Biomedical subjects

M Taira

Publications and source records attributed to M Taira.

At least 145 records · Page 8Linked to original sources

PubMed1993

Cortical cell types from spike trains.

The patterns of cell activity recorded extracellularly in the motor cortex of behaving monkeys were classified into the following three groups using a combination of cluster and discriminant analyses of 1925 spike trains: (a) cells with low discharge rate and low bursting (67.1%), (b) cells with low discharge rate but bursting (20.2%), and (c) cells with high discharge rate and low bursting (12.7%). The percentage of directionally tuned cells and of cells engaged during a memorized delay task were very similar in all three cell groups.

Animals↗

PubMed1993

Effects of post-curing by heat on the mechanical properties of visible-light cured inlay composites.

The aim of this study was to evaluate the effects of post-curing by heat on the mechanical properties of visible-light (V-L) cured three inlay composites and three posterior filling composites. One group was only photo-cured according to the manufacturers' recommended methods, while the other group was heat-treated at 100 degrees C for 15 min following initial cure by V-L. Knoop hardness, diametral tensile strength and compressive strength were measured to evaluate the mechanical properties. Cure performance was checked out by the solvent immersion test. Upon secondary-curing by heat, it was confirmed that the mechanical properties of the composites were increased moderately and the cure performance of the composites was also improved.

Composite Resins↗

PubMed1993

Radiopacity of 12 visible-light-cured dental composite resins.

The radiopacity of 12 VL-cured composite resins was determined with reference to an aluminum step-wedge. Two anterior composites were radiolucent while two anterior and one anterior/posterior composites exhibited the radiopacity equal to, or slightly greater than, that of human enamel. Three posterior and one inlay composites possessed the radiopacity equivalent to, or in tiny excess of, that of human enamel. Three posterior composites had the radiopacity, fairly exceeding that of human enamel. Chemical analyses of the filler particles were carried out with SEM/EDX. It became evident that radiopaque fillers contained at least one radiopaque oxide component such as BaO, ZrO2 and Yb2O3 with varying concentrations. In general, the radiopacity of the composite resin was linearly proportional to the amount of the radiopaque oxide in the filler. It was suggested that ZrO2 was radiopacifier equivalent to, or even stronger than, BaO.

Composite Resins↗

PubMed1993

Dental high-speed cutting of four cast alloys.

The purpose of this study was to evaluate dental high-speed cutting behaviour of four cast alloys, namely Ag-Pd-Cu-Au alloy, Ag-Zn-In-Sn alloy, Ni-Cr alloy and Ti. Weight-load cutting tests were conducted on four cast alloys, using two rotary cutting instruments, namely a diamond point and a carbide bur, both driven by an air-turbine handpiece. While the constant transverse load of 80 g was applied on the workpiece for 5s, the handpiece speed was measured during cutting as well as the volume of workpiece removal which took place. The cutting tests were repeated 10 times. We found that the cutting volumes of soft Ag-Pd-Cu-Au alloy and Ag-Zn-In-Sn alloy were considerably larger than those of hard Ni-Cr alloy and Ti. It was also clarified that the cutting effectiveness of the carbide bur was generally superior to that of the diamond point. With continuing use, however, the cutting capability of the carbide bur tended to decline while that of the diamond point remained quasi-constant.

Dental Alloys↗

PubMed1993

Histological difference between complete responders and non-responders to interferon therapy of the livers of patients with chronic hepatitis C.

