Clarification of pathway-specific inhibition by Fourier transform ion cyclotron resonance/mass spectrometry-based metabolic phenotyping studies

We have developed a metabolic profiling scheme based on direct-infusion Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS). The scheme consists of: (1) reproducible data collection under optimized FT-ICR/MS analytical conditions; (2) automatic mass-error correction and multivariate analyses for metabolome characterization using a newly developed metabolomics tool (DMASS software); (3) identification of marker metabolite candidates by searching a species-metabolite relationship database, KNApSAcK; and (4) structural analyses by an MS/MS method. The scheme was applied to metabolic phenotyping of Arabidopsis (Arabidopsis thaliana) seedlings treated with different herbicidal chemical classes for pathway-specific inhibitions. Arabidopsis extracts were directly infused into an electrospray ionization source on an FT-ICR/MS system. Acquired metabolomics data were comprised of mass-to-charge ratio values with ion intensity information subjected to principal component analysis, and metabolic phenotypes from the herbicide treatments were clearly differentiated from those of the herbicide-free treatment. From each herbicide treatment, candidate metabolites representing such metabolic phenotypes were found through the KNApSAcK database search. The database search and MS/MS analyses suggested dose-dependent accumulation patterns of specific metabolites including several flavonoid glycosides. The metabolic phenotyping scheme on the basis of FT-ICR/MS coupled with the DMASS program is discussed as a general tool for high throughput metabolic phenotyping studies.     

AAA Peroxins and Their Recruiter Pex26p Modulate the Interactions of Peroxins Involved in Peroxisomal Protein Import

Pex1p and Pex6p are required for the relocation of the import receptor Pex5p from the peroxisomal membrane to the cytosol. We herein show that mammalian Pex26p directly binds to Pex14p, the initial docking receptor of Pex5p, and interacts with Pex5p via Pex14p. The binding affinity of Pex26p to Pex14p is altered by Pex5p. Further evidence suggests that the N-terminal region in Pex26p acts as a scaffold protein to recruit Pex14p·Pex5p complex together with Pex1p·Pex6p complexes on peroxisomes. Pex26p binding to Pex14p was suppressed by overexpression of Pex1p and Pex6p in an ATP-dependent manner, whereas Pex14p was not competed out by Pex1p and Pex6p from Pex26p mutant defective in peroxisomal matrix protein import. These results suggested that peroxisome biogenesis requires Pex1p- and Pex6p-regulated dissociation of Pex14p from Pex26p. Pex1p homo-oligomer directly binds to Pex5p as assessed by a surface plasmon resonance-based assay. Moreover, cytosolic Pex1p is likely to maintain the functional oligomer of Pex5p. Taken together, in the peroxisomal protein import, AAA peroxins modulate the interaction between Pex26p and Pex14p on peroxisome membrane as well as Pex5p oligomer in the cytosol.     

First record of Adelges (Cholodkovskya) viridanus (Hemiptera: Adelgidae) in North America,with a description of the fundatrix form in Japan

Adelges (Cholodkovskya) viridanus (Cholodkovsky 1896) (Hemiptera: Adelgidae) is found throughout Eurasia where it is understood to be anholocyclic, feeding on species of larch (Larix), without host alternation. For the first time, we report this species in North America, outside of its native range, from specimens collected in an arboretum in Ohio, USA. Molecular phylogenetic analysis was inconclusive as to whether it was introduced from Europe or Asia. In addition, specimens collected from Picea jezoensis in Japan were confirmed for the first time as A. (C.) viridanus by matching DNA sequences to specimens collected on Larix. Therefore, A. (C.) viridanus is either capable of completing a host-alternating holocycle in Japan, or includes very recently diverged anholocyclic populations on Picea. Finally, we describe the adult fundatrix form, which was previously unknown.     

STIMULATORY EFFECTS OF SUBSTANCE P ON NEURITE EXTENSION AND CYCLIC AMP LEVELS IN CULTURED NEUROBLASTOMA CELLS

Abstract— Synthetic substance P initially increased cyclic AMP levels and subsequently induced neurite extension in cultured neuroblastoma N 18 cells. The magnitude of these effects depended on the concentration of fetal calf serum (FCS) in the culture medium, being more evident in the presence of a lower (0.1%) concentration of FCS.
In Eagle's medium containing 0.1% FCS, low concentrations of substance P (10⁻⁷-10⁻⁵ M) increased cyclic AMP levels and stimulated neurite extension.
In Eagle's medium containing 5%FCS, both substance P at concentrations of 10⁻⁵-10⁻³M and dibutyryl cyclic AMP at concentrations of 10⁻⁴-10⁻²M increased cyclic AMP levels and stimulated neurite extension. The activities of acetylcholinesterase, (Na⁺+ K⁺)-, HCO₃⁻ and Mg²⁺ -stimulated-ATPase were also increased. Cell growth was inhibited.
Substance P at concentrations of 10-⁷-10⁻⁵M also stimulated the adenylate cyclase activity of a particulate fraction of N 18 in a concentration-dependent manner.     

