Uptake of leucine by Chlorella symbionts of green hydra

1988 ◽  
Vol 234 (1276) ◽  
pp. 319-332 ◽  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Time Course ◽  
Algal Cell ◽  
Short Interval ◽  
Artemia Salina ◽  
Second Phase ◽  
Rapid Phase ◽  
Green Hydra ◽  
The Difference

Cells of a Chlorella sp. symbiotic with green hydra were able to take up leucine via a high-affinity transport mechanism after isolation from the symbiosis, and to incorporate sequestered amino acid into protein. The time course of uptake of leucine by Chlorella cells in the intact symbiosis was followed after hydra were fed with nauplii of the brine shrimp Artemia salina that had been labelled with radioactive leucine. Uptake proceeded in two stages, the first more rapid than the second, separated by a short interval in which there was a consistently observed decrease in the amount of radioactivity per cell. Although leucine from Artemia free amino acid pools was accumulated disproportionately by Chlorella cells in symbiosis, this was not sufficient to explain the initial rapid phase of uptake, nor could changes in rate of uptake with time after feeding be explained by changes in properties of the Chlorella cells. Rather, slower uptake in the second phase, and the decrease in amount of radioactivity per cell which preceded it, were probably due to changes in supply of amino acids to the Chlorella cells. Amino acids transported by the same system as leucine caused efflux of accumulated leucine from isolated Chlorella cells when present in high external concentrations. Thus the observed accumulation of radioactivity in symbiosis may have been the difference between unidirectional influx and unidirectional efflux of leucine dependent upon changes in external concentrations of unlabelled amino acids from Artemia or from hydra pools. This is discussed with reference to host control of algal cell division, which has been shown to be dependent upon supply of a ‘division factor’ from host food.

Single amino acid substitution of rat MRP2 results in acquired transport activity for taurocholate

2001 ◽  
Vol 281 (4) ◽  
pp. G1034-G1043 ◽  
Author(s):  
Kousei Ito ◽  
Hiroshi Suzuki ◽  
Yuichi Sugiyama
Keyword(s):  
Amino Acids ◽  
Multidrug Resistance ◽  
Amino Acid ◽  
Membrane Vesicles ◽  
Single Amino Acid ◽  
Sf9 Cells ◽  
Transport Activity ◽  
Wild Type ◽  
Cationic Amino Acids ◽  
The Difference

Multidrug resistance-associated protein 3 (MRP3), unlike other MRPs, transports taurocholate (TC). The difference in TC transport activity between rat MRP2 and MRP3 was studied, focusing on the cationic amino acids in the transmembrane domains. For analysis, transport into membrane vesicles from Sf9 cells expressing wild-type and mutated MRP2 was examined. Substitution of Arg at position 586 with Leu and Ile and substitution of Arg at position 1096 with Lys, Leu, and Met resulted in the acquisition of TC transport activity, while retaining transport activity for glutathione and glucuronide conjugates. Substitution of Leu at position 1084 of rat MRP3 (which corresponds to Arg-1096 in rat MRP2) with Lys, but not with Val or Met, resulted in the loss of transport activity for TC and glucuronide conjugates. These results suggest that the presence of the cationic charge at Arg-586 and Arg-1096 in rat MRP2 prevents the transport of TC, whereas the presence of neutral amino acids at the corresponding position of rat MRP3 is required for the transport of substrates.

Anaerobiosis: A Possible Source of Osmotic Solute for High-salinity Acclimation in Marine Molluscs

1975 ◽  
Vol 62 (3) ◽  
pp. 589-598
Author(s):  
RICHARD M. BAGINSKI ◽  
SIDNEY K. PIERCE
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cell Volume ◽  
Free Amino ◽  
Time Course ◽  
High Salinity ◽  
Gulf Coast ◽  
Total Amino Acid ◽  
Salinity Acclimation ◽  
Rapid Accumulation

1. When stressed with high-salinity exposure, cell volume is restored in ventricles of Modiolus demissus demissus by a rapid accumulation of intracellular free amino acids. 2. Although the total amino acid pool increases and remains at a constant high level thereafter, the pattern and time course of accumulation is different for each major amino acid (glycine, alanine, taurine, and proline). 3. Initially, cell volume is restored by a rapid accumulation of alanine, but later its concentration decreases while glycine and taurine accumulate. Although at first not detected, the proline concentration increases, peaks and subsequently disappears again. 4. Isolated ventricles recover normal activity after large environmental salinity increases. 5. During recovery the intracellular free amino acid changes in isolated ventricles are similar to the initial pattern of accumulation in whole animals, i.e., alanine, and to a lesser extent, proline and glycine accumulate. 6. Finally, isolated ventricles undergo a period of decreased oxygen consumption on exposure to an increased salinity. 7. These results suggest that the initial stages of high-salinity acclimation in molluscs depends upon the synthesis of amino acids via a known anaerobic biochemical pathway. Note: Contribution No. 33 from the Tallahassee, Sopchoppy and Gulf Coast Marine Biological Association.

