Biomedical subjects

M Imagawa

Publications and source records attributed to M Imagawa.

At least 73 records · Page 4Linked to original sources

PubMed1997

[In vivo evaluation of the new antithrombogenic reservoir-catheter coated with polymer blend copolymer].

We evaluated the antithrombogenicity of 4F-catheters coated with the new antithrombogenic material fluorine-acryl- styrene-urethane-silicone (FASUS) graft-block copolymer by dissecting microscopic and scanning electron microscopic observations. These catheters were temporarily used for the infusa-A-port, which was prepared for the treatment of four patients with bladder cancer. Two heparin-coated catheters were also evaluated. All FASUS-coated catheters contained thrombi consisting of red thrombi and/or fibrin thrombi. Massive red thrombus was seen at the site of curvature of the catheters, 1 cm distal to the tip of the catheter. However, the portion 20 cm distal to the tip of the catheter had no red thrombus, but contained minimal fibrin thrombus or plasma protein. The heparin-coated catheters showed the same findings as the FASUS catheters. The FASUS-coated catheters were not superior in antithrombogenicity to the heparin-coated catheters. It was concluded that the FASUS-coated catheters used in this study seemed to have problems in regard to their preshaped curvature and the material used in catheter. These aspects need to be improved.

Aged↗

PubMed1997

Utricular input to cat extraocular motoneurons.

Intracellular recordings from 200 identified extraocular motoneurons in the bilateral III, IV and VI cranial nuclei were studied to determine the connectivities between the utricular nerve and the extraocular motoneurons in cats. Stimulating electrodes were placed within the left utricular nerve, while other branches of the vestibular nerve were removed. Monosynaptic and disynaptic connections between the utricular nerve and the ipsilateral abducens motoneurons and interneurons were recorded as described previously. Stimulation of the utricular nerve evoked longer latency depolarizing and hyperpolarizing potentials in contra- and ipsilateral medial rectus motoneurons, respectively. Depolarizing and hyperpolarizing potentials with longer latencies were also recorded in the ipsilateral inferior oblique and contralateral trochlear motoneurons. The short and longer latency circuits between the utricular nerve and extraocular motoneurons may play a role in stabilizing the retinal image during head tilt and horizontal linear acceleration.

Abducens Nerve↗

PubMed1996

Identification of DNA binding-site preferences for nuclear factor I-A.

Nuclear factor I (NFI) proteins constitute a large family of DNA binding proteins. These proteins promote the initiation of adenovirus replication and regulate the transcription of viral and cellular genes. The binding sites for NFI have been reported in a wide variety of promoters, and they exhibit flexibility in their sequences. To clarify the DNA binding site of NFI-A, one of the NFI proteins, we performed a polymerase chain reaction-mediated random site selection, and determined the optimal sequence as 5'-TTGGCANNNN(G/T)CCA(G/A)-3'.

Animals↗

PubMed1996

Cloning of Xenopus TFIIS and its expression in oocytes and early embryos.

The transcriptional factor TFIIS has been cloned from Xenopus laevis. The length of the cDNA is 1668bp and contains the complete open reading frame of 303 amino acids. Xenopus TFIIS has high homologies to its human and mouse counterparts. In Northern blot analyses, TFIIS mRNAs that consisted of four different sizes were expressed relatively highly from the early stages of Xenopus oogenesis. During oocyte maturation, the pattern of Xenopus TFIIS messages showed a transient peak of expression. TFIIS mRNA occurred maternally and its level increased in later stage embryos. These data suggest that TFIIS mRNA is expressed in a developmentally regulated way in Xenopus laevis.

Amino Acid Sequence↗

PubMed1996

DNA binding specificity of the CCAAT/enhancer-binding protein transcription factor family.

CCAAT/enhancer-binding protein (C/EBP) transcription factor family members are related by a high degree of amino acid sequence identity to the basic leucine zipper DNA-binding domain and show distinct but overlapping patterns of tissue- and stage-restricted expression. Although C/EBPalpha and C/EBPbeta have been shown to recognize a consensus sequence derived from regulatory elements in virus and acute-phase response genes, the potential for more subtle differences in the binding preference of the C/EBP family has not been previously addressed. The consensus sequence of C/EBPdelta has not been reported. By using the method of polymerase chain reaction-mediated random site selection to assess the DNA binding specificity of the C/EBP family in an unbiased manner, we demonstrated the sequence preferences for C/EBP family members. With small variations, these C/EBP family members showed similar sequence preferences, and the consensus sequence was identified as RTTGCGYAAY (R = A or G, and Y = C or T). The phosphorylation of C/EBPdelta by casein kinase II increased the binding activity, but did not affect the binding specificity, whereas it was reported that the phosphorylation of C/EBPalpha and C/EBPbeta decreased the binding affinity. The specificity of action of C/EBP family members may be derived from the characteristics of each factor, including the expression profiles, the DNA binding affinities, the cofactors, and so on, in addition to the DNA binding specificities.

