D. Fischer

Serotonin protects mouse liver from cholestatic injury by decreasing bile salt pool after bile duct ligation

Obstructive cholestasis induces liver injury, postoperative complications, and mortality after surgery. Adaptive control of cholestasis, including bile salt homeostasis, is necessary for recovery and survival. Peripheral serotonin is a cytoprotective neurotransmitter also associated with liver regeneration. The effect of serotonin on cholestatic liver injury is not known. Therefore, we tested whether serotonin affects the severity of cholestatic liver injury. We induced cholestasis by ligation of the bile duct (BDL) in either wild‐type (WT) mice or mice lacking peripheral serotonin (Tph1−/− and immune thrombocytopenic [ITP] mice). Liver injury was assessed by the levels of plasma aspartate aminotransferase (AST), alanine aminotransferase (ALT) and tissue necrosis. Bile salt–regulating genes were measured by quantitative polymerase chain reaction and confirmed by western blotting and immunohistochemistry. Tph1−/− mice displayed higher levels of plasma AST, ALT, bile salts, and hepatic necrosis after 3 days of BDL than WT mice. Likewise, liver injury was disproportional in ITP mice. Moreover, severe cholestatic complications and mortality after prolonged BDL were increased in Tph1−/− mice. Despite the elevation in toxic bile salts, expression of genes involved in bile salt homeostasis and detoxification were not affected in Tph1−/− livers. In contrast, the bile salt reabsorption transporters Ostα and Ostβ were up‐regulated in the kidneys of Tph1−/− mice, along with a decrease in urinary bile salt excretion. Serotonin reloading of Tph1−/− mice reversed this phenotype, resulting in a reduction of circulating bile salts and liver injury. Conclusion: We propose a physiological function of serotonin is to ameliorate liver injury and stabilize the bile salt pool through adaptation of renal transporters in cholestasis. (HEPATOLOGY 2012;56:209–218)

Wavefront calibration testing of the James Webb Space Telescope primary mirror center of curvature optical assembly

The James Webb Space Telescope (JWST) Optical Telescope Element (OTE) consists of a 6.6 meter clear aperture, all-reflective, three-mirror anastigmat. The 18-segment primary mirror (PM) presents unique and challenging assembly, integration, alignment and testing requirements. A full aperture center of curvature optical test is performed in cryogenic vacuum conditions at the integrated observatory level to verify PM performance requirements. Two wavefront calibration tests are utilized to verify the low and mid/high spatial frequency performance of the test system. In this paper the methods and results of the wavefront calibration tests are presented.

Single-molecule DNA hybridisation studied by using a modified DNA sequencer: a comparison with surface plasmon resonance data

Current methods for the determination of molecular interactions are widely used in the analytical sciences. To identify new methods, we investigated as a model system the hybridisation of a short 7 nt oligonucleotide labelled with, structurally, very similar cyanine dyes CY3 and DY-547, respectively, to a 34 nt oligonucleotide probe immobilised in a zero-mode waveguide (ZMW) nanostructure. Using a modified commercial off-the-shelf DNA sequencer, we established the principles to measure biomolecular interactions at the single-molecule level. Kinetic data were obtained from trains of fluorescence pulses, allowing the calculation of association and dissociation rate constants (k on, k off). For the 7mer labelled with the positively charged CY3 dye, k on and k off are ~3 larger and ~2 times smaller, respectively, compared with the oligonucleotide labelled with negatively charged DY-547 dye. The effect of neighbouring molecules lacking the 7nt binding sequence on single-molecule rate constants is small. The association rate constants is reduced by only 20–35%. Hybrid dissociation is not affected, since as a consequence of the experimental design, rebinding cannot take place. Results of single-molecule experiments were compared with data obtained from surface plasmon resonance (SPR) performed under comparable conditions. A good correlation for the association rate constants within a factor of 1.5 was found. Dissociation rate constants are smaller by a factor of 2–3 which we interpreted as a result of rebinding to neighbouring probes. Results of SPR measurements tend to systematically underestimate dissociation rate constants. The amount of this deviation depends on the association rate constant and the surface probe density. As a consequence, it is recommended to work at low probe densities to keep this effect small.

