Biomedical subjects

Shiro Jimi

Publications and source records attributed to Shiro Jimi.

10 recordsLinked to original sources

PubMed2007

Thrombocytopenia in association with splenomegaly during granulocyte-colony-stimulating factor treatment in mice is not caused by hypersplenism and is resolved spontaneously.

BACKGROUND: Granulocyte-colony-stimulating factor (G-CSF) is used for hematopoietic progenitor cell (HPC) mobilization. Platelet (PLT) counts decrease during G-CSF administration. The mechanisms have not been determined, however. Because splenic pooling of PLTs caused thrombocytopenia in patients with splenomegaly and splenic enlargement was observed in G-CSF-treated donors, it was hypothesized that hypersplenism might cause G-CSF-induced thrombocytopenia. STUDY DESIGN AND METHODS: Mice were treated with several concentrations of G-CSF, and PLT count was measured. Because transfused PLTs should be cleared rapidly from the blood stream under hypersplenic state, PLT life span was studied. To determine direct role of spleen on thrombocytopenia, G-CSF was given to splenectomized mice. Because PLT count did not decrease in G-CSF-expressing transgenic mice, G-CSF was given to mice for a longer period of time and PLT count was investigated. RESULTS: PLT counts decreased while spleen weight increased in a dose-dependent manner by G-CSF treatment. No significant difference in PLT life span was found between G-CSF-treated and control mice. Histologic analysis showed no significant increase in PLT numbers trapped in either spleen or other tissue after PLT transfusion in G-CSF-treated mice. In splenectomized mice as well as in normal mice, G-CSF caused thrombocytopenia. When G-CSF was given to mice for a longer period of time, PLT counts decreased during the first 7 days and thereafter began to increase followed by returning to baseline on Day 15. CONCLUSION: Thrombocytopenia coincided with splenomegaly during G-CSF treatment, but hypersplenism was not responsible for thrombocytopenia. G-CSF-induced thrombocytopenia was a transient event and improved spontaneously despite continual G-CSF treatment.

Animals↗

PubMed2006

A novel method for preserving human lungs using a super-cooling system.

PURPOSE: To ensure the suitable preservation of isolated lungs, a super-cooling system was used to cool water to temperatures as low as -5 degrees C without freezing. DESCRIPTION: After lung tissues were obtained from patients with lung cancer, they were kept at -5 degrees C or 4 degrees C for as many as 5 days, and then they were histologically and biochemically examined. To evaluate biochemical stability, tissues after storage were passively sensitized with immunoglobulin E and then incubated with anti-immunoglobulin-E antibody. EVALUATION: Although tissues preserved at -5 degrees C for 5 days had an almost normal appearance with intact cilia on bronchial epithelium and normal endothelium, tissues stored at 4 degrees C showed degradation of these structures. Single-stranded DNA, a sign of DNA cleavage, was frequently noted in tissues stored at 4 degrees C, but only rarely observed at -5 degrees C. A significant amount of cysteinyl-leukotrienes was generated from tissues stored at -5 degrees C for 3 days, but there was no response to antibody stimulation from tissues stored at 4 degrees C. CONCLUSIONS: Super-cooling systems may provide useful applications as a novel preserving method.

Aged↗

PubMed2005

Histochemical characteristics of soleus muscle in angiotensin-converting enzyme gene knockout mice.

