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.

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).

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.

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.

On the Mathematical Basis of Zelen’s Prerandomized Designs

1985 ◽  
Vol 24 (03) ◽  
pp. 120-130 ◽  
Author(s):  
E. Brunner ◽  
N. Neumann
Keyword(s):  
Clinical Trial ◽  
Normal Distribution ◽  
Random Variables ◽  
Small Samples ◽  
Selection Effects ◽  
Sample Sizes ◽  
Mathematical Basis ◽  
Additional Assumptions

SummaryThe mathematical basis of Zelen’s suggestion [4] of pre randomizing patients in a clinical trial and then asking them for their consent is investigated. The first problem is to estimate the therapy and selection effects. In the simple prerandomized design (PRD) this is possible without any problems. Similar observations have been made by Anbar [1] and McHugh [3]. However, for the double PRD additional assumptions are needed in order to render therapy and selection effects estimable. The second problem is to determine the distribution of the statistics. It has to be taken into consideration that the sample sizes are random variables in the PRDs. This is why the distribution of the statistics can only be determined asymptotically, even under the assumption of normal distribution. The behaviour of the statistics for small samples is investigated by means of simulations, where the statistics considered in the present paper are compared with the statistics suggested by Ihm [2]. It turns out that the statistics suggested in [2] may lead to anticonservative decisions, whereas the “canonical statistics” suggested by Zelen [4] and considered in the present paper keep the level quite well or may lead to slightly conservative decisions, if there are considerable selection effects.

Interrelations of Thrombo-Embolic Diseases and Blood-Group Distribution

1963 ◽  
Vol 09 (02) ◽  
pp. 472-474 ◽  
Author(s):  
W Dick ◽  
W Schneider ◽  
K Brockmüller ◽  
W Mayer
Keyword(s):  
Normal Distribution ◽  
Blood Group ◽  
Blood Groups ◽  
The Other ◽  
Other Hand ◽  
Group Distribution

SummaryA comparison between the repartition of the blood groups in 461 patients suffering from thromboembolic disorders and the normal distribution has shown a statistically ascertained predominance of the group A1. On the other hand the blood groups 0 and A2 are distinctly less frequent than in the normal distribution.

Bankruptcy Model Construction and its Limitation in Input Data Quality

2019 ◽  
Vol 10 (2) ◽  
pp. 117-125
Author(s):  
Dana Kubíčková ◽  
◽  
Vladimír Nulíček ◽  
Keyword(s):  
Data Quality ◽  
Normal Distribution ◽  
Input Data ◽  
Model Construction ◽  
The Third ◽  
Third Stage ◽  
Discriminant Analyses ◽  
One Year ◽  
The University ◽  
Multivariate Discriminant

The aim of the research project solved at the University of Finance and administration is to construct a new bankruptcy model. The intention is to use data of the firms that have to cease their activities due to bankruptcy. The most common method for bankruptcy model construction is multivariate discriminant analyses (MDA). It allows to derive the indicators most sensitive to the future companies’ failure as a parts of the bankruptcy model. One of the assumptions for using the MDA method and reassuring the reliable results is the normal distribution and independence of the input data. The results of verification of this assumption as the third stage of the project are presented in this article. We have revealed that this assumption is met only in a few selected indicators. Better results were achieved in the indicators in the set of prosperous companies and one year prior the failure. The selected indicators intended for the bankruptcy model construction thus cannot be considered as suitable for using the MDA method.

Analytical Representation of the Density Function of Normal Distribution of Noise

2015 ◽  
Vol 47 (8) ◽  
pp. 24-40 ◽  
Author(s):  
Telman Abbas ogly Aliev ◽  
Naila F. Musaeva ◽  
Matanat Tair kyzy Suleymanova ◽  
Bahruz Ismail ogly Gazizade
Keyword(s):  
Normal Distribution ◽  
Density Function ◽  
Analytical Representation
Sign in / Sign up

Export Citation Format

Share Document