Clotting of fibrinogen. 5. Changes in pH associated with clotting of fibrinogen. Kinetic studies of the pH shift and correlation of the pH change with the release of fibrinopeptides and the ensuing polymerization

Biochemistry ◽  
1991 ◽  
Vol 30 (19) ◽  
pp. 4753-4762 ◽  
Author(s):  
Elemer Mihalyi ◽  
Juan Carlos Tercero ◽  
Teresa Diaz-Maurino
Keyword(s):  
Kinetic Studies ◽  
Ph Change ◽  
Ph Shift

scholarly journals Energization of the transport systems for arabinose and comparison with galactose transport in Escherichia coli

1981 ◽  
Vol 200 (3) ◽  
pp. 611-627 ◽  
Author(s):  
K R Daruwalla ◽  
A T Paxton ◽  
P J Henderson
Keyword(s):  
Escherichia Coli ◽  
Transport System ◽  
Membrane Vesicles ◽  
Kinetic Studies ◽  
Transport Systems ◽  
Protonmotive Force ◽  
Alkaline Ph ◽  
Ph Change ◽  
Intact Cells ◽  
Membrane Bound

1. Strains of Escherichia coli were obtained containing either the AraE or the AraF transport system for arabinose. AraE+,AraF- strains effected energized accumulation and displayed an arabinose-evoked alkaline pH change indicative of arabinose-H+ symport. In contrast, AraE-,AraF+ strains accumulated arabinose but did not display H+ symport. 2. The ability of different sugars and their derivatives to elicit sugar-H+ symport in AraE+ strains was examined. Only L-arabinose and D-fucose were good substrates, and arabinose was the only inducer. 3. Membrane vesicles prepared from an AraE+,AraF+ strain accumulated the sugar, energized most efficiently by the respiratory substrates ascorbate + phenazine methosulphate. Addition of arabinose or fucose to an anaerobic suspension of membrane vesicles caused an alkaline pH change indicative or sugar-H+ symport on the membrane-bound transport system. 4. Kinetic studies and the effects of arsenate and uncoupling agents in intact cells and membrane vesicles gave further evidence that AraE is a low-affinity membrane-bound sugar-H+ symport system and that AraF is a binding-protein-dependent high-affinity system that does not require a transmembrane protonmotive force for energization. 5. The interpretation of these results is that arabinose transport into E. coli is energized by an electrochemical gradient of protons (AraE system) or by phosphate bond energy (AraF system). 6. In batch cultures the rates of growth and carbon cell yields on arabinose were lower in AraE-,AraF+ strains than in AraE+,AraF- or AraE+,AraF+ strains. The AraF system was more susceptible to catabolite repression than was the AraE system. 7. The properties of the two transport systems for arabinose are compared with those of the genetically and biochemically distinct transport systems for galactose, GalP and MglP. It appears that AraE is analogous to GalP, and AraF to MglP.

Cumulative pattern in pH change alters response to food in the crayfish Cambarus bartoni

1994 ◽  
Vol 72 (1) ◽  
pp. 187-190 ◽  
Author(s):  
Erin Uiska ◽  
David W. Dunham ◽  
Harold H. Harvey
Keyword(s):  
Ph Change ◽  
Large Shift ◽  
Food Avoidance ◽  
Testing Period ◽  
Ph Shift ◽  
Y Maze ◽  
Acid Tolerant ◽  
Initial Tendency ◽  
Second Shift ◽  
Locomotory Response

