Replacement of ordinary water with heavy water causes a sharp reduction of the rates of both primary hydrogen ion transport (at the plasma membrane ATPase) and secondary symports (H(+)-associated transports of sugars and amino acids) in several species of yeast. At the same time, the hydrolytic activity of the ATPase is affected only very little. Likewise, the membrane potential, the delta pH and, correspondingly, the accumulation ratios of the various symported solutes are altered much less. This serves as evidence that H+ or H3O+ ions are direct participants in the various active transports of nutrients in yeast.

• MeSH
• adenosintrifosfatasy metabolismus   MeSH
• aktivní transport MeSH
• deuterium metabolismus   MeSH
• kinetika MeSH
• koncentrace vodíkových iontů MeSH
• membránové potenciály MeSH
• mitosporické houby metabolismus   MeSH
• protony * MeSH
• Rhodotorula metabolismus   MeSH
• Saccharomyces cerevisiae metabolismus   MeSH
• Saccharomycetales metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• adenosintrifosfatasy MeSH
• deuterium MeSH
• protony * MeSH

Most nutrients and ions in bacteria, yeasts, algae, and plants are transported uphill at the expense of a gradient of the electrochemical potential of protons deltamu-H+ (a type of secondary active transport). Diagnosis of such transports rests on the determination of the transmembrane electrical potential difference deltapsi and the difference of pH at the two membrane sides. The behavior of kinetic parameters K(T) (the half-saturation constant) and J(max), (the maximum rate of transport) upon changing driving ion concentrations and electrical potentials may be used to determine the molecular details of the transport reaction. Equilibrium accumulation ratios of driven solutes are expected to be in agreement with the deltapsi and deltapH measured independently, as well as with the Haldane-type expression involving K(T) and J(max). Different stoichiometries of H+/solute, as well as intramembrane effects of pH and deltapsi, may account for some of the observed inconsistencies.

• MeSH
• biologické modely MeSH
• elektrochemie MeSH
• iontový transport fyziologie   MeSH
• kinetika MeSH
• koncentrace vodíkových iontů MeSH
• membránové potenciály MeSH
• protonmotorická síla fyziologie   MeSH
• termodynamika MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Membrane vesicles obtained from Acholeplasma laidlawii accumulate glucose as well as maltose and fructose against their concentration gradient in the absence of exogenous energy sources. Glucose uptake by membrane vesicles is inhibited by anaerobiosis and by electron transfer inhibitors, such as rotenone and amytal, but not by 2-heptyl-4-hydroxyquinoline N-oxide, antimycin A, cyanide and azide. Rotenone, cyanide and amytal also produce a rapid efflux of glucose from the membrane vesicles. Arsenate, oligomycin and N,N'-dicyclohexylcarbodimide do not inhibit glucose transport. Transport of glucose is markedly inhibited by proton conductors such as CCCP and pentachlorophenol. It is concluded that glucose transport can be driven by a high-energy state of the membrane or by the membrane potential.

• MeSH
• Acholeplasma laidlawii metabolismus   MeSH
• aktivní transport účinky léků   MeSH
• amobarbital farmakologie   MeSH
• anaerobióza MeSH
• buněčná membrána metabolismus   MeSH
• chemická deprese MeSH
• fruktosa metabolismus   MeSH
• glukosa metabolismus   MeSH
• maltosa metabolismus   MeSH
• rotenon farmakologie   MeSH
• rozpřahující látky farmakologie   MeSH
• subcelulární frakce MeSH
• sulfhydrylová reagencia farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• amobarbital MeSH
• fruktosa MeSH
• glukosa MeSH
• maltosa MeSH
• rotenon MeSH
• rozpřahující látky MeSH
• sulfhydrylová reagencia MeSH

• Klíčová slova
• AORTA *, CHLORIDES *, MUSCLE, SMOOTH *, POTASSIUM *, SODIUM *,
• MeSH
• aktivní transport MeSH
• aorta * MeSH
• chloridy * MeSH
• Columbidae * MeSH
• draslík * MeSH
• elektrolyty * MeSH
• hladké svalstvo * MeSH
• ionty * MeSH
• králíci MeSH
• sodík * MeSH
• svalnatý žaludek ptáků * MeSH
• zvířata MeSH
• Check Tag
• králíci MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chloridy * MeSH
• draslík * MeSH
• elektrolyty * MeSH
• ionty * MeSH
• sodík * MeSH

