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M Imai

Publications and source records attributed to M Imai.

At least 271 records · Page 15Linked to original sources
PubMed1993

[Investigation of AZT sensitivity of HIV-1 isolates from patients treated with AZT].

AZT sensitivity was investigated on 6 HIV-1 isolates by culture method. Three of the isolates derived from 2 patients treated with AZT and the others were isolated from patients not treated with AZT. Cultures of 2 isolates (005 and 038) from a patient not treated with AZT did not show cytopathic effect (CPE) in the presence of 0.1 microM or 1.0 microM AZT. Meanwhile, cultures of isolate (043) from a patient treated with AZT for 2 months showed CPE in the presence of 0.1 microM AZT. Furthermore, cultures of isolates from patients treated with AZT for 6 months (043-2) and for 4 months (091) showed CPE in the presence of 1.0 microM AZT. HIV-1 p24 antigen was not detected by ELISA in the supernatants of cultures which did not show CPE. However, HIV-1 p24 antigen was detected in the culture supernatants which showed CPE. These results demonstrated that isolates from patients treated with AZT contained AZT-resistant variants which could replicate in the presence of 1.0 microM AZT.

Adolescent↗
PubMed1993

[Reverse transcriptase gene analysis of HIV-1 mutants cultured in the presence of AZT].

HIV-1 strains were isolated from four patients treated with AZT for more than 6 months and from three patients untreated with AZT. Isolates from patients treated with AZT have been cultured by passage of virus in cell culture in the presence of 1 microM AZT. However the isolates from patients untreated with AZT could not be cultured in the presence of AZT. The RT gene of HIV-1 isolates which had been cultured in the presence of AZT were amplified by PCR and cloned to M13 vector. Four amino acid mutations in RT gene (Asp67, Lys70, Thr215, Lys219) associated with resistance to AZT were analysed. All of the 22 clones obtained from the isolates in the presence of 1 microM AZT had mutations at codon 215(Thr-->Tyr or Phe). Some of the 22 clones also had other mutations at codon 67 (Asp-->Ser), codon 70 (Lys-->Arg) and codon 219 (Lys-->Glu or Gln). Four amino acid residues in RT gene of the isolates which had been cultured in the presence of AZT were compared to that of the isolates cultured in the absence of AZT. The clones of the isolates obtained from the patients (04 or 05) had mutations at only codon 215 Thr-->Tyr) in both the presence and the absence of AZT. All of the clones of the isolates obtained from the patients (06 or 07) had mutations at codon 215 and some of them had other mutations.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Characterization of a temperature-sensitive influenza B virus mutant defective in neuraminidase.

ts5, a temperature-sensitive mutant of influenza B virus, belongs to one of seven recombination groups. When the mutant infected MDCK cells at the nonpermissive temperature (37.5 degrees C), infectious virus was produced at very low levels compared with the yield at the permissive temperature (32 degrees C) and hemagglutinating and enzymatic activities were undetectable. However, viral protein synthesis and transport of hemagglutinin (HA) and neuraminidase (NA) to the cell surface were not affected. The NA was found as a monomer within cells even at 32 degrees C, in contrast to wild-type virus NA, existing mostly as an oligomer, but the mutant had oligomeric NA, like the wild-type virus. Its enzymatic activity was more thermolabile than that of wild-type virus. Despite the low yield, large aggregates of progeny virus particles were found to accumulate on the cell surface at the nonpermissive temperature, and these aggregates were broken by treatment with bacterial neuraminidase, with the concomitant appearance of hemagglutinating activity, suggesting that NA prevents the aggregation of progeny virus by removal of neuraminic acid from HA and cell receptor, allowing its release from the cells. Further treatment with trypsin resulted in the recovery of infectivity. When bacterial NA was added to the culture early in infection, many hemagglutinable infectious virus was produced. We also suggest that the removal of neuraminic acid from HA by NA is essential for the subsequent cleavage of HA by cellular protease. Nucleotide sequence analysis of RNA segment 6 revealed that ts5 encoded five amino acid changes in the NA molecule but not in NB.

Amino Acid Sequence↗
PubMed1993

Regulation of Na(+)-3HCO3- cotransport in rabbit proximal convoluted tubule via adenosine A1 receptor.

