The atmospheric X-ray imaging spectrometer (AXIS) instrument: Quantifying energetic particle precipitation through bremsstrahlung X-ray imaging.

The Atmospheric X-ray Imaging Spectrometer (AXIS) described in this work is a compact, wide field-of-view, hard x-ray imager. The AXIS instrument will fly onboard the Atmospheric Effects of Precipitation through Energetic X-rays (AEPEX) 6U CubeSat mission and will measure bremsstrahlung x-ray photons in the 50-240 keV range with cadmium-zinc-telluride (CZT) detectors using coded aperture optics. AXIS will measure photons generated by energetic particle precipitation for the purpose of determining the spatial scales of precipitation and estimating electron precipitation characteristics. This paper describes the design and testing of the AXIS instrument, including a summary of simulations performed that motivate the shielding, optics, and mechanical design. Testing and characterization is reported that validates the instrument design and shows that the instrument design meets or exceeds the measurement requirements necessary for AEPEX mission success.

Active Precipitation of Radiation Belt Electrons Using Rocket Exhaust Driven Amplification (REDA) of Man-Made Whistlers.

Ground-based very low frequency (VLF) transmitters located around the world generate signals that leak through the bottom side of the ionosphere in the form of whistler mode waves. Wave and particle measurements on satellites have observed that these man-made VLF waves can be strong enough to scatter trapped energetic electrons into low pitch angle orbits, causing loss by absorption in the lower atmosphere. This precipitation loss process is greatly enhanced by intentional amplification of the whistler waves using a newly discovered process called rocket exhaust driven amplification (REDA). Satellite measurements of REDA have shown between 30 and 50 dB intensification of VLF waves in space using a 60 s burn of the 150 g/s thruster on the Cygnus satellite that services the International Space Station. This controlled amplification process is adequate to deplete the energetic particle population on the affected field lines in a few minutes rather than the multi-day period it would take naturally. Numerical simulations of the pitch angle diffusion for radiation belt particles use the UCLA quasi-linear Fokker Planck model to assess the impact of REDA on radiation belt remediation of newly injected energetic electrons. The simulated precipitation fluxes of energetic electrons are applied to models of D-region electron density and bremsstrahlung X-rays for predictions of the modified environment that can be observed with satellite and ground-based sensors.

A summary of the BARREL campaigns: Technique for studying electron precipitation.

BARREL observed electron precipitation over wide range of energy and timescalesPrecipitating electron distribution is determined using spectroscopy for 19 January 2013 eventBARREL timing data has accuracy within sampling interval of 0.05 s.

Long-term instrumental parameter investigation of a Fabry-Perot spectrometer at an isolated field station.

To insure that long-term determinations of Doppler width and shift--derived from observations of atmospheric emissions--are internally consistent and reliable, we have developed a method to both continuously and nonintrusively determine and monitor the instrumental constants of the Fabry-Perot spectrometer making the observations. We have used this method at our isolated field experiment at South Pole, Antarctica, because the instrument is only accessible to us for a few days every year. Here we report both the method and the Fabry-Perot stability results for the past 22 years of operation. The method involves the description of real Fabry-Perot instrumental constants as a small departure from those of an ideal Fabry-Perot. In general, this model is applicable for most observations. However, experimentally, there are times when the small-departure model is not applicable, thus indicating how to best reduce the observations into physical quantities for the utmost consistency in the geophysical results.

rf improvements for Spallation Neutron Source H- ion source.

The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering approximately 38 mA H(-) beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.

Health care reform: analysis of narrative responses from directors of pastoral care departments.

This paper is a narrative analysis of comments written by hospital pastoral care department directors in response to the questionnaire item that asked them to write about their experience with health care reform and to make suggestions as to what the profession could do about it. Three central themes included: (1) the importance of and need for administrative support of the department, (2) the importance of departmental visibility within the institution, and (3) the challenges of embracing change. Two secondary themes were the admonishing of peer department directors concerning inadequate performance and the ministry to hospital staff during reform efforts.

Active and passive immunity against Borrelia burgdorferi decorin binding protein A (DbpA) protects against infection.

