Primitive streak-forming cells of the chick invaginate through a basement membrane

Summary Recently fibronectin was shown to appear in the development of the chick for the first time as a thin band on the epiblastic side facing the hypoblast just prior to primitive streak formation. It was thus suggested that fibronectin might be instrumental in the migration of cells that lead to axis formation during primitive streak formation. In the present work we have examined simultaneously for the presence of fibronectin and the specific basement membrane glycoprotein laminin during primitive streak formation using immunofluorescence methods. Laminin was found to be expressed between the epiblast and the hypoblast of stage XIII¹ chick blastoderms. During the immediately following process of streak formation the laminin was found to be continuously detectable throughout the area covered by the hypoblast, but disrupted on the streak area. Fibronectin was found to co-distribute with laminin in stage XIII and in the early primitive streak chick blastoderms. It is concluded that at stage XIII laminin and fibronectin form part of a basement membrane that is partially disrupted during the immediately following process of primitive streak formation in order to allow the migration of the streak-forming epiblastic cells during this morphogenetic process.     

The taxonomy of the family Paramphistomidae Fischoeder, 1901 with special reference to the morphology of species occurring in ruminants. II. Revision of the genus Paramphistomum Fischoeder, 1901

Summary The genus Paramphistomum Fischoeder, 1901 is redefined and restricted and only the following species are retained and considered valid: P. cervi (Zeder, 1790) (type species); P. liorchis Fischoeder, 1901; P. gracile Fischoeder, 1901 P. epiclitum Fischoeder, 1904; P. gotoi Fukui, 1922, P. ichikawai Fukui, 1922; P. leydeni Näsmark, 1937 and P. hiberniae Willmott, 1950. These are redescribed and illustrated. A new species, Paramphistomum cephalophi is described and illustrated from the black-fronted duiker (Cephalophus nigrifrons) in Rwanda. It differs from the rest of the species in the genus by the presence of an anterior sphincter in the pharynx and the characteristic posterior notch of the acetabular rim. Scanning electron photomicrographs of the tegumental surfaces of the species in the genus are provided. Cotylophoron indicum Stiles & Goldberger, 1910 (=Paramphistomum thapari Price & McIntosh, 1953), C. madrasense Gupta, 1958, C. chauhani Gupta & Gupta, 1972, Paramphistomum indicum Stiles & Goldberger, 1910 (in part), P. malayi Lee & Lowe, 1971 and Srivastavaia indica Singh, 1970 are considered synonyms of Paramphistomum epiclitum Fischoeder, 1904. Paramphistomum indicum Stiles & Goldberger, 1910 (in part) and P. bombayiensis Gupta & Verma in Gupta & Nakhasi, 1977 are regarded as synonyms of Paramphistomum gracile Fischoeder, 1901. P. scotiae Willmott, 1950, P. julimarinorum Velázquez-Maldonado, 1976, P. nicabrasilorum Velázquez- Maldonado, 1976, P. procapri Wang, 1979 and Cotylophoron skrjabini Mitskevich, 1958 are considered synonyms of Paramphistomum leydeni Näsmark, 1937. Cotylophoron vigisi Davydova, 1963 is considered synonymous with Paramphistomum ichikawai Fukui, 1922. Paramphistomum birmense Railliet, 1924, P. microon Railliet, 1924, P. chinensis Hsu, 1935 and P. pseudocuonum Wang, 1979 are regarded as species inquirendae.The genera Liorchis Velichko, 1966 and Srivastavaia Singh, 1970 are synonymized with Paramphistomum Fischoeder, 1901.A key to the species of the genus is provided.Part of a thesis approved by the University of London for the award of the Ph.D. degree.Part of a thesis approved by the University of London for the award of the Ph.D. degree.     

Degradation of [α-14C]hordenine in Hordeum vulgare plants

Evidence is presented indicating that intact plants of Hordeum vulgare degrade [α- ¹⁴C]hordenine to ¹⁴CO ₂.     

