22 research outputs found
Neuroinflammation, Mast Cells, and Glia: Dangerous Liaisons
The perspective of neuroinflammation as an epiphenomenon following neuron damage is being replaced by the awareness of glia and their importance in neural functions and disorders. Systemic inflammation generates signals that communicate with the brain and leads to changes in metabolism and behavior, with microglia assuming a pro-inflammatory phenotype. Identification of potential peripheral-to-central cellular links is thus a critical step in designing effective therapeutics. Mast cells may fulfill such a role. These resident immune cells are found close to and within peripheral nerves and in brain parenchyma/meninges, where they exercise a key role in orchestrating the inflammatory process from initiation through chronic activation. Mast cells and glia engage in crosstalk that contributes to accelerate disease progression; such interactions become exaggerated with aging and increased cell sensitivity to stress. Emerging evidence for oligodendrocytes, independent of myelin and support of axonal integrity, points to their having strong immune functions, innate immune receptor expression, and production/response to chemokines and cytokines that modulate immune responses in the central nervous system while engaging in crosstalk with microglia and astrocytes. In this review, we summarize the findings related to our understanding of the biology and cellular signaling mechanisms of neuroinflammation, with emphasis on mast cell-glia interactions
Evaluation of the use of PetrifilmTM EB count plates for the enumeration of Enterobacteriaceae in poultry samples
Qualidade microbiológica de filés de tilápia do Nilo (Oreochromis niloticus) durante o armazenamento em gelo
Differential Oligomerization of Alpha versus Beta Amino Acids and Hydroxy Acids in Abiotic Proto-Peptide Synthesis Reactions
The origin of biopolymers is a central question in origins of life research. In extant life, proteins are coded linear polymers made of a fixed set of twenty alpha-L-amino acids. It is likely that the prebiotic forerunners of proteins, or protopeptides, were more heterogenous polymers with a greater diversity of building blocks and linkage stereochemistry. To investigate a possible chemical selection for alpha versus beta amino acids in abiotic polymerization reactions, we subjected mixtures of alpha and beta hydroxy and amino acids to single-step dry-down or wet-dry cycling conditions. The resulting model protopeptide mixtures were analyzed by a variety of analytical techniques, including mass spectrometry and NMR spectroscopy. We observed that amino acids typically exhibited a higher extent of polymerization in reactions that also contained alpha hydroxy acids over beta hydroxy acids, whereas the extent of polymerization by beta amino acids was higher compared to their alpha amino acid analogs. Our results suggest that a variety of heterogenous protopeptide backbones existed during the prebiotic epoch, and that selection towards alpha backbones occurred later as a result of polymer evolution
Structural Characterization of Methylenedianiline Regioisomers by Ion Mobility-Mass Spectrometry, Tandem Mass Spectrometry, and Computational Strategies. 3. MALDI Spectra of 2-Ring Isomers
Characterization of methylenedianiline
(MDA) 2-ring isomers (2,2′-,
2,4′-, and 4,4′-MDA) is reported using matrix assisted
laser desorption/ionization–mass spectrometry (MALDI-MS), a
common technique used for characterizing synthetic polymers. MDA is
a precursor to methylene diphenyl diisocyanate (MDI), a hard block
component in polyurethane (PUR) synthesis. This work focuses on comparing
MALDI results to those of our previous electrospray ionization-mass
spectrometry (ESI-MS) studies. In ESI, 2-ring MDA isomers formed single
unique [M + H]<sup>+</sup> (199 Da) parent ions, whereas in MALDI
each isomer shows significant formation of three precursor ions: [M
– H]<sup>+</sup> = 197 Da, [M<sup>•</sup>]<sup>+</sup> = 198 Da, and [M + H]<sup>+</sup> = 199 Da. Structures and schemes
are proposed for the MALDI fragment ions associated with each precursor
ion. Ion mobility–mass spectrometry (IM-MS), tandem mass spectrometry
(MS/MS), and computational methods were all critical in determining
the structures for both precursor and fragment ions as well as the
fragmentation mechanisms. The present study indicates that the [M
– H]<sup>+</sup> and [M<sup>•</sup>]<sup>+</sup> ions
are formed by the MALDI process, explaining why they were not observed
with ESI
Structural Characterization of Methylenedianiline Regioisomers by Ion Mobility-Mass Spectrometry, Tandem Mass Spectrometry, and Computational Strategies: I. Electrospray Spectra of 2‑Ring Isomers
Purified methylenedianiline (MDA)
regioisomers were structurally
characterized and differentiated using tandem mass spectrometry (MS/MS),
ion mobility-mass spectrometry (IM-MS), and IM-MS/MS in conjunction
with computational methods. It was determined that protonation sites
on the isomers can vary depending on the position of amino groups,
and the resulting protonation sites play a role in the gas-phase stability
of the isomer. We also observed differences in the relative distributions
of protonated conformations depending on experimental conditions and
instrumentation, which is consistent with previous studies on aniline
in the gas phase. This work demonstrates the utility of a multifaceted
approach for the study of isobaric species and elucidates why previous
MDA studies may have been unable to detect and/or differentiate certain
isomers. Such analysis may prove useful in the characterization of
larger MDA multimeric species, industrial MDA mixtures, and methylene
diphenyl diisocyanate (MDI) mixtures used in polyurethane synthesis
Semitransparent Nanostructured Films for Imaging Mass Spectrometry and Optical Microscopy
Semitransparent porous silicon substrates have been developed
for
pairing nanostructure-initiator mass spectrometry (NIMS) imaging with
traditional optical-based microscopy techniques. Substrates were optimized
to generate the largest NIMS signal while maintaining sufficient transparency
to allow visible light to pass through for optical microscopy. Using
these substrates, both phase-contrast and NIMS images of phospholipids
from a scratch-wounded cell monolayer were obtained. NIMS images were
generated using a spatial resolution of 14 μm. Coupled with
further improvements in spatial resolution, this approach may allow
for the localization of intact biological molecules within cells without
the need for labeling
Structural Characterization of Methylenedianiline Regioisomers by Ion Mobility-Mass Spectrometry, Tandem Mass Spectrometry, and Computational Strategies. 2. Electrospray Spectra of 3‑Ring and 4‑Ring Isomers
Building on results from our previous
study of 2-ring methylenedianiline
(MDA), a combined mass spectrometry approach utilizing ion mobility-mass
spectrometry (IM-MS) and tandem mass spectrometry (MS/MS) coupled
with computational methods enables the structural characterization
of purified 3-ring and 4-ring MDA regioisomers in this current study.
The preferred site of protonation for the 3-ring and 4-ring MDA was
determined to be on the amino groups. Additionally, the location of
the protonated amine along the MDA multimer was found to influence
the gas phase stability of these molecules. Fragmentation mechanisms
similar to the 2-ring MDA species were observed for both the 3-ring
and 4-ring MDA. The structural characterization of 3-ring and 4-ring
MDA isomers using modern MS techniques may aid polyurethane synthesis
by the characterization of industrial grade MDA, multimeric MDA species,
and methylene diphenyl diisocyanate (MDI) mixtures