Biomedical subjects

N Oku

Publications and source records attributed to N Oku.

At least 37 records · Page 2Linked to original sources

PubMed2001

Overexpression of the Csk homologous kinase (Chk tyrosine kinase) induces multinucleation: a possible role for chromosome-associated Chk in chromosome dynamics.

The Csk family of non-receptor-type tyrosine kinases consists of Csk and the Csk homologous kinase Chk. Each enzyme suppresses the catalytic activity of Src family kinases by phosphorylating their C-terminal negative regulatory tyrosine residues. Ectopic and transient expression of Chk in COS-1 cells showed nuclear localization of Chk and growth inhibition. To further explore the role of Chk in cell growth, we overexpressed Chk in human immature myeloid KMT-2 cells. Chk overexpression brought about growth retardation and aberrant chromosome movement leading to multinucleation, and these events were accompanied by insufficient formation of mitotic spindles. In vitro kinase assays showed that Chk overexpression suppressed the tyrosine kinase activity of Lyn, a member of the Src family, immunoprecipitated from Triton X-100 lysates. Subcellular fractionation studies revealed that fractions of Chk and Lyn, resistant to Triton X-100 solubilization, are associated with mitotic chromosome scaffolds and spindles. Chk overexpression induced a decrease in autophosphorylation of Lyn and concomitant changes in levels of tyrosine phosphorylation of proteins associated with both fractions. These results indicate that Chk, Lyn and the tyrosine-phosphorylated proteins localize to mitotic chromosomes and spindles, suggesting that Chk-dependent tyrosine phosphorylation, presumably through Lyn, may be involved in chromosome dynamics.

Animals↗

PubMed2000

Liposomes modified with a synthetic Arg-Gly-Asp mimetic inhibit lung metastasis of B16BL6 melanoma cells.

Administration of large amounts of synthetic peptides based on the Arg-Gly-Asp (RGD) sequence has been shown to suppress tumor metastasis. To overcome the rapid degradation of peptides in the circulation, an RGD mimetic, L-arginyl-6-aminohexanoic acid (NOK), was synthesized and conjugated with phosphatidylethanolamine (PE) (NOK-PE) for liposomalization. Cell adhesion assays revealed that B16BL6 murine melanoma cells adhered to immobilized NOK-PE. This adhesion was inhibited by addition of either soluble RGDS or NOK at similar concentration in a dose-dependent manner. Administration of NOK-PE liposomes (equivalent to ca. 500 microg RGD peptides) via the tail vein completely inhibited lung colonization of B 16BL6 cells. The same dose of soluble NOK was not effective in inhibition of the tumor metastasis. In addition, injection of NOK-PE liposomes via the tail vein inhibited spontaneous lung metastasis of B16BL6 cells from the primary tumor site in the hind footpad. These results suggest that NOK, a structural mimetic of RGD, is capable of suppressing metastasis by blockade of the binding of the integrins present on tumor cells to the RGD-containing extracellular matrix.

Animals↗

PubMed2000

Usefulness of positron emission tomographic visualization for examination of in vivo susceptibility to metastasis.

BACKGROUND: Immune surveillance may play a role in protecting against the establishment of metastasis. The authors previously observed that the injection of as few as 10(4) lung metastatic B16BL6 melanoma cells/0.2 mL resulted in no metastasis and in a reduced rate of cell accumulation in the lung, the target organ. In the current study, the authors examined the correlation between metastatic potential and tumor cell trafficking by using a liver-metastatic model. METHODS: The liver-metastatic potential of RAW117-H10 cells was examined by varying the number of cells injected into mice through the portal vein. To investigate the trafficking of the cells, the authors performed positron emission tomography (PET) analysis, because advances in this technology now enable the use of PET to investigate the real-time trafficking of as few as 10(4) cells/0.2 mL. Furthermore, to clarify the role of the immune defense system, metastatic potential and cell trafficking also were examined by using macrophage-depleted mice. RESULTS: When 10(6) or 10(5) RAW117-H10 cells/0.2 mL were injected into mice, both quantities of cells caused liver metastasis, cells accumulated in the liver at a similar rate, and there was an approximately 10-fold difference in the number of accumulated cells between the two doses. However, the injection of 10(4) cells/0.2 mL did not produce metastasis, and the accumulation rate in the liver was less than one-tenth of that after the injection of 10(5) cells/0.2 mL. The treatment of mice with 2-chloroadenosine for depleting macrophages prior to the injection of 10(4) cells/0.2 mL resulted in the suppression of the fast elimination of the cells from the liver. Corresponding to this change in PET images, the injection of 10(4) cells/0.2 mL into 2-chloroadenosine-pretreated mice resulted in metastasis. CONCLUSIONS: The current study suggests that immune surveillance suppresses accumulation of tumor cells to the target and suppresses metastasis, and this effect is obvious when small numbers of tumor cells are used for the challenge. Furthermore, the immune defense system plays a role in the early stage of the metastatic process.

