Cotyledon cell development in Arabidopsis thaliana during reserve deposition

1992 ◽  
Vol 70 (1) ◽  
pp. 151-164 ◽  
Author(s):  
S. G. Mansfield ◽  
L. G. Briarty
Keyword(s):  
Arabidopsis Thaliana ◽  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Volume Fraction ◽  
Biological Membrane ◽  
Lipid Body ◽  
Cell Development ◽  
Volume Fractions ◽  
Short Period ◽  
Cotyledon Cell

Cotyledon cell development in Arabidopsis thaliana L. during reserve deposition has been analyzed qualitatively and quantitatively. Development has been related to the previously defined time scale for Arabidopsis, hours after flowering. Between 144 and 216 h after flowering the major cell changes in the cotyledon are an increase in the cell volume, a decrease in the volume fraction of cytoplasm and plastids, and an increase in lipid and vacuole volume fractions. The endoplasmic reticulum and dictyosome volume fractions are high during early reserve formation (144 – 168 h after flowering) but decrease significantly thereafter. Evidence as to the origin of the storage lipid is inconclusive, although a dual involvement of plastids and rough endoplasmic reticulum is a likely theory. The 3-nm lipid body membrane, which allows the bodies to retain their individuality during accumulation, is probably a half-unit biological membrane, derived from closely associated rough endoplasmic reticulum cisternae. Much of the evidence obtained in this study indicates that both the endoplasmic reticulum and dictyosomes are involved in protein synthesis and transport to the vacuole. The accumulation of reserves occurs in a well-defined and relatively short period during late embryogenesis (144–216 h after flowering). Key words: Arabidopsis, cotyledons, embryogenesis, reserve deposition, stereology.

scholarly journals Entangled architecture of rough endoplasmic reticulum (RER) and vacuoles enables topological damping in cytoplasm of an ultra-fast giant cell

2021 ◽  
Author(s):  
Ray Chang ◽  
Manu Prakash
Keyword(s):  
Endoplasmic Reticulum ◽  
Giant Cell ◽  
Rough Endoplasmic Reticulum ◽  
Volume Fraction ◽  
Single Cells ◽  
Cellular Systems ◽  
Confocal Imaging ◽  
Dynamics Simulation ◽  
Cellular Damage ◽  
Novel Association

Cellular systems are known to exhibit some of the fastest movements in the biological world - but little is known as to how single cells can dissipate this energy rapidly and adapt to such large accelerations without sub-cellular damage. To study intracellular adaptations under extreme forces - we investigate Spirostomum ambiguum - a giant cell (1-4mm in length) well known to exhibit ultrafast contractions (50% of body length) within 5 msec with a peak acceleration of 15g. Utilizing transmitted electron microscopy (TEM) and confocal imaging, we discover a novel association of rough endoplasmic reticulum (RER) and vacuoles throughout the cell - forming a contiguous fenestrated cubic membrane architecture that topologically entangles these two organelles. A nearly uniform inter-organelle spacing of 60nm is observed between RER and vacuoles, closely packing the entire cell. Using an overdamped molecular dynamics simulation, we demonstrate how this unique entangled metamaterial responds to external loads by rapidly dissipating energy and helps preserve spatial relationships between organelles. Because this dynamics arises primarily from entanglement of two networks incurring jamming transition at a subcritical volume fraction - we term this phenomena "topological damping". Our findings suggest a new mechanical role of RER-vacuolar meshwork as a metamaterial capable of dissipating energy in an ultra-fast contraction event.

scholarly journals Co-ordination between membrane phospholipid synthesis and accelerated biosynthesis of cytoplasmic ribonucleic acid and protein

1970 ◽  
Vol 116 (4) ◽  
pp. 617-630 ◽  
Author(s):  
J. R. Tata
Keyword(s):  
Growth Hormone ◽  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Time Course ◽  
Seminal Vesicles ◽  
Membrane Phospholipid ◽  
Phospholipid Synthesis ◽  
Membrane Phospholipids ◽  
Short Period ◽  
Microsomal Membranes

1. The rate of synthesis of membrane phospholipid was studied in rat liver and seminal vesicles by following the incorporation of [32P]orthophosphate, [14C]choline and [14C]glycerol. Particular emphasis was laid on the endoplasmic reticulum, which was fractionated into smooth microsomal membranes, heavy rough membranes, light rough membranes and free polyribosomes. 2. Phospholipid labelling patterns suggested a heterogeneity in the synthesis and turnover of the different lipid moieties of smooth and rough endoplasmic membranes. The major phospholipids, phosphatidylcholine and phosphatidylethanolamine, were labelled relatively rapidly with 32P over a short period of time whereas incorporation of radioisotope into the minor phospholipids, sphingomyelin, lysolecithin and phosphatidylinositol proceeded slowly but over a longer period of time. 3. The incorporation of orotic acid into RNA and labelled amino acids into protein of the four submicrosomal fractions was also studied. 4. Rapid growth of the liver was induced by the administration of growth hormone and tri-iodothyronine to hypophysectomized and thyroidectomized rats and by partial hepatectomy. Growth of seminal vesicles of castrated rats was stimulated with testosterone propionate. 5. The rate of labelling of membrane phospholipids was enhanced in all major subcellular particulate fractions (nuclear, mitochondrial and microsomal) during induced growth. However, it was in the rough endoplasmic reticulum that the accumulation of phospholipids, RNA and protein was most marked. The effect of hormone administration was also to accelerate preferentially the labelling with 32P of sphingomyelin relative to that of phosphatidylcholine or phosphatidylethanolamine. 6. Time-course analyses showed that, in all four growth systems studied, the enhancement of the rate of membrane phospholipid synthesis coincided with the rather abrupt increase in the synthesis of RNA and protein of the rough endoplasmic reticulum. Growth hormone and tri-iodothyronine administered to hypophysectomized rats had additive effects in all the biosynthetic processes. The latent period of action of each hormone was maintained so that two waves of proliferation of endoplasmic reticulum occurred if the hormones were administered simultaneously. 7. It is concluded that there is some mechanism in the cell that tightly co-ordinates the formation of membranes, especially those of the endoplasmic reticulum, when an increased demand is made for protein synthesis.

