scholarly journals ELECTRON MICROSCOPE STUDY OF MITOSIS IN SEA URCHIN BLASTOMERES

1961 ◽  
Vol 11 (2) ◽  
pp. 419-431 ◽  
Author(s):  
Patricia Harris
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Sea Urchin ◽  
Electron Microscope Study ◽  
Osmium Tetroxide ◽  
Mitotic Cycle ◽  
Sea Water ◽  
Strongylocentrotus Purpuratus ◽  
Double Membrane ◽  
Late Anaphase

The fine structure of cells at different stages of the mitotic cycle was studied in the blastomeres of 6-hour-old embryos of the sea urchin Strongylocentrotus purpuratus. The material was fixed in 1 per cent osmium tetroxide in sea water, buffered with veronal-acetate to pH 7.5, embedded in Araldite, and sectioned with glass knives. The aster, as it forms around the centriole, has the appearance of the endoplastic reticulum, with elements oriented radially from the centrosphere to the periphery of the cell. Anaphase structures described include the kinetochores, with bundles of fine filaments extending toward the centrioles, as well as continuous filaments passing between the chromosomes. Two cylindrical centrioles composed of parallel rods are present in each of the anaphase asters. At late anaphase, elements of the endoplasmic reticulum condense on the surface of the chromosomes to form a double membrane which already at this stage possesses pores or annuli. At telophase bundles of continuous filaments can be seen in the interzonal region. These filaments, as well as those associated with the chromosomes, have a diameter of approximately 15 mµ, and appear physically different from the astral structure.

Metabolic importance of Na+/K+-ATPase activity during sea urchin development.

1997 ◽  
Vol 200 (22) ◽  
pp. 2881-2892 ◽  
Author(s):  
P Leong ◽  
D Manahan
Keyword(s):  
Enzyme Activity ◽  
Atpase Activity ◽  
Sea Urchin ◽  
Sodium Pump ◽  
Sea Water ◽  
Strongylocentrotus Purpuratus ◽  
Lytechinus Pictus ◽  
Stimulation Of

Early stages of animal development have high mass-specific rates of metabolism. The biochemical processes that establish metabolic rate and how these processes change during development are not understood. In this study, changes in Na+/K+-ATPase activity (the sodium pump) and rate of oxygen consumption were measured during embryonic and early larval development for two species of sea urchin, Strongylocentrotus purpuratus and Lytechinus pictus. Total (in vitro) Na+/K+-ATPase activity increased during development and could potentially account for up to 77 % of larval oxygen consumption in Strongylocentrotus purpuratus (pluteus stage) and 80 % in Lytechinus pictus (prism stage). The critical issue was addressed of what percentage of total enzyme activity is physiologically active in living embryos and larvae and thus what percentage of metabolism is established by the activity of the sodium pump during development. Early developmental stages of sea urchins are ideal for understanding the in vivo metabolic importance of Na+/K+-ATPase because of their small size and high permeability to radioactive tracers (86Rb+) added to sea water. A comparison of total and in vivo Na+/K+-ATPase activities revealed that approximately half of the total activity was utilized in vivo. The remainder represented a functionally active reserve that was subject to regulation, as verified by stimulation of in vivo Na+/K+-ATPase activity in the presence of the ionophore monensin. In the presence of monensin, in vivo Na+/K+-ATPase activities in embryos of S. purpuratus increased to 94 % of the maximum enzyme activity measured in vitro. Stimulation of in vivo Na+/K+-ATPase activity was also observed in the presence of dissolved alanine, presumably due to the requirement to remove the additional intracellular Na+ that was cotransported with alanine from sea water. The metabolic cost of maintaining the ionic balance was found to be high, with this process alone accounting for 40 % of the metabolic rate of sea urchin larvae (based on the measured fraction of total Na+/K+-ATPase that is physiologically active in larvae of S. purpuratus). Ontogenetic changes in pump activity and environmentally induced regulation of reserve Na+/K+-ATPase activity are important factors that determine a major proportion of the metabolic costs of sea urchin development.

An Electron-Microscope Study of the Cytoplasmic Inclusions in the Neurones of Locusta Migratoria

1962 ◽  
Vol s3-103 (62) ◽  
pp. 147-153
Author(s):  
DOREEN E. ASHHURST ◽  
J. A. CHAPMAN
Keyword(s):  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Microscope Study ◽  
Electron Microscope Study ◽  
Locusta Migratoria ◽  
Cytoplasmic Inclusions ◽  
Double Membrane

The cytoplasmic inclusions of the neurones of adult Locusta migratoria have been examined in the electron microscope. The mitochondria are easily recognized by their cristae and outer double membranes. Electron-dense inclusions, also with an outer double membrane but possessing numerous closely spaced internal lamellae in various orientations, are probably small lipochondria. Larger and more diffuse inclusions comprising crescent-shaped aggregates of loosely packed parallel lamellae and vesicles are present; the possible significance of these larger inclusions is discussed. A system of numerous small vesicles distributed throughout the cytoplasm makes up the endoplasmic reticulum.

