Biomedical subjects

M Imai

Publications and source records attributed to M Imai.

At least 127 records · Page 7Linked to original sources

PubMed1998

Effect of a topically applied neutralizing antibody against vascular endothelial growth factor on corneal allograft rejection of rat.

BACKGROUND: Studies in corneal transplant rejection remain important because acute immunologic rejection continues to be the leading cause of human corneal transplant failure. As the permeability of vessels and the neovascularization induce cells infiltration into the graft, we considered the possibility that vascular endothelial growth factor (VEGF), a potent permeability-increasing factor and angiogenesis-mediating factor, could participate in the immune response. METHODS: As the established corneal transplant model for rejection, the corneal transplant between Lewis and Fisher rats has been reported. First, we evaluated VEGF production in the graft by immunohistochemical method in the animal model. Next, we tried to neutralize the effect of VEGF by topical administration of anti-VEGF antibody. We administered anti-VEGF antibody as eye drops for 10 days just after the transplantation of the established animal corneal transplant model. RESULTS: VEGF was strongly produced from the infiltrative cells into the graft. Anti-VEGF antibody significantly suppressed the acute rejection compared with saline or rabbit IgG. CONCLUSIONS: The inhibition of VEGF by topically applied neutralizing antibody is a new potential therapeutic strategy for the treatment of corneal transplantation.

Administration, Topical↗

PubMed1998

Molecular cloning of a second human stanniocalcin homologue (STC2).

Stanniocalcin (STC) is a Ca- and phosphate-regulating hormone produced by the corpuscles of Stannius in bony fishes. The mammalian homologue of STC has recently been reported (STC1), which stimulates the phosphate uptake of kidney. Here we report the cloning of a second mammalian stanniocalcin (STC2) from the human osteosarcoma cDNA library. STC2 has 302 amino acid residues with 34% identity with STC1 and eel STC. STC2 has a conserved N-glycosylation site and is rich in cysteines as is the case with other stanniocalcins. STC2 has the same exon-intron boundaries as STC1. The culture medium of STC2-transfected CHO cells inhibited the promoter activity of Na-phosphate cotransporter (NaPi-3) and also inhibited the phosphate uptake of a kidney cell line (OK cells). Therefore, the function of STC2 seems to be opposite to that of STC1 on Na-phosphate cotransporter. Northern blot analysis revealed multiple transcripts in number of human tissues with high levels being present in skeletal muscle and heart. STC2 was also expressed in mice widely and its expression was lower in hypophosphatemic mice (Hyp mice) in many organs. We have cloned a widely expressed new human stanniocalcin homologue which suppressed the expression of renal Na-phosphate cotransporter.

Amino Acid Sequence↗

PubMed1998

Molecular cloning of a novel member of the eukaryotic polypeptide chain-releasing factors (eRF). Its identification as eRF3 interacting with eRF1.

Yeast GST1 gene, whose product is a GTP-binding protein structurally related to polypeptide chain elongation factor-1alpha (EF1alpha), was first described to be essential for the G1 to S phase transition (GSPT) of the cell cycle, and the product was recently reported to function as a polypeptide chain release factor 3 (eRF3) in yeast. Although we previously cloned a human homologue (renamed as GSPT1) of the yeast gene, it has remained to be determined whether GSPT1 also functions as eRF3 or if another GSPT may have such a function in mammalian cells. In the present study, we isolated two mouse GSPT genes, the counterpart of human GSPT1 and a novel member of the GSPT gene family, GSPT2. Both the mouse GSPTs had a two-domain structure characterized as an amino-terminal no-homologous region (approximately 200 amino acids) and a carboxyl-terminal conserved eukaryotic elongation factor-1alpha-like domain (428 amino acids). Messenger RNAs of the two GSPTs could be detected in all mouse tissues surveyed, although the level of GSPT2 message appeared to be relatively abundant in the brain. The mouse GSPT1 was expressed in a proliferation-dependent manner in Swiss 3T3 cells, whereas the expression of GSPT2 was constant during the cell-cycle progression. Immunoprecipitation assays in COS-7 cells expressing flag epitope-tagged proteins demonstrated that not only GSPT1 but also GSPT2 was capable of interacting with eRF1. Such interaction between GSPT2 and eRF1 was also confirmed by yeast two-hybrid analysis. Taken together, these data indicated that the novel GSPT2 may interact with eRF1 to function as eRF3 in mammalian cells.

