The localization of morphogenetic factors in uncleaved eggs of Dentalium

Development ◽  
1971 ◽  
Vol 25 (1) ◽  
pp. 57-63
Author(s):  
N. H. Verdonk ◽  
W. L. M. Geilenkirchen ◽  
L. P. M. Timmermans
Keyword(s):  
Polar Lobe ◽  
Apical Tuft ◽  
Morphogenetic Factors

The effect of removing parts of unfertilized and fertilized eggs of Dentalium has been studied. Up to 70 % of the volume of a 1st polar lobe can be removed from the vegetal side of both unfertilized and fertilized eggs, without influencing apical tuft formation. The post-trochal region is reduced. These eggs form a reduced polar lobe at first cleavage. After removal of more than 70 % of the volume of a 1st polar lobe from the vegetal side of an uncleaved egg, before or after fertilization, no polar lobe is formed and larvae develop without apical tuft or post-trochal region. The polar lobe area is quantitatively determined in the uncleaved egg, but after fertilization of isolated vegetal fragments regulation occurs and the polar lobe becomes proportional in size to the fragment. Feulgen-positive granules, present at the vegetal side of the uncleaved egg, can be removed without influencing apical tuft formation. They may be important as determinants for the formation of the post-trochal region or adult structures.

Experimental studies on morphogenetic factors localized in the first and the second polar lobe of Dentalium eggs

Development ◽  
1970 ◽  
Vol 23 (1) ◽  
pp. 237-243
Author(s):  
W. L. M. Geilenkirchen ◽  
N. H. Verdonk ◽  
L. P. M. Timmermans
Keyword(s):  
Mytilus Edulis ◽  
Experimental Studies ◽  
Ilyanassa Obsoleta ◽  
Polar Lobe ◽  
Apical Tuft ◽  
The Third ◽  
Vegetal Pole ◽  
Morphogenetic Factors

During the development of several annelids and molluscs, a lobe of protoplasm is observed to protrude from the vegetal pole of the egg during the first cleavages. Removal of this polar lobe causes characteristic defects in the developing larvae as has been observed in the scaphopod, Dentalium (Wilson, 1904; Verdonk, 1968), the annelid Sabellaria (Hatt, 1932; Novikoff, 1938), the gastropod Ilyanassa obsoleta (Crampton, 1896; Clement, 1952) and the lamellibranch, Mytilus edulis (Rattenbury & Berg, 1954). In Dentalium a polar lobe is formed at the first, the second and the third cleavage. The lobes contain part of the cytoplasm, which later is confined to the D blastomere. After removal of the first polar lobe, embryos develop in which the post-trochal region and the apical tuft are absent. After removal of the second polar lobe the post-trochal region of the embryos is greatly reduced, but they develop an apical tuft (Wilson, 1904).

Protein synthesis during Ilyanassa development: effect of the polar lobe

Development ◽  
1973 ◽  
Vol 29 (2) ◽  
pp. 267-281
Author(s):  
G. Teitelman
Keyword(s):  
Protein Synthesis ◽  
Normal Development ◽  
Disc Electrophoresis ◽  
Developmental Differences ◽  
Protein Solutions ◽  
Polar Lobe ◽  
Stages Of Development ◽  
Morphogenetic Factors ◽  
Slow Moving ◽  
The One

Removal of the polar lobe at the trefoil stage of the first cleavage division of Ilyanassa embryos causes abnormalities much later in development. To determine if the developmental differences between normal and delobed embryos were reflected in alterations in protein synthesis and at what stages of development these become evident, protein solutions were separated by disc electrophoresis on basic acrylamide gels. For the analysis of the newly synthesized proteins, two protein samples, one labelled with 14C and the other with 3H, were combined in the same electrophoretic column. Each was prepared from normal embryos or lobeless embryos at different stages of development. The distribution of the two groups of differentially labelled proteins was compared by a determination, for each fraction, of the ratio of the normalized 3H/14C counts for that particular fraction (R = 3H/14C). The plot of R versus fraction number was studied for various combinations of samples. During normal development the profile of labelled proteins remains unchanged until the onset of visible differentiation. At this stage, around day 4 of development, there are changes in biosynthesis revealed by a greater emphasis on the synthesis of slow moving proteins. The profile of labelled proteins of lobeless embryos remains unchanged up to the 5th day of development. This result is correlated with the absence, in the lobeless embryos, of many of the visible differentiations. Preliminary studies revealed that the spectrum of labelled proteins of the polar lobe is identical to the one present in lobeless embryos and in normal embryos in early stages of development. This suggests the possibility that the morphogenetic factors associated with the polar lobe are not among the newly synthesized proteins. A hypothesis is presented to account for the effects on morphogenesis and protein synthesis which are produced by removal of the polar lobe.

