140 research outputs found
Induction of amiloride-sensitive sodium transport in the rat colon by mineralocorticoids
No full text Page F261: Peter C. Will, Jonathan L. Lebowitz, and Ulrich Hopfer. “Induction of amiloride-sensitive sodium transport in the rat colon by mineralocorticoids.” Page F267: the second equation in the appendix should read (See PDF) </jats:p
Universal Probability Distribution for the Wave Function of a Quantum System Entangled with Its Environment
No full textA quantum system (with Hilbert space H1) entangled with its environment (with Hilbert space H2) is usually not attributed a wave function but only a reduced density matrix ρ1. Nevertheless, there is a precise way of attributing to it a random wave function ψ1, called its conditional wave function, whose probability distribution μ1 depends on the entangled wave function ψ∈H1⊗H2 in the Hilbert space of system and environment together. It also depends on a choice of orthonormal basis of H2 but in relevant cases, as we show, not very much. We prove several universality (or typicality) results about μ1, e.g., that if the environment is sufficiently large then for every orthonormal basis of H2, most entangled states ψ with given reduced density matrix ρ1 are such that μ1 is close to one of the so-called GAP (Gaussian adjusted projected) measures, GAP(ρ1). We also show that, for most entangled states ψ from a microcanonical subspace (spanned by the eigenvectors of the Hamiltonian with energies in a narrow interval [E,E+δE]) and most orthonormal bases of H2, μ1 is close to GAP(tr2ρmc) with ρmc the normalized projection to the microcanonical subspace. In particular, if the coupling between the system and the environment is weak, then μ1 is close to GAP(ρβ) with ρβ the canonical density matrix on H1 at inverse temperature β=β(E). This provides the mathematical justification of our claim in [J. Statist. Phys. 125:1193 (2006), http://arxiv.org/abs/quant-ph/0309021] that GAP measures describe the thermal equilibrium distribution of the wave function.Peer reviewe
The Fran Lebowitz Series in Scorsese’s “Pretend It’s a City” and “Public Speaking”
No full textWriter, humorist, and style icon Fran Lebowitz, author of Social Studies (1981) and Metropolitan Life (1978), then merged in The Fran Lebowitz Reader (1994 and 2021), has been the subject of Martin Scorsese’s Pretend It’s a City (2021) and Public Speaking (2010). Both introduce Lebowitz as a storyteller, social commentator, and public intellectual who narrates her life in the style of documentary performers (Waugh) without neglecting the techniques of the cinéma vérité.
Scorsese’s two works on Fran Lebowitz do not conform to the usual biopic yet can be understood as a selective biography. In introducing Fran Lebowitz to a contemporary large audience, the combination of biographical perspective and quasi-vérité style addresses the opposition between private and public (Arendt and Habermas). Altogether, the two productions can be considered as a series with an opening (Public Speaking) and seven episodes (Pretend It’s a City) that create Martin Scorsese’s series on Fran Lebowitz. The biographical traits, paired with Lebowitz’s status as public speaker, create a double portrait, almost a doppelgänger, as a split between the Lebowitz’s performance and her representation
Molecular dynamics in a grand ensemble: Bergmann-Lebowitz model and adaptive resolution simulation
No full textThis article deals with the molecular dynamics simulation of open systems that can exchange energy and matter with a reservoir; the physics of the reservoir and its interactions with the system are described by the model introduced by Bergmann and Lebowitz (P G Bergmann and J L Lebowitz 1955 Phys. Rev. 99 578). Despite its conceptual appeal, the model did not gain popularity in the field of molecular simulation and, as a consequence, did not play a role in the development of open system molecular simulation techniques, even though it can provide the conceptual legitimation of simulation techniques that mimic open systems. We shall demonstrate that the model can serve as a tool in devising both numerical procedures and conceptual definitions of physical quantities that cannot be defined in a straightforward way by systems with a fixed number of molecules. In particular, we discuss the utility of the Bergmann-Lebowitz (BL) model for the calculation of equilibrium time correlation functions within the grand canonical adaptive resolution method (GC-AdResS) and report numerical results for the case of liquid water.Deutsche Forschungsgemeinschaft (DFG); Heisenberg grant [DE 1140/5-2]; DFG grant [DE 1140/7-1]; National High Technology Research and Development Program of China [2015AA011201]; North German Supercomputing Alliance (HLRN) [bec00100]; Heisenberg grant; [CRC 1114]SCI(E)[email protected]