Animals↗

PubMed1996

Isolation of a genomic DNA fragment having negative vitamin D response element.

The vitamin D receptor (VDR) binds to the vitamin D response element (VDRE) in the promoter region of target genes and acts as a ligand-dependent transcriptional regulator. In order to identify novel VDREs and new genes that are regulated by the active form of vitamin D [1,25-(OH)2D3], rat genomic DNA fragments bound by VDR were isolated. One of these fragments, designated as VBF5 was transcribed and the transcript was down-regulated by 1,25-(OH)2D3. These data strongly indicate that VBF5 may contain a VDRE regulating negatively an unidentified gene expression.

Animals↗

PubMed1996

Activation of glutathione transferase P gene by lead requires glutathione transferase P enhancer I.

Glutathione transferase P (GST-P) is specifically induced in rat liver and kidney by lead cation. The increase of GST-P mRNA after lead administration is blocked by actinomycin D, suggesting that GST-P production by lead is regulated at the transcriptional level. To further determine which part of the flanking region of the GST-P gene has the lead-responsive cis-element in vivo, we utilized transgenic rats with five different constructs having GST-P and/or chloramphenicol acetyl-transferase coding sequence. We studied the effect of lead on these transgenic rats and on transfected NRK (normal rat kidney) cells and found that GST-P induction by lead is indeed regulated at the transcriptional level and that the GST-P enhancer I (GPEI) enhancer is an essential cis-element required for the activation of the GST-P gene by lead. GPEI consists of two AP-1 (c-Jun/c-Fos heterodimer) site-like sequences that are palindromically arranged and can bind AP-1, c-jun mRNA in the liver increased after lead administration and GST-P, and c-Jun had patchy expression in the same hepatocytes 24 h after lead exposure. These results suggest that activation of the GST-P gene by lead is mediated in major part by enhancer GPEI and that AP-1 may be involved at least partially. GPEI has been shown to have essential sequence information for the trans-activation of the GST-P gene during chemical hepatocarcinogenesis of the rat (Morimura, S., Suzuki, T., Hochi, S., Yuki, A., Nomura, K., Kitagawa, T., Nagatsu, I., Imagawa, M., and Muramatsu, M. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 2065-2068; Suzuki, T., Imagawa, M., Hirabayashi, M., Yuki, A., Hisatake, K., Nomura, K., Kitagawa, T., and Muramatsu, M. (1995) Cancer Res. 55, 2651-2655). The present study establishes that the same enhancer element does operate in the activation of the GST-P gene by lead regardless of the trans-activators involved.

Animals↗

PubMed1996

Properties of utricular nerve-activated vestibulospinal neurons in cats.

The axonal pathway, conduction velocities, and locations of the cell bodies of utricular nerve-activated vestibulospinal neurons were studied in decerebrated or anesthetized cats using the collision test of orthodromic and antidromic spikes. For orthodromic stimulation, bipolar tungsten electrodes were placed on the utricular nerve and the other vestibular nerve branches were transected. Monopolar tungsten electrodes were positioned on both sides of the upper cervical segments (C2-4), caudal end of the cervical enlargement (C7-T1), and from the lower thoracic to the upper lumbar segments (T12-L3) and were used for antidromic stimulation of the spinal cord. Another monopolar electrode was also placed in the oculomotor nucleus to study whether utricular nerve-activated vestibulospinal neurons have ascending branches to the oculomotor nucleus. Of the 173 vestibular neurons orthodromically activated by the stimulation of the utricular nerve, 46 were second-order vestibulospinal neurons and 5 were third-order neurons. The majority of the utricular nerve-activated vestibulospinal neurons were located in the rostral part of the descending vestibular nucleus and the caudal part of the ventral lateral nucleus. Seventy-three percent of the utricular nerve-activated vestibulospinal neurons descended through the ipsilateral lateral vestibulospinal tract. Approximately 80% of these neurons reached the cervico-thoracic junction, but a few reached the upper lumbar spinal cord. Twenty-seven percent of the utricular nerve-activated vestibulospinal neurons descended through the medial vestibulospinal tract or the contralateral vestibulospinal tracts. Those axons terminated mainly in the upper cervical segments. Almost none of the utricular nerve-activated vestibular neurons had ascending branches to the oculomotor nucleus.

