The role of magnesium ion in the adenine phosphoribosyltransferase reaction

1970 ◽  
Vol 48 (3) ◽  
pp. 302-307 ◽  
Author(s):  
R. E. A. Gadd ◽  
J. Frank Henderson
Keyword(s):  
Stability Constant ◽  
Initial Velocity ◽  
Adenosine Monophosphate ◽  
Magnesium Ion ◽  
Adenine Phosphoribosyltransferase ◽  
Good Correspondence ◽  
Low Concentrations ◽  
High Concentrations ◽  
The Stability

Low concentrations of magnesium ion stimulate, and high concentrations inhibit, the adenine phosphoribosyltransferase reaction. The stability constant of the Mg–pyrophosphoryl moiety of phosphoribosylpyrophosphate was assumed to be the same as that of Mg–adenosine triphosphate; the stability constant of the Mg–phosphoryl moiety of phosphoribosylpyrophosphate was assumed to be the same as that of Mg–adenosine monophosphate, and the concentration of the monomagnesium complex of phosphoribosylpyrophosphate was calculated as a function of magnesium ion and phosphoribosylpyrophosphate concentrations. The good correspondence between these curves and those of initial velocity under the same conditions suggest that the monomagnesium complex of phosphoribosylpyrophosphate is the true substrate of this reaction.

Aggregation of Cat Platelets in Vitro

1970 ◽  
Vol 23 (03) ◽  
pp. 601-620 ◽  
Author(s):  
Th. B Tschopp
Keyword(s):  
Adenosine Monophosphate ◽  
Blood Collection ◽  
Base Line ◽  
Reversible Aggregation ◽  
Low Concentrations ◽  
Irreversible Aggregation ◽  
High Concentrations ◽  
Two Phases ◽  
Improved Technique

SummaryAggregation of cat platelets in the citrated plasma is examined by means of Born’s absorptiometer. A marked tendency of the platelets of this species to spontaneous aggregation necessitated first of all the development of an improved technique of blood collection.A hypothesis according to which 5-HT is released from the platelets, explains the absence of oscillations on the base line of the absorptiometer, the absence of platelet swelling, when ADP is added, and the effect of stirring on the aggregation curves in cat PRP. The average volume of cat platelets amounts to 10.46 μ3 when directly fixed in the blood, when fixed from PRP to 12.17 μ3, when fixed from stirred PRP to 13.51 μ3.In low concentrations (0.3-2 μM) ADP produce reversible aggregation; in narrowly restricted, individually dissimilar mean concentrations irreversible aggregation in two phases and in high concentrations, irreversible aggregation in one phase. Like ADP serotonin produces 2 phase irreversible aggregation in concentrations of 3-10 μM, but unlike ADP, the aggregation velocity decreases again with high 5-HT concentrations (>100 μM). Adrenaline does not produce aggregation and it is likely that adenosine and adenosine monophosphate inhibit the aggregation by serotonin but not by ADP. Species differences in the aggregation of human, rabbit and cat platelets are discussed.

scholarly journals Colchicine-binding protein of the liver. Its characterization and relation to microtubules.

1975 ◽  
Vol 66 (3) ◽  
pp. 609-620 ◽  
Author(s):  
C Patzelt ◽  
A Singh ◽  
Y L Marchand ◽  
L Orci ◽  
B Jeanrenaud
Keyword(s):  
High Speed ◽  
Specific Binding ◽  
Electrophoretic Analysis ◽  
Binding Activity ◽  
Low Concentrations ◽  
Electrophoretic Behavior ◽  
High Affinity Binding Site ◽  
High Concentrations

Colchicine-binding activity of mouse liver high-speed supernate has been investigated. It has been found to be time and temperature dependent. Two binding activities with different affinities for colchicine seem to be present in this high-speed supernate, of which only the high-affinity binding site (half maximal binding at 5 x 10(-6) M colchicine) can be attributed to microtubular protein by comparison with purified tubulin. Vinblastine interacted with this binding activity by precipitating it when used at high concentrations (2 x 10(-3) M), and by stabilizing it at low concentrations (10(-5) M). Lumicolchicine was found not to compete with colchicine. The colchicine-binding activity was purified from liver and compared with that of microtubular protein from brain. The specific binding activity of the resulting preparation, its electrophoretic behavior, and the electron microscope appearance of the paracrystals obtained upon its precipitation with vinblastine permitted its identification as microtubular protein (tubulin). Electrophoretic analysis of the proteins from liver supernate that were precipitated by vinblastine indicated that this drug was not specific for liver tubulin. Preincubation of liver supernate with 5 mM EGTA resulted in a time-dependent decrease of colchicine-binding activity, which was partly reversed by the addition of Ca++. However, an in vitro formation of microtubules upon lowering the Ca++ concentration could not be detected. Finally, a method was developed enabling that portion of microtubular protein which was present as free tubulin to be measured and to be compared with the total amount of this protein in the tissue. This procedure permitted demonstration of the fact that, under normal conditions, only about 40% of the tubulin of the liver was assemled as microtubules. It is suggested that, in the liver, rapid polymerization and depolymerization of microtubules occur and may be an important facet of the functional role of the microtubular system.

