DISTRIBUTION OF CATECHOLAMINERGIC NEUROTRANSMITTERS AND RELATED RECEPTORS IN HUMAN BRONCHUS-ASSOCIATED LYMPHOID TISSUE

Background: The functions of the bronchus-associated lymphoid tissue (BALT) are under the control of the autonomic nervous system ( sympathetic and parasympathetic nerve fibers). Objectives: The relationships between the adrenergic nerve fibers and beta-adrenergic receptors were studied in the human BALT with the aim to demonstrate a probable neuromodulation. Methods: Morphological observations ( staining with hematoxylineosin and scanning electron microscopy images) were carried out on samples of human BALT harvested during autopsies. Moreover, histochemical staining for norepinephrine ( adrenaline = adrenergic nerve fibers) as well as for other catecholamines was performed. Finally, beta-adrenergic receptors were stained by means of a beta-blocking, radiolabeled drug ( pindolol I-125). All our data were submitted to morphometric analysis ( quantitative analysis of images and statistical analysis of data). Results: Our results provide direct evidence of the presence and distribution of catecholaminergic nerve fibers and related beta-adrenergic receptors in BALT. beta-Adrenergic receptors are present above all in the most richly innervated part of the BALT, and are, therefore, in close relationship with their related adrenergic nerve fibers. Conclusions: Studies on the distribution of adrenergic neurotransmitters and related beta-adrenergic receptors in the human BALT are the first step for the demonstration of a probable neuromodulation of BALT. Copyright (C) 2004 S. Karger AG, Basel

Exploring short intramolecular interactions in alkylaromatic substrates

From proteins and peptides to semiconducting polymers, aliphatic chains on aromatic groups are recurring motifs in macromolecules from very diverse application fields. Fields in which molecular folding and packing determine the macroscopic physical properties that make such advanced materials appealing in the first place. Within each macromolecule, the intrinsic structure of each unit defines how it interacts with its neighbours, ultimately opening up or denying certain backbone conformations. This eventually also determines how macromolecules interact with each other. This account deals specifically with the conformational problem of many common alkylaromatic units, examining the features of an intramolecular interaction involving a side chain with as few as three methylene groups. A set of 23 model compounds featuring an intramolecular interaction between an aliphatic X-H (X = C, N, O, and S) bond and an aromatic ring was considered. Quantitative computational analysis was made possible, thanks to complete basis set extrapolated CCSD(T) calculations and NCI topological analysis, the latter of which revealed an elaborate network of dispersive and steric interactions leading to somewhat unintuitive and unexpected results, such as the higher energetic stability of certain twisted conformational isomers over those with extended side chains. Vicinal covalent effects from polarizing groups and various heteroatoms, along with the occurrence of non-dispersive phenomena, were also investigated. The conclusions drawn from the investigation include a comprehensive set of guidelines intended to aid in the prediction of the most stable conformation for this class of building blocks. Our findings affect a variety of different research fields, including the tailoring of functional materials for organic electronics and photovoltaics, with insights into a rational treatment of conformational disorder, and the study of protein- and peptide-folding preferences, putting an emphasis on peculiar interactions between the backbone and aromatic residues

Neovascularization in alkali-burned rabbit cornea

Objective: To study the neovascularization in regenerating and proliferating corneal cells following a standard alkali injury in rabbit eye. Methods: Three and six weeks after the creation of an alkali burn in the center of the right cornea of six albino rabbits, the animals were killed and histological sections from the cornea of both eyes were stained, photographed and studied for a possible formation of a neovascularization. The photographs were examined using the Quantimet image analyzer (Leica) and statistical analysis of the data was performed. Results: Sections of the injured cornea showed the formation of neovessels in the epithelial and superficial stromal layers. The neovascularization is present after 3 weeks of the corneal injury. After 6 weeks from the corneal alkali burn, neovessels are increased. Conclusions: There is a growing body of evidence suggesting that vascular abnormalities may play a crucial rolein several ocular diseases. To improve our knowledge of the vascular involvement in these conditions, there is a need for a non-invasive imaging modality capable of assessing microcirculation within ocular tissue beds both in vitro and in vivo. This study shows that ultra-high sensitive optical microangiography, associated with other experimental techniques, is an adequate technique to visualize the eye surface microcirculations and to quantify microvascular vessel density under both normal and physio-pathological conditions

