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PubMed1993

The macroscopic organization of reconstituted M13 coat protein-phospholipid systems. An EPR spectroscopy and polarizing microscope study.

The coat protein of the bacteriophage M13 in the alpha-helical state is reconstituted in macroscopically oriented systems of dioleoylphosphatidylcholine that are prepared by squeezing the reconstituted material between glass plates. The coat protein dramatically influences the macroscopic orientation of the multibilayers, as is investigated by polarizing microscopy and EPR spectroscopy of the cholestane spin label embedded in the bilayers. It is found that with increasing amounts of protein the spontaneous macroscopic orientation of the reconstituted system decreases. This effect is proposed to be due to an increase of the apparent viscosity of the lipid-protein systems with increasing amounts of protein. This is assumed to arise from a sticky effect of the C- and N-terminal protein parts that extend into the aqueous phase between the bilayers.

Capsid↗

PubMed1981

Physical properties of cholesteryl esters having 20 carbons or more.

By polarizing microscopy and differential scanning calorimetry we observed that the relative stability of the smectic and cholesteric mesophases of cholesteryl esters of acyl chain length of 20 carbons or more depends on the length of the acyl chain and its degree of unsaturation. Significantly, the addition of a single double bond to the acyl chain of a fully saturated cholesteryl ester which exhibits no mesophases (e.g., cholesteryl behenate (C22:0) and cholesteryl lignocerate (C24:0) yields an ester which displays an unusually stable smectic mesophase, bot no cholesteric mesophase. In fact, increasing unsaturation was found to have a destabilizing effect on the cholesteric phase. Similarly, a decrease in thermal stability of the cholesteric mesophase was observed with increasing thermal stability of the smectic mesophase increased in the same series. X-ray scattering data are presented on the smectic mesophase of cholesteryl erucate (C22:1) and cholesteryl nervonate (C24:1). Significant differences in molecular packing of these two monounsaturated omega = 9 cholesteryl esters in the crystalline state are demonstrated by preliminary X-ray scattering experiments.

Calorimetry, Differential Scanning↗

PubMed1984

Structural change of myofibrils during mitosis of newt embryonic myocardial cells in culture.

Newt embryonic myocardial cells can undergo mitosis in culture. The successive changes in the striation pattern of sarcomeres of myofibrils during mitosis were studied by polarization microscopy without fixing or killing the cells. Birefringence of well-organized striation patterns, i.e., bright A-bands and dark I-bands, was clearly visible in interphase cells and did not show any detectable changes during incubation for 3 h or more. Electron microscopy showed the presence of well-organized myofibrils with Z-bands in these interphase cells. When myocardial cells entered the mitotic stage, the birefringence of striation pattern of their myofibrils gradually changed with the pattern in small parts of the myofibrils gradually becoming indistinct (called 'indistinct striation' in this paper). These indistinct regions increased in size during the mitotic stage. In addition, in some regions of the indistinct striation, the birefringence of sarcomeres gradually decreased and finally disappeared (called 'disappearance of sarcomeres' in this paper). No myocardial cells underwent mitosis without these disruptive changes of the myofibril striation patterns. In the post-mitotic stage, the well-organized striation of the myofibrils reappeared. Electron microscopy showed disorganized sarcomeres without Z-bands in the regions of indistinct striation, and no well-organized myofibrils in the regions where the sarcomeres had disappeared. Thus the well-organized myofibrils with Z-bands became transiently disorganized at least in some parts, during mitosis. They were then reorganized into daughter myocardial cells.

Animals↗

PubMed1994

Injectable collagen as a pH-sensitive hydrogel.

Injectable collagen is a concentrated dispersion of phase-separated collagen fibres in aqueous solution. The structure and properties of collagen fibres are defined by the magnitudes of electrostatic and hydrophobic attractive forces between neighbouring collagen molecules within collagen fibres. The structure and mechanical properties of collagen fibre dispersions were studied by dynamic rheological measurements and by polarized microscopy. Rheological measurements were performed over pHs ranging from 6 to 9 and over temperatures ranging from 283 to 298 K. At higher pHs the fibre dispersions were found to possess more rigid fibres and stronger inter-fibre attractive forces. This response is argued to result from changes in the ionization of amino acid side chains, which result in larger net-electrostatic attractive forces. Raising the temperature caused fibres to rigidify through enhanced hydrophobic attractive forces. Gels formed by lower pH-higher temperature fibre dispersions possess different properties than gels formed at higher pHs and lower temperatures.

Animals↗

PubMed1984

Physical properties of cholesteryl esters.

