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At least 703 records · Page 39Linked to original sources
PubMed1998

[Morphologic image processing operators: reduction of partial volume effects for improved 3D visualization of CT data].

AIM: The quality of segmentation and three-dimensional reconstruction of anatomical structures in tomographic slices is often impaired by disturbances due to partial volume effects (PVE). The potential for artefact reduction by use of the morphological image processing operators (MO) erosion and dilation is investigated. DESIGN: The CT examinations of 31 patients with pathological alterations in lung or brain were segmented using automatic region growing and the MO were applied in a different number of iterations. The processed regions were 3D-reconstructed (shaded surface display, MIP, volume rendering) and the occurrence of PVE-related artefacts using the signal-to-background ratio (SBR) prior to and after MO application was compared. RESULTS: For all patients under review, the artefacts caused by PVE were significantly reduced by erosion (lung: mean SBRpre = 1.67, SBRpost = 4.83; brain: SBRpre = 1.06, SBRpost = 1.29) even with only a small number of iterations. Region dilation was applied to integrate further structures (e.g. at tumor borders) into a configurable neighbourhood for segmentation and quantitative analysis. CONCLUSIONS: The MO represent an efficient approach for the reduction of PVE artefacts in 3D-CT reconstructions and allow optimized visualization of individual objects.

Densitometry↗
PubMedDate not supplied

Data mining the NCI cancer cell line compound GI(50) values: identifying quinone subtypes effective against melanoma and leukemia cell classes.

Using data mining techniques, we have studied a subset (1400) of compounds from the large public National Cancer Institute (NCI) compounds data repository. We first carried out a functional class identity assignment for the 60 NCI cancer testing cell lines via hierarchical clustering of gene expression data. Comprised of nine clinical tissue types, the 60 cell lines were placed into six classes-melanoma, leukemia, renal, lung, and colorectal, and the sixth class was comprised of mixed tissue cell lines not found in any of the other five classes. We then carried out supervised machine learning, using the GI(50) values tested on a panel of 60 NCI cancer cell lines. For separate 3-class and 2-class problem clustering, we successfully carried out clear cell line class separation at high stringency, p < 0.01 (Bonferroni corrected t-statistic), using feature reduction clustering algorithms embedded in RadViz, an integrated high dimensional analytic and visualization tool. We started with the 1400 compound GI(50) values as input and selected only those compounds, or features, significant in carrying out the classification. With this approach, we identified two small sets of compounds that were most effective in carrying out complete class separation of the melanoma, non-melanoma classes and leukemia, non-leukemia classes. To validate these results, we showed that these two compound sets' GI(50) values were highly accurate classifiers using five standard analytical algorithms. One compound set was most effective against the melanoma class cell lines (14 compounds), and the other set was most effective against the leukemia class cell lines (30 compounds). The two compound classes were both significantly enriched in two different types of substituted p-quinones. The melanoma cell line class of 14 compounds was comprised of 11 compounds that were internal substituted p-quinones, and the leukemia cell line class of 30 compounds was comprised of 6 compounds that were external substituted p-quinones. Attempts to subclassify melanoma or leukemia cell lines based upon their clinical cancer subtype met with limited success. For example, using GI(50) values for the 30 compounds we identified as effective against all leukemia cell lines, we could subclassify acute lymphoblastic leukemia (ALL) origin cell lines from non-ALL leukemia origin cell lines without significant overlap from non-leukemia cell lines. Based upon clustering using GI(50) values for the 60 cancer cell lines laid out by the RadViz algorithm, these two compound subsets did not overlap with clusters containing any of the NCI's 92 compounds of known mechanism of action, a few of which are quinones. Given their structural patterns, the two p-quinone subtypes we identified would clearly be expected to possess different redox potentials/substrate specificities for enzymatic reduction in vivo. These two p-quinone subtypes represent valuable information that may be used in the elucidation of pharmacophores for the design of compounds to treat these two cancer tissue types in the clinic.

Algorithms↗
PubMed1992

Effect of loading on swelling-controlled drug release from hydrophobic polyelectrolyte gel beads.