We investigated the role of adenosine A1-receptor in the regulation of basolateral Na(+)-3HCO3- cotransporter in the rabbit proximal convoluted tubule (PCT) microperfused in vitro by monitoring basolateral membrane potential and intracellular pH. FK-453, a highly specific A1 antagonist, inhibited basolateral HCO3- conductance in a concentration-dependent manner (10(-10)-10(-5) M). Other A1 antagonists, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) at 10(-5) M and theophylline at 10(-3) M, also had similar effects. N6-cyclohexyladenosine (CHA) at 10(-7) M attenuated the effect of low concentration (10(-8) M) of FK-453. Either enhancement of the degradation of adenosine by 0.1 U/ml adenosine deaminase (ADA) or inhibition of adenosine release from the cells by 10(-6) M S-(4-nitrobenzyl)-6-thioinosine (NBTI) mimicked the effects of A1 antagonists. These observations suggest that endogenous adenosine is released from PCT cells and stimulates Na(+)-3HCO3- cotransporter. Both 10(-4) M 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (CPT-cAMP) and 10(-6) M forskolin also inhibited basolateral HCO3- conductance. Both 10(-6) M FK-453 and 10(-4) M CPT-cAMP decreased the initial rate as well as the magnitude of intracellular acidification induced by reduction of peritubular HCO3- concentration from 25 to 0 mM. Neither 10(-6) M FK-453 nor 10(-7) M CHA changed intracellular Ca2+ concentration as measured by fura-2 fluorescence. These results indicate that adenosine might stimulate HCO3- exit across the basolateral membrane through Na(+)-3HCO3- cotransporter by decreasing intracellular cAMP via A1-receptor activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1993

Cellular heterogeneity of ammonium ion transport across the basolateral membrane of the hamster medullary thick ascending limb of Henle's loop.

The epithelia of the medullary thick ascending limb (MAL) consists of two cell types, high (HBC) and low basolateral conductance (LBC) cell, depending on the K+ conductance of the basolateral membrane. The NH4+ conductance distinct from the K+ conductance has been suggested to exist in the proximal tubule, MAL cell, and Xenopus oocyte. The present study was designed to examine whether there is a conductive NH4+ transport system distinct from K+ conductance in two different cell types of the hamster MAL perfused in vitro. The basolateral membrane voltage (VB) was measured by impaling cells with conventional microelectrodes. Addition of NH4+ to the bath depolarized VB in a dose-dependent manner in both cell types. The response was maintained in the absence of HCO3-. When the VB deflection elicited upon 50 mM KCl or NH4Cl in the bath (delta VBK+ or delta VBNH4+) were compared, delta VBNH4+ was almost the same as delta VBK+ in the HBC cell, whereas the former was greater than the latter in the LBC. In the HBC cell, 10 mM Ba2+ in the bath equally suppressed both delta VBK+ and delta VBNH4+, whereas in the LBC cell it suppressed delta VBK+ with a small effect on delta VBNH4+, indicating that NH4+ is transported via a pathway distinct from Ba(2+)-sensitive K+ conductance. The VB deflection by NH4+ was unaffected by addition of 0.1 mM ouabain or 10 microM 5-nitro-2-(3-phenylpropylamino)-benzoate (a Cl- channel blocker) to the bath, excluding the contribution of the Na+, K+ pump or Cl- channel. An abrupt reduction of Na+ in the bath from 200 to 20 mM did not cause any changes in VB, suggesting that a nonselective cation channel may not account for the NH4+ transport. Amiloride at 10 microM inhibited delta VBNH4+ with a higher efficacy in the LBC cell. We conclude that a rheogenic NH4+ transport system independent from the K+ conductance exists in the basolateral membrane of the LBC cell of the hamster MAL, and may play some roles in the regulation of NH4+ transport.

Ammonia↗
PubMed1993

Sequence analysis of V3 loop region of HIV-1 strains prevalent in India.

The third variable (V3) domain of human immunodeficiency virus type 1 (HIV-1) env gene has been found to elicit type-specific neutralizing antibodies as well as a cytotoxic and helper T-cell response in both humans and animals. We analyzed the V3 domain of 8 HIV-1 isolates from India by using polymerase chain reactions. The V3 loops of 7 Indian isolates contained the apical tetra peptide GPGQ, while the V3 loop of one Indian isolate carried the apical tetra peptide GPGK. The amino acid sequences of the seven Indian isolates were closely related to each other, with an average of the nucleotide sequence homology of 96.0% (94.6 to 97.6%). The marked relatedness of the amino acid sequences among the seven Indian HIV-1 isolates indicated a recent and very rapid spread of this HIV-1 variant in Bombay. The amino acid sequence of the C2/V3 region of env gene of the 7 Indian isolates were homologous to the C subtype reported by Meyers et al. These findings could be useful in assessing the sources of infection and developing an AIDS vaccine.

