Biomedical subjects

Koji Nakamura

Publications and source records attributed to Koji Nakamura.

At least 19 recordsLinked to original sources

PubMed2006

Characterization of insulin protection properties of complexation hydrogels in gastric and intestinal enzyme fluids.

The objective of this study was to elucidate the mechanisms contributing to oral bioavailability of insulin by poly(methacrylic acid grafted with poly(ethylene glycol)) (P(MAA-g-EG)) hydrogels using the gastric and intestinal fluids from rats. P(MAA-g-EG) hydrogels successfully protected the incorporated insulin from enzymatic degradation by forming interpolymer complexes in the gastric fluid. The hydrogels also showed the insulin protection ability by itself. In the intestinal fluid, P(MAA-g-EG) hydrogels significantly decreased the insulin degradation rate and calcium ion levels, while protein levels was not changed. Insulin protecting effects were dependent on the fraction of the carboxylic group in the polymer networks. Moreover, the insulin degradation inhibitory effect was significantly correlated with Ca2+ deprivation ability of P(MAA-g-EG) hydrogels in the intestinal fluid, implying that the Ca2+ deprivation ability plays an important role in the inhibition of the intestinal enzyme activities. Insulin-loaded P(MAA-g-EG) (ILPs) hydrogels showed a rapid and almost complete insulin release even in the presence of intestinal proteases. These results suggested that the insulin protection ability of the hydrogels contributed to improve oral insulin absorption and that P(MAA-g-EG) hydrogels can be an excellent carrier for protecting insulin during their transit through the GI tract.

Animals↗

PubMed2005

Novel oral insulin delivery systems based on complexation polymer hydrogels: single and multiple administration studies in type 1 and 2 diabetic rats.

Insulin-loaded polymer microparticles (ILP) composed of crosslinked poly(methacrylic acid) and poly(ethylene glycol) are multi-functional carriers showing high insulin incorporation efficiency, a rapid insulin release in the intestine based on their pH-dependent complexation properties, enzyme-inhibiting effects and mucoadhesive characteristics. Thus, they are potential carriers for insulin delivery via an oral route. Recent studies suggest that the polymer composition and particle size of ILP strongly influenced insulin bioavailability. Therefore, the present study aimed at finding an optimal formulation and designing carriers for oral insulin delivery using in vivo experiments. Various types of ILPs were prepared and administered orally to healthy and type 1 and 2 diabetic rats. The most promising formulation was subsequently used for in vivo multiple oral administration studies using diabetic rats. The microparticles of diameters of <53 microm (SS-ILP) composed of a 1:1 molar ratio of methacrylic acid/ethylene glycol units showed the most pronounced hypoglycaemic effects following oral administration to healthy rats, achieving a 9.5% pharmacological availability compared to subcutaneous insulin injection. Their usefulness was also confirmed with both type 1 and 2 diabetic rat groups. In a multiple administration study, SS-ILP significantly suppressed the postprandial rise in blood glucose and showed continuous hypoglycaemic effects following 3 times/day oral administration to both diabetic rat groups in the presence of foods. These results indicate that the blood glucose levels of diabetic rats can be effectively controlled by oral SS-ILP administration, and thus SS-ILP would be a promising delivery carrier of insulin via the oral route.

Administration, Oral↗

PubMed2005

Characterization of Gly-D-Phe, Gly-L-Leu, and D-Phe as affinity ligands to thermolysin.

In this study, glycyl-D-phenylalanine (Gly-D-Phe), glycyl-L-leucine (Gly-L-Leu), and D-phenylalanine (D-Phe) were characterized for their abilities as affinity ligands to thermolysin. Each of the ligands was immobilized to the resin. The optimum pH for adsorption of thermolysin is 5.0-6.0 for each of the ligands. By the affinity column chromatography in which 2mg thermolysin was applied onto 4 ml volume of the resins at pH 5.5, the adsorption ratios based on casein hydrolysis activity were 100% for each of the ligands. However, the adsorption ratios of the resins containing Gly-L-Leu and D-Phe, unlike that of Gly-D-Phe, were progressively decreased with increasing the amounts of thermolysin applied to the column. Measurement of adsorption isotherms showed that the association constant to thermolysin at pH 5.5 of the resins containing Gly-D-Phe was (3.3+/-0.8)x10(5)M(-1), while those of Gly-L-Leu and D-Phe were approximately ten times less. This result is coincident with the observations of performances in affinity column chromatography. On the other hand, maximum thermolysin binding capacities were almost the same among the resins examined. These results indicate that Gly-D-Phe is more suitable than Gly-L-Leu and D-Phe as an affinity ligand for purification of thermolysin.

