Time-resolved fluorescence study of excitation energy transfer in the cyanobacterium Anabaena PCC 7120

Photosynthesis Research - Excitation energy transfer (EET) and trapping in Anabaena variabilis (PCC 7120) intact cells, isolated phycobilisomes (PBS) and photosystem I (PSI) complexes have been...     

Profound negative regulatory effects by resveratrol on vascular smooth muscle cells: a role of p53-p21(WAF1/CIP1) pathway

We investigated the role of resveratrol, a polyphenol rich in red wine, in cell cycle progression and apoptosis of vascular smooth muscle cells (VSMCs). Resveratrol inhibited the growth of human aortic VSMCs at concentrations as low as 1 microM. This was due to the profound dose-dependent inhibition of DNA synthesis by resveratrol. DNA synthesis was more effectively inhibited when cells were pretreated with resveratrol. Resveratrol caused a dose-dependent increase in intracellular p53 and p21(WAF1/CIP1) levels. At lower concentrations (6.25-12.5 microM), resveratrol effectively blocked cell cycle progression of serum-stimulated VSMCs without inducing apoptosis, while the higher concentration of resveratrol (25 microM) selectively induced apoptosis in the same VSMCs. Intriguingly, however, the same high concentration of resveratrol could not induce apoptosis in quiescent VSMCs. These differential biological effects of resveratrol on quiescent and proliferating VSMCs suggest that resveratrol may be capable of selectively eliminating abnormally proliferating VSMCs of the arterial walls in vivo.     

Optimization of a solid phase extraction procedure for prostaglandin E2, F2 alpha and their tissue metabolites

The primary prostaglandins PGE(2) and PGF(2 alpha) are metabolized in tissues by a series of enzymatic and non-enzymatic reactions. To measure metabolic rates and individual reaction rates it is necessary to extract the parent prostaglandins and metabolites before the separation and quantification of each compound is achieved. Here we have established and optimized a solid phase extraction (SPE) procedure to recover PGE(2), PGF(2 alpha) and their six enzymatic and non-enzymatic tissue metabolites from aqueous solutions including urine, plasma and tissue homogenate. We have used octadecyl-bonded silica gel as the stationary phase and methanol-water mixtures as binary mobile phases. The volumes and concentrations of the washing and elution solutions were optimized individually for each PG. Recoveries of all PG standards were quantitative except for PGEM, which was recovered at 80% efficiency. Biological matrix components interfered with the extraction in a PG- and matrix-specific fashion. Inclusion of 1% formic acid in the loading mixture raised recoveries from urine, plasma and tissue homogenate to >or=90%. This SPE method is the first that has been optimized by systematic elution studies for PGE(2), PGF(2 alpha) and the complement of their tissue metabolites. The procedure is simple, robust and can serve as an effective pre-purification step before downstream separation and quantification of each tissue metabolite of PGE(2) and PGF(2 alpha) from complex biological matrices.     

Anthochlor pigments and floral UV patterns in the genus Bidens

The occurrence of floral UV absorption-reflection patterns in Bidens laevis is due to a spatial segregation of anthochlor pigments in the flower head. Interspecific, UV pattern polymorphism within this genus falls generally along taxonomic (sectional) lines.     

The critical role of the intrinsic VSMC proliferation and death programs in injury-induced neointimal hyperplasia

Postangioplasty and in-stent restenosis remain ominous problems in percutaneous coronary intervention where good animal models of restenosis proneness and resistance are needed. We accidentally discovered that the carotid arteries (CAs) of the Harlan and Sasco substrains of Sprague-Dawley rats display drastically different restenosis phenotypes following balloon-induced endothelial denudation. When subjected to balloon injury, Sasco CAs exhibited significantly larger neointimal mass than did Harlan CAs at both days 14 and 32, as evidenced by a higher intima-to-media ratio and a greater number of intimal cells in Sasco CAs. This was due to a greater cell proliferation and to a less vigorous apoptosis of Sasco neointima, as assessed by 5-bromo-2'-deoxyuridine and terminal deoxynucleotidyl transferase-deoxyuridine nick-end labeling staining, respectively. At a cellular level, whereas vascular smooth muscle cells (VSMCs) isolated from Sasco and Harlan CAs were identical in morphology and in propensity to migrate, Sasco VSMCs proliferated more robustly and died far less, suggesting that under the exact same microenvironment, Sasco and Harlan VSMCs respond to growth and noxious stimuli in a drastically different fashion and that Sasco's significantly more robust neointimal proliferation after vascular injury in vivo can be accounted for by these intrinsic differences in VSMCs of these substrains in vitro. Sasco and Harlan Sprague-Dawley rats as well as VSMCs from these rats will prove to be powerful tools to study genes involved in the pathogenesis of restenosis.     

