Chromosome length values in digenomic buttercups [Ranunculaceae] and the relation to DNA content

Root-tip chromosome complement length ratios were determined in F1 hybrids combinining two haploid (n = 8) genomes each from different species, to form a series AB, AC, AD, ... AI. The observed values, for the length ratios B/A, C/A, etc., ranged from 0.53 to 1.0. It is noted that the values form a quasilinear distribution, with a slope of 1.0, when plotted against the known 4C DNA values of the species having a range from appr. 1.1 to 2.2 × 10^?11 g. Also observed, but not numerically evaluated was some apparently related variation in chromosome “width”. DNA-related variation in root-tip chromosome size in these buttercups may be three-dimensional; however, the magnitude of the observed length differentials and the 1∶1 correlation with DNA content suggest that it occupies predominantly the first dimension.     

Excretory-secretory products of Echinostoma paraensei sporocysts mediate interference with Biomphalaria glabrata hemocyte functions.

Miracidia of Echinostoma paraensei were cultured in medium containing 14C-labeled amino acids, allowed to transform into sporocysts, and their excretory/secretory products (E-S) were collected and characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography. Effects of E-S on hemocytes of Biomphalaria glabrata were also assessed. E-S collected during day 1 of culture (E-S1) contained several polypeptides, none of which were labeled, suggesting that E-S1 are largely preformed. E-S1 significantly depressed the ability of hemocytes to phagocytose sheep red blood cells (SRBC), but otherwise had little effect on hemocyte structure or behavior. E-S released by sporocysts in day-2 cultures (E-S2) and in older cultures generally were similar and also contained several polypeptides, many of which were labeled, indicating active synthesis of E-S in vitro. E-S2 strongly inhibited hemocyte uptake of SRBC. Also, hemocytes pretreated with E-S2 assumed a spherical shape and failed to spread normally. E-S obtained through 10 days of culture mediated this effect. Active components of E-S2 were greater than 100 kDa in their native configuration, were heat- and trypsin-labile, and were bound by anti-E-S antibodies. Both greater than 200- and 80-kDa bands were prominent in anti-E-S immunoprecipitates. Hemocytes derived from snails of the 13-16-R1 strain of B. glabrata (a strain resistant to infection with Schistosoma mansoni), when pretreated with E-S2, bound to sporocysts of S. mansoni but lost their ability to damage such sporocysts. E-S2 interfered with hemocyte functions in ways inferred from earlier classic in vivo studies of trematode-snail interactions.     

Isolation of root hairs from seedlings of Pisum sativum. Identification of root hair specific proteins by in situ labeling

A procedure was developed which allows the large-scale isolation of root hairs from seedlings of Pisum sativum . L. cvs. Kleine Rheinländerin and Rosa Krone. The method may yield up to 50 g fresh weight of root hairs per 3.10⁴ seedlings. In a modified form considerable amounts of root hair material may be harvested, even after incubation of the roots in aqueous solutions. Thus, detailed biochemical studies on the root hair system have become feasible.
The occurrence of specific proteins in membrane fractions of P. sativum root hairs was demonstrated as follows: Incubation of root hairs in situ with 3-azidonaphthalene-2,7-disulfonate – a strongly anionic, photoactivated fluorescent marker – followed by gel electrophoresis of membrane fractions showed the presence of root-hair specific proteins which, since the system was intact, suggests that they are on the outer surface of the cells.     

Ortstreue und Genflu? bei Inselvogelarten: Eleonorenfalke (Falco eleonorae) und Gelbschnabelsturmtaucher (Calonectris diomedea)

Summary Young birds of both species return almost exclusively to their natal colony for breeding and breeders are higly faithful to both partner and territory in subsequent years. There is no or very limited emigration to other colonies which are 2–5 km distant. The consequences of the genetic isolation are discussed: In both species the tendency to form subspecies can be detected. High mortality rates are interpreted as a mean to eliminate any degenerated bird which could result from the close interbreeding in these small and isolated populations.     

In vitro synthesis of bean (Phaseolus vulgaris) chloroplastic and cytoplasmic leucyl-tRNA synthetases. Characterization and processing of a precursor polypeptide for the chloroplast enzyme

Bean (Phaseolus vulgaris) chloroplastic and cytoplasmic leucyl-tRNA synthetases differ in their structural and catalytic properties and do not share common antigenic determinants. Polyadenylated mRNAs, prepared from young bean leaves, have been translated in vitro in a rabbit reticulocyte lysate cell-free system. The newly synthesized polypeptides have been submitted to immunoadsorption on protein A-Sepharose in the presence of the antibodies raised against the chloroplastic or the cytoplasmic leucyl-tRNA synthetase. The specificity of the immunoadsorption has been checked by competition experiments involving the pure enzymes. Bean chloroplastic leucyl-tRNA synthetase is synthesized in vitro from a polyadenylated mRNA as a precursor polypeptide of 130 kDa, which is somewhat larger than the mature enzyme of 120 kDa. Bean cytoplasmic leucyl-tRNA synthetase is synthesized in vitro as a polypeptide which has the size of the mature monomer (130 kDa). Processing of the precursor polypeptide of the chloroplastic leucyl-tRNA synthetase, yielding the mature enzyme, has been obtained by performing the in vitro translation in the presence of canine pancreatic microsomal membranes. These results suggest that in vivo bean chloroplastic leucyl-tRNA synthetase could be synthesized in the cytoplasm as a precursor which would be transported into the chloroplasts.     

Sequential appearance of epidermal growth factor in plasma membrane-associated and intracellular vesicles during endocytosis

Receptor-mediated internalization of epidermal growth factor (EGF) occurs by a process involving initially clathrin-coated pits on the cell surface and the subsequent formation of ligand-containing endosomes. Using a modified acid wash technique, cell surface-bound EGF was removed. Utilizing sucrose density centrifugation, the residual cell-associated EGF was separated into plasma membrane-associated and intracellular vesicle-associated forms. Using these procedures we have identified a transient form of cell-associated EGF that is still attached to the plasma membrane but not accessible to the extracellular fluid. This form of EGF appears to be the precursor for endosomic EGF. We suggest that this intermediate form represents the receptor-ligand complex shown by electronmicroscopy to be located in narrow-necked plasma membrane invaginations (Willingham, M. C., and Pastan, I. (1980) Cell 21, 67-77).