Impact of PI3Kα (Phosphoinositide 3-Kinase Alpha) Inhibition on Hemostasis and Thrombosis.

Objective- PI3Kα (phosphoinositide 3-kinase alpha) is a therapeutic target in oncology, but its role in platelets and thrombosis remains ill characterized. In this study, we have analyzed the role of PI3Kα in vitro, ex vivo, and in vivo in 2 models of arterial thrombosis. Approach and Results- Using mice selectively deficient in p110α in the megakaryocyte lineage and isoform-selective inhibitors, we confirm that PI3Kα is not mandatory but participates to thrombus growth over a collagen matrix at arterial shear rate. Our data uncover a role for PI3Kα in low-level activation of the GP (glycoprotein) VI-collagen receptor by contributing to ADP secretion and in turn full activation of PI3Kß and Akt/PKB (protein kinase B). This effect was no longer observed at high level of GP VI agonist concentration. Our study also reveals that over a vWF (von Willebrand factor) matrix, PI3Kα regulates platelet stationary adhesion contacts under arterial flow through its involvement in the outside-in signaling of vWF-engaged αIIbß3 integrin. In vivo, absence or inhibition of PI3Kα resulted in a modest but significant decrease in thrombus size after superficial injuries of mouse mesenteric arteries and an increased time to arterial occlusion after carotid lesion, without modification in the tail bleeding time. Considering the more discrete and nonredundant role of PI3Kα compared with PI3Kß, selective PI3Kα inhibitors are unlikely to increase the bleeding risk at least in the absence of combination with antiplatelet drugs or thrombopenia. Conclusions- This study provides mechanistic insight into the role of PI3Kα in platelet activation and arterial thrombosis.

Bronchial aspirates glucose level as indicator for methicillin-resistant Staphylococcus aureus (MRSA) in intubated mechanically ventilated patients.

This study evaluated if the level of glucose in bronchial aspirate serves as indicator for the risk of MRSA infection in intubated mechanically ventilated ICU patients. A total of 50 critically ill patients was enrolled and were under tight glycemic control to abolish the effect of hyperglycemia on bronchial secretion, if they were expected to require mechanical ventilation for more than 48 hours. Bronchial aspirates were detected for glucose and sent twice weekly for microbiological analysis and whenever an MRSA was expected. The results showed that all the patients had glucose tested in bronchial aspirates. Glucose was detected in bronchial aspirates of 28 of the 50 patients. Glucose in bronchial aspirates in these patients ranged between (2.9-5.1 mmol/l). MRSA was detected in 22 patients where 28 were MRSA free of the MRSA patients 19 had positive glucose where glucose was positive in 28 patients of them 19 (86.4%) where MRSA positive to 9 with no MRSA (32.1%).The risk of having MRSA present markedly increased significantly in the presence of glucose: (p value .001).

Prevalence of extramucosal fungal elements in sinonasal polyposis: a mycological and pathologic study in an Egyptian population.

OBJECTIVE AND HYPOTHESIS: The objective of the study was to define the true incidence of fungal elements in the nasal and sinus mucous in cases of chronic rhinosinusitis (CRS) with bilateral polyposis compared with normal controls-in an Egyptian African population-via mycological and histologic techniques. STUDY DESIGN: This study was conducted prospectively on 100 patients with the clinical diagnosis of CRS with bilateral nasal polyposis. Fifty volunteers with no history of nasal or paranasal sinus disease served as a control group. RESULTS AND CONCLUSION: The postulated criteria for the diagnosis of allergic fungal sinusitis were present in 92% of CRS with polyposis, suggesting that fungi are involved in the disease process of most CRS patients.

Evaluation of cartilage growth following sustained delivery of tgf-? Using a rat degenerated disc model - biomed 2010.

