Acquired resistance to echinostomes in four Biomphalaria glabrata strains

Four strains of Biomphalaria glabrata showed a distinctive pattern of acquired resistance to each of 3 echinostome species. Juvenile albino B. glabrata from our laboratory NIH stock developed a strong resistance to Echinostoma lindoense but only a weak one to E. paraensei and a moderate one to E. liei. Juvenile B. glabrata 10-R2 strain developed a strong acquired resistance to E. lindoense but a weak one to E. paraensei and E. liei. Juvenile B. glabrata M-RLc strain developed a strong acquired resistance to E. lindoense and a moderate one to E. paraensei and E. liei. Juvenile B. glabrata 641 strain developed a moderate acquired resistance to E. lindoense, a weak one to E. liei and no measurable resistance to E. paraensei.     

Specificity of natural resistance to trematode infections in Biomphalaria glabrata

The 10-R2 strain of Biomphalaria glabrata was strongly resistant to various strains of Schistosoma mansoni in its laboratory of origin (NIH) and to three strains of S. mansoni we tested against it. However, subsequent development of three inbred lines of B. glabrata 10-R2 snails, separately maintained in our San Francisco laboratory, showed slight loss of resistance in one colony, very much less resistance (or partial susceptibility) in another, and retention of the original resistance in a third to the Puerto Rico (PR-1) strain of S. mansoni. No selection for resistance to infection was involved in the breeding protocol for these 10-R2 lines, so the changes were apparently random ones that became established in the separate inbred substrains. In spite of their changed response to the PR-1 strain of S. mansoni, all three 10-R2 substrains retained only slightly diminished resistance to S. mansoni Lc-1 strain and an essentially undiminished resistance to irradiated Echinostoma lindoense, E. paraensei and E. liei sporocysts. This suggests that natural resistance to S. mansoni PR-1 in B. glabrata is specific, a response that differs from the host response to either S. mansoni Lc-1 or to the echinostomes.     

Competition between Rhizobium strains in nodule formation: Interaction between nodulating and non-nodulating strains

Summary Nodulation of pea cv. Afghanistan and cv. Iran by a nodulating Rhizobium strain is suppressed by the presence of a non-nodulating strain. The degree of suppression varies, dependent on the Rhizobium strains used. There is a great variation in the competitive ability of the Rhizobium strains and this is not related to the ability to form root nodules. The critical period of competition is restricted to ca. 24 hours after inoculation.     

Effects of isoproterenol on the dense core and perigranular membrane of atrial specific granules

Summary Following subcutaneous injections of isoproterenol hydrochloride (ISO), atrial cells present a large number of partly degranulated or completely clear specific granules enclosed by an intact membrane. Such profiles were never encountered in normal controls and might suggest ISO-induced release of a secretory product. Permeability of perigranular membrane was tested using the extracellular macromolecular tracer horseradish peroxidase (HRP). Reaction product was entirely absent within granules of atrial cells in which the sarcolemma was made permeable to HRP molecules by the ISO injections. This seemed to be the case even in heavily labelled cells in which the peroxidase had penetrated the mitochondrial membranes. In atrial cells impermeable to the tracer, the specific granules closely apposed to the sarcolemma were always HRP-negative. The release mechanism of a possible secretory substance from the specific granules is discussed.     

13C-NMR of methyl,methylene and carbonyl carbon atoms of methyl alkenoates and alkynoates

The carbon magnetic resonance spectra of 102 fatty acid methyl esters with cis and trans double bonds and triple bonds at various positions and in many different combinations have been investigated. A comprehensive set of chemical shift parameters has been developed for the various substituents. With the aid of these parameters, the chemical shifts of all methyl, methylene carbonyl carbon atoms can be predicted with an accuracy of ±0.1 ppm or better.     

Studies on resistance in snails. 5. Tissue reactions to Echinostoma lincloense in naturally resistant Biomphalaria glabrata.

Laboratory-raised juvenile albino Biomphalaria glabrata snails show a wide range of natural resistance to a single infection with 50 or 100 miracidia of Echinostoma lindoense. In the most resistant snails all sporocysts are destroyed in peripheral tissues soon after miracidial penetration. In less resistant snails some sporocysts reach the heart where they are encapsulated. In fully susceptible snails, all sporocysts rapidly migrate to the heart, where they mature and continue to develop. The greater part of our B. glabrata colony consists of snails in which sporocysts reaching the heart will survive, but in which a varying number of sporocysts will be destroyed in the tissues. These snails are usually considered susceptible, as they do become infected. Tissue reactions induced by sporocysts following a single infection in naturally resistant snails are similar to reactions in snails with an acquired resistance. In fully susceptible snails, the amebocyte-producing organ remains small and inactive. It is slightly to moderately stimulated in partially resistant snails in which destruction of sporocysts occurs in the tissues and surviving larvae are found in the ventricle. In snails in which amebocyte aggregates or capsules develop in the ventricle, the organ becomes markedly enlarged. Migration of sporocysts in the snail appears not to be continuous, as periodic rests seem to occur. Migration follows intrusion of the sporocyst through the tissues, induced by bodily distension and contraction, and then proceeds within the arteries against the blood flow, passing from one endothelial attachment site to another, possibly aided by negative pressure during ventricular diastole.     

