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At least 865 records · Page 48Linked to original sources

PubMed1997

Influence of hypo-osmolality on the activity of short-chain neutral amino acid carriers in trout (Salmo trutta) red blood cells.

The present study shows that in trout red blood cells the activity of some amino acid carriers, not directly involved in cell volume regulation, is affected by external osmolality. Glycine uptake has been used as the experimental approach because it was shown previously that it is effected by different carriers, namely the Na+-dependent ASC and Gly systems, as well as the Na+-independent asc and L systems. An increase in the uptake through the Gly system and the two Na+-independent carriers was found, while the ASC system appeared to be downregulated. Those systems whose activities were increased by hypo-osmolality did not share the mechanism by which this increase was obtained. Thus, the Gly system was sensitive to intracellular ionic changes, while the Na+- independent systems were mechanically stimulated, as assessed by the iso-osmotic swelling caused by ammonium chloride. On the other hand, a volume-sensitive transporter may be present in trout red blood cells, which is involved in the swelling-induced glycine movement, as can be deduced from the effect of some inhibitors such as pyridoxal phosphate, DIDS (4,4'-diisothiocyanate-stilbene-2,2'-disulfonic acid) and quinine.

Animals↗

PubMed1998

Phalangeal cone-shaped epiphyses of the hand: their natural history, diagnostic sensitivity, and specificity in cartilage hair hypoplasia and the trichorhinophalangeal syndromes I and II.

Phalangeal cone-shaped epiphyses are an ideal object for the radiologist to study with temporal reasoning, to examine their shape, diagnostic usefulness, natural history and effect on pathophysiology. Radiographs of the hands of 60 patients with cartilage hair hypoplasia (CHH), 69 with trichorhinophalangeal syndrome I (TRP I) and 11 with TRP II were examined, including 26 longitudinal observations. The early phases of cone development were recorded. In CHH a characteristic mesophalangeal type of cone in 42/47 patients of the "Age Suitable for Classification" (ASC) was detected. All 46 TRP I and 9 TRP II patients in the ASC had the previously described mesophalangeal cone type 12. However, 1/4 of these TRP I and all TRP II cases presented a milder variant of type 12: type 12 A. A complex sequence of secondary changes in the proximal interphalangeal joints in TRP I leading eventually to subluxation was recorded. It can be concluded that in the ASC the cones described are highly sensitive but not specific diagnostic indicators. In infancy and early childhood, other phalangeal changes were found, which may be of diagnostic help.

Adolescent↗

PubMed2000

Investigation of iodine-123-labelled amino acid derivatives for imaging cerebral gliomas: uptake in human glioma cells and evaluation in stereotactically implanted C6 glioma rats.

In developing iodine-123-labelled amino acid derivatives for imaging cerebral gliomas by single-photon emission tomography (SPET), we compared p-[123I]iodo-L-phenylalanine (IPA), L-[123I]iodo-1,2,3,4-tetrahydro-7-hydroxyisoquinoline-3-carboxylic acid (ITIC) and L-3-[123I]iodo-alpha-methyltyrosine (IMT) with regard to their uptake in human glioblastoma T99 and T3868 cells, and thereafter studied the mechanisms promoting the cellular uptake. The potential of the 123I-iodinated agents for use as SPET radiopharmaceuticals was evaluated in healthy experimental rats as well as in rats with stereotactically implanted C6 gliomas. The radiopharmaceutical uptake into glioblastoma cells was rapid, temperature and pH dependent, and linear during the first 5 min. Equilibrium was reached after 15-20 min, except in the case of ITIC, the initial uptake of which gradually decreased from 15 min onwards. The radioactivity concentration in glioma cells following 30-min incubation at 37 degrees C (pH 7.4) varied from 11% to 35% of the total activity per million cells (ITIC < IMT < or = IPA). Competitive inhibition experiments using alpha-(methylamino)-isobutyric acid and 2-amino-2-norbornane-carboxylic acid, known as specific substrates for systems A and L, respectively, as well as representative amino acids preferentially transported by system ASC, indicated that IPA, like IMT, is predominantly mediated by the L and ASC transport systems, while no significant involvement of the A transport system could be demonstrated. By contrast, none of the three principal neutral amino acid transport systems (A, L and ASC) appear to be substantially involved in the uptake of ITIC into glioblastoma cells. Analysis of uptake under conditions that change the cell membrane potential, i.e. in high K+ medium, showed that the membrane potential plays an important role in ITIC uptake. Alteration of the mitochondrial activity by means of valinomycin or nigericin induces a slight increase or decrease in the radiopharmaceutical uptake, suggesting a minor contribution of the mitochondria in the uptake. IPA, IMT and ITIC passed the blood-brain barrier, and thereafter showed efflux from the brain. The radioactivity concentration in healthy rat brain 15 min following intravenous injection varied from 0.07% (ITIC) to 0.27% ID/g (IPA). In comparison, the brain uptake in the stereotactically implanted C6 glioma rats was substantially higher (up to 1.10% ID/g 15 min p.i.), with tumour-to-background ratios greater than 4. These data indicate that IPA and ITIC, like IMT, exhibit interesting biological characteristics which hold promise for in vivo brain tumour investigations by SPET.

