Silver uptake, distribution, and effect on calcium, phosphorus, and sulfur uptake

Bean, corn, and tomato plants were grown in a nutrient solution labeled with ³²P, ⁴⁵Ca, or ³⁵S and varying concentrations of AgNO₃. Following a 6-hour treatment period, plants were harvested and analyzed. A low Ag⁺ concentration (50 nanomolar) inhibited the shoot uptake of the ions investigated. In the roots, Ca uptake increased whereas P and S uptake decreased.     

Topographic distribution of dopamine uptake,choline uptake,choline acetyltransferase,and GABA uptake in the striata of weaver mutant mice

The topographic distribution of dopamine (DA) uptake, choline uptake, choline acetyltransferase (ChAT) activity and GABA uptake within the striata of weaver mutant mice and control mice was determined. Uptake of [³H]dopamine, [³H]choline and [¹⁴C]GABA, as well as ChAT activity were determined in samples prepared from the dorsolateral, dorsomedial, ventrolateral and ventromedial portions of the striatum. In 45–60 day old control mice, dopamine uptake was homogeneously distributed throughout the striatum. On the other hand, striata from weaver mice exhibited an uneven distribution with the ventral aspects having greater uptake activity than the dorsal regions. Thus, although the ventral portion of the striatum is less severely affected than the dorsal portion, all areas of the striatum exhibited significantly reduced uptake rates. In 9 and 12 month old mice, choline uptake was higher in lateral than medial zones of the striatum of both genotypes and no differences were observed between genotypes. GABA uptake was higher in the ventral striatum than in the dorsal striatum but again no differences were found between weaver and control mice. The results of this study indicate that the entire weaver striatum is severely deficient in its ability to recapture dopamine and thus is functionally compromised. The results also indicate that the striatal cholinergic and GABAergic interneurons are not directly or indirectly affected by the weaver gene.Special ïssue dedicated to Dr. Morris H. Aprison     

Intracellular uptake,transport, and processing of gold nanostructures

Abstract

The emerging field of nanomedicine requires better understanding of the interface between nanotechnology and medicine. Better knowledge of the nano-bio interface will lead to better tools for diagnostic imaging and therapy. In this review, recent progress in understanding of how size, shape, and surface properties of nanoparticles (NPs) affect intracellular fate of NPs is discussed. Gold nanostructures are used as a model system in this regard since their physical and chemical properties can be easily manipulated. The NP-uptake is dependent on the physiochemical properties, and once in the cell, most of the NPs are trafficked via an endo-lysosomal path followed by a receptor-mediated endocytosis process at the cell membrane. Within the size range of 2–100 nm, Gold nanoparticles (GNPs) of diameter 50 nm demonstrate the highest uptake. Cellular uptake studies of gold nanorods (GNRs) show that there is a decrease in uptake as the aspect ratio of GNRs increases. Theoretical models support the size- and shape-dependent NP-uptake. The intracellular transport of targeted NPs is faster than untargeted NPs. The surface ligand and charge of NPs play a bigger role in their uptake, transport, and organelle distribution. Exocytosis of NPs is dependent on size and shape as well; however, the trend is different compared to endocytosis. GNPs are now being incorporated into polymer and lipid based NPs to build multifunctional devices. A multifunctional platform based on gold nanostructures, with multimodal imaging, targeting, and therapeutics; hold the possibility of promising directions in medical research.     

Intracellular uptake, transport, and processing of gold nanostructures

The emerging field of nanomedicine requires better understanding of the interface between nanotechnology and medicine. Better knowledge of the nano-bio interface will lead to better tools for diagnostic imaging and therapy. In this review, recent progress in understanding of how size, shape, and surface properties of nanoparticles (NPs) affect intracellular fate of NPs is discussed. Gold nanostructures are used as a model system in this regard since their physical and chemical properties can be easily manipulated. The NP-uptake is dependent on the physiochemical properties, and once in the cell, most of the NPs are trafficked via an endo-lysosomal path followed by a receptor-mediated endocytosis process at the cell membrane. Within the size range of 2-100 nm, Gold nanoparticles (GNPs) of diameter 50 nm demonstrate the highest uptake. Cellular uptake studies of gold nanorods (GNRs) show that there is a decrease in uptake as the aspect ratio of GNRs increases. Theoretical models support the size- and shape-dependent NP-uptake. The intracellular transport of targeted NPs is faster than untargeted NPs. The surface ligand and charge of NPs play a bigger role in their uptake, transport, and organelle distribution. Exocytosis of NPs is dependent on size and shape as well; however, the trend is different compared to endocytosis. GNPs are now being incorporated into polymer and lipid based NPs to build multifunctional devices. A multifunctional platform based on gold nanostructures, with multimodal imaging, targeting, and therapeutics; hold the possibility of promising directions in medical research.     

