Decreased brain PME/PDE ratio in bipolar disorder: a preliminary (31) P magnetic resonance spectroscopy study.

OBJECTIVES: The aim of the present study was to measure brain phosphorus-31 magnetic resonance spectroscopy ((31) P MRS) metabolite levels and the creatine kinase reaction forward rate constant (kf ) in subjects with bipolar disorder (BD). METHODS: Subjects with bipolar euthymia (n = 14) or depression (n = 11) were recruited. Healthy comparison subjects (HC) (n = 23) were recruited and matched to subjects with BD on age, gender, and educational level. All studies were performed on a 3-Tesla clinical magnetic resonance imaging system using a (31) P/(1) H double-tuned volume head coil. (31) P spectra were acquired without (1) H-decoupling using magnetization-transfer image-selected in vivo spectroscopy. Metabolite ratios from a brain region that includes the frontal lobe, corpus callosum, thalamus, and occipital lobe are expressed as a percentage of the total phosphorus (TP) signal. Brain pH was also investigated. RESULTS: Beta-nucleoside-triphosphate (ß-NTP/TP) in subjects with bipolar depression was positively correlated with kf (p = 0.039, r(2) = 0.39); similar correlations were not observed in bipolar euthymia or HC. In addition, no differences in kf and brain pH were observed among the three diagnostic groups. A decrease in the ratio of phosphomonoesters to phosphodiesters (PME/PDE) was observed in subjects with bipolar depression relative to HC (p = 0.032). We also observed a trend toward an inverse correlation in bipolar depression characterized by decreased phosphocreatine and increased depression severity. CONCLUSIONS: In our sample, kf was not altered in the euthymic or depressed mood state in BD. However, decreased PME/PDE in subjects with bipolar depression was consistent with differences in membrane turnover. These data provide preliminary support for alterations in phospholipid metabolism and mitochondrial function in bipolar depression.

Red Phosphorus: An Earth-Abundant Elemental Photocatalyst for "Green" Bacterial Inactivation under Visible Light.

Earth-abundant red phosphorus was found to exhibit remarkable efficiency to inactivate Escherichia coli K-12 under the full spectrum of visible light and even sunlight. The reactive oxygen species (•OH, •O2(-), H2O2), which were measured and identified to derive mainly from photogenerated electrons in the conduction band using fluorescent probes and scavengers, collectively contributed to the good performance of red phosphorus. Especially, the inactivated-membrane function enzymes were found to be associated with great loss of respiratory and ATP synthesis activity, the kinetics of which paralleled cell death and occurred much earlier than those of cytoplasmic proteins and chromosomal DNA. This indicated that the cell membrane was a vital first target for reactive oxygen species oxidation. The increased permeability of the cell membrane consequently accelerated intracellular protein carboxylation and DNA degradation to cause definite bacterial death. Microscopic analyses further confirmed the cell destruction process starting with the cell envelope and extending to the intracellular components. The red phosphorus still maintained good performance even after recycling through five reaction cycles. This work offers new insight into the exploration and use of an elemental photocatalyst for "green" environmental applications.

Advanced MR methods at ultra-high field (7 Tesla) for clinical musculoskeletal applications.

OBJECTIVES: This article provides an overview of the initial clinical results of musculoskeletal studies performed at 7 Tesla, with special focus on sodium imaging, new techniques such as chemical exchange saturation transfer (CEST) and T2* imaging, and multinuclear MR spectroscopy. METHODS: Sodium imaging was clinically used at 7 T in the evaluation of patients after cartilage repair procedures because it enables the GAG content to be monitored over time. Sodium imaging and T2* mapping allow insights into the ultra-structural composition of the Achilles tendon and help detect early disease. Chemical exchange saturation transfer was, for the first time, successfully applied in the clinical set-up at 7 T in patients after cartilage repair surgery. The potential of phosphorus MR spectroscopy in muscle was demonstrated in a comparison study between 3 and 7 T, with higher spectral resolution and significantly shorter data acquisition times at 7 T. RESULTS: These initial clinical studies demonstrate the potential of ultra-high field MR at 7 T, with the advantage of significantly improved sensitivity for other nuclei, such as (23)Na (sodium) and (31)P (phosphorus). CONCLUSIONS: The application of non-proton imaging and spectroscopy provides new insights into normal and abnormal physiology of musculoskeletal tissues, particularly cartilage, tendons, and muscles. KEY POINTS : • 7 T magnetic resonance provides significantly improved sensitivity for ( 23 ) Na and ( 31 ) P. • Initial clinical studies have now demonstrated ultra-high field MR operating at 7 T. • 7 T provides new insights into normal and abnormal physiology of musculoskeletal tissues.