Amino Acid Sequence↗
PubMed1993

Isoproterenol stimulates Cl- current by a Gs protein-mediated process in beta-intercalated cells isolated from rabbit kidney.

To examine the effect of isoproterenol on Cl- current and its signal transduction pathway in beta-intercalated cells (beta-IC cell), peanut agglutinin (PNA) positive cells in culture were studied by the whole-cell clamp technique. We identified these cells as beta-IC cells by PNA-binding, cell alkalinization induced by Cl- free in the superfusate, and an increase in intracellular cAMP concentration by isoproterenol, but not by vasopressin. Application of isoproterenol in the voltage-clamp mode induced an activation of Cl- current in a dose-dependent fashion and its threshold concentration was in the order of 0.01 microM and ED50 was about 0.1 microM. This effect of isoproterenol was inhibited by atenolol, a beta-adrenergic blocker. Either extracellular application of forskolin or intracellular application of cAMP mimicked the action of isoproterenol. In the presence of forskolin or cAMP, isoproterenol caused little further activation of Cl- current. A synthetic inhibitor of protein kinase A (5-24 amide) inhibited the Cl- -channel activation by isoproterenol. Isoproterenol failed to activate the current in the presence of intracellular GDP beta S. By contrast, intracellular application of GTP gamma S rendered irreversible the Cl- -channel activation by brief exposure to isoproterenol. The present studies provide direct evidence that in the PNA-binding cell, probably the beta-IC cell, the stimulation of beta-adrenoceptor activates Cl- current through the signal transduction system involving G-protein, adenylate cyclase, cAMP, and protein kinase A.

Animals↗
PubMed1993

[Blalock-Taussig shunts in infants less than 6 months of age with special reference to the long-term administration of prostaglandin E1].

Classical Blalock-Taussig (B-T) shunt operation was performed in 14 neonates (group N) and 22 infants (group P). A mean age of group N patients was thirteen days and that of group P patients was two months. Preoperatively prostaglandin E1 (PGE1) was administered in all patients and was continued for a mean of 7 days (range 2 hours to 21 days) in group N, and a mean of 78 days (range 42 to 158 days) in group P. Body weight (4359 +/- 339 g), size of subclavian artery (3.7 +/- 0.5 mm in diameter) and size of pulmonary artery (6.4 +/- 1.2 mm in diameter) at operation of group P patients were larger than those (3212 +/- 490 g, 3.4 +/- 0.4 mm, 5.1 +/- 1.3 mm) of group N. But there were no differences in operation time (165 +/- 22 minutes in group N vs 174 +/- 25 minutes in group P) and clamp time of pulmonary artery (31 +/- 10 minutes in group N vs 30 +/- 5 minutes in group P) between 2 groups. There was no operative death in both groups. There were one late death in group N and three late death in group P. Five patients in group N and nine patients in group P required additional B-T shunt at the mean follow up interval of two years.(ABSTRACT TRUNCATED AT 250 WORDS)

Alprostadil↗
PubMed1993

[Early and long-term results of sternocostal elevation combined with bridge external traction for funnel chest in children].

The purpose of the present study is to evaluate the effects of addition of a bridge external traction to our conventional sternocostal elevation technique in the surgical management of funnel chest in children. During the period from 1970 to 1979, a total of 29 children with funnel chest were treated surgically using sternocostal elevation technique (Group I). Operative technique consisted of total subperichondral resection of deformed costal cartilages (usually 3rd to 8th, bilaterally), transection of deformed portion of the sternum in 2-3 points and fixation of the sternum in elevated position using 2 Kirschner wires, and shortening resuturing of the opened perichondrium. Since 1980, an addition of the bridge external traction to our conventional sternocostal elevation technique was applied for about 10 days after operation in 82 consecutive children (Group II). The vertebral index (B/A = sagittal diameter of vertebral body/minimum sternovertebral distance), D/C ratio (maximum sagittal depth of depression of sternum/distance from anterior surface of the vertebral body to the sternum at Louis's angle) and E/C ratio (E = minimal sagittal distance from anterior surface of the vertebral body to the sternum) were measured in all cases and compared before and after operation and also between the two Groups. Preoperatively, there was no significant difference in all 3 indices between the two Groups. Postoperative B/A, D/C and E/C ratio in Group I were 0.28 +/- 0.06, 0.14 +/- 0.19, 1.09 +/- 0.32 (mean +/- SD), respectively. There were a significant drop in D/C ratio and a significant elevation in E/C ratio after operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

[Prevalence of hepatitis C virus and human immunodeficiency virus infection among Japanese female prostitutes].

