Birefringence Intensity Research Articles

Structure and Histochemistry of Embryo Envelope Tissues in the Mature Dry Seed and Early Germination of Phacelia tanacetifolia

The embryo envelope tissues in both mature dry seed and during early germination of Phacelia tanacetifolia were investigated by bright-field and fluorescence light microscopy and scanning electron microscopy. The ruminate seed had an irregularly reticulate surface owing to the presence of polygonal areas, corresponding to the cells of the seed coat. The raised margins of these cells joined at the lobe tips, where radially arranged thickenings occurred. The unitegmic seed coat was made up of three distinct layers: the frayed outer layer, the middle layer with portions rising outwards to form the radial thickenings, and the inner layer, the thickness of which was greatest in the micropylar zone. The endosperm tissue had two regions, the micropylar and the lateral endosperm, which differed in polysaccharide composition, thickness and metachromasy intensity, and presence (in the lateral endosperm) or absence (in the micropylar endosperm) of birefringence of the cell walls. Moreover, in the micropylar region, where the embryo suspensor remnant was found, Ca-oxalate crystals were scarce or absent. The presence of a partially permeable cuticle covering the seed endosperm was observed. Incubation of seeds in Lucifer Yellow CH indicated that water was able to penetrate quickly into the seed coat along the pathway formed by the radial thickenings, the raised margins of the polygonal cells and the middle layer. Afterwards, LY-CH readily infiltrated the apical portions of the seed lobes and then the whole endosperm. Following imbibition, morphological changes were found in the micropylar endosperm, such as the initial digestion of protein bodies. In addition, both in the seed coat and in the endosperm, a weaker fluorescence, probably due to leaching of polyphenolic substances, was observed. Once the seed coat was broken at the micropylar end of the seed, the endosperm cap surrounding the radicle tip had to be punctured by it so that complete germination could occur. Weakening and rupture of the micropylar endosperm are briefly discussed.

Optical Properties and Photopolymerization of Liquid Crystalline (Acetyl) (Ethyl) Cellulose/Acrylic Acid System

The structure and properties of a chiral nematic phase, which reflects one hand of circularly polarized light in a narrow region of wavelength, of fully acetylated (ethyl) cellulose [(acetyl) (ethyl) cellulose, AEC] in acrylic acid (AA) were studied in comparison with (ethyl) cellulose (EC). AEC mesophase formed right-handed chiral nematic structure while EC formed left-handed one. AEC mesophase showed higher birefringence and reflection intensity. The relationship between the reflection wavelength and the polymer concentration was negatively correlated for both AEC and EC mesophases. The relationship between the reflection wavelength and the molecular weight was also negative for AEC mesophase whereas positive for EC mesophase. AEC mesophase was solidified by photopolymerization of AA moiety. It was revealed that the optical properties of AEC mesophase could be preserved by photopolymerization, since the resulting solid material reflects selectively one hand of circularly polarized light.

A comparison of some rheophysical properties of cetyltrimethylammonium bromide/H 2 O and cetyltrimethylammonium bromide/D 2 O solutions

In this paper, we report the results of rheological and optical experiments performed on two solutions of cetyltrimethylammonium bromide in D2O and H2O. The molar concentration of surfactant is the same in both solvents, with the solvents only differing in their atomic number. Important differences in the behaviour of the shear stress and of the birefringence intensity with the shear rate are found. We try to interpret these results by referring to the difference in solubility of ionic salts in D2O and H2O.

Biomechanical, histological and immunohistological studies of patellar cartilage in an ovine model of osteoarthritis induced by lateral meniscectomy

