Statins selectively inhibit leukocyte function antigen-1 by binding to a novel regulatory integrin site.

The beta2 integrin leukocyte function antigen-1 (LFA-1) has an important role in the pathophysiology of inflammatory and autoimmune diseases. Here we report that statin compounds commonly used for the treatment of hypercholesterolemia selectively blocked LFA-1-mediated adhesion and costimulation of lymphocytes. This effect was unrelated to the statins' inhibition of 3-hydroxy-3-methylglutaryl coenzyme-A reductase; instead it occurred via binding to a novel allosteric site within LFA-1. Subsequent optimization of the statins for LFA-1 binding resulted in potent, selective and orally active LFA-1 inhibitors that suppress the inflammatory response in a murine model of peritonitis. Targeting of the statin-binding site of LFA-1 could be used to treat diseases such as psoriasis, rheumatoid arthritis, ischemia/reperfusion injury and transplant rejection.

Alymphoplasia (aly)-type nuclear factor kappaB-inducing kinase (NIK) causes defects in secondary lymphoid tissue chemokine receptor signaling and homing of peritoneal cells to the gut-associated lymphatic tissue system.

Alymphoplasia (aly) mice, which carry a point mutation in the nuclear factor kappaB-inducing kinase (NIK) gene, are characterized by the systemic absence of lymph nodes and Peyer's patches, disorganized splenic and thymic architectures, and immunodeficiency. Another unique feature of aly/aly mice is that their peritoneal cavity contains more B1 cells than normal and aly/+ mice. Transfer experiments of peritoneal lymphocytes from aly/aly mice into recombination activating gene (RAG)-2(-/-) mice revealed that B and T cells fail to migrate to other lymphoid tissues, particularly to the gut-associated lymphatic tissue system. In vivo homing defects of aly/aly peritoneal cells correlated with reduction of their in vitro chemotactic responses to secondary lymphoid tissue chemokine (SLC) and B lymphocyte chemoattractant (BLC). The migration defect of aly/aly lymphocytes was not due to a lack of expression of chemokines and their receptors, but rather to impaired signal transduction downstream of the receptors for SLC, indicating that NIK is involved in the chemokine signaling pathway known to couple only with G proteins. The results showed that the reduced serum levels of immunoglobulins (Igs) and the absence of class switch to IgA in aly/aly mice are due, at least in part, to a migration defect of lymphocytes to the proper microenvironment where B cells proliferate and differentiate into Ig-producing cells.

T cell receptor-induced calcineurin activation regulates T helper type 2 cell development by modifying the interleukin 4 receptor signaling complex.

The activation of downstream signaling pathways of both T cell receptor (TCR) and interleukin 4 receptor (IL-4R) is essential for T helper type 2 (Th2) cell development, which is central to understanding immune responses against helminthic parasites and in allergic and autoimmune diseases. However, little is known about how these two distinct signaling pathways cooperate with each other to induce Th2 cells. Here, we show that successful Th2 cell development depends on the effectiveness of TCR-induced activation of calcineurin. An inhibitor of calcineurin activation, FK506, inhibited the in vitro anti-TCR-induced Th2 cell generation in a dose-dependent manner. Furthermore, the development of Th2 cells was significantly impaired in naive T cells from dominant-negative calcineurin Aalpha transgenic mice, whereas that of Th1 cells was less affected. Efficient calcineurin activation in naive T cells upregulated Janus kinase (Jak)3 transcription and the amount of protein. The generation of Th2 cells induced in vitro by anti-TCR stimulation was inhibited significantly by the presence of Jak3 antisense oligonucleotides, suggesting that the Jak3 upregulation is an important event for the Th2 cell development. Interestingly, signal transducer and activator of transcription (STAT)5 became physically and functionally associated with the IL-4R in the anti-TCR-activated developing Th2 cells that received efficient calcineurin activation, and also in established cloned Th2 cells. In either cell population, the inhibition of STAT5 activation resulted in a diminished IL-4-induced proliferation. Moreover, our results suggest that IL-4-induced STAT5 activation is required for the expansion process of developing Th2 cells. Thus, Th2 cell development is controlled by TCR-mediated activation of the Ca(2+)/calcineurin pathway, at least in part, by modifying the functional structure of the IL-4R signaling complex.

