Effects of Amino Acid Medium on Cell Aggregation in Suspension-cultured Rice Cells

1994 ◽  
Vol 58 (2) ◽  
pp. 256-260 ◽  
Author(s):  
Takahisa Hayashi ◽  
Chieko Ohsumi ◽  
Yoji Kato ◽  
Hiroaki Yamanouchi ◽  
Kinya Toriyama ◽  
...  
Keyword(s):  
Amino Acid ◽  
Acid Medium ◽  
Cell Aggregation

A Study of Substituent Effect on the Oxidative Strengths of N-Chloroarenesulphonamides: Kinetics of Oxidation of Leucine and Isoleucine in Aqueous Acid Medium

2004 ◽  
Vol 59 (1) ◽  
pp. 63-72 ◽  
Author(s):  
Mahesha Shetty ◽  
B. Thimme Gowda
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Ionic Strength ◽  
Acid Medium ◽  
Benzene Ring ◽  
Thermodynamic Data ◽  
Substituent Effect ◽  
Kinetics Of Oxidation ◽  
Aqueous Acid ◽  
Kinetics Of

Abstract To study the variation of oxidative strengths of N-chloro-arenesulphonamides with substitution in the benzene ring, six mono- and five di-substituted N-chloro-arenesulphonamides are employed as oxidants for studying the kinetics of oxidation of two neutral amino acids, L-leucine and Lisoleucine in aqueous acid medium. The N-chloro-arenesulphonamides studied are of the constitution: ArSO2NaNCl·H2O (where Ar = C6H5, 4-CH3C6H4, 4-C2H5C6H4, 4-FC6H4, 4-ClC6H4, 4-BrC6H4, 2,3-(CH3)2C6H3, 2,4-(CH3)2C6H3, 2-CH3-4-ClC6H3, 2,4-Cl2C6H3, and 3,4-Cl2C6H3). The reactions show second order kinetics in [oxidant], fractional order in [amino acid] and inverse dependence on [H+]. Addition of the reduced product of the oxidants or variation in ionic strength of the medium has no significant effect on the rates of oxidations. A two-pathway mechanism is considered to explain the experimental results. Effective oxidizing species of the oxidants is Cl+ in different forms. Therefore the oxidising strengths of N-chloro-arenesulphonamides depend on the ease with which Cl+ is released from them. The study reveals that the introduction of substituent in the benzene ring of the oxidant affects both the kinetic and thermodynamic data for the oxidations The electron releasing groups such as CH3 generally inhibit the rates, while electron-withdrawing groups such as Cl enhance this ability, as the electron withdrawing groups ease the release of Cl+ from the reagents and hence increase the oxidising strengths. The on Ea and logA and validity of the Hammett and isokinetic relationships for the oxidations are also analysed.

Formation of abnormal mycelium ofFusarium roseum link. on a modified Czapek-d-amino acid medium

1968 ◽  
Vol 24 (4) ◽  
pp. 403-404 ◽  
Author(s):  
H. Egawa ◽  
M. Tsuda ◽  
A. Ueyama ◽  
T. Matuo
Keyword(s):  
Amino Acid ◽  
Acid Medium

scholarly journals Identical, Independent, and Opposing Roles of ppGpp and DksA in Escherichia coli

2007 ◽  
Vol 189 (14) ◽  
pp. 5193-5202 ◽  
Author(s):  
Lisa U. Magnusson ◽  
Bertil Gummesson ◽  
Predrag Joksimović ◽  
Anne Farewell ◽  
Thomas Nyström
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Amino Acid ◽  
Stationary Phase ◽  
Cell Aggregation ◽  
Phase Morphology ◽  
Deficient Mutant ◽  
Similarities And Differences ◽  
Opposing Effects ◽  
Cell Cell