scholarly journals CHANGES IN THE RIBOSOME CONTENT, PRINCIPAL MICROSOMAL PROTEIN COMPOSITION, AND SECRETORY CHARACTER OF MAMMARY EPITHELIAL ROUGH ENDOPLASMIC RETICULUM DURING DIFFERENTIATION

1974 ◽  
Vol 61 (3) ◽  
pp. 613-632 ◽  
Author(s):  
Frank Slaby ◽  
Carolyn Brown
Keyword(s):  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Protein Composition ◽  
Mammary Development ◽  
Mammary Epithelial ◽  
Density Range ◽  
Short Period ◽  
Rough Er

The equilibrium density distribution, protein composition, and secretory character of mouse mammary epithelial rough microsomes have been determined during differentiation. The density range exhibited by the rough microsomes broadens during mammary development; rough microsomes within the 1.25–1.29 g/ml density range appear soon after conception and then within the 1.30–1.34 range after the onset of lactation. The appearance of these denser microsomes represents the progressive increase of the average ribosome content of the rough endoplasmic reticulum (ER) during gestation and lactation. Fractionation of rough microsomal proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis reveals that two proteins, having molecular weights of 57,000 and 76,000, occur to a significant extent only during lactation and are then most prominent in the very dense rough microsomes of the 1.30–1.34 range. Nascent polypeptide chains discharged (by incubation with puromycin) from 17-days lactation rough microsomes in either the 1.21–1.29 or 1.30–1.34 density range are distributed equally between the intra- and extravesicular compartments. Whereas 36% of the chains are discharged intravesicularly from 1-day lactation rough microsomes in the 1.30–1.34 range, only 25% are so discharged from those in the 1.21–1.29 range. The results indicate (a) that there is no correlation between the relative levels in lactation rough microsomes of the two microsomal proteins which become prominent during lactation and the extent of secretory activity and (b) that for a short period after parturition the rough ER elements bearing high surface densities of ribosomes have a greater proportion of ribosomes synthesizing milk proteins than the rough ER elements with moderate ribosome densities.

Modification of Pineal Ultrastructure by Exogenous Hormones

1967 ◽  
Vol 25 ◽  
pp. 170-171
Author(s):  
R. A. Turner ◽  
A. E. Rodin ◽  
D. K. Roberts
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Rough Endoplasmic Reticulum ◽  
Estradiol Benzoate ◽  
Female Rats ◽  
List Type ◽  
Type Number ◽  
Pregnant Rats ◽  
Gonadal Atrophy ◽  
Pineal Ultrastructure

There have been many reports which establish a relationship between the pineal and sexual structures, including gonadal hypertrophy after pinealectomy, and gonadal atrophy after injection of pineal homogenates or of melatonin. In order to further delineate this relationship the pineals from 5 groups of female rats were studied by electron microscopy:ControlsPregnant ratsAfter 4 weekly injections of 0.1 mg. estradiol benzoate.After 8 daily injections of 150 mcgm. melatonin (pineal hormone).After 8 daily injections of 3 mg. serotonin (melatonin precursor).No ultrastructural differences were evident between the control, and the pregnancy and melatonin groups. However, the estradiol injected animals exhibited a marked increase in the amount and size of rough endoplasmic reticulum within the pineal cells.

Membrane-associated microtubular areays induced in proximal myelinated processes of dorsal root ganglia by large doses of vitamin B6

1986 ◽  
Vol 44 ◽  
pp. 368-369
Author(s):  
V.J. Montpetit ◽  
S. Dancea ◽  
L. Tryphonas ◽  
D.F. Clapin
Keyword(s):  
Animal Model ◽  
Endoplasmic Reticulum ◽  
Dorsal Root Ganglia ◽  
Rough Endoplasmic Reticulum ◽  
Dorsal Root ◽  
Vitamin B6 ◽  
Morphological Changes ◽  
Model System ◽  
Sensory Nerves ◽  
Peripheral Sensory

Very large doses of pyridoxine (vitamin B6) are neurotoxic in humans, selectively affecting the peripheral sensory nerves. We have undertaken a study of the morphological and biochemical aspects of pyridoxine neurotoxicity in an animal model system. Early morphological changes in dorsal root ganglia (DRG) associated with pyridoxine megadoses include proliferation of neurofilaments, ribosomes, rough endoplasmic reticulum, and Golgi complexes. We present in this report evidence of the formation of unique aggregates of microtubules and membranes in the proximal processes of DRG which are induced by high levels of pyridoxine.

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