Control of erythroid differentiation: asynchronous expression of the anion transporter and the peripheral components of the membrane skeleton in AEV- and S13-transformed cells

Chicken erythroblasts transformed with avian erythroblastosis virus or S13 virus provide suitable model systems with which to analyze the maturation of immature erythroblasts into erythrocytes. The transformed cells are blocked in differentiation at around the colony-forming unit- erythroid stage of development but can be induced to differentiate in vitro. Analysis of the expression and assembly of components of the membrane skeleton indicates that these cells simultaneously synthesize alpha-spectrin, beta-spectrin, ankyrin, and protein 4.1 at levels that are comparable to those of mature erythroblasts. However, they do not express any detectable amounts of anion transporter. The peripheral membrane skeleton components assemble transiently and are subsequently rapidly catabolized, resulting in 20-40-fold lower steady-state levels than are found in maturing erythrocytes. Upon spontaneous or chemically induced terminal differentiation of these cells expression of the anion transporter is initiated with a concommitant increase in the steady- state levels of the peripheral membrane-skeletal components. These results suggest that during erythropoiesis, expression of the peripheral components of the membrane skeleton is initiated earlier than that of the anion transporter. Furthermore, they point a key role for the anion transporter in conferring long-term stability to the assembled erythroid membrane skeleton during terminal differentiation

An Upper Limit on the Reflected Light from the Planet Orbiting the Star tau Bootis

The planet orbiting tau Boo at a separation of 0.046 AU could produce a reflected light flux as bright as 1e-4 relative to that of the star. A spectrum of the system will contain a reflected light component which varies in amplitude and Doppler-shift as the planet orbits the star. Assuming the secondary spectrum is primarily the reflected stellar spectrum, we can limit the relative reflected light flux to be less than 5e-5. This implies an upper limit of 0.3 for the planetary geometric albedo near 480 nm, assuming a planetary radius of 1.2 R_Jup. This albedo is significantly less than that of any of the giant planets of the solar system, and is not consistent with certain published theoretical predictions.Comment: 5 pages, 1 figure, accepted by ApJ Letter

Anticoagulative strategies in reconstructive surgery – clinical significance and applicability

Advanced strategies in reconstructive microsurgery and especially free tissue transfer with advanced microvascular techniques have been routinely applied and continously refined for more than three decades in day-to-day clinical work. Bearing in mind the success rates of more than 95%, the value of these techniques in patient care and comfort (one-step reconstruction of even the most complex tissue defects) cannot be underestimated

Achilles tendon suture deteriorates tendon capillary blood flow with sustained tissue oxygen saturation – an animal study

<p>Abstract</p> <p>Background</p> <p>Treatment of ruptured Achilles tendons currently constitutes of conservative early functional treatment or surgical treatment either by open or minimal invasive techniques. We hypothesize that an experimental Achilles tendon suture in an animal model significantly deteriorates Achilles tendon microcirculation immediately following suturing.</p> <p>Methods</p> <p>Fifteen Achilles tendons of eight male Wistar rats (275–325 g) were included. After preparation of the Achilles tendon with a medial paratendinous approach, Achilles tendon microcirculation was assessed using combined Laser-Doppler and spectrophotometry (Oxygen-to-see) regarding:</p> <p indent="1">- tendinous capillary blood flow [arbitrary units AU]</p> <p indent="1">- tendinous tissue oxygen saturation [%]</p> <p indent="1">- tendinous venous filling pressure [rAU]</p> <p>The main body of the Achilles tendon was measured in the center of the suture with 50 Hz. 10 minutes after Achilles tendon suture (6-0 Prolene), a second assessment of microcirculatory parameters was performed.</p> <p>Results</p> <p>Achilles tendon capillary blood flow decreased by 57% following the suture (70 ± 30 AU vs. 31 ± 16 AU; p < 0.001). Tendinous tissue oxygen saturation remained at the same level before and after suture (78 ± 17% vs. 77 ± 22%; p = 0.904). Tendinous venous filling pressure increased by 33% (54 ± 16 AU vs. 72 ± 20 AU; p = 0.019) after suture.</p> <p>Conclusion</p> <p>Achilles tendon suture in anaesthetised rats causes an acute loss of capillary perfusion and increases postcapillary venous filling pressures indicating venous stasis. The primary hypothesis of this study was confirmed. In contrast, tendinous tissue oxygen saturation remains unchanged excluding acute intratendinous hypoxia within the first 10 minutes after suture. Further changes of oxygen saturation remain unclear. Furthermore, it remains to be determined to what extent reduced capillary blood flow as well as increased postcapillary stasis might influence tendon healing from a microcirculatory point of view in this animal setting.</p

