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Biomedical subjects

A Yamaguchi

Publications and source records attributed to A Yamaguchi.

At least 109 records · Page 6Linked to original sources
PubMed2000

PS-liposome and ox-LDL bind to different sites of the immunodominant domain (#155-183) of CD36: a study with GS95, a new anti-CD36 monoclonal antibody.

CD36, a multifunctional adhesive receptor on a variety of cells such as monocytes and platelets, has been implicated in clearance of modified LDL and in the removal of apoptotic or senescent cells. We recently developed a new anti-CD36 monoclonal antibody, GS95. We determined the binding site of phosphatidylserine (PS)-liposome on CD36 by flow cytometric analysis of competitive bindings between phospholipid-liposomes or synthetic CD36 peptides and FITC-labeled anti-CD36 antibodies (GS95, OKM5, and FA6-152). The epitope of GS95 was mapped to the amino acid sequence #162-183 of CD36 that was partially overlapped with, but distinct from, #155-183, which has been reported as the epitopes of two commercially available antibodies, OKM5 and FA6-152. Oxidized-LDL dose-dependently inhibited bindings of both GS95 and OKM5 antibodies to platelet CD36, while PS-liposome inhibited the binding of GS95 but not OKM5 or FA6-152. These results indicate that the binding site of PS-liposome on platelet CD36 is not identical to that of oxidized-LDL and may be located in the amino acid sequence #162-183.

Adult↗
PubMed2000

Proximity of periplasmic loops in the metal-Tetracycline/H(+) antiporter of Escherichia coli observed on site-directed chemical cross-linking.

Our previous study on second-site suppressor mutations of the Tn10-encoded metal-tetracycline/H(+) antiporter suggested that Leu(30) and Ala(354), located in periplasmic loop 1-2 and 11-12, respectively, are conformationally linked to each other (Kawabe, T., and Yamaguchi, A. (1999) FEBS Lett. 457, 169-173). To determine the spatial proximity of these two residues, cross-linking gel-shift assays of the L30C/A354C double mutant were performed after the mutant had been oxidized with Cu(2+)/o-phenanthroline. The results indicated that Leu(30) and Ala(354) are close to each other but that Gly(62), which is located in cytoplasmic loop 2-3, and Ala(354) are distant from each other, as a negative control. Then, a single Cys residue was introduced into each of the six periplasmic loop regions (P1-P6), and eleven double mutants were constructed. Of these eleven double Cys mutants, the L30C/A354C and L30C/T235C mutants showed a mobility shift on oxidation, indicating that P1 is spatially close to P4 as well as P6. In contrast, the other nine mutants, L30C/S92C, L30C/S156C, L30C/S296C, S92C/S296C, S92C/T235C, S92C/A354C, S156C/T235C, S156C/S296C, and S156C/A354C, showed no mobility shift under oxidized conditions on intramolecular cross-linking. The S92C and S296C mutants showed dimerization on intermolecular cross-linking, indicating that P2 and P5 are located at the periphery of the helix bundle.

Amino Acid Sequence↗
PubMed2000

Generating sexually differentiated vocal patterns: laryngeal nerve and EMG recordings from vocalizing male and female african clawed frogs (Xenopus laevis).

Male and female African clawed frogs (Xenopus laevis) produce sexually dimorphic vocalizations; for males these include advertisement, amplectant, and growling calls, whereas female calls include ticking. Previous studies have shown that the vocal organ, the larynx, of the sexes differs in physiological properties that parallel vocal differences. However, it was not clear whether these characteristics are sufficient to explain sex differences in vocal behavior. To examine the contribution of the CNS to generating vocal patterns, we developed a preparation in which both laryngeal nerve activity and electromyograms can be recorded from awake, vocalizing frogs. Recordings reveal that the CNS of the two sexes produces patterned activity that closely matches each vocalization whereas the larynx faithfully translates nerve activity into sound. Thus, the CNS is the source of sexually differentiated vocalizations in Xenopus laevis. Furthermore, detailed analyses of compound action potentials recorded from the nerve lead us to hypothesize that neuronal activity underlying different male call types is distinct; some calls are likely to be generated by synchronous firing of motoneuron populations of either constant size or progressively larger sizes, whereas others are generated by asynchronous activity of motoneurons, a pattern shared with vocal production in females. We suggest that these distinct neuronal activity patterns in males may be subserved by two populations of motor units in males that can be distinguished by the strength of the neuromuscular synapse.