The effect of removing the polar lobe in centrifuged eggs of Dentalium

Development ◽  
1968 ◽  
Vol 19 (1) ◽  
pp. 33-42
Author(s):  
N. H. Verdonk
Keyword(s):  
Normal Distribution ◽  
Polar Lobe ◽  
Morphogenetic Substances ◽  
Apical Tuft ◽  
Trochophore Larva

Classical evidence for the existence of morphogenetic substances was provided by experiments with spiralian eggs possessing a polar lobe: Ilyanassa (Crampton, 1896; Clement, 1952, 1956, 1962); Dentalium (Wilson, 1904); Chaetopterus (Tyler, 1930); Sabellaria (Hatt, 1932; Novikoff, 1938); and Mytilus (Rattenbury & Berg, 1954). Eggs from which the polar lobe had been removed developed into embryos with specific abnormalities. In Dentalium, after removal of the polar lobe at the trefoil stage, a trochophore larva is formed without post-trochal region and apical tuft. Removal of the polar lobe at second cleavage causes a larva without post-trochal region, but with an apical tuft. Wilson concluded that specific cytoplasmic materials essential to the formation of the apical tuft are contained in the first but no longer in the second polar lobe. Centrifuging the uncleaved egg just before first cleavage will disturb the normal distribution of substances.

Local accumulation of Feulgen-positive granules in the egg cortex of Dentalium dentale L.

Development ◽  
1970 ◽  
Vol 23 (1) ◽  
pp. 245-252
Author(s):  
Lucy P. M. Timmermans ◽  
W. L. M. Geilenkirchen ◽  
N. H. Verdonk
Keyword(s):  
Polar Lobe ◽  
Apical Tuft ◽  
The Third ◽  
The One ◽  
Local Accumulation ◽  
Egg Cortex

A special feature of eggs of several species of annelids and molluscs is the formation of a polar lobe at stage-specific intervals during the cleavage phase. In the scaphopod Dentalium, a polar lobe develops at the first, the second and the third cleavage (Wilson, 1904). The cytoplasm set apart in the polar lobes is ultimately confined to the D blastomere and its derivative cells. Wilson observed that after removal of the polar lobe at the first cleavage a larva develops which lacks an apical tuft and the post-trochal region. After removal of the polar lobe at the second cleavage a larva develops which lacks most of the post-trochal region but possesses an apical tuft. A similar result to the one following the removal of the first polar lobe is obtained by removal of the vegetal one-third of an unfertilized egg.

The ultrastructure of the polar lobe of Crepidula fornicata (Gastropoda, Prosobranchia)

Development ◽  
1975 ◽  
Vol 34 (2) ◽  
pp. 419-428
Author(s):  
M. R. Dohmen ◽  
D. Lok
Keyword(s):  
Structural Features ◽  
Polar Lobe ◽  
Crepidula Fornicata ◽  
Morphogenetic Factors

Some novel structural features of the polar lobe of the egg of Crepidula are described. The significance of two kinds of aggregate is discussed in relation to the morphogenetic factors present in polar lobes generally. Surface configurations of the polar lobe are also described.

Three-Dimensional Reconstruction of Two Forms of the Chaperonin GRO EL

1990 ◽  
Vol 48 (1) ◽  
pp. 258-259
Author(s):  
J.L. Carrascosa ◽  
G. Abella ◽  
S. Marco ◽  
M. Muyal ◽  
J.M. Carazo
Keyword(s):  
Three Dimensional ◽  
The Other ◽  
Two Dimensional ◽  
Series Method ◽  
Three Dimensional Reconstruction ◽  
Structural Components ◽  
E Coli ◽  
Dimensional Reconstruction ◽  
Morphogenetic Factors ◽  
Tilt Series

