scholarly journals THE PHOTOSYNTHETIC APPARATUS OF RHODOSPIRILLUM MOLISCHIANUM

1965 ◽  
Vol 26 (2) ◽  
pp. 395-412 ◽  
Author(s):  
Sarah P. Gibbs ◽  
W. R. Sistrom ◽  
Patricia B. Worden
Keyword(s):  
Cell Membrane ◽  
Photosynthetic Apparatus ◽  
Variable Number ◽  
Electron Microscopic ◽  
Microscopic Appearance ◽  
Whole Cells ◽  
Cell Extracts ◽  
Internal Membrane ◽  
Rhodospirillum Molischianum ◽  
In Cells

By varying the light intensity and temperature during growth it is possible to obtain cultures of Rhodospirillum molischianum in which the specific bacteriochlorophyll contents differ by as much as fivefold. We used such cultures to compare the changes in the electron microscopic appearance of the cells with the changes in the amount and bacteriochlorophyll content of chromatophore material isolated from cell extracts. The cells contained a variable number of internal membranes which are invaginations of the cell membrane. The shape, size, number, and arrangement of the infoldings varied as the specific bacteriochlorophyll content of the cells changed. In cells with little bacteriochlorophyll, the invaginations were mostly tubular. In cells with larger amounts of bacteriochlorophyll, the invaginations were disc-shaped and the discs were appressed together in stacks of 2 to 10 discs each. Variations in the number of discs per stack could be accounted for by a simple statistical model. The average area per disc increased with increasing bacteriochlorophyll content. Quantitative estimations of the relative volumes occupied by membranes in cells with four different bacteriochlorophyll contents showed that the amount of internal membrane alone had no direct relationship with the bacteriochlorophyll content of the cells; however, the total amount of membrane (cell membrane plus internal membrane) was directly proportional to the bacteriochlorophyll content. The specific bacteriochlorophyll content of isolated chromatophore material was proportional to the bacteriochlorophyll content of whole cells; the total amount of chromatophore material was independent of the bacteriochlorophyll content of whole cells. Several possible explanations of this paradoxical discrepancy between the electron microscope observations and the analytical results are discussed.

THE INHIBITION OF KETO ACID OXIDATION BY PYOCYANINE

1957 ◽  
Vol 3 (2) ◽  
pp. 313-318 ◽  
Author(s):  
J. J. R. Campbell ◽  
A. M. MacQuillan ◽  
B. A. Eagles ◽  
R. A. Smith
Keyword(s):  
Escherichia Coli ◽  
Cell Membrane ◽  
Pseudomonas Fluorescens ◽  
Acid Level ◽  
Divalent Cations ◽  
Acid Oxidation ◽  
Keto Acid ◽  
Proteus Vulgaris ◽  
Whole Cells ◽  
Cell Extracts

When tested against Pseudomonas fluorescens, pyocyanine was found to stop the oxidation of a number of substrates at the keto acid level. This inhibition could be reversed by the addition of divalent cations. Of these, magnesium was most effective. The pigment was found to be similarly effective against the oxidations of Proteus vulgaris. Whole cells of Escherichia coli were not affected by the dye, whereas cell extracts were, indicating that the dye did not penetrate the cell membrane.

Electron microscopic radioautographic studies on the incorporation of 3H proline in the glomerular basement membrane (GBM) in antistreptococcal-cell-membrane (SCM) injected mice

1984 ◽  
Vol 42 ◽  
pp. 188-189
Author(s):  
R.P. Nayyar ◽  
C.F. Lange ◽  
J. L. Borke
Keyword(s):  
Body Weight ◽  
Cell Membrane ◽  
Basement Membrane ◽  
Glomerular Basement Membrane ◽  
Mesangial Matrix ◽  
Electron Microscopic ◽  
Group A ◽  
Injection Protocol

Streptococcal cell membrane (SCM) antiserum injected mice show a significant thickening of glomerular basement membrane (GBM) and an increase in mesangial matrix within 4 to 24 hours of antiserum administration (1,2,3). This study was undertaken to evaluate the incorporation of 3H proline into glomerular cells and GBM under normal and anti-SCM induced conditions. Mice were administered, intraperitoneally, 0.1 ml of normal or anti-SCM serum followed by a 10 µC/g body weight injection of 3H proline. Details of the preparation of anti-SCM (Group A type 12 streptococcal pyogenes) and other sera and injection protocol have been described elsewhere (2). After 15 minutes of isotope injection a chase of cold proline was given and animal sacrificed at 20 minutes, 1,2,4,8,24 and 48 hours. One of the removed kidneys was processed for immunofluorescence, light and electron microscopic radioautographic studies; second kidney was used for GBM isolation and aminoacid analysis.

scholarly journals Changes in Cell Membrane and Cellular Lipids in Apoptotic Cells Induced by Dolichyl Phosphate Differ from Findings in Cells Induced by Etoposide.

