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Biomedical subjects

Y Masuda

Publications and source records attributed to Y Masuda.

At least 199 records · Page 11Linked to original sources
PubMed1999

Effects of repeated selective serotonin reuptake inhibitor paroxetine treatments on mouse forced swimming.

Studies were performed in the mouse forced swimming model, a well known experimental depression model, in order to detect the mechanism of the antidepressive effects induced by repeated serotonin reuptake inhibitor (SSRI) dosing. Five-day repeat dosing of a typical SSRI, paroxetine, increased climbing, a distinctive antidepressive behavior, 1 h after but not 1 h before treatment. The coinjection of paroxetine and serum in mice treated with four repeated doses of paroxetine distinctively increased the behavior, but the coinjection of paroxetine and serum in mice without paroxetine did not. These results indicate that repeated dosing of paroxetine produces a serum substance related to the antidepressive effects induced by serotonin neuron activities. Furthermore, the behavior induced by 5-day repeated dosing of paroxetine was decreased by 100 and 10 micrograms/kg of ketanserin (5-HT2 antagonist) and 100 micrograms/kg of LY-278584 (5-HT3 antagonist). The present findings strongly suggest that repeated dosing of paroxetine produces a serum substance stimulating the antidepressive neuronal pathway sensitively mediated by 5-HT2 and 5-HT3 receptor activity.

Animals↗
PubMed1998

Dynamics of the interaction of human apurinic endonuclease (Ape1) with its substrate and product.

We investigated the interaction dynamics of human abasic endonuclease, the Ape1 protein (also called Ref1, Hap1, or Apex), with its DNA substrate and incised product using electrophoretic assays and site-specific amino acid substitutions. Changing aspartate 283 to alanine (D283A) left 10% residual activity, contrary to a previous report, but complementation of repair-deficient bacteria by the D283A Ape1 protein was consistent with its activity in vitro. The D308A, D283/D308A double mutant, and histidine 309 to asparagine proteins had 22, 1, and approximately 0. 02% of wild-type Ape1 activity, respectively. Despite this range of enzymatic activities, all the mutant proteins had near-wild-type binding affinity specific for DNA containing a synthetic abasic site. Thus, substrate recognition and cleavage are genetically separable steps. Both the wild-type and mutant Ape1 proteins bound strongly to the enzyme incision product, an incised abasic site, which suggested that Ape1 might exhibit product inhibition. The use of human DNA polymerase beta to increase Ape1 activity by eliminating the incision product supports this conclusion. Notably, the complexes of the D283A, D308A, and D283A/D308A double mutant proteins with both intact and incised abasic DNA were significantly more stable than complexes containing wild-type Ape1, which may contribute to the lower turnover numbers of the mutant enzymes. Wild-type Ape1 protein bound tightly to DNA containing a one-nucleotide gap but not to DNA with a nick, consistent with the proposal that substrate recognition by Ape1 involves a space bracketed by duplex DNA, rather than mere flexibility of the DNA.

Amino Acid Substitution↗
PubMed1998

Rapid dissociation of human apurinic endonuclease (Ape1) from incised DNA induced by magnesium.

Repair of apurinic/apyrimidinic (AP) sites is initiated by AP endonucleases, such as the human Ape1 protein (also called Hap1, Apex, and Ref1). This and related enzymes show strong dependence on divalent cations, particularly magnesium. Here we explore the role of this metal in different stages of the Ape1 reaction: substrate binding, cleavage, and product release. We examined DNA binding using an electrophoretic approach and DNA cleavage in single-turnover and steady-state reactions. Magnesium at low to moderate concentrations accelerated both substrate and product release by wild-type Ape1 protein. For a mutant Ape1 protein with an aspartate to alanine substitution at residue 308, substrate in preformed protein-DNA complexes was more efficiently cleaved before release in contrast to wild-type Ape1, whereas product release was accelerated dramatically. The magnesium dependence of steady-state AP endonuclease reactions was sigmoidal for both wild-type and the aspartate 308 to alanine protein but was not sigmoidal for an aspartate 283 to alanine derivative of Ape1. These results show that magnesium affects both DNA interactions with and phosphodiester cleavage by Ape1 and can change the rate-limiting step of the reaction. Structural studies will need to be interpreted in the context of these diverse effects of the metal.

