Cytological and cytochemical studies of centrifuged eggs of the slug Avion ater rufus L.

Development ◽  
1972 ◽  
Vol 27 (1) ◽  
pp. 1-13
Author(s):  
A. H. Sathananthan
Keyword(s):  
Electron Microscope ◽  
Cell Membrane ◽  
Sea Urchin ◽  
Cell Organelles ◽  
Chemical Substances ◽  
Important Chemical ◽  
Equatorial Band ◽  
Hyaline Zone ◽  
Egg Cortex

The stratification of various cell organelles and of important chemical substances have been studied in the eggs of the slug, after moderate centrifugation. As in other molluscs the egg contents stratify typically into three well-defined zones - lipid, L hyaline and yolky zones - but a distinct equatorial band of inclusions consisting mainly of F phagosomes and associated lysosomes was detected in the most centrifugal region of the hyaline zone. The sub-stratification of various cell inclusions in their respective zones was determined in some detail. The role of the cell membrane and egg cortex in the redistribution of these inclusions and the nature of the ergastoplasm are discussed in the light of electron-microscope studies of eggs of this slug and of the sea urchin.

The role of (bio)surfactant sorption in promoting the bioavailability of nutrients localized at the solid-water interface

1999 ◽  
Vol 39 (7) ◽  
pp. 91-98 ◽  
Author(s):  
Ryan N. Jordan ◽  
Eric P. Nichols ◽  
Alfred B. Cunningham
Keyword(s):  
Mass Transfer ◽  
Cell Membrane ◽  
Substrate Concentration ◽  
Water Interface ◽  
Industrial Systems ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Surfactant Sorption

Bioavailability is herein defined as the accessibility of a substrate by a microorganism. Further, bioavailability is governed by (1) the substrate concentration that the cell membrane “sees,” (i.e., the “directly bioavailable” pool) as well as (2) the rate of mass transfer from potentially bioavailable (e.g., nonaqueous) phases to the directly bioavailable (e.g., aqueous) phase. Mechanisms by which sorbed (bio)surfactants influence these two processes are discussed. We propose the hypothesis that the sorption of (bio)surfactants at the solid-liquid interface is partially responsible for the increased bioavailability of surface-bound nutrients, and offer this as a basis for suggesting the development of engineered in-situ bioremediation technologies that take advantage of low (bio)surfactant concentrations. In addition, other industrial systems where bioavailability phenomena should be considered are addressed.

scholarly journals Role of the Fyn Kinase in Calcium Release during Fertilization of the Sea Urchin Egg

2000 ◽  
Vol 225 (1) ◽  
pp. 253-264 ◽  
Author(s):  
W.H. Kinsey ◽  
S.S. Shen
Keyword(s):  
Sea Urchin ◽  
Calcium Release ◽  
Fyn Kinase ◽  
Sea Urchin Egg

Calcium-induced decrease in membrane fluidity of sea urchin egg cortex after fertilization

Nature ◽  
1980 ◽  
Vol 286 (5769) ◽  
pp. 185-186 ◽  
Author(s):  
Judith Campisi ◽  
Carl J. Scandella
Keyword(s):  
Membrane Fluidity ◽  
Sea Urchin ◽  
Sea Urchin Egg ◽  
Egg Cortex

An Electron Microscope study of a Small Free-living Amoeba (Hartmanella astronyxis)

1959 ◽  
Vol s3-100 (49) ◽  
pp. 13-15
Author(s):  
K. DEUTSCH ◽  
M. M. SWANN
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Cell Membrane ◽  
Nuclear Membrane ◽  
Layered Structure ◽  
Microscope Study ◽  
Electron Microscope Study ◽  
Honeycomb Structure ◽  
Free Living ◽  
Free Living Amoeba

The fine structure of a species of small free-living amoeba, Hartmanella astronyxis, has been investigated. The mitochondria resemble those of other species of amoeba. Structureless bodies of about the same size as mitochondria are sometimes found in association with them. Double membranes are common in the cytoplasm, and may show granules along their outer borders. The nuclear membrane is a double-layered structure, with a honeycomb structure evident in tangential sections. The cell membrane is also double-layered, or occasionally multi-layered.