Animals↗

PubMed2000

Manganese concentration in mouse brain after intravenous injection.

Abnormal deposit of manganese (Mn) in the basal ganglia is often observed in patients with chronic liver failure and patients receiving long-term parenteral nutrition. Based on the data that (54)Mn is transported into the brain efficiently via a transferrin-independent uptake system, Mn concentration in mouse brain was determined after intravenous (iv) injection (2 mg Mn/kg/day x 5 times) of either MnCl(2) or pH 8.6 buffer-treated MnCl(2), which has a higher affinity for transferrin than untreated MnCl(2). Brain Mn concentration was significantly increased in either case. Brain Mn concentration of MnCl(2) group was significantly higher than that of pH 8.6 buffer-treated MnCl(2) groups. Mn concentration in the caudate putamen of MnCl(2) group was also significantly higher than that of pH 8.6 buffer-treated MnCl(2) group. Ninety seconds after a single injection of MnCl(2) (2 mg Mn/kg), brain Mn concentration was remarkably increased with blood Mn level, but not 1 hr after injection. On the other hand, hepatic Mn concentration was remarkably high 1 hr after injection and the brain Mn concentration was increased again at 24 hr, followed by decrease of the hepatic Mn concentration. Relative Mn concentrations in the brain 90 sec after injection were different from those 24 hr after injection, suggesting that the mechanism of the increase of brain Mn concentration via blood Mn level is different from that via the redistribution from the liver. Mn ion and/or Mn bound to low molecular weight compounds may be involved in abnormal Mn uptake in the brain.

Animals↗

PubMed2000

Potential usage of thermosensitive liposomes for site-specific delivery of cytokines.

Long-circulating liposomes reside long in the bloodstream, and transient swelling during phase transition of liposomes with hyper-osmotic internal aqueous phase causes release of macromolecules. Here we examined the applicability of long-circulating thermosensitive liposomes for delivery of tumor necrosis factor (TNF) by the heating of a local tumor-growing site after injection of TNF-loaded liposomes into tumor-bearing mice. Glucuronate modified thermosensitive liposomes with internal solution of two-fold higher osmotic pressure and sized through 200 nm-pore, released encapsulated [(131)I] human serum albumin at 42 degrees C in vitro and showed long-circulating character in vivo. Cytotoxic action of TNF encapsulated in long-circulating thermosensitive-liposomes (LCTS-liposomes) against L929 fibrosarcoma cells was enhanced at 42 degrees C in vitro. Furthermore, the tumor growth tended to be inhibited more by hyperthermia of mice bearing Meth A sarcoma than without heating after injection of TNF encapsulated in LCTS-liposomes. These results suggest that the cytokine can be released at the tumor site from the circulating CLTS-liposomes.

Animals↗

PubMed2000

65Zn localization in rat brain after intracerebroventricular injection of 65Zn-histidine.

Previous studies have shown that 65Zn uptake in the brain expressed relative to plasma 65Zn level is enhanced by histidine infusion into the blood vessel. To study the effect of histidine on zinc uptake in the brain parenchyma via the CSF, the brains of rats injected intracerebroventricularly with 65Zn-His were subjected to autoradiography. Six days after injection, the radioactivity from 65Zn-His was distributed in the major part of the brain parenchyma higher than that from 65ZnCl(2), and relatively concentrated in the hippocampal formation, globus pallidus and hypothalamus. The radioactivity of the aqueduct was also higher in the 65Zn-His group, indicating that CSF clearance of the 65Zn-His group may be lower than that of the 65ZnCl(2) group. These results suggest an enhancement by histidine on zinc uptake in the brain parenchyma via the CSF.