Afferent Pathways↗

PubMed1996

Negative regulation of gene expression in eukaryotes.

Gene expression is mainly regulated at the transcription level. For the specific regulation of gene expression, two components are required: one is the cis-element that is the short DNA sequence in the regulatory region of the gene, and the other is the trans-acting factor that binds to the cis-element. This complex then interacts with the initiation complex, including RNA polymerase II, and regulates the gene expression. Although many elements and factors are reported as involved in the gene activation, little is known about the negative regulation of gene expression. In this study, analyses of the regulatory regions in glutathione transferase P and growth inhibitory factor genes are presented, and the mechanisms of the negative regulation are discussed.

Animals↗

PubMed1996

The sodium-driven polar flagellar motor of marine Vibrio as the mechanosensor that regulates lateral flagellar expression.

Certain marine Vibrio species swim in sea water, propelled by a polar flagellum, and swarm over surfaces using numerous lateral flagella. The polar and the lateral flagellar motors are powered by sodium- and proton-motive forces, respectively. The lateral flagella are produced in media of high viscosity, and the relevant viscosity sensor is the polar flagellum. The cell might monitor either the rotation rate of the flagellar motor or the mechanical force applied against the flagellum. To test these possibilities, we examined the effects of amiloride and its derivatives, which inhibit the rotation of the sodium-driven motor, on lateral flagellar gene (laf) expression in Vibrio parahaemolyticus. Phenamil, an amiloride analogue that inhibits swimming at micromolar concentrations, induced laf transcription in media devoid of viscous agents in a dose-dependent manner. The relationship between the average swimming speed and laf induction in the presence of various concentrations of phenamil was very similar to that observed when viscosity was changed. These results indicate that marine Vibrio sense a decrease in the rotation rate of (or the sodium influx through) the polar flagellar motor as a trigger for laf induction. Alternative mechanisms for laf induction are also discussed.

Amiloride↗

PubMed1996

Mutational screening of APP gene in patients with early-onset Alzheimer disease utilizing mismatched PCR-RFLP.

To elucidate the frequency of mutations of the beta/A4 amyloid protein precursor (APP) gene in early-onset Alzheimer disease, we designed a mismatched PCR-RFLP that can identify all kinds of missense mutations at codon 717 in addition to the seven kinds of known mutations at exon 17. When we screened mutations at exon 17 utilizing this method and the double missense mutations at exon 16 of the APP gene by PCR-RFLP, no cases revealed mutations of the APP gene among 13 familial and 54 sporadic cases, except one family (OS-1) that had previously been reported and used as a positive control of APP717(Val-->Ile). Our results support the hypothesis that mutations in the APP gene are not major causes in early-onset Alzheimer disease.

Adult↗

PubMed1996

Utriculoocular reflex arc of the cat.

1. Intracellular recordings of synaptic potentials in extraocular motoneurons were studied to determine the connectivities between the utricular nerve and the extraocular motoneurons in cats. 2. Stimulating electrodes were placed within the left utricular nerve, while other branches of the vestibular nerve were removed. Subsequently, the N1 field potentials evoked by utricular nerve stimulation were recorded in the vestibular nuclei. The potential typically grew until reaching a plateau (submaximal stimulation). Stimulus spread to the other nerve branches appeared as an additional increase in N1 amplitude after the plateau discontinued (supramaximal stimulation). 3. Intracellular recordings were made from 200 identified motoneurons in the bilateral III, IV, and VI cranial nuclei. 4. Stimulation of the utricular nerve at submaximal intensity evoked a longer latency depolarizing and hyperpolarizing potentials in contra- and ipsilateral medial rectus motoneurons, respectively. Complex potentials with longer latencies also were recorded in ipsilateral inferior oblique and contralateral trochlear motoneurons after stimulation of the utricular nerve at a submaximal intensity. Monosynaptic and disynaptic connections between the utricular nerve and ipsilateral abducens motoneurons and interneurons were recorded as described previously. 5. The results of the present study confirm our initial findings that a disynaptic pathway from the utricular nerve to contralateral trochlear motoneurons is absent or very poorly developed, whereas polysynaptic circuits from the utricular nerve to inferior oblique and trochlear motoneurons may play a role in eye rotation during head tilt.

