Tec regulates platelet activation by GPVI in the absence of Btk

The Tec family kinase Btk plays an important role in the regulation of phospholipase C gamma 2 (PLC gamma 2) downstream of the collagen receptor glycoprotein VI (GPVI) in human platelets. Platelets also express a second member of this family, Tec; however, its function has not been analyzed. To address the role of Tec, we analyzed Btk-/-, Tec-/-, and Btk/Tec double-deficient (Btk-/-/Tec-/-) platelets. Tec-/- platelets exhibit a minor reduction in aggregation to threshold concentrations of collagen or the GPVI-specific agonist collagen-related peptide (CRP), whereas responses to higher concentrations are normal. Tyrosine phosphorylation of PLC gamma 2 by collagen and CRP is not altered in Tec-/- platelets. However, Btk-/-/Tec-/- platelets exhibit a greater reduction in PLC gamma 2 phosphorylation than is seen in the absence of Btk, thus revealing an important role for Tec in this situation. Furthermore, Btk-/-/Tec-/- platelets fail to undergo an increase in Ca2+, aggregation, secretion, and spreading in response to collagen or CRP, whereas they aggregate normally to adenosine diphosphate (ADP) and spread on fibrinogen. A residual GPVI signal exists in the Btk-/-/Tec-/- platelets as CRP synergizes with ADP to mediate aggregation. These results demonstrate an essential requirement for Tec and Btk in platelet activation by GPVI and reveal a functional role for Tec in the regulation of PLC gamma 2 in the absence of Btk.     

Hemostatic markers with bolus versus prolonged heparin after carotid artery stenting

BACKGROUND: The evolving technique of carotid stenting (CS) requires optimal antithrombotic strategies to reduce periinterventional thromboembolic risk. In animal models of balloon injury, tissue factor (TF) was shown to be the major procoagulant of the atherosclerotic plaque mediating prolonged procoagulant activity. METHODS: We analyzed TF and TF-dependent hemostatic markers before and 2, 6 and 24 h after CS with two antithrombotic drug regimens. Group A (n=20) received prolonged unfractionated heparin (UFH) for 18-20 h starting at intervention next to aspirin and thienopyridine. In group B (n=16), single bolus UFH was administered next to combined antiplatelet therapy. Natural anticoagulants were determined at baseline. RESULTS: Patients with symptomatic and asymptomatic cerebrovascular disease did not differ in plasma TF levels. Furthermore, no statistically significant difference for TF, TFPI/Xa-complex and prothrombin fragment F1.2 was observed between bolus and prolonged heparin treatment. No significant change was found in time course for these parameters. Two patients (5.5%; one in each treatment group) suffered periinterventional minor stroke associated with increased levels of F1.2 and TFPI/Xa-complex. Both were resistant to activated protein C (APC ratio<1.9) due to heterozygous factor V Leiden mutation. CONCLUSIONS: No significant activation of the TF pathway was seen with both antithrombotic regimens suggesting that single bolus UFH combined with antiplatelet therapy is generally sufficient to control TF-dependent procoagulant activity after CS. However, patients with resistance to activated protein C may be at increased periinterventional stroke risk.     

Role of taurine accumulation in keratinocyte hydration

Epidermal keratinocytes are exposed to a low water concentration at the stratum corneum-stratum granulosum interface. When epithelial tissues are osmotically perturbed, cellular protection and cell volume regulation is mediated by accumulation of organic osmolytes such as taurine. Previous studies reported the presence of taurine in the epidermis of several animal species. Therefore, we analyzed human skin for the presence of the taurine transporter (TAUT) and studied the accumulation of taurine as one potential mechanism protecting epidermal keratinocytes from dehydration. According to our results, TAUT is expressed as a 69 kDa protein in human epidermis but not in the dermis. For the epidermis a gradient was evident with maximal levels of TAUT in the outermost granular keratinocyte layer and lower levels in the stratum spinosum. No TAUT was found in the basal layer or in the stratum corneum. Keratinocyte accumulation of taurine was induced by experimental induction of skin dryness via application of silica gel to human skin. Cultured human keratinocytes accumulated taurine in a concentration- and osmolarity-dependent manner. TAUT mRNA levels were increased after exposure of human keratinocytes to hyperosmotic culture medium, indicating osmosensitive TAUT mRNA expression as part of the adaptation of keratinocytes to hyperosmotic stress. Keratinocyte uptake of taurine was inhibited by beta-alanine but not by other osmolytes such as betaine, inositol, or sorbitol. Accumulation of taurine protected cultured human keratinocytes from both osmotically induced and ultraviolet-induced apoptosis. Our data indicate that taurine is an important epidermal osmolyte required to maintain keratinocyte hydration in a dry environment.     

Subantroscopic laterobasal sinus floor augmentation (SALSA): an up-to-5-year clinical study

PURPOSE: The aim of the article was to introduce a new subantroscopic laterobasal sinus augmentation (SALSA) tecnique as a minimally invasive approach to maxillary peri-implant surgery. MATERIALS AND METHODS: The SALSA technique consists of the following steps: (1) microsurgical opening of the subantral space (SAS) with detachment of the sinus membrane (SM) under supported videoendoscopy; (2) enlargement of the SAS by laterobasal tunnelling; (3) subantroscopic examination of the SAS with (4) optional reinforcement or repair of the SM; (5) implant site preparation with subantroscopic identification of the cavities; and (6) precise stepwise placement of graft material under endoscopic control. RESULTS: Since 1996, 118 sinus augmentations have been performed on 83 patients using particulate alloplastic augmentation material (tricalcium phosphate) with various amounts of autogenous bone and blood. Mean augmentation height was 8.6 mm (range, 1 to 15 mm). Twenty-eight perforations of sinus mucosa were observed without further complication (1 case of sinusitis was treated and re-augmented endoscopically). Of 211 titanium screw-type implants placed, 11 failures were observed. DISCUSSION: SALSA is a predictable surgical technique. With this minimally invasive method, adequate bone height can be achieved. CONCLUSION: SALSA may offer advantages related to lower morbidity, conservation of bone volume and blood supply, optimized view of the surgical field, and high acceptance by patients.     

