Ultrastructural changes in chloroplasts resulting from fluctuations in NaCl concentration: freeze-fracture of thylakoid membranes in Dunaliella salina

1975 ◽  
Vol 18 (2) ◽  
pp. 287-299 ◽  
Author(s):  
A.O. Pfeifhofer ◽  
J.C. Belton
Keyword(s):  
Salt Concentration ◽  
Dunaliella Salina ◽  
Unit Area ◽  
Morphological Changes ◽  
Membrane Surface ◽  
Freeze Fracture ◽  
Thylakoid Membranes ◽  
Ultrastructural Changes ◽  
Thin Sections ◽  
Number Of Particles

The structure of chloroplasts isolated from Dunaliella salina has been studied with respect to changing concentrations of sodium chloride in the culture medium. Freeze-fracture replicas and thin sections of intact chloroplasts do not exhibit any noticeable changes in structure at concentrations ranging between 3.5 and 25% NaCl. Chloroplasts isolated from algal cells that have been acclimatized to the higher salt concentration show a change in the thylakoid membranes. The thylakoid membranes appear compressed over a major portion of the membrane surface, with only the end of the thylakoid membranes unappressed. The number of particles per unit area on the B face is also altered by the salt concentration. The chloroplasts acclimatized to 25% NaCl have about 3 times the number of particles per unit area on a B face of end-membranes as on a comparable face of thylakoid membranes acclimatized to low (3.5% NaCl) salt concentration. These morphological changes can be reversed if the chloroplasts acclimatized to high or low salt concentrations are returned to a medium of different salt concentration prior to freeze-fracturing.

scholarly journals Ultrastructural changes and cyclic AMP in frog oxyntic cells.

1978 ◽  
Vol 76 (1) ◽  
pp. 31-42 ◽  
Author(s):  
K S Carlisle ◽  
C S Chew ◽  
S J Hersey
Keyword(s):  
Cyclic Amp ◽  
Acid Secretion ◽  
Surface Area ◽  
Acid Production ◽  
Morphological Changes ◽  
Membrane Surface ◽  
Ultrastructural Changes ◽  
H2 Receptor Antagonist ◽  
Histamine H2 Receptor

In vitro frog gastric mucosa was employed as a model for a combined physiological, biochemical, and ultrastructural study of the morphological changes which accompany the onset of acid secretion by the oxyntic cell. The histamine H2-receptor antagonist metiamide was used to provide a reproducible control state. Stimulation of acid production by theophylline resulted in a 10-fold increase in plasma membrane surface area and a distinct change in the conformation of mitochondrial cristae. Studies using the acid secretion inhibitors, thiocyanate and anoxia, demonstrated that neither acid production per se nor oxidative metabolism is essential for the theophylline-dependent changes in surface area. Increases in tissue cyclic AMP levels were observed under the conditions producing morphological changes. It is postulated that surface area changes induced by theophylline are controlled by cellular cyclic AMP levels.

Regular structures in membranes: the lumenal plasma membrane of the cow urinary bladder

1976 ◽  
Vol 22 (2) ◽  
pp. 355-370 ◽  
Author(s):  
S. Knutton ◽  
J.D. Robertson
Keyword(s):  
Plasma Membrane ◽  
Urinary Bladder ◽  
Cytoplasmic Membrane ◽  
Membrane Surface ◽  
Hexagonal Lattice ◽  
Freeze Fracture ◽  
Hexagonal Structure ◽  
Unit Cell ◽  
Hexagonal Array ◽  
Thin Sections

The ultrastructure of the lumenal plasma membrane of the cow urianry bladder has been studied in thin sections of glutaraldehyde- and glutaraldehyde-H2O2-fixed specimens, by negative staining and freeze fracture. A regular hexagonal array of particles confined to polygonal plaques 0-1-0-4-mum in diameter and separated by 0-02-mum interplaque areas is revealed by all 3 techniques. Cross-sections through particulate areas fixed with glutarayldehyde-H2O2 display a tetralaminar structure consisting of the usual approximately 8-nm-thick trilamellar unit membrane structure, on the external dense leaflet of which is located an additional approximately 4-nm-thick stratum which is occasionally resolved into a row of regulrly spaced approximately 4-nm-diameter particles. Non-particulate areas feature only the approximately 8-nm-thick trilamellar structure. Tangential sections reveal an hexagonal array of particles with a unit cell of approximately 16 nm. Four membrane faces can be revealed by freeze fracture and etching of membranes of the cow urinary bladder; 2 complementary split inner membrane faces (A and B) revealed by the cleaving process and the lumenal and cytoplasmic membrane surfaces exposed by etching. Face B, which belongs to the external membrane leaflet and faces the cytoplasm, displays plaques of particles arranged in a hexagonal lattice with a unit cell of approximately 16 nm. Face A, which belongs to the cytoplasmic membrane leaflet and faces the lumen, displays a complementary array of hexagonally packed pits. The hexagonally arranged particles also protrude into the lumenal membrane surface where they can occasionally be resolved into 6 approximately 5-nm-diameter subunits; the cytoplasmic surface appears smooth. Six approximately 5-nm-diameter subunits are also revealed in negatively stained preparations. The data are consistent with a model for the membrane in which the particles forming the hexagonal structure protrude above the lumenal membrane surface and also bridge most of the thickness of the membrane.

