Epicutaneous administration of hapten through patch application augments TH2 responses which can downregulate the elicitation of murine contact hypersensitivity

BACKGROUND AND OBJECTIVE

Allergic contact dermatitis and its animal model, contact hypersensitivity (CHS), have long been documented as type 1 T-cell-predominant immune responses. Although type 1/type 2 T-cell deviation has been repeatedly demonstrated to play an important role in many human diseases and their animal models, the potential of tilting type 1/type 2 T-cell differentiation of CHS by modulating the manner of administration and dosage of hapten remains unexplored. This study examined the effect of these two factors on type 1/type 2 balance of CHS.

METHODS

ELISA methods for detection of isotypes of hapten-specific antibodies and cytokine profiles of in vitro reactivation culture as well as ear-swelling assay were used to indicate type 1 or type 2 T-cell immune responses.

RESULTS

In this paper, it was demonstrated that dosage of hapten has no effect on the type 1/ type 2 T-cell balance of CHS, whereas epicutaneous administration of hapten through patch application could tilt the type 1/type 2 balance to decrease type 1 and to augment type 2 T-cell responses. Patch application-induced modulation is still effective in ever-sensitized mice and the augmented type 2 T-cell responses are persistent and increase progressively in strength after repeated immunizations. Moreover, it was demonstrated that the augmented type 2 T-cell response can downregulate the elicitation of CHS. The major mediating cells of the enhanced type 2 T-cell responses were determined to be CD4+ T cells (TH2 cells).

CONCLUSIONS

These data show that epicutaneous administration of hapten through patch application augments TH2 response which can downregulate the elicitation of murine CHS. This exploration may contribute to the understanding of regulatory mechanisms involved in contact allergy.

Impact of assay parameters on the accuracy of free PSA test: source and stability of calibrator, calibration curve fitting, and level of total PSA in the serum

The measurement of PSA is recommended for men over 50 years of age for screening of prostate cancer. However, proper differentiation of prostate cancer from benign prostate hyperplasia (BPH) relies on an accurate measurement of free PSA (fPSA) and a correct calculation of percent fPSA. Because of the extremely low concentration of fPSA in the serum, any slight deviation from its true value may produce large errors in percent fPSA calculated. Therefore, we undertook a study examining carefully those parameters of the fPSA assay which might affect the fPSA determination. We found that the integrity of the calibrator, the computer curve-fitting program selected, the source of the calibrator, and the total PSA or fPSA + PSA complexes (tPSA) concentration of the specimen all had an impact on the accuracy of the fPSA value assayed. We found that an examination of the slope of the calibration curve was important to reveal whether the calibrator had or had not been denatured during storage. We also found that the 4-parameter cure fitting program was best suited for plotting the fPSA calibration curve. The calibrator we isolated from LNCaP cells was acceptable for our assay because it had an affinity for the assay antibody very similar to that of serum fPSA. We also determined the effect of tPSA concentration on the fPSA determinations and found that within the concentration range of 4-10 ng/mL the impact on the percent fPSA calculated was not significant. We believe that our assay produces accurate fPSA values when all these assay parameters are well controlled.

Development of an immunoassay specific for the PSA-ACT complex without the problem of high background

We have developed an assay specific for the PSA-ACT (PSA-alpha 1-antichymotrypsin) complex that effectively diminishes the problem of high assay background commonly reported by other investigators. The assay follows a two-site ELISA format. Polyclonal anti-PSA antibodies were coated on the microplate to capture the PSA complex from the serum, whereas the biotinylated anti-ACT polyclonal antibodies and HRP-conjugated streptavidin were used for detection. The high background ordinarily associated with this assay was greatly reduced when milk casein was added in addition to albumin for blocking and when the Super Block was also included in the diluents for sample dilution and dilution of enzyme conjugated detecting antibodies. The assay has a sensitivity of 0.05 ng/mL. The within-run precision ranges from 4.2-7.2% and the between-run precision falls between 5.8-8.5%. Cross reactions with ACT and free PSA (fPSA) are 0.0001% and 0.02%, respectively. The highest concentration of PSA-ACT complex in the maternal sera was < 0.4 ng/mL by this assay, much less than reported in the literature. Using this improved assay, the sum of fPSA and PSA-ACT concentrations were less than that of their corresponding total PSA (tPSA) most of the time. We believe that this improved assay should be used to replace the current tPSA assay for screening, monitoring, and managing patients with prostate cancer.

