Fibroblast growth factor receptor-1-mediated endothelial cell proliferation is dependent on the Src homology (SH) 2/SH3 domain-containing adaptor protein Crk.

Stimulation of fibroblast growth factor receptor-1 (FGFR-1) expressed on endothelial cells leads to cellular migration and proliferation. We have examined the role of the Src homology (SH) 2/SH3 domain-containing adaptor protein Crk in these processes. Transient tyrosine phosphorylation of Crk in fibroblast growth factor-2-stimulated endothelial cells was dependent on the juxtamembrane tyrosine residue 463 in FGFR-1, and a Crk SH2 domain precipitated FGFR-1 via phosphorylated Tyr-463, indicating direct complex formation between Crk and FGFR-1. Furthermore, Crk SH2 and SH3 domains formed ligand-independent complexes with Shc, C3G, and the Crk-associated substrate (Cas). Tyrosine phosphorylation of C3G and Cas increased as a consequence of growth factor treatment. We examined the role of Crk in FGFR-1-mediated cellular responses by use of cells expressing chimeric platelet-derived growth factor receptor-alpha/FGFR-1 (alphaR/FR) wild type and mutant Y463F receptors. The kinase activity of alphaR/FR Y463F was intact, but both Crk and the adaptor FRS-2 were no longer tyrosine-phosphorylated in the mutant cells. Both wild type and mutant receptor cells migrated efficiently, whereas cells expressing the mutant alphaR/FR Y463F failed to proliferate and Erk2 and Jun kinase activities were suppressed in these cells. In wild type alphaR/FR cells transiently expressing an SH2 domain mutant of Crk, Erk and Jun kinase activities as well as DNA synthesis were attenuated. Our data indicate that Crk participates in signaling complexes downstream of FGFR-1, which propagate mitogenic signals.     

Multiple chromosomal rearrangements in a hybrid zone between Littorina saxatilis ecotypes

Both classical and recent studies suggest that chromosomal inversion polymorphisms are important in adaptation and speciation. However, biases in discovery and reporting of inversions make it difficult to assess their prevalence and biological importance. Here, we use an approach based on linkage disequilibrium among markers genotyped for samples collected across a transect between contrasting habitats to detect chromosomal rearrangements de novo. We report 17 polymorphic rearrangements in a single locality for the coastal marine snail, Littorina saxatilis. Patterns of diversity in the field and of recombination in controlled crosses provide strong evidence that at least the majority of these rearrangements are inversions. Most show clinal changes in frequency between habitats, suggestive of divergent selection, but only one appears to be fixed for different arrangements in the two habitats. Consistent with widespread evidence for balancing selection on inversion polymorphisms, we argue that a combination of heterosis and divergent selection can explain the observed patterns and should be considered in other systems spanning environmental gradients.     

Magnetic aqueous two-phase separation: a new technique to increase rate of phase-separation, using dextran-ferrofluid or larger iron oxide particles

A new technique to speed up the phase separation of aqueous two-phase systems is described. The technique is based on the addition of magnetically susceptible additives (ferrofluids or iron oxide particles). In a magnetic field such additives will induce a faster phase separation. In one approach, dextran-stabilized ferrofluid was added to an aqueous two-phase system containing polyethylene glycol and dextran. The ferrofluid was totally partitioned to the dextran phase. After mixing of the two-phase system, it was possible to reduce the separation time by a factor of 35 by applying a magnetic field to the system. Another approach involved the use of 1-micron iron oxide particles instead of ferrofluid. In this case also, the phase-separation time was reduced, by a factor of about 70, when the system was placed in a magnetic field. The addition of ferrofluid and/or iron oxide particles was shown to have no influence on enzyme partitioning or on enzyme activity. The partitioning of chloroplasts, on the other hand, was influenced unless the ferrofluid used had been treated with epoxysilane. A column system comprising 15 magnetic separation stages was constructed and was used for semicontinuous separation of enzyme mixtures.     

