Effect of salinity on the osmoregulatory cells in the tracheal gills of the stonefly nymph, Paragnetina media (Plecoptera: Perlidae)

1978 ◽  
Vol 56 (12) ◽  
pp. 2608-2613 ◽  
Author(s):  
N. N. Kapoor
Keyword(s):  
Plasma Membrane ◽  
Structural Changes ◽  
Apparent Loss ◽  
Paragnetina Media ◽  
Tracheal Gills

The ultrastructure of the osmoregulatory cells in the integument of the stonefly nymph, Paragnetina media, shows changes in media hypotonic, isotonic, and hypertonic to the hemolymph. Exposure to hypotonic concentration results in an increase in the plasma membrane folds, mitochondria, and microtubules in the cytoplasm. In isotonic and hypertonic concentrations, the cells show cellular disorganization and apparent loss in their function. These results suggest that the structural changes in the osmoregulatory cells are related to the osmotic condition of the medium, and these cells probably act as extrarenal sites for the absorption of ions from the hypoosmotic medium.

A study of specialized cells of the tracheal gills of Paragnetina media (Plecoptera)

1973 ◽  
Vol 51 (9) ◽  
pp. 983-986 ◽  
Author(s):  
N. N. Kapoor ◽  
K. Zachariah
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Microscopic Examination ◽  
External Environment ◽  
Electron Microscopic Examination ◽  
Active Surface ◽  
Electron Microscopic ◽  
Close Relationship ◽  
Paragnetina Media ◽  
Tracheal Gills

Light and electron microscopic examination of the gills of the plecopteran nymph Paragnetina media revealed a highly tracheated epithelium with many specialized cells. These cells show several features characteristic of the osmoregulatory tissue of other animals. In the cell, numerous mitochondria are lodged in elongated folds of the plasma membrane in such a way that they are brought into a very close relationship to an area of the cell surface. It is assumed that this arrangement provides metabolically active surface for the exchange of materials, absorption, or excretion. It is most likely that the gills can absorb salt from the water, and thus compensate for the loss of salt through the urine. The distinctive cuticular plaque which forms the interface of each cell with the external environment is featured and discussed too.

scholarly journals Proprotein Convertase 5/6 Is Critical for Embryo Implantation in Women: Regulating Receptivity by Cleaving EBP50, Modulating Ezrin Binding, and Membrane-Cytoskeletal Interactions

Endocrinology ◽  
2011 ◽  
Vol 152 (12) ◽  
pp. 5041-5052 ◽  
Author(s):  
Sophea Heng ◽  
Ana Cervero ◽  
Carlos Simon ◽  
Andrew N. Stephens ◽  
Ying Li ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cellular Localization ◽  
Structural Changes ◽  
Current Knowledge ◽  
Embryo Implantation ◽  
Critical Role ◽  
Human Endometrium ◽  
Scaffolding Protein ◽  
Proprotein Convertase ◽  
Proteomic Approach

Establishment of endometrial receptivity is vital for successful embryo implantation; its failure causes infertility. Epithelial receptivity acquisition involves dramatic structural changes in the plasma membrane and cytoskeleton. Proprotein convertase 5/6 (PC6), a serine protease of the proprotein convertase (PC) family, is up-regulated in the human endometrium specifically at the time of epithelial receptivity and stromal cell decidualization. PC6 is the only PC member tightly regulated in this manner. The current study addressed the importance and mechanisms of PC6 action in regulating receptivity in women. PC6 was dysregulated in the endometrial epithelium during the window of implantation in infertile women of three demographically different cohorts. Its critical role in receptivity was evidenced by a significant reduction in mouse blastocyst attachment of endometrial epithelial cells after PC6 knockdown by small interfering RNA. Using a proteomic approach, we discovered that PC6 cleaved the key scaffolding protein, ezrin-radixin-moesin binding phosphoprotein 50 (EBP50), thereby profoundly affecting its interaction with binding protein ezrin (a key protein bridging actin filaments and plasma membrane), EBP50/ezrin cellular localization, and cytoskeleton-membrane connections. We further validated this novel PC6 regulation of receptivity in human endometrium in vivo in fertile vs. infertile patients. These results strongly indicate that PC6 plays a key role in regulating fundamental cellular remodeling processes, such as plasma membrane transformation and membrane-cytoskeletal interface reorganization. PC6 cleavage of a crucial scaffolding protein EBP50, thereby profoundly regulating membrane-cytoskeletal reorganization, greatly extends the current knowledge of PC biology and provides substantial new mechanistic insight into the fields of reproduction, basic cellular biology, and PC biochemistry.

