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Biomedical subjects

T Masuda

Publications and source records attributed to T Masuda.

At least 145 records · Page 8Linked to original sources
PubMed2000

The long-lasting antiproliferative effect of 15-deoxyspergualin through its spermidine moiety.

15-Deoxyspergualin (DSG) inhibited growth of mouse EL-4 lymphoma cells with an IC50 0.02 microg/ml. Even though the cells were treated with DSG for only 4 hours and then washed, the antiproliferative effect lasted long with an IC50 0.4 microg/ml. DSG has spermidine and guanidine moieties in its structure. One decomposed element containing guanidine moiety inhibited the growth at higher doses than DSG, but the effect did not last long unlike DSG. While another element containing spermidine moiety did not affect the growth, it diminished the long-lasting antiproliferative effect of DSG by pretreatment of the cells. Pretreatment with polyamines such as putrescine, spermidine, and spermine also diminished the effect of DSG. Furthermore, N-alkylation of spermidine moiety in DSG abolished the antiproliferative effect. These results suggested that DSG binds to the cells through its spermidine moiety and exerts its long-lasting antiproliferative effect.

Animals↗
PubMed2000

[A case report of extensively calcified renal cell carcinoma].

A 73-year-old woman visited another hospital with complaints of occasional episodes of gross hematuria. A computed tomographic (CT) scan revealed extensive calcification in the left kidney, and she was referred to our hospital for further examinations. The physical examination was unremarkable other than mild back pain on her left side. Blood chemistry was normal. The CT scan revealed a mildly enhanced tumor of 6 cm in diameter accompanied by extensive calcification in the left kidney. Angiography revealed a hypovascular tumor in the left kidney. A left radical nephrectomy was carried out. Gross appearance of the specimen showed extensive calcification from the renal pelvic to the parenchyma of the lower pole of the left kidney. The histopathological diagnosis was renal cell carcinoma, alveolar type, mixed subtype, pT2pN0pM0.

Aged↗
PubMed2000

Focal nodular hyperplasia of the liver: direct evidence of circulatory disturbances.

Focal nodular hyperplasia of the liver is a lesion characterized by a well-circumscribed region of hyperplastic liver parenchyma and contains a stellate fibrous scar. The lesion is thought to be because of liver-cell hyperplasia that is caused by focal circulatory disturbances. We describe here a pediatric case of this lesion that provided direct histopathologic evidence of circulatory disturbances. We identified arterial and portal thrombi, as well as recanalization of arteries in the nodule. Hepatic necrosis was also seen in the lesion. We speculate that thrombosis of the hepatic artery and/or portal vein was the cause of hepatic necrosis and that reperfusion following hepatic arterial recanalization resulted in nodule formation. Although there was no stellate scar present in our case, the presence of bile ductular proliferation at the periphery of the nodule was helpful in distinguishing this lesion from adenoma and hepatocellular carcinoma. The early stage of nodular formation may explain the lack of a stellate scar in our case. The patient was treated earlier with actinomycin D and vincristine following surgical excision of Wilms' tumor. It is possible that such chemotherapy contributed to thrombosis in our case.

Antineoplastic Agents↗
PubMed2000

The multigenic family of monogalactosyl diacylglycerol synthases.

Because the synthesis of monogalactosyldiacylglycerol (MGDG) is unique to plants, identified as an important marker of the plastid envelope, involved in a key step of plastid biogenesis and is the most abundant lipid on earth, MGDG synthase activity was extensively analysed at the biochemical and physiological levels. In the present paper, we present our current knowledge on the MGDG synthase's function, structure and topology in envelope membranes, and discuss possible roles in plant cell glycerolipid metabolism. The recent discovery of a multigenic family of MGDG synthases raised the possibility that multiple isoenzymes might carry out MGDG synthesis in various tissues and developmental stages.

Amino Acid Sequence↗
PubMed2000

Transcriptional regulation by light and phytohormones of the MGD gene in cucumber.

