The eggshell of Drosophila melanogaster. I. Fine structure of the layers and regions of the wild-type eggshell

1980 ◽  
Vol 43 (1) ◽  
pp. 1-35 ◽  
Author(s):  
L.H. Margaritis ◽  
F.C. Kafatos ◽  
W.H. Petri
Keyword(s):  
Drosophila Melanogaster ◽  
Fine Structure ◽  
Freeze Fracture ◽  
Central Area ◽  
Ventral Side ◽  
Dorsal Side ◽  
Posterior Pole ◽  
Optical Diffraction ◽  
Vitelline Membrane ◽  
Freeze Fracture Electron Microscopy

The fine structure of the several layers and regional specializations in the Drosophila melanogaster eggshell has been studied by a combination of shell isolation procedures and ultrastructural techniques (conventional TEM, whole-mount TEM, SEM, HVEM, freeze-fracture electron microscopy utilizing rotary replication, shadow casting, optical diffraction and stereo imaging). The main shell consists of 5 layers: the vitelline membrane (300 nm thick), the wax layer, the innermost chorionic layer (40-50 nm), the endochorion (500-700 nm), and the exochorion (300-500 nm). The vitelline membrane consists of irregularly organized particles. The wax layer appears to contain multilayered hydrophobic plates which split tangenitally upon freeze fracturing. The innermost chorionic layer is composed of a crystalling lattice. The endochorion is made of a thin (40 nm) fenestrated floor composed of 40-nm fibres and an outer solid (200 nm) roof covered with a network of 40-nm strands. Intermittently spaced pillar connect these 2 parts. Similarities in the substructure of the floor, pillars and roof suggest that they may be composed of similar or identical structural elements. The specialized regions of the shell are the 2 respiratory appendages, the operculum area and the posterior pole. The appendages exhibit 2 sharply distinct surfaces, a dorsal side with isolated 1.5-micrometer plaques and a ventral side with strands of 40–50 nm connected in a network with openings of 70–80 nm. The operculum area, which includes the micropoyle and the collar, is distinguished by 3 unique types of cell imprints. The posterior pole contains 2 distinctive populations of cell imprints: the central area has very thin intercellular ridges and a thin, perforated, endochorionic roof, while the peripheral area contains mixed, thick and thin, intercellular ridges and serves as a transition zone to the main shell pattern. The pillars in the central area of the posterior pole have a distinct arrangement, forming one peripheral circle within each cell imprint. An analysis utilizing structural and developmental criteria indicates that as many as ten different populations of follicular epithelial cells may be involved in the construction of the various regions of the Drosophila eggshell.

scholarly journals A revised understanding of Tribolium morphogenesis further reconciles short and long germ development

2017 ◽  
Author(s):  
Matthew A. Benton
Keyword(s):  
Drosophila Melanogaster ◽  
Tribolium Castaneum ◽  
Cell Tracking ◽  
Qualitative Difference ◽  
Ventral Side ◽  
Dorsal Side ◽  
Tissue Structure ◽  
Cell Labelling ◽  
Embryonic Tissues ◽  
Differential Cell

AbstractIn Drosophila melanogaster, the germband forms directly on the egg surface and solely consists of embryonic tissue. In contrast, most insect embryos undergo a complicated set of tissue rearrangements to generate a condensed, multi-layered germband. The ventral side of the germband is embryonic, while the dorsal side is thought to be an extraembryonic tissue called the amnion. While this tissue organisation has been accepted for decades, and has been widely reported in insects, its accuracy has not been directly tested in any species. Using live cell tracking and differential cell labelling in the short germ beetle Tribolium castaneum, I show that most of the cells previously thought to be amnion actually give rise to large parts of the embryo. This process occurs via the dorsal-to-ventral flow of cells and contributes to germband extension. In addition, I show that true ‘amnion’ cells in Tribolium originate from a small region of the blastoderm. Together, my findings show that development in the short germ embryos of Tribolium and the long germ embryos of Drosophila is more similar than previously proposed. Dorsal-to-ventral cell flow also occurs in Drosophila during germband extension, and I argue that the flow is driven by a conserved set of underlying morphogenetic events in both species. Furthermore, the revised Tribolium fatemap that I present is far more similar to that of Drosophila than the classic Tribolium fatemap. Lastly, my findings show that there is no qualitative difference between the tissue structure of the cellularised blastoderm and the short/intermediate germ germband. As such, the same tissue patterning mechanisms could function continuously throughout the cellularised blastoderm and germband stages, and easily shift between them over evolutionary time.Author summaryIn many animals, certain groups of cells in the embryo do not directly contribute to adult structures. Instead, these cells generate so-called ‘extra-embryonic tissues’ that support and facilitate development, but degenerate prior to birth/hatching. In most insect species, embryos are described as having two major extra-embryonic tissues; the serosa, which encapsulates the entire embryo and yolk, and the amnion, which covers one side of the embryo. This tissue structure has been widely reported for over a century, but detailed studies on the amnion are lacking. Working in the beetle Tribolium castaneum, I used long-term fluorescent live imaging, cell tracking and differential cell labelling to investigate amnion development. In contrast to our current understanding, I show that most cells previously thought to be amnion actually form large parts of the embryo. In addition, I show how these cells ‘flow’ as a whole tissue and contribute to elongation of the embryo, and how only a relatively small number of cells form the actual amnion. Lastly, I describe how my findings show that despite exhibiting substantial differences in overall structure, embryos of Tribolium and the fruit fly, Drosophila melanogaster, utilise a conserved set of morphogenetic processes.

