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Biomedical subjects

M Horiuchi

Publications and source records attributed to M Horiuchi.

At least 127 records · Page 7Linked to original sources
PubMed1997

Secondary abnormality of carnitine biosynthesis results from carnitine reabsorptional system defect in juvenile visceral steatosis mice.

We characterized the L-carnitine transport system which is defective in the kidney of juvenile visceral steatosis (JVS) mice by using kidney slices and carnitine-related compounds, and evaluated the influence of the transport defect on the biosynthetic pathway of carnitine. The JVS mouse transport system defect, calculated as the difference in the transport activity between control and JVS mice, was simulated in control by gamma-butyrobetaine (gamma-BB) and acetyl L-carnitine. gamma-BB hydroxylase activity in the liver of JVS mice was double that of control mice, but the hepatic level of gamma-BB in JVS mice was lower than in control mice, suggesting that the conversion of gamma-BB to carnitine is not activated in the liver of JVS mice. JVS mice showed higher fractional excretions not only of L-carnitine but also of gamma-BB and acetyl L-carnitine than control mice, indicating disturbed reabsorption of gamma-BB and acetyl L-carnitine. The disturbed reabsorption of gamma-BB in JVS mice is consistent with the fact that the amount of urinary gamma-BB in JVS mice was four times that of control. The sum of the concentrations of L-carnitine, acetyl L-carnitine and gamma-BB in the urine of JVS mice was not significantly different from that of the control, suggesting no remarkable increase of biosynthesis of gamma-BB and carnitine in JVS mice. All these findings suggest that the carnitine transport system plays a role in the transport of gamma-BB and that carnitine deficiency is aggravated by the disturbed reabsorption of gamma-BB in the kidney.

Acetylcarnitine↗
PubMed1997

Angiotensin type 2 receptor dephosphorylates Bcl-2 by activating mitogen-activated protein kinase phosphatase-1 and induces apoptosis.

We examined the cellular and signaling mechanism of angiotensin II (Ang II) type 2 (AT2) receptor-induced apoptosis in PC12W (rat pheochromocytoma cell line) cells that express abundant AT2 receptor but not Ang II type 1 receptor. In these cells, nerve growth factor (NGF) inhibited the internucleosomal DNA fragmentation induced by serum depletion, whereas Ang II antagonized this NGF cell survival action and induced apoptosis. We studied the mechanism of NGF and AT2 receptor interaction on apoptosis by examining their effects on the survival factor Bcl-2. AT2 receptor activation did affect intracellular Bcl-2 protein levels. Bcl-2 phosphorylation was stimulated by NGF, whereas AT2 receptor activation blocked this NGF effect. Pretreatment with antisense oligonucleotide of mitogen-activated protein (MAP) kinase phosphatase-1 enhanced the effects of NGF on MAP kinase activation and Bcl-2 phosphorylation but attenuated the inhibitory effects of AT2 receptor on MAP kinase, Bcl-2 phosphorylation, and apoptosis. Taken together, these results suggest that MAP kinase plays a critical role in inhibiting apoptosis by phosphorylating Bcl-2. The AT2 receptor inhibits MAP kinase activation, resulting in the inactivation of Bcl-2 and the induction of apoptosis.

Animals↗
PubMed1997

Deletion of c-myb exon 9 induced by insertion of repeats.

A simple repeat was found to be inserted into exon 9 of the c-myb gene in three out of 20 bovine T lymphomas. The repeat was composed of multiple copies of a 12-nucleotide motif and had no significant homology to the sequences reported so far. Tumor cells containing the repeat expressed two kinds of c-myb mRNA: (1) are that included the repetitive sequence in exon 9, and (2) are that lacked the whole sequence of exon 9. Transfection of an expression vector containing exon and intron sequences and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of the mRNA demonstrated that the insertion of the repeat enhanced exon skipping of the transfected minigene. These observations imply that the insertion of the repeat may enhance exon skipping of the c-myb pre-mRNA. Although the transcription-activating activity by the c-Myb with the repeat was low, that by the c-Myb without exon 9 was three- to eightfold higher than the wild-type c-Myb. These data suggest that insertion of the 12-nucleotide repeat in codon 359 may result in c-Myb proteins having high- and low-transcription-activating activity.

