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1.
Drugs (Abingdon Engl) ; 31(3): 338-347, 2024.
Article in English | MEDLINE | ID: mdl-38835541

ABSTRACT

Aims: Interventions restricting temporal and spatial availability of alcohol are associated with reduced harm, but the pathways by which specific interventions have impact are poorly understood. We examined mechanisms of impact from the perspective of diverse licensing stakeholders. Methods: Fifty-three in-depth interviews were conducted with licensing stakeholders (from public health teams [PHTs], police, local authority licensing teams and lawyers, and alcohol premises licensing committees) from 20 local government areas. Interviewees were recruited as part of the Exploring the impact of alcohol licensing in England and Scotland (ExILEnS) study. Data were analyzed thematically and preliminary themes/subthemes were discussed during online groups with a different sample of public health and licensing professionals (n = 10). Findings: Most interviewees struggled to articulate how availability interventions might lead to changes in alcohol consumption or harms. Five overarching mechanisms were identified: access, visibility, premises and area-level norms, affordability, and management of the night-time economy, with specific pathways identified for certain subgroups/premises types. The mechanisms by which alcohol availability interventions may impact on alcohol consumption and harms are diverse, but were poorly understood. Conclusions: These findings will inform licensing and availability policy and advocacy, highlighting the need for further scrutiny of the evidence underpinning identified mechanisms, and primary research to address knowledge gaps.

2.
Public Health ; 184: 71-78, 2020 Jul.
Article in English | MEDLINE | ID: mdl-32248984

ABSTRACT

OBJECTIVE: Gambling operators in the United Kingdom have introduced a voluntary ban on adverts broadcast during televised sport before 21:00 (the 'whistle-to-whistle' ban). To inform debates around the potential effectiveness of this ban, we examine the frequency and nature of gambling marketing in televised broadcasts across professional sporting events. STUDY DESIGN: Frequency analysis of verbal and visual gambling marketing references during television broadcasts of football (n = 5), tennis, Formula 1, boxing and rugby union (each n = 1) from 2018. METHODS: For each gambling reference, we coded: whether it appeared in-play or out-of-play; location (e.g. pitch-side advertising); format (e.g. branded merchandise); duration (s); number of identical references visible simultaneously; brand; and presence of age restriction or harm-reduction messages. RESULTS: Boxing contained the most gambling references, on average, per broadcast minute (4.70 references), followed by football (2.75), rugby union (0.55) and tennis (0.11). Formula 1 contained no gambling references. In boxing, references most frequently appeared within the area-of-play. For football and rugby union, references most frequently appeared around the pitch border or within the area-of-play (e.g. branded shirts). Only a small minority of references were for adverts during commercial breaks that would be subject to the whistle-to-whistle ban (e.g. 2% of references in football). Less than 1% of references in boxing and only 3% of references in football contained age restriction or harm-reduction messages. CONCLUSIONS: As gambling sponsorship extends much beyond adverts in commercial breaks, the 'whistle-to-whistle' ban will have limited effect on gambling exposure. Gambling sponsorship activities rarely contain harm-reduction messages.


Subject(s)
Gambling , Marketing/statistics & numerical data , Sports , Television/statistics & numerical data , Humans , United Kingdom
3.
BMJ Open ; 5(9): e008547, 2015 Sep 11.
Article in English | MEDLINE | ID: mdl-26362665

ABSTRACT

OBJECTIVES: To explore how e-cigarettes are being promoted at point of sale in the UK and how retailers perceive market trends. SETTING: Fixed retail outlets subject to a ban on the display of tobacco products. PARTICIPANTS: Observational audit of all stores selling tobacco products (n=96) in 4 Scottish communities, conducted over 2 waves 12 months apart (2013-2014), and qualitative interviews with small retailers (n=25) in 4 matched communities. PRIMARY AND SECONDARY OUTCOME MEASURES: The audit measured e-cigarette display characteristics, advertising materials and proximity to other products, and differences by area-level disadvantage. Interviews explored retailers' perceptions of e-cigarette market opportunities and risks, and customer responses. RESULTS: The number of e-cigarette point-of-sale display units and number of brands displayed increased between waves. E-cigarettes were displayed close to products of interest to children in 36% of stores. Stores in more affluent areas were less likely to have external e-cigarette advertising than those in deprived areas. Although e-cigarettes delivered high profit margins, retailers were confused by the diversity of brands and products, and uncertain of the sector's viability. Some customers were perceived to purchase e-cigarettes as cessation aids, and others, particularly low-income smokers, as a cheaper adjunct to conventional tobacco. CONCLUSIONS: E-cigarette point-of-sale displays and number of brands displayed increased over 12 months, a potential cause for concern given their lack of regulation. Further scrutiny is needed of the content and effects of such advertising, and the potentially normalising effects of placing e-cigarettes next to products of interest to children.