The effect of oxprenolol HCl loading on the kinetics of polymer swelling and drug release from suspension-polymerized poly(methyl methacrylate-co-methacrylic acid) (PMMA/MAA) beads has been studied in detail. Within the range of variables studied, the polymer swelling rate increases with buffer pH and concentration. And an ionization-controlled swelling mechanism (analogous to the relaxation-controlled mechanism) mechanism) seems to become more rate-limiting at higher buffer concentrations. At oxprenolol HCL loading levels below 17.8%, the drug release and associated dimensional changes (in pH 7.4) exhibit an extended quasi-linear region despite the inherent limitation of spherical geometry. At higher loading levels, the drug release becomes faster and first-order in nature. This is apparently a result of the transition from a dissolved to a dispersed system above a percolation threshold (15-18% loading in the present study). As a result of competition from processes such as the reduction of bead dimension due to drug release and the dimensional increase due to polymer swelling and osmotic contributions from the drug, the transient bead diameter increases monotonically during drug release at loading levels up to 25.6%, whereas upon further increasing the drug loading, the bead diameter goes through a maximum during the early drug release, which eventually increases again as a result of the slow but continuous increase in polymer swelling due to further ionization. In all cases, both the drug release and the dimensional changes approach completion as the penetrating ionization fronts meet at the center, indicating a true swelling-controlled behavior.

Buffers↗
PubMed2001

Carbon dioxide laser treatment promotes repair of the three-dimensional network of elastic fibres in rat skin.

BACKGROUND: We have previously reported that ultraviolet (UV) B irradiation induces a loss of linearity in the three-dimensional structure of dermal elastic fibres, which results in the reduction of elastic properties of the skin and leads to wrinkle formation. We further reported that repair of wrinkles by all-trans retinoic acid is accompanied by recovery of the linearity of elastic fibres. Carbon dioxide (CO2) lasers are widely used for treating wrinkles in cosmetic surgery. OBJECTIVES: To perform CO2 laser treatment of wrinkles induced in rat skin by UVB irradiation and to evaluate changes in the three-dimensional structure of dermal elastic fibres during wrinkle repair. METHODS: Wrinkles were induced in the hind limb skin of Sprague-Dawley rats by UVB irradiation (130 mJ cm-2 three times weekly for 6 weeks), followed by CO2 laser treatment (11.3 J cm-2). The surface appearance of the skin was evaluated by replica observation 6 and 10 weeks after CO2 laser treatment followed by measurement of mechanical properties using a Cutometer. Subsequently, perfusion fixation and digestion with formic acid were performed and elastic fibres were observed by scanning electron microscopy (SEM). Image analysis of SEM micrographs was carried out to evaluate the linearity in the three-dimensional structure of elastic fibres. RESULTS: Six weeks after CO2 laser treatment, all parameters of skin mechanical properties in the UVB-irradiated group recovered to levels of the control non-irradiated group, accompanied by repair of wrinkles and a significant increase in linearity of the three-dimensional structure of elastic fibres. CONCLUSIONS: These findings indicate that CO2 laser treatment has a therapeutic potential to repair wrinkles to non-irradiated levels through recovery of the three-dimensional structure of elastic fibres.

Animals↗
PubMed2001

Three-dimensional head and upper arm orientations during kinematically redundant movements and at rest.

The three rotational degrees of freedom of the head and the upper arm exceed the number needed in a two-dimensional (2-D) facing or pointing task, respectively. Previous studies reported a reduction of the number of degrees of freedom from three to two, with one degree of freedom being a unique function of the other two (Donders' law). This study investigated whether three-dimensional (3-D) orientations of the head and arm are the same at rest and during movement for corresponding pointing or facing directions. Two separate experiments were performed: one focused on head orientations, the other focused on upper arm orientations. We instructed subjects to direct the nose or to point the extended arm in the direction of targets, which appeared in a quasi-random order at 2-s intervals. The head and upper arm orientations at rest were described by a 2-D surface with a scatter less than 3 or 4 degrees, respectively. Both for the arm and the head, orientations started and ended near the 2-D surface, but for a number of the target pairs, the orientations deviated from those predicted by the 2-D surface during movement in a way that was consistent and reproducible for movements between each target pair. For upper arm movements, we often found that deviations of arm orientations from the 2-D surface increased with increasing movement velocity. Such a positive correlation between deviation and movement velocity was not found for head movements. These results clearly indicate violations of Donders' law during movement and argue against several models for movement control found in the literature.