Alanine↗

PubMed2006

Methyl jasmonate and salicylic acid elicitation induces ginsenosides accumulation, enzymatic and non-enzymatic antioxidant in suspension culture Panax ginseng roots in bioreactors.

The effects of methyl jasmonate (MJ) and salicylic acid (SA) on changes of the activities of major antioxidant enzymes, superoxide anion accumulation (O2-), ascorbate, total glutathione (TG), malondialdehyde (MDA) content and ginsenoside accumulation were investigated in ginseng roots (Panax ginseng L.) in 4 l (working volume) air lift bioreactors. Single treatment of 200 microM MJ and SA to P. ginseng roots enhanced ginsenoside accumulation compared to the control and harvested 3, 5, 7 and 9 days after treatment. MJ and SA treatment induced an oxidative stress in P. ginseng roots, as shown by an increase in lipid peroxidation due to rise in O2- accumulation. Activity of superoxide dismutase (SOD) was inhibited in MJ-treated roots, while the activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), SOD, guaiacol peroxidase (G-POD), glutathione peroxidase (GPx) and glutathione reductase (GR) were induced in SA-treated roots. A strong decrease in the activity of catalase (CAT) was obtained in both MJ- and SA-treated roots. Activities of ascorbate peroxidase (APX) and glutathione S transferase (GST) were higher in MJ than SA while the contents of reduced ascorbate (ASC), redox state (ASC/(ASC+DHA)) and TG were higher in SA- than MJ-treated roots while oxidized ascorbate (DHA) decreased in both cases. The result of these analyses suggests that roots are better protected against the O2- stress, thus mitigating MJ and SA stress. The information obtained in this work is useful for efficient large-scale production of ginsenoside by plant-root cultures.

Acetates↗

PubMed2005

Relationship between the increase of effectiveness indexes and the increase of muscular efficiency with cycling power.

We determined the index of effectiveness (IE), as defined by the ratio of the tangential (effective force) to the total force applied on the pedals, using a new method proposed by Mornieux et al. (J Biomech, 2005), while simultaneously measuring the muscular efficiency during sub-maximal cycling tests of different intensities. This allowed us to verify whether part of the changes in muscular efficiency could be explained by a better orientation of the force applied on the pedals. Ten subjects were asked to perform an incremental test to exhaustion, starting at 100 W and with 30 W increments every 5 min, at 80 rpm. Gross (GE) and net (NE) efficiencies were calculated from the oxygen uptake and W(Ext) measurements. From the three-dimensional force's measurements, it was possible to measure the total force (F(Tot)), including the effective (F(Tang)) and ineffective force (F (Rad + Lat)). IE has been determined as the ratio between F(Tang) and F(Tot), applied on the pedals for three different time intervals, i.e., during the full revolution (IE(360 degrees)), the downstroke phase (IE(180 degrees Desc)) and the upstroke phase (IE(180 degrees Asc)). IE(360 degrees) and IE(180 degrees Asc) were significantly correlated with GE (r = 0.79 and 0.66, respectively) and NE (r = 0.66 and 0.99, respectively). In contrast, IE(180 degrees Desc) was not correlated to GE or to NE. From a mechanical point of view, during the upstroke, the subject was able to reduce the non-propulsive forces applied by an active muscle contraction, contrary to the downstroke phase. As a consequence, the term 'passive phase', which is currently used to characterize the upstroke phase, seems to be obsolete. The IE(180 degrees Asc) could also explain small variations of GE and NE for a recreational group.