The current modalities of treating symptomatic degenerative disc disease are either conservative non-surgical or surgical modalities. However, none of these modalities is a true cure for the degenerative process. Ideally, the best treatment would be preventing the progression of degeneration. The goal of our research is to identify factors that may slow or stop the degenerative process. A rat degenerative disc model induced by piercing the center of the disc was implemented. In this phase of the study, it was hypothesized that continuous sustained release of transforming growth factor (TGF-ss) would reverse the loss of cellularity associated with degenerating discs. A total of eighteen rats were divided into three equal groups. Group I served as control and groups II and III were subjected to a surgery where a 21-gauge needle was used to pierce the L4/L5 disc posteriorly. Animals in group III received TGF-ss over a four week period via a tricalcium phosphate sustained delivery device. After 4 weeks the animals were sacrificed and the traumatized discs were removed. Sections of 10 microm were taken and stained with hematoxylin and eosin and evaluated using light microscopy techniques. Using Image Pro software the area of the transition zone was calculated and the number of chondrocyte nuclei per area was determined. The results show that after four weeks, animals in group II (trauma only) showed evidence of disc degeneration with the largest decrease in cell number anterior to the site of trauma. Treatment with TGF-ss resulted in chondrocyte numbers similar to control in posterolateral views of the disc, while lateral views and views of the site directly opposite the trauma (anterior) had approximately 45% less chondrocytes per area than the control; however, the chondrocyte numbers in the anterior views were twice as many as seen in the discs retrieved from trauma only animals.

Conditional TPM3-ALK and NPM-ALK transgenic mice develop reversible ALK-positive early B-cell lymphoma/leukemia.

NPM-ALK (nucleophosmin-anaplastic lymphoma kinase) and TPM3-ALK (nonmuscular tropomyosin 3-anaplastic lymphoma kinase) are oncogenic tyrosine kinases implicated in the pathogenesis of human ALK-positive lymphoma. We report here the development of novel conditional mouse models for ALK-induced lymphomagenesis, with the use of the tetracycline regulatory system under the control of the EmuSRalpha enhancer/promoter. The expression of either oncogene resulted in the arrest of the differentiation of early B cells and lymphomagenesis. We also observed the development of skin keratoacanthoma lesions, probably because of aberrant ALK expression in keratinocytes. The inactivation of the ALK oncogene on doxycycline treatment was sufficient to induce sustained regression of both hematopoietic tumors and skin disease. Importantly, treatment with the specific ALK inhibitor (PF-2341066) also reversed the pathologic states, showing the value of these mouse models for the validation of ALK tyrosine kinase inhibitors. Thus, our results show (1) that NPM-ALK and TPM3-ALK oncogenes are sufficient for lymphoma/leukemia development and required for tumor maintenance, hence validating ALK as potentially effective therapeutic target; and (2) for the first time, in vivo, the equal tumorigenic potential of the NPM-ALK and TPM3-ALK oncogenic tyrosine kinases. Our models offer a new tool to investigate in vivo the molecular mechanisms associated with ALK-induced lymphoproliferative disorders.

Dynamic anterior cervical plating for multi-level spondylosis: Does it help?

STUDY DESIGN: Randomized controlled trial. OBJECTIVE: To compare fusion rates, time to fusion, complication rates and subsidence between 1) a static, 2) a dynamic angulation, and 3) a dynamic translation plate in anterior cervical discectomy and fusion for symptomatic degenerative cervical disease. METHODS: Thirty-six patients with two level, symptomatic cervical degenerative changes requiring surgery were randomized in a blinded fashion to receive a statically locked plate, Cervical Spine Locking Plate (CSLP) (Synthes, Paoli, PN, USA), an Atlantis Vision(®) Anterior Cervical Plate System (Medtronic, Memphis, TN, USA) which allows angular dynamization, or a Premier(®) Anterior Cervical Plate System (Medtronic) which allows translational dynamization. Structured data collection and measurement protocols were used. Intervertebral composite allograft cages were used in all groups. Identical external immobilization and antiinflammatory medication protocols were followed. X-rays were obtained at preset time points postoperatively. Assessment of the primary outcomes was blinded. Rate of and time to fusion, graft/instrumentation complications, subsidence, and reoperation for adjacent level disease were measured. Paired t-test and three-way Analysis of Variance test (ANOVA) were used to assess statistical differences between groups. RESULTS: The three groups were similar demographically. Fusion rates in the CSLP, Atlantis and Premier plate groups were 100%, 91%, and 92% respectively. Mean time to fusion was 6.1, 8.3 and 6.3 months respectively but differences were not statistically significant. Mean subsidence in the groups was 1.9, 1.6, and 2.6 mm respectively. Subsidence was found even for the static (CSLP) plate, but no statistically significant differences were found. CONCLUSIONS: We found no clinical advantage of dynamic plates over static plates with regards to fusion rates, time to fusion, subsidence, complications, or adjacent-level surgery. Static plating allows for subsidence at similar levels to dynamic plating. [Table: see text] The definiton of the different classes of evidence is available on page 83.

