PubMed Health⌕ Search

Biomedical subjects

Koji Okamoto

Publications and source records attributed to Koji Okamoto.

At least 19 recordsLinked to original sources

Genetic Testing Unveils a Novel Thrombospondin-1 Domain Containing Protein 1 Gene Variant as the Cause of Chronic Edema in a 79-Year-Old Woman.

Edema requires management tailored to its underlying etiology; however, in some cases the cause remains elusive. We describe a 79-year-old woman with lifelong unexplained peripheral edema. Comprehensive evaluation excluded common etiologies such as heart failure, renal dysfunction, and venous thrombosis. Whole-genome sequencing identified a novel homozygous splice-site variant (NM_018676.4:c.58+2T>G) in the thrombospondin-1 domain-containing protein 1 (THSD1) gene, which has previously been associated with non-immune hydrops fetalis (NIHF). This report describes, to our knowledge, the first elderly patient with chronic peripheral edema harboring a likely pathogenic THSD1 variant, suggesting that THSD1-related disease may, in rare instances, persist beyond the perinatal period and present into late adulthood. Although causality cannot be established definitively from a single case, the findings highlight the potential utility of genetic testing in adults with chronic unexplained edema.

chronic edema↗

Domains 16 and 17 of tropoelastin in elastic fibre formation.

Naturally occurring mutations are useful in identifying domains that are important for protein function. We studied a mutation in the elastin gene, 800-3G>C, a common disease allele for SVAS (supravalvular aortic stenosis). We showed in primary skin fibroblasts from two different SVAS families that this mutation causes skipping of exons 16-17 and results in a stable mRNA. Tropoelastin lacking domains 16-17 (Delta16-17) was synthesized efficiently and secreted by transfected retinal pigment epithelium cells, but showed the deficient deposition into the extracellular matrix compared with normal as demonstrated by immunofluorescent staining and desmosine assays. Solid-phase binding assays indicated normal molecular interaction of Delta16-17 with fibrillin-1 and fibulin-5. However, self-association of Delta16-17 was diminished as shown by an elevated coacervation temperature. Moreover, negative staining electron microscopy confirmed that Delta16-17 was deficient in forming fibrillar polymers. Domain 16 has high homology with domain 30, which can form a beta-sheet structure facilitating fibre formation. Taken together, we conclude that domains 16-17 are important for self-association of tropoelastin and elastic fibre formation. This study is the first to discover that domains of elastin play an essential role in elastic fibre formation by facilitating homotypic interactions.

Amino Acid Sequence↗

KAP1 dictates p53 response induced by chemotherapeutic agents via Mdm2 interaction.

KAP1 recruits many proteins involved in gene silencing and functions as an integral part of co-repressor complex. KAP1 was identified as Mdm2-binding protein and shown to form a complex with Mdm2 and p53 in vivo. We examined the role of KAP1 in p53 activation after the treatment of cells with different types of external stresses. KAP1 reduction markedly enhanced the induction of p21, a product of the p53 target gene, after treatment with actinomycin D or gamma-irradiation, but not with camptothecin. Treatment with actinomycin D, but not with camptothecin, augmented the interaction of p53 with Mdm2 and KAP1. Further, KAP1 reduction in actinomycin D-treated cells facilitated cell cycle arrest and negatively affected clonal cell growth. Thus, the reduction of KAP1 levels promotes p53-dependent p21 induction and inhibits cell proliferation in actinomycin D-treated cells. KAP1 may serve as a therapeutic target against cancer in combination with actinomycin D.

Antineoplastic Agents↗

Screening of C60 crystallization using a microfluidic system.

We have carried out screening of C60 crystallization using a simple liquid/liquid interfacial precipitation method in a microfluidic device. By controlling the time, temperature, and concentration, various metastable phases of C60 crystals were found, including tubes, spheres, open-ended hollow columns, stars, branches, and trees. The obtained C60 crystal shapes are similar to those of snow crystals. These findings suggest an urgent need to screen C60 crystallization for the development of fullerene C60 drugs.