Ammonium uptake in Lemna gibba G 1, related membrane potential changes, and inhibition of anion uptake

In N-starved (?N) fronds of Lemna gibba L. G 1, NH₄⁺ uptake rates were several-fold those of NO₃^?-supplied (+N) fronds. NO₃^?, uptake in +N-plants was slow and not inhibited by addition of NH₄⁺. However, in ?N-plants with higher NO₃^? and still higher NH₄⁺ uptake rates, addition of NH₄⁺ immediately reduced the NO₃^? uptake rates to about one third until the NH₄⁺ was consumed. The membrane potential (E_m) decreased immediately upon addition of NH₄⁺ in all fronds, but whereas depolarisation was moderate and transient in +N-plants, it was strong, up to 150 mV, in N-starved plants, where E_m remained at the level of the K⁺ diffusion potential (E_D) until NH₄⁺ was removed. In N-starved plants NH₄⁺ uptake and membrane depolarisation showed the same concentration dependence, except for an apparent linear component for uptake. Phosphate uptake was inhibited by NH₄⁺ similarly to NO₃^? uptake, but only in P- and N-starved plants, not after mere P starvation. Influx of NO₃^? and H₂PO ₄^? into the negatively charged cells of Lemna is mediated by anion/H⁺ cotransport, but NH₄⁺ influx can follow the electrochemical gradient. Its saturating component may reflect a carrier-mediated NH₄⁺ uniport, the linear component diffusion of NH₄⁺ or NH₃. Inhibition of anion/H⁺ cotransport by high NH₄⁺ influx rates may be due to loss of the proton-driving force, Δμ?H⁺, across the plasmalemma. Reversible inhibition by NH₄⁺ of the H⁺ extrusion pump may contribute to the finding that Δμ?H⁺ cannot be reconstituted in the presence of higher NH₄⁺ concentrations.     

Genes for neurotransmitter synthesis, storage, and uptake

We found that the catecholamine biosynthetic enzymes tyrosine hydroxylase (TH) (EC 1.14.16.2), dopamine beta-hydroxylase (EC 1.14.17.1), and phenylethanolamine N-methyltransferase (EC 2.1.1.28) share similar protein domains in their primary structures and that they share common gene coding sequences. In a recent report we also demonstrated that antiserums directed against choline acetyltransferase (EC 2.3.1.6), glutamic acid decarboxylase (EC 4.1.1.15), and TH cause specific complement-mediated lysis of cholinergic, gamma-aminobutyric acid-ergic, and dopaminergic subpopulations of synaptosomes, respectively. This interaction of specific antibodies to the specific subpopulation of synaptosomal membrane, e.g., recognition of antibody to TH to only the dopaminergic subpopulation of synaptosomal membrane protein, indicates that the neurotransmitter enzyme and membrane protein of its own synaptosomes may also share common protein domains. Therefore, we postulate that the specific neurotransmitter biosynthetic enzyme and a certain membrane protein of the nerve endings may share similar gene coding sequences, and that expression of these proteins may determine the phenotype of the neuron.     

Biosynthesis, release, and uptake of carnosine in primary cultures

Biosynthesis, release, and uptake of carnosine (beta-alanyl-L-histidine) in highly enriched primary cell cultures of skeletal muscle and CNS tissue have been investigated. The synthesis is restricted to muscle cells, oligodendrocytes, and ensheathing cells of olfactory bulb and increases during differentiation of these cells. Astrocytes, in contrast, do not synthesize carnosine but are equipped with a dipeptide transporter by which carnosine is taken up very efficiently.     