Isolation of the intact molecule and ectodomain of C-erbB-2 oncoprotein from SK-BR-3 cells and development of immunoassays on microplate

We isolated both the intact molecule (p185) and the ectodomain (p120) of c-erbB-2 oncoprotein from SK-BR-3 breast tumor cells. The p120 was extracted from the cells by 0.05 M phosphate buffer, pH 7.2, whereas the extraction of the p185 required the presence of a detergent, such as 1% Triton X-100 in 0.05 M Tris buffer. Protease inhibitors were also included in the extraction buffer during the isolation of p185 in order to prevent cleavage of p185 to p120 by an unknown protease apparently also present in the extract. In case there was any p120 in the p185 preparation, the p120 could be separated from p185 by chromatography on a Superose 12 column. Using the p120 and p185 as calibrators, we have established two microplate sandwich immunoassays: one measures both p185 and p120 (total assay) and the other is specific for the p185. Since capturing and detecting antibodies used in the total assay react against the extracellular domain of the c-erbB-2 oncoprotein, they can therefore be used to measure the p120 in serum and p185 in breast tumor tissue cytosol. On the other hand, the p185 specific assay uses the capturing antibody against the cytosolic domain of the oncoprotein and consequently can only measure p185 in breast tumor tissue cytosol.

Development of an assay for modulating anti-acetylcholine receptor autoantibodies using human rhabdomyosarcoma cell line

Three types of autoantibodies against the acetylcholine receptors (AChR) of skeletal muscle are detectable in patients with myasthenia gravis including binding, blocking, and modulating anti-AChR antibodies. Modulating autoantibodies correlate best with the severity of the disease, but are also technically most difficult to measure because the assay generally requires fresh human muscle cells. We have developed an assay for the modulation of anti-AChR antibodies using a rhabdomyosarcoma (RD) cell line expressing AChR on the cell surface. By decreasing the FetalClone III serum from 10% to 0.5% in Eagles Minimal Essential Medium (EMEM) we were able to increase the number of AChR on RD cells to meet the need of sensitivity of the assay. The extent of modulation was determined as the percent of AChR internalized in the presence or absence of modulating autoantibodies. Less than 6% modulation was found with the normal serum (n = 42). The CVs of both the intra- and day-to-day precision were less than 20%. When clinical samples (n = 105) were assayed in our laboratory and also at Nichols Institute, a correlation coefficient of 0.816 was obtained. The selection of RD cell line, the success of increasing the expression of the AChR on RD cells and the use of 125I alpha-bungarotoxin of high specific activity allowed the establishment of an assay which can be used in routine clinical laboratory for the measurement of modulating anti-AChR autoantibodies for the management of patients with myasthenia gravis.

Serum chromogranin A: early detection of hormonal resistance in prostate cancer patients

We monitored both chromogranin A (CgA) and neuron specific enolase (NSE) in serial serum specimens from 14 patients with prostate cancer (CAP patients) showing resistance to hormonal treatment. Elevated serum CgA was detected in 10 out of these 14 patients (71%) during treatment, and an early appearance of elevated serum CgA was found in 6 of 14 (43%) of these patients when serum tPSA levels were still in the normal range. If patients with radical prostatectomy were not included, the percentage of patients showing an early appearance of elevated serum CgA would have been much higher. Elevated serum CgA levels also were found in patients not subject to hormonal therapy. Serial specimens from two out of three prostate cancer patients, randomly selected, contained elevated serum CgA. Serum NSE was not detectable in any of the serial specimens we studied, suggesting that CgA, not NSE, should be used as a marker for neuroendocrine differentiation. We also compared the serum CgA in random serum specimens between patients with BPH (benign prostate hyperplasia) and with prostate cancer in the concentration range of serum tPSA between 3-15 ng/mL. Although serum CgA concentrations in BPH patients overlapped considerably with those levels in patients with prostate cancer, levels > 100 ng/mL should suggest prostate cancer. The early appearance of elevated serum CgA allows an early change of therapy to be made and can lead to the effective prevention of any further development of metastases.