Amino Acid Sequence↗

PubMed1998

Fatty acid omega and (omega-1)-oxidation within intrasplenically transplanted fetal hepatocytes.

BACKGROUND: The expression and enzymatic activity of the cytochrome P450 LAomega within intrasplenically transplanted hepatocytes was investigated. METHODS: Fetal hepatocytes were harvested from spontaneously hypertensive rats and transplanted into recipient adult spontaneously hypertensive rat spleens. RESULTS: Microscopic examination revealed masses of hepatocytes in the red pulp. Immunochemical studies detected cytochrome P450 LAomega in transplanted hepatocytes by 6 and 10 weeks after transplantation. Cytochrome P450 LAomega mRNA accumulates at 6 weeks after transplantation. Cytochrome P450-arachidonic acid omega/omega-1 hydroxylase activity (formation of 20/19-hydroxyeicosatetraenoic acid) was detected at 10 weeks after transplantation. CONCLUSION: These results demonstrated that fetal hepatocytes grow in the spleen and function similarly to adult hepatocytes.

Animals↗

PubMed1998

Flow-dependent activation of maxi K+ channels in apical membrane of rabbit connecting tubule.

The Ca2+-activated maxi K+ channel was found in the apical membrane of everted rabbit connecting tubule (CNT) with a patch-clamp technique. The mean number of open channels (NPo) was markedly increased from 0.007 +/- 0.004 to 0.189 +/- 0.039 (n = 7) by stretching the patch membrane in a cell-attached configuration. This activation was suggested to be coupled with the stretch-activation of Ca2+-permeable cation channels, because the maxi K+ channel was not stretch-activated in both the cell-attached configuration using Ca2+-free pipette and in the inside-out one in the presence of 10 mm EGTA in the cytoplasmic side. The maxi K+ channel was completely blocked by extracellular 1 microM charybdotoxin (CTX), but was not by cytoplasmic 33 microM arachidonic acid (AA). On the other hand, the low-conductance K+ channel, which was also found in the same membrane, was completely inhibited by 11 microM AA, but not by 1 microM CTX. The apical K+ conductance in the CNT was estimated by the deflection of transepithelial voltage (DeltaVt) when luminal K+ concentration was increased from 5 to 15 mEq. When the tubule was perfused with hydraulic pressure of 0.5 KPa, the DeltaVt was only -0. 7 +/- 0.4 mV. However, an increase in luminal fluid flow by increasing perfusion pressure to 1.5 KPa markedly enhanced DeltaVt to -9.4 +/- 0.9 mV. Luminal application of 1 microM CTX reduced the DeltaVt to -1.3 +/- 0.6 mV significantly in 6 tubules, whereas no significant change of DeltaVt was recorded by applying 33 microM AA into the lumen of 5 tubules (DeltaVt = -7.2 +/- 0.5 mV in control vs. DeltaVt = -6.7 +/- 0.6 mV in AA). These results suggest that the Ca2+-activated maxi K+ channel is responsible for flow-dependent K+ secretion by coupling with the stretch-activated Ca2+-permeable cation channel in the rabbit CNT.

Animals↗

PubMed1998

Primary structure and functional expression of a novel non-selective cation channel.

A non-selective cation channel is believed to play important roles in various tissues. A novel complementary DNA encoding non-selective cation channel was isolated from MIN6, a mouse insulin secreting beta-cell line. This channel (mNSC1) conducts predominantly monovalent cations in Xenopus oocytes and is selective for cations over anions (PK/PCl = 10). The current was completely blocked by lanthanum and niflumate. The mNSC1 of 423 amino acids contains a characteristic leucine repeat and unique membrane topology. The messenger RNA of this channel are abundant in the brain, heart, and lung. We may therefore conclude that studies with this channel will provide important information for understanding physiological functions of the excitable cells as well as non-excitable epithelia.

Amino Acid Sequence↗

PubMed1998

[Successful staged repair of corrected transposition of great arteries and mitral atresia associated with double aortic arch].

We report a rare case of corrected transposition of great arteries and mitral atresia associated with double aoric arch. The patient showed polypnea and cyanosis soon after birth. She underwent balloon atrioseptostomy at the age of 18 days and pulmonary artery banding (PAB) at 24 days. But she showed severe persistent stridor after PAB. Esophagography and left counter-current aortography revealed double aortic arch. At the age of 49 days, division of the left lesser arch and ligation of patent ductus arteriosus were performed through left lateral thoracotomy. Stridor disappeared completely following operation. She underwent total cavopulmonary connection using a 18 mm Gore-Tex graft as intraatrial conduit concomitant with pacemaker implantation at the age of 8 years. Postoperative course was uneventful. To our knowledge, this is the first successful case report of surgical correction of corrected transposition of great arteries and mitral atresia associated with double aoric arch.

