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Biomedical subjects

K Murakami

Publications and source records attributed to K Murakami.

At least 595 records · Page 33Linked to original sources
PubMed1994

Binding characteristics of a histamine H3-receptor antagonist, [3H]S-methylthioperamide: comparison with [3H](R)alpha-methylhistamine binding to rat tissues.

The release and synthesis of neuronal histamine are regulated by histaminergic autoreceptors named as histamine H3 receptors. The development of radiolabeled histamine H3 antagonists is needed to characterize the binding of antagonists to these receptors. Here we describe the binding characteristics of a new histamine H3-receptor antagonist, [3H]S-methylthioperamide (SMT), to rat tissues, and compare its binding with that of [3H](R)alpha-methylhistamine ((R)alpha MH), a selective histamine H3-receptor agonist. The binding of [3H]SMT to the membranes of rat forebrain was found to be stereoselective, saturable, reversible and temperature-dependent. Saturation binding experiments indicated a single class of high affinity sites for [3H]SMT in forebrain membranes (KD = 2.1 nM, Bmax = 24.3 pmol/g of tissue at 4 degrees C). The Bmax was approximately 3 times that of [3H](R)alpha MH binding to rat forebrain membranes (KD = 2.5 nM, Bmax = 7.3 pmol/g of tissue at 25 degrees C). Autoradiographic images of [3H]SMT binding in the brain were essentially the same as those of [3H](R)alpha MH. [3H]SMT also bound appreciably to peripheral tissues (the liver, adrenal, stomach, ileum, kidney, lung and bladder), whereas the [3H](R)alpha MH bindings to these peripheral tissues were negligible. These results indicate that [3H]SMT binds to H3 receptors primarily in the central nervous system, and that it also has high affinity toward non-H3 receptors, probably hemoproteins, in peripheral tissues.

Animals↗
PubMed1994

Sequencing and expression of sheep angiotensinogen cDNA.

A sheep liver cDNA library was screened with a BstEII fragment of human angiotensinogen cDNA to obtain sheep angiotensinogen cDNA. The cDNA sequence showed that preangiotensinogen consisted of 452 amino acid residues (49 kDa) of angiotensinogen and 24 residues of a signal peptide. Recombinant sheep angiotensinogen (56 kDa) was expressed in COS-7 cells.

Amino Acid Sequence↗
PubMed1994

Species-specific expression of the hepatic renin gene.

The catalytic reaction of renin, an aspartyl proteinase, with angiotensinogen is the rate-limiting step fo the renin-angiotensin system involved in the maintenance of blood pressure and electrolyte balance in mammals. We have characterized species-specific expression of the hepatic renin gene by RNase protection experiment, primer extension analysis, and promoter assay using an in vitro DNA transfection. RNase protection experiments revealed that the renin gene is expressed in rat liver, but neither in mouse nor in human. Primer extension analysis identified the putative promoter region of the rat renin gene, which contains TATAAAA sequence, a canonical regulatory DNA element. In order to test whether the upstream region of the renin gene with respect to the putative transcription initiation site is a functional promoter, we have examined the ability of the 5'-flanking sequences of the rat renin gene as well as the human and mouse genes to activate expression of a reporter gene containing the bacterial chloramphenicol acetyltransferase (CAT)-coding sequences, by transient transfection assays. In transfected HepG2 cells, a hepatoma cell line, only the rat renin promoter was capable of driving the CAT gene expression. These results suggested that the rat-specific renin gene expression in the liver could be primarily determined by its promoter specificity.

Animals↗
PubMed1994

Postprandial hemodynamic changes evaluated by a Doppler echocardiographic method.

To evaluate postprandial hemodynamic changes, Doppler measurements of stroke volume before and after lunch were carried out in 10 healthy volunteers (all men) with a mean age of 28 years. The stroke volume was calculated as the product of echocardiographically determined aortic valve area and the ejection flow velocity integral obtained by continuous wave Doppler. The stroke volume before lunch was 61 +/- 7 ml, which was increased to 72 +/- 8 ml 1 hour after lunch and remained constant for the next 4 hours. Five hours later the stroke volume was then decreased to the baseline. M-mode echocardiography revealed an increase in left ventricular end-diastolic dimension and ejection fraction after lunch. Another 9 healthy subjects (6 women and 3 men) with a mean age of 52 years received a 75 g oral glucose tolerance test (OGTT) instead of a common lunch; stroke volumes were not altered in association with the elevation of plasma glucose level. In conclusion, ingestion of food had a positive inotropic effect and caused circulating blood volume expansion with an increment of heart rate. Therefore, Doppler studies that are not standardized for patients' mealtimes may affect the validity of data in serial studies of left ventricular function.