Animals↗

PubMed1996

Genetic association study between senile dementia of Alzheimer's type and APOE/C1/C2 gene cluster.

Senile dementia of Alzheimer's type (SDAT) is characterized by progressive deficits of multiple cognitive functions in elderly more than 65 years of age. The APOE-epsilon 4 allele has been shown to be a risk factor for SDAT. To investigate the genetic interactions between SDAT and the APOE/APOC1/APOC2 gene cluster located at 19q13.2, we genotyped these genes in patients with SDAT and nondemented controls. Although allelic associations were found between the APOC1 locus and SDAT (p = 0.0022) as well as between the APOE locus and SDAT (p < 0.0001), no associations were detected between the APOC2 locus and SDAT. And the association between the APOE and APOC1 locus in SDAT was statistically more significant than that in controls (p < 0.001). Estimation of the haplotype frequencies indicated that the association between the APOE/APOC1 haplotype and SDAT was more significant than linkage disequilibrium between the APOE and APOC1 locus (p < 0.01). These results suggest that genetic interaction between the APOE and APOC1 gene could modify a risk factor of APOE-epsilon 4 for SDAT. The APOE/APOC1 locus was estimated to be responsible for 54.8% of SDAT in the Japanese population.

Aged↗

PubMed1996

Modulation of platelet-activating factor synthesis by recombinant interferon-alpha in human renal cell carcinoma.

Platelet-activating factor (PAF), a potent phospholipid chemical mediator of inflammation, is involved in multiple cellular functions. Since PAF has a strong effect on platelet aggregation and on the enhancement of capillary permeability, it is possible that this factor plays an important role in tumor progression. In human renal cell carcinoma (RCC), it has recently been reported that immunotherapy with interferon (IFN) is effective for the prevention of tumor recurrence and progression. To evaluate the role of PAF and the effect of interferon-alpha (IFN-alpha) on PAF production in RCC, we measured PAF content and the activity of choline phosphotransferase (CPT), an enzyme involved in the de novo biosynthesis of PAF, in RCC specimens obtained from 30 patients who had undergone radical nephrectomy for RCC, and in specimens of normal renal cortex and normal renal medulla. PAF was present in both RCC and the normal renal tissues. Although CPT activity in RCC was similar to that in normal renal cortex, CPT activity in the normal medulla was significantly higher than that in RCC and the normal cortex. No correlation was found between CPT activity and the pathological findings in RCC. Although there was no difference in CPT activity in normal renal tissues between patients treated preoperatively with IFN-alpha and those untreated, CPT activity in RCC was significantly reduced in patients who had received IFN-alpha compared with those who had not. These findings suggest that IFN-alpha may modulate the production of PAF in RCC patients.

Antineoplastic Agents↗

PubMed1996

[Regulation mechanism of specific expression of tumor marker gene during carcinogenesis].

Rat glutathione transferase P (GST-P) is expressed at low levels in the normal liver but becomes highly expressed in hyperplastic nodules and in hepatocellular carcinomas during chemical hepatocarcinogenesis. To understand the regulation mechanisms of this gene, we have characterized the 5'-flanking region and have found that GST-P gene is regulated by at least two elements: one is a strong enhancer and the other is a silencer. GST-P enhancer I (GPEI), located at -2.5 Kb, consists of two TPA-responsive element (TRE)-like sequences that are palindromically oriented with 3 bp in between. It is well known that TRE is activated by two nuclear oncogenes, c-Jun and c-Fos. Although GPEI is trans-activated by these oncogenes, it is also active in F9 embryonal carcinoma cells that lack c-Jun protein, suggesting that it can function with some trans-activator other than AP-1 (c-Jun/c-Fos heterodimer). Indeed, another protein is identified from the F9 nuclear extract. We have also identified a silencer element at 300 bp upstream from the cap site. There are several cis-elements in this region and at least three trans-acting factors bind to these elements. We purified SF-A (silencer factor A) which binds to several regions in this silencer, and determined the partial amino acid sequence. Interestingly, SF-A seemed to be a related protein to NF1 (nuclear factor 1) which is an activator for the transcription and DNA replication. Another factor SF-B (silencer factor B) has been cloned and found to be the same as LIP (liver inhibitory protein) which is a competitor for LAP (liver activator protein), both are from the same gene designated as C/EBP beta. By transfection analysis using GAL4 DNA binding domain we found LIP is not only a competitor but a direct repressor. In the normal liver, another C/EBP family member, C/EBP alpha also acts as a negative regulator, and this expression decreases during hepatocarcinogenesis, resulting in the loss of silencer function. We carried out the carcinogenesis experiments using transgenic rats harboring a chloramphenicol acetyltransferase (CAT) reporter gene with -2900 to + 59 of the GST-P gene. Liver foci and nodules produced by chemical carcinogens were found to express high levels CAT activity by both CAT assay and immunohistochemical study, while normal liver cells did not express any CAT activity. These results demonstrate that the GST-P gene is trans-activated locus-independently during rat hepatocarcinogenesis. Moreover, the similar results were obtained using transgenic rats carrying GPEI-CAT, indicating that GPEI is an important cis-element for activation of GST-P gene during hepatocarcinogenesis.

