Biomedical subjects

T Maeda

Publications and source records attributed to T Maeda.

At least 235 records · Page 13Linked to original sources

PubMed2000

[Effects of 6-degree head-down bed rest on physical fitness].

We investigated changes in enduring physical fitness during a ground-based weightlessness simulation of 6-degree head-down bed rest (HDBR). Ten healthy volunteers participated in the 6 days of HDBR. In each, their physique, muscular strength, physical fitness, cardiovascular function, and hematocrit were measured before and after HDBR. The results are as follows: (1) Thigh extensor power: the cross-sectional areas of the thigh and leg muscles were significantly decreased after HDBR, but recovered immediately afterwards. (2) Hand grip power and instantaneous power: the body response time showed no significant change before and after HDBR. (3) High physical capacity was correlated with a greater decrease in physical capacity after HDBR. (4) Remarkable functional depression appeared in the cardiovascular system compared with the gas exchange system as measured by the enduring physical fitness test. (5) The functional depression in the cardiovascular system lasted for more than 3 days after HDBR. (6) Six days of HDBR had little influence on physical fitness attributable to the inactivity and seemed to effectively simulate weightlessness for the cardiovascular system.

Activities of Daily Living↗

PubMed1999

Altered distribution of Schwann cells in the periodontal ligament of the rat incisor following resection of the inferior alveolar nerve: an immunohistochemical study on S-100 proteins.

The present study employed immunohistochemistry for the detection of S-100 proteins to reveal the alteration in the distribution of Schwann cells in the periodontal ligament of the rat incisor following resection of the inferior alveolar nerve (IAN). In normal animals, S-100-immunostaining demonstrated the profiles of Ruffini endings, primary mechanoreceptors in the periodontal ligament, in the alveolus-related part of the ligament. Under the electron microscope, S-100-like immunoreactivity (-LI) was observed in the cytoplasm of the terminal Schwann cell elements and in some axon profiles of the Ruffini endings. During the regeneration, S-100-like immunoreactive (-IR) terminal Schwann cells in the alveolus-related part of the ligament gradually decreased in number. In contrast, S-100-LI was found in the spindle-shaped cells at the shear zone (the border between alveolus-related and tooth-related parts) and in the tooth-related part, where S-100-LI was rarely detected in normal animals. Immunoelectron microscopic observations revealed that some S-100-IR spindle-shaped cells contained fibrous long spacing (FLS) fibers, suggesting that they were Schwann cells. Some regenerating axons were observed at the shear zone, but were rarely found in the tooth-related part. With the progress of the regeneration of the periodontal Ruffini endings, S-100-IR terminal Schwann cells became rearranged in the alveolus-related part by 42-56 days post injury, whereas the S-100-IR spindle-shaped Schwann cells in the shear zone and tooth-related part disappeared when the regeneration was complete.

Animals↗

PubMed1999

Fas-resistance in ATL cell lines not associated with HTLV-I or FAP-1 production.

A preventive role for human T-cell leukemia virus type-I (HTLV-I) and Fas-associated phosphatase-1 (FAP-1) in Fas-mediated apoptosis has been reported in HTLV-I-infected cells. In the present study, we examined whether these molecules increased during the acquisition of Fas-resistance in adult T-cell leukemia (ATL) cell lines. SO4, ST1 and KK1 are Fas-sensitive ATL cell lines, and produce small amounts of HTLV-I in vitro. Although their subclones RSO4 and RST1 are completely Fas-resistant, they produced an equivalent amount of HTLV-I to SO4 and ST1. Moreover, FAP-1 mRNA was not detected in these cell lines irrespective of Fas sensitivity. Thus, Fas resistance in ATL cells was not directly associated with the increased production of HTLV-I or FAP-1.

Antibodies, Monoclonal↗

PubMed1999

Phospholipids stabilize the secondary structure of the sodium-coupled branched-chain amino acid carrier of Pseudomonas aeruginosa.