Objective: To evaluate the biomechanical, histological and immunohistochemical changes induced in patellar articular cartilage (AC) in ovine stifle joints 3 months after bilateral lateral meniscectomy, a procedure known to induce experimental osteoarthritis (OA) in the femoro-tibial joint (FTJ).Methodology: Fifteen mature adult Merino female sheep were used in this study. Ten were subjected to bilateral-lateral meniscectomy, while the remaining five were used as ‘non-operated controls’ (NOC). All animals were killed 3 months post-surgery. Topographical biomechanical indentation tests were performed on each patellae using a UMIS-2000 micro-indentation system. Initial load, relaxed and unload shear moduli were determined using an elastic analytical model, while the permeability was assessed by comparing the indentation response to a simulated indentation test conducted using a poroelastic finite element model. Immunohistochemical, normal and polarized histological studies were performed on each specimen after biomechanical testing.Results: Patellar AC from meniscectomized joints exhibited an overall decrease in initial (−34%), relaxed (−32%) and unload shear modulus (−22%), and an increase in the permeability (+72%) relative to NOC cartilage (P<0.01). The most significant differences in mechanical properties occurred on the lateral and central aspects of the patellae. There were no significant histological difference in staining between sections from NOC and meniscectomized joint AC using Toluidine Blue, a dye which binds to proteoglycans. However immunohistochemical staining with monoclonal antibody MAb 3B3(−), a putative marker of early OA change in PGs, demonstrated increased binding in the lateral and central regions of patellar sections from meniscectomized joints relative to the same regions of NOC AC. Moreover polarized light microscopy of Picro Sirius red stained sections revealed a significant decrease in birefringence intensity in the superficial-middle zones of the lateral and central regions of the patellar cartilage derived from the meniscectomized joints.Conclusion: This study has demonstrated that lateral meniscectomy is a procedure which was known to induce classical OA like changes in AC and subchondral bone of the FTJ also produced an early pathological response in the patellar AC.

Flow birefringence and stress optical law of viscoelastic solutions of cationic surfactants and sodium salicylate

The optical and rheological properties of different viscoelastic solutions of surfactant are studied in order to gather experimental data used to calculate the value of the stress optical coefficient C. Three surfactants of the same family (CTAB) have been chosen; they differ by the length of the hydrocarbon chain; it concerns the dodecyltrimethylammonium bromide (C15H34BrN or DoTAB), the myristyltrimethylammonium bromide (C17H38BrN or MyTAB), and the hexadecyltrimethylammonium bromide (C19H42BrN or CTAB). Different parameters like the temperature of the solution and the salinity of the solvent have been made to vary. Flow birefringence experiments and rheological measurements are performed on these solutions in order to study the dependence of the extinction angle , of the birefringence intensity and of the shear stress with the shear rate . These data are used to check the stress optical law which turns out to be valid in a wide range of shear rates. The stress optical coefficient C is then computed: it is found to vary with the salinity of the solvent and the temperature of the solution for a given surfactant. Then, for all solutions of this work the variations of C are related to the variations of the polarizability anisotropy and the persistence length.

DUCTILITY OF UNIAXIALLY THERMOFORMED SHEET OF POLYMETHYL METHACRYLATE

Tensile ductility of uniaxially thermoformed sheets of polymethyl methacrylate (PMMA) was analyzed in their longitudinal and transverse directions in connection with their residual birefringence and deformation recovery at reheating. The intensity of the residual birefringence increased almost linearly with the increase of extension ratio. The deformation recovery at the reheating of the thermoformed sheets indicated that molecular rearrangement induced by the uniaxial stretching in the rubbery state was accompanied by little storage of internal strain energy and thus of highly entropic elongation of polymer chains. As expected from these results, specimens cut from the thermoformed sheet in its transverse direction were less ductile than those from an unstretched sheet. Yet, specimens cut in the longitudinal direction were much more ductile in comparison with the unstretched sheet despite the development of tensile stress during the rapid cooling process in the thermoforming. Data of mechanical work consumed in the longitudinal and transverse specimens during their tensile test enabled us to propose a recommendable range of residual strain remaining in the thermoformed PMMA sheet with respect to their tensile ductility.

Macromolecular strain in periodic models of porous media flows

This paper is concerned with the deformation of macromolecules in flows which model porous media and its influence on macrorheological parameters. Two flow cells (“oscillatory convergent-divergent” and “cylinder array”) have been constructed. Adding an extra cylinder to the symmetry axis of the cylinder array cell creates a stagnation point. These cells simulate important extensional components of the flows occurring in porous media, yet they possess well-defined geometries and better characterised flow fields. A numerical simulation of viscous flow in the cylinder array cell applicable to the flow regimes used in experiments has been performed. Solutions of high molecular weight polystyrene (with concentrations well below the conventional critical concentration) were used in the experiments. Birefringence measurements revealed that molecules can achieve large strains, even in extensional flows with short residence times. This observation is discussed using a dumb-bell model with conformation dependent elastic and friction coefficients. Simultaneous pressure drop measurements showed the onset of viscoelasticity coupled with an increase in birefringence intensity. Concentration effects, the influence of the stagnation point on the observed onset of viscoelasticity and a possible mechanism of thickening are discussed.

