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Biomedical subjects

Gerald M Rosen

Publications and source records attributed to Gerald M Rosen.

At least 19 recordsLinked to original sources
PubMed2006

Pseudo-PTSD.

Pseudo-posttraumatic stress disorder (pseudo-PTSD) refers to cases in which a patient's presentation is but a simulation of the actual clinical syndrome. The problem of pseudo-PTSD has been neglected by many clinicians and researchers, who often rely on the assumption that a patient's reported symptoms can be accepted as valid. The purpose of this article is to (a) consider the diverse causes of pseudo-PTSD, (b) emphasize the importance of the DSM-IV's guideline to rule out malingering, and (c) discuss the implications that pseudo-PTSD has for research and clinical practice.

Compensation and Redress↗
PubMed2006

Challenges to the PTSD construct and its database: the importance of scientific debate.

A special issue in the Journal of Anxiety Disorders on "Challenges to the PTSD construct and its database" comes at a time when the field of traumatic stress is reexamining itself and scholars are debating the validity of basic assumptions. Some have suggested that scientific debate concerning PTSD can be opposed to the interests of victims and to those who suffer the effects of severe trauma. Yet, scientific methods, and associated critiques, provide the best way to advance our knowledge, so that professionals can provide accurate information, sound advice, and non-harmful interventions to those in need.

Databases as Topic↗
PubMed2006

In vivo spin trapping of nitric oxide from animal tumors.

Spin trapping/electron paramagnetic resonance (EPR) spectroscopy allows specific detection of nitric oxide (NO) generation, in vivo. However, in order to detect an EPR signal in living organism, usually a stimulation of immune system with LPS is used to achieve higher than physiological NO levels. Here, we report non-invasive spin trapping of NO in tumors of non-treated, living animals. EPR spectroscopy was performed at S-band to detect NO in Cloudman S91 melanoma tumors growing in the tail of living, syngeneic hosts-DBA/2 mice. Iron (II) N-(dithiocarboxy)sarcosine Fe2+(DTCS)(2) was used as the spin trap. The results were confirmed by X-band ex vivo study. A characteristic three-line spectrum of NO-Fe(DTCS)(2) (A(N)=13 G) was observed (n=4, out of total n=6) in non-treated tumors and in tumors of animals treated with l-arginine. Substrate availability did not limit the detection of NO by spin trapping. Half-life time of the NO-Fe(DTCS)(2) in tumor tissue was about 60 min. The feasibility of non-invasive spin trapping/EPR spectroscopic detection of NO generated in tumor tissue in living animals, without additional activation of the immune system, was demonstrated for the first time.

Animals↗
PubMed2006

Neuronal nitric oxide synthase-induced S-nitrosylation of H-Ras inhibits calcium ionophore-mediated extracellular-signal-regulated kinase activity.

nNOS (neuronal nitric oxide synthase) is a constitutively expressed enzyme responsible for the production of NO* from L-arginine and O2. NO* acts as both an intra- and an inter-cellular messenger that mediates a variety of signalling pathways. Previous studies from our laboratory have demonstrated that nNOS production of NO* blocks Ca2+-ionophore-induced activation of ERK1/2 (extracellular-signal-regulated kinase 1/2) of the mitogen-activated protein kinases through a mechanism involving Ras G-proteins and Raf-1 kinase. Herein we describe a mechanism by which NO* blocks Ca2+-mediated ERK1/2 activity through direct modification of H-Ras. Ca2+-mediated ERK1/2 activation in NO*-producing cells could be restored by exogenous expression of constitutively active mitogen-activated protein kinase kinase 1. In contrast, exogenous expression of constitutively active mutants of Raf-1 and H-Ras only partially restored ERK1/2 activity, by 50% and 10% respectively. On the basis of these findings, we focused on NO*-mediated mechanisms of H-Ras inhibition. Assays for GTP loading and H-Ras interactions with the Ras-binding domain on Raf-1 demonstrated a decrease in H-Ras activity in the presence of NO*. We demonstrate that S-nitrosylation of H-Ras occurs in nNOS-expressing cells activated with Ca2+ ionophore. Mutation of a putative nitrosylation site at Cys118 inhibited S-nitrosylation and restored ERK1/2 activity by constitutively active H-Ras even in the presence of NO*. These findings indicate that intracellular generation of NO* by nNOS leads to S-nitrosylation of H-Ras, which interferes with Raf-1 activation and propagation of signalling through ERK1/2.

