Specialized patterns of vascular differentiation antigens in the pregnant mouse uterus and the placenta

The success of pregnancy depends on the ability of trophoblast cells to infiltrate the maternal decidua and breach uterine vessels. To ask whether the antigenic phenotype of maternal endothelial cells (EC) in the vascular zone and central decidua basalis may reflect a specialized programming of these vessels for interaction with the trophoblast, we did a survey of several mouse EC differentiation antigens, including MECA-32, MECA-99, and endoglin. Our results revealed striking differences in the phenotype of endothelial lining of vessels in the distinct compartments of the pregnant uterus during Day 9 of pregnancy and at midgestation. Vessels in the central decidua basalis and the vascular zone showed strong expression of MECA-99 but only weak expression of MECA-32, contrasting with the MECA-99(lo), MECA-32(hi) vessels in the capsularis. The vascular zone in addition stained brightly with anti-endoglin. Importantly, invading trophoblast as well as trophoblast cells lining maternal blood spaces were MECA-99(+), MECA-32(-), and endoglin(-), suggesting that the expression of MECA-99 may reflect a specialized co-programming of these trophoblast and EC for future interaction, but also that trophoblast cells may mimic selected antigenic characteristics of endothelium in association with their role in lining maternal blood spaces. In the term pregnant uterus the expression of all differentiation antigens decreased dramatically, suggesting that trophoblast cells as well as maternal EC lose their selected antigenic characteristics when the process of placentation is complete.     

Protein kinase C-lambda knockout in embryonic stem cells and adipocytes impairs insulin-stimulated glucose transport

Atypical protein kinase C (aPKC) isoforms have been suggested to mediate insulin effects on glucose transport in adipocytes and other cells. To more rigorously test this hypothesis, we generated mouse embryonic stem (ES) cells and ES-derived adipocytes in which both aPKC-lambda alleles were knocked out by recombinant methods. Insulin activated PKC-lambda and stimulated glucose transport in wild-type (WT) PKC-lambda(+/+), but not in knockout PKC-lambda(-/-), ES cells. However, insulin-stimulated glucose transport was rescued by expression of WT PKC-lambda in PKC-lambda(-/-) ES cells. Surprisingly, insulin-induced increases in both PKC-lambda activity and glucose transport were dependent on activation of proline-rich tyrosine protein kinase 2, the ERK pathway, and phospholipase D (PLD) but were independent of phosphatidylinositol 3-kinase (PI3K) in PKC-lambda(+/+) ES cells. Interestingly, this dependency was completely reversed after differentiation of ES cells to adipocytes, i.e. insulin effects on PKC-lambda and glucose transport were dependent on PI3K, rather than proline-rich tyrosine protein kinase 2/ERK/PLD. As in ES cells, insulin effects on glucose transport were absent in PKC-lambda(-/-) adipocytes but were rescued by expression of WT PKC-lambda in these adipocytes. Our findings suggest that insulin activates aPKCs and glucose transport in ES cells by a newly recognized PI3K-independent ERK/PLD-dependent pathway and provide a compelling line of evidence suggesting that aPKCs are required for insulin-stimulated glucose transport, regardless of whether aPKCs are activated by PI3K-dependent or PI3K-independent mechanisms.     

Dpp gradient formation by dynamin-dependent endocytosis: receptor trafficking and the diffusion model

Developing cells acquire positional information by reading the graded distribution of morphogens. In Drosophila, the Dpp morphogen forms a long-range concentration gradient by spreading from a restricted source in the developing wing. It has been assumed that Dpp spreads by extracellular diffusion. Under this assumption, the main role of endocytosis in gradient formation is to downregulate receptors at the cell surface. These surface receptors bind to the ligand and thereby interfere with its long-range movement. Recent experiments indicate that Dpp spreading is mediated by Dynamin-dependent endocytosis in the target tissue, suggesting that extracellular diffusion alone cannot account for Dpp dispersal. Here, we perform a theoretical study of a model for morphogen spreading based on extracellular diffusion, which takes into account receptor binding and trafficking. We compare profiles of ligand and surface receptors obtained in this model with experimental data. To this end, we monitored directly the pool of surface receptors and extracellular Dpp with specific antibodies. We conclude that current models considering pure extracellular diffusion cannot explain the observed role of endocytosis during Dpp long-range movement.     