Subject(s)
Electronic Nicotine Delivery Systems/economics , Marketing/trends , Smoking/psychology , Tobacco Industry/legislation & jurisprudence , Humans , Interviews as Topic , Perception , Residence Characteristics , Scotland
4.
J Membr Biol ; 182(3): 213-22, 2001 Aug 01.
Article in English | MEDLINE | ID: mdl-11547344

ABSTRACT

Experiments were performed to determine whether the transport properties of the ciliary epithelium vary over different regions. Rabbit iris-ciliary bodies were incubated under experimental or control conditions for 30 min before quick freezing, cryosectioning, dehydration and electron probe X-ray microanalysis. Cryosections were cut from three regions along the major axis of the iris-ciliary body, i.e., the anterior, middle and posterior (pars plicata) regions. In bicarbonate/CO2 solution, the epithelial cells of the anterior and middle regions contained more Cl and K than did those of the posterior region. These higher levels of Cl and K were reduced by the carbonic anhydrase inhibitor acetazolamide. Application of bumetanide, an inhibitor of the Na+-K+-2Cl- cotransporter, resulted in significant increases in Cl and K in the anterior and middle regions but not in the posterior region. In bicarbonate-free solution, the ratio for K/Na contents was higher in the posterior than in the two more anterior regions; Na, K and Cl contents of epithelial cells in the three regions were otherwise similar. Cell composition did not differ significantly between the crests and valleys of the posterior region. The divergent responses to perturbation of epithelial transport in the different regions provide the first demonstration of functional heterogeneity along the major axis of the iris-ciliary body. The response to inhibition of carbonic anhydrase raises the possibility that the anterior aspect of the ciliary epithelium may be the major site of aqueous humor secretion.


Subject(s)
Biological Transport/physiology , Ciliary Body/metabolism , Epithelial Cells/metabolism , Acetazolamide/pharmacology , Animals , Bicarbonates/metabolism , Bumetanide/pharmacology , Carbonic Anhydrase Inhibitors/pharmacology , Carrier Proteins/metabolism , Chlorides/metabolism , Ciliary Body/cytology , Electron Probe Microanalysis , Female , Humans , Male , Potassium/metabolism , Rabbits , Sodium/metabolism
5.
Rapid Commun Mass Spectrom ; 15(16): 1453-6, 2001.
Article in English | MEDLINE | ID: mdl-11507759

ABSTRACT

The continuous separation capability of high-field asymmetric waveform ion mobility spectrometry (FAIMS) was used in combination with complementary techniques for probing biomolecular ions in the gas phase. Gas-phase conformers of the [M + 2H](2+) ion of bradykinin were examined using a combination of FAIMS, H/D exchange, and energy-loss measurements. When FAIMS data and H/D exchange data were analyzed separately, the presence of only two conformers of the [M + 2H](2+) ion of bradykinin could be detected. However, in an experiment in which FAIMS and H/D exchange were combined, at least four different conformers of the gas-phase [M + 2H](2+) ion of bradykinin were detected, including one of very low abundance. Cross sections calculated for the four conformers, based on energy-loss measurements, were 250, 240, 250, and 244 A(2), in order of decreasing abundance.


Subject(s)
Bradykinin/chemistry , Gases , Mass Spectrometry/methods , Protein Conformation , Thermodynamics
6.
Am J Physiol Cell Physiol ; 281(3): C865-75, 2001 Sep.
Article in English | MEDLINE | ID: mdl-11502564

