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Biomedical subjects

A Maeda

Publications and source records attributed to A Maeda.

At least 55 records · Page 3Linked to original sources
PubMed2000

Identification of calponin as a novel substrate of Rho-kinase.

Calponin, an F-actin-associated protein implicated in the regulation of smooth muscle contraction, is known to be phosphorylated in vitro by protein kinase C (PKC) and Ca(2+)/calmodulin dependent protein kinase II (CaM kinase II). Unphosphorylated calponin binds to F-actin and inhibits the actin-activated myosin ATPase activity; these properties are lost on phosphorylation. In the present study, we found that Rho-kinase phosphorylated basic calponin stoichiometrically in vitro. We identified the sites of phosphorylation of calponin by Rho-kinase as Thr-170, Ser-175, Thr-180, Thr-184, and Thr-259, and prepared antibodies that specifically recognized calponin phosphorylated at Thr-170 and Thr-184. We showed that the phosphorylation of calponin by Rho-kinase inhibited the binding of calponin to F-actin. Taken together, these results suggest that calponin is a substrate of Rho-kinase and that Rho-kinase regulates the interaction of calponin with F-actin.

Actins↗
PubMed2000

Local and distant protein structural changes on photoisomerization of the retinal in bacteriorhodopsin.

The photoisomerization of the retinal in bacteriorhodopsin is selective and efficient and yields perturbation of the protein structure within femtoseconds. The stored light energy in the primary intermediate is then used for the net translocation of a proton across the membrane in the microsecond to millisecond regime. This study is aimed at identifying how the protein changes on photoisomerization by using the O-H groups of threonines as internal probes. Polarized Fourier-transform IR spectroscopy of [3-(18)O]threonine-labeled and unlabeled bacteriorhodopsin indicates that 3 of the threonines (of a total of 18) change their hydrogen bonding. One is exchangeable in D(2)O, but two are not. A comprehensive mutation study indicates that the residues involved are Thr-89, Thr-17, and Thr-121 (or Thr-90). The perturbation of only three threonine side chains suggests that the structural alteration at this stage of the photocycle is local and specific. Furthermore, the structural change of Thr-17, which is located >11 A from the retinal chromophore, implicates a specific perturbation channel in the protein that accompanies the retinal motion.

Amino Acid Sequence↗
PubMed2000

Aberrant expression of photoreceptor-specific calcium-binding protein (recoverin) in cancer cell lines.

Cancer-associated retinopathy (CAR) is an ocular manifestation of a paraneoplastic syndrome whereby immunological reactions to retinal antigens aberrantly expressed in tumor cells lead to the degeneration of retinal photoreceptor cells. In our previous study (H. Ohguro et al., Invest. Ophthalmol. Vis. Sci., 40: 82-89, 1999), recoverin, a retina-specific calcium-binding protein, and heat shock cognate protein 70 (hsc 70) were identified as autoantigens recognized by sera from patients with CAR. Therefore, we suggested that autoimmune reactions against both recoverin and hsc 70 might be involved in the pathogenesis of CAR. To elucidate the initial step of the molecular pathology of CAR, we examined the expression of recoverin and hsc 70 by reverse transcription-PCR and Western blot using cell lines of several kinds of cancers, including lung small cell carcinoma, lung adenocarcinoma, gastric cancer, pancreatic cancer, breast cancer, uterine cervical cancer, endometrial cancer, and leukemia. Recoverin was expressed in 21 of the 31 cancer cell lines. The expression levels of hsc 70 were significantly higher in cancer cell lines than in noncancerous cell lines. However, no difference in the expression levels of hsc 70 was observed between recoverin-positive and -negative cell lines. Immunofluorescence labeling by the affinity-purified recoverin antibody revealed the immunoreactivity to recoverin as a granular pattern within the cancer cells. Lung adenocarcinoma A549 cells, which did not express recoverin, exhibited a significant reduction in cell proliferation upon transfection with human recoverin cDNA. Taken together, our present data suggest that the retina-specific calcium-binding protein recoverin is expressed in more than 50% of a variety of cancer cells and may play a significant role in the cell proliferation of these tumor cells.

