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Kazuo Ikeda

Publications and source records attributed to Kazuo Ikeda.

At least 37 records · Page 2Linked to original sources
PubMed2005

Relationship of the reserve vesicle population to synaptic depression in the tergotrochanteral and dorsal longitudinal muscles of Drosophila.

We have previously demonstrated that Drosophila synapses possess two vesicle populations-a small active zone population replenished by "fast" recycling and a much larger reserve population replenished by a slower recycling mechanism that includes endosomal intermediates. In this paper, we demonstrate that the synapses onto the tergotrochanteral muscle (TTM) are very unusual in that they possess only the active zone vesicle population but not the reserve population. The depression characteristics to repetitive stimulation of the TTM were compared with those of the dorsal longitudinal muscle (DLM), the synapses of which possess both an active zone and a reserve population. It was observed that the TTM response depressed more quickly than that of the DLM. To further explore the possible contribution of the reserve population to release, using the shibire mutant, DLM synapses were experimentally constructed that possess only the active zone population, and their depression characteristics were compared with those of the same synapses possessing both populations. It was observed that responses from DLM synapses possessing only the active zone population depressed more quickly than the same synapses possessing both populations. These experiments were conducted under conditions of blocked recycling so that the difference in stimulation tolerance represents the contribution of the reserve population to release. Furthermore, the depression curve of the DLM synapses lacking a reserve population now closely approximated that of the TTM synapses. These data suggest that the reserve vesicle population of DLM synapses may contribute to transmitter release during repetitive firing at physiological frequencies (5-10 Hz).

Animals↗
PubMed2005

Induction of initial cardiomyocyte alpha-actin--smooth muscle alpha-actin--in cultured avian pregastrula epiblast: a role for nodal and BMP antagonist.

During early cardiogenesis, endoderm-derived bone morphogenetic protein (BMP) induces the expression of both heart-specific transcription factors and sarcomeric proteins. However, BMP antagonists do not inhibit the expression of the "initial heart alpha-actin"--smooth muscle alpha-actin (SMA)--which is first expressed in the anterior lateral mesoderm and then recruited into the initial myofibrils (Nakajima et al. [2002] Dev. Biol. 245:291-303). Therefore, mechanisms that regulate the expression of SMA in the heart-forming mesoderm are not well-understood. Regional explantation experiments using chick blastoderm showed that the posterolateral region of the epiblast differentiated into cardiomyocytes. Posterior epiblast cultured with or without the associated hypoblast showed that interaction between the tissues of these two germ layers at the early pregastrula stage (stages X-XI) was a prerequisite for the expression of SMA. Posterior epiblast that is cultured without hypoblast could also be induced to express SMA if TGF-beta or activin was added to the culture medium. However, neither neutralizing antibodies against TGF-betas nor follistatin perturbed the expression of SMA in cultured blastoderm. Adding BMP to the cultured blastoderm inhibited the expression of SMA, whereas BMP antagonists, such as chordin, were able to induce the expression of SMA in cultured posterior epiblast. Furthermore, adding lefty-1, a nodal antagonist, to the blastoderm inhibited the expression of SMA, and nodal plus BMP antagonist up-regulated the expression of SMA in cultured posterior epiblast. Results indicate that the interaction between the tissues of the posterior epiblast and hypoblast is necessary to initiate the expression of SMA during early cardiogenesis and that nodal and BMP antagonist may play an important role in the regulation of SMA expression.

Actins↗
PubMed2005

Induction of tumor necrosis factor-alpha in Schwann cells after gradual elongation of rat sciatic nerve.