ABSTRACT

The beta-adrenergic antagonist timolol reduces ciliary epithelial secretion in glaucomatous patients. Whether inhibition is mediated by reducing cAMP is unknown. Elemental composition of rabbit ciliary epithelium was studied by electron probe X-ray microanalysis. Volume of cultured bovine pigmented ciliary epithelial (PE) cells was measured by electronic cell sizing; Ca(2+) activity and pH were monitored with fura 2 and 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, respectively. Timolol (10 microM) produced similar K and Cl losses from ciliary epithelia in HCO/CO(2) solution but had no effect in HCO/CO(2)-free solution or in HCO/CO(2) solution containing the carbonic anhydrase inhibitor acetazolamide. Inhibition of Na(+)/H(+) exchange by dimethylamiloride in HCO/CO(2) solution reduced Cl and K comparably to timolol. cAMP did not reverse timolol's effects. Timolol (100 nM, 10 microM) and levobunolol (10 microM) produced cAMP-independent inhibition of the regulatory volume increase (RVI) in PE cells and increased intracellular Ca(2+) and pH. Increasing Ca(2+) with ionomycin also blocked the RVI. The results document a previously unrecognized cAMP-independent transport effect of timolol. Inhibition of Cl(-)/HCO exchange may mediate timolol's inhibition of aqueous humor formation.


Subject(s)
Aqueous Humor/metabolism , Ciliary Body/physiology , Cyclic AMP/physiology , Pigment Epithelium of Eye/physiology , Timolol/pharmacology , Animals , Aqueous Humor/drug effects , Bicarbonates/pharmacology , Carbon Dioxide/pharmacology , Cells, Cultured , Chlorides/metabolism , Ciliary Body/cytology , Ciliary Body/drug effects , Female , Hydrogen-Ion Concentration , Kinetics , Male , Pigment Epithelium of Eye/cytology , Pigment Epithelium of Eye/drug effects , Potassium/metabolism , Rabbits , Sodium/metabolism , Solutions
7.
J Am Soc Mass Spectrom ; 12(8): 894-901, 2001 Aug.
Article in English | MEDLINE | ID: mdl-11506222

ABSTRACT

Recent advancements in high-field asymmetric waveform ion mobility spectrometry (FAIMS) have led to significant improvements in the application of this technology to the study of protein conformers. Compared with previous work, the maximum value of the separation voltage (i.e., the dispersion voltage) has increased, thereby enabling multiple, elongated conformers of individual charge states of bovine ubiquitin to be separated in the gas phase (e.g., four conformers of each of the +11 and +12 charge states were separated). The use of a carrier gas mixture of 40% nitrogen and 60% helium changed the separation selectivity compared with pure nitrogen and enhanced the signal intensity, especially for the +14 and +15 charge states (the latter was not detected in a nitrogen carrier gas). Conformer cross sections were determined using the FAIMS/energy-loss method and found to be similar within a given charge state. The cross sections for conformers of charge states +13, + 14, and +15 plateau at about 2000 A2 suggesting that the structure of bovine ubiquitin is essentially unfolded after the addition of the 13th proton.


Subject(s)
Ubiquitins/chemistry , Algorithms , Animals , Cattle , Chemical Phenomena , Chemistry, Physical , Protein Conformation , Spectrometry, Mass, Electrospray Ionization
8.
J Anal Toxicol ; 25(2): 81-7, 2001 Mar.
Article in English | MEDLINE | ID: mdl-11300511

ABSTRACT

Morphine and codeine have been identified and measured in a human urine matrix using high-field asymmetric waveform ion mobility spectrometry (FAIMS) in a tandem combination with electrospray ionization (ESI) and mass spectrometric (MS) detection. The addition of helium to the nitrogen carrier gas resulted in a substantial improvement in the sensitivity of the ESI-FAIMS-MS instrument for the determination of morphine and codeine. Limits of detection in human urine were 60 ng/mL for morphine and 20 ng/mL for codeine with no clean-up, derivatization, or chromatographic separation of the sample prior to analysis.


Subject(s)
Codeine/urine , Morphine/urine , Spectrometry, Mass, Electrospray Ionization/methods , Humans , Sensitivity and Specificity , Spectrometry, Mass, Electrospray Ionization/instrumentation
9.
J Am Soc Mass Spectrom ; 12(12): 1320-30, 2001 Dec.
Article in English | MEDLINE | ID: mdl-11766759