ABSTRACT The recent discovery that the protein DksA acts as a coregulator of genes controlled by ppGpp led us to investigate the similarities and differences between the relaxed phenotype of a ppGpp-deficient mutant and the phenotype of a strain lacking DksA. We demonstrate that the absence of DksA and ppGpp has similar effects on many of the observed phenotypes but that DksA and ppGpp also have independent and sometimes opposing roles in the cell. Specifically, we show that overexpression of DksA can compensate for the loss of ppGpp with respect to transcription of the promoters P uspA , P livJ , and P rrnBP1 as well as amino acid auxotrophy, cell-cell aggregation, motility, filamentation, and stationary phase morphology, suggesting that DksA can function without ppGpp in regulating gene expression. In addition, ppGpp and DksA have opposing effects on adhesion. In the course of our analysis, we also discovered new features of the relaxed mutant, namely, defects in cell-cell aggregation and motility.

Efficient callus initiation from leaf of mangrove plant,Bruguiera sexangula in amino acid medium: Effect of NaCl on callus initiation

1997 ◽  
Vol 110 (1) ◽  
pp. 25-29 ◽  
Author(s):  
Tetsuro Mimura ◽  
Mari Mimura ◽  
Setsuko Washitani-Nemoto ◽  
Katsuhiro Sakano ◽  
Teruo Shimmen ◽  
...  
Keyword(s):  
Amino Acid ◽  
Acid Medium ◽  
Medium Effect ◽  
Mangrove Plant ◽  
Callus Initiation

An investigation of the nature of certain adaptive changes in bacteria

1950 ◽  
Vol 136 (885) ◽  
pp. 562-576 ◽  
Keyword(s):  
Amino Acid ◽  
Acid Medium ◽  
Ammonium Sulphate ◽  
Sodium Citrate ◽  
Nitrogen Sources ◽  
Lag Phase ◽  
Test Medium ◽  
Liquid Media ◽  
Adaptive Changes ◽  
Solid Media

Four strains of bacteria which, until trained, show a long lag before they will utilize certain new carbon or nitrogen sources, have been examined by methods involving the transfer of inocula at widely varying dilutions to liquid or solid media containing the new substrate. The strains and sources studied are ( a ) Bact. lactis aerogenes and D-arabinose, ( b ) Bact. coli mutabile and lactose , ( c ) Bact. coli and ammonium sulphate, ( d ) a coli-aerogenes intermediate and sodium citrate. With ( a ) and ( b ) in solid and liquid media and ( d ) in liquid media all or most of the dilutions which are viable in a glucose-amino-acid medium (which supports growth without lag) also show growth, though after considerable delay, in the new medium. With ( c ) the proportion of cells which grow is small and, even for parallel inocula, very sensitive to minute changes in the test medium. But in general the reason why many cells fail to grow is found to be that they have died before they have traversed the lag phase which necessarily precedes their development. The bearing of these observations on theories of mutation and adaptation is considered.

The mechanism of the oxidative deamination and decarboxylation of serine and threonine by periodate in acid medium

1985 ◽  
Vol 63 (9) ◽  
pp. 2349-2353 ◽  
Author(s):  
Rosa Pascual ◽  
Miguel A. Herráez
Keyword(s):  
Amino Acid ◽  
Acid Medium ◽  
Rate Constants ◽  
Reaction Rate ◽  
Oxidative Deamination ◽  
Experimental Conditions ◽  
Kinetics Of Oxidation ◽  
Rate Law ◽  
First Order ◽  
Kinetics Of

The kinetics of oxidation of serine and threonine by periodate have been investigated in acid medium at 10 °C. The reaction rate is first order in both periodate and amino acid, and the overall reaction follows second-order kinetics. The rates decrease with increase in [H+]. A catalytic effect of the buffers was not observed in the oxidation process. An analysis of the dependence of the rate on [H+] reveals that the reactive species under the experimental conditions are periodate monoanion and dianion and the dipolar form of the amino acid. The mechanism proposed and the derived rate law are consistent with the observed kinetics. The rate constants predicted using the derived rate law are in agreement with the observed rate constants, thus justifying this rate law and hence the proposed mechanistic scheme.

