Safety of, and biological and functional response to, a novel metallic implant for the management of focal full-thickness cartilage defects: Preliminary assessment in an animal model out to 1 year.

Focal full-thickness cartilage lesions of the human medial femoral condyle (MFC) can cause pain and functional impairment. Affected middle-aged patients respond unpredictably to existing treatments and knee arthroplasty may be required, prompting risk of revision. This study assesses the safety of, and biological and functional response to, a metallic resurfacing implant which may delay or obviate the need for traditional arthroplasty. The anatomic contour of the surgically exposed MFC of six adult goats was digitally mapped and an 11 mm diameter full-thickness osteochondral defect was created. An anchor-based Co-Cr resurfacing implant, matching the mapped articular contour, was implanted. Each goat's contralateral unoperated femorotibial joint was used as a control. Postoperative outcome was assessed by lameness examination, radiography, arthroscopy, synoviocentesis, necropsy, and histology up to 26 (n = 3) or 52 (n = 3) weeks. By postoperative week (POW) 4, goats demonstrated normal range of motion, no joint effusion, and only mild lameness in the operated limb. By POW 26 the animals were sound with only occasional very mild lameness. Arthroscopy at POW 14 revealed moderate synovial inflammation and a chondral membrane extending centrally across the implant surface. Radiographs at POWs 14 to 52 implied implant stability in the operated joints, as well as subchondral bone remodeling and mild exostosis formation in the operated and contralateral unoperated joints of some goats. By POW 26, histology revealed new trabecular bone abutting the implant. At POWs 26 and 52 MFC cartilage was metachromatic and intact in the operated and unoperated femorotibial joints. Proximal tibiae of some operated and unoperated limbs demonstrated limited subchondral bone remodeling and foci of articular cartilage fibrillation and thinning. The chondral membrane crossing the prosthesis possessed a metachromatic matrix containing singular and clustered chondrocytes. Our data imply the safety, biocompatibility, and functionality of the implant. Focal articular damage was documented in the operated joints at POWs 26 and 52, but lesions were much reduced over those previously reported in untreated defects. Expanded animal or preclinical human studies are justified.     

线栓法制作大鼠局灶性脑缺血再灌注损伤模型的改进

目的 研究一种稳定、简便的大鼠局灶性脑缺血再灌注损伤模型制作方法。方法 采用健康SD雄性大鼠，线栓法制作局灶性脑缺血再灌注损伤模型．结扎颈总动脉（CCA）及颈外动脉（ECA），不结扎翼腭动脉，用5．0头皮针于CCA结扎的远端刺一小口插入栓塞线造成缺血，拔出线栓形成再灌注。通过神经功能缺损评分、红四氮唑（TTC）染色和病理学检查等方法评价该模型的可靠性。结果动物麻醉后一般只需15min左右即可完成手术，术后大鼠神经功能缺损明显，TTC染色示脑梗塞区苍白，病理学检查显示典型病理表现。结论该方法缺血效果明确可靠，术式简便，手术时间短，不需具备显微手术操作技巧，是一种理想的制作局灶性脑缺血再灌注损伤模型的方法。     

Attempts to make models for Alzheimer''s disease

Profound reductions in cortical acetylcholine levels together with degeneration of cholinergic neurons in the basal forebrain have been reported in patients with Alzheimer's disease. A similar loss of the cholinergic neurons of the basal forebrain and impairment of learning and memory occur in animals injected with a nerve growth factor-diphtheria toxin conjugate, suggesting that this animal model is suitable to analyze cholinergic roles on learning and memory processes, and also the pathogenesis of Alzheimer's disease. In addition, animal models constructed by electrolytic or neurotoxic lesioning of the basal magnocellular nucleus, and models made by transgenetic technology were described.     

网络模式下临床医师绩效评价指标体系研究

为了充分利用医院信息网络信息，更为全面、客观地对医生进行评价，阐述建立网络模式下临床医师绩效评价指标体系的原则、方法，并对的建立指标体系的可信度及合理性进行了分析。     

Signal-to-noise ratio effects in quantitative cerebral perfusion using dynamic susceptibility contrast agents.