In the relatively acid-tolerant crayfish Cambarus bartoni, locomotory response to food was tested (as delay in response, or latency) at both a circumneutral and a sublethal acid pH. Crayfish moved through a Y-maze toward a food source. Sequential tests were at pH 7.5, 4.5, and 7.5, and then again at pH 4.5 and 7.5. One group of 21 crayfish experienced a series of smaller pH shifts (7.5 to 6.5 to 5.5 to 4.5 at 5-day intervals), immediately followed by a larger pH shift (7.5 to 4.5). A second group of 20 crayfish experienced the large shift first, and then the series of smaller shifts. Both groups showed gradually decreasing latency through the first cycle, but then a large latency increase with the second shift to pH 4.5 (P < 0.005 and P < 0.03), and subsequent recovery at pH 7.5 by the first group (P < 0.006) but not the second (P < 0.32). This effect would seem to be due to the previous pH shift, which apparently exceeded their tolerance within our 45-day testing period. An initial tendency to approach the food (P < 0.01 and P < 0.12) became food avoidance (P < 0.01) and (or) no preference during either the first or second exposure to acidic pH.

Flavin radicals, conformational sampling and robust design principles in interprotein electron transfer: the trimethylamine dehydrogenase-electron-transferring flavoprotein complex

2004 ◽  
Vol 71 ◽  
pp. 1-14
Author(s):  
David Leys ◽  
Jaswir Basran ◽  
François Talfournier ◽  
Kamaldeep K. Chohan ◽  
Andrew W. Munro ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Kinetic Studies ◽  
Molecular Assembly ◽  
Conformational Sampling ◽  
Trimethylamine Dehydrogenase ◽  
Key Residues ◽  
Electron Transferring Flavoprotein ◽  
Electron Transfer Complex

TMADH (trimethylamine dehydrogenase) is a complex iron-sulphur flavoprotein that forms a soluble electron-transfer complex with ETF (electron-transferring flavoprotein). The mechanism of electron transfer between TMADH and ETF has been studied using stopped-flow kinetic and mutagenesis methods, and more recently by X-ray crystallography. Potentiometric methods have also been used to identify key residues involved in the stabilization of the flavin radical semiquinone species in ETF. These studies have demonstrated a key role for 'conformational sampling' in the electron-transfer complex, facilitated by two-site contact of ETF with TMADH. Exploration of three-dimensional space in the complex allows the FAD of ETF to find conformations compatible with enhanced electronic coupling with the 4Fe-4S centre of TMADH. This mechanism of electron transfer provides for a more robust and accessible design principle for interprotein electron transfer compared with simpler models that invoke the collision of redox partners followed by electron transfer. The structure of the TMADH-ETF complex confirms the role of key residues in electron transfer and molecular assembly, originally suggested from detailed kinetic studies in wild-type and mutant complexes, and from molecular modelling.

Tc-99m Labeled Complexes of Aldehydes and Glutamate as Cholescintigraphic Agents

1975 ◽  
Vol 14 (04) ◽  
pp. 330-338
Author(s):  
L. G. Colombetti ◽  
J. S. Arnold ◽  
W. E. Barnes
Keyword(s):  
Nuclear Medicine ◽  
Gall Bladder ◽  
Rose Bengal ◽  
Valence State ◽  
Monosodium Glutamate ◽  
Kinetic Studies ◽  
Scintillation Camera ◽  
Blood Clearance ◽  
Lower Valence ◽  
Wire Basket

SummaryTc-99m pyridoxylidene glutamate has proven to be an excellent biliary scanning agent, far superior in many respect to the commonly used 1-131 rose bengal. The preparation of the compound as previously reported by Baker et al is too time consuming and requires the use of an autoclave which is not available in most nuclear medicine departments. In our facility, we have been preparing similar compounds using several aldehydes and monosodium glutamate to make labeled complexes having the same pharmacological characteristics. The mixture of monosodium glutamate, aldehyde, and Tc-99m pertechnetate is made slightly alkaline, purged with helium, and placed in a sealed vial. The vial, which is protected by a wire basket, is then heated in a laboratory oven at 130° C for a period of 15 to 20 minutes. During this time, the technetium is reduced to a lower valence state and bound to the complex formed. Chromatographic data show that these compounds are chemically similar to that previously reported. The compounds prepared concentrate in the gall bladder of the rabbit in less than 10 minutes. Kinetic studies have been performed on dogs with a scintillation camera and small digital computer to measure rates of blood clearance, liver and gall bladder uptake, and excretion into the intestine. The aldehyde — glutamate complex promises to be a useful scanning agent for the diagnosis of biliary and hepatocellular diseases.

