B:b interactions are essential for polymerization of variant fibrinogens with impaired holes 'a'.

BACKGROUND: Fibrin polymerization is mediated by interactions between knobs 'A' and 'B' exposed by thrombin cleavage, and holes 'a' and 'b' always present in fibrinogen. The role of A:a interactions is well established, but the roles of knob:hole interactions A:b, B:b or B:a remain ambiguous. OBJECTIVES: To determine whether A:b or B:b interactions have a role in thrombin-catalyzed polymerization, we examined a series of fibrinogen variants with substitutions altering holes 'a': gamma364Ala, gamma364His or gamma364Val. METHODS: We examined thrombin- and reptilase-catalyzed fibrinopeptide release by high-performance liquid chromatography, fibrin clot formation by turbidity, fibrin clot structure by scanning electron microscopy (SEM) and factor (F) XIIIa-catalyzed crosslinking by sodium dodecylsulfate polyacrylamide gel electrophoresis. RESULTS: Thrombin-catalyzed fibrinopeptide A release was normal, but fibrinopeptide B release was delayed for all variants. The variant fibrinogens all showed markedly impaired thrombin-catalyzed polymerization; polymerization of gamma364Val and gamma364His were more delayed than gamma364Ala. There was absolutely no polymerization of any variant with reptilase, which exposed only knobs 'A'. SEM showed that the variant clots formed after 24 h had uniform, ordered fibers that were thicker than normal. Polymerization of the variant fibrinogens was inhibited dose-dependently by the addition of either Gly-Pro-Arg-Pro (GPRP) or Gly-His-Arg-Pro (GHRP), peptides that specifically block holes 'a' and 'b', respectively. FXIIIa-catalyzed crosslinking between gamma-chains was markedly delayed for all the variants. CONCLUSION: These results demonstrate that B:b interactions are critical for polymerization of variant fibrinogens with impaired holes 'a'. Based on these data, we propose a model wherein B:b interactions participate in protofibril formation.     

对二甲苯搅拌式反应器增设导流简的流体力学

在高径比为1.0的搅拌反应器中,研究了导流筒结构及固体含量对翼型轴流桨功耗与气含率的影响.研究发现导流筒的安装会降低功耗,提高气含率;导流筒的开孔率以16.4%为佳;翼型桨排出流向上时功耗较小,气舍率较高;功耗随固体含量的增加而增大;气液两相体系中的气含率比气液固三相体系中的气含率高;并得到在开孔率为16.4%条件下,翼型轴流桨上提操作时的气含率关联式.此外,在高径比为1.5时对双层组合桨进行了研究,并得出了与单层桨类似的结论.     

Reconstruction of surgical skull defects with hydroxylapatite ceramic buttons and granules

Summary This paper is to report a new method of reconstructing surgical skull defects with hydroxylapatite ceramics. The latter consist of Ca₁₀(PO₄)₆(OH)₂ which has a biological affinity with mammalian bone minerals. The author has designed two cranioplastic materials using hydroxylapatite ceramics: apatite buttons for burr hole skull defects and apatite granules for linear skull defects. The bone defects during 100 cases of standard craniotomy were successfully reconstructed with these materials with satisfactory cosmetic results. Hydroxylapatite ceramics are characterized by the excellent biocompatibility and biostability with a resultant bony fusion.     

Graphite photoelectrochemistry 2. Photoelectrochemical studies of highly oriented pyrolitic graphite

Photoelectrochemical reduction of oxygen and other observations of sustained electrochemically generated photocurrents with graphitic (HOPG) electrodes in aqueous solutions are reported. The photocurrents were observed over a wide pH range: 0 (0.5 M H₂SO₄)–14 (1 M NaOH). Photocurrent-potential, capacitance-potential and photocurrent light action spectral measurements were performed with basal plane and edge plane HOPG electrodes in order to elucidate the origin of the observed photocurrent. The photocurrent is attributed to hot electron–hot hole pairs photogenerated by direct transition between π-electronic states of the valence and conduction bands of graphite. Photogenerated carriers, holes or electrons, are driven by the electric field in the space charge layer (scl) to the electrode ∣ electrolyte interface, where they react directly with species in the electrolyte inducing anodic or cathodic photocurrent. The potential corresponding to the change of the photocurrent sign from cathodic to anodic was attributed to the flat band potential (E_FB). The E_FB of the basal plane electrode was 0 V versus SHE regardless of pH, while for the edge plane electrode E_FB changed at a rate of 54 mV per unit of pH. The shift of E_FB of the edge plane electrode with pH is ascribed to a change of the pH dependent surface dipole formed by oxygen containing surface redox groups.     