Theoretical and simulation evidence is presented in support of the idea that the optimal manner of determining blood flow from MR perfusion studies is not necessarily obtained by setting experimental conditions to maximize either the arterial input or the measured tissue concentration level for a particular echo time (TE). The noise power in the contrast concentration curve is associated with its peak because of the nonlinear relationship between the contrast concentration and MR signal intensity curves. The optimum signal-to-noise ratio (SNR), SNR(C), for a particular contrast concentration curve can be obtained when the experimental concentration level and TE are adjusted to produce an MR intensity curve whose signal loss is 63% of the precontrast MR signal intensity. It is demonstrated that the stability of the singular valued decomposition (SVD) deconvolution approach to determine blood flow parameters is increased when the tissue curve maximum signal loss is in the range of 40-80%. The accuracy and stability of the SVD-determined blood flow parameters are affected by deviations from these optimum conditions in a manner that depends on the mean transit time (MTT) associated with the residue function. It is recommended that the experimental TE value be set so that neither the tissue nor the arterial curves are placed a region of rapidly deteriorating SNR(C).     

Channges in regional cerebral blood flow after hyperventilation in the pig with an induced focal cerebral contusion

Summary Changes in regional cerebral blood flow in anaesthetized pigs with an induced focal cerebral contusion were studied before and after two grades of hyperventilation. A reduction in arterial tension of CO₂ with 0.70mmHg and a further reduction of 0.55mmHg did not change the CO₂ reactivity. Reactivity in both injured and macroscopically normal regions was the same, revealing an average of 39.3% flow change per kPa change in CO₂ tension. Regions with low flow after the contusion had an equally big reduction apparently leading to hypoxia because global metabolic rate was unchanged.     

A Novel Extravascular Input Function for the Assessment of Drug Absorption in Bioavailability Studies

Purpose. Flexible parametric models describing the input process after extravascular drug administration are needed for the assessment of absorption rate and the use of population methods in bioavailability and bioequivalence studies. Methods. The oral concentration-time curve modeled as the product of the input and disposition function in the Laplace domain was obtained by numerical inversion methods for parameter estimation. The utility of the inverse Gaussian input density was examined using bioavailability data of an extended-release dosage form. Measures of rate of absorption and the cumulative absorbed amount profile were defined in terms of the estimated model parameters. Results. Accurate estimation of absorption parameters was achieved by simultaneous fitting of the extravascular and intravascular data (describing the latter by a triexponential function). The new input function allowed a direct estimation of both extent of absorption and mean absorption time. Conclusions. The findings suggest that the inverse Gaussian density is a useful input function. Its flexibility may reduce the effect of model misspecification in parameter estimation. All parameters can be readily interpreted in terms of the absorption process.     

基于LVQ的自发脑电信号的分类研究

为了识别在不同思维状态下的自发脑电(EEG)信号，本文用6阶自回归(AR)模型表示EEG信号，用学习矢量量化(LVQ)神经网络作分类器，分别用LVQl和LVQ2．1算法对网络进行训练，并对分类结果进行测试，比较了网络选择不同参数时对分类正确率的影响。研究表明：竞争层神经元数目直接影响了正确率，当选择最佳参数值时分类正确率为62％-83％，因人而异。     

Experimental study of the role of the local infectious focus in development ofPseudomonas aeruginosa septicemia

Department of Pathological Anatomy, Clinical-Biological Laboratory, and Laboratory of Immunology, Bacteriology, and Clinical Pharmacology, A. V. Vishnevskii Institute of Surgery, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR D. S. Sarkisov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 111, No. 3, pp. 285–287, March, 1991.     

Precision of three-dimensional CT-assisted model production in the maxillofacial area

Individual skull model fabrication was introduced into preoperative diagnostics in maxillofacial surgery in the mid-1980s. The aim of the present study was to collect information on the reproducibility of a skull model milled from hardened polyurethane foam. This model was based on the CT data of a real skull. Twenty comparative studies were carried out on both the model and the original skull, the model showing an average inaccuracy of 1.6 mm. The deviations ranged between 0.0 and 3.6 mm; the general trend favouring enlargements. The total deviation of the model as compared to the original skull was 1.8%. A convincing aspect of the model, which cannot be obtained by any other method, is its plasticity and the possibility of 3 D orientation on a lifesize model. This new method is already used in preoperative planning of corrections of post-traumatic defects and craniofacial deformities as well as in tumour surgery. Correspondence to: P. Solar