Adult↗
PubMed1995

The three-dimensional structure of NAD(P)H:quinone reductase, a flavoprotein involved in cancer chemoprotection and chemotherapy: mechanism of the two-electron reduction.

Quinone reductase [NAD(P)H:(quinone acceptor) oxidoreductase, EC 1.6.99.2], also called DT diaphorase, is a homodimeric FAD-containing enzyme that catalyzes obligatory NAD(P)H-dependent two-electron reductions of quinones and protects cells against the toxic and neoplastic effects of free radicals and reactive oxygen species arising from one-electron reductions. These two-electron reductions participate in the reductive bioactivation of cancer chemotherapeutic agents such as mitomycin C in tumor cells. Thus, surprisingly, the same enzymatic reaction that protects normal cells activates cytotoxic drugs used in cancer chemotherapy. The 2.1-A crystal structure of rat liver quinone reductase reveals that the folding of a portion of each monomer is similar to that of flavodoxin, a bacterial FMN-containing protein. Two additional portions of the polypeptide chains are involved in dimerization and in formation of the two identical catalytic sites to which both monomers contribute. The crystallographic structures of two FAD-containing enzyme complexes (one containing NADP+, the other containing duroquinone) suggest that direct hydride transfers from NAD(P)H to FAD and from FADH2 to the quinone [which occupies the site vacated by NAD(P)H] provide a simple rationale for the obligatory two-electron reductions involving a ping-pong mechanism.

Amino Acid Sequence↗
PubMed1997

Attenuated T2 relaxation by mutual cancellation of dipole-dipole coupling and chemical shift anisotropy indicates an avenue to NMR structures of very large biological macromolecules in solution.

Fast transverse relaxation of 1H, 15N, and 13C by dipole-dipole coupling (DD) and chemical shift anisotropy (CSA) modulated by rotational molecular motions has a dominant impact on the size limit for biomacromolecular structures that can be studied by NMR spectroscopy in solution. Transverse relaxation-optimized spectroscopy (TROSY) is an approach for suppression of transverse relaxation in multidimensional NMR experiments, which is based on constructive use of interference between DD coupling and CSA. For example, a TROSY-type two-dimensional 1H,15N-correlation experiment with a uniformly 15N-labeled protein in a DNA complex of molecular mass 17 kDa at a 1H frequency of 750 MHz showed that 15N relaxation during 15N chemical shift evolution and 1HN relaxation during signal acquisition both are significantly reduced by mutual compensation of the DD and CSA interactions. The reduction of the linewidths when compared with a conventional two-dimensional 1H,15N-correlation experiment was 60% and 40%, respectively, and the residual linewidths were 5 Hz for 15N and 15 Hz for 1HN at 4 degrees C. Because the ratio of the DD and CSA relaxation rates is nearly independent of the molecular size, a similar percentagewise reduction of the overall transverse relaxation rates is expected for larger proteins. For a 15N-labeled protein of 150 kDa at 750 MHz and 20 degrees C one predicts residual linewidths of 10 Hz for 15N and 45 Hz for 1HN, and for the corresponding uniformly 15N,2H-labeled protein the residual linewidths are predicted to be smaller than 5 Hz and 15 Hz, respectively. The TROSY principle should benefit a variety of multidimensional solution NMR experiments, especially with future use of yet somewhat higher polarizing magnetic fields than are presently available, and thus largely eliminate one of the key factors that limit work with larger molecules.

Anisotropy↗
PubMed2001

Inverse electronic scattering by singular values decomposition within the Fresnel-Kirchhoff formalism.

