Anti-Inflammatory properties of Salograviolide A purified from Lebanese plant Centaurea ainetensis

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Congestion and Flow Control in the Context of the Message-oriented Protocol SCTP

Abstract. Congestion and flow control are key mechanisms used to regulate the load in modern packet networks. The new IETF Stream Control Transmission Protocol (SCTP) inherited these algorithms from the Transmission Control Protocol (TCP). Although the principles used are the same, some issues arise from the fact that SCTP operates messageoriented whereas TCP operates byte-stream oriented. SCTP also supports bundling of multiple small user messages into one SCTP packet. As a consequence, the overall overhead of an SCTP packet depends on the user message size and the number of user messages that are bundled into the packet. RFC 4960 defining SCTP does not specify whether the message specific headers have to be considered when updating the parameters for congestion control. We will show that neglecting the additional headers when calculating outstanding bytes can lead to unfairness towards TCP connections. We will also show that incorrect handling of the additional memory needed to process each message in the flow control calculations will lead to an exhaustion of the receiver window resulting in a huge amount of unnecessary retransmissions. Based on experiments with the flow control of the SCTP implementations available in several operating systems, we will identify the issues and analyze them by using simulations. As a result, we will present solutions that will lead to fairness towards TCP and reduce the number of retransmissions substantially. Although we will focus on SCTP, the results are also true for other message-oriented protocols using bundling

Effect of Natural and Semisynthetic Pseudoguianolides on the Stability of NF-κB:DNA Complex Studied by Agarose Gel Electrophoresis.

The nuclear factor κB (NF-κB) is a promising target for drug discovery. NF-κB is a heterodimeric complex of RelA and p50 subunits that interact with the DNA, regulating the expression of several genes; its dysregulation can trigger diverse diseases including inflammation, immunodeficiency, and cancer. There is some experimental evidence, based on whole cells studies, that natural sesquiterpene lactones (Sls) can inhibit the interaction of NF-κB with DNA, by alkylating the RelA subunit via a Michael addition. In the present work, 28 natural and semisynthetic pseudoguianolides were screened as potential inhibitors of NF-κB in a biochemical assay that was designed using pure NF-κB heterodimer, pseudoguianolides and a ~1000 bp palindromic DNA fragment harboring two NF-κB recognition sequences. By comparing the relative amount of free DNA fragment to the NF-κB - DNA complex, in a routine agarose gel electrophoresis, the destabilizing effect of a compound on the complex is estimated. The results of the assay and the following structure-activity relationship study, allowed the identification of several relevant structural features in the pseudoguaianolide skeleton, which are necessary to enhance the dissociating capacity of NF-κB-DNA complex. The most active compounds are substituted at C-3 (α-carbonyl), in addition to having the α-methylene-γ-lactone moiety which is essential for the alkylation of RelA