羟基磷灰石/多聚左旋乳酸椎间融合器的力学评价

目的:评价羟基磷灰石和多聚左旋乳酸(hydroxyapatite/poly-L-lacticacid,HA/PLLA)制成的可吸收性腰椎椎间融合器(cage)的力学特性。方法:形状相同的HA/PLLAcage和Brantigan碳纤维cage及与cage外径相同的人尸体髂骨块各16枚,在材料实验机MTS上分别将3种椎体间置入体行压缩破坏(n=8)和压缩疲劳(n=8)试验,记录置入体压缩破坏时的最大压力、弹性系数以及1万次压力负荷后的高度变形率,并加以比较。结果:在瞬间破坏压力和弹性系数方面,HA/PLLAcage和碳纤维cage均显著高于髂骨块(P<0.05),但两种cage间差异无显著性(P>0.05)。1万次压力负荷后,两种cage的高度压缩率均显著小于髂骨块(P<0.05),且HA/PLLAcage的平均压缩率显著小于碳纤维cage(P<0.05)。结论:HA/PLLAcage和碳纤维cage较髂骨块具有更强的力学稳定性;与碳纤维cage相比,HA/PLLAcage不仅具有同等的瞬间抗破坏强度,而且具有更强的抗重复负荷变形的能力。     

关节镜下可吸收交叉钉固定腘绳肌腱重建前十字韧带

目的介绍在关节镜下腘绳肌腱移植重建前十字韧带并利用可吸收交叉钉固定的方法，探讨其临床效果。方法2005年3月至2006年3月，共治疗31例前十字韧带断裂患者。男18例，女13例；年龄19-51岁，平均34岁。致伤原因：交通伤15例，日常生活及运动损伤16例。病程为5d～36个月。合并半月板损伤12例，合并内侧副韧带Ⅰ、Ⅱ度损伤6例，Ⅲ度损伤3例，均为新鲜损伤。合并后十字韧带断裂6例。术后随访12-24个月，平均16．8个月，观察此固定方法的可靠性和疗效。以Lyscholm评分和KT-2000评价手术前后膝关节功能及稳定性。结果26例患者获得随访，所有患者均无伸膝受限，膝关节屈曲活动度均〉120°。屈膝90°时前抽屉试验均阴性；Lachman试验强阳性1例，阳性4例，阴性21例；膝关节功能Lyscholm评分为（94．6±4．2）分。KT-2000检查结果：25例双膝差距为0-4．0mm，平均2．4mm，1例患者关节不稳定，双膝差距5．5mm。结论可吸收交叉钉固定可为关节镜下腘绳肌腱移植重建前十字韧带提供早期的初始稳定性和后期的生物稳定性，是一种可靠的固定方法。     

Quantification of tissue plasma volume in the rat by contrast-enhanced magnetic resonance imaging

Magnetic resonance imaging enhanced with a macromolecular contrast medium (MMCM), albumin-Gd-DTPA, was used to estimate the plasma volume in vivo in the myocardium, lung, liver, and skeletal muscle of 10 normal rats. The plasma volumes of the same tissues in a parallel group of six rats were estimated in vitro by a conventional radioisotopic technique (¹¹¹In-transferrin). Plasma volumes of myocardium, lung, liver, and skeletal muscle estimated by the MR technique (μl plas. ia cc-¹ of tissue) were 101,109,163, and 11.0, respectively, while plasma volumes measured by the In-transferrin radioisotope technique (mg plasma g-¹ of tissue) were 78.6, 215,143, and 11-2, respectively. Assuming a ratio of densities of aerated lung to blood of 0.45 and of other tissues to blood of 1.0, correlation between the methods was excellent (R² = 0.99) indicating that MR imaging enhanced with MMCM permits reliable in vivo estimation of tissue plasma volume in the rat.     