BACKGROUND: Although limb lengthening has become a common treatment, the biochemical responses underlying the adaptation of elongated nerves are unclear. The purpose of this study was to clarify whether expression of cytokines and neurotrophins is altered in gradually elongated peripheral nerves. METHODS: Left sciatic nerves of adult rats were elongated by lengthening the femur up to 20 mm at a rate of 1, 2, or 20 mm/day. The ipsilateral and contralateral sciatic nerves of each group were resected 1, 4, 8, and 16 days after 20 mm of lengthening. mRNAs for interleukin-1beta, interleukin-6, tumor necrosis factor-alpha (TNFalpha), nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-4/5 were semiquantified by reverse transcription-polymerase chain reaction. Histological changes were assessed by immunoperoxidase and immunofluorescence staining. RESULTS: Expression of TNFalpha mRNA was markedly induced in the ipsilateral sciatic nerves of the gradually elongated, 1 mm/day and 2 mm/day groups, although to a lesser extent than in the acutely elongated, 20 mm/day group. In contrast, mRNAs for other factors remained undetectable. The mRNA level for TNFalpha in each group was highest 1 day after 20 mm of lengthening. The highly up-regulated level in the acute group declined rapidly within 4 days and slowly thereafter; in contrast, the decrease in the gradual groups was always slow. Even 16 days later, the levels in all groups remained significantly elevated. Unexpectedly, TNFalpha mRNA expression was also induced in the contralateral side of all groups. Immunohistochemical staining showed that TNFalpha-immunoreactive cells in gradually elongated nerves were also positive for S-100 protein but negative for proliferating nuclear cell antigen, indicating that TNFalpha was produced by nonproliferating Schwann cells. CONCLUSIONS: Gradual nerve elongation by limb lengthening induces production of TNFalpha in Schwann cells. Presumably, TNFalpha plays a critical role in the adaptation of peripheral nerves to elongation.

Animals↗
PubMed2005

Induction of interleukin-6 in dorsal root ganglion neurons after gradual elongation of rat sciatic nerve.

In the reconstruction of a segmental defect in injured peripheral nerves, gradual nerve elongation has become an important alternative to nerve grafting. To clarify biochemical responses in peripheral sensory neurons after nerve elongation, we examined the expression of cytokines and neurotrophins related to nerve regeneration. We first established rat elongation models by lengthening left femurs up to 20.0 mm at the rate of 1.0, 2.0, or 20.0 mm/day. In toluidine blue staining, the acutely elongated, 20-mm/day group showed nuclear eccentricity in the nerve cell body in L5 dorsal root ganglion (DRG) and axonal degeneration in the sciatic nerves; in contrast, the gradually elongated, 1- and 2-mm/day groups remained intact, indicating adaptation. Reverse transcription-polymerase chain reaction analysis revealed that interleukin-6 (IL-6) mRNA was induced in ipsilateral L4-6 DRG in an elongation rate-dependent manner. In contrast, none of the elongated groups exhibited a significant change in mRNA levels for interleukin-1beta, tumor necrosis factor-alpha, nerve growth factor, brain-derived neurotrophic factor, neurotropnin-3, and neurotrophin-4/5. Levels of IL-6 mRNA in all the elongated groups reached the maximum level at day 4 after 20-mm lengthening, while the axotomized group showed a decrease from the maximum level at day 1. Induction of IL-6 mRNA was also detected in the contralateral L4-6 DRG of all the elongated groups, but not detected in the axotomized group. In histochemical analysis, IL-6-immunoreactivity was predominant in neurofilament-positive, medium to large DRG neurons. Application of IL-6 to cultured Schwann cells increased mRNA for peripheral myelin protein 22 (PMP22), a major myelin component. These results suggest that IL-6 plays a key role in biochemical responses in peripheral sensory neurons after gradual nerve elongation.

Animals↗
PubMed2005

Therapeutic effect of topical administration of SN50, an inhibitor of nuclear factor-kappaB, in treatment of corneal alkali burns in mice.