• Klíčová slova
• GLUCOSE *, INTESTINE, SMALL *,
• MeSH
• aktivní transport MeSH
• glukosa * MeSH
• krysa rodu Rattus MeSH
• střeva * MeSH
• techniky in vitro MeSH
• tenké střevo * MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• glukosa * MeSH

Anion receptors can be used to transport ions across lipid bilayers, which has potential for therapeutic applications. Synthetic bicarbonate transporters are of particular interest, as defects in transmembrane transport of bicarbonate are associated with various diseases. However, no convenient method exists to directly observe bicarbonate transport and study the mechanisms involved. Here, an assay is presented that allows the kinetics of bicarbonate transport into liposomes to be monitored directly and with great sensitivity. The assay utilises an encapsulated europium(III) complex, which exhibits a large increase in emission intensity upon binding bicarbonate. Mechanisms involving CO2 diffusion and the dissipation of a pH gradient are shown to be able to lead to an increase in bicarbonate concentration within liposomes, without transport of the anion occurring at all. By distinguishing these alternative mechanisms from actual bicarbonate transport, this assay will inform the future development of bicarbonate transporters.

• Klíčová slova
• bicarbonate, fluorescent probes, ion transport, membranes, supramolecular chemistry,
• MeSH
• biologický transport MeSH
• hydrogenuhličitany * MeSH
• iontový transport MeSH
• kinetika MeSH
• koncentrace vodíkových iontů MeSH
• lipidové dvojvrstvy * MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• hydrogenuhličitany * MeSH
• lipidové dvojvrstvy * MeSH

1. In order to investigate mechanisms of Na+ transfer, the unidirectional maternal-fetal clearance (Kmf) of 22Na+ and of 51Cr-EDTA (a marker of paracellular diffusion) was measured across the intact or umbilically or dually perfused placenta of the anaesthetized rat. 2. The Kmf of 22Na+ in the intact preparation (18.5 +/- 2.7 microliters min-1, mean +/- S.D., n = 105 placentas) exceeded that of 51Cr-EDTA in the same experiments (1.4 +/- 0.3 microliters min-1) by more than ten times, whereas the difference in their diffusion coefficients in water was only 2-fold. In the perfused preparations the difference in the Kmf values was 6-fold. 3. Assuming that a simple model of paracellular diffusion through wide pores was one component of transfer, the Kmf of 51Cr-EDTA and the diffusion coefficients were used to calculate a component of 22Na+ clearance (Kmf,residual) and of Na+ flux (Jmf,residual) across the perfused placentas which could not be accounted for by transfer through the paracellular route. 4. Kmf,residual of 22Na+ across the dually perfused placenta was significantly lower when temperature was reduced, the temperature quotient (Q10) of the transfer being about 2. Kmf,residual was also significantly lower when 0.1 mM ouabain was perfused on the fetal side. Jmf,residual exhibited saturation kinetics characterized by an apparent Michaelis constant (Km) of 90 mM. Kmf,residual was not influenced by 0.5 mM frusemide, 0.5 mM amiloride or by 0.5 mM hydrochlorothiazide administered to the maternal side. It was significantly increased by 1 mM alanine on the maternal side suggesting that the coupled transfer of Na+ and amino acids may contribute significantly to the maternal-fetal flux of Na+. 5. These observations suggest that most (80%) of the maternal-fetal flux of Na+ across the rat placenta is effected by active transcellular transport. This transport involves passive entry of Na+ into the trophoblast from the maternal side by a largely unknown saturable mechanism and active extrusion of Na+ from trophoblast to the fetal side by Na(+)-K(+)-ATPase.