Adult↗

PubMed2004

Characterization of photosynthetic electron transport in bundle sheath cells of maize. I. Ascorbate effectively stimulates cyclic electron flow around PSI.

Redox changes of the reaction-center chlorophyll of photosystem I (P700) and chlorophyll fluorescence yield were measured in bundle sheath strands (BSS) isolated from maize (Zea mays L.) leaves. Oxidation of P700 in BSS by actinic light was suppressed by nigericin, indicating the generation of a proton gradient across the thylakoid membranes of BSS chloroplasts. Methyl viologen, which transfers electrons from photosystem I (PSI) to O2, caused a considerable decrease in the reduction rate of P700+ in BSS after turning off actinic light, showing that electron flow from the acceptor side of PSI to stromal components is critical for this reduction. Ascorbate (Asc), and to a lesser extent malate (Mal), caused a lower level of P700+ in BSS under aerobic conditions in far-red light, implying electron donation from these substances to the intersystem carriers. When Asc or Mal was added to BSS during pre-illumination under anaerobic conditions in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU), the far-red-induced level of P700+ was lowered. The results suggest Asc and Mal can cause reduction of stromal donors, which in turn establishes conditions for rapid PSI-driven P700+ reduction. Addition of these metabolites also strongly stimulated the development of a proton gradient in thylakoids under aerobic conditions in the absence of DCMU, i.e. under conditions analogous to those in vivo. Ascorbate was a much more effective electron donor than Mal, suggesting it has a physiological role in activation of cyclic electron flow around PSI.

Ascorbic Acid↗

PubMed2005

3D-resolved investigation of the pH gradient in artificial skin constructs by means of fluorescence lifetime imaging.

PURPOSE: The development of substitutes for the human skin, e.g., artificial skin constructs (ASCs), is of particular importance for pharmaceutical and dermatologic research because they represent economical test samples for the validation of new drugs. In this regard, it is essential for the skin substitutes to be reliable models of the genuine skin, i.e., to have similar morphology and functionality. Particularly important is the barrier function, i.e., the selective permeability of the skin, which is strongly related to the epidermal pH gradient. Because the pH significantly influences the permeation profile of ionizable drugs such as nonsteroidal anti-inflammatory drugs, it is of major importance to quantitatively measure the epidermal pH gradient of the ASC and compare it to that of genuine skin. METHODS: Using three-dimensional fluorescence lifetime imaging combined with two-photon scanning microscopy, we measured with submicron resolution the three-dimensional pH gradient in the epidermis of ASCs stained with 2',7'-bis-(2-carboxyethyl)-5/6-carboxyfluorescein. RESULTS: Similar to genuine skin, the surface of the artificial epidermis has an acidic character (pH 5.9), whereas in the deeper layers the pH increases up to 7.0. Moreover, the pH gradient differs in the cell interior (maximally 7.2) and in the intercellular matrix (maximally 6.6). Apart from the similitude of the pH distribution, the genuine and the artificial skin prove to have similar morphologies and to be characterized by similar distributions of the refractive index. CONCLUSIONS: Artificial skin is a reliable model of genuine human skin, e.g., in permeability studies, because it is characterized by a similar pH gradient, a similar morphology, and a similar distribution of the refractive index to that of genuine skin.

Fluoresceins↗

PubMed1980

Na+-gradient-dependent transport of L-proline and analysis of its carrier system in brush-border membrane vesicles of the guinea-pig ileum.

