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Biomedical subjects

A Shimizu

Publications and source records attributed to A Shimizu.

At least 325 records · Page 18Linked to original sources
PubMed1993

The human S mu bp-2, a DNA-binding protein specific to the single-stranded guanine-rich sequence related to the immunoglobulin mu chain switch region.

We have cloned the cDNA encoding the human homologue of S mu bp-2, which binds to single-stranded DNA with 5'-phosphorylated guanine-rich sequences related to the immunoglobulin mu chain switch (S mu) region. The deduced amino acid sequences of the mouse and human S mu bp-2 are 76.5% homologous and contain motifs conserved among helicases. We have identified a domain essential for DNA binding at residues 638-786. The binding domain is less conserved (63% homologous) than the putative catalytic domain of N-terminal half containing most of the helicase motifs (85% homologous). The human and mouse S mu bp-2 have similar, although slightly different, binding specificities. Although the mouse S mu bp-2 preferentially binds to the mouse S mu motif (GGGGT), the human S mu bp-2 binds equally well to the human (GGGCT) and mouse S mu motifs. The human S mu bp-2 gene was mapped to chromosome 11 q13.2-q13.4 by in situ hybridization.

Amino Acid Sequence↗
PubMed1993

Effects of NB-598, a potent squalene epoxidase inhibitor, on the apical membrane uptake of cholesterol and basolateral membrane secretion of lipids in Caco-2 cells.

Caco-2 cells grown on membrane filters were used as a model to study the effects of NB-598, an inhibitor of squalene epoxidase, on cholesterol absorption from the intestinal epithelia. NB-598 (10 microM) inhibited the synthesis of sterol and sterol ester from [14C]acetate without affecting the synthesis of other lipids such as phospholipids (PL), free fatty acids (FFA) and triacylglycerol (TG). When labeled lipid was apically loaded as a micellar lipid solution into Caco-2 cell cultures, NB-598 reduced basolaterally secreted radioactivity in cholesterol, cholesterol ester, PL and TG. Furthermore, NB-598 suppressed the basolateral secretion of apolipoprotein (apo) B. When microsomes prepared from control Caco-2 cells were incubated with 10 microM NB-598, acyl CoA:cholesterol acyltransferase (ACAT) activity was inhibited slightly. After incubating Caco-2 cells with 10 microM NB-598, a slight reduction in cellular ACAT activity was also observed. These results suggest that suppression of the secretion of particles containing apo B and reduction of cellular ACAT activity in the intestinal epithelia are part of the mechanism of the cholesterol-lowering effect of NB-598.

Anticholesteremic Agents↗
PubMed1993

The male preponderance in incidence of hepatocellular carcinoma in cirrhotic patients may depend on the higher DNA synthetic activity of cirrhotic tissue in men.

BACKGROUND: The relationship between the DNA synthetic activity of hepatocytes from cirrhotic liver tissue and the incidence of hepatocellular carcinoma (HCC) during a 3-year follow-up period was studied in male and female patients with posthepatitic cirrhosis. METHODS: The bromodeoxyuridine labeling index (BrdU LI) of hepatocytes was estimated in 38 cirrhotic patients (Child A stage, 23 men and 15 women) using a BrdU/anti-BrdU in vitro method. The incidence of HCC was compared between male and female cirrhotic patients during a 3-year follow-up period. RESULTS: Sixteen of 23 (69.6%) male patients belonged to the high-DNA synthesis group (BrdU LI > or = 1.5%), and only 7 (30.4%) were in the low-DNA synthesis group (BrdU LI < 1.5%). Among female patients, only 5 of 15 (33.3%) were in the high-DNA synthesis group, and 10 of 15 (66.7%) were in the low-DNA synthesis group (P < 0.05). Eleven of 23 (47.8%) male patients and 3 of 15 (20.0%) female patients had HCC develop. In the high-DNA synthesis group, 10 of 16 (62.5%) of the men and 3 of 5 (60.0%) of the women had HCC develop during the follow-up period. In contrast, only one of seven (14.3%) male patients and none of ten (0%) female patients in the low-DNA synthesis group had HCC develop. CONCLUSIONS: It was concluded that HCC developed frequently (about 60% of the time within 3 years) in patients of both sexes who were in a high-DNA synthesis group. Thus, the larger proportion of men in the high-DNA synthesis group compared with the number of women in the group (69.6% versus 33.3%) might be one possible reason for the male predominance in the development of HCC in cirrhotic patients.

