Biomedical subjects

H Akutsu

Publications and source records attributed to H Akutsu.

At least 19 recordsLinked to original sources

PubMed2001

Increased attentional blink after focal cerebral lesions.

BACKGROUND: Once a person identifies a visual object, the ability to detect a second object is impaired for the next few hundred milliseconds. This attentional blink is reported to increase in subjects with neglect due to acute right hemisphere lesions. METHOD: To examine neural substrates of the attentional blink, the authors examined the performance of 13 subjects with chronic focal brain lesions visualized by MRI and nine control subjects without neurologic impairments on a rapid serial visual presentation task that used letters as targets. RESULTS: Attentional blink length in the lesion group was more than twice that of controls (p < 0.05). The magnitude of the attentional blink deficit was greatest when the second target appeared 200 ms after the first target, recovering close to baseline by 1,200 ms. Abnormal attentional blink occurred (even in the absence of neglect) with lesions in the occipitotemporal areas (associated with "object" vision) and the prefrontal cortices (thought to mediate visual working memory). CONCLUSIONS: Attentional blink length and attentional blink magnitude measure different components of the attentional blink process. Abnormal attentional blink can occur with different chronic focal brain lesions in a network of structures for vision and attention, and it has no special status in hemispatial neglect. Abnormal attentional blink may help explain difficulties on rapid, visually demanding cognitive tasks such as reading and automobile driving and may explain performance deficits in brain damaged patients with nonspatial disorders of visual processing.

Adult↗

PubMed2001

Epigenetic instability in ES cells and cloned mice.

Cloning by nuclear transfer (NT) is an inefficient process in which most clones die before birth and survivors often display growth abnormalities. In an effort to correlate gene expression with survival and fetal overgrowth, we have examined imprinted gene expression in both mice cloned by nuclear transfer and in the embryonic stem (ES) cell donor populations from which they were derived. The epigenetic state of the ES cell genome was found to be extremely unstable. Similarly, variation in imprinted gene expression was observed in most cloned mice, even in those derived from ES cells of the same subclone. Many of the animals survived to adulthood despite widespread gene dysregulation, indicating that mammalian development may be rather tolerant to epigenetic aberrations of the genome. These data imply that even apparently normal cloned animals may have subtle abnormalities in gene expression.

Animals↗

PubMed2001

New organic superconductors beta-(BDA-TTP)2X [BDA-TTP + 2,5-bis(1,3-dithian-2ylidene)-1,3,4,6-tetrathiapentalene; X(-) = SbF6(-), AsF6(-), and PF6(-)].

The synthesis, electrochemical properties, and molecular structure of a new pi-electron donor, 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene (BDA-TTP), is described. In contrast to the hitherto-known tetrachalcogenafulvalene pi-donors providing organic superconductors, this donor contains only the bis-fused 1,3-dithiole-2-ylidene unit as a pi-electron system, yet produces a series of ambient-pressure superconductors beta-(BDA-TTP)2X [X = SbF6 (magnetic T(c) = 6.9 K, resistive T(c) = 7.5 K), AsF6 (magnetic T(c) = 5.9 K, resistive T(c) = 5.8 K), and PF6 (magnetic T(c) = 5.9 K)], which are isostructural. The values of the intermolecular overlap integrals calculated on the donor layers of these superconductors suggest a two-dimensional (2D) electronic structure with loose donor packing. Tight-binding band calculations also indicate that these superconductors have the 2D band dispersion relations and closed Fermi surfaces.

Journal Article↗

PubMed2001

Hybrid vigor, fetal overgrowth, and viability of mice derived by nuclear cloning and tetraploid embryo complementation.

