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Biomedical subjects

T Okada

Publications and source records attributed to T Okada.

At least 145 records · Page 8Linked to original sources
PubMed2001

Regulation of phospholipase C-gamma2 and phosphoinositide 3-kinase pathways by adaptor proteins in B lymphocytes.

The importance of phosphoinositide 3-kinase (PI3K) and phospholipase C (PLC)-gamma2 in B cell function and development has been highlighted by gene targeting experiments in mice. In fact, these knockout mice exhibit a profound inhibition of proliferative responses upon B cell receptor (BCR) engagement. The molecular connections between these effectors and upstream tyrosine kinases such as Syk have been studied intensively in the past few years. This mechanism involves the action of cytoplasmic adaptor molecules, which participate in forming multicomponent signaling complexes, thereby directing the appropriate subcellular localization of effector enzymes. In addition to these cytoplasmic adaptor proteins, cell surface coreceptors can be viewed as transmembrane adaptor proteins, because coreceptors can also change the localization of effector enzymes, which in turn modulates the BCR-initiated signals.

Animals↗
PubMed2001

[Appetite and regulation of food intake in uremia].

Anorexia, nausea and vomiting are common symptoms in patients with severe renal failure. Abnormalities in body fluids volume, serum electrolytes concentrations and acid-base balance and accumulations of uremic toxic substances might be primarily contributing to the suppression of appetite. However, the detailed mechanisms that cause appetite suppression in uremia are poorly understood. Impaired gastric emptying, constituents of peritoneal dialysate, plasma high leptin, high cholecystokinin and low neuropeptide Y are also considered to be contributing to appetite suppression in uremia.

Animals↗
PubMed2001

Initial remission-inducing effect of very low-dose cyclosporin monotherapy for minimal-change nephrotic syndrome in Japanese adults.

AIM: Cyclosporin A (CsA) in combination with corticosteroids can be used effectively in steroid-sensitive nephrotic syndrome. However, reports documenting the effectiveness ofCsA monotherapy against such a condition have been scarce. In 11 adults with minimal-change nephrotic syndrome, we have tried very low-dose CsA in the hope of inducing remission without using either corticosteroid or any other immunosuppressive drugs. PATIENTS AND METHODS: Indications for treatment included steroid-sensitive relapsing nephrotic syndrome (7 patients) and first-episode nephrotic syndrome (4 patients). In all patients, corticosteroid and cytotoxic agents had not been given before entry. CsA was administered orally at an initial dose of 2.4 (range 1.5 - 3.1) mg/kg per day. RESULTS: Analysis of the clinical course revealed that 8 of 11 patients entered complete remission after a mean duration of 44 +/- 31 days, whereas 3 patients failed to enter remission to CsA alone, resulting in complete remission combined with methylprednisolone pulse therapy without conventional oral prednisolone. CsA dosages and trough levels between responders and non-responders were similar. Non-responders had much higher levels of serum total cholesterol and higher daily urinary excretion of protein than those of responders, respectively. No patients had significant decrease in creatinine clearance, development of hypertension or suffered from other CsA associated serious side-effects. CONCLUSION: The present data suggest that CsA monotherapy at a very low dose could induce complete remission in adult patients with minimal-change nephrotic syndrome. Conversely, severe hypercholesterolemia would be likely to inhibit the action of CsA against nephrotic conditions.

Adult↗
PubMed2001

Biodegradable poly-D,L-lactic acid-polyethylene glycol block copolymers as a BMP delivery system for inducing bone.

