A role for adhesion and degranulation-promoting adapter protein in collagen-induced platelet activation mediated via integrin α(2) ß(1).

BACKGROUND: Collagen-induced platelet activation is a key step in the development of arterial thrombosis via its interaction with the receptors glycoprotein (GP)VI and integrin α(2) ß(1) . Adhesion and degranulation-promoting adapter protein (ADAP) regulates α(IIb) ß(3) in platelets and α(L) ß(2) in T cells, and is phosphorylated in GPVI-deficient platelets activated by collagen. OBJECTIVES: To determine whether ADAP plays a role in collagen-induced platelet activation and in the regulation and function of α(2) ß(1). METHODS: Using ADAP(-/-) mice and synthetic collagen peptides, we investigated the role of ADAP in platelet aggregation, adhesion, spreading, thromboxane synthesis, and tyrosine phosphorylation. RESULTS AND CONCLUSIONS: Platelet aggregation and phosphorylation of phospholipase Cγ2 induced by collagen were attenuated in ADAP(-/-) platelets. However, aggregation and signaling induced by collagen-related peptide (CRP), a GPVI-selective agonist, were largely unaffected. Platelet adhesion to CRP was also unaffected by ADAP deficiency. Adhesion to the α(2) ß(1) -selective ligand GFOGER and to a peptide (III-04), which supports adhesion that is dependent on both GPVI and α(2) ß(1), was reduced in ADAP(-/-) platelets. An impedance-based label-free detection technique, which measures adhesion and spreading of platelets, indicated that, in the absence of ADAP, spreading on GFOGER was also reduced. This was confirmed with non-fluorescent differential-interference contrast microscopy, which revealed reduced filpodia formation in ADAP(-/-) platelets adherent to GFOGER. This indicates that ADAP plays a role in mediating platelet activation via the collagen-binding integrin α(2) ß(1). In addition, we found that ADAP(-/-) mice, which are mildly thrombocytopenic, have enlarged spleens as compared with wild-type animals. This may reflect increased removal of platelets from the circulation.

A prospective, multicentre, observational cohort study of analgesia and outcome after pneumonectomy.

BACKGROUND: Meta-analysis and systematic reviews of epidural compared with paravertebral blockade analgesia techniques for thoracotomy conclude that although the analgesia is comparable, paravertebral blockade has a better short-term side-effect profile. However, reduction in major complications including mortality has not been proven. METHODS: The UK pneumonectomy study was a prospective observational cohort study in which all UK thoracic surgical centres were invited to participate. Data presented here relate to the mode of analgesia and outcome. Data were analysed for 312 patients having pneumonectomy at 24 UK thoracic surgical centres in 2005. The primary endpoint was a major complication. RESULTS: The most common type of analgesia used was epidural (61.1%) followed by paravertebral infusion (31%). Epidural catheter use was associated with major complications (odds ratio 2.2, 95% confidence interval 1.1-3.8; P=0.02) by stepwise logistic regression analysis. CONCLUSIONS: An increased incidence of clinically important major post-pneumonectomy complications was associated with thoracic epidural compared with paravertebral blockade analgesia. However, this study is unable to provide robust evidence to change clinical practice for a better clinical outcome. A large multicentre randomized controlled trial is now needed to compare the efficacy, complications, and cost-effectiveness of epidural and paravertebral blockade analgesia after major lung resection with the primary outcome of clinically important major morbidity.

Differential roles for the adapters Gads and LAT in platelet activation by GPVI and CLEC-2.

BACKGROUND: The adapter proteins SLP-76 and LAT have been shown to play critical roles in the activation of PLCgamma2 in platelets downstream of GPVI/FcRgamma and the C-type lectin receptor CLEC-2. SLP-76 is constitutively associated with the adapter Gads in platelets, which also binds to tyrosine phosphorylated LAT, thereby providing a potential pathway of regulation of SLP-76. OBJECTIVE: In the present study, we have compared the role of Gads alongside that of LAT following activation of the major platelet glycoprotein receptors using mice deficient in the two adapter proteins. RESULTS: Gads was found to be required for the efficient onset of aggregation and secretion in response to submaximal stimulation of GPVI and CLEC-2, but to be dispensable for activation following stronger stimulation of the two receptors. Gads was also dispensable for spreading induced through integrin alpha(IIb)beta(3) or the GPIb-IX-V complex. Further, Gads plays a negligible role in aggregate formation on collagen at an arteriolar rate of shear. In stark contrast, platelets deficient in the adapter LAT exhibit a marked decrease in aggregation and secretion following activation of GPVI and CLEC-2, and are unable to form stable aggregates on collagen at arteriolar shear. CONCLUSIONS: The results demonstrate that Gads plays a key role in linking the adapter LAT to SLP-76 in response to weak activation of GPVI and CLEC-2 whereas LAT is required for full activation over a wider range of agonist concentrations. These results reveal the presence of a Gads-independent pathway of platelet activation downstream of LAT.

