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Biomedical subjects

Yoko Yamamoto

Publications and source records attributed to Yoko Yamamoto.

50 records · Page 3Linked to original sources
PubMed2003

Site-specific PEGylation of a lysine-deficient TNF-alpha with full bioactivity.

Addition of polyethylene glycol to protein (PEGylation) to improve stability and other characteristics is mostly nonspecific and may occur at all lysine residues, some of which may be within or near an active site. Resultant PEGylated proteins are heterogeneous and can show markedly lower bioactivity. We attempted to develop a strategy for site-specific mono-PEGylation using tumor necrosis factor-alpha (TNF-alpha). We prepared phage libraries expressing TNF-alpha mutants in which all the lysine residues were replaced with other amino acids. A fully bioactive lysine-deficient mutant TNF-alpha (mTNF-alpha-Lys(-)) was isolated by panning against TNF-alpha-neutralizing antibody despite reports that some lysine residues were essential for its bioactivity. mTNF-alpha-Lys(-) was site-specifically mono-PEGylated at its N terminus. This mono-PEGylated mTNF-alpha-Lys(-), with superior molecular uniformity, showed higher bioactivity in vitro and greater antitumor therapeutic potency than randomly mono-PEGylated wild-type TNF-alpha. These results suggest the usefulness of the phage display system for creating functional mutant proteins and of our site-specific PEGylation approach.

Animals↗
PubMed2003

Synthesis of a poly(vinylpyrrolidone-co-dimethyl maleic anhydride) co-polymer and its application for renal drug targeting.

We have synthesized a polymeric drug carrier, polyvinylpyrrolidone-co-dimethyl maleic anhydride [poly(VP-co-DMMAn)], for use in renal drug delivery. About 80% of the 10-kDa poly(VP-co-DMMAn) selectively accumulated in the kidneys 24 h after intravenous administration to mice. Although this accumulated poly(VP-co-DMMAn) was gradually excreted in the urine, about 40% remained in the kidneys 96 h after treatment. Poly(VP-co-DMMAn) was taken up by the renal proximal tubular epithelial cells and no cytotoxicity was noted. Higher doses did not produce toxicity in the kidneys or other tissues. In contrast, polyvinylpyrrolidone of the same molecular weight did not show any tissue-specific distribution. Poly(VP-co-DMMAn)-modified superoxide dismutase accumulated in the kidneys after intravenous administration and accelerated recovery from acute renal failure in a mouse model. In contrast, polyvinylpyrrolidone-modified superoxide dismutase and native superoxide dismutase were not as effective. Thus, poly(VP-co-DMMAn) is a useful candidate as a targeting carrier for renal drug delivery systems.

Acute Kidney Injury↗
PubMed2003

Behavior of vacuoles during microspore and pollen development in Arabidopsis thaliana.

Using the cryo-fixation/freeze-substitution method, we studied the ultrastructural changes and behavior of vacuoles and related organelles (rER and Golgi bodies) during microspore and pollen development, and pollen maturation of Arabidopsis thaliana. In young microspores forming exine (pollen outer cell wall), vacuoles looked like those of somatic cells. In microspores during the formation of intine (inner cell wall), a large vacuole appeared which was made by fusion of pre-existing vacuoles and probably absorption of solutions. In the young pollen grain after the first mitosis, a large vacuole was divided into small vacuoles. The manner of division was not by binary fission and centripetally, but by the invagination of tonoplasts from one side to the opposite side of a vacuole. After the second mitosis, somatic type vacuoles disappeared. In mature pollen grains just before germination, membrane-bound structures containing fine fibrillar substances (MBFs) appeared. The MBFs were considered to be storage vacuoles. In pollen grains from flowers in bloom, MBFs changed to lysosomal structures with acid phosphatases (lytic vacuole). They gradually increased in number and volume, and decomposed the cytoplasm. The autolysis of pollen grains is the first finding in this study, which may contribute to the loss of ability of pollen germination after anthesis.

Arabidopsis↗
PubMed2003

Comparative genetic studies on the APRR5 and APRR7 genes belonging to the APRR1/TOC1 quintet implicated in circadian rhythm, control of flowering time, and early photomorphogenesis.

In Arabidopsis thaliana, a number of circadian-associated factors have been identified. Among those, TOC1 (TIMING OF CAB EXPRESSION 1) is believed to be a component of the central oscillator. TOC1 is a member of a small family of proteins, designated as Arabidopsis PSEUDO-RESPONSE REGULATORS (APRR1/TOC1, APRR3, APRR5, APRR7, and APRR9). Nonetheless, it is not very clear whether or not the APRR family members other than APRR1/TOC1 are also implicated in the mechanisms underlying the circadian rhythm. To address this issue further, here we characterized a set of T-DNA insertion mutants, each of which is assumed to have a severe lesion in each one of the quintet genes (i.e. APRR5 and APRR7). For each of these mutants (aprr5-11 and aprr7-11) we demonstrate that a given mutation singly, if not directly, affects the circadian-associated biological events simultaneously: (i) flowering time in the long-day photoperiod conditions, (ii) red light sensitivity of seedlings during the early photomorphogenesis, and (iii) the period of free-running rhythms of certain clock-controlled genes including CCA1 and APRR1/TOC1 in constant white light. These results suggest that, although the quintet members other than APRR1/TOC1 may not be directly integrated into the framework of the central oscillator, they are crucial for a better understanding of the molecular mechanisms underlying the Arabidopsis circadian clock.