To investigate the incidence of hepatitis C virus (HCV) and human immunodeficiency virus (HIV) infection in Japanese sexual workers, 191 out of 194 female prostitutes working in a certain district of the Tokyo metropolitan area were tested for anti-HCV, anti-hepatitis B virus (HBV), anti-HIV and anti-Treponema pallidum (TP). They were also interviewed with regard to their past history of blood transfusion, vaccination against HBV, liver diseases and repeated skin piercing treatments such as tattooing, acupuncture and intravenous drug use. Sera from 300 female blood donors (aged 20 s-40 s), of the same district, collected during the same year, were assessed for comparison. Incidence of seropositives for anti-HCV and anti-TP were found to be significantly high in the prostitute group (11.0% and 16.2%, respectively) compared to the control (0% for both). Anti-HBV seropositives were 14.1% in the prostitute group and 12.7% in the control group without significant difference and none of our subjects were found to be anti-HIV positive. Among HCV infected only 5 experienced repeated skin-piercing treatment and none underwent blood transfusion. From these results it is concluded that HCV has a potential for being transmitted by heterosexual contact, although the exact risk for infection needs to be determined by further investigation.

Adult↗
PubMed1993

[Postoperative pain relief by preanesthetic administration of buprenorphine suppository in elective mastectomy].

Seventy female patients scheduled for elective mastectomy were divided into three groups: Buprenorphine suppository (BPS) 0.4 mg group (n = 29); BPS 0.2 mg (n = 23) group; and control (scopolia extract and tannic acid suppository) group (n = 18). Suppositories were administered rectally to patients of each group one hour before induction of anesthesia. Plasma buprenorphine concentrations, sedation scores at entering the operating room, postoperative pain scores and side effects were evaluated. There were no significant differences in sedation effects of suppository among the three groups. Although there were significant differences in pain scores except at the time when patients left the operating room between BPS 0.2 mg group and the control group, postoperative pain relief in BPS 0.2 mg group was judged not enough. However, postoperative pain relief was more satisfactory in the BPS 0.4 mg group. Plasma concentrations of the BPS 0.4 mg group were higher than those of the BPS 0.2 mg group. Although nausea and vomiting were observed in 5 patients (17.2%) of the BPS 0.4 mg group and 4 patients (17.4%) of the BPS 0.2 mg group, respiratory depression and changes in blood pressure and heart rate were not observed in all groups. In conclusion, preanesthetic administration of the BPS 0.4 mg seemed to be useful for postoperative pain relief after elective mastectomy.

Adolescent↗
PubMed1993

Effect of a novel diuretic, 7-chloro-2,3-dihydro-1-(2-methylbenzoyl)-4(IH)-quinolinone-4-oxime-o- sulfonic acid, potassium salt (M17055) on Na+ and K+ transport in the distal nephron segments.

By using an in vitro microperfusion technique, we examined whether a novel loop diuretic, 7-Chloro-2,3-dihydro-1-(2-methylbenzoyl)-4(IH)-quinolinone-4-oxime-o-sul fonic acid, potassium salt (M17055), a derivative of quinolinone oxime sulfonic acids, affects Na+ and K+ transport in the distal nephron segments, including the cortical collecting duct and connecting tubule (CNT) isolated from rabbit kidneys. M17055 added to the lumen at 1 mM caused a positive deflection of transepithelial voltage (VT) by 2.2 +/- 0.4 mV. The response was less than that evoked by 10 microM amiloride (8.9 +/- 0.1 mV). In the collecting duct cell of the cortical collecting duct from normal rabbits, M17055 depolarized the basolateral membrane by 9.2 +/- 1.3 mV, whereas amiloride hyperpolarized it by 7.6 +/- 2.4 mV. In the cortical collecting duct from deoxycorticosterone acetate-treated rabbits, despite the fact that both agents depolarized the basolateral membrane of the collecting duct cell, amiloride consistently hyperpolarized the apical membrane, whereas M17055 did not cause any significant changes in apical membrane voltage. In the presence of 2mM Ba++ in the lumen, the apical membrane voltage deflection by M17055 was abolished. In addition, the magnitude of the apical membrane voltage deflection caused by an abrupt increase in luminal K+ concentration from 5 to 50 mM was significantly reduced. In the CNT, both amiloride and M17055 caused a positive deflection of VT. However, M17055 depolarized the basolateral membrane by 6.6 +/- 1.6 mV, whereas amiloride hyperpolarized it by 4.4 +/- 1.1 mV.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride↗
PubMed1993

Effects of amiloride and a novel diuretic, 7-chloro-2,3-dihydro-1-(2-methylbenzoyl)-4(1H)-quinolinone-4-oxime-o-su lfonic acid, potassium salt (M17055), on calcium transport in the rabbit connecting tubule.