Cholesteryl esters, the intracellular storage form and intravascular transport form of cholesterol, can exist in crystal, liquid crystal and liquid states. The physical state of cholesteryl esters at physiologic temperatures may be a determinant of their pathogenicity. This review has surveyed saturated aliphatic cholesteryl esters of chain length 1 to 24 carbons and a series of medium-chained unsaturated cholesteryl esters from chain lengths 14 to 24 carbons. A systematic study of transition temperatures by polarizing microscopy and enthalpies by differential scanning calorimetry has provided unifying concepts concerning the phase behavior as a function of chain length and unsaturation. Neat cholesteryl esters show chain-length dependence of transition temperature and enthalpy of both the crystal and liquid crystal transitions. Double bond position along the fatty acyl chain affected stability of the liquid crystal phases; a smectic phase was not observed for any cholesteryl ester with a double bond more proximal than delta 9. 13C NMR spectroscopy in the isotropic liquid phase has provided evidence suggesting a balance of ring-ring vs. chain-chain interactions as a determinant for isotropic liquid----cholesteric vs. isotropic liquid----smectic transitions. Specifically, anisotropic molecular motions of the steroid ring are greater for cholesteryl esters forming a cholesteric phase than a smectic phase from the melt. Chain-chain interactions apparently predominate in smectic phase formation. The X-ray diffraction patterns of cholesteryl esters as a function of chain length reveal several isostructural series and known single crystal data are presented. A chain length depending on the periodicity of the smectic phase is observed which may be different for saturated vs. unsaturated esters. In summary, the phase behavior of cholesteryl ester molecules is complex and cannot be determined a priori from the phase behavior of component cholesterol and fatty acid. The data presented here should provide insight into the biological behavior of this lipid class.

Calorimetry, Differential Scanning↗

PubMed1991

The pattern of myocardial fibrosis in chronic Chagas' heart disease.

Observations are described on the fibrillar nature and structural features of the collagenous interstices of the human myocardium in chronic chagasic cardiomyopathy, comparing them with similar observations in normal hearts, using the picrosirius red technique and polarization microscopy. A total of 28 adult hearts obtained at autopsy were used: 5 control without evidence of cardiac disease, and 23 with chronic Chagas' heart disease. The findings in the myocardium of those without Chagas' disease were in keeping with those reported in the literature. In those with Chagas' disease diffuse interstitial fibrosis could be observed in all cases, albeit to varying degree. The pattern was that of a diffuse increase in the amount of thick collagen fibers surrounding bundles of muscle fibers (perimysial matrix), varying in intensity from one area to another, and around the intramyocardial coronary vessels, combined with a less pronounced increase in the matrix of endomysial collagen. The relationship between the observed myocardial fibrosis and cardiac function, and the potential mechanisms for its production, are discussed. Further research is needed into the patterns and pathogenesis of myocardial fibrosis in order to offer possibilities for prevention and development of corrective forms of therapy for the fibrotic process.

Adult↗

PubMed1992

Changes in adrenocortical lipid fluidity of hyperfunctioning human adrenals.

Lipid droplets, the storage places of cholesterol in adrenocortical cells, exhibit a relatively uniform appearance studied by the electron microscope but they are heterogeneous in respect of their optical polarizing properties. Optical birefringency was studied in cryosections of normal and hyperfunctioning adrenal cortex by a polarizing microscope, equipped with a cold/hot stage working in the temperature range from -40 to 40 degrees C. The majority of lipid droplets in normal adrenal cortex were optically anisotropic in each cortical zone at room temperature (22 degrees C) indicating a long-range molecular order of the lipid components. The lipids of the zona glomerulosa, in the cases of Conn's and Bartter's syndromes, became anisotropic when the temperature was lowered below ambient. The birefringency of the lipids of the zona fasciculata in the case of Cushing's disease was observed at temperatures below -10 degrees C indicating ordered packing of the components of lipid droplets at this temperature. Thus the lipids were more fluid in the hyperfunctioning, hormone-producing cells--this may represent an optimal precondition for their mobilization and processing by the hydrolyzing enzyme system. The changes in fluidity of the intracellular lipids can be attributed to different functional states in the adrenal cortex. Study of the thermotropic phase transitions of the lipid droplets by polarizing microscopy may be a useful additional method for the diagnosis of some adrenocortical diseases.

Adrenal Cortex↗

PubMed2006

Optical anisotropy of alcian blue-stained acid glycosaminoglycans.