Three dimensional analysis of the eggshell from Drosophila melanogaster

1978 ◽  
Vol 36 (2) ◽  
pp. 548-549
Author(s):  
Lukas H. Margaritis ◽  
Fotis C. Kafatos
Keyword(s):  
Drosophila Melanogaster ◽  
Three Dimensional ◽  
Optical Diffraction ◽  
Vitelline Membrane ◽  
Wild Type ◽  
Glutaraldehyde Fixation ◽  
Model Case ◽  
Thin Sections ◽  
Voltage Electron ◽  
High Voltage Electron Microscope

Formation of the insect eggshell is being studied as a model case of cell differentiation. Because of the potential for genetic analysis, we are concentrating on the eggshell of Drosophila melanogaster. Here we summarize our understanding of the wild type structure as determined using a variety of ultrastructural methods. Follicles, eggshells or pure endochorion were prepared as described and studied with a Philips 301 TEM, an AMR 1000 SEM, a JSM-35 SEM, and a JEM-1000 high voltage electron microscope. Glutaraldehyde fixation (Figs. 6, 8, 9) followed by OsO4, (Figs. 1, 3, 4, 7, 10, 11) was used.Thin sections (Fig. 1) of stage 14 follicles reveal the following layers of the mature eggshell from the oocyte surface outwards: vitelline membrane (VM), intermediate chorionic layer (ICL), endochorion (END) and exochorion(EX). The amorphous VM and the loosely fibrous EX appear simple in structure. The ICL has been purified and shown by negative staining to have a prominent crystalline structure (Fig. 2) which has been further investigated by optical diffraction and filtering.

Image Analysis of Intramembrane Particles in Freeze-Fractured Biomembranes Using Computer Simulation Techniques

1975 ◽  
Vol 33 ◽  
pp. 214-215
Author(s):  
D.J. Benefiel ◽  
R.S. Weinstein
Keyword(s):  
Membrane Proteins ◽  
Freeze Fracture ◽  
Integral Membrane Proteins ◽  
Systematic Evaluation ◽  
Intramembrane Particles ◽  
Modeling Methods ◽  
Simulation Techniques ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron ◽  
Computer Simulation Techniques

Intramembrane particles (IMP or MAP) are components of most biomembranes. They are visualized by freeze-fracture electron microscopy, and they probably represent replicas of integral membrane proteins. The presence of MAP in biomembranes has been extensively investigated but their detailed ultrastructure has been largely ignored. In this study, we have attempted to lay groundwork for a systematic evaluation of MAP ultrastructure. Using mathematical modeling methods, we have simulated the electron optical appearances of idealized globular proteins as they might be expected to appear in replicas under defined conditions. By comparing these images with the apearances of MAPs in replicas, we have attempted to evaluate dimensional and shape distortions that may be introduced by the freeze-fracture technique and further to deduce the actual shapes of integral membrane proteins from their freezefracture images.

scholarly journals Gravity determines the direction of nerve roots sedimentation in the lumbar spinal canal

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Jun Yang ◽  
Zhiyun Feng ◽  
Nian Chen ◽  
Zhenhua Hong ◽  
Yongyu Zheng ◽  
...  
Keyword(s):  
Lumbar Spine ◽  
Mr Imaging ◽  
Spinal Canal ◽  
Ventral Side ◽  
Lateral Position ◽  
Dorsal Side ◽  
Mr Images ◽  
Nerve Roots ◽  
Cross Sectional ◽  
Dural Sac

Abstract Objectives To investigate the role of gravity in the sedimentation of lumbar spine nerve roots using magnetic resonance (MR) imaging of various body positions. Methods A total of 56 patients, who suffered from back pain and underwent conventional supine lumbar spine MR imaging, were selected from sanmen hospital database. All the patients were called back to our hospital to perform MR imaging in prone position or lateral position. Furthermore, the sedimentation sign (SedSign) was determined based on the suspension of the nerve roots in the dural sac on cross-sectional MR images, and 31 cases were rated as positive and another 25 cases were negative. Results The mean age of negative SedSign group was significantly younger than that of positive SedSign group (51.7 ± 8.7 vs 68.4 ± 10.5, P < 0.05). The constitutions of clinical diagnosis were significantly different between patients with a positive SedSign and those with a negative SedSign (P < 0.001). Overall, nerve roots of the vast majority of patients (48/56, 85.7%) subsided to the ventral side of the dural sac on the prone MR images, although that of 8 (14.3%) patients remain stay in the dorsal side of dural sac. Nerve roots of only one patient with negative SedSign did not settle to the ventral dural sac, while this phenomenon occurred in 7 patients in positive SedSign group (4% vs 22.6%, P < 0.001). In addition, the nerve roots of all the five patients subsided to the left side of dural sac on lateral position MR images. Conclusions The nerve roots sedimentation followed the direction of gravity. Positive SedSign may be a MR sign of lumbar pathology involved the spinal canal.

Structure, Expression, and Hormonal Control of Genes from the Mosquito, Aedes aegypti, Which Encode Proteins Similar to the Vitelline Membrane Proteins of Drosophila melanogaster

1993 ◽  
Vol 155 (2) ◽  
pp. 558-568 ◽  
Author(s):  
Yonggu Lin ◽  
Martha T. Hamblin ◽  
Marten J. Edwards ◽  
Carolina Barillas-Mury ◽  
Michael R. Kanost ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Membrane Proteins ◽  
Aedes Aegypti ◽  
Hormonal Control ◽  
Vitelline Membrane

scholarly journals Freeze-fracture Electron Microscopy on Microbubbles Used as Theranostics or Made of Lung Surfactant

2010 ◽  
Vol 16 (S2) ◽  
pp. 1172-1173
Author(s):  
B Papahadjopoulos-Sternberg ◽  
J Ackrell
Keyword(s):  
Electron Microscopy ◽  
Lung Surfactant ◽  
Freeze Fracture ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Sign in / Sign up

Export Citation Format

Share Document