Biomedical subjects

Y Akamatsu

Publications and source records attributed to Y Akamatsu.

At least 19 recordsLinked to original sources

PubMed1998

Relationship between mandibular position and the coordination of masseter muscle activity during sleep in humans.

Although bruxism has been regarded as having a possibly important role in the aetiology of craniomandibular disorders, the activity of masticatory muscles relative to mandibular position during sleep grinding as recorded by electromyography (EMG) has not yet been clarified. Surface EMGs of the bilateral superficial masseter muscles were recorded simultaneously with mandibular position during sleep from 12 volunteers for three consecutive nights. The incidence of two mandibular positions were recorded with magnetic sensors for both left- and right-sided mandibular grinding. One of the mandibular positions was the canine edge-to-edge position, and the other was the midpoint between the intercuspal position and the canine edge-to-edge position. The mode of the working/ balancing activity ratio ranged from 1/10 to 2/10, showing the marked predominance of balancing side masseter muscle activity during sleep grinding. During sleep grinding, EMG bursts of masseter muscle were observed mainly with mediotrusive mandibular movement from the canine edge-to-edge position. From the results of the present study, it is suggested that muscular dynamics during sleep are unique compared to that during voluntary clenching, and exert a greater mechanical load to the balancing side temporomandibular joint.

Adult↗

PubMed1998

Distinct roles of RAG1 and RAG2 in binding the V(D)J recombination signal sequences.

The RAG1 and RAG2 proteins initiate V(D)J recombination by introducing double-strand breaks at the border between a recombination signal sequence (RSS) and a coding segment. To understand the distinct functions of RAG1 and RAG2 in signal recognition, we have compared the DNA binding activities of RAG1 alone and RAG1 plus RAG2 by gel retardation and footprinting analyses. RAG1 exhibits only a three- to fivefold preference for binding DNA containing an RSS over random sequence DNA. Although direct binding of RAG2 by itself was not detected, the presence of both RAG1 and RAG2 results in the formation of a RAG1-RAG2-DNA complex which is more stable and more specific than the RAG1-DNA complex and is active in V(D)J cleavage. These results suggest that biologically effective discrimination between an RSS and nonspecific sequences requires both RAG1 and RAG2. Unlike the binding of RAG1 plus RAG2, RAG1 can bind to DNA in the absence of a divalent metal ion and does not require the presence of coding flank sequence. Footprinting of the RAG1-RAG2 complex with 1, 10-phenanthroline-copper and dimethyl sulfate protection reveal that both the heptamer and the nonamer are involved. The nonamer is protected, with extensive protein contacts within the minor groove. Conversely, the heptamer is rendered more accessible to chemical attack, suggesting that binding of RAG1 plus RAG2 distorts the DNA near the coding/signal border.

Animals↗

PubMed1998

Effect of oxatomide on experimental allergic rhinitis in guinea pigs.

We have investigated the effect of oxatomide, an antiallergic agent, on experimental allergic rhinitis in sensitized guinea pigs. Oxatomide (1 and 10 mg/kg, p.o.) significantly inhibited the sneeze response and nasal rubbing after antigen challenge. Oxatomide (10 and 30 mg/kg) reduced the increase in nasal vascular permeability induced by the antigen-antibody reaction. The decreases in nasal cavity volume caused by nasal mucosal swelling 10 min, 30 min and 6 hr after antigen challenge were significantly inhibited by oxatomide (30 mg/kg). These results indicate that oxatomide inhibits the experimental allergic rhinitis in guinea pigs.

Animals↗

PubMed1998

A single-chain immunotoxin against carcinoembryonic antigen that suppresses growth of colorectal carcinoma cells.

