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Biomedical subjects

J Brink

Publications and source records attributed to J Brink.

45 records · Page 3Linked to original sources
PubMed1975

Early predictors of incomplete recovery in children with Guillain-Barr'e polyneuritis.

Case histories of 47 children with strict criteria for Landry-Guillain-Barré-Strohl polyneuritis admitted to a rehabilitation facility from late 1959 through 1972 were analyzed retrospectively. The children were followed to full recovery (good to normal strength in all muscle groups) or for three years without full recovery. The data were then compared statistically for possible predictive indicators of recovery or lack of recovery within three years. The most significant early predictor of incomplete recovery was the time interval between the greatest weakness and beginning improvement; a period longer than 18 days of plateau before gains are evident is indicative of incomplete recovery within limits of 99% confidence.

Cerebrospinal Fluid Proteins↗
PubMedDate not supplied

Applications of a slow-scan CCD camera in protein electron crystallography.

A Gatan 1024 x 1024 slow-scan charge-coupled device (CCD) camera has been interfaced to a JEOL4000EX electron cryomicroscope and explored for its usefulness in the electron crystallographic analysis of thin, glucose-embedded crystals of crotoxin complex kept at -125 degrees C. We show that the camera allows for an on-line assessment of the crystals' crystallinity, flatness, and thickness. Intensities obtained from electron diffraction patterns acquired with the camera have been statistically analyzed and were found to be consistent with theoretically expected values. A quantitative analysis of the diffraction intensity as function of the accumulated electron dose suggests the possibility of recording up to 250 diffraction patterns with 3.5 A resolution from a single crotoxin complex crystal 128 A thick. Tilt series of 125 electron diffraction patterns with 3.5 A data acquired from a single crystal are shown to be practically feasible. The current study demonstrates for the first time the effectiveness of using a slow-scan CCD camera for electron diffraction data collection from thin protein crystals at near atomic resolution.

Crotoxin↗
PubMedDate not supplied

Processing of electron diffraction patterns acquired on a slow-scan CCD camera.

We have developed two software packages for the processing of electron diffraction patterns acquired on a slow-scan CCD camera. Automated indexing and processing of these electron diffraction patterns is possible using a program called AUTO. To obtain a set of reliable reflections, AUTO applies a number of corrections, which are necessary due to the acquisition of the patterns with a slow-scan CCD camera. To index and process unknown lattices in electron diffraction patterns obtained from, for instance, a new protein or a new crystal form, an interactive program called EDP is available. It supports indexing in an interactive manner through a graphical user interface. Processing of the electron diffraction pattern is done using a script created by EDP. Both packages run on UNIX platforms, with EDP requiring the X Window System.

Automation↗
PubMedDate not supplied

Computer image analysis of two-dimensional crystals of beef heart NADH: ubiquinone oxidoreductase fragments. I. Comparison of crystal structures in various negative stains.

We investigated the structure of two-dimensional crystals from bovine heart mitochondrial NADH: ubiquinone oxidoreductase. A detailed description of uranyl acetate-stained crystals demonstrated that they are composed of fragments in a spatial arrangement according to space group P4212 [J. Brink, S. Hovmöller, C.I. Ragan, M.W.J. Cleeter, E.J. Boekema and E.F.J. van Bruggen, European J. Biochem. 166 (1987) 287]. To gain more structural information on the crystal structure and to assess the effects of various negative stains on the structure preservation and appearance, we examined stained crystals by means of electron microscopy and image analysis. The space group P4212 appeared to be present for several stains tested, i.e. ammonium molybdate, uranyl acetate, uranyl nitrate and uranyl sulphate. Use of phosphotungstic acid and silicotungstate resulted in a reduction of symmetry to pseudo-P4212 or p4. Use of sodium tungstate led to a considerable loss of resolution to 3.8 nm at best, whereas otherwise 1.5 to 1.9 nm could be demonstrated. The lattice vectors were not affected by the stains; they were determined as a = b = 14.9 +/- 0.25 nm with gamma = 89.8 degrees +/- 0.6 degrees. Image analysis showed the presence of similar structures with the molybdate and uranyl compounds. Differences were observed in the case of the tungstate type of stains. Furthermore, the analysis revealed the complete absence of the four small pores of 2.0 nm diameter in the unit cell. This effect was observed irrespective of the type of stain and supporting film, and could be ascribed only to the glow-discharge treatment of the supporting film. The observed difference must be caused by changed interactions between the protein, stain and supporting film. Application of correspondence analysis and clustering algorithms to the various reconstructed images of the crystals showed that they could be separated into several clusters. Each of these clusters corresponded on the average to only one type of stain, whereas a further division according to the specific uranyl compounds was observed. This study therefore shows that under identical preparation conditions subtle differences between individual stains can be detected.