Adsorption↗

PubMed2005

Structural requirements of Dictyostelium differentiation-inducing factors for their stalk-cell-inducing activity in Dictyostelium cells and anti-proliferative activity in K562 human leukemic cells.

The differentiation-inducing factor-1 (DIF-1) is a lipophilic signal molecule (chlorinated alkylphenone) that induces stalk-cell differentiation in the cellular slime mould Dictyostelium discoideum. It has also been shown that DIF-1 and its derivative (DIF-3) suppress cell growth in mammalian tumor cells. In the present study, in order to assess the chemical structure-effect relationship of DIF derivatives and to develop useful agents for the study of both Dictyostelium development and cancer biology, we synthesized 28 analogues of DIF-1 and DIF-3 and investigated their stalk-cell-inducing activity in Dictyostelium HM44 cells (mutant strain) and anti-proliferative activity in human leukemia K562 cells. HM44 cells are defective in endogenous DIF-1 production and should be suitable for the assay for stalk-cell-inducing activity of DIF analogues. DIF-1 and some of its derivatives at nanomolar levels were good stalk-cell inducers in HM44 cells, whereas DIF-3 and some DIF-3 derivatives at micromolar levels were potent anti-proliferative agents in K562 cells. We also tried to search for antagonistic molecules against DIF-1 and DIF-3 but failed to find such molecules from the analogues used here. The present findings would give us hints for identifying the target molecule(s) of DIFs and also for developing novel anti-cancer drugs.

Antineoplastic Agents↗

PubMed2005

IL-6 blocks a discrete early step in lymphopoiesis.

Animals lacking Src homology 2 domain-containing inositol 5-phosphatase (SHIP) display a reduction in lymphopoiesis and a corresponding enhancement of myelopoiesis. These effects are mediated at least in part by elevated levels of interleukin 6 (IL-6). Here, we show the lymphopoiesis block in SHIP-/- mice is due to suppression of the lymphoid lineage choice by uncommitted progenitors. The suppression can be reproduced in vitro with recombinant IL-6, and IL-6 acts directly on hematopoietic progenitors. The block is partially overcome in SHIP-/- IL-6-/- double-deficient animals. IL-6 does not suppress but actually enhances proliferation of lymphoid-committed progenitors, indicating the IL-6 target cells are hematopoietic stem cells or multipotent progenitors. The findings suggest a mechanism for the lymphopenia that accompanies proinflammatory diseases.

Animals↗

PubMed2005

[The state and results of countermeasures for mental health at a certain apparel company].

We speculated that there would be more occupational stress in an apparel company than in other areas of business, because employees work long hours and under poor conditions. We investigated 66 employees of an apparel company who visited an occupational physician to consult about their mental health. There were 561 male and 387 female employees in that company. The employees who had visited an occupational physician had worked long every day under poor conditions, and they had been required to be more artistic than other employees in that company. Female employees visited occupational physicians more than males. Apparel companies, use a system of "specialty store retailer of Private-label Apparel (SPA)", and several sections make special trademark "brands". These sections compete with each other. Employees must plan, design, make patterns, and sew new dresses in a 7-day cycle. They are extremely busy and this therefore creates stress. We came to the conclusion that many apparel companies were stressful workplaces. It is important that a psychiatrist examines employees who occupational physicians have diagnosed as unhealthy. Frequent consultation with occupational physicians is as important as a psychiatrists examination. Managers must manage absence, efficiency, and written correspondence of all employees. These are useful signs of mental disorder. When employees return to work after sick leave, rehabilitation in the workplace after absence is useful. The employee should work for only two hours a day at first. Working hours are then extended gradually. The employee can then return to work easily if this rehabilitation program is followed.

Clothing↗

PubMed2005

Application of sterylglucoside-containing particles for drug delivery.

Recent advances in biotechnology have promoted biomolecular targeting of drugs, peptides and genes in the treatment and management of major diseases and infections. Therapeutic development of drugs and delivery systems may have various objectives: Systemic drugs require optimal delivery and uptake at target sites; peptide drugs require alternative routes of administration, such as nasal or intestinal absorption; gene medicines need to be delivered efficiently, safely and selectively to diseased areas. The propensity of ligand-modified liposomes to carry drugs and genes to desirable sites has been extensively examined and current reports show considerable progress in this field. Sterylglucoside (SG) is a novel absorption-enhancer of peptide drugs across nasal and intestinal mucosae. Physico-chemical properties and biodistribution of liposomes incorporating SG were studied and compared against the profiles of aglycon and sitosterol derivatives of SG. It was shown that SG particles aided colon drug delivery and increased bioavailability of peptide drugs after nasal and intestinal administration. In addition, they were able to enhance anticancer effects in liver cancer chemotherapy. Biological fate and interaction of SG with hepatocytes support the novel proposition of liver-targeting SG-liposomes.