scholarly journals OBSERVATIONS ON THE FINE STRUCTURE OF LUTEIN CELLS

1962 ◽  
Vol 12 (1) ◽  
pp. 101-113 ◽  
Author(s):  
Allen C. Enders
Keyword(s):  
Electron Microscopy ◽  
Endothelial Cells ◽  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Steroid Hormones ◽  
Osmium Tetroxide ◽  
Secretory Activity ◽  
Corpora Lutea ◽  
Pericapillary Space ◽  
Lutein Cell

Corpora lutea from the period of delayed implantation and from early postimplantation stages of the armadillo, mink, and rat were fixed in buffered osmium tetroxide-sucrose or potassium permanganate. After rapid dehydration, the portions of the corpora lutea were embedded in either methacrylate or epoxy resin. Examination of the lutein cells by electron microscopy revealed the presence, in the better preserved material, of an extensive development of tubular agranular endoplasmic reticulum. Although the membranes of the endoplasmic reticulum are the most striking feature of the lutein cells of both stages of the three animals examined, very numerous large mitochondria with cristae that exhibit a variety of forms tending toward villiform, and protrusions and foldings of the lutein cell margins on the pericapillary space are also characteristic of these cells. Certain minor differences in the lutein cells of the species examined are also noted. No indications of conversion of mitochondria into lipid, of accumulation of lipid in the Golgi area, or of the protrusion of lutein cells into spaces between the endothelial cells, as suggested by other authors, were noted in these preparations. Some of the difficulties inherent in the visualization of the secretory activity of cells producing steroid hormones are briefly discussed.

scholarly journals ON THE FINE STRUCTURE OF THE CAMBIUM OF FRAXINUS AMERICANA L

1966 ◽  
Vol 31 (1) ◽  
pp. 79-93 ◽  
Author(s):  
Lalit M. Srivastava
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Osmium Tetroxide ◽  
Coated Vesicles ◽  
Fraxinus Americana ◽  
Parenchyma Cells ◽  
Rough Er ◽  
Cambial Cells ◽  
Peripheral Cytoplasm

The fine structure of ash cambium was studied after glutaraldehyde-osmium tetroxide fixation. The fusiform and ray initials are essentially alike, and both have the basic complement of organelles and membranes typical of parenchyma cells. The varied behavior of the two types of initials and the role of cambium in oriented production of the xylem and phloem are still unexplained phenomena. Actively growing cambial cells are highly vacuolate. They are rich in endoplasmic reticulum of the rough cisternal form, ribosomes, dictyosomes, and coated vesicles. Microtubules are present in the peripheral cytoplasm. The plasmalemma appears to be continuous with the endoplasmic reticulum and produces coated vesicles as well as micropinocytotic vesicles with smooth surfaces. The plastids have varying amounts of an intralamellar inclusion which may be a lipoprotein. The quiescent cambium is deficient in rough ER and coated vesicles and has certain structures which may be condensed proteins.

FINE STRUCTURE IN DETACHED, SENESCING WHEAT LEAVES

1965 ◽  
Vol 43 (6) ◽  
pp. 747-755 ◽  
Author(s):  
Michael Shaw ◽  
M. S. Manocha
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Osmium Tetroxide ◽  
Mesophyll Cells ◽  
Laboratory Bench ◽  
Detached Leaves ◽  
Petri Dishes ◽  
Wheat Leaves ◽  
Cytoplasmic Ribosomes

Detached leaves of Little Club wheat were allowed to senesce on water or on kinetin (10 mg/l.) in petri dishes on the laboratory bench. Samples taken at intervals of 24 to 48 hours for 8 to 10 days were fixed in permanganate or osmium tetroxide, embedded, usually in araldite or epon, and examined by electron microscopy. Abnormalities were noted in the endoplasmic reticulum (ER) of the mesophyll cells 2 days after the leaves were detached; ER and cytoplasmic ribosomes were not present after 4 or 5 days. Swelling of the mitochondria and degeneration of the cristae, collapse of the chloroplast grana, and abnormalities in nuclear structure were noted after 3 days. Vacuolar contraction occurred in some cells after 4 days but the plasma membrane usually remained unbroken until the seventh or eighth day, by which time the mitochondria were no longer recognizable and most of the chloroplasts and nuclei had also disintegrated.Kinetin induced an increase in the amount of ER and ribosomes and markedly delayed the degeneration of cellular fine structure.

scholarly journals THE FINE STRUCTURE OF DIFFERENTIATING XYLEM ELEMENTS

1965 ◽  
Vol 24 (3) ◽  
pp. 415-431 ◽  
Author(s):  
James Cronshaw ◽  
G. Benjamin Bouck
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Fine Structure ◽  
Secondary Wall ◽  
Osmium Tetroxide ◽  
Light And Electron Microscopy ◽  
Wall Thickening ◽  
Direction Parallel ◽  
Secondary Wall Thickening ◽  
Xylem Elements