Animals↗
PubMed2000

Role of the charge interaction between Arg(70) and Asp(120) in the Tn10-encoded metal-tetracycline/H(+) antiporter of Escherichia coli.

We reported that the positive charge of Arg(70) is mandatory for tetracycline transport activity of Tn10-encoded metal-tetracycline/H(+) antiporter (TetA(B)) (Someya, Y., and Yamaguchi, A. (1996) Biochemistry 35, 9385-9391). Arg(70) may function through a charge-pairing with a negatively charged residue in close proximity. Therefore, we mutated Asp(66) and Asp(120), which are only two negatively charged residues located close to Arg(70) in putative secondary structure of TetA(B) and highly conserved throughout transporters of the major facilitator superfamily. Site-directed mutagenesis studies revealed that Asp(66) is essential, but Asp(120) is important for TetA(B) function. Surprisingly, when Asp(120) was replaced by a neutral residue, the R70A mutant recovered tetracycline resistance and transport activity. There was no such effect in the Asp(66) mutation. The charge-exchanged mutant, R70D/D120R, also showed significant drug resistance and transport activity (about 50% of the wild type), although the R70D mutant had absolutely no activity, and the D120R mutant retained very low activity (about 10% of the wild type). Both the R70C and D120C mutants were inactivated by N-ethylmaleimide. Mercuric ion (Hg(2+)), which gives a positive charge to a SH group of a Cys residue through mercaptide formation, had an opposite effect on the R70C and D120C mutants. The activity of the R70C mutant was stimulated by Hg(2+); however, on the contrary, the D120C mutant was partially inhibited. On the other hand, the R70C/D120C double mutant was almost completely inactivated by Hg(2+), probably because the side chains at positions 70 and 120 are bridged with Hg(2+). The close proximity of positions 70 and 120 were confirmed by disulfide cross-linking formation of the R70C/D120C double mutant when it was oxidized by copper-(1,10-phenanthroline). These results indicate that the positive charge of Arg(70) requires the negative charge of Asp(120) for neutralization, probably for properly positioning transmembrane segments in the membrane.

Antiporters↗
PubMed2000

Telomerase activity in colorectal cancer and its relationship to bcl-2 expression.

BACKGROUND AND OBJECTIVES: Telomerase is thought to be responsible for cell immortality, and bcl-2 has been demonstrated to regulate apoptosis. Recent studies have shown a wide occurrence of telomerase activation and bcl-2 deregulation in human carcinoma cells. METHODS: We examined telomerase activity in tissues from 50 patients with colorectal carcinoma with a telomeric repeat amplification protocol assay. We also investigated the relationship between telomerase activity and expression of bcl-2 in 37 colorectal carcinoma specimens. RESULTS: We detected telomerase activity in 33 (66%) of 50 colorectal carcinomas, whereas no activity was detected in the adjacent noncancerous mucosa of 13 tumor specimens. There was no correlation between pathological stage and telomerase activity. Telomerase activity in the bcl-2-expressing cases was higher than that in the bcl-2-non-expressing cases. CONCLUSIONS: Expression of bcl-2 may be related to telomerase activity in colorectal carcinomas.

Adenocarcinoma↗
PubMed2000

Manipulation of globular DNA molecules for sizing and separation.

Handling large DNA molecules, such as chromosomal DNA, has become necessary due to recent developments in genome science. However, large DNA molecules are fragile and easily broken by shear stress accompanying flow in solution. This fragility causes difficulties in the preparation and handling of large DNA molecules. This study demonstrates the transition of DNA from a coiled to a globular form, which is highly condensed. This state suppresses DNA fragmentation due to shear stress in solution. The transition enables large DNA molecules to undergo mechanical manipulation. We confirmed that the fluorescence intensity of stained globular DNA increases with increasing length, suggesting that the resistance of globular DNA to shear stress is the factor that allows analysis of large DNA by flow cytometry.

DNA, Fungal↗
PubMed2000

Hepatic vein reconstruction by external iliac vein graft using vascular clips.

