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K Sakurada

Publications and source records attributed to K Sakurada.

At least 37 records · Page 2Linked to original sources
PubMed1999

Identification of cis-9,10-methylenehexadecanoic acid in submitochondrial particles of bovine heart.

Submitochondrial particles of bovine heart were hydrolyzed by phospholipase A2 and the products were analyzed by liquid chromatography electrospray ionization-mass spectrometry. We found a fatty acid with a molecular mass of 268 Da and a retention time longer than that of linoleic acid. Next, we synthesized organically cis-9,10-methylenehexadecanoic acid, which has a molecular mass similar to that of the extracted fatty acid, and characterized its high performance liquid chromatography and gas chromatography-mass spectrometry profiles. Using these data we were able to identify endogenous cis-9,10-methylenehexadecanoic acid in rat and human heart and liver tissues that had been hydrolyzed by phospholipase A2. This fatty acid was not detected in tissue extracts that had not been hydrolyzed by phospholipase A2. Similar amounts of cis-9, 10-methylenehexadecanoic acid were measured in tissue extracts after total hydrolysis. These results suggest that cis-9, 10-methylenehexadecanoic acid is a fatty acid component, in the sn-2 position, of phospholipids in some mammalian tissue.

Animals↗
PubMed1999

A 'keyhole lesion' gunshot wound in an adipocere case.

A corpse completely converted into adipocere and showing two adjacent bone defects--a typical gunshot entrance wound and a keyhole lesion--is reported. Postmortem changes, a comminuted fracture of the cranial base, and destruction of the bullets made it impossible to determine the direction of fire through the keyhole lesion. Gunshot wounds may show various atypical forms, including keyhole lesions, and especially in old corpses, the distinction between an entrance wound and an exit wound can be very difficult, even if a careful complete autopsy is performed.

Journal Article↗
PubMed1999

Nurr1, an orphan nuclear receptor, is a transcriptional activator of endogenous tyrosine hydroxylase in neural progenitor cells derived from the adult brain.

Adult rat-derived hippocampal progenitor cells express many of the molecules implicated in midbrain dopaminergic determination, including FGF receptors 1, 2 and 3, the sonic hedgehog receptor components Smo and Ptc, and the region-specific transcription factors Ptx3 and Nurr1. Here we use undifferentiated progenitors to probe the events leading to the dopaminergic phenotype and find that the influences of Nurr1 can be temporally and mechanistically uncoupled from the patterning influences of sonic hedgehog and FGF-8 or the more generic process of neuronal differentiation itself. In gain-of-function experiments, Nurr1 is able to activate transcription of the tyrosine hydroxylase gene by binding a response element within a region of the tyrosine hydroxylase promoter necessary for midbrain-specific expression. This activation is mediated through a retinoid X receptor independent mechanism and occurs in all precursors, regardless of differentiation status. Overexpression of Nurr1 does not affect proliferation or stimulate neuronal differentiation and has no influence on the expression of other dopaminergic markers. This uncoupling of tyrosine hydroxylase expression from other dopaminergic markers suggests that the midbrain dopaminergic identity is dictated by a combination of pan-dopaminergic (e.g., Shh/FGF-8) and region-specific (Nurr1) mechanisms.

Age Factors↗
PubMed1999

[Iron].

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Female↗
PubMed1999

Cadmium accumulation augments contraction and phosphoinositide hydrolysis of vascular smooth muscles.

Effects of cadmium accumulation in blood vessels on vasoconstriction and hydrolysis of phosphoinositides were investigated using aortas isolated from rats. The aortic strips were incubated with cadmium chloride (10 microM) for 24 hr and then washed out (cadmium accumulation). In the cadmium-accumulated aortas, contractile responses to KCl and 5-hydroxytryptamine were augmented compared to the control incubated with a vehicle. The degree of the augmentation by cadmium was higher in 5-hydroxytryptamine contraction than in KCl contraction. The level of 5-hydroxytryptamine-induced contraction relative to KCl-induced contraction (expressed as percent of maximum KCl contraction in each strip) was also significantly increased in the cadmium-accumulated aortas as compared to the control. Cadmium pretreatment augmented 5-hydroxytryptamine-stimulated inositol monophosphate accumulation, while there was no difference in the basal level of inositol monophosphate between the cadmium-accumulated aortas and the control. These results suggest that cadmium accumulation increases vasocontractility, in part because of the facilitation of phosphoinositide hydrolysis.

Animals↗
PubMed1998

Calcium is required for quasi-lipoxygenase activity of hemoproteins.