Monitoring percent free PSA in serial specimens: improvement of test specificity, early detection, and identification of occult tumors

We have measured the serum concentration of prostate specific antigen (tPSA) and determined the percent free PSA (% fPSA) in serial specimens from 64 patients with prostate cancer, 35 patients with benign prostate hyperplasia (BPH), and 3 patients with prostitis. We found that the % fPSAs were not a constant for individual patients during the course of the disease. When we compared only the % fPSA of the first specimen of serial specimens from individual patients, who were largely untreated, 37% of BPH specimens were above 22%, whereas only 1.6% cancer samples were above that value. We also found that 67% of cancer specimens and 14% of BPH samples were below 8%, respectively. Although % fPSA distribution pattern remained similar between two types of specimens, less differentiation was found between BPH and prostate cancer in random specimens compared to the study using first specimens of an individual patient's serial samples. Percent fPSA apparently are affected by treatment. However, the most important benefit for the determination of % fPSA appears to be the sensitivity of % fPSA to identify occult tumors when the tPSAs were in the normal concentration range. Determination of % fPSA also seems to improve the specificity of tPSA, not only during screening for the differentiation between BPH and prostate cancer, but also during monitoring of treatment and recurrence.

Advantages of replacing the total PSA assay with the assay for PSA-alpha 1-antichymotrypsin complex for the screening and management of prostate cancer

Several advantages become immediately apparent when the prostate specific antigen (PSA, or tPSA) assay is replaced by the assay specific for the serum PSA-alpha 1-antichymotrypsin (PSA-ACT) complex. For instance, random contributions to the tPSA value by various serum minor PSA isoforms can be avoided, making possible the determination of a more accurate relation of the PSA-ACT concentration to the tumor activity. Discrepancies in percent free PSA (% fPSA) values from the same specimens due to the use of different commercial kits also can be eliminated, mainly because the PSA-ACT assay does not have the problems in antibody selection and calibrator preparation usually associated with the tPSA assay. We found that at the present time different cutoffs of % fPSA for the differentiation of BPH from prostate cancer must be established for each individual tPSA assay. Cutoffs established using values from one tPSA assay should not be used for making clinical decisions when their tPSA values are determined by a different kit. Moreover, when we monitored the patients during treatment with serum tPSA, specific fPSA, and specific PSA-ACT complex assays simultaneously, it was clear that any interpretation of the patient's clinical status based on tPSA values alone could be misleading. Because there is less PSA-ACT complex in BPH specimens relative to that found in cancer serum samples, expressing fPSA as "fPSA/PSA-ACT x 100" and measuring PSA-ACT complex concentrations instead of tPSA during screening improve the measurable contrast between BPH and prostate cancer. Although individually modest, collectively these advantages can add up to considerable improvements.

Algicidal effect of peridinium bipes on microcystis aeruginosa

Peridinium bipes exerted an inhibitory effect on the growth of Microcystis aeruginosa. The algicidal action of water-soluble extract from P. bipes was studied. After treatment with P. bipes extract, the absorption spectrum of M. aeruginosa culture changed markedly, particularly in the ranges of 500 approximately 650 and 420 approximately 460 nm. An increase in absorption in this wavelength resulted from a leakage of phycobilines, both phycocyanin and allophycocyanin, from the treated cells. However, no leakage of chlorophyll was detected. The leakage of phycobilines was a short-term effect, detectable within 1 h of incubation. Both the plasmalemma and thylakoid membranes in M. aeruginosa cells were damaged and distorted in fine structure after treatment with P. bipes extract. It is assumed that algicide from P. bipes exerts its effect on the cell membranes, giving rise to changes in membrane permeability and a dissociation of phycobiline assemblages, but not of chlorophyll complex, on the thylakoid membranes. As a result, phycobilines were leaked out from the cells.

