Biomedical subjects

Takehiro Nakamura

Publications and source records attributed to Takehiro Nakamura.

At least 19 recordsLinked to original sources

PubMed2006

Skp2 controls adipocyte proliferation during the development of obesity.

The increase in the mass of adipose tissue during the development of obesity can arise through an increase in cell size, an increase in cell number, or both. Here we show that long term maintenance of C57BL/6 mice on a high fat diet (for approximately 25 weeks) induces an initial increase in adipocyte size followed by an increase in adipocyte number in white adipose tissue. The latter effect was found to be accompanied by up-regulation of expression of the gene for the F-box protein Skp2 as well as by downregulation of the cyclin-dependent kinase inhibitor p27(Kip1), a principal target of the SCF(Skp2) ubiquitin ligase, in white adipose tissue. Ablation of Skp2 protected mice from the development of obesity induced either by a high fat diet or by the lethal yellow agouti (A(y)) mutation, and this protective action was due to inhibition of the increase in adipocyte number without an effect on adipocyte hypertrophy. The reduction in the number of adipocyte caused by Skp2 ablation also inhibited the development of obesity-related insulin resistance in the A(y) mutant mice, although the reduced number of beta cells and reduced level of insulin secretion in Skp2-deficient mice resulted in glucose intolerance. Our observations thus indicate that Skp2 controls adipocyte proliferation during the development of obesity.

Adipocytes↗

PubMed2006

The role of complement C3 in intracerebral hemorrhage-induced brain injury.

Activation of the complement cascade contributes to brain injury after intracerebral hemorrhage (ICH). However, a recent study found that complement C5 deficient mice had enhanced ICH-induced brain injury. The present study, therefore, investigated the role of complement C3 (which is upstream from C5) in ICH. Male complement C3 deficient and sufficient mice had an intracerebral infusion of 30-muL autologous whole blood. The mice were killed and the brains were sampled for edema, Western blotting, immunohistochemistry and histologic analysis. Behavioral tests including forelimb use asymmetry test and corner turn were also performed before and after ICH. Compared to complement C3 sufficient mice, C3 deficient mice had less brain edema, lower hemeoxygenase-1 levels, less microglia activation and neutrophil infiltration around the clot after ICH. In addition, the C3-deficient mice had less ICH-induced forelimb use asymmetry deficits compared with C3-sufficient mice. These results suggest complement activation may affect heme metabolism and the inflammatory response after ICH suggesting that complement C3 is an important factor causing ICH-induced brain injury.

Animals↗

PubMed2006

Tumor necrosis factor-alpha increases in the brain after intracerebral hemorrhage and thrombin stimulation.

OBJECTIVE: The goals of this study were 1) to determine the effects of intracerebral hemorrhage (ICH) on brain tumor necrosis factor (TNF)-alpha levels, which are still controversial; 2) to investigate the role of TNF-alpha in ICH-induced brain injury; 3) to examine the effects of thrombin on brain TNF-alpha levels; and 4) to elucidate the role of TNF-alpha in thrombin-induced neuroprotection. METHODS: Autologous whole blood and thrombin were injected into the right caudate of rats or mice. Brain TNF-alpha was then determined by enzyme-linked immunosorbent assay and immunohistochemistry. Brain edema and neurological deficits were also examined. RESULTS: Perihematomal TNF-alpha levels increased after ICH. ICH-induced brain edema was less in TNF-alpha knockout mice compared with wild-type mice (P < 0.05). Intracerebral infusion of thrombin also caused an increase in brain TNF-alpha levels. Thrombin preconditioning reduced thrombin-induced brain edema, but this effect was not blocked by a neutralizing TNF-alpha antibody. CONCLUSION: Increase of perihematomal TNF-alpha levels contributes to brain edema formation after ICH. Thrombin may be a major mediator of ICH-induced TNF-alpha production, but thrombin-induced brain tolerance may not be TNF-alpha mediated.

Animals↗

PubMed2006

Long-term effects of experimental intracerebral hemorrhage: the role of iron.