BACKGROUND: Bone morphogenetic proteins (BMPs) are biologically active molecules capable of eliciting new bone formation. In combination with biomaterials, these proteins can be used in a clinical setting as bone-graft substitutes to promote bone repair. Collagen from animal sources has previously been the preferred carrier material in animal experiments. More recently, synthetic biodegradable polymers have been tested as a delivery vehicle for osteoinductive agents. In earlier studies performed in our laboratory, it was found that the polylactic acid homopolymers (PLA650) and poly-D,L-lactic acid-polyethylene glycol block copolymers (PLA650-PEG200) are viscous liquids that can be used as BMP delivery systems. METHODS: To obtain new PLA-PEG polymers that exhibit greater plasticity, the molecular sizes of PLA and PEG segments in the copolymer chains were increased. Plastic PLA-PEG polymers with various molecular sizes and PLA/PEG ratios were synthesized, mixed with recombinant human (rh) BMP-2, and implanted into the dorsal muscles of mice for 3 weeks to evaluate their capacity to elicit new bone formation. To compare the plastic PLA-PEG polymer with the liquid PLA650-PEG200 polymer, these two polymers were combined with rhBMP-2, implanted, and harvested after 3 weeks. Bone mineral content (BMC), bone area, and bone mineral density (BMD) of the ectopic new bone were measured by means of single energy X-ray absorptiometry (SXA). RESULTS: All of the PLA6,500-PEG3,000 implants with 10 or 20 microg of rhBMP-2 showed new bone formation. In contrast, little or no bone formation was seen in other plastic PLA-PEG implants with rhBMP-2. Control implants that lacked rhBMP-2 did not show new bone formation. Radiographic and histologic examinations showed that the PLA6,500-PEG3,000 implants with rhBMP-2 harvested 3 weeks after implantation had normal bone characteristics with hematopoietic marrow and osseous trabeculae. SXA analysis showed that the values for bone mineral content (BMC), bone area, and bone mineral density (BMD) of new bone resulting from the use of plastic PLA6,500-PEG3,000 polymers with rhBMP-2 were significantly higher than those obtained with the liquid PLA650-PEG200 polymers (p < 0.001 for each of the three values). CONCLUSIONS: These results indicate that the PLA6,500-PEG3000 block copolymer with plastic properties works effectively as a BMP delivery system. These data suggest that the total molecular size and ratio of PLA size to PEG size is an essential factor in determining the efficacy of a BMP delivery system. After implantation, it is possible that the PLA6,500-PEG3,000 pellets might have absorbed tissue fluids and become swollen, resulting in bone formation that exceeded the size of the original implants. This expansion characteristic is a potentially beneficial property, given the intended practical application of the polymer in the repair of bone defects. CLINICAL RELEVANCE: New synthetic biodegradable delivery systems will play an important role in the clinical applications of rhBMPs in which local formation of bone via an osteoinductive graft material is needed. Further pre-clinical and clinical work is necessary to establish the safety of these implants before they are adopted for widespread clinical use.

Animals↗
PubMed2001

[A case of advanced gastric cancer with multiple liver metastases in an elderly patient that responded dramatically to UFT therapy].

An 88-year-old female patient suffering from Borrmann type 3 advanced gastric cancer complicated by multiple hepatic metastases underwent a total gastrectomy. A small dose of 200 mg/day of UFT was administered orally every day postoperatively. At postoperative month 6, a marked diminishment of the hepatic metastatic lesions was noted. Resection of the primary lesion with a regimen of a small oral dose of UFT was remarkably effective in this elderly gastric cancer patient with complications from multiple hepatic metastases.

Adenocarcinoma↗
PubMed2001

Characterization of a thrombin-like serine protease, Kangshuanmei, isolated from the venom of a Chinese snake, Agkistrodon halys brevicaudus stejneger.

An enzyme, referred to as Kangshuanmei, was isolated from the venom of the Chinese snake Agkistrodon halys brevicaudus stejneger by gel filtration chromatography followed by affinity chromatography. Kangshuanmei is composed of a single polypeptide chain with a molecular weight of approximately 34,000, estimated by SDS-PAGE. The enzyme hydrolyzed both benzoyl-arginine ethyl ester and H-D-Phe-Pip-Arg-p-nitroanilide, specific substrates for thrombin. The protease activity of Kangshuanmei was inhibited by 4-(2-aminoethyl)-benzensulfonyl fluoride, but was not affected by EDTA. The enzyme acted on human fibrinogen to form a fibrin clot and released three fragments. These fragments were shown to be fibrinopeptide A, fibrinopeptide B, and the Bbeta1-42 peptide of fibrinogen, respectively. These results indicate that Kangshuanmei is a thrombin-like serine protease with coagulant activity. However, the enzyme did not induce activation of blood coagulation factor XIII, unlike thrombin. Moreover, antithrombin-III, the specific thrombin inhibitor in plasma, had no inhibitory effect on the thrombin-like amidolytic activity of Kangshuanmei. The N-terminal amino acid sequence of the enzyme up to 50 residues was determined by a peptide sequencer. The N-terminal sequence of Kangshuanmei was highly homologous to most thrombin-like serine proteases from the venom of the snakes of the crotalidae family.