Optical anisotropy as dispersion of birefringence (DB) (birefringence studied for light of different wavelengths) and linear dichroism (LD) (selective absorption of polarized light) in stained substrates reflects their macromolecular orientation states. Birefringence interference colors of alcian blue (AB)-stained glycosaminoglycans (GAG) and glycoconjugates observed with polarization microscopy have been found to vary, although their staining characteristics under unpolarized light are practically the same. We investigated the optical anisotropy of GAG-AB and some glycoconjugate-AB complexes used as standards, to provide a basis for interpreting results for AB-stained materials in situ. Filamentous preparations of hyaluronic acid (HA), chondroitinsulfates, proteoglycans, and a mucus sulfoglycoconjugate were studied. Anomalous DB (birefringence sign changing with the wavelength of the incident light) was generally observed, but LD was seen only in the AB-HA complex. LD simultaneous to anomalous DB characteristics on the AB-HA complex were assumed to be caused by a maximally oriented helical conformation of the HA. For the other AB-GAG studied, the optical anisotropic characteristics were suggestive of some degree of folding of their chains into a tertiary structure. The profiles of the anomalous DB curves for the AB-stained sulfoglycoconjugate differed from those of the other materials, probably due to different organization of its dye-binding sites.

Alcian Blue↗

PubMed2004

In vitro microleakage of adhesive-sealed dentin with lactic acid and saliva exposure: a radio-isotope analysis.

OBJECTIVES: The aim of this study was to evaluate the dentin-protective potential of two dentin-bonding systems (Syntac and Clearfil SE Bond) on artificial saliva and lactic acid exposure. METHODS: Radiochemical analysis in combination with polarization-microscopy was used in the current study. Different applications in MOD preparations in irradiated human molars were compared. Untreated cavities and cavities covered with flowable resin served as controls. Forty-eight specimens were immersed in artificial saliva (pH 7.5), 48 in lactic acid (pH 4). Activity of (32)P was measured between days 1 and 21 and loss of mineralized tissue was estimated. RESULTS: In lactic acid, cavities sealed with single bond, double bond or bond plus cavity sealer application resulted in significantly lower mineralized tissue loss compared to negative controls (p < 0.05). Upon both saliva and lactic acid exposure, bonding plus sealer application proved to be the most protective treatment (p < 0.05). CONCLUSIONS: Based on these in vitro findings it may be advisable to use a filled cavity sealer or a flowable resin to protect dentin from demineralization. The radiochemical analysis appeared to be valuable in evaluating the protective potential of bonding agents against dentin demineralization.

Acid Etching, Dental↗

PubMed1998

The influence of polymer molecular weight in lamellar gels based on PEG-lipids.

We report x-ray scattering, rheological, and freeze-fracture and polarizing microscopy studies of a liquid crystalline hydrogel called Lalpha,g. The hydrogel, found in DMPC, pentanol, water, and PEG-DMPE mixtures, differs from traditional hydrogels, which require high MW polymer, are disordered, and gel only at polymer concentrations exceeding an "overlap" concentration. In contrast, the Lalpha,g uses very low-molecular-weight polymer-lipids (1212, 2689, and 5817 g/mole), shows lamellar order, and requires a lower PEG-DMPE concentration to gel as water concentration increases. Significantly, the Lalpha,g contains fluid membranes, unlike Lbeta' gels, which gel via chain ordering. A recent model of gelation in Lalpha phases predicts that polymer-lipids both promote and stabilize defects; these defects, resisting shear in all directions, then produce elasticity. We compare our observations to this model, with particular attention to the dependence of gelation on the PEG MW used. We also use x-ray lineshape analysis of scattering from samples spanning the fluid-gel transition to obtain the elasticity coefficients kappa and B; this analysis demonstrates that although B in particular depends strongly on PEG-DMPE concentration, gelation is uncorrelated to changes in membrane elasticity.

Biophysical Phenomena↗

PubMed1999

Solubilization of ubiquinone-10 in the lamellar and bicontinuous cubic phases of aqueous monoolein.

Using X-ray diffraction measurements and polarizing microscopy, the solubilization of ubiquinone-10 (UQ10) was investigated in the lamellar and reversed bicontinuous cubic phases of aqueous monoolein (MO, 86 wt% of monooleoylglycerol). At 25 degrees C and UQ10 content below 0.5 wt%, a partial phase diagram of the MO/UQ10/H2O system indicated the same sequence of hydration-induced phases as found in the MO/H2O system. This low amount of coenzyme had no effect on the MO bilayer thickness and swelling behavior of phases, but it promoted thermotropic Q230-->HII phase transition. We suggested that the effect was determined by the UQ10 partitioning into the HII phase regions where the MO chains must be stressed upon the phase transition. At UQ10 contents above 0.5 wt%, a solid 'UQ10-rich' phase appeared inside the initially homogeneous phases within a few days. It was proposed that this process was driven by the coenzyme lateral diffusion in the MO bilayer.