The utility of hepatic vein reconstruction following resection of segments VII and VIII plus the right hepatic vein (RHV) is still controversial. The purpose of this study was to investigate the surgical benefits of hepatic vein reconstruction using stapled vascular clips and the draining area of hepatic vein using angiographic computed tomography (CT) to determine strict indications for hepatic vein reconstruction. Five patients underwent RHV reconstruction by external iliac vein graft using stapled vascular clips (VCS clips) following resection of segments VII and VIII, regardless of whether an inferior right hepatic vein (IRHV) was present. In eight other patients CT during arterial portography (CTAP) under temporary RHV occlusion using a balloon catheter was performed to determine the drainage area of the RHV. Operating times were 240 to 400 minutes (mean 336 +/- 59 minutes), and the mean hepatic vein reconstruction time was 26 +/- 5 minutes. There were no complications related to the surgery. Follow-up examinations showed patency of the graft in all cases; three patients are still alive with long-term graft patency of 10 to 24 months. CTAP under RHV occlusion demonstrated that segment VI and part of segment V were almost hypoattenuated in cases of absent or small IRHV, although those segments were hyperattenuated in thick IRHV and RHV-IRHV communicating patients. In conclusion, this anastomotic technique using vascular clips resulted in sound patency of the graft, which was accomplished by a simple technique. Preoperative CT AP with the RHV occlusion method can be useful for determining whether hepatic vein reconstruction is necessary.

Aged↗
PubMed2000

Assessment of decalcifying protocols for detection of specific RNA by non-radioactive in situ hybridization in calcified tissues.

For the best performance of in situ analysis of specific RNA expression in calcified tissues, it is necessary to choose an appropriate protocol to decalcify the tissues. We evaluated the usefulness of various acid-based decalcifying reagents with reference to 28 S rRNA staining by in situ hybridization using a thymine-thymine dimerized oligonucleotide probe. The reagents evaluated were 10% nitric acid, 10% HCl, 5% formic acid, 5% trichloroacetic acid, Morse's solution, Plank-Rychlo's solution, and K-CX solution, all of which are commonly used to decalcify tissues, and their effects on retention of morphology and RNA were compared with EDTA-based solutions. When normal mouse mandible was used as a model tissue, well-preserved morphology of ameloblasts was obtained from sections decalcified with Morse's solution, 10% HCl, Plank-Rychlo's solution, and K-CX solution, and best retention of 28 S rRNA was obtained with 5% formic acid and Morse's solution. We recommend Morse's solution to decalcify tissues to be processed for the rapid analysis of specific RNA expression. Indeed, we detected specific mRNAs strongly in sections treated with Morse's solution, and quantitative analysis showed that the ratio of signal intensities of 28 S rRNA and the specific mRNAs correlated with each other depending on decalcifying solutions.

Animals↗
PubMed2000

Hepatectomy for cholangiocarcinoma complicated with right umbilical portion: anomalous configuration of the intrahepatic biliary tree.

The right umbilical portion (right-sided round ligament) has been discussed as an intrahepatic portal venous anomaly associated with "left-sided gallbladder" in several reports. We treated two patients with right umbilical portion (RUP) associated with cholangiocarcinoma. Left hepatectomies were performed, preserving the residual hepatic blood flow and biliary continuity. From our experience in these patients we propose the presence of anomalous configuration of the intrahepatic biliary tree in RUP, because both patients showed medial segmental bile ducts ramified from the right and left hepatic ducts. In general, although the medial segmental bile duct ramified from the left, we surmised that this abnormal bilateral drainage pattern may not be a rare phenomenon in RUP. Special attention may be required to focus on the anatomy of the portal tributaries and biliary ramifications in RUP.

Bile Duct Neoplasms↗
PubMed2000

Early and late surgical outcomes of acute type A aortic dissection in patients aged 75 years and older.

BACKGROUND: With the general increase in human lifespan, aortic surgeons are faced with an increasing prevalence of acute type A aortic dissection in the elderly. In this study, we reviewed early and late surgical outcomes of acute type A dissection (operation within 48 hours after onset) in patients aged 75 years and older. METHODS: Between 1990 and 1999, 109 patients underwent emergency operation for acute type A dissection at Omiya Medical Center. Twenty-three patients were aged 75 years and older (elderly group, mean age, 79.1 +/- 4.7 years) and 86 were younger than 75 years old (younger group, mean age, 58.7 +/- 10.8 years). Early and late outcomes of both groups were compared. RESULTS: The hospital mortality rates were 13.0% (3 of 23) in the elderly group and 10.5% (9 of 86) in the younger group (p = 0.71). In the elderly, actuarial survival rate (including the operative mortality rate) at 1, 3, and 5 years was 78% +/- 9% for each point. In the younger group, the rates were 88% +/- 4% at 1 year, 83% +/- 4% at 3 years, and 81% +/- 5% at 5 years (p = 0.57). Actuarial event-free rates were 84% +/- 8% at 1 year, 77% +/- 11% at 3 years, and 77% +/- 11% at 5 years in the elderly group. In the younger group, the rates were 96% +/- 2% at 1 year, 88% +/- 4% at 3 years, and 81% +/- 7% at 5 years (p = 0.27). CONCLUSIONS: No significant differences in the hospital mortality, actuarial survival, or event-free rates were observed between the two groups. Operation for type A acute aortic dissection in patients aged 75 years or older can be performed with acceptable risk of death, and long-term results are satisfactory.