Differential effects of diethylcarbamazine, tetracycline and the combination on Brugia pahangi adult females in vitro

Anti-filarial effects of diethylcarbamazine (DEC), tetracycline (TC) and the combination on Brugia pahangi adult females were studied in 7-day cell-free culture, in terms of microfilaria release, parasite motility, MTT assay for parasite viability and embryogram. TC 50 μg/ml (TC50) effectively reduced microfilaria release from day 1 of culture. Combined with DEC 100 μg/ml (DEC100) or DEC 500 μg/ml (DEC500), microfilaria release reduced further and synergistically. TC50 also reduced motility, but DEC100 and DEC500 did not. The combination of TC50 and DEC500 reduced motility synergistically. The MTT assay supported the results of motility study in general. The embryogram showed that only DEC500 reduced the total number of intrauterine embryos, especially ova, indicating that DEC500 inhibited early embryogenesis. TC50 did not affect the total number of embryos, but resulted in apparent accumulation of microfilariae in the uterus, suggesting that the drug inhibited release of microfilariae in this in vitro system. These results clarified different anti-female mechanisms between DEC and TC. A PCR-based study showed that endosymbiont bacteria, Wolbachia, in B. pahangi females decreased significantly after TC treatment. However, this study could not determine whether the effects of TC were direct or Wolbachia-mediated.     

Standing up to the challenge of standing: a siphon does not support cerebral blood flow in humans

Model studies have been advanced to suggest both that a siphon does and does not support cerebral blood flow in an upright position. If a siphon is established with the head raised, it would mean that internal jugular pressure reflects right atrium pressure minus the hydrostatic difference from the brain. This study measured spinal fluid pressure in the upright position, the pressure and the ultrasound-determined size of the internal jugular vein in the supine and sitting positions, and the internal jugular venous pressure during seated exercise. When the head was elevated approximately 25 cm above the level of the heart, internal jugular venous pressure decreased from 9.5 (SD 2.8) to 0.2 (SD 1.0) mmHg [n = 15; values are means (SD); P < 0.01]. Similarly, central venous pressure decreased from 6.2 (SD 1.8) to 0.6 (SD 2.6) mmHg (P < 0.05). No apparent lumen was detected in any of the 31 left or right internal veins imaged at 40 degrees head-up tilt, and submaximal (n = 7) and maximal exercise (n = 4) did not significantly affect internal jugular venous pressure. While seven subjects were sitting up, spinal fluid pressure at the lumbar level was 26 (SD 4) mmHg corresponding to 0.1 (SD 4.1) mmHg at the base of the brain. These results demonstrate that both for venous outflow from the brain and for spinal fluid, the prevailing pressure approaches zero at the base of the brain when humans are upright, which negates that a siphon supports cerebral blood flow.     

Photochemical Reaction Dynamics of the Primary Event of Vision Studied by Means of a Hybrid Molecular Simulation

The photoisomerization reaction dynamics of a retinal chromophore in the visual receptor rhodopsin was investigated by means of hybrid quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations. The photoisomerization reaction of retinal constitutes the primary step of vision and is known as one of the fastest reactions in nature. To elucidate the molecular mechanism of the high efficiency of the reaction, we carried out hybrid ab initio QM/MM MD simulations of the complete reaction process from the vertically excited state to the photoproduct via electronic transition in the entire chromophore-protein complex. An ensemble of reaction trajectories reveal that the excited-state dynamics is dynamically homogeneous and synchronous even in the presence of thermal fluctuation of the protein, giving rise to the very fast formation of the photoproduct. The synchronous nature of the reaction dynamics in rhodopsin is found to originate from weak perturbation of the protein surroundings and from dynamic regulation of volume-conserving motions of the chromophore. The simulations also provide a detailed view of time-dependent modulations of hydrogen-out-of-plane vibrations during the reaction process, and identify molecular motions underlying the experimentally observed dynamic spectral modulations.     

Monomer-dimer transition of the conserved N-terminal domain of the mammalian peroxisomal matrix protein import receptor, Pex14p

Pex14p is a central component of the peroxisomal matrix protein import machinery. In the recently determined crystal structure, a characteristic face consisting of conserved residues was found on a side of the conserved N-terminal domain of the protein. The face is highly hydrophobic, and is also the binding site for the WXXXF/Y motif of Pex5p. We report herein the dimerization of the domain in the isolated state. The homo-dimers are in equilibrium with the monomers. The homo-dimers are completely dissociated into monomers by complex formation with the WXXXF/Y motif peptide of Pex5p. A putative dimer model shows the interaction between the conserved face and the PXXP motif of another protomer. The model allows us to discuss the mechanism of the oligomeric transition of the full-length Pex14p modulated by the binding of other peroxins.     

Mutations in the peroxin Pex26p responsible for peroxisome biogenesis disorders of complementation group 8 impair its stability, peroxisomal localization, and interaction with the Pex1p x Pex6p complex

Peroxisome biogenesis disorders (PBDs) are fatal autosomal recessive diseases and are caused by impaired peroxisome biogenesis. PBDs are genetically heterogeneous and classified into 13 complementation groups (CGs). CG8 is one of the most common groups and has three clinical phenotypes, including Zellweger syndrome (ZS), neonatal adrenoleukodystrophy, and infantile Refsum disease (IRD). We recently isolated PEX26 as the pathogenic gene for PBD of CG8. Pex26p functions in recruiting to peroxisomes the complexes of the AAA ATPase peroxins, Pex1p and Pex6p. In the present work, we identified four distinct mutations in PEX26 from five patients of CG8 PBD including 2 with ZS and 3 with IRD, in addition to 7 mutant alleles in 8 patients in the first report describing the pathogenic PEX26 gene for CG8 PBD. Phenotype-genotype analyses revealed that temperature-sensitive (ts) peroxisome assembly gave rise to a milder IRD in contrast to the non-ts phenotype of the cells from ZS patients. Furthermore, we present several lines of evidence that show that the instability, insufficient binding to Pex1p x Pex6p complexes, or mislocalization of patient-derived Pex26p mutants is most likely responsible for the CG8 PBDs.