Optical anisotropy of toluidine blue-stained transformed cell nuclei.

Changes in chromatin order with cell transformation were studied in terms of optical anisotropy (birefringence) in toluidine blue-stained NIH 3T3 and Balb/3T3 cells. The transformed NIH 3T3 cell lines used were obtained by transfection with the T24 cell H-ras oncogene and the whole genomic DNA of MCF-7 human breast carcinoma cells. C2PO and PAP2 cell lines were used as representatives of Ha-ras-transformed NIH 3T3 cells with poor and high metastatic ability, respectively. The chromatin of all cells examined exhibited metachromasy and a birefringence of greenish-yellow interference color. The highest birefringence intensity was found in the chromatin granules of the most frequent nuclear phenotype of ras- and MCF-7 DNA-transformed cells, with the exception of the cells with high metastatic ability, in which a faint birefringence was observed. The differences in chromatin birefringence intensity are assumed to indicate differences in chromatin stereoarrangement with cell transformation. In the case of the highly tumorigenic and/or highly metastatic transformants the faint birefringence is assumed to be associated with the heterogeneous and complex physiological processes that may require a relatively less ordered arrangement of the chromatin.

Experimental study of the induced flow birefringence of a suspension of rigid particles at the transition from Couette flow to Taylor vortex flow

The flow birefringence induced in solutions of rigid particles is studied experimentally in the region of the axisymmetrical Taylor vortex flow which arises once the velocity gradient G in the annular gap of a conventional Couette cell reaches a critical value G c . The measurements are performed for several values of G > G c and for 10 radial observation points in the annular gap. Solutions of two types of rigid particles are investigated: the first is a suspension of flattened clay particles like bentonite, while the second contains rod-like particles of tobacco mosaic virus (TMV). The variations of the birefringence intensity Δn and of the extinction angle κ measured in the domain of the axisymmetrical flow show a different behavior according to the shape of the particle in solution. This fact is confirmed theoretically with a good agreement for the measurements performed with solutions of flat particles.

Vector solitons in fiber waveguides with a random birefringence

A study is made of the propagation of soliton pulses in single-mode fiber waveguides with a birefringence that gives rise to a nonlinear interaction between the polarizations and to a difference between their group velocities. It is shown that a vector soliton decays if a parameter representing the birefringence intensity exceeds a certain critical value. The case when the birefringence can be described by a random function is of special interest. It is demonstrated that fluctuations of the birefringence then split the vector solitons into separate polarizations and the characteristic distance governing such splitting is calculated analytically.

Temperature-dependent birefringence patterns in Xenopus rod outer segments

Results reported here show that the birefringence of disk membranes in Xenopus rod photoreceptors depends upon the temperature at which the disks were assembled. Portions of the outer segments produced by the assembly of new disks while frogs are exposed to constant darkness and an ambient temperature of 25 degrees C have a higher birefringence than portions assembled at 18 degrees C. The intensity of birefringence reflects molecular-level structure and macromolecular-level organization of the disk membranes. It has been shown previously that increasing the ambient temperature enhances the rate of assembly of disk membranes in Xenopus rod outer segments. It also has been shown that disk membranes are assembled most frequently in the hours following light onset, and that disks assembled in the light have a lower birefringence than disks assembled in the dark. Therefore, although light and increased temperature both enhance the rate of disk membrane assembly, they have opposite effects upon the birefringence of Xenopus rod outer segments.

