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At least 721 records · Page 40Linked to original sources
PubMed2006

The structural basis of interlamellar cohesion in the intervertebral disc wall.

The purpose of this study was to investigate the structural mechanisms that create cohesion between the concentric lamellae comprising the disc annulus. Sections, 50-60 microm thick, were obtained using a carefully chosen cutting plane that incorporated the fibrous component in alternating lamellae as in-plane and cross-sectioned arrays. These sections were then subjected to microtensile stretching both across (radial) and along (tangential) the in-plane fibre direction, in their fully hydrated state. Structural responses were studied by simultaneously viewing the sections using high-resolution Nomarski interference contrast light microscopy. Additional bulk samples of annulus were fixed while held in a constant, radially stretched state in order to investigate the potential for interlamellar separation to occur in a state more representative of the intact disc wall. The study has provided a detailed picture of the structural architecture creating disc wall cohesion, revealing a complex hierarchy of interconnecting relationships within the disc wall, not previously described. Importantly, because our experimental approach offers a high-resolution view of the response of the interlamellar junction to deformation in its fully hydrated condition, it is a potentially useful method for investigating subtle changes in junction cohesion resulting from both early degeneration and whole-disc trauma.

Animals↗
PubMed1996

The use of micromachined surfaces to investigate the cell behavioural factors essential to osseointegration.

OBJECTIVE: Although currently available implants can be used to achieve osseointegration under well-defined conditions, a greater understanding of cell behaviour is required to improve the designs and embark on actual tissue engineering. MATERIALS AND METHODS: We employed micromachined substrata to investigate some of the main behavioural responses of osteoblasts from rat fetal calvaria to surface topography. In particular, confocal laser scanning microscopy (CLSM), differential interference contrast microscopy, time-lapse cinemicrography, immunofluorescence, digital radiography and image analysis were used to investigate cell adhesion, cell shape and cytoskeleton distribution, tissue organization, cell differentiation, and microenvironment. RESULTS AND CONCLUSIONS: A grooved surface permitted the attachment of more cells than a smooth one. Cell shape and cytoskeleton were strikingly influenced as early as 20 min after cell attachment, when the cytoskeleton begins to align with the topography. Some grooved surfaces appeared to promote osteogenesis in vitro as assessed by the production of bone-like nodules. Moreover, these nodules align with the topography in vitro, and preliminary results indicate that bone-like tissue also aligns with grooves when such surfaces are implanted in vivo.

Actins↗
PubMed1996

An investigation into the physical stability of a neonatal parenteral nutrition formulation.

The physical stability of a neonatal parenteral nutrition formulation has been examined using differential interference contrast (DIC) microscopy. In vitro studies indicated that particle size increases occur immediately after mixing the Intralipid emulsion with the amino acid/glucose solution, while simulation of clinical administration indicated that larger droplets were observed at the end of the catheter approximately 1 h after administration commenced. Microscopic observation of adjacent droplets of the two fluids showed reversible aggregation occurring almost immediately. It was concluded that the current method of administering this neonatal emulsion does not prevent droplet coalescence.

Drug Stability↗
PubMed2002

Vapor transport growth of organic solids in microgravity and unit gravity: some comparisons and results to date.

Thin films of an organic nonlinear optical (NLO) material, N, N-dimethyl-p-(2,2-dicyanovinyl) aniline (DCVA), have been grown in space and on the ground by physical vapor transport in an effusive ampoule arrangement. The thin film growth technique developed on the ground is a direct result of information gleaned from experiments in microgravity. This paper covers the results of our experimental investigations for establishing "ideal" terrestrial conditions for deposition of a DCVA film. The active control during the deposition process was exercised by three deposition variables: the material source temperature, the background pressure external to the growth ampoule and the substrate temperature. Successful growth occurred when the difference in temperature between the source material and the copper substrate was 14 degrees C and the background nitrogen pressure was such that the transport was either diffusive or convective. A qualitative diffusion limited boundary was estimated to occur at a pressure of approximately 20 torr. We have probed the DCVA thin films with visible-near infrared reflection absorption spectroscopy, polarized Fourier transform infrared spectrometry, differential interference contrast optical microscopy, and stylus profilometry.