Apoptosis↗
PubMed2006

Acetoxymethoxycarbonyl nitroxides as electron paramagnetic resonance proimaging agents to measure O2 levels in mouse brain: a pharmacokinetic and pharmacodynamic study.

Measurement of O(2) concentration and distribution in brain is essential to understanding the pathophysiology of stroke. Low-frequency electron paramagnetic resonance (EPR) spectroscopy with a paramagnetic probe is an attractive imaging modality that can potentially map O(2) concentration in the brain. In a previous study, we demonstrated that, after intraperitoneal administration of 3-acetoxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (1) to mice, this nitroxide crossed the blood-brain barrier into brain tissue where, after hydrolysis, 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (2) was liberated and entrapped. This pilot study suggested that nitroxide 1 is a proimaging agent that can deliver nitroxide 2 to brain tissue, where O(2) levels can be estimated. In the present study, we conducted a series of pharmacokinetic and pharmacodynamic experiments designed to assess the uptake of structurally disparate nitroxides into brain tissue and retention, after hydrolysis, of the anions of the corresponding nitroxide acids. From these findings, nitroxide 1 and trans-3,4-di(acetoxymethoxycarbonyl)-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl (5) meet the requirement as EPR proimaging agents for mapping O(2) distribution in the brain following stroke.

Animals↗
PubMed2006

Inducible nitric oxide synthase catalyzes ethanol oxidation to alpha-hydroxyethyl radical and acetaldehyde.

The physiologic function of nitric oxide synthases, independent of the isozyme, is well established, metabolizing L-arginine to L-citrulline and nitric oxide (NO). This enzyme can also transfer electrons to O2, affording superoxide (O2*-) and hydrogen peroxide (H2O2). We have demonstrated that NOS1, in the presence of L-arginine, can biotransform ethanol (EtOH) to alpha-hydroxyethyl radical (CH3*CHOH). We now report that a competent NOS2 with l-arginine can, like NOS1, oxidize EtOH to CH3*CHOH. Once this free radical is formed, it is metabolized to acetaldehyde as shown by LC-ESI-MS/MS and HPLC analysis. These observations suggest that NOS2 can behave similarly to cytochrome P-450 in the catalysis of acetaldehyde formation from ethanol via the generation of alpha-hydroxyethyl radical when L-arginine is present.

Acetaldehyde↗
PubMed2006

Use of 3-acetoxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl as an EPR oximetry probe: potential for in vivo measurement of tissue oxygenation in mouse brain.

Measurement of oxygen concentration and distribution in the brain is essential for understanding the pathophysiology of stroke. Low-frequency electron paramagnetic resonance (EPR) spectroscopy with a paramagnetic probe is an attractive imaging modality that potentially can be used to map O(2) concentration in the brain. We examined two nitroxides, 3-methoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl [2] and 3-acetoxymethoxycarbonyl-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl [3], as pro-imaging agents to deliver 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl [1] across the blood-brain barrier (BBB). In primary cultured neurons, nitroxide [3] but not [2] was hydrolyzed by intracellular esterases to [1], which, being anionic at physiologic pH, was well retained intracellularly. In contrast, [2] was not well retained by neurons. In vivo pharmacokinetic and pharmacodynamic studies in mice suggested that esterase-labile nitroxide [3] crossed the BBB, and was converted to [1] and retained. Retention occurred in brain tissue and not in the extensive vasculature, as evidenced by the fact that removal of blood by whole-body saline perfusion did not eliminate the nitroxide EPR signal from the brain. The EPR linewidths of [1] and [3] were more O(2)-sensitive than that of the commonly-used oximetry probe 4-oxo-2,2,6,6-tetramethylpiperidine-d(16)-1-(15)N-oxyl [4]. Moreover, we used [3] in vivo to estimate O(2) concentration in mouse brains. These results indicate that nitroxide [3] could be useful for mapping O(2) distribution in the brain following stroke.

