Characterization of Transport Systems for Solutes at the Blood Side of Endothelial and Parenchymal Cells by Single Circulation Paired-Tracer Dilution: A Review of Recent Studies

1991 ◽  
pp. 87-106
Author(s):  
David L. Yudilevich ◽  
Luis A. Sobrevía ◽  
L. Felipe Barros
Keyword(s):  
Transport Systems ◽  
Tracer Dilution ◽  
Parenchymal Cells ◽  
Paired Tracer Dilution

Uptake and asymmetric efflux of amino acids at maternal and fetal sides of placenta

1981 ◽  
Vol 241 (3) ◽  
pp. C106-C112 ◽  
Author(s):  
B. M. Eaton ◽  
D. L. Yudilevich
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Guinea Pig ◽  
Cellular Uptake ◽  
Transport Systems ◽  
Acid Transport ◽  
Dilution Technique ◽  
Acidic Amino Acids ◽  
Tracer Dilution ◽  
Paired Tracer Dilution

Unidirectional uptake of eighteen amino acids into the syncytiotrophoblast was measured from both the maternal and fetal circulations of isolated dually perfused guinea pig placentas using a single-circulation, paired-tracer dilution technique. A bolus containing a tritiated amino acid and L-[14C]glucose (extracellular marker) was injected intra-arterially into one circulation, and both venous outflows were sequentially sampled. The maximal cellular uptake (Umax) on the injection side was determined from (1-[3H]/[14C]) values and used to calculate the unidirectional influx. Umax values for neutral and basic amino acids ranged between 15 and 58% and were similar on both sides of the trophoblast. Uptake of the acidic amino acids and taurine was minimal. Amino acid influx from either circulation was followed by rapid tracer backflux and transplacental transfer. Tracer efflux was asymmetric and preferentially directed towards the fetal side. It is suggested that amino acid transport systems are present on both surfaces of the placenta and that net transfer from mother to fetus is the result of asymmetric efflux from the trophoblast.

scholarly journals A paired-tracer dilution method for characterizing membrane transport in the perfused rat hindlimb. Effects of insulin, feeding and fasting on the kinetics of sugar transport

1983 ◽  
Vol 214 (3) ◽  
pp. 737-743 ◽  
Author(s):  
M J Rennie ◽  
J P Idström ◽  
G E Mann ◽  
T Scherstén ◽  
A C Bylund-Fellenius
Keyword(s):  
Contractile Activity ◽  
Sugar Transport ◽  
Transport Processes ◽  
Dilution Method ◽  
Mammalian Muscle ◽  
Tracer Dilution ◽  
Kinetics Of ◽  
Paired Tracer Dilution ◽  
Feeding And Fasting

We have applied the paired-tracer dilution method to the study of transport processes in a mixed mammalian muscle preparation, the perfused rat hindlimb. The method is suitable for the characterization of the kinetic parameters of sugar and amino acid transport and its regulation by hormones, contractile activity, hypoxia, etc. Insulin stimulates sugar transport by increasing the Vmax. of the process 2-3 fold, but its affinity is unchanged. Starvation increases the affinity of sugar transport in perfused skeletal muscle.

scholarly journals Mass isolation and culture of rat kupffer cells.

1975 ◽  
Vol 141 (1) ◽  
pp. 1-10 ◽  
Author(s):  
A C Munthe-Kaas ◽  
T Berg ◽  
P O Seglen ◽  
R Seljelid
Keyword(s):  
Electron Microscopy ◽  
Tissue Culture ◽  
Liver Perfusion ◽  
K Cells ◽  
Highly Active ◽  
Transmission Electron ◽  
Acid Dnase ◽  
Collagenase Perfusion ◽  
Parenchymal Cells