Correlations between the microscopic and chemical changes in wood during peatification and early coalification: a canonical variant study

The microscopic and chemical evolution of wood from peats and lignites were investigated in order to achieve a better understanding of the processes associated with the origin of cell-wall-derived huminite macerals in low-rank coals and the relationships between maceral appearance and maceral chemistry. Correlations between the observed microscopic and chemical trends were determined using canomical correlation analyses. These analyses showed that: (1) the birefringence intensity displayed by huminite macerals and pre-macerals generally decreases during peatification and early coalification as their carbohydrate fractions become progressively depolymerized and hydrolyzed (primarily through the action of microbial and fungal enzymes); (2) the intrinsic color of cells walls becomes progressively during peatification and early coalification as the phenolic components of lignins become increasingly dominant and oxidized; and (3) the primary fluorescence intensity of huminite macerals and pre-macerals decreases during peatification and early coalification due to changes in their electronic configurations arising from the partial depolymerization and side-chain modification of the lignin-derived polymers that comprise them. Similarly, changes in the general spectral fluorescence distribution of huminites and pre-huminites (for example the peak wavelength and Q ratio), are also broadly correlated with the aforementioned lignin modifications.

Peatification and early coalification of wood as deduced by quantitative microscopic methods

Quantitative microscopic examinations of 114 peatified woods, 72 lignitic woods and their recent equivalents have been made. Petrographic analysis incorporated multimode illumination in the examination of microtomed thin-sections of each wood. Semi-quantitative determinations of the relative degree of: (1) intrinsic color of cell walls in transmitted light, (2) microbial presence/absence, and (3) birefringence were determined. In addition, quantitative fluorescence was used to characterize the primary fluorescence for each wood. Several trends in the evolution of cell-wall-derived pre-maceral and maceral materials were quantified in greater detail than in previous investigations. Discriminant analyses and correlation analysis of the large data set(s) further supported the observed trends. In general, the peatification and early coalification of woody cell walls is marked by an increase in the color alteration index (i.e. darkening of tissue), an initial increase (during the surface litter stage) followed by a gradual decrease in the presence of fungal remains, and a rapid decrease in the relative intensity of cell wall birefringence. Primary fluorescence intensity decreases slowly during peatification (averaging 78% of recent cell walls) and more rapidly upon conversion to lignite (averaging only 13% of recent cell walls). λ max, alteration, and spectral area were shown to decrease slightly during incipient peatification and then gradually increase during lignitization. The Q ratio and chromaticity values increase throughout the conversion process.

Flow birefringence study at the transition from laminar to Taylor vortex flow

We have studied the birefringence induced by the flow in a liquid containing very fine particles in the vicinity of the transition between the Couette flow and the Taylor vortex flow. We derive at first an analytical expression of the axisymmetrical hydrodynamical field and then the angular velocity of a particle in the flow. The resolution of the diffusion equation leads to the orientation distribution function F. On condition of some simplifying but realistic hypotheses, we show that the extinction angle χ and the birefringence Δn of the solution are the same as the properties of an equivalent stratified medium composed of very thin layers the orientation of which varies continuously. The results concerning the velocity profile and the critical Taylor number are in good agreement with other sources ; the theoretical computation of χ and Δn are then compared to experimental curves realized with solutions of bentonite and T.M.V. ; interesting conclusions can be drawn on the influence of the shape of the particles on the behavior of the angle of extinction and of the birefringence intensity in the region of the Taylor vortex flow.

EFFECTS OF CRYOPROTECTANTS IN MINIMIZING PHYSICOCHEMICAL CHANGES OF BOVINE NATURAL ACTOMYOSIN DURING FROZEN STORAGE

Physicochemical changes in bovine natural actomyosin extracted from prerigor semimembranosus muscle were investigated during frozen storage at −28°C as affected by the addition of cryoprotectants (5.6% Polydextrose® or 5.6% mixture (1:1) of sucrose and sorbitol). Proteins were destabilized during freezing and frozen storage as reflected by decreases in protein solubility, the visual appearance of aggregates in protein sols, decrease in intensity of flow birefringence, intrinsic viscosity and ATPase activity, and changes in size, shape, or charge of the protein (especially myosin) as evidenced by nondenaturing electrophoresis. These effects were reduced to some extent by the two cryoprotectant treatments.

Bond polarizability anisotropy: Resolution of the sign ambiguity

AbstractAn internally consistent “valence–optical” scheme of additive bond and group polarizabilities, obtained from analysis of electric birefringence, refractivity and Raman intensity data, is shown to apply to a series of compounds of Group IVB elements. For all M‐halogen bonds considered (M = Si, Ge or Sn; halogen = C1, Br or I), only the positive option for ±γ, the bond anisotropy from Raman intensities, is compatible with the scheme. The negative alternatives for γ lead to results which are anomalous and in some instances not physically meaningful. This procedure permits a definitive resolution of the problem of the sign ambiguity in ±γM‐halogen.