scholarly journals Antibacterial Peptides Resistance in Staphylococcus aureus: Various Mechanisms and the Association with Pathogenicity

Genes ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1527
Author(s):  
Miki Kawada-Matsuo ◽  
Mi Nguyen-Tra Le ◽  
Hitoshi Komatsuzawa
Keyword(s):  
Staphylococcus Aureus ◽  
Antimicrobial Peptides ◽  
Antibacterial Peptides ◽  
Low Concentrations ◽  
Component Systems ◽  
Two Component Systems ◽  
Resistant Strains ◽  
Resistant Mutants ◽  
High Concentrations

Staphylococcus aureus is a bacterium that mainly colonizes the nasal cavity and skin. To colonize the host, it is necessary for S. aureus to resist many antibacterial factors derived from human and commensal bacteria. Among them are the bacteria-derived antimicrobial peptides (AMPs) called bacteriocins. It was reported that some two-component systems (TCSs), which are signal transduction systems specific to bacteria, are involved in the resistance to several bacteriocins in S. aureus. However, the TCS-mediated resistance is limited to relatively low concentrations of bacteriocins, while high concentrations of bacteriocins still exhibit antibacterial activity against S. aureus. To determine whether we could obtain highly bacteriocin-resistant mutants, we tried to isolate highly nisin A-resistant mutants by exposing the cells to sub-minimum inhibitory concentrations (MICs) of nisin A. Nisin A is one of the bacteriocins produced by Lactococcus lactis and is utilized as a food preservative worldwide. Finally, we obtained highly nisin A-resistant mutants with mutations in one TCS, BraRS, and in PmtR, which is involved in the expression of pmtABCD. Notably, some highly resistant strains also showed increased pathogenicity. Based on our findings, this review provides up-to-date information on the role of TCSs in the susceptibility to antibacterial peptides. Additionally, the mechanism for high antimicrobial peptides resistance and its association with pathogenicity in S. aureus is elucidated.

Role of cell replication in regulation of Na-coupled hexose transport in LLC-PK1 epithelial cells

1986 ◽  
Vol 250 (2) ◽  
pp. C314-C318 ◽  
Author(s):  
A. Moran ◽  
J. S. Handler ◽  
M. Hagan
Keyword(s):  
Epithelial Cells ◽  
Ionizing Radiation ◽  
Thymidine Incorporation ◽  
Regulatory Process ◽  
Hexose Transport ◽  
Cell Replication ◽  
Response Data ◽  
Low Concentrations ◽  
High Concentrations

The glucose concentration in growth medium has been shown to regulate the number of sodium-coupled glucose transporters in LLC-PK1 epithelial cells. Epithelia grown in high concentrations of glucose express fewer transporters than epithelia grown in low concentrations of glucose. In the present work, the effect of a dose of ionizing radiation sufficient to block the incorporation of thymidine was examined in order to gauge the importance of cell replication in the hexose transport regulatory process. The low rate of thymidine incorporation in the plateau phase was completely eliminated by ionizing radiation. Under conditions of irradiation that completely blocked thymidine incorporation, down-regulation, namely the loss of alpha-methylglucoside-concentrating capacity, brought about by switching the epithelium from low to high glucose-containing medium, is independent of the irradiation and therefore most likely is also independent of cell replication. In contrast, the up-regulatory phenomenon is strongly impaired by radiation. This impairment may be due to specific radiation impairment of gene expression necessary for the up-regulatory process. It is apparent from the dose-response data that up-regulation is not inhibited by irradiation in a simple manner and is not inhibited at the same radiation dose as cell replication.

H+ current response to CO2 and carbonic anhydrase inhibition in turtle bladder

1976 ◽  
Vol 231 (2) ◽  
pp. 565-572 ◽  
Author(s):  
JH Schwartz
Keyword(s):  
Carbonic Anhydrase ◽  
Maximum Rate ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Current Response ◽  
Low Concentrations ◽  
Ph Stat ◽  
High Concentrations ◽  
Co2 Addition