To assess whether heterozygosity of the donor cell genome was a general parameter crucial for long-term survival of cloned animals, we tested the ability of embryonic stem (ES) cells with either an inbred or F(1) genetic background to generate cloned mice by nuclear transfer. Most clones derived from five F(1) ES cell lines survived to adulthood. In contrast, clones from three inbred ES cell lines invariably died shortly after birth due to respiratory failure. Comparison of mice derived from nuclear cloning, in which a complete blastocyst is derived from a single ES cell, and tetraploid blastocyst complementation, in which only the inner cell mass is formed from a few injected ES cells, allows us to determine which phenotypes depend on the technique or on the characteristics of the ES cell line. Neonatal lethality also has been reported in mice entirely derived from inbred ES cells that had been injected into tetraploid blastocysts (ES cell-tetraploids). Like inbred clones, ES cell-tetraploid pups derived from inbred ES cell lines died shortly after delivery with signs of respiratory distress. In contrast, most ES cell-tetraploid neonates, derived from six F(1) ES cell lines, developed into fertile adults. Cloned pups obtained from both inbred and F(1) ES cell nuclei frequently displayed increased placental and birth weights whereas ES cell-tetraploid pups were of normal weight. The potency of F(1) ES cells to generate live, fertile adults was not lost after either long-term in vitro culture or serial gene targeting events. We conclude that genetic heterozygosity is a crucial parameter for postnatal survival of mice that are entirely derived from ES cells by either nuclear cloning or tetraploid embryo complementation. In addition, our results demonstrate that tetraploid embryo complementation using F(1) ES cells represents a simple, efficient procedure for deriving animals with complex genetic alterations without the need for a chimeric intermediate.

Animals↗

PubMed2001

Purification and characterization of homo- and hetero-dimeric acetate kinases from the sulfate-reducing bacterium Desulfovibrio vulgaris.

Two distinct forms of acetate kinase were purified to homogeneity from a sulfate-reducing bacterium Desulfovibrio vulgaris Miyazaki F. The enzymes were separated from the soluble fraction of the cells on anion exchange columns. One acetate kinase (AK-I) was a homodimer (alpha(S)(2)) and the other (AK-II) was a heterodimer (alpha(S)alpha(L)). On SDS-PAGE, alpha(L) and alpha(S) subunits migrated as bands of 49.3 and 47.8 kDa, respectively, but they had an identical N-terminal amino acid sequence. A rapid HPLC method was developed to directly measure ADP and ATP in assay mixtures. Initial velocity data for AK-I and AK-II were collected by this method and analyzed based on a random sequential mechanism, assuming rapid equilibrium for the substrate binding steps. All kinetic parameters for both the forward acetyl phosphate formation and the reverse ATP formation catalyzed by AK-I and AK-II were successfully determined. The two enzymes showed similar kinetic properties in Mg(2+) requirement, pH-dependence and magnitude of kinetic parameters. These results suggest that two forms of acetate kinase are produced to finely regulate the enzyme function by post-translational modifications of a primary gene product in Desulfovibrio vulgaris.

Acetate Kinase↗

PubMed2001

Functions and ATP-binding responses of the twelve histidine residues in the TF1-ATPase beta subunit.

The C2 proton signals of all (twelve) histidine residues of the TF1 beta subunit in the 1H-NMR spectrum have been identified and assigned by means of pH change experiments and site-directed substitution of histidines by glutamines. pH and ligand titration experiments were carried out for these signals. Furthermore, the ATPase activity of the reconstituted alpha3beta3gamma complex was examined for the twelve mutant beta subunits. Two of three conserved histidines, namely, His-119 and 324, were found to be important for expression of the ATPase activity. The former fixes the N-terminal domain to the central domain. His-324 is involved in the formation of the interface essential for the alpha3beta3gamma complex assembly. The other conserved residue, His-363, showed a very low pK(a), suggesting that it is involved in the tertiary structure formation. On the binding of a nucleotide, only the signals of His-173, 179, 200, and 324 shifted. These histidines are located in the hinge region, and its proximity, of the beta subunit. This observation provided further support for the conformational change of the beta monomer from the open to the closed form on the binding of a nucleotide proposed by us [Yagi et al. (1999) Biophys. J. 77, 2175-2183]. This conformational change should be one of the essential driving forces in the rotation of the alpha3beta3gamma complex.

