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PubMed1989

Changes seen in lymph nodes draining the sites of large joint prostheses.

We report the histological findings seen in the lymph nodes draining the sites of large joint prostheses. Two patients underwent multiple prosthetic joint replacements. In one patient, the regional lymph nodes were enlarged during the revision of a total hip prosthesis, and a representative lymph node was resected. The other patient had undergone a pelvic lymph node dissection as part of a staging procedure for prostatic carcinoma. By light microscopy, the lymph nodes from both patients showed markedly dilated nodal sinuses filled with macrophages containing abundant eosinophilic, PAS-positive, granular material. Polarization microscopy revealed needle-like particles within the cytoplasm of the macrophages. We believe that the histological appearance of the lymph nodes represents a florid foreign body reaction to fragments of polyester or polyethylene derived from the articulating surfaces of the joint prostheses and transported to the regional lymph nodes via the lymphatic circulation. Sinus histiocytosis seen in the lymph nodes draining the sites of joint prostheses may resemble, and must be distinguished from, other conditions invoking a sinus pattern of lymphadenopathy, as well from benign and malignant diseases that involve the lymph nodes in a pattern mimicking sinus histiocytosis.

Adult↗

PubMed2001

Microtubule flux mediates poleward motion of acentric chromosome fragments during meiosis in insect spermatocytes.

We applied a combination of laser microsurgery and quantitative polarization microscopy to study kinetochore-independent forces that act on chromosome arms during meiosis in crane fly spermatocytes. When chromosome arms located within one of the half-spindles during prometa- or metaphase were cut with the laser, the acentric fragments (lacking kinetochores) that were generated moved poleward with velocities similar to those of anaphase chromosomes (approximately 0.5 microm/min). To determine the mechanism underlying this poleward motion of detached arms, we treated spermatocytes with the microtubule-stabilizing drug taxol. Spindles in taxol-treated cells were noticeably short, yet with polarized light, the distribution and densities of microtubules in domains where fragment movement occurred were not different from those in control cells. When acentric fragments were generated in taxol-treated spermatocytes, 22 of 24 fragments failed to exhibit poleward motion, and the two that did move had velocities attenuated by 80% (to approximately 0.1 microm/min). In these cells, taxol did not inhibit the disjunction of chromosomes nor prevent their poleward segregation during anaphase, but the velocity of anaphase was also decreased 80% (approximately 0.1 microm/min) relative to untreated controls. Together, these data reveal that microtubule flux exerts pole-directed forces on chromosome arms during meiosis in crane fly spermatocytes and strongly suggest that the mechanism underlying microtubule flux also is used in the anaphase motion of kinetochores in these cells.

Anaphase↗

PubMed1997

The source of NMR-detected motional anisotropy of water in blood vessel walls.

2H Double quantum-filtered (DQF) NMR spectroscopy of deuterated water is sensitive to the presence of order in biological systems. This is because the only nuclei that are detected are those with residual quadrupolar interactions due to their anisotropic motion. In the present study, samples of aorta, coronary and carotid arteries, and vena cava were studied in parallel by 2H DQF NMR and by light microscopy. The average quadrupolar splitting, calculated from the NMR data, varies considerably among the different blood vessels, with high reproducibility for each type of vessel. Polarization microscopy examinations using collagen-specific staining with picrosirius red, have shown a variety of color profiles for the different blood vessels. These reflect different physical modes of aggregation (packing and thickness) of collagen fibers. A correlation was found between the NMR parameters and the color profiles of the picrosirius red-stained sections. Treating the blood vessels with 90% formic acid resulted in the elimination of the 2H DQF NMR signal. Histological analysis demonstrated a complete degradation of collagen and muscle, whereas the elastin filaments were preserved. Evidence is given that the 2H DQF NMR signal is dominated by the contribution of water molecules interacting with the collagen fibers.

Animals↗

PubMed2002

Evidence for a new ferroelectric switching liquid crystalline phase formed by a carbosilane based dendrimer with banana-shaped mesogenic units.

The first carbosilane dendrimer with peripheral bent-core mesogenic units is reported. This material forms a liquid crystalline phase which is stable over a wide temperature range and forms an LC glass on cooling. Polarizing microscopy, X-ray diffraction, and dielectric and electrooptic investigations reveal the presence of a novel liquid crystalline phase, in which the molecules are tilted and adapt a polar order within the layers, but without long-range correlation between the layers. By applying external electric fields, switching into a ferroelectric organization can be achieved. Once formed the ferroelectric states are stable and can be switched between the different polarization states.