p-Nitrophenylphosphatase Activity Catalyzed by Plasma Membrane (Ca2++Mg2+)ATPase: Correlation with Structural Changes Modulated by Glycerol and Ca2+

2001 ◽  
Vol 21 (1) ◽  
pp. 25-32 ◽  
Author(s):  
Gutemberg G. Alves ◽  
Luis Maurício T. R. Lima ◽  
Maely P. Fávero-Retto ◽  
Adriana P. Lemos ◽  
Carlos E. Peres-Sampaio ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Synergistic Effect ◽  
Phosphatase Activity ◽  
Structural Changes ◽  
Center Of Mass ◽  
Binding Domain ◽  
Dependent Manner ◽  
Dose Dependent ◽  
Substrate Binding Domain

The plasma membrane (Ca2++Mg2+)ATPase hydrolyzes pseudo-substrates such as p-nitrophenylphosphate. Except when calmodulin is present, Ca2+ ions inhibit the p-nitrophenylphosphatase activity. In this report it is shown that, in the presence of glycerol, Ca2+ strongly stimulates phosphatase activity in a dose-dependent manner. The glycerol- and Ca2+-induced increase in activity is correlated with modifications in the spectral center of mass (average emission wavenumber) of the intrinsic fluorescence of the enzyme. It is concluded that the synergistic effect of glycerol and Ca2+ is related to opposite long-term hydration effects on the substrate binding domain and the Ca2+ binding domain.

scholarly journals FINE STRUCTURE OF THE SPERMATOZOON OF HYDROIDES HEXAGONUS (ANNELIDA), WITH SPECIAL REFERENCE TO THE ACROSOMAL REGION

1961 ◽  
Vol 10 (2) ◽  
pp. 211-230 ◽  
Author(s):  
Arthur L. Colwin ◽  
Laura Hunter Colwin
Keyword(s):  
Plasma Membrane ◽  
Granular Material ◽  
Structural Changes ◽  
Outer Zone ◽  
Natural Fracture ◽  
Limited Area ◽  
Acrosomal Vesicle ◽  
Acrosomal Membrane ◽  
Inner Surface ◽  
Egg Membrane

This paper describes in some detail the structure of the acrosomal region of the spermatozoon of Hydroides as a basis for subsequent papers which will deal with the structural changes which this region undergoes during fertilization. The material was osmium-fixed and mild centrifugation was used to aggregate the spermatozoa from collection to final embedding. The studies concern also the acrosomal regions of frozen-thawed sperm prepared by a method which previously had yielded extracts with egg membrane lytic activity. The plasma membrane closely envelops four readily recognizable regions of the spermatozoon: acrosomal, nuclear, mitochondrial, and flagellar. The acrosome consists of an acrosomal vesicle which is bounded by a single continuous membrane, and its periphery is distinguishable into inner, intermediate, and outer zones. The inner and intermediate zones form a pocket into which the narrowed apex of the nucleus intrudes. Granular material adjoins the inner surface of the acrosomal membrane, and this material is characteristically different for each zone. Centrally, the acrosomal vesicle is spanned by an acrosomal granule: its base is at the inner zone and its apex at the outer zone. The apex of the acrosomal granule flares out and touches the acrosomal membrane over a limited area. In this limited area the adjoining granular material of the outer zone is lacking. The acrosomal membrane of the inner zone is invaginated into about fifteen short tubules. The acrosomal membrane of the outer zone is closely surrounded by the plasma membrane. At the apex of the acrosomal region a small apical vesicle is sandwiched between the plasma membrane and the acrosomal membrane. Numerous frozen-thawed specimens and occasional specimens not so treated show acrosomal regions at the apex of which there is a well defined opening or orifice. Around the rim or lip of this orifice plasma and acrosomal membranes may even be fused into a continuum. The evidence indicates that the apical vesicle and the parts of the plasma and acrosomal membranes which surround it constitute a lid, and the rim of this lid constitutes a natural "fracture line" or rim of dehiscence. Should fracture occur, the lid would be removed and the acrosomal vesicle would be open to the exterior.