Inhibition of T helper cell type 2 cell differentiation and immunoglobulin E response by ligand-activated Valpha14 natural killer T cells.

Murine Valpha14 natural killer T (NKT) cells are thought to play a crucial role in various immune responses, including infectious, allergic, and autoimmune diseases. Because Valpha14 NKT cells produce large amounts of both interleukin (IL)-4 and interferon (IFN)-gamma upon in vivo stimulation with a specific ligand, alpha-galactosylceramide (alpha-GalCer), or after treatment with anti-CD3 antibody, a regulatory role on helper T (Th) cell differentiation has been proposed for these cells. However, the identity of the cytokine produced by Valpha14 NKT cells that play a dominant role on the Th cell differentiation still remains controversial. Here, we demonstrate by using Valpha14 NKT-deficient mice that Valpha14 NKT cells are dispensable for the induction of antigen-specific immunoglobulin (Ig)E responses induced by ovalbumin immunization or Nippostrongylus brasiliensis infection. However, upon in vivo activation with alpha-GalCer, Valpha14 NKT cells are found to suppress antigen-specific IgE production. The suppression appeared to be IgE specific, and was not detected in either Valpha14 NKT- or IFN-gamma-deficient mice. Consistent with these results, we also found that ligand-activated Valpha14 NKT cells inhibited Th2 cell differentiation in an in vitro induction culture system. Thus, it is likely that activated Valpha14 NKT cells exert a potent inhibitory effect on Th2 cell differentiation and subsequent IgE production by producing a large amount of IFN-gamma. In marked contrast, our studies have revealed that IL-4 produced by Valpha14 NKT cells has only a minor effect on Th2 cell differentiation.

Musculoskeletal symptoms and neurological investigations in adrenocortical insufficiency: a case report and literature review.

OBJECTIVES: Various forms of adrenocortical insufficiency can cause musculoskeletal symptoms such as muscle pain, tautness of the limbs, arthralgia, and flexion contractures. However, the findings of neurological investigations are inconclusive and have not been well summarized. METHODS: We report the case of a 61-year-old man with isolated adrenocorticotropic hormone deficiency who presented with musculoskeletal symptoms, including flexion contractures. We performed three neurological investigations: nerve conduction studies, electromyography, and muscle biopsy analysis. Further, we reviewed reports of 16 patients with various forms of adrenocortical insufficiency and musculoskeletal symptoms by considering the findings of these three investigations. RESULTS: From the literature review, we found that (a) analysis of muscle biopsy is the most sensitive technique, followed by electromyography and then nerve conduction studies; and (b) the longer the duration of the musculoskeletal symptoms, the greater the incidence of abnormal findings with all three techniques. CONCLUSIONS: Physicians may prioritize neurological investigations, depending on these findings.

Nerve growth factor stimulation of the Ras-guanine nucleotide exchange factor and GAP activities.

The biological activity of Ras proteins is thought to be controlled by the guanine nucleotide exchange factor and the guanosine triphosphatase activating protein (GAP). Treatment of rat pheochromocytoma PC-12 cells with nerve growth factor (NGF) increased the amount of active Ras guanosine triphosphate complex and stimulated the activities of both the guanine nucleotide exchange factor and GAP. In PC-12 cells that overexpressed the tyrosine kinase encoded by the trk proto-oncogene (a component of the high-affinity NGF receptor), the NGF-induced activation of the regulatory proteins was potentiated. These results suggest that the NGF receptor system enhances the activities of both the guanine nucleotide exchange factor and GAP and that the activation of Ras might be controlled by the balance in activity between these two regulatory proteins.

How does higher ultrafiltration within the conventional clinical range impact the volume status of hemodialysis patients?