Crystallization↗

Interaction between liposomes and RBC in microvessels in vivo.

Liposomes are phospholipid vesicles that can serve as carriers of biologically active agents in vitro and in vivo. Here, we describe the movement of liposomes suspended with blood flowing in capillaries. Liposomes were coated with a polymer to extend their lifespan in rat mesenteric blood vessels and detected by fluorescent staining. Liposome activity was observed by intravital microscopy using a high-speed camera system at 5 and 60 min after liposome administration. Liposome velocity was determined using two-dimensional cross-correlation, and blood flow was measured by high-resolution PIV (particle image velocimetry). The results showed that the motion of polymer-coated liposome followed the phase averaged velocity distribution of heartbeats while flowing with red blood cells in microvessels. Liposome particles tend to move toward the near blood vessel wall in the low velocity of blood flow.

Animals↗

The novel F-box protein Mfb1p regulates mitochondrial connectivity and exhibits asymmetric localization in yeast.

Although it is clear that mitochondrial morphogenesis is a complex process involving multiple proteins in eukaryotic cells, little is known about regulatory molecules that modulate mitochondrial network formation. Here, we report the identification of a new yeast mitochondrial morphology gene called MFB1 (YDR219C). MFB1 encodes an F-box protein family member, many of which function in Skp1-Cdc53/Cullin-F-box protein (SCF) ubiquitin ligase complexes. F-box proteins also act in non-SCF complexes whose functions are not well understood. Although cells lacking Mfb1p contain abnormally short mitochondrial tubules, Mfb1p is not essential for known pathways that determine mitochondrial morphology and dynamics. Mfb1p is peripherally associated with the mitochondrial surface. Coimmunoprecipitation assays reveal that Mfb1p interacts with Skp1p in an F-box-dependent manner. However, Mfb1p does not coimmunoprecipitate with Cdc53p. The F-box motif is not essential for Mfb1p-mediated mitochondrial network formation. These observations suggest that Mfb1p acts in a complex lacking Cdc53p required for mitochondrial morphogenesis. During budding, Mfb1p asymmetrically localizes to mother cell mitochondria. By contrast, Skp1p accumulates in the daughter cell cytoplasm. Mfb1p mother cell-specific asymmetry depends on the F-box motif, suggesting that Skp1p down-regulates Mfb1p mitochondrial association in buds. We propose that Mfb1p operates in a novel pathway regulating mitochondrial tubular connectivity.

Amino Acid Motifs↗

Efficacy of darbepoetin in doxorubicin-induced cardiorenal injury in rats.

This study was intended to elucidate the efficacy of an erythropoietin analog in cardiorenal dysfunction syndrome using a rodent model. Cardiorenal dysfunction was induced using doxorubicin hydrochloride (DXR). Lower doses (3 microg/kg) and higher doses (30 microg/kg) of darbepoetin alfa (DA) were used for intervention. Blood examinations for creatinine, blood urea nitrogen, iron, and hemoglobin were performed until 11 weeks after starting DA administration. Urine collection was performed 10 weeks after starting DA, and protein, iron, and N-acetyl-beta-D-glucosaminidase levels and antioxidation capacity of DA were determined. The dry left ventricular heart weight was measured, when the animals were sacrificed 11 weeks after starting DA administration. Histological analyses were performed for interstitial fibrotic changes and iron deposition in the kidney. Administration of DA markedly improved anemia to the normal control level and significantly alleviated DXR-induced increases of creatinine, blood urea nitrogen, renal interstitial fibrosis, renal iron deposition, and dry left ventricular weight, but serum and urinary iron and urinary protein and N-acetyl-beta-D-glucosaminidase levels were unchanged. The urinary total radical-trapping antioxidant capacity was improved to the normal control level in DA-treated animals. DA reduced the DXR-induced cardiorenal injury. This improvement was achieved, when anemia was corrected to the normal control level.