Monogalactosyldiacylglycerol (MGDG) synthase catalyses formation of MGDG, a major structural lipid of chloroplasts. We have already cloned a cDNA for the synthase from a cucumber cDNA library and shown that expression of this gene is regulated by light and a phytohormone, cytokinin. In the present study, we report the molecular basis for transcriptional regulation by light and cytokinin in detail. First, in terms of the enzyme activity, gradual increases in activity mediated by light and cytokinin treatments were observed. At the same time, however, the changes in the mRNA level showed different profiles, with a transient peak during the early stages of light and cytokinin treatment. The interval between the peak level of mRNA and enzyme activation implies the existence of a post-transcriptional regulatory system. In addition, a genomic clone of MGDG synthase isolated from a cucumber genome library was used for a motif search in databases, and this revealed that putative cis-acting elements for light and phytohormones exist in the 5'-upstream region of the MGD cucumber gene. Detailed analysis of this region for light- and cytokinin-responsive activity was performed using a -90 truncated 35 S minimal promoter/luciferase (LUC) reporter gene. It resulted in high levels of LUC expression in etiolated cucumber cotyledons in response to illumination and cytokinin treatment. These results indicate that this 5'-upstream region is involved in light- and cytokinin-enhanced MGD gene expression, and that light- and cytokinin-responsive enhancements of the MGDG synthase activity are regulated, at least in part, at the level of transcription.

Adenine↗
PubMed2000

Genome-wide expression-monitoring of jasmonate-responsive genes of Arabidopsis using cDNA arrays.

Jasmonates are generally considered to mediate signalling, such as defence responses, flowering and senescence. However, factors involved in the jasmonate signal-transduction pathway remain unclear. To clarify the functions and signalling mechanisms of jasmonates on a genome-wide level, we adopted a cDNA macroarray technique. We prepared nylon filters of a cDNA macroarray on which 2880 independent expressed sequence tag clones of Arabidopsis were blotted, and hybridized (33)P-labelled single-strand DNAs synthesized from mRNAs of methyl jasmonate (MeJA)-treated and untreated Arabidopsis plants to the nylon filters. By analysing the data from the cDNA macroarray, we identified many function-known and unknown genes as MeJA-responsive genes, and confirmed that the profiles of the expression showed good agreement with Northern-blot analysis. These results demonstrate the efficiency of the cDNA macroarray for systematically analysing jasmonate-responsive genes on a genome-wide scale.

Acetates↗
PubMed2000

Effects of aging on EMG variables during fatiguing isometric contractions.

The purpose of this study was to evaluate the neuromuscular adaptation that occurred with aging, by comparing young and aged subjects with respect to changes in surface EMG from the tibialis anterior muscle during fatiguing contractions. EMG variables such as the averaged rectified value (ARV), median frequency (MDF), and muscle fiber conduction velocity (MFCV) were calculated during maximal (MVC, 3 sec) and submaximal (60% MVC, 60 sec) isometric contractions. Muscular force, ARV, MDF, and MFCV during MVC were significantly greater in the young than in the elderly (p < 0.05). EMG amplitude increased and the waveform slowed in all subjects during submaximal contractions, indicating the development of local muscle fatigue. As fatigue progressed, the ARV increased and the MDF and MFCV decreased significantly (p < 0.01). The fatigue-induced changes in the MDF and MFCV were significantly smaller in aged than in young subjects (p < 0.05), a trend also seen in the ARV change, which means that the elderly cannot be fatigued as much as the young with contractions of the same relative intensity. These results as a whole suggest that the aged subjects hold an adaptive motor strategy to cope with age-related neuromuscular deteriorations, due to the decline of motor unit activation and selective atrophy of fast twitch muscle fibers.

Adult↗
PubMed2000

Innervation zones of the upper and lower limb muscles estimated by using multichannel surface EMG.

