Morphologic characterization of osteoblast-like cell cultures isolated from newborn rat calvaria

Summary Two methods for harvesting osteoblast-like cell populations from newborn (10 days) rat calvaria were compared. The first one consisted in culturing the periosteum-free bones and then trypsinizing the cells on the bone surface. The second one involved the migration of the osteoblasts on glass fragments before trypsinization. Since the plating efficiency, the proportion of alkaline phosphatase-positive cells, the population doubling time, and the calcium deposition were more adequate, the second method was used to further characterize the behavior of the cultures. During the first week of culture, the cells featured shapes similar to those observedin vivo on the surface of periosteum-free calvaria. They formed multilayers and, in the presence of ascorbic acid, synthetized an organic matrix containing exclusively type I collagen. Later, small amounts of type III collagen appeared. The cells were embedded in the matrix and progressively acquired the morphologic phenotype of osteocyte-like cells. The matrix mineralized in the presence of β-glycerophosphate. The technique of dropinoculation (high concentration of cells in a small volume of medium) promoted the multilayer formation and the achievement of large mineralized plates (about 1 cm²) in 3 weeks of culture.     

Primary repair of tetralogy of Fallot in infancy

From June 1983 to April 1988, 100 consecutive infants with symptomatic tetralogy of Fallot (without pulmonary atresia) were operated on. Ages ranged from 0.5 to 12 months (mean 7.3 +/- 3.7). Twenty patients were 0.5 to 3 months, 21 were 3 to 6 months, and 59 were 6 to 12 months of age. Mean weight was 6.5 kg +/- 1.7. Seventy patients received a transannular patch. The hospital mortality rate was 3% and there were no late deaths. Cumulative follow-up was 180 patient-years. Causes of death included hypoplastic pulmonary arteries (4 and 5 months old) and right ventricular failure (4 months old). The most important factors influencing right ventricular outflow tract reconstruction were neither weight (p = 0.90) nor age (p = 0.05) but rather were the ratio between weight and pulmonary arterial outflow tract diameter (p = 0.0005) and the ratio between body surface area and pulmonary arterial outflow tract diameter (p less than 0.0001). The last 48 patients were operated on with no deaths. During this period, operative management differed essentially in myocardial protection with blood cardioplegia. The predicted 30-day survivorship after repair was 90% to 99% (95% confidence limits). No ventricular arrhythmias have been detected after repair (mean follow-up 22.2 months). Mean right ventricular/left ventricular end-diastolic dimension ratio was (0.53 +/- 0.10 with M-mode echocardiography. These early results encourage us to proceed with primary repair of infants with symptomatic tetralogy of Fallot thanks to improved surgical management and enhanced myocardial protection.     

Perimetric variability: Importance of criterion level

Perimetry suffers from considerable variability of results. A new technique for estimating individual criterion levels in normal subjects exposes the important role of psychological variables. The analysis depends on features peculiar to acuity perimetry. It can be accommodated in the regular examination. The results can be used to compensate for practice effects in serial examinations and to tighten the range of normal limits. The reduction in variation between normal subjects amounted to 57 per cent.     

FRACTURE OF ABUTMENT SCREW SUPPORTING A CEMENTED IMPLANT-RETAINED PROSTHESIS WITH EXTERNAL HEXAGON CONNECTION: A CASE REPORT WITH SEM EVALUATION

One of the causes of implant failures in cemented implant-retained prostheses is the fracture of abutment screw or UCLA abutment. This article reports a case of simultaneous fracture of two UCLA abutments screws occurring in an implant-supported prosthesis placed in the mandibular molar region. The fractured structures were examined under scanning electron microscopy to investigate the probable causes of the failure, which were not related to failures on materials or fabrication of the screws, but rather were due to shear forces. The misfit in cemented prostheses may be the most likely cause of shear force generation.     

Physiological role of the putative ammonium transporter RhCG in the mouse.