We evaluated the therapeutic efficacy of topical administration of SN50, an inhibitor of nuclear factor-kappaB, in a corneal alkali burn model in mice. An alkali burn was produced with 1 N NaOH in the cornea of C57BL/6 mice under general anesthesia. SN50 (10 microg/microl) or vehicle was topically administered daily for up to 12 days. The eyes were processed for histological or immunohistochemical examination after bromodeoxyuridine labeling or for semi-quantification of cytokine mRNA. Topical SN50 suppressed nuclear factor-kappaB activation in local cells and reduced the incidence of epithelial defects/ulceration in healing corneas. Myofibroblast generation, macrophage invasion, activity of matrix metalloproteinases, basement membrane destruction, and expression of cytokines were all decreased in treated corneas compared with controls. To elucidate the role of tumor necrosis factor (TNF)-alpha in epithelial cell proliferation, we performed organ culture of mouse eyes with TNF-alpha, SN50, or an inhibitor of c-Jun N-terminal kinase (JNK) and examined cell proliferation in healing corneal epithelium in TNF-alpha-/- mice treated with SN50. An acceleration of epithelial cell proliferation by SN50 treatment was found to depend on TNF-alpha/JNK signaling. In conclusion, topical application of SN50 is effective in treating corneal alkali burns in mice.

Administration, Topical↗
PubMed2005

Expression of Smad7 in mouse eyes accelerates healing of corneal tissue after exposure to alkali.

Damage to the cornea from chemical burns is a serious clinical problem that often leads to permanent visual impairment. Because transforming growth factor (TGF)-beta has been implicated in the response to corneal injury, we evaluated the effects of altered TGF-beta signaling in a corneal alkali burn model using mice treated topically with an adenovirus (Ad) expressing inhibitory Smad7 and mice with a targeted deletion of the TGF-beta/activin signaling mediator Smad3. Expression of exogenous Smad7 in burned corneal tissue resulted in reduced activation of Smad signaling and nuclear factor-kappaB signaling via RelA/p65. Resurfacing of the burned cornea by conjunctival epithelium and its differentiation to cornea-like epithelium were both accelerated in Smad7-Ad-treated corneas with suppressed stromal ulceration, opacification, and neovascularization 20 days after injury. Introduction of the Smad7 gene suppressed invasion of monocytes/macrophages and expression of monocyte/macrophage chemotactic protein-1, TGF-beta1, TGF-beta2, vascular endothelial growth factor, matrix metalloproteinase-9, and tissue inhibitors of metalloproteinase-2 and abolished the generation of myofibroblasts. Although acceleration of healing of the burned cornea was also observed in mice lacking Smad3, the effects on epithelial and stromal healing were less pronounced than those in corneas treated with Smad7. Together these data suggest that overexpression of Smad7 may have effects beyond those of simply blocking Smad3/TGF-beta signaling and may represent an effective new strategy for treatment of ocular burns.

Adenoviridae↗
PubMed2005

Therapeutic effects of adenoviral gene transfer of bone morphogenic protein-7 on a corneal alkali injury model in mice.

An alkali burn in the cornea is a common serious clinical problem often leading to permanent visual impairment. Since transforming growth factor-beta (TGF-beta) is involved in the response to corneal injury, we evaluated the therapeutic effects of adenoviral gene transfer of mouse bone morphogenic protein-7 (BMP-7), which has antagonistic effects on TGF-beta in tissue fibrosis. Burned cornea did not express endogenous BMP-7 mRNA and protein. Resurfacing of the burned cornea by invading conjunctival epithelium was accelerated by adenoviral introduction of BMP-7. Exogenous BMP-7 expression also suppressed myofibroblast generation, appearance of monocytes/macrophages and expression of MCP-1, TGF-betas, and collagen I alpha2 chain in the affected stroma. Ectopic BMP-7 did not suppress stromal neovascularization throughout the interval studied and also did not reduce VEGF mRNA expression at Day 10. Ectopic BMP-7 in burned corneal tissue resulted in activation of Smad1/5/8 signaling and partial suppression of the phospho-Smad2 signal. These data suggest that overexpression of BMP-7 is an effective strategy for treatment of ocular alkali burns.

