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Biomedical subjects

H Okazaki

Publications and source records attributed to H Okazaki.

At least 37 records · Page 2Linked to original sources
PubMed2001

Functional assessment of canine kidneys after acute vascular occlusion on Gd-DTPA-enhanced dynamic echo-planar MR imaging.

RATIONALE AND OBJECTIVES: To assess the alteration in renal transit of gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) in dog kidneys after acute vascular occlusion on dynamic echo-planar imaging (EPI). METHODS: Dynamic 240-ms EPI series (repetition time/echo time/inversion time [TR/TE/TI] = 3000/42.1/100 ms) of the midcoronal plane of both kidneys of dogs anesthetized by intravenous administration of phenobarbital sodium and ketamine hydrochloride were obtained before and after ligation of the left renal vein (n = 6) or artery (n = 6) for 40 minutes after a 2-second-rate bolus injection of a 0.05 mmol/kg dose of Gd-DTPA. Renal Gd-DTPA transit was analyzed on the time-DeltaR2* curves in each layer of the outer cortex (OC), juxtamedullary cortex and outer zone of the medulla (JMC-OM), and the inner zone of the medulla (IM). The results were compared with those in six normal animals and those of a fast gradient-echo T1-weighted dynamic study performed in other vein- (n = 6) or artery- (n = 6) occluded animals and six normal animals. The histopathological basis of the altered Gd-DTPA transit was also evaluated. RESULTS: The dynamic EPI showed rapid Gd-DTPA transit through each of the five concentric layers, with three separate peaks on the time-DeltaR2* curves. The vein-occluded kidneys showed immediate swelling, with a significant increase in the cross-sectional area proportion of the JMC-OM layer compared with normals (32% +/- 2% vs 24% +/- 2%, P < 0.0001) and intensely congested capillaries, tubular, obliterated material, and gradual and persistent enhancement of the OC and JMC-OM layers but poor Gd-DTPA migration to the IM layer. The artery-occluded kidneys showed a significant reduction in the entire cross-sectional area compared with normals (1352 +/- 69 vs 1432 +/- 47 mm(2), P < 0.05) and poor enhancement, with significant decreases in the area under the time-DeltaR2* curve of the OC and JMC-OM layers compared with the vein-occluded kidneys (79 +/- 50 vs 324 +/- 108 and 82 +/- 42 vs 326 +/- 113, respectively; both P < 0.0001), despite minimal histological damage. In both models, the nonaffected kidneys showed significant increases in the area under the time-DeltaR2* curves compared with baseline. The time course of vascular and tubular Gd-DTPA transit was more detailed by the EPI study than by the T1-weighted imaging study. CONCLUSIONS: Echo-planar imaging has an excellent ability to follow the rapid, renal Gd-DTPA transit through the regional anatomy of the canine kidney. After venous occlusion, the JMC-OM layer may be the most affected site, primarily causing renal swelling and interruption of tubular Gd-DTPA transit and concentration. In contrast, an initial block of vascular Gd-DTPA inflow is the primary effect of arterial occlusion. Nonaffected kidneys seem to compensate by increasing excretion of Gd-DTPA.

Acute Disease↗
PubMed2001

Identification of liver X receptor-retinoid X receptor as an activator of the sterol regulatory element-binding protein 1c gene promoter.

In an attempt to identify transcription factors which activate sterol-regulatory element-binding protein 1c (SREBP-1c) transcription, we screened an expression cDNA library from adipose tissue of SREBP-1 knockout mice using a reporter gene containing the 2.6-kb mouse SREBP-1 gene promoter. We cloned and identified the oxysterol receptors liver X receptor (LXRalpha) and LXRbeta as strong activators of the mouse SREBP-1c promoter. In the transfection studies, expression of either LXRalpha or -beta activated the SREBP-1c promoter-luciferase gene in a dose-dependent manner. Deletion and mutation studies, as well as gel mobility shift assays, located an LXR response element complex consisting of two new LXR-binding motifs which showed high similarity to an LXR response element recently found in the ABC1 gene promoter, a reverse cholesterol transporter. Addition of an LXR ligand, 22(R)-hydroxycholesterol, increased the promoter activity. Coexpression of retinoid X receptor (RXR), a heterodimeric partner, and its ligand 9-cis-retinoic acid also synergistically activated the SREBP-1c promoter. In HepG2 cells, SREBP-1c mRNA and precursor protein levels were induced by treatment with 22(R)-hydroxycholesterol and 9-cis-retinoic acid, confirming that endogenous LXR-RXR activation can induce endogenous SREBP-1c expression. The activation of SREBP-1c by LXR is associated with a slight increase in nuclear SREBP-1c, resulting in activation of the gene for fatty acid synthase, one of its downstream genes, as measured by the luciferase assay. These data demonstrate that LXR-RXR can modify the expression of genes for lipogenic enzymes by regulating SREBP-1c expression, providing a novel link between fatty acid and cholesterol metabolism.

