Cytoplasmic membrane transplants in early Xenopus embryos indicate cell-cycle-specific effects

Fragments of rough endoplasmic reticulum or Golgi complex isolated from normal adult rat liver homogenates were injected into one cell of cleaving two-cell Xenopus laevis embryos and the effects on development were monitored during early cleavage by morphological analysis. Scanning electron microscopy revealed the formation of large cells on the injected side of the embryos. Such large cells were not present in controls and thus were considered to have been formed as a consequence of delayed cleavage. Delay of cleavage was obtained with as little as 1 ng of membrane protein giving a ratio of membrane protein to embryo protein of 1:105. Cytological observations of microinjected embryos confirmed the occurrence of delayed cytokinesis and suggested that nuclear division became asynchronous. Since rough microsomes from proliferating tissues (i.e., livers with primary tumors and livers undergoing regeneration) showed little or no effect on cytokinesis after microinjection into early embryos, we conclude that cytoplasmic membranes may exhibit cell-cycle-specific properties important for normal development.Key words: rough endoplasmic reticulum and Golgi membranes, hepatectomy, hepatocellular carcinoma, cell cycle, membrane transplants, Xenopus embryos, cleavage arrest.

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THE SECRETORY PATHWAYS OF RAT SERUM GLYCOPROTEINS AND ALBUMIN

The Journal of Cell Biology ◽

10.1083/jcb.52.2.231 ◽

1972 ◽

Vol 52 (2) ◽

pp. 231-245 ◽

Cited By ~ 102

Author(s):

Colvin M. Redman ◽

M. George Cherian

Keyword(s):

Endoplasmic Reticulum ◽

Membrane Protein ◽

Rough Endoplasmic Reticulum ◽

Serum Proteins ◽

Rat Serum ◽

Secretory Pathways ◽

Specific Antisera ◽

Microsome Fraction

These studies compare the secretory pathways of newly formed rat serum glycoproteins and albumin by studying their submicrosomal localization at early times after the beginning of their synthesis and also by determining the submicrosomal site of incorporation of N-acetylglucosamine, mannose, galactose, and leucine into protein. N-acetylglucosamine, mannose, and galactose were only incorporated in vitro into proteins from membrane-attached polysomes and not into proteins from free polysomes. Mannose incorporation occurred in the rough endoplasmic reticulum, was stimulated by puromycin but not by cycloheximide, and 90% of the mannose-labeled protein was bound to the membranes. Galactose incorporation, by contrast, occurred in the smooth microsome fraction and 89% of the radioactive protein was in the cisternae. Albumin was mostly recovered (98%) in the cisternae, with negligible amounts in the membranes. To determine whether the radio-active sugars were being incorporated into serum proteins or into membrane protein, the solubilized in vivo-labeled proteins were treated with specific antisera to rat serum proteins or to albumin. Immunoelectrophoresis of the 14C-labeled leucine membrane and cisternal proteins showed that the membranes contained radioactive serum glycoprotein but no albumin, while the cisternal fraction contained all of the radioactive albumin and some glycoproteins. The results indicate that newly formed serum glycoproteins remain attached to the membranes of the rough endoplasmic reticulum after they are released from the membrane-attached polysomes, while albumin passes directly into the cisternae.

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Modification of Pineal Ultrastructure by Exogenous Hormones

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100060866 ◽

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.

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Use of Uranium-Labeled Antibodies for Electron Microscopic Localization of Various Antigens in Mammalian Cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100060696 ◽

1967 ◽

Vol 25 ◽

pp. 136-137

Author(s):

J. P. Petrali ◽

E. J. Donati ◽

L. A. Sternberger

Keyword(s):

Endoplasmic Reticulum ◽

Hela Cells ◽

Mammalian Cells ◽

Specific Antiserum ◽

Electron Microscopic ◽

E Coli ◽

Cytoplasmic Membranes ◽

Viral Progeny ◽

Ultrathin Sections ◽

Electron Microscopic Localization

Specific contrast is conferred to subcellular antigen by applying purified antibodies, exhaustively labeled with uranium under immunospecific protection, to ultrathin sections. Use of Seligman’s principle of bridging osmium to metal via thiocarbohydrazide (TCH) intensifies specific contrast. Ultrathin sections of osmium-fixed materials were stained on the grid by application of 1) thiosemicarbazide (TSC), 2) unlabeled specific antiserum, 3) uranium-labeled anti-antibody and 4) TCH followed by reosmication. Antigens to be localized consisted of vaccinia antigen in infected HeLa cells, lysozyme in monocytes of patients with monocytic or monomyelocytic leukemia, and fibrinogen in the platelets of these leukemic patients. Control sections were stained with non-specific antiserum (E. coli).In the vaccinia-HeLa system, antigen was localized from 1 to 3 hours following infection, and was confined to degrading virus, the inner walls of numerous organelles, and other structures in cytoplasmic foci. Surrounding architecture and cellular mitochondria were unstained. 8 to 14 hours after infection, antigen was localized on the outer walls of the viral progeny, on cytoplasmic membranes, and free in the cytoplasm. Staining of endoplasmic reticulum was intense and focal early, and weak and diffuse late in infection.

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

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100143468 ◽

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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TMCC3 localizes at the three-way junctions for the proper tubular network of the endoplasmic reticulum

Biochemical Journal ◽

10.1042/bcj20190359 ◽

2019 ◽

Vol 476 (21) ◽

pp. 3241-3260

Author(s):

Sindhu Wisesa ◽

Yasunori Yamamoto ◽

Toshiaki Sakisaka

Keyword(s):

Endoplasmic Reticulum ◽

Membrane Proteins ◽

Membrane Protein ◽

Mammalian Cells ◽

Coiled Coil ◽

Transmembrane Domains ◽

Domain Family ◽

Coiled Coil Domain ◽

U2os Cells ◽

Er Membrane

The tubular network of the endoplasmic reticulum (ER) is formed by connecting ER tubules through three-way junctions. Two classes of the conserved ER membrane proteins, atlastins and lunapark, have been shown to reside at the three-way junctions so far and be involved in the generation and stabilization of the three-way junctions. In this study, we report TMCC3 (transmembrane and coiled-coil domain family 3), a member of the TEX28 family, as another ER membrane protein that resides at the three-way junctions in mammalian cells. When the TEX28 family members were transfected into U2OS cells, TMCC3 specifically localized at the three-way junctions in the peripheral ER. TMCC3 bound to atlastins through the C-terminal transmembrane domains. A TMCC3 mutant lacking the N-terminal coiled-coil domain abolished localization to the three-way junctions, suggesting that TMCC3 localized independently of binding to atlastins. TMCC3 knockdown caused a decrease in the number of three-way junctions and expansion of ER sheets, leading to a reduction of the tubular ER network in U2OS cells. The TMCC3 knockdown phenotype was partially rescued by the overexpression of atlastin-2, suggesting that TMCC3 knockdown would decrease the activity of atlastins. These results indicate that TMCC3 localizes at the three-way junctions for the proper tubular ER network.

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