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Results for “Biological Transport, Active”

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At least 19 recordsLinked to original sources
PubMed2001

Cl(-)-ATPases: biological active transporters.

Five widely documented mechanisms of chloride transport across plasma membranes are: anion-coupled antiport; sodium and hydrogen-coupled symport; Cl- channels; and an electrochemical coupling process. No genetic evidence has yet been provided for primary active chloride transport despite numerous reports of cellular Cl(-)-stimulated ATPases co-existing, in the same tissue, with uphill chloride transport that could not be accounted for by the five common chloride transport processes. Cl(-)-stimulated ATPase activity is a common property of practically all biological cells with the major location being of mitochondrial origin. It also appears that plasma membranes are sites of Cl(-)-stimulated ATPase activity. Recent studies of Cl(-)-stimulated ATPase activity and active chloride transport in the same membrane system, including liposomes, suggest a mediation by the ATPase in net movement of chloride up its electrochemical gradient across plasma membranes. Further studies, especially from a molecular biological perspective, are required to confirm a direct transport role to plasma membrane-localized Cl(-)-stimulated ATPases.

Adenosine Triphosphatases↗
PubMed1998

Protein kinase C activation increases transepithelial transport of biologically active insulin.

Protein kinase C activation leads to tight junctional leakiness and, consequently, to increased transepithelial (paracellular) solute flux across epithelial barriers. This leakiness is shown here to result in as much as a 20-fold increase in the transepithelial flux of insulin. Using an epithelial/fibroblast coculture model, this transepithelially transported insulin is shown to be biologically active. The 3T3 fibroblasts situated on one side of the epithelial barrier exhibited increased insulin binding and resulting DNA synthesis when the epithelial junctions were made leaky to insulin on the opposite side of the epithelial barrier. The dramatically enhanced permeability of macromolecules across epithelial cell layers undergoing protein kinase C activation may play a significant role in epithelial cancer, immunology, and drug delivery.

3T3 Cells↗
PubMed1988

Transport of biologically active material in laser cutting.

The transport of biologically active material during laser cutting with CO2 and Er lasers is demonstrated. This transport mechanism removes particles from the surface of gelatin, agar, and liver samples into the depth of the laser-formed craters. The transport phenomenon is explained by a contraction and condensation of enclosed hot water vapor. We show by cultivating transported bacteria in agar that biological particles can survive the shock of the transport. Determination of the numbers of active cells evidences a more pronounced activity of the cultivated bacteria after impact with an Er laser than with a CO2 laser.

Agar↗
PubMed1987

The mutual binding exclusion mechanism in active transport across biological membranes.

The coupling mechanism of sarcoplasmic reticulum ATPase is based on the reciprocal influence of calcium binding and phosphorylation domains. Cooperative calcium binding activates the enzyme, permitting utilization of ATP by transfer of its terminal phosphate to the enzyme. Occupancy of the phosphorylation domain then produces internalization and dissociation of the bound calcium. Hydrolytic cleavage of Pi completes the catalytic and transport cycle. Conversely, the phosphorylated enzyme intermediate can be formed with Pi in the absence of Ca2+. This intermediate is then destabilized by calcium binding, permitting formation of ATP by phosphoryl transfer to ADP.

Animals↗
PubMedDate not supplied

[Molecular mechanisms of receptor-mediated endocytosis and their use in directed transport of biologically active compounds].

The review considers the general and specific mechanisms of receptor-mediated endocytosis of various endogenic and exogenic bioactive compounds. The application of these mechanisms for developing of effective approaches to site-directed transport of bioactive compound to certain target cells and tissues and ways of their employment in biology and medicine are discussed.

Animals↗
PubMed1977

Energetics and molecular biology of active transport in bacterial membrane vesicles.

Bacterial membrane vesicles retain the same sidedness as the membrane in the intact cell and catalyze active transport of many solutes by a respiration-dependent mechanism that does not involve the generation of utilization of ATP or other high-energy phosphate compounds. In E. coli vesicles, most of these transport systems are coupled to an electrochemical gradient of protons (deltamuH+, interior negative and alkaline) generated primarily by the oxidation of D-lactate or reduced phenazine methosulfate via a membrane-bound respiratory chain. Oxygen or, under appropriate conditions, fumarate or nitrate can function as terminal electron acceptors, and the site at which deltamuH+ is generated is located before cytochrome b1 in the respiratory chain. Certain (N-dansyl)aminoalkyl-beta-D-galactopyranosides (Dns-gal) and N(2-nitro-4-azidophenyl)aminoalkyl 1-thio-beta-D-galactopyranosides (APG) are competitive inhibitors of lactose transport but are not transported themselves. Various fluorescence techniques, direct binding assays, and photoinactivation studies demonstrate that the great bulk of the lac carrier protein (ca. 95%) does not bind ligand in the absence of energy-coupling. Upon generation of a deltamuH+ (interior negative and alkaline), binding of Dns-gal and APG-dependent photoinactivation are observed. The data indicate that energy is coupled to the initial step in the transport process, and suggest that the lac carrier protein may be negatively charged.