Borrelia burgdorferi, the spirochete that causes Lyme disease, binds decorin, a collagen-associated extracellular matrix proteoglycan found in the skin (the site of entry for the spirochete) and in many other tissues. Two borrelial adhesins that recognize this proteoglycan, decorin binding proteins A and B (DbpA and DbpB, respectively), have recently been identified. Infection of mice by low-dose B. burgdorferi challenge elicited antibodies against DbpA and DbpB that were sustained at high levels, suggesting that these antigens are expressed in vivo. Scanning immunoelectron microscopy showed that DbpA was surface accessible on intact borreliae. Passive administration of DbpA antiserum protected mice from infection following challenge with heterologous B. burgdorferi sensu stricto isolates, even when serum administration was delayed for up to 4 days after challenge. DbpA is the first antigen target identified that is capable of mediating immune resolution of early, localized B. burgdorferi infections. DbpA immunization also protected mice from B. burgdorferi challenge; DbpB immunization was much less effective. DbpA antiserum inhibited in vitro growth of many B. burgdorferi sensu lato isolates of diverse geographic, phylogenetic, and clinical origins. In combination, these findings support a role for DbpA in the immunoprophylaxis of Lyme disease and suggest that DbpA vaccines have the potential to eliminate early-stage B. burgdorferi infections.

Quantitative disassembly and reassembly of human papillomavirus type 11 viruslike particles in vitro.

The human papillomavirus (HPV) capsid is primarily composed of a structural protein denoted L1, which forms both pentameric capsomeres and capsids composed of 72 capsomeres. The L1 protein alone is capable of self-assembly in vivo into capsidlike structures referred to as viruslike particles (VLPs). We have determined conditions for the quantitative disassembly of purified HPV-11 L1 VLPs to the level of capsomeres, demonstrating that disulfide bonds alone are essential to maintaining long-term HPV-11 L1 VLP structure at physiological ionic strength. The ionic strength of the disassembly reaction was also important, as increased NaCl concentrations inhibited disassembly. Conversely, chelation of cations had no effect on disassembly. Quantitative reassembly to a homogeneous population of 55-nm, 150S VLPs was reliably achieved by the re-formation of disulfide linkages following removal of reducing agent at near-neutral pH and moderate NaCl concentration. HPV-11 L1 VLPs could also be dissociated by treatment with carbonate buffer at pH 9.6, but VLPs could not be regenerated following carbonate treatment. When probed with conformationally sensitive and/or neutralizing monoclonal antibodies, both capsomeres generated by disulfide reduction of purified VLPs and reassembled VLPs formed from capsomeres upon removal of reducing agents exhibited epitopes found on the surface of authentic HPV-11 virions. Antisera raised against either purified VLP starting material or reassembled VLPs similarly neutralized infectious HPV-11 virions. The ability to disassemble and reassemble VLPs in vitro and in bulk allows basic features of capsid assembly to be studied and also opens the possibility of packaging selected exogenous compounds within the reassembled VLPs.

Effects of the androgenic/anabolic steroid stanozolol on GABAA receptor function: GABA-stimulated 36Cl- influx and [35S] TBPS binding.

We have recently demonstrated that androgenic/anabolic steroids modulate in vitro ligand binding to the benzodiazepine binding site(s) associated with the gamma-aminobutyric acidA (GABAA) receptor complex (Masonis and McCarthy, 1995). One androgenic/anabolic steroid in particular, stanozolol, appears to stabilize the GABAA receptor in a moderate-affinity state for benzodiazepine binding. In the present study, we demonstrate the effects of stanozolol on the functional responsiveness of the GABAA receptor. After pre-incubation with stanozolol, we observed a decrease in the Emax and EC50 values for GABA-stimulated 36Cl- influx into cortical synaptoneurosomes. Moreover, in the presence of stanozolol, flunitrazepam-enhanced GABA-stimulated 36Cl- influx was lost, and the GABAA receptor was stabilized in a functional state that was resistant to further desensitization by agonist. Stanozolol does not appear to reduce GABA-stimulated 36Cl- influx by acting as a channel blocker at the well-characterized channel blocker binding site, as illustrated by the GABA-sensitive biphasic effects of stanozolol on [35S] t-butylbicyclophosphorothionate binding. These results demonstrate a novel, nongenomic mechanism for androgenic/anabolic steroidal modulation of CNS function.

Direct interactions of androgenic/anabolic steroids with the peripheral benzodiazepine receptor in rat brain: implications for the psychological and physiological manifestations of androgenic/anabolic steroid abuse.

