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H Hama

Publications and source records attributed to H Hama.

At least 55 records · Page 3Linked to original sources
PubMed1996

[Transient heterogeneous enhancement on dual-phase helical CT of liver].

Transient heterogeneous enhancement was seen on the arterial phase of dual phase helical CT of the liver. The shape of the enhancement was appeared wedged or patchy. These phenomena without liver tumor were observed in 23 (2.3%) of 1012 patients with suspected hepatobiliary disease. Plain CT showed no attenuation difference in the liver. Twenty-two of these 23 cases were diagnosed as scarred liver, A-P shunt caused by liver biopsy, acute cholecystitis, liver abscess, liver cirrhosis, or advanced pancreas head cancer. The diagnosis of one case was uncertain. These phenomena were thought to be caused by 1) a regional direct increase in hepatic arterial flow due to arterial-portal (A-P) shunt, or hypervascular tumor ; or 2) a compensatory increase in hepatic arterial flow as a result of decreased portal venous flow caused by tumor invasion or severe liver cirrhosis.

Adolescent↗
PubMed1996

Automated DNA typing of ACTBP2: a comparison of allelic ladder with GS 2500 as internal marker.

A comparison was made between the size values of the alleles measured by the internal size marker of Genescan (GS 2500) and the size values measured by an allelic ladder constructed by our laboratory in the application of Genescan software for the typing of the ACTBP2 system. The measurement by GS 2500 showed a greater than 2 bp divergence (SD = 0.893) while the measurement by the allelic ladder showed only 0.1 bp divergence (SD = 0.008). Thus in genotyping of ACTBP2 by Genescan software, the method presented here of using the allelic ladder as the size marker instead of GS 2500 is easier and more reliable.

Alleles↗
PubMed1996

[Preliminary study of radiological image transmission with B-ISDN].

We evaluated the utility of image transmission using broad band ISDN (B-ISDN). The B-ISDN network links Tohoku University Hospital (TUH), interfaced with CDDI, and Tohoku University Department of Technology, interfaced with FDDI (including Tohoku University Computer Center interfaced with Ethernet), at 10km distance interfaced to a Unix workstation. Voluminous radiographic images like MRI 3-D images of the pelvic organs digitized at 5-20 megabytes were transmitted at mean data rates of 1.03Mbps (CDDI-Ethernet) and 30.1Mbps (FDDI-CDDI) with no image distortion. Initially the image data are transmitted to the Computer Center & Department of Technology, then processed and relayed to TUH. B-ISDN can provide fast, accurate image transmission.

Computer Communication Networks↗
PubMed1995

Ultraviolet B irradiation increases endothelin-1 and endothelin receptor expression in cultured human keratinocytes.

The effect of ultraviolet B (UVB) irradiation on endothelin-1 (ET-1) and ET receptor expression was examined using cultured normal human keratinocytes. Keratinocytes secreted ET-1 in the medium at a level of 2.1 pg/day/10(5) cells. UVB irradiation up to 10 mJ/cm2 increased ET-1 secretion 3-fold, and potentiated expression of mRNA for ET-1. Both ETA and ETB receptor mRNAs were detected in keratinocytes, and their expression was up-regulated by 5 mJ/cm2 UVB irradiation.

Base Sequence↗
PubMed1995

GLY113-->ASP can restore activity to the ASP51-->SER mutant in the melibiose carrier of Escherichia coli.

ASP51 in the putative membrane-spanning helix 2 of the melibiose carrier of Escherichia coli was replaced by SER. This mutation caused failure of the cell to transport melibiose and failure to ferment melibiose on indicator plates. A melibiose-positive revertant was isolated from these plates and was found to have two additional mutations, GLY113-->ASP (in helix 4) and PHE16-->LEU (in helix 1). The double mutant ASP51-->SER/GLY113-->ASP was constructed and showed accumulation of melibiose. On the other hand ASP51-->SER/PHE16-->LEU showed no activity. It is concluded that the new carboxyl group at position 113 compensates for the loss of the carboxyl group at position 51.

Amino Acid Sequence↗
PubMed1995

A study of physiological response during emotional imaging.

We inspected Lang's bio-informational theory and furthered the research. 24 subjects were divided into two groups, a stimulus group (S-group) and a response group (R-group) for scripts with Joy, Anger, and Neutral emotions. In the training session, the S-group was instructed to image the scripts as vividly as possible, while the R-group was instructed to concentrate on physiological and physical responses in addition to what was asked of the S-group. On the test day, subjects imaged two Neutral scripts, two standard emotional scripts, and two personally relevant emotional scripts. Indices were physiological response (blood pressure) and subjects' ratings for imaging. We confirmed that emotional scripts increased physiological responses more than nonemotional scripts did. The results suggested that the differences in the scripts' content affected blood pressure and subjects' ratings of imaging.