Modeling Sustainability of Arctic Communities: An Interdisciplinary Collaboration of Researchers and Local Knowledge Holders

How will climate change affect the sustainability of Arctic villages over the next 40 years? This question motivated a collaboration of 23 researchers and four Arctic communities (Old Crow, Yukon Territory, Canada; Aklavik, Northwest Territories, Canada; Fort McPherson, Northwest Territories, Canada; and Arctic Village, Alaska, USA) in or near the range of the Porcupine Caribou Herd. We drew on existing research and local knowledge to examine potential effects of climate change, petroleum development, tourism, and government spending cutbacks on the sustainability of four Arctic villages. We used data across eight disciplines to develop an Arctic Community Synthesis Model and a Web-based, interactive Possible Futures Model. Results suggested that climate warming will increase vegetation biomass within the herd’s summer range. However, despite forage increasing, the herd was projected as likely to decline with a warming climate because of increased insect harassment in the summer and potentially greater winter snow depths. There was a strong negative correlation between hypothetical, development-induced displacement of cows and calves from utilized calving grounds and calf survival during June. The results suggested that climate warming coupled with petroleum development would cause a decline in caribou harvest by local communities. Because the Synthesis Model inherits uncertainties associated with each component model, sensitivity analysis is required. Scientists and stakeholders agreed that (1) although simulation models are incomplete abstractions of the real world, they helped bring scientific and community knowledge together, and (2) relationships established across disciplines and between scientists and communities were a valuable outcome of the study. Additional project materials, including the Web-based Possible Futures Model, are available at http://www.taiga.net/sustain.     

Radiation-force assisted targeting facilitates ultrasonic molecular imaging

Ultrasonic molecular imaging employs contrast agents, such as microbubbles, nanoparticles, or liposomes, coated with ligands specific for receptors expressed on cells at sites of angiogenesis, inflammation, or thrombus. Concentration of these highly echogenic contrast agents at a target site enhances the ultrasound signal received from that site, promoting ultrasonic detection and analysis of disease states. In this article, we show that acoustic radiation force can be used to displace targeted contrast agents to a vessel wall, greatly increasing the number of agents binding to available surface receptors. We provide a theoretical evaluation of the magnitude of acoustic radiation force and show that it is possible to displace micron-sized agents physiologically relevant distances. Following this, we show in a series of experiments that acoustic radiation force can enhance the binding of targeted agents: The number of biotinylated microbubbles adherent to a synthetic vessel coated with avidin increases as much as 20-fold when acoustic radiation force is applied; the adhesion of contrast agents targeted to alpha(v)beta3 expressed on human umbilical vein endothelial cells increases 27-fold within a mimetic vessel when radiation force is applied; and finally, the image signal-to-noise ratio in a phantom vessel increases up to 25 dB using a combination of radiation force and a targeted contrast agent, over use of a targeted contrast agent alone.     

A reduced model of the fluorescence from the cyanobacterial photosynthetic apparatus designed for the in situ detection of cyanobacteria

Fluorometric determination of the chlorophyll (Chl) content of cyanobacteria is impeded by the unique structure of their photosynthetic apparatus, i.e., the phycobilisomes (PBSs) in the light-harvesting antennae. The problems are caused by the variations in the ratio of the pigment PC to Chl a resulting from adaptation to varying environmental conditions. In order to include cyanobacteria in fluorometric analysis of algae, a simplified energy distribution model describing energy pathways in the cyanobacterial photosynthetic apparatus was conceptualized. Two sets of mathematical equations were derived from this model and tested. Fluorescence of cyanobacteria was measured with a new fluorometer at seven excitation wavelength ranges and at three detection channels (650, 685 and 720 nm) in vivo. By employing a new fit procedure, we were able to correct for variations in the cyanobacterial fluorescence excitation spectra and to account for other phytoplankton signals. The effect of energy-state transitions on the PC fluorescence emission of PBSs was documented. The additional use of the PC fluorescence signal in combination with our recently developed mathematical approach for phytoplankton analysis based on Chl fluorescence spectroscopy allows a more detailed study of cyanobacteria and other phytoplankton in vivo and in situ.     

