Regulation of the friction coefficient of articular cartilage by TGF‐β1 and IL‐1β

Articular cartilage functions to provide a low‐friction surface for joint movement for many decades of life. Superficial zone protein (SZP) is a glycoprotein secreted by chondrocytes in the superficial layer of articular cartilage that contributes to effective boundary lubrication. In both cell and explant cultures, TGF‐β1 and IL‐1β have been demonstrated to, respectively, upregulate and downregulate SZP protein levels. It was hypothesized that the friction coefficient of articular cartilage could also be modulated by these cytokines through SZP regulation. The friction coefficient between cartilage explants (both untreated and treated with TGF‐β1 or IL‐1β) and a smooth glass surface due to sliding in the boundary lubrication regime was measured with a pin‐on‐disk tribometer. SZP was quantified using an enzyme‐linked immunosorbant assay and localized by immunohistochemistry. Both TGF‐β1 and IL‐1β treatments resulted in the decrease of the friction coefficient of articular cartilage in a location‐ and time‐dependent manner. Changes in the friction coefficient due to the TGF‐β1 treatment corresponded to increased depth of SZP staining within the superficial zone, while friction coefficient changes due to the IL‐1β treatment were independent of SZP depth of staining. However, the changes induced by the IL‐1β treatment corresponded to changes in surface roughness, determined from the analysis of surface images obtained with an atomic force microscope. These findings demonstrate that the low friction of articular cartilage can be modified by TGF‐β1 and IL‐1β treatment and that the friction coefficient depends on multiple factors, including SZP localization and surface roughness. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:249–256, 2009     

Bilateral electrical stimulation of a congenitally-deaf ear and of an acquired-deaf ear

Two identical multichannel intracochlear prostheses were implanted in the same patient. The first prosthesis, implanted in the congenitally-deaf right ear, elicited clear sound perception but no speech recognition. After 2 years, a second prosthesis, implanted in the acquired-deaf left ear, enabled the patient to understand speech without lip-reading. Brainstem and middle-latency evoked potentials were similar with electrical stimulation of both ears and resembled those evoked by acoustic stimuli in subjects with normal hearing. Cortical electric and magnetic responses differed for right- and left-sided electrical stimulation suggesting that stimulation of the congenitally-deaf ear elicited an abnormal activation of the auditory cortex. These results suggest that only cortical responses were affected by the different histories of deafness of the ears.     

A survey of physicians' attitudes to transfusion practice in critically ill patients in the UK

This study aimed to examine the attitudes of intensivists and haematologists to the use of blood and blood products using a scenario-based postal questionnaire. One hundred and sixty-two intensivists and 77 haematologists responded to the survey. In four scenarios, the baseline haemoglobin thresholds for red cell transfusion ranged from 6 to 12 g.dl(-1). There was significant variation between scenarios (p <0.005). Increasing age, high Acute Physiology and Chronic Health Status II score, surgery, acute respiratory distress syndrome, septic shock and lactic acidosis significantly (p <0.005) modified the transfusion threshold. There were greater variations in the baseline threshold for platelet transfusion. The majority of respondents (72.3%) selected a baseline haemoglobin threshold between 9 and 10 g.dl(-1). The thresholds for platelet transfusion were far less consistent.     

Are stentless valves hemodynamically superior to stented valves? A prospective randomized trial

BACKGROUND: Although stentless aortic bioprostheses are believed to offer improved outcomes, hemodynamic benefits remain unsubstantiated. METHODS: Fifty-three patients were randomized to receive the stented C-E pericardial valve (CE) and 46 patients the Toronto Stentless Porcine valve (SPV). Annuli were sized for the optimal insertion of both valve types, such that surgeons were required to commit to specific valve sizes before randomization. Echocardiographic measurements and functional status (Duke Activity Status Index) were assessed at 3 and 12 months postoperatively. RESULTS: Although cardiopulmonary bypass times (CE: 118.6+/-36.3 minutes; SPV: 148.5+/-30.9 minutes; p = 0.0001) and aortic cross-clamp times (CE: 95.4+/-28.6 minutes; SPV: 123.6+/-24.1 minutes; p = 0.0001) were significantly prolonged in the SPV group, perioperative morbidity and mortality was similar between groups. Neither valve offered a superior internal diameter for any given annular diameter (mean decrease in left ventricular outflow tract diameter after valvular implantation: SPV: 3.4+/-1.11 mm versus CE: 3.7+/-1.33 mm; p = 0.25). Although labeled mean valve size was significantly larger in the SPV group, the actual mean valve size based on internal valvular diameter was no different between groups (CE: 21.9+/-2.0 mm; SPV: 22.3+/-2.0 mm; p = 0.286). Although effective orifice areas increased, and mean and peak transvalvular gradients decreased in both groups over time, no differences were demonstrated between groups at 12 months. Similarly, although significant regression of left ventricular mass was accomplished in both groups over time, no differences were demonstrated between groups. Finally, Duke Activity Status Index scores of functional status improved in both groups over time; however, no differences were noted between groups at 12 months postoperatively. CONCLUSIONS: Although offering excellent outcomes, stentless valves did not demonstrate superior hemodynamic indices in comparison to stented valves up to 12 months after implantation.     

Phrenic nerve palsy: a rare complication of indwelling subclavian vein catheter

The use of central venous catheters as access for hemodialysis has become common in children with end-stage renal disease. Phrenic nerve palsy is an unusual complication of this procedure. We report a case of delayed right diaphragmatic palsy due to phrenic nerve damage resulting from an indwelling right subclavian catheter in a 3-year-old child. Received: 29 March 1999 / Revised: 16 July 1999 / Accepted: 17 July 1999