The eggshell of Drosophila melanogaster. II. New staging characteristics and fine structural analysis of choriogenesis

1986 ◽  
Vol 64 (10) ◽  
pp. 2152-2175 ◽  
Author(s):  
Lukas H. Margaritis
Keyword(s):  
Electron Microscopy ◽  
Light And Electron Microscopy ◽  
Dark Field ◽  
Posterior Pole ◽  
Follicle Cells ◽  
Vitelline Membrane ◽  
Simultaneous Formation ◽  
Last Stage ◽  
Flocculent Material ◽  
Factor C

The characteristics of the stages of choriogenesis have been identified using light and electron microscopy. Nine stages have been discerned (11A, 11B, 12A, 12B, 12C, 13A, 13B, 14A, 14B), replacing the four stages used so far (11, 12, 13, 14). Characteristics used to determine the stage of the choriogenesis include (a) the size of oocyte as compared with the whole follicle, (b) the length of the chorionic appendages, and (c) the fine structure of the chorionic layers at the main shell and at the specialized regions. Factors a and b were detected by dark-field light microscopy on living follicles, whereas factor c was studied with electron microscopy. At stage 11A the vitelline membrane has just been completed. At stage 11B the follicle cells secrete the wax layer and the respiratory appendages start to form. Stage 12A follicles secrete endochorion at the anterior pole and the appendages elongate, whereas at stage 12B the main shell follicle cells start to secrete endochorion complex. Stage 12C shows initiation of pillar formation at the main shell and 150 μm long appendages. Stage 13A is characterized by 200 μm long appendages and formation of endochorionic cavities at the main shell, through the participation of a "flocculent" material. At stage 13B the endochorionic "roof is formed, which is completed at stage 14A by the simultaneous formation of the "roof network." The last stage, 14B, exhibits 300 μm long appendages and the secretion of exochorion over the entire follicle. The above stages are accompanied by region-specific formation of specialized structures which include the respiratory appendages, the operculum, the posterior pole, the micropyle, and the collar.

scholarly journals OOCYTE DIFFERENTIATION AND VITELLOGENESIS IN THE ROACH PERIPLANETA AMERICANA

1964 ◽  
Vol 20 (1) ◽  
pp. 131-155 ◽  
Author(s):  
Everett Anderson
Keyword(s):  
Nuclear Envelope ◽  
Phase Contrast ◽  
Periplaneta Americana ◽  
Light And Electron Microscopy ◽  
Internal Surface ◽  
Follicle Cells ◽  
Growth Stages ◽  
Cytoplasmic Organelle ◽  
Last Stage ◽  
Oocyte Differentiation

The ovary of the roach Periplaneta americana has been studied by techniques of light and electron microscopy. Each ovariole (panoistic type) contains a linear array of oocytes in varying stages of development. Newly formed oocytes become encased by a layer of follicle cells and begin pinocytosis. All subsequent growth stages of the oocytes are dependent, in part, on this phenomenon. All of the pinocytotic caveolae show an unique surface modification; i.e., on their internal surface they have an amorphous or filamentous substance and their external surface is studded with many fine radially oriented spike-like projections. The pinosomes of early oocytes do not contain a demonstrable internal structure; they are thought to contain nutritive substances for the developing oocytes rather than yolk precursors. When the oocyte enters its last stage of growth, characterized by yolk deposition, the caveolae become filled with a dense material which is thought to be the precursors of yolk. Hence the conclusion is drawn that yolk formation is independent of any cytoplasmic organelle system of the oocyte and that the precursors of this deutoplasmic substance are manufactured outside the ovary and are internalized by the process of pinocytosis. Under the phase-contrast microscope the nucleoli of early oocytes are large irregular masses and show the phenomenon of nucleolar emission (fragmentation). These "emissions" become randomly dispersed in the nucleoplasm and some of them come to be intimately associated with the fenestrated nuclear envelope. After this process ceases, the main nucleolar mass becomes vacuolated. Electron micrographs suggest that the constituent particles of the nucleolar emissions migrate from the nucleus through patent pores of the nuclear envelope.