Journal Article↗

PubMed2002

Spin-polarized scanning tunneling microscopy with antiferromagnetic probe tips.

We have performed low temperature spin-polarized scanning tunneling microscopy (SP-STM) of two monolayers Fe on W(110) using tungsten tips coated with different magnetic materials. We observe stripe domains with a magnetic period of 50 +/- 5 nm. Employing Cr as a coating material we recorded SP-STM images with an antiferromagnetic probe tip. The advantage of its vanishing dipole field is most apparent in external magnetic fields. This new approach resolves the problem of the disturbing influence of a ferromagnetic tip in the investigation of soft magnetic materials and superparamagnetic particles.

Journal Article↗

PubMed1992

Morphological changes in liposomes caused by polymerization of encapsulated actin and spontaneous formation of actin bundles.

Spherical giant liposomes that had encapsulated skeletal-muscle G-actin were made by swelling a dried lipid mixture of dimyristoyl phosphatidylcholine/cardiolipin, 1:1 (wt/wt), in a solution of G-actin/CaCl2 at 0 degree C. Polymerization of the encapsulated G-actin into actin filaments was achieved by raising the temperature to 30 degrees C. We observed the subsequent shape changes of the liposomes by dark-field and differential interference-contrast light microscopy. After approximately 40 min, which was required for completion of actin polymerization, two shapes of liposome were evident: dumbbell and disk. Elongation of the dumbbell-shaped liposomes was concomitant with actin polymerization. Polarization microscopy showed that actin filaments formed thick bundles in the liposomes and that these filaments lay contiguous to the periphery of the liposome. Localization of actin filaments in the liposomes was confirmed by observation of rhodamine phalloidin-conjugated actin filaments by fluorescence microscopy. Both dumbbell- and disk-shaped liposomes were rigid and kept their shapes as far as actin filaments were stabilized. In contrast, liposomes containing bovine serum albumin were fragile, and their shapes continually fluctuated from Brownian motion, indicating that the actin bundles served as mechanical support for the liposome shapes.

Actin Cytoskeleton↗

PubMed1994

Analysis of polarity of bovine and rabbit embryos by scanning electron microscopy.

Cellular polarization during preimplantation development of the embryo is believed to be a crucial event in the transition of a zygote to a blastocyst stage embryo with morphologically and functionally differentiated cell types. While extensive studies have been done on polarity development in mouse embryos, little information is available in other species, particularly in cattle. The objective of this study was to examine the initiation of polarity by microvilli distribution on blastomeres of cattle and rabbit embryos using scanning electron microscopy (SEM). Bovine embryos were obtained by in vitro fertilization of in vitro-matured follicular oocytes. Rabbit embryos of various stages were collected from superovulated rabbits. Intact embryos and isolated blastomeres were examined in both species. Blastomeres from 1- to 8-cell embryos in both cattle and rabbits showed no polarity. The onset of transitional polarization of microvillous distribution occurred in some blastomeres of cattle embryos at the 9- to 15-cell stage; but typical, distinct polarity was not manifested until after the 16-cell stage with approximately 40% polar cells per embryo. In the rabbit blastomere polarity occurred one cell cycle later, with 46% polar cells per embryo after the 32-cell stage. The difference in cell numbers at the time polarity is evident is probably related to the different cell stages for embryo compaction and blastocyst formation in the two species.

Animals↗

PubMed2002

Three-dimensional high-resolution second-harmonic generation imaging of endogenous structural proteins in biological tissues.

We find that several key endogenous protein structures give rise to intense second-harmonic generation (SHG)-nonabsorptive frequency doubling of an excitation laser line. Second-harmonic imaging microscopy (SHIM) on a laser-scanning system proves, therefore, to be a powerful and unique tool for high-resolution, high-contrast, three-dimensional studies of live cell and tissue architecture. Unlike fluorescence, SHG suffers no inherent photobleaching or toxicity and does not require exogenous labels. Unlike polarization microscopy, SHIM provides intrinsic confocality and deep sectioning in complex tissues. In this study, we demonstrate the clarity of SHIM optical sectioning within unfixed, unstained thick specimens. SHIM and two-photon excited fluorescence (TPEF) were combined in a dual-mode nonlinear microscopy to elucidate the molecular sources of SHG in live cells and tissues. SHG arose not only from coiled-coil complexes within connective tissues and muscle thick filaments, but also from microtubule arrays within interphase and mitotic cells. Both polarization dependence and a local symmetry cancellation effect of SHG allowed the signal from species generating the second harmonic to be decoded, by ratiometric correlation with TPEF, to yield information on local structure below optical resolution. The physical origin of SHG within these tissues is addressed and is attributed to the laser interaction with dipolar protein structures that is enhanced by the intrinsic chirality of the protein helices.