硫杂蒽酮类光引发剂的合成

合成了12种烷基、烷氧基和硝基取代的硫杂蒽酮类化合物。其中,三种烷氧基取代的硫杂蒽酮是用相转移催化法制得的。几种新的化合物,经红外光谱、质谱和元素分析等方法鉴定,确证了其结构。测定了化合物的紫外吸收光谱。结果表明,硫杂蒽酮类化合物的2-位上是斥电子基时,其最大吸收波长要向红移动;若2-位上是吸电子基时则向紫移动。     

Simple Trends in the Methylene and α‐Substituent Regions of NMR Spectra of Vinyl Polymers

Summary: Chemical shift trends in the methylene and α substituent regions of ¹³C NMR spectra of vinyl polymers have been analyzed in terms of a three‐state rotational isomeric states (RIS) model and the γ‐gauche effect. In this framework, it has been demonstrated that the three sequencing rules observed for poly(propylene) can also be expected to work for many other vinyl polymers. The first two rules, justified in terms of the conformational perturbability of stereosequences, turn out to be respected by a considerable number of NMR spectra. On the other hand, the same spectral data are in substantial disagreement with the third rule. An explanation is proposed for this breakdown.

Sketches of the three conformations expected for rotation on the two prochiral bonds flanking the methine carbon of a vinyl polymer.     

Computer Simulations of the “Hairy Rod” Model

Summary: Using extensive Molecular Dynamics simulations we study the behavior of very rigid polyelectrolytes with hydrophobic side chains that are known to form cylindrical micelles in aqueous solution. We investigate the stability of such micelles with respect to hydrophobicity, Coulomb interaction, and micellar size. We show that for the parameter range relevant for poly(p‐phenylene sulfonate)s (PPP) one finds a stable finite micellar size close to the experimental parameter region. We also point out that our model has some similarities to DNA solutions with added condensing agents, hinting to the possibility that the size of DNA aggregates is under certain circumstances thermodynamically limited.

DNA‐like morphologies of the polyelectrolytes.     

Synthesis of Diene‐Functionalized Macromonomers via Functionalization with Hexa‐1,3,5‐triene

The reaction of poly(styryl)lithium (PSLi) with hexa‐1,3,5‐triene (HXT) was studied as a route to diene‐functionalized macromonomers. When PSLi was reacted with 1.5 molar equivalents of HXT for 2.5 h at ?10 °C in toluene, it was found that the diene‐functionalized macromonomer was obtained in high yield; however, oligomerization of the HXT was observed by matrix‐assisted laser absorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). Oligomerization was eliminated by running the reaction with only 1.2 molar equivalents of HXT to PSLi and allowing the reaction to run for 15 min at ?10 °C in toluene. The resulting polymer exhibited high diene chain‐end functionality and no oligomerization was observed by MALDI‐TOF MS. ¹³C NMR spectroscopy and the attached‐proton test (APT), along with calculated chemical shifts, showed the presence of both the 1,2‐ and 1,4‐addition chain‐end structures. Further analysis by the reaction of the functional polymer with maleic anhydride indicated that 18 wt.‐% of the product was unreactive, either because of a 1,4‐addition chain‐end structure or a nonfunctional polymer. The structure of the maleic anhydride‐modified polymer was determined by MALDI‐TOF MS and ¹³C NMR spectroscopy. Preliminary work on the reactivity of the diene‐functionalized macromonomers was performed by the addition of a large excess of PSLi to a solution of macromonomer followed by characterization by size‐exclusion chromatography (SEC).

The formation of hexa‐1,3,5‐triene‐functionalized polystyrenes and their reaction with maleic anhydride.     