For functional reconstitution of bacterial cotransporters (carriers or permeases) including the sodium-coupled branched-chain amino acid carrier (LIV-II carrier) of Pseudomonas aeruginosa, the presence of phospholipid is required through the process of solubilization and purification of the transporters from the bacterial membranes, suggesting the possibility that phospholipid may stabilize the structure of the cotransporter proteins to be in a functional form. In this study, this possibility was examined by studying the effect of denaturant on the secondary structure of the LIV-II carrier purified in the absence and presence of phospholipid using circular dichroism (CD) spectroscopy. CD spectra of the purified LIV-II carrier solubilized in n-octyl-beta-D-glucopyranoside (OG), OG/dioleoylphosphatidylethanolamine (DOPE)/dioleoylphosphatidylglycerol (DOPG) mixture, and dispersed into DOPE/DOPG small unilamellar vesicles were measured in the absence of denaturant. The three spectra were very similar and had a trough at 222 nm with mean residue molar ellipticity of -23000 deg.cm(2)/dmol and a shoulder at 208 nm. CD spectral analyses with three different methods (S.W. Provencher, J. Glöckner, Estimation of globular protein secondary structure from circular dichroism, Biochemistry 20 (1981) 33-37; J.Y. Yang, C.-S.C. Wu, H.Z. Martinez, Calculation of protein conformation from circular dichroism, Methods Enzymol. 130 (1986) 208-269; N. Sreerama, R.W. Woody, A self-consistent method for the analysis of protein secondary structure from circular dichroism, Anal. Biochem. 209 (1993) 32-44) revealed that the LIV-II carrier solubilized in OG/DOPE/DOPG mixture contained 69-75% alpha-helix and 0-9% beta-sheet. Addition of 6 M guanidine hydrochloride decreased 48% of the amplitude at 222 nm of the CD spectrum of the carrier solubilized in OG alone and 9-14% of the CD amplitude of the carrier solubilized in OG/DOPE/DOPG or OG/dioleoylphosphatidylcholine mixture and dispersed in liposomes composed of DOPE/DOPG. These results show that the ordered secondary structure of the LIV-II carrier is partially unfolded in OG without phospholipid by denaturant but is greatly stabilized with phospholipids with oleoyl chains independently of their polar head group composition and suggest that the alpha-helical structure of the carrier is mainly embedded in the lipid environment.

Bacterial Proteins↗

PubMed1999

Automated determination of 5-fluorouracil and its metabolite in urine by high-performance liquid chromatography with column switching.

We report a quantitative assay of 5-fluorouracil (FU) and its metabolite, 5-fluorodihydrouracil (FDHU) in human urine by used a column-switching high-performance liquid chromatographic method. The analyses were carried out using a molecular exclusion column for sample purification, and a cation-exchange column for separation. Each sample required only 40 min to analyze, and required no preparation other than filtration. Linearity was verified up to 1000 nmol/ml (r > 0.993). The recovery of FU was 96-101%; recovery of FDHU was 96-105%. The imprecision (RSD) for FU (10-100 nmol/ml) was < 1.5%, same-day (n = 5), and < 1.8%, day-to-day (n = 5). The imprecision (RSD) for FDHU (10-100 nmol/ml) was < 3.2%, same-day (n = 5), and < 4.0%, day-to-day (n = 5). The detection limits were, respectively, 0.1 nmol/ml. We measured FU and FDHU in urine of seven cancer patients after oral administration of FU. The cumulative quantity ratio of the FDHU and FU (FDHU/FU) excreted in their urine within 120 min after FU administration was a constant value in all seven patients. Based on these results, we believe that our method provides a useful tool for evaluating FU metabolism.

Breast Neoplasms↗

PubMed1999

Cholinergic neurons with monoamine oxidase type B (MAOB)-activity in the laterodorsal tegmental nucleus of the mouse.

No neurons in the laterodorsal tegmental nucleus (LDTg) show monoamine oxidase (MAO) activity in the rat or monkey. However, in our recent study, many LDTg neurons with MAO type B (MAOB)-activity were found in MAOA-deficient mice that were derived from C3H mouse line. In the present study, LDTg neurons with MAOB-activity were found not only in normal C3H mouse but also in BALB/C and C57BL/6 mouse lines: MAO histochemistry revealed LDTg neurons with MAO-activity even after pharmacological suppression of MAOA-activity with clorgyline, a specific MAOA inhibitor, but not after pharmacological suppression of MAOB-activity with deprenyl, a specific MAOB inhibitor. LDTg neurons with MAOB-activity also showed NADPH-diaphorase-activity, a marker of cholinergic neurons.

Animals↗

PubMed1999

NeuroD is required for differentiation of the granule cells in the cerebellum and hippocampus.

NeuroD, a bHLH transcription factor, is implicated in differentiation of neurons and pancreatic beta cells. NeuroD-null mice die shortly after birth due to severe neonatal diabetes. To examine if there is postnatal neuronal phenotype in these mice, we rescued them from neonatal lethality by introducing a transgene encoding the mouse neuroD gene under the insulin promoter. These mice survive to adulthood but display severe neurological phenotype due to neuronal deficit in the granule layers of the cerebellum and hippocampus. We show here that NeuroD is required for these postnatally generated microneurons to undergo proper differentiation, the absence of which results in cell death.