Transport of L-proline was studied with membrane vesicles prepared from the brush borders of the guinea-pig ileum. The presence of an Na+ gradient from outside to inside of the vesicles stimulated L-proline uptake. Accumulation of amino acid in the vesicles reached a maximum 30 s after incubation, then decreased due to efflux and finally equilibrated at a level nearly identical to that shown in the absence of an Na+ gradient in 30 min. The peak level of the uptake was 3.5-times greater than the final equilibrium level. The equilibrium level of L-proline uptake decreased with increasing medium osmolarity. Extrapolation to infinite medium osmolarity, that is, under the condition of zero intravesicular space, showed no uptake, indicating transport of L-proline into membrane vesicles. The initial rate of uptake for 15 s was enhanced with increasing concentrations of Na+ in the external medium. A small part of the L-proline transport occurred by simple diffusion in addition to Na+-gradient-dependent transport. When L-proline concentrations were varied and transport due to diffusion was subtracted, the initial rate of uptake dependent on Na+ gradient (out greater than in) obeyed Michaelis-Menten kinetics with Km and V values of 0.67 mM and 2.73 nmol/15 s per mg protein, respectively. Evidence was obtained which indicates that L-cysteine is a substract specific for transport through system ASC (alanine-, serine-, and cysteine-preferring) and that transport in the presence of an Li+ gradient (out > in) also takes palce by the ASC system. The uptake of L-proline in the presence of an Na+ gradient (out > in) was inhibited 90% by a large excess of alpha-(methylamino)-isobutyrate, the model substrate specific for the A system (alanine-preferring). This indicates than 90% of Na+-gradient-dependent L-proline uptake is supported by the A system. The remaining 10% of L-proline uptake was found to be catalyzed by the ASC system, since L-proline uptake equivalent to this alpha-(methylamino)-isobutyrate-uninhibited part was demonstrated in the presence of Li+ gradient.

Aminoisobutyric Acids↗

PubMed1986

Effect of extracellular potassium on amino acid transport and membrane potential in fetal human fibroblasts.

The distribution ratio of the lipophilic cation tetraphenylphosphonium (TPP+) has been used to estimate the electrical potential difference across the plasma membrane in cultured human fibroblasts. These cells exhibit a membrane potential markedly influenced by the diffusion potential of K+. High extracellular potassium concentrations depolarize human fibroblasts and depress the activity of transport systems A, ASC (both serving for zwitterionic amino acids), X-AG (for anionic amino acids), and y+ (for cationic amino acids). High doses (100 microM) of the K+-ionophore valinomycin hyperpolarize the cells. This condition enhances the activity of systems A, ASC and y+. Transport systems L (for neutral amino acids) and x-C (for anionic amino acids) are insensitive to changes in extracellular K+ or to valinomycin. System X-AG is inhibited by the addition of 100 microM valinomycin, but the effect of the ionophore appears to be potential-independent. These results indicate that: (a) the activity of systems L and x-C is potential-independent and (b) the activity of systems A, ASC, X-AG and y+ is sensitive to alterations of external [K+] associated to changes in membrane potential.

Amino Acids↗

PubMed1990

Opposite effects of methylene blue and ascorbate on lipid peroxidation in muscles. Correlation with the redox state. I. Experiments on satisfied frogs.

Homogenates of heart, stomach and rectus abdominis muscles of the frog have shown different degrees of malondialdehyde (MDA) formation. MDA content was highest in heart, and lowest in stomach musculature. The resultant tissue redox-state potential (RSP) and redox potential (E'0) in homogenates determined potentiometrically also showed differences with opposite signs in relation to MDA levels. An electron acceptor, methylene blue (MB), decreased but an electron donor, ascorbate (Asc), increased the MDA level in each of the muscles. These effects were dependent upon the concentration of MB and Asc and proportional to the control MDA content in each muscle. Thus an inverse interdependence between MDA level and redox state existed even when a positive change in redox potentials was induced by MB, and also when a negative change was induced by Asc. Since there was a close negative correlation between the changes of MDA concentration and redox potential in the homogenates, it is strongly suggested that the changes of redox state in muscle are implicated in the processes leading to lipid peroxidation (LP).