Animals↗

PubMed2005

[Successful rituximab treatment in a patient with refractory hairy cell leukemia-Japanese variant and suffering from acute respiratory distress].

A 69-year-old man was referred to our hospital because of thrombocytopenia and was diagnosed as having hairy cell leukemia-Japanese variant (HCL-Jv) in December 2000. In June 2002, he was treated with pentostatin for progression of thrombocytopenia, but his response was incomplete. In addition, the number of hairy cells (HCs) in his peripheral blood (PB) began gradually to increase. He received treatment with interferon-alpha and cladribine, but he failed to respond completely to these treatments. The HCs in his PB decreased after splenic irradiation in July, 2004. However, he was admitted with acute respiratory distress in November. His white blood cell count was 123.1 X 10(9)/L with 91% HCs. Radiography and computed tomography of his chest revealed ground-glass opacity in both lungs. A bone marrow (BM) aspirate indicated increased cellularity with an 84% HC infiltration level. Based on these findings, we diagnosed pulmonary infiltration by HCs. Rituximab was administered weekly at a dose of 375 mg/m2, and he also received low-dose melphalan in a supportive role. After 8 courses of rituximab therapy, the HCs disappeared in his PB and BM, and his pulmonary infiltrates subsided. These results suggest that rituximab may be a very effective treatment for refractory HCL-Jv.

Aged↗

PubMed2004

Generation cycles in Indonesian lady beetle populations may occur as a result of cannibalism.

Generation cycles, population cycles with a period of approximately one generation, have been observed in a variety of field and laboratory studies. Such dynamics are predicted to arise through the effects of resource competition and cannibalism or involve consumer-natural enemy interactions. We first show, using a new highly simplified model, that generation cycles are a very common outcome of strongly age-structured intraspecific interactions involving cannibalism. We then analyse a series of unique long-term time-series of ladybeetle (Coccinellidae) abundances from tropical Indonesia. Some of the time-series display clear generation cycles, and we argue that there is strong evidence that these are caused by intraspecific cannibalism.

Animals↗

PubMed2004

A novel carbon skeletal trichothecane, tenuipesine A, isolated from an entomopathogenic fungus, Paecilomyces tenuipes.

Tenuipesine A (1), a novel trichothecane with an unprecedented carbon-migrated skeleton that embodies of a cyclopropane ring, was isolated from cultivated fruiting bodies of Paecilomyces tenuipes (Isaria japonica), a popular entomopathogenic fungi employed in folk medicine and health foods in China, Korea, and Japan. The structure was determined on the basis of two-dimensional NMR data. Its stereochemistry was elucidated by spectroscopic data and the chemical transformation of the coexisting trichothecene, 4beta-acetoxy-12,13-epoxytrichothec-9-ene-3alpha,15-diol (2). [structure: see text]

Cyclopropanes↗

PubMed2004

Mucosal insulin delivery systems based on complexation polymer hydrogels: effect of particle size on insulin enteral absorption.

Insulin-loaded polymer (ILP) microparticles composed of poly(methacrylic acid) and poly(ethylene glycol), which have pH-dependent complexation and mucoadhesive properties have been thought to be potential carriers for insulin via an oral route. Nevertheless, further optimization of the polymer delivery system is required to improve clinical application. Therefore, the effect of particle size of the ILP (L-ILP: 180-230 microm, S-ILP: 43-89 microm, SS-ILP: <43 microm) on insulin absorption was studied in the in situ loop system, hypothesizing smaller particle sizes of ILP could induce bigger hypoglycemic effects due to increase mucoadhesive capacity. To verify the hypothesis, the adhesive capacities of differently sized ILPs to the mucosal tissues were evaluated. Additionally, the intestinal site-specificity of ILP for insulin absorption was investigated. Intra- and inter-cellular integrity and/or damage were also examined by lactate dehydrogenase leakage and membrane electrical resistance change to ensure the safety of ILP as a carrier for oral route. As hypothesized, the smaller sized microparticles (SS-ILP) showed a rapid burst-type insulin release and higher insulin absorption compared with the microparticles having larger sizes, resulting in greater hypoglycemic effects without detectable mucosal damage. In fact, SS-ILP demonstrated higher mucoadhesive capacity to the jejunum and the ileum than those of L-ILP. Moreover, SS-ILP's enhancement effect of insulin mucosal absorption showed a site-specificity, demonstrating maximum effect at the ileal segment. These results imply that the particle size and delivery site are very important factors for ILP with respect to increasing the bioavailability of insulin following oral administration.

