FcR gamma-chain is essential for both surface expression and function of human Fc gamma RI (CD64) in vivo

Most Ig receptors exist as hetero-oligomeric complexes with separate ligand binding (alpha) and signal transducing (beta, gamma, or zeta) subunits. For Fc gamma RIIIa and Fc epsilon RI, association with the FcR gamma-chain is essential for surface expression. However, the human high affinity IgG receptor, hFc gamma RI, was found to be surface- expressed by itself in transient transfection models. We have now analyzed the integrity of hFc gamma RI expression in more detail in stable transfectants. In vitro we noted that, in the absence of FcR gamma-chain, surface expression of hFc gamma RI rapidly declined to background levels, in both IIA1.6 B cells and NIH3T3 fibroblasts. The effect of FcR gamma-chain on hFc gamma RI surface expression in vivo was evaluated by using two newly generated transgenic mouse lines, selectively expressing hFc gamma RI on myeloid cells. These transgenic mice were crossed with FcR gamma-chain-deficient mice. Analysis of blood monocytes and peritoneal macrophages showed that surface expression of hFc gamma RI was reduced by approximately 80%. The remaining approximately 20% of receptors were still capable of binding IgG-opsonized RBC, suggesting FcR gamma-chain not to be critical for hFc gamma RI ligand-binding capacity. Importantly, however, hFc gamma RI signaling capacity was lost in FcR gamma-chain-deficient cells. No phagocytosis could be observed using either ligand sensitized (EA- IgG2a) or CD64-targeted erythrocytes (using a bispecific antibody) in both hFc gamma RI transgenic lines. This documents the FcR gamma-chain to be indispensable for both surface membrane expression and function of human Fc gamma RI in vivo.     

Knowledge of pressure ulcer prevention: a cross-sectional and comparative study among nurses

Background  

Pressure ulcers are a common, painful and costly condition. Results of a 1991 study into the knowledge among Dutch hospital nurses on the usefulness of measures to prevent pressure ulcers showed moderate knowledge. Results were confirmed by subsequent studies. In recent years, Dutch guidelines have been updated and the attention given to pressure ulcer care has been increased. This was expected to improve pressure ulcer care and to increase nurses' knowledge. The aims of the current study were to investigate (1) how much nurses employed in Dutch hospitals know about the usefulness of 28 preventive measures considered in the most recent national pressure ulcer guideline; (2) whether differences in knowledge exist between nurses working in hospitals that audit pressure ulcers and those employed in hospitals that do not; and (3) to study whether knowledge among Dutch hospital nurses regarding the usefulness of preventive measures had changed between 1991 and 2003.     

Biochemical and behavioural characterization of EMPA,a novel high-affinity,selective antagonist for the OX2 receptor

Background and purpose:

The OX₂ receptor is a G-protein-coupled receptor that is abundantly found in the tuberomammillary nucleus, an important site for the regulation of the sleep-wake state. Herein, we describe the in vitro and in vivo properties of a selective OX₂ receptor antagonist, N-ethyl-2-[(6-methoxy-pyridin-3-yl)-(toluene-2-sulphonyl)-amino]-N-pyridin-3-ylmethyl-acetamide (EMPA).

Experimental approach:

The affinity of [³H]EMPA was assessed in membranes from HEK293-hOX₂-cells using saturation and binding kinetics. The antagonist properties of EMPA were determined by Schild analysis using the orexin-A-or orexin-B-induced accumulation of [³H]inositol phosphates (IP). Quantitative autoradiography was used to determine the distribution and abundance of OX₂ receptors in rat brain. The in vivo activity of EMPA was assessed by reversal of [Ala¹¹,D-Leu¹⁵]orexin-B-induced hyperlocomotion during the resting phase in mice and the reduction of spontaneous locomotor activity (LMA) during the active phase in rats.

