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Biomedical subjects

K Kitada

Publications and source records attributed to K Kitada.

At least 55 records · Page 3Linked to original sources
PubMed1997

Electromyogram patterns during plantarflexions at various angular velocities and knee angles in human triceps surae muscles.

To investigate the influence of the various knee angles and ankle angular velocities on synergistic muscle activities, the surface electromyograms (EMG) were recorded from the triceps surae muscles, i.e. lateral gastrocnemius (LG), medial gastrocnemius (MG) and soleus (SOL) muscles. Six healthy young men performed ankle plantarflexions at three ankle angular velocities of 6, 30 and 60 degrees.s-1 and three knee angles of 0, 30 and 60 degrees (0 degree equalling full extension) under constant load (5% and 10% maximal voluntary contraction). At the fully-extended knee angle (0 degree), peak values of integrated EMG (peak iEMG) during ankle plantarflexions were significantly increased (P < 0.05) in MG and in LG, but significantly decreased (P < 0.05) in SOL with increasing angular velocity. On the other hand, although the patterns of variation of the peak iEMG in each muscle at flexed knee angles (30 and 60 degrees) were very similar to the patterns seen at the fully-extended knee angle, there were no significant differences among angular velocities. During ankle plantarflexions at any of the angular velocities (6, 30 and 60 degrees.s-1) the peak iEMG were significantly increased (P < 0.05) in SOL, but were significantly decreased (P < 0.05) in MG following increases in the knee angles. These results would suggest the possibility of selective recruitment of motor units in humans depending on the angular velocity; however, this behaviour would appear to be weakened by fixing at flexed knee angles which cause an inhibitory influence on gastrocnemius muscles and a facilitative influence on SOL.

Adult↗
PubMed1997

Regulation by tetracycline of gene expression in Saccharomyces cerevisiae.

A convenient system for the control of gene expression in Saccharomyces cerevisiae was developed. Tetracycline-responsive promoters were constructed by fusing the tetracycline operator (tetO) to the S. cerevisiae HOP1 promoter. When fused to the tetracycline repressor (tetR), trans-activation domains of both GAL4 and HAP4 were capable of promoting transcription from the tetO-HOP1 chimeric promoter, but the tetR-HAP4 fusion activator was the more efficient transcriptional activator. Addition of tetracycline nearly completely repressed activator-dependent transcription from the tetO-HOP1 promoter. Moreover, tetracycline-dependent repression of YEF3, CDC28 and RAM2 expression impaired cell growth. Thus, this system is useful for the elucidation of gene function in S. cerevisiae.

Gene Expression Regulation, Fungal↗
PubMed1997

Experimental endocarditis induction and platelet aggregation by Streptococcus anginosus, Streptococcus constellatus and Streptococcus intermedius.

A total of 18 'Streptococcus milleri' strains including the ATCC type strains of Streptococcus anginosus, Streptococcus constellatus and Streptococcus intermedius were compared with Streptococcus oralis ATCC10557 for their ability to induce infective endocarditis in catheterized rats. Three days after intravenous injection of 10(8) colony-forming units all 8 S. anginosus strains tested produced infective vegetations and bacteremia in almost all rats whereas 5 S. constellatus strains and the S. oralis strain produced infective vegetations and bacteremia less frequently and 5 S. intermedius strains only occasionally. The vegetations infected with the S. anginosus strains harbored microbial cells in significantly higher numbers that those with the other strains. No strong correlation was found between the endocardial infectivity and platelet-aggregating capacity of these strains. The platelet-aggregating strains were members of the Lancefield groups F and G or ungroupable but not of group A or C.

Animals↗
PubMed1996

Isolation of a Candida glabrata centromere and its use in construction of plasmid vectors.

A centromere has been isolated from Candida glabrata by functional selection based on the lethality of the SUP11 gene at high copy number. Nucleotide sequence analysis revealed a centromeric structure similar to that of Saccharomyces cerevisiae: the two highly conserved elements CDEI (8 bp) and CDEIII (26 bp) are separated by a 79-bp A+T-rich element, CDEII. Three centromere-bearing plasmid vectors with different selection markers have been constructed. These plasmids were highly stable in mitosis (< 1% loss rate per generation) and exist in one or two copies per cell.

Base Sequence↗
PubMed1996

A point mutation within each of two ATP-binding motifs inactivates the functions of elongation factor 3.