Sequential endocrine changes and behaviour during oestrus and metoestrus in repeat breeder and virgin heifers

The aim of the experiment was to study the oestrous behaviour and the peripheral blood plasma profiles of luteinizing hormone (LH), progesterone and the prostaglandin metabolite, 15-keto-13,14-dihydro-PGF₂, during oestrus and metoestrus in repeat breeder (RBH) and virgin heifers (VH). Ten animals of each category were utilized. The RBH had a history of at least three inseminations without conception, and the VH were sexually mature animals not previously inseminated or mated. Oestrous symptoms were recorded and blood collected from the onset of prooestrus to 7 days after oestrus. The animals were inseminated during oestrus and their embryos were collected by a nonsurgical technique 7 days after insemination. The morphology of the embryos was evaluated.

The duration of oestrus was longer (P < 0.05) in the RBH (31.5 ± 3.6 h) than in the VH (23.8 ± 2.0 h). No differences in duration of prooestrus or in the interval from the end of oestrus to postoestrous bleeding were found between the heifer categories. The interval from the onset of oestrus to the preovulatory LH peak was longer (P < 0.05) in the RBH (12.2 ± 2.8 h) than in the VH (4.8 ± 1.5 h). There was a lower LH release in the RBH than in the VH, measured as the magnitude of the preovulatory LH peak (P < 0.05; 28.0 ± 4.0 vs. 40.7 ± 3.6 μg/l) or as the area under the curve of the LH peak (P < 0.01; 1141 ± 164 vs. 1765 ± 144 mm²). The progesterone levels were higher (P < 0.05) in the RBH than in the VH during the interval 5–48 h and lower (P < 0.05) during the interval 121–168 h after the LH peak. Peaks of the prostaglandin metabolite were seen during oestrus in both heifer groups. There were more prostaglandin metabolite peaks in the RBH than in the VH during the interval 13–24 h after the LH peak. Fewer normal embryos (P < 0.05) and more degenerated embryos (P < 0.01) were found in the RBH than in the VH group 7 days after insemination. No apparent relation was found between the morphology of the embryos and the hormonal changes.

The result of the study indicates a hormonal imbalance in the RBH. The hormonal asynchronism starts before or early in oestrus, which presumably leads to a sequence of improper hormonal changes responsible for the elevated embryonic loss in repeat breeder animals.     

Cell fusions in mammals

Cell fusions are important to fertilization, placentation, development of skeletal muscle and bone, calcium homeostasis and the immune defense system. Additionally, cell fusions participate in tissue repair and may be important to cancer development and progression. A large number of factors appear to regulate cell fusions, including receptors and ligands, membrane domain organizing proteins, proteases, signaling molecules and fusogenic proteins forming alpha-helical bundles that bring membranes close together. The syncytin family of proteins represent true fusogens and the founding member, syncytin-1, has been documented to be involved in fusions between placental trophoblasts, between cancer cells and between cancer cells and host cells. We review the literature with emphasis on the syncytin family and propose that syncytins may represent universal fusogens in primates and rodents, which work together with a number of other proteins to regulate the cell fusion machinery.     

Inside Back Cover: Development of a 3‐dimensional tissue lung phantom of a preterm infant for optical measurements of oxygen—Laser‐detector position considerations (J. Biophotonics 3/2018)

The picture depicts the different 3d‐printed organs, thorax, lungs, heart and bone. Assembled it is used as an optical phantom of a preterm infant for performing percutaneous optical measurements of the gas content in the lungs. In order to simulate the optical properties of the tissue, the heart and thorax can be filled with liquid phantoms, a mixture of Intralipid and Indian Ink. Further details can be found in the article by Jim Larsson et al. ( e201700097 ).

     

Endogenous polyamines are intimately associated with highly condensed chromatin in vivo. A fluorescence cytochemical and immunocytochemical study of spermine and spermidine during the cell cycle and in reactivated nuclei

Polyamines are low molecular weight aliphatic polycations essential for cell proliferation and differentiation. By immunocytochemistry, as well as by two independent fluorescence cytochemical methods, we show that polyamines are associated with highly condensed chromatin in nucleated erythrocytes and in metaphase and anaphase chromosomes. In other cells, polyamines mainly occur in cytoplasm. The association between polyamines and DNA in condensed chromatin is so close that DNase treatment is necessary for making polyamines available for reaction with antibodies. Studies of chick/HeLa cell heterokaryons reveal that polyamines disappear from the chick erythrocyte nuclei concomitantly with DNA decondensation and initiation of RNA synthesis. Our data strongly suggest that polyamines are important for chromatin condensation in vivo.