Antigens, Neoplasm↗
PubMed2000

Cbl suppresses B cell receptor-mediated phospholipase C (PLC)-gamma2 activation by regulating B cell linker protein-PLC-gamma2 binding.

Accumulating evidence indicates that the Cbl protein plays a negative role in immune receptor signaling; however, the mode of Cbl action in B cell receptor (BCR) signaling still remains unclear. DT40 B cells deficient in Cbl showed enhanced BCR-mediated phospholipase C (PLC)-gamma2 activation, thereby leading to increased apoptosis. A possible explanation for the involvement of Cbl in PLC-gamma2 activation was provided by findings that Cbl interacts via its Src homology 2 (SH2) domain with B cell linker protein (BLNK) after BCR ligation. BLNK is a critical adaptor molecule for PLC-gamma2 tyrosine phosphorylation through its binding to the PLC-gamma2 SH2 domains. As a consequence of the interaction between Cbl and BLNK, the BCR-induced recruitment of PLC-gamma2 to BLNK and the subsequent PLC-gamma2 tyrosine phosphorylation were inhibited. Thus, our data suggest that Cbl negatively regulates the PLC-gamma2 pathway by inhibiting the association of PLC-gamma2 with BLNK.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Isolated resection of segment 8 for liver tumors: a new approach for anatomical segmentectomy.

HYPOTHESIS: Isolated resection of segment 8 (the right anterosuperior liver segment) is one of the most difficult hepatectomies to perform because of the location of segment 8, the relation between section 8 and the main intrahepatic vessels, and the absence of any anatomical landmarks. The few reports that deal with isolated resection of section 8 generally describe the use of a deep wedge transparenchymal transection. DESIGN: Original surgical technique. PATIENTS AND METHODS: The proposed technique is based on the extraparenchymal isolation and temporary clamping of the right anterior artery and portal branches, causing ischemic demarcation on the liver surface, which corresponds to the anatomical borders of the right paramedian segments (5 and 8). The liver is widely transected along the main hepatic fissure; then the pedicles of segment 8 are selectively ligated inside the parenchyma, and the resection is accomplished. This technique was used in 10 patients: 5 with hepatocellular carcinoma on cirrhosis and 5 with liver metastases. RESULTS: The mean operation time was 253 minutes. Intraoperative blood loss was minimal in all cases, and 7 patients did not require blood transfusion. Slight complications developed in 3 patients, and there was no operative death. The mean hospital stay was 9.3 days. CONCLUSIONS: This operative procedure is safe and ensures a complete anatomical resection of segment 8. The wide opening of the liver parenchyma facilitates hemostasis and makes it possible to obtain a correct resection margin. This technique is recommended for limited metastatic lesions located in segment 8 or for hepatocellular carcinoma arising in a cirrhotic liver.

Adult↗
PubMed2000

Double-Modulation Submillimeter-Wave Spectroscopy of HOC(+) in the nu(2) Excited Vibrational State.

The submillimeter-wave rotational transitions of HOC(+) in the nu(2) excited state are first detected using the double-modulation method, and the precise transition frequencies and the much improved molecular constants are obtained. The measurements of the ground state HOC(+) and DOC(+) submillimeter-wave lines are extended up to the 840-GHz region. It is found that the higher order centrifugal distortion constant, H, is necessary to fit the observed transition frequencies to the experimental accuracy. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Reciprocal effect of unsulfated and sulfated forms of cholecystokinin-octapeptide on gastric acid secretion in the rat.

The sulfated and unsulfated forms of cholecystokinin-octapeptide (CCK-8) were compared, with respect to their effect on gastric acid secretion, in the rat. Unsulfated CCK-8 stimulated acid secretion in a dose-dependent manner, while the sulfated form was without stimulatory effect; thus, sulfation of the tyrosine residue in the seventh position from the C terminus completely abolished the gastrin-like action of CCK-8. Compared with pentagastrin and human gastrin II, unsulfated CCK-8 gave lower calculated maximal response. While sulfated CCK-8 given alone had no effect on acid secretion, it caused marked inhibition of the plateau response to submaximal pentagastrin. This inhibition was surmountable with higher doses of pentagastrin, suggesting a competitive type of inhibition. It is, therefore, concluded that lack of sulfation of the tyrosine residue in the seventh position does not exclude CCK-8 from occupying the gastrin receptor; but does prevent the hormone-receptor interaction that leads to the secretory response. These observations in the rat are different from those in the dog where desulfation of tyrosine renders the CCK analog, caerulein, ineffective in its ability to stimulate acid secretion.