2002 ◽  
Vol 51 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Akiko HORIUCHI ◽  
Etsuko YASUGI ◽  
Chizu IWASAKI ◽  
Keiji FUJIMOTO ◽  
Mieko OSHIMA
Keyword(s):  
Cell Membrane ◽  
Apoptotic Cells ◽  
Dolichyl Phosphate ◽  
Cellular Lipids ◽  
In Cells

Physiological Significance of Overproduced Carotenoids in Transformants of the Cyanobacterium Synechococcus PCC7942

1999 ◽  
Vol 54 (3-4) ◽  
pp. 191-198
Author(s):  
Navassard V. Karapetyan ◽  
Ute Windhövel ◽  
Alfred R. Holzwarth ◽  
Peter Böger
Keyword(s):  
Protein Complexes ◽  
Photosynthetic Apparatus ◽  
Fluorescence Emission ◽  
Fluorescence Induction ◽  
Carotenoid Content ◽  
Excitation Spectra ◽  
Fluorescence Excitation ◽  
Whole Cells ◽  
Fluorescence Excitation Spectra ◽  
Synechococcus Pcc7942

Abstract The functional location of carotenoids in the photosynthetic apparatus of -crtB and -pys transformants of the cyanobacterium Synechococcus PCC7942 was studied and compared with a control strain -pFP 1-3. These transformants overproduce carotenoids due to the insertion of an additional foreign phytoene synthase gene. A higher carotenoid content was found for -crtB and -pys transformants both in whole cells and isolated membranes; the -crtB transformant was also enriched with chlorophyll. 77-K fluorescence emission and excitation spectra of the phycobilin-free membranes were examined for a possible location of overproduced carotenoids in pigment-protein complexes in situ. A similar ratio of the amplitudes of fluorescence bands at 716 and 695 nm emitted by photosystems I and II, found for the three strains, indicates that the stoichiometry between photosystems of the transformants was not changed. Overproduced carotenoids are not located in the core antenna of photosys­ tem I, since 77-K fluorescence excitation spectra for photosystem I of isolated membranes from the studied strains do not differ in the region of carotenoid absorption. When illuminated with light of the same intensity but different quality, absorbed preferentially by either carotenoids, chlorophylls or phycobilins, respectively, oxygen evolution was found always higher in the transformants -crtB and -pys than in -pFP 1-3 control cells. Identical kinetics of fluorescence induction of all strains under carotenoid excitation did not reveal a higher activity of photosystem II in cells enriched with carotenoids. It is suggested that overproduced carotenoids of the transformants are not involved in photosynthetic light-harvesting; rather they may serve to protect the cells and its membranes against photodestruction.

Ultrastructural Changes in Euglena After Ultraviolet Irradiation

1973 ◽  
Vol 13 (3) ◽  
pp. 799-809
Author(s):  
A. MICHAELS ◽  
A. GIBOR
Keyword(s):  
Ultraviolet Light ◽  
Ultraviolet Irradiation ◽  
Euglena Gracilis ◽  
Structural Changes ◽  
Ultrastructural Changes ◽  
Electron Microscopic ◽  
Bleaching Process ◽  
In Cells

The structural changes associated with the ultraviolet-induced bleaching of light-grown cells of Euglena gracilis were investigated. Our light- and electron-microscopic observations of the bleaching process indicate that there is a continuity of plastid structure in cells 5 generations after receiving a bleaching dose of ultraviolet light. There seems to be a continuous dilution of the plastid thylakoids and a decrease in plastid size in the bleaching cells. There also seems to be a change in the position of the plastids in relation to the mitochondria in the bleaching cells. The plastids and possibly the mitochondria are the only organelles which are affected by the ultraviolet irradiation. The continuity of plastids in bleaching cells of Euglena is discussed in relation to the proposed effect of the ultraviolet light.

