scholarly journals Histological evidence for a supraspinous ligament in sauropod dinosaurs

2015 ◽  
Vol 2 (10) ◽  
pp. 150369 ◽  
Author(s):  
Ignacio A. Cerda ◽  
Gabriel A. Casal ◽  
Rubén D. Martinez ◽  
Lucio M. Ibiricu
Keyword(s):  
Upper Cretaceous ◽  
Polarized Light ◽  
Main Axis ◽  
Histological Evidence ◽  
Histological Features ◽  
Tensile Forces ◽  
Primary Bone ◽  
Oriented Parallel ◽  
Metaplastic Ossification ◽  
Bone Remains

Supraspinous ossified rods have been reported in the sacra of some derived sauropod dinosaurs. Although different hypotheses have been proposed to explain the origin of this structure, histological evidence has never been provided to support or reject any of them. In order to establish its origin, we analyse and characterize the microstructure of the supraspinous rod of two sauropod dinosaurs from the Upper Cretaceous of Argentina. The supraspinous ossified rod is almost entirely formed by dense Haversian bone. Remains of primary bone consist entirely of an avascular tissue composed of two types of fibre-like structures, which are coarse and longitudinally (parallel to the main axis of the element) oriented. These structures are differentiated on the basis of their optical properties under polarized light. Very thin fibrous strands are also observed in some regions. These small fibres are all oriented parallel to one another but perpendicular to the element main axis. Histological features of the primary bone tissue indicate that the sacral supraspinous rod corresponds to an ossified supraspinous ligament. The formation of this structure appears to have been a non-pathological metaplastic ossification, possibly induced by the continuous tensile forces applied to the element.

scholarly journals THE CHANGING PATTERN OF BIREFRINGENCE IN PLASMODIA OF THE SLIME MOLD, PHYSARUM POLYCEPHALUM

1965 ◽  
Vol 25 (2) ◽  
pp. 361-374 ◽  
Author(s):  
Hiromichi Nakajima ◽  
Robert D. Allen
Keyword(s):  
Physarum Polycephalum ◽  
Cytoplasmic Streaming ◽  
Channel Wall ◽  
Polarized Light ◽  
Orthogonal Arrays ◽  
Slime Mold ◽  
Wall Material ◽  
Shuttle Streaming ◽  
Oriented Parallel ◽  
Birefringent Fibrils

Plasmodia of the acellular slime mold, Physarum polycephalum, reveal a complex and changing pattern of birefringence when examined with a sensitive polarizing microscope. Positively birefringent fibrils are found throughout the ectoplasmic region of the plasmodium. In the larger strands they may be oriented parallel to the strand axis, or arranged circularly or spirally along the periphery of endoplasmic channels. Some fibrils exist for only a few minutes, others for a longer period. Some, particularly the circular fibrils, undergo changes in birefringence as they undergo cyclic deformations. In the ramifying strand region and the advancing margin there is a tendency for fibrils of various sizes to become organized into mutually orthogonal arrays. In some plasmodia the channel wall material immediately adjacent to the endoplasm has been found to be birefringent. The sign of endoplasmic birefringence is negative, and its magnitude is apparently constant over the streaming cycle. The pattern of plasmodial birefringence and its changes during the shuttle streaming cycle of Physarum are considered in the light of several models designed to explain either cytoplasmic streaming alone or the entire gamut of plasmodial motions. The results of this and other recent physical studies suggest that both streaming and the various other motions of the plasmodium may very likely be explained in terms of coordinated contractions taking place in the fibrils which are rendered visible in polarized light.

Influence of taphonomy on histological evidence for vertebral pneumaticity in an Upper Cretaceous titanosaur from South America

2020 ◽  
Vol 108 ◽  
pp. 104337 ◽  
Author(s):  
Tito Aureliano ◽  
Aline M. Ghilardi ◽  
Julian C.G. Silva-Junior ◽  
Agustín G. Martinelli ◽  
Luiz Carlos Borges Ribeiro ◽  
...  
Keyword(s):  
South America ◽  
Upper Cretaceous ◽  
Histological Evidence

scholarly journals Intraosseous Schwannoma of the Mandible

2012 ◽  
Vol 1 (1) ◽  
pp. 48-50 ◽  
Author(s):  
Timuçin Baykul ◽  
Hasan Onur Simsek ◽  
Muge Cina Aksoy ◽  
Cagri Can
Keyword(s):  
Peripheral Nerve ◽  
Schwann Cells ◽  
Bone Tumors ◽  
Osteolytic Lesion ◽  
Histological Features ◽  
Primary Bone Tumors ◽  
Intraosseous Schwannoma ◽  
Radiologic Examination ◽  
Primary Bone