Interaction, uptake, and processing of LbL-coated microcarriers by PMNs

Functionalized microcarriers or hollow capsules transporting active agents offer the opportunity for drug delivery inside cells. A promising application of these drug delivery systems is the direct transport as well as the release of immobilized antiinflammatory substances (AIS) into polymorphonuclear leukocytes (PMNs), which play a key role in the course of inflammatory processes. The intended delivery of AIS into the inflamed tissue could alleviate tissue destruction taking place during chronic inflammation, as well as facilitate the termination of these processes. In this study, the capability of functionalized CaCO(3) microcarriers as AIS transporter system targeted at PMNs is investigated. The time-dependent interaction of protamine sulfate and dextran sulfate multilayer-coated 5 μm ± 1 μm CaCO(3) carriers with PMNs, in comparison with the usage of SiO(2) carriers as monodisperse model system of defined sizes (1, 3, and 5 μm), reveals a sufficient carrier/cell interaction and uptake for coincubation periods between 2 and 24 h. Furthermore, the microcarriers are exposed to an environment simulating primary granule/phagosomal conditions after phagocytosis by means of PMN stimulation. The incubation of CaCO(3) microcarriers with cell supernatant demonstrates a partial multilayer decomposition (three to five layers) within 24 h, allowing the gradual release of AIS within the short PMN life span. This observation suggests a potential application for this drug delivery system inside immunologically active cells and may open the way to new alternatives in the treatment of chronic processes.     

Adenosine uptake, transport, and metabolism in human erythrocytes

Using rapid kinetic techniques, we have determined the kinetics of zero-trans influx and equilibrium exchange of adenosine, and its uptake and in situ phosphorylation at 25 degrees C in human erythrocytes which were pretreated with 2'-deoxycoformycin to inhibit deamination of adenosine. Both the Km and Vmax for adenosine transport were about 300 times higher than those for the in situ phosphorylation of adenosine (Km about 0.2 microM), so that the first order rate constants for both processes were about the same. In contrast, the first order rate constant for adenosine deamination by untreated, intact cells was about 20% of that of adenosine transport or phosphorylation. These kinetic properties of the various steps, in combination with substrate inhibition of adenosine phosphorylation above 1 microM adenosine, assure that, at extracellular concentrations of physiological relevance (less than 1 microM), adenosine is very rapidly and efficiently salvaged by the erythrocytes and converted to ATP, whereas at extracellular concentrations of 10 microM or higher, practically all adenosine transported into the cells is deaminated. When the concentration of adenosine was 0.1 microM, a 10% (v/v) suspension of erythrocytes depleted the extracellular fluid of adenosine within 1 min of incubation at 25 degrees C.     

Lipoprotein lipase: genetics,lipid uptake,and regulation

Lipoprotein lipase (LPL) regulates the plasma levels of triglyceride and HDL. Three aspects are reviewed. 1) Clinical implications of human LPL gene variations: common mutations and their effects on plasma lipids and coronary heart disease are discussed. 2) LPL actions in the nervous system, liver, and heart: the discussion focuses on LPL and tissue lipid uptake. 3) LPL gene regulation: the LPL promoter and its regulatory elements are described.     

Tetracyclines: antibiotic action,uptake, and resistance mechanisms

Tetracyclines probably penetrate bacterial cells by passive diffusion and inhibit bacterial growth by interfering with protein synthesis or by destroying the membrane. A growing number of various bacterial species acquire resistance to the bacteriostatic activity of tetracycline. The two widespread mechanisms of bacterial resistance do not destroy tetracycline: one is mediated by efflux pumps, the other involves an EF-G-like protein that confers ribosome protection. Oxidative destruction of tetracycline has been found in a few species. Several efflux transporters, including multidrug-resistance pumps and tetracycline-specific exporters, confer bacterial resistance against tetracycline. Single amino acids of these carrier proteins important for tetracycline transport and substrate specificity have been identified, allowing the mechanism of tetracycline transport to begin to emerge. Received: 19 January 1996 / Accepted: 1 March 1996     

Imprinting, digoxin uptake and storage in Tetrahymena

Tetrahymenas after a single exposure to high concentration of digoxin, release glycoside into the culture medium even three days after removal of the drug. After nine or fifteen days, however, this effect subsides. Re-administration of digoxin causes the digoxin consumption (storage) of Tetrahymenas to increase. This observation indicates that the digoxin imprinting previously demonstrated in mammals occurs also in Tetrahymena. The experiments raise the possibility that also Tetrahymenas are capable of producing a digoxin-like substance detectable by radioimmunoassay.     