Factor V from Human Plasma

1961 ◽  
Vol 05 (01) ◽  
pp. 001-020
Author(s):  
Douglas M. Surgenor ◽  
Nancy A. Wilson ◽  
Anne S. Henry
Keyword(s):  
Human Serum ◽  
Human Plasma ◽  
Kinetic Data ◽  
Human Factor ◽  
Kinetic Studies ◽  
Partial Purification ◽  
Factor V ◽  
Two Stage ◽  
Plasma Factor ◽  
Tissue Thromboplastin

SummaryA method is described for the partial purification of a human plasma factor which accelerates the conversion of prothrombin to thrombin in the presence of tissue thromboplastin. This factor may be dried from the frozen state, and may be kept in stable dry form for long periods of time. The quantitative assay of this activity is done in a classical two-stage prothrombin system using tissue thromboplastin and calcium. From its properties, it is concluded that this activity corresponds to factor V, labile factor and plasma Ac-globulin.Chemical and kinetic studies reveal that human factor V is active in plasma and is destroyed by thrombin. Human serum has little or no factor V activity.These results thus fail to support the postulated activation of factor V during clotting. All of the kinetic data are consistent with an enzymatic role for factor V in the formation of tissue prothrombin activator (thromboplastin).

Preparation of a Viable Population of Indium-111- Labelled Human Blood Platelets

1979 ◽  
Vol 42 (05) ◽  
pp. 1473-1482 ◽  
Author(s):  
A Dup Heyns ◽  
P N Badenhorst ◽  
H Pieters ◽  
M G Lötter ◽  
P C Minnaar ◽  
...  
Keyword(s):  
Platelet Rich Plasma ◽  
Blood Platelets ◽  
Kinetic Studies ◽  
Physiological Saline ◽  
Human Platelets ◽  
Autologous Plasma ◽  
Platelet Suspension ◽  
Viable Population ◽  
Indium 111

SummaryFactors influencing labelling of human platelets with 111Indium-8-hydroxyquinoline ([111In]-oxine) in a physiological saline medium were investigated. The efficiency of labelling is influenced by time of incubation, concentration of oxine, and pH of the incubating medium. It was found that a viable platelet population could be labelled under the following conditions: (1) centrifugation of platelet rich plasma in polystyrene conical tubes at 800 g for 15 min; (2) resuspension of the platelet pellet in saline, pH 5.5; (3) incubating for 30 min at 22°C with [111In]-oxine at a concentration of 6.25 mg oxine/litre platelet suspension; (4) washing once with platelet poor autologous plasma (PPP); and (5) finally resuspending the platelets in PPP. The labelled platelets aggregated normally with collagen and ADP. Electron microscopy, done immediately after labelling, showed internal organelle reorganization characteristic of activated platelets. These ultrastructural features were reversible on incubation in PPP at 37°C for 30 min. The 111In is not released from aggregated platelets and the label does not elute from incubated platelets for at least five hr. We conclude that human platelets thus labelled are suitable for in vivo kinetic studies.

Insulin secretion in the spiny mouse (Acomys cahirinus). Dose and time kinetic studies with glucose in vivo and in vitro

Diabetes ◽  
1975 ◽  
Vol 24 (12) ◽  
pp. 1094-1100 ◽  
Author(s):  
A. Rabinovitch ◽  
A. Gutzeit ◽  
A. E. Renold ◽  
E. Cerasi
Keyword(s):  
Insulin Secretion ◽  
Kinetic Studies ◽  
Spiny Mouse ◽  
Acomys Cahirinus
Sign in / Sign up

Export Citation Format

Share Document