镁锌合金在动物体内降解及其相容性

背景:研究发现镁离子可以促进成骨细胞的生长,但镁合金存体内的相容性和降解性尚不清楚.目的:观察镁锌合金在动物体内的生物相容性及其在体内降解和新骨形成情况.设计、时间及地点:随机对照动物实验,于2008-03/11在上海交通大学附属第六人民医院动物实验室完成.材料:镁锌合金棒由上海奥芮济材料和医学技术有限公司提供,含镁94%,含锌6%.聚丙交酯棒由京同公司提供.方法:48只新西兰大白兔随机分成镁锌合金组和聚丙交酯组,每组24只.在左侧股骨髁钻成直径0.45 cm,长1 cm的孔,分别植入镁锌合金棒和聚丙交酯棒.主要观察指标:植入前第1天,植入后第1天、第1,2,5,10周测镁锌合金组动脉血镁离子,镁锌合金组和聚丙交酯组白蛋白、碱性磷酸酶、钤丙转氨酶、尿酸、肌酐水平.植入后3,6,12,18周植入材料部位拍摄X射线片,摄片后取股骨髁,脱钙后苏水精伊红染色组织学观察和骨量分析.结果:镁锌合金组各血清学指标存第1周内均有不同程度提高,但第2周开始下降,变化无显著性意义.两组其他各生化指标变化芹异无显著性意义.X射线片在3周显示镁锌合金组材料旁有气体产生,6周发现有成骨.12周时骨密度明显增加,12周气体自行消失.而聚丙交酯组无气体产生,有成骨.18周时镁锌合金组成骨多于聚丙交酯组(P<0.05).结论:镁锌合金在动物体内降解时有新骨替代形成,具有良好的生物相容性.     

种植体材料钛与种植体上部结构合金间电偶的腐蚀性

背景:大多数和钛种植体接触的牙科金属修复部分,会引起电偶腐蚀的发生.偶对在种植体界面产生带正电的局部环境,这会直接影响组织状况,尤其是骨吸收.目的:评价TA2型商业纯钛分别与金合金、钴铬合金、钛合金及镍铬合金在体外的电偶腐蚀行为.方法:在人工唾液中体外模拟TA2型商业纯钛分别与金合金、钴铬合金、钛合金及镍铬合金接触时的回路,测量其作用15 h的混合电位和电偶电流值并描绘电流时间曲线.结果与结论:4组合金接触8 h后电流达到稳定,稳定后电偶电流值排列顺序为钛/金合金<钛/钴铬合金<钛/钛合金<钛/镍铬合金.提示钛/金合金组电偶腐蚀最小,金合金是最适合作为种植义齿上部结构的材料;钛/镍铬合金组电偶腐蚀最大,镍铬合金是最不适合作为种植义齿上部结构的材料.     

体内生物反应器与体内骨组织工程

近年来，骨组织工程研究在种子细胞、支架材料和构建技术3个主要方面均取得了巨大进展，但复合体外培养细胞的骨组织工程产品临床应用仍面临挑战。体内骨组织工程是以受体自身机体作为生物反应器，单纯应用生物材料而不外加细胞或生长因子，在骨或非骨环境构建形成骨移植物修复自体骨缺损的技术。有关研究显示这是一种调动机体自我再生能力的组织工程新策略，具有切实可行的应用前景。     

In vivo thrombus formation

Summary.  Thrombus formation, including platelet adhesion, activation, secretion and aggregation as well as tissue factor-initiated thrombin generation and fibrin formation, has been studied in the past using in vitro systems, often with isolated components. Given the complexity of hemostasis and thrombosis, many of the concepts that have been developed to explain these processes are being revisited by studying thrombus formation in live animals using intravital microscopy and genetically altered mice. Although much of the dogma that has evolved has been confirmed by in vivo studies of thrombus formation, there have also been conflicts between old concepts and new direct observations. In vivo studies of the initiation of thrombus formation, platelet accumulation and thrombin generation have provided evidence for the participation of novel proteins and identified new pathways and mechanisms.     

In vivo and ex vivo epi-mode pump-probe imaging of melanin and microvasculature

We performed epi-mode pump-probe imaging of melanin in excised human pigmented lesions and both hemoglobin and melanin in live xenograft mouse melanoma models to depths greater than 100 μm. Eumelanin and pheomelanin images, which have been previously demonstrated to differentiate melanoma from benign lesions, were acquired at the dermal-epidermal junction with cellular resolution and modest optical powers (down to 15 mW). We imaged dermal microvasculature with the same wavelengths, allowing simultaneous acquisition of melanin, hemoglobin and multiphoton autofluorescence images. Molecular pump-probe imaging of melanocytes, skin structure and microvessels allows comprehensive, non-invasive characterization of pigmented lesions.     

