24 research outputs found
Non-chiral bosonization of strongly inhomogeneous Luttinger liquids
Non-chiral bosonization (NCBT) is a non-trivial modification of the standard
Fermi-Bose correspondence in one spatial dimensions made in order to facilitate
the study of strongly inhomogeneous Luttinger liquids (LL) where the properties
of free fermions plus the source of inhomogeneities are reproduced exactly. The
formalism of NCBT is introduced and limiting case checks, fermion commutation
rules, point splitting constraints, etc. are discussed. The Green functions
obtained from NCBT are expanded in powers of the fermion-fermion interaction
strength (forward scattering short-range only) and compared with the
corresponding terms obtained using standard fermionic perturbation theory.
Lastly, the Green functions obtained from NCBT are inserted into the
Schwinger-Dyson equation which is the equation of motion of the Green functions
and serves as a non-perturbative confirmation of the method. Some other
analytical approaches like functional bosonization and numerical techniques
like DMRG, which can be used to obtain the correlation functions in 1D, are
briefly discussed
An automated microfluidic system for efficient capture of rare cells and rapid flow-free stimulation
Cell fates are controlled by environmental stimuli that rapidly change the activity of intracellular signaling. Studying these processes requires rapid manipulations of micro-environmental conditions while continuously observing single cells over long periods of time. Current microfluidic devices are unable to simultaneously i) efficiently capture and concentrate rare cells, ii) conduct automated rapid media exchanges via diffusion without displacing non-adherent cells, and iii) allow sensitive high-throughput long-term time-lapse microscopy. Hematopoietic stem and progenitor cells pose a particular challenge for these types of experiments as they are impossible to obtain in very large numbers and are displaced by the fluid flow usually used to change culture media, thus preventing cell tracking. Here, we developed a programmable automated system composed of a novel microfluidic device for efficient capture of rare cells in independently addressable culture chambers, a custom incubation system, and user-friendly control software. The chip's culture chambers are optimized for efficient and sensitive fluorescence microscopy and their media can be individually and quickly changed by diffusion without non-adherent cell displacement. The chip allows efficient capture, stimulation, and sensitive high-frequency time-lapse observation of rare and sensitive murine and human primary hematopoietic stem cells. Our 3D-printed humidification and incubation system minimizes gas consumption, facilitates chip setup, and maintains stable humidity and gas composition during long-term cell culture. This approach now enables the required continuous long-term single-cell quantification of rare non-adherent cells with rapid environmental manipulations, e.g. of rapid signaling dynamics and the later stem cell fate choices they control.ISSN:1473-0197ISSN:1473-018
A Novel GATA2 Protein Reporter Mouse Reveals Hematopoietic Progenitor Cell Types
In this study, Schroeder and colleagues generated a GATA2VENUS protein reporter mouse line with normal GATA2 expression and localization, e.g., in the urogenital, auditory, and nervous systems. The authors also profiled GATA2 protein expression across hematopoietic cell types, identified heterogeneity within populations currently assumed to be homogeneous, and demonstrate an earlier monocyte-mast cell lineage bifurcation point.ISSN:2213-671
Open-source personal pipetting robots with live-cell incubation and microscopy compatibility
Liquid handling robots have the potential to automate many procedures in life sciences. However, they are not in widespread use in academic settings, where funding, space and maintenance specialists are usually limiting. In addition, current robots require lengthy programming by specialists and are incompatible with most academic laboratories with constantly changing small-scale projects. Here, we present the Pipetting Helper Imaging Lid (PHIL), an inexpensive, small, open-source personal liquid handling robot. It is designed for inexperienced users, with self-production from cheap commercial and 3D-printable components and custom control software. PHIL successfully automates pipetting (incl. aspiration) for e.g. tissue immunostainings and stimulations of live stem and progenitor cells during time-lapse microscopy using 3D printed peristaltic pumps. PHIL is cheap enough to put a personal pipetting robot within the reach of most labs and enables users without programming skills to easily automate a large range of experiments.ISSN:2041-172
Open-source personal pipetting robots with live-cell incubation and microscopy compatibility
