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1.
Phys Rev Lett ; 131(14): 143401, 2023 Oct 06.
Article in English | MEDLINE | ID: mdl-37862657

ABSTRACT

We report here on the realization of light-pulse atom interferometers with large-momentum-transfer atom optics based on a sequence of Bragg transitions. We demonstrate momentum splitting up to 200 photon recoils in an ultracold atom interferometer. We highlight a new mechanism of destructive interference of the losses leading to a sizable efficiency enhancement of the beam splitters. We perform a comprehensive study of parasitic interferometers due to the inherent multiport feature of the quasi-Bragg pulses. Finally, we experimentally verify the phase shift enhancement and characterize the interferometer visibility loss.

2.
Article in English | MEDLINE | ID: mdl-36078472

ABSTRACT

(1) Background: In the emergency department (ED), ordering urine tests in patients without symptoms of a urinary tract infection can lead to inappropriate antimicrobial treatment. We aimed to identify factors contributing to the unnecessary ordering of urinalyses in the ED. (2) Methods: An online survey study among nurses and physicians working in the EDs of five hospitals in the Netherlands was conducted. (3) Results: The overall response rate was 26% (221/850; 85 nurses and 136 physicians). The vast majority of the respondents reported knowing when to order urine tests (197/221; 90%). Almost two-thirds of the respondents (145/221; 66%) agreed that they ordered urinalyses because it is rapid and non-invasive to patients. Most nurses (66/86; 78%) said they informed the doctor if they thought the urine test would not contribute to the patient's diagnosis, but only one-third of the physicians agreed with this statement (44/136; 32%). Most respondents (160/221; 72%) thought guidelines or protocols about urinalyses in the ED would be functional. (4) Conclusions: These results suggest urinalyses were frequently ordered in the ED to achieve a fast work process. Nurses and physicians could improve their communication about the indications for urine tests. Developing diagnostic guidelines for urine testing may be convenient.


Subject(s)
Urinalysis , Urinary Tract Infections , Anti-Bacterial Agents/therapeutic use , Emergency Service, Hospital , Humans , Records , Urinalysis/methods , Urinary Tract Infections/diagnosis , Urinary Tract Infections/drug therapy , Urinary Tract Infections/epidemiology
3.
Semin Cancer Biol ; 52(Pt 2): 1-11, 2018 10.
Article in English | MEDLINE | ID: mdl-29428479

ABSTRACT

Cancer immunotherapy is demonstrating impressive clinical benefit in different malignancies and clinical oncologists are increasingly turning their attention to immune-oncology. It is now well recognized that innate and adaptive immune cells infiltrating tumors are associated with clinical outcomes and responses to treatments, and can be harnessed to patients' benefit. Considerable advances have also been made in understanding how cancers escape from immune attack. Targeting of immunological escape processes regulated by the expression of immune checkpoint receptors and ligands and the down-modulation of tumor antigen presentation is the basis of immuno-oncology treatments. Despite recent achievements, there remain a number of unresolved issues in order to successfully implement cancer immunotherapy in many cancers. Importantly, clinical biomarkers are still needed for better optimization of emerging combination immunotherapies and better treatment tailoring. In this review, we summarize the function of innate and adaptive immune cells in anti-tumor immunity and the general mechanisms exploited by tumor cells to escape and inhibit immune responses as well as therapeutic strategies developed to overcome these mechanisms and discuss emerging biomarkers in immuno-oncology.


Subject(s)
Neoplasms/immunology , Neoplasms/therapy , Animals , Antigen Presentation/immunology , Antigens, Neoplasm/immunology , Humans , Immunotherapy/methods , Medical Oncology/methods , Tumor Escape/immunology , Tumor Microenvironment/immunology
4.
Ann Oncol ; 29(4): 1056-1062, 2018 04 01.
Article in English | MEDLINE | ID: mdl-29145561

