in diabetic subjects. It is remarkable that the day-to-day variability of UAE collapses when UAE crosses the level which has been used to define microalbuminuria.

Aged↗
PubMed2000

Analysis of induced currents in a rat exposed to 50 Hz linearly and circularly polarized magnetic fields.

This paper presents a numerical analysis of currents induced in a rat by linearly and circularly polarized magnetic fields of 50 Hz. Special focus was placed on pineal gland and retina of rats since these organs were often associated with the changes of melatonin synthesis and concentration. Induced currents in two MRI-based rat models with resolutions of up to 0.125 mm(3) were calculated by using the impedance method. We characterized the induced currents by amplitude and polarization. Calculated induced current densities were extremely small, i.e., < 30 microA/m(2) for both linearly and circularly polarized magnetic fields of 1.41 microT (peak). There were no significant differences in amplitude nor polarization of induced currents in the pineal gland between the linearly and the circularly polarized magnetic fields when the polarization was in a vertical plane. In contrast, the magnetic fields rotating in the horizontal plane produced most circularly polarized currents both in the pineal gland and in the retina.

Animals↗
PubMed2000

Biological and morphological effects on the brain after exposure of rats to a 1439 MHz TDMA field.

We investigated the effects of exposure to a 1439 MHz TDMA (Time Division Multiple Access) field, as used in cellular phones, on the permeability of the blood-brain barrier (BBB), on the morphological changes of the brain, and on body-mass fluctuations. Male Sprague-Dawley (SD) rats were divided into three groups of eight rats each. The rats in the EM(+) group, which had their heads arrayed in a circle near the central antenna of an exposure system, were exposed to a 1439 MHz field for one hour a day. The rats in EM(-) group were also in the exposure system, however, without high-frequency electromagnetic wave (HF-EMW) exposure. The animals in the control group were neither placed in the system nor exposed to HF-EMWs. The exposure period was two or four weeks. The energy dose rate peaked at 2 W/kg in the brain; the average over the whole body was 0.25 W/kg. The changes in the permeability of BBB were investigated by Evans blue injection method and by immunostaining of serum albumin. HF-EMWs had no effect on the permeability of BBB. The morphological changes in the cerebellum were investigated by assessing the degeneration of Purkinje cells and the cell concentration in the granular layer. No significant changes were observed in the groups of rats exposed to HF-EMWs for two or four weeks. Averaged body masses were not affected by HF-EMWs exposure. In conclusion, a 1439 MHz TDMA field did not induce observable changes in the permeability of the BBB, morphological changes in the cerebellums, or body mass changes in rats, as evaluated by the conventional methods.

Animals↗
PubMed2000

[Normal and abnormal daily variability of urinary excretion of albumin].

Urinary albumin excretion (UAE) is very variable from day to day. We analyzed day-to-day UAE in 207 elderly (60-75 years) inpatients (134 with and 73 without diabetes mellitus) attending the department of internal medicine of the Angers University hospital. Twenty-four-hour urine was collected 3 times during a 5-10 day hospitalization period. One-hundred-fifty-one patients (73%) displayed normoalbuminuria (UAE < 30 mg/24 h in 2 or 3 measures) while 56 patients (27%) had microalbuminuria (UAE within 30-300 mg/24 h in 2 or 3 measures). As the raw data of UAE was not normally distributed, we transformed UAE into the variable z = log(log(k+ UAE)) where k is an integer. We found that z has a gaussian distribution for k = 2. Mean value and coefficient of variation of z in the 3 measurements were used to define the level and the temporal intra-individual variability of UAE. Expressed in term of z, the day-to-day intra-individual variability of UAE showed a potent change (from large variability to small variability) at the particular level z = 1.25, corresponding to UAE = 30.8 mg/24 h, which is precisely the level currently used to define microalbuminuria in diabetic subjects.

Aged↗
PubMed1999

Partial nucleotide sequencing of the NS3/helicase region of hepatitis G virus to prove vertical transmission.