Animals↗

PubMed2000

Hepatic zinc response via metallothionein induction after tumor transplantation.

Based on previous findings that liver zinc and metallothionein (MT) levels increase after tumor transplantation, zinc metabolism in tumor-bearing mice was studied to clarify the role of zinc-MT in host defense systems. Zinc in the hepatic cytosolic MT fraction did not increase in tumor-bearing mice fed a zinc-deficient diet, suggesting that dietary zinc is necessary for apo-MT induction in the liver after tumor transplantation and is then incorporated into the apo-MT. When (65)ZnCl(2) was intravenously injected, liver (65)Zn levels in the tumor-bearing mice were higher than those in control mice for 72 h after the injection. Pancreatic and blood (65)Zn levels in tumor-bearing mice were lower than those in controls for 24 h (pancreas) and 6 h (blood) after the injection. These findings indicate that the hepatic zinc response via MT induction influences zinc metabolism in the body after tumor transplantation. Moreover, (65)Zn uptake in the liver of MT-deficient tumor-bearing mice was lower than that in control tumor-bearing mice 1 h after injection. (65)Zn uptake in the tumor and blood (65)Zn levels in the MT-deficient tumor-bearing mice were higher than those in the control tumor-bearing mice. Tumor weight increased more in MT-deficient mice than in control mice. The formation of zinc-MT in the liver of tumor-bearing mice might decrease blood zinc availability for tumors and other tissues, such as the pancreas.

Animals↗

PubMed2000

Relationship between brain zinc and transient learning impairment of adult rats fed zinc-deficient diet.

The relationship between brain zinc and learning behavior was studied based on the data of 65Zn localization in the hippocampal formation. Learning behavior, tested by passive avoidance performance, of 6-week-old rats improved significantly compared to that of 4-week-old rats and it was maintained at 20 weeks of age. When 8-week-old rats were fed zinc-deficient diet for 4 weeks, the learning behavior was significantly impaired. However, it was recovered to almost normal level by feeding with control (zinc-adequate) diet for 5 weeks. These results demonstrate that a proper zinc supply to the brain is necessary for improvement and maintenance of learning ability. Although an appreciable decrease in brain zinc was not observed in the rats fed zinc-deficient diet for 4 weeks, significant decrease of hippocampal zinc was observed in rats fed zinc-deficient diet for 12 weeks. Moreover, synaptosomal zinc in the hippocampal formation and cerebral cortex was significantly decreased by the 12 weeks of zinc deprivation. These results suggest that the decrease of vesicular zinc in the hippocampal formation and cerebral cortex is involved in the transient learning impairment of adults rats.

Age Factors↗

PubMed2000

Neural plasticity detected in short- and long-term cochlear implant users using PET.

The interaction of listening to words and watching sign language in short-term and long-term cochlear implant (CI) users who have learned sign language after becoming deaf was measured using PET. In short-term CI users the auditory cortex was inactive while in long-term CI users it was fully activated with the simultaneous presentation of auditory and visual input. The result suggests the possibility that the interference of rival modalities may be diminished with experience and the preference switchover from the visual input to the auditory input could be accomplished by means of the neural plasticity persisting in the mature human auditory cortex.

Adolescent↗

PubMed2000

Functional brain areas used for the lifting of objects using a precision grip: a PET study.

Positron emission tomography (PET) was performed in 10 normal volunteers to investigate regional cortical and subcortical activation induced by the lifting of an object repetitively using a precision grip between the index finger and thumb. Data were obtained for three object weights (4, 200 and 600 g) and a resting condition. Grip and lift forces on a similar object and the activity of selected muscles in the hand, arm and shoulder were also recorded in separate lifting trials. A comparison between all movement conditions and the resting condition revealed significant activation of the primary motor (M1), primary sensory (S1), dorso-caudal premotor (PM), caudal supplementary motor (SMA) and cingulate motor (CMA) cortices contralateral to the hand used. On the ipsilateral side, activation of the M1, caudal SMA and inferior parietal cortex (BA 40) was also found. In the subcortical areas, the bilateral hemispheres and right vermis of the cerebellum, left basal ganglia and thalamus were activated. Behavioral adaptation to a heavier object weight was revealed in a nearly proportional increase of both grip and lift forces, prolonged force application period and a higher level of hand and arm muscle activities. An increase in the rCBF associated with these changes was noted in several cortical and subcortical areas. However, consistent object weight-dependent activation was observed only in the M1/S1 contralateral to the hand used.

