Differences of microvascular endothelium in the bovine corpus luterum of pregnancy and the corpus luteum of the estrous cycle

Summary— The purpose of the present study was to investigate potential modulations of endothelial cells of the bovine corpus luteum (CL) during pregnancy. Luteal endothelia of pregnant and non-pregnant cows were isolated and purity of cultures was verified by flow cytometric quantification of three independent endothelial markers (von Willebrand factor, angiotensin converting enzyme, Bandeiraea simplicifolia agglutinin I ligands). Different cellular parameters including light and electron microscopical investigation of morphology and growth characteristics as well as quantification of cellular lectin binding sites were compared. Extensive heterogeneity between luteal endothelial cells in pregnant and non-pregnant animals could be demonstrated, reflected in functional attributes like angiogenic activity, ultrastructural characteristics and the quantitative expression of cellular carbohydrates. Two different morphological types of cells (‘cobblestone growth pattern’ and ‘arcuate growth pattern’) were isolated from the CL of pregnancy as well as from the cyclic CL. Spontaneous angiogenic activities, including cellular migration in band-like structures and formation of ring-like structures, were observed in endothelial cells isolated from the CL of pregnant cows exclusively. This strongly suggests that microvascular luteal endothelium of pregnant animals, in contrast to the one of non-pregnant animals, is able to produce quantitatively and/or qualitatively specific angiogenesis factor(s). Heterogeneity between luteal endothelial cells in the pregnant and non-pregnant animal could also be demonstrated by quantification of lectin (Bandeiraea simplicifolia agglutinin I, concanavalin A, Dolichos biflorus agglutinin, Ulex europaeus agglutinin I, wheat germ agglutinin) binding sites: quantitative expression of specific endothelial cell surface carbohydrates could be correlated to be status of pregnancy, thus emphasizing the actual need of quantification of lectin binding.     

The extrinsic proteins of photosystem II: update

Planta - Recent investigations have provided important new insights into the structures and functions of the extrinsic proteins of Photosystem II. This review is an update of the last major review...     

Absence of the PsbQ protein results in destabilization of the PsbV protein and decreased oxygen evolution activity in cyanobacterial photosystem II

We have previously reported that cyanobacterial photosystem II (PS II) contains a protein homologous to PsbQ, the extrinsic 17-kDa protein found in higher plant and green algal PS II (Kashino, Y., Lauber, W. M., Carroll, J. A., Wang, Q., Whitmarsh, J., Satoh, K., and Pakrasi, H. B. (2002) Biochemistry 41, 8004-8012) and that it has regulatory role(s) on the water oxidation machinery (Thornton, L. E., Ohkawa, H., Roose, J. L., Kashino, Y., Keren, N., and Pakrasi, H. B. (2004) Plant Cell 16, 2164-2175). In this work, the localization and the function of PsbQ were assessed using the cyanobacterium Synechocystis sp. PCC 6803. From the predicted sequence, cyanobacterial PsbQ is expected to be a lipoprotein on the luminal side of the thylakoid membrane. Indeed, experiments in this work show that upon Triton X-114 fractionation of thylakoid membranes, PsbQ partitioned in the hydrophobic phase, and trypsin digestion revealed that PsbQ was highly exposed to the luminal space of thylakoid membranes. Detailed functional assays were conducted on the psbQ deletion mutant (DeltapsbQ) to analyze its water oxidation machinery. PS II complexes purified from DeltapsbQ mutant cells had impaired oxygen evolution activity and were remarkably sensitive to NH(2)OH, which indicates destabilization of the water oxidation machinery. Additionally, the cytochrome c(550) (PsbV) protein partially dissociated from purified DeltapsbQ PS II complexes, suggesting that PsbQ contributes to the stability of PsbV in cyanobacterial PS II. Therefore, we conclude that the major function of PsbQ is to stabilize the PsbV protein, thereby contributing to the protection of the catalytic Mn(4)-Ca(1)-Cl(x) cluster of the water oxidation machinery.     