Induction of tumor-specific T cell response by cognating tumor cells with foreign antigen-primed Th cells

Sufficient CD4+ T cell help is very important in generating specific cytotoxic T cell responses. The inadequate activation of tumor-specific Th cells leads to failure of antitumor immunity. In general, each individual consists of some primed Th cells responding to certain antigens. If these tumor non-specific pre-primed Th cells can provide sufficient help, the generation of tumor-specific T cells may be enhanced. In the present study, we tested this hypothesis by cognating and reactivating pre-primed ovalbumin (OVA)-specific Th cells with OVA-pulsed tumor cells which could simultaneously present both OVA and tumor-associated antigen on the same cell. We clearly demonstrated that immunization of OVA-sensitized mice with OVA-pulsed P388 cells, but not unpulsed P388 cells, led to the induction of P388-specific cytotoxicity and tumor resistance. Both CD4+ and CD8+ tumor-specific cytotoxic T cells were detected in vitro, but only CD8+ T cells played the major effector role in preventing the growth of challenged tumor in vivo. Taken together, our study demonstrated that the immunogenicity of tumor cells can be enhanced effectively by cognating pre-primed foreign antigen-specific Th cells with tumor cells. These findings have potential implications in developing methods to control tumor growth.

Development of a three-dimensional topographic map display for capillary electrophoresis/mass spectrometry with an ion trap/reflectron time-of-flight mass spectrometer detector: applications to tryptic digests of isoforms of myelin basic protein

A three-dimensional (3-D) contour map format has been developed to display the large amount of data continuously collected throughout an on-line capillary separation using an ion trap storage/reflectron time-of-flight detector (IT/reTOF). The resulting data are displayed on a single computer screen with a mass-to-charge ratio value-elution time-intensity representation. The intensity of various components is represented by 16 different colors so that the mass-to-charge ratio value, the elution time, and the intensity can be conveniently determined for each component. In addition, the mass spectrum and total ion chromatogram or total ion electropherogram (TIE) are shown on the same screen as the 3-D map that enables the correlation of a single spot in the 3-D map to the peaks in the TIE and the corresponding mass spectrum. The 3-D map has been used to identify various posttranslational modification sites of bovine myelin basic protein charge isomers, where the datafiles of tryptic digests of proteins analyzed by capillary electrophoresis/mass spectrometry were processed by this software and a comparison could be performed among the isoforms. The feature of in-screen integration over both the separation domain and the mass domain makes the acquisition of the selected ion chromatogram very convenient and greatly improves the ability to detect modified components present in low amounts.

On-line analysis by capillary separations interfaced to an ion trap storage/reflectron time-of-flight mass spectrometer

The interface of high-resolution capillary separation methods to time-of-flight mass spectrometry (TOF-MS) has generated considerable interest since TOF can provide the rapid and sensitive detection required by high resolution separations. In recent years, our laboratory has developed a variety of high-resolution capillary separation methods interfaced to TOF-MS via an ion trap storage/reflectron time-of-flight (IT/reTOF) instrument. Using this hybrid configuration, detection of fast separations at very low detection levels has been successfully performed for on-line separations of peptides and protein digests using electrospray ionization. In this report, we review the current status in our laboratory of interfacing high-performance liquid chromatography, capillary electrophoresis, and capillary electrochromatography to an IT/reTOF-MS instrument and various applications that have been developed involving this technology.