Animals↗

PubMed2004

Hydrophobic interaction chromatography at low salt concentration for the capture of monoclonal antibodies.

We evaluated hydrophobic interaction chromatography (HIC) at low salt concentration for the capture of proteins from feed stocks by using monoclonal antibodies as model samples. It was indicated that the HIC at low salt concentration on critical hydrophobicity supports has a potential for capturing hydrophobic monoclonal antibodies directly from large volumes of feed stocks and recovering bound monoclonal antibodies in high yield. On the other hand, the HIC at low salt concentration did not seem so useful for the capture of weakly hydrophobic monoclonal antibodies. The recovery of weakly hydrophobic monoclonal antibodies from columns packed with critical hydrophobicity supports was not quantitative and significantly decreased as the residence time of the monoclonal antibodies in the columns became longer.

Antibodies, Monoclonal↗

PubMed2004

Effect of chromatographic conditions on resolution in high-performance ion-exchange chromatography of proteins on macroporous anion-exchange resin.

We explored chromatographic conditions to obtain high resolution in protein separations by ion-exchange chromatography (IEC) on a macroporous anion-exchange resin of 10 microm in particle diameter. We studied effects of flow-rate, gradient time (steepness of salt concentration gradient) and column length on resolution in wide ranges. It was found that very high resolutions are attainable at long gradient times with long columns. The resolution continuously became higher as the gradient time and the column length became longer except in some special cases. The dependence of resolution on gradient time was particularly great when the column was long and the gradient time for the change of 0-0.5 M NaCl was longer than 2 h. On the other hand, the effect of flow-rate on resolution was very small. Although the separations at long gradient times with long columns have not been popular in high-performance IEC and it takes several hours for one separation, such separations should be advantageous when very high resolutions are required like in proteomics research.

Anion Exchange Resins↗

PubMed2004

Oral insulin delivery using P(MAA-g-EG) hydrogels: effects of network morphology on insulin delivery characteristics.

Hydrogels of poly(methacrylic acid-g-ethylene glycol) were prepared using different reaction water contents in order to vary the network mesh size, swelling behavior and insulin loading/release kinetics. Gels prepared with greater reaction solvent contents swelled to a greater degree and had a larger network mesh size. All of the hydrogels were able to incorporate insulin and protected it from release in acidic media. At higher pH (7.4), the release rates increased with reaction solvent content. Using a closed loop animal model, all of the insulin loaded formulations produced significant insulin absorption in the upper small intestine combined with hypoglycemic effects. In these studies, bioavailabilities ranged from 4.6% to 7.2% and were dependent on reaction solvent content.

Administration, Oral↗

PubMed2004

Src homology 2-containing 5-inositol phosphatase (SHIP) suppresses an early stage of lymphoid cell development through elevated interleukin-6 production by myeloid cells in bone marrow.

The Src homology (SH)2-containing inositol 5-phosphatase (SHIP) negatively regulates a variety of immune responses through inhibitory immune receptors. In SHIP(-/-) animals, we found that the number of early lymphoid progenitors in the bone marrow was significantly reduced and accompanied by expansion of myeloid cells. We exploited an in vitro system using hematopoietic progenitors that reproduced the in vivo phenotype of SHIP(-/-) mice. Lineage-negative marrow (Lin(-)) cells isolated from wild-type mice failed to differentiate into B cells when cocultured with those of SHIP(-/-) mice. Furthermore, culture supernatants of SHIP(-/-) Lin(-) cells suppressed the B lineage expansion of wild-type lineage-negative cells, suggesting the presence of a suppressive cytokine. SHIP(-/-) Lin(-) cells contained more IL-6 transcripts than wild-type Lin(-) cells, and neutralizing anti-IL-6 antibody rescued the B lineage expansion suppressed by the supernatants of SHIP(-/-) Lin(-) cells. Finally, we found that addition of recombinant IL-6 to cultures of wild-type Lin(-) bone marrow cells reproduced the phenotype of SHIP(-/-) bone marrow cultures: suppression of B cell development and expansion of myeloid cells. The results identify IL-6 as an important regulatory cytokine that can suppress B lineage differentiation and drive excessive myeloid development in bone marrow.