Animals↗
PubMed1997

A novel gene suppressed in the ventricle of carnitine-deficient juvenile visceral steatosis mice.

In order to clarify the pathogenesis and pathophysiology of cardiac hypertrophy in carnitine-deficient juvenile visceral steatosis (JVS) mice, we performed mRNA differential display analysis with total RNA extracted from the ventricles of control and JVS mice at 14 days of age. We identified four up-regulated genes, two known and two unknown, and a novel down-regulated gene. Northern blot analysis with a novel cDNA probe derived from the down-regulated gene fragment 8A2 revealed three mRNA species of 1.1-, 1.3-, and 2.6-kb. The 1.1- and 1.3-kb mRNA species were found only in the heart, and the 2.6-kb species was found in the heart, kidney and brain, but not in skeletal muscle or liver. The 1.1- and 1.3-kb species were down-regulated in the ventricles of JVS mice, but not in the auricles, and increased to the control level with carnitine treatment. We isolated cDNA clones from ventricle RNA, termed CDV-1 (carnitine deficiency-associated gene expressed in ventricle) and from brain RNA, termed CDV-1R (CDV-1-related gene) by 5'- and 3'-RACE analyses. The entire nucleotide sequence except the 5'-terminal 64 bp of CDV-1 cDNA was completely identical to the 992 bp sequence from the 3'-end of CDV-1R cDNA. The CDV-1 cDNA contained an open reading frame predicting a peptide of 107 amino acids, which composed the C-terminal portion of CDV-1R peptide consisting of 414 amino acids.

Amino Acid Sequence↗
PubMed1997

Interferon regulatory factor-1 up-regulates angiotensin II type 2 receptor and induces apoptosis.

The expression of the angiotensin II type 2 (AT2) receptor is developmentally and growth regulated. In cultured R3T3 cells, expression of this receptor is markedly induced at the confluent state and with serum deprivation. In this study we demonstrated that the removal of serum from culture media resulted in the induction of apoptosis in these cells and the addition of angiotensin II further enhanced apoptosis. We have previously identified an interferon regulatory factor (IRF) binding motif in the mouse AT2 receptor gene promoter region. In this report, we observed that serum removal increased IRF-1 expression, with a rapid and transient decrease of IRF-2. To prove that the changes in IRFs after serum removal mediated apoptosis and up-regulated AT2 receptor, we transfected antisense oligonucleotides for IRF-1 or IRF-2 into R3T3 cells and observed that IRF-1 antisense oligonucleotide attenuated apoptosis and abolished the up-regulation of AT2 receptor. IRF-2 antisense oligonucleotide pretreatment did not affect the onset of apoptosis after serum removal; instead, it increased AT2 receptor binding and enhanced angiotensin II-mediated apoptosis. Taken together, these results suggest that increased IRF-1 after serum starvation contributes to the induction of apoptosis and that increased IRF-1 up-regulates the AT2 receptor expression after serum starvation, resulting in enhanced angiotensin II-mediated apoptosis.

3T3 Cells↗
PubMed1997

Alternative usage of exon 1 of bovine PrP mRNA.

Here we report two types of bovine prion protein (PrP) mRNA that possessed different lengths of the 5'-untranslated region and were expressed in various bovine tissues. The two mRNA species were transcribed from identical positions but differed in the usage of the splice site for exon 1/intron. One mRNA possessed exon 1 consisting of 53 nucleotides and the other possessed exon 1 consisting of 168 nucleotides. Usage of exons 2 and 3 was identical for the two mRNA species. The two mRNA species were detected in all but spleen tissue; the mRNA possessing 168-nt exon 1 was not detected in bovine spleen. This is the first report on the tissue-specific alternative splicing of PrPc mRNA in any other species. Only a low level of PrPc appeared to be present in bovine spleen. These results suggested the possibility that the mRNA possessing 53-nt exon 1 was inefficiently translated into Prp; however, in vitro translation analysis showed no marked difference in translational efficiency between the two mRNA species.