Adult↗

PubMed2000

Possible role of immune surveillance at the initial phase of metastasis produced by B16BL6 melanoma cells.

The relationship among the real-time trafficking of lung metastatic B16BL6 cells, metastatic potential, and the injected number of the cells was examined, since the smaller the number of tumor cells injected, the more clearly the immune defense may be observed. When 1x10(6) or 1x10(5) B16BL6 cells were injected into mice via the tail vein, both numbers of cells accumulated in the lung at a similar rate: there was an approximately 10-fold difference in the number of accumulated cells between the two doses. Elimination from the lung was not dependent on the cell number but on the proportion of accumulated cells. However, the injection of 1x10(4) cells resulted in lung accumulation less than one-tenth of that obtained with 1x10(5) cell injection. Metastasis was observed when 1x10(5) or 1x10(6) B16BL6 cells were injected, but not after injection of 1x10(4) cells. To clarify the roles of the immune defense system at the initial phase of metastasis, we challenged macrophage-depleted mice with 1x10(4) tumor cells. Treatment of mice with 2-chloroadenosine prior to the tumor cell challenge cancelled the suppression of not only metastasis but also the lung accumulation. Furthermore, the administration of 2-chloroadenosine following the tumor cell challenge had little effect on the metastatic potential. These results suggest that the immune surveillance whose action was obvious at the low dose of challenged tumor cells functions strongly at the initial phase but not at the advanced stages of the metastatic process, and that macrophages play an important role in the suppression of metastasis.

2-Chloroadenosine↗

PubMed2000

Suppression of GD1alpha ganglioside-mediated tumor metastasis by liposomalized WHW-peptide.

GD1alpha ganglioside-replica peptides were recently isolated from a phage-displayed random pentadecapeptide library by assaying for inhibition of adhesion of RAW117-H10 lymphosarcoma cells to hepatic sinusoidal microvessel endothelial (HSE) cells. We show here that the Trp-His-Trp (WHW) peptide was identified as a minimal sequence of the GD1alpha-replica peptide WHWRHRIPLQLAAGR. The addition of WHW peptide-attached liposomes displayed efficient inhibition of liver metastasis of RAW117-H10 cells as well as of GD1alpha-mediated adhesion of RAW117-H10 cells to HSE cells in vitro. These results suggest that engineered liposomes for peptide delivery are applicable to treatment for metastasis.

Amino Acid Sequence↗

PubMed2000

The neural basis of perceptual and conceptual word priming--a PET study.

Positron emission tomography scans were obtained in 13 normal subjects during perceptual and conceptual word priming tasks with the aim to investigate the neural system specific to the two priming conditions. In the prescan phase, subjects were primed perceptually or conceptually with two separate procedures, while in the scan phase, they performed the same stem completion task. Therefore we could compare the results of the two priming tasks in a direct manner. A fixation control task and a baseline task (completion of stems that did not correspond to previously seen words) were also given. A specific blood flow decrease was found in the left inferior temporal cortex in the perceptual word priming condition and in the left superior temporal / inferior parietal cortex in the conceptual word priming condition. Each blood flow change may reflect transient changes in the cortical areas subserving the processing of the perceptual and conceptual components of word priming.

Adult↗

PubMed2000

New isomalabaricane triterpenes from the marine sponge Stelletta globostellata that induce morphological changes in rat fibroblasts.

Three new isomalabaricane triterpenes, 29-hydroxystelliferin D (2), 3-epi-29-hydroxystelliferin E (3), and 3-epi-29-hydroxystelliferin A (4), were isolated from the marine sponge Stelletta globostellata. Their structures, including absolute stereochemistry, were determined on the basis of spectral data and chemical methods. Rat fibroblasts treated with 0.2 microM of 2-4 exhibited unusual morphological characteristics, followed by death in 5 days.