A preliminary report on the effects of sustained administration of corticosteroid on traumatized disc using the adult male rat model.

STUDY DESIGN: A novel degenerative disc disease model and sustained delivery method for corticosteroid in male Sprague-Dawley albino rats. OBJECTIVES: To develop a model of degenerative disc disease and to determine the effect of continuous sustained release of corticosteroid on the process of degeneration within the traumatized disc. SUMMARY OF BACKGROUND DATA: The current modalities of treating symptomatic degenerative disc disease are either conservative or surgical. However, there is no cure for the degenerative process and prevention, therefore, is the ideal treatment. An understanding of the mechanisms involved in disc degeneration is crucial to develop new methods for prevention and treatment, including appropriate delivery systems and dosages of repair factors. METHODS: The L5-L6 intervertebral disc was pierced with a 23-gauge needle in 18 rats. The animals received either sham or corticosterone-charged tricalcium phosphate ceramic capsules. The rats were euthanized at 4 weeks. Chondrocytes in the transition zone areas were counted and compared statistically. RESULTS: The surgical technique induced degeneration of the nucleus without evidence of inflammation at adjacent levels when compared with nontraumatized controls. The number of chondrocytes per area was significantly less in the sham group than in the control group. Corticosteroid treatment showed chondrocyte numbers similar to control in 4 of 5 different views of the disc. The anterior region of the disc had 50% less chondrocytes per area than the control; however, the chondrocyte numbers were 50% greater than in the same site from discs of sham animals. CONCLUSIONS: The results show the development of a degenerative disc animal model that can be used to test the effects of growth enhancing factors in disc repair. Administration of continuous sustained release of corticosterone can slow the process of degeneration within the traumatized disc in the rat model.

Management of back pain in patients with previous back surgery.

The 80,000 or so patients a year who continue to have chronic, disabling back pain after one or more spinal surgeries are said to have failed back surgery syndrome. There are no controlled studies to guide physicians in the management of these patients. Six anatomical abnormalities of the spine most commonly result in back surgery, and 7 undesirable outcomes lead to failed back surgery syndrome. On the basis of 5 large retrospective studies and our clinical experience, we suggest a systematic approach to these patients. This approach is focused on determination of the specific anatomical abnormality responsible for ongoing symptoms, an abnormality that may or may not be related to the initial abnormality for which surgery was performed. One or more of 5 nonsurgical treatment options may be useful to prevent the need for further surgery, as each subsequent surgery has a lower likelihood of success.

Effect of low power laser treatment on a traumatized disc in a rat model.

This study investigated the effects of low power laser on the healing process of a traumatized disc in an animal model. The experimental design consisted of 14 rats divided into the following three groups: Animals in group I (n = 5) served as controls with no surgery. Animals in group II (n = 5), the sham group, received a surgically created defect in the disc at L4/L5 level and received no other treatment. Animals in the third group (n = 4) received a similar defect to L4/L5 in similar fashion as described for animals in the sham group (group II) with the exception that they received laser of 830 nm wavelength treatment or irradiation for a period of 4 weeks. The animals were euthanized at 30 days post-implantation using overdose of isoflurane. The discs were then harvested in addition to the vital organs, the reproductive organs, and sample of the adjacent skeletal muscles. The hard and soft tissues were evaluated histopathologically by following laboratory standard techniques. The results of this study indicated that the discs of the laser treated animals healed in a greater magnitude than the sham group. Image analysis revealed that there was more disc formation in the laser irradiated animals than the sham. In conclusion, data obtained from this study demonstrated that laser irradiation delivered on traumatized discs resulted in a remarkable increase in discs regeneration and healing following trauma.