We have investigated how point mutations in the two ATP-binding motifs (G(463)PNGCGK(469)ST and G(701)PNGAGK(707)ST) of elongation factor 3 (EF-3) affect ribosome-activated ATPase activity of EF-3, polyphenylalanine synthesis, and growth of Saccharomyces cerevisiae. The point mutation impaired the ribosome-activated ATPase activity of EF-3, when glycine(463 and 701) and lysine(469 and 707) were replaced with valine and arginine, respectively. Thus, each glycine and lysine residue in both ATP-binding motifs is indispensable for EF-3's binding with ATP and the ensuing generation of ribosome-activated ATPase activity. Additionally, the mutant EF-3s did not catalyze polyphenylalanine synthesis in vitro when each glycine(463 and 701) was replaced with valine. The mutant EF-3s did not support cell growth in TEF3-disrupted S. cerevisiae, when each lysine(469 and 707) and glycine(463) was replaced with arginine and valine, respectively. Thus, each of the two ATP-binding motifs of EF-3 is indispensable for the ribosome-activated ATPase activity of EF-3, which is required for protein synthesis and cell growth in S. cerevisiae.

Adenosine Triphosphatases↗
PubMed1996

Morphological changes in the triads and sarcoplasmic reticulum of rat slow and fast muscle fibres following denervation and immobilization.

We observed the morphological features of the membrane systems (sarcoplasmic reticulum, transverse tubules and triads) involved with the excitation-contraction coupling in rat soleus and extensor digitorum longus muscle following two disuse protocols: denervation and immobilization. The immobilized positions were: maximum dorsal flexor (soleus were stretched and extensor digitorum longus were shortened), maximum plantar flexor (soleus were shortened and extensor digitorum longus were stretched), and midway between the dorsal flexor and plantar flexor. The arrangement of the membrane systems was disordered following both disuse conditions. Increases in transverse tubule network were apparent; there were clearly more triads than in normal fibres, and pentadic and heptadic structures (i.e., a close approximation of two or three transverse tubule elements with three or four elements of terminal cisternae of sarcoplasmic reticulum) were frequently appeared following both denervation and immobilization. The most notable difference between the influence of denervation and immobilization on the membrane systems is the time at which the pentads and heptads appeared. They appeared much earlier (1 week after denervation) in denervated than in immobilized (3 or 4 weeks after immobilization) muscle fibres. On the other hand, the frequency of pentads and heptads is clearly related to the fibre type (significantly higher in extensor digitorum longus) and to extent of atrophy. The different influences of immobilization in each leg position suggest that disuse, but with neurotrophic factor(s), influences on the membrane systems were affected by sarcomere length, and the neurotrophic factor(s) and muscle activity were not always necessary to form new membrane systems in disuse skeletal muscle fibres.

Animals↗
PubMed1996

Cloning of the rat steroid sulfatase gene (Sts), a non-pseudoautosomal X-linked gene that undergoes X inactivation.

Although the human steroid sulfatase (STS) gene has been cloned and characterized in detail, several attempts to clone its mouse homologue, with either anti-human STS antibodies or human STS cDNA probes, have failed, suggesting a substantial divergence between these genes. However, partial amino-terminal sequence from purified rat liver STS is very similar to its human counterpart, and sequence comparisons have revealed several domains that are conserved among all the sulfatases characterized to date. Thus, we used a degenerate-primer RT-PCR approach to amplify a 321-bp fragment from rat liver cDNA, which was used as a probe to clone and characterize the complete cDNA. Comparison of the protein coding region between the rat and human genes showed 66% homology both at the DNA and the protein levels. STS activity was conferred to STS(-) A9 cells upon transfection with a rat Sts expression construct, indicating the authenticity of the cloned cDNA. While Sts has been shown to be located in the mouse pseudoautosomal region, both physical and genetic mapping demonstrate that Sts is not pseudoautosomal in the rat. The overall genomic organization of rat Sts and human STS is very similar, except that the insertion site for intron 1 in the rat is 26 bp upstream from that in the human. Rat Sts is only 8.2 kb long, while the human STS spans over 146 kb.

Amino Acid Sequence↗
PubMed1996

Immunochemical characterization of the carbohydrate antigens of serotype k and Lancefield group G "Streptococcus milleri".

Carbohydrate antigens of the serotype k/Lancefield group G "Streptococcus milleri" were extracted by autoclaving whole cells of the type k reference strain Streptococcus anginosus K214-2K. The type k and group G antigen molecules are separated from each other and partially purified by a DEAE-Sephadex A25 column chromatography followed by a Sephadex G-100 gel filtration. In the double diffusion and the immunoelectrophoresis, the type k and group G antigen preparations obtained yielded single bands with their homologous antisera respectively. The type k antigen preparation contained principally glycerol, rhamnose, ribitol, galactose and glucose in a molar ratio of 0.54:1.20:0.43:0.33:1.00. The quantitative precipitin inhibition test indicated that beta(1-6)glucosyl-glucose (gentiobiose) sequence played a major role in immunodeterminant structure. Thus, the type k antigen of "S. milleri" appears to be a new carbohydrate type antigen that is chemically different from any Ottens type antigen. In contrast, the group G antigen preparation contained high proportion of rhamnose in addition to glucose, N-acetylglucosamine and N-acetylgalactosamine in a molar ratio of 6.45:1.00:0.24:1.15, and the rhamnose residue was involved in the immunodominant epitope, being in good agreement with the previously proposed chemical structure of the group antigen.