Glycosaminoglycans in the human cornea: age-related changes

Abstract AIM: To investigate possible age-related changes in glycosaminoglycans (GAGs) in the human cornea. The substances today called GAGs were previously referred to as mucopolysaccharides. METHODS: Samples of human cornea were taken from 12 younger (age 21 ± 1.2) and 12 older (age 72 ± 1.6) male subjects. Samples were weighed, homogenized, and used for biochemical and molecular analyses. All the quantitative results were statistically analyzed. RESULTS: The human cornea appears to undergo age-related changes, as evidenced by our biochemical and molecular results. The total GAG and hyaluronic acid counts were significantly higher in the younger subjects than in the older subjects. The sulfated heavy GAGs, such as chondroitin, dermatan, keratan, and heparan sulfate, were lower in the younger subjects than in the older subjects. DISCUSSION: GAGs of the human cornea undergo numerous age-related changes. Their quantity is significantly altered in the elderly in comparison with younger subjects. GAGs play an important role in age-related diseases of the human cornea

Molecular modeling of the interaction of protein L with antibodies

Protein L (PpL) is a bacterial protein which is used in the affinity chromatography stage of the production of monoclonal antibodies because of its ability to form high affinity complexes with the light chains of immunoglobulins. In the present work, the binding interfaces between one domain of PpL and antigen-binding fragments (Fab) have been investigated adopting molecular dynamics with the aim of determining the binding contribution of the residues located at the Fab-PpL interface. Because it is known that PpL binds antibodies through two distinct binding sites with different affinities, simulations were performed for both sites to determine interaction free energies to assess the relative binding contribution of the two sites. Mutational studies were then performed only on the dominant binding site. The binding free energy was evaluated with the molecular mechanics Poisson-Boltzmann surface area (MMPBSA) and umbrella sampling/weighted histogram analysis methods. Key residues for the formation of the dominant binding site complex were identified by means of alanine scanning performed both for the Fab and PpL domains. Residues of the light chain of the antibody that contribute most to binding were found to be located between SER7 and VAL13. Four residues from PpL are important for the stability of the complex: PHE839, LYS840, GLU849, and TYR853. Three residues of PpL that do not contribute to the interaction were mutated to histidine (HIS), which changes its protonation state as a function of pH, to find whether this could allow us to control the binding interaction energy. This can be useful in the elution stage of the affinity chromatography purification of antibodies if PpL is used as a ligand. These residues are GLN835, THR836, and ALA837. Molecular dynamics simulations with both protonated and unprotonated HIS were performed to mimic how changing pH may reflect on protein- ligand interaction energies. The MMPBSA approach was used to evaluate the variation of the affinity of the mutated systems with reference to the wild type. Our results show that these mutations could help in disrupting the complex under acidic conditions without impairing the affinity of PpL for the light chains at higher pHs

Theoretical and kinetic modelling study of phenol and phenoxy radical decomposition to CO and C5H6/C5H5 in pyrolysis conditions

Bio-oils from biomass fast-pyrolysis are an economically viable solution to reduce carbon footprint [1]. Lignin-derived bio-oils are a complex mixture of oxygenated species, including phenolic compounds such as phenol, anisole, guaiacol, catechol and vanillin (20-30% in weight) [2]. Hence, an accurate characterization of the pyrolysis and combustion kinetics of phenolic species, starting from phenol, is essential to assess the technical viability of these biooils. Furthermore, phenol plays a key role in the mechanism of oxidation of benzene, a building block of PAHs chemistry, precursors of soot and PM [3]. Finally, substituted phenolic species have recently gained attention for their antiknock properties and are being considered as possible octane boosters [4]. Nevertheless, the kinetics of phenol has not been systematically addressed yet, and the available experimental data are limited. Therefore, a theoretical approach for the prediction of accurate kinetics provides a major contribution to improve the current knowledge. This work investigates with ab initio methods the two main decomposition pathways of phenol: 1) the molecular pathway forming C5H6+CO, and 2) the radical pathway forming C6H5O+H. This latter pathway justifies the additional investigation of the decomposition of phenoxy radical (C6H5O) to CO and cyclopentadienyl (C5H5). For a consistent investigation of phenol kinetics, also the H-abstraction reactions from cyclopentadiene are included. The kinetic constants thus obtained are included in the CRECK kinetic model and validated with experimental data