Bovine and guinea pig heart homogenates, porcine leukocyte homogenate, and human hemolysate were found to vigorously oxidize linoleic acid, with lipoxygenase-like activity, to its hydroperoxy, epoxy, hydroxy-epoxy, and keto compounds in the presence of calcium chloride. In the absence of calcium, the reaction was significantly reduced. Attempts to characterize this quasi-lipoxygenase activity revealed that calcium potentiated the quasi-lipoxygenase activities of hemoproteins (hemoglobin, myoglobin, myeloperoxidase, catalase, cytochrome c) and hemin at the physiological pH of 7.5. Lipid peroxidation by hemoproteins was inhibited by albumin and erythrocyte membranes in blood, as well as by a low concentration of calcium in cells. However, it seems possible that in extracellular fluid, which contains a high concentration of calcium and a low concentration of albumin, hemoprotein released from damaged cells could oxidize unsaturated fatty acids derived by phospholipase-A2 from phospholipids of damaged cellular membranes. In a model of quasi-lipoxygenase activation under such conditions, lipids of erythrocyte membranes were oxidized by hemoglobin in the presence of phospholipase-A2 and calcium. The effect of nitrogen oxide, paraquat, and bleomycin on oxidation by hemoproteins and hemin was also discussed.

Animals↗
PubMed1998

HA1077, a protein kinase inhibitor, inhibits calponin phosphorylation on Ser175 in porcine coronary artery.

Calponin is a thin filament-associated protein which has been implicated in the modulation of the contractile state of smooth muscle via its interaction with actin and inhibition of the actin-activated myosin Mg-ATPase. This inhibitory effect is alleviated by phosphorylation of calponin at Ser175 in vitro by protein kinase C. The issue of calponin phosphorylation in intact smooth muscle in response to agonists that activate protein kinase C is controversial. We have produced a monoclonal antibody that specifically recognizes calponin phosphorylated at Ser175 and used it to analyze calponin phosphorylation in porcine coronary arterial smooth muscle stimulated with prostaglandin F2alpha or phorbol 12,13-dibutylate (PDB). Calponin phosphorylation increased rapidly in response to prostaglandin F2alpha concomitant with the increase in tension. Calponin was then dephosphorylated while force was maintained. Tension development in response to PDB was significantly slower, but again calponin phosphorylation paralleled force development. In this case, calponin dephosphorylation was very slow, consistent with prolonged activation of protein kinase C. The protein kinase inhibitors, HA1077 (1-5-(isoquinoline sulfonyl)-homopiperazine HCl) and HA1100 (1-hydroxy HA1077; 1-(hydroxy-5-isoquinoline sulfonyl-homopiperazine), inhibited tension development and calponin phosphorylation in a concentration-dependent manner with similar ED50 values in response to prostaglandin F2alpha and PDB. These results support physiological roles for calponin in force development in smooth muscle in response to agonists which trigger protein kinase C activation and in the latch state, i.e., force maintenance at low energy cost. Furthermore, the vasodilator effect of HA1077 and HA1100 is more likely due to inhibition of protein kinase C than of myosin light chain kinase.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1998

Calcium ions potentiate lipoxygenase activity of cytochrome c at the physiological pH.

Cytochrome c oxidized linoleic acid, with lipoxygenase-like activity, to 9-hydroperoxy-10,12-octadecadienoic acid (9-HpODE), 13-hydroperoxy-9,11-octadecadienoic acid (13-HpODE), 13-keto-9,11-octadecadienoic acid (13-KODE), and hydroxy-epoxy-octadecenoic acids (HEPOs) in the presence of calcium chloride at the physiological pH of 7.5. In the absence of calcium, the reaction was remarkably reduced. Statistically significant increase of 13-KODE was observed 1 min after the reaction was started by adding calcium. Calcium chloride at concentrations as low as 30 microM caused statistically significant increase of 13-KODE production in the presence of 1 microM cytochrome c, and cytochrome c at concentrations as low as 10 nM caused statistically significant increase of 13-KODE production in the presence of 2 mM calcium. The addition of bleomycin enhanced the reaction, and the addition of adriamycin attenuated the reaction. The same oxidized linoleic acid products were found in the submitochondrial particles which were hydrolyzed by phospholipase-A2 in the presence of calcium. Lipoxygenase activity potentiated by calcium may be involved in the lipid peroxidation in the submitochondrial particles hydrolyzed by phospholipase-A2.

Animals↗
PubMed1998

Modulation of platelet activating factor-induced glycogenolysis in the perfused rat liver after administration of endotoxin in vivo.