Carbon-Oxygen Lyases↗
PubMed1998

Effects of various N-terminal fragments of glucagon-like peptide-1(7-36) on food intake in the neonatal chick.

Recently, the suppressive effect on food intake by the central administration of glucagon-like peptide-1 (GLP-1) has been confirmed in both rats and chicks. The importance of the N-terminal amino acid, histidine, for the bioactivity of GLP-1(7-36) in the central nervous system was suggested, though the role for C-terminal amino acids in the central nervous system has not been reported. The present study was done to elucidate the central effect of N-terminal fragments of GLP-1(7-36) on food intake of the neonatal chick. Intracerebroventricular (i.c.v.) administration of mammalian GLP-1(7-36) inhibited food intake of chicks, but the fragments of GLP-1(7-16) and GLP-1(7-26) did not show the suppressive effect on food intake. Furthermore, the extended fragments, GLP-1(7-30) and GLP-1(7-33), also had no effects on food intake. It is concluded that C-terminal amino acids of GLP-1(7-36) have an important role for the bioactivity in the central nervous system with special reference to feeding behavior.

Amino Acid Sequence↗
PubMed1998

Appearance and distribution of two Ca2+-binding proteins during development of the cochlea in the musk shrew.

In the developing cochlea of the musk shrew, Suncus murinus, the localization of two Ca2+-binding protein, calbindin and calmodulin, which are thought to play different roles in the nervous system, was examined during gestational and postpartum periods. Calbindin is thought to play a Ca2+ buffering role, while calmodulin activates other proteins. Cochleae from the musk shrews sacrificed from gestational day (GD) 15 to postnatal day (PP) 9 and as adults, were immunohistochemically analyzed. The localization and order of appearance of calmodulin in sensorineural elements were similar to those of calbindin, except for timing of appearance. Calmodulin-staining was recognized first in the spiral ganglion neurons on GD21, followed by the inner hair cells (IHCs) on GD23 and outer hair cells (OHCs) on GD26, while calbindin immunoreactivity in the spiral ganglion neurons on GD19, the IHCs on GD21 and the OHCs on GD23. In hair cells, during development, immunostaining of calbindin and calmodulin was initially seen in the cytoplasm, followed by the cuticular plate. Cytoplasmic staining then decreased in mature hair cells. Non-sensorineural components also showed positivity for both calbindin and calmodulin. The lateral wall of the cochlear duct was positive for calbindin, while the stria vascularis was positive for calmodulin. Immunoreactivity for calbindin was present earlier than that of calmodulin in sensorineural elements, suggesting that in the developing cochlea, calbindin and calmodulin have different functions and that Ca2+ buffering capacity, which is regulated by Ca2+ buffer proteins, such as calbindin, may be required before trigger proteins, such as calmodulin, function.

Aging↗
PubMed1998

Expression, purification, and reconstitution of receptor for pituitary adenylate cyclase-activating polypeptide. large-scale purification of a functionally active G protein-coupled receptor produced in Sf9 insect cells.

Human pituitary adenylate cyclase-activating polypeptide (PACAP) receptor was expressed in Sf9 insect cells and Chinese hamster ovary (CHO) cells. The recombinant receptor in Sf9 cell membranes had low affinity for 125I-PACAP27 (Kd = 155.3 pM) and was insensitive to guanosine 5'-O-3-thiotriphosphate (GTPgammaS), whereas the receptor in CHO membranes had a high affinity (Kd = 44.4 pM) and was GTPgammaS sensitive. The receptor in Sf9 membranes was converted to a high affinity state (Kd = 20-40 pM) following solubilization with digitonin. A large quantity (2 mg from 8 liters of insect cells) of the purified PACAP receptors (Bmax = 23.9 nmol/mg of protein) were obtained in a digitonin-induced high affinity state (Kd = 17.3 pM) using biotinylated ligand affinity chromatography. The apparent molecular weight of the purified receptor (Mr = 48,000) was smaller than that of the receptor from CHO cells (Mr = 58,000) due to differences in asparagine-linked sugar chains. The purified receptor reverted to a low affinity state (Kd = 182.6 pM) upon reconstitution into lipid vesicles, however, the receptor reconstituted with Gs protein had a high affinity (Kd = 40.2 pM) and was GTPgammaS sensitive. [35S]GTPgammaS binding to the reconstituted Gs protein was enhanced by PACAP27 and PACAP38 (EC50 = 42.5 and 9.4 pM, respectively) but not by antagonist PACAP(6-38), indicating that the purified receptor was functionally active.

