Progressive Rupture Research Articles

The Effect of a New Intraocular Irrigating Solution Containing Dextran on Rabbit Corneal Endothelium

This study investigated the effect of a balanced salt solution for intraocular irrigation containing 2% dextran 40. The effect of this solution was compared to that of a normal saline solution (0.9%) and balanced salt solution (Alcon). Following incubation of rabbit corneas for up to 72 h at 4 degrees C, the incubated corneas were studied by staining with Nitroblue Tetrazolium and by scanning electron microscopy. Insignificant changes occurred during the first 24 h of incubation. However, corneas stored in the dextran containing solution showed slightly smaller endothelial cells with tight junctions after 72 h. Endothelial cells showed progressive membrane rupture and eventual disappearance when incubated in normal saline for over 24 h at 4 degrees C.

The subcellular localization of ACh synthesis in rat striatal synaptosomes investigated with the use of triton X-100.

Abstract—The regulation of [14C]ACh synthesis was studied in rat striatal synaptosomes incubated in presence of various concentrations of Triton X‐100, using [2‐14C]pyruvate or [6‐14C]glucose as precursors. The progressive rupture of the cytoplasmic and mitochondrial compartments induced by the non‐ionic detergent was followed by studying the release, into the incubating medium, of lactate dehydrogenase and choline acetyltransferase (ChAc) and of fumarate hydratase, respectively. [3H]Choline uptake (1 μm) was measured to determine the activity of the high affinity choline permease. 14CO2 formation from [2‐14C]pyruvate was used as an index of the Krebs cycle activity.The rate of [14C]ACh synthesis from [2‐14C] pyruvate was dependent on the Triton X‐100 concentration; the ester formation decreased between 0·001% (v/v) and 0·010%, but increased again beyond this concentration of detergent. This last phenomenon was interpreted as the result of an extracellular synthesis of ACh involving pyruvate dehydrogenase and ChAc. At 0·002% Triton X‐100 the 14CO2 formation was not affected, indicating a normal mitochondrial activity. The decrease of [14C]ACh synthesis observed up to this detergent concentration could be correlated to the decline of the highaffinity choline permease activity. In these experimental conditions, the ester synthesis could not be restored by the addition of large amounts of choline in the incubating medium suggesting that the molecules of choline must cross the high‐affinity choline permease system in order to be acetylated. This could indicate a close association between the permease and choline acetyltransferase.

Non-rheumatic 'subvalvar' mitral regurgitation. Surgical pathology and results of operation in 37 patients.

Thirty-seven patients with non-rheumatic subvalvar mitral regurgitation are reported, representing 16% of all patients with mitral regurgitation submitted to open operation over a five-and-a-half-year period. In 22 older patients with `idiopathic9 chordal lesions, the commonest finding was rupture of chordae to the posterior leaflet. The aortic leaflet chordae were most frequently involved following myocardial infarction (7 patients) or bacterial endocarditis (3 patients). Three other younger patients had ruptured chordae and two patients had rupture of the posteromedial papillary muscle following acute myocardial infarction. The mitral valve was repaired in 16 patients with ruptured chordae, of whom only eight obtained a satisfactory late result. In the other 21 patients the valve was replaced with a mounted aortic homograft or a Starr-Edwards prosthesis. It is concluded that mitral valve repair should be reserved for patients with symmetrical rupture of the chordae controlling the centre of the posterior leaflet, as regurgitation may reappear after other forms of repair due to progressive rupture of other abnormal chordae or breakdown of the repair. The early and late mortality in the patients with a definite antecedent myocardial infarction was much higher than in the other groups, and emergency valve replacement soon after rupture of the papillary muscle was unsuccessful in both patients.

Energy flux of strong earthquakes

In this paper, the energy flux of strong earthquakes at a station is determined considering the progressive rupture of a fault as the source of earthquakes. It is found that the motion of the source and the relative position of the station with respect to the fault are important in determining the energy density, the energy flux and the duration of the earthquake at this station. There is a “sphere of influence” beyond which the source may be assumed to be stationary. The analytical results are in good agreement with those of the 5 strong motion records obtained very near the fault from the Parkfield event of 27th June, 1966. 21 strong motion records are studied for energy densities at the stations from which a magnitude-energy relationship is obtained which agrees closely with other existing relationships.

The scale effect on the phenomenon of progressive rupture in cohesionless soils: E. E. de Beer. Proc. 6th ICOSOMFE, 11 (3/3), 13–17

IN THE PROBLEMS OF THE ULTIMATE BEARING CAPACITY OF COHESIONLESS SOILS THE PHENOMENON OF PROGRESSIVE RUPTURE PLAYS A ROLE WHOSE IMPORTANCE INCREAEES WITH THE TRANSVERSE DIMENSIONS OF THE FOOTING. THEREFORE, THE BEARING CAPACITY FACTORS V SUB G = 1/2 N SUB GAMMA FOUND IN TESTS ON SMALL MODEL FOOTINGS MAY NOT IN THE CASE OF DENSE SANDS BE TRANSPOSED WITHOUT CORRECTION TO THE CASE OF REAL FOOTINGS. /LCPC/RRL/A/