The effect of endotoxin treatment in vivo on platelet activating factor (PAF)-induced glycogenolysis was studied in the perfused rat liver. The addition of PAF (20 nM) to the perfusate increased glucose production concomitant with suppression of oxygen consumption in control rats without endotoxin treatment. At 6 h after endotoxin administration, PAF caused severe suppression of oxygen consumption, but glucose production was greatly inhibited. At 24 h after endotoxin treatment, PAF caused less suppression of oxygen consumption than the control, and glucose production was partially restored. The metabolic responses in the control rat were abolished by the simultaneous presence of cyclooxygenase- and lipoxygenase-inhibitors. Combined use of leukotriene (LT) D4- and thromboxane (Tx) A2-receptor antagonists inhibited the metabolic responses in the rat given endotoxin 6 h before. The efflux of Tx B2 during PAF-infusion decreased 24 h after endotoxin treatment, and Tx A2 receptor antagonist, but not LT D4 receptor antagonist, prevented the suppression of oxygen consumption. These results suggest that different eicosanoids are involved in PAF-induced glycogenolysis in different stages of endotoxemia, and that LT D1 may also play a role in PAF-induced glycogenolysis.

Animals↗
PubMed1998

Dynamics of myosin light chain phosphorylation at Ser19 and Thr18/Ser19 in smooth muscle cells in culture.

Using the specific antibodies pLC1 and pLC2 for mono- and diphosphorylated 20-kDa myosin light chain (MLC20) at Ser19 and at both Thr18 and Ser19, respectively, we visualized the dynamics of the MLC20 phosphorylation in rabbit aortic smooth muscle cells (cell line SM-3) stimulated with PGF2alpha. In the resting state, the diphosphorylated form was located in the peripheral region of the cell, such as the leading edge or the adhesion plaque, and the monophosphorylated form was located not only in the peripheral region but also on a discontinuous fibrillary structure along the long axis of the cell. After stimulation with 30 microM PGF2alpha, although localization of the monophosphorylated form changed little, the content of the diphosphorylated form increased and the distribution spread along the fibrillary structure to an extent the same as or similar to that of the monophosphorylated form, which colocalized with actin filament bundles. The diphosphorylation of MLC20 was more sensitive to protein kinase inhibitors, HA-1077, HA-1100, staurosporine, wortmannin, and ML-9, than was the monophosphorylation. In light of these observations, we propose that MLC20 diphosphorylation and monophosphorylation are regulated by different mechanisms.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1997

Possible roles of an adult T-cell leukemia (ATL)-derived factor/thioredoxin in the drug resistance of ATL to adriamycin.

Chemotherapy for adult T-cell leukemia (ATL) has been reported to fail to induce complete remission because of drug resistance in most patients. We have examined the expression of an ATL-derived factor (ADF)/thioredoxin in relation to resistance to adriamycin (ADM) in various T-cell leukemia cell lines including ATL cell lines. Immunoblot analysis demonstrated that ATL cell lines expressed ADF/thioredoxin at levels 2.8 to 12 times those of other T-cell acute lymphocytic leukemia (T-ALL) cell lines, and that ATL cell lines were 2 to 15 times more resistant to ADM than other T-ALL cell lines. Therefore, we established ADM-resistant cell lines from three different ATL cell lines, and examined the correlation between ADM resistance and expression of ADF/thioredoxin. ADM-resistant ATL cell lines were also found to be resistant to other drugs such as cisplatin and etoposide, and they expressed ADF/thioredoxin at levels 5 to 10 times those of parent ATL cell lines. Diamide and sodium selenite, which have been reported to inhibit ADF/thioredoxin, restored the sensitivity to ADM in ATL and ADM-resistant ATL cell lines. The MDR-1 gene product, a membrane P-glycoprotein (Pgp), was not expressed on ATL cell lines or ADM-resistant ATL cell lines. Topoisomerase II and glutathione peroxidase activities in T-cell leukemia cell lines were not correlated with ADM resistance. These results suggest that ADF/thioredoxin may play an important role in the drug resistance of ATL cells to ADM.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

The important balance between cytokines derived from type 1 and type 2 helper T cells in the control of graft-versus-host disease.

We have investigated cytokine mRNA expression in the peripheral blood mononuclear cells of 20 patients who received allogeneic hematopoietic stem cell transplants to assess the cytokine network after transplantation. IL-4 mRNA expression decreased in five of five (100%) patients with > or = grade III (severe) acute GVHD and increased in 10 of 22 (45%) patients without severe GVHD. In contrast, IL-12 mRNA expression increased in two of two (100%) patients with severe GVHD, but increased in only six of 18 (33%) patients without severe GVHD. Furthermore, IL-10 and/or IL-13 mRNA expression increased in 19 of 22 (86%) patients without severe GVHD, but increased in only one of three (33%) patients with severe GVHD. In patients with allogeneic PBSCT who had severe acute GVHD, the cytokine mRNA expression in patients with allogeneic PBSCT, who had no severe GVHD, showed a similar pattern to that in patients with allogeneic BMT. IL-4 mRNA expression increased in three of five (60%) patients and IL-10 and/or IL-13 mRNA expression increased in five of five (100%) patients. In contrast, IL-12 mRNA expression increased in only one of three (33%) patients. Serum IL-4 concentration in allogeneic PBSCT patients in the early engraftment phase was relatively high, while serum IL-12 concentration was low. These findings suggest that severe GVHD may be related to the cytokine imbalance between type 1 helper T (Th1) cells and type 2 helper T (Th2) cells.