Adult↗
PubMed1994

Morphometric analysis of the kidney lesions in mixed connective tissue disease (MCTD).

We examined histopathological changes of the kidney in patients with mixed connective tissue disease (MCTD) including those of glomeruli, arteries and interstitium by morphometric method. All specimens examined were collected from 25 autopsy cases diagnosed as MCTD according to the criteria for this disease proposed by the MCTD committee sponsored by the Japanese government. Clinical evidence of renal dysfunction such as proteinuria was present in 16 out of 25 cases (64%). Histopathologically, membranous type glomerular lesion was found most frequently (40%), followed by membrano-proliferative (6.7%) and mesangioproliferative types (6.7%). Nine cases had no glomerular lesion. Severe arterial lesion such as necrotizing angiitis was not found in our kidney specimens. However, morphometry revealed a high incidence of intimal thickening in the renal arteries of these patients as compared to control cases, showing this to be one of the most common features of MCTD with clinical importance. This type of arterial lesion, also seen in kidneys in other types of collagen diseases, may suggest an etiology common to them. The severity of the renal interstitial lesion in MCTD was intermediate between that of systemic lupus erythematosus (SLE) and progressive systemic sclerosis (PSS), poly-or dermatomyositis (PM/DM).

Adult↗
PubMed1994

Evaluation of renal function by dynamic MR imaging: effect of water load.

The aim of this study was to investigate the usefulness of magnetic resonance (MR) imaging in the evaluation of renal function, with particular attention to the effects of water load. Ten healthy volunteers underwent dynamic MR imaging after an injection of gadolinium diethylene-triaminepenta-acetic acid (Gd-DTPA) as a contrast agent to evaluate renal function by the following four methods: the positive method [longitudinal relaxation time (T1) shortening is the dominant effect], the negative method [transverse relaxation time (T2) shortening is the dominant effect] and two intermediate methods by switching the Gd-DTPA concentrations used in the positive and negative methods. A prolonged cortical peak time and a reduced medullary peak level were observed by the positive method under a dehydrated condition, suggesting that these variables were slightly influenced by Gd-DTPA concentrated in the medulla. By the negative method, low signals due to T2* (T2* is the effective transverse relaxation time, typically shorter than T2) shortening appeared in the medulla under normal conditions, but these signals were unclear when the subject was under an overhydrated condition. These results indicate that water metabolism, in addition to imaging parameters and Gd-DTPA dose levels, should be considered when renal function is evaluated by dynamic MR imaging. Analysis of both the pattern of MR images and the time-signal intensity curves may be useful in the evaluation of renal function. The results also indicate that the positive method is preferred when the patient is overhydrated as it allows the evaluation of the local renal kinetic function by recording changes in the regional contrast agent levels.

Adult↗
PubMed1994

Establishment of an animal model for chronic gastritis with Helicobacter pylori: potential model for long-term observations.

OBJECTIVES: To assess the suitability of an established experimental model for chronic gastritis associated with Helicobacter pylori for use in long-term observations. DESIGN: In a 3-year follow-up study of acute gastritis induced by H. pylori using an established experimental model with Japanese monkeys, we compared H. pylori-infected animals (n = 6) with a non-infected control group (n = 7). Colonization by H. pylori, gastritis scores, volume of intracellular periodic acid-Schiff-positive substances and the height of antral glands were investigated every 3 months for 3 years and compared with those of a control group. RESULTS: In the infected group, persistent colonization with H. pylori was demonstrated by culture and histological examinations. Gastritis scores were significantly higher than those of the control group, and the histological findings were quite similar to those of chronic active gastritis observed in humans. Simultaneously, significant decreases in the contents of periodic acid-Schiff-positive substances and in the height of antral glands were also demonstrated in infected animals. CONCLUSION: In Japanese monkeys, persistent colonization with H. pylori caused chronic gastritis quite similar to that observed in humans, thus providing a suitable animal model for evaluating the long-term prognosis of H. pylori infection.

Animals↗
PubMed1994

[The pulmonary air meniscus sign in a case of sclerosing hemangioma].