Autoantibodies against oxidized LDL. A potential marker for atherosclerosis

Oxidized LDL, not the native LDL, promotes atherosclerosis. However, ox-LDL is usually undetectable in the blood circulation. Autoantibodies against ox-LDL (gamma ox-LDL), on the other hand, are not only measurable in the blood but may also reflect the extent of in vivo oxidation of native LDL and provide any early sign of risk for atherosclerosis. Current assay for gamma ox-LDL needs improvement. Routine clinical application of this assay has to wait until all parameters of this assay are defined and characterized.

Protein digest analysis by pressurized capillary electrochromatography using an ion trap storage/reflectron time-of-flight mass detector

Pressurized capillary electrochromatography (pCEC) has been coupled to an ion trap storage/reflectron time-of-flight mass spectrometer for the analysis of peptide mixtures and protein digests. Taking advantage of the electroosmotic flow, high separation efficiency has been achieved in pCEC due to a relatively flat flow profile and the use of smaller packing materials. A supplementary pressure was used in these experiments which suppressed bubble formation and also allowed the tuning of the elution of peptides using the electrical field. In this work, a fast separation of a six-peptide mixture has been successfully performed. Using columns only 6 cm long, a tryptic digest of bovine cytochrome c was fully separated in around 14 min by properly tuning the applied voltage and the supplementary pressure. In addition, relatively complex protein digests, such as a tryptic digest of chicken ovalbumin, were analyzed using this pCEC/MS system, and more than 20 peaks were resolved in the total ion current chromatogram within 17 min. The use of an ion trap storage/reflectron time-of-flight mass spectrometer as an on-line detector further increased the resolving power of the pCEC by unambiguously identifying coeluting components. The nonscanning property of the time-of flight mass analyzer and the ion signal integration capability of the ion trap were successfully combined to provide rapid and sensitive full-mass range detection in these experiments.

Use of a polybrene capillary coating in capillary electrophoresis for rapid analysis of hemoglobin variants with on-line detection via an ion trap storage/reflectron time-of-flight mass spectrometer

A polybrene capillary coating in capillary electrophoresis (CE) has been used for rapid analysis of hemoglobin variant digests. The use of the polybrene capillary coating has allowed sufficient separation to resolve the large number of digest products formed upon tryptic digestion of the whole protein, so that prior separation of the hemoglobin alpha and beta chains is not required. The resolution of the digest peaks obtained by CE is sufficient so that even single amino acid substitutions can easily be detected using UV absorption detection. The digest is further analyzed by capillary electrophoresis separation with on-line detection using electrospray ionization interfaced to the ion trap storage/reflectron time of flight device (CE/ESI-IT/reTOF), where a comparison of the total ion electropherograms and mass spectra of the mutant and normal hemoglobins can detect the presence of a mutation site. The CE separation and mass analysis can be accomplished in typically 10-15 min. The unique capability of the CE/ESI-IT/reTOF system for detection of fast separations with narrow peaks that may be under 1 s fwhm is demonstrated. The speed of this system is essential for resolution of the large number of peaks that are separated in a short time duration using CE separations.

Hyperhomocyst(e)inemia is associated with impaired endothelium-dependent vasodilation in humans

BACKGROUND

Hyperhomocyst(e)inemia is a risk factor for atherosclerosis and is prevalent in the elderly. The objective of this study was to determine whether hyperhomocyst(e)inemia is associated with impaired endothelium-dependent vasodilation in humans.

METHODS AND RESULTS

High-resolution vascular ultrasonography was used to study endothelium-dependent and -independent vasodilation in a nonatherosclerotic peripheral conduit artery of 26 elderly hyperhomocyst(e)inemic subjects and 15 age- and sex-matched subjects with normal homocysteine levels. Flow-mediated, endothelium-dependent (nitric oxide-mediated) vasodilation was assessed by measuring the percent change in brachial artery diameter during reactive hyperemia. Endothelium-independent vasodilation was assessed after the administration of 0.4 mg sublingual nitroglycerin. Endothelium-dependent vasodilation was significantly impaired in the hyperhomocyst(e)inemic subjects compared with control subjects (3.7 +/- 0.6% versus 8.1 +/- 1.2%; P = .004), whereas endothelium-independent vasodilation was not different between the two groups (10.1 +/- 1.6% versus 9.3 +/- 1.5%; P = NS). In a linear regression analysis with serum homocysteine concentration, folic acid, age, sex, cholesterol (serum total, LDL, or HDL cholesterol), mean arterial blood pressure, use of antihypertensive medication, and baseline brachial artery diameter included as covariates, serum homocysteine concentration emerged as the only significant predictor of flow-mediated vasodilation.