Alitretinoin↗
PubMed2001

Isolated medulla oblongata function after severe traumatic brain injury.

The objective was to report the first pathologically confirmed case of partly functionally preserved medulla oblongata in a patient with catastrophic traumatic brain injury.A patient is described with epidural haematoma with normal breathing and blood pressure and a retained coughing reflex brought on only by catheter suctioning of the carina. Multiple contusions in the thalami and pons were found but the medulla oblongata was spared at necropsy. In conclusion, medulla oblongata function may persist despite rostrocaudal deterioration. This comatose state ("medulla man") closely mimics brain death.

Brain↗
PubMed2001

Troglitazone inhibits atherosclerosis in apolipoprotein E-knockout mice: pleiotropic effects on CD36 expression and HDL.

Atherosclerotic coronary heart disease is a common complication of the insulin resistance syndrome that can occur with or without diabetes mellitus. Thiazolidinediones (TZDs), which are insulin-sensitizing antidiabetic agents, can modulate the development of atherosclerosis not only by changing the systemic metabolic conditions associated with insulin resistance but also by exerting direct effects on vascular wall cells that express peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a nuclear receptor for TZDs. Here we show that troglitazone, a TZD, significantly inhibited fatty streak lesion formation in apolipoprotein E-knockout mice fed a high-fat diet (en face aortic surface lesion areas were 6.9+/-2.5% vs 12.7+/-4.7%, P<0.05; cross-sectional lesion areas were 191 974+/-102 911 micrometer(2) vs 351 738+/-175 597 micrometer(2), P<0.05; n=10). Troglitazone attenuated hyperinsulinemic hyperglycemia and increased high density lipoprotein cholesterol levels. In the aorta, troglitazone markedly increased the mRNA levels of CD36, a scavenger receptor for oxidized low density lipoprotein, presumably by upregulating its expression, at least in part, in the macrophage foam cells. These results indicate that troglitazone potently inhibits fatty streak lesion formation by modulating both metabolic extracellular environments and arterial wall cell functions.

Animals↗
PubMed2001

Benzene-extracted components are important for the major activity of diesel exhaust particles: effect on interleukin-8 gene expression in human bronchial epithelial cells.

Epidemiologic and experimental studies suggest that diesel exhaust particles (DEPs) may be related to increasing respiratory mortality and morbidity. We have shown that DEPs augmented the production of inflammatory cytokines by human airway epithelial cells in vitro. To better understand the mechanisms of their proinflammatory activities, we studied the effects of several components extracted from DEPs on interleukin (IL)-8 expression in human bronchial epithelial cell line BEAS-2B and normal human airway epithelial cells obtained from very peripheral airways by an ultrathin bronchoscope. We used several agents active on signal transduction pathways in cytokine expression, such as the protein kinase C inhibitor staurosporin, antioxidant agents including N-acetyl cysteine (NAC) and pyrrolidine dithiocarbamate (PDTC), and p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580. Benzene-extracted components showed effects mimicking DEPs on IL-8 gene expression, release of several cytokines (IL-8; granulocyte macrophage colony-stimulating factor; and regulated on activation, normal T cells expressed and secreted) and nuclear factor (NF)-kappa B activation. We also found that NAC, PDTC, and SB203580 suppressed the activities of DEPs and their benzene extracts, suggesting the roles of oxidants-mediated NF-kappa B activation and p38MAPK pathways. Finally, benzo[a]pyrene, one of the important compounds included in the benzene component, replicated the activities shown by DEPs.

Acetylcysteine↗
PubMed2001

Transfer of canine embryos at various developmental stages recovered by hysterectomy or surgical uterine flushing.