Animals↗

PubMed2004

Hepatocyte proliferation and tissue remodeling is impaired after liver injury in oncostatin M receptor knockout mice.

Oncostatin M (OSM) is a member of the IL-6 family of cytokines. Mice deficient in the OSM receptor (OSMR(-/-)) showed impaired liver regeneration with persistent parenchymal necrosis after carbon tetrachloride (CCl(4)) exposure. The recovery of liver mass from partial hepatectomy was also significantly delayed in OSMR(-/-) mice. In contrast to wildtype mice, CCl(4) administration only marginally induced expression of tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 genes in OSMR(-/-) mice, correlating with the increased gelatinase activity of matrix metalloproteinase (MMP)-9 and matrix degradation in injured livers. The activation of STAT3 and expression of immediate early genes and cyclins were decreased in OSMR(-/-) liver, indicating that OSM signaling is required for hepatocyte proliferation and tissue remodeling during liver regeneration. We also found that CCl(4) administration in IL-6(-/-) mice failed to induce OSM expression and that OSM administration in IL-6(-/-) mice after CCl(4) injection induced the expression of cyclin D1 and proliferating cell nuclear antigen, suggesting that OSM is a key mediator of IL-6 in liver regeneration. Consistent with these results, administration of OSM ameliorated liver injury in wildtype mice by preventing hepatocyte apoptosis as well as tissue destruction. In conclusion, OSM and its signaling pathway may provide a useful therapeutic target for liver regeneration.

Animals↗

PubMed2004

Expression of Dlk/Pref-1 defines a subpopulation in the oval cell compartment of rat liver.

We previously showed that Dlk, a transmembrane protein containing six epidermal growth factor like repeats in its extracellular domain, is strongly expressed in hepatoblasts in murine fetal liver. Here, we examined the expression of Dlk in oval cells, which are adult hepatic progenitors, in the rat 2-acetylaminofluorene/partial hepatectomy (2AAF/PH) model. Reverse transcription polymerase chain reaction analysis showed that Dlk expression was significantly induced in the regenerating liver at day 12 and 14 after PH, when many oval cells were present in periportal areas. Immunofluoresence staining analysis revealed that Dlk(+) cells expressed oval cell markers, cytokeratin 19 (CK19) and alpha-fetoprotein, indicating that Dlk is expressed in oval cells. However, Dlk(+) cells accounted for only about 20% of total CK19(+) oval cells. Dlk(+) cells were localized more distantly from the portal vein than Dlk(-) cells, and were adjacent to mature hepatocytes, though Dlk(+) cells were surrounded by the basal membrane as other oval cells. Furthermore, at day 12 after PH, only 3% of Dlk(+) oval cells expressed Ki67, whereas about 13% of total oval cells expressed Ki67, indicating that Dlk(+) oval cells are less proliferative than Dlk(-) oval cells. Taken together, these results demonstrate that Dlk is expressed in a subpopulation of oval cells and that Dlk(+) cells represent intermediate cells between Dlk(-) oval cells and mature hepatocytes.

Animals↗

PubMed2004

[Postoperative laryngeal edema presumably due to hypoalbuminemia causing acute airway obstruction after extubation in a patient after nephrectomy].

We report here a case of upper airway obstruction occurring after extubation in a 55-yr-old 60 kg man after elective nephrectomy. Anesthesia was maintained with O2 (33%), N2O, sevoflurane (1.5-2%), and propofol infusion (2 mg x kg(-1) x hr(-1)). Blood loss was 1,965 ml, part of which was substituted by blood transfusion and albumin infusion. After surgery, the patient recovered uneventfully and could be extubated shortly. Twenty minutes after extubation, he developed dyspnea progressively with stridor and became cyanotic despite the use of oxygen mask and assisted ventilation. Oxygen saturation decreased gradually, and bradycardia (<30 beats x min(-1)) and severe hypotension were also observed. Cardiopulmonary resuscitation using epinephrine was immediately started. Re-intubation of the trachea was difficult due to severe edema, but eventually performed using a tube of a smaller size (internal diameter 7.0 mm). Subsequent investigations using a fiberscope confirmed extensive soft tissue swelling, maximal at the level of the vocal cord and extending up- and down-wards to the trachea, indicating that the obstruction is caused by severe laryngeal edema. We believe that edema may have been caused by hypoalbuminemia (1.3 g x dl(-1)) at the end of operation. Therefore, it should be noted that hypoalbuminemia may cause laryngeal edema leading to acute airway obstruction.

Acute Disease↗