Piretanide-dextran and piretanide-polyethylene glycol interact with high affinity with the Na+ 2 Cl− K+ cotransporter in the thick ascending limb of the loop of Henle

Piretanide blocks the Na⁺ 2Cl^– K⁺ cotransporter protein in the thick ascending limb (TAL) of the loop of Henle reversibly. When tested from the luminal side in isolated perfused cTAL segments it leads to a half maximal inhibition (IC₅₀) of the equivalent short circuit current (I_sc) at a concentration of 10^–6 mol/l. From the basolateral side it has no effect on I_sc up to 10^–4 mol/l. The present study was designed to search for high affinity blockers of the Na⁺ 2Cl^– K⁺ cotransporter with large molecular weight in an attempt to use these macromolecules for antibody-labelling or affinity separation of this transport-protein. Amino-ethyl-dextran or amino-ethyl-polyethylene glycol (M.W. 5kd) were coupled to isothiocyanato-piretanide (ISO-PIR) at room temperature in DMSO. The resulting compounds dextran-sulfonylurea-piretanide (PIR-DEX) and polyethylene glycol-sulfonylurea-piretanide (PIR-PEG) (M.W. 5.38kd) were purified and tested in isolated perfused cTAL segments. IC₅₀ values for ISO-PIR, PIR-DEX and PIR-PEG were estimated from dose response curves after their addition to the lumen or bath perfusate, respectively. ISO-PIR, PIR-DEX and PIR-PEG acted from the lumen side at 3·10^–6, 6·10^–6 and 2·10^–6 mol/l. The inhibitory effect was easily reversible. From the basolateral side no effect for any compound was seen at up to 10^–4 mol/l. In clearance experiments PIR-DEX was given to female Wistar rats as an i.v. bolus (25 mol/kg) and the diuretic urine was collected. After dialysis (exclusion limit 2.5kd) the dialysed urine and the dialysate were tested in isolated perfused cTAL segments. The dialysates had no effect on I_sc, but the dialysed urine inhibited I_sc by 35% from the luminal side. The present data show: High molecular derivatives of piretanide with dextran or polyethylene glycol moieties block the Na⁺ 2Cl^– K⁺ cotransporter in cTAL segments at roughly the same low concentration as piretanide itself. Our data exclude a metabolism of these piretanide compounds in the kidney. Since these macromolecular probes can probably not enter the cell their inhibitory effect indicates that the binding site for piretanide diuretics on the Na⁺ 2Cl^– K⁺ cotransporter is exposed on the surface of the luminal cell membrane.This study was supported by Deutsche Forschungsgemeinschaft Gr 480/9     

Formation of Regular Hole Pattern in Polymer Films

Ordered macroporous materials recently have attracted much attention. A method that utilizes the condensation of monodisperse water droplets on a polymer solution is proposed for the preparation of honeycomb microporous films. Our results show that it is a general method that can be used for patterning a wide range of polymers. The presence of water vapor and polymer is necessary for the formation of regular holes in films. The formation of hexagonal packing instead of other kinds of packing takes place because the hexagonal packing has the lowest free energy. The formation mechanisms of regular hole pattern and imperfections in the hexagonal packing are proposed.

Hexagonal hole structures in a PMMA film.     

Effect of a Polymeric Additive on the Pore‐Size Distribution and Shrinking Process of a Hydrogel Network

A systematic comparison of the effect of architectural modifications to the network structure on the internal microstructure of N‐isopropylacrylamide (NIPA) based hydrogels showed that the addition of a second component to the network significantly increased the proportion of macropores in the network. The second components considered were short poly(N‐isopropylacrylamide) (PNIPAM) chains grafted to the network backbone, high‐molecular‐weight polyacrylamide (PAM) chains, or microsphere particles of PNIPAM. Structures are proposed for each of the modified gel networks taking into account the new structural information. Through a combination of the pore size and network structure data reported here, and with the shrinking data obtained previously, shrinking mechanisms are proposed for each of the modified network structures. In all cases, the enhanced shrinking rates were directly caused by the presence of the second component, which acted as nuclei for shrinking (graft‐PNIPAM and PNIPAM microspheres) or as water‐release channels (PAM gel), and indirectly caused by the second components via their affect on the network microstructure.

Proposed structures for the architecturally modified gels based on the pore‐size information. Graft‐PNIPAM gel. The freely mobile graft chains prevent chains from meeting resulting in larger pores.