Animals↗
PubMed2006

Importance of nitric oxide synthase in the control of infection by Bacillus anthracis.

The spore-forming, gram-positive bacterium Bacillus anthracis, the causative agent of anthrax, has achieved notoriety due to its use as a bioterror agent. In the environment, B. anthracis exists as a dormant endospore. Upon infection, germination of endospores occurs during their internalization within the phagocyte, and the ability to survive exposure to antibacterial killing mechanisms, such as O2*-, NO*, and H2O2, is a key initial event in the infective process. Macrophages generate NO* from the oxidative metabolism of L-arginine, using an isoform of nitric oxide synthase (NOS 2). Exposure of murine macrophages (RAW264.7 cells) to B. anthracis endospores up-regulated the expression of NOS 2 12 h after exposure, and production of NO* was comparable to that achieved following other bacterial infections. Spore-killing assays demonstrated a NO*-dependent bactericidal response that was significantly decreased in the presence of the NOS 2 inhibitor L-N6-(1-iminoethyl)lysine and in L-arginine-depleted media. Interestingly, we also found that B. anthracis bacilli and endospores exhibited arginase activity, possibly competing with host NOS 2 for its substrate, L-arginine. As macrophage-generated NO* is an important pathway in microbial killing, the ability of endospores of B. anthracis to regulate production of this free radical has important implications in the control of B. anthracis-mediated infection.

Animals↗
PubMed2006

Risk of false positives when identifying malingered profiles using the trauma symptom inventory.

The Trauma Symptom Inventory (TSI; Briere, 1995) is a 100-item self-report measure of posttraumatic symptomatology that includes an Atypical Response (ATR) validity scale designed to differentiate honest from malingered profiles. In this study, using an analogue design to experimentally manipulate honest and malingered responses on the TSI, we found that proposed ATR cut scores produce a significant risk of false positives. Furthermore, the functioning of proposed cut scores worsened when we used posttraumatic stress disorder relevant samples and low estimates of malingering base rates. In light of these findings, the TSI should be used with caution when assessing claims of posttraumatic stress in forensic or disability settings.

Adult↗
PubMed2005

A comparative study of neuronal and inducible nitric oxide synthases: generation of nitric oxide, superoxide, and hydrogen peroxide.

Nitric oxide synthases (NOS) independent of the isozyme, produce nitric oxide (.NO), superoxide (O2.-), and hydrogen peroxide (H2O2). Since .NO has been implicated in many physiological processes, the importance of O2.- and H2O2 in regulating cell signaling by .NO cannot be overlooked. Before addressing these questions, we investigated the production of .NO, O2.-, and H2O2 by purified NOS. NOS 1 and NOS 2 were chosen, as the flux of .NO from each isozyme supports differential biological activity. We found that the initial rate and sustained production of .NO was considerably greater for NOS 2 as compared to NOS 1. In the absence of L-arginine, however, NOS 1 generation of O2.- and H2O2 was found to be substantially greater than that measured for NOS 2. Differences between NOS 1 and NOS 2 production of .NO, O2.-, and H2O2 may define the specific physiologic function of each isozyme.

Hydrogen Peroxide↗
PubMed2005

Is there stereoselectivity in spin trapping superoxide by 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide?

[reaction: see text] Ester-containing nitrones, including 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide 5, have been reported to be robust spin traps for superoxide (O2*-). Using a chiral column, we have been able to isolate the two enantiomers of nitrone 5. With enantiomerically pure nitrone 5a and 5b we explored whether one of these isomers was solely responsible for the EPR spectrum of aminoxyl 6. Data obtained demonstrate that the spin trapping of O2*- by nitrone 5a and nitrone 5b affords the identical EPR spectra and lifetimes in homogeneous aqueous solution and exhibits the same ratio of cis and trans isomers. Quantum chemical modeling in vacuo also finds no difference, aside from the expected optical activity, arising from the difference in stereochemistry.

