scholarly journals CHLOROPLAST STRUCTURE AND FUNCTION IN ac-20, A MUTANT STRAIN OF CHLAMYDOMONAS REINHARDI

1970 ◽  
Vol 44 (3) ◽  
pp. 531-539 ◽  
Author(s):  
R. K. Togasaki ◽  
R. P. Levine
Keyword(s):  
Mutant Strain ◽  
Sodium Acetate ◽  
Co2 Fixation ◽  
Structure And Function ◽  
Pentose Phosphate ◽  
Carboxylase Activity ◽  
Whole Cells ◽  
Photosynthetic Carbon ◽  
Photosynthetic Carbon Metabolism ◽  
And Function

A mutant strain of the green alga Chlamydomonas reinhardi, ac-20, is described in which both the rate of CO2 fixation by whole cells and the rate of carboxylation of ribulose-1,5-diphosphate in cell-free extracts are reduced, particularly when sodium acetate is present in the growth medium. Of the enzymes of the reductive pentose phosphate cycle tested, only ribulose-1,5-diphosphate carboxylase activity is reduced in the mutant strain, and it appears that the low carboxylase activity limits the strain's rate of photosynthetic carbon metabolism. Evidence is presented to show that the fluctuation in the level of the enzyme activity in the presence or absence of acetate results from the fluctuation in the level of some factor(s) limiting the rate of synthesis of the protein.

scholarly journals CHLOROPLAST STRUCTURE AND FUNCTION IN ac-20, A MUTANT STRAIN OF CHLAMYDOMONAS REINHARDI

1970 ◽  
Vol 44 (3) ◽  
pp. 540-546 ◽  
Author(s):  
R. P. Levine ◽  
A. Paszewski
Keyword(s):  
Electron Transport ◽  
Mutant Strain ◽  
Electron Transport Chain ◽  
Co2 Fixation ◽  
Photosynthetic Electron Transport ◽  
Structure And Function ◽  
Wild Type ◽  
Carboxylase Activity ◽  
Transport Chain ◽  
And Function

Photosynthetic electron transport is markedly affected in mixotrophic cells of ac-20 because they lack the capacity to form the wild-type level of cytochrome 559, as well as Q, the quencher of fluorescence of photochemical system II. The other components of the electron-transport chain, as well as reactions dependent upon photochemical system I, are unaffected in the mutant strain. These observations are discussed in terms of the previously reported effects of the ac-20 mutation on CO2 fixation and ribulose-1,5-diphosphate carboxylase activity.

The effects of nitrate, nitrite, and ammonia on photosynthetic carbon metabolism of Acetabularia chloroplast preparations compared with spinach chloroplasts and whole cells of Acetabularia and Dunaliella

1972 ◽  
Vol 50 (12) ◽  
pp. 2545-2551 ◽  
Author(s):  
F. Winkenbach ◽  
B. R. Grant ◽  
R. G. S. Bidwell
Keyword(s):  
Amino Acids ◽  
Carbon Metabolism ◽  
Membrane Structure ◽  
Ammonium Ions ◽  
Whole Cells ◽  
Spinach Chloroplasts ◽  
Photosynthetic Carbon ◽  
Photosynthetic Carbon Metabolism ◽  
Photosynthetic Products ◽  
Acetabularia Mediterranea

Nitrogen was supplied in the form of nitrate, nitrite, or ammonium ions to whole cells of Dunaliella tertiolecta, to whole cells and chloroplast preparations of Acetabularia mediterranea, and to spinach chloroplasts, while they were photosynthesizing in 14CO2. The 14C labeling patterns in these experiments provide information on several aspects of the photosynthesis, nitrogen metabolism, and physical properties of these systems. The rates and products of photosynthesis are affected in different ways by different ions, depending on the penetration of each ion, its toxicity, and on the ability of the system under test to synthesize amino acids. Thus the ions that penetrate spinach chloroplasts, while they may inhibit photosynthesis, do not affect the distribution of 14C among photosynthetic products because no amino acids are formed. The large differences in behavior between Acetabularia whole cells and chloroplast preparations from these cells suggest that the membrane structure surrounding cytoplasmic droplets in the latter may be tonoplast rather than plasmalemma in origin.