Agkistrodon↗
PubMed2001

Adult T-cell leukemia showing different immunophenotypes in invaded organs.

We report here a case of adult T-cell leukemia (ATL) who presented acute renal failure and skin eruption. Renal and skin biopsies showed diffuse invasion of ATL cells. Furthermore, the surface phenotype of tumor cells taken from the bone marrow (BM) or peripheral blood (PB)(CD4-CD8-) differed from that of cells taken from the kidney or skin (CD4+CD8-). These findings suggested that CD4-CD8-ATL cells in the BM and PB had differentiated to CD4+CD8- cells in the kidney and skin.

Acute Kidney Injury↗
PubMed2001

[Usefulness of three-dimensional color Doppler sonography for the differential diagnosis of subpleural lesions].

The purpose of our investigation was to assess the usefulness of three-dimensional color Doppler sonography (velocity mode and power mode) for the differential diagnosis of subpleural lesions. Thirty lesions (11 pneumonias, 5 lung abscesses, 11 primary lung cancers, 3 metastatic lung cancers) were examined. Three-dimensional images were reconstructed by a maximum intensity projection method. Three-dimensional representations of intralesional blood flow became available for all lesions approximately 11 seconds after scanning. In every case, the entire vasculature of the tumor, the pneumonia, the abscess, or the inflamed region of the lung was appreciated more easily from three-dimensional images than from two-dimensional images. We classified the color flow pattern of subpleural lesions depicted by color flow imaging into seven groups. Color flow was depicted better by the three-dimensional color Doppler power mode than the velocity mode. Three-dimensional color flow patterns observed in power mode, patterns of the pneumonias and the lung cancers differed significantly. Our results suggest that the three-dimensional color Doppler power mode is useful for the differential diagnosis of subpleural lesions.

Adult↗
PubMed2001

[Serial changes in body composition in patients with chronic renal failure on peritoneal dialysis].

Nutritional status is one of the most important factors affecting mortality and morbidity in chronic dialysis patients. There are, however, few data on serial body composition changes in these patients. To investigate serial changes in body composition in patients on peritoneal dialysis, we measured intracellular fluid volume(ICF), extracellular fluid volume(ECF), body protein volume(BPV), body fat volume(BFV) and bone mineral content(BMC) using multifrequency bioelectrical impedance analysis (MF-BIA). MF-BIA was performed in 35 patients, consisting of 21 men and 14 women with a mean age of 51.3 +/- 10.9 years, before and after one year of observation. At the baseline in male patients, ICF was 37.0 +/- 3.4%, ECF 19.7 +/- 1.6%, BPV 20.7 +/- 1.7%, BFV 18.1 +/- 6.6% and BMC 4.5 +/- 0.4% of body weight, and in female patients ICF was 34.4 +/- 2.6%, ECF 17.8 +/- 1.9% BPV 19.0 +/- 1.6%, BFV 24.4 +/- 6.2% and BMC 4.5 +/- 0.4% of body weight. In the group of patients whose body weight increased more than 3 kilograms(n = 9), the increase rate of BFV was 32.3 +/- 20.2%, significantly higher than that of the other segments(p < 0.001). On the other hand, in the group of patients whose body weight decreased more than 3 kilograms(n = 5), each segment showed the same extent of decrease and there was no significant difference in the decrease rates among each segment. In the group of patients whose body weight was stable(n = 21), changes in each body composition segment were extremely small. It could be concluded that the body weight increase is due mainly to increase in BFV and body weight decrease results from a concurrent decrease in each body composition segment in peritoneal dialysis patients.

Adult↗
PubMed2000

Naming of animals and tools: a functional magnetic resonance imaging study of categorical differences in the human brain areas commonly used for naming visually presented objects.