Characterization of a femoral segmental nonunion model in laboratory rats: report of a novel surgical technique.

The literature is lacking conclusive results regarding the exact mechanism of maximizing the fracture healing stages with minimal traumatic side effects. This observation mandates the development of a novel surgical procedure using small animals as a model to study fracture healing in the presence of osteoinductive agents. Previously, stabilization of osteotomies in small animal models has mainly been accomplished using Kirschner wires, but the rat's tremendous ability to heal an osteotomy stabilized by this method has masked the effects of osteoinductive agents. Thus, this study proposes using a modified 20-hole, 1.5-mm stainless-steel plate to stabilize a 5-mm segmental defect. Thirty of 32 adult male rats were fully weight-bearing within 2 days and were followed over a 15-week period. Two animals showed evidence of fixation failure due to technical error, and the animals were humanely sacrificed. At the end of the study, the fractures were stable with significantly less bone formation evident when compared to controls (p < .001). Therefore, this technique can effectively be used to evaluate compounds that will enhance bone formation and allows for stable fixation of the control with minimal callus formation or bony ingrowth. The goal of this article is to allow other investigators to reproduce this technique as well as outline the advantages and disadvantages of this novel plating technique versus the former Kirschner wire technique for the study of osteoinductive agents using small animals as a model.

Roles of the C-terminal tyrosine residues of LAT in GPVI-induced platelet activation: insights into the mechanism of PLC gamma 2 activation.

Linker for activation of T cells (LAT) is an adaptor protein required for organization of the signaling machinery downstream of the platelet collagen receptor, the glycoprotein VI (GPVI). Here, we investigated the effect of LAT mutations on specific signaling pathways and on platelet functions in response to GPVI triggering by convulxin (Cvx). Using mice containing tyrosine to phenylalanine mutations of the adaptor, we show the crucial role played by the tyrosine residues at positions 175, 195, and 235 in the phosphorylation of LAT and in the whole pattern of protein tyrosine phosphorylation in response to Cvx. These 3 C-terminal tyrosine residues are important to recruit the tyrosine kinase Fyn, which may be involved in LAT phosphorylation. Efficient phosphoinositide 3-kinase (PI3K) activation requires the 3 C-terminal tyrosine residues of LAT but not its tyrosine 136. Interestingly, single mutation of the tyrosine 136 results in the loss of phospholipase C gamma2 (PLCgamma2) activation without affecting its PI3K-dependent membrane association, and is sufficient to impair platelet responses to Cvx. Thus, activation of PLCgamma2 via GPVI is dependent on 2 complementary events: its interaction with the tyrosine 136 of LAT and its membrane location, which itself requires events mediated by the 3 C-terminal tyrosines of LAT.

A quantitative analysis of strain at adjacent segments after segmental immobilization of the cervical spine.

STUDY DESIGN: A biomechanical study on human cadaveric cervical spines with segmental fixation. OBJECTIVES: To quantify the strains across all segments of the spine after simulated fusion. SUMMARY OF BACKGROUND DATA: Clinical evidence suggests that degenerative changes occur at adjacent levels after cervical fusion. This may, in part be due to increased stress and motion at the adjacent segments. MATERIALS AND METHODS: Seven fresh frozen human cervical cadaveric spines were used. The spines were mounted onto frames at C2 and C7. Biomechanical testing was performed on a modified MTS tester. The specimens were tested in rotation control. To simulate fusion, a block was used to replace the disc. Fixation was enhanced using an anterior plate and stainless steel wire through the spinous processes. Testing was then performed with the same displacement magnitudes used for the intact spine. Displacement across 5 disc spaces was recorded using extensometers. The same preparation and testing was done for 1, 2, and 3-level simulated fusions. All data were normalized to the individual intact specimen. RESULTS: After 1-level simulated fusion at C5-6, flexion-extension rotation increased by 60% at the superior adjacent level (C4-5) and by 15% at the adjacent inferior level (C6-7). Lateral bending increased by 51% at C4-5 and by 16% at C6-7. Axial rotation increased by 25% at C4-5 and by 200% at C6-7. Flexion-extension, lateral bending and axial rotation increased at all other segments, not only at adjacent segments, after 1, 2 and 3-level fixation. CONCLUSIONS: Cervical fusion results in increased strains at adjacent levels, and to all other levels, inferiorly and superiorly. This study represents the first to quantify the increased strain at all adjacent levels.