To elucidate the mechanisms of relative anticalciuric effect of a diuretic, 7-chloro-2,3-dihydro-1-(2-methylbenzoyl)-4(1H)-quinolinone-4-oxime-o-sul fonic acid, potassium salt (M17055), having sites of action on the Henle's loop plus the distal nephron segments, we measured intracellular calcium concentration ([Ca++]i) of the rabbit connecting tubule perfused in vitro by using the microscopic fluorometry with fura 2. First, we confirmed that parathyroid hormone increases [Ca++]i by a mechanism mediated by cyclic AMP. We also confirmed that the Na+/Ca++ exchanger in the basolateral membrane is essential for the extrusion of Ca++ across this membrane. In the presence of 10 nM parathyroid hormone in the bath, the elimination of Na+ from the lumen decreased [Ca++]i, supporting the view that a decrease in Na+ supply from the apical membrane enhances the Na+/Ca++ exchanger in the basolateral membrane. Under a similar condition, the addition of 10 microM amiloride in the lumen also decreased [Ca++]i, further supporting the view that the inhibition of Na+ entry across the apical membrane causes similar effect as does Na+ elimination. Under a similar condition, the addition of 1 mM M17055 in the lumen exerted a similar effect on [Ca++]i as did amiloride. Because M17055 did not further decrease [Ca++]i when Na+ was eliminated from the lumen, the effect of M17055 is mediated by an inhibition of Na+ entry across the apical membrane. From these observations we conclude that either inhibition or diminution of Na+ entry across the apical membrane of the connecting tubule increases the Ca++ extrusion across the basolateral membrane via the Na+/Ca++ exchanger.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride↗
PubMed1992

Transcription in vivo within the replication origin of the Escherichia coli chromosome: a mechanism for activating initiation of replication.

Within the replication origin, oriC, of the Escherichia coli chromosome, novel in vivo transcripts were detected which proceeded rightward and whose production was activated by DnaA protein. In contrast, DnaA protein repressed the previously described ori-L leftward transcription. The former should introduce negative supercoiling, and the latter positive supercoiling, into the 13-mers. The effects of transcription on the initiation of replication were also investigated by making constructs with promoters placed near oriC. Transcription was found to enhance the origin activity only when it was oriented in such a way as to introduce negative supercoiling into the 13-mers. From these results, we propose that transcription within oriC regulates replication initiation by altering the topology of the 13-mer region.

Base Sequence↗
PubMed1992

Systemic atrioventricular valve replacement in an infant with corrected transposition of the great arteries.

A 3-month-old infant with corrected transposition of the great arteries and severe systemic atrioventricular valve regurgitation due to "Ebstein-like anomaly" is reported. Through a right thoracotomy and longitudinal left atrial incision, a 19-mm St. Jude Medical valve was implanted into the annulus without removing the native valve. He is doing well 7 months after operation.

Ebstein Anomaly↗
PubMed1992

User and manufacturer's requirements for IMAC standardization in Japan.

Many radiologists and radiological technologists understand that Picture Archiving and Communication Systems (PACS) are useful not only for image management but also for improving the quality of patient care. However, such systems have not yet been widely installed in hospitals. In order to determine why radiologists have not installed a PACS in their hospitals, we carried out a written survey of 400 Japanese hospitals asking them to describe the current image management activities, the problems inherent in PACS and the problems related to standardization. 216 hospitals responded, and the following suggestions were compiled concerning possible improvements to PACS. (1) PACS benefit needs to be improved with respect to patient care. (2) The cost of PACS should be reduced. (3) The system should be easier to operate and should save time. (4) Standardization is needed to allow simplified, cost-effective networking. We also carried out a written survey of 25 PACS and related equipment manufacturers asking them to describe the opinions inherent in current PACs and the problems related to standardization. Ten manufacturers responded, and the various suggestions were compiled concerning possible improvements to the PAC system.

Japan↗