We have engineered an anti-carcinoembryonic antigen (CEA) single-chain immunotoxin derived from humanized anti-CEA antibody (hMN14) and a truncated Pseudomonas exotoxin (PE), PE40. The purified anti-CEA immunotoxin (hMN14(Fv)-PE40) was first measured for binding affinity against a CEA-positive colorectal carcinoma cell line and compared with its parental IgG and the monovalent Fab fragment. The Ka of sFv-PE40, Fab, and IgG were 5 x 10(7), 6 x 10(7), and 3 x 10(8) M(-1), respectively. There was no significant affinity loss by conversion of Fab to the single-chain Fv, but these monovalent forms were 5-6-fold reduced in affinity compared with the parental IgG. In cytotoxicity assays, the hMN14(Fv)-PE40 showed specific growth suppression of CEA-expressing colon cancer cell lines MIP-CEA (high CEA) and LS174T (moderate CEA) with IC50s of 12 ng/ml (0.2 nM) and 69 ng/ml (1.1 nM). These IC50s correlated inversely with the surface expression of CEA, such that 50% killing was equivalent for each cell type when expressed in toxin molecules bound/cell (3000-5000). The presence of soluble CEA up to 1000 ng/ml did not affect the cytotoxicity against CEA-expressing cells, with 50% suppression only at 4000 ng/ml that correlated with the binding Kd of the single-chain Fv. The stability of the hMN14(Fv)-PE40 molecule at 37 degrees C was confirmed by bioassay and by lack of aggregation. Our hMN14(Fv)-PE40 may be clinically useful for tumors with high CEA expression without affecting normal tissues with low or absent CEA, even in patients with high soluble antigen levels.

ADP Ribose Transferases↗

PubMed1997

Occurrence of sustained increase in QT dispersion following exercise in patients with residual myocardial ischemia after healing of anterior wall myocardial infarction.

Our objective was to evaluate the effect of exercise on QT dispersion over the next 3 hours, as seen on a standard 12-lead electrocardiogram in patients with healed myocardial infarction with or without residual ischemia. We measured QT and QTc dispersion before, immediately after, and 1 and 2 hours after symptom-limited, dynamic treadmill exercise tests in 28 patients with healed anterior wall myocardial infarction with (group I, n = 18) and without (group II, n = 10) residual ischemia. The same protocol was followed in 5 group I patients after successful performance of coronary angioplasty. QT and QTc dispersion did not change immediately after exercise in group II. These parameters increased in group I (QT dispersion at rest [mean +/- SD] 57 +/- 22 ms, and after exercise 87 +/- 27 ms; QTc dispersion at rest 62 +/- 25 ms, and after exercise 114 +/- 36 ms). The increases in QT and QTc dispersion were sustained for at least 2 hours. After a successful coronary angioplasty in 5 patients, these parameters no longer increased with exercise. Thus, QT dispersion increased for at least 2 hours after exercise in patients who had residual ischemia after healing of myocardial infarction. Data obtained in 5 of these patients after coronary angioplasty support the idea that residual ischemia plays a key role in the sustained increase in QT dispersion after exercise.

Aged↗

PubMed1997

Redox regulation of the DNA binding activity in transcription factor PEBP2. The roles of two conserved cysteine residues.

Transcription factor PEBP2/CBF consists of a DNA binding subunit, alpha, and a regulatory subunit, beta. The alpha subunit has an evolutionarily conserved 128-amino acid region termed "Runt domain" that is responsible for both DNA binding and heterodimerization with the beta subunit. The Runt domain in all mammalian submembers of the alpha subunit contains two conserved cysteine residues, and its DNA binding activity undergoes redox regulation. To investigate the mechanism of this redox regulation, we performed site-directed mutagenesis of the two conserved cysteines in the Runt domain of the mouse PEBP2alphaA homolog. Substitution of Cys-115 to serine resulted in a partially impaired DNA binding, which remained highly sensitive to a thiol-oxidizing reagent, diamide. Conversely, the corresponding substitution of Cys-124 caused an increased DNA binding concomitant with an increased resistance to diamide. In contrast, substitution of either cysteine to aspartate was destructive to DNA binding to marked extents. These results have revealed that both Cys-115 and Cys-124 are responsible for the redox regulation in their own ways with low and high oxidizabilities, respectively. We have also found that two cellular thiol-reactive proteins, thioredoxin and Ref-1, work effectively and synergistically for activation of the Runt domain. Interestingly, the beta subunit further enhanced the activation by these proteins and reciprocally prevented the oxidative inactivation by diamide. These findings collectively suggest the possibility that the Runt domain's function in vivo could be dynamically regulated by the redox mechanism with Trx, Ref-1, and the beta subunit as key modulators.