We examined the histochemical characteristics of soleus muscle in the angiotensin-converting enzyme (ACE) gene (Ace in mice, ACE in humans) knockout mice. Serial sections of soleus muscle of wild-type (Ace+/+, n=20) and heterozygous mutant (Ace+/-, n=24) mice were stained for myosin adenosine triphosphatase activity to identify different muscle fiber types. Capillaries were visualized by amylase-periodic acid-Schiff staining. ACE activity in the serum and gastrocnemius muscle was higher in male mice than in female mice. Female and male Ace+/- mice had markedly lower ACE activity in the serum and the gastrocnemius muscle than did female and male Ace+/+ mice, respectively. In both male and female mice, the composition of fiber types (type I and IIa) did not differ significantly between Ace+/+ and Ace+/- mice. There was no significant gender difference in capillary density. Ace+/- mice had significantly more capillaries around type IIa fibers (5.44 +/- 0.18 vs. 5.01 +/- 0.13, p<0.05) than Ace+/+ mice. The differences in the number of capillaries around type I fibers and in the number of capillaries around per fiber (capillary:fiber ratio) between Ace+/- and Ace+/+ mice were not significant (p<0.1). There was no significant difference in the mean cross-sectional area occupied by one capillary and the number of capillaries per fiber area between Ace+/+ and Ace+/- mice. In conclusion, knockout of the Ace gene in mice increased capillary density, as expressed by the mean number of capillaries around type IIa fibers. This finding suggests a possible mechanism for the cardioprotective effects of ACE inhibitors.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2004

Long-term cadmium exposure accelerates age-related mitochondrial changes in renal epithelial cells.

Long-term cadmium exposure leads to mitochondrial dysfunction in the proximal tubular epithelial cells. Mitochondrial DNA deletion may contribute to the pathogenesis of cadmium-induced nephropathy. The aim of our study is to clarify the accumulation of mitochondrial DNA deletion and mitochondrial dysfunction in the renal cortex of rats injected three times/week with 1 ml of 1 mM CdCl2 or saline for 80 weeks. After 40-week cadmium injection, mitochondrial number diminished, and cadmium in the renal cortex reached a saturation level. At this time interval, nearly 30% of cadmium in the whole cell fraction was found in the mitochondria. Cytochrome c oxidase (COX) activity in the proximal tubular epithelial cells decreased after 40-week exposure of cadmium. Oxidized phosphatidylcholine (oxPC) started to accumulate in the cytochrome c-positive mitochondria in some tubular epithelial cells after 80-week exposure. After 40 weeks, accumulation of the 4834-bp deletion in mitochondrial DNA was evident in both control and cadmium-treated groups. However, the amount of accumulated mitochondrial DNA deletion tended to increase after 40-week exposure, and was significantly greater after 80 weeks of exposure, compared to the control. Our results indicate that long-term cadmium exposure in rats accelerates accumulation of 4834-bp mitochondrial DNA deletions and impairment of mitochondrial function associated with accumulation of oxidized product.

Adenosine Triphosphate↗

PubMed2004

Mechanisms of cell death induced by cadmium and arsenic.

Cadmium (Cd) and arsenic (As) are known toxic metals in humans. As trioxide (As(2)0(3)) has been recently used as a mitochondria-targeting drug in acute promyelocytic leukemia. In the present study, we examined the intracellular action of these metals using rat kidney tubular cells and cells tolerant to the metals. The cells were cultured with CdCl(2) (1-10 micro M) or As(2)O(3) (1-2.5 micro M). Cells tolerant to Cd and As (Cd-T and As-T, respectively) were defined as cells that survived at toxic concentrations of each metal. Both Cd and As induced cell toxicity in a dose-dependent fashion, which was accompanied by fragmented DNA and decreased mitochondrial membrane potential. Intracellular glutathione (GSH) increased with the increase of Cd and As concentration. In Cd-T and As-T cells, GSH levels were twice those observed in normal cells. When each metal-tolerant culture was exposed to the other different metal, i.e., As or Cd, the protective property was maintained. However, when buthionine sulfoximine (BSO) was added to the metal-tolerant cultures, apoptosis was restored in both Cd-T and As-T. Our results indicate that (1) although GSH is increased in NRK52E by the addition of Cd and As, mitochondria-mediated apoptosis can be still induced, (2) the protective property against metal-induced cytotoxicity is identical in Cd-T and As-T cultures, and (3) although GSH was higher in the metal-tolerant cell lines, depression of GSH by BSO induced apoptosis. We conclude that Cd- and As-induced apoptosis is mediated by an identical mechanism involving intracellular GSH reactive oxidation.

Animals↗

PubMed2004

Cadmium-induced nephropathy in rats is mediated by expression of senescence-associated beta-galactosidase and accumulation of mitochondrial DNA deletion.

