Follicle cell bridges in the mosquito ovary: syncytia formation and bridge morphology

1978 ◽  
Vol 31 (1) ◽  
pp. 137-143
Author(s):  
A. Fiil
Keyword(s):  
Culex Pipiens ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Nurse Cells ◽  
Serial Sections ◽  
Intercellular Bridges ◽  
Syncytia Formation

In the mosquito, Culex pipiens quinqefasciatus, the follicle cells enveloping the oocyte and the nurse cells are connected by intercellular bridges. The bridges are formed by incomplete cytokinesis, and they persist for more than 30 h after their formation. Reconstructions from serial sections showed that one syncytial group contained at least 32 cells; several cells continued outside the series. The cells in a syncytium divide asynchronously; this results in an irregular, branched orgainzation. The bridges may be either embedded in the cytoplasm of the cells, or they may form an extracellular connexion.

scholarly journals INTERCELLULAR MIGRATION OF CENTRIOLES IN THE GERMARIUM OF DROSOPHILA MELANOGASTER

1970 ◽  
Vol 45 (2) ◽  
pp. 306-320 ◽  
Author(s):  
Anthony P. Mahowald ◽  
Joan M. Strassheim
Keyword(s):  
Follicle Cell ◽  
Cell Cluster ◽  
Follicle Cells ◽  
Oocyte Nucleus ◽  
Nurse Cells ◽  
Serial Sections ◽  
Cell Border ◽  
Ring Canals ◽  
Egg Chambers ◽  
Stage 1

A cluster of centrioles has been found in the early Drosophila oocyte. Since the oocyte is connected to 15 nurse cells by a system of intercellular bridges or ring canals, the possibility that the cluster of centrioles arose in the germarium from an intercellular migration of centrioles from the nurse cells to the oocyte was analyzed in serial sections for the electron microscope. Initially, all of the 16 cells of the future egg chambers possess centrioles, which are located in a juxtanuclear position. At the time the 16 cell cluster becomes arranged in a lens-shaped layer laterally across the germarium, the centrioles lose their juxtanuclear position and move towards the oocyte. By the time the 16 cell cluster of cells is surrounded by follicle cells (Stage 1), between 14 and 17 centrioles are found in the oocyte. Later, these centrioles become located between the oocyte nucleus and the follicle cell border and become aggregated into a cluster less than 1.5 µ in its largest dimension. The fate of these centrioles in the oocyte is not known. The fine structure of the germarium and the early oocyte is also described.

A targeted gene silencing technique shows that Drosophila myosin VI is required for egg chamber and imaginal disc morphogenesis

1999 ◽  
Vol 112 (21) ◽  
pp. 3677-3690 ◽  
Author(s):  
W. Deng ◽  
K. Leaper ◽  
M. Bownes
Keyword(s):  
Gene Silencing ◽  
Imaginal Disc ◽  
Developmental Stages ◽  
Expression System ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Myosin Vi ◽  
Nurse Cells ◽  
Cell Shapes ◽  
Egg Chamber

We report that Drosophila unconventional myosin VI, encoded by Myosin heavy chain at 95F (Mhc95F), is required for both imaginal disc and egg chamber morphogenesis. During oogenesis, Mhc95F is expressed in migrating follicle cells, including the border cells, which migrate between the nurse cells to lie at the anterior of the oocyte; the columnar cells that migrate over the oocyte; the centripetal cells that migrate between the oocyte and nurse cells; and the dorsal-anterior follicle cells, which migrate to secrete the chorionic appendages. Its function during development has been studied using a targeted gene silencing technique, combining the Gal4-UAS targeted expression system and the antisense RNA technique. Antibody staining shows that the expression of myosin 95F is greatly decreased in follicle cells when antisense Mhc95F RNA is expressed. Interfering with expression of Drosophila myosin VI at various developmental stages frequently results in lethality. During metamorphosis it results in adult flies with malformed legs and wings, indicating that myosin VI is essential for imaginal disc morphogenesis. During oogenesis, abnormal follicle cell shapes and aberrant follicle cell migrations are observed when antisense Mhc95F is expressed in follicle cells during stages 9 to 10, suggesting that the Drosophila myosin VI is required for follicle cell epithelial morphogenesis.

