Dual capacity for nutrient uptake in Tetrahymena. V. Utilization of amino acids and proteins

1979 ◽  
Vol 36 (1) ◽  
pp. 343-353
Author(s):  
E. Orias ◽  
L. Rasmussen
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Tetrahymena Thermophila ◽  
Amino Acid Uptake ◽  
Food Vacuole ◽  
Transport Systems ◽  
Acid Uptake ◽  
Vacuole Formation ◽  
Carrier Mediated Transport ◽  
Food Vacuoles

We investigated the relative contributions of phagocytosis and plasma membrane transport to the uptake of amino acids and a protein (egg albumin) in amounts which allow Tetrahymena thermophila to grow and multiply. We used a mutant capable of indefinite growth without food vacuole formation (phagocytosis) and its wild type (phagocytosis-competent) isogenic parental strain. Our results suggest that phagocytosis is not required for free amino acid uptake, most or all of which can be attributed to carrier-mediated transport systems, apparently located on the plasma membrane. In contrast, phagocytosis is required for utilization of the protein. Proteins can supply required amino acids in amounts sufficient for growth only when food vacuoles are formed. We conclude that Tetrahymena thermophila either possesses no endocytic mechanisms at the cell surface other than food vacuole formation or, if it does, these putative mechanisms are not capable of nutritionally meaningful rates of protein uptake.

Amino acid uptake systems in Bacteroides ruminicola

1979 ◽  
Vol 25 (10) ◽  
pp. 1161-1168 ◽  
Author(s):  
Roselynn M. W. Stevenson
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Nitrogen Sources ◽  
Amino Acid Uptake ◽  
Defined Medium ◽  
High Rate ◽  
Transport Systems ◽  
Acid Uptake ◽  
Chemical Structures ◽  
Kinetic Inhibition

Uptake of amino acids by Bacteroides ruminicola was observed in cells grown in a complete defined medium, containing ammonia as the nitrogen source. A high rate of uptake occurred only in fresh medium, as an inhibitory substance, possibly acetate, apparently accumulated during growth. All amino acids except proline were taken up and incorporated into cold trichloroacetic acid precipitable material. Different patterns of incorporation and different responses to 2,4-dinitrophenol and potassium ferricyanide indicated multiple uptake systems were involved. Kinetic inhibition patterns suggested six distinct systems were present for amino acid uptake, with specificities related to the chemical structures of the amino acids. Thus, the failure of free amino acids to act as sole nitrogen sources for growth of B. ruminicola is not due to the absence of transport systems for these compounds.

Liver uptake of amino acids and carbohydrates during a single circulatory passage

1975 ◽  
Vol 228 (4) ◽  
pp. 1155-1161 ◽  
Author(s):  
WM Pardridge ◽  
LS Jefferson
Keyword(s):  
Amino Acids ◽  
Glutamic Acid ◽  
Aspartic Acid ◽  
Amino Acid Uptake ◽  
Ringer Solution ◽  
Transport Systems ◽  
Test Substance ◽  
Acid Uptake ◽  
Liver Uptake ◽  
Rapid Injection

The uptake of 14C-labeled amino acids and carbohydrates by liver following rapid injection into the portal vein was measured relative to a simultaneously injected highly diffusible reference, tritium-labeled water, (3HOH). A 0.25-ml bolus of buffered Ringer solution containing 1-2 muCi of the 14C-labeled test substance and 3-6 muCi of 3HOH was administered by rabid portal injection in anesthetized rats. Circulation was terminated after a single passage of the bolus through the hepatic microvasculature and the tissue was immediately macerated, solubilized, and subjected to liquid scintillation counting. Liver uptake indices (LUI) were calculated from the ratio of 14C to 3H in liver tissue relative to the same ratio in the injection mixture. LUI's of five carbohydrates were measured: sucrose (24.3 percent), inulin (27.7 percent), D-mannitol (80.2 percent), D-glucose (96.8 percent) and L-glucose (26.7 percent). The LUI for cholic acid was 127.1 percent. Among 18 amino acids tested, the LUI's were the highest for the acidic ones (L-aspartic acid, 100.0 percent and L-glutamic acid, 86.4 percent) and lowest for the basic ones (L-arginine, 37.4 percent and L-lysine, 31.4 percent). Stereospecificity for glucose and alanine uptake, saturation kinetics for glutamic acid (Km equal to 4.8 mM) and aspartic acid (Km equal to 2.7 mM), and cross-inhibition among uptake of the acidic amino acids were observed. These findings confirmed the applicability of a technique which was originally developed for studies of amino acid uptake in brain to characterization of transport systems in liver.