Liver histology was compared in patients with chronic hepatitis C to note the differences between responders and non-responders to interferon treatment. Fifty-eight patients were administered interferon in varying doses and over various periods, and were then followed up for 1 year. According to the improvement status of serum alanine aminotransferase (ALT) levels during this period, the patients were classified into complete responders who showed complete normalization of ALT; partial responders who exhibited a significant decrease, but not complete normalization of ALT; and non-responders who did not reveal any significant decrease of ALT. Before application of the interferon treatment, liver biopsies were analyzed in four parameters and given scores from 0 to 5 for three groups in cord with no prior knowledge of the efficacy. The parameters included necroinflammation, fibrosis/lobular distortion, portal lymphocytic reaction and portal (or fibrous septal) outline destruction. Results indicated that there were no significant differences in the score of necroinflammation and portal lymphocytic reaction between the complete responder group and the non-responder group. In contrast, the complete responder group exhibited weaker fibrosis/lobular distortion and less portal outline destruction than the non-responder group. The partial responder group was more akin to the former group in these parameters. Thus, it is safe to conclude that liver histology may predict the efficacy of interferon treatment.

Adult↗

PubMed1993

A glycine-1008 to valine mutation in the insulin receptor in a woman with type A insulin resistance.

We examined the insulin receptor gene in a Japanese woman with type A insulin resistance. Acanthosis nigricans and polycystic ovary were present. A 75-g oral glucose tolerance test showed a diabetic pattern, and fasting insulinemia was 780 pmol/L. Insulin binding was normal, but autophosphorylation and tyrosine kinase activity were reduced in partially purified insulin receptors from Epstein-Barr virus-transformed lymphocytes. The nucleotide sequence for all 22 exons of the insulin receptor gene was determined by direct sequencing of genomic DNA amplified with the polymerase chain reaction. Substitution of valine for glycine at codon 1008 in the tyrosine kinase domain was identified in one allele. This was the same mutation found in another patient, but there was no relationship between the two families. The father had the same mutation in one allele and impaired glucose tolerance with mild hyperinsulinemia, but the mother and two brothers had normal glucose tolerance. We conclude that a single mutant allele in the tyrosine kinase domain caused the insulin resistance.

Adult↗

PubMed1993

Hardness and fracture toughness of commercial core composite resins.

One important mechanical property of core composite resins is fracture toughness, KIC, which expresses serviceability in the oral cavity, such as the resistance to marginal fracture. KIC values of eight commercial core composite resins were examined by the single-edge notched-beam (S.E.N.B.) method. Two composites containing about 80 wt% Si3N4 fillers exhibited both the highest KIC value of around 2.0 MN.m-3/2 and the highest hardness value. The other six composites containing 66 to 86 wt% SiO2-based fillers had KIC values of around 1.2 to 2.0 MN.m-3/2, and there was a tendency toward higher KIC values as hardness increased. It was speculated that the clinical acceptability of core composite resins could be broadened, if dental clinicians selected composites with higher KIC values.

Composite Resins↗

PubMed1993

Regulatory interactions during embryogenesis in Xenopus laevis.

During amphibian embryogenesis, axis definition and the specification of the mesoderm and neural plate depend on cell interactions. These interactions are mediated by peptide growth factors and other diffusible molecules including retinoic acid (RA). Several genes encoding transcription factors are known to be immediate early or delayed early responses to the action of growth factors and retinoids in the embryo. By the criterion of cycloheximide (CHX) resistance, goosecoid (gsc), Xlim-1, Xbra, Mix.1, XFKH1/pintallavis/XFD1, and Xnot are immediate early response genes in mesoderm/induction. Among these, gsc, Xnot and XFKH1 are superinduced by CHX, suggesting that their regulation depends in part on rapid turnover of the mRNA. RA is known to induce Xlim-1 in Xenopus embryos and to lead to anterior malformations. We show that 9-cis RA, the ligand of the RXR receptor class, is more effective than all-trans RA in generating these biological effects.

Animals↗

PubMed1993

[A case of successful tissue plasminogen activator in young-onset pulmonary embolism].