Animals↗

PubMed1999

Physical interaction and functional antagonism between the RNA polymerase II elongation factor ELL and p53.

ELL was originally identified as a gene that undergoes translocation with the trithorax-like MLL gene in acute myeloid leukemia. Recent studies have shown that the gene product, ELL, functions as an RNA polymerase II elongation factor that increases the rate of transcription by RNA polymerase II by suppressing transient pausing. Using yeast two-hybrid screening with ELL as bait, we isolated the p53 tumor suppressor protein as a specific interactor of ELL. The interaction involves respectively the transcription elongation activation domain of ELL and the C-terminal tail of p53. Through this interaction, ELL inhibits both sequence-specific transactivation and sequence-independent transrepression by p53. Thus, ELL acts as a negative regulator of p53 in transcription. Conversely, p53 inhibits the transcription elongation activity of ELL, suggesting that p53 is capable of regulating general transcription by RNA polymerase II through controlling the ELL activity. Elevated levels of ELL in cells resulted in the inhibition of p53-dependent induction of endogenous p21 and substantially protected cells from p53-mediated apoptosis that is induced by genotoxic stress. Our observations indicate the existence of a mutually inhibitory interaction between p53 and a general transcription elongation factor ELL and raise the possibility that an aberrant interaction between p53 and ELL may play a role in the genesis of leukemias carrying MLL-ELL gene translocations.

Cell Compartmentation↗

PubMed1999

Analysis of genomic instability in squamous cell carcinoma of the head and neck using the random amplified polymorphic DNA method.

Using the random amplified polymorphic DNA (RAPD) method, we identified genomic instability in head and neck squamous cell carcinoma (HNSCC) tissues. We extracted DNA from tumor and corresponding normal tissues of 30 HNSCC patients and amplified with ten random 10-mer arbitrary primers by the RAPD method. Genomic instabilities, which appeared as banding pattern changes between normal and tumor DNA, were detected by at least one primer in all tumor tissues. Moreover, there was significant correlation between the frequency of genomic instability and the degree of tumor differentiation. These results indicate a possible association of genomic instability with malignant potential of head and neck cancer.

Carcinoma, Squamous Cell↗

PubMed1999

Fas gene mutation in the progression of adult T cell leukemia.

Fas antigen (Apo-1/CD95) is an apoptosis-signaling cell surface receptor belonging to the tumor necrosis factor receptor superfamily. Adult T cell leukemia (ATL) cells express Fas antigen and show apoptosis after treatment with an anti-Fas monoclonal antibody. We established the ATL cell line KOB, which showed resistance to Fas-mediated apoptosis, and found that KOB expressed two forms of Fas mRNA, the normal form and a truncated form. The truncated transcript lacked 20 base pairs at exon 9, resulting in a frame shift and the generation of a premature stop codon at amino acid 239. The same mutation was detected in primary ascitic cells and peripheral blood cells. The mutation was not detected in lymph node cells, however, although all of the primary ATL cells were of the same clonal origin. A retroviral-mediated gene transfer of the truncated Fas to Jurkat cells rendered the cells resistant to Fas-mediated apoptosis, suggesting a dominant negative interference mechanism. These results indicate that an ATL subclone acquires a Fas mutation in the lymph nodes, enabling the subclone to escape from apoptosis mediated by the Fas/Fas ligand system and proliferate in the body. Mutation of the Fas gene may be one of the mechanisms underlying the progression of ATL.

Aged↗

PubMed1999

A radicicol-related macrocyclic nonaketide compound, antibiotic LL-Z1640-2, inhibits the JNK/p38 pathways in signal-specific manner.

Macrocyclic nonaketide compounds, radicicol and its two analogues, 87-250904-F1 and LL-Z1640-2, have various biological activities. Here we show that these compounds inhibit signal-dependent transcriptional activation with different specificity with distinct mechanism. Although all three compounds inhibited PMA-induced AP-1 transcriptional activity in cell-based reporter assay, these compounds exhibited differential effects in separate transcriptional reporter assays for NF-kappaB and glucocorticoid receptor. Next we found that one of these compounds, LL-Z1640-2, was a signal-specific inhibitor of the JNK/p38 pathways. In contrast to LL-Z1640-2, radicicol and 87-250904-F1 did not inhibit JNK/p38 activation. Recently, radicicol was reported as an inhibitor of activated-Ras-induced ERK activation. These results indicated that radicicol and LL-Z1640-2 showed distinct specificity to various MAP kinase pathways despite their structural similarity. Furthermore, LL-Z-1640-2 inhibited anisomycin-induced but not TNF-induced JNK/p38 activation, indicating that the inhibition mechanism is signal-specific.

