scholarly journals Ocular elongation and retraction in foveated reptiles

2021 ◽  
Author(s):  
Ashley M. Rasys ◽  
Shana H. Pau ◽  
Katherine E. Irwin ◽  
Sherry Luo ◽  
Paul A. Trainor ◽  
...  
Keyword(s):  
Photoreceptor Cell ◽  
Eye Development ◽  
Three Dimensional ◽  
Spherical Shape ◽  
Dimensional Structure ◽  
List Type ◽  
Anolis Sagrei ◽  
Pit Formation ◽  
Brown Anole ◽  
Chamaeleo Calyptratus

AbstractBackgroundPronounced asymmetric changes in ocular globe size during eye development have been observed in a number of species ranging from humans to lizards. In contrast, largely symmetric changes in globe size have been described for other species like rodents. We propose that asymmetric changes in the three-dimensional structure of the developing eye correlate with the types of retinal remodeling needed to produce areas of high photoreceptor density. To test this idea, we systematically examined three-dimensional aspects of globe size as a function of eye development in the bifoveated brown anole, Anolis sagrei.ResultsDuring embryonic development, the anole eye undergoes dynamic changes in ocular shape. Initially spherical, the eye elongates in the presumptive foveal regions of the retina and then proceeds through a period of retraction that returns the eye to its spherical shape. During this period of retraction, pit formation and photoreceptor cell packing are observed. We found a similar pattern of elongation and retraction associated with the single fovea of the veiled chameleon, Chamaeleo calyptratus.ConclusionsThese results, together with those reported for other foveated species, support the idea that areas of high photoreceptor packing occur in regions where the ocular globe asymmetrically elongates and retracts during development.Key FindingsThe eyes of the brown anole, Anolis sagrei, and veiled chameleon, Chamaeleo calyptratus undergo dynamic asymmetrical changes in ocular shape during development.In both species, asymmetric elongation and retraction of the ocular globe is associated with fovea morphogenesis.Pit formation and photoreceptor cell packing in the foveal area occur when the corresponding region of the ocular globe is retracting relative to adjacent regions.

scholarly journals Development and retinal remodeling in the brown anole lizard (Anolis sagrei)

2021 ◽  
Author(s):  
Ashley M. Rasys ◽  
Shana H. Pau ◽  
Kathrine E. Irwin ◽  
Sherry Luo ◽  
Hannah Q Kim ◽  
...  
Keyword(s):  
Photoreceptor Cell ◽  
Present Model ◽  
General Rule ◽  
Model Systems ◽  
Anolis Sagrei ◽  
Retina Development ◽  
Pit Formation ◽  
Brown Anole ◽  
High Acuity ◽  
Retinal Remodeling

Background. The fovea, a pit in the retina, is believed to be important for high-acuity vision and is a feature found in the eyes of humans and a limited number of vertebrate species that include certain primates, birds, lizards, and fish. At present, model systems currently used for ocular research lack a foveated retina and studies investigating fovea development have largely been limited to histological and molecular studies in primates. As a result, progress towards understanding the mechanisms involved in regulating fovea development in humans is limited and is completely lacking in other, non-primate, vertebrates. To address this knowledge gap, we provide here a detailed histological atlas of retina and fovea development in the bifoveated Anolis sagrei lizard, a novel reptile model for fovea research. We also further test the hypothesis that retinal remodeling, which leads to fovea formation and photoreceptor cell packing, is related to asymmetric changes in eye shape. Results. Anole retina development follows the conventional spatiotemporal patterning observed in most vertebrates, where retina neurogenesis begins within the central retina, progresses throughout the temporal retina, and concludes in the nasal retina. One exception to this general rule is that areas that give rise to the fovea undergo retina differentiation prior to the rest of the retina. We find that retina thickness changes dynamically during periods of ocular elongation and retraction. During periods of ocular elongation, the retina thins, while during retraction it becomes thicker. Ganglion cell layer mounding is also observed in the temporal fovea region just prior to pit formation. Conclusions. Anole retina development parallels that of humans, including the onset and progression of retinal neurogenesis followed by changes in ocular shape and retinal remodeling that leads to pit formation in the retina. We propose that anoles are an excellent model system for fovea development research.

scholarly journals Anterior eye development in the brown anole, Anolis sagrei

2021 ◽  
Author(s):  
Ashley M. Rasys ◽  
Shana H. Pau ◽  
Katherine E. Irwin ◽  
Sherry Luo ◽  
Douglas B. Menke ◽  
...  
Keyword(s):  
Trabecular Meshwork ◽  
Ciliary Body ◽  
Eye Development ◽  
Anterior Segment ◽  
List Type ◽  
Anolis Sagrei ◽  
Schlemm’S Canal ◽  
Ciliary Process ◽  
Schlemm's Canal ◽  
Brown Anole