Autonomous and non-autonomous differentiation of ectoderm in different sea urchin species

Development ◽  
1995 ◽  
Vol 121 (5) ◽  
pp. 1497-1505 ◽  
Author(s):  
A.H. Wikramanayake ◽  
B.P. Brandhorst ◽  
W.H. Klein
Keyword(s):  
Sea Urchin ◽  
Strongylocentrotus Purpuratus ◽  
Protein A ◽  
Cellular Interactions ◽  
V Protein ◽  
Lytechinus Pictus ◽  
Sea Urchin Embryo ◽  
Oral Ectoderm ◽  
Temporal And Spatial

During early embryogenesis, the highly regulative sea urchin embryo relies extensively on cell-cell interactions for cellular specification. Here, the role of cellular interactions in the temporal and spatial expression of markers for oral and aboral ectoderm in Strongylocentrotus purpuratus and Lytechinus pictus was investigated. When pairs of mesomeres or animal caps, which are fated to give rise to ectoderm, were isolated and cultured they developed into ciliated embryoids that were morphologically polarized. In animal explants from S. purpuratus, the aboral ectoderm-specific Spec1 gene was activated at the same time as in control embryos and at relatively high levels. The Spec1 protein was restricted to the squamous epithelial cells in the embryoids suggesting that an oral-aboral axis formed and aboral ectoderm differentiation occurred correctly. However, the Ecto V protein, a marker for oral ectoderm differentiation, was detected throughout the embryoid and no stomodeum or ciliary band formed. These results indicated that animal explants from S. purpuratus were autonomous in their ability to form an oral-aboral axis and to differentiate aboral ectoderm, but other aspects of ectoderm differentiation require interaction with vegetal blastomeres. In contrast to S. purpuratus, aboral ectoderm-specific genes were not expressed in animal explants from L. pictus even though the resulting embryoids were morphologically very similar to those of S. purpuratus. Recombination of the explants with vegetal blastomeres or exposure to the vegetalizing agent LiCl restored activity of aboral ectoderm-specific genes, suggesting the requirement of a vegetal induction for differentiation of aboral ectoderm cells.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of neurohumours in early embryogenesis

Development ◽  
1970 ◽  
Vol 23 (3) ◽  
pp. 549-569
Author(s):  
G. A. Buznikov ◽  
A. N. Kost ◽  
N. F. Kucherova ◽  
A. L. Mndzhoyan ◽  
N. N. Suvorov ◽  
...  
Keyword(s):  
Sea Urchin ◽  
Functional Activity ◽  
Early Onset ◽  
Active Sites ◽  
Physiological Effect ◽  
Early Embryogenesis ◽  
Dopamine Synthesis ◽  
Direct Involvement ◽  
Misgurnus Fossilis

In previous papers (Buznikov, Chudakova & Zvezdina, 1964; Buznikov, Chudakova, Berdysheva & Vyazmina, 1968) we reported that fertilized eggs of the sea-urchin Strongylocentrotus dröbachiensis synthesized a number of neurohumours, such as serotonin (5-hydroxytryptamine, 5-HT), acetylcholine (ACh), adrenalin (A), noradrenalin (NA) and dopamine. Synthesis of 5-HT was also demonstrated in the fertilized eggs of the loach Misgurnus fossilis and some marine Invertebrata. In experiments with sea-urchin embryos we were able to trace regular changes in the level of 5-HT, ACh, A and NA, related to the first cleavage divisions. This early onset of neurohumour synthesis, as well as regular changes in their level, suggests their direct involvement in the regulation of the first cleavage divisions. The functional activity of neurohumours (M) in adult organisms is realized through their reaction with the active sites of corresponding receptors (R) according to the following equation:The magnitude of the physiological effect under certain conditions is linearly proportional to the number of complexes MR formed (Turpayev, 1962; Ariëns, 1964).

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