Alternative Splicing↗
PubMed1997

Genomic organization and polymorphism of human angiotensin II type 2 receptor: no evidence for its gene mutation in two families of human premature ovarian failure syndrome.

Angiotensin II type 2 (AT(2)) receptor is highly expressed in the fetal tissues and decreases rapidly after birth. AT(2) receptor is re-expressed in the adult atretic ovarian follicles. Recently, it has been reported that AT(2) receptor mediates apoptosis. Primarily, we have cloned human AT(2) receptor cDNA and mapped it to the X-chromosome. To further analyze the organization and function of the AT(2) receptor gene, in this study we cloned the human AT(2) receptor genomic DNA. Human AT(2) receptor gene is composed of three exons and two introns. Primer extension analysis revealed a putative transcription initiation site at 24 bp downstream from TATA box. Furthermore, we identified a polymorphism (C-A) in 3' untranslated region of exon 3, which may be a useful genetic marker for genetic analysis of human X-linked inherited disease. In this study, we postulated that the patients with premature ovarian failure, which has been reported to be linked with X-chromosome abnormality, have AT(2) receptor mutation that may contribute to the early onset of atresia. We examined the entire coding sequence of this receptor in two different families of sisters with premature ovarian failure (POF) but found no changes in nucleotide sequences.

Base Sequence↗
PubMed1997

AT1 and AT2 angiotensin receptor gene expression in human heart failure.

BACKGROUND: The availability of selective antagonists for angiotensin II receptors has focused interest on the gene expression of angiotensin II-receptor subtypes in the human heart. METHODS AND RESULTS: We analyzed expression of the AT1 and AT2 subtypes of the angiotensin II receptor in ventricular myocardium taken from 9 donor hearts before implantation and from 12 patients with heart failure (6 with dilated cardiomyopathy and 6 with ischemic heart disease). Competitive reverse transcription-polymerase chain reaction with synthetic RNA internal standards was used to detect mRNA for both subtypes and to quantify relative differences in levels between failing and non-failing ventricular myocardium. AT1- and AT2-receptor mRNA could be detected in all samples. AT1-receptor gene expression was 2.5-fold greater in nonfailing hearts than in patients with failing hearts (P = .015). There was no significant difference in AT2-receptor mRNA expression in failing and nonfailing hearts. CONCLUSIONS: The level of expression of the angiotensin AT1 receptor appears to decrease in the failing human ventricle whereas the level of AT2 expression is unaffected. These changes parallel the changes found in human ventricular myocardium at the receptor level, suggesting that the changes in receptor level may result from changes in gene expression or mRNA stability.

Adult↗
PubMed1997

Potentiation by DSP-4 of EEG slowing and memory impairment in basal forebrain-lesioned rats.

The effects of cholinergic and noradrenergic depletion, alone and in combination, on spatial memory and electroencephalogram (EEG) activity were investigated. Basal forebrain-lesioned rats exhibited a significant decrease in cortical choline acetyltransferase activity and spatial memory impairment. In the cortical EEG, the basal forebrain lesion induced EEG slowing such as an increase in delta power activity and a decrease in beta power activity. Noradrenergic depletion following a treatment with DSP-4 (N-2-(chloroethyl)-N-ethyl-2-bromobenzylamine) had no effect on cortical choline acetyltransferase activity and spatial memory, but it aggravated the cognitive impairment induced by the basal forebrain lesion. DSP-4 itself increased delta power activity in non-lesioned rats, whereas DSP-4 potentiated the EEG slowing induced by the basal forebrain lesions. Systemic administration of tetrahydroaminoacridine at 1 or 3 mg/kg, i.p., ameliorated the memory deficits and EEG slowing induced by the basal forebrain lesion. However, the drug could not attenuate the EEG slowing and memory impairment in rats that had received a combination of DSP-4 and basal forebrain lesion. These results suggest that noradrenergic depletion aggravated the EEG slowing and the spatial memory impairment induced by cholinergic dysfunction and may decrease the efficacy of an anticholinesterase agent in reversing the cortical cholinergic hypofunction.