Targeted sustained delivery of tobramycin at the site of a femoral osteotomy.

Complex fractures are difficult to manage because of the increased risk of secondary infection. Traditional treatments include debridment and local administration of antibiotics. Local antibiotic therapy is a safe technique resulting in high local concentration of antibiotics with minimal systemic levels. Local antibiotics effectively control infection in animal models. The length of implantation and the need for removal of the delivery vehicle places the patient at risk for additional surgical procedure as well as delays the fixation procedure. Development of a bioresorbable carrier that can deposit therapeutic concentrations of antibiotics locally without side-effects will provide positive outcomes for the patient. Tricalcium phosphate lysine (TCPL) ceramic capsules containing tobramycin were implanted at the site of a femoral osteotomy delivered therapeutic concentrations of the drug locally and reduced the incidence of infection compared to TCPL capsule which were uncharged by 50%. In addition, the ceramic material was osteoconductive and animals in TCPL + TOB and TCPL carrier alone showed evidence of osteoblast alkaline phosphatase activity for a period of 15 weeks. Neither the carrier nor the carrier containing antibiotics displayed untoward effects on body weight, vital organs and reproductive organs over a 15 week period. The results from this study demonstrated that TCPL can be used as an effective osteoconductive material capable of delivering therapeutic concentrations of antibiotics over 15 week period.

SHP1 tyrosine phosphatase negatively regulates NPM-ALK tyrosine kinase signaling.

Anaplastic large-cell lymphoma (ALCL) is frequently associated with the 2;5 translocation and expresses the NPM-ALK fusion protein, which possesses a constitutive tyrosine kinase activity. We analyzed SHP1 tyrosine phosphatase expression and activity in 3 ALK-positive ALCL cell lines (Karpas 299, Cost, and SU-DHL1) and in lymph node biopsies (n = 40). We found an inverse correlation between the level of NPM-ALK phosphorylation and SHP1 phosphatase activity. Pull-down and coimmunoprecipitation experiments demonstrated a SHP1/NPM-ALK association. Furthermore, confocal microscopy performed on ALCL cell lines and biopsy specimens showed the colocalization of the 2 proteins in cytoplasmic bodies containing Y664-phosphorylated NPM-ALK. Dephosphorylation of NPM-ALK by SHP1 demonstrated that NPM-ALK was a SHP1 substrate. Downregulation of SHP1 expression by RNAi in Karpas cells led to hyperphosphorylation of NPM-ALK, STAT3 activation, and increase in cell proliferation. Furthermore, SHP1 overexpression in 3T3 fibroblasts stably expressing NPM-ALK led to the decrease of NPM-ALK phosphorylation, lower cell proliferation, and tumor progression in nude mice. These findings show that SHP1 is a negative regulator of NPM-ALK signaling. The use of tissue microarrays revealed that 50% of ALK-positive ALCLs were positive for SHP1. Our results suggest that SHP1 could be a critical enzyme in ALCL biology and a potential therapeutic target.

Evaluation of insulin-like growth factor-1 and parathyroid hormone on growth characteristics of MG-63 cells.