ABSTRACT

Background: CD73 is an ecto-enzyme that promotes tumor immune escape through the production of immunosuppressive extracellular adenosine in the tumor microenvironment. Several CD73 inhibitors and adenosine receptor antagonists are being evaluated in phase I clinical trials. Patients and methods: Full-face sections from formalin-fixed paraffin-embedded primary breast tumors from 122 samples of triple-negative breast cancer (TNBC) from the BIG 02-98 adjuvant phase III clinical trial were included in our analysis. Using multiplex immunofluorescence and image analysis, we assessed CD73 protein expression on tumor cells, tumor-infiltrating leukocytes and stromal cells. We investigated the associations between CD73 protein expression with disease-free survival (DFS), overall survival (OS) and the extent of tumor immune infiltration. Results: Our results demonstrated that high levels of CD73 expression on epithelial tumor cells were significantly associated with reduced DFS, OS and negatively correlated with tumor immune infiltration (Spearman's R= -0.50, P < 0.0001). Patients with high levels of CD73 and low levels of tumor-infiltrating leukocytes had the worse clinical outcome. Conclusions: Taken together, our study provides further support that CD73 expression is associated with a poor prognosis and reduced anti-tumor immunity in human TNBC and that targeting CD73 could be a promising strategy to reprogram the tumor microenvironment in this BC subtype.


Subject(s)
5'-Nucleotidase/immunology , Triple Negative Breast Neoplasms/immunology , Antibodies, Monoclonal/immunology , Disease-Free Survival , Female , GPI-Linked Proteins/immunology , Humans , Prognosis
5.
Rev Sci Instrum ; 88(11): 113115, 2017 Nov.
Article in English | MEDLINE | ID: mdl-29195392

ABSTRACT

We present a magnetic trap for cold atoms near a surface of a millimeter-sized atom chip. The trap allows us to capture a large number of atoms with modest electrical currents (40 A) and to generate large magnetic gradients (>300 G cm-1). Here we report a mixture containing 6 × 109 atoms for the two rubidium isotopes 87Rb and 85Rb. This device does not require cleanroom facilities nor micro-machining technologies which makes its construction easier. In addition our design allows the implementation of an optical dipole trap with a laser beam passing through the chip.

6.
Eur J Vasc Endovasc Surg ; 49(1): 77-82, 2015 Jan.
Article in English | MEDLINE | ID: mdl-25453237

ABSTRACT

OBJECTIVE: Toe systolic pressure is a component of the standard vascular and diabetic foot assessment. Until now,clinicians have measured only first toe pressure given a lack of evidence for measurements of the other toes. In diabetic patients, first toe measurements are often not possible because of ulceration or amputation. It was hypothesized that the adjacent second toe systolic pressure measurements would be interchangeable with those of the first toe. METHODS: A prospective study was performed on 100 participants with diabetes mellitus. Duplicate systolic toe pressures were measured in the first toe and adjacent second toe using the Systoe Automated Toe Pressure System, Systoe Photophlethysmograph Sensor Cuff, and occlusion cuffs measuring 120 x 25 mm for the first toe and 90 x 15 mm for the second toe. Correlation analysis was followed by Ordinary Least Products regression to detect and distinguish fixed and proportional bias between the two toe measurements. The acceptable limits of interchangeable results were defined as 5-10 mmHg. RESULTS: Correlation coefficient r » 0.908; p < 0.001. Eighty-two percent of the variations in the second toe measurements were accounted for by knowing the first toe measurements and vice versa. Ordinary Least Products regression showed no fixed or proportional bias between the two methods of measurement: second toe systolic pressure = (-0.579) + (1.038) * first toe systolic pressure. Repeatability analysis showed a 0.5%variation between duplicate measurements. CONCLUSIONS: This is the first study which demonstrates that second toe systolic pressures are interchangeable with those of the first toe. Second toe pressures can be used in diabetic patients whose first toe pressures cannot be assessed.