Amino Acid Sequence↗

PubMed1997

Cloning and expression of human liver rhodanese cDNA.

cDNA for the human rhodanese (thiosulfate; cyanide sulfurtransferase, EC 2.8.1.1) was cloned from a human fetal liver cDNA library. Sequencing of the cDNA revealed an open reading frame that encodes a 297-residue polypeptide with a calculated mass of 33,427 daltons. When the rhodanese cDNA was transiently expressed in Escherichia coli and Cos7 cells, the rhodanese activity increased 40-fold and 150-fold, respectively. Sequence homology analysis showed that the human rhodanese is 89.6% identical to bovine, 90.2% identical to rat, 91.2% identical to mouse and Chinese hamster, and 71.4% similar to avian counterparts, respectively, and that rhodanese was highly conserved across evolution.

Amino Acid Sequence↗

PubMed1997

A simple screening for mutant DNA binding proteins: application to murine transcription factor PEBP2alpha subunit, a founding member of the Runt domain protein family.

Mouse transcription factor PEBP2 (polyomavirus enhancer-binding protein (2) is composed of two distinct subunits alpha and beta. The alpha subunit has an ability to bind the specific DNA sequences, which is enhanced by formation of a heterodimer with the beta subunit. The DNA binding and heterodimerization activities of the alpha subunit are both localized within a 128-amino-acid (aa) region termed as the Runt domain for its homology to the Drosophila segmentation gene runt. To characterize the molecular determinants for these activities, the Runt domain was randomly mutagenized and produced in E. coli as a secreted form. Using E. coli culture supernatant, the DNA binding and heterodimerization of mutant Runt domains were analyzed by gel retardation assay. Nine randomly picked single-aa substitution mutants showed various functional alterations in DNA binding and heterodimerization either separately or simultaneously. This observation suggests that the structure of Runt domain is highly ordered and is quite sensitive to modulations in its primary structure. The method presented here provides a simple and quick method to characterize a large number of mutant DNA binding proteins.

Amino Acid Sequence↗

PubMed1997

Changes in psychophysiological functions during night shift in nurses. Influence of changing from a full-day to a half-day work shift before night duty.

The effects of changing from a full-day to a half-day shift work before a night duty shift on physiological and psychological functions during the night shift were investigated in 12 healthy unmarried nurses working on the same ward of a university hospital. Three shift patterns, i.e., a day shift following a day shift, a night shift following a day shift, and a night shift following a half-day shift, were studied in terms of physical activity level, sympathetic and parasympathetic activity levels, cortisol, prolactin, NK cell activity, and changes in mood states. The change to the half-day shift increased the duration of sleep before night duty by about 86 min and brought wake-up times forward by about 1 h, resulting in increases in rest and time before work. In addition, the change was revealed to reduce the influence of reversed-phase circadian rhythms on autonomic nervous activity during the night shift. The score for sleepiness was significantly lower at 0500 hours following a half-day shift. There were some marginal but not significant differences in the scores reflecting the degree of vigor, tiredness and irritation during the night shift. Although the prolactin concentration was significantly decreased at the start of the night shift after the half-day shift, there was no difference in cortisol concentration or NK cell activity between the usual night shift after a day shift and the night shift after the half-day shift. The half-day shift was not observed to cause any marked change in the fixed biorhythms of these nurses. The cortisol and NK cell activity levels were low during the night shift, suggesting that the night shift itself is a high stress level, which is prejudicial to biodefense.