Collection and analysis of absorbate from proximal straight tubules

1981 ◽  
Vol 241 (6) ◽  
pp. F597-F604 ◽  
Author(s):  
D. W. Barfuss ◽  
J. A. Schafer
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Epithelial Cells ◽  
Water Absorption ◽  
Glucose Concentration ◽  
Volume Absorption ◽  
Steady Rate ◽  
Straight Tubules ◽  
The Difference ◽  
Solute Composition

When isolated segments of rabbit proximal straight tubules were perfused under oil at 37 degrees C, we observed that droplets of absorbate formed on the peritubular surface. Volume absorption under these conditions was the same as with customary aqueous bathing solutions when calculated either from the rate of absorbate formation (0.39 +/- 0.03 nl X min-1 X mm-1) or from the difference in measured perfusion and collection rates (0.37 +/- 0.04 nl X min-1 X mm-1). Absorbate formation continued at a steady rate for at least 2 h but was inhibited by 71% at 28 degrees C. The absorbate was found to have a composition that differed from the perfusate, as would be expected in the presence of preferential absorption of glucose, amino acids, and HCO-3. The Cl- concentration in the absorbate was 11.2 +/- 1.8 mM less than in the perfusate. The glucose concentration in the absorbate was 4.5 mM compared with 0.9 mM in the perfusate. Finally, the nonmetabolizable amino acid cycloleucine, which was added to the perfusate at 0.35 mM, had a concentration of 2.9 mM in the epithelial cells compared with 1.6 mM in the absorbate. These data establish the usefulness of this technique for examining solute and water absorption in the proximal nephron and show that the absorbate can differ considerably in solute composition from the luminal perfusate.

scholarly journals 131 MODIFICATION OF AMINO ACID CONCENTRATIONS IN MEDIUM BY PIG EMBRYOS FROM THE ZYGOTE TO THE BLASTOCYST STAGE

2005 ◽  
Vol 17 (2) ◽  
pp. 216
Author(s):  
P. Booth ◽  
T. Watson ◽  
H. Leese
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Embryonic Development ◽  
Amino Acid Profile ◽  
Blastocyst Stage ◽  
Morula Stage ◽  
Amino Acid Profiles ◽  
The Difference ◽  
Amino Acid Concentrations

Pre-implantation embryos can produce and consume amino acids in a manner dependent upon stage of embryonic development (Partridge and Leese 1996 Reprod. Fert. Dev. 8, 945) that may also be predictive of subsequent viability (Houghton et al. 2002 Hum. Reprod. 17, 999). To examine these relationships in the pig, the appearance or depletion of 18 amino acids from a presumptive near-physiological mixture was determined by HPLC in porcine in vitro-produced embryos from the zygote to the blastocyst stage. Cumulus oocyte complexes derived from slaughterhouse prepubertal pig ovaries were matured for 40 h in modified TCM-199 before being fertilized (Day 0) with frozen thawed semen in tris-based medium. After 6 h, presumptive zygotes were denuded and cultured in groups of 20 in NCSU medium modified to contain a physiological mixture of 18 amino acids including 0.1 mM glutamine (NCSUaa). Groups of 2–10 embryos (dependent on stage) were removed on Day 0 (1 cell), Day 1 (2- and 4-cell), Day 4 (compact morula), and Day 6 (blastocyst) and placed in 4 μL NCSUaa for 24 h. After incubation, the embryos were removed and the medium analyzed by HPLC. Each stage was replicated 3–9 times. Since amino acid profiles of 2- and 4-cell embryos were not different, data were combined. Overall, arginine (1.19 ± 0.33), glutamine (0.78 ± 0.34) and threonine (0.05 ± 0.04) were significantly (P < 0.01) depleted from the medium whereas alanine (0.21 ± 0.1), glycine (0.20 ± 0.06), asparagine (0.13 ± 0.5), lysine (0.1 ± 0.03), isoleucine (0.08 ± 0.01), valine (0.05 ± 0.01), leucine (0.04 ± 0.02), phenylalanine (0.03 ± 0.01), and histidine (0.02 ± 0.04) significantly (P < 0.05) accumulated (mean of the 4 sampling timepoints; all values pmol/embryo/h ± SEM). The difference between amino acid accumulation and depletion (balance) was approximately equivalent between Day 0 and the morula stage although turnover (sum of depletion and accumulation) steadily decreased during this period from 3.1 on Day 0 to 1.35 pmol/embryo/h at the morula stage. However, at the blastocyst stage, turnover and balance increased to 6.32 and 2.42 pmol/embryo/h, respectively, i.e. net appearance occurred. Notable changes in amino acid profile during development included decreases in accumulation of asparagine, glutamate, and glycine in the medium and the depletion of glutamine over Days 0, 1, and 4, followed by reversal of these trends by Day 6. These data suggest that pig embryos can alter the accumulation and depletion rates of amino acids in a manner that is dependent on the specific amino acid and the stage of embryonic development. This work was supported by BBSRC.