3T3 Cells↗

PubMed1999

Secretagogue-induced exocytosis recruits G protein-gated K+ channels to plasma membrane in endocrine cells.

Stimulation-regulated fusion of vesicles to the plasma membrane is an essential step for hormone secretion but may also serve for the recruitment of functional proteins to the plasma membrane. While studying the distribution of G protein-gated K+ (KG) channels in the anterior pituitary lobe, we found KG channel subunits Kir3.1 and Kir3.4 localized on the membranes of intracellular dense core vesicles that contained thyrotropin. Stimulation of these thyrotroph cells with thyrotropin-releasing hormone provoked fusion of vesicles to the plasma membrane, increased expression of Kir3.1 and Kir3.4 subunits in the plasma membrane, and markedly enhanced KG currents stimulated by dopamine and somatostatin. These data indicate a novel mechanism for the rapid insertion of functional ion channels into the plasma membrane, which could form a new type of negative feedback control loop for hormone secretion in the endocrine system.

Amino Acid Sequence↗

PubMed1999

Estrogen replacement therapy decreases platelet-activating factor-acetylhydrolase activity in post-menopausal women.

OBJECTIVE: To examine the effects of estrogen replacement therapy on plasma platelet-activating factor-acetylhydrolase (PAF-AH) activity and the lipoprotein profile in post-menopausal women. METHOD: Eight post-menopausal women received conjugated equine estrogen (0.625 mg/day) orally for a period of 10 weeks. PAF-AH activity and lipid levels were measured in plasma samples obtained from each subject prior to treatment and after 2, 6, and 10 weeks of estrogen therapy. RESULTS: Within 2 weeks of initiating estrogen treatment, a significant reduction in PAF-AH activity (-26%) was observed. Estrogen also caused significant decreases in total cholesterol (-8%), low-density lipoprotein-cholesterol (-24%), and the ratio of apolipoprotein B to A-II (-19%). On the other hand, levels of both high-density lipoprotein-cholesterol (18%) and triglyceride (31%) were elevated. CONCLUSION: Estrogen exerts a favorable effect on the lipoprotein profile, but decreased plasma PAF-AH activity may facilitate platelet aggregation thereby opposing protective effect of estrogen-replacement therapy with respect to thrombotic complications.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed1999

Enhanced repair of benzo(a)pyrene-induced DNA damage in human cells treated with thymidine dinucleotides.

The small DNA fragment thymidine dinucleotide (pTpT) stimulates photoprotective responses in mammalian cells and intact skin. These responses include increased melanogenesis (tanning) and enhanced repair of DNA damage induced by ultraviolet (UV) light. Here we show that pTpT treatment of human keratinocytes enhances their repair of DNA damaged by the chemical carcinogen benzo(a)pyrene (BP), as determined by increased expression of a transfected BP-damaged reporter plasmid containing the chloramphenicol acetyltransferase (CAT) gene. The pTpT-enhanced repair of this BP-damaged plasmid is accomplished at least in part through activation of the p53 tumor suppressor protein and transcription factor, because p53-null H1299 cells showed enhanced repair only if previously transfected with a p53-expression vector. To elucidate the mechanism of this enhanced DNA repair, we examined the expression of p21 and proliferating cell nuclear antigen (PCNA), proteins known to be regulated by p53, as well as the XPA protein, which is mutated in the inherited repair-deficient disorder xeroderma pigmentosum (XP) group A and is necessary for the recognition of UV-induced DNA photoproducts. The p53, PCNA and XPA proteins were all up-regulated within 48 h after the addition of pTpT. Taken together, these data demonstrate that pTpT-enhanced repair of DNA damaged by either UV irradiation or chemical mutagens can be achieved in human cells by exposure to small DNA fragments at least in part through the activation of p53 and increased expression of p53-regulated genes.

Benzo(a)pyrene↗

PubMed1999

Role of serotonergic neurons in L-DOPA-derived extracellular dopamine in the striatum of 6-OHDA-lesioned rats.