Occurrence of intercellular bridges between follicle epithelial cells in the ovary of Apis mellifica queens

1977 ◽  
Vol 24 (1) ◽  
pp. 195-202
Author(s):  
P.S. Ramamurty ◽  
W. Engels
Keyword(s):  
Epithelial Cells ◽  
Developmental Stages ◽  
Light And Electron Microscopy ◽  
Follicle Cell ◽  
Dense Material ◽  
Follicle Cells ◽  
Electron Dense Material ◽  
Intercellular Bridges ◽  
Additional Layer ◽  
Apis Mellifica

Hitherto unknown intercellular bridges or fusomes between the follicle epithelial cells investing the oocytes of Apis mellifica queens have been observed both with light and electron microscopy. Usually each follicle cell has 2–3 intercellular bridges. In surfacial paraffin sections, the intercellular bridges can be seen to connect a series of follicle cells which may be branching. The intercellular bridges lie close to the egg cortex and this position is relatively constant. The width of the fusomal ring canal varies in different developmental stages. In stages 3 and 4 of oogenesis, which are the main vitellogenic stages, the intercellular bridges measure 0-5 micron, while in stages 1 and 2 they have a diameter ranging from 1–5 to 3–5 micron. In these stages the intercellular bridges are provided with numerous transverse microfilaments which disappear later. The fusomal lips are thickened and consist of electron-dense material and an additional layer of less electron-dense material both inside and outside. Ribosomes flow across the bridge. The intercellular bridges may serve to synchronize the differentiation and functional activity of the follicle epithelium during the course of oogenesis.

Memoirs: Certain Phenomena of Tenthredinid Oogenesis as Revealed Mainly by Feulgen's Nuclear-Reaction

1930 ◽  
Vol s2-73 (292) ◽  
pp. 617-630
Author(s):  
R.A. R. GRESSON
Keyword(s):  
Nurse Cell ◽  
Chemical Change ◽  
Follicle Cell ◽  
Nuclear Material ◽  
Methyl Blue ◽  
Follicle Cells ◽  
Nuclear Chromatin ◽  
Nurse Cells ◽  
Cell Nuclei ◽  
Nucleolar Material

1. By the use of Feulgen's ‘nuclealreaktion’ certain points of Tenthredinid oogenesis have been subjected to closer study. The chromatin of the early nurse-cells of Allantus pallipes exists in the form of granules, the majority of which occur close to the nuclear membrane. In the older cells a nuclear network appears in which is distributed granules of chromatin. In Thrinax mixta, where the ovarioles were more highly developed, the chromatin of the nurse-cells occurs as granules scattered through the nucleus; a nuclear network is not present, but certain granules appear to be connected by a thread. The granules which were shown to surround the nurse-cell nuclei (in material treated by Bensley's method and also by fixation in Bouin's picro-formol and subsequently stained in iron haematoxylin) and which were formerly regarded as chromatin emissions from the nurse-cell nuclei (9) were not revealed by Feulgen's technique. They therefore cannot be regarded as chromatin. Their precise nature and origin remains undetermined. 2. The nucleoli of the early nurse-cells of both species, as revealed by Mann's methyl-blue eosin, are faintly basophil. Later they break up into a number of basophil bodies which undergo fragmentation; formerly (technique and reference as in 1) the basophil nucleolus and the basophil bodies originating from it were termed ‘nuclear material’ undergoing fragmentation. While this basophil nucleolar material presents a fragmented appearance, it increases in amount as evidenced by the large number of basophil bodies present in the older nurse-cell nuclei. This material is utilized for the nourishment of the egg after the latter engulfs the nurse-cell nuclei. Nucleolar extrusions to the cytoplasm do not occur. 3. The behaviour of the chromatin of the follicle-cell nuclei is similar to that of the nurse-cell nuclei except that in Allantus pallipes the nuclear chromatin network as demonstrated by Feulgen's technique disappears in the older cells. 4. The nucleoli of the follicle-cells are basophil. They become broken up in the older cells, but in most cases the resulting masses remain in contact. Nucleolar extrusions to the cytoplasm do not occur. 5. The occurrence of deeply basophil material in the cytoplasm of the follicle-cells of Thrinax mixta stained with Mann's methyl-blue eosin, formerly described for Bouin fixed material stained in iron haematoxylin (9), suggests that some substance in solution may be passed into the ooplasm; extrusion of granules from the follicle-cells to the ooplasm does not take place. 6. The absence or non-visibility of chromatin (Feulgen's technique) from the oocytes of Thrinax mixta, and its disappearance from the older oocytes of Allantus pallipes , would indicate that the chromatin undergoes a chemical change during oogenesis such as suggested by Koch for Chilopods. 7. The oxyphil and basophil nucleoli of the oocytes do not react to Feulgen's technique for chromatin; this agrees with Ludford's findings for the mouse and for Limnaeastagnalis.