Immunocytochemistry of the acellular slime mold Physarum polycephalum: IV. Differentiation and dynamics of the polygonal actomyosin system

The polygonal arrangement of actomyosin fibrils in different stages of the acellular slime mold Physarum polycephalum is correlated with morphogenetic processes at the cell surface. Light and electron microscopic investigations on both endoplasmic drops and thin-spread small plasmodia demonstrate that the differentiation of a polygonal pattern depends on a transient deficiency of plasma membrane invaginations. Glycerol-extracted specimens show condensation and drastic spatial changes in the organization of the polygonal net after addition of ATP, thus indicating contractile properties of this system. Observations with the polarizing microscope reveal rhythmic changes in fibrillar birefringence intensity corresponding to the protoplasmic streaming activity, i.e., birefringence increases during contraction and decreases during relaxation. Cell fusion experiments, local irradiation with blue light (450 nm), and chemical treatment by impeding the mitochondria1 function with DNP (2,4-di-nitrophenol) demonstrate morphological as well as physiological interdependences of the actomyosin system, the motive force generation, and the expression of a locomotor polarity in plasmodia of Physarum polycephalum.

Flow visualization of cellulose acetate–acetone solutions

AbstractThe flow behavior of four cellulose acetate–acetone solutions varying from 20.00% to 28.18% solids concentration was observed using flow visualization techniques at 24°C with an industrial‐type dry spinning system. Fibrous particulate matter entertained in the solutions and crossed polars revealed the streamlines and the birefringence due to flow in glass spinnerets. The streamlines of the four solutions were radially convergent at all obtainable throughputs. The crossed polars revealed a cone of birefringence with the order of the interference colors decreasing upstream of the capillary inlet. The intensity and extent of birefringence varied somewhat with concentration and throughput. Except for kneeing, the emerging extrudates were undeformed. The kneeing was not a result of flow instability a t the capillary inlet but was due to another, undetermined instability. A separate study of the kneeing revealed both a concentration dependence and hysteresis. The birefringence of the emerging extrudates was a function of both concentration and throughput, and it yielded some information about the structure of the solutions.

An analysis of the birefringence intensity from gels of hemoglobin S.

The intensity of light transmitted by a polycrystallinc sample placed between crossed Polaroids may be treated as a sum of intensities over areas which are small compared to the domain size. We subdivide the total measurement area, A, into small incremental area units, Ax Ay, and specify the values of parameters in this small area by the notation P(z,y). I f Ax dy is chosen to be small compared to a single domain of the liquid crystal, then for fibers of deoxyhemoglobin S a given area, Ax Ay, ma,y be approximated as uniaxial, having its optic axis at an angle y with respect to the polarizer axis. For thin samples we may neglect absorption and the light intensity from this small area is given by (Born & Wolf, 1959) :

Electrophysiological and endocrinological correlates during the metamorphic degeneration of a muscle fibre in Galleria mellonella (L.) (Lepidoptera).

ABSTRACT Excitatory postsynaptic potentials (e.p.s.p.s), membrane resting potentials, and intensity of birefringence were measured from the two principal planta retractor muscles (PPRMs) of the first pair of prolegs during metamorphosis of Galleria mellonella. This was done to determine whether cessation of efferent nerve impulses to these single fibres signals their degeneration. E.p.s.p.s were elicited reflexively by brushing the insect’s last abdominal segment. Though they become attenuated, e.p.s.p.s can be recorded until 11-12 hr. after pupal ecdysis. By this time the membrane resting potential has dropped from c. 55 mV. to less than 18 mV., and the intensity of birefringence has become minimal. Continuous electromyographic records taken during the initial 18 hr. after pupal ecdysis suggest that the PPRMs are being excited regularly as they degenerate. No ‘sparing effect’ on the degeneration of the PPRMs could be detected when programmed, current-limited stimuli were administered to pupae via chronically implanted electrodes. Removing all acknowledged endocrines by transecting newly emerged pupae has negligible effect on the decrease of the PPRM birefringence, but greatly retards the degradation of the membrane resting potential and e.p.s.p.s. This retardation can be alleviated by injecting the steriod hormone 20-hydroxyecdysone.