Aniline Compounds↗
PubMed1992

Morphology and dynamics of protruding spirochete periplasmic flagella.

We recently characterized the three-dimensional shape of Treponema phagedenis periplasmic flagella (PFs). In the course of these studies, we observed protrusions on swimming cells that resembled PFs. Here we present a detailed characterization of the shape, structure, and motion of these protrusions. Although protrusion formation occurred primarily in wild-type cells during the stationary phase, a large fraction of exponential-phase cells of cell cylinder helicity mutants (greater than 90% of mutant T-52) had protrusions. These results suggest that cells bearing protrusions can still participate in cell division. T. phagedenis protrusions had the identical helix handedness, pitch, and diameter to those of purified PFs. Protrusions were not present on mutants unable to synthesize PFs, but were present in all motile revertants which regained PFs. These results, taken together with electron microscope observations, suggest that protrusions consist of PFs surrounded by an outer membrane sheath. To analyze protrusion movements, we held cells against a coverglass surface with optical tweezers and observed the motion of protrusions by video-enhanced differential interference contrast light microscopy. Protrusions were found to gyrate in both clockwise and counterclockwise directions, and direct evidence was obtained that protrusions rotate. Protrusions were also observed on Treponema denticola and Borrelia burgdorferi. These were also left-handed and had the same helix handedness, pitch, and diameter as purified PFs from their respective species. The PFs from T. denticola had a helix diameter of 0.26 microns and a helix pitch of 0.78 micron; PFs from B. burgdorferi had a helix diameter of 0.28 micron and a helix pitch of 1.48 microns. Protrusions from these spirochete species had similar structures and motion to those of T. phagedenis. Our results present direct evidence that PFs rotate and support previously proposed models of spirochete motility.

Borrelia burgdorferi Group↗
PubMedDate not supplied

Early hair cell loss in experimental hydrops.

One, 2, and 4 months after surgical obliteration of the endolymphatic sac, the sequence of degenerative changes in the organ of Corti of the guinea pig was studied. The block surface technique with interference differential (Nomarski) microscopy was used for this investigation to study the morphological changes in the organ of Corti. The hair cell loss was calculated and mapped in cytocochleograms. One month postoperatively a minimal loss of only outer hair cells was observed in the apical cochlear turn. At 2 months a progression of outer hair cell loss was seen, which proceeded in the 4-month group. At 4 months the inner hair cells showed a slight tendency to degenerate, again beginning in the most apical part of the cochlea.

Animals↗
PubMed1977

Behaviour of kinetochore fibres in Haemanthus katherinae during anaphase movements of chromosomes.

A laser light source along with a new method of preparing endosperm cells of Haemanthus katherinae for differential interference contrast (DIC) microscopy has led to increased visibility of kinetochore fibres. Little information is available concerning the behaviour of these fibres during anaphase in living cells. In metaphase, kinetochore fibres are seen as distinct bundles of microtubules, here referred to as 'filaments', extending from the kinetochore to the 'diffuse' pole. They possess an apparent globular substructure which corresponds to the moving 'particles or states' described previously from ciné films. In early anaphase, the filaments of each kinetochore fibre lose their parallel orientation characteristic of metaphase and splay out so that the more peripheral filaments intermingle with those of other kinetochore fibres. This process begins at the poles and proceeds as a wave toward the kinetochores as chromosomal movement progresses. This behaviour has been examined in relation to a number of proposed models for the mechanism of chromosome movement and has been found to place some constraints on some models but to be consistent with any model that hypothesizes that chromosomes move as a consequence of cumulative cohesive lateral interactions of microtubules.

Anaphase↗
PubMed1990

Simultaneous investigation of intracellular Ca2+ increase and morphological events upon fertilization in the sand dollar egg.