Chaperonins are a class of proteins characterized by their role as morphogenetic factors. They trantsiently interact with the structural components of certain biological aggregates (viruses, enzymes etc), promoting their correct folding, assembly and, eventually transport. The groEL factor from E. coli is a conspicuous member of the chaperonins, as it promotes the assembly and morphogenesis of bacterial oligomers and/viral structures.We have studied groEL-like factors from two different bacteria:E. coli and B.subtilis. These factors share common morphological features , showing two different views: one is 6-fold, while the other shows 7 morphological units. There is also a correlation between the presence of a dominant 6-fold view and the fact of both bacteria been grown at low temperature (32°C), while the 7-fold is the main view at higher temperatures (42°C). As the two-dimensional projections of groEL were difficult to interprete, we studied their three-dimensional reconstruction by the random conical tilt series method from negatively stained particles.

Effects of cytochalasin B on meiosis and development of fertilized and activated eggs of Sabellaria alveolata L. (Polychaete Annelid)

Development ◽  
1974 ◽  
Vol 31 (1) ◽  
pp. 61-74
Author(s):  
G. Peaucellier ◽  
P. Guerrier ◽  
J. Bergerard
Keyword(s):  
Cytochalasin B ◽  
Polar Body ◽  
Polar Lobe ◽  
Developmental Abnormalities ◽  
Drug Concentrations ◽  
Internal Mechanism ◽  
Polar Body Extrusion

1. Unfertilized, fertilized and activated eggs of Sabellaria alveolata were submitted to cytochalasin B concentrations ranging from 0·1 to 20 μg/ml. Their behaviour was studied either in vivo or in acetocarmine squash preparations. 2. Polar body extrusion, cytokinesis and polar lobe formation are completely inhibited by cytochalasin B concentrations as low as 0·3–0·5 μg/ml. 3. Caryotype determinations demonstrate that chromosomal meiotic and mitotic processes are not affected by the drug. Thus, polyploid embryos usually developed from fertilized eggs whilst they did not from activated ones. This is related to the contrasting behaviour of meiotic and cleavage centres. While the latter duplicates at each cycle, the former cannot replicate at the end of meiosis. This leads to an abortive monastral stage even if inhibition of polar body extrusion has provided the egg with two or four centres. These observations suggest the existence of an internal mechanism regulating the number of effective centrioles at the end of meiosis. They demonstrate also that the main cause of developmental failure in activated eggs cannot be related to ploidy. 4. Eggs treated throughout meiosis with moderate drug concentrations developed into swimming larvae. However, frequent developmental abnormalities affecting lobe dependent structures were obtained even if polar lobe formation was unimpaired. This suggests either that cytochalasin B has irreversibly affected some decisive cortical element or that previously described activating processes, which begin with polar lobe formation, are actually exerted on specific materials segregated during meiosis.

The development of Bithynia tentaculata (Prosobranchia, Gastropoda) after removal of the polar lobe

Development ◽  
1974 ◽  
Vol 31 (2) ◽  
pp. 415-422
Author(s):  
James N. Cather ◽  
Nico H. Verdonk
Keyword(s):  
Bilateral Symmetry ◽  
Columnar Epithelium ◽  
Polar Lobe ◽  
Bithynia Tentaculata

The polar lobe of the egg of Bithynia, with a volume of less than 1% of that of the egg, was surgically removed. Lobeless embryos form no mesentoblast cell nor mesoderm bands. They fail to establish bilateral symmetry and to form eyes, foot, operculum, shell, etc. They always differentiate larval head cells, ganglia, larval liver and mesenchyme and sometimes columnar epithelium, stomodeal entrance cells, endodermal tubes and muscles. These results are discussed in relation to the structure of the lobe, the analysis of development of Bithynia and to similar experiments in other species.

Changes in transcellular ionic currents associated with polar lobe formation in embryos of Bithynia

Development ◽  
1991 ◽  
Vol 112 (2) ◽  
pp. 451-459
Author(s):  
D. Zivkovic ◽  
R. Dohmen
Keyword(s):  
Ionic Currents ◽  
Vibrating Probe ◽  
Polar Lobe ◽  
Probe Technique

Using the vibrating probe technique, we have measured currents ranging from 0.05 to 3.00mAcm-2 around polar-

Sign in / Sign up

Export Citation Format

Share Document