Adult↗

PubMed1997

Liver transplantation for severe hypoxemia caused by patent ductus venosus.

The authors describe the case of a 9-year-old girl who underwent liver transplantation because she suffered from severe hypoxemia caused by patent ductus venosus (PDV). Generally, severe hypoxemia (PaO2 < 50 mm Hg in room air or < 300 mm Hg in pure oxygen) is not an indication for liver transplantation because the hypoxemia may not be improved, and may lead to a fatal outcome. PDV, which is associated with mild liver dysfunction, is not an indication for liver transplantation by itself. But in our patient, most of the mesenteric venous flow directly entered the systemic circulation through the PDV just like the portosystemic shunt, and this caused the pulmonary arteriovenous shunt and hypoxemia. Thus, the authors operated on the patient in an attempt to restore her pulmonary function. Nitric oxide (10 to 20 ppm) was added to the inhaled gas to dilate the functional pulmonary capillaries and to deliver sufficient oxygen after the transplantation. Although the patient suffered various complications after the operation, the final results were excellent.

Angiography, Digital Subtraction↗

PubMed1997

Analysis of bilirubin fraction in the bile for early diagnosis of acute rejection in living related liver transplantation.

The diagnosis of acute rejection in liver transplantation usually needs hepatic biopsy, but hepatic biopsy sometimes involves severe complications. We analyzed biliary bilirubin fraction after living related liver transplantation by using high performance liquid chromatography (HPLC) and investigated availability for the early diagnosis of acute rejection retrospectively. Nine children with liver cirrhosis due to biliary atresia were included in this study, who underwent living related liver transplantation at The Second Department of Surgery, Tohoku University School of Medicine. Bile was collected daily from a biliary canulae inserted into the hepatic duct of the graft under aseptic and without exposure to the light. We measured the proportion of bilirubin diglucuronide (BDG), bilirubin monoglucuronide (BMG) and unconjugated bilirubin (UCB) of bile pigments in the bile by HPLC. In three of four patients with acute rejection, BDG + BMG (= Bc) was above 85% and BDG/Bc ratio was below 0.6 at the time of hepatic biopsy. After rejection therapy, BDG/Bc ratio increased in their bile. The remaining one case with acute rejection as well as bile duct injury due to arterial thrombosis of S2, Bc was below 85%, and BDG/Bc ratio was below 0.6. In four of the other five patients who had several severe complications, i.e., arterial or portal vein thrombosis, bile stasis due to cholangitis and sepsis due to necrotizing myofascitis, Bc was below 85% and BDG/Bc ratio was below 0.6. We concluded that analysis of biliary bilirubin fraction after liver transplantation could be reliable as a noninvasive maker and valuable for the early diagnosis of acute rejection.

Acute Disease↗

PubMed1997

Changes in osteosclerosis of the osteoarthritic knee after high tibial osteotomy.

Radiographically demonstrated osteosclerosis was quantitatively evaluated in knees with medial compartmental osteoarthritis by dual xray absorptiometry. Bone density was measured in various areas of 144 knees with medial compartmental osteoarthritis, 23 knees of which were treated with high tibial osteotomy. The bone mineral density of the medial femoral and tibial condyles was greater than that of the lateral femoral and tibial condyles in all knees with medial compartmental osteoarthritis. The ratios of bone mineral density of the medial condyles to that of the lateral condyles were found to increase significantly with the progression of osteoarthritis. There was a significant positive regression line correlation between those ratios and the increase of varus deformity as expressed by the standing femorotibial angle. The former were calculated to be 1.0 when the latter was nearly 170 degrees (10 degrees anatomic valgus angulation). The ratio of bone mineral density of the medial femoral condyles to the lateral femoral condyles decreased sharply in all 23 knees within 1 year after high tibial osteotomy.

Absorptiometry, Photon↗

PubMed1997

[Recovery process from myocardial stunning after transient ischemia: assessment with pulsed wave Doppler transmitral flow pattern].

