PubMed Health⌕ Search

Biomedical subjects

M Pezolet

Publications and source records attributed to M Pezolet.

7 recordsLinked to original sources
PubMed1994

Morphological, physical and chemical evaluation of the Vascugraft arterial prosthesis: comparison of a novel polyurethane device with other microporous structures.

In this study the morphology, physical properties, surface chemical characteristics and microstructure of the Vascugraft arterial prosthesis have been investigated. This is a novel microporous polyurethane device, recently developed by the company Braun-Melsungen AG in Germany for use as a small calibre arterial substitute. This comparative study included two other synthetic grafts: the Mitrathane prosthesis, a hydrophilic prototype polyetherurethane urea graft with closed internal pores, and the commercially successful expanded polytetrafluoroethylene reinforced Goretex prosthesis with an open microporous structure. The Vascugraft prosthesis contains a network of fused microfibres of varying thickness and orientation which provide open and communicating pores similar in size to those in the Goretex material. In addition, they extend from one side of the graft wall to the other. As well as having superior longitudinal and radial compliance to the reinforced Goretex device, the Vascugraft prosthesis has more than adequate bursting and suture retention strengths. Through the use of contact angle measurements, electron spectroscopy for chemical analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry and molecular weight analysis by size exclusion chromatography, the surface of the Vascugraft prosthesis has been shown to be uniquely hydrophobic, as well as containing carbonate groups within an aliphatic polyesterurethane polymer. In addition, variations in micro-phase separation structure of hard and soft segment domains between different sizes and batches of product are marginal. Because of the interesting physical and chemical properties, it is recommended that in vitro biocompatibility and biostability studies be undertaken prior to using the prosthesis in animal or clinical trials.

Animals↗
PubMed1984

A restatement of melittin-induced effects on the thermotropism of zwitterionic phospholipids.

Perturbations induced by melittin on the thermotropism of dimyristoyl-, dipalmitoyl-, distearoylphosphatidylcholine and natural sphingomyelin are investigated and rationalized from data obtained by fluorescence polarization, differential scanning calorimetry and Raman spectroscopy. Depending on the technique and/or experimental conditions used, the observed effects differ at the same lipid to protein molar ratio, due to partial binding of melittin. The binding is more efficient for tetrameric than for monomeric melittin, but in both cases its affinity is weaker for phosphatidylcholine dispersions in the gel phase than for sonicated vesicles. For temperatures T greater than or equal to Tm efficient binding occurs whatever the initial state of the lipids is. One can summarize the effects induced by melittin on the transition temperature as follows: No upward shift is observed on synthetic phosphatidylcholines when lipid degradation is avoided. This is achieved by using highly purified melittin, phospholipase inhibitors, and/or non-hydrolysable lipids. Melittin monomer does not change Tm. When melittin tetramer is stabilized, it decreases Tm by 10-15 deg. C. The transition broadens, and is finally abolished for Ri less than or equal to 2. Very similar results are found for natural sphingomyelin. Fluorescence polarization indicates similar changes in order and dynamics of the acyl chains for all lipid studied. For T less than or equal to Tm, fluorescence and Raman show that melittin decreases the amount of CH2 groups in 'trans' conformation and the intermolecular order of the chains. According to fluorescence data, there is an increase of the rigid-body orientational order at T greater than or equal to Tm, while from Raman the positional intermolecular order decreases without significant change in the CH2 groups 'trans'/'gauche' ratio.

Bee Venoms↗
PubMed1982

Structure-function relationships for cardiotoxins interacting with phospholipids.

Four cardiotoxins (CTX I-IV) from Naja mossambica mossambica were compared for their ability to interact with phospholipid vesicles and their capacity to bind erythrocytes. It is concluded that the affinity of the toxins always increases in the order: I approximately equal to II less than III less than IV. The binding is specific for charged lipids even in lipid mixtures. Proteolytic attack of the free and lipid-bound cardiotoxin indicates that at least the first loop Leu1-Thr13 is at the lipid contact. Tryptic and synthetic peptides constitutive of this loop are shown to interact with lipids. Arg5 residue increases the affinity toward the bilayer. The Raman spectra of lipid-bound cardiotoxin indicate a secondary and tertiary structure mainly similar to that of the free toxin. On charged lipids cardiotoxins induce a decrease of the enthalpy and an increase of disorder without change in the transition temperature; at saturating amounts of toxin the transition is abolished. In binary mixtures of phosphatidylcholine and charged lipids the observed effects can be accounted by a phase separation induced by the toxin.

