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J Grainger

Publications and source records attributed to J Grainger.

At least 19 recordsLinked to original sources
PubMed1998

Separation of polycyclic aromatic hydrocarbon metabolites by gamma-cyclodextrin-modified micellar electrokinetic chromatography with laser-induced fluorescence detection.

Using a modified micellar buffer consisting of gamma-cyclodextrin (gamma-CD) and sodium dodecyl sulfate (SDS), we have obtained separations of hydroxy-polycyclic aromatic hydrocarbons (hydroxyPAHs). These compounds are oxidative products of mammalian PAH metabolism. The analytes were detected with a commercial laser-induced fluorescence (LIF) detector. A number of hydroxyPAH isomers could be separated by changes in gamma-CD concentration. Baseline resolution of 12 hydroxyPAHs was obtained using 30 mM borate, 60 mM SDS and 40 mM gamma-CD. The particular site substitution of the hydroxy group can produce changes in the hydroxyPAH fluorescence spectrum, and the effect of optical filter selection was studied for the LIF detection. The mass detection limits were in the (0.08-0.5) x 10(-15) mol range. To our knowledge, this is the first report of the separation of metabolic products of PAHs (and several positional isomers) using gamma-CD and micellar electrokinetic chromatography.

Chromatography, Liquid↗
PubMed1997

Effects of orthographic neighborhood in visual word recognition: cross-task comparisons.

Effects of orthographic neighborhood in visual word recognition in Spanish were examined in 5 paradigms: progressive demasking, standard lexical decision, lexical decision with blocking of neighborhood density, naming, and semantic categorization. The results showed inhibitory effects of neighborhood frequency in the progressive-demasking task, in both lexical-decision tasks, as well as for low-density words in the naming task, and for high-density words in the semantic-categorization task. Higher levels of neighborhood density produced an inhibitory trend in the progressive-demasking task, facilitation in lexical decision (significant only when neighborhood density was blocked), and a robust facilitation effect in naming (only for words with higher frequency neighbors). A global analysis across tasks and one simulation study helped outline some of the underlying task-specific and task-independent mechanisms.

Decision Making↗
PubMed1997

Masked orthographic priming in bilingual word recognition.

Two lexical decision experiments tested the influence of briefly presented orthographically related primes on target word recognition in bilinguals. The prime stimuli were high-frequency words either from the same language as that of the target or from the other language known by the bilingual subjects. When the prime and target were from the same language, orthographically related primes systematically inhibited target word recognition, whereas orthographically dissimilar primes did not. When the prime and target were words from different languages, the amount of inhibition increased as a function of subjects' level of proficiency in the prime word's language, with highly proficient bilinguals showing practically equivalent amounts of within and across language inhibitory priming. These results strongly suggest that a printed string of letters can simultaneously activate lexical representations in both of the bilingual's languages (insofar as these share the same alphabet), even when subjects are performing a monolingual task.

Humans↗
PubMed1997

Extensive maternal representation of DNA-binding proteins that interact with regulatory target sites of the Strongylocentrotus purpuratus CyIIIa gene.

Nine different embryonic transcription factors interact at specific target sites in the cis-regulatory domain of the Strongylocentrotus purpuratus CyIIIa gene. We tested eight of these site sequences and show here that for every one a DNA-binding protein was present in unfertilized egg cytoplasm. The concentrations of active DNA-binding proteins per egg were estimated. We also present a new and convenient method for preparation of a material cytoplasmic fraction that retains these factors in active form.

Actins↗
PubMed1996

How initial fixation position influences visual word recognition: a comparison of French and Arabic.

The position the eye initially fixates in a written word influences the ease with which this word is recognized. Prior research has shown that the function relating ease of word recognition and initial fixation position in the word is not symmetric. Word recognition is generally superior when the initial fixation is left rather than right of the center of the word. This asymmetry in the function relating initial fixation position to word identifiability could be due to (a) hemispheric specialization, (b) reading habits, or (c) variations in lexical constraint. The present experiments tested these alternative explanations by comparing the effects of initial fixation position in prefixed and suffixed words in French and Arabic. The results show that, contrary to both the hemispheric specialization and reading habit hypotheses, the average initial fixation curves for Arabic are asymmetric neither to the left nor to the right but depend on the morphological structure of the stimuli, thus lending support to the lexical constraint hypothesis.

Adult↗
PubMed1996

Orthographic processing in visual word recognition: a multiple read-out model.