Long-term exposure to cadmium (Cd) induces perturbation of kidney proximal tubular epithelial cells. Mitochondrial dysfunction in renal cortical cells may contribute to the pathogenesis of Cd-induced nephropathy. In this study, we examined the accumulation of mitochondrial DNA (mtDNA) with a large deletion and cellular senescence in the renal cortex. Wistar rats at 8 weeks of age were intraperitoneally injected with 1 mL of 1 mM CdCl(2) or saline, 3 times/week for 5, 20, 40, or 80 weeks. Mitochondrial Cd content in the renal cortex was quantified by atomic absorption analysis. Cytochrome c oxidase (CCO) and senescence-associated beta-galactosidase (SA-beta-gal) activity were determined in renal cortex by enzyme-histochemistry. mtDNA in total DNA extracted from the renal cortex was amplified by PCR, and mtDNA deletions, including 4,834-bp (nt8118-nt12937) deletion, were determined and semiquantified. After 40 weeks of Cd injection, Cd levels in the renal cortex reached a saturation level, and 30% of the level of the whole-cell fraction was found in the mitochondria. CCO activity in the renal cortex, which was predominantly found in proximal tubular cells, decreased after 40 weeks of Cd exposure. Expression of SA-beta-gal was detected primarily in the proximal tubular cells and significantly increased after 80 weeks of Cd exposure. After 40 weeks of study, accumulation of 4,834-bp deletion in mtDNA was evident in both groups of rats; however, the amount of the deletion was significantly greater in Cd-treated rats than in control rats. Our results indicate that long-term Cd exposure induced a post-regenerative state of proximal tubular cells, which accelerated accumulation of 4,834-bp mtDNA deletions in the renal cortex, suggesting that Cd may be a senescence acceleration factor for kidney proximal tubular epithelial cells, which results in Cd-induced nephropathy.

Animals↗

PubMed2004

Basement membrane-type heparan sulfate proteoglycan (perlecan) and low-density lipoprotein (LDL) are co-localized in granulation tissues: a possible pathogenesis of cholesterol granulomas in jaw cysts.

BACKGROUND: As perlecan contains a low-density lipoprotein (LDL) receptor-like repeats in the second domain of its core protein, LDL may be bound to perlecan, which is rich in granulation tissues. We wanted to study if this is the case in the cyst wall of radicular cysts, which are often associated with cholesterol granuloma. METHODS: Thirty-three specimens of radicular cyst with cholesterol granulomas were immunohistochemically examined for comparative localizations of perlecan, apoprotein B (apo B), and oxidized LDL (Ox-LDL), and for mRNA expression levels for perlecan. RESULTS: Myxoid or edematous stroma of immature granulation tissues was strongly positive for perlecan and simultaneously for apo B and Ox-LDL. Macrophages including foamy cells scattered in the granulation tissues were also immunopositive for Ox-LDL and occasionally for apo B. In situ hybridization showed that fibroblasts, endothelial cells, and pericytes had strong signals for perlecan, which was also confirmed by RT-PCR. CONCLUSION: These results suggest that perlecan, which is abundantly produced and accumulated in the cyst wall of immature granulation tissue, traps Ox-LDL locally, and that Ox-LDL is phagocytosed by macrophages. Thus, LDL-laden foamy macrophages are aggregated in the granulation tissue, and free cholesterol from ruptured macrophages may be concentrated locally to be crystallized, which may induce foreign body granulomas in the cyst wall.

Animals↗

PubMed2003

Mitochondrial DNA deletion of proximal tubules is the result of itai-itai disease.