Adult↗
PubMed1995

Possible sources of endothelin-1 in damaged rat brain.

We investigated the sources of endothelin-1 (ET-1) detected in the damaged brain tissue of rats after cold injury. ET-1 in the injured sites was increased 1-5 days after the injury. Physiologic observations revealed that breakdown of the blood-brain barrier occurred and that plasma-derived albumin exuded into the brain parenchyma after cold injury. Radiolabeled ET-1, which was injected into the left cardiac ventricle, was detected in the tissue at the injury site, and ET-1-like immunoreactivity was observed in the brain capillaries in the damaged tissues. TGF-beta 1, which is a tissue regeneration factor, potently induced the expression of ET-1 mRNA in cultured astrocytes. These results suggest that ET-1 is produced through a variety of ways in the damaged brain.

Animals↗
PubMed1994

Endothelin-1 activates mitogen-activated protein kinases through two independent signalling pathways in rat astrocytes.

Northern blot analysis and displacement study revealed that the endothelin (ET) receptor functionally expressed in rat primary cultured astrocytes is the ETB receptor. Mitogen-activated protein kinases (MAP kinases) in the cells were activated by 10 nM ET-1, a dose that maximally stimulated phosphoinositide hydrolysis. This activation was potently inhibited by pretreatment of the cells with phorbol 12-myristate 13-acetate (PMA) which leads to protein kinase C (PKC) down-regulation and was slightly inhibited by pretreatment with pertussis toxin (PTX). Pretreatment of the cells with PMA plus PTX completely inhibited the ET-1-augmented MAP kinase activity. Activation of MAP kinases was also induced by 0.1 nM ET-1, which hardly stimulated phosphoinositide hydrolysis. This activation was fully inhibited by pretreatment with PTX but insensitive to pretreatment with PMA. ET-1-stimulated production of inositol phosphates was not affected by pretreatment with PTX. These results suggest that activation of MAP kinases secondary to stimulation of the ETB receptor with ET-1 in rat primary cultured astrocytes was mediated through two independent signalling pathways. PKC-dependent pathway and PTX-sensitive G protein-mediated pathway.

Animals↗
PubMed1994

Replacement of alanine 58 by asparagine enables the melibiose carrier of Klebsiella pneumoniae to couple sugar transport to Na+.

The melibiose carrier of Klebsiella pneumoniae couples sugar transport to H+ and Li+, while that of Escherichia coli uses Na+ besides the other two cation species (Hama and Wilson, 1992). We have shown that the K. pneumoniae melibiose carrier is capable of recognizing Na+ when the amino-terminal 81 residues are replaced by the corresponding region of the E. coli melibiose carrier (Hama and Wilson, 1993). In this amino-terminal region there are 5 residues that are not conserved between the two carriers. In this study, we changed each of the 5 residues of the K. pneumoniae carrier to the one in the E. coli carrier. The substitutions are Ile-36-->Val, Val-43-->Leu, Leu-54-->Trp, Ala-58-->Asn, and Cys-68-->Ala. With four of the five mutants, Ile-36-->Val, Val-43-->Leu, Leu-54-->Trp, and Cys-68-->Ala, sugar accumulation was not affected by Na+. In striking contrast, melibiose and methyl-1-thio-beta-D-galactopyranoside accumulation was greatly stimulated by Na+ with the Ala-58-->Asn mutant. Furthermore, Na+ uptake coupled to downhill melibiose transport was observed with the Ala-58-->Asn mutant. These results indicate that the Ala-58-->Asn substitution enables the K. pneumoniae melibiose carrier to couple sugar transport to Na+. It is clear that the Asn-58 residue (Asn-54 in the E. coli carrier) is involved in Na+ recognition.

Base Sequence↗
PubMed1994

Symptomatic type D (separated) medial plica: clinical features and surgical results.

The clinical presentation and results of surgery in 20 cases of symptomatic type D (separated) medial plica were reviewed. The group was composed of cases with a fenestration (14 knees), reduplication (two knees), and tear (four knees). Based on preoperative symptoms and clinical presentation, the patients were divided into two groups: the first group had symptoms localized to the medial compartment (11 knees), and the second group had symptoms and/or signs in the patellofemoral joint and/or lateral compartment (nine knees). The symptoms of the second group mimicked those of lateral meniscal tear or patella subluxation, and no definite preoperative diagnosis was possible. Two patients showed difficulty of full extension "active extension test." Excellent or good results were obtained with surgery in all patients after an average follow-up of 39 months. Although resection of the type D medial plica resulted in a favorable outcome, special attention should be made in preoperative diagnosis of this type of plicae.