The peripheral benzodiazepine receptor (PBR) is a mitochondrial protein involved in regulating steroid synthesis and transport. We report here the effects of androgenic/anabolic steroids (AAS) on the binding of the PBR-specific ligand [3H] PK11195 to male rat brain cortical synaptoneurosomes. Two synthetic AAS, stanozolol and 17beta-testosterone cypionate (17beta-cyp), significantly inhibited 1 nM [3H] PK11195 binding at concentrations greater than 5 and 25 microM, respectively. Stanozolol was the most effective inhibitor, reducing [3H] PK11195 binding by up to 75%, compared to only 40% inhibition by 17beta-cyp, at 50 microM AAS concentration. Two other AAS, 17alpha-methyltestosterone and nortestosterone decanoate, were incapable of inhibiting [3H] PK11195 binding at concentrations up to 50 microM. On the basis of Scatchard/Rosenthal analysis, [3H] PK11195 binds to two classes of binding sites, and the inhibition of [3H] PK11195 binding by stanozolol appears to be allosteric, primarily reducing binding to the higher affinity [3H] PK11195 binding site. These results, in combination with earlier studies indicating the direct effects of AAS on the function of additional central nervous system receptor complexes, suggest that the behavioral and psychological effects of AAS result from the interactions of AAS with multiple regulatory systems in the brain.

Snake venom toxins, unlike smaller antagonists, appear to stabilize a resting state conformation of the nicotinic acetylcholine receptor.

Previous studies have shown that the pattern and degree of 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine ([125I]TID) photoincorporation into the nicotinic acetylcholine receptor (nAChR) can be used as a sensitive measure of nAChR conformation. Upon desensitization by prolonged exposure to agonists, certain drugs and detergents, or reconstitution into desensitizing lipids, the levels of [125I]TID incorporation into the subunits of the nAChR are dramatically reduced. In this study, we characterized the effects of the snake venom proteins alpha-bungarotoxin and alpha-cobrotoxin, as well as the smaller antagonists tubocurarine and gallamine, on [125I]TID incorporation into the subunits of both partially-purified nAChR in native lipids, or affinity-purified nAChR reconstituted into different combinations of lipids. Unlike all other compounds previously tested, alpha-bungarotoxin and alpha-cobrotoxin reproducibly increased the level of [125I]TID incorporation into all four subunits of nAChR reconstituted into dioleoylphosphatidylcholine, dioleoylphosphatidic acid and cholesterol. Gallamine had little or no effect on [125I]TID incorporation at any concentration tested (0.1 microM-5 mM). Tubocurarine had no effect on [125I]TID incorporation at low concentrations, but at higher concentrations reduced the level of [125I]TID labeling. The snake venom proteins may shift the population of nAChR, which exists as a mixture of resting state and desensitized conformations, entirely to the resting state. However, the binding of the snake venom toxins does not appear sufficient to induce the resting state conformation in nAChR which have been desensitized by other means, such as solubilization in desensitizing detergents or reconstitution in densitizing lipids.

Direct effects of the anabolic/androgenic steroids, stanozolol and 17 alpha-methyltestosterone, on benzodiazepine binding to the. gamma-aminobutyric acid(a) receptor.

Various exogenous and endogenous steroids have been demonstrated to have both enhancing and inhibiting effects on ligand binding to the gamma-aminobutyric acid(A) receptor (GABAA receptor) in previous studies. In the present study we have explored the possibility that an additional class of synthetic steroidal compounds, anabolic/androgenic steroids (AAS), mediate some of their CNS effects through direct interaction with the GABAa receptor. At micromolar concentrations, two AAS, stanozolol and 17 alpha-methyltestosterone (17 alpha-MT), significantly inhibited 1 nM [3H]flunitrazepam ([3H]Fln) binding to rat brain cerebrocortical membranes. Inhibition of 1 nM [3H]Fln binding by stanozolol was similar for both males and females (approximately 50% inhibition at 50 microM stanozolol). 17 alpha-MT was much less efficacious, but did significantly inhibit 1 nM [3H]Fln binding at concentrations > 10 microM. In equilibrium binding assays, stanozolol (50 microM) raised the apparent KD for [3H]Fln binding. The observed changes in the [3H]Fln binding curve, when analyzed by Rosenthal analysis, reveal complex equilibrium binding behavior. In females, the Rosenthal plot was best fit by a two site binding model. Stanozolol (50 microM) inhibited binding to the higher affinity site in a manner consistent with competitive inhibition, increasing the KD without changing the BMAX. However, the effect of stanozolol on the binding to the low affinity site was more complex, with an increase in the the KD and the BMAX. In males the data were best fit by a single binding site model. This single site exhibited a slight increase in the KD and a decrease in the BMAX in the presence of 50 microM stanozolol.(ABSTRACT TRUNCATED AT 250 WORDS)

Secondary structure of the nicotinic acetylcholine receptor: implications for structural models of a ligand-gated ion channel.

