The Conversion of Yolk into Cytoplasm in the Chick Blastoderm as shown by Electron Microscopy

Development ◽  
1958 ◽  
Vol 6 (1) ◽  
pp. 149-161
Author(s):  
Ruth Bellairs
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Embryonic Development ◽  
Light Microscopy ◽  
Morphological Changes ◽  
Primitive Streak ◽  
Single Stage ◽  
Embryonic Cells ◽  
Chick Blastoderm ◽  
Almost All

In almost all embryos yolk becomes converted into cytoplasm. It has not previously been possible to describe in any detail the morphological changes involved in this process; indeed, when the yolk drops contained within embryonic cells are examined by light microscopy they seem to remain in much the same condition until they are suddenly used up. For this reason they have frequently been considered to be nothing but ‘inert, inactive’ stores of food. By using an electron microscope, however, it has been possible to trace some of the morphological changes which take place in the chick when intra-cellular yolk drops are converted into cytoplasm, and to show that these are not confined to a single stage of embryonic development. Moreover, the discovery of mitochondria within the yolk drops suggests that the yolk drops are not ‘inert’. The following stages have been examined: medium and long primitive streak (as defined by Waddington, 1932, and Abercrombie, 1950), head process, head fold, and 10–16 pairs of somites.

Selective Sampling and Orientation of Non-Homogeneous Tissues

1968 ◽  
Vol 26 ◽  
pp. 98-99
Author(s):  
C. C. Clawson ◽  
L. W. Anderson ◽  
R. A. Good
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Random Sampling ◽  
New Method ◽  
Microscope Examination ◽  
Small Areas ◽  
Selective Sampling ◽  
Large Numbers ◽  
Specific Orientation

Investigations which require electron microscope examination of a few specific areas of non-homogeneous tissues make random sampling of small blocks an inefficient and unrewarding procedure. Therefore, several investigators have devised methods which allow obtaining sample blocks for electron microscopy from region of tissue previously identified by light microscopy of present here techniques which make possible: 1) sampling tissue for electron microscopy from selected areas previously identified by light microscopy of relatively large pieces of tissue; 2) dehydration and embedding large numbers of individually identified blocks while keeping each one separate; 3) a new method of maintaining specific orientation of blocks during embedding; 4) special light microscopic staining or fluorescent procedures and electron microscopy on immediately adjacent small areas of tissue.

Characterization of submicrometer fluid Inclusions in minerals by Analytical/Transmission Electron Microscopy and electron diffraction

1990 ◽  
Vol 48 (4) ◽  
pp. 424-424
Author(s):  
George Guthrie ◽  
David Veblen
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Microscope ◽  
Electron Diffraction ◽  
Light Microscopy ◽  
Fluid Inclusions ◽  
Energy Dispersive Spectrometer ◽  
Analytical Transmission Electron Microscopy ◽  
Transmission Electron

The nature of a geologic fluid can often be inferred from fluid-filled cavities (generally <100 μm in size) that are trapped during the growth of a mineral. A variety of techniques enables the fluids and daughter crystals (any solid precipitated from the trapped fluid) to be identified from cavities greater than a few micrometers. Many minerals, however, contain fluid inclusions smaller than a micrometer. Though inclusions this small are difficult or impossible to study by conventional techniques, they are ideally suited for study by analytical/ transmission electron microscopy (A/TEM) and electron diffraction. We have used this technique to study fluid inclusions and daughter crystals in diamond and feldspar.Inclusion-rich samples of diamond and feldspar were ion-thinned to electron transparency and examined with a Philips 420T electron microscope (120 keV) equipped with an EDAX beryllium-windowed energy dispersive spectrometer. Thin edges of the sample were perforated in areas that appeared in light microscopy to be populated densely with inclusions. In a few cases, the perforations were bound polygonal sides to which crystals (structurally and compositionally different from the host mineral) were attached (Figure 1).

In vitro development of isolated ectoderm from axolotl gastrulae

Development ◽  
1984 ◽  
Vol 80 (1) ◽  
pp. 321-330
Author(s):  
Jonathan M. W. Slack
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Outer Layer ◽  
Microscope Examination ◽  
Animal Pole ◽  
In Vitro Development ◽  
Electron Microscope Examination ◽  
Vitro Development

The development of ectoderm isolated from the animal pole of axolotl gastrulae is monitored by light microscopy, electron microscopy and analysis of newly synthesized proteins, glycoproteins and glycolipids. When control embryos are undergoing neurulation it is shown that the explants autonomously begin to express epidermal markers and do not express mesodermal markers. However the results suggest that not all the cells become epidermal and electron microscope examination shows that only the outer layer does so, the inner cells remaining undifferentiated.