Animals↗

PubMed1976

A study of the physicochemical interactions between biliary lipids and chlorpromazine hydrochloride. Bile-salt precipitation as a mechanism of phenothiazine-induced bile secretory failure.

Since chlorpromazine hydrochloride [2-chloro-10-(3-dimethylaminopropyl)-phenothiazine hydrochloride] is commonly implicated in causing bile-secretory failure in man and is secreted into bile, we have studied the physicochemical interactions of the drug with the major components of bile in vitro. Chlorpromazine hydrochloride molecules are amphiphilic by virtue of possessing a polar tertiary amine group linked by a short paraffin chain to a tricyclic hydrophobic part. At pH values below the apparent pK (pK'a 7.4) the molecules are water-soluble cationic detergents. We show that bile salts in concentrations above their critical micellar concentrations are precipitated from solution by chlorpromazine hydrochloride as insoluble 1:1 salt complexes. In the case of mixed bile-salt/phosphatidylcholine micellar solutions, however, the degree of precipitation is inhibited by the phospholipid in proportion to its mole fraction. With increases in the concentration of chlorpromazine hydrochloride or bile salt, micellar solubilization of the precipitated complexes results. Sonicated dispersions of the negatively charged phospholipid phosphatidylserine were also precipitated, but dispersions of the zwitterionic phospholipid phosphatidylcholine were not. Chlorpromazine hydrochloride efficiently solubilized these membrane phospholipids as mixed micellar solutions when the drug:phospholipid molar ratio reached 4:1. Polarizing-microscopy and X-ray-diffraction studies revealed that the precipitated complexes were amorphous and potentiometric studies confirmed the presence of a salt bond. Some dissociation of the complex occurred in the case of the most polar bile salt (Ks 0.365). As canalicular bile-salt secretion determines much of bile-water flow, we propose that complexing and precipitation of bile salts by chlorpromazine hydrochloride and its metabolites may be physicochemically related to the reversible bile-secretory failure produced by this drug.

Animals↗

PubMed2000

Heteroplasmic conjugates formed by the fusion of starfish oocyte pairs with a 12 minute time difference in the maturation phase.

Two starfish oocytes with a 12 min time difference in the maturation phase were fused together with electric pulses to make a heteroplasmic conjugate. The starfish used were Asterina pectinifera. The emergence of the first meiotic spindle and the extrusion of the polar bodies in the conjugate were timed. Under polarization microscopy two meiotic spindles emerged with a time difference of 10-11 min, which is close to the time difference in the maturation phase between the original oocytes before fusion. In contrast, subsequent formation of the first two polar bodies occurred successively with a short time lag of 1-3 min between them. Times for the formation of both polar bodies were midway between the anticipated times for polar body formation in respective non-fused control oocytes. Thus, in one nucleus the meiotic division was delayed, while in another nucleus it was accelerated, in a single heteroplasmic conjugate. These two sets of observations indicate the presence of a certain control system that regulates progression of the cell cycle at a point during the period from the entry into metaphase through to late anaphase of meiosis I in starfish oocytes. This type of cell cycle control in starfish oocytes is obviously distinct from the currently accepted view of the cell cycle control by the spindle assembly checkpoint that monitors unattached kinetochores of mitotic chromosomes.

Animals↗

PubMed2006

Isotropic-nematic phase transition of nonaqueous suspensions of natural clay rods.

A novel model system for studying the behavior of hard colloidal rods is presented, consisting of sterically stabilized particles of natural sepiolite clay. Electron microscopy and scattering results confirmed that the organophilic clay particles were individual, rigid rods when dispersed in organic solvents. With a length-to-diameter ratio of approximately 27, the particles showed nematic ordering for volume fractions phi > 0.06. Polarizing microscopy revealed that the phase separation process involved nucleation, growth, and coalescence of nematic domains. The phase volumes and particle concentrations in the coexisting phases were determined. The dependence of these quantities on the total concentration of the suspension agrees well with Onsager's [Ann. N. Y. Acad. Sci. 51, 627 (1949)] isotropic-nematic phase transition theory extended to bidisperse and polydisperse rod systems, and with previous experimental results for rigid rodlike particles. Particle size distributions were obtained by analyzing transmission electron microscopy images. A significant fractionation with respect to rod length (but not diameter) was observed in the coexisting isotropic and nematic phases. The relative polydispersity of both daughter phases was distinctly smaller than that of the parent suspension. The phase behavior of these daughter fractions agrees well with the predictions for hard spherocylinders of corresponding aspect ratios. An isotropic-nematic-nematic phase equilibrium was seen to develop in phase separated samples after 1 month standing and is ascribed to the effect of polydispersity and possibly gravity. The second nematic phase appearing is dominated by very long rods.