ABSTRACT Schwannoma originates from Schwann cells of peripheral nerve sheaths and account for 1% of benign primary bone tumors. The site most commonly involved is the mandible. We present a 47-year-old woman with schwannoma at mandible. Neurosensory examination comprised paresthesia at left side of the mandible. Radiologic examination showed a well-defined unilocular osteolytic lesion which located in the left side of the mandible. The lesion was surgically curetted. The patient is under our follow-up. In this report, clinical and histological features and treatment of the schwannoma are discussed. How to cite this article Simsek HO, Aksoy MC, Can C, Baykul T. Intraosseous Schwannoma of the Mandible. Int J Exper Dent Sci 2012;1(1):48-50.

Spectroscopic studies of trans -l,6-diphenyl-1,3,5-hexatriene in ordered liquid crystal solutions

1973 ◽  
Vol 335 (1602) ◽  
pp. 387-405 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Liquid Crystal ◽  
Fluorescence Polarization ◽  
Polarized Light ◽  
Spectroscopic Studies ◽  
Main Axis ◽  
Electronic Transitions ◽  
Absorption Data ◽  
Fluorescence Methods ◽  
Crystal Mixture

A detailed study has been made of the absorption spectrum of all trans-1,6 diphenyl-1,3,5- hexatriene dissolved in a nematic liquid crystal mixture (1.95:1 cholesteryl chloride and cholestryl laurate (by mass)) using polarized light. Apart from two transitions with moments directed along the molecular axis a transition between these two perpendicular to the main axis has been discovered. This is attributed to a 1A -1G transition, predicted by theory. The application of ordered system s to the resolution of transitions in the absorption spectrum has been checked by a comparison with fluorescence polarization methods. A theory has been developed for the treatment of absorption data in ordered media and the effects of distribution of molecular orientations examined. The technique presented is found to be better in several respects than fluorescence methods for identification of electronic transitions.

High Voltage Electron Microscopy of Ion-Milled Dental Enamel

1974 ◽  
Vol 32 ◽  
pp. 60-61
Author(s):  
L. D. Ackerman ◽  
S. H. Y. Wei
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Third Molar ◽  
Polarized Light ◽  
Dental Enamel ◽  
Longitudinal Section ◽  
Ion Milling ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron

Mature human dental enamel has presented investigators with several difficulties in ultramicrotomy of specimens for electron microscopy due to its high degree of mineralization. This study explores the possibility of combining ion-milling and high voltage electron microscopy as a means of circumventing the problems of ultramicrotomy.A longitudinal section of an extracted human third molar was ground to a thickness of about 30 um and polarized light micrographs were taken. The specimen was attached to a single hole grid and thinned by argon-ion bombardment at 15° incidence while rotating at 15 rpm. The beam current in each of two guns was 50 μA with an accelerating voltage of 4 kV. A 20 nm carbon coating was evaporated onto the specimen to prevent an electron charge from building up during electron microscopy.

Freeze-etch observations on the tight junctions of sertoli cells grown in organ culture with FSH

1978 ◽  
Vol 36 (2) ◽  
pp. 340-341
Author(s):  
Rita Meyer ◽  
Zoltan Posalaky ◽  
Dennis Mcginley
Keyword(s):  
Organ Culture ◽  
Tight Junctions ◽  
Sertoli Cell ◽  
Germ Cells ◽  
Sertoli Cells ◽  
Barrier Function ◽  
Cell Junction ◽  
Intramembranous Particles ◽  
Junctional Complexes ◽  
Oriented Parallel

The Sertoli cell tight junctional complexes have been shown to be the most important structural counterpart of the physiological blood-testis barrier. In freeze etch replicas they consist of extensive rows of intramembranous particles which are not only oriented parallel to one another, but to the myoid layer as well. Thus the occluding complex has both an internal and an overall orientation. However, this overall orientation to the myoid layer does not seem to be necessary to its barrier function. The 20 day old rat has extensive parallel tight junctions which are not oriented with respect to the myoid layer, and yet they are inpenetrable by lanthanum. The mechanism(s) for the control of Sertoli cell junction development and orientation has not been established, although such factors as the presence or absence of germ cells, and/or hormones, especially FSH have been implicated.

