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M Imagawa

Publications and source records attributed to M Imagawa.

At least 109 records · Page 6Linked to original sources
PubMed1993

Secondary structure of the oct-3 POU homeodomain as determined by 1H-15N NMR spectroscopy.

Most of the 1H and 15N magnetic resonances of the 66 amino acid long POU homeodomain of mouse Oct-3 have been assigned by the combined use of the two-dimensional homonuclear, and two- and three-dimensional heteronuclear NMR methods. The sequential NOE connectivities and amide proton exchange measurements indicate the presence of three helical regions within the domain. The positions of the three helices correspond well to those of other homeodomains, the three-dimensional structures of which have already been determined. The present NMR study provides the first experimental evidence for the existence of a helix-turn-helix motif in the oct-3 POU homeodomain.

Amino Acid Sequence↗
PubMed1993

Trans-activation of glutathione transferase P gene during chemical hepatocarcinogenesis of the rat.

Glutathione transferase P (GST-P; glutathione transferase, EC 2.5.1.18) is known to be specifically expressed at high levels in precancerous lesions and in hepatocellular carcinomas from a very early phase of chemically induced hepatocarcinogenesis in the rat. The almost invariable occurrence of this phenotype in these lesions strongly suggests a mechanism by which GST-P gene is activated together with a crucial transforming gene of liver cells. To distinguish the two alternative possibilities--either the GST-P gene is coactivated with a closely located transforming gene by a cis mechanism or it is activated in trans by a common trans-acting factor--we carried out carcinogenesis experiments using transgenic rats harboring the bacterial chloramphenicol acetyltransferase reporter gene ligated to the upstream regulatory sequence of the GST-P gene. In each of three independent lines tested, liver foci and nodules produced by chemical carcinogens (Solt-Farber procedure) were found to express high levels of chloramphenicol acetyltransferase activity, indicating clearly that the GST-P gene is activated by a trans mechanism during hepatocarcinogenesis.

Animals↗
PubMed1993

Pharmacokinetics of beta-methyldigoxin in subjects with normal and impaired renal function.

Beta-methyldigoxin (beta-MD) was administered orally (0.2 mg) to 24 patients with various degrees of renal function, to investigate its pharmacokinetic characteristics related to renal function. Serum and urine collected until 120 hours after dosing were assayed for beta-MD and digoxin by high-performance liquid chromatography and fluorescence polarization immunoassay method. The steady-state volume of distribution decreased proportionately as creatinine clearance (CLCR) decreased, although steady-state volume of distribution of hemodialysis patients had large interindividual variability, and their mean value was not different from that of patients with normal renal function. Both renal clearance of beta-MD and digoxin were significantly correlated with CLCR (r = .820, P < .001 and r = .822, P < .01, respectively), and the slope of regression line for beta-MD was only 44% that for digoxin. Significantly reduced urinary excretion of total drug (beta-MD plus digoxin) was shown in patients with CLCR below 50 mL/minute/1.48 m2. This study suggests that the dosage modification is not necessary until CLCR decreases to below 50 mL/minute/1.48 m2, but careful attention should be given in the use of beta-MD in patients with CLCR below this value.

Adult↗
PubMed1992

The dyad palindromic glutathione transferase P enhancer binds multiple factors including AP1.

Glutathione Transferase P (GST-P) gene expression is dominantly regulated by an upstream enhancer (GPEI) consisting of a dyad of palindromically oriented imperfect TPA (12-O-tetradecanoyl-phorbol-13-acetate)-responsive elements (TRE). GPEI is active in AP1-lacking F9 cells as well in AP1-containing HeLa cells. Despite GPEI's similarity to a TRE, c-jun co-transfection has only a minimal effect on transactivation. Antisense c-jun and c-fos co-transfection experiments further demonstrate the lack of a role for AP1 in GPEI mediated trans-activation in F9 cells, although endogenously present AP1 can influence GPEI in HeLa cells. Co-transfection of delta fosB with c-jun, which forms an inactive c-Jun/delta FosB heterodimer that binds TRE sequences, inhibits GPEI-mediated transcription in AP1-lacking F9 cells as well as AP1-containing HeLa cells. These data suggest novel factor(s) other than AP1 are influencing GPEI. Binding studies reveal multiple nucleoproteins bind to GPEI. These factors are likely responsible for the high level of GPEI-mediated transcription observed in the absence of AP1 and during hepatocarcinogenesis.

Animals↗
PubMed1992

Connections between utricular nerve and dorsal neck motoneurons of the decerebrate cat.

1. We studied connections between the utricular (UT) nerve and dorsal neck motoneurons in decerebrate cats. Electrodes were fixed in place on the UT nerve under visual observation; the other branches of the vestibular nerve were transected. 2. The N1 field potential evoked by UT nerve stimulation was recorded in the vestibular nuclei at the start of each experiment. The potential typically grew until it reached a plateau. Stimulus spread (if any) to the central ends of other nerve branches was revealed by an additional increase in N1 amplitude after the plateau was reached. 3. We recorded intracellularly from 55 motoneurons in C1-C3. Some were identified as having axons in the dorsal rami, which innervate dorsal neck muscles. Others projected in nerves that were not available for stimulation. 4. UT nerve stimulation evoked synaptic potentials in essentially all motoneurons studied. The predominant pattern consisted of disynaptic excitatory postsynaptic potentials in ipsilateral motoneurons and inhibitory postsynaptic potentials that were at least trisynaptic in contralateral motoneurons. 5. The results demonstrate the presence of short-latency connections between the utricular nerve and dorsal neck motoneurons. The functional role of this pathway remains to be investigated.