The distribution of innervation zones was investigated in 3 subjects for 17 muscles and 8 muscle groups in the upper and lower limb, by detecting bi-directional propagation of motor unit action potentials (MUAPs) with the multichannel surface electrode array. Clarification of the distribution of innervation zones depended on the ease in detecting the propagation of MUAPs and the actual scattering of innervation zones, which were closely related with muscle morphology with respect to the arrangements of muscle fibers. In muscles having fibers running parallel to each other, such as the biceps brachii, intrinsic hand muscles, vastus lateralis and medialis, tensor fasciae latae, peronei, soleus, tibialis anterior, and hypothenar muscles in the foot, it was relatively easy to detect the propagating MUAPs, and the innervation zones were distributed in a relatively narrow band around muscle belly. On the other hand, in muscles with a complicated structure including pinnation of muscle fibers, in-series muscle fibers and aponeurotic tissues, such as the deltoid, flexors and extensors in the forearm, rectus femoris, sartorius, hamstrings and gastrocnemius, it was more difficult to detect the propagating MUAPs and to identify the innervation zones, which were widely scattered or distributed in complex configurations. The distribution of the innervation zones clarified in the present study can be used to find the optimal location of electrodes in surface EMG recordings and of stimulus electrodes in the functional and therapeutic electrical stimulations. It may also be useful in motor point biopsy for diagnosis of neuromuscular diseases as well as in the botulinum toxin injection for the treatment of spasticity.

Action Potentials↗
PubMed1999

Cloning of chlorophyllase, the key enzyme in chlorophyll degradation: finding of a lipase motif and the induction by methyl jasmonate.

Chlorophyllase (Chlase) is the first enzyme involved in chlorophyll (Chl) degradation and catalyzes the hydrolysis of ester bond to yield chlorophyllide and phytol. In the present study, we isolated the Chlase cDNA. We synthesized degenerate oligo DNA probes based on the internal amino acid sequences of purified Chlase from Chenopodium album, screened the C. album cDNA library, and cloned a cDNA (CaCLH, C. album chlorophyll-chlorophyllido hydrolase). The deduced amino acid sequence (347 aa residues) had a lipase motif overlapping with an ATP/GTP-binding motif (P-loop). CaCLH possibly was localized in the extraplastidic part of the cell, because a putative signal sequence for endoplasmic reticulum is at the N terminus. The amino acid sequence shared 37% identity with a function-unknown gene whose mRNA is inducible by coronatine and methyl jasmonate (MeJA) in Arabidopsis thaliana (AtCLH1). We expressed the gene products of AtCLH1 and of CaCLH in Escherichia coli, and they similarly exhibited Chlase activity. Moreover, we isolated another full-length cDNA based on an Arabidopsis genomic fragment and expressed it in E. coli, demonstrating the presence of the second Arabidopsis CLH gene (AtCLH2). No typical feature of signal sequence was identified in AtCLH1, whereas AtCLH2 had a typical signal sequence for chloroplast. AtCLH1 mRNA was induced rapidly by a treatment of MeJA, which is known to promote senescence and Chl degradation in plants, and a high mRNA level was maintained up to 9 h. AtCLH2, however, did not respond to MeJA.

Acetates↗
PubMed1999

Magnesium insertion by magnesium chelatase in the biosynthesis of zinc bacteriochlorophyll a in an aerobic acidophilic bacterium Acidiphilium rubrum.

To elucidate the mechanism for formation of zinc-containing bacteriochlorophyll a in the photosynthetic bacterium Acidiphilium rubrum, we isolated homologs of magnesium chelatase subunits (bchI, -D, and -H). A. rubrum bchI and -H were encoded by single genes located on the clusters bchP-orf168-bchI-bchD-orf320-crtI and bchF-N-B-H-L as in Rhodobacter capsulatus, respectively. The deduced sequences of A. rubrum bchI, -D, and -H had overall identities of 59. 8, 40.5, and 50.7% to those from Rba. capsulatus, respectively. When these genes were introduced into bchI, bchD, and bchH mutants of Rba. capsulatus for functional complementation, all mutants were complemented with concomitant synthesis of bacteriochlorophyll a. Analyses of bacteriochlorophyll intermediates showed that A. rubrum cells accumulate magnesium protoporphyrin IX monomethyl ester without detectable accumulation of zinc protoporphyrin IX or its monomethyl ester. These results indicate that a single set of magnesium chelatase homologs in A. rubrum catalyzes the insertion of only Mg(2+) into protoporphyrin IX to yield magnesium protoporphyrin IX monomethyl ester. Consequently, it is most likely that zinc-containing bacteriochlorophyll a is formed by a substitution of Zn(2+) for Mg(2+) at a step in the bacteriochlorophyll biosynthesis after formation of magnesium protoporphyrin IX monomethyl ester.