The fine structure of the vertical lobe of Octopus brain

1970 ◽  
Vol 258 (827) ◽  
pp. 379-394 ◽  
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Synaptic Vesicles ◽  
Structural Organization ◽  
Amacrine Cells ◽  
Large Cell ◽  
Inhibitory Effect ◽  
Tactile System

Although much is known about the structural organization and connexions of the various lobes of the octopus brain from light microscopy, this is the first attempt at a detailed analysis of one of the lobes— the vertical lobe, with the electron microscope. The vertical lobe consists of five lobules. The median superior frontal (MSF) axons enter each lobule from the MSF lobe. The MSF axons contain both microtubules and neurofilaments. The varicosities of the MSF axons contain both agranular and dense-cored vesicles and synapse with trunks of the amacrine cells. These trunks run together in bundles termed amacrine tracts into the centres of the lobules. The amacrine trunks contain microtubules but no neurofilaments. The trunks contain large and small agranular synaptic vesicles and synapse with what are in all probability branches of the trunks of the large cells. These trunks contain microtubules but no neurofilaments. They run out through the bases of the lobules probably without forming synaptic contacts within the lobule. Fibres signalling ‘pain’ (nocifensor) enter the lobules from below. They can be recognized by their content of neurofilaments. Their terminals contain numerous very small synaptic vesicles and a few larger and dense-cored ones. These ‘pain’ fibres appear to synapse mostly with processes of the large cells. J. Z. Young has shown that the vertical lobe is especially concerned with the integrative action of the visual system, linked with the chemo-tactile system. Electron microscopy supports Young’s suggestion that the superior frontal and interconnected vertical lobe systems constitute a loop which could sustain a positive feed-back mechanism (MSF —> amacrine -> large cell -> lateral superior frontal -> MSF) while the ‘pain’ (nocifensor) input could exert a suppressor (inhibitory) effect on the loop by its action on the large cells.

Quantitative Fiber Mixture Analysis by Scanning Electron Microscopy

1992 ◽  
Vol 62 (7) ◽  
pp. 423-431 ◽  
Author(s):  
F.-J. Wortmann ◽  
G. Wortmann
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Practical Importance ◽  
Statistical Limit ◽  
Substantial Progress ◽  
Reproducible Method ◽  
Analysis Errors ◽  
Scanning Electron

Labeling textile blends requires identification and quantification of their fibrous components. Blends of specialty animal fibers with sheep's wool are of special, practical importance; for these the light microscope is the traditional tool of analysis. To investigate the actual applicability of light microscopy for analyzing such blends as an alternative to the scanning electron microscope (SEM), we analyzed in detail the results of round trials conducted in the seventies. The results confirm that light microscopy, in general, is neither an objective nor a reproducible method for analyzing wool/specialty fiber blends. Though there was substantial progress with subsequent round trials, the data suggest that there is a fundamental statistical limit to the pass/fail rate, i.e., the ratio of correct versus incorrect analyses in a round trial that can be achieved by light microscopy. Even allowing for generous error limits, this effect leaves an intolerable element of chance for the correctness of analysis. Such performance is in pronounced contrast to that of the SEM method, where round trials have shown that laboratories that perform well reach analysis errors for specialty fiber/wool blends that are within or close to the natural error limits of microscopic analyses.

Comparison of Larval Stored Product Beetle Mandibles by Light Microscope and Scanning Electron Microscope

1981 ◽  
Vol 64 (1) ◽  
pp. 199-224
Author(s):  
John E Kvenberg
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Light Microscopy ◽  
Light Microscope ◽  
Morphological Characteristics ◽  
Scanning Electron ◽  
Conventional Light Microscopy

Abstract Larval stored product beetle mandibles were studied by comparing images made by scanning electron microscopy with those made by conventional light microscopy. Discussion of morphological characteristics is based on illustrations of 25 species

Human Karyotype as Seen by Scanning Electron Microscopy of Smeared Lymphocytes

1977 ◽  
Vol 35 ◽  
pp. 400-401
Author(s):  
Mark E. Gettner ◽  
Myron C. Ledbetter ◽  
Philip S. Woods
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Peripheral Lymphocyte ◽  
Resolving Power ◽  
Sem Observation ◽  
Observation Methods ◽  
Karyotype Morphology ◽  
Scanning Electron