Animals↗
PubMed1992

Complex regulation of a tumor marker expression. Enhancer and silencer of the GST-P gene.

Glutathione transferase P (GST-P) is expressed at high levels in precancerous lesions and hepatocellular carcinomas from a very early stage of chemically-induced hepatocarcinogenesis in the rat. To explore the molecular mechanisms of its specific activation, we are investigating the regulation mechanisms of the GST-P gene expression. By using gene technology, we have identified a strong enhancer, GPEI, at 2.5 Kb and a silencer region at about 400 bp upstream from the transcription start site. GPEI has a palindromic structure composed of two TPA-responsive element (TRE)-like sequences and binds at least three proteins including AP-1 (c-jun/c-fos). The silencer is composed of several sequences resembling each other and binds at least three proteins including SF-B/LAP/LIP. To determine whether the GST-P gene is activated together with a putative hepato-oncogene because they are located close to each other (cis-mechanism), or because they share a trans-acting factor that can activate both genes simultaneously (trans-mechanism), transgenic rats were produced with GST-P control region connected to the CAT reporter. The results unequivocally demonstrate that GST-P gene is activated position-independently by a trans-mechanism.

Animals↗
PubMed1992

[Clinical study of total parathyroidectomy and autotransplantation for secondary hyperparathyroidism].

From April 1983 to September 1991 total parathyroidectomy (PTX) and parathyroid autotransplantation were carried out in 27 patients for secondary hyperparathyroidism. Of these patients, 13 were males and 14 were females. Their average age was 43 years old and their mean duration of dialysis was 126.4 months. As preoperative clinical symptoms, bone pain was observed in 19 cases, joint pain in 18, decrease of height in 7, pruritus in 3, muscle pain in 2, red eyes in 2 and others in 2. As roentgenographic findings, subperiosteal bone resorption and skull-salt and pepper were demonstrated in 26 cases, rugger jersey spine in 15, soft tissue calcification in 11, and pathological fractures in 4. Four parathyroid glands were removed in 23 cases, three glands in 4. Serum calcium level decreased remarkably within 24 hours after parathyroidectomy in all cases. The average total weight of parathyroid glands was 4.48 g. The preoperative diagnostic accuracy of echogram was 94% and that of CT scan was 90%. The clinical improvement after PTX was excellent in 12 cases and good in 11. The roentgenographic improvement of skull and/or finger bone more than one year after PTX was excellent in 11 cases and good in 11. Judging from histopathological findings of the bone, the clinical and roentgenographic improvement was observed better in the osteitis fibrosa group than in mild group. A significant correlation was found between the level of preoperative c-PTH and the weight of resected parathyroid glands. The level of preoperative ALP correlated with intact-PTH and was higher in the osteitis fibrosa group than in the mild group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Congenital pelvic arteriovenous fistula in a male. A case report].

A congenital arteriovenous fistula (AV fistula) in the true pelvis is extremely rare, especially in males. We present a case of this disease with pollakiuria and intrarectal discomfort. Diagnosis was made by computed tomography and magnetic resonance imaging and confirmed by cine angiography. Because the AV fistula involved the bladder, prostate and rectum, ligation of the main feeding arteries was performed. He also had benign prostatic hypertrophy and was treated by conservative therapy because of a high risk of massive bleeding in surgical treatment.

Arteriovenous Fistula↗
PubMed1992

Analysis of glutathione transferase P gene regulation with liver cells in primary culture.

Glutathione transferase P (GST-P) gene is specifically and highly activated during rat chemical hepatocarcinogenesis. We have previously cloned the GST-P gene and have identified putative regulatory regions. To further explore regulatory mechanisms, deletion constructs of the GST-P gene fused to the chloramphenicol acetyltransferase (CAT) structural gene were introduced into primary cultured rat hepatocytes by electroporation, and their activity was determined. The expression of the GST-P-CAT fusion gene is quite low in these cells as compared to that in both a rat fibroblast cell line, 3Y1 cells, and a rat hepatoma cell line, dRLh84. The presence of the strong enhancer GPEI did not elicit any enhancing activity at its original position, or when it was located 3' of the CAT gene, although this element does enhance CAT activity significantly when located adjacent to the promoter. Cotransfection of neither c-jun nor c-fos expression vector, nor both vectors, could enhance the CAT activity, even though GPEI consists of two phorbol ester response element-like sites. Furthermore, the expression of jun family gene was not correlated with GST-P gene expression either in primary cultured hepatocytes or in hepatoma cell lines.

Animals↗
PubMed1991

SF-B that binds to a negative element in glutathione transferase P gene is similar or identical to trans-activator LAP/IL6-DBP.