In vivo muscle amino acid transport involves two distinct processes

2004 ◽  
Vol 287 (1) ◽  
pp. E136-E141 ◽  
Author(s):  
Sharon Miller ◽  
David Chinkes ◽  
David A. MacLean ◽  
Dennis Gore ◽  
Robert R. Wolfe
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Interstitial Fluid ◽  
Muscle Blood Flow ◽  
Amino Acid Uptake ◽  
Transport Systems ◽  
Acid Uptake ◽  
Acid Transport ◽  
Rate Limiting

We have tested the hypothesis that transit through the interstitial fluid, rather than across cell membranes, is rate limiting for amino acid uptake from blood into muscle in human subjects. To quantify muscle transmembrane transport of naturally occurring amino acids, we developed a novel 4-pool model that distinguishes between the interstitial and intracellular fluid compartments. Transport kinetics of phenylalanine, leucine, lysine, and alanine were quantified using tracers labeled with stable isotopes. The results indicate that interstitial fluid is a functional compartment insofar as amino acid kinetics are concerned. In the case of leucine and alanine, transit between blood and interstitial fluid was potentially rate limiting for muscle amino acid uptake and release in the postabsorptive state. For example, in the case of leucine, the rate of transport between blood and interstitial fluid compared with the corresponding rate between interstitial fluid and muscle was 247 ± 36 vs. 610 ± 95 nmol·min−1·100 ml leg−1, respectively ( P < 0.05). Our results are consistent with the process of diffusion governing transit from blood to interstitial fluid without selectivity, and of specific amino acid transport systems with varying degrees of efficiency governing transit from interstitial fluid to muscle. These results imply that changes in factors that affect the transit of amino acids from blood through interstitial fluid, such as muscle blood flow or edema, could play a major role in controlling the rate of muscle amino acid uptake.

scholarly journals ADF/Cofilin Is Not Essential but Is Critically Important for Actin Activities during Phagocytosis in Tetrahymena thermophila

2013 ◽  
Vol 12 (8) ◽  
pp. 1080-1086 ◽  
Author(s):  
Nanami Shiozaki ◽  
Kentaro Nakano ◽  
Yasuharu Kushida ◽  
Taro Q. P. Noguchi ◽  
Taro Q. P. Uyeda ◽  
...  
Keyword(s):  
Tetrahymena Thermophila ◽  
Food Vacuole ◽  
Content Type ◽  
Vacuole Formation ◽  
Future Studies ◽  
Cellular Events ◽  
Food Vacuoles

ABSTRACT ADF/cofilin is a highly conserved actin-modulating protein. Reorganization of the actin cytoskeleton in vivo through severing and depolymerizing of F-actin by this protein is essential for various cellular events, such as endocytosis, phagocytosis, cytokinesis, and cell migration. We show that in the ciliate Tetrahymena thermophila , the ADF/cofilin homologue Adf73p associates with actin on nascent food vacuoles. Overexpression of Adf73p disrupted the proper localization of actin and inhibited the formation of food vacuoles. In vitro , recombinant Adf73p promoted the depolymerization of filaments made of T. thermophila actin (Act1p). Knockout cells lacking the ADF73 gene are viable but grow extremely slowly and have a severely decreased rate of food vacuole formation. Knockout cells have abnormal aggregates of actin in the cytoplasm. Surprisingly, unlike the case in animals and yeasts, in Tetrahymena , ADF/cofilin is not required for cytokinesis. Thus, the Tetrahymena model shows promise for future studies of the role of ADF/cofilin in vivo .

