Mesodermal metamerism in the teleost, Oryzias latipes (the medaka)

Previous studies of the metameric pattern in mesodermal tissues of chick, mouse, turtle, and amphibian embryos have indicated that segmental characteristics exist along the entire length of the embryo. This paper describes this phenomenon in a fish embryo, for some differences in the cranial segmental plan exist between the anamniote and the amniote embryos hitherto studied. Embryos of the cyprinodont, Oryzias latipes, were fixed at various times, the examined by means of stereo scanning electron microscopy. As in other vertebrate embryos, the first indication of mesodermal metamerism in this fish embryo is the occurrence of somitomeres, which are orderly, tandemly arranged units of uncondensed mesenchymal cells in the paraxial mesoderm. As many as ten somitomeres can be observed caudal to the last formed somite to the elongating tail region. In addition, 7 somitomeres are present rostral to the first definitive somite, which is segment number eight. As in other vertebrate embryos examined, somitomeres in Oryzias embryos are circular, bilaminar arrays of paraxial mesoderm that form before any indications of segmentation can be seen with the light microscope. In the trunk region these mesodermal units condense to give rise to definitive somites, but in the head they eventually disperse. Despite a fundamentally different mode of gastrulation and a relatively small number of cells in the newly formed somitomeres, cranial segmentation in Oryzias embryos was found to be more similar in number to the metameric pattern of the embryos of the bird, reptile, and mammal than to the situation found in the two amphibians studied thus far.     

Selective illumination of single photoreceptors in the house fly retina: local membrane turnover and uptake of extracellular horseradish peroxidase (HRP) and Lucifer Yellow

Summary Single photoreceptor cells in the compound eye of the housefly Musca domestica were selectively illuminated and subsequently compared electron-microscopically with the unilluminated photoreceptors in the immediate surroundings. The rhabdomeres of the illuminated cells remain largely unaffected, but the cells show an increase in the number of coated pits, various types of vesicles, and degradative organelles; some of the latter organelles are described for the first time in fly photoreceptors. Coated pits are found not only at the bases of the microvilli, but also in other parts of the plasma membrane. Degradative organelles, endoplasmic reticulum (ER) and mitochondria aggregate in the perinuclear region. The rough ER and smooth ER are more elaborate, the number of Golgi stacks, free ribosomes and polysomes is increased, and the shape and distribution of heterochromatin within the nuclei are altered. Illuminated photoreceptors also interdigitate extensively with their neighbouring secondary pigment cells. These structural changes in illuminated fly photoreceptor cells indicate an increase in membrane turnover and cellular metabolism. When applied to the eye, Lucifer Yellow spreads into the extracellular space and is taken up only by the illuminated photoreceptor cells. These cells show the same structural modifications as above. Horseradish peroxidase applied in the same way is observed in pinocytotic vesicles and degradative organelles of the illuminated cells. Hence, the light-induced uptake of extracellular compounds takes place in vivo at least partially as a result of an increase in pinocytosis.     

Membrane-damaging action of ricin on DPPC and DPPC-cerebrosides assemblies

Perturbations induced by a toxic lectin (ricin) on lipid organisation of model membranes prepared with DPPC and DPPC-cerebrosides mixtures have been analysed by Raman and infrared spectroscopy, two powerful and non-invasive methods. Our approach involves the observation of changes in the vibrational spectra of liquid multilayers in the PO ₂ ^- , C=0 and CH₂ spectral regions for two lipid: ricin molar ratios (225:1, 75:1).The interfacial and polar regions of the multilayers, analysed by FTIR, appear to be perturbed by the protein. With both kinds of membranes, ricin mainly perturbs the C=0 ester groups of the sn-2 acylchain of DPPC. In the PO ₂ ^- stretching region, the frequency shifts are correlated with changes in polar group hydration.In the hydrophobic core of the multilayer membrane studied by Raman spectroscopy, the interaction of ricin is associated with changes in lipid packing. These perturbations depend upon the lipid composition of the membrane. With DPPC membranes, an affect is detected at temperatures lower than T _m .It corresponds to a decrease of the lipid ordering. With DPPC-cer membranes, the protein increases the acylchain packing order regardless of the temperature of the experiments (10°C<T<75°C). No perturbation of T _m is observed after addition of ricin to either DPPC or DPPC-cer membranes.The different perturbations detected by Raman and FTIR suggest that ricin mainly interacts with the interfacial domains of the membranes.     