A horizontal apparatus for isoelectric protein purification in a segmented immobilized pH gradient

A modification of the previously described apparatus (Faupel et al. (1987) J. Biochem. Biophys. Methods 15, 147-162), for recycling isoelectric focusing in a segmented immobilized pH gradient, is here reported. The most important improvements are: (1) a horizontal, vs. the previously vertical assembly; (2) a reduction of the thickness of the central flow chamber to 6 mm, vs. the previous 3 cm length and (3) the introduction, at both gel extremities of each Immobiline segment, of polypropylene filters, thus efficiently blocking the gel in situ. The advantages are: (i) the spontaneous removal of air bubbles, which in the vertical apparatus tend to accumulate in the ceiling of the flow chamber and to obstruct the flow of electric current; (ii) a more efficient hydraulic flow with a reduced chance of heating the liquid stream in the flow chamber, due to its reduced length along the separation path and (iii) a reduced risk of gel detachment from the tube walls, due to osmotic swelling caused by focused protein zones in the gel phase and by the fixed Immobiline charges in the polyacrylamide matrix.     

Novel Tools to Analyze the Function of Salmonella Effectors Show That SvpB Ectopic Expression Induces Cell Cycle Arrest in Tumor Cells

In order to further characterize its role in pathogenesis and to establish whether its overproduction can lead to eukaryotic tumor cell death, Salmonella strains able to express its virulence factor SpvB (an ADP-ribosyl transferase enzyme) in a salicylate-inducible way have been constructed and analyzed in different eukaryotic tumor cell lines. To do so, the bacterial strains bearing the expression system have been constructed in a ∆purD background, which allows control of bacterial proliferation inside the eukaryotic cell. In the absence of bacterial proliferation, salicylate-induced SpvB production resulted in activation of caspases 3 and 7 and apoptotic cell death. The results clearly indicated that controlled SpvB production leads to F-actin depolimerization and either G1/S or G2/M phase arrest in all cell lines tested, thus shedding light on the function of SpvB in Salmonella pathogenesis. In the first place, the combined control of protein production by salicylate regulated vectors and bacterial growth by adenine concentration offers the possibility to study the role of Salmonella effectors during eukaryotic cells infection. In the second place, the salicylate-controlled expression of SpvB by the bacterium provides a way to evaluate the potential of other homologous or heterologous proteins as antitumor agents, and, eventually to construct novel potential tools for cancer therapy, given that Salmonella preferentially proliferates in tumors.     

Regulation of Rhodopsin-eGFP Distribution in Transgenic Xenopus Rod Outer Segments by Light

The rod outer segment (OS), comprised of tightly stacked disk membranes packed with rhodopsin, is in a dynamic equilibrium governed by a diurnal rhythm with newly synthesized membrane inserted at the OS base balancing membrane loss from the distal tip via disk shedding. Using transgenic Xenopus and live cell confocal imaging, we found OS axial variation of fluorescence intensity in cells expressing a fluorescently tagged rhodopsin transgene. There was a light synchronized fluctuation in intensity, with higher intensity in disks formed at night and lower intensity for those formed during the day. This fluctuation was absent in constant light or dark conditions. There was also a slow modulation of the overall expression level that was not synchronized with the lighting cycle or between cells in the same retina. The axial variations of other membrane-associated fluorescent proteins, eGFP-containing two geranylgeranyl acceptor sites and eGFP fused to the transmembrane domain of syntaxin, were greatly reduced or not detectable, respectively. In acutely light-adapted rods, an arrestin-eGFP fusion protein also exhibited axial variation. Both the light-sensitive Rho-eGFP and arrestin-eGFP banding were in phase with the previously characterized birefringence banding (Kaplan, Invest. Ophthalmol. Vis. Sci. 21, 395–402 1981). In contrast, endogenous rhodopsin did not exhibit such axial variation. Thus, there is an axial inhomogeneity in membrane composition or structure, detectable by the rhodopsin transgene density distribution and regulated by the light cycle, implying a light-regulated step for disk assembly in the OS. The impact of these results on the use of chimeric proteins with rhodopsin fused to fluorescent proteins at the carboxyl terminus is discussed.