ANALYSIS OF SPATIAL DISTRIBUTIONS OF CELLULAR MOLECULES DURING MECHANICAL STRESSING OF CELL SURFACE RECEPTORS USING CONFOCAL MICROSCOPY

Confocal laser scanning microscopy represents a suitable technique to study the localization of cellular components in three dimension. The authors used this technique to analyse cellular events related to mechanical stimulation of integrin receptors on the cell surface. By performing optical sections the distribution of integrin receptors on the apical surface of an osteoblastic cell was determined. Concerning intracellular compartimentalization of signal transduction events, it was demonstrated that mechanical stimulation of integrins induced their linkage to the cytoskeleton. Cytoskeletally associated proteins like vinculin and talin accumulated in the vicinity of the site where the mechanical stress was applied to integrins on the cell surface. Optical sections revealed that clustering of these proteins proceeded to the base of the cell with gradually decreasing extent. In summary, it was demonstrated that the local distribution of cellular components is an important factor in mechanically induced signal transduction.     

Molecular phylogenetics of Braconidae (Hymenoptera: Ichneumonoidea), based on multiple nuclear genes,and implications for classification

This study examined subfamilial relationships within Braconidae, using 4 kb of sequence data for 139 taxa. Genetic sampling included previously used markers for phylogenetic studies of Braconidae (28S and 18S rDNA) as well as new nuclear protein‐coding genes (CAD and ACC). Maximum likelihood and Bayesian inference of the concatenated dataset recovered a robust phylogeny, particularly for early divergences within the family. This study focused primarily on non‐cyclostome subfamilies, but the monophyly of the cyclostome complex was strongly supported. There was evidence supporting an independent clade, termed the aphidioid complex, as sister to the cyclostome complex of subfamilies. Maxfischeria was removed from Helconinae and placed within its own subfamily within the aphidioid complex. Most relationships within the cyclostome complex were poorly supported, probably because of lower taxonomic sampling within this group. Similar to other studies, there was strong support for the alysioid subcomplex containing Gnamptodontinae, Alysiinae, Opiinae and Exothecinae. Cenocoeliinae was recovered as sister to all other subfamilies within the euphoroid complex. Planitorus and Mannokeraia, previously placed in Betylobraconinae and Masoninae, respectively, were moved to the Euphorinae, and may share a close affiliation with Neoneurinae. Neoneurinae and Ecnomiinae were placed as tribes within Euphorinae. A sister relationship between the microgastroid and sigalphoid complexes was also recovered. The helconoid complex included a well‐supported lineage that is parasitic on lepidopteran larvae (macrocentroid subcomplex). Helconini was raised to subfamily status, and was recovered as sister to the macrocentroid subcomplex. Blacinae was demoted to tribal status and placed within the newly circumscribed subfamily Brachistinae, which also contains the tribes Diospilini, Brulleiini and Brachistini, all formerly in Helconinae.     

Vitellogenin uptake and vitellin localization in insect follicles examined using monoclonal antibodies and confocal scanning microscopy

Summary

Confocal scanning immunofluorescent microscopy and monoclonal antibodies were used to examine the route of uptake of vitellogenin (VG) by vitellogenic follicles and the ooplasmic localization of vitellin (VN) in the cricket, Acheta domesticus, and the stick insect, Carausius morosus. Uptake and cytoplasmic regionalization of a non-vitellogenic sulfated protein, sp 157/85, by C. morosus oocytes were also examined. By indirect immunofluorescence VG in both species and sp 157/85 were visualized in spaces between follicle cells and in peripheral yolk spheres. One cricket VG polypeptide had a regionalized distribution in the folliclular epithelium, and VN polypeptides in both species and sp 157/85 in C. morosus had regionalized distributions within the ooplasm. Localization of sp 157/85 to the anterior pole of the oocyte appeared to be stage-specific.     