A 57-year-old woman was admitted to our hospital because of a slowly growing pulmonary tumor with a 34 year history. Chest roentgenogram on admission showed a 42 mm sharply demarcated solitary tumor in the left upper lobe. Chest CT revealed a slit-like pulmonary air meniscus. Left upper lobectomy was performed. A specimen from the resected lung histologically showed solid, papillary and hemorrhagic patterns, and the diagnosis of pulmonary sclerosing hemangioma was therefore made. Pulmonary air meniscus sign in pulmonary sclerosing hemangioma is rare. We think one possible mechanism in the production of an air meniscus sign in sclerosing hemangioma is bleeding in communication with a bronchus.

Female↗
PubMed1994

[A case of anti-phospholipid antibody syndrome associated with typical mesangiolysis].

An 18-years-old female was admitted to our hospital because of severe edema, that had developed within one week, and massive proteinuria. She has been given treatment for mild proteinuria and Raynaud's phenomenon. Before the edema developed, she complained of recurrent attack of migraine associated with scintillating scotoma. At admission, she was suffering from butterfly erythema, hydropericardium and ascites. The results of tests for antinuclear antibodies and ENA antibodies were negative, but those for BFP and IgG-anticardiolipin antibody were positive, and the platelet and complement levels were low. Renal biopsy revealed typical mesangiolysis without any sign of hyperplastic nephritis. Electron microscopy demonstrated the deposition of microfibrillar structures in the mesangial areas. She was diagnosed as having SLE-antiphospholipid antibody syndrome. After the administration of prednisolone 40mg/day, the edema, Raynaud's sign and proteinuria disappeared. Migraine was improved by the additional use of warfarin, and the platelet count was normalized. These findings suggest that in this case, acute nephrotic symptom developed due to hemangioendothelial injury caused by anti-phospholipid antibody.

Adolescent↗
PubMed1994

Complex formation between lamin A and the retinoblastoma gene product: identification of the domain on lamin A required for its interaction.

The retinoblastoma susceptibility gene product (pRB) has been known to function as a negative regulator of cell growth. Recent observations suggest that its biological activity might be modulated by an interaction with nuclear structures. By using in vitro binding assays, we have found that pRB can associate with lamin A, which has been known to be one of the major nuclear matrix proteins. A series of GST-lamin A deletion mutants was constructed to define the amino acid sequence required for binding to pRB. A GST-lamin A (247-355) contained an activity to associate with pRB, while the other constructs, such as GST-lamin A (37-244) or GST-lamin A (356-571), could not bind to pRB. Within the pRB-binding domain of lamin A, there exists the short amino acid sequence which is also present in the pRB-binding region of the transcription factor E2F-1. The similar experiments using a set of GST-RB deletion mutants revealed that a region containing the E1A-binding pocket B and the carboxy-terminal portion of pRB was responsible for binding to lamin A.

Amino Acid Sequence↗
PubMed1994

Combined therapy in children and adolescents with IgA nephropathy.

We retrospectively evaluated renal outcome in a total of 38 children and adolescents with IgA nephropathy who were selected for 6-month therapy for clinical (proteinuria > 1 g/m2/24 hour) and pathologic (mesangial proliferation, crescent formation, and tubulo-interstitial changes) features suggestive of progressive renal failure. Seventeen patients (group A) were treated with a combination of prednisolone, cyclophosphamide and dipyridamole, and the remaining patients (21; group B) were treated with the same drugs plus warfarin. All the patients were followed-up for more than 2 years (range 2-10 years, mean 4.8). In both groups, the mean urinary protein excretion value was significantly reduced after the therapy, compared with that at entry into the therapy. The significant reduction continued for up to 6 years in group A and up to 5 years in group B. Creatinine clearance was stable until 5-6 years after the trial in both groups, but 4 patients progressed to end-stage renal failure after that period. Post-therapy biopsy was performed in 14 patients, and was compared with the pre-therapy biopsy. The activity score had improved in both groups, but the chronicity score did not. These results indicate that there was a temporary effect and limited benefit with this treatment of combined drugs for children and adolescents with IgA nephropathy. The additive effect of warfarin was not substantiated.

Adolescent↗
PubMed1994

Immunopathologic study and characterization of the phenotype of transformed cells in sheep with bovine leukemia virus-induced lymphosarcoma.