The effect of L-dihydroxyphenylalanine (L-DOPA) on extracellular dopamine (DA) in the striatum was determined by microdialysis in 6-hydroxydopamine (6-OHDA)-lesioned rats treated with and without the serotonergic neurotoxin 5,7-dihydroxytryptamine (5,7-DHT). At the same time the intensity of L-DOPA-induced rotational behavior was assessed. In 6-OHDA-lesioned rats treated with 5,7-DHT, L-DOPA (50 mg/kg, i.p.) increased extracellular DA only to 20% of that measured in animals not treated with 5,7-DHT. Likewise, 6-OHDA-lesioned rats treated with 5,7-DHT exhibited a significantly lower number of L-DOPA-induced rotations. These results suggest that serotonergic terminals in the striatum can convert exogenously administered L-DOPA into DA that can be released into the extracellular space.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1999

(3-substituted benzyl)thiazolidine-2,4-diones as structurally new antihyperglycemic agents.

A series of 3-[(2,4-dioxothiazolidin-5-yl)methyl]benzamide derivatives was prepared as part of a search for antidiabetic agents. A structure-activity relationship study of these compounds led to the identification of 5-[(2,4-dioxothiazolidin-5-yl)methyl]-2-methoxy-N-[[4-(trifluorome thyl)-phenyl]methyl]benzamide (KRP-297) as a candidate drug for the treatment of diabetes mellitus.

Animals↗

PubMed1999

Effects of morphine on the distribution of Fos protein in the trigeminal subnucleus caudalis neurons during experimental tooth movement of the rat molar.

The present study was undertaken to disclose temporal changes in the distribution of Fos-like immunoreactive (-IR) neurons in the trigeminal subnucleus caudalis (SpVc), one of the important relay nuclei for processing the nociceptive information from the oro-facial regions, following induction of experimental tooth movement in rat upper molars. Furthermore, the effect of morphine and naloxone on the levels of Fos-IR neurons in the SpVc was examined. The experimental tooth movement was induced by insertion of an elastic rubber between the first and second upper molars. In normal animals, Fos-IR neurons were rarely observed in the SpVc. Immediately after insertion of the elastic band, the distribution of Fos-IR neurons was comparable to that observed in normal animals. The number of Fos-IR neurons increased significantly from 1 to 4 h following the induction of experimental tooth movement, reaching a maximum at 2 h, and then decreasing gradually. Most of the neurons were localized in the dorsomedial portion of the superficial layers of the ipsilateral SpVc near the obex, but a few were observed at the ventral portion of the SpVc. The neurons at the superficial layers and ventral portion of the contralateral SpVc also showed Fos-like immunoreactivity, but their numbers were significantly smaller than those on the ipsilateral side. Pretreatment with morphine (3 and 10 mg/kg, i.p.) significantly reduced the induction of Fos-IR neurons at the superficial layers of the ipsilateral SpVc in a dose-dependent manner, and its effect was antagonized by the subsequent treatment of naloxone (2 mg/kg, i.p.). Naloxone pretreatment enhanced the expression of Fos-IR neurons on the ipsilateral SpVc. The present results of a reduction of Fos-IR neurons by morphine pretreatment suggest that the induction of Fos-IR neurons may be due to the noxious stimulation caused by induction of experimental tooth movement.

Analgesics, Opioid↗

PubMed1999

Immunohistochemical localization of S-100beta in the dental pulp of the rat molar.

The present study was undertaken to reveal whether S-100alpha or S-100beta or both are present in the nerve fibers in the rat molar tooth pulp. No immunoreactivity for S-100alpha was observed in the molar pulp. In the root pulp, thick smooth-surfaced structures accompanying the blood vessel showed S-100beta-like immunoreactivity (-LI), and occasionally a very few thin beaded elements exhibited S-100beta-LI. In the coronal pulp, S-100beta-like immunoreactive (-IR) structures arborized repeatedly and extensively; they had a predominantly thick, smooth-surfaced appearance, though parts appeared thin and beaded. Numerous thin varicose S-100beta-IR structures ran through the odontoblast cell layer, and further penetrated into the predentin alongside the dentinal tubules. They could be traced for approximately 10-20 micrometers into the predentin from the pulp-predentin border. Immunoelectron microscopy revealed that the Schwann cells in the root pulp showed S-100beta-LI, and that S-100beta-LI was present in the axoplasm as well as Schwann cells in the coronal pulp. The S-100beta-IR axons were rarely surrounded by S-100beta-IR Schwann cells. In the predentin, S-100beta-IR nerve fibers terminated in a position close to the odontoblast processes. The present findings indicate that S-100beta, not S-100alpha, is present in the axon in the dental pulp and predentin as well as in the Schwann cells.

Animals↗