Adult↗
PubMed1993

DNA synthesis activities of hepatocytes from noncancerous cirrhotic tissue and of hepatocellular carcinoma (HCC) cells from cancerous tissue can predict the survival of hepatectomized patients with HCC.

BACKGROUND: There is a concept that a cancer often maintains some of the traits of the background tissue cells. Thus, the possibility exists that the DNA synthetic activity of the hepatocytes in cirrhotic tissue affects that of hepatocellular carcinoma (HCC) cells. METHODS: DNA synthesis activity of hepatocytes from background cirrhotic tissue and HCC cells from cancerous tissue was studied in 30 patients with liver cirrhosis (LC) and HCC who had undergone hepatectomy; the study was done using the bromodeoxyuridine (BrdU)-anti-BrdU in vitro method. The correlation between the BrdU labeling index (LI) of hepatocytes from noncancerous cirrhotic tissue and that of HCC cells was studied. The relationship between both BrdU LI values and the survival after hepatectomy also was studied. RESULTS: A significant correlation (r = 0.572; P < 0.001) was identified between the BrdU LI for HCC and that for noncancerous cirrhotic tissue. A significant correlation (r = -0.572; P < 0.05) was found between the BrdU LI of HCC cells and the survival after hepatectomy. A significant correlation (r = -0.678; P < 0.01) was observed between the BrdU LI of the noncancerous cirrhotic tissue and the survival. CONCLUSIONS: It was concluded that a significant correlation existed between DNA synthesis of hepatocytes from the background cirrhotic tissue and that of HCC cells and that DNA synthesis activity of hepatocytes from noncancerous cirrhotic tissue and that of HCC cells from cancerous tissue could predict the survival of patients with HCC who had undergone hepatectomy.

Adult↗
PubMed1993

Isolation of cDNA encoding a binding protein specific to 5'-phosphorylated single-stranded DNA with G-rich sequences.

We have isolated the cDNA encoding a binding protein to the sequence motif of the immunoglobulin S mu region by the southwestern method. The binding protein designated S mu bp-2 specifically binds to 5'-phosphorylated single-stranded DNA containing 5'-G and GGGG stretches. The amino acid sequence deduced from the cDNA sequence showed that the S mu bp-2 belongs to the putative helicase superfamily which is involved in replication, recombination and repair. Expression of S mu bp-2 mRNA is ubiquitous and augmented in spleen cells stimulated with lipopolysaccharide and interleukin 4 which also induce class switching. The S mu bp-2 gene is conserved among vertebrates. Possible involvement of S mu bp-2 in class switching is discussed.

Amino Acid Sequence↗
PubMed1993

The complete murine immunoglobulin class switch region of the alpha heavy chain gene-hierarchic repetitive structure and recombination breakpoints.

A 7255-base pair (bp) sequence, including the previously sequenced murine segments of I alpha, S alpha, and C alpha, has been completed. Homology matrix comparison revealed a switch repetitive region of 4.2 kilobases (kb) composed of 20-80-bp homology runs, including the previously assigned S alpha region. We distinguished several stretches of duplication, i.e. the central 0.8-kb repetitive region, with some 80-bp staggered consensus repeats containing 20-30-bp subsets, made up of the primordial pentamers CTG(A/G)G. All the break-points of the S alpha switch recombination, including those generated by the translocation of the c-myc protooncogene and those catalyzed by bacterial extracts, are located within the consensus sequence subsets of the 4.2-kb repetitive region.