Actuarial Analysis↗
PubMed2000

Extensive intraglomerular thrombi of monoclonal IgM-kappa in a patient with malignant lymphoma.

We describe an 80-year-old man who developed malignant lymphoma (ML) complicated by extensive intraglomerular thrombi of immunoglobulin M (IgM)-kappa monoclonal immunoglobulin. The clinical picture was characterized by nephrotic syndrome and systemic lymphadenopathy. Laboratory examination showed mild anemia and a small amount of monoclonal IgM-kappa in the blood. The histopathologic findings and surface immunoglobulin analysis of the lymph node biopsy specimen were consistent with CD5-positive diffuse large B-cell (type, IgM-kappa) lymphoma. The subsequent renal biopsy showed a massive deposition of amorphous material in the glomerular capillary lumens, subendothelial areas, and mesangium. Nodular glomerulosclerosis was not found. An immunofluorescent study showed that the deposits consisted of IgM-kappa monoclonal immunoglobulin. Ultrastructurally, the deposits were composed of granular electron-dense material. Chemotherapy was effective for both the ML and nephrotic syndrome, and the patient's urine analysis results returned to normal. The histopathologic manifestations of this case are rare, and the pathogenesis of these glomerular lesions was obviously associated with ML.

Aged↗
PubMed2000

Cloning and embryonic expression patterns of the zebrafish Runt domain genes, runxa and runxb.

We isolated zebrafish homologues of the Runt-related transcription factor gene family (Runx family), runxa and runxb, and analyzed their developmental expression patterns. The deduced amino acid sequence of Runxa was highly homologous to that of AML1 (also called CBFA2, PEBP2alphaB or Runx1), a critical regulator of mammalian hematopoiesis expressed in cells of the hematopoietic lineage as well as other tissues. During zebrafish development, the runxa gene was not expressed in hematopoietic tissues but in the olfactory placodes and cells attached to the otic vesicles. We identified three kinds of runxb transcripts, which encoded two types of proteins with different N-terminal regions. The Runxb proteins were highly similar to AML2 (CBFA3, PEBP2alphaC or Runx3). The expression sites of the shared region of runxb mRNAs during development were the trigeminal ganglions, dorsal neurons of the neural tube and the lateral line primordia. These findings show that expression patterns of the zebrafish Runx genes are distinct from that of the mammalian genes.

Animals↗
PubMed2000

Evaluation of Abdominal Tumors with

Purpose: The purpose of this study was to evaluate the diagnostic usefulness of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET).Procedures: We performed FDG-PET in 22 patients with suspected primary or recurrent cancer (23 cases). The FDG-PET findings were compared with the final diagnosis, which was obtained by histological examination of resected, or biopsy specimens and the clinical course.Results: In all patients, the sensitivity, specificity, and the accuracy of FDG-PET were 93.8%, 85.7%, 91.3%, respectively. In the patients with colo-rectal cancer, the sensitivity, specificity, and accuracy were 92.9%, 100%, 94.4%, respectively.Conclusions: FDG-PET was considered to be clinically useful for the detection of primary or recurrent malignant tumors, and for differentiating recurrent tumors from inflammatory scars.

Journal Article↗
PubMed2000

Reduction in bone formation and elevated bone resorption in ovariectomized rats with special reference to acute inflammation.

Changes in bone modeling and remodeling in the tibia of growing rats within 30 days of ovariectomy (ovx) were evaluated by histomorphometric, mechanical; and biochemical means. Three days after ovx, suppressed bone formation was seen. This was shown by reduced osteoid volume, osteoblast surface, and bone formation rate in the secondary spongiosa, and a reduced longitudinal growth rate in the growth plate. In addition, the alkaline phosphatase and tartrate-resistant acid phosphatase activity in bone marrow supernatants was suppressed in conjunction with elevated serum sialic acid levels, indicating inflammation. Although estrogen deprivation itself may provoke the inflammatory process, the serum sialic acid level in the ovx group returned to the baseline level within 5 days after surgery, while that of estradiol in the ovx group remained consistently lower. This suggests that surgical stress, not estrogen deprivation, is the primary cause of the inflammatory response shortly after ovx. A significant difference (p < 0.01) between the ovx and sham rats was seen in the osteoclast surface, which peaked on day 7 in the ovx rats. On day 14 postovariectomy, the bone formation rate peaked and remained constant until day 30. In the ovx rats, there was a sustained reduction in the serum albumin level until day 30. Estrogen deprivation may be the primary cause of these changes, because both surgical ovx and medical oophorectomy with gonadotropin-releasing hormone agonist (G(nRHa) reduce the serum albumin level. In numerous studies dealing with changes after ovx in rats, we have observed: 1) a transient reduction in bone formation in relation to inflammatory changes evoked by ovx surgery, and 2) a sustained reduction in the serum albumin level for at least 30 days after ovx that is possibly due to estrogen deprivation.