BACKGROUND: The pathogenesis of itai-itai disease continues to be controversial, although cadmium (Cd) poisoning which arises via polluted water and rice in Japan is likely involved. Until recently, however, a well-defined animal model for Cd intoxication was not available. An animal model for itai-itai disease was produced in rats by low-dose Cd treatment, intraperitoneally for a period of 70-80 weeks. Osteomalacia followed the renal damage. RESULTS: A gene deletion in the mitochondrial DNA was found in the mitochondria of the proximal tubule cells of rats with chronic Cd intoxication, as was shown by the increased smaller PCR product seen by gel electrophoresis in one DNA region, where ATPase and cytochrome oxidase genes are located. However, the PCR product was different from that seen with a gene deletion associated with aging: del4834bp. Renal damage from Cd intoxication initially caused mitochondrial dysfunction indicated by the disturbance in reabsorption in the proximal tubules and decreased amounts of ATP, ATPase, and cytochrome oxidase with gradually progressing tubular proteinuria, and, finally, chronic renal failure with tubulointerstitial damage throughout the renal cortex. These gave rise to osteomalacia, subsequently. CONCLUSION: We concluded that in Cd poisoning, a mitochondrial gene deletion in the mitochondria of the proximal tubule cells was the primary event for the pathogenesis of osteomalacia in itai-itai disease.

Absorption↗

PubMed2002

Streptozotocin, an O-GlcNAcase inhibitor, blunts insulin and growth hormone secretion.

Type 2 diabetes mellitus results from a complex interaction between nutritional excess and multiple genes. Whereas pancreatic beta-cells normally respond to glucose challenge by rapid insulin release (first phase insulin secretion), there is a loss of this acute response in virtually all of the type 2 diabetes patients with significant fasting hyperglycemia. Our previous studies demonstrated that irreversible intracellular accumulation of a glucose metabolite, protein O-linked N-acetylglucosamine modification (O-GlcNAc), is associated with pancreatic beta-cell apoptosis. In the present study, we show that streptozotocin (STZ), a non-competitive chemical blocker of O-GlcNAcase, induces an insulin secretory defect in isolated rat islet cells. In contrast, transgenic mice with down-regulated glucose to glucosamine metabolism in beta-cells exhibited an enhanced insulin secretion capacity. Interestingly, the STZ blockade of O-GlcNAcase activity is also associated with a growth hormone secretory defect and impairment of intracellular secretory vesicle trafficking. These results provide evidence for the roles of O-GlcNAc in the insulin secretion and possible involvement of O-GlcNAc in general glucose-regulated hormone secretion pathways.

Acetylglucosamine↗

PubMedDate not supplied

Mechanisms of small globular protein-induced plasma membrane permeability and cytotoxicity in U87-MG human malignant glioblastoma cells.

BACKGROUND: Small globular protein (SGP) is an artificially designed protein that forms small pores on lipid bilayer membranes. The anti-tumor effect of SGP has been reported in several papers. However, the exact mechanism underlying SGP-induced cell death remains to be determined. MATERIALS AND METHODS: The mechanisms of SGP-mediated cytotoxicity were examined using cultured malignant glioblastoma cells (U87-MG). Morphological changes were observed under a light microscope. Ultrastructural changes were examined by electron microscopy. Changes in membrane permeability were evaluated by measuring the extracellular release of lactate dehydrogenase (LDH) and intracellular calcium concentration ([Ca2+]i). A new cell viability assay was also conducted using DAPI/calcein fluorescent-double staining methods. RESULTS: SGP cytotoxic effects were strongly influenced by fetal bovine serum (FBS) concentration in culture media. After 30 min of incubation, cytotoxic effects were noted at SGP concentrations greater than 1.5 microM. [Ca2+]i increased immediately after SGP addition. Extracellular efflux of LDH increased linearly with SGP doses (r(2) =0.936), and occurred even at concentrations less than 1.5 microM. Non-viable and viable cells were simultaneously detected by fluorescent staining with DAPI and calcein-AM, respectively. After 30 min of incubation with SGP, DAPI-positive nuclei were evident at concentrations higher than 1.5 microM. Cultures were then maintained in 10% FBS-containing media for 24 h before addition of calcein-AM. Calcein-positive cells were found at SGP concentrations lower than 1.5 5M. Cells positive for both DAPI and calcein appeared at a concentration of 1.5 microM. CONCLUSION: Our results indicate that SGP induces rapid but transient cytotoxicity, which may be beneficial in local therapy of malignant brain tumors.

Antineoplastic Agents↗