An increase in intracellular Ca2+ concentration ([Ca2+]) and morphological were simultaneously observed by epifluorescence and differential interference contrast (DIC) microscopy during fertilization of the sand dollar, Clypeaster japonicus. [Ca2+], which was detected by a Ca2+ indicator, Fluo-3, initially increased just beneath the sperm-attached site on the egg surface 8.6 sec after attachment. The increase spread into the egg as a concentric sphere to the egg center and, thereafter, propagated in the egg cytoplasm as a planar wave rather than a spherical wave. It reached the site opposite the initiation site across the egg 24.2 sec after initiation. The fertilization envelope (FE) began to elevate 10.3 sec after the initiation of the increase in [Ca2+] and 21.2 sec after sperm attachment.

Aniline Compounds↗
PubMed1985

Formation of the notochord in living ascidian embryos.

The dynamic behaviour of cells during formation of the notochord in the ascidian, Ciona intestinalis, was examined by means of Differential Interference Contrast (DIC) microscopy and time-lapse videorecording. The initial rudiment is formed in part as a consequence of the pattern of mitotic divisions as the blastopore shifts posteriorly. Vertical and horizontal rearrangements produce an elongate rod of disc-shaped cells stacked end to end. Further elongation is accompanied by a cell shape change. Some cell growth or swelling is indicated to occur later in development, but this growth appears to contribute mostly to an increase in the diameter, and only insignificantly to the length of the notochord. Intracellular vacuoles that appear around 13 h after fertilization increase in size and fuse at about 16 h form intercellular ones. These in turn merge to form the central matrix core of the notochord at around 18 to 20 h. As the notochord elongates and cells change in shape, the basal surfaces bleb actively. This surface activity may be related to formation of the perinotochordal sheath.

Animals↗
PubMed1980

The energy distribution about the image of a point.

A mathematical formulation is presented of the three dimensional distribution of intensity in the image of a bright point. Other equivalent formulations have been described before, but this one appears to have certain practical advantages. The formulation has been used in computer programs to provide tomograms and isophote contour maps of the intensity distribution. A following paper will describe the application of the formulation to differential interference contrast-microscopy.

Light↗
PubMed1994

Fragility and structure of hemoglobin S fibers and gels and their consequences for gelation kinetics and rheology.

Pathogenesis in sickle cell disease depends on whether red blood cells can pass the microvasculature during the delay time before hemoglobin S gelation and cell rigidification occur. Here we observe individual hemoglobin S fibers by differential interference contrast (DIC) microscopy and show that hemoglobin S gels and fibers are fragile and easily broken by mechanical perturbation, and that breakage results in vast acceleration of gelation kinetics due to the creation of new, growing fiber-ends. Hence, in vivo this may be an important factor, in addition to hemoglobin concentration and degree of deoxygenation, that governs delay time and pathogenesis. Pathogenesis also depends on gel rheology and cell rigidification, which depend on fiber cross-linking. We show different mechanisms by which X-shaped, Y-shaped, and "zippering" cross-links form. Finally, we estimate the "on" rate constant for fiber growth to be about 200 mmol/(L.s) and obtain a value for the heterogeneous nucleation rate at 13.5 mmol/L heme.

Gels↗
PubMed1978

Characterization of columnar absorptive epithelial cells isolated from rat jejunum.

The origin and yield of cells isolated from rat jejunum have been assessed; 80-90% of the mature columnar absorptive cells but none of the Paneth, endocrine or regenerating crypt cells were recovered by the methods described. The structural integrity of the isolated cells was tested by phase contrast-, Nomarski interference- and fluorescence light-microscopy; and also by transmission electron microscopy; the isolated cells appeared structurally intact by all microscopic criteria applied. The isolated cells were judged to be functionally intact because they satisfied a number of tests designed to answer three logically related questions, namely: was the cell-surface membrane intact; were the cells able to accumulate selected solutes against a concentration gradient from the exterior medium; and were the cells able to perform biochemical functions which depended upon the integrated activities of several subcellular structures? The isolated cells did retain and accumulate selected solutes, respired at a steady rate on endogenous substrates, showed enhanced respiration on exogenous glucose and glutamine, maintained favourable intracellular proportions of adenine nucleotides (ATP:ADP:AMP), and synthesized cell protein from extracellular amino acids in proportion to the time of incubation. The isolated cells accounted for 80% of the lactic acid produced by intact rat jejunum under similar conditions of incubation.