The inverse scattering technique we presented previously to enable a sample reconstruction from the diffraction figures obtained by electronic projection microscopy is reforrmulated within the Fresnel-Kirchhoff formalism, which describes the sample as a two-dimensional mask. The method relies on the use of singular values decomposition techniques, thus providing the best least-squares solutions and enabling a reduction of noise. The technique is applied to the analysis of a two-dimensional nanometric sample that is observed in Fresnel conditions with an electronic energy of 40 eV. The algorithm turns out to provide results with a mean relative error around 1% and to be very stable against random noise.

Journal Article↗
PubMed2003

Investigation of the convergence of the mixed displacement-pressure formulation for three-dimensional poroelastic materials using hierarchical elements.

Recently, a mixed pressure displacement [u, P] formulation based on Biot's poroelasticity equations has been presented for porous materials. This model leads to a reduction of the number of degrees of freedom required for the modeling of three-dimensional porous media in comparison to classical displacement-displacement [u, U] formulations. In this paper, an extension of the [u, P] formulation based on hierarchical elements is presented. First, a variant of the weak integral form of the [u, P] formulation is presented and its numerical implementation using hierarchical elements is detailed, together with the application of boundary and loading conditions. Numerical results are presented to show the accuracy and performance of the present approach. In particular, the importance of correctly capturing the coupling effects between the two phases is highlighted.

Journal Article↗
PubMed1986

Analysis of proteins in rabbit pulmonary surfactant using monoclonal antibodies.

We have used monoclonal antibodies developed against the apolipoproteins associated with pulmonary surfactant purified from rabbit lavage fluid to study the expression of epitopes common to these proteins. The pulmonary surfactant contained nearly 20 proteins, of which at least 10 were not derived from serum. Electrophoresis, with sulfhydryl reduction of these proteins indicated apparent molecular weights of approximately 155, 135, 125, and 115 X 10(3) (high-molecular-weight group); 80, 70, and 60 X 10(3) (intermediate group); and 18 through 10 X 10(3) (low-molecular-weight group). Two-dimensional polyacrylamide gel electrophoresis, in which the proteins were electrophoresed without reduction in the first dimension, but with sulfhydryl reduction in the second dimension, revealed that the 80, 70, and 60 X 10(3) proteins dissociated into proteins of nominal molecular weights of 40, 35, and 30 X 10(3), respectively. In contrast, the 125 and 115 X 10(3) proteins of the high-molecular-weight group contained a protein which could only be reduced to a minimum molecular weight of 55 to 60 X 10(3). Monoclonal antibodies generally were of three types: those that reacted strongly with the high-molecular-weight group and weakly with the intermediate group; those that reacted conversely; and those that reacted only with the low-molecular-weight group. Our results indicate that at least two different surfactant apolipoproteins, with differing minimum molecular weights in SDS-polyacrylamide gel electrophoresis, have common epitopes. Although these results cannot certify a physiological relationship between these proteins, they suggest that the intracellular synthesis or extracellular processing of surfactant apolipoproteins may be more complicated than predicted by the findings of previous experiments, perhaps involving the posttranslational assembly of one surfactant protein into oligomers which resist dissociation under the conditions used for the analyses.

Animals↗
PubMed2006

Towards determining details of anaerobic growth coupled to ferric iron reduction by the acidophilic archaeon 'Ferroplasma acidarmanus' Fer1.

Elucidation of the different growth states of Ferroplasma species is crucial in understanding the cycling of iron in acid leaching sites. Therefore, a proteomic and biochemical study of anaerobic growth in 'Ferroplasma acidarmanus' Fer1 has been carried out. Anaerobic growth in Ferroplasma spp. occurred by coupling oxidation of organic carbon with the reduction of Fe(3+); but sulfate, nitrate, sulfite, thiosulfate, and arsenate were not utilized as electron acceptors. Rates of Fe(3+) reduction were similar to other acidophilic chemoorganotrophs. Analysis of the 'F. acidarmanus' Fer1 proteome by 2-dimensional polyacrylamide gel electrophoresis revealed ten key proteins linked with central metabolic pathways > or =4 fold up-regulated during anaerobic growth. These included proteins putatively identified as associated with the reductive tricarboxylic acid pathway used for anaerobic energy production, and others including a putative flavoprotein involved in electron transport. Inhibition of anaerobic growth and Fe(3+) reduction by inhibitors suggests the involvement of electron transport in Fe(3+)reduction. This study has increased the knowledge of anaerobic growth in this biotechnologically and environmentally important acidophilic archaeon.