Adenosine Triphosphate↗

PubMed2001

Offspring from normal mouse oocytes injected with sperm heads from the azh/azh mouse display more severe sperm tail abnormalities than the original mutant.

Sperm with abnormalities in the position and shape of the head were obtained from the azh/azh mutant and injected into the cytoplasm of mature mouse oocytes to determine whether sperm from the offspring display both head (club shape) and tail (looping, folding, and fusion) abnormalities observed in the mutant donor. Although quantitative differences were observed among the three examined offspring, we found that abnormalities in sperm head shape were less frequent than in the donor mutant, but that tail malformations predominated. In addition, we found that the frequency of tail abnormalities increased during sperm epididymal transit. A typical defect was the multiple folding of the sperm tail and eventual fusion of closely apposed plasma membranes. As a consequence, sperm forward motility and natural fertility were compromised. Results of this study indicate that the azh/azh mutant and offspring generated by intracytoplasmic sperm injection provide a valuable model for determining the role of the manchette and keratin-containing outer dense fibers and fibrous sheath during spermiogenesis. Furthermore, our findings stress the risk of enhancing a phenotypic abnormality caused by mutant male genotypes introduced through bypassing the biologic mechanisms of natural sperm selection during fertilization.

Animals↗

PubMed2001

Identification of a small tetraheme cytochrome c and a flavocytochrome c as two of the principal soluble cytochromes c in Shewanella oneidensis strain MR1.

Two abundant, low-redox-potential cytochromes c were purified from the facultative anaerobe Shewanella oneidensis strain MR1 grown anaerobically with fumarate. The small cytochrome was completely sequenced, and the genes coding for both proteins were cloned and sequenced. The small cytochrome c contains 91 residues and four heme binding sites. It is most similar to the cytochromes c from Shewanella frigidimarina (formerly Shewanella putrefaciens) NCIMB400 and the unclassified bacterial strain H1R (64 and 55% identity, respectively). The amount of the small tetraheme cytochrome is regulated by anaerobiosis, but not by fumarate. The larger of the two low-potential cytochromes contains tetraheme and flavin domains and is regulated by anaerobiosis and by fumarate and thus most nearly corresponds to the flavocytochrome c-fumarate reductase previously characterized from S. frigidimarina to which it is 59% identical. However, the genetic context of the cytochrome genes is not the same for the two Shewanella species, and they are not located in multicistronic operons. The small cytochrome c and the cytochrome domain of the flavocytochrome c are also homologous, showing 34% identity. Structural comparison shows that the Shewanella tetraheme cytochromes are not related to the Desulfovibrio cytochromes c(3) but define a new folding motif for small multiheme cytochromes c.

Amino Acid Sequence↗

PubMed2001

Beneficial effect of troglitazone, an insulin-sensitizing antidiabetic agent, on coronary circulation in patients with non-insulin-dependent diabetes mellitus.

Evidence is increasing for small vessel remodeling and disturbance of endothelium-dependent vasodilation in diabetic patients. Insulin increases vascular wall thickening and produces endothelial dysfunction. Troglitazone, a new insulin-sensitizer antidiabetic agent, is considered to reduce plasma insulin level and the present study assessed its effect on the coronary circulation of the patients with non-insulin-dependent diabetes mellitus (NIDDM). Analysis of the myocardial washout rate with adenosine triphosphate-stress thallium-201 scintigraphy was used to estimate coronary circulation, and for estimation of insulin sensitivity, the homeostasis model insulin resistance index (HOMA-R) was calculated. Patients were treated with monotherapy of either troglitazone (200 mg bid, n=12) or glibenclamide (2.5 mg daily, n=12) for 3 months. Age-, sex- and risk factors-matched subjects without NIDDM were employed as a control. Fasting plasma glucose and hemoglobin A1c were similarly decreased by troglitazone or glibenclamide. Plasma insulin level (pmol/L) decreased from 66.6+/-10.8 to 39.0+/-7.2 with troglitazone, but was unchanged by glibenclamide (58.8+/-7.2 to 66.0+/-10.8). The diabetic groups had a significantly lower washout rate than controls, which was improved by troglitazone, but not by glibenclamide. In addition, the increase in washout rate correlated significantly with the decrease in HOMA-R in the troglitazone group. In conclusion, troglitazone can restore coronary circulation by improving insulin resistance in patients with NIDDM.