Animals↗

PubMed1996

Phylogenetic development of brain and brain sulci in primates.

The purpose of this study was to investigate the phylogenetic development of the cerebrum and cerebral sulcus in primates. The species selected were Macacus, Hylobates, Pan and Homo sapiens. These samples are classified as old world monkeys (Cercopithecidae), anthropoid apes (Pongidae), and Man (Hominidae). Although these four species divided up and went their separate ways from about the Oligocene era, the pattern of the cerebral sulci is similar. Of various cerebral sulci, the cingulate and calcarine sulci were selected, because they run on the medial surface of the cerebrum. The length of these sulci and fronto-occipital (FO) length were measured by a "cotton-thread" method. With the increase of size (FO-length) and weight of the brain, these sulci became longer, but there were no significant differences in the ratio of the calcarine sulcus to the FO-length among these four species. On the contrary, the ratio of the cingulate sulcus to the FO-length in Pan and Homo sapiens was significantly higher than in the other species, indicating that this ratio becomes higher with the phylogenetic development. The results of the present study suggest that the ratios of these sulci to the FO-length can be used as good indices to assess the degree of the phylogenetic development of the brain.

Animals↗

PubMed1995

CCAAT/enhancer-binding proteins alpha and beta interact with the silencer element in the promoter of glutathione S-transferase P gene during hepatocarcinogenesis.

We have previously identified a silencer in the glutathione S-transferase P (GST-P) gene which is strongly and specifically expressed during chemical hepatocarcinogenesis. At least three trans-acting factors bind to multiple cis-elements in the silencer. One of them, Silencer Factor-B (SF-B), is identical with CCAAT/enhancer-binding protein beta (C/EBP beta) and binds to GST-P Silencer 1 (GPS1). Many C/EBP beta binding sites are recognized by each of the C/EBP isoforms. Western blot analyses of C/EBP isoforms during chemical hepatocarcinogenesis revealed a decrease of C/EBP alpha expression. However, there was no change in C/EBP beta level. In the nuclear extracts from normal liver, C/EBP alpha was the dominant form that bound to GPS1, whereas both C/EBP alpha and C/EBP beta bound to GPS1 in the nuclear extracts from carcinogenic liver. Furthermore, transfection assays showed that C/EBP alpha not only repressed the GST-P promoter activity but also attenuated the transcriptional stimulation by C/EBP beta. These observations strongly suggest that the ratio of C/EBP alpha to C/EBP beta is one of the important factors for the GST-P silencer activity, and the decrease of this ratio during hepatocarcinogenesis reduces the silencer activity and, consequently, increases the GST-P expression.

Animals↗

PubMed1995

CTG triplet repeat in mouse growth inhibitory factor/metallothionein III gene promoter represses the transcriptional activity of the heterologous promoters.

Growth inhibitory factor/metallothionein III (GIF/MT-III) is expressed specifically in brain, and neither mRNA nor protein is detected in other organs. This tissue-specific expression might be regulated by negative elements as well as positive elements, such as tissue-specific enhancers. To investigate the repression mechanisms of this gene in organs other than the brain, transfection experiments were performed by using various deletion mutants. Interestingly, a 25 x CTG repeat in the promoter region seemed to contribute to the repression activity. Moreover, the repression activity of this 25 x CTG repeat was also observed in various promoters and in a direction and position independent manner, indicating that this element could act as a silencer. However, no binding protein was detected by gel-shift and footprint analyses. These results strongly suggest that the CTG repeat functions as a negative element, and that this effect is caused by unknown mechanisms, rather than by interactions between specific cis-elements and specific trans-acting factors as reported previously. It is also possible that the CTG repeat functions as a general silencer in many genes.

Alzheimer Disease↗