Structure, subunit topology, and actin-binding activity of the Arp2/3 complex from Acanthamoeba

The Arp2/3 complex, first isolated from Acanthamoeba castellani by affinity chromatography on profilin, consists of seven polypeptides; two actin-related proteins, Arp2 and Arp3; and five apparently novel proteins, p40, p35, p19, p18, and p14 (Machesky et al., 1994). The complex is homogeneous by hydrodynamic criteria with a Stokes' radius of 5.3 nm by gel filtration, sedimentation coefficient of 8.7 S, and molecular mass of 197 kD by analytical ultracentrifugation. The stoichiometry of the subunits is 1:1:1:1:1:1:1, indicating the purified complex contains one copy each of seven polypeptides. In electron micrographs, the complex has a bilobed or horseshoe shape with outer dimensions of approximately 13 x 10 nm, and mathematical models of such a shape and size are consistent with the measured hydrodynamic properties. Chemical cross-linking with a battery of cross-linkers of different spacer arm lengths and chemical reactivities identify the following nearest neighbors within the complex: Arp2 and p40; Arp2 and p35; Arp3 and p35; Arp3 and either p18 or p19; and p19 and p14. By fluorescent antibody staining with anti-p40 and -p35, the complex is concentrated in the cortex of the ameba, especially in linear structures, possibly actin filament bundles, that lie perpendicular to the leading edge. Purified Arp2/3 complex binds actin filaments with a Kd of 2.3 microM and a stoichiometry of approximately one complex molecule per actin monomer. In electron micrographs of negatively stained samples, Arp2/3 complex decorates the sides of actin filaments. EDC/NHS cross-links actin to Arp3, p35, and a low molecular weight subunit, p19, p18, or p14. We propose structural and topological models for the Arp2/3 complex and suggest that affinity for actin filaments accounts for the localization of complex subunits to actin-rich regions of Acanthamoeba.     

Tilidine does not affect human sphincter of Oddi motility--a randomized, controlled study

AIM: To investigate the effects of intravenous pentazocine and tilidine on sphincter of Oddi motility. METHODS: Twenty patients with suspected sphincter of Oddi dysfunction were enrolled in a prospective, double-blind study. Sphincter of Oddi motility was assessed by means of endoscopic manometry after injection of 0.9% saline, as well as after randomized dosing with either 30 mg pentazocine i.v. (n = 10) or 50 mg tilidine i.v. (n = 10). RESULTS: Pentazocine significantly increased the sphincter of Oddi baseline pressure from 32 +/- 21 mmHg (saline) to 41 +/- 19 mmHg (P = 0.002), whereas tilidine did not alter the sphincter baseline pressure (34 +/- 15 mmHg saline vs. 36 +/- 16 mmHg tilidine, P = 0.16). Furthermore, pentazocine increased the phasic sphincter contraction amplitude (108 +/- 16 mmHg saline vs. 121 +/- 18 mmHg pentazocine, P = 0.004), but tilidine was without any effect (125 +/- 24 mmHg saline vs. 125 +/- 21 mmHg tilidine, P = 0.93). The phasic sphincter of Oddi contraction frequency and duration were not influenced either by pentazocine or by tilidine. CONCLUSION: In contrast to 30 mg of pentazocine, 50 mg of tilidine does not affect sphincter of Oddi motility. Therefore, tilidine can be used during endoscopic manometry and for analgesia in pancreatobiliary disease.     

Post-hoc Rasch analysis of optimal categorization of an ordered-response scale

The purpose of this study was to determine the optimal categorization of a self-efficacy ordered-response scale using the Rasch analysis and compare the performance of the Rasch statistics and parameter estimates with conventional statistics. A 50-item scale to measure psychomotor self-efficacy was administered to a total of 2,022 children, including 1,009 boys and 1,013 girls. The data analysis started by collapsing the original five adjacent categories into two, three, and four categories, and a total of 14 data sets were derived. Each of these data sets, including the original one, was analyzed using the Rasch rating scale model, and a set of Rasch model-data fit, category, and separation statistics and parameter estimates, as well as three conventional statistics, were computed and compared. It was found that, instead of the five-category construct designed, the best order of category meanings of the scale in respondents' perceptions was a three-category construct. The Rasch threshold estimates were sensitive indexes in determining the order of the categorization, and that item separation statistics were useful in determining the optimal categorization after its order was confirmed. The commonly used coefficient alpha was found not helpful at all in determining the optimal categorization. The Rasch analysis was demonstrated to be a useful post-hoc analytic approach in determining the optimal categorization of an ordered-response scale.     