To investigate the neural substrates for naming objects and their category-dependency, we performed functional magnetic resonance imaging (fMRI) with naming of animals and tools. Naming objects, irrespective of their category, activated left frontal to bilateral parietal regions and occipital to posterior temporal regions. Within these areas, naming animals caused more activation of the primary visual cortex bilaterally and the ventral occipital cortex to the inferior temporal area on the right side. Naming tools caused more activation of the posterior part of the left middle temporal area, the rostral part of the left inferior parietal lobule, and the left inferior frontal cortex. These findings suggest that the neural network for naming objects has discrete category-dependent nodes through which pertinent conceptual knowledge may be mediated.

Adult↗
PubMed2000

HSP70 and ribosomal protein L2: novel 5S rRNA binding proteins in Escherichia coli.

A Northwestern analysis of Escherichia coli total proteins with radiolabeled 5S rRNA identified two novel 5S rRNA interacting proteins, a 70 kDa and a 37 kDa protein, and three ribosomal proteins reported on already. The N-terminal sequencing of the 70 kDa protein separated by SDS-PAGE from the high-salt-washed fraction of crude ribosome led to the discovery of a polypeptide identical in its first 10 amino acid residues to E. coli heat shock protein 70. The N-terminal eight amino acid sequence of the 37 kDa protein extracted from the high-salt-washed ribosome is identical to that of the ribosomal protein L2. In addition, the interaction of these proteins with 5S rRNA has been confirmed with gel mobility shift assays.

Amino Acid Sequence↗
PubMed2000

Effect of a novel bifunctional endothelin receptor antagonist, IRL 3630A, on guinea pig respiratory mechanics.

This study characterized the in vitro pharmacological properties of a newly developed endothelin receptor antagonist, N-butanesulfonyl-[N-(3, 5-dimethylbenzoyl)-N-methyl-3-[4-(5-isoxazolyl)-phenyl]-(D)- alanyl]-( L)-valineamide sodium salt (IRL 3630A), and its in vivo effects on respiratory mechanics were determined. IRL 3630A showed highly balanced affinities to human endothelin ET(A) and ET(B) receptors, giving apparent K(i) values of 1.5 and 1.2 nM, respectively. This compound also potently antagonized the endothelin-1-induced intracellular Ca(2+) increases in both embryonic bovine tracheal (EBTr) cells expressing endothelin ET(A) receptors and human Girardi heart (hGH) cells expressing endothelin ET(B) receptors. In guinea pig isolated tracheas having both endothelin ET(A) and ET(B) receptors, IRL 3630A greatly inhibited endothelin-1-induced contraction (pA(2)=7.1), which was partially or scarcely suppressed by the endothelin ET(A) receptor antagonist cyclo[-(D)-Trp-(D)-Asp-(L)-Pro-(D)-Val-(L)-Leu-] (BQ-123) or the endothelin ET(B) receptor antagonist N-(3, 5-dimethylbenzoyl)-N-methyl-3-(4-phenyl)-(D)-phenylalanyl-(L)-t ryptop han (IRL 2500), respectively. Bolus i.v. injections of IRL 3630A administered into anaesthetized guinea pigs at 10 and 30 microg/kg inhibited endothelin-1 (1.3 microg/kg)-induced changes in respiratory resistance and compliance in a dose dependent manner, whereas both sodium 2-benzo[1, 3]dioxol-5-yl-4-(4-methoxy-phenyl)-4-oxo-3-(3,4, 5-trimethoxy-benzyl)-but-2-enoate (an endothelin ET(A) receptor antagonist: PD 156707) and IRL 2500 at doses of up to 30 microg/kg did not affect endothelin-1-induced changes in respiratory mechanics, reflecting the in vitro results. IRL 3630A is thus an effective bifunctional endothelin receptor antagonist, and will be useful in clarifying the role of endothelin in pulmonary diseases such as bronchial asthma.

Airway Resistance↗
PubMed2000

Expectation of pain enhances responses to nonpainful somatosensory stimulation in the anterior cingulate cortex and parietal operculum/posterior insula: an event-related functional magnetic resonance imaging study.