In dogs, embryo transfer (ET) techniques such as induciton of excessive ovulation and synchronization of estrus have not progressed well. Therefore, using embryos at various developmental stages, ET was investigated in dogs from a beagle colony in which the ovulation days were close, as estimated by the progesterone level. Embryos were, recovered 8-11 days after ovulation (4-9 days after mating) by excising the oviducts and uteri (excision method) in 16 animals and by surgical flushing of the uteri at laparotomy (surgical method) in 3 animals. In 24 dogs with -4 to +2 days of difference in the timing of ovulation between donor and recipient dogs, 1-10 embryos at the 8-cell to blastocyst stages were transferred per animal. The mean embryo recovery rate by the excision method (97.1%) was significantly higher than that by the surgical method (42.5%) (p<0.01). Twelve (57.1%) of 21 animals with -1 to +2 days difference in ovulation day became pregnant after the transfer of 8-cell to blastocyst stage embryos. Although 3 dogs with -4 to -2 days of difference of ovulation day underwent ET of morula or compacted morula, none of these dogs became pregnant. The mean ratio of the number of newborns to the number of transferred embryos was only 51.9%. The mean duration of the period between ovulation and delivery in the pregnant recipients was 65.8 days, which tended to be longer than that in natural mating. These results demonstrate that pregnancy can be induced by ET at the 8-cell to blastocyst stage in dogs with -1 to +2 days difference in ovulation day.

Animals↗
PubMed2001

(99m)Tc-sestamibi retention characteristics during pharmacologic hyperemia in human myocardium: comparison with coronary flow reserve measured by Doppler flowire.

UNLABELLED: The aim of the study was to investigate the increase in myocardial (99m)Tc-methoxyisobutylisonitrile (sestamibi) retention in humans during pharmacologic vasodilation. METHODS: For calculation of the increase in (99m)Tc-sestamibi retention during hyperemia, baseline and adenosine triphosphate (ATP)-induced hyperemic stress sestamibi studies were performed using a same-day rest-stress protocol. On the injection of sestamibi, left ventricular dynamic data were obtained for 90 s. The increase in sestamibi retention from baseline to hyperemia was calculated by the formula [abstract: see text] where Cm(h)(t) and Cm(b)(t) are myocardial counts on the tomographic image, and Cb(b)(tau) and Cb(h)(tau) are the left ventricular blood-pool counts during the first transit of sestamibi at baseline and during hyperemia, respectively. Coronary flow increase during intravenous ATP stress was measured using intracoronary Doppler flow guide wire and compared with the scintigraphic results of 28 measurements in 22 patients. RESULTS: Sestamibi retention increased as coronary flow velocity increased but plateaued at >2.5-3 times baseline flow velocity. The relationship between the increase in sestamibi retention (Y) and the increase in flow (X) is expressed as follows: Y = 0.44 + 0.60X - 0.068X(2) (r = 0.82). CONCLUSION: In humans, the increase in (99m)Tc-sestamibi myocardial retention underestimates coronary flow reserve, particularly at high flow rates. Knowledge of these tracer retention characteristics will contribute to a more comprehensive understanding of the manner and interpretation of stress sestamibi imaging.

Adenosine Triphosphate↗
PubMed2001

[Clinical and bacteriological studies of ceftriaxone (CTRX) once daily administration in pediatric patients with respiratory tract infections].