Same-section correlative light and electron microscopy

1989 ◽  
Vol 47 ◽  
pp. 896-897
Author(s):  
C.L. Rieder ◽  
S.P. Alexander ◽  
S.S. Bowser
Keyword(s):  
Electron Microscopy ◽  
Small Volume ◽  
Light And Electron Microscopy ◽  
Dark Field ◽  
Ultrastructural Examination ◽  
Immunofluorescent Localization ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Texas Red ◽  
Good Contrast

Epoxy embedded biological material, sectioned for conventional, intermediate or high-voltage electron microscopy (EM), can be visualized within the section with good contrast and detail by phase-contrast or dark-field light microscopy (LM). The contrast of such material is not substantially influenced by the type of embedding resin or section support substrate. It is, however, influenced by the type of fixation (glutaraldehyde with and without osmium postfixation), by heavy metal (uranyl and lead) staining, and by the section thickness. The ability to examine the specimen with the LM, within a section cut for EM, allows each section to be rapidly screened for content prior to examination in the EM. We have found this approach to be particularly useful for studies requiring the ultrastructural examination of a selected area or structure which is large enough to be visualized with the LM but which comprises only a small volume of the embedded material (e.g., centrosomes and nuclei within oocytes; specific regions of large protists.)Same section LM-EM can also be extended to sections cut from cells stained prior to embedding for the immunofluorescent localization of antigens using fluorescein, rhodamine or Texas red-conjugated antibodies. Under these conditions the sections show high resolution patterns of antigen-specific fluorescence against a background void of autoflouorescence. The fidelity in the correlation between the distribution of immunofluorescently labeled antigens and the ultrastructure in the same section can be extended to structures as small as a single microtubule or just a few actin filaments . This approach of same section correlative fluorescence microscopy (FLM) and EM can eliminate the need, in many instances, to employ more complex procedures such as immunoferritin or immunogold for labeling antigens for ultrastructural detection.

An electron microscopic study of vitellogenesis and egg membrane formation in Lytta nuttalli Say (ColeopterarMeloidae)

1970 ◽  
Vol 48 (4) ◽  
pp. 651-657 ◽  
Author(s):  
P. R. Sweeny ◽  
N. S. Church ◽  
J. G. Rempel ◽  
Wendy Frith
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Follicle Cells ◽  
Vitelline Membrane ◽  
Electron Microscopic ◽  
Yolk Formation ◽  
Membrane Formation ◽  
Electron Dense Material ◽  
Egg Membrane ◽  
Pass Through

Vitellogenesis and egg membrane formation in the terminal ovarian follicles of Lytta nuttatii were investigated by electron microscopy. Three kinds of yolk globules are produced. They apparently are composed predominantly of carbohydrates, lipids, and proteins, respectively. The "carbohydrate" and "lipid" yolk are assembled in the ooplasm, the former by rough endoplasmic reticulum and the latter by Golgi complexes. Their production begins early in oogenesis. "Proteid" yolk formation begins somewhat later. The "proteid" yolk globules evidently are formed from exfraovarian materials that pass through large spaces that develop between the follicular epithelial cells, then through the oocyte plasma membrane by pinocytosis. Fairly late in development, glycogen granules appear in the inner ooplasm. In the nearly fully grown follicle, the "membranous system" of the vitelline membrane is elaborated. It probably is formed largely from an electron-dense material of undetermined origin that accumulates outside the bases of the oocyte plasma membrane microvilli. Immediately after completion of the vitelline membrane, the chorion is laid down, presumably from dense globules of material produced by Golgi complexes in the follicle cells.