Unrecognized hand ischemia after intraarterial drug injection: successful management of a "near miss" event

<p>Abstract</p> <p>Background</p> <p>Complications arising from accidental intraarterial drug injections have been described in the past. However, given the multitude of injected substances and complex pathophysiology, guidelines regarding diagnosis and management of patients with intraarterial injections remain vague. As such it remains unclear, when to expect limb ischemia and whether and for how long to monitor patients after intraarterial injections.</p> <p>Case report</p> <p>We present the case of a "near miss event" in an i.v. drug abuser presenting to the emergency department 3 hours after injection of water dissolved zolpidem (Ambien™) tablets into the right ulnar artery. Chief complaint was forearm pain. Clinical examination at the time revealed no concern for limb ischemia and patient was discharged. The patient returned unplanned 18 hours after injection with an ischemic right hand. Angiography revealed no flow in the distal ulnar artery and minimal flow in the palmar arch. Emergent intraarterial thrombolysis with Urokinase was performed and restored hand perfusion. Clinical follow-up 3 months after injury showed full recovery with regular recapillarisation and normal Allen test.</p> <p>Conclusion</p> <p>This case report highlights the need to rigorously monitor patients with suspected intraarterial injections for potential delayed onset of limb ischemia. This is to our knowledge the first described case report of a successful revascularization after prolonged ischemia with delayed onset after zolpidem injection. We recommend close monitoring of these patients for at least 24 hours in addition to starting prophylactic anticoagulation.</p

Schwann Cell Metabolic Activity in Various Short-Term Holding Conditions: Implications for Improved Nerve Graft Viability

Strategies for improvement of nerve regeneration and optimal conditions to prevent Schwann cell (SC) loss within a nerve transplant procedure are critical. The purpose of this study was to examine SC viability, which plays an important role in peripheral nerve regeneration, under various incubation conditions up to three hours. To address this issue, Schwann cell metabolic activity was determined using different independent test methods. The following experimental conditions were compared: SCs prepared from nerves were incubated in (1) isotonic saline solution (2) Dulbecco's modified Eagles medium as used for cell culturing, (3) Hannover bioreactor medium, and (4) Leibovitz's medium. SC metabolic activity of excised rat sciatic nerve was determined at 4°C, 18°C, and 37°C over 3 hrs. The results indicate that SC activity was optimized by the usage of Leibovitz's medium or HBRM at 37°C. Greater SC viability at the time of surgical nerve grafting could contribute to improved axonal regeneration and remyelination after nerve transplantation, and thus more successful functional recovery

Modified minimally invasive extensor carpi radialis longus tenodesis for scapholunate dissociation:A prospective observational study

Background: Scapholunate dissociation is the most common form of carpal instability. However, there is no gold standard for operative treatment. In this prospective observational study on 54 patients, a modified minimally invasive dynamic extensor carpi radialis longus tenodesis is described, which is characterized by a smaller approach and application of a cannulated screw and washer for tendon fixation.Methods: Quick-Disabilities of Arm, Shoulder and Hand (DASH)-questionnaire results, post-operative satisfaction, range of motion and grip strength are analyzed.Results: A median Quick-DASH of 54.6 was observed pre-operatively which significantly improved to a median of 28.4 after the procedure (p &lt;0.001). Median follow-up was 24 months. Of 46 completely followed-up patients, 31 patients (67.4%) reported that they were satisfied with the outcome. Thirty-seven patients (80.4%) would recommend the procedure to a friend. Thirty-five patients (76.1%) reported some kind of complaint in the operated hand during follow-up. There was no association of severity of symptoms and co-morbidities with the outcome. Neither palmar flexion, nor dorsal extension was significantly different between the operated and non-operated wrist. The operated wrists were observed to have less grip strength than non-operated wrists.Conclusions: The presented method seems to be as successful as other techniques described in literature. It is less invasive, thus more patient friendly without harming feasibility of future salvage options. However, post-operative complaint rate was quite high.</p