Journal Article↗

PubMed1970

Cytoplasmic filaments of Amoeba proteus. I. The role of filaments in consistency changes and movement.

The role of filaments in consistency changes and movement in a motile cytoplasmic extract of Amoeba proteus was investigated by correlating light and electron microscopic observations with viscosity measurements. The extract is prepared by the method of Thompson and Wolpert (1963). At 0 degrees C, this extract is nonmotile and similar in structure to ameba cytoplasm, consisting of groundplasm, vesicles, mitochondria, and a few 160 A filaments. The extract undergoes striking ATP-stimulated streaming when warmed to 22 degrees C. Two phases of movement are distinguished. During the first phase, the apparent viscosity usually increases and numerous 50-70 A filaments appear in samples of the extract prepared for electron microscopy, suggesting that the increase in viscosity in caused, at least in part, by the formation of these thin filaments. During this initial phase of ATP-stimulated movement, these thin filaments are not detectable by phase-contrast or polarization microscopy, but later, in the second phase of movement, 70 A filaments aggregate to form birefringent microscopic fibrils. A preparation of pure groundplasm with no 160 A filaments or membranous organelles exhibits little or no ATP-stimulated movement, but 50-70 A filaments form and aggregate into birefringent fibrils. This observation and the structural relationship of the 70 A and the 160 A filaments in the motile extract suggest that both types of filaments may be required for movement. These two types of filaments, 50-70 A and 160 A, are also present in the cytoplasm of intact amebas. Fixed cells could not be used to study the distribution of these filaments during natural ameboid movement because of difficulties in preserving the normal structure of the ameba during preparation for electron microscopy.

Adenosine Triphosphate↗

PubMed1996

Visceral Aluminum Deposition In Chronic Renal Insufficiency. (Light Microscopy and X-ray Microanalysis).

Aluminum is a common element in our environment, but has been proved to be toxic, mainly in chronic renal insufficiency. Most cases of ALU intoxication occur during hemodialysis due to treatment of aluminum-containing drugs. In the present case, we describe visceral manifestations of aluminum deposition in a middle aged, multidialysed, male patient. Light and polarization microscopy examinations and X-ray microanalysis revealed amorph, extracellular aluminum deposits in various parenchymal organs causing failure of heart, lung and kidney functions. There were no anamnestic data concerning aluminum-containing drugs or occupational exposure.

Journal Article↗

PubMed1999

Lead Resistance in Two Bacterial Isolates from Heavy Metal-Contaminated Soils.

> Abstract Microorganisms have developed mechanisms of coping with a variety of toxic metals; however, few studies have explored microbial resistance to lead. In this study, the overall mechanisms of a lead-resistant Pseudomonas marginalis and a lead-resistant Bacillus megaterium isolated from two different metal-contaminated soils were investigated. The P.marginalis had a higher lead resistance level at 2.5mM total lead as compared to 0.6 mM for B. megaterium. Resistance to soluble lead was much lower, 0.3 and 0.1 mM, respectively. The degree of lead resistance and the mechanism of lead resistance for these two isolates corresponded with their environmental lead exposure. When viewed with transmission electron microscopy, P.marginalis, isolated from a soil contaminated with high total but undetectable soluble lead, showed extracellular lead exclusion. B.megaterium, from a soil with both high total and soluble lead levels, was less resistant with an intracellular cytoplasmic accumulation of lead as observed with TEM. Polarization microscopy indicated that while P.marginalis produced a high amount of an extracellular polymer implicated in the organism's mechanism of lead resistance, B.megaterium produced no discernable extracellular polymeric substances. The study of these two organisms demonstrated differences in how soil microorganisms respond to environmental lead exposure, including the novel mechanism of intracellular sequestration of lead.

Journal Article↗

PubMed2003

Anchoring-mediated interaction of edge dislocations with bounding surfaces in confined cholesteric liquid crystals.

We employ the fluorescent confocal polarizing microscopy to image edge dislocations in cholesteric liquid crystals. Surface anchoring at the bounding plates determines the structure and behavior of defects. Two types of plates set in-plane director orientation but differ in the type of associated anchoring potentials. Plates with strong polar anchoring and nonzero azimuthal anchoring repel the dislocations, while plates with weak polar anchoring and no azimuthal anchoring allow the dislocations to escape through the boundary. To explain the results, we propose a coarse-grained model of cholesteric anchoring.