颅骨钻孔联合腰池引流治疗外伤性进展型硬膜下积液临床观察

目的：探讨治疗外伤性进展型硬膜下积液的有效方法。方法：选取35例外伤性进展型硬膜下积液患者,采用颅骨钻孔引流联合持续腰池引流的方法治疗25例,单纯颅骨钻孔引流10例。结果：35例外伤性进展型硬膜下积液患者中,25例采用颅骨钻孔引流联合持续腰池引流的方法治疗全部治愈,10例单纯颅骨钻孔引流术后恢复6例、复发4例。结论：颅骨钻孔引流联合持续腰池引流的方法,是治疗外伤性进展型硬膜下积液的有效方法。     

“创可贴”贴护腹腔镜手术戳孔的临床应用与探讨

目的：探讨腹腔镜术后创可贴贴护腹部戳孔的效果及其安全性。方法：将本院2008年1～12月,行腹腔镜手术的患者246例,随机分成两组,即观察组（123例）和对照组（123例）。将观察组123例患者腹腔镜手术后腹部戳孔用创可贴贴护,对照组123例患者腹腔镜术后腹部戳孔用无菌纱布覆盖,普通胶布固定。两组患者术后均常规应用抗生素预防感染及腹部戳孔换药2～3次。结果：观察组123例中,无一例切口裂开,术后切口愈合率为100％,术后5d如期出院。对照组123例中,有43例腹壁皮肤切口对合不良或皮肤裂开,且裂口处有分泌物,占34．9％,给予加强腹部戳孔换药,延期出院,并加用抗生素后,痊愈出院。结论：创可贴贴护腹部戳孔的方法,简单、方便、安全、易操作,Ⅰ期愈合率高,给医患双方均带来了好处,值得临床推广应用。     

清远市公共场所集中空调通风系统污染状况

目的了解清远市区集中空调通风系统送风微生物污染状况。方法于2007年采集济远市区14家宾馆、酒店的集中式空调系统125个送风口，分别进行细菌总数、真菌总数、B-溶血性链球菌检测。结果所调查的14家单位有9家微生物超标，合格率为35．7％；125个空调送风口有21个点微生物超标，合格率为83．2％。结论清远市区宾馆、酒店集中空调系统送风微生物污染较为严重，应加强公共场所集中空调系统的卫生监督管理。     

Mechanisms for pumping fluid through cementless acetabular components with holes

The pumping of fluid and polyethylene wear debris from the joint space to the retroacetabular bone is implicated in the pathogenesis of osteolysis. Three possible mechanisms for this pumping: pressure gradients, diaphragm pumping, and piston pumping were studied in vitro in a laboratory model. The simulated activities of rising from a chair and climbing stairs produced high-pressure gradients and high angles of loading that could pump fluid through the apical hole to the retroacetabular bone. A noncongruent liner acted as a diaphragm pump, producing pressures 6 times higher than that seen with a congruent liner. Pistoning motion of the liner produced pressures 8 times higher than when no pistoning occurs. These pumping mechanisms could be mitigated by the use of acetabular components without holes.     

Radiation cataract formation diminished by vitamin E in rat lenses in vitro

Eye lens cataract is a late effect of exposure to ionizing radiation. Depending on the dose and quality of radiation impinging on the lens, the development of a clinically discernible cataract usually takes several months in animal models, when the lens is irradiated in situ. However, we have developed a rapid in vitro assay with the isolated intact rat lens to study the effect of radiation and influence of antioxidants as protective agents. After only 24 hr of post-irradiation incubation at 35.5 degrees C in complete medium 199 + 10% foetal calf serum, damage in the form of globular degeneration subcapsularly and 'holes' in the cortical fibre cells is detectable. Doses as low as 0.10 Gy seem to be capable of causing some damage, and vitamin E (2.4 microns) in the medium confers some protection to the irradiated lens.     

Osseous drill holes to promote granulation tissue: radiologic appearance

Skin grafting following extensive soft-tissue loss is often delayed until adequate granulation tissue can be generated. Surgical drill holes into the marrow cavity promote development of granulation tissue. This article illustrates the radiology appearance of these drill holes in four patients.