A major role for Scar/WAVE-1 downstream of GPVI in platelets.

BACKGROUND: The small GTPase Rac1 plays a critical role in lamellipodia assembly in platelets on matrix proteins in the absence or presence of G protein-coupled receptor (GPCR) agonists. Rac mediates actin assembly via Scar/WAVE, a family of scaffolding proteins that direct actin reorganization by relaying signals from Rac to the Arp2/3 complex. OBJECTIVE: To evaluate the role of Scar/WAVE-1 in mediating platelet activation and cytoskeletal reorganization. METHODS AND RESULTS: Using specific antibodies, we demonstrate that murine platelets, like human platelets, express Scar/WAVE-1 and Scar/WAVE-2. Lamellipodia formation in Scar/WAVE-1(-/-) platelets is markedly inhibited on immobilized collagen-related peptide (CRP) and on laminin, both of which signal through the collagen receptor GPVI. In contrast, lamellipodia formation on collagen, which requires release of the GPCR agonists ADP and thromboxane A(2), is not altered. Immobilized fibrinogen supports limited formation of lamellipodia in murine platelets, which is not altered in Scar/WAVE-1(-/-) platelets. As with Rac1(-/-) platelets, Scar/WAVE-1(-/-) platelets exhibit a marked inhibition of aggregation in response to CRP, whereas the response to the GPCR agonist thrombin is not altered. Platelet aggregation on immobilized collagen under shear, which is dependent on signaling by matrix and GPCR agonists, was unaltered in the absence of Scar/WAVE-1. CONCLUSION: This study demonstrates a major role for Scar/WAVE-1 in mediating platelet cytoskeletal reorganization and aggregate formation downstream of activation by GPVI but not by GPCR agonists.

Regulation of in vitro and in vivo immune functions by the cytosolic adaptor protein SKAP-HOM.

SKAP-HOM is a cytosolic adaptor protein representing a specific substrate for the Src family protein tyrosine kinase Fyn. Previously, several groups have provided experimental evidence that SKAP-HOM (most likely in cooperation with the cytosolic adaptor protein ADAP) is involved in regulating leukocyte adhesion. To further assess the physiological role of SKAP-HOM, we investigated the immune system of SKAP-HOM-deficient mice. Our data show that T-cell responses towards a variety of stimuli are unaffected in the absence of SKAP-HOM. Similarly, B-cell receptor (BCR)-mediated total tyrosine phosphorylation and phosphorylation of Erk, p38, and JNK, as well as immunoreceptor-mediated Ca(2+) responses, are normal in SKAP-HOM(-/-) animals. However, despite apparently normal membrane-proximal signaling events, BCR-mediated proliferation is strongly attenuated in the absence of SKAP-HOM(-/-). In addition, adhesion of activated B cells to fibronectin (a ligand for beta1 integrins) as well as to ICAM-1 (a ligand for beta2 integrins) is strongly reduced. In vivo, the loss of SKAP-HOM results in a less severe clinical course of experimental autoimmune encephalomyelitis following immunization of mice with the encephalitogenic peptide of MOG (myelin oligodendrocyte glycoprotein). This is accompanied by strongly reduced serum levels of MOG-specific antibodies and lower MOG-specific T-cell responses. In summary, our data suggest that SKAP-HOM is required for proper activation of the immune system, likely by regulating the cross-talk between immunoreceptors and integrins.

GPVI and integrin alphaIIb beta3 signaling in platelets.

This review summarizes recent developments in our understanding of the molecular basis of platelet activation by two distinct types of surface receptor, the immunoglobulin GPVI, and the integrin alphaIIb beta3 (also known as GPIIbIIIa). These two classes of receptor signal through similar yet distinct tyrosine kinase-based signaling cascades leading to activation of phospholipase C gamma2. The significance of these signaling cascades in platelet adhesion and platelet aggregation at arterial rates of shear is discussed.

Difficult Airway Society guidelines for management of the unanticipated difficult intubation.