水稻铁吸收、转运及调控的分子机制研究进展

铁是水稻生长和发育所必需的营养元素之一。研究表明,水稻既可以以螯合物的形式从土壤中吸收Fe³⁺、Fe²⁺,又可以直接转运根际土壤中游离的Fe²⁺。科研人员已经鉴定了很多参与铁离子吸收和转运的重要分子元件,包括转运蛋白、酶、螯合物等,同时也挖掘了部分调控这些分子元件表达的上游基因。碱性土壤的高pH值影响水稻对铁离子的吸收和利用,因此,科研人员通过改良碱性土壤中铁离子的利用效率来改良水稻的耐碱性,并取得了一定的成效。本文主要对上述内容进行了综述,并对该领域未来的研究方向进行了展望。     

Iron uptake,trafficking and homeostasis in plants

Iron is an essential micronutrient with numerous cellular functions, and its deficiency represents one of the most serious problems in human nutrition worldwide. Plants have two major problems with iron as a free ion: its insolubility and its toxicity. To ensure iron acquisition from soil and to avoid iron excess in the cells, uptake and homeostasis are tightly controlled. Plants meet the extreme insolubility of oxidized iron at neutral pH values by deficiency-inducible chelation and reduction systems at the root surface that facilitate uptake. Inside the cells the generation of highly toxic hydroxyl radicals by iron redox changes is avoided by intricate chelation mechanisms. Organic acids, most notably nicotianamine, and specialized proteins bind iron before it can be inserted into target molecules for biological function. Uptake and trafficking of iron throughout the plant is therefore a highly integrated process of membrane transport and reduction, trafficking between chelator species, whole-plant allocation and genetic regulation. The improvement of crop plants with respect to iron efficiency on iron-limiting soils and to iron fortification for human nutrition has been initiated by breeding and biotechnology. These efforts have to consider molecular and physiological evidence to overcome the inherent barriers and problems of iron metabolism.     

Oxygen uptake, acidification of medium and nitrate uptake induced by blue light in nitrate-starved Chlorella cells

Blue light-induced oxygen uptake of the colorless mutant of Chlorella kessleri (No. 9.80) was 30-40% higher in the presence of exogenous glycine than in its absence. None of the other amino acids tested had this effect. Moreover, mutant cells in which glutamine synthetase was inhibited by methionine sulphoximine, accumulated approximately 65% more ammonium ions under blue irradiation in the presence of exogenous glycine than in its absence. The protein kinase C inhibitors, staurosporine or K252a, reduced the enhancement of oxygen uptake by approximately 40%. The present results indicate that blue light-dependent deamination of endogenous glycine might be a prerequisite for enhanced oxygen uptake in Chlorella. This blue light-induced oxygen uptake was not influenced by the inhibitors of protein phosphatase, calyculin A or okadaic acid. On the contrary, calyculin A and okadaic acid had a marked effect on the acidification of the suspension medium and nitrate uptake induced by blue light in Chlorella cells. The different responses to the inhibitors of protein kinase and phosphatase suggest the presence of different pathways among the blue light signal transduction operating on oxygen uptake, acidification of the medium and nitrate uptake in Chlorella.     

Factors affecting uptake of measles,mumps, and rubella immunisation.

OBJECTIVE--To study factors affecting uptake of measles, mumps, and rubella immunisation. DESIGN--Cohort study using data from computerised child health systems. SETTING--10 health districts in North East Thames and North West Thames regions. SUBJECTS--7841 children born in January to March 1990 and resident in the districts up till the end of October 1991. MAIN OUTCOME MEASURES--Overall uptake of measles, mumps, and rubella immunisation, variation of uptake among groups of children, and odds ratio of being vaccinated against measles, mumps, and rubella. RESULTS--The overall uptake rate of measles, mumps, and rubella immunisation for the study cohort in the 10 districts was 82%. Wide variation was identified among children with different demographic characteristics. Lower uptake was associated with absent or incomplete primary immunisation, including omission of pertussis vaccine. Other factors affecting uptake included the type of resident district, birth order, where registered for immunisation (general practitioner or clinic), and one parent family status. CONCLUSIONS--Many districts have difficulties in meeting the 90% target for measles, mumps, and rubella immunisation, mainly because of the characteristics of their local population. To increase overall coverage, the health service should target families with adverse factors, especially those whose children have missed previous immunisations.