Aorta, Thoracic↗

PubMed1998

Quantification of cosmesis for patients affected by adolescent idiopathic scoliosis.

The aim of this study was to quantify cosmesis for patients affected by adolescent idiopathic scoliosis. Eight nonmedical judges were asked to examine photographs of 40 patients with adolescent idiopathic scoliosis, and to score the cosmesis of their backs without any information. Various parameters were measured from radiographs, Moiré topographies, and physical measurements of patients, and these were compared with the cosmetic scores of the judges. The judges' scoring proved to be reliable. The cosmetic scores showed a significant correlation with the Cobb angle, hump severity, asymmetry of the waist line, circumference of the chest, and obesity. Multivariate analysis produced equations to calculate the cosmetic score for the back. This equation is thought to have a useful clinical application.

Adolescent↗

PubMed1998

Thrombin-antithrombin III complex in acute retinal vein occlusion.

PURPOSE: To determine whether quantitative differences in systemic hypercoagulable state could be identified among patients with retinal vein occlusion at various sites of occlusion. METHODS: The value of thrombin-antithrombin III complex was determined in 57 patients with retinal vein occlusion within 1 month after the subjective onset of retinal vein occlusion and in 15 age-matched normal controls. RESULTS: Levels of log thrombin-antithrombin III complex were significantly higher in the patients with proximal retinal vein occlusion in which the occlusion site is at the optic disc (mean +/- SD, 0.493 +/- 0.389) than in those with distal retinal vein occlusion in which the occlusion site is away from the optic disc (0.312 +/- 0.150, P = .025) and in the normal controls (0.294 +/- 0.151, P = .020). There was no significant difference between the distal retinal vein occlusion and the normal controls (P = .720). More patients with proximal retinal vein occlusion showed elevated thrombin-antithrombin III complex values more than 3.9 ng/ml than those with distal retinal vein occlusion (8/29 vs 1/28, P = .025). Of nine patients showing an initial value of thrombin-antithrombin III complex of more than 3.9 ng/ml, repeated measurements were obtained in eight patients, who showed reduced value of thrombin-antithrombin III complex in the normal range in several months. CONCLUSIONS: A systemic hypercoagulable state, which could be demonstrated with the elevation of thrombin-antithrombin III complex value, may contribute more to the development of retinal vein occlusion with thrombus at or near the trunk of the central retinal vein than those with thrombus at branch veins away from the optic disc in the retina.

Acute Disease↗

PubMed1998

Fusion of influenza virus with the endosomal membrane is inhibited by monoclonal antibodies to defined epitopes on the hemagglutinin.

Epitopes on the hemagglutinin (HA) of A/seal/Massachusetts/1/80 (H7N7) influenza virus were mapped by genetic analysis of variants selected with monoclonal antibodies (MAbs). Electron microscopic studies demonstrated that the sites and the directions to which hemagglutination-inhibiting (HI) MAbs and non-HI MAbs bound were different on the HA molecule. Morphological analysis revealed that HI MAbs blocked attachment of the virus to the cells, while non-HI MAbs did not. Virus particles bound with non-HI MAbs were then found in the intracellular vacuoles. Together with the electron microscopic findings, a fluorescence dequenching assay indicated that non-HI MAbs inhibited the fusion of virus with the intracellular vacuolar membrane. It was thus shown that non-HI neutralizing MAbs did not inhibit attachment of the virus to the host cell receptor, but inhibited the fusion step in intracellular vacuoles. The results support the hypothesis that anti-HA MAbs which lack HI activity neutralize viral infectivity by interfering with the low pH-induced conformational change in the HA molecule, resulting in inhibition of the fusion step in the viral replication process (Kida, H., Yoden, S., Kuwabara, M., Yanagawa, R., 1985. Interference with a conformational change in the HA molecule of influenza virus by antibodies as a possible neutralization mechanism. Vaccine 3, 219-222).

Animals↗

PubMed1998

Prognosis in severe motor and intellectual disabilities syndrome complicated by epilepsy.