Cyclic N-Oxides↗
PubMed2005

Role of superoxide in the germination of Bacillus anthracis endospores.

The spore forming Gram-positive bacterium Bacillus anthracis, the causative agent of anthrax, has achieved notoriety due to its use as a bioterror agent. In the environment, B. anthracis exists as a dormant endospore. Germination of endospores during their internalization within the myeloid phagocyte, and the ability of those endospores to survive exposure to antibacterial killing mechanisms such as superoxide (O(2)*-, is a key initial event in the infective process. We report herein that endospores exposed to fluxes of O(2)*- typically found in stimulated phagocytes had no effect on viability. Further endospores of the Sterne strain of B. anthracis were found to scavenge O(2)*-, which may enhance the ability of the bacterium to survive within the hostile environment of the phagolysosome. Most intriguing was the observation that endospore germination was stimulated by a flux of O(2)*- as low as 1 microM/min. Data presented herein suggest that B. anthracis may co-opt O(2)*- which is produced by stimulated myeloid phagocytes and is an essential element of host immunity, as a necessary step in productive infection of the host.

Bacillus anthracis↗
PubMed2005

L-arginine regulates neuronal nitric oxide synthase production of superoxide and hydrogen peroxide.

Tetrahydrobiopterin (H(4)B) in the absence of L-arginine has been shown to be an important factor in promoting the direct formation of hydrogen peroxide (H(2)O(2)) at the expense of superoxide (O(2)(*-)) by neuronal nitric oxide synthase (NOS1) [Rosen GM, Tsai P, Weaver J, Porasuphatana S, Roman LJ, Starkov AA, et al. Role of tetrahydrobiopterin in the regulation of neuronal nitric-oxide synthase-generated superoxide. J Biol Chem 2002;277:40275-80]. Based on these findings, it is hypothesized that L-arginine also shifts the equilibrium between O(2)(*-) and H(2)O(2). Experiments were designed to test this theory. As the concentration of L-arginine and N(omega)-hydroxyl-L-arginine increases, the rate of NADPH consumption for H(4)B-bound NOS1 decreased resulting in lower rates of both O(2)(*-) and H(2)O(2) generation, while increasing the rate of nitric oxide (*NO) production. At saturating concentrations of L-arginine or N(omega)-hydroxyl-L-arginine (50microM), NOS1 still produced O(2)(*-) and H(2)O(2). Both L-arginine and N(omega)-hydroxyl-L-arginine have greater impact on the rate of generation of O(2)(*-) than on H(2)O(2).

Animals↗
PubMed2005

Synthesis and biological testing of aminoxyls designed for long-term retention by living cells.

Owing to recent advances in electron paramagnetic resonance (EPR) imaging methodologies, it is now potentially possible to track and image, in real time in vivo, cells that had been tagged with aminoxyl spin probes. We had previously reported that living cells can accumulate 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxyl [1] to high (millimolar) intracellular concentrations through passive incubation with the corresponding acetoxymethyl (AM) ester [2]. In the present study, we show that under physiological conditions aminoxyl [1] is rapidly extruded by cells through an organic anion transport mechanism, resulting in an intracellular exponential lifetime (t(1/e) or tau) of just 9.84 min at 37 degree C. Through successive rational structural modifications, we arrived at (2,2,5,5-tetramethylpyrrolidin-1-oxyl-3-ylmethyl)amine-N,N-diacetic acid [10], which can still be accumulated by cells to high intracellular concentrations, but which, with an intracellular exponential lifetime of tau]= 114 min, is well retained by cells for long periods of time, where one expects 14% retention even after 5 h. These results suggest that it should be feasible to use EPR imaging to perform in vivo tracking of populations of cells that have accumulated high intracellular levels of aminoxyls.

Electron Spin Resonance Spectroscopy↗
PubMed2005

Spin trapping nitric oxide from neuronal nitric oxide synthase: A look at several iron-dithiocarbamate complexes.