Amino Acid Sequence↗
PubMed1978

Laser Raman investigation of intact single muscle fibers. On the state of water in muscle tissue.

Laser Raman spectroscopy has been used to investigate the state of water in intact single muscle fibers of the giant barnacle (Balanus nubilus). The spectra in the region of the O-H (or O-2H) stretching modes of water in unfrozen fibers show that there is no appreciable difference between the shape and relative intensity of the Raman bands due to the water molecules located inside a muscle fiber and those of the corresponding bands in the spectrum of pure water. The presence of significant amounts of "structured" intracellular water, greater than approx. 5% of the total water content, in these fibers is thus excluded. The Raman spectra of frozen fibers have also been recorded in order to evaluate the amount of intracellular water which remains unfrozen at temperatures below the normal freezing point of water. We have been able to reproduce these spectra by assuming that the spectrum of a frozen fiber is the sum of the individual spectra of water and ice. To calculate the amount of unfrozen water from these curve fittings, it was also necessary to determine the intensities of the water and ice Raman bands relative to one another. We have found the I(ice)/I(water) ratio is 1.07 +/- 0.01 for H2O and 1.05 +/- 0.03 for 2H2O With these figures, we have calculated that for a fiber with a normal water content of 80%, 20% of the water molecules remain in the supercooled state of -5 degrees C, which corresponds to 1 g of water per g of fiber dry weight. This amount of bound water was also found to be independent of the water content of the fibers.

Animals↗
PubMed1978

Laser Raman investigations of intact single muscle fibers. Protein conformations.

Raman spectra, in the frequency region of the protein vibrations, of intact single muscle fibers of the giant barnacle are presented. Strong bands at 1521 and 1156 cm-1 in the spectra are attributed to resonance-enhanced Raman bands of membrane-bound beta-carotene. Many bands of the myofibrillar proteins are also observed, and at least three spectral features confirm that these proteins adopt a predominantly alpha-helical structure: (1) the amide I band at 1648 cm-1, (2) the weak scattering in the amide III region, and (3) a strong skeletal C-C stretching band at 939 cm-1. Deuterated fibers have also been examined in order to find the exact shape of the amide III band. The presence in the fibers of paramyosin, which is only found in catch muscles, is also apparent from the spectra.

Animals↗
PubMed1976

Laser Raman investigation of the conformation of human immunoglobulin G.

Laser Raman spectra of human immunoglobulin G in neutral solution, as well as in the lyophilized and alkaline-denatured states are presented. In the spectrum of the native protein, the amide III band appears at 1240 cm-1 and is assigned to the presence of beta-sheet structure. From its intensity, using a procedure described in this paper, we evaluate the beta-structure content to 37 +/- 4%. This result is supported by the strong amide I' band at 1667 cm-1 and by the presence in the spectra of two bands at 991 and 1078 cm-1, respectively assigned to the C-C and C-N skeletal stretching modes. The differences between the spectrum of the lyophilized powder and that of the solution show that the lyophilization process induces conformational changes that perturb the local environment of some of the tryptophan residues and alter the secondary structure of immunoglobulin G. The beta-structure appears to be more uniform and more abundant in solution. When the protein is denatured at pH 11, the amide III and amide I'bands, which become weaker and broader, shift in frequency from 1240 to 1248 cm-1 and from 1667 to 1656 cm-1 respectively. These changes indicate a decrease in the amount of beta-structure and a transition toward a much more disordered conformation. During the denaturation, the intensities of many bands of the aromatic chromophores change, notably the tryptophan peaks at 879, 1359 and 1573 cm-1.

Humans↗