scholarly journals Ultrastructural aspects of the intercellular bridges between female bee germ cells

2006 ◽  
Vol 66 (1b) ◽  
pp. 309-315 ◽  
Author(s):  
K. Patrício ◽  
C. Cruz-Landim
Keyword(s):  
Endoplasmic Reticulum ◽  
Dynamic Behavior ◽  
Germ Cells ◽  
Nurse Cells ◽  
Intercellular Bridges ◽  
Thick Filaments ◽  
Plasmic Membrane ◽  
Germline Cells ◽  
Cytoskeletal Elements

The germline cells in the ovary of the female bee are interconnected by intercellular bridges kept open by cytoskeletal reinforcements in the plasmic membrane. These bridges among the germline cells display a dynamic behavior and probably act in the determination of the oocyte among the cells of the clone formed by the premeiotic mitoses, subsequently forming a pathway that enables the products synthesized by the nurse cells to reach the oocyte during its maturation. The cytoskeletal elements in the intercellular bridges of bee gonads are basically microfilaments and microtubules, but another type of filament (thick, of non-defined nature, associated with elements of the endoplasmic reticulum) is present in the bridges between the premeiotic cystocytes. This filament crosses the bridge, using microfilaments to fasten itself to the plasmic membrane. These filaments appear to control the span of the bridge. Upon completion of the proliferation phase the cystocytes take on a rosette shape, and a fusome formed by the convergence of the bridges appears at their center. The thick filaments are not present in this conformation. The differentiation of the oocyte and the nurse cells leads to a new change, in which the bridges are reoriented to convey the content of the future nurse cells to the oocyte.

scholarly journals Memoirs: The Cyplasmic Inclusions of the Germ-Cells

1917 ◽  
Vol s2-62 (248) ◽  
pp. 555-611
Author(s):  
J. BRONTÉ GATENBY
Keyword(s):  
Cell Volume ◽  
Germ Cells ◽  
Helix Aspersa ◽  
The Other ◽  
Nurse Cells ◽  
Axial Filament ◽  
Probable Function ◽  
Early Spermatid ◽  
The Individual

(1) The ovotestis of Helix aspersa is formed of fingerlike diverticula. The latter are hollow at their lower ends, which connect to the hermaphrodite duct, while the upper ends contain more yolk, and are filled completely with metamorphosing male cells. (2) According to the manner of derivation--that is, the nutrimental conditions of the locality from which new cells arise, and the number (if any) of times which these new cells divide--there are quite wide differences in the individual generations derived from and under such varying conditions. (3) These differences are found in nucleus, mitochondria, Nebenkern, and general cell volume. (4) The mitochondria vary in size and number, and such variation seems to be caused by the varying number of spermatogonial divisions in different regions of the ovotestis. (5) In the early spermatid smaller mitochondria, the micromitochondria appear in an unknown way near the region from which the axial filament takes its origin from the centro some applied to the nucleus. These micromitochondria are about one-fourth the size of the other, or macromitochondria. No perceptible variation in size of the micromitochondria of various generations has been found. (6) The micromitochondria form the front sheath of the sperm; the hind region of the micromitochondrial sheath intercommunicates with the macromitochondrial sheath, which follows behind. (7) The Nebenkern does not apparently become absorbed into the substance of the mitochondrial sheath. A sloughing off appears to take place. (8) The minute cytology of the derivation of the sperms, eggs, and nurse-cells is described. (9) The determination of the sex of the indifferent cell seems to be brought about by a variety of causes. The explanation of femaleness by presence of yolk cells is held to be inadequate, for male progerminative cells also appear in regions choked with yolk. (10) The probable function of the Nebenkern is discussed.