Animals↗
PubMed1997

Structural properties and RNA-binding activities of two RNA recognition motifs of a mouse neural RNA-binding protein, mouse-Musashi-1.

mouse-Musashi-1 (m-Msi-1) is an RNA-binding protein, abundantly expressed in the developing mammalian central nervous system (CNS). m-Msi-1 contains two RNA recognition motifs (RRMs). In this study, we found that the N-terminal RRM of m-Msi-1 (MMA) binds strongly to poly(G) and weakly to poly(U) in a way similar to that of the full-length m-Msi-1 protein characterized previously. The C-terminal RRM of m-Msi-1 (MMB), however, does not bind to RNA. In addition, the circular dichroism (CD) spectra of the two RRMs showed that the alpha-helical content of MMA is significantly higher than that of MMB, indicating that some differences in the secondary structure may be responsible for the distinct RNA binding properties of MMA and MMB.

Amino Acid Sequence↗
PubMed1997

Three-dimensional examination of bone structure around hydroxyapatite implants using digital image processing.

This study introduced a new method for three-dimensional (3D) examination of the bone structure around an implant and presented 3D bone-implant contact rates. A block of nondecalcified implant tissue was ground gradually at an interval of 80 micrograms for the collection of serial two-dimensional (2D) images. An image of the stained block surface was instantly recorded by a charge-couple device (CCD) camera and computer-aided system. A 3D model was reconstructed from 60-70 sheets of serial 2D images. The 3D bone structure around the implant was shown in perspective and displayed all sides of the implant. The bone-implant contact rate depended on the cutting position and direction in the specimen. The 3D model will be necessary and valuable for the biomechanical study of dynamic bone changes around implants.

Animals↗
PubMed1997

Pancreatic secretory trypsin inhibitor as a diagnostic marker for adult-onset type II citrullinemia.

Adult-onset type II citrullinemia is characterized by which deficiency of argininosuccinate synthetase (ASS) protein is found specifically in the liver of patients. Our recent study using differential messenger RNA (mRNA) display showed that the expression of human pancreatic secretory trypsin inhibitor (hPSTI) mRNA increases significantly in the liver of all type II patients tested. In the present work, we found that the concentration of hPSTI protein was higher in the liver of type II patients than controls. Because it is well known that PSTI is a secretory protein and because serum PSTI has been proposed as a marker of pancreatic and nonpancreatic diseases, we measured the hPSTI level in the blood of type II patients and compared it with other serum markers such as elastase 1, trypsin, phospholipase A2, alpha-fetoprotein, CA19-9, and C-reactive protein (CRP). We found a significant increase in serum hPSTI level with no change in the other serum markers. These results suggest that serum hPSTI is useful as a diagnostic marker for adult-onset type II citrullinemia.

Adult↗
PubMed1997

Altered expression of atrial natriuretic peptide and contractile protein genes in hypertrophied ventricle of JVS mice with systemic carnitine deficiency.

To characterize cardiac hypertrophy in juvenile visceral steatosis (JVS) mice with systemic carnitine deficiency, we investigated how the hypertrophy develops and whether it is associated with altered expression of any specific genes, especially atrial natriuretic peptide (ANP) and contractile protein genes, in the hypertrophied ventricle. Cardiac hypertrophy in JVS mice became apparent at 10 days after birth and progressed during development. The hypertrophy was observed in the ventricles but not in the atria. ANP mRNA was more intensively expressed in JVS ventricles than in control even at 5 days. Carnitine administration ameliorated the cardiac hypertrophy and suppressed the augmentation of ANP mRNA in the ventricles. Isoform change of expression of alpha-actin genes from cardiac to skeletal was seen in the ventricles of JVS mice at 2 weeks. There was no difference in the ratio of beta-myosin heavy chain mRNA to alpha-myosin heavy chain mRNA between control and JVS mice at 5 days, but at 2 weeks the ratio was significantly lower in JVS mice than in control. These results suggest that the molecular characteristics of cardiac hypertrophy caused by carnitine deficiency are different from those of cardiac hypertrophy caused by aortic constriction.