Electron Microscopic Study of Penetration of Newcastle Disease Virus into Cells Leading to Formation of Polykaryocytes

1967 ◽  
Vol 2 (1) ◽  
pp. 71-76
Author(s):  
N. MEISELMAN ◽  
A. KOHN ◽  
D. DANON
Keyword(s):  
Epithelial Cells ◽  
Cell Membrane ◽  
Newcastle Disease Virus ◽  
Microscopic Study ◽  
Disease Virus ◽  
Newcastle Disease ◽  
Cell Membranes ◽  
Viral Envelope ◽  
Electron Microscopic ◽  
Input Multiplicity

Treatment of FL or Lu 106 epithelial cells with Newcastle disease virus (NDV) at an input multiplicity of 500 EID50 per cell induces in these cells the formation of polykaryocytes at the end of 2-3 h of contact. Electron micrographs of such NDV-treated monolayers after 2-10 min of incubation show the presence of virions adsorbed to the cell membranes, in vacuoles and with the viral envelope partly fused with the cell membrane. In polykaryocytes induced by NDV, remnants of cell membranes showing numerous breaks may still be present after 3 h.

A scale associated protein of Apedinella radians (Pedinellophyceae) and its possible role in the adhesion of surface components

1993 ◽  
Vol 104 (2) ◽  
pp. 391-398
Author(s):  
A. Koutoulis ◽  
M. Ludwig ◽  
R. Wetherbee
Keyword(s):  
Monoclonal Antibody ◽  
Monoclonal Antibodies ◽  
Cell Membrane ◽  
Cell Surface ◽  
Immunofluorescence Microscopy ◽  
Endomembrane System ◽  
Thin Sections ◽  
Specific Location ◽  
Whole Cells

Monoclonal antibodies have been generated against cell surface components of the unicellular phytoflagellate Apedinella radians (Pedinellophyceae). One monoclonal antibody, designated Arg 1E5/1B1, labels a scale associated protein (SAP) of 145 kDa. Immunofluorescence microscopy of whole cells as well as immunoelectron microscopy of whole cell mounts and thin sections using Arg 1E5/1B1 have shown that the SAP is located on the proximal surface of body scales and spine-scales. Its specific location suggests that the SAP may play a role in the adhesion of these surface components to the cell membrane and/or to one another. The potential of monoclonal antibody Arg 1E5/1B1 as a tool to study cell surface morphogenesis and the role of the endomembrane system in A. radians is discussed.

beta-Carotene is Accumulated, Metabolized, and Possibly Converted to Retinol in Human Breast Carcinoma Cells (MCF-7)

2004 ◽  
Vol 74 (3) ◽  
pp. 171-177 ◽  
Author(s):  
Torres ◽  
Borojevic ◽  
Trugo
Keyword(s):  
Breast Carcinoma ◽  
Beta Carotene ◽  
Human Breast Carcinoma ◽  
Breast Carcinoma Cell Line ◽  
Human Breast ◽  
Cell Extracts ◽  
Human Breast Carcinoma Cells ◽  
Dose Dependent ◽  
Mcf 7 ◽  
In Cells

The aims of the present study were to investigate the uptake, accumulation, and metabolism of beta-carotene by the human breast carcinoma cell line MCF-7. Beta-carotene uptake was time- and dose-dependent, and independent of cell polarity. Beta-carotene accumulation in cells was linear as a function of its concentration in medium (1.3–4.1 mumol/L). It was accompanied by increasing amounts of retinol, which accumulated in cells following a sigmoid pattern, and by other four putative metabolites. Beta-apocarotenals, epoxides, endoperoxides, retinal, retinoic acid, and retinyl esters were not detected in cell extracts. Beta-carotene and its metabolites did not induce alterations in cell morphology or subcellular localization of epithelial mucins. Beta-carotene and retinol were released from cells that had previously accumulated beta-carotene, and were further incubated in beta-carotene- and retinol-free medium, but intracellular retinol content remained constant whereas b-carotene decreased. In conclusion, beta-carotene added to culture medium in physiological concentrations (1–6 mumol/L) is taken up and metabolized in MCF-7 cells, and is possibly converted to retinol.

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