Subject(s)
Blood Pressure Determination/methods , Diabetes Mellitus/physiopathology , Diabetic Foot/diagnosis , Peripheral Arterial Disease/diagnosis , Toes/blood supply , Adult , Aged , Aged, 80 and over , Blood Pressure Determination/instrumentation , Diabetic Angiopathies/diagnosis , Diabetic Angiopathies/physiopathology , Diabetic Foot/physiopathology , Equipment Design , Female , Humans , Male , Middle Aged , Peripheral Arterial Disease/physiopathology , Prospective Studies , Reproducibility of Results , Systole
7.
Bioresour Technol ; 128: 769-73, 2013 Jan.
Article in English | MEDLINE | ID: mdl-23186662

ABSTRACT

The electrical performance of microbial fuel cells in steady-state is usually investigated by standard characterisation methods that reveal many important parameters e.g. maximum power. This paper introduces a novel "bi-directional" method to study how the acquisition parameters (i.e. sweep rate and sweep regime) can influence measurements and consequently performance estimations. The investigation exhibited considerable differences (hysteresis) between the forward and backward characterisation regimes, indicating a difficulty to reach steady-state under certain conditions. Moreover, it is found that fast sweep rates (time-step of 2 min) can lead to an overestimation of the short-circuit currents, while prolonged operation with high external loads leads to maximum power overestimation and extended conditioning at high currents can result in its underestimation.


Subject(s)
Bioelectric Energy Sources , Computer-Aided Design , Energy Transfer , Models, Theoretical , Computer Simulation , Equipment Design , Equipment Failure Analysis
8.
Water Sci Technol ; 64(10): 2052-8, 2011.
Article in English | MEDLINE | ID: mdl-22105128

ABSTRACT

Pine bark is a low cost sorbent originating from the forest industry. In recent years, it has been found to show promise as an adsorbent for metals and organic substances in contaminated water, especially landfill leachates and storm water. This study aims to investigate if pine bark can replace commercial adsorbents such as active carbon. An industrial effluent, collected from a treatment plant of a demilitarization factory, was diluted to form concentration ranges of contaminants and shaken with pine bark for 24 hours. Metals (e.g. Pb, Zn, Cd, As and Ni) and explosives, e.g., 2,4,6-trinitrotoluene (TNT), were analysed before and after treatment. The aim of the experiment was twofold; firstly, it was to investigate whether metals are efficiently removed in the presence of explosives and secondly, if adsorption of explosive substances to pine bark was possible. Langmuir and Freundlich isotherms were used to describe the adsorption process where this was possible. It was found that metal uptake was possible in the presence of TNT and other explosive contaminants. The uptake of TNT was satisfactory with up to 80% of the TNT adsorbed by pine bark.


Subject(s)
Industrial Waste/analysis , Metals, Heavy/isolation & purification , Pinus/chemistry , Trinitrotoluene/isolation & purification , Water Pollutants, Chemical/isolation & purification , Water Purification/methods , Adsorption , Cost-Benefit Analysis , Explosive Agents/isolation & purification , Models, Theoretical , Pilot Projects , Plant Bark/chemistry , Sweden , Water Purification/economics
9.
Phys Rev Lett ; 104(22): 220602, 2010 Jun 04.
Article in English | MEDLINE | ID: mdl-20867158

ABSTRACT

We study the horizontal expansion of vertically confined ultracold atoms in the presence of disorder. Vertical confinement allows us to realize a situation with a few coupled harmonic oscillator quantum states. The disordered potential is created by an optical speckle at an angle of 30° with respect to the horizontal plane, resulting in an effective anisotropy of the correlation lengths of a factor of 2 in that plane. We observe diffusion leading to non-gaussian density profiles. Diffusion coefficients, extracted from the experimental results, show anisotropy and strong energy dependence, in agreement with numerical calculations.