Collagenase perfusion of the liver followed by pronase treatment of the cell suspension thus obtained gave a quantitative recovery of viable nonparenchymal liver cells (NPC). From these NPC, Kupffer (K) cells can be purified by attachment to tissue culture dishes. Tail vein injection of carbon 1-2 h before liver perfusion permitted stepwise calculation as well as visualization of carbon-containing K cells. When these K cells have been put into tissue culture medium with serum and incubated overnight, they exhibit typical macrophage characteristics. Phase-contrast and transmission electron microscopy showed typical macrophage morphology and scanning electron microscopy revealed well-spread cells with cytoplasmic projections and ruffled membranes. Endocytosis studies using radioactive colloidal gold and inert latex particles also indicated that these cells are highly active in pinocytosis and phagocytosis. Further characterization of K cells is the identification of Fc receptor on their membranes. Studies on lysosomal enzymes showed that purified K cells possess higher specific activities in beta-glucuronidase, acid DNase, and cathepsin D than in purified parenchymal cells.

scholarly journals Identification and Characterization of Citrus Chlorotic Spot Virus, a New Dichorhavirus Associated with Citrus Leprosis-Like Symptoms

Plant Disease ◽  
2018 ◽  
Vol 102 (8) ◽  
pp. 1588-1598 ◽  
Author(s):  
C. Chabi-Jesus ◽  
P. L. Ramos-González ◽  
A. D. Tassi ◽  
O. Guerra-Peraza ◽  
E. W. Kitajima ◽  
...  
Keyword(s):  
Virus Strain ◽  
Viral Vectors ◽  
Morphological Characterization ◽  
Spot Virus ◽  
Chlorotic Spot ◽  
Bipartite Genome ◽  
Citrus Leprosis ◽  
Average Size ◽  
Parenchymal Cells

Local chlorotic spots resembling early lesions characteristic of citrus leprosis (CL) were observed in leaves of two sweet orange (Citrus sinensis L.) trees in Teresina, State of Piauí, Brazil, in early 2017. However, despite the similarities, these spots were generally larger than those of a typical CL and showed rare or no necrosis symptoms. In symptomatic tissues, transmission electron microscopy revealed the presence of viroplasms in the nuclei of the infected parenchymal cells and rod-shaped particles with an average size of approximately 40 × 100 nm, resembling those typically observed during infection by dichorhaviruses. A bipartite genome of the putative novel virus, tentatively named citrus chlorotic spot virus (CiCSV) (RNA1 = 6,518 nucleotides [nt] and RNA2 = 5,987 nt), revealed the highest nucleotide sequence identity values with the dichorhaviruses coffee ringspot virus strain Lavras (73.8%), citrus leprosis virus N strain Ibi1 (58.6%), and orchid fleck virus strain So (56.9%). In addition to citrus, CiCSV was also found in local chlorotic lesions on leaves of the ornamental plant beach hibiscus (Talipariti tiliaceum (L.) Fryxell). Morphological characterization of mites recovered from the infected plants revealed at least two different types of Brevipalpus. One of them corresponds to Brevipalpus yothersi. The other is slightly different from B. yothersi mites but comprises traits that possibly place it as another species. A mix of the two mite types collected on beach hibiscus successfully transmitted CiCSV to arabidopsis plants but additional work is required to verify whether both types of flat mite may act as viral vectors. The current study reveals a newly described dichorhavirus associated with a citrus disease in the northeastern region of Brazil.

scholarly journals Nucleoside uptake in rat liver parenchymal cells

1996 ◽  
Vol 317 (3) ◽  
pp. 835-842 ◽  
Author(s):  
Joan MERCADER ◽  
Mireia GOMEZ-ANGELATS ◽  
Belén del SANTO ◽  
Javier CASADO ◽  
Antonio F. FELIPE ◽  
...  
Keyword(s):  
Rat Liver ◽  
Nucleoside Transport ◽  
Transport Systems ◽  
Dependent Manner ◽  
Transport Activity ◽  
Liver Parenchymal ◽  
Uridine Uptake ◽  
High Concentrations ◽  
Parenchymal Cells ◽  
Dose Dependent