Our objective is to take advantage of the resolving power of the scanning electron microscope (SEM) to study details of karyotype morphology for which the light microscope is limited. To the best of our knowledge the SEM has not been used to study karyotypes. To demonstrate the feasibility of this, we chose initially to examine a standard method used in light microscopy, namely the Carnoy-fixed peripheral lymphocyte chromosome technique that has found such universal favor (1), and to modify it for SEM observation. Methods were devised to permit observation and indexing by light microscopy prior to SEM observation. We report here our preliminary results using cells smeared on subbed slides then osmium ligated, and cells smeared on aluminum coated glass without metal staining. Both types of preparations were Giemsa stained and were observed uncoated.

scholarly journals Embryonic development of Girardia tigrina (Girard, 1850) (Platyhelminthes, Tricladida, Paludicola)

2008 ◽  
Vol 68 (4) ◽  
pp. 889-895 ◽  
Author(s):  
DC. Vara ◽  
AM. Leal-Zanchet ◽  
HM. Lizardo-Daudt
Keyword(s):  
Nervous System ◽  
Embryonic Development ◽  
Digestive System ◽  
Random Distribution ◽  
Morphological Changes ◽  
Subsequent Stage ◽  
Embryonic Cells ◽  
Thin Sections ◽  
Glycol Methacrylate ◽  
Inner Organs

The embryonic development of freshwater triclads is mainly known from studies of species of Dendrocoelum, Planaria, Polycelis, and, more recently, Schmidtea. The present study characterizes the development of Girardia tigrina (Girard, 1850) by means of optical microcopy using glycol methacrylate semi-thin sections. 94 cocoons were collected in the period from laying to hatching, with intervals of up to twenty-four hours. The sequence of morphological changes occurring in the embryo permitted the identification of nine embryonic stages. At the time of cocoon laying, numerous embryos were dispersed among many yolk cells, with a rigid capsule covering the entire cocoon. In the first stage (approx. up to 6 hours after cocoon laying), yolk cells and embryonic cells showed random distribution. Stage II (between 12 and 24 hours after cocoon laying) is characterized by aggregates of blastomeres, which later aggregate forming an enteroblastula. Approximately 2 days after cocoon laying (stage III), formation of the embryonic epidermis and embryonic digestive system took place, the latter degenerating during the subsequent stage. Stage V (until the fourth day) is characterized by the formation of the definitive epidermis. Between 4 and 6 days after laying, organogenesis of the definitive inner organs starts (stage VI). Approximately 14 days after laying (stage IX), formation of the nervous system is completed. At this stage, the embryo shows similar characteristics to those of newly hatched juveniles. The hatching of Girardia tigrina occurs in the period between twelve to twenty-two days after cocoon laying.

scholarly journals AN ELECTRON MICROSCOPE STUDY OF THE ENDOPLASMIC RETICULUM IN NEWT NOTOCHORD CELLS AFTER DISTURBANCE WITH ULTRASONIC TREATMENT AND SUBSEQUENT REGENERATION

1964 ◽  
Vol 20 (1) ◽  
pp. 175-183 ◽  
Author(s):  
G. G. Selman ◽  
A. Jurand
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Ultrasonic Treatment ◽  
Electron Microscope Study ◽  
Triturus Alpestris ◽  
Notochord Cells ◽  
Parallel Arrays ◽  
Subsequent Regeneration

Ultrasonic treatment of the tails of Triturus alpestris tadpoles, at intensities of 8 to 15 watts/cm2, at 1 megacycle/sec., for 5 minutes, disrupted the epidermis and caused pycnosis in individual cells of the muscle and neural tube, but caused no damage to the notochord that could be detected by light microscopy. Electron microscopy showed that this ultrasonic treatment disordered nearly all the endoplasmic reticulum (ER) of the notochord cells into irregularly rounded vesicles, but within 3 hours after treatment some parallel arrays of normal endoplasmic reticulum were seen near, and continuous with, the outer nuclear membrane. In addition, a re-ordering of the previously disordered ER took place throughout the cytoplasm, in some cases. A classification was made of the state of the ER as shown in electron micrographs of material fixed immediately, 3, and 24 hours after treatment. This showed that more than half the total endoplasmic reticulum in notochord cells was normal again by 24 hours after treatment.

Scanning electron microscopy of sporangia of Coelomomyces

1973 ◽  
Vol 51 (7) ◽  
pp. 1325-1330 ◽  
Author(s):  
C. E. Bland ◽  
J. N. Couch
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Light Microscopy ◽  
Undescribed Species ◽  
Scanning Electron

The scanning electron microscope is used in an examination of the sporangia of 18 described and 3 undescribed species of Coelomomyces. As a possible aid to taxonomy, those species considered in this study are grouped into eight morphologically recognizable groups. The complementary use of light microscopy and scanning electron microscopy in studies of this type is emphasized.

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