Animals↗
PubMed1998

Post-traumatic guitar-shaped deformity of the tympanic membrane.

We report a unique case of post-traumatic guitar-shaped deformity of the tympanic membrane in an 8-year-old boy. After a traffic accident, he exhibited bleeding from the ear, incomplete facial palsy and a conductive hearing loss on the left side. Although his symptoms gradually improved, the deformity of the tympanic membrane and external auditory canal persisted. The tympanic membrane appeared to be duplicated. Careful examination using an otoscope was required for accurate diagnosis. Without knowledge of the deformity, the physician could easily misinterpret the appearance of the tympanic membrane. Formation of cholesteatoma was not observed and the normal migration of the epithelium in the external auditory canal seemed to be maintained. However, we were concerned that tubal dysfunction could eventually induce the retraction and atrophy of the tympanic membrane to ultimately form a cholesteatoma. We therefore recommend patients such as this to be evaluated periodically because of the risk of tubal dysfunction and cholesteatoma.

Accidents, Traffic↗
PubMed1998

Nocturnal variation in human sympathetic baroreflex sensitivity.

To determine whether or not there are nocturnal variations in sympathetic baroreflex sensitivity (BRS), we measured spontaneous sympathetic BRSs in eight normal subjects (average 24.5 years old) between 2300 and 0700 h. Electrocardiogram, blood pressure, polysomnography, and muscle sympathetic nerve activity (MSA) using microneurography were recorded. We defined cardiac 'baroreflex sequences' as those that contain three or more adjacent pulses, with the systolic blood pressure and the subsequent pulse interval either continuously increased or decreased. A similar analysis was applied to sympathetic BRSs. We selected three or more adjacent pulses during which diastolic blood pressures continuously increased or decreased. Total activity in MSA was defined as burst per minute x burst amplitude and we calculated the regression coefficients between the diastolic blood pressure and the subsequent total activities in MSA. The regression coefficients were classified as either negative or positive ones. When they were less than zero, we termed them 'baroreflex sequences'. Cardiac and sympathetic BRSs were estimated from the average slope of the baroreflex sequences. Sympathetic BRS was significantly lower during sleep than while subjects were awake in the evening (P < 0.05), and it remained low after the subjects woke up in the morning (P < 0.05). Conversely, cardiac BRS had a tendency to increase during sleep in the night, but not statistically significant. This sympathetic BRS pattern may contribute to diurnal haemodynamic variables and may account, at least in part, for the connection between circadian rhythm and cardiovascular disease.

Adult↗
PubMed1998

Osteoma with cholesteatoma in the external auditory canal.

We report an unusual case of a 13-year-old girl with a benign osteoma associated with a cholesteatoma in the external auditory canal and serous otitis media. The osteoma was located in the antero-inferior wall of the right external auditory canal. A cholesteatoma was present between the osteoma and the tympanic membrane. Computed tomography revealed a soft tissue density within the external auditory canal and in the middle ear cleft. The shadow in the middle ear cleft was considered to represent the serous otitis media. Surgical removal of the osteoma and cholesteatoma proved successful, and no recurrences or complications have occurred in the first year postoperatively.

Adolescent↗
PubMed1998

One-to-one synchronization between the cardiac sympathetic nerve stimuli and heart beats in rats.