Rat liver parenchymal cells express Na+-dependent and Na+-independent nucleoside transport activity. The Na+-dependent component shows kinetic properties and substrate specificity similar to those reported for plasma membrane vesicles [Ruiz-Montasell, Casado, Felipe and Pastor-Anglada (1992) J. Membr. Biol. 128, 227–233]. This transport activity shows apparent Km values for uridine in the range 8–13 μM and a Vmax of 246 pmol of uridine per 3 min per 106 cells. Most nucleosides, including the analogue formycin B, cis-inhibit Na+-dependent uridine transport, although thymidine and cytidine are poor inhibitors. Inosine and adenosine inhibit Na+-dependent uridine uptake in a dose-dependent manner, reaching total inhibition. Guanosine also inhibits Na+-dependent uridine uptake, although there is some residual transport activity (35% of the control values) that is resistant to high concentrations of guanosine but may be inhibited by low concentrations of adenosine. The transport activity that is inhibited by high concentrations of thymidine is similar to the guanosine-resistant fraction. These observations are consistent with the presence of at least two Na+-dependent transport systems. Na+-dependent uridine uptake is sensitive to N-ethylmaleimide treatment, but Na+-independent transport is not. Nitrobenzylthioinosine (NBTI) stimulates Na+-dependent uridine uptake. The NBTI effect involves a change in Vmax, it is rapid, dose-dependent, does not need preincubation and can be abolished by depleting the Na+ transmembrane electrochemical gradient. Na+-independent uridine transport seems to be insensitive to NBTI. Under the same experimental conditions, NBTI effectively blocks most of the Na+-independent uridine uptake in hepatoma cells. Thus the stimulatory effect of NBTI on the concentrative nucleoside transporter of liver parenchymal cells cannot be explained by inhibition of nucleoside efflux.

scholarly journals Isolation and characterization of mutants that produce the allantoin-degrading enzymes constitutively in Saccharomyces cerevisiae.

1982 ◽  
Vol 2 (9) ◽  
pp. 1088-1095 ◽  
Author(s):  
G Chisholm ◽  
T G Cooper
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Enzyme Synthesis ◽  
Common Element ◽  
Transport Systems ◽  
New Class ◽  
Degrading Enzymes ◽  
Isolation And Characterization ◽  
Nitrogen Repression ◽  
Internal Induction

Degradation of allantoin, allantoate, or urea by Saccharomyces cerevisiae requires the participation of four enzymes and four transport systems. Production of the four enzymes and one of the active transport systems is inducible; allophanate, the last intermediate of the pathway, functions as the inducer. The involvement of allophanate in the expression of five distinct genes suggested that they might be regulated by a common element. This suggestion is now supported by the isolation of a new class of mutants (dal80). Strains possessing lesions in the DAL80 locus produce the five inducible activities at high, constitutive levels. Comparable constitutive levels of activity were also observed in doubly mutant strains (durl dal80) which are unable to synthesize allophanate. This, with the observation that arginase activity remained at its uninduced, basal level in strains mutated at the DAL80 locus, eliminates internal induction as the basis for constitutive enzyme synthesis. Mutations in dal80 are recessive to wild-type alleles. The DAL80 locus has been located and is not linked to any of the structural genes of the allantoin pathway. Synthesis of the five enzymes produced constitutively in dal80-1-containing mutants remains normally sensitive to nitrogen repression even though the dal80-1 mutation is present. From these observations we conclude that production of the allantoin-degrading enzymes is regulated by the DAL80 gene product and that induction and repression of enzyme synthesis can be cleanly separated mutationally.

Regulation and characterization of two inducible amino-acid transport systems in Chlorella vulgaris

Planta ◽  
1983 ◽  
Vol 159 (5) ◽  
pp. 404-410 ◽  
Author(s):  
Norbert Sauer ◽  
Ewald Komor ◽  
Widmar Tanner
Keyword(s):  
Amino Acid ◽  
Chlorella Vulgaris ◽  
Amino Acid Transport ◽  
Transport Systems ◽  
Acid Transport
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