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Biomedical subjects

P Rochon

Publications and source records attributed to P Rochon.

13 recordsLinked to original sources
PubMed1998

Azocarbazole Polymethacrylates as Single-Component Electrooptic Materials.

A series of amorphous azobenzene and carbazole-containing polymers was prepared, which incorporates both electrooptic activity and photoconductivity into a single multifunctional structural unit. The polymers were cast as thin films and were shown to be suitable for photoinducing birefringence reversibly with polarized light, as well as for the inscription of photorefractive diffraction gratings after electric field poling. Since the polymer series encompasses a range of spacer lengths (from 3 to 10 methylene groups) between the multifunctional side chains and the polymer backbone, these materials are suitable for study of the influence of chromophore mobility on these optical phenomena. The extent of orientational order which could be photoinduced in the films was found to decrease with increasing spacer length, as did the photoconductivity and the photorefractive two-beam optical coupling gain. In thin films of polymers with the highest glass transition temperature, a birefringence of 0.065 could be photoinduced, with a time constant of <0.8 s. A two-beam optical gain of 0.024 µm-1 was also demonstrated in films of the polymer with the highest glass transition temperature, although this gain was exceeded by absorption losses.

Journal Article↗
PubMed1991

Characterization and differentiation of some complex dextran sulfate preparations of medicinal interest.

Dextran sulfate samples from different sources were examined by 1H and 13C NMR spectroscopy to differentiate the samples on the basis of extent and sites of sulfation. The anomeric (H-1) signal proved to be a good indicator ranging from no sulfation (as in dextran) to virtually complete sulfation at positions 2 and 3, whereas the relative intensity of the H-4 signal afforded a measure, conversely, of the degree of sulfation at position 4. Three different dextran sulfate tablet formulations were found by NMR to contain similar dextran sulfate material that was characterized by a high degree of sulfation at positions 2 and 3. Position 4 of dextran appears to be less readily amenable to substitution. Quasi-elastic light scattering (QELS) analysis of aqueous dispersions of the bulk dextran sulfate samples and formulated tablets permitted additional particle size and homogeneity differentiation. None of the dextran sulfate materials showed either anti-factor Xa activity or marked anticoagulant activity.

Anticoagulants↗
PubMed1990

Chemical composition, particle size range, and biological activity of some low molecular weight heparin derivatives.

Several low molecular weight (LMW) heparin sodium derivatives from different sources, as well as some related regular heparin sodium preparations, were examined for chemical composition by high field (300 MHz) 1H NMR spectroscopy, for particle size range by quasi-elastic light scattering (QELS) methods, and for anti-coagulation potency and anti-factor Xa activity by the standard U.S. Pharmacopeial assays described for regular heparin. The NMR spectra provided insight into possible modes of depolymerization used to generate the LMW heparins, as well as into the presence of dermatan sulfate or other chemical contaminants. The QELS analysis permitted the heparin preparations to be characterized and compared by virtue of their distinctive particle size distributions.

Dermatan Sulfate↗
PubMed1990

Physicochemical characterization of the First World Health Organization International Standard for low molecular weight heparin derivatives.

High-field (300 MHz) 1H NMR spectral analysis and particle size distribution analysis employing the quasielastic light scattering (QELS) technique were performed on samples of the 1st International Standard for low molecular weight (LMW) heparin derivatives recently selected by the World Health Organization (WHO). We propose that the results of these analyses, which showed that the material is highly homogeneous in particle size and retains spectral features characteristic of its porcine mucosal origin, form an appropriate basis for physicochemical comparison between the "Standard" and other LMW heparin preparations.

Animals↗
PubMed1990

The formation of multilamellar vesicles from saturated phosphatidylcholines and phosphatidylethanolamines: morphology and quasi-elastic light scattering measurements.

The aggregation properties of diacyl phosphatidylcholines (PC) and phosphatidylethanolamines (PE), with linear symmetrical saturated chains, were characterized at temperatures below and above the lipid solid to fluid transition. PEs in the solid state form bundles of closely apposed flat bilayer stacks which at the solid to fluid transition temperature fold into closed multilamellar vesicles. On the other hand, PCs in the solid state form extended multilayer sheets. At the solid to fluid transition, multilamellar vesicles appear to "bud off" from the surface. Quasi-elastic light scattering (QELS) measurements indicated that for the PEs, bundle size is independent of acyl chain length n, but that the sizes of vesicles which form at the solid to fluid transition are positively correlated with n. The results of temperature jump experiments showed that once the transition temperature was reached, vesicle formation was largely complete within 30 s.

Calorimetry, Differential Scanning↗
PubMed1989

Examination of a possible role for dermatan sulfate in the aggregation of commercial heparin samples.

A wide range of commercial heparin preparations were examined by the technique of quasi-elastic light scattering (QELS) for size distribution and evidence for aggregation in relation to determined dermatan sulfate (DS) content. No correlation could be found between DS content and state of aggregation. The possible interaction of DS with heparin was further studied by QELS in a control experiment in which known quantities of DS were added to a heparin sodium preparation known to be low in DS. The effect of increasing DS content was to slightly decrease the measured most probable size of the samples and also to decrease the size spread. The biological activity (as measured by the official test) of the heparin samples, including those treated with additional DS, was found to fall within the accepted limits, independent of the aggregation state of the samples. Overall, there is no direct, observable effect that links DS to the observed aggregation of commercial heparin samples, although DS itself is known to self-associate.

Chemistry, Pharmaceutical↗
PubMed1987

Aggregation of commercial heparin samples in storage.

The size distribution of heparin aggregates in commercial heparin preparations was examined with the technique of quasi-elastic light scattering. The size distributions were initially examined to determine if any relationship existed between the physical state of the heparin preparation, its age, and its biological activity. It was found that commercial heparin samples change their aggregation state in storage. The amount of aggregation appears to be related to the amount of time in storage and to the storage history. Storage of the samples under conditions of refrigeration and handling represents the storage history that most noticeably increases the aggregation state of the heparin preparations. These aggregates, once formed, appear to be stable. The biological activity of the heparin samples (as measured by the official test) was found to still fall within the accepted limits, independent of the aggregation state of the samples. It is not known what effect, if any, a change in the physical state of the commercial preparation should have on its biological activity.

Drug Stability↗
PubMed1987

Interaction of hepatic asialoglycoprotein receptor with dimyristoyl phosphatidylcholine vesicles.

The hepatocyte membrane asialoglycoprotein receptor (ASGP-R) was extracted from rabbit liver, purified, and then incubated with preformed vesicles of dimyristoyl phosphatidylcholine. The association of protein with lipid was dependent on vesicle size and the best results were achieved with small vesicles of about 20 nm diameter. The ligand binding capacity of ASGP-R-vesicle complexes was also measured and found to be approximately sevenfold greater than free receptor in aqueous buffer and twofold greater than receptor solubilized in Triton X-100. Most likely, the reconstitution procedure used in these experiments does not result in transmembrane insertion of the receptor. ASGP-R probably resides on the surface of the vesicle, held there primarily by weak hydrophobic forces.

Animals↗