Crystallization↗

PubMed2000

Thermotropic and lyotropic properties of long chain alkyl glycopyranosides. Part I: monosaccharide headgroups.

A systematic structure variation of a classical amphiphile (dodecyl-beta-D-glucopyranoside) is performed, demonstrating the influence of anomeric linkage, configuration, ring size and flexibility as well as electric charges on the mesophase behaviour. In addition, we have investigated the thermotropic and lyotropic properties of some long chain alkyl glycosides with monosaccharide headgroups. The thermotropism was measured with polarizing microscopy and differential scanning calorimetry, and additionally the lyotropism with FTIR spectroscopy and X-ray diffraction.

Calorimetry, Differential Scanning↗

PubMed2001

Molecular mechanism for the crystallization of bacteriorhodopsin in lipidic cubic phases.

Crystals of transmembrane proteins may be grown from detergent solutions or in a matrix of membranous lipid bilayers existing in a liquid crystalline state and forming a cubic phase (in cubo). While crystallization in micellar solutions appears analogous to that for soluble proteins, crystallization in lipidic matrices is poorly understood. As this method was shown to be applicable to several membrane proteins, understanding its mechanism will facilitate a rational design of crystallization, minimizing the laborious screening of a large number of parameters. Using polarization microscopy and low-angle X-ray diffraction, experimental evidence is provided to support a mechanistic model for the in cubo crystallization of bacteriorhodopsin in a lipid matrix. Membrane proteins are thought to reside in curved lipid bilayers, to diffuse into patches of lower curvature and to incorporate into lattices which associate to form highly ordered three-dimensional crystals. Critical testing of this model is necessary to generalize it to other membrane proteins.

Bacteriorhodopsins↗

PubMed2001

Preparation and blood compatibility of polysiloxane/liquid-crystal composite membranes.

Polysiloxane/liquid crystal composite membrane was first suggested to be used as biomaterials. In this work, the polydimethyl-methylhydrosiloxane and polydimethyl-methylethylenesilosiane, as a substrate, were blended with cholesteryl oleyl carbonate (COC) in tetrahydrofuran, and then crosslinked into membranes on glass plates by means of the platinum catalyst at 110 degrees C for 20 min. The effects of the liquid-crystal content in composite membranes on the formation of liquid-crystal phase were verified by the observation of optical polarization microscopy. The relationship between the morphology of the composite membranes and blood compatibility was identified by the dynamic blood-clotting tests, haemolysis ratio measurement, platelet adhesion and SEM observation. The results show that the blood-compatibility of composite membranes with the concentration of liquid crystal 20, 30% (wt) is more excellent than that of other composite membranes.

Biocompatible Materials↗

PubMed1999

Blood-compatibility of polyurethane/liquid crystal composite membranes.

Polyurethane/liquid crystal composite membranes were first suggested to be used as biomaterials. In our work, three series of polyurethane/liquid crystal composite membranes based on three different kinds of liquid crystal compounds [N-(-4-methyoxybenzylidene)-4'-heptylaniline, 4-pentyl-4'-nitrile-biphenyl and cholesteryl oleyl carbonate] were prepared by casting on glass plates from a tetrahydrofuran (THF) solution of polymer and liquid crystal at room temperature. In our opinion, the formation of liquid crystal phase on the composite membrane surface is the basic requirement for getting better biomaterial. The result of this work is in accordance with our opinion. The effect of liquid crystal content on the formation of liquid crystal phase was identified by the observation of optical polarization microscopy (OPM). The results showed that the content of liquid crystal in composite membrane must be more than 30% (wt) in order to form liquid crystal phase on the composite membrane surface. The blood-compatibility of the composite membranes was assessed from SEM observation of the platelet's adhesion to membrane's surface, blood clotting time and haemolysis ratio. The observation of platelet's adhesion showed that the platelets gathered together on the pure polyurethane films, but the amount of platelets which were adherent on the surface covered by the liquid crystal phase was fewer than that of pure polyurethane film when platelet-rich plasma was allowed to be in contact with the membranes for 1 h at room temperature. The determination of blood clotting time and haemolysis ratio showed that these polyurethane/liquid crystal composite membranes, in which the content of liquid crystal was more than 30% (wt), appear to be beneficial in improving the blood compatibility and reducing the thrombogenicity.

Biocompatible Materials↗

PubMed2001

Influence of chlorhexidine species on the liquid crystalline structure of vehicle.