Key results:

[³H]EMPA bound to human and rat OX₂-HEK293 membranes with K_D values of 1.1 and 1.4 nmol·L⁻¹ respectively. EMPA competitively antagonized orexin-A-and orexin-B-evoked accumulation of [³H]IP at hOX₂ receptors with pA₂ values of 8.6 and 8.8 respectively. Autoradiography of rat brain confirmed the selectivity of [³H]EMPA for OX₂ receptors. EMPA significantly reversed [Ala¹¹,D-Leu¹⁵]orexin-B-induced hyperlocomotion dose-dependently during the resting phase in mice. EMPA, injected i.p. in rats during the active phase, reduced LMA dose-dependently. EMPA did not impair performance of rats in the rotarod procedure.

Conclusions and implications:

EMPA is a high-affinity, reversible and selective OX₂ receptor antagonist, active in vivo, which should prove useful for analysis of OX₂ receptor function.     

Regulation by FK506 and rapamycin of Ca2+ release from the sarcoplasmic reticulum in vascular smooth muscle: the role of FK506 binding proteins and mTOR

Background and purpose:

The sarcoplasmic reticulum (SR), regulates the cytoplasmic Ca²⁺ concentration ([Ca²⁺]_cyto) in vascular smooth muscle. Release from the SR is controlled by two intracellular receptor/channel complexes, the ryanodine receptor (RyR) and the inositol 1,4,5-trisphosphate receptor (IP₃R). These receptors may be regulated by the accessory FK506-binding protein (FKBP) either directly, by binding to the channel, or indirectly via FKBP modulation of two targets, the phosphatase, calcineurin or the kinase, mammalian target of rapamycin (mTOR).

Experimental approach:

Single portal vein myocytes were voltage-clamped in whole cell configuration and [Ca²⁺]_cyto measured using fluo-3. IP₃Rs were activated by photolysis of caged IP₃ and RyRs activated by hydrostatic application of caffeine.

Key results:

FK506 which displaces FKBP from each receptor (to inhibit calcineurin) increased the [Ca²⁺]_cyto rise evoked by activation of either RyR or IP₃R. Rapamycin which displaces FKBP (to inhibit mTOR) also increased the amplitude of the caffeine-evoked, but reduced the IP₃-evoked [Ca²⁺]_cyto rise. None of the phosphatase inhibitors, cypermethrin, okadaic acid or calcineurin inhibitory peptide, altered either caffeine- or IP₃-evoked [Ca²⁺]_cyto release; calcineurin did not contribute to FK506-mediated potentiation of RyR- or IP₃R-mediated Ca²⁺ release. The mTOR inhibitor {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002, like rapamycin, decreased IP₃-evoked Ca²⁺ release.

Conclusions and implications:

Ca²⁺ release in portal vein myocytes, via RyR, was modulated directly by FKBP binding to the channel; neither calcineurin nor mTOR contributed to this regulation. However, IP₃R-mediated Ca²⁺ release, while also modulated directly by FKBP may be additionally regulated by mTOR. Rapamycin inhibition of IP₃-mediated Ca²⁺ release may be explained by mTOR inhibition.     

Oxidative degradation of cholesteryl esters in low-density lipoproteins: analysis by liquid chromatography-light scattering and protection by a new synthetic antioxidant, S20478

Summary— Cholesteryl esters in the hydrophobic core of low-density lipoprotein (LDL) particles constitute a major molecular target during copper-mediated oxidation. To facilitate the rapid analysis and quantitation of the oxidative degradation of LDL cholesteryl esters, we describe a new approach based on light scattering detection following separation by HPLC. We have applied this approach to the evaluation of the protective capacity of a new synthetic antioxidant, S20478, during oxidation of LDL in the presence of copper ions. HPLC separation of cholesterol and the four major molecular species of cholesteryl esters (C16:0, C18:1, C18:2 and C20:4) of LDL was achieved in a single run of 20 min with high sensitivity (50 ng) and low background. Time course studies of the oxidative modification of LDL (ratio LDL protein: copper, 100 μg/mL: 1μM) revealed that the content of unsaturated cholesteryl esters (C20:4 and C18:2) decreased (–30% and –15%, respectively) within 90 min of copper-mediated oxidation, while only minor degradation (up to 15%) of monounsaturated (C18:1) and saturated (C16:0) esters occurred. At 24 hours of oxidation, only traces (< 5%) of the C20:4 and C18:2 esters were detectable; whereas 52% of the C18:1 ester remained (P < 0.01). Of the saturated esters, only minor proportions (35% or less) underwent oxidative modification. In addition, some 81% of free cholesterol was conserved as the native sterol. The synthetic antioxidant, S20478 (50 μM) was capable of inhibiting the initiation and the propagation of copper-mediated LDL oxidation as determined by the time- and dose-dependant inhibition of the formation of conjugated dienes and thiobarbituric acid-reactive substances, as well as the conservation of the net electrical charge of LDL; indeed S20478 conserved cholesteryl esters in their native form up to 24 hours. However, after prolonged exposure to copper ions (48 hours), only 47% of the unsaturated esters remained (C18:2, P < 0.05). Nonetheless, S20478 (10 μM) was more efficient in inhibiting copper-mediated LDL oxidation as compared to probucol at the same concentration. These findings suggest that S20478 may be of potential interest in a new antioxidant approach to therapeutic stabilisation and regression of atherosclerotic plaques. Moreover, this method should prove useful in the assessment of the integrity of native LDL, and provides a new chemical marker of the degree of LDL oxidation.     