Differentiation in Trypanosoma brucei: host-parasite cell junctions and their persistence during acquisition of the variable antigen coat

1985 ◽  
Vol 74 (1) ◽  
pp. 1-19 ◽  
Author(s):  
L. Tetley ◽  
K. Vickerman
Keyword(s):  
Electron Microscopy ◽  
Trypanosoma Brucei ◽  
Morphological Changes ◽  
Freeze Fracture ◽  
Tsetse Fly ◽  
Cell Junctions ◽  
Surface Coat ◽  
Thin Sections ◽  
Variable Antigen ◽  
Host Parasite

Acquisition of the variable antigen-containing surface coat of Trypanosoma brucei occurs at the metacyclic stage in the salivary glands of the tsetse fly vector. The differentiation of the metacyclic trypanosome in the gland has been studied by scanning electron microscopy and by transmission electron microscopy of thin sections and freeze-fracture replicas. The uncoated epimastigote trypanosomes (with a prenuclear kinetoplast) divide while attached to the salivary gland epithelium brush border by elaborate branched flagellar outgrowths, which ramify between the host cell microvilli and form punctate hemidesmosome-like attachment plaques where they are indented by the microvilli. These outgrowths become reduced as the epimastigotes transform to uncoated trypomastigotes (with postnuclear kinetoplast), which remain attached and capable of binary fission. The flagellar outgrowths disappear but the attachment plaques persist as the uncoated trypomastigotes (premetacyclics) stop dividing and acquire the surface coat to become ‘nascent metacyclics’. Coat acquisition therefore occurs in the attached trypanosome and not, as previously believed, after detachment. Coating is accompanied by morphological changes in the glycosomes and mitochondrion of the parasite. Freeze-fracture replicas of the host-parasite junctional complexes show membrane particle aggregates on the host membrane but not on the parasite membrane. It is suggested that disruption of the complex occurs when maximum packing of the glycoprotein molecules has been achieved in the trypanosome surface coat, releasing the metacyclic trypanosome into the lumen of the gland.

scholarly journals On the mechanism of rapid plasma membrane and chloroplast envelope expansion in Dunaliella salina exposed to hypoosmotic shock.

1986 ◽  
Vol 102 (1) ◽  
pp. 289-297 ◽  
Author(s):  
M Maeda ◽  
G A Thompson
Keyword(s):  
Plasma Membrane ◽  
Surface Area ◽  
Thin Section ◽  
Dunaliella Salina ◽  
Membrane Surface ◽  
Freeze Fracture ◽  
Chloroplast Envelope ◽  
Outer Envelope ◽  
High Concentration ◽  
Selective Fusion

Dunaliella salina cells rapidly diluted from their normal 1.71 M NaCl-containing growth medium into medium containing 0.86 M NaCl swelled within 2--4 min to an average volume 1.76 X larger and a surface area 1.53 X larger than found in control cells. Morphometric analysis of thin section electron micrographs revealed that certain organelles, including the chloroplast, nucleus, and some types of vacuoles, also expanded in surface area as much or more than did the entire cell. It is likely that glycerol, the most important osmotically active intracellular solute, was present in high concentration within these organelles as well as in the cytoplasm itself. Thin section and freeze-fracture electron microscopy were utilized to trace the origin of membrane material whose addition permitted the large increase in plasma membrane surface area and the equally large growth of the chloroplast outer envelope. The findings indicated that the plasma membrane's expansion resulted from its selective fusion with numerous small (less than or equal to 0.25 micron diam) vesicles prevalent throughout the cytoplasm. In contrast, new membrane added to the chloroplast outer envelope was drawn from an entirely different source, namely, elements of the endoplasmic reticulum.