Cloning, characterization and developmental gene regulation of the flagellar gene, PFR-2, in Leishmania mexicana
No full textProtozoan parasites of the genus Leishmania have evolved a complex life cycle involving two divergent host organisms. Within each respective host, specific morphological and biochemical changes are required. However, little is known about how Leishmania regulate their genes. This study sought to identify developmentally regulated genes and study the mechanism of their developmental gene regulation. Flagellar genes were characterized since the flagellum is developmentally controlled. Complex polyclonal antisera raised against total flagella protein was used to screen a promastigote cDNA expression library. Positive cDNA clones were subjected to Northern analysis to identify candidates for developmentally regulated mRNAs. Two cDNAs, fla2 and fla8, were identified as encoding developmentally regulated, flagellar genes. These two cDNAs encode the two major paraflagellar rod proteins in Leishmania mexicana, PFR-2 and PFR-1. The gene(s) encoding PFR-2 were cloned and found to be present in the genome as a tandem array of three genes that are transcribed polycistronically along with two upstream and two downstream transcripts. Transcription of the PFR-2 locus is not decreased in amastigote nuclei indicating that developmental regulation is post-transcriptional. Transient transfection and stabe transfection experiments indicate that the downstream intergenic region separating PFR-2C from the downstream transcript, D1, confers a 3.3-fold developmental gene regulation. This is similar to developmental regulation of the D1 transcript suggesting that a cis-acting element in the PFR-2C-D1 intergenic region coordinately controls both upstream and downstream transcripts. This control of gene expression is most likely due to control of RNA processing since both trans-splicing of the downstream gene and polyadenylation of the upstream gene are coupled processes
Genetic dissection of the Leishmania paraflagellar rod
No full textThe paraflagellar rod (PFR) is a unique network of cytoskeletal filaments that lies alongside the axoneme in the flagella of most trypanosomatids. While little is known about how two major Leishmania mexicana PFR protein components, PFR1 and PFR2, assemble into this complex structure, previous analysis of PFR2 null mutants demonstrated that the PFR is essential for proper cell motility. The structural roles of PFR1 and PFR2 are now examined through comparison of PFR2 null mutants with new PFR1 null mutant and PFR1/PFR2 double null mutant parasites. Both PFR1 and PFR2 were essential for PFR formation and cell motility. When elimination of one PFR gene prevented assembly of a native PFR structure, the other PFR protein accumulated at the distal flagellar tip. Comparison of PFR substructures remaining in each mutant revealed that: (1) fibers that attach the PFR to the axoneme did not contain PFR1 or PFR2, and assemble in the absence of a PFR. (2) PFR1 was synthesized and transported to the flagella in the absence of PFR2, where it formed a stable association with the axoneme attachment fibers. (3) PFR2 was synthesized and transported to the flagella in the absence of PFR1, though it was not found associated with the axoneme attachment fibers. (4) PFR1 and PFR2 were located throughout the subdomains of the PFR. These data suggest that while PFR filaments contain both PFR1 and PFR2, the PFR is attached to the axoneme by interaction of PFR1 with the axoneme attachment fibers
2024-2025: Distinguished Visiting Author, Elisa Gonzalez
No full textStudent Fellows: Benjamin Harvey, Abigail Lebowitz, Aelan Lee, May Mastrantonio, Ryan Robertsonhttps://docs.rwu.edu/bermont-fellowship/1011/thumbnail.jp
Molecular and genomic analysis of mRNA stability in Leishmania mexicana