Aggregation of bovine anterior cruciate ligament fibroblasts or marrow stromal cells promotes aggrecan production

The development of a tissue‐engineered alternative for current ligament grafts requires the creation of a fibrocartilaginous interface between the engineered ligament midsubstance and bone tissue. Therefore, the focus of this study was to examine the potential for cartilaginous extracellular matrix (ECM) formation by altering culture parameters for bovine anterior cruciate ligament (ACL) fibroblasts and marrow stromal cells (MSCs). Specifically, cells were cultured without chondrogenic media supplements on aggrecan‐coated surfaces, tissue culture‐treated control surfaces, and nonadhesive surfaces that promoted cell aggregation, and examined over 14 days. Aggrecan‐coated surfaces promoted the aggregation of ACL fibroblasts and MSCs within 24 h after seeding. Aggrecan gene expression was significantly upregulated in cell aggregates, regardless of how cell clustering was induced, with as much as 10.9 ± 1.2‐fold upregulation in ACL fibroblasts and 9.7 ± 1.1‐fold in MSCs after 3 days, compared to control surfaces. Dimethylmethylene blue (DMMB) results and immunostaining verified the presence of aggrecan in ACL fibroblast and MSC aggregates throughout the culture period. Results indicate that ACL fibroblasts retained the ability to alter their gene expression and produce aggrecan, though MSCs, in general, had a more consistent response to aggregation. These findings support the use of aggregate‐inducing materials to encourage production of aggrecan and suggest that altering the degree of clustering could produce a range of phenotypes from a single cell source. As such, this represents a first step which may inform future approaches to producing tissue‐engineered ligament grafts. Biotechnol. Bioeng. 2011; 108:151–162. © 2010 Wiley Periodicals, Inc.     

Leaf dynamics of a deciduous forest canopy: no response to elevated CO<Subscript>2</Subscript>

Leaf area index (LAI) and its seasonal dynamics are key determinants of terrestrial productivity and, therefore, of the response of ecosystems to a rising atmospheric CO₂ concentration. Despite the central importance of LAI, there is very little evidence from which to assess how forest LAI will respond to increasing [CO₂]. We assessed LAI and related leaf indices of a closed-canopy deciduous forest for 4 years in 25-m-diameter plots that were exposed to ambient or elevated CO₂ (542 ppm) in a free-air CO₂ enrichment (FACE) experiment. LAI of this Liquidambar styraciflua (sweetgum) stand was about 6 and was relatively constant year-to-year, including the 2 years prior to the onset of CO₂ treatment. LAI throughout the 1999–2002 growing seasons was assessed through a combination of data on photosynthetically active radiation (PAR) transmittance, mass of litter collected in traps, and leaf mass per unit area (LMA). There was no effect of [CO₂] on any expression of leaf area, including peak LAI, average LAI, or leaf area duration. Canopy mass and LMA, however, were significantly increased by CO₂ enrichment. The hypothesized connection between light compensation point (LCP) and LAI was rejected because LCP was reduced by [CO₂] enrichment only in leaves under full sun, but not in shaded leaves. Data on PAR interception also permitted calculation of absorbed PAR (APAR) and light use efficiency (LUE), which are key parameters connecting satellite assessments of terrestrial productivity with ecosystem models of future productivity. There was no effect of [CO₂] on APAR, and the observed increase in net primary productivity in elevated [CO₂] was ascribed to an increase in LUE, which ranged from 1.4 to 2.4 g MJ^–1. The current evidence seems convincing that LAI of non-expanding forest stands will not be different in a future CO₂-enriched atmosphere and that increases in LUE and productivity in elevated [CO₂] are driven primarily by functional responses rather than by structural changes. Ecosystem or regional models that incorporate feedbacks on resource use through LAI should not assume that LAI will increase with CO₂ enrichment of the atmosphere.     