To evaluate the role of CO2 and carbonic anhydrase (CA) in H+ transport (JH) by turtle urinary bladder the effect of CO2 addition, with and without addition of CA inhibitiors, was examined on JH. Since in the presence of exogenous CO2 and HCO3- the pH stat-measured rate of mucosal (M) acidification underestimates JH by the rate of electroneutral HCO3- secretion, the reverse short-circuit current (RSCC) applied across ouabain-treated bladders was used to estimate JH. That the RSCC is a measure of JH was demonstrated by: 1) in the absence of added CO2 and HCO3- the rate of M acidification totally accounted for the RSCC, and 2) increases in RSCC with CO2 addition occurred without changes in Na+ and K+ fluxes or the coupled ration of HCO3- secretion for Cl-absorption. When serosal (S) percent CO2 was progressively progressively increased JH achieved a maximum rate of 64 +/- 3 muA (SE) with 4.5% CO2. At higher S percent CO2 JH did not change, suggesting that factors other than the rate of CO2 hydration were rate limiting. The maximum rate of JH was not decreased by low concentrations of CA inhibitors (acetazolamide, 5 X 10(-5) M), although the percent CO2 at which this maximum rate occurred increased to 8.5%. The increased percent CO2 requirement for the maximum rate of JH with low concentrations of CA inhibitors suggests that these agents alter JH by decreasing the rate of enzymatic CO2 hydration. At high concentrations (acetazolamide, 5 X 10(-4) M) these inhibitors decrease the maximum rate of JH in the presence of CO2, implying that these inhibitors at higher concentrations directly interfere with the H+ transport system.

THE EFFECT OF ANGIOTENSIN ON RAT INTESTINAL FLUID TRANSFER

1970 ◽  
Vol 48 (1) ◽  
pp. 39-NP ◽  
Author(s):  
N. T. DAVIES ◽  
K. A. MUNDAY ◽  
B. J. PARSONS
Keyword(s):  
Fluid Transport ◽  
Direct Action ◽  
Rat Jejunum ◽  
Intestinal Fluid ◽  
Low Concentrations ◽  
Fluid Transfer ◽  
High Concentrations ◽  
Dose Dependent ◽  
Everted Sacs

SUMMARY Fluid transfer by isolated everted sacs of rat jejunum, ileum and intact colon prepared from adrenalectomized-nephrectomized rats 48 h after operation was reduced when compared with that of sacs prepared from untreated controls (P < 0·001). Angiotensin at 10−10 g/ml significantly (P < 0·01) stimulated fluid transfer by intestinal sacs prepared from the adrenalectomized-nephrectomized rats; all three regions of gut were equally sensitive. Fluid transfer was similarly reduced in stripped colon sacs prepared from adrenalectomized-nephrectomized rats. Angiotensin had a dose-dependent biphasic action on fluid transfer by stripped colon sacs: low concentrations (10−11 and 10−12 g/ml) stimulated (P < 0·05), whilst high concentrations (10−9 and 10−8 g/ml) inhibited fluid transfer (P < 0·01). Histological examination of the colon preparations showed that the stripping procedure removed the ganglia, indicating that both angiotensin effects were due to direct action on the colon mucosa. The significance of these results is discussed in relation to the role of angiotensin in the control of salt and fluid transport by the mammalian kidney and other epithelial tissues.

The Effects of Selenium on Toxicity of Copper on Rape

2012 ◽  
Vol 610-613 ◽  
pp. 288-291 ◽  
Author(s):  
Chun Yan Chao ◽  
Deng Jun Ma
Keyword(s):  
Metallic Copper ◽  
Experimental Treatment ◽  
Experimental Simulation ◽  
Copper Accumulation ◽  
Sewage Irrigation ◽  
Low Concentrations ◽  
The Law ◽  
High Concentrations ◽  
Soil Accumulation

To research the effect of how Se alleviate the harm brought by copper, we investigated the root length, stem, leaves, aberration by Cu colza in copper and Se-Cu compounds. The experimental simulation of sewage irrigation methods, the general consumption of rapeseed selected as experimental material, using the method of comparison, were dealing with a single copper, different concentrations selenium and copper concentrations were compared with experimental treatment. The Experiments were divided into three groups of treatment, respectively with a single copper, low concentrations selenium and copper and high concentrations of selenium and copper processing of rape. The focus is research the effect of selenium on the toxicity of copper. The result shows that the law of heavy metals like copper accumulation in the soil as well as in the migration and accumulation in rape and the law of metallic copper in the role of selenium in the soil accumulation as well as in the migration and accumulation in rape. The copper in the soil and rape are determinated by AAS. The results show that Selenium effectively alleviate the toxicity of copper on rape, and the ability of ease is high concentrations of selenium intensity than low concentrations of selenium.

scholarly journals Detection of acyl-CoA-binding protein in human red blood cells and investigation of its role in membrane phospholipid renewal

1995 ◽  
Vol 306 (3) ◽  
pp. 793-799 ◽  
Author(s):  
H Fyrst ◽  
J Knudsen ◽  
M A Schott ◽  
B H Lubin ◽  
F A Kuypers
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Human Liver ◽  
Plasma Membranes ◽  
Binding Protein ◽  
Human Red Blood Cells ◽  
Low Concentrations ◽  
Membrane Bound ◽  
High Concentrations