Acetylglucosaminidase↗

Measurement of RBC deformation and velocity in capillaries in vivo.

Red blood cells (RBC) become deformed while flowing through capillaries. We captured images of blood flow in capillaries and of RBC in the rat mesentery using a high-speed camera at 2000 frames/s and then directly measured and estimated the deformation and velocity of RBC in a non-uniform capillary. The distribution of the capillary diameter was determined by image processing. We applied a deformation index and simple modeling to observe RBC deformation in capillaries. The average capillary diameter was approximately 6.2 microm, and the average velocity of RBC was about 1.85 mm/s. The average deformation index of RBC in the capillary was about 1.55. The present results showed that RBC in capillaries generally assume a specific shape depending on external forces such as the velocity of the blood flow and capillary diameter in vivo.

Animals↗

Peripheral arterial occlusive disease is more prevalent in patients with hemodialysis: comparison with the findings of multidetector-row computed tomography.

BACKGROUND: Peripheral arterial occlusive disease (PAOD) influences the mortality of patients on hemodialysis therapy. Although the ankle-brachial pressure index (ABI) is used widely to detect PAOD, it yields false-negative results because of calcifications of vascular walls. To more accurately assess the prevalence of PAOD, we investigated which noninvasive method, among ABI, toe-brachial pressure index, transcutaneous Po(2), and skin perfusion pressure (SPP), had superior sensitivity and specificity to the others. METHODS: Multidetector-row computed tomography was performed in 36 hemodialysis patients. We then compared the 4 noninvasive methods with findings of multidetector-row computed tomography and calculated the sensitivity and specificity of each method by means of receiver operating characteristic analysis. Irrespective of symptoms, PAOD is defined as the presence of complete obstruction in the case of lesions below the knee or more than 75% stenosis for lesions above the knee. RESULTS: Seven of 36 patients (19.4%) had an ABI less than 0.9. Sensitivity of the ABI was only 29.9%, whereas an SPP set at 50 mm Hg was more accurate, with sensitivity of 84.9% and specificity of 76.9%. A total of 41.4% of patients had an SPP less than 50 mm Hg. For lesions located above the knee, toe-brachial pressure index provided sensitivity of 91.7% and specificity of 86.7%. CONCLUSION: SPP is the most useful tool for detecting PAOD in hemodialysis patients, with accuracy of 84.9%. There is a strong possibility that more patients than previously expected have early PAOD.

Adult↗

Far lateral extraforaminal facet cyst causing L5 radiculopathy.

Most synovial cysts of the lumbar spine appear as intraspinal extradural masses adjacent to the facet joint. Almost all symptomatic synovial cysts are located within the spinal canal and or the neural foramen. To our knowledge, only 6 cases of symptomatic extraspinal synovial cysts have been described in the literature. The authors report a case of lumbar radiculopathy caused by a synovial cyst located in the far lateral extraforaminal area. The patient underwent decompression of the L5 nerve root with recapping right isthmectomy and facetectomy. Postoperative recovery was uneventful, and the patient was totally pain free with no motor deficit. Symptomatic synovial cysts are uncommon lesions that are associated with degenerative disease of the spine. Juxtafacet cysts should be considered in the differential diagnosis of space-occupying lesions at the extraforaminal areas. Recapping isthmectomy and facetectomy are useful procedures for a synovial cyst located in the far lateral extraforaminal area.

Cysts↗

LDL-apheresis reduces P-Selectin, CRP and fibrinogen -- possible important implications for improving atherosclerosis.