A 16-year-old boy was admitted to the hospital because of chest pain, dyspnea, and syncope. Physical examination revealed blood pressure of 100/60 mmHg, regular pulse of 120 beats/min, and respiratory rate of 30/min. Pulsation of the right ventricle was palpable in the left margin of the parasternum. An increased second sound was audible in the second inter-costal lesion of the left subclavicle mid-line. Results of blood tests were close to normal limits, except for slight leukocytosis and elevation of the LDH value. Analysis of artery blood gas showed hypoxia. The chest x-ray film showed cardiac enlargement. The value of systolic pulmonary artery pressure was estimated to be 47 mmHg by the cardiac echogram, which revealed enlargement of the right ventricle. Pulmonary embolism was suspected from the above findings. The value of pulmonary artery pressure was found to be 49/19 mmHg by Swan-Ganz catheter. Angiography of the pulmonary artery revealed filling defects of right in the right pulmonary artery. Tissue plasminogen activator was injected directly to the right pulmonary artery. After that, chest pain and dyspnea were relieved. In addition, arterial oxygen improved and pulmonary artery pressure decreased. At the 6th day after admission, the defect in the pulmonary artery angiography disappeared. Deep vein thrombosis of both femoral veins was recognized as a cause of pulmonary embolism by angiography of the femoral vein.

Adolescent↗

PubMed1993

[Bacteriological and clinical studies in 23 cases of thoracic empyema--the role of oral streptococci and anaerobes].

The bacteriology of empyema fluid and the clinical background of 23 cases from July 1987 through July 1992 were studied. Nineteen cases were male and 4 female, with a mean age of 59.6 years (range; 33 to 84 y.o.). There were 15 cases of community-acquired infection and 8 of nosocomial infection. Acute pneumonia and/or lung abscess developed into empyema in 19 cases. Sixteen cases had associated predisposing conditions, such as diabetes, chronic bronchitis, disorders with dysphagia, and excess alcohol intake. Forty-one strains were isolated from empyema in 22 cases. The predominant organisms, in order of prevalence, were "Streptococcus milleri" group (11 strains), Peptostreptococcus spp. (6), Prevotella spp. (6), Fusobacterium spp. (5) and other viridans streptococci (3). The majority of streptococcal infections, which were primarily caused by "S. milleri" group, were mixed with anaerobes and/or aerobes/facultatives. These results demonstrate that oral streptococci, especially "S. milleri" group, and anaerobes play a significant role as pathogens in empyema.

Adult↗

PubMed1992

Elevated expression of the ornithine decarboxylase gene in human esophageal cancer.

The mechanisms involved in sustaining the high levels of ornithine decarboxylase (ODC) activity in human cancers are not well defined. We examined the level of expression of ODC mRNA together with ODC activity in surgically excised human cancers, including esophagus, stomach, colon, and liver tumors, the objective being to determine whether the ODC mRNA level correlates with enhancement of ODC activity in these cancers. Among these tumors, the esophageal cancers had the highest ODC activity (120 +/- 43.9 pmol of CO2/h/mg of protein), compared with the stomach (37.6 +/- 13.7), colon (22.8 +/- 5.9), and liver (10.2 +/- 5.6) cancers. A remarkable increase in ODC mRNA was seen in all of the esophageal cancers. The ratio of ODC mRNA in the tumors, relative to the paired normal tissues, was 14.6 +/- 3.7. Some increase was noted in some of the stomach (2.9 +/- 0.9) and colon (2.1 +/- 0.9) cancers, but there was no increase in the liver tumors (0.9 +/- 0.2). A significant correlation was noted between ODC activity and mRNA expression in cancerous and noncancerous tissues of the esophagus, stomach, and colon, thereby suggesting that increased steady-state mRNA may be responsible for the high ODC activity in these tumors. Southern blot analysis of the DNA from the esophageal cancers revealed no amplification or significant rearrangement of the gene. Mechanisms sustaining high ODC mRNA levels in esophageal cancers may be an enhancement of the promoter activity of this gene or stabilization of the mRNA.

Blotting, Northern↗

PubMed1992

The motor cortex and the coding of force.

