Knot security in simple sliding knots and its relationship to rotator cuff repair: how secure must the knot be?

We sought to determine which simple sliding knot configurations would have adequate strength for rotator cuff repair. Four knot configurations were tied with both No. 1 polydioxanone suture and No. 2 Ethibond suture (Ethicon, Somerville, NJ) using 3 different tying techniques: hand-tie, standard knot pusher, and cannulated double-diameter knot pusher. The knots were then tested to failure on a materials testing system. The weakest standard knot configuration was S=S=S=S. The other 3 knot configurations (S//S//S//S, SxSxSxS, and S//xS//xS//xS) generally failed in the 35 to 50 N range. Ultimate strength in this range can be shown to be adequate to withstand, without suture failure, a maximal contraction of a repaired rotator cuff tear within the rotator crescent, assuming certain conditions are met (suture anchors placed 1 cm apart, 2 sutures per anchor). More complex knots are not necessary for adequate knot security. However, the same configuration with only 1 suture per anchor will not be strong enough because the suture will fail under maximum physiological load. This study shows that we can predict the adequacy of a given knot configuration under maximum physiological loading conditions.

Cyclosporin A protects lung function from hyperoxic damage.

Cyclosporin A (CsA), an inhibitor of protein phosphatase 2B (calcineurin), has been shown to play a role in exocytosis and neutrophil mobility. Hyperoxia (>95% oxygen for 72 h) causes lung injury and reduces lung compliance. This model is indicative of deficiencies in surfactant and elicits a vigorous immune response leading to further damage. We examined the effects of CsA on surfactant-secreting lung alveolar type II cells. CsA enhances ATP-stimulated increases in whole cell capacitance in the presence of 2 mM extracellular Ca2+. This measurement corresponds with increases in exocytosis. Because of its effect on the immune system and exocytosis from type II cells, CsA was examined for its protective effects against hyperoxia-induced lung damage in mice. We found that CsA (50 mg. kg-1. day-1) attenuated hyperoxia-induced reductions in lung compliance when administered before or during 72 h of >95% oxygen (P < 0.05). CsA (10 mg. kg-1. day-1) also had a protective effect against hyperoxia-induced changes in neutrophil infiltration, capillary congestion, edema, and hyaline membrane formation. Wet lung weight-to-dry lung weight ratios did not show any significant changes after hyperoxia or hyperoxia plus CsA (P < 0. 05). CsA may be useful to treat patients undergoing prolonged high-oxygen therapy and possibly other lung injuries.

Successful revascularization of a partially avulsed foot in a 6-year-old child.

The foot of a 6-year-old child was revascularized successfully following an avulsion and partial amputation through the tibiotalar joint. Partial degloving had disrupted the anterior and posterior tibial arteries with resultant ischemia. We excised the entire damaged segment of the posterior tibial artery and performed a reverse saphenous vein graft, end-to-end reconstruction of the defect. Peroneal and tibial nerve function returned within 5 months. Four years later, the patient has regained full, painless range of motion and normal strength and sensibility with no evidence of premature growth plate closure or avascular necrosis of the talus.

A disease resistance gene in Arabidopsis with specificity for the avrPph3 gene of Pseudomonas syringae pv. phaseolicola.

The avirulence gene avrPph3 from Pseudomonas syringae pv. phaseolicola was tested for its ability to convert virulent P. syringae pv. tomato strain DC3000 to avirulence on Arabidopsis. In F2 plants from a cross between resistant and susceptible ecotypes, the ratio of resistant to susceptible plants was approximately 3:1, indicating that resistance to DC3000(avrPph3) is determined by a single dominant locus, which we have designated RPS5. RPS5 was mapped to chromosome 1, between restriction fragment length polymorphism markers m241 and g3786.

A disease resistance gene in Arabidopsis with specificity for two different pathogen avirulence genes.

The RPS3 and RPM1 disease resistance loci of Arabidopsis confer resistance to Pseudomonas syringae strains that carry the avirulence genes avrB and avrRpm1, respectively. We have previously shown that RPS3 and RPM1 are closely linked genetically. Here, we show that RPS3 and RPM1 are in fact the same gene. We screened a mutagenized Arabidopsis population with a P. syringae strain carrying avrB and found 12 susceptible mutants. All 12 mutants were also susceptible to an isogenic strain carrying avrRpm1, indicating a loss of both RPS3 and RPM1 functions. No mutants were recovered that lost only RPS3 function. Genetic analysis of four independent mutants revealed that the lesions were in RPS3. Thus, a single gene in Arabidopsis confers resistance that is specific to two distinct pathogen avirulence genes--a gene-for-genes interaction. This observation suggests that the RPS3/RPM1 gene product can bind multiple pathogen ligands, or alternatively, that it does not function as a receptor.