Acetylation↗

PubMed2000

Polycation liposomes, a novel nonviral gene transfer system, constructed from cetylated polyethylenimine.

A novel gene transfer system was developed by using liposomes modified with cetylated polyethylenimine (PEI, MW 600). This polycation liposome, PCL, showed remarkable transfection efficiency as monitored by the expression of the GFP reporter gene. Most conventional cationic liposomes require phosphatidylethanolamine or cholesterol as a component, although PCLs did not. Egg yolk phosphatidylcholine- and dipalmitoylphosphatidylcholine-based PCL were as effective as dioleoylphosphatidylethanolamine-based PCLs for gene transfer. Concerning the cytotoxicity against COS-1 cells and hemolytic activity, the PCL was superior to conventional cationic liposome preparations. Furthermore, the transfection efficacy of PCLs was enhanced, instead of being diminished, in the presence of serum. Effective gene transfer was observed in all eight malignant and two normal cells line tested, as well as in COS-1 cells. We also examined the effect of the molecular weight of PEI on PCL-mediated gene transfer, and observed that PEI with a MW of 1800 Da was as effective as that with one of 600, but that PEI of 25,000 was far less effective. Finally, an in vivo study was done in which GFP was effectively expressed in mouse liver after injection of PCL via the portal vein. Thus, PCL represents a new system useful for transfection and gene therapy.

Animals↗

PubMed2000

Increase in basal level of Hsp70, consisting chiefly of constitutively expressed Hsp70 (Hsc70) in aged rat brain.

Alteration of proteins in the function and higher structure has been observed in aged organisms. Stress proteins, which have a role to protect proteins from denaturation, may respond to the protein denaturation with aging. We found that the basal level of Hsp70, consisting chiefly of constitutively expressed Hsp70 (Hsc70), in 24-month-old Wistar rats was significantly higher in some parts of the brain than that in 6-month-old rats. On the other hand, the basal level of Hsp70 was significantly lower in 24-month-old rats after restricted feeding, which is known to suppress aging, than those fed the diet ad libitum. In the pons, medulla, striatum, and thalamus of 24-month-old rat brain, the level of Hsp70 increased and the denaturation of the cytosol proteins was suppressed. These results suggest that the expression of Hsp70, mostly Hsc70, increases with aging and may have a role to suppress protein denaturation.

Aging↗

PubMed2000

Development of a Simple Cell Invasion Assay System.

Cell invasion assay is important for studying various biological events, such as inflammation, cancer metastasis, and angiogenesis. In this study, we developed a simple method for the quantification of cell invasion by using a culture insert with fluorescence blocking micropore membrane (FBM). Fluorescence labeled cells were simply added to a culture insert with a 8 micrompore FBM precoated with Matrigel and incubated for an appropriate duration. Then, the FBM was examined under a fluorescence microscope to count the invaded cell number. By this method, accurate invasion assay is easily performed without the steps of fixation and staining of cells and removal of cells which do not invade.

Biological Assay↗

PubMed2000

Magnetic resonance lymphography of profundus lymph nodes with liposomal gadolinium-diethylenetriamine pentaacetic acid.

Lymphography, especially imaging of profundus lymph nodes, is a useful tool for diagnosis of cancer metastases in lymph nodes. However, positive enhancement agents for magnetic resonance lymphography (MRL) have not been available, since the positive imaging agents so far introduced are low-molecular-weight materials that are not trapped in lymph nodes. For the purpose of improved positive enhanced MRL, we employed liposomes as carriers of a positive enhancer, gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). Magnetic resonance (MR) imaging was performed after subcutaneous injection of Gd-liposomes into the hind feet of rabbits which had reactive enlarged retroperitoneal lymph nodes. As a result, not only popliteal but also profundus retroperitoneal lymph nodes were positively enhanced by Gd-liposomes, especially after 20 min massage of the injected sites. Gd-Liposomes containing dipalmitoylphosphatidylglycerol were more effective than Gd-liposomes containing palmityl-D-glucuronide, a type of long-circulating liposomes, suggesting that liposomal accumulation in lymph node is, at least partly, mediated by the trapping of liposomes by macrophages. These data show that liposomes modified with Gd-DTPA are effective for positive enhancement of both regional and profundus lymph nodes in MR lymphography.

Animals↗