Adenosine Triphosphate↗

PubMed2001

A simple, rapid, and highly efficient gene expression system for multiheme cytochromes c.

The genes of tetraheme cytochrome c3 and hexadecaheme high-molecular-weight cytochrome c from Desulfovibrio vulgaris could be overexpressed as holoproteins in Shewanella oneidensis TSP-C using pUC-type vectors of E. coli. Surprisingly, S. oneidensis was transformed directly by pUC-type vectors through electroporation. The yields of the recombinant proteins in this expression system were much higher than the previously reported ones.

Cytochrome c Group↗

PubMed2001

[Impact of high remnant-like lipoproteins on the function of peripheral arterial endothelium in patients with hyperlipidemia and normolipidemia: estimation using Doppler flow analysis].

OBJECTIVES: Cholesterol levels of remnant-like lipoprotein (RLP-cholesterol: RLP-C), which reflect remnant lipoproteins, are associated with coronary arterial endothelial functions and cardiovascular events. The influence of RLP-C on peripheral vascular endothelial functions in patients with hyperlipidemia and normolipidemia was evaluated based on the reactivity of the antecubital artery to acetylcholine (Ach) and isosorbide dinitrate (ISDN) using a Doppler guidewire. METHODS: Protocol 1: Five patients were selected, and the dose-response of the antecubital artery was evaluated by administering Ach (0.5, 5, and 50 micrograms/30 sec) or ISDN (0.025, 0.25, and 2.5 mg/30 sec). An index of vascular reactivity (brachial artery response: BR) was determined by dividing the maximal blood flow velocity after the administration of Ach or ISDN by resting blood flow velocity. Protocol 2: BR was evaluated in 48 patients after administering Ach 50 micrograms or ISDN 2.5 mg. Subsequently, these patients were divided into the following three groups based on early morning RLP-C levels: Group L (n = 11), RLP-C < 2.0 mg/dl (minimal detectable level); Group M (n = 21), 2.0 mg/dl < or = RLP-C < 5.0 mg/dl; and Group H (n = 16), 5.0 mg/dl < or = RLP-C. The factors that regulate BR-Ach 50 micrograms were also evaluated in 34 normolipidemic patients. RESULTS: Protocol 1: BR dose-dependently increased after the administration of Ach and ISDN. Protocol 2: BR-Ach 50 micrograms was significantly less in Group H (3.1 +/- 0.8) than in Groups M (3.8 +/- 0.9, p < 0.03) and L (4.2 +/- 0.9, p < 0.01). However, there were no significant differences in BR-ISDN 2.5 mg between the three groups. Univariate analysis in normolipidemic patients revealed that BR-Ach 50 micrograms was correlated with age (r = -0.355, p < 0.05), RLP-C (r = -0.488, p < 0.01), low-density lipoprotein cholesterol (r = -0.382, p < 0.03), systolic blood pressure (r = -0.354, p < 0.05), and diastolic blood pressure (r = -0.406, p < 0.02). Multivariate analysis using these five factors as independent variables revealed that age, RLP-C, and low-density lipoprotein cholesterol regulated BR-Ach 50 micrograms. CONCLUSIONS: Peripheral vascular endothelial dysfunction may occur in patients with high levels of RLP-C. RLP-C is an independent lipid factor that regulates peripheral vascular endothelial functions even in normolipidemic patients.

Acetylcholine↗

PubMed2000

X-Chromosome inactivation in cloned mouse embryos.