Comparative Morphology of Intercellular Bridges Between Developing Germ Cells of the Ovary

1970 ◽  
Vol 28 ◽  
pp. 328-329
Author(s):  
J. R. Ruby ◽  
R. F. Dyer ◽  
R. G. Skalko ◽  
R. F. Gasser ◽  
E. P. Volpe
Keyword(s):  
Germ Cells ◽  
Rana Pipiens ◽  
Comparative Morphology ◽  
Dense Material ◽  
Individual Species ◽  
Microscope Examination ◽  
Electron Dense Material ◽  
Intercellular Bridges ◽  
Cytoplasmic Side ◽  
Intercellular Connections

An electron microscope examination of fetal ovaries has revealed that developing germ cells are connected by intercellular bridges. In this investigation several species have been studied including human, mouse, chicken, and tadpole (Rana pipiens). These studies demonstrate that intercellular connections are similar in morphology regardless of the species.Basically, all bridges are characterized by a band of electron-dense material on the cytoplasmic side of the tri-laminar membrane surrounding the connection (Fig.l). This membrane is continuous with the plasma membrane of the conjoined cells. The dense material, however, never extends beyond the limits of the bridge. Variations in the configuration of intercellular connections were noted in all ovaries studied. However, the bridges in each individual species usually exhibits one structural characteristic seldom found in the others. For example, bridges in the human ovary very often have large blebs projecting from the lateral borders whereas the sides of the connections in the mouse gonad merely demonstrate a slight convexity.

scholarly journals Thermal Dynamic Behavior in Bi-Zone Habitable Cell with and without Phase Change Materials

Proceedings ◽  
2020 ◽  
Vol 63 (1) ◽  
pp. 41
Author(s):  
Hanae El Fakiri ◽  
Lahoucine Ouhsaine ◽  
Abdelmajid El Bouardi
Keyword(s):  
Thermal Behavior ◽  
Thermal Comfort ◽  
Phase Change ◽  
Dynamic Behavior ◽  
Phase Change Materials ◽  
Energy Performance ◽  
High Energy ◽  
Water Heater ◽  
Simplified Modeling

The thermal dynamic behavior of buildings represents an important aspect of the energy efficiency and thermal comfort of the indoor environment. For this, phase change material (PCM) wallboards integrated into building envelopes play an important role in stabilizing the temperature of the human comfort condition. This article provides an assessment of the thermal behavior of a “bi-zone” building cell, which was built based on high-energy performance (HEP) standards and heated by a solar water heater system through a hydronic circuit. The current study is based on studying the dynamic thermal behavior, with and without implantation of PCMs on envelope structure, using a simplified modeling approach. The evolution of the average air temperature was first evaluated as a major indicator of thermal comfort. Then, an evaluation of the thermal behavior’s dynamic profile was carried out in this study, which allowed for the determination of the PCM rate anticipation in the thermal comfort of the building cell.

Studies on Determination of Natural Frequencies of Industrial Turbine Blades

1995 ◽  
Author(s):  
Mahesh M. Bhat ◽  
V. Ramamurti ◽  
C. Sujatha
Keyword(s):  
Steam Turbine ◽  
Dynamic Behavior ◽  
Turbine Blade ◽  
Natural Frequencies ◽  
Complex Structure ◽  
Turbine Blades ◽  
Blade Root ◽  
Steam Turbine Blade ◽  
Manufacturing Tolerances

Abstract Steam turbine blade is a very complex structure. It has geometric complexities like variation of twist, taper, width and thickness along its length. Most of the time these variations are not uniform. Apart from these geometric complexities, the blades are coupled by means of lacing wire, lacing rod or shroud. Blades are attached to a flexible disc which contributes to the dynamic behavior of the blade. Root fixity also plays an important role in this behavior. There is a considerable variation in the frequencies of blades of newly assembled turbine and frequencies after some hours of running. Again because of manufacturing tolerances there can be some variation in the blade to blade frequencies. Determination of natural frequencies of the blade is therefore a very critical job. Problems associated with typical industrial turbine bladed discs of a 235 MW steam turbine are highlighted in this paper.