Adenine Nucleotides↗
PubMed1994

Filopodia initiate choices made by sensory neuron growth cones at laminin/fibronectin borders in vitro.

Localized expression of environmental cues is thought to provide directional information to migrating neuronal growth cones by enhancing or suppressing axon outgrowth over limited regions. To investigate how such a mechanism may function in vivo, we observed growth cones of embryonic chick dorsal root ganglion neurons at a substratum border between the extracellular matrix components laminin and fibronectin in vitro using time-lapse phase-contrast and interference reflection microscopy. We found that patterns of laminin and fibronectin could locally promote or suppress the direction of growth cone migration. While migrating on either laminin or fibronectin, at least 79% of growth cones changed their rate and/or direction of outgrowth upon contact with the alternative substratum, in a manner suggesting that growth cones were selecting one substratum over the other. Complex changes in growth cone behavior were initiated by filopodial contact with the alternate substratum, suggesting that filopodia were providing intracellular signals to the growth cone. Using interference reflection microscopy, we have found that selection of a substratum is independent of the degree of close contact to the substratum. We conclude that spatially localized ECM components can direct axon outgrowth by mechanisms based on intracellular signaling through growth cone filopodia.

Animals↗
PubMed1980

Adhesion plaques of Rous sarcoma virus-transformed cells contain the src gene product.

Another intracellular location of the Rous sarcoma virus (RSU) src gene product (pp60src) has been detected within RSV-transformed cells by indirect immunofluorescence. By using rabbit anti-tumor serum specific for pp60src, a speckled pattern of fluorescence was found on the ventral surface of RSV (Schmidt-Ruppin strain)-transformed normal rat kidney cells. Several tests indicated that this pattern was specific for pp60src. In addition, interference-reflection microscopy was used to visualize cellular adhesion plaques, which are the points at which cells attach to the substratum. Simultaneous immunofluorescence and interference-reflection microscopy indicated that the speckles of pp60src fluorescence corresponded exactly to the adhesion plaque structures. The presence of pp60src within the adhsion plaques was further demonstrated by indirect immunofluorescences on isolated adhesion plaques that remained bound to glass after removal of the cells. pp60src also was observed in adhesion plaques of RSV-tranformed chicken embryo fibroblasts (CEF) and mouse fibroblasts, as well as CEF infected with the temperature-sensitive RSV mutant tsNY68 and grown at permissive temperature. At nonpermissive temperature, pp60src was not detectable in adhesion plaques of the tsNY68-infected CEF. Adhesion plaques serve as focal points of microfilament bundle attachment, and thse results suggest that pp60src interacts directly with cellular cytoskeletal components.

Animals↗
PubMed1986

Analysis of structural changes during hypotonic swelling in Ehrlich ascites tumor cells.

Studies were undertaken to quantify structural changes associated with swelling of Ehrlich ascites tumor cells in hypotonic medium. Cells transferred from isotonic (294 mosmol/kg H2O) to hypotonic (98 mosmol/kg H2O) medium swelled rapidly. Subsequently, approximately 40% of the water initially gained was lost, a phenomenon referred to as volume-regulatory decrease (VRD). During the initial rapid cell swelling, blister-like protrusions or blebs were formed on the cell surface. These blebs were examined by routine light microscopy, differential interference-contrast (DIC) microscopy, and scanning and transmission electron microscopy. Microscopic observations and the distribution of ATPase antibodies indicated that the blebs were formed from plasma membrane. During VRD, the blebs coalesced to form a smooth but expanded membrane surface that appeared to be separated from the original cytoplasm by a layer of less dense ground substance. Computer-assisted morphometry from digitized DIC images of the initial swelling phase indicated that all of the volume gained was sequestered in the blebs. We suggest that bleb formation may allow increases in cell volume without disruption of cytoplasmic organization and may be a protective response to a variety of stressful stimuli. The subsequent VRD is accompanied by reduction of this expanded compartment.

Animals↗