Although it is known that LDL-apheresis improves coronary artery stenosis (CAS) as well as ischemic limbs seen in patients with peripheral arterial occlusive disease (PAOD), the underlying mechanisms remain still unknown. LDL-apheresis might exert its favorable action through anti-inflammatory effects. We studied whether or not serum or plasma levels of P-selectin, high sensitivity C-reactive protein (hsCRP), monocyte chemoattractant protein-1 (MCP-1) or fibrinogen could be reduced in patients with PAOD before and after 10 sessions of LDL-apheresis. Sixteen patients (12 patients with hemodialysis, HD) with PAOD were enrolled in the present study. LDL-apheresis was carried out 10 times (treated plasma of 3000 mL) over 5 weeks. Serum levels of P-selectin were significantly reduced from 516 +/- 153 to 290 +/- 52 ng/mL before and after 10-sessions of LDL-apheresis, respectively (P < 0.05). Likewise, serum levels of hsCRP decreased from 9.118 +/- 2.649 to 5.587 +/- 2.445 mg/L (P < 0.01); and plasma fibrinogen levels statistically decreased from 196 +/- 9.82 to 149 +/- 7.97 mg/dL (P < 0.01), whereas serum levels of MCP-1 were not significantly changed. The favorable actions of LDL-apheresis might include anti-inflammatory effects, which could lead to an improvement of CAS and PAOD. Moreover, this intervention might be applicable for patients with atherosclerotic cardiovascular disorders, particularly in patients with HD.

Adult↗

Differential roles of ATM- and Chk2-mediated phosphorylations of Hdmx in response to DNA damage.

The p53 tumor suppressor plays a major role in maintaining genomic stability. Its activation and stabilization in response to double strand breaks (DSBs) in DNA are regulated primarily by the ATM protein kinase. ATM mediates several posttranslational modifications on p53 itself, as well as phosphorylation of p53's essential inhibitors, Hdm2 and Hdmx. Recently we showed that ATM- and Hdm2-dependent ubiquitination and subsequent degradation of Hdmx following DSB induction are mediated by phosphorylation of Hdmx on S403, S367, and S342, with S403 being targeted directly by ATM. Here we show that S367 phosphorylation is mediated by the Chk2 protein kinase, a downstream kinase of ATM. This phosphorylation, which is important for subsequent Hdmx ubiquitination and degradation, creates a binding site for 14-3-3 proteins which controls nuclear accumulation of Hdmx following DSBs. Phosphorylation of S342 also contributed to optimal 14-3-3 interaction and nuclear accumulation of Hdmx, but phosphorylation of S403 did not. Our data indicate that binding of a 14-3-3 dimer and subsequent nuclear accumulation are essential steps toward degradation of p53's inhibitor, Hdmx, in response to DNA damage. These results demonstrate a sophisticated control by ATM of a target protein, Hdmx, which itself is one of several ATM targets in the ATM-p53 axis of the DNA damage response.

14-3-3 Proteins↗

18F-fluorodeoxyglucose positron emission tomography in a case of retroperitoneal fibrosis.

A patient with recurrent abdominal pain was admitted to our hospital. Computed tomography showed a soft dense mass surrounding the abdominal aorta at the infrarenal level, which was compatible with retroperitoneal fibrosis. (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography showed abnormal uptake of (18)F-FDG into these lesions. Two months after the initiation of corticosteroid therapy, the abnormal uptake of (18)F-FDG had ceased along with a reduction in the fibrous mass surrounding the abdominal aorta.

Abdominal Pain↗

Attenuation of folic acid-induced renal inflammatory injury in platelet-activating factor receptor-deficient mice.

Platelet-activating factor (PAF), a potent lipid mediator with various biological activities, plays an important role in inflammation by recruiting leukocytes. In this study we used platelet-activating factor receptor (PAFR)-deficient mice to elucidate the role of PAF in inflammatory renal injury induced by folic acid administration. PAFR-deficient mice showed significant amelioration of renal dysfunction and pathological findings such as acute tubular damage with neutrophil infiltration, lipid peroxidation observed with antibody to 4-hydroxy-2-hexenal (day 2), and interstitial fibrosis with macrophage infiltration associated with expression of monocyte chemoattractant protein-1 and tumor necrosis factor-alpha in the kidney (day 14). Acute tubular damage was attenuated by neutrophil depletion using a monoclonal antibody (RB6-8C5), demonstrating the contribution of neutrophils to acute phase injury. Macrophage infiltration was also decreased when treatment with a PAF antagonist (WEB2086) was started after acute phase. In vitro chemotaxis assay using a Boyden chamber demonstrated that PAF exhibits a strong chemotactic activity for macrophages. These results indicate that PAF is involved in pathogenesis of folic acid-induced renal injury by activating neutrophils in acute phase and macrophages in chronic interstitial fibrosis. Inhibiting the PAF pathway might be therapeutic to kidney injury from inflammatory cells.