Animals↗
PubMedDate not supplied

Computer image analysis of two-dimensional crystals of beef heart NADH: ubiquinone oxidoreductase fragments. II. Comparison of frozen hydrated and negatively stained specimens.

Two-dimensional crystals of bovine NADH: ubiquinone oxidoreductase fragments were studied by cryo-electron microscopy and computer image analysis at two focus settings. The lattice parameters of the crystals were determined as a = 14.5 +/- 0.2 nm, b = 14.8 +/- 0.3 nm with gamma = 87.8 degrees +/- 0.2 degrees. Translation and rotation alignment resulted in a final resolution of 1.38 (close-to-focus) or 1.9 nm (1.3 microns underfocus). When only translational alignment was employed 1.6 nm resolution resulted (close-to-focus case). The application of a further correction procedure surprisingly lowered the achieved resolution to 2.2 nm. A combination of the projected structures for the two focus settings in Fourier space resulted in a noise-free image displaying enhanced image contrast for reciprocal spacings from 1/5.0 to 1/1.4 nm-1. The structure in amorphous ice comprises four separate quasi-identical motifs, each resembling a distorted triangle. Two symmetry-related (p2) motifs reveal a pore-like feature. In negative stain the structure has p4mm symmetry. The absence of in-plane symmetry elements (i.e. twofold rotation and screw axes) and other differences might be accounted for (at least in part) if the crystal studied was slightly tilted.

Animals↗
PubMedDate not supplied

Orthopedic management of acquired cerebrospasticity in childhood.

Of 221 children with head injuries and resultant deep coma followed for long-term problems, 156 became totally independent, functional individuals, only 61 lacking normal cognition and speech. Reconstructive surgical procedures for residual spasticity was necessary in 45 patients. Achilles lengthenings were the most common procedure performed; after Achilles lengthenings, toe flexor releases were most often required. Twenty children had anoxia from drowning or anesthesia problems; 7 of these had spastic hip deformities or dislocations, all within 6 months of the anoxic event. Progressive cerebrospastic syndromes and post-infectious cerebrospasticity most often require orthotic devices for their orthopedic management.

Achilles Tendon↗
PubMedDate not supplied

Biocor No- React stentless aortic valve--short-term results.

OBJECTIVES: Short-term results of the bioprosthetic Biocor No-React composite porcine stentless aortic valve (Biocor Industria e Pesquisas LTDA, Belo Horizonte, Brazil) implanted in patients in whom anticoagulation was thought to be contraindicated or expected to be non-compliant. METHODS: Retrospective review of 52 consecutive prospective patients in whom this valve was implanted, between September 1994 and May 1998. RESULTS: Average age was 44 +/- 17 years; 75% of patients were operated on for rheumatic heart disease and combined procedures were done in 40% of cases. Early mortality was 5.8%, and related to pre-operative ejection fraction ( P < 0.03), New York Heart Association (NYHA) class (P < 0.01), and bacterial endocarditis (P < 0.04). On discharge, 84% of survivors were in NYHA class I and 16% in class II. The average postoperative prosthetic valve peak gradient on echocardiography was 19.9 +/- 11 mmHg and was related to pre-operative ejection fraction and smaller valve sizes. Postoperative residual trivial or mild aortic regurgitation was seen in 19 patients (36.6%), resolved on follow-up in 10 cases, and did not correlate with structural deterioration, re-operation, mortality, or widening of the non-coronary sinus. The non-coronary aortic sinus was widened on closure, because of perceived crowding of the adjacent stentless valve commisures, in 52% of cases. This was thought to be related to the use of an oblique as opposed to transverse aortotomy. Patient survival, inclusive of operative deaths, was 88.5%, and event-free survival was 80.0% at 4 years. CONCLUSION: The short-term results of this stentless aortic valve in a young predominantly third-world population group are acceptable, and appear to be superior to the results for mechanical valves in a similar patient group. We would recommend a transverse aortotomy above the sinotubular ridge to be the more appropriate aortotomy incision when using stentless aortic valves.

Adolescent↗