Detection of ATP by "in line" 31P magnetic resonance spectroscopy during oxygenated hypothermic pulsatile perfusion of pigs' kidneys.

OBJECT: To demonstrate that adenosine triphosphate (ATP), which provides a valuable biomarker for kidney viability in the context of donation after cardiac death (DCD) transplantation, can be detected by means of (31)P magnetic resonance spectroscopy (MRS) if kidneys are perfused with oxygenated hypothermic pulsatile perfusion (O(2)+HPP). MATERIALS AND METHODS: Porcine kidney perfusion was carried out using a home made, MR-compatible HPP-machine. Consequently, kidney perfusion could be performed continuously during magnetic resonance imaging and magnetic resonance spectroscopy recording. (31)P MR spectroscopy consisted of 3-dimensional chemical shift imaging (CSI), which allowed for the detection of ATP level in line. (31)P CSI was performed at 3 tesla in 44 min with a nominal voxel size of 6.1 cc. RESULTS: (31)P CSI enabled the detection of renal ATP when pO(2) was equal to 100 kPa. With pO(2) of 20 kPa, only phosphomonoester, inorganic phosphate and nicotinamide adenine dinucleotide could be found. Semi-quantitative analysis showed that ATP level was 1.3 mM in normal kidney perfused with pO(2) of 100 kPa. CONCLUSIONS: This combined technology may constitute a new advance in DCD organ diagnostics prior to transplantation, as it allows direct assessment of ATP concentration, which provides a reliable indicator for organ bioenergetics and viability. In this study, kidneys presenting no warm ischemia were tested in order to establish values in normal organs. The test could be easily integrated into the clinical environment and would not generate any additional delay into the transplantation clinical workflow.

Measurement of human skeletal muscle oxidative capacity by 31P-MR spectroscopy: a cross-validation with in vitro measurements.

PURPOSE: To cross-validate skeletal muscle oxidative capacity measured by (31)P-MR spectroscopy with in vitro measurements of oxidative capacity in mitochondria isolated from muscle biopsies of the same muscle group in 18 healthy adults. MATERIALS AND METHODS: Oxidative capacity in vivo was determined from PCr recovery kinetics following a 30-s maximal isometric knee extension. State 3 respiration was measured in isolated mitochondria using high-resolution respirometry. A second cohort of 10 individuals underwent two (31)P-MRS testing sessions to assess the test-retest reproducibility of the method. RESULTS: Overall, the in vivo and in vitro methods were well-correlated (r = 0.66-0.72) and showed good agreement by Bland Altman plots. Excellent reproducibility was observed for the PCr recovery rate constant (CV = 4.6%; ICC = 0.85) and calculated oxidative capacity (CV = 3.4%; ICC = 0.83). CONCLUSION: These results indicate that (31)P-MRS corresponds well with gold-standard in vitro measurements and is highly reproducible.

31P MR spectroscopic imaging detects regenerative changes in human liver stimulated by portal vein embolization.