ABSTRACT

A tandem FAIMS-FAIMS system for ion trapping at room temperature and atmospheric pressure is described. The first FAIMS device consisted of a side-to-side configuration (sFAIMS) suitable for ion separation, whereas the second FAIMS device was appropriate for ion trapping (tFAIMS). Ions pre-selected by the sFAIMS entered the tFAIMS and were captured by virtual trapping fields at the hemispherical tip of the inner electrode. The use of the sFAIMS, with wider electrode diameters, and consequently better ion separation efficiency than the tFAIMS, lowered the number of background ions captured in the trapping region of tFAIMS, and thus reduced the space charge effects in the trap. This tandem device was coupled to a laboratory built time-of-flight mass spectrometer and was evaluated using the electrospray generated [M + 2H]2+ ion of gramicidin S. The half-time (t1/2) of the exponential decay of the ion cloud in tFAIMS, determined by monitoring the residual intensity of ions extracted from the ion trapping region of tFAIMS after various delay times, was about 2 s.


Subject(s)
Gramicidin/chemistry , Algorithms , Spectrometry, Mass, Electrospray Ionization
10.
Anal Chem ; 72(19): 4577-84, 2000 Oct 01.
Article in English | MEDLINE | ID: mdl-11028613

ABSTRACT

The continuous gas-phase ion separation and atmospheric pressure focusing properties of high-field asymmetric waveform ion mobility spectrometry (FAIMS) offer significant advantages for the mass spectrometric analysis of tryptic digests of proteins. In this study, tryptic peptides of pig hemoglobin were examined by ESI-FAIMS-MS using a newly designed FAIMS device. The new, hemispherical geometry of the inner electrode served to deliver the ions, via the gas flows, to the center axis of the FAIMS analyzer, improving the sensitivity relative to previous prototypes. Mass spectra collected using this new FAIMS showed significantly less chemical background noise than conventional ESI-MS, while maintaining approximately the same absolute sensitivity as that observed with ESI-MS. As a consequence of the ion separation in FAIMS, the identification of the tryptic fragments was simplified and some peptides, such as the triply protonated WAGVANALAHK3+, that were obscured by the intense background of ESI-MS, were readily detected using ESI-FAIMS-MS. In addition, the FAIMS device was shown to separate isobaric ions at m/z 532.4. Correlations between CV and mass-to-charge ratio, as well as CV and ionic collision cross section, were evaluated for 38 peptide ions identified in the tryptic digest. The correlation between the CV of the peptide and the mass-to-charge ratio is very poor, indicating good orthogonality between the separation by FAIMS and the separation by mass spectrometry.


Subject(s)
Hemoglobins/chemistry , Amino Acid Sequence , Animals , Mass Spectrometry , Molecular Sequence Data , Swine , Trypsin/pharmacology
11.
Rapid Commun Mass Spectrom ; 14(16): 1538-42, 2000.
Article in English | MEDLINE | ID: mdl-10931550

ABSTRACT

A combination of electrospray ionization, high-field asymmetric waveform ion mobility spectrometry, and mass spectrometry (ESI-FAIMS/MS) was used to analyze standard solutions of microcystins-LR, -RR, and -YR. The ability of FAIMS to separate ions in the gas phase reduced the amount of background in the mass spectrum without compromising the absolute signal for these microcystins. This reduction in background resulted in a ten-fold improvement in the signal-to-background ratio over conventional ESI-MS. Detection limits, using direct infusion, were determined to be 4, 2, and 1 nM for microcystins-LR, -RR, and -YR, respectively.


Subject(s)
Carcinogens/analysis , Mass Spectrometry/methods , Peptides, Cyclic/analysis , Bacterial Toxins/analysis , Mass Spectrometry/instrumentation , Microcystins , Sensitivity and Specificity
12.
J Am Soc Mass Spectrom ; 11(8): 738-45, 2000 Aug.
Article in English | MEDLINE | ID: mdl-10937797

ABSTRACT

High-field asymmetric waveform ion mobility spectrometry (FAIMS) was used to separate gas-phase conformers of bovine ubiquitin produced by electrospray ionization. These conformers were sampled by a triple quadrupole mass spectrometer where energy-loss experiments, following the work of Douglas and co-workers, were used to determine their cross sections. The measured cross sections for some conformers were readily altered by the voltages applied to the interface ion optics, therefore very gentle mass spectrometer interface conditions were required to preserve gas-phase conformers separated by FAIMS. Cross sections for 19 conformers (charge states +5 through +13) were measured. Two conformers for the +12 charge state, which were readily separated in FAIMS, were found to have similar cross sections. Based on a method to calibrate the collision gas thickness, the cross sections measured using the FAIMS/energy-loss method were compared with literature values determined using drift tube ion mobility spectrometry. The comparison illustrated that the conformers of bovine ubiquitin that were identified using drift tube ion mobility spectrometry were also observed using the FAIMS device.