Adenoviridae↗
PubMed2005

Inhibition of p38MAP kinase suppresses fibrotic reaction of retinal pigment epithelial cells.

Proliferative vitreoretinopathy (PVR) is one of the major causes of the failure of retinal detachment surgery. Its pathogenesis includes a fibrotic reaction by the retinal pigment epithelium and other retina-derived non-neural cells, leading to fixation of the detached retina. We examined the role of p38 mitogen-activated protein kinase (MAPK) in transforming growth factor (TGF)-beta2-dependent enhancement of the fibrogenic reaction in a human retinal pigment epithelial cell line, ARPE-19, and also evaluated the therapeutic efficacy of inhibiting p38MAPK by adenoviral gene transfer of dominant-negative (DN) p38MAPK in a mouse model of PVR. Exogenous TGF-beta2 activates p38MAPK in ARPE-19 cells. It also suppresses cell proliferation, but this was unaffected by addition of the p38MAPK inhibitor, SB202190. SB202190 interfered with TGF-beta2-dependent cell migration and production of collagen type I and fibronectin, but had no effect on basal levels of these activities. While SB202190 did not affect phosphorylation of the C-terminus of Smads2/3, it did suppress the transcriptional activity of Smads3/4 as indicated by a reporter gene, CAGA12-Luc. Gene transfer of DN-p38MAPK attenuated the post-retinal detachment fibrotic reaction of the retinal pigment epithelium in vivo in mice, supporting its effectiveness in preventing/treating PVR.

Animals↗
PubMed2005

Cell type-specific intervention of transforming growth factor beta/Smad signaling suppresses collagen gene expression and hepatic fibrosis in mice.

BACKGROUND & AIMS: Transforming growth factor beta and its intracellular mediators, Smad proteins, play important roles in stimulating collagen gene transcription and, thus, could be the targets for treating hepatic fibrosis. However, intervention of transforming growth factor beta/Smad signaling affects physiological signal transduction as well and may cause serious adverse effects on clinical application. Here we have attempted to suppress hepatic fibrosis by expressing a transforming growth factor beta/Smad antagonist selectively in collagen-producing cells only in the fibrotic liver. METHODS: Recombinant adenoviruses expressing either green fluorescent protein or a transforming growth factor beta/Smad signal repressor, YB-1, were injected into mice untreated or treated with carbon tetrachloride. Green fluorescent protein expression was analyzed under a confocal laser scanning microscope. Antifibrotic effects of YB-1 overexpression were examined by luciferase assays and histological examination with transgenic reporter mice. RESULTS: When the CAG expression unit was used as a control, green fluorescent protein was strongly expressed in a large number of hepatocytes in both normal and carbon tetrachloride-treated liver. In contrast, green fluorescent protein expression driven by a tissue-specific enhancer of the mouse alpha2(I) collagen gene ( COL1A2 ) was detected in activated hepatic stellate cells in carbon tetrachloride-induced fibrotic liver, but not in untreated normal liver. No green fluorescent protein fluorescence was observed in any other organs when the COL1A2 enhancer was used. Adenovirus-mediated YB-1 expression under the control of the COL1A2 enhancer significantly decreased COL1A2 promoter activity after carbon tetrachloride injection and subsequently suppressed the progression of hepatic fibrosis. CONCLUSIONS: These results validate a new concept of the therapy for hepatic fibrosis to achieve cell type-specific gene expression only in the fibrotic liver, with little damage to other organs.

Adenoviridae↗
PubMed2005

Nodular fasciitis of the ulnar nerve at the palm.

A 42-year-old woman complained of progressive induration in the right palm. As the mass was impossible to separate from the ulnar nerve, we excised the mass together with the digital nerve and grafted 4cm of the sural nerve. The final diagnosis was nodular fasciitis.

Adult↗
PubMed2004

FK778 and FK506 combination therapy to control acute rejection after rat liver allotransplantation.