The relationship between oöcyte and follicle in the hen's ovary as shown by electron microscopy

Development ◽  
1965 ◽  
Vol 13 (2) ◽  
pp. 215-233
Author(s):  
Ruth Bellairs
Keyword(s):  
Electron Microscopy ◽  
Cell Membrane ◽  
Raw Materials ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Vitelline Membrane ◽  
Zona Radiata ◽  
Golgi Bodies ◽  
Pass Through ◽  
The Relationship

In the adult hen each oöcyte is surrounded by a capsule of follicle cells and all the raw materials that enter the oöcyte must pass through this capsule. It is not surprising, therefore, that the morphological relationships between the follicle and the oöcyte are of a highly specialized nature. Several workers have studied them, mainly by light microscopy, but their findings have not been unanimous, largely because of difficulties in resolving fine details. For instance, although it has frequently been suggested that certain structures pass from the follicle cell into the oöcyte, these structures have been interpreted by different authors as Golgi bodies, as mitochondria or as fat drops. Similarly, there have been several different theories about the relationship between the cell membrane of the oöcyte, the zona radiata and the vitelline membrane.

Evaluation of the dark field method for large association of spread DNA

1978 ◽  
Vol 36 (2) ◽  
pp. 190-191
Author(s):  
Douglas C. Barker
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Mitochondrial Dna ◽  
Extraction Method ◽  
Field Method ◽  
Dark Field ◽  
Kinetoplast Dna ◽  
Field Electron ◽  
Field Electron Microscopy ◽  
Dark Field Electron

A number of satisfactory methods are available for the electron microscopy of nicleic acids. These methods concentrated on fragments of nuclear, viral and mitochondrial DNA less than 50 megadaltons, on denaturation and heteroduplex mapping (Davies et al 1971) or on the interaction between proteins and DNA (Brack and Delain 1975). Less attention has been paid to the experimental criteria necessary for spreading and visualisation by dark field electron microscopy of large intact issociations of DNA. This communication will report on those criteria in relation to the ultrastructure of the (approx. 1 x 10-14g) DNA component of the kinetoplast from Trypanosomes. An extraction method has been developed to eliminate native endonucleases and nuclear contamination and to isolate the kinetoplast DNA (KDNA) as a compact network of high molecular weight. In collaboration with Dr. Ch. Brack (Basel [nstitute of Immunology), we studied the conditions necessary to prepare this KDNA Tor dark field electron microscopy using the microdrop spreading technique.

Elastic Scattering in Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 252-253
Author(s):  
J. Langmore ◽  
M. Isaacson ◽  
J. Wall ◽  
A. V. Crewe
Keyword(s):  
Electron Microscopy ◽  
Elastic Scattering ◽  
Cross Section ◽  
Quantum Noise ◽  
Dark Field ◽  
Elastic Cross Section ◽  
Biological Molecules ◽  
Dark Field Microscopy ◽  
Field Systems ◽  
Effects Of Radiation

High resolution dark field microscopy is becoming an important tool for the investigation of unstained and specifically stained biological molecules. Of primary consideration to the microscopist is the interpretation of image Intensities and the effects of radiation damage to the specimen. Ignoring inelastic scattering, the image intensity is directly related to the collected elastic scattering cross section, σɳ, which is the product of the total elastic cross section, σ and the eficiency of the microscope system at imaging these electrons, η. The number of potentially bond damaging events resulting from the beam exposure required to reduce the effect of quantum noise in the image to a given level is proportional to 1/η. We wish to compare η in three dark field systems.

A Preparation of High Resolution Standards for Electron Microscopy. Part II

1971 ◽  
Vol 29 ◽  
pp. 160-161
Author(s):  
Akira Tanaka ◽  
David F. Harling
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Carbon Black ◽  
Single Crystal ◽  
Dark Field ◽  
Graphitized Carbon Black ◽  
Graphitized Carbon ◽  
Dark Field Imaging ◽  
Crystal Films ◽  
Micro Holes

In the previous paper, the author reported on a technique for preparing vapor-deposited single crystal films as high resolution standards for electron microscopy. The present paper is intended to describe the preparation of several high resolution standards for dark field microscopy and also to mention some results obtained from these studies. Three preparations were used initially: 1.) Graphitized carbon black, 2.) Epitaxially grown particles of different metals prepared by vapor deposition, and 3.) Particles grown epitaxially on the edge of micro-holes formed in a gold single crystal film.The authors successfully obtained dark field micrographs demonstrating the 3.4Å lattice spacing of graphitized carbon black and the Au single crystal (111) lattice of 2.35Å. The latter spacing is especially suitable for dark field imaging because of its preparation, as in 3.), above. After the deposited film of Au (001) orientation is prepared at 400°C the substrate temperature is raised, resulting in the formation of many square micro-holes caused by partial evaporation of the Au film.

