Ownership and control in a competitive industry

We study a differentiated product market in which an investor initially owns a controlling stake in one of two competing firms and may acquire a non-controlling or a controlling stake in a competitor, either directly using her own assets, or indirectly via the controlled firm. While industry profits are maximized within a symmetric two product monopoly, the investor attains this only in exceptional cases. Instead, she sometimes acquires a noncontrolling stake. Or she invests asymmetrically rather than pursuing a full takeover if she acquires a controlling one. Generally, she invests indirectly if she only wants to affect the product market outcome, and directly if acquiring shares is profitable per se. --differentiated products,separation of ownership and control,private benefits of control

Lack of influence of the COX inhibitors metamizol and diclofenac on platelet GPIIb/IIIa and P-selectin expression in vitro

BACKGROUND: The effect of non-steroidal anti-inflammatory drugs (NSAIDs) for reduced platelet aggregation and thromboxane A(2 )synthesis has been well documented. However, the influence on platelet function is not fully explained. Aim of this study was to examine the influence of the COX-1 inhibiting NSAIDs, diclofenac and metamizol on platelet activation and leukocyte-platelet complexes, in vitro. Surface expression of GPIIb/IIIa and P-selectin on platelets, and the percentage of platelet-leukocyte complexes were investigated. METHODS: Whole blood was incubated with three different concentrations of diclofenac and metamizol for 5 and 30 minutes, followed by activation with TRAP-6 and ADP. Rates of GPIIb/IIIa and P-selectin expression, and the percentage of platelet-leukocyte complexes were analyzed by a flow-cytometric assay. RESULTS: There were no significant differences in the expression of GPIIb/IIIa and P-selectin, and in the formation of platelet-leukocyte complexes after activation with ADP and TRAP-6, regarding both the time of incubation and the concentrations of diclofenac and metamizol. CONCLUSIONS: Accordingly, the inhibitory effect of diclofenac and metamizol on platelet aggregation is not related to a reduced surface expression of P-selectin and GPIIb/IIIa on platelets

Mu-surrogate light chain physicochemical interactions of the human preB cell receptor: implications for VH repertoire selection and cell signaling at the preB cell stage.

International audienceThe surrogate light chain (SL) composed of the A-like and VpreB polypeptides is organized as two Ig domains and an extra-loop structure. It associates to the mu-chain in preB cells. We have produced human VpreB, SL, two Fdmu (VH-CH1), and the two corresponding Fab-like (Fdmu-SL) recombinant proteins in baculovirus. The correctness of the general conformation of the proteins was assessed by epitope mapping and affinity measurements using a new batch of anti-VpreB mAbs. Plasmon resonance analysis showed that both VpreB and the entire SL associated with the Fdmu fragments, with Kd values of 3x10(-8) M for VpreB-Fdmu and of 10(-9) to 10(-10) M, depending upon the V(H), for SL-Fdmu. These results indicate that the A-like chain, in addition to be covalently bound to the Cmu1 domain, also interacts with the VH domain. Therefore, a dual role of the SL emerges: 1) interaction of the C-domain of A-like would release the mu-chain from its interaction with binding protein in the endoplasmic reticulum, and 2) interaction of a part of A-like and most of VpreB would bind to VH, ensuring a "quality control" of the native heavy chain that represents the first step of selection of the B cell repertoire. We also demonstrated that two Fab-like fragments did not interact with each other, suggesting that activation of the cell surface preB receptor does not involve aggregation neither in cis nor in trans of the Fab-like structures

The human (PsiL+mu-) proB complex: cell surface expression and biochemical structure of a putative transducing receptor.

International audienceThe surrogate light chain (PsiL) associates with mu and Igalpha-Igbeta chains to form the preB-cell receptor that plays a critical role in early B-cell differentiation. Discrepancies exist in human concerning the existence of PsiL+mu- proB cells and the biochemical structure of such a proB-cell complex remains elusive. Among new antihuman VpreB monoclonal antibodies (MoAbs), 5 of the gamma kappa isotype bound to recombinant and native VpreB protein with high affinity. They recognized 4 discrete epitopes, upon which 2 were in the extra-loop fragment. Such MoAbs detected the PsiL at the cell surface of either preB or on both proB and preB cells. The previously reported SLC1/SLC2 MoAbs recognize a conformational epitope specific for the mu/PsiL association in accordance with their preB-cell reactivity. Using the proB/preB 4G7 MoAb, PsiL cell surface expression was detected on normal bone marrow, not only on CD34(-)CD19(+) preB but also on CD34(+)CD19(+) proB cells. Futhermore, this MoAb identified PsiL+mu- fresh proB leukemic cells of the TEL/AML1 type. Biochemical studies showed that, at the proB stage, the PsiL is associated noncovalently with two proteins of 105 and 130 kD. Triggering of this complex induces intracellular Ca2+ flux, suggesting that the PsiL may be involved in a new receptor at this early step of the B-cell differentiation