OBJECT: Intracerebral hemorrhage (ICH) causes brain atrophy and neurological deficits. The mechanisms of brain atrophy after ICH are poorly understood, although recent evidence suggests that some ICH-induced brain injury results from the products of hemoglobin degradation, including iron. In this study the authors examine the role of iron in brain atrophy and neurological deficits following ICH. METHODS: Male Sprague-Dawley rats received an infusion of either 100 microl autologous whole blood or saline into the right caudate. Hematoxylin and eosin staining was used for histological examination, and iron levels and ferritin immunoreactivities were also examined. Deferoxamine was used as an iron chelator. Over the duration of the experiment, the rats underwent behavioral testing (forelimb placing, forelimb use asymmetry, and corner turn tests). Brain atrophy in the caudate with prolonged neurological deficits occurred after ICH. Although partial functional recovery occurred with time, residual neurological deficits were still detectable at 3 months postprocedure. Iron accumulation and ferritin upregulation were present in the ipsilateral caudate. Deferoxamine reduced brain atrophy and improved behavioral outcomes, and it also reduced brain ferritin immunoreactivity. CONCLUSIONS: An ICH results in an accumulation of iron in the brain that is not cleared within 3 months and that contributes to brain tissue loss and neurological deficits posthemorrhage. Iron chelation may be a useful therapy for patients with ICH.

Animals↗

PubMed2006

[Case of severe eosinophilic pneumonia, induced by several antibiotics, requiring mechanical ventilation].

We report a case of severe eosinophilic pneumonia induced by several antibiotics, requiring mechanical ventilation. A 44-year-old man had been admitted previously to a different hospital because of a high fever and dry cough continuing for a week. Although bacterial pneumonia was diagnosed and he had been treated with several antibiotics, his respiratory state worsened gradually and he was refered to our hospital with severe hypoxia. He needed mechanical ventilation on the fifth hospital day. TBLB identified eosinophilic pneumonia. Although we discontinued all antibiotics and started steroid therapy, he became feverish and his leukocyte count, which was neutrophil dominant, elevated again. We suspected bacterial pneumonia and administered antibiotics that he had never received before. However we had to discontinue these antibiotics soon because of a further inflammatory response. His condition then improved gradually and he was weaned from mechanical ventilation. It is rare for drug-induced eosinophilic pneumonia to become so severe that mechanical ventilation is necessary. We thought that an allergic reaction may have been induced by the series of several antibiotics, inducing severe pneumonia.

Adult↗

PubMed2005

Oxidative DNA injury after experimental intracerebral hemorrhage.

Our previous studies have demonstrated that DNA injury occurs in the brain after intracerebral hemorrhage (ICH). DNA damage can result from at least two pathways, either endonuclease-mediated DNA fragmentation or oxidative injury. The present study investigated the occurrence of the latter after ICH and the role of iron in such injury. Male Sprague-Dawley rats received an infusion of autologous whole blood or ferrous iron into the right basal ganglia. Control rats just had a needle insertion (sham). The rats were sacrificed 1, 3, or 7 days later. 8-Hydroxyl-2'-deoxyguanosine (8-OHdG) was analyzed by immunohistochemistry while the number of apurnic/apyrimidinic abasic sites (AP sites) was also quantified. 8-OHdG and AP sites are two hallmarks of DNA oxidation. Dinitrophenyl (DNP) was measured by Western blotting to compare the time course of protein oxidative damage to that of DNA. DNA repair Ku proteins were measured by Western blot analysis. DNA damage was also examined using DNA polymerase I-mediated biotin-dATP nick translation (PANT) labeling. An increase of 8-OHdG, AP sites and DNP levels and a decrease of Ku levels were observed. Abundant PANT-positive cells were also observed in the perihematomal area 3 days after ICH. In addition, intracerebral infusion of iron increased brain DNP levels and resulted in DNA injury. These results suggest that oxidative stress contributes to DNA damage and brain injury after ICH. Reducing DNA oxidative damage (for example, through iron chelation) may be a therapeutic target for ICH.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2005

Deletion of Cdkn1b ameliorates hyperglycemia by maintaining compensatory hyperinsulinemia in diabetic mice.

The protein p27(Kip1) regulates cell cycle progression in mammals by inhibiting the activity of cyclin-dependent kinases (CDKs). Here we show that p27(Kip1) progressively accumulates in the nucleus of pancreatic beta cells in mice that lack either insulin receptor substrate 2 (Irs2(-/-)) or the long form of the leptin receptor (Lepr(-/-) or db/db). Deletion of the gene encoding p27(Kip1) (Cdkn1b) ameliorated hyperglycemia in these animal models of type 2 diabetes mellitus by increasing islet mass and maintaining compensatory hyperinsulinemia, effects that were attributable predominantly to stimulation of pancreatic beta-cell proliferation. Thus, p27(Kip1) contributes to beta-cell failure during the development of type 2 diabetes in Irs2(-/-) and Lepr(-/-) mice and represents a potential new target for the treatment of this condition.