Liquid handling robots have the potential to automate many procedures in life sciences. However, they are not in widespread use in academic settings, where funding, space and maintenance specialists are usually limiting. In addition, current robots require lengthy programming by specialists and are incompatible with most academic laboratories with constantly changing small-scale projects. Here, we present the Pipetting Helper Imaging Lid (PHIL), an inexpensive, small, open-source personal liquid handling robot. It is designed for inexperienced users, with self-production from cheap commercial and 3D-printable components and custom control software. PHIL successfully automated pipetting for e.g. tissue immunostainings and stimulations of live stem and progenitor cells during time-lapse microscopy. PHIL is cheap enough for any laboratory member to have their own personal pipetting robot(s), and enables users without programming skills to easily automate a large range of experiments
Blood stem cell PU.1 upregulation is a consequence of differentiation without fast autoregulation
Transcription factors (TFs) regulate cell fates, and their expression must be tightly regulated. Autoregulation is assumed to regulate many TFs' own expression to control cell fates. Here, we manipulate and quantify the (auto)regulation of PU.1, a TF controlling hematopoietic stem and progenitor cells (HSPCs), and correlate it to their future fates.We generate transgenic mice allowing both inducible activation of PU.1 and noninvasive quantification of endogenous PU.1 protein expression. The quantified HSPC PU.1 dynamics show that PU.1 up-regulation occurs as a consequence of hematopoietic differentiation independently of direct fast autoregulation. In contrast, inflammatory signaling induces fast PU.1 up-regulation, which does not require PU.1 expression or its binding to its own autoregulatory enhancer. However, the increased PU.1 levels induced by inflammatory signaling cannot be sustained via autoregulation after removal of the signaling stimulus.We conclude that PU.1 overexpression induces HSC differentiation before PU.1 up-regulation, only later generating cell types with intrinsically higher PU.1.ISSN:0022-1007ISSN:1540-0069ISSN:1540-953
Automated Microfluidic System for Dynamic Stimulation and Tracking of Single Cells
Dynamic
environments determine cell fate decisions and function.
Understanding the relationship between extrinsic signals on cellular
responses and cell fate requires the ability to dynamically change
environmental inputs in vitro, while continuously observing individual
cells over extended periods of time. This is challenging for nonadherent
cells, such as hematopoietic stem and progenitor cells, because media
flow displaces and disturbs such cells, preventing culture and tracking
of single cells. Here, we present a programmable microfluidic system
designed for the long-term culture and time-lapse imaging of nonadherent
cells in dynamically changing cell culture conditions without losing
track of individual cells. The dynamic, valve-controlled design permits
targeted seeding of cells in up to 48 independently controlled culture
chambers, each providing sufficient space for long-term cell colony
expansion. Diffusion-based media exchange occurs rapidly and minimizes
displacement of cells and eliminates shear stress. The chip was successfully
tested with long-term culture and tracking of primary hematopoietic
stem and progenitor cells, and murine embryonic stem cells. This system
will have important applications to analyze dynamic signaling inputs
controlling fate choices
Automated Microfluidic System for Dynamic Stimulation and Tracking of Single Cells
Dynamic
environments determine cell fate decisions and function.
Understanding the relationship between extrinsic signals on cellular
responses and cell fate requires the ability to dynamically change
environmental inputs in vitro, while continuously observing individual
cells over extended periods of time. This is challenging for nonadherent
cells, such as hematopoietic stem and progenitor cells, because media
flow displaces and disturbs such cells, preventing culture and tracking
of single cells. Here, we present a programmable microfluidic system
designed for the long-term culture and time-lapse imaging of nonadherent
cells in dynamically changing cell culture conditions without losing
track of individual cells. The dynamic, valve-controlled design permits
targeted seeding of cells in up to 48 independently controlled culture
chambers, each providing sufficient space for long-term cell colony
expansion. Diffusion-based media exchange occurs rapidly and minimizes
displacement of cells and eliminates shear stress. The chip was successfully
tested with long-term culture and tracking of primary hematopoietic
stem and progenitor cells, and murine embryonic stem cells. This system
will have important applications to analyze dynamic signaling inputs
controlling fate choices