Determination of the Effect of Sloshing on the Railcar-Track Dynamic Behavior

2021 ◽  
pp. 131-140
Author(s):  
Juan Carlos Jauregui-Correa ◽  
Frank Otremba ◽  
Jose A. Romero-Navarrete ◽  
Gerardo Hurtado-Hurtado
Keyword(s):  
Dynamic Behavior

Dynamic behavior of endoplasmic reticulum in living cells

Cell ◽  
1988 ◽  
Vol 54 (1) ◽  
pp. 37-46 ◽  
Author(s):  
Christopher Lee ◽  
Lan Bo Chen
Keyword(s):  
Endoplasmic Reticulum ◽  
Dynamic Behavior ◽  
Living Cells

Studies on the site of addition of sialic acid and glucosamine to rat α1-acid glycoprotein

1977 ◽  
Vol 55 (4) ◽  
pp. 408-414 ◽  
Author(s):  
J. C. Jamieson
Keyword(s):  
Endoplasmic Reticulum ◽  
Sialic Acid ◽  
Rat Liver ◽  
Golgi Complex ◽  
Smooth Endoplasmic Reticulum ◽  
Main Site ◽  
Acid Glycoprotein ◽  
Membrane Bound ◽  
Polypeptide Chains

Ultrasonic extracts of rough and smooth endoplasmic reticulum fractions and Golgi fractions from rat liver were examined by immunoelectrophoresis using antiserum to α1-acid glycoprotein. Rough endoplasmic reticulum fractions contained only sialic acid free α1-acid glycoprotein, whereas smooth endoplasmic reticulum and Golgi fractions also contained sialic acid containing α1-acid glycoprotein. Determination of the sialic acid contents of immune precipitates isolated from the extracts suggested that the Golgi complex was the main site of addition of sialic acid to α1-acid glycoprotein. Immunological studies on puromycin extracts of polyribosomes showed that polypeptide chains of α1-acid glycoprotein and albumin were assembled mainly on membrane-bound polyribosomes. Evidence is presented from incorporation studies with labelled leucine and glucosamine that initial glycosylation of α1-acid glycoprotein occurs mainly or entirely after release of nascent polypeptide from the ribosomal site.

scholarly journals Ooplasmic flow cooperates with transport and anchorage in Drosophila oocyte posterior determination

2018 ◽  
Vol 217 (10) ◽  
pp. 3497-3511 ◽  
Author(s):  
Wen Lu ◽  
Margot Lakonishok ◽  
Anna S. Serpinskaya ◽  
David Kirchenbüechler ◽  
Shuo-Chien Ling ◽  
...  
Keyword(s):  
Germ Cells ◽  
Cytoplasmic Streaming ◽  
Rna Binding ◽  
Early Stage ◽  
Rna Binding Protein ◽  
Myosin V ◽  
Actin Cortex ◽  
Microtubule Motor ◽  
Actin Motor

The posterior determination of the Drosophila melanogaster embryo is defined by the posterior localization of oskar (osk) mRNA in the oocyte. Defects of its localization result in a lack of germ cells and failure of abdomen specification. A microtubule motor kinesin-1 is essential for osk mRNA posterior localization. Because kinesin-1 is required for two essential functions in the oocyte—transport along microtubules and cytoplasmic streaming—it is unclear how individual kinesin-1 activities contribute to the posterior determination. We examined Staufen, an RNA-binding protein that is colocalized with osk mRNA, as a proxy of posterior determination, and we used mutants that either inhibit kinesin-driven transport along microtubules or cytoplasmic streaming. We demonstrated that late-stage streaming is partially redundant with early-stage transport along microtubules for Staufen posterior localization. Additionally, an actin motor, myosin V, is required for the Staufen anchoring to the actin cortex. We propose a model whereby initial kinesin-driven transport, subsequent kinesin-driven streaming, and myosin V–based cortical retention cooperate in posterior determination.

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