10.
Antimicrob Agents Chemother ; 50(2): 625-31, 2006 Feb.
Article in English | MEDLINE | ID: mdl-16436719

ABSTRACT

SPD754 (AVX754) is a deoxycytidine analogue nucleotide reverse transcriptase inhibitor (NRTI) in clinical development. These studies characterized the in vitro activity of SPD754 against NRTI-resistant human immunodeficiency virus type 1 (HIV-1) and non-clade B HIV-1 isolates, its activity in combination with other antiretrovirals, and its potential myelotoxicity and mitochondrial toxicity. SPD754 was tested against 50 clinical HIV-1 isolates (5 wild-type isolates and 45 NRTI-resistant isolates) in MT-4 cells using the Antivirogram assay. SPD754 susceptibility was reduced 1.2- to 2.2-fold against isolates resistant to zidovudine (M41L, T215Y/F, plus a median of three additional nucleoside analogue mutations [NAMs]) and/or lamivudine (M184V) and was reduced 1.3- to 2.8-fold against isolates resistant to abacavir (L74V, Y115F, and M184V plus one other NAM) or stavudine (V75T/M, M41L, T215F/Y, and four other NAMs). Insertions at amino acid position 69 and Q151M mutations (with or without M184V) reduced SPD754 susceptibility 5.2-fold and 14- to 16-fold, respectively (these changes gave values comparable to or less than the corresponding values for zidovudine, lamivudine, abacavir, and didanosine). SPD754 showed similar activity against isolates of group M HIV-1 clades, including A/G, B, C, D, A(E), D/F, F, and H. SPD754 showed additive effects in combination with other NRTIs, tenofovir, nevirapine, or saquinavir. SPD754 had no significant effects on cell viability or mitochondrial DNA in HepG2 or MT-4 cells during 28-day exposure at concentrations up to 200 microM. SPD754 showed a low potential for myelotoxicity against human bone marrow. In vitro, SPD754 retained activity against most NRTI-resistant HIV-1 clinical isolates and showed a low propensity to cause myelotoxicity and mitochondrial toxicity.


Subject(s)
Anti-HIV Agents/pharmacology , Deoxycytidine/analogs & derivatives , Reverse Transcriptase Inhibitors/pharmacology , Bone Marrow/drug effects , DNA, Mitochondrial/analysis , Deoxycytidine/pharmacology , Deoxycytidine/toxicity , HIV-1/drug effects , Humans , Mitochondria/drug effects
11.
Cell Signal ; 16(9): 1023-32, 2004 Sep.
Article in English | MEDLINE | ID: mdl-15212763

ABSTRACT

Molecular and biochemical analysis indicates that nuclear transcription factor kappaB (NF-kappaB)-inducing kinase (NIK) mediates IKK activation and NF-kappaB transcriptional activity. However, gene deletion studies suggest that NIK triggers gene expression without affecting IkappaBalpha degradation and NF-kappaB DNA binding activity. In order to investigate the role of NIK in NF-kappaB transcriptional activity, we used mouse embryonic fibroblasts (MEF) derived from wild-type (wt) and IkappaB kinase gamma (IKKgamma) gene deficient (IKKgamma(-/-)) mice. We report that although TNF-induced NF-kappaB transcriptional activity is abolished in IKKgamma(-/-) cells, adenoviral gene delivery of NIK (Ad5NIK) still enhanced transcriptional activity and IL-6 mRNA accumulation. Moreover, NIK targets the transactivation function of NF-kappaB through stimulation of the transactivation domain (TAD) of RelA (S536) in IKKgamma(-/-) cells. Interestingly, Ad5NIK, but not TNF, induces RelA S536 and p38 mitogen-activated protein kinase (MAPK) phosphorylation in IKKgamma(-/-) cells. Functional analysis demonstrated that Ad5NIK-induced NF-kappaB transcriptional activity, IL-6 mRNA expression and RelA phosphorylation are inhibited by the p38 inhibitor SB203580, suggesting a role for this MAPK in NIK signaling to NF-kappaB. These data demonstrate for the first time the presence of an IKKgamma-independent NIK/p38 MAPK-dependent signaling pathway that activates NF-kappaB and induces pro-inflammatory gene expression through RelA phosphorylation.


