Total Synthesis and Revision of Stereochemistry of a Natural Benzo[g]isochromene Stereodiad Isolated from Rubia philippinensis.

This study presents a total synthesis and revision of the stereochemical configuration of the conformationally flexible natural product benzo[g]isochromene stereodiad alongside its diastereomeric counterparts. The highlights of the synthesis are the TiCl4-mediated diastereoselective aldol reaction, Pd-catalyzed lactonization, and Schmidt glycosidation. Our efforts using total synthesis disclosed herein proved that a previously assigned structure required revision.

Survival of endothelial cells in vitro on Paclitaxel-loaded coronary stents.

Coronary stents that are developed for use with balloon angioplasty are known to cause acute occlusion and long-term stenosis. It is likely that a controlled release of drugs at the site of stent implantation might inhibit the proliferation of vascular smooth muscle cells (VSMC) and reduce restenosis. However, if the drug is necrotic and affects cell survival near the implant, it may interrupt the local tissue regeneration. Different methods have been used for the immobilization of drugs with stents to get an effective concentration that inhibits cell proliferation. The objective of this study is to assess the effectiveness of Paclitaxel-loaded stents by immobilization with a biodegradable polymer, to inhibit cell proliferation. The cells used for the evaluation are human umbilical vein endothelial cells (HUVEC) and the proliferation rate of these cells on the drug-coated stent is compared against an uncoated stent for a 72-h period. Evaluations were also made to differentiate between cell apoptosis and necrosis to prove that the drug released is not deleterious to the surrounding tissue. While a similar initial cell adhesion is observed in bare and coated stents, the proliferation of HUVEC is negligible when grown on a drug-coated stent (p < 0.001). By specific staining techniques, the cells on the drug-coated stents are found to be apoptotic and not necrotic, throughout the evaluation period. In vitro leukocyte adhesion and platelet deposition on the drug-coated stents are found to be low when they are exposed to human blood and platelet-rich plasma (PRP), suggesting that the coated stents may not be thrombogenic in vivo. Therefore, drug coating of stents using the described technique may have a considerable promise for the prevention of neointimal proliferation, restenosis, and associated failure of angioplasty.

Protease action and generation of beta-thromboglobulin-like protein followed by platelet activation.

Beta-thromboglobulin (beta-TG) is a platelet-specific protein present in the alpha-granules and secreted into the surrounding medium on cell activation. The sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of platelet releasate after inhibition of metalloproteinases with ethyleneglycol-bis-(beta-aminoethyl ether) N,N'-tetra acetic acid (EGTA) showed disappearance of an 8.0-kDa band. In the absence of the cation chelators, a 48-kDa band disappeared and concurrently, the 8.0-kDa band intensity increased suggesting that the former may be the immediate precursor of the latter. The Western blot stained using specific antibodies, isolated from single-cell clones of hybridoma, against 8.0 kDa protein recognized not only 48 and 8.0 kDa bands but few others too. The data suggests that one or more high molecular weight protein is released from alpha-granules and is broken down into smaller fragments after release to form beta-thromboglobulin (beta-TG)-like proteins by the action of metal dependent proteases.

Protease action and generation of beta-thromboglobulin-like protein followed by platelet activation.

beta-Thromboglobulin (betaTG) is a platelet specific protein present in the alpha-granules and secreted into the surrounding medium on cell activation. The sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of platelet releasate after inhibition of metalloproteinases with ethyleneglycol-bis-(beta-aminoethyl ether)N,N'-tetra acetic acid (EGTA) showed disappearance of an 8.0-kDa band. In the absence of the cation chelators, a 48-kDa band disappeared and concurrently, the 8.0-kDa band intensity increased suggesting that the former may be the immediate precursor of the latter. The Western blot stained using specific antibodies, isolated from single-cell clones of hybridoma, against 8.0-kDa protein recognized not only 48- and 8.0-kDa bands but few others too. The data suggest that one or more high molecular weight (HMW) protein is released from alpha-granules and is broken down into smaller fragments after release to form beta-thromboglobulin (beta-TG)-like proteins by the action of metal-dependent proteases.

Procedure for quantification of platelet adhesion to biomaterials by radioscintigraphy.

Detection of adhered platelets on biomaterial surface that has blood-contacting application is an important test to assess its thrombogenicity. Usually, for measurement of platelet adhesion, after exposure to platelet-rich plasma (PRP) under standardized conditions the test surface is rinsed to remove non-adherent cells and is analyzed under scanning electron microscopy (SEM) to detect morphology of adhered cell and degree of aggregate formation. However, being a qualitative test it is unlikely to give an accurate estimate of platelets adhered to the surface. On the other hand, use of radiolabels enables quantification of platelets deposited on a material or device. Because of high gamma emission of (111)In, it can be used for radioscintigraphy, however, its short half life (2.5 days) is a major hurdle in using it for quantification of platelet adhesion. (125)I is a relatively strong radiolabel that is easily tagged to most of the proteins and has a relatively long half-life (60 days). The major objectives of this study are to standardize the labeling conditions to get good (125)I activity on platelets, while maintaining normal cell function after they are labeled. Considering all possible uncertainties, quantity of isotope and platelets to be used and the conditions of iodination reaction are established to get repeatable and reproducible labeling of platelets. Further, it is demonstrated that (125)I-platelets can be used to determine total number of cells adhered to titanium surface, which is known to be used as a blood-contacting biomaterial.

Suitability of measurement of swirling as a marker of platelet shape change in concentrates stored for transfusion.

Platelet discoid shape is known to correlate with in vivo viability after transfusion. Measurement of shape change requires invasive sampling and laborious assays, which is difficult to perform in a blood transfusion center as a routine test for quality control of stored platelets. The objective of this study was to establish suitability of swirling assessment in stored platelet suspension as a routine test for quality check, by comparing platelet shape change measurement carried out in parallel. The study was done in two types of bags obtained from different manufactures (Groups 1 and 2). Platelet concentrates (PC) were stored for 120 h and samples drawn at 24-h intervals, optical analysis at 540 nm was carried out to quantify shape change in response to an agonist adenosine diphosphate (ADP). The same bags were subjected to swirling assessment, by two blood bank personnel independently and graded as positive (+, ++, +++) or as negative, based on the silky appearance of the suspension. Swirling negative platelets were prepared by storing platelets at 4 degrees C for 24 h and were compared with swirling positive platelets. Other parameters studied in the samples drawn at 24-h intervals were platelet count, mean platelet volume, and blood gases. Swirling assessment results correlated well with shape change measurement at each study period with a P value significant at 0.02 and 0.04 for group 1 and 2 bags, respectively. In the negative swirling controls, extent of shape change was lower than the extent in test bags, showing reduced capacity to respond to ADP at 4 degrees C. The results of the study indicate that by simple swirling measurements, stored PC can be monitored for loss of discoid shape before they are transfused. Gas tension and pH were with in permissible limits. Therefore, inspection of swirling can be a reliable method of quality control as it correlates with platelet function. The platelets that retain the discoid shape in vitro at the time of transfusion are expected to be functional in vivo.