Animals↗

PubMed2005

Role of Krüppel-like factor 15 (KLF15) in transcriptional regulation of adipogenesis.

Krüppel-like zinc finger transcription factors (KLFs) play diverse roles during cell differentiation and development in mammals. We have now shown by microarray analysis that expression of the KLF15 gene is markedly up-regulated during the differentiation of 3T3-L1 preadipocytes into adipocytes. Inhibition of the function of KLF15, either by expression of a dominant negative mutant or by RNA interference, both reduced the expression of peroxisome proliferator-activated receptor gamma (PPARgamma) and blocked adipogenesis in 3T3-L1 preadipocytes exposed to inducers of adipocyte differentiation. However, the dominant negative mutant of KLF15 did not affect the expression of CCAAT/enhancer-binding protein beta (C/EBPbeta) elicited by inducers of differentiation in 3T3-L1 preadipocytes. In addition, ectopic expression of KLF15 in NIH 3T3 or C2C12 cells triggered both lipid accumulation and the expression of PPARgamma in the presence of inducers of adipocyte differentiation. Ectopic expression of C/EBPbeta, C/EBPdelta, or C/EBPalpha in NIH 3T3 cells also elicited the expression of KLF15 in the presence of inducers of adipocyte differentiation. Moreover, KLF15 and C/EBPalpha acted synergistically to increase the activity of the PPARgamma2 gene promoter in 3T3-L1 adipocytes. Our observations thus demonstrate that KLF15 plays an essential role in adipogenesis in 3T3-L1 cells through its regulation of PPAR gamma expression.

3T3-L1 Cells↗

PubMed2005

Holo-transferrin and thrombin can interact to cause brain damage.

BACKGROUND AND PURPOSE: Previous studies have suggested that delayed release of hemoglobin degradation products, particularly iron, is involved in intracerebral hemorrhage (ICH)-induced brain injury. However, a recent study found evidence of iron-induced brain injury soon after ICH. This study, therefore, examined whether another iron-containing component of blood, holo-transferrin (holo-Tf), might also induce brain injury either alone or in combination with thrombin, another factor involved in early ICH-induced brain injury. METHODS: Male Sprague-Dawley rats received an intracerebral infusion of holo-Tf, apo (noniron-loaded)-Tf, thrombin, or a combination of Tf with thrombin into the right basal ganglia. The rats were euthanized 24 hours later for measurement of brain edema and assessment of DNA damage (single- and double-strand breaks and 8-hydroxyl-2'-deoxyguanosine immunohistochemistry). Iron distribution was examined histochemically. RESULTS: Holo-Tf, apo-Tf, and the dose of thrombin used (1 U) all failed to induce brain edema when administered alone. However, the combination of holo-Tf with thrombin (but not apo-Tf with thrombin) caused brain edema, DNA damage, and intracellular iron accumulation in the ipsilateral basal ganglia. CONCLUSIONS: These results suggest that in addition to hemoglobin-bound iron, Tf-bound iron may contribute to ICH-induced brain injury and that thrombin may contribute to the latter by facilitating cellular iron uptake.

Animals↗

PubMed2005

Parietal lipomeningocele--case report.

A 2-month-old female infant had had a parietal mass since birth. Neuroimaging revealed a lipoma under the splenium of the corpus callosum that was connected to the subcutaneous lipoma via a bone defect in the cranium bifidum of the parietal region. At the age of 5 months, partial resection of only the extracranial mass was carried out. The histological diagnosis was lipoma. She grew up normally without neurological disorders during follow up for 12 years after the surgery. In the present case, the intracranial lipoma was associated with the cranium bifidum, and dysraphism was possibly involved in the pathogenesis. Resection of only the extracranial subcutaneous tumor can be performed for cosmetic reasons.

Brain Neoplasms↗

PubMed2005

Improvement of cerebral arterial stenosis associated with Basedow's disease. Case report.