scholarly journals CHLOROPLAST STRUCTURE AND FUNCTION IN ac-20, A MUTANT STRAIN OF CHLAMYDOMONAS REINHARDI

1970 ◽  
Vol 44 (3) ◽  
pp. 547-562 ◽  
Author(s):  
Ursula W. Goodenough ◽  
R. P. Levine
Keyword(s):  
Mutant Strain ◽  
Minimal Medium ◽  
Structure And Function ◽  
Membrane Organization ◽  
Chloroplast Structure ◽  
Wild Type ◽  
Fold Reduction ◽  
Membrane Reorganization ◽  
And Function ◽  
Photosynthetic Properties

The fine structure of the ac-20 strain of Chlamydomonas reinhardi is described. Cells grown mixotrophically in the presence of acetate have a highly disordered chloroplast membrane organization and usually lack pyrenoids. Chloroplast ribosome levels are only 5–10% of wild-type levels. Cells grown phototrophically without acetate possess more chloroplast ribosomes and have more normal membrane and pyrenoid organization. Chloroplast ribosome levels rise rapidly when cells are transferred from acetate to minimal medium, whereas membrane reorganization occurs only after a lag. These results, combined with earlier studies of the photosynthetic properties of the mutant strain, suggest that proper membrane organization, Photosystem II activity, and ribulose-1,5-diphosphate carboxylase formation are dependent on the presence of chloroplast ribosomes. Other chloroplast components tested are unaffected by a 10-fold reduction in levels of chloroplast ribosomes.

Disruption of Dictyostelium PI3K genes reduces [32P]phosphatidylinositol 3,4 bisphosphate and [32P]phosphatidylinositol trisphosphate levels, alters F-actin distribution and impairs pinocytosis

1998 ◽  
Vol 111 (2) ◽  
pp. 283-294 ◽  
Author(s):  
K. Zhou ◽  
S. Pandol ◽  
G. Bokoch ◽  
A.E. Traynor-Kaplan
Keyword(s):  
Cell Motility ◽  
Mutant Strain ◽  
Actin Filaments ◽  
Cell Structure ◽  
Structure And Function ◽  
Phosphatidylinositol 3 Kinase ◽  
And Function ◽  
Phosphatidylinositol 3

To understand how phosphatidylinositol 3-kinase (PI3K) modulates cell structure and function, we examined the molecular and cellular defects of a Dictyostelium mutant strain (pik1(Delta)2(Delta)) missing two (DdPIK1 and 2) of three PI3K genes, which are homologues of the mammalian p110 subunit. Levels of [32P]phosphatidylinositol 3, 4 bisphosphate (PI(3,4)P2) and [32P]phosphatidylinositol trisphosphate (PIP3) were reduced in pik1(Delta)2(Delta), which had major defects in morphological and functional correlates of macropinocytosis. This was accompanied by dramatic deficits in a subset of F-actin-enriched structures such as circular ruffles, actin crowns and pseudopodia. Although pik1(Delta)2(Delta) were mobile, they failed to aggregate into streams. Therefore we conclude that PIK1 and 2, possibly through modulation of the levels of PIP3 and PI(3,4)P2, regulate the organization of actin filaments necessary for circular ruffling during macropinocytosis, the extension of pseudopodia and the aggregation of cells into streams, but not the regulation of cell motility.

Biological Products: Molecular Structure and Function

2021 ◽  
pp. 130-157
Keyword(s):  
Mammalian Cells ◽  
Living Cells ◽  
Structure And Function ◽  
Peptide Bonds ◽  
Biological Products ◽  
Whole Cells ◽  
Drug Products ◽  
Small Molecule Drugs ◽  
And Function ◽  
Molecular Structure And Function

This chapter analyses biological products that are defined by the method of manufacture and distinguished by a production process that separates biological drug products from orthodox, ‘small molecule’ drugs. It explains how biological products are synthesised by a variety of living cells, such as bacteria, fungi, or mammalian cells. It also refers to the types of modern biological therapies that range among proteins, nucleic acids, and whole cells. The chapter discusses monoclonal antibodies, which is considered the largest class of biological products in clinical use and are designed to attach to diseased cells, like cancer cells, that are expressing abnormal proteins on their surface. It describes proteins as chains of amino acids linked to each other chemically by peptide bonds, hence the alternative term ‘polypeptides’.