To study whether cloning resets the epigenetic differences between the two X chromosomes of a somatic female nucleus, we monitored X inactivation in cloned mouse embryos. Both X chromosomes were active during cleavage of cloned embryos, followed by random X inactivation in the embryo proper. In the trophectoderm (TE), X inactivation was nonrandom with the inactivated X of the somatic donor being chosen for inactivation. When female embryonic stem cells with two active X chromosomes were used as donors, random X inactivation was seen in the TE and embryo. These results demonstrate that epigenetic marks can be removed and reestablished on either X chromosome during cloning. Our results also suggest that the epigenetic marks imposed on the X chromosomes during gametogenesis, responsible for normal imprinted X inactivation in the TE, are functionally equivalent to the marks imposed on the chromosomes during somatic X inactivation.

Alleles↗

PubMed2000

Compound radiofrequency-driven recoupling pulse sequences for efficient magnetization transfer by homonuclear dipolar interaction under magic-angle spinning conditions

The maximum of the transferred magnetization in rotating powdered solids under the radiofrequency-driven recoupling (RFDR) pulse sequence is enhanced by reducing the orientation dependence of the effective recoupled homonuclear dipolar interaction. The compound RFDR (CRFDR) pulse sequence for this enhancement consists of RFDR pulse units (tau(i)-pi-tau(R)-pi-1171;tau(i)) with different tau(i), where tau(R) is the sample rotation period, tau(i) and 1171;tau(i) (=tau(R) - tau(i)) are delays, and pi is a 180 degrees pulse. The delay tau(i) modifies the zero-quantum spin operators and the sample rotation-angle dependence of the recoupled dipolar Hamiltonian. The CRFDR pulse sequences were optimized for mixing by varying tau(i). Numerical simulation for the two-spin system only with a dipolar interaction and isotropic chemical shifts indicates that the transfer efficiency of CRFDR averaged over the powder is about 70%, which is 30% higher than the efficiency of the RFDR pulse over a broad range of about 1/tau(R) in resonance frequency difference. The CRFDR sequences need about 60% longer mixing times to maximize the transferred magnetizaion in comparison with the original RFDR sequence. Chemical shift anisotropy, the other dipolar interactions, and relaxation generally reduce the enhancement by CRFDR. Experiments for fully (13)C-labeled alanine, however, show that the maximum of the magnetization transferred with CRFDR from the carboxyl to alpha carbon is about 15% greater than that with RFDR. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Serum concentrations of soluble Fas antigen and soluble Fas ligand in mother and newborn.

We measured soluble Fas antigen and soluble Fas ligand, which are considered to be an apoptotic substance, in maternal serum, umbilical cord serum and amniotic fluid during cesarean section at full term pregnancy. Seventeen healthy parturients with no fetal distress were studied. Soluble Fas antigen showed no different levels between these measurement sites. Soluble Fas ligand showed a difference, in which umbilical serum level was significantly higher than maternal serum and amniotic fluid levels. The present results suggest high serum levels of soluble Fas ligand in newborn. However, the reason for this evidence is entirely unknown.

Adult↗

PubMed2000

Concentrative relationship between polymorphonuclear elastase and urinary trypsin inhibitor in amniotic fluid.

In the amniotic fluid, urinary trypsin inhibitor (UTI) seems to inhibit polymorphonuclear elastase (PMNE) activity. The PMNE and UTI concentrations in normal amniotic fluid at 16-20 and 38-40 gestational weeks were measured. The PMNE concentration increased significantly at 38-40 weeks, whereas UTI concentration decreased significantly. According to concentrative relationships between both substances, PMNE may be activated more at the full term pregnancy. Since PMNE-induced tissue injury potentially causes degradation of amniotic collagen, the present result suggests that the quotient of PMNE and UTI concentrations is a reliable index to estimate the occurrence of rupture of the membranes.

Abortion, Induced↗

PubMed2000

Distal superior cerebellar artery aneurysm in a patient with systemic lupus erythematosus: case report.