Sequence mutations in teleost cardiac troponin C that are permissive of high Ca2+ affinity of site II

2003 ◽  
Vol 284 (5) ◽  
pp. C1176-C1184 ◽  
Author(s):  
Todd E. Gillis ◽  
Chris D. Moyes ◽  
Glen F. Tibbits
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Cardiac Troponin ◽  
Troponin C ◽  
Fluorescent Reporter ◽  
Cardiac Troponin C ◽  
The Difference ◽  
Higher Sensitivity

Cardiac myofibrils isolated from trout heart have been demonstrated to have a higher sensitivity for Ca2+ than mammalian cardiac myofibrils. Using cardiac troponin C (cTnC) cloned from trout and mammalian hearts, we have previously demonstrated that this comparatively high Ca2+ sensitivity is due, in part, to trout cTnC (ScTnC) having twice the Ca2+ affinity of mammalian cTnC (McTnC) over a broad range of temperatures. The amino acid sequence of ScTnC is 92% identical to McTnC. To determine the residues responsible for the high Ca2+ affinity, the function of a number of ScTnC and McTnC mutants was characterized by monitoring an intrinsic fluorescent reporter that monitors Ca2+ binding to site II (F27W). The removal of the COOH terminus (amino acids 90–161) from ScTnC and McTnC maintained the difference in Ca2+ affinity between the truncated cTnC isoforms (ScNTnC and McNTnC). The replacement of Gln29 and Asp30 in ScNTnC with the corresponding residues from McNTnC, Leu and Gly, respectively, reduced Ca2+ affinity to that of McNTnC. These results demonstrate that Gln29 and Asp30 in ScTnC are required for the high Ca2+ affinity of site II.

Amino acid fluxes in rat thin limb segments of Henle’s loop during in vitro microperfusion

1999 ◽  
Vol 277 (2) ◽  
pp. F204-F210 ◽  
Author(s):  
Olga H. Brokl ◽  
William H. Dantzler
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Apparent Movement ◽  
Transepithelial Transport ◽  
Acid Transport ◽  
Henle's Loop ◽  
Vasa Recta ◽  
The Difference

Amino acids are apparently recycled between loops of Henle and vasa recta in the rat papilla in vivo. To examine more closely papillary amino acid transport, we measured transepithelial fluxes ofl-[14C]alanine and [14C]taurine in thin limbs of Henle’s loops isolated from rat papilla and perfused in vitro. In descending thin limbs (DTL) in vitro, unidirectional bath-to-lumen fluxes tended to exceed unidirectional lumen-to-bath fluxes for both radiolabeled amino acids, although the difference was statistically significant only for taurine. In ascending thin limbs (ATL) in vitro, unidirectional lumen-to-bath fluxes tended to exceed unidirectional bath-to-lumen fluxes, although the difference was again statistically significant only for taurine. These results are compatible with apparent directional movements of amino acids in vivo. However, none of the unidirectional fluxes was saturable or inhibitable, an observation compatible with apparent reabsorption from the ATL in vivo but not compatible with apparent movement from vasa recta to DTL in vivo. There was no evidence of net active transepithelial transport when concentrations of radiolabeled amino acids were matched on both sides of perfused tubule segments. These data suggest that regulation of amino acid movement in vivo may involve the vasa recta, not the DTL of Henle’s loops. The data also suggest that transepithelial movement of amino acids in thin limbs of Henle’s loop may occur via a paracellular route.