Bacteria↗
PubMed1993

Diffusion versus iontophoresis in the transport of gentamicin in the burned rabbit ear model.

This experimental study demonstrates that iontophoresis can be used to transport biologically active gentamicin into auricular cartilage. Fifty female New Zealand White rabbits were divided into three groups: live controls with unburned ears, live animals with burn-injured ears (deep or partial-thickness), and euthanized animals with unburned ears. Each group was then divided into subgroups that received gentamicin transported by iontophoresis or diffusion. In ears subjected to iontophoresis, adequate gentamicin activity could be demonstrated only in the cartilage of euthanized animals with unburned ears and live animals with full-thickness burned ears. Diffusion did not transport a detectable level of gentamicin in any instance. Diffusion is ineffective in the transport of gentamicin and should not be used as a primary method of treatment for ear chondritis. Iontophoresis did not transport active gentamicin across partial-thickness burns, presumably because the migrating antibiotic molecules were dispersed throughout the body by the circulation. However, if the circulation is destroyed, as in a full-thickness burn, iontophoresis can move the biologically active gentamicin into the cartilage.

Animals↗
PubMed2002

Role of overlapping glycosylation sequons in antigenic properties, intracellular transport and biological activities of influenza A/H2N2 virus haemagglutinin.

The haemagglutinin (HA) protein of influenza A/H2N2 virus possesses five oligosaccharide attachment sites, two of which have overlapping glycosylation sequons at positions 20-23 (NNST) and 169-172 (NNTS). Here, the role of these two oligosaccharide attachment sites is investigated with regard to antigenic property, intracellular transport and biological activity of the HA protein. Glycosylation-site HA mutants with mutation(s) in their overlapping glycosylated sequons, each of which had one or two oligosaccharide attachment sites removed, were constructed. Comparison of electrophoretic mobility between the wt and mutant HA proteins showed that both Asn residues 20 and 21 and Asn residues 169 and 170 could be used for glycosylation. Analysis of reactivity of the mutants with anti-HA monoclonal antibodies suggested that amino acid changes at these two positions result in a conformational change of the HA molecule. Even if oligosaccharide chains linked to Asn 20 or 21 and Asn 169 or 170 are eliminated, the antigenic properties, intracellular transport and biological activities are not influenced strongly. Thus it is reasonable to conclude that the two overlapping glycosylation sequons at positions 20-23 and 169-172 are conserved among all of the HAs of influenza A/H2N2 viruses because conservation of the amino acid sequence itself rather than that of N-glycosylation is essential for the formation of the proper conformation, intracellular transport and biological activities of the H2 subtype HA.

Animals↗
PubMedDate not supplied

[Conformational mechanism for transforming energy during active ion transport in a biological membrane].

A statistical model of active transport of ions in the biomembrane is presented. The coefficient of energy conversion for linear and non-linear processes in this system is obtained. It is shown that in the linear case this coefficient is equal to that obtained in linear thermodynamics. On the basis of the maximum of this coefficient transport parameters for ions are found. The results of the statistical model are in a good agreement with the experiments on the biological membranes.

Biological Transport, Active↗
PubMed2001

Cl(-)-ATPases: Novel primary active transporters in biology.

Five widely documented mechanisms of chloride transport across plasma membranes are anion-coupled antiport, sodium and hydrogen-coupled symport, Cl(-)channels, and an electrochemical coupling process. No genetic evidence has yet been provided for primary active chloride transport despite numerous reports of cellular Cl(-)-stimulated ATPases co-existing, in the same tissue, with uphill chloride transport that could not be accounted for by the five common chloride transport processes. Cl(-)-stimulated ATPase activity is a common property of practically all biological cells with the major location being of mitochondrial origin. It also appears that plasma membranes are sites of Cl(-)-stimulated ATPase activity. Recent studies of Cl(-)-stimulated ATPase activity and active chloride transport in the same membrane system, including liposomes, suggest a medication by the ATPase in net movement of chloride up its electrochemical gradient across plasma membranes. Further studies, especially from a molecular biological perspective, are required to confirm a direct transport role to plasma membrane-localized Cl(-)-stimulated ATPases. J. Exp. Zool. 289:215-223, 2001.

Adenosine Triphosphatases↗
PubMed1995

Transport of biologically active interferon-gamma across human skin in vitro.