Subject(s)
Ubiquitins/chemistry , Algorithms , Animals , Cattle , Chemical Phenomena , Chemistry, Physical , Mass Spectrometry , Protein Conformation
13.
Clin Exp Pharmacol Physiol ; 27(1-2): 100-6, 2000.
Article in English | MEDLINE | ID: mdl-10696536

ABSTRACT

1. Glaucoma is a worldwide disease affecting approximately 1-2% of the population aged over 35 years in industrial countries and is a major cause of blindness. 2. Glaucoma is usually associated with an increased intraocular pressure reflecting an imbalance between the rate of production of fluid (the aqueous humor) by the ciliary epithelial cells and its drainage from the eye. Therefore, it is important to understand how this secretion is produced. This requires a knowledge of ciliary epithelial cell composition, which has, in the past, proved difficult to obtain in mammalian preparations. 3. We have recently used the technique of electron-probe X-ray microanalysis to determine this composition under a variety of in vitro conditions. 4. Our results have led to a new model for this secretion that emphasizes the potential secretory role of the Na+/K+/2Cl- cotransporter.


Subject(s)
Aqueous Humor/physiology , Ciliary Body/physiology , Epithelial Cells/physiology , Ion Transport/physiology , Animals , Aqueous Humor/chemistry , Bicarbonates/pharmacology , Chlorides/metabolism , Electron Probe Microanalysis , Epithelial Cells/diagnostic imaging , Epithelial Cells/drug effects , Humans , Ion Transport/drug effects , Potassium/metabolism , Rabbits , Radiography , Sodium/metabolism
14.
J Am Soc Mass Spectrom ; 11(12): 1125-33, 2000 Dec.
Article in English | MEDLINE | ID: mdl-11118120

ABSTRACT

Effects of carrier gas type (N2, O2, CO2, N2O, and SF6) on changes in the ratio of high- to low-field ion mobility, Kh/K, of cesium, gramicidin S, tetrahexylammonium, heptadecanoic acid, and aspartic acid in fields of up to 67 Td are presented. The theory of the mobility of ions at high E/N in different gases is discussed. Plots of Kh/K as a function of the ionic energy parameter, E/N, for the five ions in each of the gases were derived from experimental data collected using a high-field asymmetric waveform ion mobility spectrometer. The change in the ratio of high- to low-field ion mobility of cesium in carrier gases of O2 and N2 showed excellent agreement with literature values. The behavior of cesium in O2 and N2 is used to illustrate that the ratio Kh/K as a function of effective temperature is invariant with gas type as long as the well depth of the interaction potential significantly exceeds thermal energy. From these results, it appears that the well depth of the interaction potential of the heavier ions studied here, including gramicidin S, tetrahexylammonium, and heptadecanoic acid, with bath gases such as N2 and O2, is shallow relative to thermal energy.

15.
J Environ Monit ; 2(5): 393-7, 2000 Oct.
Article in English | MEDLINE | ID: mdl-11254038

ABSTRACT

High-field asymmetric waveform ion mobility spectrometry (FAIMS) separates perchlorate from interfering isobaric ions of bisulfate and dihydrogenphosphate in the gas-phase. The use of a new FAIMS prototype and waveform generator, along with the use of a mixed carrier gas, in this electrospray ionisation (ESI)-FAIMS-mass spectrometry (MS) study gave a detection limit for perchlorate in a relatively "clean" matrix of tap water of 0.050 ppb. Flow injection analysis (FIA) of dilutions of fortified waste water, a fortified river water certified reference material (CRM; SLRS-4, National Research Council of Canada), and a fortified human urine Standard Reference Material (SRM; 2381, National Institute of Standards and Technology) gave detection limits of 0.37 ppb, 0.50 ppb, and 4.8 ppb, respectively, in the undiluted matrices.