scholarly journals Structural changes after transmitter release at the frog neuromuscular junction.

1981 ◽  
Vol 88 (3) ◽  
pp. 564-580 ◽  
Author(s):  
J E Heuser ◽  
T S Reese
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicle ◽  
Structural Changes ◽  
Frog Neuromuscular Junction ◽  
Vesicle Membrane ◽  
Intramembrane Particles ◽  
Synaptic Vesicle Exocytosis ◽  
Quick Freezing ◽  
Vesicle Exocytosis ◽  
Active Zones

The sequence of structural changes that occur during synaptic vesicle exocytosis was studied by quick-freezing muscles at different intervals after stimulating their nerves, in the presence of 4-aminopyridine to increase the number of transmitter quanta released by each stimulus. Vesicle openings began to appear at the active zones of the intramuscular nerves within 3-4 ms after a single stimulus. The concentration of these openings peaked at 5-6 ms, and then declined to zero 50-100 ms late. At the later times, vesicle openings tended to be larger. Left behind at the active zones, after the vesicle openings disappeared, were clusters of large intramembrane particles. The larger particles in these clusters were the same size as intramembrane particles in undischarged vesicles, and were slightly larger than the particles which form the rows delineating active zones. Because previous tracer work had shown that new vesicles do not pinch off from the plasma membrane at these early times, we concluded that the particle clusters originate from membranes of discharged vesicles which collapse into the plasmalemma after exocytosis. The rate of vesicle collapse appeared to be variable because different stages occurred simultaneously at most times after stimulation; this asynchrony was taken to indicate that the collapse of each exocytotic vesicle is slowed by previous nearby collapses. The ultimate fate of synaptic vesicle membrane after collapse appeared to be coalescence with the plasma membrane, as the clusters of particles gradually dispersed into surrounding areas during the first second after a stimulus. The membrane retrieval and recycling that reverse this exocytotic sequence have a slower onset, as has been described in previous reports.

Maturation of reticulocytes: formation of exosomes as a mechanism for shedding membrane proteins

1992 ◽  
Vol 70 (3-4) ◽  
pp. 179-190 ◽  
Author(s):  
R. M. Johnstone
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Transferrin Receptor ◽  
Structural Changes ◽  
Surface Proteins ◽  
Multivesicular Bodies ◽  
Red Cell ◽  
Nucleoside Transporter ◽  
Selective Loss ◽  
Anion Transporter

The transferrin receptor is a member of a group of reticulocyte surface proteins that disappear from the membranes of reticulocytes as the cells mature to the erythrocyte stage. The selective loss of membrane proteins appears to be preceded by the formation of multivesicular bodies (MVBs). At the reticulocyte stage, many species of mammalian red cells including man, and one nucleated avian species (chicken), contain these intracellular structures in both natural and induced anemias. Also characteristic of blood containing reticulocytes is the presence of circulating vesicles (exosomes), which contain proteins and lipids characteristic of the plasma membrane. These exosomes appear to arise from the contents of the MVBs, after the fusion of MVBs with the plasma membrane. The proteins in the exosomes are those frequently lost during red cell maturation (e.g., transferrin receptor). The major transmembrane proteins (such as the anion transporter) are fully retained into the mature red cell, indicating a highly selective mechanism of recognition of a specific group of proteins. The exosomes are largely devoid of soluble proteins and proteins associated with lysozomes or mitochondria. A speculative model is proposed which addresses the questions of the maturation-induced structural changes in a class of membrane proteins, their recognition and selective loss involving exosome formation, and the release of exosomes to the circulation.Key words: transferrin receptor, nucleoside transporter, reticulocyte maturation, multivesicular bodies, 70-kilodalton protein.