PURPOSE: Several studies have suggested epidermal uptake of cytokines, such as interferons, can be facilitated using topical liposomal formulations. We have evaluated the in vitro transport of biologically active recombinant human interferon-gamma (rhIFN-gamma) into and through split-thickness human skin to assess this possibility. METHODS: Skin samples were exposed to rhIFN-gamma under various conditions involving hydrated and dry surface conditions in the presence and absence of liposomes. A new low-level ELISA and an anti-viral bioassay were used to quantitate transported rhIFN-gamma. Immunohistochemical staining for ICAM-1 expression by keratinocytes was used to visualize the extent and distribution of rhIFN-gamma transport. RESULTS: Apparent steady-state transport of rhIFN-gamma occurred within the first 5 hours of exposure with approximately 10% of transported rhIFN-gamma demonstrating bioactivity. While the permeability of rhIFN-gamma across human skin under drying conditions was enhanced by the presence of liposomes, no augmentation of permeability was observed when the skin was kept hydrated. Liposomal formulations of rhIFN-gamma had greater transport rates than aqueous formulations when the applied formulations were allowed to dry after dosing. CONCLUSIONS: Our results demonstrate the transport of biologically active rhIFN-gamma across human skin in vitro and suggest a role for stratum corneum hydration as one possibility for the augmented cytokine transport.

Adult↗
PubMed2002

Effect of addition of new oligosaccharide chains to the globular head of influenza A/H2N2 virus haemagglutinin on the intracellular transport and biological activities of the molecule.

The haemagglutinin (HA) of influenza A/H2N2 virus possesses six antigenic sites (I-A to I-D, II-A and II-B), and sites I-A, I-B and I-C are located in the regions corresponding to sites A, B and D on the H3 HA. We demonstrated previously that most escape mutants selected by mAbs to site I-A, I-B or I-C had acquired a new oligosaccharide at position 160, 187 or 131, respectively, but this has never occurred during circulation of A/H2N2 virus in humans. Here, to examine whether the H2 HA has the potential to gain two new oligosaccharides on its tip, 31 double escape mutants were isolated by using a single escape mutant with an oligosaccharide at position 160, 187 or 131 as a parental virus and a mAb to an antigenic site different from that to which the mAb used for selection of the parental virus was directed as a selecting antibody, but there were no mutants with two new oligosaccharides. Glycosylation-site HA mutants containing one to three oligosaccharides at positions 160, 187 and 131 were also constructed and their intracellular transport and biological activities were analysed. The results showed that all of the mutant HAs were transported to the cell surface but exhibited a decrease in both receptor-binding and cell-fusing activities. Thus, influenza A/H2N2 virus may have failed to increase the number of oligosaccharides on the HA because, if this happens, the biological activities of the HA are reduced, decreasing the ability of the virus to replicate in humans.

Animals↗
PubMed2001

Role of individual oligosaccharide chains in antigenic properties, intracellular transport, and biological activities of influenza C virus hemagglutinin-esterase protein.

The hemagglutinin-esterase (HE) glycoprotein of influenza C virus is composed of three domains: a stem domain active in membrane fusion (F), an acetylesterase domain (E), and a receptor-binding domain (R). The protein contains eight N-linked glycosylation sites, four (positions 26, 395, 552, and 603) in the F domain, three (positions 61, 131, and 144) in the E domain, and one (position 189) in the R domain. Here, we investigated the role of the individual oligosaccharide chains in antigenic properties, intracellular transport, and biological activities of the HE protein by eliminating each of the glycosylation sites by site-specific mutagenesis. Comparison of electrophoretic mobility between the wild-type and the mutant proteins showed that while seven of the glycosylation sites are used, one (position 131) is not. Analysis of reactivity of the mutants with anti-HE monoclonal antibodies demonstrated that glycosylation at position 144 is essential for the formation of conformation-dependent epitopes. It was also evident that glycosylation at the two sites in the F domain (positions 26 and 603), in addition to that in the E domain (position 144), is required for the HE molecule to be transported from the endoplasmic reticulum and that mutant HEs lacking one of these three sites failed to undergo the trimer assembly. Removal of an oligosaccharide chain at position 144 or 189 resulted in a decrease in the esterase activity. By contrast, two mutants lacking an oligosaccharide chain at position 26 or 603, which were defective not only in cell surface expression but in trimerization, possessed full-enzyme activity, suggesting that the HE monomers present within the cell have acetylesterase activity. Fusion activity of cells expressing each of mutant HEs was found to be comparable with the ability of the protein to be transported to the cell surface, suggesting that there is no specific oligosaccharide chain that plays a critical role in promoting membrane fusion.

Acetylesterase↗