Insulin-like Growth Factor-1 (IGF-1) and Parathyroid hormones (PTH) are major endocrine secretions that contribute to bone formation. The purpose of this experiment was to examine MG-63 bone like cells after treatment with PTH and IGF-1 in low (1 ug), medium (5 ug), and high (50 ug) dosage levels. MG-63 cells were plated onto a 24 well tissue culture plate at a density of 1 x 1--5 cells per well. The experiment was designed to evaluate cell counts, cell damage (MDA), protein levels, calcium levels, alkaline phosphatase levels, and cellular morphology after 24, 48, and 72 hours post incubation with IGF-1 and PTH. Both hormones stimulated cellular mitotic division as evidenced by morphology and cell numbers. There was an inverse relationship between dose and cell number with the lower dose of IGF-1 and PTH causing the most increase. In both hormones, the exposure to the highest dose induced the largest MDA level increase. However, in the protein levels, few changes in protein levels were found with IGF-1, but PTH showed an increase of protein levels over the time periods. Morphological evaluation showed prominent nucleoli and cellular division throughout both treatments, however the cells with IGF-1 became extremely elongated and the cells with PTH became rather plump. The information gathered suggests that IGF-1 and PTH have an anabolic effect on MG-63 and the effect is dose dependent with both treatments with the lower dose being more effective.

Endoscopic removal of an implant from the maxillary sinus: a case report.

Slippage of an implant into the maxillary sinus is an exceptional complication that may occur during immediate implant placement. In this study, removal of a displaced implant into the maxillary sinus with the aid of endoscopy via buccal window approach is reported. Management of such a rare complication is also addressed.

Does endotoxin contribute to aseptic loosening of orthopedic implants?

Aseptic loosening of orthopedic implants caused by wear particles is a major clinical problem. This review examines the hypothesis that bacterial endotoxin contributes to aseptic loosening. Clinical findings support this hypothesis: bacterial biofilms exist on many implants from patients with aseptic loosening and antibiotics in bone cement reduce the rate of aseptic loosening. Three approaches were used to demonstrate that adherent endotoxin increases bioactivity of titanium particles. These experiments measured cytokine production and osteoclast differentiation in vitro and murine calvarial osteolysis in vivo. First, removal of >99.9% of the adherent endotoxin from titanium particles significantly ablates their biological activity. Second, adding lipopolysaccharide back to these "endotoxin-free" particles restores their biological activity. Third, cells or mice that are genetically hyporesponsive to endotoxin are significantly less responsive to titanium particles than are wild-type controls. Other investigators have confirmed and extended these results to include virtually all orthopedically relevant types of particles, including authentic titanium alloy particles retrieved from patients with loosening. Our recent studies suggest that adherent endotoxin on orthopedic implants may also inhibit initial osseointegration of the implants. Taken together, these studies suggest that bacterial endotoxin may have a significant role in induction of aseptic loosening.

Stimulation of osteogenesis by means of sustained delivery of various natural androgenic hormones.

Sex steroids play an essential role in the maintenance of bone health throughout life, and the mechanisms by which these effects are mediated in a subject of much controversy. Osteoblast cells appear to be stimulated by androgens in vitro, however their use in vivo is limited due to the virilizing side effects as well as alterations in the lipoprotein profiles. The use of targeted sustained release of anabolic steroids may stimulate fracture healing without untoward side effects. The specific aims were: (1) to compare fracture healing in a rat femoral defect model using tricalcium phosphate lysine (TCPL) drug delivery systems to deliver T, DHT and AED for long duration; (2) to quantify the level of steroid delivered from the system; and (3) to use bone histomorphometric techniques to analyze new bone formation at the defect site. A total of 125 adult male Sprague Dawley were obtained and acclimatized for two weeks in the animal care prior surgical procedures. All animals were kept on a 12-hour day/night cycle and were fed Purina rodent chow and water ad libitum. The animals were randomly divided into five equal groups (n = 25 per group). Group 1 animals were used as the intact control. Group 2-5 animals were placed under anesthesia and a standard approach was used to create a 6-mm defect using a dental burr in the midshaft of the femur. Group 2 animals were implanted with a sham TCPL delivery system adjacent to the defect. Animals in groups 3, 4, and 5 received a TCPL delivery system loaded with T, DHT, and AED, respectively. Animals were weighed, x-rayed, and blood samples were drawn on a weekly basis. The rats were sacrificed after 3, 6, 9 12 and 15 weeks and reproductive, vital organs, and fracture calluses were collected and analyzed. Morphometric analysis of the femurs revealed that the use of sustained delivery of DHT induced remarkable bone ingrowth compared to the sham and other experimental groups. All treated femurs appeared healthy and normal bone architecture was observed by the end of the 6 week phase. Measurements of the inner perimeter of the bone on the endosteal side showed significant reduction in the androgens treated animals. The quantitative findings confirms our preliminary studies and endorsing the previous data that the sustained delivery of T or its metabolite (DHT) can stimulate the osteoblastic activities in which eventually causes an increase in the cortical bone density.