The free radical, nitric oxide ( radicalNO), is responsible for a myriad of physiological functions. The ability to verify and study radicalNO in vivo is required to provide insight into the events taking place upon its generation and in particular the flux of radicalNO at relevant cellular sites. With this in mind, several iron-chelates (Fe2+(L)2) have been developed, which have provided a useful tool for the study and identification of radicalNO through spin-trapping and electron paramagnetic resonance (EPR) spectroscopy. However, the effectiveness of radicalNO detection is dependent on the Fe2+(L)2 complex. The development of more efficient and stable Fe2+(L)2 chelates may help to better understand the role of radicalNO in vivo. In this paper, we present data comparing several proline derived iron-dithiocarbamate complexes with the more commonly used spin traps for radicalNO, Fe2+-di(N-methyl-D-glutamine-dithiocarbamate) (Fe2+(MGD)2) and Fe2+-di(N-(dithiocarboxy)sarcosine) (Fe2+(DTCS)2). We evaluate the apparent rate constant (kapp) for the reaction of radicalNO with these Fe2+(L)2complexes and the stability of the corresponding Fe2+(NO)(L)2 in presence of NOS I.

Cations, Divalent↗
PubMed2004

Superoxide dismutase versus ferricytochrome C: determining rate constants for the spin trapping of superoxide by cyclic nitrones.

Given that spin trapping/electron paramagnetic resonance (EPR) spectroscopy has become the primary technique to identify important biologically generated free radicals, such as superoxide (O(2)(*-)), in vitro and in vivo models, evaluation of the efficiency of specific spin traps to identify this free radical is paramount. Recently, a family of ester-containing nitrones has been prepared, which appears to have distinct advantages for spin trapping O(2)(*-) compared to the well-studied spin traps 5,5-dimethyl-1-pyrroline N-oxide 1 and 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide 2. An important determinant in the selection of a spin trap is the rate constant (k(app)) for its reaction with O(2)(*-), and several different methods have been employed in estimating this k(app). In this paper, the two most frequently used scavengers of O(2)(*-), ferricytochrome c and Cu/Zn-SOD, were evaluated as competitive inhibitors for spin trapping this free radical. Data presented herein demonstrate that SOD is the preferred compound when determining the k(app) for the reaction of O(2)(*-) with spin traps. Using this model, the k(app) for the reaction of nitrone 1, 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide 3, and 5-methoxycarbonyl-5-methyl-1-pyrroline N-oxide 4 with O(2)(*)(-) was estimated to be 24.6 +/- 3.1, 73.0 +/- 12, and 89.4 +/- 1.0 M(-1) s(-1) at pH 7.0, respectively. Several other comparative studies between known spin traps were also undertaken.

Cytochromes c↗
PubMed2004

The effect of divalent cations on neuronal nitric oxide synthase activity.

Neuronal nitric oxide synthase (NOS I) is a Ca(2+)/calmodulin-binding enzyme that generates nitric oxide (NO*) and L-citrulline from the oxidation of L-arginine, and superoxide (O(2)*(-)) from the one-electron reduction of oxygen (O(2)). Nitric oxide in particular has been implicated in many physiological processes, including vasodilator tone, hypertension, and the development and properties of neuronal function. Unlike Ca(2+), which is tightly regulated in the cell, many other divalent cations are unfettered and can compete for the four Ca(2+) binding sites on calmodulin. The results presented in this article survey the effects of various divalent metal ions on NOS I-mediated catalysis. As in the case of Ca(2+), we demonstrate that Ni(2+), Ba(2+), and Mn(2+) can activate NOS I to metabolize L-arginine to L-citrulline and NO*, and afford O(2)*(-) in the absence of L-arginine. In contrast, Cd(2+) did not activate NOS I to produce either NO* or O(2)*(-), and the combination of Ca(2+) and either Cd(2+), Ni(2+), or Mn(2+) inhibited enzyme activity. These interactions may initiate cellular toxicity by negatively affecting NOS I activity through production of NO*, O(2)*(-) and products derived from these free radicals.

Arginine↗