Phycobilisome integrity and functionality in lipid unsaturation and xanthophyll mutants in Synechocystis

Photosynthesis Research - The major light-harvesting system in cyanobacteria, the phycobilisome, is an essential component of the photosynthetic apparatus that regulates the utilization of the...     

Tyrosine kinase inhibitors block the glucocorticoid stimulation of prostaglandin endoperoxide H synthase expression in amnion cells.

Human amnion cells in primary culture respond to glucocorticoids in a characteristic fashion by the increased expression of the inducible prostaglandin endoperoxide H synthase isoenzyme, PGHS-2. Since PGHS-2 induction by agonists generally involves tyrosine kinases, we examined the possibility that the glucocorticoid stimulation of PGHS-2 in the amnion cells is tyrosine kinase dependent. PGHS-2 expression was stimulated in confluent, serum-starved amnion cells with dexamethasone, and the effect of the tyrosine kinase inhibitors herbimycin A and tyrphostins AG126, AG1288, and A1 on enzyme activity induction was determined. All four inhibitors blocked the increase of PGHS activity in a concentration-dependent manner with IC50 values of 0.077 +/- 0.05, 15.38 +/- 5.14, 20.91 +/- 3.1, and 29.77 +/- 8.21 microM, respectively (mean +/- SE, n = 4). Dexamethasone increased (approximately twofold) the tyrosine phosphorylation of 120-, 110-, and 77-kDa proteins in cell extracts, and herbimycin A selectively blocked the phosphorylation of the 110-kDa phosphoprotein. The stimulation of the steady-state level of PGHS-2 mRNA by dexamethasone was also inhibited by herbimycin A. These results suggest that glucocorticoids induce PGHS-2 expression in amnion cells with the involvement of tyrosine kinase(s). The role of tyrosine kinase dependent mechanisms in the control of amnion cell responsiveness to corticosteroids remains to be established.     

Dexamethasone stimulates arachidonic acid conversion to prostaglandin E2 in human amnion cells

The purpose of this investigation was to study the mechanism of stimulation of PGE2 output from human amnion epithelial cells by the synthetic glucocorticoid dexamethasone. Cells incubated in serum-free pseudo-amniotic fluid produced very low levels of PGE2, even when arachidonic acid (1 microM) was present. Pretreatment of cells with dexamethasone (50 nM) for 21 h increased the PGE2 output 6- to 7-fold in 2-h incubations only in the presence of arachidonic acid. The RNA synthesis inhibitor, actinomycin D (1 microgram/ml), and the protein synthesis inhibitor, cycloheximide (40 micrograms/ml), each blocked dexamethasone-stimulated arachidonic acid conversion to PGE2. The time course of these events suggests that dexamethasone first initiates RNA synthesis. Acetylsalicylic acid, a specific and irreversible blocker of prostaglandin endoperoxide H synthase (cyclooxygenase), was used to determine whether dexamethasone could stimulate new enzyme synthesis. Cells treated first with acetylsalicylic acid (30 min) then dexamethasone (22 h) produced as much PGE2 in response to 1 microM arachidonate as did cells exposed to dexamethasone only. Exposing cells to acetylsalicylic acid after dexamethasone completely eliminated PGE2 output. These data suggest that dexamethasone stimulates the synthesis of prostaglandin endoperoxide H synthase.     

Prostaglandin synthesis regulation in human amnion tissue: involvement of protein kinase C and dependence on ribonucleic acid and protein synthesis.

The role of protein kinase C (PKC) in the control of prostaglandin production by the human amnion was studied. Amnion membranes delivered spontaneously at term were minced and treated with phorbol esters, protein kinase inhibitors, cycloheximide, and actinomycin D; prostaglandin E2 (PGE2) output then was determined. Untreated tissue produced 3.97 +/- 1.13 ng PGE2/micrograms DNA/14 h (mean +/- SEM, n = 19). Phorbol dibutyrate and 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulated PGE2 output up to 20-fold in a concentration-dependent manner with potencies corresponding to their efficacy as PKC activators. Four-beta-phorbol and 4-methoxy-TPA, which do not stimulate PKC, did not affect PGE2 output. Stimulation by TPA was blocked by staurosporine (IC50 = 57 nM) and H7; however, these PKC inhibitors did not decrease basal prostaglandin production. Cycloheximide inhibited basal and TPA-promoted PGE2 production and amino acid incorporation. Actinomycin D abolished TPA stimulation without decreasing unstimulated prostaglandin synthesis. These results show that amnion PGE2 production after labor is not maintained by PKC action, but PKC activation in this tissue causes a protein synthesis-dependent and RNA synthesis-dependent increase of PGE2 output. However, basal PGE2 production is dependent upon protein synthesis which, presumably, utilizes pre-existing mRNAs.