Clinical studies of ceftriaxone (CTRX) were performed at a dose of 40 mg/kg once daily to evaluate its pharmacokinetics, and clinical and bacteriological efficacies in pediatric patients with respiratory tract infections. The following results were obtained. 1. Of 45 patients, clinical responses to CTRX were excellent in 34 (75.6%), good in 9 (20.0%) and poor in 2 (4.4%), indicating the overall efficacy rate of 95.6%. 2. Haemophilus influenzae (23 strains), Streptococcus pneumoniae (20 strains) and Moraxella catarrhalis (17 strains) were isolated from the patients as the main causative organisms. MIC90 of CTRX against these detected bacteria was < or = 0.06 microgram/ml with H. influenzae [beta-lactamase (-)/ABPC (S)], 0.25 microgram/ml with H. influenzae (BLNAR), 0.05 microgram/ml with PSSP, 1.0 microgram/ml with PISP/PRSP and 2.0 micrograms/ml with M. catarrhalis, respectively. 3. The eradication rate of causative organisms was 90.0% (27/30). 4. Serum levels of CTRX after administration of a 1-hour intravenous drip infusion of 40 mg/kg were investigated in 12 patients. Mean serum level at 24 hours after the administration was 9.4 +/- 2.8 micrograms/ml, which covered the level of MIC90 throughout the 24 hours. 5. No adverse reactions related to CTRX were observed. As the approved dosage of CTRX in pediatric patients is twice daily, while it is once daily in adults, there have been few reports on the efficacy of once-daily CTRX in pediatrics. According to the results of the study, it is suggested that once-daily CTRX for the pediatric patients with respiratory tract infections is useful. Further studies might be required to establish outpatient parenteral antibiotic therapy (OPAT) in pediatric infections.

Ceftriaxone↗
PubMed2000

Sterol regulatory element-binding protein-1 is regulated by glucose at the transcriptional level.

In vivo studies suggest that sterol regulatory element-binding protein (SREBP)-1 plays a key role in the up-regulation of lipogenic genes in the livers of animals that have consumed excess amounts of carbohydrates. In light of this, we sought to use an established mouse hepatocyte cell line, H2-35, to further define the mechanism by which glucose regulates nuclear SREBP-1 levels. First, we show that these cells transcribe high levels of SREBP-1c that are increased 4-fold upon differentiation from a prehepatocyte to a hepatocyte phenotype, making them an ideal cell culture model for the study of SREBP-1c induction. Second, we demonstrate that the presence of precursor and mature forms of SREBP-1 protein are positively regulated by medium glucose concentrations ranging from 5. 5 to 25 mm and are also regulated by insulin, with the amount of insulin in the fetal bovine serum being sufficient for maximal stimulation of SREBP-1 expression. Third, we show that the increase in SREBP-1 protein is due to an increase in SREBP-1 mRNA. Reporter gene analysis of the SREBP-1c promoter demonstrated a glucose-dependent induction of transcription. In contrast, expression of a fixed amount of the precursor form of SREBP-1c protein showed that glucose does not influence its cleavage. Fourth, we demonstrate that the glucose induction of SREBP could not be reproduced by fructose, xylose, or galactose nor by glucose analogs 2-deoxy glucose and 3-O-methyl glucopyranose. These data provide strong evidence for the induction of SREBP-1c mRNA by glucose leading to increased mature protein in the nucleus, thus providing a potential mechanism for the up-regulation of lipogenic genes by glucose in vivo.

Animals↗
PubMed2000

Promoter analysis of the mouse sterol regulatory element-binding protein-1c gene.

Recent data suggest that sterol regulatory-binding protein (SREBP)-1c plays a key role in the transcriptional regulation of different lipogenic genes mediating lipid synthesis as a key regulator of fuel metabolism. SREBP-1c regulates its downstream genes by changing its own mRNA level, which led us to sequence and analyze the promoter region of the mouse SREBP-1c gene. A cluster of putative binding sites of several transcription factors composed of an NF-Y site, an E-box, a sterol-regulatory element 3, and an Sp1 site were located at -90 base pairs of the SREBP-1c promoter. Luciferase reporter gene assays indicated that this SRE complex is essential to the basal promoter activity and confers responsiveness to activation by nuclear SREBPs. Deletion and mutation analyses suggest that the NF-Y site and SRE3 in the SRE complex are responsible for SREBP activation, although the other sites were also involved in the basal activity. Gel mobility shift assays demonstrate that SREBP-1 binds to the SRE3. Taken together, these findings implicate a positive loop production of SREBP-1c through the SRE complex, possibly leading to the overshoot in induction of SREBP-1c and its downstream genes seen in the livers of refed mice. Furthermore, reporter assays using larger upstream fragments indicated another region that was inducible by addition of sterols. The presence of the SRE complex and a sterol-inducible region in the same promoter suggests a novel regulatory link between cholesterol and fatty acid synthesis.

Animals↗
PubMed2000

The NH2-terminal region of focal adhesion kinase reconstitutes high affinity IgE receptor-induced secretion in mast cells.