Animals↗
PubMed1993

Membrane cofactor protein (MCP, CD46) in seminal plasma and on spermatozoa in normal and "sterile" subjects.

A sperm protein of molecular mass 43 kDa (the spermatozoa membrane cofactor protein, smMCP) and a seminal plasma protein of 60 kDa (ssMCP) were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by immunoblotting with four monoclonal antibodies (mAb) against membrane cofactor protein (MCP, CD46). These proteins served as factor I cofactors for the cleavage of methylamine-treated C3 (C3ma), the activity of which was blocked by M75, an MCP cofactor-activity-blocking mAb. Thus, these semen proteins are antigenic and functional homologous of MCP. On SDS-PAGE analysis these MCP migrated as single-band proteins which differed from the two-band forms of MCP expressed on other cells. smMCP was N-glycosylated but not O-glycosylated, while ssMCP was O-glycosylated: after deglycosylation of these proteins bands were detected at 38-40 kDa and 43 kDa on SDS-PAGE, respectively. These semen MCP are therefore, structurally different from the conventional MCP. ssMCP in both normal and "sterile" subject groups was determined by sandwich enzyme-linked immunosorbent assay. Seminal plasma in the two groups contained 250-700 ng/ml ssMCP. The difference between the two groups was marginal, although samples from normal subjects tended to show higher concentrations of ssMCP than samples from "sterile" subjects. No molecular difference was observed with ssMCP and smMCP in the two groups by SDS-PAGE/immunoblotting analysis. Immunohistochemical analysis suggested that MCP was positive in glandular epithelial cells and the lumen of the prostate, and in most intra-lumen cells of the testis. Using antibody M177, solubilized prostate and testis were analyzed by immunoblotting and compared with other cell MCP. The major band of MCP in the testis, but not in the prostate, was of 60 kDa, which aligned with ssMCP. No band of testis or prostate MCP, however, aligned with smMCP. ssMCP may be produced in the testis, while the origin of smMCP remains unknown. We hypothesize that ssMCP is important in the survival of spermatozoa, protecting them against local secretion of immunoglobulin and complement in the female genital tract, and that smMCP, which is expressed on acrosome-reacted spermatozoa, plays an essential role in the interaction of spermatozoa with oocytes.

Antigens, CD↗
PubMed1993

Decreased blood coagulation activities in carbohydrate-deficient glycoprotein syndrome.

The carbohydrate-deficient glycoprotein (CDG) syndromes are a newly recognized group of inherited metabolic diseases. We report a Japanese brother and sister with a CDG syndrome. Both patients showed decreased activities of blood coagulation Factor XI and of the coagulation inhibitor protein C. In one of them there was also a somewhat decreased activity of Factor IX and of antithrombin III. Isoelectric focusing of antithrombin III revealed a decrease of negatively charged fractions and an increase of more cathodal bands. Furthermore, there was a discrepancy between activity and antigen level of Factor VIII and protein C. The patients had an incidental deficiency of factor XII. This is the first detailed report on blood coagulation systems in the CDG syndromes. These blood coagulation abnormalities may explain at least in part the thrombotic or haemorrhagic complications of the CDG syndromes.

Antithrombin III↗
PubMed1993

Apoptosis and cell desquamation in repair process of ischemic tubular necrosis.

To elucidate the role of apoptosis and cell desquamation in the repair phase of acute tubular necrosis, morphological findings after 60 min ischaemia were investigated in rats. A morphometric analysis of the cell proliferation and of the epithelial cellularity of reconstructing tubules was performed. The kinetics of apoptosis and cell desquamation were also examined. Ischaemia and reperfusion injury resulted in widespread necrosis of tubules at day 1. Subsequently, a regenerative epithelial hyperplasia took place in the early stage. The most marked increase in cellularity in the damaged tubules was on day 6, when the tubules became lined by hyperplastic epithelial cells with papillary clusters. The number of papillary clusters decrease up to day 8, and during this period many desquamated cells from the clusters were observed in the tubular lumen. In the later stage, hyperplastic epithelial cells were reduced to their original cellularity and during this period the number of apoptotic cells obviously increased, while the damaged tubules were reconstructed. We conclude that epithelial overproduction occurs in the early phase after tubular necrosis, and excess hyperplastic epithelial cells regress during the repair process by cell desquamation and apoptosis, both of which are essential for the recovery of the original tubular structure.