Journal Article↗

PubMed2006

Collagen fiber orientation near a fractured dental implant after a 5-year loading period: case report.

PURPOSE: Fracture of an implant is one of the possible complications of dental implants. It is a quite rare event but of high clinical relevance. Nevertheless, it represents an important opportunity for evaluating the peri-implant bone-tissue response to implant overloading in human beings. The aim of the present study was a scanning electron microscopy evaluation of a screw-shaped implant retrieved because of fracture and a birefringence analysis of the tissue near the fractured implant. MATERIALS AND METHODS: There was 1 fractured screw-shaped implant retrieved from a patient with a trephine bur, and it was processed for histology. The specimen was analyzed under both scanning electron microscopy and circularly polarized light microscopy. RESULTS: The scanning electron microscopy fractography analysis showed the typical signs of a fatigue-fracture, with large plastic deformations on the implant. The fracture seemed to start from the internal coil of the implant. Under circularly polarized light microscopy investigation, a bone-implant contact percentage of 81.6% +/- 1.5% (mean +/- standard deviation) was found. The amount of the transverse collagen fibers was of 68.3%, and the amount of the longitudinal collagen fibers was of 31.7%. The difference was statistically significant for z = 2.247 (P = 0.025). CONCLUSION: The fracture of the implant was most probably correlated to a fatigue of the material mainly associated to a lesion of the internal coil. The high level of bone-implant contact percentage was correlated to a predominant transverse collagen fiber orientation of the collagen fibers in the peri-implant bone.

Bone Remodeling↗

PubMed1978

Tubulin and actin in paired nonneoplastic and spontaneously transformed neoplastic cell lines in vitro: fluorescent antibody studies.

Pairs of nonneoplastic and spontaneously transformed neoplastic cells were derived from rat, mouse and hamster embryos. The neoplastic cells of each pair had poorly spread cellular morphology, grew in agarose in vitro and produced invasive sarcomas in vivo; the nonneoplastic cells exhibited none of these properties. The distribution of microtubules and microfilament bundles (stress fibers or actin cables) was examined in five such paired lines and in 3T3 and SV40-transformed 3T3 cells by indirect immunofluorescent microscopy of fixed cells treated with rabbit antibody prepared against bovine brain tubulin or guinea pig smooth muscle actin, respectively. Actin cables in all the neoplastic cells appeared thinner and more sparse than in the paired nonneoplastic cells. These differences were also observed in living cells with polarization microscopy. In contrast, microtubules appeared similar in neoplastic and nonneoplastic cells, both in areas of thin peripheral lamellar cytoplasm which allowed a clear visualization of fine, curving microtubules and in regions of thick, central endoplasm which obsecured individual microtubules. In fact, the main morphological difference between neoplastic and nonneoplastic cells was the relative amount of lamellar cytoplasm or endoplasm, rather than the appearance of microtubles in either region. Thus the distinctive growth properties and retracted cellular morphology of neoplastic cells in this study did not correlate with decreased or disorganized microtubules, but with thin and sparse actin cables.

Actins↗

PubMed2006

Assembly of biliary lipids in native hepatic bile after orthotopic liver transplantation: A biochemical and ultra-structural study in humans.

BACKGROUND: In gallbladder bile, lipids aggregate as micelles and vesicles, yet the presence of lamellae remains controversial. Little is known on lipid assembly in dilute hepatic bile. Liver transplantation represents a condition in which bile is diluted immediately after transplant and tends to normalize thereafter. AIM: To study biliary lipidic carriers after liver transplantation in relation to the increasing bile lipid concentration. METHODS: Three bile samples were harvested from six patients (3M/3F) with normal post-transplant outcome: sample 1 at days 2-3, sample 2 at 1 week, and sample 3 at 2 weeks after transplant. Samples were analyzed by biochemical, morphological and quasi-elastic light scattering methodology. RESULTS: Lipid concentration increased from 0.6g/dl at day 2-3 to 3.6g/dl at week 2. Electron microscopy showed the presence of unilamellar vesicles in all samples. Large amorphous particles interpreted as proteic aggregates were also present at day 2-3, while lamellae coexisted with vesicles later. Quasi-elastic light scattering data were consistent with electron microscopic findings. Liquid crystals were observed at polarizing microscopy with increasing bile lipid concentration. CONCLUSIONS: Normalization of biliary lipid secretion after liver transplantation is associated with: (i) increased proportion of vesicles and reduction of their size; (ii) presence of lamellae.

Journal Article↗