The aim of this study was to investigate the influence of three chlorhexidine species, chlorhexidine base and its salts (diacetate and digluconate), on the physico-chemical features of liquid crystalline systems and on drug transport through lipophilic membranes. Nonionic surfactant, Synperonic A7 (PEG(7)-C(13--15)) was selected for the preparation of the liquid crystalline systems. Mixtures of different ratios of Synperonic A7 and water were prepared. The liquid crystalline systems were characterized using polarizing microscopy, small-angle neutron scattering and transmission electron microscopy. Membrane transport was also examined. The addition of chlorhexidine species to the liquid crystalline system modified the structure of the liquid crystalline system. As a result of liquid crystal--drug interaction, the solubility of chlorhexidine base and its diffusion through lipophilic membranes increased in comparison with those of the chlorhexidine salts.

Chemical Phenomena↗

PubMed2000

Morphology and significance of the left ventricular collagen network in young patients with hypertrophic cardiomyopathy and sudden cardiac death.

BACKGROUND: Hypertrophic cardiomyopathy (HCM) is a primary cardiac disease with a diverse clinical spectrum, in which many of the abnormal structural and pathophysiologic features are consequences of inappropriate left ventricular hypertrophy. METHODS: We analyzed the amount, distribution and structure of the cardiac collagen network in transmural sections of the ventricular septum (thickness 17 to 40 mm, mean 25 mm) in 16 previously asymptomatic children and young adults with HCM (11 to 31 years of age, mean 20 years) who died suddenly. The morphologic appearance and volume fractions of interstitial (matrix) and perivascular (adventitial) collagen were analyzed with polarization microscopy and computerized videodensitometry in picrosirius red-stained sections. Findings were compared with 16 structurally normal hearts, 5 with systemic hypertension and 6 infants who died of HCM. RESULTS: Adults and young children with HCM had an eightfold greater amount of matrix collagen compared with normal controls (14.1 +/- 8.8% vs. 1.8 +/- 1% of the tissue section; p < 0.0001), and a threefold increase compared with patients with systemic hypertension (4.5 +/- 1.3%; p < 0.001) and infants with HCM (4.0 +/- 2.4%; p < 0.001). Compared with normal controls and hypertensives, adults and young children (and infants) with HCM showed increased numbers and thickness of each collagen fiber component of the matrix (perimysial coils, pericellular weaves and struts), which were often arranged in disorganized patterns. In HCM patients, the amount of collagen was not a consequence of other clinical, demographic and morphologic disease variables. CONCLUSIONS: Left ventricular collagen matrix in young, previously asymptomatic patients with HCM who died suddenly is morphologically abnormal and substantially increased in size. The enlarged matrix collagen compartment is present in HCM at an early age, further expands during growth, is partially responsible for increased ventricular septal thickness and likely represents a primary morphologic abnormality in this disease. These findings support the view that the complex HCM disease process is not confined to sarcomere protein abnormalities, but also involves connective tissue elements.

Adolescent↗

PubMed1997

Factors determining the refractive effects of intrastromal photorefractive keratectomy with the picosecond laser.

PURPOSE: To determine the relationship between laser parameters and tissue removal with picosecond laser intrastromal photorefractive keratectomy (ISPRK) and to assess the effect of the parameters on the healing process and the long-term refractive changes. SETTING: Medical Laser Center Lübeck, Germany. METHODS: A modified Intelligent Surgical Lasers (ISL) 2001 system with a cone angle of 30 degrees was used for in vitro investigations of the laser effects in water and on the porcine cornea. Photographic methods were used to determine the plasma volume and to investigate the thickness of the intrastromal bubble layer as a function of the laser pulse energy, the number of layers in which the pulses were applied, and the layer separation. The data were used to calculate the amount of tissue removal. Histologic evaluation was done by polarization microscopy after Sirius-red staining. RESULTS: The laser pulses produced a sponge-like appearance of the stroma in a layer extending through about one third the corneal thickness, accompanied by mechanical distortions of the stromal lamellae. Thermal changes were weak. Tissue removal was impaired by the cavitation bubbles from preceding laser pulses. The amount of evaporated tissue depended only weakly on laser pulse energy and number of layers in which the pulses were applied. The maximum amount of tissue that could be evaporated without damaging the outer corneal layers was a 10.0 microm thick layer. With a 6.0 mm optical zone, the tissue removal produced an immediate refractive effect of only 0.85 diopter. CONCLUSIONS: Intrastromal PRK does not work as originally envisioned because the amount of evaporated tissue is very small. The greater long-term refractive changes observed in animal experiments and clinical studies must therefore be due to the healing response of the cornea. Because the refractive effects are strongly influenced by the healing response of the cornea, they are poorly predictable.

Animals↗