In vivo probes: problems and perspectives

Devices constructed for potential use as invasive bioprobes incorporate a selective receiving site for molecular or ionic recognition, and a transducer which is capable of translating a perturbation of physical chemistry of the determinant-site reaction (interaction) into a usable signal. Four types are envisioned--implants for general hospital use, transient-use probes to replace classical blood tests, short-term implantable probes and the long-term variety. Performance criteria are selectivity, sensitivity, fast response, site-reversible, small, rugged, inexpensive, biocompatible, calibratible, facile use by non-expert personnel and ease of telemetry. These demands, not surprisingly, create enormous challenges to the sensor specialist. With respect to biocompatibility the sensor must not be involved in infection, clot formation or antigenic response, and, furthermore, protein adsorption, etc., which can affect the sensor response should be avoided. Calibration remains a problem of monumental proportions. Many devices drift from calibrated levels even in in vitro experiments, let alone in the implanted milieu. One solution has been to carry out on-line switching between patient blood and standard solutions. However, this type of approach leaves a lot to be desired with respect to portability. Another method which is attracting increasing attention is the chemometric or artificial intelligence system involving compensation by multi-sensor array configurations. Sensitivity and limit-of-detection have attracted little research due to the overwhelming nature of other difficulties. In the present paper we evaluate a number of these technical problems and discuss the architecture of devices that are currently available. Finally, some thoughts as to priorities for re-directing sensor research in the bioprobe area are presented.     

纳米羟基磷灰石膜聚氨酯复合材料的体内组织相容性

背景：纳米羟基磷灰石与聚氨酯复合材料在体外实验中具有良好的相容性。目的：验证纳米羟基磷灰石膜聚氨酯复合材料在大鼠体内的组织相容性。方法：将18只SD大鼠随机分为复合材料组、聚氨酯组和对照组,复合材料组和聚氨酯组分别将纳米羟基磷灰石膜聚氨酯复合材料、聚氨酯植入大鼠背部肌肉内,对照组仅作切开缝合,未植入任何材料。结果与结论：①大体观察：术后12周,各组切口与周围皮肤几乎无界限,聚氨酯组及复合材料组囊壁与材料融合较好,对照组皮肤己恢复正常。②组织学观察：术后4,8,12周,聚氨酯组及复合材料组切口周围组织中淋巴细胞数、中性粒细胞数及毛细血管量均高于对照组（P〈0．05）,复合材料组切口周围组织中淋巴细胞数、中性粒细胞数及毛细血管量均少于聚氨酯组（P〈0．05）。证实纳米羟基磷灰石膜聚氨酯复合材料具有较好的组织相容性。     

In vivo stability of cryoprecipitate fibrinogen

Because of its lower hepatitis risk, cryoprecipitate has been advocated as a substitute for commercial fibrinogen. Previous literature on cryofibrinogen has demonstrated a short blood t1/2, rendering it unsuitable for therapeutic use. The in vivo clearance of 131I- cryoprecipitate was compared with that of 125I-standard fibrinogen. A small amount of cryoprecipitate was rapidly cleared and apparently was cryofibrinogen. However, the bulk of the cryoprecipitate was cleared with a normal half life, as was cryoprecipitated that was in 10-bag pools. The data indicated cryoprecipitate was an effective in vivo form of fibrinogen and thus the preferred fibrinogen source because of its combining normal t1/2 with single donor procurement.     

In vivo micro-MRI of intracortical neurovasculature

This work describes a methodology for in vivo MR imaging of arteries and veins within the visual cortex of the cat brain. Very high magnetic fields (9.4 T) and small field-of-view 3D acquisitions were used to image the neurovasculature at resolutions approaching the microscopic scale. A combination of time-of-flight MR angiography and T*(2)-weighted imaging, using both endogenous BOLD contrast and an exogenous iron-oxide contrast agent, provided high specificity for distinguishing between arteries and veins within the cortex. These acquisition techniques, combined with 3D image processing and display methods, were used to detect and visualize intracortical arteries and veins with diameters smaller than 100 microm. This methodology can be used for visualizing the neurovasculature or building models of the vascular network and may benefit a variety of research applications including fMRI, cerebrovascular disease and cancer angiogenesis.     