Ammonium excretion into urine is a major process essential to the regulation of acid-base homeostasis. We have shown that Rh-type proteins, including renal RhCG, belong to the Mep/Amt family of ammonium transporters and promote bi-directional ammonium transport upon heterologous expression in yeast. To study the physiological role of RhCG and to test a potential function in ammonium excretion, we have generated mice bearing an invalidation of the corresponding gene.     

System for prostate brachytherapy and biopsy in a standard 1.5 T MRI scanner.

A technique for transperineal high-dose-rate (HDR) prostate brachytherapy and needle biopsy in a standard 1.5 T MRI scanner is demonstrated. In each of eight procedures (in four patients with intermediate to high risk localized prostate cancer), four MRI-guided transperineal prostate biopsies were obtained followed by placement of 14-15 hollow transperineal catheters for HDR brachytherapy. Mean needle-placement accuracy was 2.1 mm, 95% of needle-placement errors were less than 4.0 mm, and the maximum needle-placement error was 4.4 mm. In addition to guiding the placement of biopsy needles and brachytherapy catheters, MR images were also used for brachytherapy treatment planning and optimization. Because 1.5 T MR images are directly acquired during the interventional procedure, dependence on deformable registration is reduced and online image quality is maximized.     

Streptococci from root canals in teeth with apical periodontitis receiving endodontic treatment.

OBJECTIVES: The object of this study was to investigate the diversity among streptococcal species isolated from root canals in conjunction with endodontic therapy and to characterize their production of extracellular proteins. STUDY DESIGN: Consecutive root canal samples (RCS) taken as bacteriological controls during root canal treatment of teeth with apical periodontitis were analyzed in a total of 100 clinical cases. Bacteria were isolated and classified by selective media and gas liquid chromatography. Streptococcal strains were identified by carbohydrate fermentation, hydrolysis of aesculin/arginine, and production of enzymes. Releases of extracellular proteins by streptococci and Enterococcus spp in fluid culture media were examined with SDS-PAGE and 2-dimension gel electrophoresis (2 DE). Extracellular proteins produced were quantified and qualitatively analyzed. Specific proteins were targeted with Western immunoblot assays. Comparisons were made with type strains. RESULTS: Of a total of 241 bacterial strains recovered in the first samples submitted, Streptococcus gordonii, S anginosus, and S oralis were the most frequently isolated streptococci. In 49 of 89 resubmitted samples showing bacterial growth, S gordonii and S oralis still predominated among streptococci. Other common bacterial isolates were Enterococcus spp, Lactobacillus paracasei, and Olsenella uli. Quantitative and qualitative differences in extracellular protein production were observed among clinical isolates and laboratory streptococcal strains. In similar conditions for growth, S intermedius, S anginosus, S oralis, and S gordonii were strong producers of extracellular proteins (>3.0 microg/mL), while Enterococcus spp and S mutans were weak. Whole cell protein extracts showed a different profile from that of extracellular proteins. The chaperone protein DnaK was recognized to be produced extracellularly by S gordonii, S oralis, S anginosus, and S parasanguis. CONCLUSIONS: Being strong producers of extracellular proteins and by virtue of common presence in teeth undergoing endodontic therapy, S gordonii, S anginosus, and S oralis may be of pathogenic significance in posttreatment apical periodontitis.     

Concerning the differentiability of the energy function in vector quantization algorithms.

The adaptation rule of Vector Quantization algorithms, and consequently the convergence of the generated sequence, depends on the existence and properties of a function called the energy function, defined on a topological manifold. Our aim is to investigate the conditions of existence of such a function for a class of algorithms including the well-known 'K-means' and 'Self-Organizing Map' algorithms. The results presented here extend several previous studies and show that the energy function is not always a potential but at least the uniform limit of a series of potential functions which we call a pseudo-potential. It also shows that a large number of existing vector quantization algorithms developed by the Artificial Neural Networks community fall into this class. The framework we define opens the way to studying the convergence of all the corresponding adaptation rules at once, and a theorem gives promising insights in that direction.