Anaerobiosis↗
PubMed1999

Optimized preoperative planning of calcaneal fractures using spiral computed tomography.

The aim of this study was the evaluation of spiral-CT examinations in preoperative planning of calcaneal fractures supported by 3D reconstructions after electronic disarticulation. We examined 45 patients with 47 calcaneal fractures with diagnostic spiral-CT examinations in a prospective study. In addition to the conventional axial slices and sagittal reconstructions, 3D reconstructions prior to and after electronic disarticulation were performed and rated by orthopaedic surgeons and radiologists. The following diagnostic criteria were rated: involvement of articular facets, number of fragments and hindfoot deformities. Axial slices were considered to be the gold standard, because not all patients underwent surgical treatment. Axial slices showed involvement of 90 articular facets (100 %). Three-dimensional reformations after electronic disarticulation depicted 82 fractures (82 of 90, 91 %), sagittal reconstructions 63 fractures (63 of 90, 70 %). Three-dimensional reconstructions without electronic disarticulation showed five fractures (5 of 90, 5.5 %). The number of fragments was demonstrated best on sagittal reconstructions (two, three or four fragments); five fragments were diagnosed best on axial slices, and 3D reconstruction without electronic disarticulation showed only a very small number of fragments, due to overlaying bones. Hindfoot deformities (lateralisation, varus deformation, shortening) were demonstrated best on axial slices, except in terms of showing height reduction, which was demonstrated better on sagittal and 3D reconstructions. Three-dimensional reconstructions after electronic disarticulation support a clear understanding of the 3D position of the fragments and of their displacement in comparison with 3D reconstruction without electronic disarticulation, which is essential for an effective surgical reduction. Due to the potential manipulation of surface-oriented 3D reconstructions, regardless of whether electronic disarticulation is used, this imaging technique should not be considered in an isolated framework. Three-dimensional images without electronic disarticulation are superfluous in any case.

Calcaneus↗
PubMed1998

Three-dimensional vascular imaging using Doppler ultrasound.

BACKGROUND: We have evaluated the efficacy of using three-dimensional reconstruction of amplitude Doppler imaging data to quantitatively assess carotid artery bifurcation stenoses. METHODS: Sixty-four consecutive frames of amplitude (power) Doppler images are stored to be reassembled into a three-dimensional image representing the patent lumen. These images can then be rotated by any angle necessary to clearly view the vascular anatomy and to make quantitative ultrasound caliper measurements of the stenotic lumen and normal vessel caliber. RESULTS: Three-dimensional Doppler images accurately classified 53 of 61 vessels (87%) into categories of stenosis compared with angiography. All stenoses with >60% diameter reduction were detected and classified as such, for a sensitivity of 100%. CONCLUSIONS: Three-dimensional vascular imaging based on amplitude (power) Doppler data provides an accurate noninvasive technique for quantitative diagnosis of carotid bifurcation atherosclerotic disease, with selectable viewing projections that eliminate vessel overlap and other artifacts, and complements the hemodynamic data already available with two-dimensional duplex ultrasound.

Aged↗
PubMed1994

Reduction of 3'-azido-3'-deoxythymidine (AZT) and AZT nucleotides by thiols. Kinetics and product identification.