The Harvest Smart PRePTM system versus the Friadent-Schütze platelet-rich plasma kit

An important reason to improve methods for isolating platelet-rich plasma (PRP) is the potential use of autogenous platelet growth factors. In addition to the Curasan PRP kit (Curasan, Kleinostheim, Germany) and the platelet concentrated collection system (PCCSTM) system, two new methods for the preparation of PRP by the surgeon are now available. This study compared the suitability of these new methods for the preparation of PRP. Whole blood was drawn from 54 healthy donors (33 men and 21 women) aged 23-79 years (38.0 +/- 17.7 years). PRP was prepared from each donor's blood using both the Smart PRePTM system (Harvest Technologies Corporation, Munich, Germany) and the Friadent-Schütze method (PRP kit; Friadent-Schütze, Vienna, Austria). The platelet count in donor whole blood was 276 810 +/- 59 440 /microl. Platelet counts differed significantly between the Smart PRP preparation (1227 890 +/- 312 440 platelets/microl) and the Friadent-Schütze PRP preparation (1440 500 +/- 501 700 platelets/microl) (sign test, P < 0.001). The Smart PRePTM system had a significantly higher collection efficiency (63.4 +/- 7.9%) than the Friadent-Schütze kit (49.6 +/- 13.6%) (sign test, P < 0.001). The leukocyte contents in the two platelet concentrates were similar (Smart PRePTM, 19 261 +/- 8082 platelets/microl; Friadent-Schütze, 21 691 +/- 16 430). Transforming growth factor (TGF)-beta1 and platelet-derived growth factor (PDGF)-AB were higher in the Friadent-Schütze PRP (TGF-beta1, 196.8 +/- 109.6 ng/ml; PDGF-AB, 251.6 +/- 115.4 ng/ml) than in the Smart PRePTM (TGF-beta1, 77.2 +/- 54.8 ng/ml; PDGF-AB, 208 +/- 85.2 ng/ml). The sign test indicated significant differences between the two methods in the concentrations of TGF-beta1 (P < 0.001) and PDGF-AB (P < 0.01). Insulin-like growth factor (IGF)-1 levels in the two PRP preparations were similar (Friadent-Schütze PRP, 72.8 +/- 22.3 ng/ml; Smart PRePTM, 91.4 +/- 21.3 ng/ml). The Smart PRePTM system was superior with respect to ease of handling and preparation time. It also had a significantly higher platelet collection efficiency than the Friadent-Schütze PRePTM kit. The Friadent-Schütze PRP kit offers a slight advantage in the resulting PRP platelet concentration. However, this is easily compensated for in the Smart PRePTM system by reducing the volume of the resulting PRP.     

Intrapulmonary shunt after cardiopulmonary bypass: the use of vital capacity maneuvers versus off-pump coronary artery bypass grafting

OBJECTIVES: It has been proved in human subjects and animals that atelectasis is a major cause of intrapulmonary shunting and hypoxemia after cardiopulmonary bypass. Animal studies suggest that shunting can be prevented entirely by a total vital capacity maneuver performed before termination of bypass. This study aimed to test this theory in human subjects and to evaluate possible advantages of off-pump coronary artery bypass grafting. METHODS: Twenty-four patients scheduled for coronary artery bypass grafting were randomly assigned to receive no total vital capacity maneuver (control group, n = 12) or standard total vital capacity maneuvers (TVCM group, n = 12). Additionally, 12 consecutive patients undergoing off-pump coronary artery bypass grafting (off-pump group) were studied. Systemic and central hemodynamics, the pattern of breathing, and ventilatory mechanics were evaluated after induction of anesthesia, after sternotomy, after cardiopulmonary bypass and skin closure, and 4 hours after extubation. RESULTS: The use of total vital capacity maneuvers reduced (P <.05) intrapulmonary shunting after termination of cardiopulmonary bypass. However, shunting increased (P <.05) in all groups (control group, 8.2% +/- 3.3% vs 25.6% +/- 8.1%; TVCM group, 8.7% +/- 3.4% vs 24.4% +/- 8.5%; and off-pump group, 7.8% +/- 2.8% vs 14.0% +/- 5.3%) after extubation, but the increase was significantly (P <.05) less pronounced in the off-pump group. Furthermore, pulmonary compliance decreased (P <.05) in all groups except the off-pump group after extubation. Duration of hospital and intensive care unit stay was significantly shorter (P <.05) in the off-pump group than in the other groups. CONCLUSION: The development of intrapulmonary shunting and hypoxemia after coronary artery bypass grafting can be substantially reduced by performance of total vital capacity maneuvers while patients are mechanically ventilated. However, off-pump coronary artery bypass surgery is superior in preventing shunting and hypoxemia after bypass grafting in the immediate and early postoperative periods, probably leading to substantially shorter intensive care unit and hospital stays.