AbstractBackgroundAnterior eye development has been explored in different vertebrate species ranging from fish to mammals. However, missing from this diverse group is a representative of reptiles. A promising candidate to fill this void is the brown anole, Anolis sagrei, which is easily raised in the laboratory and for which genome editing techniques exist. Here we provide a detailed histological analysis of the development of the anterior structures of the eye in A. sagrei, which include the cornea, iris, ciliary body, lens, trabecular meshwork, and sclera ossicles.ResultsDevelopment of the anterior segment in Anoles proceeds as for other vertebrates with the lens forming first followed by the cornea, then the iris, ciliary body, trabecular meshwork, and sclera ossicles. The onset of these latter structures occurs first temporally than nasally. Unlike the eyes of mammals and birds, anoles possess a remarkably thin cornea, flat ciliary body, and a trabecular meshwork that lacks an obvious Schlemm’s canal.ConclusionsThis study highlights several features present in anoles and represents an important step towards understanding reptile eye development.Key FindingsThe anole cornea epithelium is thin, composed mainly of a single basal cell layer.The ciliary body lacks a ciliary process.Iris and ciliary body formation occur in a spatiotemporal fashion, developing first temporally then nasally.The anole trabecular meshwork is composed of a spongiform tissue and lacks a Schlemm’s canal.

Conformation of Ribosomes from Escherichia Coli

1974 ◽  
Vol 32 ◽  
pp. 210-211
Author(s):  
M. Boublik ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Binding Sites ◽  
Ribosomal Proteins ◽  
Fluorescent Dyes ◽  
Protein Biosynthesis ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Dimensional Structure ◽  
Complete Understanding ◽  
And Function

The present knowledge of the three-dimensional structure of ribosomes is far too limited to enable a complete understanding of the various roles which ribosomes play in protein biosynthesis. The spatial arrangement of proteins and ribonuclec acids in ribosomes can be analysed in many ways. Determination of binding sites for individual proteins on ribonuclec acid and locations of the mutual positions of proteins on the ribosome using labeling with fluorescent dyes, cross-linking reagents, neutron-diffraction or antibodies against ribosomal proteins seem to be most successful approaches. Structure and function of ribosomes can be correlated be depleting the complete ribosomes of some proteins to the functionally inactive core and by subsequent partial reconstitution in order to regain active ribosomal particles.

Three-Dimensional Reconstruction Using Stereo Pairs from Serial Thick Sections

1977 ◽  
Vol 35 ◽  
pp. 562-563
Author(s):  
Robert Glaeser ◽  
Thomas Bauer ◽  
David Grano
Keyword(s):  
Three Dimensional ◽  
Dimensional Structure ◽  
Serial Sections ◽  
Thin Sections ◽  
3 Dimensional ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Dimensional Reconstruction ◽  
Stereo Imagery ◽  
Whole Mounts

In transmission electron microscopy, the 3-dimensional structure of an object is usually obtained in one of two ways. For objects which can be included in one specimen, as for example with elements included in freeze- dried whole mounts and examined with a high voltage microscope, stereo pairs can be obtained which exhibit the 3-D structure of the element. For objects which can not be included in one specimen, the 3-D shape is obtained by reconstruction from serial sections. However, without stereo imagery, only detail which remains constant within the thickness of the section can be used in the reconstruction; consequently, the choice is between a low resolution reconstruction using a few thick sections and a better resolution reconstruction using many thin sections, generally a tedious chore. This paper describes an approach to 3-D reconstruction which uses stereo images of serial thick sections to reconstruct an object including detail which changes within the depth of an individual thick section.

Electron Microscopy of Cytoplasmic Contractile Proteins

1978 ◽  
Vol 36 (3) ◽  
pp. 606-614 ◽  
Author(s):  
T.D. Pollard ◽  
P. Maupin
Keyword(s):  
Electron Microscopy ◽  
Actin Filaments ◽  
Three Dimensional ◽  
Uranyl Acetate ◽  
Contractile Proteins ◽  
Dimensional Structure ◽  
X Ray Diffraction ◽  
Cytoplasmic Matrix ◽  
Computer Image Processing ◽  
Nonmuscle Cells

In this paper we review some of the contributions that electron microscopy has made to the analysis of actin and myosin from nonmuscle cells. We place particular emphasis upon the limitations of the ultrastructural techniques used to study these cytoplasmic contractile proteins, because it is not widely recognized how difficult it is to preserve these elements of the cytoplasmic matrix for electron microscopy. The structure of actin filaments is well preserved for electron microscope observation by negative staining with uranyl acetate (Figure 1). In fact, to a resolution of about 3nm the three-dimensional structure of actin filaments determined by computer image processing of electron micrographs of negatively stained specimens (Moore et al., 1970) is indistinguishable from the structure revealed by X-ray diffraction of living muscle.