Primary mirror segment assembly integration and alignment for the James Webb Space Telescope

The Optical Telescope Element (OTE) consists of a 6.6 m, all-reflective, three-mirror anastigmat. The 18-segment primary mirror (PM) presents unique and challenging assembly, integration and alignment verification requirements. Each mirror segment is mechanically integrated with the Primary Mirror Backplane Support Structure (PMBSS) using compound angle shims to compensate for global alignment and local co-planarity errors. The processes used to determine the mechanical shim prescription, primary mirror alignment and integration, and placement verification are discussed. In an effort to reduce process uncertainty and program risk, the JWST program recently conducted a PMSA Integration Demonstration at ITT. Through this activity, full scale demonstrations of the Ground Support Equipment (GSE) and critical integration processes were successfully completed. The results of these demonstrations indicate that the equipment, processes, and procedures developed by ITT meet the critical requirements for PMSA placement.

James Webb Space Telescope Primary Mirror Integration: Testing the Multiwavelength Interferometer on the Test Bed Telescope

The James Webb Space Telescope (JWST) integration includes a center of curvature test on its 18 primary mirror segment assemblies (PMSAs). This important test is the only ground test that will demonstrate the ability to align all 18 PMSAs. Using a multi-wavelength interferometer (MWIF) integrated to the test bed telescope (TBT), a one-sixth scale model of the JWST, we verify our ability to align and phase the 18 PMSAs. In this paper we will discuss data analysis and test results when using the MWIF to align the segments of the TBT in preparation for alignment of the JWST.

Current status of the TPF formation flying interferometer concept

This paper describes the current status of the technical program aiming to demonstrate the viability of a formation-flying mid-infrared nulling interferometer architecture for the Terrestrial Planet Finder (TPF) program. Until recently the TPF project was considering four architectures, with the goal of selecting one in the 2006 timeframe. In April 2004, the project office opted instead to follow a path leading to a small (4x6m) visible-light coronagraph, to launch around 2014, and a formation-flying interferometer (FFI), to launch before 2020. The FFI is proposed to satisfy the full TPF science goal to completely survey 150 stars for evidence of terrestrial planets similar to Earth, while the coronagraph will perform a survey of 30-50 stars at visible wavelength. FFI trade studies conducted since mid-2003 have focused on key factors driving overall flight segment mass and performance, including launch vehicle packaging, deployment approach, thermal design (particularly the thermal shield configuration), structural design, and formation flying approach. This paper summarizes the results of the recent design trades, with discussion of the primary requirements that drive the baseline design concept. Analyses supporting the baseline design are summarized, and areas for future study are discussed.

Single molecule interactions studied by using a modified DNA sequencer: a comparison with surface plasmon resonance

In this study we established the principles for using a commercial off-the-shelf DNA sequencer (RS, Pacific Biosciences) to measure biomolecular interactions. Binding between single oligonucleotides immobilized at the bottom of a nanowell to a complementary DNA strand was used as a model system. The influence of the labeling dye on the hybridization of a 7mer oligonucleotide was investigated. The resulting association and dissociation rate constants (kon and koff) and the calculated dissociation constants (Kd) were compared to data obtained from surface plasmon resonance (SPR) measurements. In the present study we identified a good agreement of the determined kinetic constants by the two methods investigated.

Design concepts for the EST mount

The EST has unique an optical layout, with an on-axis Gregorian tube system and the altitude axis behind the M1 mirror unit - a great challenge for the mount designer in regard of balancing. Three different structural design concepts and various alternatives for the bearing and drive systems were investigated. Hydrostatic bearings with direct drives are compared with roller bearings and geared drives. The influence of available bearing and drive technology were investigated by FE calculations, dynamic analysis and end-to-end simulations. The finally recommended design concept is based on large-diameter segmented roller bearings and so-called pinion motors in both axes.

In-process testing for cryo-figuring 1.5 meter diameter auto-collimating flats

Three auto-collimating flats (ACFs) of 1.5 meter clear aperture are being manufactured for use in the JSC Cryo-Optical Metrology test of the James Webb Space Telescope. In-process interferometric testing of the ACFs is used to guide their surface-figure processing. The surface measurement is performed in a vacuum chamber at both room (+20 °C) and cryogenic (-240 °C) temperatures. With a 12-inch beam diameter FizCam interferometer, sub-aperture measurements are taken across the ACF diameter at multiple rotations. These measurements are stitched together to compute the surface figure. The figure change between room-temperature and cryogenic temperature is measured and used to enable cryo-figuring based on room-temperature measurements. The data analysis is calibrated to account for gravity sag on test-set optics and surface aberrations caused by vacuum pressure and temperature gradients on vacuum-chamber windows. The first ACF is complete and meets specification with surface error of less than 75 nm RMS.