• MeSH
• aktivní transport účinky léků   MeSH
• anestezie MeSH
• difuze MeSH
• diuretika farmakologie   MeSH
• EDTA metabolismus   MeSH
• fenazon metabolismus   MeSH
• kinetika MeSH
• krysa rodu Rattus MeSH
• maternofetální výměna látek fyziologie   MeSH
• nízká teplota MeSH
• ouabain farmakologie   MeSH
• placenta metabolismus   MeSH
• potkani Wistar MeSH
• sodík metabolismus   MeSH
• techniky in vitro MeSH
• těhotenství MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• těhotenství MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• diuretika MeSH
• EDTA MeSH
• fenazon MeSH
• ouabain MeSH
• sodík MeSH

Ion transport was measured in jejunal biopsies using short-circuit current (SCC) as an index of net electrogenic ion transport. Increases in SCC associated with stimulation of Cl- secretion were observed in control tissues, but CF tissues did not exhibit such a response, indicating a failure of intestinal Cl- secretion. The rise in SCC associated with Na(+)-linked glucose absorption was greater in CF tissues than in controls, reflecting an enhanced active absorption of glucose.

• MeSH
• aktivní transport MeSH
• cystická fibróza metabolismus   MeSH
• intestinální absorpce MeSH
• ionty MeSH
• jejunum metabolismus   MeSH
• lidé MeSH
• techniky in vitro MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• ionty MeSH

The Drosophila salivary glands (SGs) were well known for the puffing patterns of their polytene chromosomes and so became a tissue of choice to study sequential gene activation by the steroid hormone ecdysone. One well-documented function of these glands is to produce a secretory glue, which is released during pupariation to fix the freshly formed puparia to the substrate. Over the past two decades SGs have been used to address specific aspects of developmentally-regulated programmed cell death (PCD) as it was thought that they are doomed for histolysis and after pupariation are just awaiting their fate. More recently, however, we have shown that for the first 3-4 h after pupariation SGs undergo tremendous endocytosis and vacuolation followed by vacuole neutralization and membrane consolidation. Furthermore, from 8 to 10 h after puparium formation (APF) SGs display massive apocrine secretion of a diverse set of cellular proteins. Here, we show that during the period from 11 to 12 h APF, the prepupal glands are very active in calcium oxalate (CaOx) extrusion that resembles renal or nephridial excretory activity. We provide genetic evidence that Prestin, a Drosophila homologue of the mammalian electrogenic anion exchange carrier SLC26A5, is responsible for the instantaneous production of CaOx by the late prepupal SGs. Its positive regulation by the protein kinases encoded by fray and wnk lead to increased production of CaOx. The formation of CaOx appears to be dependent on the cooperation between Prestin and the vATPase complex as treatment with bafilomycin A1 or concanamycin A abolishes the production of detectable CaOx. These data demonstrate that prepupal SGs remain fully viable, physiologically active and engaged in various cellular activities at least until early pupal period, that is, until moments prior to the execution of PCD.

• Klíčová slova
• Drosophila, anion extrusion, calcium oxalate, fruitfly salivary glands, labial nephridia, prestin,
• MeSH
• aktivní transport fyziologie   MeSH
• Drosophila melanogaster MeSH
• protein-serin-threoninkinasy genetika   metabolismus   MeSH
• proteiny Drosophily genetika   metabolismus   MeSH
• proteiny přenášející anionty biosyntéza   genetika   metabolismus   MeSH
• slinné žlázy metabolismus   MeSH
• šťavelan vápenatý metabolismus   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fray protein, Drosophila MeSH Prohlížeč
• prestin protein, Drosophila MeSH Prohlížeč
• protein-serin-threoninkinasy MeSH
• proteiny Drosophily MeSH
• proteiny přenášející anionty MeSH
• šťavelan vápenatý MeSH

Neither exit nor counterflow efflux of thiamin, taken up previously by an active transport, were found in Saccharomyces cerevisiae, in either the wild type or a mutant with a lower rate of thiamin phosphorylation. Complete inhibition of thiamin phosphorylation by oxythiamin did not lead to any release of thiamin taken up by the cell.

• MeSH
• aktivní transport účinky léků   MeSH
• fosforylace MeSH
• kinetika MeSH
• mutace MeSH
• oxythiamin farmakologie   MeSH
• Saccharomyces cerevisiae genetika   růst a vývoj   metabolismus   MeSH
• thiamin antagonisté a inhibitory   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• oxythiamin MeSH
• thiamin MeSH