AIMS: The higher ultrafiltration (UF) induces poor outcomes. The impact of higher UF on the volume status was investigated. METHODS: 60 hemodialysis (HD) patients were divided into three groups according to the ratio of total UF to post-dialysis body weight (TUF/PDW) (<3%, 3-5%, > or =5%). ANP, the ratio of extracellular water to total body water and excess fluid mass (ExF/PDW) by bioimpedance spectroscopy, inferior vena cava diameter by ultrasound were measured at the end of HD. The ratio of post-HD blood volume to pre-HD (BVpost/BVpre) and standardized filtration coefficients (Lpst) of the microvasculature in the vicinity of PDW were calculated. RESULTS: Only Lpst and BVpost/BVpre showed significant differences among the three groups. A stepwise multiple linear regression model revealed that BVpost/BVpre was correlated with TUF/PDW, ExF/PDW and Lpst (R = 0.778, p < 0.001), independently. CONCLUSION: Higher UF causes decreases in BVpost/BVpre and Lpst. BVpost/BVpre was determined by TUF/PDW, ExF/PDW and Lpst.

Upper cervical spine movement during intubation: fluoroscopic comparison of the AirWay Scope, McCoy laryngoscope, and Macintosh laryngoscope.

BACKGROUND: The AirWay Scope (AWS) is a new fibreoptic intubation device, which allows visualization of the glottic structures without alignment of the oral, pharyngeal, and tracheal axes, and thus may be useful in patients with limited cervical spine (C-spine) movement. We fluoroscopically evaluated upper C-spine movement during intubation with the AWS or Macintosh or McCoy laryngoscope. METHODS: Forty-five patients, with normal C-spine, scheduled for elective surgery were randomly assigned to one of the three intubation devices. Movement of the upper C-spine was examined by measuring angles formed by adjacent vertebrae during intubation. Time to intubation was also recorded. RESULTS: Median cumulative upper C-spine movement was 22.3 degrees, 32.3 degrees, and 36.5 degrees with the AWS, Macintosh laryngoscope, and McCoy laryngoscope, respectively (P<0.001, AWS vs, Macintosh and McCoy). The AWS reduced maximum movement of the C-spine at C1/C2 in comparison with the Macintosh or McCoy laryngoscope (P=0.012), and at C3/C4 in comparison with the McCoy laryngoscope (P=0.019). Intubation time was significantly longer in the AWS group than in the Macintosh group (P=0.03). CONCLUSIONS: Compared with the Macintosh or McCoy laryngoscope, the AWS produced less movement of upper C-spine for intubation in patients with a normal C-spine.

Inhibition of NADPH oxidase 4 activates apoptosis via the AKT/apoptosis signal-regulating kinase 1 pathway in pancreatic cancer PANC-1 cells.

Pancreatic adenocarcinoma is an aggressive human malignancy and is characterized by resistance to apoptosis. Recently, NADPH oxidase (Nox) 4-mediated generation of intracellular reactive oxygen species (ROS) was proposed to confer antiapoptotic activity and thus a growth advantage to pancreatic cancer cells. The signaling mechanism by which Nox4 transmits cell survival signals remains unclear. Here, we show that both a flavoprotein inhibitor, diphenylene iodonium (DPI), and small interfering RNAs designed to target Nox4 mRNA (siNox4RNAs) inhibited superoxide production in PANC-1 pancreatic cancer cells, and depletion of ROS by DPI or siNox4RNAs induced apoptosis. Parallely, DPI treatment and siNox4RNA transfection blocked activation of the cell survival kinase AKT by attenuating phosphorylation of AKT. Furthermore, AKT phosphorylation of apoptosis signal-regulating kinase 1 (ASK1) on Ser-83 was reduced by DPI and siNox4RNAs. When ASK1Ser83Ala (an AKT phosphorylation-defective ASK1 mutant) was introduced into PANC-1 cells, this mutant alone induced apoptosis. But, addition of DPI or co-transfection of siNox4RNA had no additive effect, indicating that the mutant can substitute for these reagents in apoptosis induction. Taken together, these findings suggest that ROS generated by Nox4, at least in part, transmit cell survival signals through the AKT-ASK1 pathway in pancreatic cancer cells and their depletion leads to apoptosis.