PURPOSE: First, to evaluate hepatocyte phospholipid metabolism and energetics during liver regeneration stimulated by portal vein embolization (PVE) using proton-decoupled (31)P MR spectroscopic imaging ((31)P-MRSI). Second, to compare the biophysiologic differences between hepatic regeneration stimulated by PVE and by partial hepatectomy (PH). MATERIALS AND METHODS: Subjects included six patients with hepatic metastases from colorectal cancer who were scheduled to undergo right PVE before definitive resection of right-sided tumor. (31)P-MRSI was performed on the left liver lobe before PVE and 48 h following PVE. Normalized quantities of phosphorus-containing hepatic metabolites were analyzed from both visits. In addition, MRSI data at 48 h following partial hepatectomy were compared with the data from the PVE patients. RESULTS: At 48 h after PVE, the ratio of phosphomonoesters to phosphodiesters in the nonembolized lobe was significantly elevated. No significant changes were found in nucleoside triphosphates (NTP) and Pi values. The phosphomonoester (PME) to phosphodiester (PDE) ratio in regenerating liver 48 h after partial hepatectomy was significantly greater than PME/PDE 48 h after PVE. CONCLUSION: (31)P-MRSI is a valid technique to noninvasively evaluate cell membrane metabolism following PVE. The different degree of biochemical change between partial hepatectomy and PVE indicates that hepatic growth following these two procedures does not follow the same course.

Simultaneous acquisition of phosphocreatine and inorganic phosphate images for Pi:PCr ratio mapping using a RARE sequence with chemically selective interleaving.

The ratio of inorganic phosphate to phosphocreatine (Pi:PCr) is a validated marker of mitochondrial function in human muscle. The magnetic resonance imaging rapid acquisition with relaxation enhancement (RARE) pulse sequence can acquire phosphorus-31 ((31)P) images with higher spatial and temporal resolution than traditional spectroscopic methods, which can then be used to create Pi:PCr ratio maps of muscle regions. While the (31)P RARE method produces images that reflect the content of the (31)P metabolites, it has been limited to producing an image of only one chemical shift in a scan. This increases the scan time required to acquire images of multiple chemical shifts as well as the likelihood of generating inaccurate Pi:PCr maps due to gross motion. This work is a preliminary study to demonstrate the feasibility of acquiring Pi and PCr images in a single scan by interleaving Pi and PCr chemical shift acquisitions using a chemically selective radiofrequency excitation pulse. The chemical selectivity of the excitation pulse evaluated and the Pi:PCr maps generated using the interleaved Pi and PCr acquisition method with the subject at rest and during exercise are compared to those generated using separate Pi and PCr acquisition scans. A paired t test indicated that the resulting Pi:PCr ratios for the exercised forearm muscle regions were not significantly different between the separate Pi and PCr acquisition method (3.18±1.53) (mean±standard deviation) and the interleaved acquisition method (3.41±1.66). This work demonstrates the feasibility of creating Pi:PCr ratio maps in human muscle with Pi and PCr images acquired simultaneously by interleaving between the Pi and PCr resonances in a single scan.

Characterisation of ATP analogues to cross-link and label P2X receptors.

P2X receptors are a distinct family of ATP-gated ion channels with a number of physiological roles ranging from smooth muscle contractility to the regulation of blood clotting. In this study we determined whether the UV light-reactive ATP analogues 2-azido ATP, ATP azidoanilide (ATP-AA) and 2',3'-O-(4-benzoylbenzoyl)-ATP (BzATP) can be used to label the ATP binding site of P2X1 receptors. These analogues were agonists, and in patch clamp studies evoked inward currents from HEK293 cells stably expressing the P2X1 receptor. Following irradiation in the presence of these compounds subsequent responses to an EC50 concentration of ATP were reduced by >65%. These effects were partially reversed by co-application of ATP or suramin with the photo-reactive ATP analogue at the time of irradiation. In autoradiographic studies radiolabelled 2-azido [gamma32P] ATP and ATP-AA-[gamma32P] cross-linked to P2X1 receptors and this binding was reduced by co-incubation with ATP. These studies demonstrate that photo-reactive ATP analogues can be used to label P2X receptor and may prove useful in elucidating the ATP binding site at this novel class of ATP binding proteins.