Arabidopsis↗
PubMed2003

Chondromodulin I is a bone remodeling factor.

Chondromodulin I (ChM-I) was supposed from its limited expression in cartilage and its functions in cultured chondrocytes as a major regulator in cartilage development. Here, we generated mice deficient in ChM-I by targeted disruption of the ChM-I gene. No overt abnormality was detected in endochondral bone formation during embryogenesis and cartilage development during growth stages of ChM-I(-/-) mice. However, a significant increase in bone mineral density with lowered bone resorption with respect to formation was unexpectedly found in adult ChM-I(-/-) mice. Thus, the present study established that ChM-I is a bone remodeling factor.

Alleles↗
PubMed2003

[Use of propofol for painful procedures in cancer pain management].

BACKGROUND: Patients with intractable cancer pain often require non-pharmacological analgesic treatment that is accompanied by procedure-related pain. Previous works have shown that propofol infusion in adjunction to regional anesthesia provides appropriate sedation during such painful procedures. However, there are a few reports of its use to reduce procedure-related pain in terminal cancer patients. We report cases of propofol sedation during percutaneous vertebroplasty (PVP) in patients with metastatic vertebral compression fracture. METHODS: Propofol was infused during PVP in eleven cancer patients after obtaining written informed consent. The infusion rate of propofol was adjusted using a target-controlled infusion pump to achieve appropriate sedation levels under monitoring bispectral index of the electroencepharogram. Hepatic and renal functions were evaluated using common serum markers, which were determined using standard hospital laboratory methods. RESULTS: The duration of the procedure was 65.5 +/- 5.5 (mean +/- SD) min. The required infusion rate was 8.66 +/- 1.50 mg.kg-1.hr-1. The interval from the termination of the infusion until emergence was 10.7 +/- 4.2 min. No life-threatening complications or significant changes in liver and renal functions were observed. CONCLUSIONS: Propofol can be used effectively and safely for sedation during PVP in terminal cancer patients.

Aged↗
PubMed2002

Successive changes in community structure of an ethylbenzene-degrading sulfate-reducing consortium.

The microbial community structure and successive changes in a mesophilic ethylbenzene-degrading sulfate-reducing consortium were for the first time clarified by the denaturing gradient gel electrophoresis (DGGE) analysis of the PCR amplified 16S rRNA gene fragments. At least ten bands on the DGGE gel were detected in the stationary phase. Phylogenetic analysis of the DGGE bands revealed that the consortium consisted of different eubacterial phyla including the delta subgroup of Proteobacteria, the order Sphingobacteriales, the order Spirochaetales, and the unknown bacterium. The most abundant band C was closely related to strain mXyS1, an m-xylene-degrading sulfate-reducing bacterium (SRB), and occurred as a sole band on DGGE gels in the logarithmic growth phase that 40% ethylbenzene was consumed accompanied by sulfide production. During further prolonged incubation, the dominancy of band C did not change. These results suggest that SRB corresponds to the most abundant band C and contributes mainly to the degradation of ethylbenzene coupled with sulfate reduction.

Benzene Derivatives↗
PubMed2002

Preparation and biological activities of a bivalent poly(ethylene glycol) hybrid containing an active site and its synergistic site of fibronectin.

A bivalent poly(ethylene glycol) or PEG hybrid of fibronectin-related peptides was prepared. An active site peptide (RGD) and its synergistic site peptide (PHSRN) of fibronectin were conjugated with an amino acid-type PEG (aaPEG) to form PHSRN-aaPEG-RGD. A moderate spatial array between RGD and PHSRN in fibronectin may be required for synergic activity. The bivalent hybrid exhibited potent cell spreading activity and exhibited potent anti-metastatic activity in a model of experimental metastasis with B16-BL6 cells in mice. PEG may serve as a spacer for maintaining the desired spatial array.

Amino Acids↗
PubMed2002

Molecular design of bioconjugated cell adhesion peptide with a water-soluble polymeric modifier for enhancement of antimetastatic effect.