UNLABELLED: Problems with tracheal intubation are infrequent but are the most common cause of anaesthetic death or brain damage. The clinical situation is not always managed well. The Difficult Airway Society (DAS) has developed guidelines for management of the unanticipated difficult tracheal intubation in the non-obstetric adult patient without upper airway obstruction. These guidelines have been developed by consensus and are based on evidence and experience. We have produced flow-charts for three scenarios: routine induction; rapid sequence induction; and failed intubation, increasing hypoxaemia and difficult ventilation in the paralysed, anaesthetised patient. The flow-charts are simple, clear and definitive. They can be fully implemented only when the necessary equipment and training are available. The guidelines received overwhelming support from the membership of the DAS. DISCLAIMER: It is not intended that these guidelines should constitute a minimum standard of practice, nor are they to be regarded as a substitute for good clinical judgement.

The laryngeal mask and VBM laryngeal tube compared during spontaneous ventilation. A pilot study.

BACKGROUND AND OBJECTIVE: The laryngeal tube is a variant of the oesophageal obturator airway. The manufacturer claims that it is an alternative to ventilation with a facemask, laryngeal mask or endotracheal tube. To date, published studies have only involved controlled ventilation. We wished to find out if its use in spontaneous ventilation was equivalent to using the laryngeal mask airway. METHODS: We have compared the laryngeal tube with the laryngeal mask in a randomized prospective study involving patients breathing spontaneously under general anaesthesia. Criteria and a scoring system were used for the comparison. A sequential analysis chart with P=0.01 was chosen for each of two anaesthetists. RESULTS: Only seven and 10 pairs of patients were required to indicate that the laryngeal tube was poorer at airway maintenance than the laryngeal mask. Of the 17 patients who had received the laryngeal tube, successful airway maintenance was only possible in seven. In the remaining 10 patients, the laryngeal tube was abandoned and the rescue airway was the laryngeal mask in all cases. All 17 patients randomized to the laryngeal mask were successfully managed. CONCLUSIONS: We conclude that the laryngeal tube is not a satisfactory device for management of the airway during spontaneous ventilation.

Vintage helminths yield valuable molecules.

Museum and archival collections of parasites are available throughout the world but, although they represent a huge diversity of species and forms, they tend to be used solely for reference to morphology, if at all. As biochemical techniques begin to overcome the problems associated with ancient, degraded and formalin-fixed tissues, the value of such collections increases. Molecular data are now available for rare, elusive and extinct species, as well as those densely sampled for epidemiological, biogeographical or clinical collections. Here, Elisabeth Herniou, Auriol Pearce and Tim Littlewood describe some of the advances and pitfalls associated with retrieving DNA from formalin-fixed helminth material and suggest just some of the new ways that parasitologists can tap into these resources.

Evaluation of the Upsherscope. A new rigid fibrescope.

A new, rigid intubating fibrescope, the Upsherscope, was evaluated in clinical practice. Intubation was attempted in 200 adult patients and was successful in 191, with a median intubation time of 38 s, range 14-154 s. Intubation was straightforward in just under half of the patients. Difficulties were encountered in picking up the epiglottis, in passing the tracheal tube between the vocal cords and with secretions interfering with the view. In two patients known to be difficult to intubate, the Upsherscope was successful in one patient using an awake technique and failed in the other.

Fibreoptic intubation. Influence of tracheal tube tip design.

A randomised study was carried out in 60 patients to assess the influence of tracheal tube tip design on the ease of railroading a tracheal tube during fibreoptic intubation. A new design of tracheal tube with a tapered tip, without a bevel, was compared with a tracheal tube of standard design. The new design was found to be greatly superior in both oro- and nasotracheal fibreoptic intubation, when compared with the traditional tracheal tube (p < 0.001). The shape of the tip of a tracheal tube is an important determinant of the ease of railroading the tube over an inserted fibrescope.

Percutaneous balloon pericardiotomy for the treatment of cardiac tamponade and large pericardial effusions: description of technique and report of the first 50 cases.