Alanine transport systems in isolated basal plasma membrane of human placenta

1989 ◽  
Vol 256 (3) ◽  
pp. C630-C637 ◽  
Author(s):  
S. D. Hoeltzli ◽  
C. H. Smith
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Plasma Membranes ◽  
Transport Systems ◽  
Acid Uptake ◽  
Plasma Membrane Vesicles ◽  
Basal Plasma Membrane ◽  
Sodium Dependent ◽  
Basal Plasma ◽  
System 2

Concentrative transfer of amino acids from mother to fetus is affected by transport across both microvillous (maternal-facing) and basal (fetal-facing) plasma membranes of the human placental syncytiotrophoblast. Isolated basal plasma membrane vesicles were used to elucidate transport systems for neutral amino acids across this membrane. The concentration dependence and inhibition of zero-trans-alanine uptake were studied and four pathways for alanine uptake were defined as follows: 1) a sodium-dependent system shared by methylaminoisobutyric acid, which has the characteristics of an A system; 2) a sodium-dependent system resistant to inhibition by methylaminoisobutyric acid, which has the characteristics of an ASC system; 3) a sodium-independent system which may resemble an L system; 4) nonsaturable uptake. The microvillous membrane of the syncytiotrophoblast possesses systems similar to 1 and 3, but system 2 is unique to the basal plasma membrane. Active and passive transport of amino acids across both microvillous and basal plasma membranes may contribute to trophoblast amino acid uptake and nutrition and to the transfer of amino acids to the fetus.

Peptide uptake from the gastrointestinal tract of sheep

1994 ◽  
Vol 1994 ◽  
pp. 95-95
Author(s):  
M. R. Hipólito-Reis ◽  
J. C. MacRae ◽  
F. R. C. Backwell
Keyword(s):  
Amino Acids ◽  
Gastrointestinal Tract ◽  
Amino Acid Uptake ◽  
Peptide Transport ◽  
Transport Systems ◽  
Total Amino Acid ◽  
Acid Uptake ◽  
Ruminant Species ◽  
Peptide Uptake ◽  
Distinct Peptide

It is known that uptake of di- and tripeptides by distinct peptide transport systems is an important biological process by which amino acids are absorbed from the gastrointestinal tract (Rubino et al 1971; Webb and Bergman, 1991). However, until recently it was generally accepted that absorbed peptides had to be completely hydrolysed in to free amino acids within the enterocyte (Krzysik and Adibi, 1977) prior to their transport into the circulation. Nevertheless, it has been suggested that, in ruminant species at least, a substantial proportion of the total amino acid uptake from the gastrointestinal tract may be in the form of peptides (Webb, 1990; Seal and Parker, 1991; Webb and Bergman, 1991) and that a large part of this absorption may occur across the stomach region (i.e. rumen and omasum) (Webb, 1990). Consequently, the present study was designed to assess the uptake of amino acids in the form of low molecular weight peptides across the gastrointestinal tract of growing lambs.

Influence of insulin on amino acid uptake by lung slices

1977 ◽  
Vol 42 (2) ◽  
pp. 216-220 ◽  
Author(s):  
C. A. Gregorio ◽  
D. Massaro
Keyword(s):  
Amino Acids ◽  
Plasma Membrane ◽  
Amino Acid ◽  
Kinetic Analysis ◽  
Concentration Gradient ◽  
Diffusion Constant ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Rat Lung ◽  
Energy Dependent

We examined the transport of amino acids by rat lung slices using mainly 14C-labeled alpha-aminoisobutyric acid ([14C]AIB) as a nonmetabolized amino acid. We found that [14C]AIB is accumulated by the lung in an energy-dependent fashion against a concentration gradient. The uptake is saturable, stereospecific, and follows Michaelis-Menten kinetics suggesting enzyme or carrier mediation across the plasma membrane. Insulin increases the uptake of [14C]AIB and insulin plus glucose increases its uptake even more. The diffusion constant (KD) in the presence of glucose, insulin, or glucose plus insulin is the same, 0.29 h-1; the Vmax is also the same, 83.0 mmol-1–1-h-1, under these three conditions. The apparent Km is 14.0 mM with glucose, 9.0 mM with insulin, and 4.0 mM in the presence of glucose and insulin. We conclude that the uptake of [14C]AIB is increased by insulin, and insulin plus glucose, and, based on this kinetic analysis, this is due to an increased affinity of the transport sites for AIB (decreased Km, unchanged Vmax, and KD).