Acyl-CoA-binding protein (ACBP) has been identified in a number of tissues and shown to affect the intracellular distribution and utilization of acyl-CoA. We have detected ACBP in the cytosol but not the membrane of human red blood cells and, using an e.l.i.s.a. with antibodies prepared against human liver ACBP, found that its concentration was 0.5 microM. To investigate the role of ACBP in human red blood cells, we added purified human liver ACBP and radiolabelled acyl-CoA to isolated membranes from these cells. ACBP prevented high concentrations of acyl-CoA from binding to the membrane but could not keep the acyl-CoA in the aqueous phase at low concentrations. This suggested the presence of a pool in the membrane with a binding affinity for acyl-CoA that was greater than that of ACBP for acyl-CoA. In the presence of lysophospholipid, this membrane-bound pool of acyl-CoA was rapidly used as a substrate by acyl-CoA:lysophospholipid acyltransferase (LAT) to generate phospholipid from lysophospholipid. We also found that ACBP-bound acyl-CoA was preferred over free acyl-CoA as a substrate by LAT. These results are the first documentation that human red blood cells contain ACBP and that this protein can affect the utilization of acyl-CoA in plasma membranes of these cells. The interactions between acyl-CoA, ACBP and the membrane suggest that there are several pools of acyl-CoA in the human red blood cell and that ACBP may have a role in regulating their distribution and fate.

Transport and exchange diffusion of l-tryptophan in Ehrlich cells

1961 ◽  
Vol 200 (5) ◽  
pp. 1063-1068 ◽  
Author(s):  
John A. Jacquez
Keyword(s):  
Amino Acid ◽  
Initial Velocity ◽  
The Other ◽  
Preliminary Loading ◽  
Exchange Diffusion ◽  
Diaminobutyric Acid ◽  
Low Concentrations ◽  
Ehrlich Ascites ◽  
Ehrlich Ascites Cells ◽  
High Concentrations

The initial velocity of uptake of l-tryptophan by Ehrlich ascites cells can be explained as the sum of two processes: diffusion and an active transport that shows a saturation effect. Azaserine, l-2,4 diaminobutyric acid, l-histidine, and l-leucine, at low concentrations, increase the initial velocity of uptake of l-tryptophan but compete with l-tryptophan at high concentrations. Preliminary loading of the cells with glycine decreases the initial tryptophan flux: preliminary loading of the ascites cells with azaserine or tryptophan markedly increases the initial flux of uptake of the other amino acid.

Expression of tenascin mRNA in mesoderm during Xenopus laevis embryogenesis: the potential role of mesoderm patterning in tenascin regionalization

Development ◽  
1992 ◽  
Vol 116 (1) ◽  
pp. 147-157
Author(s):  
M. Umbhauer ◽  
J.F. Riou ◽  
J. Spring ◽  
J.C. Smith ◽  
J.C. Boucaut
Keyword(s):  
Cdna Probe ◽  
Pcr Amplification ◽  
Lateral Plate ◽  
Complex Process ◽  
Low Concentrations ◽  
Tailbud Stage ◽  
Series Of Experiments ◽  
High Concentrations ◽  
Restricted Pattern

In Xenopus embryos, the extracellular matrix (ECM) protein tenascin (TN) is expressed dorsally in a very restricted pattern. We have studied the spatial and temporal expression of TN mRNA in tailbud-stage embryos by RNAase protection and in situ hybridization using a cDNA probe for Xenopus TN obtained by PCR amplification. We report that TN transcripts are principally expressed in cells dispersed around the neural tube and notochord as well as in myotome and sclerotome cells. No TN mRNA could be detected in lateral plate mesoderm, but expression was detectable beneath tail fin epidermis. In a second series of experiments, we studied the expression of TN mRNA and protein in combinations between animal and vegetal stage-6 blastomeres and in stage-8 blastula animal caps treated with activin A or basic fibroblastic growth factor (b-FGF). Isolated animal cap tissue cultured alone differentiates into epidermis, which expresses neither TN protein nor TN mRNA. TN expression is, however, elicited in response to isolated dorsal vegetal blastomeres and in response to high concentrations of activin, both of which treatments lead to formation of muscle and/or notochord. Low concentrations of activin, and ventral vegetal blastomeres, treatments that induce mesoderm of ventral character, are poor inducers of TN. However, b-FGF, which also induces ventral mesoderm, elicits strong expression. These results indicate that TN regionalization is a complex process, dependent both on the pattern of differentiation of mesodermal tissues and on the agent with which they are induced. The data further show that “ventral mesoderm” induced by low concentrations of activin is distinct from that induced by b-FGF, and imply that activin induces ventral mesoderm of the trunk while b-FGF induces posterior mesoderm of the tailbud.

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