Changes in the cellular permeability of the embryonic axis inGcer arietinum L. seeds during germination

The effect of short chain fatty acids on the cellular permeability of embryonic axis inGcer arietinum seeds was studied. Octanoic (OCT) and nonanoic (NON) adds, which reduce both germination and growth of the embryonic axis and raise the inhibitor effects of the supraoptimal temperatures (30?C), induce a greater ionic efflux into the medium (conductivity). NON reduces glucose (3-0-MG) and K⁺ (⁸⁶Rb) uptake during the germinative process, this action being counteracted by fusicoccin (FC) at optimal (25?C) and supraoptimal temperatures (30 ?C). Tonoplast and plasmalemma increase their permeability to the K⁺ efflux when NON is present. Addition of NON+FC gives rise to higher values in the efflux rate, the vacuolar compartment being the most affected. Temperatures around zero (2 ?C) notably reduce the isotope efflux from cytosol and vacuole. NON acid does not significantly affect the efflux of³H-ABA, suggesting that it does not cause any important changes in the phytohormone compartmentation.     

Schistosoma mansoni: pairing of male worms with artificial surrogate females

To determine whether male worms provide any specific polypeptides to females, we produced extruded alginate fibers that resembled the size and shape of mature female worms. Males clasped these surrogate "female worms" and remained "paired" with them for long periods. On polyacrylamide gel electrophoresis, fibers clasped for several days showed bands at approximately 40 and 46 kDa which were never found in fibers incubated in the same medium but not clasped by males. We believe that these may be substances transferred from male worms during normal pairing. Males biosynthetically labeled with [14C]leucine were permitted to pair with fibers, which took up a broad range of polypeptides visualized on long autoradiographic exposure to gels.     

Complete characterization of the gene coding for the Epstein-Barr virus major membrane antigen gp 220/340 and selective expression of a secreted form of gp 220

The gene which encodes the Epstein-Barr gp 220/340 was inserted into a eukaryotic expression vector. A cDNA clone corresponding to the mature mRNA coding for gp 220 was isolated from an Epstein-Barr virus cDNA library and inserted in the same expression vector, enabling us to identify the precise location of the intron within the gp 220/340 coding sequence. The recombinant plasmids direct the expression of membrane proteins detected by immunofluorescence experiments using an anti-gp 220/340 monoclonal antibody in transfected human cells. The region of the gp 220/340 gene encoding the domain for membrane anchorage was removed from the two recombinant plasmids and the sequence containing the intron produced secreted forms of both truncated gp 220 and gp 340 whereas only the former was obtained with the intronless sequence.     

Comparison of chemical analyses of boat and helicopter-collected water samples

Helicopters can be used to collect water samples from many lakes over a wide geographic area within a relatively short time period. Here we report the results from an experiment in which sequential water samples from a lake were collected first from a nonmotorized boat and then immediately afterward from a helicopter. No significant differences were found between the means of the measurement of 20 chemical parameters for the two methods of collection. When compared to obtaining samples from a boat, collection of samples from a helicopter platform had no effect on the content of the water samples.     

A new cellular model of response to estrogens: a bioluminescent test to characterize (anti) estrogen molecules

With the aim of quickly and easily characterizing new estrogen or anti-estrogen molecules, we developed a cellular model in which estrogenic action can be detected by bioluminescence. This model is based on MCF-7 cells stably transfected with a receptor gene which allows expression of the firefly luciferase enzyme under control of the estrogen regulatory element of the Xenopus vitellogenin A2 gene. A stably transfected cell line (cultured for more than eight months without loss of the chimeric estrogenic response) was established by cotransfection of a neomycin resistance gene and cloning under selective pressure. Subcloning luminescent clones was accomplished by using a single-photon detecting camera. This cellular model allowed the study of an estrogenic activity either in whole-cell or in cell-free experiments by detection of the induced luciferase. Estradiol induced the luciferase activity in a dose-dependent manner at subnanomolar concentrations. The induced luciferase activity reached a maximum level as early as 24 hours after the cells were incubated with estradiol. The antiestrogen 4-hydroxy-tamoxifen inhibited the luciferase activity induced by estradiol. The cross-reactivity of ligands, such as dexamethasone, progesterone, testosterone, aldosterone, calcitriol, oxysterol and retinoic acid, were also studied, showing an estradiol specificity for a 24-hour incubation time.