In vitro binding and functional studies of Ac-RYYRIK-ol and its derivatives, novel partial agonists of the nociceptin/orphanin F/Q receptor.

Following the discovery of nociceptin/orphanin FQ (N/OFQ) peptide receptor (NOP) and its endogenous ligand, an extensive search has started to find selective agonists and antagonists targeting this novel receptor-ligand system due to their therapeutic potentials. By the help of the combinatorial chemistry a series of hexapeptides with a general formula of Ac-RYY-R/K-W/I-R/K-NH(2) having high NOP receptor affinity and selectivity were identified. On the basis of this information we developed a number of novel compounds. The detailed structure-activity studies on the partial agonist Ac-RYYRIK-NH(2) are reported in this communication. Besides the modifications on N- and C-terminal, Arg-Cit exchange was performed on the template structure. The novel hexapeptides were analyzed in radioligand binding, functional biochemical [(35)S]GTPgammaS binding assays by using membranes from rat brains and Chinese hamster ovary cells expressing human NOP receptor. The agonist/antagonist properties were also tested on in the mouse vas deferens bioassay. C-terminal modification yielded a high affinity, selective and potent NOP ligand (Ac-RYYRIK-ol) with a partial agonist property. Several analogs of this compound were synthesized. The presence of the positively charged arginine residue at the first position turned out to be crucial for the biological activity of the hexapeptide. The N-terminal modifications with various acyl groups (ClAc, pivaloyl, formyl, benzoyl, mesyl) decreased the affinity of the ligand towards the receptor and the intrinsic activity for stimulating the G-protein activation was also decreased. The structure-activity studies on the hexapeptide derivatives provided some basic information on the structural requirements for receptor binding and activation.

Toward bicelle stability with ether-linked phospholipids: temperature, composition, and hydration diagrams by 2H and 31P solid-state NMR.

Phosphorus and deuterium wide line NMR was used to determine diagrams of binary mixtures of 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine (DIOMPC) and 1,2-di-O-hexyl-sn-glycero-3-phosphocholine (DIOHPC) ether-phospholipids. By varying the hydration, h, the temperature, T, and the mole fraction, X, of long-chain ether-phospholipids, we delineated the conditions for which such systems are oriented by the magnetic field, in the presence of 100 mM KCl. The 3D domain is found for X = 62-90%, T = 27-50 degrees C, and h = 70-98%. At 80% hydration, the domain shape (X = 70-90% and T = 27-42 degrees C) is close to that already observed for ester-phospholipids mixtures (Raffard, G.; Steinbruckner, S.; Arnold, A.; Davis, J. H.; Dufourc, E. J. Langmuir 2000, 16, 7655-7662) where disc-shaped bicelles of 300-600 A have been found by electron microscopy (Arnold, A.; Labrot, T.; Oda, R.; Dufourc, E. J. Biophys. J. 2002, 83, 2667-2680). Systems made of ether-linked lipids are much more stable on time and acidic conditions than those made of ester lipids. Assuming that the disc-shaped species are also found with ether lipids, their diameter as determined from integration of phosphorus NMR lines ranges from 240 to 440 A +/- 10%; it is generally independent of hydration and temperature but decreases with decreasing long-chain lipid content, X. The structure and the dynamics of water in the DIOMPC-DIOHPC were characterized by (2)H NMR. Water exchanges between the membrane surface where it is bound and a bulk isotropic pool lead to an average ordered state for temperatures in the bicelle region and above, thus offering a larger thermal span for structural studies of dissolved molecules.

M opsin phosphorylation in intact mammalian retinas.