Focal adhesion kinase (FAK) is tyrosine-phosphorylated by adherence of cells and also by FcepsilonRI aggregation in RBL-2H3 mast cells. Using phosphorylation site-specific antibodies, we observed that FcepsilonRI activation in these cells led to an increase in FAK phosphorylation at the same tyrosine residues that are phosphorylated by integrin-induced activation. Previous studies in the 3B6 line, a FAK-deficient variant of the RBL-2H3 cells, suggest that FAK plays a role in FcepsilonRI-induced secretion. Stable cell lines expressing either full-length or truncated forms of FAK were isolated after transfection of the FAK-deficient 3B6 variant cells. The NH(2) domain of FAK, which lacks the enzymatic and the COOH-terminal regions, was sufficient to reconstitute secretion. The different truncated forms of FAK were still tyrosine-phosphorylated after FcepsilonRI aggregation. Therefore, the kinase domain and the COOH-terminal region are not essential for FcepsilonRI-induced tyrosine phosphorylation of FAK or for secretion. Taken together, our data demonstrate that the reconstitution of secretion is dissociated from FAK activation and that the NH(2)-terminal region of FAK is the only critical element that may play a role in FcepsilonRI-induced secretion by acting as an adaptor or linker molecule.

Animals↗
PubMed2000

Absence of ACAT-1 attenuates atherosclerosis but causes dry eye and cutaneous xanthomatosis in mice with congenital hyperlipidemia.

Acyl-CoA:cholesterol acyltransferase (ACAT) catalyzes esterification of cellular cholesterol. To investigate the role of ACAT-1 in atherosclerosis, we have generated ACAT-1 null (ACAT-1-/-) mice. ACAT activities were present in the liver and intestine but were completely absent in adrenal, testes, ovaries, and peritoneal macrophages in our ACAT-1-/- mice. The ACAT-1-/- mice had decreased openings of the eyes because of atrophy of the meibomian glands, a modified form of sebaceous glands normally expressing high ACAT activities. This phenotype is similar to dry eye syndrome in humans. To determine the role of ACAT-1 in atherogenesis, we crossed the ACAT-1-/- mice with mice lacking apolipoprotein (apo) E or the low density lipoprotein receptor (LDLR), hyperlipidemic models susceptible to atherosclerosis. High fat feeding resulted in extensive cutaneous xanthomatosis with loss of hair in both ACAT-1-/-:apo E-/- and ACAT-1-/-:LDLR-/- mice. Free cholesterol content was significantly increased in their skin. Aortic fatty streak lesion size as well as cholesteryl ester content were moderately reduced in both double mutant mice compared with their respective controls. These results indicate that the local inhibition of ACAT activity in tissue macrophages is protective against cholesteryl ester accumulation but causes cutaneous xanthomatosis in mice that lack apo E or LDLR.

Animals↗
PubMed2000

Edg-6 as a putative sphingosine 1-phosphate receptor coupling to Ca(2+) signaling pathway.

The endothelial differentiation gene-6 (Edg-6) was recently identified as an orphan G-protein-coupled receptor. Its predicted amino acid sequence is very close to Edg family of receptor proteins whose ligand is supposed to be lysophosphatidic acid (LPA) or lysosphingolipid such as sphingosine 1-phosphate (S1P) and sphingosylphosphorylcholine (SPC). Transfection of the Edg-6 into Chinese hamster ovary (CHO) cells and K562 cells resulted in the appearance of high-affinity [(3)H]S1P binding activity. Among lipids employed, S1P and, even though less potent, SPC, displaced the [(3)H]S1P binding, but LPA was inactive. In Edg-6-transfected CHO cells, an increase in cytosolic Ca(2+) concentration in response to S1P or SPC was clearly enhanced without change in the LPA-induced action as compared with the vector-transfected cells. The enhancement of the Ca(2+) response was associated with a significant accumulation of inositol phosphate, reflecting activation of phospholipase C. Similar enhancement of Ca(2+) response to S1P or SPC was also observed in Edg-6-expressing K562 cells. These lipid-induced actions in CHO cells and K562 cells expressing Edg-6 were markedly suppressed by pertussis toxin treatment. We conclude that Edg-6 is one of S1P or lysosphingolipid receptors that couple to phospholipase C-Ca(2+) system through pertussis toxin-sensitive G-proteins.