Subject(s)
Perchlorates/urine , Sodium Compounds/urine , Spectrometry, Mass, Electrospray Ionization/methods , Water Pollutants, Chemical/analysis , Environmental Monitoring , Humans , Perchlorates/analysis , Sensitivity and Specificity , Sodium Compounds/analysis , Waste Disposal, Fluid , Water Supply
16.
Anal Chem ; 71(20): 4747-52, 1999 Oct 15.
Article in English | MEDLINE | ID: mdl-10546539

ABSTRACT

The lower limit of detection for low molecular weight polar and ionic analytes using electrospray ionization-mass spectrometry (ESI-MS) is often severely compromised by an intense background that obscures ions of trace components in solution. Recently, a new technique, referred to as high-field asymmetric waveform ion mobility spectrometry (FAIMS), has been shown to separate gas-phase ions at atmospheric pressure and room temperature. A FAIMS instrument is an ion filter that may be tuned, by control of electrical voltages, to continuously transmit selected ions from a complex mixture. This capability offers significant advantages when FAIMS is coupled with ESI, a source that generates a wide variety of ions, including solvent clusters and salt adducts. In this report, the tandem arrangement of ESI-FAIMS-MS is used for the analysis of haloacetic acids, a class of disinfection byproducts regulated by the US EPA. FAIMS is shown to effectively discriminate against background ions resulting from the electrospray of tap water solutions containing the haloacetic acids. Consequently, mass spectra are simplified, the selectivity of the method is improved, and the limits of detection are lowered compared with conventional ESI-MS. The detection limits of ESI-FAIMS-MS for six haloacetic acids ranged between 0.5 and 4 ng/mL in 9:1 methanol/tap water (5 and 40 ng/mL in the original tap water samples) with no preconcentration, derivatization, or chromatographic separation prior to analysis.


Subject(s)
Bromine Compounds/analysis , Chlorine Compounds/analysis , Disinfectants/analysis , Water Supply/analysis , Acetates/analysis , Indicators and Reagents , Mass Spectrometry
17.
J Am Soc Mass Spectrom ; 10(6): 492-501, 1999 Jun.
Article in English | MEDLINE | ID: mdl-27518046

ABSTRACT

High field asymmetric waveform ion mobility spectrometry (FAIMS) provides atmospheric pressure, room temperature, low-resolution separation of gas-phase ions. The FAIMS analyzer acts as an ion filter that can continuously transmit one type of ion, independent of m/z. The combination of FAIMS with electrospray ionization and mass spectrometry (ESI-FAIMS-MS) is a powerful technique and is used in this study to investigate the cluster ions of leucine enkephalin (YGGFL). Separation by FAIMS of leucine enkephalin ions having the same m/z (m/z 556.5), [M + H](+) and [2M + 2H](2+), was observed. In addition, four complex ions of leucine enkephalin, [2M + H](+), [4M + 2H](2+), [6M + 3H](3+), and [8M + 4H](4+), all having m/z 1112, were shown to be separated in FAIMS. Fragmentation of ions as the result of harsh conditions within the mass spectrometer interface (FAIMS-MS) was shown to provide similar information to that obtained from MS/MS experiments in conventional ESI-MS.

18.
Anal Chem ; 71(13): 2346-57, 1999 Jul 01.
Article in English | MEDLINE | ID: mdl-21662783

ABSTRACT

High-field asymmetric waveform ion mobility spectrometry (FAIMS) is a new technique that separates gas-phase ions at atmospheric pressure (760 Torr) and room temperature. A FAIMS instrument acts as an ion filter and can be set to continuously transmit one type of ion. Despite the stringent requirement for a flow of clean, dry gas in the FAIMS analyzer region, a method of coupling electrospray to FAIMS has been developed. The identity of the electrospray ions separated by FAIMS was determined using mass spectrometry (FAIMS-MS). The theory of FAIMS is discussed, and electrospray FAIMS-MS spectra of several compounds in modes P1, P2, N1, and N2 are presented. Ions appearing in P1 and N1 modes tend to have mobilities that increase as a function of increasing electric field strength, whereas ions appearing in P2 and N2 modes tend to have mobilities that decrease. In general, low-mass ions are focused in P1 and N1 modes, whereas larger ions (e.g., proteins) are focused in P2 and N2 modes. Short-chain peptides, (Gly)(n) where n = 1-6, are shown to cross over from P1 mode into P2 mode as the chain length increases. The removal of the low-mass solvent cluster ions, combined with a reduction of the background noise in electrospray FAIMS-MS, results in an improved signal-to-noise ratio for mass spectra of larger ions (e.g., cyctochrome c) when compared with conventional electrospray-MS. Preliminary results also suggest that various charge states of cytochrome c can be distinguished by FAIMS, implying that the ion mobility of these species at high electric field strength is sensitive to the structure of the protein ion. The linearity of response of electrospray FAIMS-MS was investigated using leucine enkephalin and shows the calibration curve to be linear for ∼3 orders of magnitude.