Consequences of long-term selenium-deficient diet on the prostacyclin and thromboxane release from rat aorta

It is known that peroxides, which are increased during Se deficiency because of reduced glutathione peroxidase (GSH-Px) activity, can influence the prostacyclin I₂/thromboxane A₂ (PGI₂/TXA₂) ratio. In this study we analyzed the PGI₂ and TXA₂ formation of aortas of long-term Se-deficient rats. Despite low GSH-Px activity in the Se-deficient group, the basal PGI₂ and TXA₂ formation was not different versus control animals (PGI₂: 2295 ± 1134 pg/mg vs 2940 ± 1134 pg/mg; TXA₂: 3.83 ± 1.06 pg/mg vs 5.67 ± 2.99 pg/mg). However, we checked the capacity of the aortas of Se-deficient rats to compensate for a suddenly increased peroxide concentration. After peroxide stimulation, the PGI₂ release was significantly lower in the Se-deficient group compared to the control group (PGI₂: 3507 ± 1829 pg/mg vs 7986 ± 2636 pg/mg). Again, the TXA₂ release did not show any differences. The release ratio of PGI₂/TXA₂ decreased under peroxide stress in Se-deficient animals. Although long-term Se deficiency showed a relatively well-balanced metabolism under resting conditions, sudden stress, accompanied by an excessive radical production, cannot be compensated.     

NS-417, a Novel Compound with Neurotrophic-Like Effects

NS-417 (5-(4-Chlorophenyl)-8-methyl-6-7-8-9-tetrahydro-1-H-pyrrolo[3.2-h]isoquinoline-2,3-dione-3-oxim hydrochloric acid salt) belongs to a new chemical series of compounds. NS-417 rescued differentiated PC12 cells from death induced by withdrawal of serum and nerve growth factor. Furthermore, NS-417 stimulated neurotrophic factor-induced neurite outgrowth in undifferentiated PC12 cells. In accordance with this observation, NS-417 potentiated NGF-induced signaling, such as activation of the extracellular signal-regulated kinases ERK1 and ERK2 and the Akt kinase. NS-417 also enhanced ERK activation induced by 10 minutes stimulation with NGF, bFGF or EGF in PC12 cells. In addition to the effect in PC12 cells, NS-417 increased the number of tyrosine hydroxylase (TH) positive cells in cultures established from dissociated E14 rat ventral mesencephali.     

Robust circadian rhythmicity of Per1 and Per2 mutant mice in constant light,and dynamics of Per1 and Per2 gene expression under long and short photoperiods

The Per1 and Per2 genes are components of the mammalian circadian clock. Mutations in these genes alter phase resetting in response to a nocturnal light pulse, and Per2 mutant mice are known to become arrhythmic in constant darkness. We show that under constant light conditions, Per2 mutant mice exhibit robust activity rhythms as well as body temperature rhythms with a period length that is less than 24 h. In Per1 mutants, the period length of both activity and body temperature rhythms is longer than 24 h in constant light. Per1 mutants prolong their period length (tao) when illuminance is increased, whereas Per2 mutants shorten their endogenous period. Additionally, the authors show that the circadian pattern of Per1 and Per2 gene expression in mice is modified under different photoperiods and that there is a mutual influence of these genes on their timing of expression. We propose that, in mice, the phase relationship between Per1 and Per2 gene expression might be critical for transducing day length information to the organism. Per1 could be part of a morning oscillator tracking dawn, and Per2 could be part of an evening oscillator tracking dusk.