Animals↗
PubMed2000

Identification of 142 single nucleotide polymorphisms in 41 candidate genes for rheumatoid arthritis in the Japanese population.

Single-nucleotide polymorphisms (SNPs) can make an important contribution to our understanding of genetic backgrounds that may influence medical conditions and ethnic diversity. We undertook a systematic survey of genomic DNA for SNPs located not only in coding sequences but also in non-coding regions (e.g., introns and 5' flanking regions) of selected genes. Using DNA samples from 48 Japanese patients with rheumatoid arthritis (RA) as templates, we surveyed 41 genes that represent candidates for RA, screening a total of 104 kb of DNA (30 kb of coding sequences and 74 kb of non-coding DNA). Within this 104 kb of genomic sequences we identified 163 polymorphisms (1 per 638 bases on average), of which 142 were single-nucleotide substitutions and the remainder, insertions or deletions. Of the coding SNPs, 52% were non-synonymous substitutions, and non-conservative amino acid changes were observed in a quarter of those. Sixty-nine polymorphisms showed high frequencies for minor alleles (more than 15%) and 20 revealed low frequencies (<5%). Our results indicated a greater average distance between SNPs than others have reported, but this disparity may reflect the type of genes surveyed and/or the relative ethnic homogeneity of our test population.

Alleles↗
PubMed2000

Long-term observation on hearing change in patients with chronic otitis media.

OBJECTIVE: Very few reports are available in the literature to clarify the natural long course of hearing change in an individual patient with chronic otitis media (COM). We reviewed hearing change in patients suffering from perforated COM without an operation. METHODS: Eighty-seven ears of 70 patients had COM with tympanic perforation and were observed without an operation. The mean follow-up period was 10.7 years (5-22 years) and the mean age at the first examination was 51.3 years. To minimize the effect of aging, 23 patients with normal ear drums on the other side were further analyzed. RESULTS: All 87 ears tended to show deterioration of hearing gradually under long observation. In 23 patients, hearing deterioration was 0.13 dB/year in the control side and 0.61 dB/year in the COM side (P < 0.02). Although elevation of bone conduction hearing level tended to be larger at high frequencies than at low and middle frequencies, there was no significant difference between COM and normal ears. CONCLUSIONS: Air conduction hearing levels deteriorated with the passage of time and surgery is recommended at the early stage of COM to prevent progress of hearing loss.

Adult↗
PubMed2000

BCAP: the tyrosine kinase substrate that connects B cell receptor to phosphoinositide 3-kinase activation.

Tyrosine phosphorylation of adaptor proteins permits the B cell antigen receptor (BCR)-associated protein tyrosine kinases to regulate downstream effector molecules. Here, we report the identification of a novel B cell adaptor for phosphoinositide 3-kinase (PI3K), termed BCAP. Tyrosine phosphorylation of BCAP is mediated by Syk and Btk, thereby providing binding site(s) for the p85 subunit of PI3K. Disruption of the BCAP gene in the DT40 B cell line inhibits BCR-mediated phosphatidylinositol 3,4,5-trisphosphate generation, leading to impaired Akt response. Moreover, recruitment of PI3K to glycolipid-enriched microdomains (GEMs) is significantly attenuated in the absence of BCAP. Hence, these data suggest that BCAP bridges BCR-associated kinases to the PI3K pathway by regulating PI3K localization.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Regulation of the phospholipase C-gamma2 pathway in B cells.

