Metallothionein-I-transgenic mice are not protected from acute cadmium-metallothionein-induced nephrotoxicity

Mice pretreated with Zn have increased renal metallothionein (MT) levels and are protected from CdMT nephrotoxicity. To determine whether MT is important in this Zn-induced protection against CdMT-induced nephrotoxicity, MT-transgenic mice that have high levels of MT in their kidneys (10-fold over control mice) have been studied to determine whether they are resistant to CdMT-induced nephrotoxicity. Mice were injected with CdMT (0.1-0.6 mg Cd/kg, iv) and kidney injury was evaluated 24 hr later. CdMT produced renal toxicity in a dose-dependent manner. At a nephrotoxic dose of CdMT (0.4 mg Cd/kg), urinary protein and glucose excretion were increased 30- and 60-fold, respectively, in control mice. However, similar increases in protein and glucose excretion were also observed in MT-transgenic mice. CdMT also induced a similar dose-dependent proximal tubular cell necrosis in both control and MT-transgenic mice in a dose-dependent manner. Treatment of control mice with Zn (100 micromol/kg, sc x 2 days) increased renal MT to levels similar to those of untreated MT-transgenic mice and protected against CdMT-induced renal injury. Furthermore, when Zn (25-100 micromol/kg, sc) was given immediately before CdMT injection (i.e., without preinduction of MT), it was still effective in preventing CdMT nephrotoxicity. We conclude that Zn-induced protection against CdMT nephrotoxicity does not appear to be due to induction of renal MT.     

Gastric pacing improves emptying and symptoms in patients with gastroparesis

BACKGROUND & AIMS: No effective treatment is available for patients with gastroparesis refractory to standard medical therapy. The aim of this study was to investigate the effects of gastric pacing on gastric electrical activity, gastric emptying, and symptoms in patients with gastroparesis. METHODS: Nine patients with gastroparesis participated in this study. Four pairs of cardiac pacing wires were implanted on the serosa of the stomach. The protocol consisted of two portions: a temporary inpatient study period and an outpatient study for a period of 1 month or more. RESULTS: Gastric pacing entrained the gastric slow wave in all subjects and converted tachygastria in 2 patients into regular 3-cpm slow waves. Gastric emptying was significantly improved after the outpatient treatment with gastric pacing. The gastric retention at 2 hours was reduced from 77.0% +/- 3.3% to 56.6% +/- 8.6% (P < 0.05). Symptoms of gastroparesis were substantially reduced at the end of the outpatient treatment (1.51 +/- 0.46 vs. 2.84 +/- 0.61; P < 0.04). Eight of 9 patients no longer relied on jejunostomy tube feeding, and no adverse events were noted related to the pacing unit. CONCLUSIONS: Gastric pacing seems to be able to improve symptoms of gastroparesis and to accelerate gastric emptying in patients with gastroparesis. More controlled studies are necessary to further investigate the role of gastric pacing in clinical practice.     

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Mate choice and mate competition influence male body size in Japanese medaka

A sexual size dimorphism usually occurs when size-dependent reproductive advantages exist in only one sex. Studies on Japanese medaka, Oryzias latipes, have demonstrated reproductive size advantages in females but not in males, even though males and females are similar in body size. We conducted mate-choice and mate-copying tests in which a female could first associate with, then mate with, either a large (>/=1 sd+X standard length) or a small male (相似文献   

Developmentally regulated gene expression of thrombomodulin in postimplantation mouse embryos

Embryonic lethality of thrombomodulin-deficient mice has indicated an essential role for this regulator of blood coagulation in murine development. Here, the embryonic expression pattern of thrombomodulin was defined by surveying beta-galactosidase activity in a mouse strain in which the reporter gene was placed under the regulatory control of the endogenous thrombomodulin promoter via homologous recombination in embryonic stem cells. The murine trophoblast was identified as a previously unrecognized anatomical site where TM expression is conserved between humans and mice and may exert a critical function during postimplantation development. Targeted reporter gene expression in mesodermal precursors of the endothelial cell lineage defined thrombomodulin as an early marker of vascular differentiation. Analysis of the thrombomodulin promoter in differentiating ES cells and in transgenic mice provided evidence for a disparate and cell type-specific gene regulatory control mechanism in the parietal yolk sac. The thrombomodulin promoter as defined in this study will allow the targeting of gene expression to the parietal yolk sac of transgenic mice and the initiation of investigations into the role of parietal endoderm in placental function.     

Treatment with anti-interleukin-10 monoclonal antibody enhances early resistance to but impairs complete clearance of Listeria monocytogenes infection in mice

Mice that received an anti-interleukin-10 (anti-IL-10) neutralizing monoclonal antibody (MAb) (SXC-1) prior to infection with Listeria monocytogenes initially demonstrated resistance to the infection, as indicated by reduced recovery of L. monocytogenes from their spleens and livers during the first 5 days after challenge. Anti-IL-10 MAb-treated mice then demonstrated reduced resistance during the later stage of infection, as indicated by persistent infection with L. monocytogenes in their livers 11 days after challenge. Aspartate aminotransferase (AST) levels (a measure of liver damage) in the sera of control mice increased between 1 and 5 days after challenge, while anti-IL-10 MAb-treated mice maintained lower AST levels. At 7 days after challenge, AST levels in the sera of control mice decreased as the numbers of organisms declined. In contrast, AST levels increased as the infections persisted in anti-IL-10 MAb-treated mice. The AST levels in serum reflected liver histopathology as anti-IL-10 MAb-treated mice exhibited fewer granulomatous lesions and less necrosis of liver tissue than the control mice during the first 5 days after challenge. Anti-IL-10 MAb treatment altered the expression of inflammatory cytokine mRNAs during L. monocytogenes infection. Control MAb-treated mice exhibited increased expression of tumor necrosis factor alpha and granulocyte-macrophage colony-stimulating factor mRNA in their lives during L. monocytogenes infection, but this increase did not occur in anti-IL-10 MAb-treated mice. Gamma interferon mRNA expression in the livers of the control MAb-treated mice was increased between 1 and 5 days after L. monocytogenes challenge and then decreased at 7 days after challenge. In contrast, gamma interferon mRNA expression in the livers of anti-IL-10 MAb-treated mice was not decreased until 7 days after challenge. These results indicate that endogenous IL-10 has both beneficial and detrimental effects on the host response to L. monocytogenes infection in mice.     