The relation of cellular activity in the motor cortex to the direction of two-dimensional isometric force was investigated under dynamic conditions in monkeys. A task was designed so that three force variables were dissociated: the force exerted by the subject, the net force, and the change in force. Recordings of neuronal activity in the motor cortex revealed that the activity of single cells was directionally tuned and that this tuning was invariant across different directions of a bias force. Cell activity was not related to the direction of force exerted by the subject, which changed drastically as the bias force changed. In contrast, the direction of net force, the direction of force change, and the visually instructed direction all remained quite invariant and congruent and could be the directional variables, alone or in combination, to which cell activity might relate.

Animals↗

PubMed1992

Molecular cloning and expression of human myocardial cGMP-inhibited cAMP phosphodiesterase.

We have cloned a cDNA for a myocardial cGMP-inhibited cAMP phosphodiesterase (cGI PDE) from a human heart cDNA library in lambda Zap II. The open reading frame [3.5 kilobases (kb)] of cDNA clone n.13.2 (7.7 kb) encodes a protein of 125 kDa. In Northern blots of total human ventricle RNA, a single mRNA species (8.3 kb) hybridized with a 4-kb EcoRI restriction fragment of clone n.13.2 cDNA (containing the entire open reading frame). The carboxyl-terminal region of the deduced amino acid sequence of the cGI PDE contains the putative catalytic domain conserved among mammalian PDE families. A partial cDNA clone, n.2, encoding a truncated, 54-kDa cGI PDE containing the conserved domain was expressed as a catalytically active fusion protein in Escherichia coli. cAMP hydrolytic activity was inhibited by cGMP and OPC 3911 but not by rolipram. Thus, this report provides direct proof that the conserved domain contains the catalytic core of cGI PDEs.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1992

Promoter regions of the human X-linked housekeeping genes PRPS1 and PRPS2 encoding phosphoribosylpyrophosphate synthetase subunit I and II isoforms.

The 5' regions of the human phosphoribosylpyrophosphate synthetase subunit I and II genes (PRPS1 and PRPS2, respectively) were isolated and sequenced. A comparison of the nucleotide sequences between human and rat PRPS1 genes revealed that the sequences around the transcription initiation sites were conserved over 56 nucleotides, and that a TATA-like sequence, a CCAAT box and three putative Sp1 binding sites were present at almost the same positions in the GC-rich sequences. Two major transcription initiation sites were localized in the human PRPS1, one of the two was located 27 nucleotides downstream from the TATA-like sequence, while the upstream initiation site was in the TATA-like sequence. The promoter region of the human PRPS2 gene was also GC-rich and contained a TATA-like sequence, four Sp1 binding sites and a homopyrimidine stretch. The initiation sites were localized at 90 nucleotides upstream from the ATG initiation codon. Chloramphenicol acetyltransferase (CAT)/promoter fusion assays showed that a 2.0 kb region (human PRPS1) and a 1.1 kb region (human PRPS2) possessed the promoter activities in four cell lines. The CAT activities in the three human cell lines tended to correlate with the steady-state mRNA levels of the PRPS1 and PRPS2 genes. These results suggest that the 5' flanking regions cloned contribute to the cell-differential expression of these two genes.

Amino Acid Sequence↗

PubMed1992

Isoflavonoids, genistein, psi-tectorigenin, and orobol, increase cytoplasmic free calcium in isolated rat hepatocytes.

Isoflavonoid compounds, genistein, psi-tectorigenin and orobol have been implicated as inhibitors of tyrosine-specific protein kinase and phosphatidylinositol turnover. These compounds have been frequently used as a pharmacological tool to assess signal transduction pathways in various cell systems. In the course of analyzing signaling pathways in rat hepatocytes, we obtained an unexpected finding that these compounds transiently increase cytoplasmic free calcium. Since the Ca2+ mobilizing effect was observed in 1 microM calcium containing buffer, the source of the Ca2+ may be intracellular stores. Thus, when interpreting data obtained using these compounds, caution is needed.

