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.

The relation of the two blastomeres to the polar lobe in Dentalium

Development ◽  
1968 ◽  
Vol 20 (1) ◽  
pp. 101-105
Author(s):  
N. H. Verdonk
Keyword(s):  
Normal Development ◽  
Bilateral Symmetry ◽  
Polar Lobe ◽  
Posterior Side ◽  
First Case

Experiments on the influence of the polar lobe on the development of molluscs have shown that after removal of the polar lobe cleavage is radially symmetrical and indications of bilateral symmetry do not appear (Wilson, 1904: Dentalium; Clement, 1952: Ilyanassa). In normal development the polar lobe fuses with one of the two cells of the trefoil stage, and this cell becomes the posterior side of the embryo. The question now arises whether the polar lobe fuses in an arbitrary way with one of the blastomeres at first cleavage, which then becomes the CD cell. Another possibility is that one of the two blastomeres at the trefoil stage is already predetermined to become the CD cell, with which the polar lobe always fuses. In the first case dorsoventrality is determined epigenetically; in the second case it is preformed. Morgan (1936) tried to solve this question by removing one of the blastomeres at the trefoil stage in Ilyanassa.

The structure of a morphogenetic cytoplasm, present in the polar lobe of Bithynia tentaculata (Gastropoda, Prosobranchia)

Development ◽  
1974 ◽  
Vol 31 (2) ◽  
pp. 423-433
Author(s):  
M. R. Dohmen ◽  
N. H. Verdonk
Keyword(s):  
Methyl Green ◽  
Polar Lobe ◽  
Developmental Effects ◽  
Bithynia Tentaculata ◽  
Further Development

In the first polar lobe of the egg of Bithynia tentaculata a cup-shaped mass of small vesicles is described, which fills the greater part of the lobe. It is named the ‘vegetal body’. With methyl green–pyronin the vegetal body stains clearly, but after treatment with RNase no staining occurs, thus indicating the presence of RNA. The first polar lobe of Bithynia is of great importance for further development of the embryo and it is argued that the vegetal body could be a morphogenetic cytoplasm, responsible for the developmental effects of the polar lobe.

Ultrastructure of the Omphalomesenteric Duct Rest in the Umbilical Cord at Term

1982 ◽  
Vol 40 ◽  
pp. 250-251
Author(s):  
B. A. Clark ◽  
T. Okagaki
Keyword(s):  
Umbilical Cord ◽  
Umbilical Vein ◽  
Meckel’S Diverticulum ◽  
Meckel's Diverticulum ◽  
Columnar Epithelium ◽  
Omphalomesenteric Duct ◽  
Umbilical Arteries

Vestiges of the omphalomesenteric or vitello-intestinal duct and the pathologic implications attributed to these remnants have been treated in great detail by several investigators. Persistence of the omphalomesenteric duct is associated with such conditions as Meckel's diverticulum, umbilical fistula, mucosal polyps, and sinuses or cysts of the umbilicus. Remnants of the duct in the umbilical cord, although infrequent, are located outside of the triangle formed by the two umbilical arteries and the umbilical vein, are usually discontinuous and are often represented by a small lumen lined by cuboidal or columnar epithelium. This study will examine the ultrastructure of these cells.

Fine structure of the retina of the giant scallop, Placopecten magellanicus

1984 ◽  
Vol 42 ◽  
pp. 312-313
Author(s):  
C.V.L. Powell
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Light Intensity ◽  
Scanning Electron Microscope ◽  
Eye Development ◽  
Preliminary Observation ◽  
Columnar Epithelium ◽  
Placopecten Magellanicus ◽  
Environmental Light ◽  
Scanning Electron

The overall fine structure of the eye in Placopecten is similar to that of other scallops. The optic tentacle consists of an outer columnar epithelium which is modified into a pigmented iris and a cornea (Fig. 1). This capsule encloses the cellular lens, retina, reflecting argentea and the pigmented tapetum. The retina is divided into two parts (Fig. 2). The distal retina functions in the detection of movement and the proximal retina monitors environmental light intensity. The purpose of the present study is to describe the ultrastructure of the retina as a preliminary observation on eye development. This is also the first known presentation of scanning electron microscope studies of the eye of the scallop.

scholarly journals A Case Report of Primordial Odontogenic Tumor That Required Distinction from a Dentigerous Cyst

Reports ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 4
Author(s):  
Sawako Ono ◽  
Hotaka Kawai ◽  
Shintaro Sukegawa ◽  
Kiyofumi Takabatake ◽  
Keisuke Nakano ◽  
...  
Keyword(s):  
Root Resorption ◽  
Dentigerous Cyst ◽  
Fibrous Tissue ◽  
Clinical Findings ◽  
Odontogenic Tumor ◽  
Columnar Epithelium ◽  
Solid Mass ◽  
Histological Differentiation ◽  
Second Molar ◽  
Primordial Odontogenic Tumor

Primordial odontogenic tumor (POT) is a rare odontogenic tumor characterized by a variably cellular loose fibrous tissue with areas similar to the dental papilla and covered by cuboidal to columnar epithelium. We herein report a case of POT in a 14-year-old boy. Computed tomography (CT) exhibited a round cavity with a defined cortical border circumscribing the tooth of the second molar. However, the gross finding was a solid mass, not a cyst. Histologically, the tumor consisted of dental papillalike myxoid connective tissue covered by columnar epithelium. Therefore, although the clinical diagnosis was dentigerous cyst (DC), we diagnosed POT based on histologic findings. Clinical findings of POT resemble DC, but the clinical behavior of POT is different to DC, such as cortical expansion and root resorption of teeth. Therefore, histological differentiation of POT from DC is critical for accurate diagnosis.

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