Ultrastructural Pathology of Ischemic Myocardium as Revealed by the Freeze Fracture Technique

1975 ◽  
Vol 33 ◽  
pp. 426-427
Author(s):  
M. Ashraf ◽  
W. Mayr
Keyword(s):  
Coronary Artery ◽  
Cell Injury ◽  
Freeze Fracture ◽  
Coronary Artery Occlusion ◽  
Myocardial Cell ◽  
Artery Occlusion ◽  
Ischemic Myocardium ◽  
Ultrastructural Changes ◽  
Acute Ischemia ◽  
Thin Sections

Myocardial cells undergo extensive ultrastructural changes during ischemia, easily observed after 30 minutes of coronary artery occlusion. Although various membranous organelles remain intact during acute ischemia, biochemical evidence indicates several metabolic alterations in affected cells. Since cell membranes and membranes of intracellular organelles play an important role in the pathogenesis of myocardial cell injury, changes in their interiors could be informative. However, such changes are not easily detectable in conventional thin sections. This study examined ultrastructural alterations in the membranous organelles of ischemic myocardium using the freeze-fracture technique to improve detection of such changes.After 5 and 24 hours of coronary artery occlusion the hearts from dogs and rats were perfused with buffered glutaraldehyde. Small pieces of the left ventricle were dipped in Freon 22 and immediately frozen in liquid nitrogen before fracturing in a Balzer's freeze-etch apparatus at -100 or -120°C.

Ultrastructural changes related to functional activity in gastric oxyntic cells

1981 ◽  
Vol 241 (5) ◽  
pp. G349-G358 ◽  
Author(s):  
J. G. Forte ◽  
J. A. Black ◽  
T. M. Forte ◽  
T. E. Machen ◽  
J. M. Wolosin
Keyword(s):  
Alternative Hypothesis ◽  
Membrane Surface ◽  
Apical Cell ◽  
Freeze Fracture ◽  
Weight Of Evidence ◽  
Ultrastructural Changes ◽  
Morphological Evidence ◽  
Apical Surface ◽  
Oxyntic Cell ◽  
Macromolecular Tracers

When stimulated to secrete HCl the gastric oxyntic cell undergoes profound morphological change. The identifiable apical cell surface is greatly expanded in the stimulated oxyntic cell as compared with nonsecreting ones. To account for this change, one hypothesis proposes that the expanded surface is derived from the fusion of cytoplasmic tubulovesicular membranes with the existing limited apical membrane surface. An alternative hypothesis suggests that the tubulovesicular compartment is actually confluent with the apical surface at all times and that the morphological appearance follows the expansion of this supercollapsed compartment as HCl secretion commences. A variety of morphological evidence is reviewed here including transmission electron microscopy during various stages of secretion and inhibition, analysis of freeze-fracture replicas, penetration of macromolecular tracers, and membrane surface-staining characteristics. It is concluded that the weight of evidence favors a membrane fusion process. Moreover, recent comparative studies of membrane fractions from resting and secreting stomachs show different morphological and functional properties that are also consistent with a fusion hypothesis as a fundamental event in the membrane transformation of the oxyntic cell.

Comparison of quantified coated pit profiles in thin sections and freeze-fracture replicas of granular epithelial cells of the toad urinary bladder

1992 ◽  
Vol 50 (1) ◽  
pp. 720-721
Author(s):  
Nancy L. Shinowara ◽  
Jenchang Yu ◽  
Thomas A. Palaia
Keyword(s):  
Apical Membrane ◽  
Unit Area ◽  
Collecting Duct ◽  
Freeze Fracture ◽  
Toad Urinary Bladder ◽  
Granular Cells ◽  
Coated Pits ◽  
Thin Sections ◽  
Membrane Changes ◽  
Apical Membranes

It is well known that stimulation of granular cells by arginine vasopressin (AVP) results in apical membrane changes, including an increased water permeability and an associated exocytotic delivery of aggregates of intramembrane particles, Endocytotic clathrin-coated pits appear in stimulated collecting duct principal cells, which transport water in mammalian kidneys. Recently, presumptive coated pits (CPs), identified in replicas, were reported in apical membranes of stimulated granular cells. This study describes the comparison of structurally defined sectioned-CPs (s-CPs per unit membrane length with presumptive, replicated-CPs (r-CPs) per unit area in bladders when initial CP formation was expected.