Subject(s)
NF-kappa B/metabolism , Protein Serine-Threonine Kinases/metabolism , Transcriptional Activation , p38 Mitogen-Activated Protein Kinases/metabolism , Animals , Cell Line , Cell Nucleus/metabolism , Gene Deletion , I-kappa B Kinase , Interleukin-6/genetics , Mice , Mice, Knockout/genetics , Mutagenesis , NF-kappa B/genetics , Phosphorylation , Protein Serine-Threonine Kinases/genetics , Protein Transport , RNA, Messenger/metabolism , Transcription Factor RelA , Transfection , p38 Mitogen-Activated Protein Kinases/antagonists & inhibitors , NF-kappaB-Inducing Kinase
12.
Am J Physiol Gastrointest Liver Physiol ; 286(6): G1000-8, 2004 Jun.
Article in English | MEDLINE | ID: mdl-14726307

ABSTRACT

Several effects of bile acids (BAs) on colonic epithelial cells (CECs) have been described, including induction of proliferation and apoptosis. Some of these effects are mediated through activation of the NF-kappa B transcriptional system. In this study, we investigated the molecular mechanisms underlying the BA-induced gene expression in CECs. The human CEC line HT-29 and primary human CECs were treated with dilutions of salts of deoxycholic acid (DCA) and taurodeoxycholic acid (TDCA). NF-kappa B binding activity was analyzed with EMSA, RelA translocation with immunofluorescence, and I kappa B alpha- and RelA-phosphorylation with Western blot analysis. IL-8 mRNA and protein expression were assessed by quantitative PCR and ELISA. Functional impact of NF-kappa B activation was determined by blocking the proteasome activity with MG132 or by preventing IKK activity with a dominant-negative IKK beta delivered by adenoviral dominant-negative (dn) IKK beta (Ad5dnIKK beta). DCA and TDCA induced IL-8 expression in a dose- and time-dependent manner. It is interesting that DCA but not TDCA induced I kappa B alpha-phosphorylation, RelA translocation, and NF-kappa B binding activity. Accordingly, the proteasome inhibitor MG132 blocked DCA- but not TDCA-induced IL-8 gene expression. In contrast, TDCA-induced IL-8 gene expression correlated with enhanced RelA phosphorylation, which was blocked by Ad5dnIKK beta. Our data suggest that DCA-induced signal transduction mainly utilized the I kappa B degradation and RelA nuclear translocation pathway, whereas TDCA primarily induced IL-8 gene expression through RelA phosphorylation. These differences may have implications for the understanding of the pathophysiology of inflammation and carcinogenesis in the gut.


Subject(s)
Colon/metabolism , Deoxycholic Acid/pharmacology , Interleukin-8/metabolism , Intestinal Mucosa/metabolism , NF-kappa B/metabolism , Signal Transduction/drug effects , Taurodeoxycholic Acid/pharmacology , Bile Acids and Salts/pharmacology , Cells, Cultured , Colon/cytology , Colon/drug effects , Gene Expression/drug effects , Humans , Interleukin-8/genetics , Intestinal Mucosa/cytology , Intestinal Mucosa/drug effects , RNA, Messenger/metabolism , Time Factors
13.
Phytochemistry ; 57(3): 459-67, 2001 Jun.
Article in English | MEDLINE | ID: mdl-11393527

ABSTRACT

High molecular weight lipids were isolated from Chlorella emersonii, Scenedesmus communis and Tetraedron minimum, thin trilaminar outer wall (TLS)-containing freshwater microalgae producing an insoluble non-hydrolysable biopolymer (i.e. algaenan). Molecular weight determination by gel permeation chromatography indicated that their molecular weights range from ca. 400 to 2000 Da. Flash pyrolysis with in situ methylation using tetramethylammonium hydroxide (TMAH) and alkaline hydrolysis showed that the high molecular weight lipids isolated from C. emersonii and S. communis are mainly composed of saturated n-C26 and n-C28 fatty acids and alcohols and of saturated n-C30 and n-C32 alpha,omega-diols and omega-hydroxy acids. In contrast the high molecular weight lipids isolated from T. minimum are predominantly composed of long-chain fatty acids and omega-hydroxy acids. Aromatic moieties were also identified in small amounts in the thermochemolysate and in the hydrolysate. Chemical structural models containing long-chain mono- and polyesters were proposed for the high molecular weight lipids isolated from the three microalgae in agreement with analytical and spectroscopic data. Structural similarity between the outer cell wall of these microalgae and the cuticular membrane of higher plants is suggested.