The role of von Willebrand factor and fibrinogen in platelet aggregation under varying shear stress.

Exposure of platelets to shear stress leads to aggregation in the absence of exogenous agonists. We have now found that different adhesive proteins and platelet membrane glycoproteins are involved in aggregation depending on the shear stress conditions and the concentration of divalent cations in the medium. When blood is collected with trisodium citrate as anticoagulant, which causes a decrease in the levels of external ionized calcium ([Ca2+]o), platelet aggregation can be induced under low shear force (12 dyn/cm2) and is mediated by fibrinogen binding to the glycoprotein IIb-IIIa complex. Aggregates formed under these conditions are not stable, and when shear force is increased to 68 dyn/cm2, disaggregation results. By contrast, platelets from blood collected with hirudin as anticoagulant, wherein [Ca2+]o is within normal plasma levels, do not undergo low shear-induced aggregation; however, after exposure to a shear force above 80 dyn/cm2, aggregation is observed but only when von Willebrand factor is present and can interact with both its platelet binding sites, glycoprotein Ib-IX and glycoprotein IIb-IIIa. Fibrinogen is not involved in high shear-induced aggregation which, in fact, occurs normally in patients with severe afibrinogenemia. Thus, von Willebrand factor in the absence of exogenous agonists can mediate platelet aggregation in experimental conditions that may mimic the hemorheological situation of partially occluded arteries. This pathway of platelet aggregation involving only one adhesive ligand and two membrane adhesion receptors may play a relevant role in thrombogenesis.

Modulation of maturation and ribosomal protein S6 phosphorylation in Xenopus oocytes by microinjection of oncogenic ras protein and protein kinase C.

Using Xenopus oocytes as a model system, we investigated the possible involvement of ras proteins in the pathway leading to phosphorylation of ribosomal protein S6. Our results indicate that microinjection of oncogenic T24 H-ras protein (which contains valine at position 12) markedly stimulated S6 phosphorylation on serine residues in oocytes, whereas normal ras protein (which contains glycine at position 12) was without effect. The S6 phosphorylation activity in the cell extract from T24 ras protein-injected oocytes was increased significantly. In addition, injection of protein kinase C potentiated the induction of maturation and S6 phosphorylation by the oncogenic ras protein. A similar potentiation was detected when T24 ras protein-injected oocytes were incubated with active phorbol ester. These findings suggest that ras proteins activate the pathway linked to S6 phosphorylation and that protein kinase C has a synergistic effect on the ras-mediated pathway.

Serum retinol levels are associated with brain volume loss in patients with multiple sclerosis.

BACKGROUND: Although predicting future brain volume loss (BVL) in patients with multiple sclerosis (MS) is important, studies have shown only a few biomarkers that can predict BVL. OBJECTIVES: The aim of this study is to elucidate the association between longitudinal BVL and serum biomarker candidates. METHODS: This single-center, retrospective, observational study intended to cover MS patients during January 2008 to March 2016. Patients who underwent brain MRI two times at intervals of >24 months and had a blood test to measure biomarker candidates at the time or within three months of the MRI scan were included. Evaluation of brain volume was performed by using SIENAX and SIENA in the FMRIB software library. RESULTS: Twenty-three patients with MS were included in this study. We found that serum retinol binding protein (RBP) levels were significantly correlated with percentage brain volume change (PBVC) (p = 0.0079). Furthermore, best subset selection of multiple linear regression models identified baseline normalized brain volume and serum RBP as the best predictors of PBVC. CONCLUSIONS: Our study shows that lower serum retinol levels are associated with greater longitudinal BVL and that serum RBP and can be a predictor of BVL.