Adolescent↗
PubMed1994

Enhancement of serine-sensitivity by a gene encoding rhodanese-like protein in Escherichia coli.

When cells of Escherichia coli are grown on lactate (or other carbon sources), an addition of serine to the medium causes growth inhibition. This growth inhibition is caused by inhibition by serine of homoserine dehydrogenase I, which is involved in threonine-isoleucine biosynthesis [Hama, H., Sumita, Y., Kakutani, Y., Tsuda, M., & Tsuchiya, T. (1990) Biochem. Biophys. Res. Commun. 168, 1211-1216]. We have cloned and sequenced genes which enhance the serine-sensitivity. Two open reading frames were found and designated as sseA and sseB. Introduction of either sseA or sseB gene, or both, into E. coli cells enhanced the serine-sensitivity. The sseA gene elicited stronger enhancement than sseB. The deduced amino acid sequence of SseA showed considerable similarity with that of bovine liver rhodanese, which catalyzes sulfur transfer from thiosulfate. We observed a twofold increase in rhodanese activity in E. coli cells harboring a plasmid carrying the sseA gene. The position of sseA in the genetic map is around 52'. However, sseA is different from cysM, which codes for O-acetylserine sulfhydrylase-B, an enzyme catalyzing sulfur transfer from thiosulfate to O-acetylserine, the map position of which is also around 52'.

Amino Acid Sequence↗
PubMed1994

Loss of contractile activity of endothelin-1 induced by electrical field stimulation-generated free radicals.

1. Electrical field stimulation (EFS; 10 V, 10 Hz, 2 ms) of porcine coronary artery strips precontracted with 10 nM endothelin-1 (ET-1) for 5 min caused a biphasic response, consisting of a slight contraction during EFS and a marked and irreversible relaxation just after EFS. This irreversible relaxation after EFS has never been investigated. In the present study, we have investigated the mechanism of the relaxation after EFS. 2. The EFS-induced response was not affected by the presence or absence of endothelium and was insensitive to 10 microM tetrodotoxin (TTX). 3. In the presence of free radical scavengers (40 u ml-1 superoxide dismutase (SOD), 1200 u ml-1 catalase or 80 mM D-mannitol), the relaxation after EFS was significantly inhibited. Moreover, relaxation after EFS was not observed in porcine coronary artery strips precontracted with 20 mM KCl. 4. In a cascade experiment, EFS of Krebs-Ringer solution containing 10 nM ET-1 induced marked suppression of the contractile activity of ET-1 in porcine coronary artery strips, which was in accord with the observed decrease in release of immunoreactive ET-1 (ir-ET-1). This effect of EFS was significantly inhibited by each of the free radical scavengers, 3 mM vitamin C, 40 u ml-1 SOD, 1200 u ml-1 catalase and 80 mM D-mannitol. 5. The exchange of 95% O2/5% CO2 gas for 95% N2/5% CO2 gas significantly inhibited the EFS-induced decrease in release of ir-ET-1. 6. Neither superoxide anions generated by xanthine (10 JM) plus xanthine oxidase (0.1 micro ml-1) nor hydrogen peroxide (10 microM) exogenously added to Krebs-Ringer solution containing 10 nM ET-1 affected the level of ir-ET-1.7. Generation of hydroxyl radicals was detected in the EFS-applied Krebs-Ringer solution. The EFS-induced generation of hydroxyl radicals was dependent on the period of stimulation and 02-bubbling, and significant generation of hydroxyl radicals was detectable with stimulation of over 5 min.Moreover, hydroxyl radicals generated in 50 mM NaCl solution containing 10 nM ET-1 by H202 plus Fe2 , i.e. the Fenton reaction, significantly decreased the level of ir-ET-l.8. These findings suggest that oxygen-derived hydroxyl radicals generated by EFS of porcine coronary artery strips inactivate ET-1, probably by structural modification. Thus, porcine coronary artery strips precontracted with ET-1 are potently relaxed by EFS.

Animals↗
PubMed1994

Effect of 6-hydroxydopamine injection into the arcuate hypothalamic nucleus on the osmotic release of vasopressin in conscious rats.