3'-Azido-3'-deoxythymidine (AZT), AZT 5'-monophosphate, and AZT 5'-triphosphate (AZTTP) were reduced by dithiothreitol with second-order rate constants of 2.30 x 10(-3), 1.50 x 10(-3), and 7.46 x 10(-4) M-1 s-1, respectively. Handlon and Oppenheimer reported that AZT is quantitatively reduced by thiols to 3'-amino-3'-deoxythymidine (Handlon, A. L., and Oppenheimer, N. J. (1988) Pharm. Res. (N.Y.) 5, 297-299). In the present report, multiple products of this reaction were identified by the techniques of UV spectroscopy, phosphate analysis, coelution with authentic standards from reversed-phase high pressure liquid chromatography, two-dimensional NMR spectroscopy, and mass spectrometry. The product mixture from reduction of AZT 5'-monophosphate at pH 7.1 and 25 degrees C was composed of 2,3'-anhydro-beta-D-threo-thymidine 5'-monophosphate (6.4%), 3'-amino-3'-deoxythymidine 5'-monophosphate (19.6%), beta-D-threo-thymidine 5'-monophosphate (6.8%), thymine and 3-amino-2,3-dideoxyribal 5-monophosphate (8.9%), beta-D-threo-thymidine 3',5'-cyclic monophosphate (9.1%), 3'-deoxy-2',3'-didehydrothymidine 5'-monophosphate (31.5%), and 3',5'-anhydro-beta-D-threo-thymidine (17.8%). Thymine and 3',5'-anhydro-beta-D-threo-thymidine were also products of reduction of AZT and AZTTP. Furthermore, the nucleosides of the above monophosphates were products of reduction of AZT, and the corresponding triphosphates were products of reduction of AZTTP. The product ratios were dependent on the level of phosphorylation of AZT and on the pH of the reaction. Mechanisms for formation of these products are proposed.

Antiviral Agents↗
PubMed2006

Association of Cryptosporidium with bovine faecal particles and implications for risk reduction by settling within water supply reservoirs.

Artificial cow pats were seeded with Cryptosporidium oocysts and subjected to a simulated rainfall event. The runoff from the faecal pat was collected and different particle size fractions were collected within settling columns by exploiting the size-dependent settling velocities. Particle size and Cryptosporidium concentration distribution at 10 cm below the surface was measured at regular intervals over 24 h. Initially a large proportion of the total volume of particles belonged to the larger size classes (> 17 microm). However, throughout the course of the experiment, there was a sequential loss of the larger size classes from the sampling depth and a predominance of smaller particles (< 17 microm). The Cryptosporidium concentration at 10 cm depth did not change throughout the experiment. In the second experiment samples were taken from different depths within the settling column. Initially 26% of particles were in the size range 124-492 microm. However, as these large particles settled there was an enrichment at 30 cm after one hour (36.5-49.3%). There was a concomitant enrichment of smaller particles near the surface after 1 h and 24 h. For Pat 1 there was no difference in Cryptosporidium concentration with depth after 1 h and 24 h. In Pat 2 there was a difference in concentration between the surface and 30 cm after 24 h. However, this could be explained by the settling velocity of a single oocyst. The results suggested that oocysts are not associated with large particles, but exist in faecal runoff as single oocysts and hence have a low (0.1 m(d-1)) settling velocity. The implications of this low settling velocity on Cryptosporidium risk reduction within water supply reservoirs was investigated through the application of a three-dimensional model of oocyst fate and transport to a moderately sized reservoir (26 GL). The model indicated that the role of settling on oocyst concentration reduction within the water column is between one and three orders of magnitude less than that caused by advection and dilution, depending on the strength of hydrodynamic forcing.

Animals↗
PubMed1994

Decreased phosphorylation of four 20-kDa proteins precedes staurosporine-induced disruption of the actin/myosin cytoskeleton in rat astrocytes.