In vivo mapping of brain myo-inositol

Myo-Inositol (MI) is one of the most abundant metabolites in the human brain located mainly in glial cells and functions as an osmolyte. The concentration of MI is altered in many brain disorders including Alzheimer's disease and brain tumors. Currently available magnetic resonance spectroscopy (MRS) methods for measuring MI are limited to low spatial resolution. Here, we demonstrate that the hydroxyl protons on MI exhibit chemical exchange with bulk water and saturation of these protons leads to reduction in bulk water signal through a mechanism known as chemical exchange saturation transfer (CEST). The hydroxyl proton exchange rate (k=600 s(-1)) is determined to be in the slow to intermediate exchange regime on the NMR time scale (chemical shift (?ω)>k), suggesting that the CEST effect of MI (MICEST) can be imaged at high fields such as 7 T (?ω=1.2×10(3)rad/s) and 9.4 T (?ω=1.6×10(3) rad/s). Using optimized imaging parameters, concentration dependent broad CEST asymmetry between ~0.2 and 1.5 ppm with a peak at ~0.6 ppm from bulk water was observed. Further, it is demonstrated that MICEST detection is feasible in the human brain at ultra high fields (7 T) without exceeding the allowed limits on radiofrequency specific absorption rate. Results from healthy human volunteers (N=5) showed significantly higher (p=0.03) MICEST effect from white matter (5.2±0.5%) compared to gray matter (4.3±0.5%). The mean coefficient of variations for intra-subject MICEST contrast in WM and GM were 0.49 and 0.58 respectively. Potential overlap of CEST signals from other brain metabolites with the observed MICEST map is discussed. This noninvasive approach potentially opens the way to image MI in vivo and to monitor its alteration in many disease conditions.     

In vivo pharmacodynamic activity of daptomycin

Daptomycin is a lipopeptide antibiotic with activity against a wide range of gram-positive bacteria. We used the neutropenic murine thigh model to characterize the pharmacodynamics of daptomycin. ICR/Swiss mice were rendered neutropenic with cyclophosphamide; and the thigh muscles of the mice were infected with strains of Staphylococcus aureus, Streptococcus pneumoniae, and Enterococcus faecium. Animals were treated by subcutaneous injection of daptomycin at doses of 0.20 to 400 mg/kg of body weight/day divided into one, two, four, or eight doses over 24 h. Daptomycin exhibited linear pharmacokinetics, with an area under the concentration-time curve (AUC) from time zero to infinity/dose of 9.4 and a half-life of 0.9 to 1.4 h. The level of protein binding was 90%. Free daptomycin exhibited concentration-dependent killing and produced in vivo postantibiotic effects (PAEs) of 4.8 to 10.8 h. Nonlinear regression analysis was used to determine which pharmacokinetic (PK) or pharmacodynamic (PD) parameter was important for efficacy by using free drug concentrations. The peak concentration/MIC (peak/MIC) ratio and 24-h AUC/MIC ratio were the PK and PD parameters that best correlated with in vivo efficacy (R(2) = 83 to 87% for peak/MIC and R(2) = 86% for the AUC/MIC ratio, whereas R(2) = 47 to 50% for the time that the concentration was greater than the MIC) against standard strains of S. aureus and S. pneumoniae. The peak/MIC ratios required for a bacteriostatic effect ranged from 12 to 36 for S. pneumoniae, 59 to 94 for S. aureus, and 0.14 to 0.25 for E. faecium. The AUC/MIC ratios needed for a bacteriostatic effect ranged from 75 to 237 for S. pneumoniae, 388 to 537 for S. aureus, and 0.94 to 1.67 for E. faecium. The free daptomycin concentrations needed to average from one to two times the MIC over 24 h to produce a bacteriostatic effect and two to four times the MIC over 24 h to produce greater than 99% killing. The long PAE and potent bactericidal activity make daptomycin an attractive option for the treatment of infections caused by gram-positive bacteria.     

In vitro and in vivo antibacterial activities of telithromycin

BACKGROUND: Telithromycin is one of the ketolides, characterised by a 3-keto group instead of L-cladinose and a C(11)-C(12) carbamate link by an alkyl chain to a pyridinum and imidazolium ring side chain. We evaluated in vitro and in vivo antibacterial activities of telithromycin against gynaecological pathogens. METHODS: In the vitro study, the antibacterial activity of telithromycin against 180 isolates (isolated in the year 2000) of Streptococcus agalactiae (n = 33), Enterococcus faecalis (n = 22), Neisseria gonorrhoeae (n = 30), Peptostreptococcus anaerobius (n = 20), Finegoldia magna (n = 20), Bacteroides fragilis (n = 25) and Prevotella bivia (n = 30) was compared with that of erythromycin A, clarithromycin, azithromycin, ampicillin and levofloxacin. In the in vivo study, the efficacy of telithromycin was evaluated using experimental intra-abdominal abscesses in mice caused by B. fragilis (minimum inhibitory concentration of telithromycin 0.5 mg/l). RESULTS: In the in vitro study, telithromycin inhibited more than 50% of clinical isolates of S. agalactiae, E. faecalis, N. gonorrhoeae, P. anaerobius, F. magna, B. fragilis and P. bivia at concentrations of 0.016, 0.063, 0.063, 0.032, 0.032, 0.5 and 0.25 mg/l, respectively. Telithromycin inhibited more than 90% of these clinical isolates at concentrations of 0.016, 4, 0.125, 0.063, 0.063, 4 and 1 mg/l, respectively. In the in vivo study, telithromycin inhibited abscess formation and significantly decreased viable cell counts in abscesses in comparison with the untreated group. CONCLUSIONS: These in vitro and in vivo antibacterial activities suggest that telithromycin could be a potential candidate for the treatment of bacterial infections complicated by chlamydial infection.