We have previously identified a silencer (negative enhancer) in glutathione transferase P (GST-P) gene which is strongly and specifically induced during hepatocarcinogenesis of the rat. At least three trans-acting factors bind to multiple cis-elements located in this silencer. One of these factors, SF-B (Silencer Factor B) specifically binds to GPS1 (GST-P Silencer 1) and has been cloned by a Southwestern protocol. Analysis of DNA and deduced amino acid sequence reveals that SF-B clone is most likely identical to an IL-6 inducible trans-activator LAP/IL6-DBP. Binding efficiency of SF-B to GPS1 is indistinguishable from that to IL6-responsive element found in C-reactive protein gene. The possibility that SF-B/LAP/IL6-DBP functions as a dual positive and negative regulator is discussed.

Amino Acid Sequence↗
PubMed1991

Stringent integrity requirements for both trans-activation and DNA-binding in a trans-activator, Oct3.

POU-specific and POU-homeo domains of Oct3 were produced in Echerichia coli for characterization of DNA binding to the octamer sequence. POU domain protein including A, B and H domains could bind to the octamer sequence efficiently and specifically, and DNase I footprint analysis gave an indistinguishable protection pattern between recombinant POU protein of Oct3 and native Oct3 from undifferentiated P19 cells. Truncated mutants, which contained B-specific and H domains or the H domain only, showed no binding activity, indicating that both of POU-specific and POU-homeo domains are essential for binding activity to octamer sequence. Furthermore, a 6 amino acid deletion from the N-terminal region of the A-specific domain is enough to destroy the binding activity. As for trans-activation, the N-terminal region is essential and sufficient. Deletion of the N-terminal proline-rich region rapidly eliminated trans-activating activity. These data strongly indicate the stringent integrity requirements for both trans-activation and DNA-binding domains in Oct3.

Amino Acid Sequence↗
PubMed1991

Lower lumbar branching of caudal medullary expiratory neurons of the cat.

Extracellular spike activities of medullary expiratory (E) neurons in the caudal ventral respiratory group were recorded in cats anesthetized with sodium pentobarbital. The majority of E neurons extended their axons in the lower lumbar or the sacral segments and distributed collaterals in L5-L7. These results suggest that E neurons are involved not only in respiratory activities but also in the respiratory modulated motor activities of the lower lumbar segments.

Animals↗
PubMed1991

Silencer binding proteins function on multiple cis-elements in the glutathione transferase P gene.

The glutathione transferase P (GST-P) gene is specifically expressed during chemical hepatocarcinogenesis of the rat, whereas mRNA of this gene is virtually undetectable in normal liver. We have previously identified a stretch of DNA, that acted negatively in transcription, at 400 bp upstream from the cap site of the rat GST-P gene. Further characterization has revealed that this negative fragment functions in an orientation and position independent manner, suggesting that it is acting as a silencer. This silencer consists of multiple negative elements to which nuclear factors bind. This silencer is active not only in rat non-hepatoma and hepatoma cells but also in human and mouse cell lines, suggesting that these elements function as general regulators of basal gene expression. At least two proteins bind to this silencer fragment, one of which, designated SF-A (Silencer Factor A), has been partially purified. SF-A binds to several regions in this silencer, and likely plays an important role on negative regulation of this gene.

Animals↗
PubMed1991

The neuronal organization of horizontal semicircular canalactivated inhibitory vestibulocollic neurons in the cat.

1. The somatic location and axonal projections of inhibitory vestibular nucleus neurons activated by the horizontal semicircular canal nerve (HCN) were studied in anesthetized cats. Cats were anesthetized with ketamine hydrochloride and pentobarbital sodium. 2. Intracellular recordings were obtained from 11 neck extensor motoneurons which were identified by antidromic activation from the dosal rami (DR) in the C1 segment. Stimulation of the ipsilateral (i-) HCN and the ipsilateral abducens (AB) nucleus evoked IPSPs in the motoneurons. These IPSPs were fully or partially occluded when they were evoked simultaneously. 3. Intracellular recordings were obtained from 8 AB motoneurons. Stimulation of the i-HCN and the i-C1DR motoneuron pool evoked IPSPs in the AB motoneurons. These IPSPs were also partially occluded when they were evoked simultaneously, which implied that some HCN-activated neurons inhibit both i-AB motoneurons and ipsilateral neck motoneurons. 4. Unit activity was extracellularly recorded from 30 vestibular neurons that were activated monosynaptically by i-HCN stimulation. Their axonal projections were determined by stimulating the i-AB nucleus and the i-C1DR motoneuron pool. Eight neurons were activated by both stimuli, and were termed vestibulooculo-collic (VOC) neurons. Their axonal branching was examined by means of local stimulation in and around the i-AB nucleus and the i-C1DR motoneuron pool. Eighteen neurons were antidromically activated from the i-C1DR motoneuron pool but not from the i-AB nucleus. These were termed vestibulo-collic (VC) neurons. Four neurons were activated from the i-AB nucleus but not from the ventral funiculus in the C1 segment, and were termed vestibulo-ocular (VO) neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Abducens Nerve↗