We investigated the prognosis of epilepsy in 54 patients with severe motor and intellectual disabilities syndrome (SMIDS). The prevalence of epilepsy was 75.7% in our institution for SMIDS. We assessed activities of daily living (ADL) of them at the onset of epilepsy and at present, according to the scores in locomotion, language, toileting, dressing and feeding. Among them, patients with uncontrolled epilepsy constituted 40.3%. ADL scores worsened in the uncontrolled group, while they improved in other cases. Early seizure control is very important in SMIDS for improving patients' quality of life.

Activities of Daily Living↗

PubMed1998

Role of the primary auditory cortex in auditory selective attention studied by whole-head neuromagnetometer.

In order to identify the human cortical areas involved in the auditory attention, neuromagnetic fields were recorded from 12 healthy adults with a 122-channel whole-head magnetometer while the subjects performed the auditory selective attention task. Randomized sequence of 900 Hz (P=0.9) and 950 Hz (P=0.1) tones was presented to each ear with random interstimulus intervals across ears ranging from 300 to 500 ms. Subjects were asked to pay attention to the designated ear (attended ear) and to count the number of the 950 Hz tones presented to the attended ear. Twelve sessions were performed for each subject, among which the attended ear was changed alternately in a counterbalanced order among subjects. In seven out of twelve subjects, averaged neuromagnetic fields in response to frequent tones presented to the attended ear showed attention-related deflection over the bilateral temporal areas starting at around 100 ms after the stimulus presentation. Although the dipole moment for N100m in the attended condition showed significant increase compared to that in the non-attended condition, locations of the two equivalent current dipoles in the auditory cortex were not significantly different from each other. Moreover, a simulation study supported the enhancement of N100m rather than participation of additional dipoles in the auditory selective attention task. These results suggest that the primary auditory cortex plays a main role in the auditory selective attention starting as early as 100 ms after the stimulus presentation.

Adult↗

PubMed1998

Effective lowly cytotoxic analogs of an HIV-cell fusion inhibitor, T22 ([Tyr5,12, Lys7]-polyphemusin II).

A tachyplesin peptide analog, T22 ([Tyr5,12, Lys7]-polyphemusin II), and its shortened congener, TW70 (des-[Cys8,13, Tyr9,12]-[D-Lys10, Pro11]-T22) have strong anti-human immunodeficiency virus (HIV) activity, comparable to that of 3'-azido-2', 3'-dideoxythymidine (AZT). T22 and TW70 are extremely basic peptides, containing 5 Arg residues and 3 Lys residues. The number of positive charges might be related in part to high collateral cytotoxicities of T22 and TW70. Here we have synthesized several analogs, in which the number of positive charges has been reduced through amino acid substitutions using Glu or L-citrulline. As a result, several effective compounds have been found which possess higher selectivity indexes (SIs, 50% cytotoxic concentration/50% effective concentration) than those of T22 and TW70. Higher SIs were attributed mainly to a decrease in cytotoxicity.

Amino Acid Sequence↗

PubMed1998

Downsizing of an HIV-cell fusion inhibitor, T22 ([Tyr5,12, Lys7]-polyphemusin II), with the maintenance of anti-HIV activity and solution structure.

T22 ([Tyr5,12,Lys7]-polyphemusin II) has been shown to have strong anti-human immunodeficiency virus (HIV) activity comparable to that of 3'-azido-2',3'-dideoxythymidine (AZT). T22, an 18-residue peptide amide, takes an antiparallel beta-sheet structure that is maintained by two disulfide bridges. Herein we synthesized several shortened analogs of T22 in order to search for a more suitable lead compound. A 14-residue analog having one disulfide bridge, TW70 (des-[Cys8,13, Tyr9,12]-[D-Lys10, Pro11]-T22), was found to have highly potent activity comparable to that of T22, and to take an antiparallel beta-sheet structure similar to that of T22. This indicates that the molecular size of T22 can be reduced without loss of activity or significant change in the secondary structure, and that TW70 may represent a novel lead compound. Furthermore, modifying the N-terminal alpha-amino group of TW70 with a fluoresceinthiocarbamoyl group, and the epsilon-amino group of D-Lys8 at the turn portion with a 5-aminopentanoyl group remarkably increased the selectivity index (50% cytotoxic concentration/50% effective concentration).

Amino Acid Sequence↗

PubMed1998

Pharmacophore identification of a chemokine receptor (CXCR4) antagonist, T22 ([Tyr(5,12),Lys7]-polyphemusin II), which specifically blocks T cell-line-tropic HIV-1 infection.