Animals↗
PubMed2000

Nucleolin as the earliest target molecule of autoantibodies produced in MRL/lpr lupus-prone mice.

To elucidate the autoantigen against which autoantibodies are produced in the earliest phase of the disease process of systemic lupus erythematosus (SLE), serum samples were collected individually and serially from 10 NZB/NZW F1 and 10 MRL/lpr mice. Using immunoblots with mouse thymoma cell (EL-4) lysates as substrates, all mice were found to generate autoantibody against an either 150-kDa, 110-kDa, 75-kDa, or 55-kDa molecule in as early as 4 weeks. Anti-DNA antibodies occurred almost at the same time or after those against these four molecules. The number of antigens reactive with autoantibodies in immunoblots increased gradually with age. Antibodies against histone molecules were produced after 8 weeks of age. Among the four antigens, the 110-kDa molecule was identified as nucleolin, which is an abundant nucleolar phosphoprotein. Nucleolin binds DNA, RNA, and nucleic acid-binding proteins such as histone H1. Nucleolin is a target of granzyme A of cytotoxic T cells, and autoantibodies against it are found in sera from patients with SLE as well as from those with various viral infections. These results indicate that nucleolin is one of the immunodominant molecules that break down self-tolerance and initiate autoantibody-spreading in a mouse model of SLE.

Aging↗
PubMed2000

Relationships among serum triacylglycerol, fat pad weight, and lipolysis in iron-deficient rats.

We studied the relationships among serum triacylglycerol (TG), fat pad weight, and lipolytic response to norepinephrine (NE) in iron-deficient rats. We used male Sprague-Dawley International Golden Standard rats. The rats were randomly divided into four groups: two iron-adequate groups for 1 week (1A) and 5 weeks (5A), and two iron-deficient groups for 1 week (1D) and 5 weeks (5D), based on the AIN-93G diet. Iron-deficient treatment caused a significant decrease in hemoglobin (Hb) and hematocrit (Hct) values and an increase in relative heart weight in 1D and 5D rats. Although serum TG was not affected by the 1-week iron-deficient treatment, it was significantly increased by 5-week iron-deficient treatment. The 1-week iron-deficient treatment significantly decreased the relative weight of the retroperitoneal fat pads, but not that of the epididymal fat pads. On the other hand, the 5-week iron-deficient treatment significantly decreased the relative weight of both fat pads; the degree of decrease was 41% and 32% for retroperitoneal and epididymal fat pads, respectively. Basal lipolysis significantly decreased in the epididymal adipocytes from 1D rats, whereas lipolytic response to NE markedly increased. No effect due to the 5-week treatment on basal lipolysis was observed in either retroperitoneal or epididymal adipocytes. In addition, lipolytic response to NE significantly increased in the retroperitoneal, but not the epididymal adipocytes. These results demonstrate that the effects of an iron-deficient diet on fat pad weight are different, depending on the duration of the treatment and the location of fat pads. In addition, iron deficiency-caused hypertriacylglycerolmia may be predominantly related to the increase in lipolysis in retroperitoneal rather than in epididymal adipocytes. The data further show that the increase in lipolysis of epididymal adipocytes occurs in the earlier stage prior to a severe iron-deficient state.

Journal Article↗
PubMed2000

Thiamin is decomposed due to Anaphe spp. entomophagy in seasonal ataxia patients in Nigeria.

A fairly high activity of a relatively heat-resistant thiaminase was detected and characterized from the pupae of an African silkworm Anaphe spp. which had been the putative cause of a seasonal ataxia and impaired consciousness in Nigerians. The thiaminase in the buffer extract of Anaphe pupae was type I (thiamin: base 2-methyl-4-aminopyrimidine methyl transferase EC 2.5.1.2), and the optimal temperature and pH were 70 degrees C and 8.0-8.5, respectively. Based on gel filtration chromatography, the molecules were estimated to be 200 kDa. Second substrates which could be utilized by the thiaminase were pyridoxine, amino acids, glutathione, taurine and 4-aminopyridine. Thiamin phosphate esters were inactive as substrates. This is the first report describing an insect thiaminase. Our results indicate the necessity of thorough heat treatment for the detoxification of the African silkworm, making the worm a safe source of high-quality protein.

Animals↗