The influence of fluid shear on the structure and material properties of sulphate-reducing bacterial biofilms

Biofilms of sulphate-reducing Desulfovibrio sp. EX265 were grown in square section glass capillary flow cells under a range of fluid flow velocities from 0.01 to 0.4 m/s (wall shear stress, tau(w), from 0.027 to 1.0 N/m(2)). In situ image analysis and confocal scanning laser microscopy revealed biofilm characteristics similar to those reported for aerobic biofilms. Biofilms in both flow cells were patchy and consisted of cell clusters separated by voids. Length-to-width ratio measurements (l(c):w(c)) of biofilm clusters demonstrated the formation of more "streamlined" biofilm clusters (l(c):w(c)=3.03) at high-flow velocity (Reynolds number, Re, 1200), whereas at low-flow velocity (Re 120), the l(c):w(c) of the clusters was approximately 1 (l(c):w(c) of 1 indicates no elongation in the flow direction). Cell clusters grown under high flow were more rigid and had a higher yield point (the point at which the biofilm began to flow like a fluid) than those established at low flow and some biofilm cell aggregates were able to relocate within a cluster, by travelling in the direction of flow, before attaching more firmly downstream.

Sonographic findings of tensor fascia lata tendinopathy: another cause of anterior groin pain

OBJECTIVE

To describe the sonographic appearances of the normal tensor fascia lata (TFL) origin and to describe the sonographic changes that were present in the TFL of a group of athletes presenting with anterior groin pain.

DESIGN

The sonographic appearances of the TFLs of 40 healthy asymptomatic volunteers were evaluated. The TFLs of approximately 200 patients aged between 16 and 55 years presenting with anterior groin pain were evaluated in the course of routine sonographic assessment of the hip. Twelve abnormal TFLs were identified in 12 patients aged between 16 and 53 years. A retrospective review of the appearance of the normal and abnormal tendon with respect to its overall size and echotexture was made.

RESULTS

The normal TFL has a thin ribbon-like appearance with a clearly defined fibrillar pattern and a mean anteroposterior (AP) size of 2.1 mm (range 1.5-3.1 mm). In the patient cohort the TFL typically appeared enlarged and contained a cone-shaped area of hypoechogenicity based on the iliac crest within the deep fibers of the origin. The TFL origin was enlarged up to 2 1/2 times its normal size. The mean AP size of the abnormal TFL was 4.7 mm (range 3.1-7.0 mm).

CONCLUSION

Tendinopathy of the TFL is a cause of anterior groin pain. Sonography can be used to depict changes in the TFL, confirming the diagnosis and assessing the severity of the tendinopathy.

Influence of surfaces on sulphidogenic bacteria

Sulphidogenic bacteria in oil reservoirs are of great economic importance in terms of souring, fouling and corrosion. Mixed cultures containing these bacteria were isolated from chalk formations in North Sea oil reservoirs. These were thermophilic cultures, growing optimally at 60°C. Oil formations are porous matrices, providing a very large surface area and ideal conditions for bacterial attachment, survival and growth. This study included assessments of sulphide production rates of thermophilic (t-)sulphidogen consortia with and without additional surfaces. The availability of a surface contributed significantly to the rate and extent of sulphide generation. Surfaces were offered in varying amounts to growing planktonic cultures: significantly more sulphide was produced from cultures in contact with a surface than from identical cultures in the absence of a surface. In another series of experiments, t-sulphidogens were added to chalk rock chips in the presence of nutrients and incubated for several months. This resulted in rapid sulphide generation, the final concentration being related to the initial nutrient concentration. Subsequent nutrient addition resulted in renewed sulphide generation. It is suggested that bacteria in reservoirs can withstand long periods of nutrient deprivation while attached within the porous rock matrix and opportunistically utilise nutrients when they become available.

The use of regional, low dose streptokinase in recently thrombosed arterial grafts

Between August 1983 and January 1985, 20 patients aged 33-77 years, with occluded lower limb bypass grafts, were on 23 occasions treated with streptokinase via intra-arterial infusion. Streptokinase (5000 units/h) was effective in clearing occluded grafts in 15 patients on 16 occasions. The median duration of occlusion in these patients was 5 days and the median duration of streptokinase infusions was 24 h. Completion angiography following streptokinase thrombolysis revealed five graft stenoses and 12 outflow stenoses or occlusions. In two grafts no cause for graft failure could be identified. These results permitted the surgeon to make an accurate pre-operative assessment of the definitive therapy required to ensure graft patency.