Animals↗

PubMed1983

A solid-phase immunoenzymatic technique for the enumeration of specific antibody-secreting cells.

A sensitive immunoassay is described for the detection of idiotype- and isotype-specific antibody-secreting cells (ASC), based upon the well established principles of ELISA. Single cell suspensions containing ASC are incubated on solid phase to which specific antigen has been chemically conjugated. Antibody attaches to the latter within the immediate microenvironment of the ASC, producing localized zones of bound antibody which are subsequently developed as visual 'spots' in the ELISA. This assay system has sensitivity and specificity at least equivalent to haemolytic plaque assays.

Animals↗

PubMed1986

Enumeration of antibody-secreting cells by immunoprinting: sequential readout of different antibody isotypes on individual cell monolayers employing the ELISA plaque assay.

A technique is described for obtaining 'prints' of the antibody output of individual antibody-secreting cells (ASC), by repeated exposure of an immobilized ASC monolayer to coverslips coated with antigen. Zones of bound antibody on the coverslips (each being the 'print' of an individual ASC) are subsequently visualized by ELISA technology.

Antibody-Producing Cells↗

PubMed1992

Amplified ELISPOT assay for the detection of HIV-specific antibody-secreting cells in subhuman primates.

A novel immunoenzyme amplification technique has been evaluated in an ELISPOT assay for the detection of antigen-specific antibody-secreting cells (ASC) in monkeys. In this assay, mononuclear cells containing putative ASC are incubated for a few hours in antigen-coated wells. Following removal of the cells, zones of solid phase bound antibodies secreted by individual ASC are visualized in four consecutive steps. First, a primary biotinylated anti-immunoglobulin (Ig) reagent is added followed by enzyme-labelled avidin. The amplification procedure comprises the addition of biotinylated anti-enzyme antibodies in the third stage, followed by enzyme-conjugated avidin and substrate. When evaluated in a modified ELISPOT assay for the detection of simian B cells secreting antibodies to the envelope glycoprotein gp120 of the human immunodeficiency virus type 1 (HIV-1), this amplification procedure proved to be suitable even when using anti-human Ig antisera as primary antibody reagents. This development should be useful for other ELISPOT assays where species specific anti-Ig reagents are not always available and, most importantly, for enumerating cells producing immunoreactive substances in such minute amounts that they may escape detection by conventional ELISPOT assays. Furthermore, a functional simian HIV-specific ELISPOT assay could prove valuable for assessing the humoral immunogenicity of future candidate vaccines against the acquired immunodeficiency syndrome (AIDS).

Animals↗

PubMed1990

Effect of sepsis on amino acid transport system A and its response to insulin in incubated rat skeletal muscle.

The effect of sepsis on neutral amino acid transport systems A, ASC, and L, was studied in incubated rat soleus (SOL) muscles. We also examined the effects of plasma from septic rats and of varying concentrations of insulin (10 to 10(5) microU/mL), added in vitro to incubated muscles, on system A amino acid transport. Sepsis was induced by cecal ligation and puncture (CLP) in rats weighing 40 to 60 g. Control rats were sham-operated. System A activity was assessed by determining uptake of 2-(methylamino)isobutyrate (MeAIB) 16 hours after CLP or sham-operation. System ASC was studied by measuring uptake of alpha-aminoisobutyric acid (AIB) in the presence of 25 mmol/L MeAIB and 25 mmol/L 2-amino-2-norbornane carboxylic acid (BCH) to inhibit uptake by systems A and L. System L activity was defined as sodium-independent uptake of cycloleucine. MeAIB uptake was reduced by 28% in muscles of septic rats, while amino acid transport by systems ASC and L was almost identical in muscles from control and septic rats. Addition of plasma from septic rats to incubated normal SOL muscles inhibited MeAIB uptake by 31%. Addition of insulin to the incubation medium resulted in increased uptake of MeAIB, both in nonseptic and septic muscle. The lowest hormone concentration tested that significantly enhanced MeAIB uptake in nonseptic muscle was 10(2) microU/mL and in septic muscle 10 microU/mL. The results suggest that sepsis in rats specifically inhibits amino acid transport system A and that reduced muscle amino acid uptake may be caused by a circulating factor in sepsis.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed1991

Presence of cells producing antiheart autoantibodies in the inflammatory infiltrate of chronic chagasic myocarditis.