Acetobacteraceae↗
PubMed1999

Automatic activation in the human primary motor cortex synchronized with movement preparation.

The human primary motor cortex during a unilateral finger reactive movement to visual stimuli was examined by magnetoencephalography (MEG) measurement. The brain activity related to movement execution (the motor activity contralateral to the movement side) was estimated based on movement onset conditions and reaction times. The movement onset conditions were: (1) a simple reaction time task with a visual stimulus, (2) a Go/NoGo task with different colored stimuli and (3) a Go/NoGo task with different position stimuli. Dipole source estimation was done, and the time course of the motor activity was calculated. The results showed that not only the visual response but also the contralateral motor activity was evoked by the stimulus in all cases, and even when the NoGo stimulus was given. The motor activity in the primary motor cortex was conjectured to consist of two dominant components: the first component for the movement preparation and the second component for the movement execution. Because the first component happened with a constant delay time from the stimulus even in the NoGo case, the first component, coming through a fast pathway for signals from visual stimulus processing to the motor cortex without any intervening cognitive processing, was conjectured to make the motor cortex prepare for the forthcoming movement onset automatically regardless of the stimulus instruction.

Adult↗
PubMed1999

Total synthesis of reveromycin B.

[formula: see text] The stereoselective total synthesis of reveromycin B (2), a novel polyketide-type antibiotic, has been accomplished.

Anti-Bacterial Agents↗
PubMed1999

Bacteriological investigation of an outbreak of Clostridium perfringens food poisoning caused by Japanese food without animal protein.

An outbreak of Clostridium perfringens food poisoning occurred in a senior citizen's home in Japan. Japanese food, spinach boiled with fried bean curd, was considered to be the causative food as a result of the detection of the C. perfringens enterotoxin gene by nested PCR. The number of enterotoxin-positive C. perfringens was enumerated as 4.3 x 10(5)/g in the causative food by the MPN method combined with nested PCR. By cultivation, enterotoxin-positive C. perfringens was isolated from all the fecal specimens of patients tested and the causative food. The isolates from patients were serotypable, heat-resistant and the majority produced enterotoxin, however most isolates from the causative food were nonserotypable, enterotoxin-negative and heat-sensitive.

Aged↗
PubMed1999

Tau expression in denervated rat muscles.

We studied whether denervation affects the expression of tau, in particular phosphorylated tau, and how it is degraded in rat soleus muscles. Immunoblot analysis showed a high molecular weight, approximately 110 kDa (big tau), in normal muscle. Tau levels increased significantly in denervated muscles treated with chloroquine (a lysosomotrophic agent) and in untreated ones, as compared to levels of similarly treated contralateral, innervated muscles. Most of the tau in the innervated and denervated muscles was phosphorylated. Immunohistochemically, tau and beta-tubulin colocated in the sarcoplasm of innervated, saline-treated (intact) muscle, but the staining intensities were very weak. Both proteins, however, were expressed extensively in these areas in the denervated muscles from saline-treated rats. In the denervated muscle of chloroquine-treated rats there were numerous autophagic vacuoles in the sarcoplasm, and phosphorylated-tau accumulation was marked within these vacuoles, indicative that tau first was taken into autophagic, vacuoles by nonselective autophagy then degraded via the lysosomal as well as the nonlysosomal calpain system. Our findings suggest that phosphorylated big tau accumulates with beta-tubulin in denervated muscular atrophy, possibly in order to maintain or preserve the integrity of the muscle fiber during progressive atrophy or regeneration.

Animals↗