CONCLUSIONS

These data indicate that hyperhomocyst(e)inemia is associated with impaired endothelium-dependent vasodilation in humans and suggest that the bioavailability of nitric oxide is decreased in hyperhomocyst(e)inemic humans.

Open-tubular capillary electrochromatography with an on-line ion trap storage/reflectron time-of-flight mass detector for ultrafast peptide mixture analysis

In this work, a novel open-tubular column (OTC) capillary electrochromatography (CEC) system has been coupled to an on-line ion trap storage/reflectron time-of-flight mass spectrometer for ultrafast peptide mixture analysis. Reversed-phase OTCs prepared by the sol-gel process were coated with an amine, which greatly enhanced the electroosmotic flow in an acidic buffer solution and considerably reduced nonspecific adsorption between the peptides and the column wall. A six-peptide mixture could be separated to baseline within 3 min on this system. A full mass range detection speed of 8 Hz was used in all these experiments, which was sufficiently rapid to maintain the high efficiency of ultrafast separations. Because of the high duty cycle of the mass spectrometer and the column path length-independent concentration-sensitive feature of the electrospray ionization process, high-quality total ion chromatograms could be obtained with injections of only 1-2 fmol of peptide samples. A concentration limit of detection of 1 x 10(-6) M was also achieved due to the preconcentration capability of CEC. In addition, a novel gradient CEC device was demonstrated which did not result in a pressure-driven flow. A tryptic digest of horse heart myoglobin was successfully separated on the gradient CEC system within 6 min. The use of the mass spectrometer increased the resolving power of this system by clearly identifying coeluting components.

The use of on-line capillary electrophoresis/electrospray ionization with detection via an ion trap storage/reflectron time-of-flight mass spectrometer for rapid mutation-site analysis of hemoglobin variants

Capillary electrophoresis/electrospray ionization using an ion trap storage/reflectron time-of-flight mass spectrometer detector (CE/ESI-IT/reTOF) is used to provide a rapid and sensitive method for analyzing structural variants in the hemoglobin (Hb) beta-chain. The Hb alpha- and beta-chains are separated and the beta-chain is digested by trypsin. The digest is analyzed by CE/ESI-IT/reTOF where a comparison of the total ion electrophorograms and mass spectra of the mutant and normal hemoglobins (Hbs) can detect the presence of a mutation site. In addition, collision-induced dissociation in the vacuum interface-skimmer region can be used to pinpoint the identity of such a site. The unique capability of the CE/ESI-IT/reTOF system for accurately detecting fast separations with narrow peaks that may be under 1 s full width at half maximum is demonstrated. The speed of this system is essential for resolution of the large number of peaks that are separated in a short time duration using CE separations.

Development of a capillary high-performance liquid chromatography tandem mass spectrometry system using SWIFT technology in an ion trap/reflectron time-of-flight mass spectrometer

In this work a capillary high-performance liquid chromatography/tandem mass spectrometry system has been developed in a quadrupole ion trap/reflectron time-of-flight mass spectrometer. The broadband excitation for isolating a precursor ion is achieved by generating the stored waveform inverse Fourier transform waveform in real time. Following the isolation and cooling periods, an auxiliary AC voltage (tickle) is applied to the entrance end cap of the ion trap to generate collision induced dissociation. The amplitude of the tickle voltage is optimized on-line using a feedback method which involves having two computers communicating with each other. This system has been tested with a 4-peptide mixture and tandem mass spectra were obtained for each peptide.