Acetylgalactosamine↗
PubMed1995

Cloning of the Candida glabrata TRP1 and HIS3 genes, and construction of their disruptant strains by sequential integrative transformation.

The Candida glabrata (Cg) TRP1 and HIS3 genes have been isolated by complementation of the Saccharomyces cerevisiae (Sc) trp1 and his3 mutants, respectively. Cg TRP1 encodes a polypeptide of 217 amino acids (aa), whose aa sequence is 58% identical to that of Sc TRP1. Cg HIS3 encodes a polypeptide of 210 aa, whose aa sequence is 73% identical to that of the Sc HIS3. Both Cg TRP1 and HIS3 were disrupted by sequential integrative transformation where the Sc URA3 was used as a selection marker for transformation. The resulting auxotrophic strain of his3- and trp1- was used to examine the ability of the Sc genes to complement the Cg mutations; Sc HIS3 and TRP1 complemented the Cg his3- and trp1- mutations, respectively.

Aldose-Ketose Isomerases↗
PubMed1995

KatG sequence deletion is not the major cause of isoniazid resistance in Japanese and Yemeni Mycobacterium tuberculosis isolates.

One of the mechanisms of isoniazid resistance to Mycobacterium tuberculosis has been proved to be the chromosomal deletion of katG. Based on this finding, 22 isoniazid-resistant isolates of M. tuberculosis obtained in Japan and Yemen were analysed for katG by polymerase chain reaction and catalase activity. Only six (27%) of the 22 isolates were compatible with the mechanism (lack of amplification of katG and loss of catalase activity). In contrast, eight isolates (36%) were katG positive but catalase activity-negative and eight (36%) were positive for both factors, indicating that isoniazid resistance is multifactorial and the deletion of katG was not the major cause of resistance in the isolates examined in this study.

Bacterial Proteins↗
PubMed1995

Successful treatment of Pneumocystis carinii Pneumonia in mice with benanomicin A (ME1451).

Benanomicin A (BNM-A) has antimycotic activities via binding to mannan in the cell walls of fungi. Anti-Pneumocystis carinii activity of the agent was examined in the P. carinii-infected BALB/c nu/nu female mouse model because P. carinii also possesses mannan in the membranes. The infected mice were treated with intraperitoneal injections of six doses of BNM-A (1, 2.5, 5, 10, 30, and 100 mg/kg of body weight), 4 mg of pentamidine isethionate per kg, 100 mg of sulfamethoxazole per kg combined with 20 mg of trimethoprim per kg (co-trimoxazole), or saline for 21 days. Each dosage group consisted of 10 mice. During treatment, five mice in the control group (saline) died, whereas 8 to 10 mice in all treatment groups survived. Almost the same efficacies were obtained for the groups treated with 5 mg or more and 10 mg or more of BNM-A per kg regarding the weight and number, respectively, of cysts found in the lungs as were obtained for the groups treated with pentamidine isethionate and co-trimoxazole. Overall, a dose of 10 mg of BNM-A per kg was effective against P. carinii pneumonia infection in the mice. Thus, BNM-A is a good candidate for a novel treatment for P. carinii pneumonia as a compound with a new mechanism of action against P. carinii.

Animals↗
PubMed1994

Multi-gene family of major surface glycoproteins of Pneumocystis carinii: full-size cDNA cloning and expression.

The major surface glycoprotein (MSG) of Pneumocystis carinii plays a crucial role in the fatal pneumonia caused by this organism in AIDS patients. A cDNA encoding a full-length MSG polypeptide was isolated from a lambda library of rat-derived P. carinii cDNAs. The deduced MSG, referred to as the MSG5 subtype, is a 120,765-Da protein composed of 1,076 amino acids and contains an anchoring hydrophobic sequence at the C-terminus of the protein. Sequence analyses of cloned MSG-cDNAs revealed an MSG-gene family with approximately 70% protein sequence identity between subtypes. P. carinii karyotype hybridization analyses indicated that the MSG gene family members are scattered throughout most of the P. carinii chromosomes. These recombinant MSG proteins reacted with the antiserum from P. carinii-infected rats, as expected, and antiserum generated against P. carinii-infected mice, indicating the existence of common determinants in MSG polypeptides. The family of MSG proteins is rich in cysteine residues and these cysteines are highly conserved in all MSG subtypes regardless of species specificity, suggesting the structural and/or functional importance of these cysteines. The pathobiological significance of the MSG gene family and its sequence diversity in P. carinii is discussed.

Amino Acid Sequence↗