Animals↗

Lumbar chance fracture in an adult snowboarder: unusual mechanism of a chance fracture.

STUDY DESIGN: A case of a Chance fracture in an adult snowboarder following a fall is presented. The mechanism of this fracture is reported. OBJECTIVE: To increase awareness of the spinal injuries in snowboarders and to propose the mechanism of this unusual fracture. SUMMARY OF BACKGROUND DATA: Chance fractures rarely occur in adults and are very unusual in children. Nearly all of the reported cases are in conjunction with lap-type seat belt injuries. To the authors' knowledge, this is the first reported case of a lumbar Chance fracture in an adult snowboarder. METHODS: A 25-year-old snowboarder sustained an L1 Chance fracture following a fall backward. The patient was placed in a hyperextension cast, and the cast was changed to a thoracolumbar orthosis after 12 weeks. RESULTS: Complete bony union was obtained with body cast immobilization, and an excellent functional restoration was obtained. CONCLUSIONS: Chance fractures are horizontal splitting fractures of the posterior elements of the vertebrae, and the mechanism of the injury is that of a hyperflexion of the spine over a fulcrum. A Chance-type fracture can be seen in an adult snowboarder, when acute hyperflexion of the spine occurs following a fall backward.

Accidental Falls↗

Recognition sites of glycine tRNA for glycyl-tRNA synthetase from hyperthermophilic archaeon, Aeropyrum pernix K1.

To elucidate the tRNA recognition sites of glycine tRNA from an extreme thermophilic and aerobic archaeon, Aeropyrum pernix K1, we examined glycylation activities using in vitro mutant glycine tRNA transcripts and recombinant A. pernix glycyl-tRNA synthetase. The recognition nucleotides were determined to be C35 and C36 of anticodon, C2-G71 and G3-C70 base-pairs of acceptor stem. However, discriminator base A73 was not recognized by glycyl-tRNA synthetase.

Aeropyrum↗

DNA damage-induced phosphorylation of MdmX at serine 367 activates p53 by targeting MdmX for Mdm2-dependent degradation.

Understanding how p53 activity is regulated is crucial in elucidating mechanisms of cellular defense against cancer. Genetic data indicate that Mdmx as well as Mdm2 plays a major role in maintaining p53 activity at low levels in nonstressed cells. However, biochemical mechanisms of how Mdmx regulates p53 activity are not well understood. Through identification of Mdmx-binding proteins, we found that 14-3-3 proteins are associated with Mdmx. Mdmx harbors a consensus sequence for binding of 14-3-3. Serine 367 (S367) is located within the putative binding sequence for 14-3-3, and its substitution with alanine (S367A) abolishes binding of Mdmx to 14-3-3. Transfection assays indicated that the S367A mutation, in cooperation with Mdm2, enhances the ability of Mdmx to repress the transcriptional activity of p53. The S367A mutant is more resistant to Mdm2-dependent ubiquitination and degradation than wild-type Mdmx, and Mdmx phosphorylated at S367 is preferentially degraded by Mdm2. Several types of DNA damage markedly enhance S367 phosphorylation, coinciding with increased binding of Mdmx to 14-3-3 and accelerated Mdmx degradation. Furthermore, promotion of growth of normal human fibroblasts after introduction of Mdmx is enhanced by the S367 mutation. We propose that Mdmx phosphorylation at S367 plays an important role in p53 activation after DNA damage by triggering Mdm2-dependent degradation of Mdmx.

14-3-3 Proteins↗