A Preliminary Study of the Fixation Mechanism of Collagen Reaction with a Polyepoxy Fixative

1993 ◽  
Vol 16 (7) ◽  
pp. 537-544 ◽  
Author(s):  
R. Tu ◽  
R.C. Quijano ◽  
C.L. Lu ◽  
S. Shen ◽  
E. Wang ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Great Promise ◽  
Fixation Time ◽  
Denaturation Temperature ◽  
Amino Acid Analyzer ◽  
Direct Indication ◽  
Preliminary Study ◽  
The Difference ◽  
Fixation Reaction

A new biomaterial has been developed by fixing native collagens with a polyepoxy compound (PC) fixative. Prior studies have shown that this biomaterial has comparable properties as compared to collagen fixed with glutaraldehyde (GA) and thus has a great promise for use as an implantable bioprosthesis. The purpose of this study was to understand the mechanism of the amino acids-PC reactions in the fixation process. Bovine arteries were fixed with PC under various pH, concentration and temperature conditions as a function of fixation time. Individual amino acid components in the fresh and the fixed arteries were assayed using a Beckman amino acid analyzer to determine the degree of tanning. The denaturation temperature (Td) was also measured on each sample. Since the denaturation temperature is a direct indication of cross-linking of individual amino acids with the fixative, the difference in the degree of tanning for the same increase in Td may be indicative of the quantity of the masked, non-cross-linked amino acids. The fixation reaction data indicated that not all amino acids were cross-linked upon contacting the PC fixative. Masking appeared to be more substantial with a fixation at higher pH values.

Localization of amino acid neurotransmitters following in vitro ischemia and anoxia in the rat retina

2001 ◽  
Vol 18 (3) ◽  
pp. 413-427 ◽  
Author(s):  
GENEVIEVE A. NAPPER ◽  
MICHAEL J. PIANTA ◽  
MICHAEL KALLONIATIS
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cellular Localization ◽  
Time Course ◽  
Enzymatic Reactions ◽  
Glutamate Metabolism ◽  
Accumulation Time ◽  
Glucose Levels ◽  
Acid Loading

Glutamate and γ-aminobutyric acid (GABA) are two of the dominant neurotransmitters in the retina and brain. The production/degradation of glutamate and GABA involves an intricate interrelationship between neurons and glia, as well as aerobic and anaerobic metabolic pathways. The aim of this work was to develop an in vitro model of retinal ischemia/anoxia and determine the changes in cellular localization of glutamate and GABA and the time course for such changes. After anoxic/ischemic insult, glutamate and GABA rapidly accumulate within glia with GABA showing a quicker time course and larger magnitude change. The accumulation time constant for both glutamate and GABA under anoxic conditions was dependent upon glucose concentration: high glucose levels resulted in delayed glial amino acid loading. The differences in time constants between GABA and glutamate glial loading most likely reflect the multitude of glutamate degradation pathways compared to the single aerobically dependent GABA pathway. Oxygen availability and reduced glucose (hypoglycemia) lead to an almost immediate increase (within 1 min) of glutamate and GABA labelling within glia. In addition, altered labelling patterns were found under anoxic/ischemic conditions for amino acids involved in glutamate transamination reactions: aspartate, leucine, alanine, and ornithine. These changes are consistent with alterations of equilibria of enzymatic reactions involved in glutamate metabolism, and thus support a role for all four amino acids in glutamate metabolism within a variety of retinal neurons.

Short-interval absorption and metabolism of some amino acids in Trypanosoma gambiense

Parasitology ◽  
1972 ◽  
Vol 64 (3) ◽  
pp. 379-387 ◽  
Author(s):  
L. H. Chappell ◽  
G. C. Southworth ◽  
C. P. Read
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Short Interval ◽  
Cysteic Acid ◽  
Transaminase Activity ◽  
Glutamate Pyruvate Transaminase ◽  
Glutamate Pyruvate ◽  
High Level ◽  
Rate Limiting ◽  
Trypanosoma Gambiense

During 2 min incubations of Trypanosoma gambiense (bloodstream form) with [U-14C]glucose (1 mM) over 60% of absorbed label was detected in free alanine. In the presence of 12·5 mM unlabelled alanine, the amount of alanine synthesized from glucose was reduced by less than 10%. These data support previous observations on the high level of transaminase activity in African human trypanosomes.Alanine, aspartate and glutamate were metabolized to various other free amino acids whereas a significant amount of label derived from [14C]arginine could not be accounted for by amino acid assay.The sulphur containing amino acids, cysteic acid and taurine, were apparently synthesized from alanine, glutamate and arginine. The significance of these syntheses is poorly understood.Following incubations of trypanosomes for 2 min in exogenous amino acids the internal free pool became imbalanced due to accumulation and metabolism of the substrate amino acid.Evidence obtained indicated that the level of free endogenous glutamate may be rate limiting for the glutamate-pyruvate transaminase system.

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