The adhesive interaction of tumor cells with various components of the extracellular matrix (ECM), such as laminin and fibronectin appears to play a crucial role in tumor metastasis. It has been reported that adhesive peptides, such as Tyr-Ile-Gly-Ser-Arg (YIGSR) in laminin and Arg-Gly-Asp (RGD), inhibited adhesion and invasion of various tumor cells to ECM in vitro, and exhibited inhibitory effects on pulmonary metastasis of B16-BL6 melanoma cells in mice. However, large doses of these peptides were required for significant anti-metastatic effects in vivo, probably due to their rapid degradation by various peptidases and their rapid excretion from the blood into the urine. To overcome these problems, the development of an appropriate drug delivery system (DDS) is required to improve in vivo stability and prolong plasma half-lives. Several strategies such as peptide-cyclization and D-amino acid substation have been reported to improve stability in blood by inhibiting enzymatic degradation. However, even these approaches have proven insufficient to overcome rapid renal clearance from the circulation. On the other hand, bioconjugation with water-soluble polymeric modifiers could markedly prolong the plasma half-lives by not only increasing peptidase resistance but also impeding renal excretion. In addition, it is possible to strictly control the in vivo pharmacokinetics of a peptide by introducing functional molecules with targeting or slow release capacities to the polymeric modifier. In this review we demonstrate with reference to our recent studies that bioconjugation of adhesive peptides with the appropriate polymeric modifier can enhance antimetastatic activity and may facilitate therapeutic use.

Animals↗
PubMed2002

Aluminum toxicity is associated with mitochondrial dysfunction and the production of reactive oxygen species in plant cells.

Potential mechanisms of Al toxicity measured as Al-induced inhibition of growth in cultured tobacco cells (Nicotiana tabacum, nonchlorophyllic cell line SL) and pea (Pisum sativum) roots were investigated. Compared with the control treatment without Al, the accumulation of Al in tobacco cells caused instantaneously the repression of mitochondrial activities [monitored by the reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and the uptake of Rhodamine 123] and, after a lag of about 12 h, triggered reactive oxygen species (ROS) production, respiration inhibition, ATP depletion, and the loss of growth capability almost simultaneously. The presence of an antioxidant, butylated hydroxyanisol, during Al treatment of SL cells prevented not only ROS production but also ATP depletion and the loss of growth capability, suggesting that the Al-triggered ROS production seems to be a cause of ATP depletion and the loss of growth capability. Furthermore, these three late events were similarly repressed in an Al-tolerant cell line (ALT301) isolated from SL cells, suggesting that the acquisition of antioxidant functions mimicking butylated hydroxyanisol can be a mechanism of Al tolerance. In the pea root, Al also triggered ROS production, respiration inhibition, and ATP depletion, which were all correlated with inhibition of root elongation. Taken together, we conclude that Al affects mitochondrial functions, which leads to ROS production, probably the key critical event in Al inhibition of cell growth.

Adenosine Triphosphate↗
PubMed2002

[Serum lactate dehydrogenase and CD4+/CD8+ lymphocyte ratio predict survival in terminally ill cancer patients].

Accurate estimation of survival is important for effective palliative medicine of patients with cancer. In most clinical practice, however, the life expectancy has been predicted based on subjective evaluations. The purpose of this study was to find objective biological markers that can contribute to accurate prediction of survival in terminally ill cancer patients. Consecutive terminally ill cancer patients admitted to the Palliative Care Center in Tohoku University hospital from January to May 2001 were approached for this study. Forty-eight blood samples were obtained from 25 patients who provided a written informed consent. Common serum enzyme markers were determined using standard hospital laboratory methods. Cellular immunity status was evaluated by peripheral blood lymphocyte-subset analysis using flow cytometry. Mean patient survival was 33.5 +/- 21.6 (1-80) days. Multiple regression analysis revealed that lactate dehydrogenase (LDH) and the CD4+/CD8+ ratio were significantly associated with survival (r = 0.64, p < 0.0001). Further prospective studies are warranted to validate the usefulness of these determinants for accurate prediction of survival.

Adult↗
PubMed2001

Isolation of aluminum-tolerant cell lines of tobacco in a simple calcium medium and their responses to aluminum.

Aluminum (Al)-tolerant cell lines (ALT301 and ALT401) of tobacco were isolated in a simple calcium (Ca) solution from ethyl methane sulfonate (EMS)-treated suspension cultured tobacco cells (Nicotiana tabacum L. cv. Samsun, a cell line SL) at the logarithmic phase of growth. A highly tolerant cell line ALT301 exhibited the accumulation of Al and the deposition of callose to the same extent as the parental SL cells during the exposure to Al. However, the Al-treated ALT301 cells grew much better than the Al-treated SL cells after transfer to Al-free growth medium. Compared to SL cells, ALT301 cells were more tolerant to toxicity of copper and iron, but not to that of lanthanum. These results suggest that ALT301 cells have an internal tolerance mechanism, which makes cells grow normally in spite of Al accumulation and Al-induced lesion represented by the deposition of callose. This tolerance mechanism seems also to be effective against copper and iron toxicity. A slightly tolerant cell line ALT401 also accumulated Al to the same degree as SL cells, but deposited significantly less callose than did SL cells (43% of SL). The growth of ALT401 cells after Al treatment was only slightly better than that of SL cells. Thus, it seems that ALT401 cells have a mechanism to protect cells only from the Al-induced deposition of callose, which is not enough to overcome the Al-induced inhibition of growth. The different phenotypes exhibited by these Al-tolerant cell lines suggest that the deposition of callose is not directly related to the inhibition of growth in Al-treated cells.

Journal Article↗