INTERACTION OF EXOGENOUS OUABAIN AND CHRONIC MINERALOCORTICOID TREATMENT IN THE KIDNEY OF THE CONSCIOUS SHEEP

1. Ouabain is known to have natriuretic effects only at high doses, and therefore if endogenously produced ouabain has a role in the regulation of sodium excretion, the renal response to ouabain must be increased substantially in certain physiological situations. The aim of this study is to determine whether treatment with the mineralocorticoid, aldosterone, potentiates that natriuretic response to ouabain. 2. Six conscious sheep received renal arterial infusion of either vehicle or aldosterone (3 μg/h). Forty hours after commencement of infusion ouabain was infused into the renal artery at 400 μg/h for 60min. A second infusion of ouabain was administered on the 6th day of aldosterone treatment. 3. In the absence of aldosterone, the effects on sodium excretion produced by ouabain infusion at 400 μg/h into the renal artery were variable and not statistically significant. Ouabain infusion after 40 h of aldosterone treatment increased sodium excretion from 40 ± 14 to 676 ± 69 μmol/min in the second hour following cessation of ouabain infusion (P< 0.001). Ouabain infusion after 6 days of aldosterone treatment increased sodium excretion similarly. Ouabain-stimulated sodium excretion was significantly greater during aldosterone treatment compared to vehicle treatment (P<0.05). In contrast, no enhancement of effect was observed after acute treatment with aldosterone. 4. These results demonstrate potentiation of the natriuretic response to ouabain infusion by chronic mineralocorticoid treatment and suggest a potential role of endogenous digitalislike factor in the physiological control of sodium homeo stasisaldo sterone, endogenous digitalis-like factor, ouabain, sodium excretion.     

人工神经元网络用于复方氯丙嗪的含量测定

将误差反向传播(BP)的人工神经元网络(ANN)模型，用于复方氯丙嗪紫外重叠光谱分 析。对ANN模型的参数进行了优化。采用f(x)二1/(1+e^-x)作为网络节点的输入输出转换函数的三 层神经网络具有较佳性能，当取隐含节点数为15时，该网络预测结果的最小平均相对误差为1.22％， 将研制的ANN模型用于复方氯丙嗪含量测定，其结果与药品标准法和偏最小二乘法(PLs)一致。     

庆大霉素在小鼠的时辰毒性及时辰药代动力学

本文研究了庆大霉素对小鼠的毒性及其药代动力学的昼夜节律性变化。雄性ICR小鼠自实验前两周置于标准的明期和暗期下饲养,自由进食进水。毒性实验剂量为庆大霉素290mg/kg,Sc:药代动力学实验剂量为45 mg/kg,Sc。结果表明,庆大霉素毒性及药代动力学因用药时间不同呈明显的昼夜节律性变化。明期中点用药毒性最大,血药浓度最高,AUC值最大:暗期用药毒性小,血药浓度低,AUC值小。提示了庆大霉素毒性的昼夜节律变化与其药代动力学的的昼夜节律变化有密切关系。