The tyrosine phosphatase 1B regulates linker for activation of T-cell phosphorylation and platelet aggregation upon FcgammaRIIa cross-linking.

Human platelets express the receptor for immunoglobulin G, FcgammaRIIa, that triggers cell aggregation upon interaction with immune complexes. Here, we report that the rapid tyrosine phosphorylation of the Linker for Activation of T-cell (LAT) in human platelets stimulated by FcgammaRIIa cross-linking was followed by its complete dephosphorylation in an alphaIIb/beta3 integrin-dependent manner. Concomitant to LAT dephosphorylation, the protein tyrosine phosphatase 1B (PTP1B) was activated through a mechanism involving its proteolysis by calpains downstream of integrins. Both PTP1B and LAT were associated with the actin cytoskeleton complex formed during platelet aggregation. Moreover, phospho-LAT appeared as a good substrate of activated PTP1B in vitro and these two proteins interacted upon platelet activation by FcgammaRIIa cross-linking. The permeant substrate-trapping PTP1B (TAT-PTP1B D181A) partly inhibited LAT dephosphorylation in human platelets, strongly suggesting that this tyrosine phosphatase was involved in this regulatory pathway. Using a pharmacological inhibitor, we provide evidence that PTP1B activation and LAT dephosphorylation processes were required for irreversible platelet aggregation. Altogether, our results demonstrate that PTP1B plays an important role in the integrin-mediated dephosphorylation of LAT in human platelets and is involved in the control of irreversible aggregation upon FcgammaRIIa stimulation.

Validity of self-assessment outcome questionnaires: patient-physician discrepancy in outcome interpretation.

Patient outcome following total hip arthroplasty (THA) was evaluated using a previously described patient assessment outcome index questionnaires. The questionnaire was distributed to 263 patients who underwent cementless THA. One hundred and three patients responded to the self-administered questionnaire and had updated clinical evaluation. We obtained a modified Harris Hip Score (HHS) based on patient assessments of their own pain and function and compared it with the clinical HHS obtained at the patients' last office visit. The mean follow up period was 4 years. Statistical analysis was performed between the two scores. The correlation between the scores from the self-administered questionnaire and the patients' last office visit revealed a fairly low correlation coefficient (r = 0.467, p < 0.001). Relative lack of correlation between the HHS's obtained from these two sources was especially noted for patients with a pain score of 30 points or less. These 26 patients were subsequently interviewed in detail about their pain to further explain these differences. The etiology of the perceived "hip pain" was found to be secondary to trochanteric bursitis in 13 patients, lumbar spondylosis in 7 patients, arthrosis of the contralateral hip in 5 patients, and from other causes in 8 patients. Pain that was hip related (anterior thigh or groin) was present in only 5 out of the 26 patients with a pain score of 30 or less. Another source of discrepancy between the total scores of the HHS was found to be on behalf of the physician in evaluating the presence of a limp. We also found that patients' expectations had changed from their preoperative expectations. Although outcome measures developed and administered by clinicians are subject to bias from several sources, results of this study suggest that self administered patient outcome measures also have their limitations. The validity of self-administered patient outcome questionnaires can be severely impacted by the patients' understanding of the questions asked, as even the most seemingly simple questions are subject to misinterpretation.