BACKGROUND: The authors describe a case of ruptured distal superior cerebellar artery (SCA) aneurysm in a patient with systemic lupus erythematosus (SLE). CASE DESCRIPTION: A 31-year-old female who had been treated for SLE for 13 years presented with a subarachnoid hemorrhage. Cerebral angiography demonstrated an aneurysm arising from the cisternal portion of the left superior cerebellar artery. The patient underwent early endovascular coil embolization and was discharged from our hospital without neurological deficit. CONCLUSION: Aneurysms arising from peripheral segments of cerebellar arteries are rare, and delayed surgical clipping has been recommended for these lesions. In addition, the outcomes of SLE patients with ruptured cerebral aneurysms are reported to be very poor due to the systemic complications of SLE. However, our patient had a favorable outcome with early endovascular treatment for the ruptured aneurysm and with appropriate medical treatment for the accompanying SLE. Therefore, early endovascular coil embolization is worthy of consideration among the options for therapeutic intervention in these conditions.

Adult↗

PubMed2000

The influence of left ventricular geometry on coronary vasomotion in patients with essential hypertension.

The objective of this study was to assess the influence of left ventricular (LV) geometric pattern on coronary vasomotion in patients with essential hypertension. We studied 34 hypertensive patients, who had never been treated, with angiographically normal coronary arteries. Patients were classified into four LV geometric patterns by echocardiography: normal, concentric remodeling, eccentric hypertrophy, and concentric hypertrophy. The responses of coronary vasomotion in left anterior descending artery to vasoactive agents (acetylcholine, isosorbide dinitrate, adenosine triphosphate) were examined using a Doppler guidewire and quantitative coronary angiography. The percent increase in coronary blood flow evoked with acetylcholine (endothelium-dependent vasomotion) showed lowest in concentric hypertrophy, followed by eccentric hypertrophy, concentric remodeling, and normal geometry. The significant linear relationship between acetylcholine-induced coronary blood flow and LV mass was noted. There was no difference in the percent increase in coronary blood flow evoked with isosorbide dinitrate (endothelium-independent vasomotion of conduit vessel) among the four groups. The percent increase in coronary blood flow evoked with adenosine triphosphate (endothelium-independent vasomotion of resistant vessel) was significantly lower in patients with concentric hypertrophy than in the other three groups. The results in this study suggest that coronary vasomotion may be associated with LV geometry in patients with hypertension. The endothelium-dependent vasodilation is impaired progressively as LV hypertrophy advances. The endothelium-independent vasodilation of microvessels is impaired only in concentric hypertrophy. This advanced abnormality of coronary vasomotion may contribute to the high cardiovascular morbidity and mortality in patients with concentric hypertrophy.

Acetylcholine↗

PubMed2000

Further evidence that sperm nuclear proteins are necessary for embryogenesis.

We have recently presented evidence that the structural integrity of the mouse sperm nuclear matrix may be necessary for the proper unpackaging of sperm DNA for participation in embryogenesis. It is likely that the sperm nuclear matrix contributes to the organisation of the sperm DNA and its disturbance can seriously damage the paternal genome or its expression. In this work, we confirm our previous data and further suggest that even very subtle changes in the sperm nuclear structure may have a significant impact on embryo development. As reported previously, dithiothreitol (DTT) in the presence of an ionic detergent, ATAB, destabilized the nuclear matrix as measured by the halo assay, and oocytes injected with these nuclei failed to develop. We also discovered that omitting the protease inhibitor PMSF from the buffers used to extract spermatozoa prevented sperm injected into oocytes from participating in development. The organization of DNA into loop domains by the nuclear matrix in these nuclei appeared normal, as measured by the halo assay. Oocytes injected with sperm nuclei that had been washed with ATAB in the presence of phenylmethylsulphonyl fluoride (PMSF) but in the absence of DTT resulted in live births. Neither DTT treatment nor the absence of PMSF would be expected to disrupt the integrity of the paternal DNA. The data therefore suggest that even very subtle alterations in the structural proteins of the nucleus are enough to deprive sperm DNA of the ability to contribute to embryonic development.

Animals↗