OBJECTIVES: This study describes the technique, clinical characteristics and results of the first 50 patients undergoing percutaneous balloon pericardiotomy as part of a multicenter registry. BACKGROUND: Percutaneous balloon pericardiotomy involves the use of a percutaneous balloon dilating catheter to create a nonsurgical pericardial window. METHODS: Patients eligible for percutaneous balloon pericardiotomy had either cardiac tamponade (n = 36) or a moderate to large pericardial effusion (n = 14). In addition to clinical follow-up, serial echocardiograms and chest X-ray films were obtained. RESULTS: The procedure was considered successful in 46 patients after a mean follow-up period of 3.6 +/- 3.3 months. Two patients required an early operation, one for bleeding from a pericardial vessel and one for persistent pericardial catheter drainage. Two patients required a late operation for recurrent tamponade. Minor complications of the procedure included fever in 6 of the first 37 patients (studied before the prophylactic use of antibiotic agents), thoracentesis or chest tube placement in 8 and a small spontaneously resolving pneumothorax in 2. Despite the short-term success of this procedure, the long-term prognosis of the 44 patients with malignant pericardial disease remained poor (mean survival time 3.3 +/- 3.1 months). CONCLUSIONS: Percutaneous balloon pericardiotomy is successful in helping to manage large pericardial effusions, particularly in patients with a malignant condition. It may become the preferred treatment to avoid a more invasive procedure for patients with pericardial effusion and a limited life expectancy.

Antegrade selective coronary angiography via the transseptal approach in a patient with severe vascular disease.

We describe a case of a woman with severe vascular disease in whom retrograde access to the aortic root was limited by both aortoiliac and axillary disease. Transseptal catheterization was performed in anticipation of percutaneous aortic valvuloplasty. Selective antegrade angiography was successfully performed using catheters introduced through the transseptal sheath.

Fade profiles during spontaneous offset of neuromuscular blockade: vecuronium and gallamine compared.

The characteristics of the train-of-four (TOF) response have been studied electromyographically during the onset and the spontaneous offset of neuromuscular blockade induced with vecuronium or gallamine. During the onset of blockade, at 75% depression of initial twitch height, gallamine was associated with significantly more TOF fade than vecuronium. Both agents were associated with significantly less fade during onset than during spontaneous offset. When the two neuromuscular blocking drugs were compared during spontaneous offset they showed a similar degree of fade during early offset (up to 50% recovery of initial twitch height). However, during late spontaneous offset, when the initial twitch height had recovered to 75% of control values, vecuronium was associated with more fade than gallamine.

Assessment of a new nasopharyngeal airway.

A new design of nasopharyngeal airway, which incorporates an introducer, was compared with a standard red rubber airway. The new airway was more frequently of the correct length, but the incidence of bleeding (12.5%) was not significantly different from that with the red rubber airway (27.5%).

Factors affecting train-of-four fade.

The characteristics of the train-of-four response during neuromuscular blockade with two agents, atracurium and vecuronium, have been compared. During onset of blockade, at 75% depression of the initial twitch, atracurium was associated with significantly more fade than was vecuronium, and larger doses of atracurium were associated with less fade than smaller doses of the same agent. In addition, with both agents, the degree of fade at a given amount of initial twitch depression was significantly less during onset than during spontaneous offset of action. The degree of train-of-four fade bears no fixed relationship to depression of the initial twitch.

Smoking and anesthesia: preoperative abstinence and perioperative morbidity.

Much less is known of the effects of stopping smoking than of continuing to smoke, and many of the studies on smoking cessation are concerned with long-term effects rather than effects within 48 hr. Studies concerned with this period are required, especially in terms of postoperative respiratory morbidity, before an authoritative assessment can be made of the benefits and risks of stopping smoking in the short period before operation. Present studies are convincing that great benefit will accrue in the cardiovascular system, mainly from carbon monoxide and nicotine elimination, after 12-24 h. A few days may greatly improve ciliary beating and 1-2 weeks provide a significant reduction in sputum volume. However, a minimum period of 4-6 weeks would seem appropriate to greatly influence postoperative respiratory morbidity, although the statement that "one needs 4-6 weeks to influence postoperative respiratory morbidity" must not be misapplied and become "there is no point in giving up smoking unless it is 4-6 weeks prior to operation." There are no proven disadvantages to the respiratory system from stopping smoking in the short term, and it seems unwise to sacrifice proven advantages for a theoretic consideration that sputum may become "stickier" and more difficult to clear. Less is known with regard to the time course of offset of smoking effects on drug metabolism and the immune system, although 6-8 weeks would be expected to produce some benefit.(ABSTRACT TRUNCATED AT 250 WORDS)

Atracurium for short surgical procedures in day patients.

Atracurium was studied in day-stay patients undergoing short surgical procedures requiring tracheal intubation. In a dose of 0.25 mg kg-1 and with an anaesthetic technique using enflurane, tracheal intubation could be performed in all patients within 3 min and was readily reversible, unless the duration of surgery was less than 20 min. The administration of an antagonist was indicated in nearly all patients in whom surgery lasted for less than 30 min.