One-to-one synchronization of heart rate to the cardiac sympathetic nerve stimuli was observed in Sprague-Dawley rats. Propranolol and L-propranolol, but not D-propranolol, blocked 1:1 synchronization evoked by the nerve stimulation. Thus, 1:1 synchronization is entirely ascribable to neurally released norepinephrine. When a single volley was applied to the cardiac sympathetic nerve, there was a significant abbreviation of the respective cardiac cycle at which the stimulus fell. The mean latency was 33.1 +/- 2.29 ms (mean +/- SE). The extent of the abbreviation of the cardiac cycle was linearly correlated to the interval between P wave and a nerve stimulus. These results ensure that the effect of the sympathetic nerve stimulation is phase dependent and that the sympathetic nerve can entrain the heart beat as well as the parasympathetic nerve can.

Adrenergic alpha-Agonists↗
PubMed1998

Levels of soluble Fas in patients with myocarditis, heart failure of unknown origin, and in healthy volunteers.

This study showed that serum levels of sFas were elevated in patients with myocarditis, and that this elevation was correlated with sIL-2R level as a marker of T-cell activation. Therefore, sFas levels may be associated with T-cell activation in patients with myocarditis, and elevation of sFas may inhibit apoptosis in activated T cells, leading to persistent cell-mediated destruction of myocytes in myocarditis.

Adult↗
PubMed1998

Activation of AP-1 is required for bufalin-induced apoptosis in human leukemia U937 cells.

In a previous study, we demonstrated that bufalin caused apoptosis in human leukemia U937 cells by the anomalous activation of mitogen-activated protein kinase (MAPK) via a signaling pathway that included Ras, Raf-1 and MAPK kinase-1. We report here the effect of bufalin on c-Jun N-terminal protein kinase (JNK), a member of the MAPK family, and on the signaling pathway downstream of MAPKs in U937 cells. When U937 cells were treated with 10(-8) M bufalin, the activity of JNK1 was markedly elevated 3 h after the start of treatment and remained so for 9 h. This activation of JNK and the induction of apoptosis by bufalin were suppressed by expression of antisense mRNA for MAPK kinase-1. c-Jun was translocated from the cytoplasm to the nucleus after treatment of U937 cells with bufalin. The transcriptional activity of AP-1 was transiently enhanced by the treatment with bufalin and this activation was suppressed by the expression of antisense mRNA for MAPK kinase-1. Both curcumin (1,7-bis[4-hydroxy-3-methoxy-phenyl]-1,6-heptadiene-3,5-dione), an inhibitor of the biosynthesis of AP-1, and the expression of dominant negative c-Jun inhibited the activation of AP-1 and the induction of apoptosis by bufalin. Expression of a constitutively active mutant form of MAPK kinase-1 induced the activation of AP-1 and subsequent apoptosis in U937 cells. These results suggest that the activation of AP-1 via a MAPK cascade that includes JNK is required for the induction of apoptosis by bufalin in U937 cells.

Antineoplastic Agents↗
PubMed1998

Programmed cell death in the development of the mouse external auditory canal.

Programmed cell death (PCD) is an essential event for development. The purpose of this work was to ascertain how PCD, in vivo designated apoptosis, is involved in the development of the external auditory canal. We performed a time sequence study of the distribution of apoptosis during the development of external auditory canal (EAC) of the mouse. ICR mice ranging in age from embryonic day 11.5 (E11.5) to 12 days after birth (DAB) were used in the present study. A part of each head including both ears was removed and was processed according to its purpose. Light and electron microscopy for morphological studies and TUNEL method (Gavrieli et al. [1992] J Cell Biol., 119:493-501) for histochemical studies were used. On E11.5, distinct TUNEL-positive staining occurred in the branchial arch. Between E15.5 and 1DAB, TUNEL-positive cells were observed throughout the EAC and the number of these cells decreased with age. On E15.5 and E16.5, numerous TUNEL-positive cells were observed in a cavity remained in the epithelial plate. Transmission electron microscopy revealed that these cells had the features of apoptosis. From 3-12 DAB, no apoptosis was observed in the EAC except for the terminal differentiation of the skin of the EAC. Apoptosis was not observed during recanalization of the EAC, but occurred during the formation of the epithelial plate. The investigation established that PCD is involved in the formation of the epithelial plate, whereas only cornification of the epithelium of the EAC is associated with recanalization.