The influence of larval crowding on the development time of populations of Drosophila melanogaster on chemically defined medium

1968 ◽  
Vol 46 (3) ◽  
pp. 493-497 ◽  
Author(s):  
Barrie Cohen
Keyword(s):  
Drosophila Melanogaster ◽  
Amino Acid ◽  
Acid Medium ◽  
Initial Density ◽  
Defined Medium ◽  
Chemically Defined Medium ◽  
Complex Situation ◽  
Insect Populations ◽  
Larval Crowding ◽  
New Formula

Work with Drosophila melanogaster, cultured on chemically defined amino acid medium, showed that at extreme larval densities the average time to pupation and eclosion of the survivors of the insect population is a decreasing function of the initial density. Evidence is presented which illustrates that at extreme densities larval development rate is significantly increased. Possible causes of this phenomenon are cited. It is stressed, however, that a very complex situation exists and more experimentation, particularly biochemical analysis, will be necessary to arrive at the proper causative factors. A new formula is presented for a chemically defined medium for Drosophila melanogaster, and detailed methods of preparation given. The new formula will support an estimated 200 larvae through complete development to adult flies on 5 ml of medium. It is thought that the system utilizing the development of Drosophila melanogaster on chemically defined amino acid medium is a fundamental one for the experimental analysis of developing insect populations.

scholarly journals Tyrosine Residue in Exon 14 of the Cytoplasmic Domain of Platelet Endothelial Cell Adhesion Molecule-1 (PECAM-1/CD31) Regulates Ligand Binding Specificity

1997 ◽  
Vol 138 (6) ◽  
pp. 1425-1435 ◽  
Author(s):  
Julie Famiglietti ◽  
Jing Sun ◽  
Horace M. DeLisser ◽  
Steven M. Albelda
Keyword(s):  
Cell Adhesion ◽  
Endothelial Cell ◽  
Amino Acid ◽  
Tyrosine Phosphorylation ◽  
Adhesion Molecule ◽  
Cell Adhesion Molecule ◽  
Cell Aggregation ◽  
Ligand Specificity ◽  
Platelet Endothelial Cell Adhesion ◽  
Endothelial Cell Adhesion

Platelet/endothelial cell adhesion molecule (PECAM-1) is a cell adhesion molecule of the immunoglobulin superfamily that plays a role in a number of vascular processes including leukocyte transmigration through endothelium. The presence of a specific 19– amino acid exon within the cytoplasmic domain of PECAM-1 regulates the binding specificity of the molecule; specifically, isoforms containing exon 14 mediate heterophilic cell–cell aggregation while those variants missing exon 14 mediate homophilic cell–cell aggregation. To more precisely identify the region of exon 14 responsible for ligand specificity, a series of deletion mutants were created in which smaller regions of exon 14 were removed. After transfection into L cells, they were tested for their ability to mediate aggregation. For heterophilic aggregation to occur, a conserved 5–amino acid region (VYSEI in the murine sequence or VYSEV in the human sequence) in the mid-portion of the exon was required. A final construct, in which this tyrosine was mutated into a phenylalanine, aggregated in a homophilic manner when transfected into L cells. Inhibition of phosphatase activity by exposure of cells expressing wild type or mutant forms of PECAM-1 to sodium orthovanadate resulted in high levels of cytoplasmic tyrosine phosphorylation and led to a switch from heterophilic to homophilic aggregation. Our data thus indicate either loss of this tyrosine from exon 14 or its phosphorylation results in a change in ligand specificity from heterophilic to homophilic binding. Vascular cells could thus determine whether PECAM-1 functions as a heterophilic or homophilic adhesion molecule by processes such as alternative splicing or by regulation of the balance between tyrosine phosphorylation or dephosphorylation. Defining the conditions under which these changes occur will be important in understanding the biology of PECAM-1 in transmigration, angiogenesis, development, and other processes in which this molecule plays a role.

Sign in / Sign up

Export Citation Format

Share Document