We have previously found that T22 ([Tyr(5,12), Lys7]-polyphemusin II) has strong anti-human immunodeficiency virus (HIV) activity, and that T22 inhibits T cell-line-tropic HIV-1 infection mediated by CXCR4/fusin. T22 is an 18-residue peptide amide, which takes an antiparallel beta-sheet structure that is maintained by two disulfide bridges. Structure-activity relationship (SAR) studies on T22 have disclosed the contributions of each region of T22 to activity or cytotoxicity, and have provided the following useful information to develop new CXCR4 antagonists: The number of Arg residues in the N-terminal and C-terminal regions of T22 is closely related to anti-HIV activity. Addition of a variety of functional groups at the N-terminal end results in increases in activity. Disulfide rings, especially the major disulfide loop, are indispensable for anti-HIV activity and maintenance of the beta-sheet structure. Trp3 can be replaced by other aromatic residues (Tyr, Phe and L-2-naphthylalanine). Between two repeats of Tyr-Arg-Lys, which are a characteristic structure in T22, Tyr-Arg-Lys in the N-terminal portion is more closely associated with anti-HIV activity and maintenance of the beta-sheet structure. A positive charge in the side chain at the (i + 1) position of the beta-turn region is necessary for strong activity. Through these studies, we have found several compounds having higher selectivity indexes (50% cytotoxic concentration/50% effective concentration) than that of T22.

Amino Acid Sequence↗

PubMed1998

Sleep problems in the aged in relation to senility.

As a part of an epidemiologic survey of dementia in a community of aged persons, correlation between sleep complaints and physical illness and senility were studied. A total of 3302 randomly sampled aged individuals(aged > or = 65 years) were studied using a questionnaire. In this sample the prevalence of poor sleep and habitual snoring did not increase with age. The prevalence of excessive daytime sleepiness showed an increase with age. Male predominance of habitual snoring and female predominance of poor sleep were observed. Female predominance of excessive daytime sleepiness was noted among the aged 70 and over. Age-related excessive daytime sleepiness was significantly correlated with senility.

Aged↗

PubMed1998

[Evaluation of a PCR assay commercial kit for quantification of human immunodeficiency virus type-1 RNA].

We studied a basic evaluation of the reliability and usefulness of the test results to assess the validity of the kit "AMPLICOR HIV-1 Monitor" as a laboratory tool, by determining the reproducibility, linearity on dilution, possible effects of interference on the results, and correlation with the results obtained at outside facilities. Furthermore, we compared the HIV-1 RNA load between blood samples obtained from HIV-1 subtype B and E. The HIV-1 RNA load measurement was made according to the pre-determined methods of this kit, in blood samples obtained from HIV-positive outpatients. Simultaneous reproducibility was 23.08%-32.95% in C.V.% and linearity was maintained between 110 copies/ml and 2,184,277 copies/ml, demonstrating favorable performance of the kit. The institution correlation between two facilities were also favorable. Fluctuation of measurement by interference was absent for bilirubin, hemoglobin and chyle, but was significant for heparin.

Evaluation Studies as Topic↗

PubMed1998

[Quantitation of viral load in patients infected with HIV-1 subtype E or A].

Quantitation of viral load in a HIV infected person gives important information for monitoring of the clinical status of the patients and evaluation of anti viral effects of admininstred drugs. Although conventional Amplicor HIV-1 monitor system (Roche's conventional method) is used widely, the sensitivity of this system is not enough for measurement of subtype E and A giving lower titer of these subtype viruses than the actual quantity. In Japan, HIV-1 subytpe B cases used to be predominant but recently subtype E cases are increasing especially among heterosexuals thus it becomes required to increase the sensitivity of measurement of HIV-1 RNA of subtype E or A. Therefore we establised the Kanagawa primer method using newly developed subtype E and A primers added to the primers of Roche's conventional method. The results were compared with the conventional Amplicor and also with Roche's new version method which contained new primers. Kanagawa primer method gave 4 to 16 times more sensitive results as compared with Roche's conventional method for subtype E measurement. As for subtype A case, Kanagawa primer method gave a value 1.2 x 10(4) copies/ml while it was undetectable by Roche's conventional method. Roche's new version method showed equal sensitivity of Kanagawa primer method. As for subtype B, the results of these three methods showed no difference. Addition of our newly developed subtype E and A primers to the Roche's conventional method enabled to measure subtype E and A with high sensitivity. For quantitative measurement of HIV-1 RNA, it is important to consider the subtype of the virus in test samples.

Acquired Immunodeficiency Syndrome↗