To study non-parental transmission of hepatitis G virus and/or GB virus C (HGV/GBV-C), we sequenced and compared the NS3/helicase region of the virus for five HGV/GBV-C RNA-positive mothers and their 11 children who had experienced neither blood transfusion nor overt hepatitis and were negative for HBV, HCV and HIV, except in one mother coinfected with HCV. The nucleotide sequences of the familial HGV/GBV-C isolates showed high similarity of 99-100% (mean 99.8%, 100% at the deduced amino acid level) between mother and her child(ren) in each family. These findings strongly suggest the spontaneous occurrence of mother-to-child transmission of HGV/GBV-C as reported previously. They also suggest that nucleotide sequence analysis on the NS3/helicase region of HGV/GBV-C may be a useful tool to study HGV/GBV-C transmission.

Adult↗
PubMed1999

Oxidation of Benzyl Alcohol with Cu(II) and Zn(II) Complexes of the Phenoxyl Radical as a Model of the Reaction of Galactose Oxidase.

Profound insights into the catalytic mechanism of galactose oxidase (GO) are offered by new models of the active form of the metalloenzyme. The important role of the Cu(II) center in the oxidation of benzyl alcohol to benzaldehyde by the Cu(II)-phenoxyl radical complex of ligand 1 has been revealed by comparison with the reactivity of the corresponding Zn(II)-phenoxyl radical complex; py=2-pyridyl.

Journal Article↗
PubMed1999

Prevalence and persistence of a novel DNA TT virus (TTV) infection in Japanese haemophiliacs.

To clarify the clinical implication of a newly discovered 'TT virus (TTV)', we assayed TTV DNA in sera from 50 haemophiliacs by a seminested-PCR. TTV DNA was detected in 75% (35/50), which was a much higher prevalence than for HBV (HBc-Ab), HCV RNA, or HGV RNA. In particular, TTV DNA was found in 44.4% (4/8) of patients who had been treated only with virally inactivated factor VIII concentrates. Elevated ALT levels were observed in patients with HCV RNA and TTV DNA; however, the elevation in TTV DNA was obtained from patients co-infected with HCV RNA (62.9%, 22/35). There was no significant difference in ALT levels between TTV DNA-positive and DNA-negative in patients without HCV RNA. 85.3% (35/41) of TTV DNA-positive sera in 1990 were again positive for TTV DNA in 1995. These findings suggest that many haemophiliacs have been infected with TTV. Although TTV infection was not associated with serum ALT elevation, persistent TTV infection may contribute to cryptogenic hepatic failure in haemophiliacs.

Adolescent↗
PubMed1999

[Causes of death (1983-1997) in patients infected with human immunodeficiency virus by contaminated blood coagulation factor products: report of the clinical study group on prevention and treatments of HIV infection].

Our group conducted a national survey of patients who had died of acquired immunodeficiency syndrome (AIDS) after being infected with human immunodeficiency virus type 1 (HIV-1) by contaminated blood coagulation factor products. A total of 1446 hospitals, clinics, and other health-care institutions throughout Japan were enrolled in the study, which was supported by the Japanese government Ministry of Health and Welfare with a health sciences grant for research on HIV/AIDS. Of the 1434 registered patients who had been infected with HIV-1 by contaminated blood coagulation factor products, 493 (34%) had died as of Oct. 30, 1997. Most were hemophiliacs. The average CD4+ cell count was 25/microliter for the 398 who died of complications from AIDS, compared to an average of 158/microliter for those who died of other causes. Pneumocystis carinii pneumonia, cytomegalovirus infection, and atypical mycobacterial disease were the main causes of death in patients with AIDS. The annual death rate for AIDS patients in Japan dropped dramatically in 1997, 1 year later than a similar trend observed in the United States. The introduction and widespread adoption of new and effective drugs and treatment regimens for HIV-1 and opportunistic infections will be essential life-saving measures.

Acquired Immunodeficiency Syndrome↗