Megakaryocytes derived from human embryonic stem cells: a genetically tractable system to study megakaryocytopoiesis and integrin function.

BACKGROUND: The platelet fibrinogen receptor, a heterodimer consisting of integrin subunits alpha(IIb) and beta(3), is required for platelet aggregation, spreading, and hemostasis. Platelet agonists such as thrombin and adenosine diphosphate (ADP) lead to the activation of alpha(IIb)beta(3), thereby enhancing its affinity and avidity for binding fibrinogen (inside-out signaling). Furthermore, fibrinogen binding to alpha(IIb)beta(3) triggers cytoskeletal changes and granule release (outside-in signaling). AIM: Genetic approaches to characterize the molecular pathways involved in alpha(IIb)beta(3) signaling are not possible with anucleate blood platelets. Therefore, we have established an OP9 stromal cell co-culture system to generate megakaryocytes from human embryonic stem cells (hESCs). RESULTS: alpha(IIb)beta(3) activation, measured by soluble fibrinogen binding to hESC-derived megakaryocytes, /GPIbalpha(+) cells, is readily detectable following stimulation with known platelet agonists. Dose-response curves for peptide agonists specific for the two platelet thrombin receptors, protease-activated receptor 1 (PAR1) and PAR4, show a relative responsiveness that mirrors that of human platelets, and sub-maximal ADP responses are augmented by epinephrine. Moreover, hESC-derived megakaryocytes undergo lamellipodia formation, actin filament assembly, and vinculin localization at focal adhesions when plated on a fibrinogen-coated surface, characteristic of alpha(IIb)beta(3) outside-in signaling. Undifferentiated hESCs genetically modified by lentiviral infection can be cloned and maintained in an undifferentiated state and then differentiated into megakaryocytes capable of alpha(IIb)beta(3) activation. CONCLUSION: Using hESCs, we have developed a renewable source of human megakaryocytes, and a genetically tractable system for studying megakaryocytopoiesis and alpha(IIb)beta(3) signaling in the native cellular environment.

Retrospective analysis of the prognostic significance of DNA ploidy patterns and S-phase fraction in gastric carcinoma.

Paraffin-embedded tumor samples from 493 gastric carcinoma patients were analyzed by DNA flow cytometry. The results were correlated with clinicopathological findings and S-phase fractions measured by in vivo bromodeoxyuridine (BrdUrd) labeling. Of the 493 patients, 183 (37%), 225 (46%), and 85 (17%) showed diploidy, single DNA-aneuploidy, and DNA-multiploidy patterns, respectively. When the DNA histogram and all the clinicopathological parameters were entered simultaneously into the Cox regression model, DNA ploidy, liver metastasis, peritoneal dissemination, and nodal status emerged as independent prognostic parameters. The relative risk of death was twofold higher in single DNA-aneuploid and threefold higher in DNA-multiploid tumors than in DNA-diploid tumors. BrdUrd labeling indices (LIs) also proved to be an independent prognostic factor. Multiploid tumors showed the highest median BrdUrd LI associated with the most frequent peritoneal dissemination and liver metastasis. The simultaneous evaluation of DNA ploidy patterns and BrdUrd LIs gave more prognostic information than the determination of tumor DNA ploidy only. Namely, DNA diploid, together with low BrdUrd LIs, was associated with favorable prognosis, whereas DNA aneuploid with high BrdUrd LIs was related to the poorest prognosis. These results indicate that DNA ploidy and BrdUrd labeling indices may be possibly useful prognostic factors for gastric carcinoma.

Estimation of the width of free margin with a significant impact on local recurrence in surgical resection of oral squamous cell carcinoma.