Studies on resistance in snails. 6. Escape of Echinostoma lindoense sporocysts from encapsulation in the snail heart and subsequent loss of the host's ability to resist infection by the same parasite.

Formation of amebocyte aggregates in the ventricular cavity of Biomphalaria glabrata, induced by developing sporocysts of Echinostoma lindoense, does not always result in destruction of the parasites, as the sporocysts occasionally escape encapsulation in the heart. When this occurs, a remarkable loss of protective capacity follows and the host snails become highly susceptible to reinfection with the same species--even more so than in control susceptible snails exposed for the first time. Although the amebocyte-producing organ is considerably enlarged after a first infection and shows numerous mitoses, the amebocytes produced by snails harboring an "escaped" infection in the heart appear unable to attack the parasites of the first or of the second exposure. Instead, the amebocytes produced accumulate in the loose connective tissues between the liver lobuli, where early developmental stages of the parasites do not occur. These amebocytes apparently have lost their ability to recognize the parasites as foreign.     

In situ hybridization at the electron microscope level: hybrid detection by autoradiography and colloidal gold

In situ hybridization has become a standard method for localizing DNA or RNA sequences in cytological preparations. We developed two methods to extend this technique to the transmission electron microscope level using mouse satellite DNA hybridization to whole mount metaphase chromosomes as the test system. The first method devised is a direct extension of standard light microscope level using mouse satellite DNA hybridization to whole mount metaphase chromosomes as the test system. The first method devised is a direct extension of standard light microscope in situ hybridization. Radioactively labeled complementary RNA (cRNA) is hybridized to metaphase chromosomes deposited on electron microscope grids and fixed in 70 percent ethanol vapor; hybridixation site are detected by autoradiography. Specific and intense labeling of chromosomal centromeric regions is observed even after relatively short exposure times. Inerphase nuclei present in some of the metaphase chromosome preparations also show defined paatterms of satellite DNA labeling which suggests that satellite-containing regions are associate with each other during interphase. The sensitivity of this method is estimated to at least as good as that at the light microscope level while the resolution is improved at least threefold. The second method, which circumvents the use of autoradiogrphic detection, uses biotin-labeled polynucleotide probes. After hybridization of these probes, either DNA or RNA, to fixed chromosomes on grids, hybrids are detected via reaction is improved at least threefold. The second method, which circumvents the use of autoradiographic detection, uses biotin-labeled polynucleotide probes. After hybridization of these probes, either DNA or RNA, to fixed chromosomes on grids, hybrids are detected via reaction with an antibody against biotin and secondary antibody adsorbed to the surface of over centromeric heterochromatin and along the associated peripheral fibers. Labeling is on average ten times that of background binding. This method is rapid and possesses the potential to allow precise ultrastructual localization of DNA sequences in chromosomes and chromatin.     

ERRATUM: New Body Mass Estimates for Omomys carteri,a Middle Eocene Primate From North America. Am J Phys Anthropol 109:41–52.

Payseur BA, Covert HA, Vinyard CJ, Dagosto M. 1999. New Body Mass Estimates for Omomys carteri, a Middle Eocene Primate From North America. Am J Phys Anthropol 109:41–52. This article included an incomplete Table 2. The final two columns, showing “Intercept” and “SEE” data were omitted. The complete Table 2, with these two columns included, is provided below.     

Real-time imaging of the dynamics of secretory granules in growth cones

Secretory granules containing a hybrid protein consisting of the regulated secretory protein tissue plasminogen activator and an enhanced form of green fluorescent protein were tracked at high spatial resolution in growth cones of differentiated PC12 cells. Tracking shows that granules, unlike synaptic vesicles, generally are mobile in growth cones. Quantitative analysis of trajectories generated by granules revealed two dominant modes of motion: diffusive and directed. Diffusive motion was observed primarily in central and peripheral parts of growth cones, where most granules diffused two to four orders of magnitude more slowly than comparably sized spheres in dilute solution. Directed motion was observed primarily in proximal parts of growth cones, where a subset of granules underwent rapid, directed motion at average speeds comparable to those observed for granules in neurites. This high-resolution view of the dynamics of secretory granules in growth cones provides insight into granule organization and release at nerve terminals. In particular, the mobility of granules suggests that granules, unlike synaptic vesicles, are not tethered stably to cytoskeletal structures in nerve terminals. Moreover, the slow diffusive nature of this mobility suggests that secretory responses involving centrally distributed granules in growth cones will occur slowly, on a time scale of minutes or longer.