Molecular Dynamics Simulation on Physical Properties of Liquid Lead, Bismuth and Lead-bismuth Eutectic (LBE)

Molecular dynamics method was applied to simulate the physical properties of liquid metals: lead, bismuth and a binary alloy--lead-bismuth eutectic (LBE). The embedded atom method (EAM), an empirical model rooted in density-functional theory, was used to represent the many-body interaction within the liquid metals. The atomic-scale interactions, structure and thermal physical properties of lead, bismuth and LBE were obtained through the simulation, and then compared to the available experimental results. The theoretical results of the physical properties calculated through the MD simulations are in good agreements with the available experimental data

Detailed kinetics of pyrolysis and combustion of catechol and guaiacol, as reference components of bio-Oil from biomass

Fast biomass pyrolysis is an effective process to produce bio-oils thus allowing to partially replace nonrenewable fossil fuels. Bio-oils are complex mixtures with a great amount of large oxygenated organic species, such as substituted phenolic components. Although experimental and kinetic modeling studies of phenol and anisole pyrolysis and combustion are available in the literature, only a minor attention has been devoted to kinetic mechanisms of substituted phenolic species, such as catechol and guaiacol. Multiple substitutions on aromatic ring can originate proximity effects and thus significantly modify bond energies, consequently affecting reaction pathways. Careful evaluations of bond dissociation energies and reference kinetic parameters, based on theoretical computations, are first performed. Guaiacol and catechol pyrolysis and combustion reactions are then compared with the corresponding phenol and anisole mechanisms. This kinetic study allows to identify some preliminary rate rules useful to validate a detailed kinetic mechanism of bio-oil pyrolysis and combustion

Analysis of acetic acid gas phase reactivity: Rate constant estimation and kinetic simulations

The gas phase reactivity of acetic acid was investigated combining first principle calculations with kinetic simulations. Rate constants for the unimolecular decomposition of acetic acid were determined integrating the 1D master equation over a Potential Energy Surface (PES) investigated at the M06-2X/aug-cc-pVTZ level. Energies were computed at the CCSD(T)/aug-cc-pVTZ level using a basis set size correction factor determined at the DF-MP2/aug-cc-pVQZ level. Three decomposition channels were considered: CO2+ CH4, CH2CO + H2O, and CH3+ COOH. Rate constants were computed in the 700-2100 K and 0.1-100 atm temperature and pressure ranges. The simulations show that the reaction is in fall off above 1200 K at pressures smaller than 10 atm. Successively, the PESs for acetic acid H-abstraction by H, OH, OOH, O2, and CH3were investigated at the same level of theory. Rate constants were computed accounting explicitly for the formation of entrance and exit van der Waals wells and their collisional stabilization. Energy barriers were determined at the CASPT2 level for H-abstraction by OH of the acidic H, since it has a strong multireference character. The calculated rate constant is in good agreement with experiments and supports the experimental finding that at low temperatures it is pressure dependent. The calculated rate constants were used to update the POLIMI kinetic model and to simulate the pyrolysis and combustion of acetic acid. It was found that acetic acid decomposition and the formation of its direct decomposition products can be reasonably predicted. The formation of secondary products, such as H2and C2hydrocarbons, is underpredicted. This suggests that reaction routes not incorporated in the model may be active. Some hypotheses are formulated on which these may be