BACKGROUND: In organ transplantation, several immunosuppressants are currently used to control graft rejection. Clinically, no single immunosuppressive agent can completely prevent posttransplantation immunoreaction; thus, combination therapy is usually performed. Novel agents with more powerful immunosuppressive activity and less toxicity need to be developed. METHODS: Lewis rat livers were orthotopically transplanted into Brown-Norway recipients. FK778 was administered orally from day 0 to day 6 to prevent acute rejection and from day 7 to day 13 to rescue ongoing rejection. To assess the combined effects, recipients were treated with intramuscular injection of FK506 and oral administration of FK778 from day 0 to day 6. Blood chemistry and histopathologic findings were measured to determine the patient's general condition and the graft condition. Allospecific antibodies were measured using enzyme-linked immunosorbent assays. The FK778 trough concentration was examined by using high-performance liquid chromatography. RESULTS: The acute immune response was suppressed by FK778 alone in a dose-dependent manner. The optimal FK778 dosage was determined to be 20 mg/kg per day, because adverse effects (weight loss and intestinal bleeding) occurred at 30 mg/kg per day. FK778 treatment from day 7 to day 13 rescued liver grafts from ongoing rejection. The intramuscular FK506 (0.125 mg/kg per day) injection and the oral FK778 (20 mg/kg per day) gavages suppressed acute liver graft rejection effectively and maintained better graft condition compared with monotherapy. CONCLUSIONS.: FK778 treatment effectively prevented acute rejection and rescued ongoing rejection after liver transplantation. The optimal dosage was determined to be 20 mg/kg per day. Combination therapy with FK506 was more beneficial than FK778 monotherapy.

Acute Disease↗
PubMed2004

Regulatory role of vHL/HIF-1alpha in hypoxia-induced VEGF production in hepatic stellate cells.

Activated hepatic stellate cells (HSCs) produce cyclooxygenase-2 (COX-2) protein to induce vascular endothelial growth factor (VEGF) production that participates in angiogenesis in injured liver. To reveal the unknown regulatory mechanism, we used hypoxic atmosphere mimicking injured-tissue microenvironment to induce VEGF expression in a rat hepatic stellate cell line (T6-HSCs). The present study showed that hypoxia up-regulated the protein levels of COX-2 and hypoxia-inducible factor-1-alpha (HIF-1alpha), but rapidly effected degradation of von Hippel-Lindau (vHL) protein. As a result, expression of VEGF in HSCs was markedly elevated; and pretreatment with COX-2 inhibitors (nimesulide or indomethacin) could significantly ameliorate the angiogenic event. Collectively, hypoxic HSCs increased accumulation of HIF-1alpha protein and induced VEGF expression in a time-dependent manner. Inhibition of COX-2 activities would prevent vHL protein from degradation and suppress HIF-1alpha up-regulation. Thus, vHL/HIF-1alpha has a regulatory role in COX-2-mediated VEGF production in hypoxic stellate cells in injured liver.

Animals↗
PubMed2004

Sulfur-containing amino acids attenuate the development of liver fibrosis in rats through down-regulation of stellate cell activation.

BACKGROUND/AIMS: We tested the pharmacological action of sulfur-containing amino acids on the development of liver fibrosis in rats and on the function of cultured stellate cells. METHODS: Liver fibrosis was induced in rats by thioacetamide administration or by ligating the common bile duct. DNA synthesis of cultured stellate cells was evaluated by BrdU incorporation. The expression of proteins and phospho-proteins was determined by western blot analysis. mRNA expression was evaluated by RT-PCR. RESULTS: Oral administration of l-cysteine or l-methionine attenuated the deposition of collagen in liver tissues in the two fibrotic models, accompanying a reduction in the expression of smooth muscle alpha-actin and platelet-derived growth factor receptor beta and mRNAs of collagens, transforming growth factor-betas and tissue inhibitors of matrix metalloproteinase. In cultured stellate cells, l-cysteine and l-methionine suppressed the DNA synthesis and the expression of growth factor receptors, smooth muscle alpha-actin and type I collagen. They hampered the phosphorylation of p44/42 MAPK and Akt under platelet-derived growth factor-BB stimulation. Stellate cells were found to express methionine adenosyltransferase 2A. CONCLUSIONS: l-Cysteine and l-methionine regulate the activation of stellate cells. Their oral supply aids the suppression of the progression of liver fibrosis.