Identification of calcium oxalate crystals in dried or fixed tobacco leaf

1984 ◽  
Vol 42 ◽  
pp. 288-289
Author(s):  
Vicki L. Baliga ◽  
Mary Ellen Counts
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Calcium Oxalate ◽  
Growth And Development ◽  
Polarized Light ◽  
Calcium Oxalate Crystals ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

Calcium is an important element in the growth and development of plants and one form of calcium is calcium oxalate. Calcium oxalate has been found in leaf seed, stem material plant tissue culture, fungi and lichen using one or more of the following methods—polarized light microscopy (PLM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray diffraction.Two methods are presented here for qualitatively estimating calcium oxalate in dried or fixed tobacco (Nicotiana) leaf from different stalk positions using PLM. SEM, coupled with energy dispersive x-ray spectrometry (EDS), and powder x-ray diffraction were used to verify that the crystals observed in the dried leaf with PLM were calcium oxalate.

Differential polarization imaging of sickled cells

1988 ◽  
Vol 46 ◽  
pp. 62-63
Author(s):  
Marcos F. Maestre
Keyword(s):  
Optical Properties ◽  
Theoretical Approach ◽  
Polarized Light ◽  
Polarization Microscopy ◽  
Spectroscopic Techniques ◽  
Polarization Imaging ◽  
Circularly Polarized Light ◽  
Circularly Polarized ◽  
Microscopic Scale ◽  
Chiral Structures

Recently we have developed a form of polarization microscopy that forms images using optical properties that have previously been limited to macroscopic samples. This has given us a new window into the distribution of structure on a microscopic scale. We have coined the name differential polarization microscopy to identify the images obtained that are due to certain polarization dependent effects. Differential polarization microscopy has its origins in various spectroscopic techniques that have been used to study longer range structures in solution as well as solids. The differential scattering of circularly polarized light has been shown to be dependent on the long range chiral order, both theoretically and experimentally. The same theoretical approach was used to show that images due to differential scattering of circularly polarized light will give images dependent on chiral structures. With large helices (greater than the wavelength of light) the pitch and radius of the helix could be measured directly from these images.

High-resolution measurement of birefringent fine structure in living cells using a new polarized light microscope

1995 ◽  
Vol 53 ◽  
pp. 54-55
Author(s):  
Rudolf Oldenbourg
Keyword(s):  
Light Microscope ◽  
Fluorescent Dyes ◽  
Polarized Light ◽  
Processing System ◽  
Video Camera ◽  
Molecular Organization ◽  
Computer Assisted ◽  
Image Recording ◽  
Birefringent Crystal ◽  
Technological Advances

The recent renaissance of the light microsope is fueled in part by technological advances in components on the periphery of the microscope, such as the laser as illumination source, electronic image recording (video), computer assisted image analysis and the biochemistry of fluorescent dyes for labeling specimens. After great progress in these peripheral parts, it seems timely to examine the optics itself and ask how progress in the periphery facilitates the use of new optical components and of new optical designs inside the microscope. Some results of this fruitful reflection are presented in this symposium.We have considered the polarized light microscope, and developed a design that replaces the traditional compensator, typically a birefringent crystal plate, with a precision universal compensator made of two liquid crystal variable retarders. A video camera and digital image processing system provide fast measurements of specimen anisotropy (retardance magnitude and azimuth) at ALL POINTS of the image forming the field of view. The images document fine structural and molecular organization within a thin optical section of the specimen.

Discovery of intracellular 2,8 dihydroxyadenine crystals in bovine lymphatic and hepatic cells

1987 ◽  
Vol 45 ◽  
pp. 906-907
Author(s):  
W. E. Rigsby ◽  
D. M. Hinton ◽  
V. J. Hurst ◽  
P. C. McCaskey
Keyword(s):  
Polarized Light ◽  
Paraffin Sections ◽  
Tissue Samples ◽  
Whole Cells ◽  
Tissue Sections ◽  
Hepatic Cells ◽  
Slaughter House ◽  
Mammalian Tissues ◽  
Carbon Coated ◽  
Cellular Components

Crystalline intracellular inclusions are rarely seen in mammalian tissues and are often difficult to positively identify. Lymph node and liver tissue samples were obtained from two cows which had been rejected at the slaughter house due to the abnormal appearance of these organs in the animals. The samples were fixed in formaldehyde and some of the fixed material was embedded in paraffin. Examination of the paraffin sections with polarized light microscopy revealed the presence of numerous crystals in both hepatic and lymph tissue sections. Tissue sections were then deparaffinized in xylene, mounted, carbon coated, and examined in a Phillips 505T SEM equipped with a Tracor Northern X-ray Energy Dispersive Spectroscopy (EDS) system. Crystals were obscured by cellular components and membranes so that EDS spectra were only obtainable from whole cells. Tissue samples which had been fixed but not paraffin-embedded were dehydrated, embedded in Spurrs plastic, and sectioned.

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