Primitive endothelial cell lines from the porcine embryonic yolk sac

Endothelial cell lines have been established from cells that were isolated from porcine yolk sacs from day 18 and day 22 embryos and propagated in vitro under various growth conditions. After expansion in vitro, the general properties of the cells proved similar for the different media used. The endothelial cells expressed cell surface receptors for acetylated low-density lipoprotein and also expressed cell surface-associated angiotensin-converting enzyme. The cells showed a characteristically high level of binding for Bandeiraea simplicifolia lectin I and Dolichos biflorus agglutinin but did not bind significant amounts of Ulex europaeus lectin I. The cells expressed low but serologically detectable levels of Class I major histocompatibility complex (MHC) antigens but failed to bind antibodies directed against Class II MHC antigens. Alpha5beta1 integrins were weakly expressed, whereas vascular cell adhesion molecule-1 (CD106) and alphavbeta3 integrins were not detected. Three-dimensional tube formation was readily observed in cultures grown on Matrigel and occurred even in uncoated plastic dishes in the absence of Matrigel. In contrast to most of the adult porcine endothelial cells, yolk sac-derived endothelial cells did not possess serologically detectable receptors for porcine growth hormone (GH), an observation consistent with the finding that GH did not increase the proliferative rate of these cells. Electron microscopic examination demonstrated the presence of Weibel-Palade bodies, tight endothelial cell junctions, and typical rough endoplasmic reticulum. Exposure of the cells to either concanavalin-A-stimulated porcine splenocyte culture supernatants or to human tumor necrosis factor alpha did not cause upregulation of VCAM-1 or Class II MHC antigens. Addition of porcine interferon-gamma led to an increase in the level of expression of Class I MHC. Yolk sac endothelial cells from day 22 embryos showed a low but detectable level of expression of Class II MHC antigens, whereas the endothelial cells from day 18 embryos showed no expression of Class II antigens after interferon-gamma stimulation. The cells maintained competence to develop vascular structures in vitro and could do so after coinjection with murine tumor cells into adult, immunocompromised mice.     

Homologs of plant PsbP and PsbQ proteins are necessary for regulation of photosystem ii activity in the cyanobacterium Synechocystis 6803

The mechanism of oxygen evolution by photosystem II (PSII) has remained highly conserved during the course of evolution from ancestral cyanobacteria to green plants. A cluster of manganese, calcium, and chloride ions, whose binding environment is optimized by PSII extrinsic proteins, catalyzes this water-splitting reaction. The accepted view is that in plants and green algae, the three extrinsic proteins are PsbO, PsbP, and PsbQ, whereas in cyanobacteria, they are PsbO, PsbV, and PsbU. Our previous proteomic analysis established the presence of a PsbQ homolog in the cyanobacterium Synechocystis 6803. The current study additionally demonstrates the presence of a PsbP homolog in cyanobacterial PSII. Both psbP and psbQ inactivation mutants exhibited reduced photoautotrophic growth as well as decreased water oxidation activity under CaCl(2)-depleted conditions. Moreover, purified PSII complexes from each mutant had significantly reduced activity. In cyanobacteria, one PsbQ is present per PSII complex, whereas PsbP is significantly substoichiometric. These findings indicate that both PsbP and PsbQ proteins are regulators that are necessary for the biogenesis of optimally active PSII in Synechocystis 6803. The new picture emerging from these data is that five extrinsic PSII proteins, PsbO, PsbP, PsbQ, PsbU, and PsbV, are present in cyanobacteria, two of which, PsbU and PsbV, have been lost during the evolution of green plants.     

A Y chromosome-linked factor impairs NK T development

Valpha14 invariant (Valpha14i) NK T cell development is unique from mainstream T cell selection, and the polygenic factors that influence NK T cell ontogeny are still unclear. In this study, we report the absence of Valpha14i NK T cells in B6.IFN-alphabetaR1-/- male mice, whereas both the conventional T and NK cell populations are relatively unaffected. The lack of Valpha14i NK T cells in the B6.IFN-alphabetaR1-/- males is not due to an insufficient level of CD1d1 or a defect in CD1d1-Ag presentation, but it is intrinsic to the male Valpha14i NK T cells. This surprising defect displays >or=99% penetrance in the male population, whereas female mice remain unaffected, indicating the deficiency is not X linked. Analysis of the Valpha14i NK T cell compartment in B6.Tyk2-/-, B6.STAT1-/-, 129.IFN-alphabetaR1-/-, and B6.IFN-alphabetaR1-/+ mice demonstrate that the deficiency is linked to the Y chromosome, but independent of IFN-alphabeta. This is the first study demonstrating that Y-linked genes can exclusively impact Valpha14i NK T development and further highlight the unique ontogeny of these innate T cells.     

Climate change and marine life

A Marine Climate Impacts Workshop was held from 29 April to 3 May 2012 at the US National Center of Ecological Analysis and Synthesis in Santa Barbara. This workshop was the culmination of a series of six meetings over the past three years, which had brought together 25 experts in climate change ecology, analysis of large datasets, palaeontology, marine ecology and physical oceanography. Aims of these workshops were to produce a global synthesis of climate impacts on marine biota, to identify sensitive habitats and taxa, to inform the current Intergovernmental Panel on Climate Change (IPCC) process, and to strengthen research into ecological impacts of climate change.