Animals↗
PubMed1993

Anterograde and retrograde decremental conduction over left-sided accessory atrioventricular pathways in the Wolff-Parkinson-White syndrome.

The electrophysiologic properties of left-sided accessory pathways (APs) were examined by cardiac stimulation in 55 patients with Wolff-Parkinson-White syndrome. Atrioventricular and ventriculoatrial conduction times were assessed at the coronary sinus level nearest to the AP and then plotted graphically as a function of coupling interval (for atrial and ventricular refractory period determinations). Of 29 patients with anterograde conduction over the AP, 10 (34%) exhibited decremental conduction. However, only two (7%) had a maximal decrement equal to or more than 30 msec. In the other eight (27%) patients the maximal decrement ranged from 10 to 20 msec. The longest coupling interval at which anterograde decremental conduction was demonstrated ranged from 260 to 440 msec (346 +/- 52 msec). The shortest coupling interval ranged from 240 to 320 msec (265 +/- 24 msec). The anterograde decremental conduction zone was 91 +/- 55 msec. Of 51 patients with retrograde conduction over the AP, 23 (45%) exhibited decremental conduction. However, only eight (15%) had a maximal decrement equal to or greater than 30 msec. In the other 15 (29%) patients the maximal decrement ranged from 10 to 25 msec. The longest coupling interval was 338 +/- 70 msec. The shortest coupling interval was 275 +/- 42 msec. The retrograde decremental conduction zone was 72 +/- 47 msec. There was a significant inverse correlation between the AP effective refractory period and the maximal decrement (r = -0.42; p < 0.05). The comparison of maximal ventriculoatrial conduction time with the maximal decrement revealed a positive correlation (r = 0.63; p < 0.01). These data reveal that minimal decremental conduction over left-sided APs is not an uncommon finding and stress that care should be taken in evaluation of conduction over these connections.

Adolescent↗
PubMed1993

Characterization of double potentials in a functionally determined reentrant circuit. Multiplexing studies during interruption of atrial flutter in the canine pericarditis model.

OBJECTIVES: We tested the hypothesis that double potentials recorded during atrial flutter in a functionally determined reentrant circuit reflect activation of the reentrant wave front around an area of functional conduction block. BACKGROUND: The center of the atrial flutter reentrant circuit in the sterile pericarditis canine model is characterized by double potentials. METHODS: We studied 11 episodes of atrial flutter in eight dogs during interruption of atrial flutter while pacing the atria. A multielectrode mapping system was used to record simultaneously from 190 electrodes on the right atrium (location of reentry). RESULTS: Interruption of atrial flutter occurred when the orthodromic wave front from the pacing impulse blocked in an area of slow conduction in the reentrant circuit. The response of the double potential with interruption of atrial flutter depended on the location of the recording site relative to this area of block. Two types of response were seen. When the double potential was recorded orthodromically distal to this area of block, interruption of atrial flutter was associated with disappearance of the second deflection, and continued pacing after interruption of atrial flutter was not associated with reappearance of the second potential. When the double potential was recorded at a site orthodromically proximal to the area of block, interruption of atrial flutter was not associated with disappearance of the second potential, and when rapid atrial pacing was continued, the double potential remained despite disappearance of the atrial flutter reentrant circuit. CONCLUSIONS: Double potentials represent functional conduction block in the center of the reentrant circuit, with each deflection of the double potential reflecting activation on either side of the area of functional block. The data also demonstrate that double potentials are not limited to a reentrant circuit, as they were recorded on either side of an area of block in the absence of such a circuit.

Action Potentials↗
PubMed1993

An experimental study of the sealing ability of a dentinal apical plug treated with bonding agent.