Memoirs: The Rôles of the Nurse-cells, Oocytes and Follicle-cells in Tenthredinid Oogenesis

1928 ◽  
Vol s2-71 (284) ◽  
pp. 541-561
Author(s):  
A. D. PEACOCK ◽  
R.A. R. GRESSON
Keyword(s):  
Nuclear Membrane ◽  
Nurse Cell ◽  
Follicle Cell ◽  
Narrow Channel ◽  
Nuclear Material ◽  
Follicle Cells ◽  
Nurse Cells ◽  
Accessory Nuclei ◽  
Dark Staining ◽  
The Common

1. Ovary formation in Tenthredinidae follows the general hymenopterous plan. 2. Nurse-cell phenomena are as follows: the nuclei of the first nutritive chamber are surrounded by a chromatin cloud and many of them contain irregular darkly-staining masses of nuclear material, which masses may also be present in the riper chambers; the granules given off from the nuclei into the chromatin cloud eventually become surrounded by a vesicle and give rise to the ‘secondary’ or ‘accessory’ nuclei. 3. Oocyte nucleolar phenomena show the following: the nucleoli in Thrinax mixta and Platycampus luridiventris give rise to buds which become free; in one case buds were observed close to the inner surface of the nuclear membrane in Allantus (Emphytus) pallipes are shown what are apparently later stages of this process, viz. the passage of the buds through the nuclear membrane into the egg substance and their formation there into accessory nuclei. 4. The fate of the nurse-cells is shown in the older nutritive chambers and oocytes--the cell boundaries become indistinct and some of the cytoplasm, together with contained accessory nuclei, passes by a narrow channel into the oocyte. The cytoplasmic flow becomes more marked in the last chamber. In the final stages, shown in the last chamber, all the cells lose their boundaries and the common cytoplasm passes into the oocyte, carrying with it the free nuclei to their engulfment and absorption in the ooplasm. 5. Some of the follicle-cells surrounding the last oocyte in Pristiphora padi, and the fifth, sixth, and seventh of Thrinax mixta, contain granular dark-staining material which may completely fill the cell, these granules probably originating from the nucleus. They pass out of the follicle-cell into the egg where they become surrounded by vesicles, and, finally, present an appearance indistinguishable from that of accessory nuclei. 6. Secondary or accessory nuclei, therefore, have a threefold origin, namely, from the nuclei, of nurse-cells and oocytes and from follicle-cells, their source of derivation in the last being the follicular nuclei. 7. The follicle-cells of the distal pole of the last oocyte of one ovariole of Pristiphora padi have processes which insinuate themselves into the ooplasm. 8. The phenomena of oogenesis described in these four species of sawflies, while embracing certain which have not hitherto been recorded, conform, in essentials, with those already discovered for Hymenoptera generally.

Juvenile hormone increases ouabain-binding capacity of microsomal preparations from vitellogenic follicle cells

1983 ◽  
Vol 61 (7) ◽  
pp. 826-831 ◽  
Author(s):  
T. T. Ilenchuk ◽  
K. G. Davey
Keyword(s):  
Juvenile Hormone ◽  
Binding Capacity ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Follicular Epithelium ◽  
Curvilinear Relationship ◽  
Scatchard Analysis ◽  
Ouabain Binding ◽  
Binding Characteristics ◽  
Brain Microsomes

A comparison has been made of the effects of juvenile hormone (JH) on the binding characteristics for ouabain of microsomes prepared from brain and from cells of the follicular epithelium surrounding previtellogenic or vitellogenic oocytes in Rhodnius. JH has no effect on the binding of ouabain to brain microsomes and decreases the Kd, but does not alter the Bmax for previtellogenic follicle cells. For vitellogenic follicle cells, Scatchard analysis reveals a curvilinear relationship, which is interpreted as indicating that a new population of JH-sensitive ouabain-binding sites develops as the follicle cell enters vitellogenesis. These results are related to earlier data obtained on the effect of JH on ATPase activity, volume changes in isolated follicle cells, and the development of spaces between the cells of the follicular epithelium.

maelstrom is required for an early step in the establishment of Drosophila oocyte polarity: posterior localization of grk mRNA

Development ◽  
1997 ◽  
Vol 124 (22) ◽  
pp. 4661-4671 ◽  
Author(s):  
N.J. Clegg ◽  
D.M. Frost ◽  
M.K. Larkin ◽  
L. Subrahmanyan ◽  
Z. Bryant ◽  
...  
Keyword(s):  
Nurse Cell ◽  
Egf Receptor ◽  
Mrna Localization ◽  
Follicle Cells ◽  
Rna Transport ◽  
Nurse Cells ◽  
Loss Of Function ◽  
Cell Fates ◽  
Early Step ◽  
Novel Protein