Thrombomodulin modulates growth of tumor cells independent of its anticoagulant activity

Thrombomodulin (TM), recognized as an essential vessel wall cofactor of the antithrombotic mechanism, is also expressed by a wide range of tumor cells. Tumor cell lines subcloned from four patients with malignant melanoma displayed a negative correlation between TM expression and cell proliferation in vitro and in vivo. Overexpression of wild-type TM decreased cell proliferation in vitro and tumor growth in vivo. TM mutants with altered protein C activation capacity lead to a similar effect. In contrast, transfection of melanoma cells with mutant TM constructs, in which a portion of the cytoplasmic or lectin domain was deleted, abrogated the antiproliferative effect associated with overexpression of wild-type TM. Experiments performed with either peptide agonists/antagonists of the thrombin receptor, with hirudin, or with inhibitors of thrombin-TM interaction did not alter the growth inhibitory effect of TM overexpression. These data suggest that TM exerts an effect on cell proliferation independent of thrombin and the thrombin receptor, possibly related to the binding of novel ligands to determinants in the lectin domain which might trigger signal transduction pathways dependent on the cytoplasmic domain.     

Effects of HCO3- on cell composition of rabbit ciliary epithelium: a new model for aqueous humor secretion

PURPOSE: To determine whether the Na+-K+-2Cl- symport or the parallel Na+/H+ and Cl-/HCO3- antiports provide the dominant pathway for NaCl uptake into the ciliary epithelium. Both pathways are known to support NaCl entry from the stroma into the pigmented ciliary epithelial (PE) cells, after which Na+ and Cl- diffuse across the gap junctions into the nonpigmented ciliary epithelial (NPE) cells and are released into the aqueous humor. METHODS: Rabbit iris ciliary bodies were preincubated in HCO3-/CO2-containing or HCO3-/CO2-free solutions before quick freezing, cryosectioning, dehydration, and electron probe x-ray microanalysis. RESULTS: The NPE and the PE cells contained more K and Cl when incubated with bicarbonate. Inhibition of carbonic anhydrase with 0.5 mM acetazolamide had little effect in HCO3--free medium but prevented the increase in Cl in both cell types in HCO3-/CO2 solution. Inhibition of the Na+-K+-2Cl- symport with 10 to 500 microM bumetanide caused Cl loss from both cell types in HCO3--free solution, but bumetanide produced a paradoxical increase in Cl and Na in HCO3-/CO2 solution. Together, acetazolamide and bumetanide resulted in significant Cl loss in HCO3--free solution and prevented the gains of Cl and Na in HCO3-/CO2 solution. CONCLUSIONS: The present results indicate that the dominant entry pathway of NaCl from the stroma into the ciliary epithelial syncytium is through an acetazolamide-inhibitable Cl-/HCO3 and a parallel Na+/H+ antiport. The dominant release pathways into the aqueous humor appear to be a Na+-K+-2Cl-symport, which can be outwardly directed under physiological conditions, together with the Na+/K+-exchange pumps and Cl- channels.     

Strategies for positioning fluorescent probes and crosslinkers on formyl peptide ligands

Chemoattractant receptors represent a major subset of the G-protein coupled receptor (GPCR) family. One of the best characterized, the N-formyl peptide receptor (FPR), participates in host defense responses of neutrophils. The features of the ligand which regulate its interaction with the FPR are well-known. By manipulating these features we have developed new ligands to probe structural and mechanistic aspects of the peptide-receptor interaction. Three ligand groups have been developed: 1) ligands containing a Lys residue located in positions 2 through 7 that can be conjugated to FITC (N-formyl-Met1-Lys2-Phe3-Phe4, N-formyl-Met1-Leu2-Lys3-Phe4, N-formyl-Met1-Leu2-Phe3-Lys4, N-formyl-Met1-Leu2-Phe3-Phe4-Lys5, N-formyl-nLeu1-Leu2-Phe3-nLeu4-Tyr5-Lys6 and N-formyl-Met1-Leu2-Phe3-Phe4-Gly5-Gly6-Lys7; 2) fluorescent pentapeptide ligands (N-formyl-Met-X-Phe-Phe-Lys(FITC) where X = Leu, Ala, Val or Gly); and 3) small crosslinking ligands where the photoaffinity crosslinker 4-azidosalicylic acid (ASA) was conjugated to Lys in positions 3 and 4 and p-benzoyl-phenylalanine (Bpa) was located in position 2 in N-formyl-Met1-Bpa2-Phe3-Tyr4. The peptides were characterized according to activity and affinity in human neutrophils and cell lines transfected with FPR. All of the peptides were agonists, with parallel affinity and activity. In the first group, the peptide activity decreases as Lys is placed closer to the N-formyl group and the activity is improved by 1-3 orders of magnitude by conjugation with FITC. In the second group, the dissociation rate of the peptide from the receptor increases as position 2 is replaced by aliphatic amino acids with smaller alkyl groups. In the third group, crosslinking ligands remain biologically active, display nM affinity and covalently label the FPR.