Subject(s)
Cell Wall/chemistry , Chlorella/chemistry , Chlorophyta/chemistry , Membrane Lipids/chemistry , Chlorophyta/isolation & purification , Hydrolysis , Indicators and Reagents , Membrane Lipids/isolation & purification , Molecular Conformation , Molecular Structure , Molecular Weight , Species Specificity , Spectroscopy, Fourier Transform Infrared
14.
Phytochemistry ; 54(4): 369-80, 2000 Jun.
Article in English | MEDLINE | ID: mdl-10897477

ABSTRACT

The neutral lipid profiles of nine species of thin trilaminar outer wall (TLS)-containing freshwater and marine microalgae from the class of Chlorophyceae were studied with emphasis on the relationship between the lipid content and the occurrence of insoluble non-hydrolysable biopolymer (i.e. algaenan). All the freshwater microalgae produce a highly aliphatic algaenan. In sharp contrast, no algaenan was isolated from the two marine microalgae, Chlorella marina and Chlorella minutissima marina, supporting the absence of a close relationship between the presence of TLS and the occurrence of algaenan. High molecular weight straight-chain hydrocarbons (C23-C29) were identified in most of the algaenan-producing microalgae and in the algaenan-devoid C. minutissima marina, whereas only low molecular weight hydrocarbons were detected in algaenan-producing Scenedesmus subspicatus and in algaenan-devoid C. marina. Sterols, phytol and fatty alcohols were the major constituents of the polar fraction of the neutral lipids of all the microalgae investigated. High molecular weight saturated or mono-unsaturated alcohols were detected in C. emersonii and in all the microalgae belonging to the genus Scenedesmus. High amounts of saturated C30 and C32 alpha,omega-diols were also detected in S. subspicatus, S. armatus and S. pannonicus. Three classes of lipids were encountered in very small amounts in the medium polarity fraction of the neutral lipids of the microalgae investigated: (i) Monoesters composed predominantly of saturated C16 or C18 fatty acids and saturated C8, C16 or C18 alcohols and (ii) long-chain methyl ketones from C25 to C31 were detected in several species and (iii) methyl esters of fatty acids ranging from C16 to C28 were identified in all the microalgae. Attempts to use the neutral lipid composition and particularly the unusual long-chain lipids, as specific indicators of the occurrence of algaenan in TLS-containing microalgae were unsuccessful.


Subject(s)
Biopolymers/chemistry , Cell Wall/chemistry , Eukaryota/chemistry , Membrane Lipids/chemistry , Alcohols/chemistry , Eukaryota/ultrastructure , Hydrocarbons/chemistry , Microscopy, Electron , Species Specificity
15.
J Biol Chem ; 275(33): 25556-61, 2000 Aug 18.
Article in English | MEDLINE | ID: mdl-10840032

ABSTRACT

Odontoblasts form a layer of cells responsible for the dentin formation and possibly mediate early stages of sensory processing in teeth. Several classes of ion channels have previously been identified in the odontoblast or pulp cell membrane, and it is suspected that these channels assist in these events. This study was carried out to characterize the K(Ca) channels on odontoblasts fully differentiated in vitro using the patch clamp technique and to investigate the HSLO gene expression encoding the alpha-subunit of these channels on odontoblasts in vivo. In inside-out patches, K(Ca) channels were identified on the basis of their K(+) selectivity, conductance, voltage, and Ca(2+) dependence. In cell-attached patches, these channels were found to be activated by application of a negative pressure as well as an osmotic shock. By reverse transcription-polymerase chain reaction, a probe complementary to K(Ca) alpha-subunit mRNA was constructed and used for in situ hybridization on human dental pulp samples. Transcripts were expressed in the odontoblast layer. The use of antibodies showed that the K(Ca) channels were preferentially detected at the apical pole of the odontoblasts. These channels could be involved in mineralization processes. Their mechanosensitivity suggests that the fluid displacement within dentinal tubules could be transduced into electrical cell signals.