Sonographic detection of focal changes in the liver hilus in patients receiving corticosteroid therapy

OBJECTIVE: While diffuse deposition of fat may occur with corticosteroid (CS) administration both in the liver and in other organs, comparatively little is known about focal changes in the liver under corticosteroid medication. Therefore, we evaluated pattern and extent of focal hepatic steatosis by ultrasound (US) in patients receiving corticosteroids. SUBJECTS AND METHODS: 93 patients with known inflammatory bowel disease (IBD) received corticosteroids during a period of at least six weeks prior to the ultrasound examination and 28 IBD-patients had no corticosteroids within the last three years. 13 additional patients received corticosteroids for other reasons than IBD for > 1 year. 80 healthy volunteers served as controls. Focal changes of the liver as assessed by high resolution ultrasound (Acuson 128, 3.5 and 5 MHz) were defined as areas of brighter echogenicity compared to the general aspect of the liver. The size of the hyperechoic areas was documented (photoprint). RESULTS: 40/93 IBD-patients with corticosteroids (43%) had definite areas of brighter echos in the hilus region of the liver. In IBD-patients without corticosteroids only one patient showed a focal brighter echogenicity, whereas in the non-IBD group with corticosteroids 8/13 had focal lesions (62%). In the control group only four healthy subjects showed brighter areas (5%). CONCLUSION: Bright focal areas in the liver hilus occur in > 40% of IBD-patients during corticosteroid medication. This phenomenon occurs in IBD-patients as frequently and as intense as in other patients with longstanding corticosteroid therapy. There is a hilar area of the liver with typical size and location which reacts to corticosteroid administration with hyperechoic reflexes at ultrasound investigation. This is important to know when it comes to the differential diagnosis of focal changes.     

A system for classifying mechanical injuries of the eye (globe). The Ocular Trauma Classification Group

PURPOSE: To develop a classification system for mechanical injuries of the eye. METHODS: The Ocular Trauma Classification Group, a committee of 13 ophthalmologists from seven separate institutions, was organized to discuss the standardization of ocular trauma classification. To develop the classification system, the group reviewed trauma classification systems in ophthalmology and general medicine and, in detail, reports on the characteristics and outcomes of eye trauma, then established a classification system based on standard terminology and features of eye injuries at initial examination that have demonstrated prognostic significance. RESULTS: This system classifies both open-globe and closed-globe injuries according to four separate variables: type of injury, based on the mechanism of injury; grade of injury, defined by visual acuity in the injured eye at initial examination; pupil, defined as the presence or absence of a relative afferent pupillary defect in the injured eye; and zone of injury, based on the anteroposterior extent of the injury. This system is designed to be used by ophthalmologists and nonophthalmologists who care for patients or conduct research on ocular injuries. An ocular injury is classified during the initial examination or at the time of the primary surgical intervention and does not require extraordinary testing. CONCLUSIONS: This classification system will categorize ocular injuries at the time of initial examination. It is designed to promote the use of standard terminology and assessment, with applications to clinical management and research stud ies regarding eye injuries.     

A novel incremental principal component analysis and its application for face recognition.

Principal component analysis (PCA) has been proven to be an efficient method in pattern recognition and image analysis. Recently, PCA has been extensively employed for face-recognition algorithms, such as eigenface and fisherface. The encouraging results have been reported and discussed in the literature. Many PCA-based face-recognition systems have also been developed in the last decade. However, existing PCA-based face-recognition systems are hard to scale up because of the computational cost and memory-requirement burden. To overcome this limitation, an incremental approach is usually adopted. Incremental PCA (IPCA) methods have been studied for many years in the machine-learning community. The major limitation of existing IPCA methods is that there is no guarantee on the approximation error. In view of this limitation, this paper proposes a new IPCA method based on the idea of a singular value decomposition (SVD) updating algorithm, namely an SVD updating-based IPCA (SVDU-IPCA) algorithm. In the proposed SVDU-IPCA algorithm, we have mathematically proved that the approximation error is bounded. A complexity analysis on the proposed method is also presented. Another characteristic of the proposed SVDU-IPCA algorithm is that it can be easily extended to a kernel version. The proposed method has been evaluated using available public databases, namely FERET, AR, and Yale B, and applied to existing face-recognition algorithms. Experimental results show that the difference of the average recognition accuracy between the proposed incremental method and the batch-mode method is less than 1%. This implies that the proposed SVDU-IPCA method gives a close approximation to the batch-mode PCA method.     

A critical evaluation of the application of capillary electrophoresis to the detection and determination of 1,4-benzodiazepine tranquilizers in formulations and body materials

Studies of the capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) behaviour of 1,4-benzodiazepines have seen application in subject areas such as the development of pharmaceuticals, therapeutic drug monitoring and forensic toxicology. In the development of pharmaceuticals, pKa determinations by CZE can be used in preclinical studies whereas analytical data on the detection and determination of 1,4-benzodiazepines is of value primarily in raw material/formulation assay and in the analysis of body fluids in clinical studies. The capillary electrophoresis (CE) techniques, which generally have inferior limits of detection (LOD) to rival techniques such as gas chromatography (GC) and high-performance liquid chromatography (HPLC), are particularly applicable in forensic toxicology where reasonably high concentrations of these drugs can be encountered. It is anticipated that, with the interfacing of CZE and capillary electrochromatography (CEC) with mass spectrometry (MS) techniques, the excellent selectivity of CZE and particularly CEC will be effectively combined with the sensitivity of MS and the identification capabilities of tandem mass spectrometry (MS/MS) and MS hyphenated (MSn) techniques.