Sustained left ventricular systolic dysfunction after transient myocardial ischemia is well known as "myocardial stunning", but little is known about the recovery in left ventricular diastolic function. Changes in left ventricular systolic and diastolic performance following dobutamine-induced ischemia were investigated in 13 patients with chest pain syndrome and normal coronary arteries (control) and 34 patients with coronary artery disease. Two-dimensional echocardiography and pulsed wave Doppler transmitral flow velocity curves were recorded at baseline, after infusion of a peak dose of dobutamine and at 20 min and 2 hours after dobutamine infusion. In control subjects, left ventricular ejection fraction and the peak early diastolic filling velocity increased at the peak dose of dobutamine. At 20 min after the cessation of dobutamine infusion, these values were restored to the baseline levels. In patients with coronary artery disease, ejection fraction and peak velocity increased at the peak dose of dobutamine but decreased at 20 min after infusion compared with baseline values despite the restoration of heart rate and blood pressure. Although ejection fraction increased at 2 hours compared with 20 min after infusion, peak velocity did not increase. Left ventricular diastolic dysfunction may be sustained longer than systolic dysfunction after transient myocardial ischemia.

Aged↗

PubMed1996

Functional dissection of the alpha and beta subunits of transcription factor PEBP2 and the redox susceptibility of its DNA binding activity.

The mouse transcription factor PEBP2 is a heterodimer of two subunits: a DNA binding subunit alpha and its partner subunit beta. The alpha subunit shares a region of high homology, termed the Runt domain, with the products of the Drosophila melanogaster segmentation gene runt and the human acute myeloid leukemia-related gene AML1. To study the molecular basis for the DNA binding and heterodimerization functions of this factor, we constructed series of deletions of the alpha and beta subunits and examined their activities by electrophoretic mobility shift and affinity column assays. The minimal functional region of the alpha subunit for DNA binding and dimerization was shown to coincide with the Runt domain. On the other hand, the region of the beta subunit required for heterodimerization was localized to the N-terminal 135 amino acids. Furthermore, it was found that the DNA binding activity of the Runt domain is regulated by a reduction/oxidization (redox) mechanism and that its reductively activated state, which is extremely labile, is stabilized by the beta subunit. These findings add a new layer to the mechanism and significance of the regulatory interplay between the two subunits of PEBP2.

Animals↗

PubMed1996

Immunochemical identification of the pssA gene product as phosphatidylserine synthase I of Chinese hamster ovary cells.

We have previously shown that a Chinese hamster ovary (CHO) cell mutant defective in phosphatidylserine synthase I recovers the enzyme activity on transfection with a pssA cDNA clone isolated from the parental CHO-K1. The resultant transfectant, CDT-1, exhibited about 20-fold higher specific activity of the enzyme in the membrane fraction than CHO-K1 cells. Polyclonal antibodies against two peptides of the predicted pssA product cross-reacted with a membrane protein having an apparent molecular mass of 42 kDa, which was overproduced in CDT-1 cells. By immunoprecipitation with the antibody, phosphatidylserine synthase I activity as well as the 42-kDa protein was eliminated from solubilized membrane proteins of CDT-1 cells. Both the enzyme activity and the 42-kDa protein of CHO-K1 cells were enriched in the mitochondria-associated membrane fraction and the microsome fraction, but neither was enriched in the mitochondria fraction or the cytosol fraction. These results suggest that the pssA gene encodes phosphatidylserine synthase I.

Animals↗

PubMed1996

Isolation and characterization of neutralizing single-chain antibodies against Xenopus mitogen-activated protein kinase kinase from phage display libraries.