Subject(s)
Calcium/metabolism , Gene Expression , Odontoblasts/metabolism , Potassium Channels, Calcium-Activated , Potassium Channels/chemistry , Potassium Channels/metabolism , Adolescent , Cell Differentiation , Cell Membrane/metabolism , Cells, Cultured , DNA, Complementary/metabolism , Dental Pulp/cytology , Dental Pulp/growth & development , Dental Pulp/metabolism , Humans , Immunohistochemistry , In Situ Hybridization , Large-Conductance Calcium-Activated Potassium Channel alpha Subunits , Large-Conductance Calcium-Activated Potassium Channels , Neurons/metabolism , Odontoblasts/cytology , Patch-Clamp Techniques , Potassium Channels/biosynthesis , Pressure , RNA, Messenger/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Stress, Mechanical
16.
Proc Natl Acad Sci U S A ; 97(9): 4950-5, 2000 Apr 25.
Article in English | MEDLINE | ID: mdl-10781103

ABSTRACT

Duchenne muscular dystrophy results from the lack of dystrophin, a cytoskeletal protein associated with the inner surface membrane, in skeletal muscle. The cellular mechanisms responsible for the progressive skeletal muscle degeneration that characterizes the disease are still debated. One hypothesis suggests that the resting sarcolemmal permeability for Ca(2+) is increased in dystrophic muscle, leading to Ca(2+) accumulation in the cytosol and eventually to protein degradation. However, more recently, this hypothesis was challenged seriously by several groups that did not find any significant increase in the global intracellular Ca(2+) in muscle from mdx mice, an animal model of the human disease. In the present study, using plasma membrane Ca(2+)-activated K(+) channels as subsarcolemmal Ca(2+) probe, we tested the possibility of a Ca(2+) accumulation at the restricted subsarcolemmal level in mdx skeletal muscle fibers. Using the cell-attached configuration of the patch-clamp technique, we demonstrated that the voltage threshold for activation of high conductance Ca(2+)-activated K(+) channels is significantly lower in mdx than in control muscle, suggesting a higher subsarcolemmal [Ca(2+)]. In inside-out patches, we showed that this shift in the voltage threshold for high conductance Ca(2+)-activated K(+) channel activation could correspond to a approximately 3-fold increase in the subsarcolemmal Ca(2+) concentration in mdx muscle. These data favor the hypothesis according to which an increased calcium entry is associated with the absence of dystrophin in mdx skeletal muscle, leading to Ca(2+) overload at the subsarcolemmal level.


Subject(s)
Calcium/metabolism , Muscle Fibers, Skeletal/physiology , Muscle, Skeletal/physiology , Muscular Dystrophy, Animal/physiopathology , Potassium Channels/physiology , Sarcolemma/physiology , Animals , Humans , Mice , Mice, Inbred C57BL , Mice, Inbred Strains , Mice, Inbred mdx , Muscle, Skeletal/physiopathology , Patch-Clamp Techniques , Reference Values
17.
Am J Physiol Cell Physiol ; 278(3): C473-9, 2000 Mar.
Article in English | MEDLINE | ID: mdl-10712235

ABSTRACT

High-conductance Ca(2+)-activated K(+) (K(Ca)) channels were studied in mouse skeletal muscle fibers using the patch-clamp technique. In inside-out patches, application of negative pressure to the patch induced a dose-dependent and reversible activation of K(Ca) channels. Stretch-induced increase in channel activity was found to be of the same magnitude in the presence and in the absence of Ca(2+) in the pipette. The dose-response relationships between K(Ca) channel activity and intracellular Ca(2+) and between K(Ca) channel activity and membrane potential revealed that voltage and Ca(2+) sensitivity were not altered by membrane stretch. In cell-attached patches, in the presence of high external Ca(2+) concentration, stretch-induced activation was also observed. We conclude that membrane stretch is a potential mode of regulation of skeletal muscle K(Ca) channel activity and could be involved in the regulation of muscle excitability during contraction-relaxation cycles.