The purpose of this study was to estimate the width of free margin with a significant impact on local recurrence in surgical resection of oral squamous cell carcinoma (OSCC). Clinical and pathological data of 127 consecutive patients who underwent radical resection of OSCC were analyzed retrospectively. The local control rate was compared between patients with clear, close, and involved surgical margins, changing the required width of free margin for the definition of 'close surgical margin' (from 1 to 5mm). If a free margin of within 1, 2, or 4mm was judged a close margin, the risk of local recurrence was significantly different among the patients with clear, close, and involved surgical margins. If the definition of close margin was within 5mm of the resection margin, the difference between clear and close margin did not reach statistical significance. The results of this study suggest that 5mm of clearance at the surgical resection margin should be the index of oncological surgery. More than 5mm of histological free margin around OSCC is not justified in terms of the risk management of local recurrence and the resultant morbidity.

Evaluation of the level of progression of extracapsular spread for cervical lymph node metastasis in oral squamous cell carcinoma.

Only a few reports on the level of progression of extracapsular spread (ECS) have been published. The aim of this study was to evaluate the efficacy of the level of progression of ECS in identifying those patients with oral squamous cell carcinoma (OSCC) at a high risk of recurrence who would benefit most from the intensification of adjuvant therapy. The level of progression of ECS for cervical lymph node metastasis in OSCC was divided into three types (A-C), and their relationships with patient prognosis were examined. ECS was observed in 87 of 441 patients with OSCC. The recurrence rate in patients with type C, which was defined as macroscopic tumour invasion into perinodal fat or muscle tissue, was high (69.8%), with 13 cases of death due to distant metastasis. The 3-year disease-specific survival rate for patients with type C was 49.0% and these patients also had a significantly poorer prognosis (P<0.01). The results of the multivariate analysis suggested that the prognosis of ECS in OSCC patients was associated with the level of progression of ECS, especially type C (P<0.01). Overall, the results of this study suggest that the level of progression of ECS is a useful prognostic factor in OSCC patients.

Reduced protein kinase C activity in a ras-resistant cell line derived from Ki-MSV transformed cells.

We have examined phosphatidylinositol turnover and C-kinase distribution in a flat cellular ras-resistant cell line (C11) derived from Kirsten murine sarcoma virus (Ki-MSV) transformed NIH/3T3 cells (DT). This cell type has been shown to express high levels of the p21 Ki-ras gene product yet is resistant to the transforming effects of this protein. Our data indicate that C11 cells have reduced levels of total C-kinase activity when compared to NIH/3T3 cells and do not retain the ability to phosphorylate the growth associated 80-kDa C-kinase substrate either in vivo or in vitro. Furthermore, whilst the steady state levels of diacylglycerol and the sum of inositol phosphates are elevated in DT cells, in C11 cells these levels are reduced to an amount equivalent to that seen in NIH/3T3 cells. These data indicate a correlation between a protein kinase C dependent pathway and resistance to transformation by ras.

Isoform-specific insertion near the Grb2-binding domain modulates the intrinsic guanine nucleotide exchange activity of hSos1.

Two human hSos1 isoforms (Isf I and Isf II; Rojas et al., Oncogene 12, 2291-2300, 1996) defined by the presence of a distinct 15 amino acid stretch in one of them, were compared biologically and biochemically using representative NIH3T3 transfectants overexpressing either one. We showed that hSos1-Isf II is significantly more effective than hSos1-Isf I to induce proliferation or malignant transformation of rodent fibroblasts when transfected alone or in conjunction with normal H-Ras (Gly12). The hSos1-Isf II-Ras cotransfectants consistently exhibited higher saturation density, lower cell-doubling times, increased focus-forming activity and higher ability to grow on semisolid medium and at low serum concentration than their hSos1-Isf I-Ras counterparts. Furthermore, the ratio of GTP/GDP bound to cellular p21ras was consistently higher in the hSos1-Isf II-transfected clones, both under basal and stimulated conditions. However, no significant differences were detected in vivo between Isf I- and Isf II-transfected clones regarding the amount, stability and subcellular localization of Sos1-Grb2 complex, or the level of hSos1 phosphorylation upon cellular stimulation. Interestingly, direct Ras guanine nucleotide exchange activity assays in cellular lysates showed that Isf II transfectants consistently exhibited about threefold higher activity than Isf I transfectants under basal, unstimulated conditions. Microinjection into Xenopus oocytes of purified peptides corresponding to the C-terminal region of both isoforms (encompassing the 15 amino acid insertion area and the first Grb2-binding motif) showed that only the Isf II peptide, but not its corresponding Isf I peptide, was able to induce measurable rates of meiotic maturation, and synergyzed with insulin, but not progesterone, in induction of GVBD. Our results suggest that the increased biological potency displayed by hSos1-Isf II is due to higher intrinsic guanine nucleotide exchange activity conferred upon this isoform by the 15 a.a. insertion located in proximity to its Grb2 binding region.