MAP kinase kinase (MAPKK) is a dual specificity protein kinase that phosphorylates and activates MAP kinase in vivo. In this study, four mouse monoclonal single-chain Fv (scFv) antibodies (Y1-6, Y1-7, Y3-6, and Y3-11) that can specifically bind to Xenopus MAPKK were isolated from combinatorial scFv-displaying phage libraries. Three scFv clones (Y1-6, Y1-7, and Y3-6) were shown to efficiently inhibit MAPKK activity in vitro. Point mutation (D98K) at VH-CDR3 of one (Y1-6) of these three clones markedly reduced its neutralizing activity. The wild-type scFv (Y1-6) inhibited the Mos-induced MAP kinase activation and germinal vesicle breakdown when injected into immature Xenopus oocytes, whereas the mutant scFv, Y1-6 (D98K), did not. The three neutralizing scFv clones (Y1-6, Y1-7, and Y3-6) were shown to bind to NH2-terminal residues 1-23 of Xenopus MAPKK, whereas the epitope of a Y3-11 clone with no neutralizing activity was shown to lie between residues 33 and 67 of MAPKK. Furthermore, a synthetic peptide (the N16 peptide) corresponding to residues 2-17 of MAPKK suppressed the neutralizing activity of the wild-type Y1-6, and a rabbit polyclonal antibody against the N16 peptide was found to possess a strong neutralizing activity against MAPKK. These results demonstrate that the neutralizing antibodies characterized here inhibit the kinase activity of MAPKK by binding to the NH2-terminal segment of MAPKK.

Amino Acid Sequence↗

PubMed1996

Post-translational processing of the phosphatidylserine decarboxylase gene product in Chinese hamster ovary cells.

We have isolated a full-length cDNA clone of the Chinese hamster ovary (CHO) pssC gene, which encodes mitochondrial phosphatidylserine decarboxylase. The cDNA clone is capable of increasing phosphatidylserine decarboxylase activity to 11-fold in CHO-K1 cells. The pssC gene product predicted from the cDNA sequence is composed of 409 amino acid residues. In an in vitro translation system coupled with in vitro transcription, the cDNA clone directs the formation of a protein with an apparent molecular mass of 46 kDa. In CHO-K1 cells, the cDNA clone leads to the production of two major peptides with apparent molecular masses of 38 and 34 kDa, as determined by Western blotting with an antibody raised against a recombinant pssC protein. When CHO-K1 cells transfected with the cDNA clone are labelled with [35S]methionine for a short period, proteins immunoprecipitated with the antibody lack radioactive 38 and 34 kDa peptides, but contain two radioactive peptides with apparent molecular masses of 46 and 42 kDa instead. The pssC gene product predicted from the cDNA sequence has, near its C-terminus, a unique Leu-Gly-Ser-Thr sequence which is known as a processing site for Escherichia coli phosphatidylserine decarboxylase. A mutant pssC cDNA clone, in which Ser378 in the conserved sequence is replaced by Ala, leads to overproduction of 46, 42 and 38 kDa peptides, but not a 34 kDa peptide. This mutant clone is incapable of increasing phosphatidylserine decarboxylase activity, in contrast to the wild-type clone. These results indicate that the processing at the Leu-Gly-Ser-Thr sequence is essential for formation of the active enzyme. Thus, the pssC gene product is converted into mature phosphatidylserine decarboxylase through multiple steps of post-translational processing.

Amino Acid Sequence↗

PubMed1996

A new method for recording mandibular position during nocturnal bruxism.

Experimental equipment for recording mandibular excursive position during nocturnal bruxism has been devised. The equipment consists of chromium-cobalt alloy cast frameworks for each upper and lower dental arch and two pairs of tiny magnetic sensors and magnets, capable of electromyographic (EMG) recordings of the bilateral masseter muscles and simultaneously recording mandibular position. The two subjects tested were confirmed to be bruxing during sleeping. Although EMG records for the two subjects showed a common EMG pattern as a bruxer, the sensor records revealed that one subject was a bilateral bruxer and the other bruxed almost unilaterally. The present study demonstrated that this newly devised equipment is practical for studying mandibular position during nocturnal bruxism.

Adult↗