Scaling of colonization processes in streams: Parallels and lessons from marine hard substrata

Abstract Understanding colonization processes specifically requires a comprehensive understanding of the frequency and scales over which dispersal occurs, which in turn determines the degree of linkage within and between populations and possibly results in metapopulation structure. What is our level of such knowledge for stream systems? We examine colonization processes in streams using a framework produced by analogous literature on sessile, marine species, which are comparatively well-known and may provide insights for stream biota. For simplicity, we separate dispersal into two, somewhat artificial scales: microscale (between habitat patches - cm to m) and mesoscale (between groups of patches - tens to thousands of metres), and consider dispersal links between them. Traditional views on dispersal developed similarly in both systems, with a strong initial focus on mesoscale dispersal followed by an awareness that some species do not disperse usually over these scales and that there are a wide range of dispersal profiles. In both habitats, there are few data on actual dispersal distances, and longevities are sometimes used to infer them instead. Organisms can be transported by water currents (marine larvae, stream larvae) or wind (adult insects), the directions and strengths of which are relatively predictable at mesoscales. However, behavioural choices of organisms during dispersal can change their potential dispersal distances and directions markedly. Additionally, predictability of transport processes at microscales is very poor. As a consequence, simple, lone biological measures (like longevity) or simple, lone physical measures (like discharge) are useless for predicting dispersal frequencies and scales in most cases. Mortality during dispersal is also extremely important but there are few data; this represents a major information gap in both sets of literature. Finally, if organisms end dispersal by searching for and being able to respond to specific cues, then we may be able to predict colonization by looking at the distribution of such cues; different cues are likely though to vary greatly in space and time. There is potential for dispersal ‘structure’ to develop in rivers of different hydrology, and for sets of correlated life-history characters to result in dispersal at particular scales, but there are very few stream studies that bear on these issues unambiguously. Progress in understanding the scales of dispersal, in both habitats, will require a lot more studies designed formally to test clear hypotheses about the scales of dispersal, rather than continuing a status quo of generating essentially anecdotal information     

Electrophysiological Measurements on the Root of Atriplex hastata

The ion contents and membrane potentials of the cells of young,hydroponically cultured seedlings of Atriplex hastata L. var.salina, Wallr. have been measured at several different NaClconcentrations. The total tissue concentrations of Na⁺ and Cl^–increase as external NaCl increases, but there is always a markedexcess of internal Na⁺ over Cl^–; this is balanced by endogenousorganic anion formation with a concomitant extrusion of H⁺ tothe bathing solution. Membrane potentials of the root cells remain essentially invariantwith changes in external NaCl at approx. –130 mV; thereis no evidence of a radial gradient of potential across theroot. The potential seems to contain a cyanide-sensitive electrogeniccomponent, also invariant with NaCl concentration, of about–70 mV, and a diffusion component. The electrogenic componentseems likely to be a H⁺ efflux, probably through a H⁺ uniportATPase.     

The Exchange of RNA and Protein During Conjugation in Tetrahymena*

SYNOPSIS. Exchange of cytoplasm in Tetrahymena pyriformis, syngen 1, has been demonstrated by growing cells of 1 mating type in medium supplemented with H³-uridine or H³-histidine, washing, mixing with cells of an unlabeled, starved mating type, sampling conjugants at different times, and preparing autoradiographs. It was found that cytoplasmic interchange begins soon after the mates unite, and has become extensive before the end of the 1st prezygotic prophase (micronuclear crescent stage). When the RNA in one mating type had been labeled with H³-uridine, the activity was distributed almost evenly between the mates by late stages of conjugation. These results are consistent with electron micrographs of this syngen showing small pores in the attachment region of the mates, and many free ribosomes in the cytoplasm (8,11). By contrast, when protein in one mating type had been labeled with H³-histidine, these cells at late conjugation remained about twice as active as their originally unlabeled mates, presumably because of the physical characteristics of some structures which incorporated the amino acid (for example, cilia and membranes of the cell surface; cytoplasmic bodies, such as mitochondria, larger than the pores). That the radioactivity in the originally unlabeled cells came from their mates and not from the environment is indicated by the continued presence of inactive non-conjugants after 1 and 2 days in the mating type mixtures. Other cells which did acquire small amounts of active cytoplasm probably had engaged in abortive conjugation, separating from labeled mates before forming and exchanging pronuclei.     

Some Factors Inducing Formation of Metacyclic Stages of Trypanosoma cruzi

ABSTRACT Epimastigotes of Trypanosoma cruzi , Peru strain, incubated in Contreras'artificial triatomine urine transformed into metacyclic trypomastigotes within 48 h at 28° C when 10 mM L-proline or L-glutamate was added to the medium. Smaller numbers of metacyclic stages were induced in the presence of glucose or L-alanine. The L-leucine and L-isoleucine, 2 amino acids known to inhibit proline catabolism, inhibited proiine-induced metacyclogenesis. Cells gassed with 5% CO₂ showed significantly faster rates and higher levels of transformation than those not gassed, therefore indicating the additional importance of CO₂ for transformation.