Chagasic myocarditis is associated with the appearance of circulating antiheart autoantibodies. In order to find out if there was local synthesis of those antibodies we investigated, by means of a solid immunoenzymatic technique, the presence of cells secreting antibody (ASC) against syngeneic soluble heart antigens in the mononuclear cell (MNC) population isolated from the hearts of mice chronically infected with Trypanosoma cruzi. In seven animals the number of ASC ranged between 300 and 2080 per 10(6) MNC. A similar number of cells was observed when the assay was carried out with T. cruzi-soluble antigens. When the ASC were enumerated in an assay simultaneously with both antigens, their number doubled that found in the single antigen assay, suggesting that there was no cross-reactivity between the heart and the parasite antigens. These results indicate that some of the cells in the inflammatory infiltrate of chronic chagasic myocarditis synthesize IgG autoantibodies against heart antigens, a phenomenon which may lead to a local concentration of antibody large enough to induce tissue damage.

Animals↗

PubMed1993

atonal is a proneural gene that directs chordotonal organ formation in the Drosophila peripheral nervous system.

In the Drosophila peripheral nervous system, proneural genes of the achaete-scute complex (ASC) are required for formation of the precursors of external sense organs but not of chordotonal organs. We report the isolation of a gene, atonal (ato), with evidence that it is a proneural gene for the formation of chordotonal organs. This gene is expressed in the proneural clusters and sense organ precursors that give rise to the embryonic and adult chordotonal, but not external sense, organs. Chordotonal organs are eliminated in embryos carrying chromosomal deficiencies that remove ato. Like the ASC products, ato protein contains a basic-helix-loop-helix region and heterodimerizes with daughterless protein to bind to E boxes. Moreover, ectopic expression of ato promotes the formation of extra sense organs. Despite similar proneural properties, we find that ectopic expression of the ASC genes promotes external sense organ formation exclusively, whereas ato promotes chordotonal organ formation preferentially. Thus, proneural genes are major determinants of neuronal identity.

Amino Acid Sequence↗

PubMed1994

In vitro activation and detection of antibody-secreting cells from Trypanosoma congolense-infected cattle.

B cells from the peripheral blood and spleen of Trypanosoma congolense-infected cattle and from the peripheral blood of an uninfected cohort were analysed for ability to secrete antibody and for expression of surface antigens before and after in vitro culture with interleukin-2, lipopolysaccharide and pokeweed mitogen. Antibody-secreting cells (ASC) were only detected in lymphocytes from peripheral blood after in vitro stimulation. The frequency of ASC was greater in cultures of lymphocytes from infected cattle than from the uninfected cohort. The frequency of ASC was positively correlated with the number of B cells expressing the transferring receptor but not with the expression of the CD5 antigen.

Animals↗

PubMed1987

Influenza-specific antibody-secreting cells and B cell memory in the murine lung after immunization with wild-type, cold-adapted variant and inactivated influenza viruses.

The development of regional B cell responses was studied in mice immunized intranasally with different influenza virus vaccines. The ca-variant virus was 100-fold less efficient than the parental virus in the induction of influenza virus-specific antibody secreting cells (ASCs) in the lung and failed to induce ASCs in the spleen. The ca-variant virus was also less efficient in priming for secondary IgG and IgA responses generated in vitro in both lung and spleen cell cultures. Protection against homotypic challenge in mice immunized by different vaccine strategies correlated with the development of pulmonary B cell responses rather than splenic responses. In particular, protection correlated with the presence of ASCs and IgG and IgA memory in the lung at the time of challenge.

Animals↗