A 29-year-old female presented with Basedow's disease manifesting as sudden vomiting, diarrhea, fever over 38 degrees C, transient aphasia, and numbness in her extremities. These symptoms were considered due to cerebral ischemia at a local clinic. Magnetic resonance angiography indicated stenosis of the bilateral distal internal carotid arteries and the bilateral proximal anterior cerebral and middle cerebral arteries. Thyroid swelling and exophthalmos were observed. She was transferred to our hospital. Endocrine function tests showed hyperthyroidism. The diagnosis was Basedow's disease. Her symptoms disappeared after receiving intravenous drip infusion of fluid replacement, and antithyroid and antiplatelet medication. After she became euthyroid, cerebral angiography and magnetic resonance angiography revealed improvement of the stenosis of the cerebral arteries. Stenosis of the terminal portion of the internal carotid artery associated with Basedow's disease is extremely rare. Conservative treatment mainly including antithyroid medications for Basedow's disease, and antiplatelet drugs and intravenous replacement fluid for the ischemic manifestations should be the first choice of treatment unless immediate vascular reconstruction is necessary.

Adult↗

PubMed2005

Mechanical thrombolysis for treatment of acute sinus thrombosis--case report.

A 55-year-old woman presented with consciousness disorders. Computed tomography revealed hemorrhage in the left temporoparietal region. The angiographic diagnosis was progressive sinus thrombosis from the superior sagittal sinus to the bilateral transverse sinuses. Her condition deteriorated despite heparin administration. Therefore, mechanical thrombolysis was performed for sinus thrombosis using a balloon catheter, in addition to supportive thrombolytic therapy with urokinase, resulting in sinus patency. Mechanical thrombolysis is an effective therapeutic modality for sinus thrombosis refractory to heparin administration.

Catheterization↗

PubMed2005

Estrogen therapy for experimental intracerebral hemorrhage in rats.

OBJECT: The aims of this study were to determine the following: whether there are sex differences in intracerebral hemorrhage (ICH) induced brain injury in rats, whether delayed administration of 17beta-estradiol can reduce ICH-induced brain damage, and whether these effects are estrogen receptor (ER)-dependent. METHODS: Male and female Sprague-Dawley rats received an infusion of 100 microl autologous whole blood into the right basal ganglia. Twenty-four hours later the rats were killed. The effects of 17beta-estradiol on ICH-induced brain injury were examined by measuring brain edema and neurological deficits. Both ER-alpha and hemeoxygenase (HO)-1 were investigated through Western blot and immunohistochemical analysis. Brain edema was significantly less severe in female compared with that in male rats. The ER antagonist ICI 182,780 exacerbated ICH-induced brain edema in female but not in male rats, indicating that ER-alpha activation during ICH is protective in female rats. Administration of exogenous 17beta-estradiol in male, but not in female, rats significantly attenuated brain edema, neurological deficits, and ICH-induced changes in HO-1 when given 2 hours after hemorrhage. The effects of exogenous 17beta-estradiol occurred through an ER-independent mechanism. CONCLUSIONS: Results in this study indicate that 17beta-estradiol could be a potential therapeutic agent for ICH.

Animals↗

PubMed2004

Role of MAPK phosphatase-1 (MKP-1) in adipocyte differentiation.

Both time-dependent modulation of intracellular signaling molecules and sequential induction of transcriptional regulators are essential for the differentiation of preadipocytes into adipocytes. We have now shown that the activity, but not the abundance, of p42/p44 mitogen-activated protein kinase (MAPK) is down-regulated during adipocyte differentiation. This decrease in p42/p44 MAPK activity does not appear to be a direct effect of hormonal inducers of differentiation but rather represents a characteristic event of adipocyte differentiation that is achieved through a persistent change in intracellular signaling. Although the phosphorylation or abundance of MEK, an upstream kinase for p42/p44 MAPK, was not altered during differentiation, the abundance of MAPK phosphatase-1 (MKP-1), a negative regulator of p42/p44 MAPK, was increased with a time course similar to that of the down-regulation of p42/p44 MAPK activity. Ectopic expression of MKP-1 in preadipocytes reduced and depletion of endogenous MKP-1 in mature adipocytes increased the activity of p42/p44 MAPK. Prevention of the up-regulation of MKP-1 abundance in preadipocytes by expression of Mkp-1 antisense RNA resulted in persistence of p42/p44 MAPK activation and blocked differentiation, effects that were reversed by the MEK inhibitor PD98059. These results suggest that MKP-1 plays an essential role in adipocyte differentiation through down-regulation of p42/p44 MAPK activity.

3T3-L1 Cells↗

PubMed2004

Delayed precursor cell markers expression in hippocampus following cold-induced cortical injury in mice.