Actins↗
PubMed1997

Use of interimplant displacement to measure mandibular distortion during jaw movements in humans.

It has been reported that the mandibular body and the dental arch distort during jaw movements because of contraction of the jaw muscles. In the present study the relative position between two biointegrated implants approx. 10 mm apart was measured during maximum opening and protrusive movements of the jaw using a magnetic sensor system. Mandibular distortion was evaluated as the change in the sensor signal. In all participants the distal implant deviated to the lingual side relative to the mesial implant and the deviation with jaw protrusion was larger than that with opening movement. The linear displacement of the two implants ranged from 8 to 25 microns during maximum opening and from 10 to 37 microns during jaw protrusion. Further investigation is required to establish the mechanism of this mandibular distortion, which may be of relevance to implant therapy.

Adult↗
PubMed1997

Characterization of differentiation antigens expressed in bovine lymphosarcomas.

To characterize the cell-surface antigens expressed in tumour cells derived from bovine leukosis and to determine their cell lineages, the immunophenotypes of the tumour cells from 13 bovine lymphosarcomas were examined with 13 monoclonal antibodies (mAbs). Of 13 cattle with lymphosarcomas, four were identified clinically as having the thymic-type sporadic bovine leukosis (SBL) and one as having the skin-type; two had enzootic bovine leukosis (EBL) and six were untypable. Flow cytometric analysis revealed that the tumour cells from nine cases were of T-cell lineage (BoCD5+, BoCD2+ or BoCD2-) and two were of B-cell lineage (MHC-II+, BoCD5+, IgM+); there were two bovine leukaemia virus-infected cattle (EBL). T-cell tumours appeared to originate from immature (BoCD4-, BoCD8-) T cells, but there was no significant relationship between clinical type (EBL, calf-, skin- and thymic-type) and tumour-cell immunophenotype.

Animals↗
PubMed1997

p53 mutation as a potential cellular factor for tumor development in enzootic bovine leukosis.

Mutations of p53 in the lymphocytes from peripheral blood and from tumoral lymph nodes in six naturally occurring bovine leukemia virus (BLV)-infected cows were examined. A point mutation of the p53 gene was found in three of six (50%) BLV-infected cows. These p53 gene mutations resulted in amino acid substitutions of codons 144, 167 and 241. The BLV-infected cow in the tumor stage had abnormally proliferating monoclonal B-lymphocytes having the p53 mutation. However, the mutation was not found in somatic cells, except for tumor cells. These results show that p53 mutation plays an important role in the pathogenesis of BLV-induced neoplasms, and that the B-lymphocyte bearing p53 mutations may be a target cell for tumor formation of enzootic bovine leukosis.

Animals↗
PubMed1997

Sensitive enzyme-linked immunosorbent assay for detection of PrP(Sc) in crude tissue extracts from scrapie-affected mice.

An enzyme-linked immunosorbent assay (ELISA) was developed that detects PrP(Sc) in crude extracts from brain and spleen tissue of scrapie-affected mice with high sensitivity and specificity. Brain tissue was homogenized in 8% Zwittergent 3-12 and 0.5% Sarkosyl. The homogenate was treated with collagenase and DNase I and then subjected to proteinase K digestion. Precipitates containing PrP(Sc) were obtained by ultracentrifugation. Spleen tissue was homogenized in 4% Triton X-100 and 0.5% Sarkosyl, and the homogenate was treated firstly with collagenase and DNase I, and secondly with proteinase K. PrP(Sc) was then extracted with 6.25% Sarkosyl and precipitated through salting-out with NaCl and by ultracentrifugation. When PrP(Sc) was dissolved in 3-4 M guanidine thiocyanate and adsorbed to microtiter plates, strong and specific reactions to the formation of antigen-antibody complexes could be detected by ELISA. The sensitivity of PrP(Sc)-detection for this ELISA, as measured by serial dilution of scrapie material in tissue homogenates from uninfected animals, was equal or higher than that attained by Western blot. This ELISA is more rapid than Western blot and seems to be more suitable for screening large numbers of animals. It also has potential application for the diagnosis of the transmissible spongiform encephalopathies.

Animals↗