The changes in protein phosphorylation and cytoskeletal structure preceding the dramatic morphological changes in staurosporine-treated rat astrocytes were examined, and the dependence of these effects on protein kinase C (PKC) was studied. Fluorescence and photoelectron microscopy revealed that a 20-min exposure to the kinase inhibitor staurosporine at 100 nM substantially decreased the thickness and linear appearance of actin microfilament bundles (stress fibers) prior to major changes in cell shape, while 60 min of staurosporine depleted virtually all microfilament bundles and caused arborization and contraction of the cell body. The distribution of myosin light chain (MLC) labeling within the cytoplasm was also dramatically altered by staurosporine, progressing from a linear punctate pattern coincident with the linear pattern of filamentous actin to a diffuse pattern in cells in which microfilament dissolution was taking place. Two-dimensional gel analysis of astrocyte phosphoproteins demonstrated 50-80% reduction of 32P incorporation into four 20-kDa spots, one of which was recognized by an antibody to MLC, following a 15-min treatment with 100 nM staurosporine. Depletion of functinal PKC from astrocytes by a 24-h exposure to phorbol myristate acetate prior to staurosporine exposure did not reduce the extent of the cytoskeletal alterations or alter the decrease in protein phosphorylation. Two other protein kinase inhibitors which affect astrocyte morphology, H-7 and the MLC kinase inhibitor ML-9, were also observed to disrupt microfilament bundles with accompanying decreases in 32P incorporation into these same phosphoproteins, whereas the more selective PKC inhibitor Ro 31-8220 did not do either. The early onset of decreased phosphorylation of the 20-kDa proteins supports a direct relationship between the rapid dissociation of myosin light chain from actin microfilament bundles, the disruption of actin patterns, and the subsequent morphological alterations. These data also suggest that staurosporine and H-7 may exert their effects via a pathway involving inhibition of MLC kinase.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1987

On the macromolecular composition of the zona pellucida from porcine oocytes.

The chemical and immunological relation between the glycoprotein components of the pig oocyte zona pellucida resolved by two-dimensional polyacrylamide gel electrophoresis was investigated. After disulfide bond reduction, four microheterogeneous glycoprotein components with apparent molecular weights of 25K, 55K, 65K, and 90K were resolved. When disulfide bonds were left unreduced, two microheterogeneous glycoprotein components were resolved with apparent molecular weights of 55K and 90K. Actin was present, but as a contaminant of the zona pellucida rather than as a true component. The structural relation of these components was investigated using deglycosylation with trifluoromethane-sulfonic acid, limited proteolysis with Staphylococcus aureus V8 protease, amino acid and carbohydrate composition analyses, sequence analysis, and monoclonal antibodies. The 25K and 65K components comigrated with the 90K component when disulfide bonds were not reduced. When the intermolecular disulfide bonds crosslinking the two components were reduced, the 25K and 65K components behaved independently. The 25K and 65K components were derived from the 90K glycoprotein family by proteolysis. The 25K component originated from the C-terminal end, and the 65K component from the N-terminal end of the 90K glycoprotein. The 55K component was composed of two chemically and antigenically distinct glycoproteins, termed 55K alpha and 55K beta, that electrophoretically comigrated. The N-terminal amino acid of the 55K alpha family was blocked. The 55K beta family had an N-terminal amino acid sequence of Asp-Val-Pro-Thr-Ile-Gly-Leu-Ser-X-Ala-Pro-Thr. Thus, the two to four electrophoretic components of the zona pellucida observed on gel electrophoresis are derived from three glycoprotein families.

Actins↗
PubMed2006

Dynamic mechanical studies of hydrolytic degradation in isotropic and oriented Maxon B.

Hydrolytic degradation studies have been undertaken on Maxon B, a bioresorbable block copolymer of polyglycolic acid (PGA) and polytrimethylene carbonate (TMC). Isotropic and oriented samples were studied by dynamic mechanical measurements over a wide range of temperatures. In addition to mechanical tests, water content and mass loss were also determined on the degraded samples. At early stages of degradation water content was the dominant factor and plasticisation lead to reductions in the glass transition temperatures of the PGA and TMC components. Orientation was shown to give significant improvements in the mechanical properties, including overall increases in modulus and an increase in the glass transition temperature of the PGA component, which is important for the behaviour at body temperature (37 degrees C). Oriented samples also showed significantly less reduction in mechanical properties on degradation. Simple one-dimensional Takayanagi models were used to provide useful insight into the understanding of the mechanical behaviour.

Biocompatible Materials↗