Animals↗
PubMed1998

A novel 90-kDa tyrosine-phosphorylated protein associated with TCR complex in thymocytes.

Ligation of the TCR-CD3 complex initiates a cascade of tyrosine phosphorylation that results in T cell activation. Initial activation of tyrosine kinases depends on the phosphorylation of activation motifs on CD3 chains. We previously found that a 90-kDa protein was tyrosine phosphorylated upon TCR cross-linking and the induction of the phosphorylation was dependent on the structure of the CD3 complex. In this study, we further characterized p90 phosphorylation. Phosphorylation of p90 was induced only by stimulation through the TCR-CD3 complex but not by other kinds of stimulation including CD28- or hydrogen peroxide-mediated activation and was dynamically regulated. Phosphorylated p90 was associated with the TCR-CD3 complex upon T cell activation. In a normal T cell population, thymocytes but not splenic T cells induced the tyrosine phosphorylation of p90 upon TCR cross-linking. These results suggest that p90 is a novel phosphoprotein associated with the TCR-CD3 complex and may play a role in TCR signaling during thymocyte differentiation.

Animals↗
PubMed1998

Changes in plasma free and sulfoconjugated dopamine in patients with congenital heart disease who underwent cardiac operation.

It has been suggested that plasma sulfoconjugated dopamine (DA) may serve as a source or reservoir for free DA in plasma. Moreover, it has also been reported that the plasma levels of conjugated DA may be used as an index predicting heart failure in patients with heart disease. Therefore, in the present study, we have measured the plasma levels of free and sulfoconjugated DA in patients with congenital heart disease who underwent total corrective operations. The patients were divided into two groups with (6 patients with tetralogy of Fallot, TOF) or without (5 patients with ventricular septal defect without pulmonary hypertension, VSD) cyanosis (mean age of 2.11 years). Blood samples were collected before and after operation from the patients, and plasma free and sulfoconjugated DA levels were measured using high performance liquid chromatography. Preoperative levels of free DA in patients in both groups were higher than the level in age matched control subjects. The plasma level of conjugated DA in TOF was higher than that in the controls and was the highest in VSD before operation. DA infusion early after operation caused a rise in plasma free and conjugated DA, however, the levels of increased free DA were lower in the VSD than in the TOF group. After discontinuing DA infusion, the plasma levels of free DA remained higher, while those of conjugated DA decreased to a level lower than the preoperative values in both groups. As the plasma levels of free and sulfoconjugated DA vary with hemodynamics, it was assumed that the difference in the plasma sulfoconjugated DA level between the groups before operation was due to the influence of pulminary blood flow on catecholamine homeostasis. Since the decrease in conjugated DA has been postulated to be an index of sustained heart failure, it is conceivable that it takes a long time for patients who underwent cardiac operations in infancy to recover from heart failure.

Child, Preschool↗
PubMed1998

[A case of reoperation 24 years after repair of absent pulmonary valve syndrome with anomalous origin of the left pulmonary artery].

We experienced a case of a 38-year-old woman with a persistent cough, 24 years after repair of absent pulmonary valve syndrome with anomalous origin of the left pulmonary artery. The right pulmonary artery was massively dilated, thus it caused the compression of the bronchi, which was thought to result in her respiratory symptom. This dilatation of the right pulmonary artery seemed to have progressed because of the following two reasons. The first is the pulmonary hypertension caused by the late reconstruction of the left pulmonary artery. The second is residual pulmonary stenosis and regurgitation after the initial operation without a pulmonary valve insertion. We performed a reoperation consisting of reconstruction of the right ventricular outflow tract using a valved conduit and plication of the right pulmonary artery. Her postoperative course has been without any complications and satisfactory for the past 2 years.

Adult↗