No full textThe protozoan parasite Leishmania undergoes dramatic morphological and biochemical changes as it differentiates between the promastigote and amastigote forms. The molecular mechanisms used to modulate gene expression in this organism are predominately post-transcriptional. We examined the Leishmania mexicana transcriptome using high-density whole-genome oligonucleotide microarrays designed from the genome data of a closely related species, Leishmania major. Statistical analysis on array hybridization data representing 8160 predicted coding regions revealed 182 genes (2.2% of all genes) whose steady-state mRNA levels show at least 2-fold differential regulation between promastigotes and lesion-derived amastigotes. Sample comparison of promastigotes to axenic amastigotes resulted in only 31 genes (0.4%) that meet the same statistical criteria for differential regulation. The reduced number of regulated genes is a consequence of a decrease in the magnitude of the transcript expression in cells under axenic conditions. A nine-nucleotide 3\u27UTR regulatory element, termed the paraflagellar rod (PFR) regulatory element (PRE) is both necessary and sufficient for the observed higher levels of PFR2 mRNA in promastigotes compared to amastigotes, and it functions by shortening the half-life of transcripts in the amastigote stage. The PRE is present in the 3\u27UTR of all L. mexicana PFR genes known to date, including PFR1 and PFR4 . Northern analyses show that mRNA of PFR1, PFR4, and two additional genes that share this cis element are enriched in the promastigote stage. Block substitution analyses revealed that the presence of the PRE is responsible for the observed regulation of PFR4 and also has a measurable role in the regulation of PFR1. Our studies show that interspecies hybridization on microarrays can be used to analyze closely related protozoan parasites, that axenic culture conditions may alter amastigote transcript abundance, and that there is only a relatively modest change in abundance of a few mRNAs between morphologically distinct promastigote and amastigote cultured cells. Although our microarray data present evidence of an alternative paradigm for eukaryotic differentiation with minimal contributions from changes in mRNA abundance, we show that PRE-dependent mRNA stability is the primary means of regulation in a family of functionally related promastigote-enriched genes in Leishmania mexicana
2024-2025: Distinguished Visiting Author, Elisa Gonzalez
No full textStudent Fellows: Benjamin Harvey, Abigail Lebowitz, Aelan Lee, May Mastrantonio, Ryan Robertsonhttps://docs.rwu.edu/bermont-fellowship/1011/thumbnail.jp
Role of cytoplasmic dynein-2 in Leishmania mexicana
No full textLeishmania mexicana is a parasitic protozoan that exists in two distinct morphologic forms, the flagellated promastigote in the insect vector, and the non-flagellated amastigote in the vertebrate host. The promastigote flagellum is used for motility and attachment in the insect gut, and may also have a sensory role. Cytoplasmic dynein-2 is a retrograde motor involved in the assembly and maintenance of flagella in Chlamydomonas and the sensory cilia in Caenorhabditis elegans. Eukaryotic organisms with cilia or flagella typically express a single cytoplasmic dynein-2 heavy chain. In contrast, Leishmania and another kinetoplastid, Trypanosoma, have two cytoplasmic dynein-2s\u27. We have identified and sequenced the cytoplasmic dynein-2 heavy chain genes in Leishmania mexicana designated LmxDHC2.1 and LmxDHC2.2 . Quantitative RT-PCR showed that transcript of both genes is present in wild type promastigotes and amastigotes in equal abundance. To determine which of the two L. mexicana dynein-2 homologues is involved in flagella assembly both genes were independently disrupted by homologous gene replacement. I was unable to disrupt LmxDHC2.1 as all the transformants obtained were aneuploid and still contained a wild type copy of the gene, suggesting that LmxDHC2.1 is an essential gene. In contrast, disruption of LmxDHC2.2 resulted in immotile promastigotes that had a rounded cell body. Ultra-structural analysis revealed non-emergent flagella that lacked the paraflagellar rod and the axoneme was deficient in dynein arms, radial spokes, and the central pair microtubules. Western blot analysis confirmed the absence of paraflagellar rod proteins PFR1 and PFR2, and also confirmed that although they assume amastigote morphology, these cells express proteins consistent with the promastigote stage. These results show that LmxDHC2.2 is required for flagellar assembly and also participates in the maintenance of promastigote cell shape. Together, these findings demonstrate that the two dynein-2 heavy chain isoforms of Leishmania perform distinct functions
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