Subject(s)
Calcium/physiology , Muscle Contraction/physiology , Muscle Fibers, Skeletal/physiology , Muscle, Skeletal/physiology , Potassium Channels/physiology , Adenosine Triphosphate/pharmacology , Animals , Calcium/pharmacology , In Vitro Techniques , Mice , Mice, Inbred C57BL , Muscle Contraction/drug effects , Muscle Fibers, Skeletal/drug effects , Patch-Clamp Techniques
18.
J Physiol ; 520 Pt 2: 417-29, 1999 Oct 15.
Article in English | MEDLINE | ID: mdl-10523411

ABSTRACT

1. Intracellular free calcium concentration ([Ca2+]i) was measured with the fluorescent indicator indo-1 in single skeletal fibres enzymatically isolated from the flexor digitorum brevis and interosseus muscles of control and dystrophic mdx C57BL/10 mice. Measurements were taken from a portion of fibre that was voltage clamped to allow detection of depolarization-induced changes in [Ca2+]i. 2. The mean (+/- s.e.m.) initial resting [Ca2+]i from all control and mdx fibres tested was 56 +/- 5 nM (n = 72) and 48 +/- 7 nM (n = 57), respectively, indicating no significant overall difference between the two groups. However, when comparing a batch of control and mdx fibres obtained from mice older than approximately 35 weeks, resting [Ca2+]i was significantly lower in mdx (16 +/- 4 nM, n = 11) than in control fibres (71 +/- 10 nM, n = 14). 3. Changes in [Ca2+]i elicited by short (5-35 ms) depolarizing pulses from -80 to 0 mV showed similar properties in control and mdx fibres. After a 5 ms duration pulse the mean time constant of [Ca2+]i decay was, however, significantly elevated in mdx as compared to control fibres, by a factor of 1.5-2. For longer pulses, no significant difference could be detected. 4. In response to 50 ms duration depolarizing pulses of various amplitudes the threshold for detection of an [Ca2+]i change and the peak [Ca2+]i reached for a given potential were similar in control and mdx fibres. 5. Overall results show that mdx skeletal muscle fibres are quite capable of handling [Ca2+]i at rest and in response to membrane depolarizations.


Subject(s)
Calcium/metabolism , Muscle Fibers, Skeletal/metabolism , Muscle, Skeletal/metabolism , Age Factors , Animals , Fluorescent Dyes , Fluorometry , Indoles , Male , Mice , Mice, Inbred mdx , Patch-Clamp Techniques
19.
Can J Vet Res ; 63(1): 13-7, 1999 Jan.
Article in English | MEDLINE | ID: mdl-9918328

ABSTRACT

The involvement of both intracellular and extracellular calcium, as well as the activation of protein kinase C (PKC), in phorbol myristate acetate (PMA)-stimulated respiratory burst in bovine neutrophils has been studied. PMA significantly stimulated the superoxide anion production by these cells. The increased production of superoxide anion was inhibited by BAPTA/AM, an intracellular calcium ([Ca2+]i) chelator, but not affected by EGTA, an extracellular calcium ([Ca2+]0) chelator. PMA also induced PKC activation, and a PKC inhibitor, calphostin C, blocked the stimulatory effect of PMA on superoxide anion production by the neutrophils. Therefore, we conclude that PMA-induced respiratory burst in bovine neutrophils is [Ca2+]i- but not [Ca2+]0-dependent, and also requires PKC activation.


Subject(s)
Calcium Channels/physiology , Calcium/metabolism , Neutrophils/physiology , Protein Kinase C/metabolism , Respiratory Burst/physiology , Animals , Cattle , Superoxides/pharmacology , Tetradecanoylphorbol Acetate/pharmacology
20.
Chemosphere ; 38(4): 783-94, 1999 Feb.
Article in English | MEDLINE | ID: mdl-10903111

ABSTRACT

Partial least squares (PLS) modeling was applied to investigate number-average molecular weights (Mn) and weight-average molecular weights (Mw) of fulvic acids (FAs) in relation to the corresponding UV/VIS spectra. The Mn and Mw values were determined by size exclusion chromatography (SEC). The impact of pH control, wavelength range and density as well as smoothing and derivation of spectra were tested. It was found that PLS models based on absorbance spectra can be a fast and powerful complement to existing techniques employed for determination of molecular weights of FAs. Control of pH of the FA solutions is important for the performance of the models. The models were also compared with the best univariate alternatives.

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