Structure and function of neural networks in the retina

1988 ◽  
Vol 46 ◽  
pp. 26-27
Author(s):  
Peter Sterling
Keyword(s):  
Ganglion Cells ◽  
Three Dimensional ◽  
Structure And Function ◽  
Synaptic Connections ◽  
Visual Axis ◽  
One Dimensional ◽  
Cat Retina ◽  
Ultrathin Sections ◽  
And Function ◽  
Insight Into

The synaptic connections in cat retina that link photoreceptors to ganglion cells have been analyzed quantitatively. Our approach has been to prepare serial, ultrathin sections and photograph en montage at low magnification (˜2000X) in the electron microscope. Six series, 100-300 sections long, have been prepared over the last decade. They derive from different cats but always from the same region of retina, about one degree from the center of the visual axis. The material has been analyzed by reconstructing adjacent neurons in each array and then identifying systematically the synaptic connections between arrays. Most reconstructions were done manually by tracing the outlines of processes in successive sections onto acetate sheets aligned on a cartoonist's jig. The tracings were then digitized, stacked by computer, and printed with the hidden lines removed. The results have provided rather than the usual one-dimensional account of pathways, a three-dimensional account of circuits. From this has emerged insight into the functional architecture.

Osseointegration interface of calcified bone and endosseous implants

1992 ◽  
Vol 50 (2) ◽  
pp. 1096-1097
Author(s):  
K.E. Krizan ◽  
J.E. Laffoon ◽  
M.J. Buckley
Keyword(s):  
Structure And Function ◽  
Titanium Implants ◽  
En Bloc ◽  
Endosseous Implants ◽  
Ultrastructural Studies ◽  
The Past ◽  
Cacodylate Buffer ◽  
One Year ◽  
And Function

With increase use of tissue-integrated prostheses in recent years it is a goal to understand what is happening at the interface between haversion bone and bulk metal. This study uses electron microscopy (EM) techniques to establish parameters for osseointegration (structure and function between bone and nonload-carrying implants) in an animal model. In the past the interface has been evaluated extensively with light microscopy methods. Today researchers are using the EM for ultrastructural studies of the bone tissue and implant responses to an in vivo environment. Under general anesthesia nine adult mongrel dogs received three Brånemark (Nobelpharma) 3.75 × 7 mm titanium implants surgical placed in their left zygomatic arch. After a one year healing period the animals were injected with a routine bone marker (oxytetracycline), euthanized and perfused via aortic cannulation with 3% glutaraldehyde in 0.1M cacodylate buffer pH 7.2. Implants were retrieved en bloc, harvest radiographs made (Fig. 1), and routinely embedded in plastic. Tissue and implants were cut into 300 micron thick wafers, longitudinally to the implant with an Isomet saw and diamond wafering blade [Beuhler] until the center of the implant was reached.

Use of human autoantibodies and immunoelectron microscopy to study structure and function of the nucleolus and nuclear bodies

1992 ◽  
Vol 50 (1) ◽  
pp. 506-507
Author(s):  
Robert L. Ochs
Keyword(s):  
Electron Microscopy ◽  
Structure And Function ◽  
Nuclear Bodies ◽  
Nuclear Interior ◽  
Coiled Bodies ◽  
Interchromatin Granules ◽  
And Function ◽  
Conventional Electron Microscopy ◽  
Perichromatin Granules ◽  
Perichromatin Fibrils

By conventional electron microscopy, the formed elements of the nuclear interior include the nucleolus, chromatin, interchromatin granules, perichromatin granules, perichromatin fibrils, and various types of nuclear bodies (Figs. 1a-c). Of these structures, all have been reasonably well characterized structurally and functionally except for nuclear bodies. The most common types of nuclear bodies are simple nuclear bodies and coiled bodies (Figs. 1a,c). Since nuclear bodies are small in size (0.2-1.0 μm in diameter) and infrequent in number, they are often overlooked or simply not observed in any random thin section. The rat liver hepatocyte in Fig. 1b is a case in point. Historically, nuclear bodies are more prominent in hyperactive cells, they often occur in proximity to nucleoli (Fig. 1c), and sometimes they are observed to “bud off” from the nucleolar surface.

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