Although behavioral studies suggest that pain distress may alter the perception of somatic stimulation, neural correlates underlying such alteration remain to be clarified. The present study was aimed to test the hypothesis that expectation of pain might amplify brain responses to somatosensory stimulation in the anterior cingulate cortex (ACC) and the region including parietal operculum and posterior insula (PO/PI), both of which may play roles in regulating pain-dependent behavior. We compared brain responses with and subjective evaluation of physically identical nonpainful warm stimuli between two psychologically different contexts: one linked with pain expectation by presenting the nonpainful stimuli randomly intermixed with painful stimuli and the other without. By applying the event-related functional magnetic resonance imaging technique, brain responses to the stimuli were assessed with respect to signal changes and activated volume, setting regions of interest on activated clusters in ACC and bilateral PO/PI defined by painful stimuli. As a result, the uncertain expectation of painful stimulus enhanced transient brain responses to nonpainful stimulus in ACC and PO/PI. The enhanced responses were revealed as a higher intensity of signal change in ACC and larger volume of activated voxels in PO/PI. Behavioral measurements demonstrated that expectation of painful stimulus amplified perceived unpleasantness of innocuous stimulus. From these findings, it is suggested that ACC and PO/PI are involved in modulation of affective aspect of sensory perception by the uncertain expectation of painful stimulus.

Adult↗
PubMed2000

Self-amplification system for recombinant adeno-associated virus production.

A recently reported system for recombinant adeno-associated virus (rAAV) production does not require infection of a helper virus and depends on the transfection with a huge amount of three plasmids: AAV-vector, AAV-helper, and adenovirus-helper plasmids. Toward simplifying rAAV production, as a first step, we tested the use of the rAAV itself instead of the AAV-vector plasmid as a source of rAAV DNA and determined the optimal timing of infection and dose of the input rAAV. When 293 cells were infected just after transfection with 100 particles/cell of rAAV, irrespective of the purity, CsCl-purified or crude, up to 2000 particles/cell of rAAV were produced (9- to 20-fold self-amplification), a yield comparable to that obtained by an adenovirus-free transfection. These results indicate that infection of rAAV can greatly reduce the amount of plasmid DNA for a large-scale transfection. This strategy will also be useful when applied to packaging cell lines inducibly expressing Rep and Cap proteins.

Cells, Cultured↗
PubMed2000

Diversity of voltage-gated sodium channels in the ascidian larval nervous system.

To gain insight into the origin of the molecular diversity of voltage-gated sodium channels (NaVs), a putative sodium channel gene (TuNa2) was cloned from the protochordate ascidian. TuNa2 showed two unusual features in its primary structure; (1) lysine in the P-region of the third repeat, a critical site determining ion selectivity, was changed to glutamic acid, predicting that the ionic permeability would not be rigidly sodium-selective (2) the III-IV linker, determinant of fast inactivation, was only weakly conserved. In contrast with a pan-neuronally expressed NaV (TuNa1), expression of TuNa2 was confined to subsets of neurons including motor neurons, suggesting that TuNa2 plays specialized roles in electrical activities unique to these neurons. Basic FGF, a neural inducer in the ascidian embryo, induces TuNa2 RNA expression in the ectodermal cells at lower doses than that required for TuNa1 gene expression. Thus, two types of NaV may play distinct roles and their gene expressions are controlled by distinct mechanisms.

Amino Acid Sequence↗
PubMed2000

Crystal structure of rhodopsin: A G protein-coupled receptor.

Heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs) respond to a variety of different external stimuli and activate G proteins. GPCRs share many structural features, including a bundle of seven transmembrane alpha helices connected by six loops of varying lengths. We determined the structure of rhodopsin from diffraction data extending to 2.8 angstroms resolution. The highly organized structure in the extracellular region, including a conserved disulfide bridge, forms a basis for the arrangement of the seven-helix transmembrane motif. The ground-state chromophore, 11-cis-retinal, holds the transmembrane region of the protein in the inactive conformation. Interactions of the chromophore with a cluster of key residues determine the wavelength of the maximum absorption. Changes in these interactions among rhodopsins facilitate color discrimination. Identification of a set of residues that mediate interactions between the transmembrane helices and the cytoplasmic surface, where G-protein activation occurs, also suggests a possible structural change upon photoactivation.

Amino Acid Motifs↗