The aim of the present study was to evaluate a role in vasopressin secretion of the catecholaminergic neurons, including the tuberohypophysial dopaminergic neurons situated in the arcuate hypothalamic nucleus. A neurotoxin, 6-hydroxydopamine (6 g/l), was injected locally into the arcuate nucleus and its effects on catecholamine levels of the hypothalamic tissue and the neurointermediate lobe, and on the plasma vasopressin concentrations before and during i.v. infusion (0.1 ml kg-1 min-1) of isotonic (0.15 mol/l) or hypertonic saline (2.5 mol/l), were examined in conscious rats. The infusion of hypertonic saline produced increases of plasma vasopressin 15 and 30 min later, accompanied by elevations of plasma osmolality, sodium, chloride and arterial pressure. The vasopressin response was potentiated markedly by the 6-hydroxydopamine injection performed 8 days before, which hardly affected the responses of the other variables. Histological examination indicated that the injection sites of 6-hydroxydopamine in those rats had been located in the area ranging from rostral to medial arcuate nucleus. The i.v. infusion of isotonic saline did not change plasma vasopressin, osmolality, sodium, chloride or arterial pressure, regardless of the presence or absence of pretreatment with 6-hydroxydopamine. It was confirmed that when 6-hydroxydopamine was injected into the arcuate nucleus region 8 days before, noradrenaline and adrenaline concentrations of the hypothalamic tissue containing the injection site were decreased remarkably, although we could not detect any significant alteration in the dopamine concentration of the hypothalamic tissue or the neurointermediate lobe. On the basis of these results, we concluded that catecholaminergic neurons in the arcuate nucleus may act to inhibit osmotic vasopressin secretion.

Animals↗
PubMed1993

Cation-coupling in chimeric melibiose carriers derived from Escherichia coli and Klebsiella pneumoniae. The amino-terminal portion is crucial for Na+ recognition in melibiose transport.

The melibiose carrier of Escherichia coli couples sugar transport to H+, Na+, and Li+, while that of Klebsiella pneumoniae utilizes only H+ and Li+. We made five chimeric carriers derived from the two carriers to identify the region(s) involved in Na+ recognition. The chimeric carriers E2K10, E4K8, E6K6, E8K4, and E10K2 have the amino-terminal 77, 144, 197, 298, and 349 amino acid residues derived from E. coli and the rest derived from K. pneumoniae, respectively. Melibiose accumulation through the chimeric carriers E2K10, E4K8, and E6K6 was strongly stimulated by Na+ and Li+ as is the case with the E. coli carrier. On the other hand, there was very little stimulation with the carriers E8K4 and E10K2. These results suggest that, 1) the amino-terminal 77 amino acids of the E. coli carrier, which has 5 different and 4 fewer amino acids than the K. pneumoniae carrier, have a crucial role in Na+ recognition in melibiose transport and 2) the carboxyl-terminal half of the carrier also forms a part of the Na+ recognition site which may be distorted in chimeric structures. In contrast with melibiose accumulation, there was very little Na+ stimulation of TMG (methyl-1-thio-beta-D-galactopyranoside) transport and no Na+ stimulation was observed in lactose transport with any of the chimeric carriers, whereas in E. coli Na+ stimulates TMG and lactose transport. These results suggest that there is no universal Na+ recognition site for all the sugar substrates. Instead different parts of the carrier seem to participate in cation recognition for different sugar substrates.

Base Sequence↗
PubMed1993

Evaluation for roles of brain prostaglandins in the catecholamine-induced vasopressin secretion in conscious rats.

To evaluate roles of prostaglandins (PGs) in vasopressin (AVP) secretion elicited by stimulating alpha-adrenergic and dopaminergic receptors in the periventricular region, we examined in conscious rats the effects of intracerebroventricular (i.c.v.) injections of a cyclooxygenase inhibitor meclofenamate on the plasma AVP responses to i.c.v. applications of angiotensin II (ANG II), phenylephrine and dopamine. I.c.v. injections of 58 pmol ANG II produced, 5 and 15 min later, augmentations of plasma AVP accompanied by elevations of arterial pressure and tendencies of reduction in heart rate. Similarly, the administrations of 0.53 mumol phenylephrine or dopamine enhanced plasma AVP 5 min later, without altering arterial pressure and heart rate significantly. Meclofenamate (0.31 mumol) applied i.c.v. 30 min prior to the administrations of ANG II remarkably inhibited the AVP and pressor responses to this peptide. However, the responses of plasma AVP, arterial pressure and heart rate to phenylephrine or dopamine were not affected by the i.c.v. administrations of 0.31 mumol meclofenamate. The injections of meclofenamate followed by the administrations of a vehicle for ANG II and the catecholamines were without effect on plasma AVP and the cardiovascular parameters. Plasma osmolality, sodium, potassium and chloride in all the groups mentioned above were not significantly changed during experiments. These results suggest that PGs generated in the periventricular region, despite their probable stimulatory roles in the ANG II-evoked AVP secretion, may not participate in the AVP-releasing mechanisms activated by dopaminergic and alpha-adrenergic receptors, supporting the view that PGs and the catecholamines may facilitate AVP release via separate pathways.

Angiotensin II↗