We describe a mutant, maelstrom, that disrupts a previously unobserved step in mRNA localization within the early oocyte, distinct from nurse-cell-to-oocyte RNA transport. Mutations in maelstrom disturb the localization of mRNAs for Gurken (a ligand for the Drosophila Egf receptor), Oskar and Bicoid at the posterior of the developing (stage 3–6) oocyte. maelstrom mutants display phenotypes detected in gurken loss-of-function mutants: posterior follicle cells with anterior cell fates, bicoid mRNA localization at both poles of the stage 8 oocyte and ventralization of the eggshell. These data are consistent with the suggestion that early posterior localization of gurken mRNA is essential for activation of the Egf receptor pathway in posterior follicle cells. Posterior localization of mRNA in stage 3–6 oocytes could therefore be one of the earliest known steps in the establishment of oocyte polarity. The maelstrom gene encodes a novel protein that has a punctate distribution in the cytoplasm of the nurse cells and the oocyte until the protein disappears in stage 7 of oogenesis.

Studies on the Ovarian Follicle Cells of Drosophila

1963 ◽  
Vol s3-104 (67) ◽  
pp. 297-320
Author(s):  
R. C. KING ◽  
ELIZABETH A. KOCH
Keyword(s):  
Ovarian Follicle ◽  
Protein A ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Vitelline Membrane ◽  
Membrane Material ◽  
Adjacent Layer ◽  
Membrane Formation ◽  
Precursor Material ◽  
Egg Shell

Studies are described of the ultrastructure of the follicle cells which invest the oocyte of Drosophila melanogaster at the time of vitelline membrane formation. Of particular interest are organelles made up of endoplasmic reticulum organized into a husk of concentric lamellae which surround lipidal droplets. These epithelial bodies are seen only at the time the vitelline membrane is being formed, and it is assumed therefore that the lipidal material of the epithelial body may be utilized somehow in the fabrication of the vitelline membrane. Cytochemical studies have shown this membrane to contain at least 5 classes of compounds; a protein, two lipids (which may be distinguished by differences in their resistance to extraction by various solvents), and 2 polysaccharides (1 neutral and 1 acidic). Studies were made of vitelline membrane formation in the ovaries of flies homozygous for either of 2 recessive, female-sterile genes (tiny and female sterile). In the case of the ty mutation vitelline membrane material is sometimes secreted between follicle and nurse cells, while in the mutant fes vitelline membrane is observed in rare instances to be secreted between follicle cells and an adjacent layer of tumour cells. In the latter case the vitelline membrane shows altered cytochemical properties. The fact that vitelline membrane can be secreted by follicle cells not adjacent to an oocyte demonstrates that it is the follicle cell rather than the oocyte that plays the major role in the secretion of the precursor material of the vitelline membrane. Subsequently the follicle cells secrete the egg-shell, or chorion, which is subdivided into a dense, compartmented, inner endochorion, and a pale, outer exochorion. A description is given of the ultrastructure of the follicle cells during the secretion of the endochorion and the exochorion. The endochorion contains a protein, a polysaccharide, and a lipid, all of which may be distinguished cytochemically from the vitelline membrane compounds. The exochorion contains large amounts of acidic mucopolysaccharides. Specialized follicle cells form the micropylar apparatus and the chorionic appendages. The formation of the chorion and chorionic appendages is discussed in the light of information gained from abnormalities of the chorions and chorionic appendages seen in ty and fs 2.1 oocytes. Subsequent to the time the egg leaves the ovariole a layer of waterproofing wax is secreted between the vitelline membrane and the chorion.

Intercellular bridges between follicle cells and oocyte during the differentiation of follicular epithelium in Lacerta sicula Raf

1978 ◽  
Vol 33 (1) ◽  
pp. 341-350
Author(s):  
P. Andreuccetti ◽  
C. Taddei ◽  
S. Filosa
Keyword(s):  
Follicle Cells ◽  
Follicular Epithelium ◽  
Intercellular Bridges ◽  
Cytoplasmic Material ◽  
Function Transfer ◽  
Pyriform Cells

Intercellular bridges first appear during lizard oogenesis when follicles are rather small (150 microgram in diameter); at this stage they form connecting links between the oocyte and follicle cells, which have not yet differentiated into pyriform cells. Later on, when the follicles have become larger (1 mm) and the follicular epithelium appears constituted by 3 types of cells (small, intermediate and pyriform cells) they form connecting links between the oocyte and both intermediate and pyriform cells. The establishment of intercellular bridges between pyriform cells and the oocyte precedes the complete differentiation of the former, which excludes the possibility that the fusion between pyriform cells and oocyte occurs only after these cells are completely differentiated. In still larger follicles (up to 2 mm in diameter), during the degeneration of the pyriform cells, the occurrence, inside the bridges, of mitochondria and other cytoplasmic material suggests that these cells at the end of their function transfer their contents into the oocyte.

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