The Morphology of Vacuolated Cells in the Liver Following Administration of Vitamin A.

1973 ◽  
Vol 31 ◽  
pp. 408-409
Author(s):  
Odell T. Minick ◽  
Hidejiro Yokoo ◽  
Fawzia Batti
Keyword(s):  
Electron Microscopy ◽  
Body Weight ◽  
Vitamin A ◽  
Light And Electron Microscopy ◽  
Liver Cells ◽  
Prominent Feature ◽  
Vascular Space ◽  
Vacuolated Cell ◽  
Vacuolated Cells ◽  
Vacuolated Cytoplasm

Vacuolated cells in the liver of young rats were studied by light and electron microscopy following the administration of vitamin A (200 units per gram of body weight). Their characteristics were compared with similar cells found in untreated animals.In rats given vitamin A, cells with vacuolated cytoplasm were a prominent feature. These cells were found mostly in a perisinusoidal location, although some appeared to be in between liver cells (Fig. 1). Electron microscopy confirmed their location in Disse's space adjacent to the sinusoid and in recesses between liver cells. Some appeared to be bordering the lumen of the sinusoid, but careful observation usually revealed a tenuous endothelial process separating the vacuolated cell from the vascular space. In appropriate sections, fenestrations in the thin endothelial processes were noted (Fig. 2, arrow).

Electron Microscopy of the Shape of Small Metal Particles

1977 ◽  
Vol 35 ◽  
pp. 300-301
Author(s):  
M. Jose Yacaman
Keyword(s):  
Electron Microscopy ◽  
Metal Particle ◽  
Field Experiments ◽  
Size Range ◽  
Dark Field ◽  
Metal Particles ◽  
Bragg Condition ◽  
Crystal Particle ◽  
Small Metal Particle ◽  
Small Metal Particles

In the Study of small metal particles the shape is a very Important parameter. Using electron microscopy Ino and Owaga(l) have studied the shape of twinned particles of gold. In that work electron diffraction and contrast (dark field) experiments were used to produce models of a crystal particle. In this work we report a method which can give direct information about the shape of an small metal particle in the amstrong- size range with high resolution. The diffraction pattern of a sample containing small metal particles contains in general several systematic and non- systematic reflections and a two-beam condition can not be used in practice. However a N-beam condition produces a reduced extinction distance. On the other hand if a beam is out of the bragg condition the effective extinction distance is even more reduced.

Zero-loss omega-filtered REM and RHEED on the new Zeiss 912

1991 ◽  
Vol 49 ◽  
pp. 616-617
Author(s):  
J.C.H. Spence ◽  
J. Mayer
Keyword(s):  
Electron Microscopy ◽  
Materials Science ◽  
Surface States ◽  
Ccd Camera ◽  
Dark Field ◽  
Ion Pump ◽  
Magnetic Imaging ◽  
Reflection Electron Microscopy ◽  
Diffraction Patterns ◽  
Large Background

The Zeiss 912 is a new fully digital, side-entry, 120 Kv TEM/STEM instrument for materials science, fitted with an omega magnetic imaging energy filter. Pumping is by turbopump and ion pump. The magnetic imaging filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient parallel (area) detection. The energy loss intensity distribution may also be displayed on the screen, and recorded by scanning it over the PMT supplied. If a CCD camera is fitted and suitable new software developed, “parallel ELS” recording results. For large fields of view, filtered images can be recorded much more efficiently than by Scanning Reflection Electron Microscopy, and the large background of inelastic scattering removed. We have therefore evaluated the 912 for REM and RHEED applications. Causes of streaking and resonance in RHEED patterns are being studied, and a more quantitative analysis of CBRED patterns may be possible. Dark field band-gap REM imaging of surface states may also be possible.

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