Transfer Cell Development And Immunolocalization Of A Senescence Associated Gene (Sag14) In Senescing Arabidopsis Thaliana Leaves.

1999 ◽  
Vol 5 (S2) ◽  
pp. 1252-1253
Author(s):  
W. A. Russin ◽  
L. M. Weaver ◽  
R. M. Amasino
Keyword(s):  
Gene Expression ◽  
Arabidopsis Thaliana ◽  
Leaf Senescence ◽  
Cell Structure ◽  
Membrane Surface ◽  
Cell Development ◽  
Transfer Cell ◽  
Ultrastructural Changes ◽  
Mrna Levels ◽  
Thin Sections

Leaf senescence is an orderly, active process in which nutrients in a leaf are reclaimed and mobilized to other parts of the plant. It is considered to be the final stage in leaf development. During senescence leaves undergo highly coordinated changes in cell structure, metabolism, and gene expression. For example, chloroplasts undergo obvious structural modifications during leaf senescence. Regarding gene expression, genes with steady-state mRNA levels that increase during senescence are often referred to as senescence-associated genes, or SAGs.In order to study ultrastructural changes that occur during senescence, portions of fully expanded, mid-senescent, and fully senescent Arabidopsis thaliana leaves were chemically fixed using vacuum-accelerated microwave processing. Thin sections were observed for ultrastructural changes such as development of transfer cells that are characterized by the presence of cell wall ingrowths. Transfer cell development is correlated with an increased capacity of tissues to take up materials, related partly to an increase in plasma membrane surface area.

Gap junctions in the prothoracic glands of the tobacco hornworm, Manduca sexta

1992 ◽  
Vol 50 (1) ◽  
pp. 706-707
Author(s):  
Ji-da Dai ◽  
M. Joseph Costello ◽  
Lawrence I. Gilbert
Keyword(s):  
Gap Junctions ◽  
Small Molecules ◽  
Manduca Sexta ◽  
Freeze Fracture ◽  
Cell Communication ◽  
Cellular Level ◽  
Thin Sections ◽  
Prothoracic Glands ◽  
Polyhydroxylated Steroids ◽  
Stimulation Of

Insect molting and metamorphosis are elicited by a class of polyhydroxylated steroids, ecdysteroids, that originate in the prothoracic glands (PGs). Prothoracicotropic hormone stimulation of steroidogenesis by the PGs at the cellular level involves both calcium and cAMP. Cell-to-cell communication mediated by gap junctions may play a key role in regulating signal transduction by controlling the transmission of small molecules and ions between adjacent cells. This is the first report of gap junctions in the PGs, the evidence obtained by means of SEM, thin sections and freeze-fracture replicas.

TURBIDITY OF SUSPENSIONS AND MORPHOLOGY OF RED HALOPHILIC BACTERIA AS INFLUENCED BY SODIUM CHLORIDE CONCENTRATION

1960 ◽  
Vol 6 (5) ◽  
pp. 535-543 ◽  
Author(s):  
Dinah Abram ◽  
N. E. Gibbons
Keyword(s):  
Sodium Chloride ◽  
Salt Concentration ◽  
Morphological Changes ◽  
Halophilic Bacteria ◽  
Chloride Concentration ◽  
Chloride Content ◽  
Wall Structure ◽  
Abrupt Decrease ◽  
High Sodium ◽  
Rigid Cell Wall

The optical densities of suspensions of cells of Halobacterium cutirubrum, H. halobium, or H. salinarium, grown in media containing 4.5 M sodium chloride, increase as the salt concentration of the suspending medium decreases, until a maximum is reached at about 2 M; below this concentration there is an abrupt decrease in optical density. The cells are rod shaped in 4.5 M salt and change, as the salt concentration decreases, through irregular transition forms to spheres; equal numbers of transition forms and spheres are present at the point of maximum turbidity, while spheres predominate at lower salt concentrations. Cells suspended in 3.0 M salt, although slightly swollen, are viable, but viability decreases rapidly with the more drastic changes in morphology at lower salt concentrations. Cells grown in the presence of iron are more resistant to morphological changes but follow the same sequence. Cells "fixed" with formaldehyde, at any point in the sequence, act as osmometers and do not rupture in distilled water although their volume increases 10–14 times. The results indicate that the red halophilic rods require a high sodium chloride content in their growth or suspending medium to maintain a rigid cell wall structure.

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