In B lymphocytes, a signaling complex that contributes to cell fate decisions is the B-cell antigen receptor (BCR), with different extents of receptor engagement leading to such outcomes as cell death, survival, or proliferation. Here, based upon the available genetic and biochemical data of the BCR signal components, we discuss several mechanisms by which BCR signals are propagated and modified, with specific emphasis on the phospholipase C (PLC)-gamma2-calcium pathway Gene-targeting experiments in DT40 chicken B cells highlighted the importance of the intracellular protein tyrosine kinases Syk and Btk in PLC-gamma2 activation. Until recently, the molecular mechanism underlying the double requirement for Syk and Btk in PLC-gamma2 activation remained unclear, but new data suggest that an adapter molecule, B-cell linker protein (alternatively named SLP-65 or BASH), phosphorylated by Syk, provides docking sites for Btk SH2 domain as well as PLC-gamma2 SH2 domains, thus bringing Btk into close proximity with PLC-gamma2. The activated Btk then phosphorylates PLC-gamma2, leading to its activation. The activated PLC-gamma2 converts phosphatidylinositol 4,5-bisphosphate into the second messenger inositol 1,4,5-trisphosphate (IP3), which in turn binds to IP3 receptors located on the endoplasmic reticulum (ER). Binding of IP3 to the IP3 receptors is essential for triggering a calcium release from the ER and subsequent entry of extracellular calcium. Balancing these activation signals in the PLC-gamma2-calcium pathway are the inhibitory receptors expressed on B cells, FcyRII and paired immunoglobin-like receptor (PIR)-B. Although both FcyRII and PIR-B inhibits the BCR-mediated [Ca2+]i increase, the inhibitory mechanisms of these receptors are distinct. The FcyRII-mediated inhibitory signal is dependent on lipid phosphatase SHIP, whereas the PIR-B requires redundant functions of protein phosphatases SHP-1 and SHP-2. Thus, PIR-B and FcgammaRII inhibit calcium signals by utilizing two distinct signaling molecules, thereby contributing to setting threshold levels for activation signals as well as terminating activation responses.

Animals↗
PubMed2000

Epstein-Barr virus infection to Epstein-Barr virus-negative nasopharyngeal carcinoma cell line TW03 enhances its tumorigenicity.

Almost all nasopharyngeal carcinomas (NPCs) are infected by Epstein-Barr virus (EBV), but most ex vivo NPC cells lose EBV genomes during passages. In this study, an EBV-negative NPC cell line, TW03, established from EBV-carrying NPC was reinfected with EBV by cocultivation with irradiated Akata cells carrying recombinant EBV containing a neomycin-resistant gene. The reinfected EBV (+) TW03 cells expressed EBERs and EBNA1, but not EBNA2, lytic proteins (ZEBRA and EA-D), or LMP1. They had an epithelial appearance similar to that of EBV (-) TW03 cells. The doubling times of EBV (+) and EBV (-) TW03 cells were almost identical. However, the EBV (+) TW03 cells formed larger colonies with ragged contours in anchorage-independent cultures. An in vitro invasion assay showed that EBV (+) TW03 cells had a higher invasive activity than EBV (-) TW03 cells (p < 0.01). Both EBV (-) and EBV (+) TW03 cells formed poorly differentiated squamous cell carcinomas in SCID and nude mice. EBV (+) TW03 cells showed a higher tumorigenicity to nude mice (12 of 13) than EBV (-) TW03 cells (1 of 9) (p < 0.001). In the severe combined immunodeficiency (SCID) tumors of EBV (+) TW03 cells, not all of the tumor cells were EBER-1 positive. EBER-1 was more frequently detected in the peripheral regions and daughter nodules of the tumors than in the central areas. The microdissection polymerase chain reaction showed that the EBER-1-negative TW03 cells in the EBV (+) TW03 SCID tumors lost EBV genomes. EBER-1-negative cells showed as high a rate of Ki-67 positivity as EBER-1-positive cells, indicating that the former were proliferating rather than dead or dying. In horny pearls, keratinizing cells were ZEBRA-positive and EBER-negative. Loss of EBV genomes was not associated with squamous differentiation. These data indicated that reinfection of EBV promotes the tumorigenicity of EBV (-) TW03 cells by enhancing the invading activity.

Animals↗
PubMed2000

Inhibition of growth of melanoma cells by CD95 (Fas/APO-1) gene transfer in vivo.