Placental amino acid uptake. III. Transport systems for neutral amino acids

1976 ◽  
Vol 230 (3) ◽  
pp. 706-710 ◽  
Author(s):  
RH Enders ◽  
RM Judd ◽  
TM Donohue ◽  
CH Smith
Keyword(s):  
Amino Acids ◽  
Competitive Inhibition ◽  
Amino Acid Uptake ◽  
Transport Systems ◽  
Acid Uptake ◽  
Transport Pathways ◽  
Neutral Amino Acids ◽  
Placental Transport ◽  
L System

The human placenta is known to concentrate nearly all amino acids intracellularly for transfer to the fetus. To clarify the mechanism and regulation of this process we have determined the specificity of the principal placental transport systems for neutral amino acids. With the use of competitive inhibition techniques, three transport systems of overlapping specificity have been elucidated. These correspond approximately to the "A", "L", and "ASC" systems of Christensen and associates. In the placenta the specificity of these systems is as follows: A system - alpha aminoisobutyric acid (AIB), glycine, proline, N-methylalanine, alanine, serine, threonine, and glutamine; L system - isoleucine, valine, phenylalanine, BCH, alanine, serine, threonine, and glutamine; and ASC system - alanine, serine, threonine, and glutamine. Placental AIB uptake previously has been shown to increase with preincubation of tissue in vitro. This increase has now been found to be limited to the A system. Activity of the other two systems is essentially unaffected, demonstrating that the transport pathways are separately regulated.

Exocytosis, endocytosis and membrane recycling in Tetrahymena thermophila

1988 ◽  
Vol 89 (4) ◽  
pp. 515-520
Author(s):  
ARNO TIEDTKE ◽  
PETER HÜNSELER ◽  
JORGE FLORIN-CHRISTENSEN ◽  
MONICA FLORIN-CHRISTENSEN
Keyword(s):  
Cell Lines ◽  
Tetrahymena Thermophila ◽  
Food Vacuole ◽  
Secondary Effect ◽  
Membrane Recycling ◽  
Acid Hydrolase ◽  
Wild Type ◽  
Acid Hydrolases ◽  
Vacuole Formation ◽  
Food Vacuoles

Mutant and wild-type cell lines of Tetrahymena thermophila were used to investigate a possible connection between acid hydrolase secretion and the major processes through which membranes are recycled in this ciliated protozoon. These processes consist of food vacuole formation (endocytosis), and food vacuole egestion and mucocyst release (both exocytosis). We have found that a mutant (MS-1, see−) blocked in hydrolase secretion is not blocked in either food vacuole formation or egestion and that it has normal mucocyst exocytosis. Another line of experiments with wild-type cells showed also that hydrolase secretion and endocytosis are independent of each other. Thus, sucrose (0.1m) did not interfere with hydrolase secretion, but blocked food vacuole formation. Furthermore, release of acid hydrolases was selectively stimulated by dibucaine without any effect on food vacuole egestion. Finally, exocytosis of mucocysts could occur without simultaneous release of acid hydrolases, as when cells were exposed to (0.15M-NaCl, which evokes a massive secretory response of mucocysts. Our results demonstrate that formation and egestion of food vacuoles and exocytosis of mucocysts are unrelated to secretion of acid hydrolases. Furthermore, they suggest that secretion of acid hydrolases is not a secondary effect of membrane recycling through these processes.

Uptake of amino acids by the marine centric diatom Cyclotella cryptica

1974 ◽  
Vol 20 (8) ◽  
pp. 1109-1118 ◽  
Author(s):  
Ming Sai Liu ◽  
Johan A. Hellebust
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
High Capacity ◽  
Kinetic Studies ◽  
Amino Acid Uptake ◽  
Transport Systems ◽  
Strong Temperature Dependence ◽  
Acid Uptake ◽  
Centric Diatom ◽  
High Concentration

The transport systems for all of the amino acids studied, with the exception of isoleucine, obey saturation kinetics. The strong inhibition of the process by cyanide and dinitrophenol provides evidence that energy is required. Additional evidence for the requirement of energy for amino acid transport is the strong temperature dependence (Q10 about 2) and the high concentration ratios measured for transported amino acids.Transport parameters (Ks and Vmax) for several amino acids were determined from data for two different concentration ranges. The results of the kinetic studies indicate the presence of two or more transport systems that become saturated at different substrate concentrations for each of the amino acids. The presence of a high affinity – high capacity transport system for arginine indicates that this amino acid may be utilized efficiently by the diatom when present at low concentrations in the natural environment.Interactions between pairs of amino acids suggest that several transport systems are available. There appears to be one system for ornithine and arginine, one for glutamate and aspartate, and several for neutral amino acids.Restriction of nitrogen in the growth medium produces a marked increase in the rate of amino acid uptake, indicating that amino acids are acquired more rapidly from the medium by nitrogen-limited cells.

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