Differentiating xylem elements of Avena coleoptiles have been examined by light and electron microscopy. Fixation in 2 per cent phosphate-buffered osmium tetroxide and in 6 per cent glutaraldehyde, followed by 2 per cent osmium tetroxide, revealed details of the cell wall and cytoplasmic fine structure. The localized secondary wall thickening identified the xylem elements and indicated their state of differentiation. These differentiating xylem elements have dense cytoplasmic contents in which the dictyosomes and elements of rough endoplasmic reticulum are especially numerous. Vesicles are associated with the dictyosomes and are found throughout the cytoplasm. In many cases, these vesicles have electron-opaque contents. "Microtubules" are abundant in the peripheral cytoplasm and are always associated with the secondary wall thickenings. These microtubules are oriented in a direction parallel to the microfibrillar direction of the thickenings. Other tubules are frequently found between the cell wall and the plasma membrane. Our results support the view that the morphological association of the "microtubules" with developing cell wall thickenings may have a functional significance, especially with respect to the orientation of the microfibrils. Dictyosomes and endoplasmic reticulum may have a function in some way connected with the synthetic mechanism of cell wall deposition.

scholarly journals Comparison of quick-frozen and chemically fixed sea-urchin eggs: structural evidence that cortical granule exocytosis is preceded by a local increase in membrane mobility

1984 ◽  
Vol 72 (1) ◽  
pp. 23-36 ◽  
Author(s):  
D.E. Chandler
Keyword(s):  
Sea Urchin ◽  
Large Scale ◽  
Osmium Tetroxide ◽  
Plasma Membranes ◽  
Strongylocentrotus Purpuratus ◽  
Cortical Granule ◽  
Granule Exocytosis ◽  
Purple Sea Urchin ◽  
Membrane Blebs ◽  
Cortical Granule Exocytosis

Eggs of the purple sea-urchin, Strongylocentrotus purpuratus, were fertilized and fixed with 2% glutaraldehyde at various stages during cortical granule exocytosis. Fixation resulted in membrane blebs being formed precisely at the point of incipient granule fusion. These blebs pinched off to form the membranous vesicles frequently seen in exocytic pockets and in the perivitelline space. In contrast, eggs that were fixed with osmium tetroxide or were quick-frozen without chemical fixation, showed no signs of bleb or vesicle formation. Rather, fusion of each granule appeared to begin at a single minute pore, 30–50 nm in diameter, which then enlarged. We suggest that formation of blebs during glutaraldehyde fixation is an artifact that is caused by a highly localized and transient increase in membrane mobility. Normally, this increased mobility facilitates fusion of granule and plasma membranes, but in the presence of glutaraldehyde it leads to large-scale distortions of these fusing membranes.

Fine Structure of Sea Urchin Sperm Membranes

1970 ◽  
Vol 28 ◽  
pp. 312-313
Author(s):  
S. Inoue ◽  
A. Buday ◽  
G.H. Cousineau
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Sea Urchin ◽  
Sea Water ◽  
Sea Urchins ◽  
Water Mixture ◽  
Thin Sections ◽  
Surface Replica ◽  
Sperm Membrane ◽  
Surface Replica Method

From electron microscope studies of thin sections it is known that the entire surface of a spermatozoon of sea urchin is covered by a plasma membrane, or sperm membrane, of an approximate thickness of 100Å (1). In these experiments the surface replica method was applied for the study of the fine structure of the sperm membrane.Spermatozoa from Strongylocentrotus purpuratus (sea urchins supplied by the Pacific Biomarine Supply Company, Venice, Calif.) were washed several times by centrifugation in Millipore-filtered sea water. After fixation in a 2.5% glutaraldehyde-paraformaldehyde (sea water mixture at 4°C) for an hour, spermatozoa were washed with sea water and then with distilled water for several times. A few drops of specimen were dried on a glass slide and the surface replica was prepared according to the method previously described (2) with the exception that the spermatozoa were decomposed in 18 N H2SO4 for about 20 hours at room temperature. The replica films were examined with a JEM-7A electron microscope.

The Fine Structure of Calcoblasts in the Regenerating Sea Urchin Spine

1972 ◽  
Vol 30 ◽  
pp. 162-163
Author(s):  
Barry M. Heatfield ◽  
Dorothy F. Travis
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Calcium Carbonate ◽  
Sea Urchin ◽  
Basal Lamina ◽  
Strongylocentrotus Purpuratus ◽  
Extracellular Fluid ◽  
Cell Types ◽  
Thin Sections ◽  
Sea Urchin Spine

The endoskeleton of echinoderms is composed of fenestrated calcium carbonate (calcite) permeated by interconnecting channels filled with a variety of cell-types and extracellular fluid containing collagen fibrils. To identify and characterize skeletogenic cells and explore the mechanism of skeleton growth in echinoderms, tissues of regenerating spines of the sea urchin Strongylocentrotus purpuratus were examined by electron microscopy.The tip of the young regenerate is composed of two layers of tissue: an outer epidermis and an inner calcified dermis separated by a thin basal lamina (Fig. 1). In the apical dermis the skeleton consists of longitudinally oriented microspines interconnected by horizontal calcite bridges. During preparation of thin sections, skeletal mineral was lost, leaving a hole, indicated by (ms) in Figs. 1, 2, and 4.

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