Aequorin↗

PubMed1992

In vitro corrosion fatigue of 316L cold worked stainless steel.

The corrosion resistance of 316L cold worked stainless steel depends upon its thin protective oxide layer; and if this is partially broken down, corrosion resistance depends upon its tendency for repassivation. Since the intended function of stainless-steel implants is to sustain musculoskeletal forces, research toward the stability of the oxide film during dynamic loading in simulated bodylike fluids is warranted. A pilot corrosion fatigue study was, therefore, performed on uniaxial tension fatigue specimens cycled to various maximum stress levels near their yield point while immersed in 37 degrees C isotonic saline solution, and combined with the electrochemical insult of (a) imparting an 800 mV vs. SCE anodic potential for 20 s to stimulate local film breakdown, and then (b) returning to a constant 200 mV vs. SCE anodic potential and maintaining that potential during cyclic loading until the specimens broke in two. During the anodic polarization by continuously monitoring the current it was possible to (a) observe the repassivation and corrosion behavior following stimulation, and (b) detect crack initiation, crack propagation and failure onset. The combined effects of accelerated corrosion and mechanical fatiguing disturbed the repassivation tendency and reduced the crack initiation times and the fatigue lives as compared to air and saline controls. As the maximum cyclic load levels were increased, the fatigue lives were further foreshortened.

Cold Temperature↗

PubMed1992

The role of growth factors in embryonic induction in Xenopus laevis.

Establishment of the body pattern in all animals, and especially in vertebrate embryos, depends on cell interactions. During the cleavage and blastula stages in amphibians, signal(s) from the vegetal region induce the equatorial region to become mesoderm. Two types of peptide growth factors have been shown by explant culture experiments to be active in mesoderm induction. First, there are several isoforms of fibroblast growth factor (FGF), including aFGF, bFGF, and hst/kFGF. FGF induces ventral, but not the most dorsal, levels of mesodermal tissue; bFGF and its mRNA, and an FGF receptor and its mRNA, are present in the embryo. Thus, FGF probably has a role in mesoderm induction, but is unlikely to be the sole inducing agent in vivo. Second, members of the transforming growth factor-beta (TGF-beta) family. TGF-beta 2 and TGF-beta 3 are active in induction, but the most powerful inducing factors are the distant relatives of TGF-beta named activin A and activin B, which are capable of inducing all types of mesoderm. An important question relates to the establishment of polarity during the induction of mesoderm. While all regions of the animal hemisphere of frog embryos are competent to respond to activins by mesoderm differentiation, only explants that include cells close to the equator form structures with some organization along dorsoventral and anteroposterior axes. These observations suggest that cells in the blastula animal hemisphere are already polarized to some extent, although inducers are required to make this polarity explicit.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Motor cortical activity in a memorized delay task.

Two rhesus monkeys were trained to move a handle on a two-dimensional (2D) working surface in directions specified by a light at the plane. They first captured with the handle a light on the center of the plane and then moved the handle in the direction indicated by a peripheral light (cue signal). The signal to move (go signal) was given by turning off the center light. The following tasks were used: (a) In the non-delay task the peripheral light was turned on at the same time as the center light went off. (b) In the memorized delay task the peripheral light stayed on for 300 ms and the center light was turned off 450-750 ms later. Finally, (c) in the non-memorized delay task the peripheral light stayed on continuously whereas the center light went off 750-1050 ms after the peripheral light came on. Recordings in the arm area of the motor cortex (N = 171 cells) showed changes in single cell activity in all tasks. In both delay tasks, the neuronal population vector calculated every 20 ms after the onset of the peripheral light pointed in the direction of the upcoming movement, which was instructed by the cue light. Moreover, the strength of the population signal showed an initial peak shortly after the cue onset in both the memorized and non-memorized delay tasks but it maintained a higher level during the memorized delay period, as compared to the non-memorized task.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