Distinct Populations of Hepatic Stellate Cells in the Mouse Liver Have Different Capacities for Retinoid and Lipid Storage

Hepatic stellate cell (HSC) lipid droplets are specialized organelles for the storage of retinoid, accounting for 50–60% of all retinoid present in the body. When HSCs activate, retinyl ester levels progressively decrease and the lipid droplets are lost. The objective of this study was to determine if the HSC population in a healthy, uninjured liver demonstrates heterogeneity in its capacity for retinoid and lipid storage in lipid droplets. To this end, we utilized two methods of HSC isolation, which leverage distinct properties of these cells, including their vitamin A content and collagen expression. HSCs were isolated either from wild type (WT) mice in the C57BL/6 genetic background by flotation in a Nycodenz density gradient, followed by fluorescence activated cell sorting (FACS) based on vitamin A autofluorescence, or from collagen-green fluorescent protein (GFP) mice by FACS based on GFP expression from a GFP transgene driven by the collagen I promoter. We show that GFP-HSCs have: (i) increased expression of typical markers of HSC activation; (ii) decreased retinyl ester levels, accompanied by reduced expression of the enzyme needed for hepatic retinyl ester synthesis (LRAT); (iii) decreased triglyceride levels; (iv) increased expression of genes associated with lipid catabolism; and (v) an increase in expression of the retinoid-catabolizing cytochrome, CYP2S1. Conclusion: Our observations suggest that the HSC population in a healthy, uninjured liver is heterogeneous. One subset of the total HSC population, which expresses early markers of HSC activation, may be “primed” and ready for rapid response to acute liver injury

Topology of molecular machines of the endoplasmic reticulum: a compilation of proteomics and cytological data

The endoplasmic reticulum (ER) is a key organelle of the secretion pathway involved in the synthesis of both proteins and lipids destined for multiple sites within and without the cell. The ER functions to both co- and post-translationally modify newly synthesized proteins and lipids and sort them for housekeeping within the ER and for transport to their sites of function away from the ER. In addition, the ER is involved in the metabolism and degradation of specific xenobiotics and endogenous biosynthetic products. A variety of proteomics studies have been reported on different subcompartments of the ER providing an ER protein dictionary with new data being made available on many protein complexes of relevance to the biology of the ER including the ribosome, the translocon, coatomer proteins, cytoskeletal proteins, folding proteins, the antigen-processing machinery, signaling proteins and proteins involved in membrane traffic. This review examines proteomics and cytological data in support of the presence of specific molecular machines at specific sites or subcompartments of the ER

Broadband Coupling into a Single-Mode, Electroactive Integrated Optical Waveguide for Spectroelectrochemical Analysis of Surface-Confined Redox Couples

Pushing the sensitivity of spectroelectrochemical techniques to routinely monitor changes in spectral properties of thin molecular films (i.e., monolayer or submonolayer) adsorbed on an electrode surface has been a goal of many investigators since the earliest developments in this field. 1 It was initially recognized that exploiting the evanescent field generated by total internal reflection at the interface of an optically transparent electrode (such as a thin film of tin oxide or indium tin oxide (ITO) on glass or quartz) has the inherent advantage of selectively probing only the near-surface region, as opposed to bulk sampling with transmission based techniques. Furthermore, by utilizing the multiple reflections in an attenuated total reflectance (ATR) geometry, an enhancement in sensitivity can be realized, and as the thickness of the ATR element is decreased, the number of reflections increases, yielding a substantial sensitivity enhancement. [2][3][4][5][6] Itoh and Fujishima were the first to show the advantages of reducing the thickness of an ATR element overcoated with a transparent conductive oxide to the integrated optical waveguide (IOW) regime. Using a four-mode, gradient index waveguide coated with a transparent, conductive tin oxide layer, they demonstrated large sensitivity enhancements, relative to a single pass transmission experiment, for spectroelectrochemical measurements of methylene blue. 7,8 Other research groups subsequently described similar gradient index, multilayer, electroactive waveguide structures, but they did not make use of the technology to explore the spectroelectrochemistry of (sub)monolayer coverage films. [9][10][11][12][13] We recently described a single-mode, electroactive planar IOW (the EA-IOW) having a step refractive index profile. It was fabricated by sputtering a Corning 7059 glass layer (400 nm) over soda lime glass or quartz, followed by a 200-nm layer of SiO 2

THE 3540 {\AA} ELECTRONIC TRANSITION OF MALONALDEHYDE

$^{1}$ P.R. Bunker, B. M. Landsberg and B.P. Winnewisser, J. Mol. Spectrose. 74, 9-25 (1979).Author Institution:The 3540{\AA} vibronic band system of malonaldehyde (normal- and $d_{2}$-isotopes) has been partially analyzed and it represents an $n\to\pi^{*} (1^{1}B_{1}\leftrightarrow; 1^{1}A_{1})$ electronic transition with an origin band at 3538.3{\AA} ($28262cm^{-1}$) in the normal isotope. The vibrational structure consists of more than 100 vibronic components. Two principal progressions in $^{1}B_{1}$ state vibrations are found and they are of magnitude $185cm^{-1}$ and $1300cm^{-1}$. The $185cm^{-1}$ vibration apparently corresponds to an in-plane ring deformation and the $1300cm^{-1}$ vibration corresponds to the carbonyl stretching vibration reduced by $360cm^{-1}$ relative to its ground state value. Tunneling effects are prominent in the spectrum and these features may be explained by using a treatment of malonaldehyde vibrations similar to the semirigid bender Hamiltonian model advanced by Bunker, et al.(1) for non-rigid moledules with one large-amplitude vibration. Rotational band contours and Herzberg-Teller intensity found in this band system are also discussed

THE 1B1 (nπ∗)←11A1^{1}B_{1}\, (n\pi^{*})\leftarrow 1^{1}A_{1}, ELECTRONIC BAND SYSTEM OF MALONDIALDEHYDE

Author Institution: Department of Chemistry,, University of Cincinnati,The $^{1}B_{1}\, (n\pi^{*})\leftarrow 1^{1} A_{1}$ electronic band system in the normal isotope of malondialdehyde vapor has been measured and contains approximately 150 vibronic components. Analysis of the prominent vibronic bands leads to identification of $^{1}B_{1}$ state fundamentals of 1297 and $185\, cm^{-1}$. The former frequency is attributed to a totally-symmetric carbonyl stretching vibration; the latter is tentatively assigned to a non-totally-symmetric, in-plane vibration whose potential function is double-welled. This is the first reported instance of the measurement of a highly-structured $\pi^{*} \rightarrow n$ transition in a small organic molecule in which there is an intramolecular hydrogen bond in the vapor phase monomer

THE VIBRATIONAL SPECTRUM OF FLUOROBENZENE

Author Institution: Department of Chemistry, University of CincinnatiThe high resolution infrared spectra of three fluorobenzene isotopes (normal-, pentadeutero-, and paradeutero-) were obtained and interpreted. Using the homology among isotopes as a guide, an accurate determination of most of the fundamental vibrations was made. The $a_{2}$ vibrations were particularly interesting in this respect. The invariance of these vibrations between the normal- and paradeutero- isotopes allowed determination of their values with certainty from their appearance in combination and overtone bands. Other significant results of this work include major reassignments of fundamentals from previously reported values