The deactivation of visual pigments involved in phototransduction is critical for recovering sensitivity after exposure to light in rods and cones of the vertebrate retina. In rods, phosphorylation of rhodopsin by rhodopsin kinase (GRK1) and the subsequent binding of visual arrestin completely terminates phototransduction. Although signal termination in cones is predicted to occur via a similar mechanism as in rods, there may be differences due to the expression of related but distinct gene products. While rods only express GRK1, cones in some species express only GRK1 or GRK7 and others express both GRKs. In the mouse, cone opsin is phosphorylated by GRK1, but this has not been demonstrated in mammals that express GRK7 in cones. We compared cone opsin phosphorylation in intact retinas from the 13-lined ground squirrel (GS) and pig, cone- and rod-dominant mammals, respectively, which both express GRK7. M opsin phosphorylation increased during continuous exposure to light, then declined between 3 and 6 min. In contrast, rhodopsin phosphorylation continued to increase during this time period. In GS retina homogenates, anti-GS GRK7 antibody blocked M opsin phosphorylation by 73%. In pig retina homogenates, only 20% inhibition was observed, possibly due to phosphorylation by GRK1 released from rods during homogenization. Our results suggest that GRK7 phosphorylates M opsin in both of these mammals. Using an in vitro GTPgammaS binding assay, we also found that the ability of recombinant M opsin to activate G(t) was greatly reduced by phosphorylation. Therefore, phosphorylation may participate directly in the termination of phototransduction in cones by decreasing the activity of M opsin.

Developmental profile of ErbB receptors in murine central nervous system: implications for functional interactions.

The ErbB family, ErbB1 (also known as the epidermal growth factor receptor EGFR), ErbB2, ErbB3, and ErbB4 comprise a group of receptor tyrosine kinases that interact with ligands from the epidermal growth factor (EGF) superfamily, subsequently dimerize, catalytically activate each other by cross-phosphorylation, and then stimulate various signaling pathways. To gain a better understanding of in vivo functions of ErbB receptors in the central nervous system, the current study examined their mRNA expression throughout development in the mouse brain via in situ hybridization. EGFR, ErbB2, and ErbB4 exhibited distinct but sometimes overlapping distributions in multiple cell types within germinal zones, cortex, striatum, and hippocampus in prenatal and postnatal development. In addition, a subpopulation of cells positive for ErbB4 mRNA in postnatal cortex and striatum coexpressed mRNA for either EGFR or GAD67, a marker for gamma-aminobutyric acid (GABA)ergic interneurons, suggesting that both ErbB4 and EGFR are coexpressed in GABAergic interneurons. In contrast, ErbB3 mRNA was not detected within the brain during development and only appeared in white matter tracts in adulthood. Together, these findings suggest that ErbB receptors might mediate multiple functions in central nervous system development, some of which may be initiated by EGFR/ErbB4 heterodimers in vivo.

Effect of tumor necrosis factor-alpha on the reciprocal G-protein-induced regulation of norepinephrine release by the alpha2-adrenergic receptor.

Alpha2-adrenergic receptors control norepinephrine (NE) release and tumor necrosis factor-alpha (TNF) production from neurons. TNF regulates NE release, depending on alpha2-adrenergic receptor functioning. The relationship between TNF production in the brain and alpha2-adrenergic receptor activation could have profound control over NE release. TNF and alpha2-adrenergic regulation of NE release was investigated in rat hippocampal slices incubated with pertussis toxin (PTX). The alpha2-adrenergic receptor couples to Galpha(i/o)-proteins to inhibit NE release; however, in slices preexposed to PTX, alpha2-adrenergic receptor activation facilitates NE release. TNF exposure subsequent to PTX restores alpha2-adrenergic inhibition of NE release. PTX exposure of hippocampal slices prevents agonist-induced increases in Galpha(i/o) labeling with a GTP analog; after subsequent TNF exposure, agonist-induced increases in Galpha(i/o) labeling are restored. TNF regulation of NE release transforms from inhibition to facilitation depending on alpha2-adrenergic receptor activation following PTX exposure. Therefore, TNF directs the coupling of the alpha2-adrenergic receptor, ultimately affecting NE release.