19.
Invest Ophthalmol Vis Sci ; 39(9): 1631-41, 1998 Aug.
Article in English | MEDLINE | ID: mdl-9699552

ABSTRACT

PURPOSE: To determine whether the Na+-K+-2Cl- symport or the parallel Na+/H+ and Cl-/HCO3- antiports provide the dominant pathway for NaCl uptake into the ciliary epithelium. Both pathways are known to support NaCl entry from the stroma into the pigmented ciliary epithelial (PE) cells, after which Na+ and Cl- diffuse across the gap junctions into the nonpigmented ciliary epithelial (NPE) cells and are released into the aqueous humor. METHODS: Rabbit iris ciliary bodies were preincubated in HCO3-/CO2-containing or HCO3-/CO2-free solutions before quick freezing, cryosectioning, dehydration, and electron probe x-ray microanalysis. RESULTS: The NPE and the PE cells contained more K and Cl when incubated with bicarbonate. Inhibition of carbonic anhydrase with 0.5 mM acetazolamide had little effect in HCO3--free medium but prevented the increase in Cl in both cell types in HCO3-/CO2 solution. Inhibition of the Na+-K+-2Cl- symport with 10 to 500 microM bumetanide caused Cl loss from both cell types in HCO3--free solution, but bumetanide produced a paradoxical increase in Cl and Na in HCO3-/CO2 solution. Together, acetazolamide and bumetanide resulted in significant Cl loss in HCO3--free solution and prevented the gains of Cl and Na in HCO3-/CO2 solution. CONCLUSIONS: The present results indicate that the dominant entry pathway of NaCl from the stroma into the ciliary epithelial syncytium is through an acetazolamide-inhibitable Cl-/HCO3 and a parallel Na+/H+ antiport. The dominant release pathways into the aqueous humor appear to be a Na+-K+-2Cl-symport, which can be outwardly directed under physiological conditions, together with the Na+/K+-exchange pumps and Cl- channels.


Subject(s)
Aqueous Humor/metabolism , Bicarbonates/pharmacology , Carrier Proteins/physiology , Ciliary Body/cytology , Epithelial Cells/metabolism , Models, Biological , Pigment Epithelium of Eye/metabolism , Animals , Antiporters/physiology , Biological Transport/drug effects , Bumetanide/pharmacology , Carbonic Anhydrase Inhibitors/pharmacology , Carrier Proteins/antagonists & inhibitors , Chloride-Bicarbonate Antiporters , Chlorides/metabolism , Ciliary Body/metabolism , Electron Probe Microanalysis , Female , Male , Potassium/metabolism , Rabbits , Sodium/metabolism , Sodium-Hydrogen Exchangers/physiology , Sodium-Potassium-Chloride Symporters
20.
J Pharmacokinet Biopharm ; 24(1): 79-101, 1996 Feb.
Article in English | MEDLINE | ID: mdl-8827584

ABSTRACT

When the two-compartment model with absorption is fitted to data by nonlinear least squares, in general six different outcomes can be obtained, arising from permutation of the three exponential rate constants. The existence of multiple solutions in this sense is analogous to the flip-flop phenomenon in the one-compartment model. It is possible for parameter estimates to be inconsistent with the underlying physical model. Methods for recognizing such illegal estimates are described. Other common difficulties are that estimated values for two of the rate constants are almost identical with very large standard deviations, or that the parameter estimation algorithm converges poorly. Such unwanted outcomes usually signal a local (false) minimum of the sum of squares. They can be recognized from the ratio of largest to smallest singular value of the Jacobian matrix, and are, in principle, avoidable by starting the estimation algorithm with different initial values. There also exists a class of data sets for which all outcomes of fitting the usual equations are anomalous. A better fit to these data sets (smaller sum of squares) is obtained if two of the relevant rate constants are allowed to take complex conjugate values. Such data sets have usually been described as having "equal rate constants." A special form of the model equation is available for parameter estimation in this case. Precautions relating to its use are discussed.


Subject(s)
Least-Squares Analysis , Pharmacokinetics
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