The secondary structure and effects of two ligands, carbamylcholine and tetracaine, on the secondary structure of affinity-purified nicotinic acetylcholine receptor (nAChR) from Torpedo has been studied using Fourier transform infrared spectroscopy (FTIR). FTIR spectra of the nAChR were acquired in both 1H2O and 2H2O buffer and exhibit spectral features indicative of a substantial alpha-helical content with lesser amounts of beta-sheet and random coil structures. The resolution enhancement techniques of Fourier self-deconvolution and Fourier derivation reveal seven component bands contributing to both the amide I band and amide I' band contours in 1H2O and 2H2O, respectively. Curve-fitting estimates of the nAChR secondary structure are consistent with the qualitative analysis of the FTIR spectra as follows: 39% alpha-helix, 35% beta-sheet, 6% turn, and 20% random coil. Of particular interest is the estimated alpha-helical content as this value places restrictions on models of the nAChR transmembrane topology and on the types of secondary structures that may contribute to functional domains, such as the ligand-binding site. The estimated alpha-helical content is sufficient to account for four transmembrane alpha-helices in each nAChR subunit as well as a substantial portion of the extracellular and/or the cytoplasmic domains. FTIR spectra were also acquired in the presence and absence of 1 mM carbamylcholine and 5 mM tetracaine to examine the effects of ligand binding on the secondary structure of the nAChR. The similarity of the spectra, even after spectral deconvolution, indicates that the secondary structure of the nAChR is essentially unaffected by desensitization.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of drugs on the incorporation of a conformationally-sensitive, hydrophobic probe into the ion channel of the nicotinic acetylcholine receptor.

The pattern of incorporation of the hydrophobic photolabel 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine([125I]TID) into the nicotinic acetylcholine receptor (AChR) is a sensitive measure of AChR conformation (resting state or desensitized). We determined the ability of tetracaine, dibucaine, procaine, lidocaine, chlorpromazine or phencyclidine to inhibit [125I]TID photolabeling of the AChR as a function of drug concentration, both as a measure of the ability of these drugs to desensitize the AChR, and to characterize the [125I]TID binding site. To localize the site(s) of drug action, experiments were performed in the absence and presence of saturating concentrations of alpha-bungarotoxin (BgTx), to block drug binding to the agonist binding site. On the basis of the concentration dependence of their effects, which was not altered by the presence of BgTx, tetracaine and dibucaine appeared to block [125I]TID incorporation competitively, suggesting that the high-affinity [125I]TID binding site is the non-competitive blocker binding site presumed to exist in the interior of the AChR ion channel. Procaine, chlorpromazine, lidocaine and phencyclidine blocked [125I]TID incorporation at lower concentrations in the absence of BgTx than in its presence, suggesting that these drugs block incorporation by inducing desensitization when bound to their high-affinity non-competitive blocker binding sites and that BgTx countered the drug effect by allosterically stabilizing the resting state.

Laryngeal response to passively induced hypocapnia during NREM sleep in normal adult humans.

Passively induced hypocapnia in animals activates vocal cord adductor muscles and decreases the glottic aperture. The purpose of this study was to determine if passively induced hypocapnia has similar effects in normal adult humans in stage 3/4 non-rapid-eye-movement (NREM) sleep. Hypocapnia was induced by hyperventilating the subjects with a positive-pressure ventilator via a nose mask. At hypocapnic levels below the CO2 apneic threshold, abrupt cessation of mechanical ventilation was followed by an apnea. In protocol 1, intramuscular electromyographic recordings of intrinsic laryngeal muscles were obtained in nine subjects. Activity of the posterior cricoarytenoid muscle, a vocal cord abductor, disappeared during passive hyperventilation. The muscle remained electrically silent during an apnea, but phasic inspiratory activity reappeared with the first respiratory effort. The thyroarytenoid and arytenoideus muscles, both vocal cord adductors, were electrically silent during spontaneous breathing in NREM sleep. Hypocapnia was frequently associated with activation of both adductor muscles. Once activated, the adductor muscles remained tonically active during an ensuring apnea. In protocol 2, a fiber-optic scope was advanced transnasally into the hypopharynx to determine glottic aperture size during passively induced hypocapnic apnea. In the seven subjects who achieved stable NREM sleep, the glottic aperture during an apnea was smaller than at any time throughout the respiratory cycle during spontaneous breathing just before positive-pressure ventilation. The results suggest that the decrease in glottic aperture observed during an induced hypocapnic apnea is due to suppression of the posterior cricoarytenoid muscle and/or activation of vocal cord adductor muscles.