Adult↗
PubMed1997

A 39,X/40,XY true hermaphrodite mouse with normal ovarian function.

A cryptorchid mouse with a 39,X/40,XY chromosome constitution was identified among 414 offspring born in the departmental XO mouse breeding colony. This mouse had a small testis on the left, with no sign of spermatogenesis, and a normal ovary on the right with several corpora lutea.

Animals↗
PubMed1997

Phosphorylation of myosin light chain in resting platelets from NIDDM patients is enhanced: correlation with spontaneous aggregation.

Platelet function in patients with NIDDM is enhanced. We have found that spontaneous aggregation (i.e., the formation of small-sized aggregates in the absence of agonist stimulation) occurs at a high rate in platelets from NIDDM patients. We then investigated basal myosin light chain 20 (MLC) phosphorylation, which plays a key role in platelet shape change and aggregation, using a monoclonal antibody against a phosphorylation site (serine 19 residue) in the MLC molecule in platelets from these patients. Standard calibration curves obtained from purified MLC or the phosphorylated form of myosin light chain 20 (MLC-P) were linear within the range of 0-150 ng for MLC and 0-3 ng for MLC-P. The amount of MLC or MLC-P in platelets was estimated, and basal MLC phosphorylation was calculated. Platelets were obtained from 9 young healthy control subjects, 13 age- and sex-matched nondiabetic control subjects, and 13 patients with NIDDM. The basal MLC phosphorylation in platelets was significantly higher in the NIDDM patients than in the control subjects, irrespective of age. These findings suggest that platelets from NIDDM patients are activated in vivo. Platelets obtained from NIDDM patients generated spontaneous aggregation, the degree of which was significantly higher than that in control subjects. Platelet spontaneous aggregation correlated well with basal MLC phosphorylation. These findings suggest that increases in basal MLC in platelets may be one factor leading to hyperaggregability of platelets in these patients.

Adult↗
PubMed1997

Low levels of serum soluble c-kit relates to delayed engraftment after bone marrow transplantation.

Serum soluble c-kit concentrations were measured in 28 patients undergoing bone marrow transplantation (BMT). The c-kit levels in patients with delayed engraftment (time to leukocyte recovery > 1.0 x 10(9)/L being more than 20 days after BMT) were significantly lower than those in patients with early engraftment (time to leukocyte recovery being less than 19 days after BMT) from the start of conditioning until day 100 after BMT. The data from this study indicates that the measurement of serum soluble c-kit concentrations may be a useful indicator of engraftment.

Adolescent↗
PubMed1997

Phorbol ester enhancement of IL-3-dependent proliferation of primitive hematopoietic progenitors of mice in culture.

Protein kinase C (PKC) is a Ca++- and phospholipid-dependent protein kinase activated by diacylglycerol that is either released from cell membranes in response to certain growth factors or mimicked by 12-O-tetradecanoyl phorbol-13-acetate (TPA). We studied the effects of TPA on interleukin-3 (IL-3)-dependent colony formation of mouse bone marrow cells from mice injected with 5-fluorouracil 2 days before examination in order to clarify the significance of PKC in the proliferation of primitive hematopoietic progenitors. Although TPA alone did not support colony formation, TPA in combination with IL-3 increased colony numbers from 1.5 to 2 times that formed with IL-3 and vehicle. TPA increased not only the granulocyte/macrophage colonies, but also the multilineage colonies. A sequential colony count showed that TPA, unlike IL-6, did not hasten the appearance of colonies. Because TPA enhanced IL-3-dependent colony formation derived from lineage-negative marrow cells obtained from mice that received 5-FU 2 days before, it is possible that it might act directly on primitive progenitors. Prolonged pretreatment of marrow cells with TPA prevented TPA-augmented colony growth. Calphostin C, a specific PKC inhibitor, and certain specific tyrosine kinase inhibitors, such as genistein and herbimycin A, abrogated the enhancing effects of TPA on IL-3-dependent colony formation. These data suggest that TPA had a direct effect on the primitive progenitors and enhanced IL-3-dependent colony formation via activation of PKC and certain tyrosine kinases.

Animals↗