Significance of Development and Reversion of Collaterals on MRI in Early Neurologic Improvement and Long-Term Functional Outcome after Intravenous Thrombolysis for Ischemic Stroke.

BACKGROUND AND PURPOSE: Predicting response to rtPA is essential in the era of endovascular therapy for stroke. The purpose of this study was to elucidate prognostic factors of early neurologic improvement and long-term outcome with respect to the development and reversion of leptomeningeal collaterals in recanalization therapy after acute ischemic stroke. MATERIALS AND METHODS: We analyzed consecutive patients with proximal MCA occlusion treated with rtPA from 2007 to 2012 at 2 hospital stroke centers. All patients routinely underwent brain MR imaging before rtPA. To assess the reversion of collateral signs, we included patients who underwent follow-up MR imaging. We assessed the development and reversion of collaterals by using a combination of 2 MR imaging collateral markers, the hyperintense vessel sign and the posterior cerebral artery laterality sign. Early neurologic improvement was defined as a decrease in the NIHSS score of ≥10 or a score of ≤2 at 24 hours of treatment. RESULTS: Early neurologic improvement was observed in 22 of 48 eligible patients. The development of collaterals at arrival (15/22 versus 9/26, P = .042) was significantly associated with early neurologic improvement. Multivariate analysis adjusting for other variables showed that the development of collaterals at arrival (OR, 4.82; 95% CI, 1.34-19.98; P = .015) was independently associated with early neurologic improvement. Reversion of collaterals was significantly associated with successful recanalization (P < .001), and multivariate analysis showed that the reversion of collaterals was an independent prognostic factor of long-term functional outcome (OR, 5.07; 95% CI, 1.38-22.09; P = .013). CONCLUSIONS: Our results indicate that the development of leptomeningeal collaterals plays a crucial role in achieving early neurologic improvement, and reversion of collaterals predicts a favorable outcome via arterial recanalization after rtPA treatment for acute stroke.

Structural basis of integrin-mediated signal transduction.

Integrins are a family of alpha/beta heterodimers of cell adhesion receptors that mediate cell-extracellular matrix and cell-cell interactions. Both alpha and beta subunits have a large extracellular domain and a short cytoplasmic domain. The alpha subunit has seven sequence repeats of 60-70 residues in its N-terminal region. The beta-propeller model, in which seven four-stranded beta-sheets are arranged in a torus around a pseudosymmetry axis, has been proposed as a structural model of these seven repeats. Several predicted loops critical for ligand binding have been identified in the upper face of the proposed beta-propeller model. Several alpha subunits (e.g., alpha 2, alpha L and alpha M) have I-domains of about 200 residues inserted between their second and third repeats. These I-domains adopt a Rossman-fold structure and have major ligand and cation binding sites (the MIDAS site) on their surfaces. The beta subunit has an I-domain-like structure in its N-terminal region. This structure includes multiple sequences/conserved oxygenated residues critical for ligand binding (e.g., Asp-119 in beta 3), and non-conserved residues critical for ligand specificities. Several "activation-dependent" epitopes have been identified in the Cys-rich (stalk) region of beta 1. It has yet to be determined how these multiple ligand binding sites in the alpha and beta subunits are involved in ligand binding, and how conformational changes on activation/ligand occupancy relate to signal transduction.