A teflon granuloma presenting as an endotracheal nodule.

A 55-year-old woman underwent bronchoscopic evaluation for hemoptysis. A small polypoid endotracheal nodule was discovered approximately 2.0 cm distal to the left true vocal cord. The lesion was sampled with a cytologic brush. Epithelioid histiocytes and numerous giant cells with asteroid bodies were seen, and there was abundant intracellular refractile material of irregular shape. Review of the medical history revealed that the patient had undergone Teflon injection of a paralyzed left true vocal cord. A diagnosis of Teflon granuloma was made.

Osteitis pubis as a complication of transrectal needle biopsy of the prostate.

We report a case of osteitis pubis complicating transrectal needle biopsy of the prostate. This case best supports direct trauma to the symphysis pubis as an etiology. A literature review of osteitis pubis is presented.

Effects of lipids and detergents on the conformation of the nicotinic acetylcholine receptor from Torpedo californica.

The hydrophobic, photoreactive probe 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)diazirine ([125I]TID) was used to characterize the effects of lipids and detergents on acetylcholine receptor (AChR) conformation. Affinity purified AChR reconstituted into dioleoylphosphatidylcholine (DOPC), dioleoylphosphatidic acid (DOPA), and cholesterol showed the same pattern of [125I]TID-labeling and demonstrated the same reduction in labeling of all four subunits upon desensitization by the agonist carbamylcholine, as partially purified AChR in native lipids. On the basis of the patterns of [125I]TID incorporation, reconstitution into DOPC/DOPA also appeared to stabilize the resting (functional) conformation of the AChR, while reconstitution in DOPC/cholesterol or DOPC alone largely desensitized the AChR. The effects of lipids on the functional state of the AChR was determined independently by measuring the ability of AChR reconstituted into different lipid combinations to undergo the change in affinity for agonist diagnostic of desensitization. The dramatic reduction in the apparent levels of [125I]TID associated with the subunits of the AChR observed upon agonist-induced desensitization was shown not to be due to a change in affinity for tightly bound lipid. Solubilization of affinity purified AChR reconstituted into DOPC/DOPA/cholesterol by the non-ionic detergents octyl glucoside, Triton X-100, and Tween 20 (final detergent concentration = 1%) was shown to produce the same pattern of [125I]TID-labeling as desensitization by agonist, while solubilization in 1% sodium cholate appeared to stabilize a conformation of the AChR more similar to the resting state.

Probing conformational changes in the nicotinic acetylcholine receptor by Fourier transform infrared difference spectroscopy.

We have developed a Fourier transform infrared (FTIR) difference method for probing conformational changes that occur upon the binding of ligands to the nicotinic acetylcholine receptor (nAChR). Our approach is to deposit reconstituted nAChR membranes in a thin film on the surface of a germanium internal reflection element, acquire FTIR spectra in the presence of bulk aqueous solution using attenuated total reflection, and then trigger conformational changes by sequentially flowing a buffer either with or without an agonist past the film surface. Using the fluorescent probe, ethidium bromide, it is demonstrated that the method of nAChR film deposition does not affect the ability of the receptor to undergo the resting-to-desensitized state transition. The difference of FTIR spectra of nAChR films recorded in the presence and absence of agonists reveal highly reproducible infrared bands that are not observed in the difference of spectra recorded with only buffer flowing past the film surface. Some of the bands are assigned to changes in protein secondary structure and to changes in the structure of individual amino acid residues. Bands arising from the vibrations of the agonist bound to the receptor are also observed. The results demonstrate that FTIR difference spectroscopy can detect structural changes in the nAChR that occur upon the binding of ligands. The technique will be an effective method for investigating nAChR structure and function as well as receptor-drug interactions.