Amino Acids, Sulfur↗
PubMed2004

Transient adenoviral gene transfer of Smad7 prevents injury-induced epithelial-mesenchymal transition of lens epithelium in mice.

We examined the effect of adenovirus-mediated transient expression of Smad7, an inhibitory Smad in TGFbeta/activin signaling, on injury-induced epithelial-mesenchymal transition (EMT) of lens epithelium in mice. A volume of 3 microl of adenoviral solution was injected into the right lens of adult male C57BL/6 mice (n=56) at the time of capsular injury made using a hypodermic needle under general anesthesia. A mixture of recombinant adenovirus carrying CAG promoter-driven Cre (Cre adv) and mouse Smad7 complementary DNA (Smad7 adv) was administered to induce Smad7 expression, while control lenses were treated with Cre adv alone. After healing intervals of 2, 3, 5, and 10 days, animals were killed 2 h after labeling with bromodeoxyuridine (BrdU) and eyes were processed for histology. During healing, marked expression of Smad7 was observed in lens epithelial cells in the Smad7 adv group with loss of nuclear translocation of Smads2/3, while little Smad7 and abundant nuclear Smads2/3 were seen in cells in the Cre adv group. Lens epithelial cells in the Cre adv control group exhibited a fibroblastic appearance at days 5 and 10 and the capsular break was sealed with fibrous tissue, while Smad7 adv-treated cells around the capsular break retained their epithelial morphology and the break was not sealed. Expression of snail mRNA, and alpha-smooth muscle actin, lumican, and collagen VI proteins, markers of EMT, was observed in control-treated eyes, but not in cells of the Smad7 adv group at day 5 with minimal expression at day 10. Additionally, cell proliferation increased in epithelium infected with Smad7 adv consistent with suppression of injury-induced upregulation of TGFbeta1 in epithelium. We conclude that gene transfer of Smad7 in mice prevents injury-induced EMT of lens epithelial cells and sealing of the capsular break with fibrous tissue.

Actins↗
PubMed2004

Intramedullary bone cementing for the treatment of Colles fracture in elderly patients.

Eighteen patients with Colles fractures, mean age 70 years (range 55-91), were treated by intramedullary bone cementing. The best indication for this technique was an unstable extra-articular Colles fracture with osteoporosis. Bone cement was packed into the canal that was made by curettage of intramedullary cancellous bone from the dorsal fracture site. Intramedullary cementing caused little bleeding from the medullary canal and no irritation of the extensor tendons. Because of rigid fixation, patients could use the affected hand for light activities without any external orthosis the day after surgery. Cortical healing was seen in all cases within three months and there was no cement loosening or other complications during the mean 28 month (range 6-43) follow up period. Intramedullary bone cementing is one of the optimal treatments for Colles fractures in elderly patients.

Age Factors↗
PubMed2004

Posterior interosseous nerve injury complicating ulnar osteotomy for a missed Monteggia fracture.

We describe a 6-year-old boy with a posterior interosseous nerve injury after an ulnar osteotomy for a chronic Monteggia lesion. Although the first consultant did an ulnar osteotomy to reduce the radial head, the posterior interosseous nerve palsy did not recover. Next we found that the posterior interosseous nerve had been drawn into the radiocapitellar joint. It is important to confirm interposition of the nerve at the radiocapitellar joint during corrective osteotomy for a chronic Monteggia lesion.

Child↗