A New 1000kv Electron Microscope

1969 ◽  
Vol 27 ◽  
pp. 100-101
Author(s):  
J.L. Williams ◽  
K. Heathcote ◽  
E.J. Greer
Keyword(s):  
Electron Microscope ◽  
Direct Observation ◽  
High Voltage ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Specimen Thickness ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
Dynamic Experiments ◽  
Conventional Instrument

High Voltage Electron Microscope already offers exciting experimental possibilities to Biologists and Materials Scientists because the increased specimen thickness allows direct observation of three dimensional structure and dynamic experiments on effectively bulk specimens. This microscope is designed to give maximum accessibility and space in the specimen region for the special stages which are required. At the same time it provides an ease of operation similar to a conventional instrument.

High-voltage electron microscopy of maxillary gland of spirochete-infected brine shrimp: lesion of efferent tubule

1988 ◽  
Vol 46 ◽  
pp. 362-363
Author(s):  
G. E. Tyson ◽  
M. J. Song
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Brine Shrimp ◽  
Natural Populations ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
Infected Adult

Natural populations of the brine shrimp, Artemia, may possess spirochete- infected animals in low numbers. The ultrastructure of Artemia's spirochete has been described by conventional transmission electron microscopy. In infected shrimp, spirochetal cells were abundant in the blood and also occurred intra- and extracellularly in the three organs examined, i.e. the maxillary gland (segmental excretory organ), the integument, and certain muscles The efferent-tubule region of the maxillary gland possessed a distinctive lesion comprised of a group of spirochetes, together with numerous small vesicles, situated in a cave-like indentation of the base of the tubule epithelium. in some instances the basal lamina at a lesion site was clearly discontinuous. High-voltage electron microscopy has now been used to study lesions of the efferent tubule, with the aim of understanding better their three-dimensional structure.Tissue from one maxillary gland of an infected, adult, female brine shrimp was used for HVEM study.

Mitochondrial Reconstructions Based on Serial Thick Sections and HVEM

1975 ◽  
Vol 33 ◽  
pp. 286-287
Author(s):  
Jerome J. Paulin
Keyword(s):  
Imaging Techniques ◽  
Three Dimensional ◽  
Posterior Pole ◽  
Dimensional Structure ◽  
Stereo Imaging ◽  
Thin Sections ◽  
Anatomical Features ◽  
The Past ◽  
Cellular Components ◽  
Mitochondrial Reticulum

Within the past decade it has become apparent that HVEM offers the biologist a means to explore the three-dimensional structure of cells and/or organelles. Stereo-imaging of thick sections (e.g. 0.25-10 μm) not only reveals anatomical features of cellular components, but also reduces errors of interpretation associated with overlap of structures seen in thick sections. Concomitant with stereo-imaging techniques conventional serial Sectioning methods developed with thin sections have been adopted to serial thick sections (≥ 0.25 μm). Three-dimensional reconstructions of the chondriome of several species of trypanosomatid flagellates have been made from tracings of mitochondrial profiles on cellulose acetate sheets. The sheets are flooded with acetone, gluing them together, and the model sawed from the composite and redrawn.The extensive mitochondrial reticulum can be seen in consecutive thick sections of (0.25 μm thick) Crithidia fasciculata (Figs. 1-2). Profiles of the mitochondrion are distinguishable from the anterior apex of the cell (small arrow, Fig. 1) to the posterior pole (small arrow, Fig. 2).

Electron crystallographic determination of the 3-D structure of staurolite at atomic resolution

1991 ◽  
Vol 49 ◽  
pp. 540-541
Author(s):  
Kenneth H. Downing ◽  
Hu Meisheng ◽  
Hans-Rudolf Went ◽  
Michael A. O'Keefe
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Atomic Resolution ◽  
Dimensional Structure ◽  
Structure Information ◽  
Resolution Electron ◽  
Scattering Effects ◽  
High Resolution Images ◽  
Effects Of Radiation

With current advances in electron microscope design, high resolution electron microscopy has become routine, and point resolutions of better than 2Å have been obtained in images of many inorganic crystals. Although this resolution is sufficient to resolve interatomic spacings, interpretation generally requires comparison of experimental images with calculations. Since the images are two-dimensional representations of projections of the full three-dimensional structure, information is invariably lost in the overlapping images of atoms at various heights. The technique of electron crystallography, in which information from several views of a crystal is combined, has been developed to obtain three-dimensional information on proteins. The resolution in images of proteins is severely limited by effects of radiation damage. In principle, atomic-resolution, 3D reconstructions should be obtainable from specimens that are resistant to damage. The most serious problem would appear to be in obtaining high-resolution images from areas that are thin enough that dynamical scattering effects can be ignored.

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