The purpose of this study was to examine the possibility of neuronal remodeling and repair after cold-induced brain injury using immunoassay of nestin and 3CB2 (potential precursor cell markers). Male ddN strain mice were subjected to cold-induced cortical injury. Animals were divided into the following six groups: (1) 1 day after injury, (2) 1 week after injury, (3) 2 weeks after injury, (4) 1 month after injury, (5) sham controls, and (6) normal controls. Western blot analysis (n = 3 in each group) and histological examination (n = 5 in each group) were performed. At 1 day and 1 week after injury, TUNEL-positive cells were observed, while immunoreactivity of nestin and 3CB2 was absent. At 1 month after injury, expression of both nestin and 3CB2 was observed in the ipsilateral hippocampus. Nestin was expressed in GFAP- or 3CB2-positive astrocytes at 1 month after injury, and nestin expression with TUC-4 (immature neuron marker) was present in the hippocampal cell layer. The findings demonstrate delayed nestin expression in both glia and neuronlike cells after brain injury. The present study suggests that the delayed nestin expression in glia and neuron-like cells might be part of the adaptation to injury.

Animals↗

PubMed2004

Intracerebral hemorrhage in mice: model characterization and application for genetically modified mice.

Gene knockout or transgenic animals may assist in elucidating the mechanisms of brain injury after intracerebral hemorrhage (ICH). However, almost all commercially available transgenic or knockout animals are mice. The purpose of this study was to develop an ICH model in mice and to investigate the influence of gender and complement C5 genetic differences on outcome after ICH. Male and female C57BL/6 mice and C5-deficient and -sufficient control mice were anesthetized and then received an injection of 30 microL autologous whole blood into the right basal ganglia. Brain water content was studied at 1 and 3 days after ICH. Behavioral tests (fore-limb use asymmetry and corner turn test) were performed at 1, 3, 7, 14, 21, or 28 days after ICH. In male mice, brain water content was significantly increased in the ipsilateral basal ganglia 1 and 3 days after ICH, compared with saline injection controls (P < 0.01). There were marked neurological deficits 1 and 3 days after ICH, with progressive recovery over 28 days. In contrast, although brain edema and behavioral deficits were similar at 1 day after ICH in female and male mice, female mice showed reduced edema at 3 days and a faster recovery of behavioral deficits after ICH. 17 beta-estradiol treatment in male mice markedly reduced ICH-induced edema (P < 0.01). Brain water content was significantly increased in C5-deficient mice compared with C5-sufficient at 3 days after ICH (P < 0.05). These findings suggest that the mouse ICH model is a reproducible and feasible model. These results also suggest that gender and complement C5 are factors affecting brain injury after ICH.

Animals↗

PubMed2004

Deferoxamine-induced attenuation of brain edema and neurological deficits in a rat model of intracerebral hemorrhage.

OBJECT: Previous studies undertaken by the authors have indicated that iron accumulation and oxidative stress in the brain contribute to secondary brain damage after intracerebral hemorrhage (ICH). In the present study the authors investigate whether deferoxamine, an iron chelator, can reduce ICH-induced brain injury. METHODS: Male Sprague-Dawley rats each received an infusion of 100 microl of autologous whole blood into the right basal ganglia and were killed 1, 3, or 7 days later. Iron distribution was examined histochemically (enhanced Perls reaction). The effects of deferoxamine on ICH-induced brain injury were examined by measuring brain edema and neurological deficits. Immunohistochemical analysis was performed to investigate 8-hydroxyl-2'-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage, and Western blot analysis was performed to measure the amount of apurinic/apyrimidinic endonuclease/redox effector factor-1 (APE/Ref-1), a repair mechanism for DNA oxidative damage. Iron accumulation was observed in the perihematomal zone from 1 day after ICH. Deferoxamine attenuated brain edema, neurological deficits, and ICH-induced changes in 8-OHdG and APE/Ref-1. CONCLUSIONS: Deferoxamine and other iron chelators may be potential therapeutic agents for ICH. They may act by reducing the oxidative stress caused by the release of iron from the hematoma.

Animals↗

PubMed2004

[Disorder of carbohydrate metabolism].

The worldwide epidemic of type 2 diabetes and impaired glucose tolerance is a crucial health problem. Since disorder of carbohydrate metabolism causes arteriosclerosis in combination with other metabolic abnormalities such as hypertension, hyperlipidemia and obesity, it has now been recognized as one manifestation of the metabolic syndrome, a condition characterized by insulin resistance. In this article, we summarize the current our knowledge on how disorder of carbohydrate metabolism influences insulin resistance and arteriosclerosis in part of metabolic syndrome.

Carbohydrate Metabolism↗