Interaction of CD95 ligand with its cognate receptor CD95 induces apoptotic cell death. Alterations in this pathway within tumor cells can result in escape from apoptosis and from immune surveillance. Melanoma cells recently were found to escape an immune attack via high expression of CD95 ligand, thereby inducing apoptosis of activated T lymphocytes. When screening four human melanoma cell lines for expression of CD95 and CD95 ligand, respectively, an inverse correlation was found, i.e., cells expressing high levels for CD95 ligand (CD95L(high)) were almost negative for CD95 and vice versa. Since coexpression of CD95 and CD95 ligand may lead to apoptosis by autocrine suicide or fratricide, it was tested whether overexpression of CD95 in CD95L(high) melanoma cells results in apoptotic cell death. Upon transfection with a cytomegalovirus-promoter-driven expression vector encoding the CD95 gene, CD95L(high) melanoma cells underwent apoptosis at a much higher level than CD95L(low) melanoma cells. Apoptosis appeared to be due to the activation of CD95 as cell death was inhibited by cotransfection with a dominant negative mutant for the CD95 signaling protein, Fas-associated protein with death domain. Tumor progression of CD95L(high) melanoma cells transplanted into nude mice was significantly reduced when recipient animals were injected with liposomes containing the CD95 expression vector. As demonstrated by immunohistochemistry and TUNEL staining, in vivo transfected tumor cells expressed CD95 and underwent apoptotic cell death. Hence, this study indicates that delivery of the CD95 gene inhibits tumor growth in vivo and thus might be a therapeutic strategy to treat tumor cells that express high levels of CD95 ligand. J Invest Dermatol 115:1008-1014 2000

Apoptosis↗
PubMed2000

Polymyositis associated with primary cytomegalovirus infection.

A case of polymyositis associated with primary cytomegalovirus infection in a 17-y-old girl is reported. The girl exhibited fever, sore throat, progressive myalgia and muscle weakness with elevated creatine kinase, atypical lymphocytosis and myopathic features in the electromyogram. Histopathologically, biopsied muscle met the criteria for polymyositis. Primary cytomegalovirus infection was proven by seroconversion of IgG as well as IgM antibodies. This is the first report of an association between cytomegalovirus infection and polymyositis.

Adolescent↗
PubMed2000

Diurnal variation in the P300 component of human cognitive event-related potential.

Diurnal variation in the P300 component of the human cognitive event-related potential (ERP) was examined. The P300 component is considered to be a measure of neuroelectric activity related to cognitive functions such as attention allocation and information processing. Nine diurnally active healthy male subjects whose sleep-wake rhythms were synchronized prior to the experiment were studied. The P300 components oral temperature, heart rate, left- and right-hand grip strength, reaction time, subjectively rated sleepiness, attention level, and fatigue were measured at 08:00, 11:00, 14:00, 17:00, and 20:00. Significant diurnal variations in P300 latency, P300 amplitude, oral temperature, heart rate, left- and right-hand grip strength, subjectively rated sleepiness, and attention level were observed. The P300 latency at 08:00 was significantly longer than at 11:00, 17:00, and 20:00, while the P300 amplitude at 08:00 was significantly greater than at 17:00 and 20:00. The P300 latency was correlated positively with subjectively rated sleepiness and negatively correlated with subjectively rated attention level. These results suggest the existence of diurnal variation in human cognitive functions.

Adult↗
PubMed2000

Circadian rhythm abnormalities of wrist activity of institutionalized dependent elderly persons with dementia.

BACKGROUND: The study objective was to clarify the descriptive characteristics of circadian rhythm abnormalities of wrist activity of the institutionalized elderly with dementia. METHODS: We studied 82 elderly persons with dementia who were institutionalized in a long-term medical care facility. The ambulatory continuous monitoring of their wrist activity was conducted for 7 days at 1-minute intervals. The time series data were analyzed using the double-plotted chronogram, spectral analysis was performed using the fast Fourier transformation and periodogram analysis was performed as well. RESULTS: The frequency of circadian rhythm abnormalities of wrist activity rhythm in elderly persons with dementia was 57.3% (47 out of 82). The abnormalities were classified into four categories: severely impaired circadian rhythm type with no boundary between day and night, free-running rhythm type, decreased circadian amplitude type, and accentuation of ultradian rhythm type. CONCLUSION: This four-category classification system provides a scientific approach for studying the mechanisms of circadian activity rhythm abnormalities of elderly persons with dementia.

Activity Cycles↗