scholarly journals Stay in Touch—The Cortical ER of Moss Protonemata in Osmotic Stress Situations

Plants ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 421 ◽  
Author(s):  
Dominik Harant ◽  
Ingeborg Lang
Keyword(s):  
Plasma Membrane ◽  
Cell Biology ◽  
Laser Scanning ◽  
Structural Changes ◽  
Physcomitrella Patens ◽  
Dynamic Network ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Natural State ◽  
Cell Cortex

Plasmolysis is usually introduced to cell biology students as a tool to illustrate the plasma membrane: hypertonic solutions cause the living protoplast to shrink by osmotic water loss; hence, it detaches from the surrounding cell wall. What happens, however, with the subcellular structures in the cell cortex during this process of turgor loss? Here, we investigated the cortical endoplasmic reticulum (ER) in moss protonema cells of Physcomitrella patens in a cell line carrying a transgenic ER marker (GFP-HDEL). The plasma membrane was labelled simultaneously with the fluorescent dye FM4-64 to achieve structural separation. By placing the protonemata in a hypertonic mannitol solution (0.8 M), we were able to follow the behaviour of the cortical ER and the protoplast during plasmolysis by confocal laser scanning microscopy (CLSM). The protoplast shape and structural changes of the ER were further examined after depolymerisation of actin microfilaments with latrunculin B (1 µM). In its natural state, the cortical ER is a dynamic network of fine tubes and cisternae underneath the plasma membrane. Under acute and long-term plasmolysis (up to 45 min), changes in the protoplast form and the cortical ER, as well as the formation of Hechtian strands and Hechtian reticula, were observed. The processing of the high-resolution z-scans allowed the creation of 3D models and gave detailed insight into the ER of living protonema cells before, during and after plasmolysis.

scholarly journals PHYSICOCHEMICAL DIFFERENCES BETWEEN FRAGMENTS OF PLASMA MEMBRANE AND ENDOPLASMIC RETICULUM

1966 ◽  
Vol 30 (3) ◽  
pp. 601-621 ◽  
Author(s):  
Donald F. Hoelzl Wallach ◽  
Virendra B. Kamat ◽  
Mitchell H. Gail
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Structural Changes ◽  
Ionic Composition ◽  
Ehrlich Ascites Carcinoma ◽  
Theoretical Background ◽  
Refractive Indices ◽  
Ehrlich Ascites ◽  
Isoelectric Ph ◽  
Turbidity Increase

Specific turbidities, densities, and refractive indices of fragments of plasma membrane (PM) and endoplasmic reticulum (ER) from Ehrlich ascites carcinoma have been measured. A spherical shell model of specified dimensions and refractive index was established for PM fragments. The ionic composition of the dispersion medium was varied systematically. Increases in Γ/2 caused increases in the turbidity of both PM and ER suspensions, the greatest effects being observed with Ca2+ and Mg2+. In the case of PM this effect is attributable mainly to aggregation, whereas "structural" changes account for most of the turbidity increase with ER. The pH was also varied systematically to obtain pH- density and turbidity profiles and to establish the isoelectric pH of the two membrane types (PM—3.6; ER—4.35). Turbidity was maximum at "isoelectric" pH, which corresponds in each case to the region of minimum charge on the particle surfaces. Both PM and ER show large increases of density at the "isoelectric" pH, but only ER shows substantial structurally based turbidity increase under these conditions. Both PM and ER show operation of electrostatic attractions near "isoelectric" pH. PM has been shown to have ionically distinctive inner and outer surfaces while ER shows no such dissymmetry. The necessary theoretical background for interpretation of turbidity and density measurements is included, as well as a discussion of the limitations of our conclusions and the biological importance of our results.

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