scholarly journals Active accumulation of very diluted biomolecules by nano-dispensing for easy detection below the femtomolar range

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
S. Grilli ◽  
L. Miccio ◽  
O. Gennari ◽  
S. Coppola ◽  
V. Vespini ◽  
...  
Keyword(s):  
Active Accumulation

Renal excretory transport of organic acids: inhibition by oxypurines

1959 ◽  
Vol 197 (5) ◽  
pp. 1107-1110 ◽  
Author(s):  
Agamemnon Despopoulos
Keyword(s):  
Uric Acid ◽  
Oxidative Phosphorylation ◽  
Organic Acids ◽  
Rabbit Kidney ◽  
Kidney Cortex ◽  
Hydroxyl Groups ◽  
Carbonyl Groups ◽  
Oxygen Utilization ◽  
Inhibitory Potency ◽  
Active Accumulation

Uric acid inhibited the active accumulation of p-aminohippurate (PAH) by surviving slices of rabbit kidney cortex without affecting oxygen utilization or oxidative phosphorylation. The inhibitory potency of uric acid was compared with that of several desoxyurates and N-methylated urates. In general, the desoxyurates were less potent and the N-methylated urates more potent inhibitors than uric acid. The data suggest that the inhibitory reaction requires the presence of all three oxygen atoms of the urate molecule. These appear to function as carbonyl groups rather than as enolic hydroxyl groups in a predominantly nonionic reaction.

scholarly journals Structural requirements for active intestinal sugar transport. The involvement of hydrogen bonds at C-1 and C-6 of the sugar

1968 ◽  
Vol 109 (1) ◽  
pp. 61-67 ◽  
Author(s):  
J. E. G. Barnett ◽  
W. T. S. Jarvis ◽  
K A Munday
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Active Transport ◽  
Transport Process ◽  
Sugar Transport ◽  
Ideal Structure ◽  
Rat Intestine ◽  
Structural Requirements ◽  
The Ideal ◽  
Active Accumulation

1. A series of d-galactose derivatives substituted at C-1 and C-6 were tested for active accumulation by everted segments of hamster and rat intestine. 2. d-Galactose and 6-deoxy-6-fluoro-d-galactose were accumulated far more rapidly than 6-deoxy- and 6-chloro-6-deoxy-d-galactose, and this is interpreted as due to hydrogen-bonding at C-6 during the transport process. 3. 6-Bromo-6-deoxy- and 6-deoxy-6-iodo-d-galactose were not actively transported, indicating that the allowed size of substituent at C-6 lies between that of chlorine and bromine atoms. 4. Similar results were obtained at C-1. Both methyl α-d-galactopyranoside and methyl β-d-galactopyranoside were well transported, but methyl β-d-thiogalactopyranoside and 1-deoxy-d-galactose were not transported; d-galactopyranosyl fluoride was transported, but only poorly. Again hydrogen-bonding is suggested. 5. It is proposed that d-glucose is the ideal structure for active transport and that binding occurs at C-1, C-2, C-3, C-4 and C-6. Loss of two or more of these bonds usually causes loss of active transport. 6. By plotting Lineweaver–Burk plots of the rates of transport of the galactose derivatives, the apparent V and Km values were obtained. With hamster intestine both these values were very reproducible. Contrary to expectation, V varied for different sugars. 7. The Ki of some of the analogues modified at C-1 and C-6 was determined with methyl α-d-glucoside as substrate. 8. An attempt to alkylate the carrier by using methyl 3,4-anhydro-α-d-galactoside was unsuccessful. There was no evidence that this compound was bound to the carrier.

scholarly journals ACTIVE ACCUMULATION OF SODIUM BY ROOTS OF FIVE AQUATIC SPECIES

1973 ◽  
Vol 72 (5) ◽  
pp. 1075-1080 ◽  
Author(s):  
U. H. SHEPHERD ◽  
D. J. F. BOWLING
Keyword(s):  
Aquatic Species ◽  
Active Accumulation

scholarly journals Evidence that activation of 2-deoxy-d-glucose transport in rat thymocyte suspensions results from enhanced coupling between transport and hexokinase activity

1989 ◽  
Vol 260 (1) ◽  
pp. 143-152 ◽  
Author(s):  
R J Naftalin ◽  
R J Rist
Keyword(s):  
Glucose Transport ◽  
Sugar Transport ◽  
Free Solution ◽  
Sugar Transporter ◽  
External Concentration ◽  
Hexokinase Activity ◽  
High Affinity ◽  
Hexose Phosphate ◽  
Degree Of Coupling ◽  
Active Accumulation