The purpose of this study was to evaluate the sealing ability of a dentinal apical plug treated with a bonding agent. Ninety human lower premolars were used. The teeth were divided into three groups. in groups 1 and 2, to prepare an apical isthmus of 1 mm in length, the first apical seat was prepared with a #45 K file 1 mm short of the anatomical apex and with a #60 K file 2 mm short for the second apical seat. Dry dentin fillings were packed in the apical isthmus with a #60 K file. In group 1, the root canal was obturated with gutta-percha and Canals root canal sealer by the lateral condensation method. In group 2, following an application of the bonding agent to the plug, the root canal was obturated in the same way. In group 3 (control), a single apical seat was prepared with a #60 K file 1 mm short of the apex and the root canal was obturated similarly. The teeth of three groups were immersed in a 1% methylene blue solution for 1, 2, and 4 wk. Dye penetration depth from the apical foramen was determined. Group 2 showed no leakage after 4 wk. Groups 1 and 3 showed dye penetration into the root canal, and in these two groups dye penetration increased with time.

Composite Resins↗
PubMed1993

Electrophysiological effects of a new class III antiarrhythmic agent (E-4031) on the conduction and refractoriness of the in vivo human atrium.

OBJECTIVE: The aim was to test the efficacy of a new class III drug, E-4031, on human atrial muscle in vivo. METHODS: Electrophysiological measurements were performed in 10 patients, age 54(SD 11) years, before and during the continuous infusion of E-4031 (0.15 microgram.kg-1.min-1) which followed an initial dose of 9 micrograms.kg-1 x 5 min-1. Extrastimuli at 500 ms were delivered from the right atrial appendage, high lateral right atrium, and low lateral right atrium. The effective refractory period, repetitive atrial firing zone, and fragmented atrial activity zone were assessed at three sites in the right atrium. The conduction delay zone from the stimulus artefact to the distal electrode pair at the coronary sinus was also measured. RESULTS: E-4031 caused a significant increase in overall right atrial effective refractory period from 210(SD 29) to 232(26) ms (p < 0.001, n = 30 sites). There were significant decreases in the incidence of repetitive atrial firing (67% to 37%: p < 0.005), in the repetitive atrial firing zone [23(20) to 11(22) ms: p < 0.01], and in the fragmented atrial activity zone [15(22) to 3(8) ms: p < 0.005], but no significant change in the conduction delay zone. However, E-4031 significantly prolonged the longest coupling interval that elicited conduction delay, from 249(31) ms to 267(28) ms (p < 0.01). E-4031 had no effect on the conduction time except at coupling intervals close to the atrial effective refractory period. CONCLUSION: These results suggest that E-4031 has a potential effect in the treatment of human paroxysmal atrial fibrillation.

Anti-Arrhythmia Agents↗
PubMed1993

Synthesis and regulation of trans-mRNA encoding the immunoglobulin epsilon heavy chain.

We have detected an immunoglobulin heavy-chain trans-mRNA of the epsilon class in which the variable region of the human transgenic mu chain is correctly spliced to the first exon of the endogenous mouse epsilon constant region. Together with our previous observations, all the endogenous isotypes that are targets of class switching have proved to be expressed as trans-mRNA. This indicates that immunoglobulin trans-mRNA synthesis is a general mechanism to express a second heavy-chain isotype with the variable region of the transgenic mu chain. Synthesis of epsilon trans-mRNA is regulated in a way similar to the trans-mRNAs of the gamma subclasses or class switching to epsilon, i.e., interleukin-4 can induce the germline transcript of the epsilon constant region, but costimulation with lipopolysaccharide is necessary for epsilon trans-mRNA expression. The amount of epsilon trans-mRNA induced is similar to that of gamma 1 and higher than expected as judged from the rate of class switching to epsilon. All these data are consistent with our previous hypothesis that trans-mRNA is synthesized by a trans-splicing mechanism and that this mechanism is involved in the simultaneous multiple-isotype expression of immunoglobulin in a single B lymphocyte.

Animals↗