Alkaline Phosphatase↗
PubMed2000

Effects of various decalcification protocols on detection of DNA strand breaks by terminal dUTP nick end labelling.

To analyse DNA strand breaks by terminal deoxy(d)-UTP nick-end labelling (TUNEL) in calcified tissues including bones and teeth, it is important to decalcify the tissues first. However, the effects of decalcifying reagents on the integrity of DNA are largely unknown. In the present study, we evaluated the usefulness of various decalcifying reagents including 10% EDTA (pH 7.4), 5% trichloroacetic acid (TCA), 5% formic acid, 5% HCl, 10% nitric acid, Plank-Rychlo's solution, Morse's solution and K-CX solution in TUNEL staining. Mouse maxilla was selected as the experimental system. Apoptotic cells naturally occurring in the epithelium were analysed. Tissues were assessed by soft X-ray imaging to confirm complete decalcification. The time required for decalcification of the tissue was 7 days with 10% EDTA and 2 days with other decalcifiers. Decalcified tissues were stained with Methyl/Green-Pyronine Y or 4',6-diamidino-2-phenylindole for assessment of DNA integrity. Nuclei of epithelial cells were strongly positive for both dyes after decalcification with 10% EDTA, 5% TCA, Morse's solution and 5% formic acid. The other reagents failed to retain DNA. Our results demonstrated good TUNEL staining of the maxilla treated with 10% EDTA or 5% TCA. Based on the required time for processing and the signal-noise ratio, we recommend 5% TCA as the decalcifying reagent to analyse for DNA strand breaks.

Animals↗
PubMed2000

A pathway of neuronal apoptosis induced by hypoxia/reoxygenation: roles of nuclear factor-kappaB and Bcl-2.

As a model of the reperfusion injury found in stroke, we have exposed neurons to hypoxia followed by reoxygenation. Neurons treated with hypoxia/reoxygenation (H/R) respond by activating nuclear factor-kappaB (NFkappaB), releasing cytochrome c from their mitochondria, and ultimately dying. Further supporting an apoptotic mechanism, expression of the antiapoptotic Bcl-2 and Bcl-x proteins was increased following H/R. In this model, adenoviral-mediated transduction of lkappaB expression inhibited NFkappaB activation and significantly accelerated cytochrome c release and caspase-dependent neuronal death. At the same time, expression of mutated lkappaB prevented the increased expression of endogenous Bcl-2 and Bcl-x. In the presence of mutated lkappaB, singular overexpression of only Bcl-2 by adenoviral-mediated transduction significantly inhibited cytochrome c release, caspase-3-like activation, and cell death in response to H/R. These findings suggest a pathway where NFkappaB activation induces overexpression of Bcl-2 and Bcl-x, which function to prevent apoptotic cell death following H/R treatments.

Aerobiosis↗
PubMed2000

Endocapillary proliferative glomerulonephritis in a patient with parvovirus B19 infection.

A 45-year-old woman developed acute nephritic syndrome after erythema infectiosum. Laboratory data on admission showed decreased serum C3, C4, and CH50 levels and the presence of both immunoglobulin (Ig) M and IgG antibodies to human parvovirus B19 (HPV). A renal biopsy showed diffuse endocapillary proliferative glomerulonephritis. Immunofluorescence microscopy indicated 2+ granular staining for IgG, IgM, and C3 over the mesangial area and along glomerular capillary walls. HPV antigen was also detected in glomeruli by immunohistochemistry. Electron microscopy showed electron-dense deposits in the subendothelial space and the paramesangial area. These findings suggest that immune complex-type glomerulonephritis is caused by glomerular deposition of HPV antigen-antibody complexes in some patients with HPV infection.

Antigen-Antibody Complex↗