1. Suspensions of rat thymocytes accumulate free 2-deoxy-D-glucose (2-dGlc) within the cytosol to a concentration approx. 25-fold above the external concentration. This active accumulation was enhanced by 40 nM-phorbol 12-myristate 13-acetate (phorbol). 2. The Km for zero-trans uptake in control cells was 2.3 +/- 0.14 mM and Vmax. was 0.41 +/- 0.08 mumol/min per 10(10) cells (n = 6). In cells treated with phorbol (40 nM) the Km for zero-trans uptake was 1.2 +/- 0.13 mM and Vmax. 0.46 +/- 0.03 mumol/min per 10(10) cells (n = 6). The Km was decreased significantly by phorbol (P less than 0.01). 3. Phorbol-dependent activation of thymocytes delayed exit of free 2-dGlc into sugar-free solution and prevented exchange exit. Activation had no effect on 3-O-methyl D-glucoside (3-OMG) exit. 4. Coupling of 2-dGlc transport to hexokinase activity was determined by observing the effects of various concentrations of unlabelled cytosolic 2-dGlc on influx of labelled 2-dGlc into the hexose phosphate pool. In control cells this coupling was 0.81 +/- 0.02 and in phorbol-activated cells it was 0.92 +/- 0.01 (P less than 0.01). 5. The high-affinity inhibitor of hexokinase, mannoheptulose, inhibited uptake of 2-dGlc in both control and phorbol-treated cells. These data are consistent with a model for activation of sugar transport in which hexokinase activity is integrated with the sugar transporter at the endofacial surface. The results suggest that phorbol increases the degree of coupling transport with hexokinase activity, thereby leading to an increase in the rate of uptake of 2-dGlc, a decrease in exit of free 2-dGlc from the cytosol and an increase in free 2-dGlc accumulation.

scholarly journals Structural requirements for active intestinal transport. Spatial and bonding requirements at C-3 of the sugar

1969 ◽  
Vol 114 (3) ◽  
pp. 569-573 ◽  
Author(s):  
J. E. G. Barnett ◽  
A. Ralph ◽  
K A Munday
Keyword(s):  
Hydrogen Bond ◽  
Competitive Inhibition ◽  
Intestinal Transport ◽  
Hydroxyl Group ◽  
Structural Requirements ◽  
Relative Affinity ◽  
Electronegative Atom ◽  
Active Accumulation

Analogues of d-glucose modified at C-3, and in some cases at a second position, were prepared and tested for active accumulation by everted segments of hamster intestine. Their relative affinity for the sugar carrier was measured by tissue/medium ratio, Michaelis–Menten kinetics and competitive inhibition of d-galactose or methyl α-d-glucoside transport. d-Glucose and its 3-deoxy-3-fluoro, 3-chloro-3-deoxy and to a smaller extent its 3-bromo-3-deoxy derivatives, bound and were transported more strongly than 3-deoxy-d-glucose and other sugars not containing an electronegative atom in the gluco configuration at C-3. 3-Deoxy-d-galactose, 3,6-dideoxy-d-glucose and d-gulose, which have two alterations from the d-glucose structure, were not, or only very weakly, transported. The results are interpreted as indicating the presence of a hydrogen bond from the carrier to the hydroxyl group at C-3 of d-glucose. Spatial requirements are also discussed. New syntheses are reported for 3-chloro-3-deoxy- and 3-bromo-3-deoxy-d-glucose and 3,6-dideoxy-d-glucose.

SMA Selectively Codes the Active Accumulation of Temporal, Not Spatial, Magnitude

2015 ◽  
Vol 27 (11) ◽  
pp. 2281-2298 ◽  
Author(s):  
Jennifer T. Coull ◽  
Pom Charras ◽  
Maxime Donadieu ◽  
Sylvie Droit-Volet ◽  
Franck Vidal
Keyword(s):  
Working Memory ◽  
Visual Cortex ◽  
Stimulus Duration ◽  
Occipital Cortex ◽  
Line Stimulus ◽  
Temporal Domain ◽  
Stimulus Distance ◽  
Spatial Domains ◽  
Dynamic Trajectory ◽  
Active Accumulation

Estimating duration depends on the sequential integration (accumulation) of temporal information in working memory. Using fMRI, we directly compared the accumulation of information in temporal versus spatial domains. Participants estimated either the duration or distance of the dynamic trajectory of a moving dot or, in a control condition, a static line stimulus. Comparing the duration versus distance of static lines activated an extensive cortico-striatal network. By contrast, comparing the duration versus distance of dynamic trajectories, both of which required sequential integration of information, activated SMA alone. Indeed, activity in SMA, as well as right inferior occipital cortex, increased parametrically as a function of stimulus duration and also correlated with individual differences in the propensity to overestimate stimulus duration. By contrast, activity in primary visual cortex increased parametrically as a function of stimulus distance. Crucially, a direct comparison of the parametric responses to duration versus distance revealed that activity in SMA increased incrementally as a function of stimulus duration but not as a function of stimulus distance. Collectively, our results indicate that SMA responds to the active accumulation of information selectively in the temporal domain.

scholarly journals The ‘active’ accumulation of tetracycline by Escherichia coli

1969 ◽  
Vol 112 (1) ◽  
pp. 12P.1 ◽  
Author(s):  
T J Franklin ◽  
B Higginson
Keyword(s):  
Escherichia Coli ◽  
Active Accumulation
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