The Accessory Molecule Lgp55 Plays a Role Early in Murine Fetal Thymocyte Differentiation

A rat IgM monoclonal antibody, PA3-795, inhibits the antigen-specific responses of mouse T-cell hybridomas. It recognizes a heavily glycosylated cell-surface protein, designated Lgp55, that is detectable after activation on mature T cells. During fetal life, Lgp55 is found at high levels on newly immigrant thymic T-cell precursors prior to surface expression of other T-lineage molecules. High levels of expression are also found on thymocytes in the outer cortex of adult mice. Thymocytes at later stages of differentiation bear decreasing amounts of surface Lgp55, and none is detectable on “single-positive” thymocytes in the thymic medulla or on resting mature T cells from the periphery. Addition of monoclonal anti-Lgp55 to fetal thymus organ culture decreases the output of “mature” CD4 singlepositive thymocytes when it is begun before fetal day 13.5. These findings suggest that Lgp55 contributes to cell-cell interactions that regulate very early steps in T-cell development in the mouse

Non-affine mechanics of entangled networks inspired by intermediate filaments

Inspired by massive intermediate filament (IF) reorganization in superstretched epithelia, we examine computationally the principles controlling the mechanics of a set of entangled filaments whose ends slide on the cell boundary. We identify an entanglement metric and threshold beyond which random loose networks respond non-affinely and nonlinearly to stretch by self-organizing into structurally optimal star-shaped configurations. A simple model connecting cellular and filament strains links emergent mechanics to cell geometry, network topology, and filament mechanics. We identify a safety net mechanism in IF networks and provide a framework to harness entanglement in soft fibrous materials.Comment: 23 pages, 16 figures; expanded discussion of non-affinity, added supplementary data on interaction with frictional background at fast loading rates, modified title, results unchange

Recombination of H(3+) and D(3+) ions with electrons

Flowing-afterglow measurements in decaying H3(+) or D3(+) plasmas suggest that de-ionization does not occur by simple binary recombination of a single ion species. We find that vibrational excitation of the ions fails to provide an explanation for the effect, contrary to an earlier suggestion. Instead, we suggest that collisional stabilization of H3** Rydberg molecules by ambient electrons introduces an additional dependence on electron density. The proposed mechanism would permit plasma de-ionization to occur without the need for dissociative recombination by the mechanism of potential-surface crossings

Vector Competence of Ixodes scapularis and Ixodes ricinus (Acari: Ixodidae) for Three Genospecies of Borrelia burgdorferi

The vector competence of 2 tick species, Ixodes ricinus (L.) and Ixodes scapularis Say, was determined and compared for 3 genospecies of Borrelia burgdorferi. The 3 genospecies of B. burgdorferi used in the following experiments were Borrelia burgdorferi sensu stricto (B-31 and B-31.D1 clone), Borrelia afzelii (strain Pgau.C3), and Borrelia garinii (strain VS286 and VSBP). Spirochetes from all 5 strains were inoculated intradermally into outbred mice; larval ticks of both species were subsequently fed on those mice and replete larvae were assayed for infection by culture in BSK-H media every 7 d for 4 wk. Infection frequencies in I. scapularis exposed to the 5 strains were as follows: B-31 (90%), B-31.D1 (83%), Pgau.C3 (87%), VS286 (10%), and VSBP (5%). The comparable infection frequencies for /. ricinus were B-31 (3%), B-31.D1 (3%), Pgau.C3 (90%), VS286 (5%), and VSBP (3%). Resultant nymphal /. scapularis successfully transmitted B-31, B-31.D1, Pgau.C3, and VS286 to outbred mice. /. ricinus nymphs transmitted Pgau.C3 and VS286. Both species failed to transmit strain VSB

Signal peptide peptidase (SPP) dimer formation as assessed by fluorescence lifetime imaging microscopy (FLIM) in intact cells

BACKGROUND: Signal peptide peptidase (SPP) is an intramembrane cleaving protease identified by its cleavage of several type II membrane signal peptides. Conservation of intramembrane active site residues demonstrates that SPP, SPP family members, and presenilins (PSs) make up a family of intramembrane cleaving proteases. Because SPP appears to function without additional protein cofactors, the study of SPP may provide structural insights into the mechanism of intramembrane proteolysis by this biomedically important family of proteins. Previous studies have shown that SPP isolated from cells appears to be a homodimer, but some evidence exists that in vitro SPP may be active as a monomer. We have conducted additional experiments to determine if SPP exists as a monomer or dimer in vivo. RESULTS: Fluorescence lifetime imaging microscopy (FLIM) can be is used to determine intra- or intermolecular interactions by fluorescently labeling epitopes on one or two different molecules. If the donor and acceptor fluorophores are less than 10 nm apart, the donor fluorophore lifetime shortens proportionally to the distance between the fluorophores. In this study, we used two types of fluorescence energy transfer (FRET) pairs; cyan fluorescent protein (CFP) with yellow fluorescent protein (YFP) or Alexa 488 with Cy3 to differentially label the NH2- or COOH-termini of SPP molecules. A cell based SPP activity assay was used to show that all tagged SPP proteins are proteolytically active. Using FLIM we were able to show that the donor fluorophore lifetime of the CFP tagged SPP construct in living cells significantly decreases when either a NH2- or COOH-terminally YFP tagged SPP construct is co-transfected, indicating close proximity between two different SPP molecules. These data were then confirmed in cell lines stably co-expressing V5- and FLAG-tagged SPP constructs. CONCLUSION: Our FLIM data strongly suggest dimer formation between two separate SPP proteins. Although the tagged SPP constructs are expressed throughout the cell, SPP dimer detection by FLIM is seen predominantly at or near the plasma membrane

Juror Perceptions of Bystander and Victim Intoxication by Different Substances

This study examined the effects of bystander or victim intoxication during a crime on juror perceptions and decision-making. Mock jurors (N = 261) read testimony from a bystander or victim to an assault, who mentioned that they had consumed alcohol, cannabis, amphetamines, or no substances prior to the crime. Participants delivered a verdict, rated the defendant’s guilt, and rated the bystander/victim on their honesty, credibility, and cognitive competence. Witness intoxication and witness role did not influence defendant guilt. However, participants judged any witness intoxicated by amphetamines as less credible and cognitively competent than a sober witness. Furthermore, victims were judged to have lower credibility, cognitive competence, and honesty than bystanders. These findings suggest that jurors’ decision-making about defendant guilt might not be influenced by witness intoxication or witness type. A witness’ testimony, however, might be evaluated as less credible when delivered by a victim or an amphetamine-intoxicated witness

Juror Perceptions of Bystander and Victim Intoxication by Different Substances

This study examined the effects of bystander or victim intoxication during a crime on juror perceptions and decision-making. Mock jurors (N = 261) read testimony from a bystander or victim to an assault, who mentioned that they had consumed alcohol, cannabis, amphetamines, or no substances prior to the crime. Participants delivered a verdict, rated the defendant’s guilt, and rated the bystander/victim on their honesty, credibility, and cognitive competence. Witness intoxication and witness role did not influence defendant guilt. However, participants judged any witness intoxicated by amphetamines as less credible and cognitively competent than a sober witness. Furthermore, victims were judged to have lower credibility, cognitive competence, and honesty than bystanders. These findings suggest that jurors’ decision-making about defendant guilt might not be influenced by witness intoxication or witness type. A witness’ testimony, however, might be evaluated as less credible when delivered by a victim or an amphetamine-intoxicated witness