We used monoclonal antibodies and immunohistologic examination of lymph nodes, to elucidate the pathogenesis of lymphosarcoma induced by infection with bovine leukemia virus (BLV). The superficial cervical lymph nodes from 3 BLV-infected but apparently healthy sheep and 5 sheep with full-blown lymphosarcoma were examined. We also investigated the integration of bovine leukemia provirus by use of Southern blotting. In lymph nodes from sheep lacking clinical signs of infection, in which the provirus had been integrated at multiple sites in the genome, many large hypertrophic follicles were observed in the cortex. These follicles had germinal centers consisting of CD4+T cells and B cells that expressed surface IgM (sIgM) and major histocompatibility complex (MHC) class-II antigens, but not B cell-specific B2 molecule. The percentage of CD4+T cells in the cortex was significantly (P < 0.05) higher than that of the controls and sheep with lymphosarcoma. In all sheep with lymphosarcoma, the lymph nodes were completely destroyed by proliferating neoplastic cells, and in addition, small atrophic follicles, which consisted of normal B-cell marker-positive cells, were seen near the trabecula and the subcapsule. In these instances, neoplastic cells appeared to be a monoclonal population derived from a single CD5- B-cell lineage and to be classified as 2 types, CD5-CD4-CD8-B2+MHC class-II+sIgM+ and CD5-CD4-CD8-B2+MHC class-II+sIgM-. Moreover, CD8+T cells infiltrated diffusely throughout the tumorous lymph nodes apart from the atrophic follicles, and CD4+ cells were observed around atrophic follicles. Both types of T cells were small-size, normal lymphocytes with round and noncleaved nuclei, and were apparently non-neoplastic cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

A mutation of furin causes the lack of precursor-processing activity in human colon carcinoma LoVo cells.

Furin has been proposed to be the endoprotease responsible for precursor cleavage at Arg-X-Lys/Arg-Arg (RXK/RR) sites within the constitutive secretory pathway. However, there was a possibility that other protease(s) is involved in this cleavage. We here characterized furin in human colon carcinoma LoVo cells, since these cells lacked the endogenous processing activity toward RXK/RR sites and recovered the activity by transfection of furin cDNA. Furin cDNA cloned from LoVo cells had one nucleotide deletion in the region covering the homo B domain which is essential for the endoproteolytic activity. LoVo cells transfected with a furin construct with the mutation showed no activity. Based on these data, we conclude that furin is the endoprotease that is involved in the precursor cleavage at RXK/RR sites within the constitutive secretory pathway.

Amino Acid Sequence↗
PubMed1993

Identification of an isoform with an extremely large Cys-rich region of PC6, a Kex2-like processing endoprotease.

In the previous study [1993, J. Biochem. (Tokyo) 113, 132-135] we identified PC6, a member of the Kex2 family of processing endoproteases. In this study, we identified another cDNA encoding an isoform of PC6, and designated it as PC6B and redesignated the originally identified PC6 as PC6A. PC6B had a very large Cys-rich region consisting of 22-times repeats of a Cys-rich motif, and a putative transmembrane domain which is not present in PC6A. A PC6B transcript was found mainly in the intestine, while PC6A transcripts were in various tissues. These results suggest distinct roles of PC6A and PC6B in endoproteolytic processing of precursor proteins.

Amino Acid Sequence↗
PubMed1993

Proximal and core DNA elements are required for efficient angiotensinogen promoter activation during adipogenic differentiation.

Angiotensinogen is abundantly expressed in adipose tissue as well as in liver where it is mainly produced. To address the mechanism of this adipogenic expression, promoter regions of the mouse angiotensinogen gene are fused to the chloramphenicol acetyltransferase reporter gene and stably transfected into 3T3-L1 preadipocytes. Promoter activity correlates well with an increase of mRNA levels during adipogenic differentiation, thereby demonstrating that the induction is primarily due to transcriptional activation. Deletion analysis indicates that the proximal promoter region from -96 to +22 is able to mediate the chloramphenicol acetyltransferase induction and identifies two transcriptionally active regions: AGE1 (position -399 to -139) and AGE2 (position -96 to -52). Heterologous promoter assay reveals that AGE1 behaves with a constitutive enhancer-like property and that AGE2 functions as a differentiation-inducible activator. Gel shift experiments show that AGE2 specifically binds a novel factor (AGF2), which is induced upon differentiation. Furthermore, a constitutive factor (AGF3) binds to the core promoter region including the exon 1 (from -6 to +22, AGE3). Mutations within either AGE2 or AGE3 that disrupt nuclear factors binding in vitro dramatically reduced the chloramphenicol acetyltransferase activation in the native promoter context. These results suggest that both AGE2 and AGE3 are necessary for mediating efficient activation of the mouse angiotensinogen promoter during adipogenic differentiation.

3T3 Cells↗