[Nasopharyngoscopic analysis of the velopharyngeal function in normal and cleft lip and palate patients]

The speech problem in patients born with cleft lip and palate is mainly due to the insufficiency of the velopharyngeal (VP) valving mechanism, manifested as in visually seen nasal emission, and auditorily perceived hypernasality and articulation disorders. Evaluations of resonance and VP function can be conducted by: (1) perceptual rating scale based on speech pathologist's subjective judgement and (2) objective instrumental assessment, by the use of specific instrument. Nasopharyngoscopy has been commonly used clinically to diagnose VP function. The purpose of this study is: using nasopharyngoscopy to investigate the differences in VP mechanism between those with VP competence and VP incompetence in the dimension of velar displacement, lateral pharyngeal wall (LPW) displacement, degree of VP closure and pattern of VP closure. Ninty-eight subjects were studied from June 1990 to August 1991. They were divided into 4 groups: (1) group 1: normals with normal speech; (2) group 2: cleft of lip only, with normal speech; (3) group 3: cleft palate without nasal emission, but normal articulation; (4) group 4: cleft palate with nasal emission, with or without articulation error. Age range was from 6-47 years old with equal sex distribution. Ten Chinese sentences were used for standard test sentences, and were grouped according to Mandarin phonological distinctive features into 5 categories: (1) nasals; (2) vowels; (3) plosives; (4) fricatives/affricates; (5) connected number counting. The result indicates that the insufficient velar displacement to contact posterior pharyngeal wall is a determining factor causing velopharyngeal insufficiency in group 4; however, the lateral pharyngeal wall movement is not significantly different among 4 groups. Coronal pattern of velopharyngeal closure is the most common pattern among 4 groups of speakers.

Use of an ion trap storage/reflectron time-of-flight mass spectrometer as a rapid and sensitive detector for capillary electrophoresis in protein digest analysis

An ion trap storage (IT)/reflectron time-of-flight mass spectrometer (reTOFMS) has been coupled to capillary electrophoresis (CE) via a sheathless microelectrospray ionization method. This hybrid mass spectrometer has proved to be a rapid and sensitive detector for CE, where mass spectra could be acquired at a speed sufficient to maintain the high-resolution capabilities of CE separations. The nonscanning property of the time-of-flight mass analyzer can provide a full mass range spectral acquisition speed of up to 25 spectra/s with a data system developed in our laboratory. For the work reported herein, a spectral acquisition speed of 4 spectra/s was found to be optimal for maintaining the quality of the separation while achieving high sensitivity. Tryptic digests of bovine cytochrome c and beta-lactoglobulin A were analyzed using the CE/IT/reTOFMS combination, resulting in total ion electropherograms similar to those obtained using UV absorption detection. Taking advantage of the ion storage capability of the ion trap, a detection limit in the lowfemtomole range was routinely obtained for these digests using the total ion electrophoretic mode and CE capillaries of typical dimensions (41 microns i.d.). This high sensitivity was achieved while maintaining a resolution of approximately 1500 for mass identification using the capabilities of the IT/reTOF device. Due to the high acquisition speed and the mass discrimination capabilities of the mass detector, all the peaks in the total ion electropherograms, including some totally or partially unresolved peaks, could be unambiguously identified.

Encoding operation and transcoding as the major loci of the frequency effect

The present study used a lexical naming task as well as a regular naming task and a lexical decision task for locating the frequency effects in lexical decision and naming. The naming of Chinese characters in the lexical naming task (pseudocharacters also presented as in the lexical decision task) involves decision processes, while they are absent in the regular naming task. Since naming a Chinese character necessarily involves lexical access, a decision component of the frequency effect in lexical decision can be isolated. This procedure will not work for alphabetic orthographies, because sublexical processes underestimate the frequency effect in the regular naming task. As a consequence, not only can a prelexical component of the frequency effect in lexical decision be estimated, but a postlexical component of the frequency effect in naming can be estimated.