A model of orthographic processing is described that postulates read-out from different information dimensions, determined by variable response criteria set on these dimensions. Performance in a perceptual identification task is simulated as the percentage of trials on which a noisy criterion set on the dimension of single word detector activity is reached. Two additional criteria set on the dimensions of total lexical activity and time from stimulus onset are hypothesized to be operational in the lexical decision task. These additional criteria flexibly adjust to changes in stimulus material and task demands, thus accounting for strategic influences on performance in this task. The model unifies results obtained in response-limited and data-limited paradigms and helps resolve a number of inconsistencies in the experimental literature that cannot be accommodated by other current models of visual word recognition.

Adult↗
PubMed1995

Letter-position coding in random constant arrays.

The processing of letter-position information in randomly arranged consonant strings was investigated using a masked prime variant of the alphabetic decision (letter/nonletter classification) task. In Experiment 1, primes were uppercase consonant trigrams (e.g., FMH) and targets were two uppercase Xs accompanied by the target letter or a nonletter (e.g., XMX X%X). Response times were systematically faster when target letters were present in the prime string than when target letters were not present in the primer string. These constituent letter-priming effects were significantly stronger when the target letter appeared in the same position in the prime and target stimuli. This contrast between position-specific and position-independent priming was accentuated when subjects responded only when all the characters in the target string were letters (multiple alphabetic decision) in Experiment 2 and 3. In Experiment 4, when prime exposure duration was varied, it was found that position-specific priming develops earlier than position-independent priming. Finally, Experiment 5 ruled out a perceptual-matching interpretation of these result. An interpretation is offered in terms of position-specific and position-independent letter-detector units in an interactive-activation framework.

Humans↗
PubMed1995

The incremental priming technique: a method for determining within-condition priming effects.

A novel priming technique is applied in two experiments using an alphabetic decision and a lexical decision task to study effects of repetition, and form-related priming on letter and word recognition. The incremental priming technique consists of a gradual increase of the prime's informational value (operationalized as prime intensity). The minimum prime-intensity level serves as a within-condition baseline for each priming condition. Thus, we can define any priming effect with respect to two baseline conditions: one is the minimum-intensity condition of the particular priming condition (within-condition baseline), and the other is a different priming condition (across-condition baseline). This double-baseline approach makes measuring of priming effects more reliable and imposes stronger constraints on our interpretations of these effects.

Arousal↗
PubMed1994

Field-amplified sample stacking in micellar electrokinetic chromatography for on-column sample concentration of neutral molecules.

On-column concentration of neutral molecules was achieved for the first time in micellar electrokinetic chromatography by means of field-amplified sample stacking. The stacking process was accomplished by dissolving the neutral analytes in a low-concentration micellar solution that was still above the critical micelle concentration. The lower total ionic strength in the sample buffer compared to the electrophoresis buffer allowed the negatively charged micelles to migrate rapidly into the boundary between the sample and the running buffer where they slow down. This field-amplified sample stacking was achieved by using normal or reversed electrode polarity and produced a 75-85-fold increase in sensitivity for 1,2,4,7- and 1,2,4,8-tetrachlorodibenzo-p-dioxins. The peak area counts obtained from the sample stacking process were proportional to the sample volume injected, and the stacking efficiency was dependent on the micellar concentration. The best stacking efficiency was obtained when the micelle concentration was slightly higher than the critical micelle concentration. When the injection volume was relatively small, the normal-polarity stacking procedure produced a higher stacking efficiency. However, when the injection volume was large, reversed polarity produced a higher stacking efficiency because the non-uniform distribution of the electrical field strength had been eliminated.

Chromatography↗
PubMed1994

Effects of orthography are independent of phonology in masked form priming.

Briefly presented forward-masked primes that share letters with a word target have been shown to facilitate performance in different word recognition tasks. However, in all the experiments that have previously reported these facilitatory effects, related primes not only shared more letters with the target than did unrelated primes (orthographic priming), but they also shared more phonemes (phonological priming). The stimuli used in the present experiments allow us to separate out the effects of orthographic priming from phonological priming. Varying prime exposure duration from 14 to 57 msec, it is shown that effects of orthography follow a distinct time-course from the effects of phonology, and that orthographic facilitation does not result from a confound with phonological prime-target overlap.

Humans↗
PubMed1994

Chemical characterization and disposition studies with 1,2,7,8-tetrabromodibenzofuran in the rat.

Polybrominated dibenzo-p-dioxins and dibenzofurans have been identified as potential environmental contaminants. The present studies were designed to characterize the chemical disposition of a tetrabrominated dibenzofuran. The isomer-specific pattern of 1,2,7,8-tetrabromodibenzofuran (TBDF) was chemically characterized using high-pressure liquid chromatography, gas chromatography/mass spectrometry, infrared absorption, and proton nuclear magnetic resonance techniques. The absorption, distribution, and elimination of 1,2,7,8-[4,6-3H]-TBDF were examined in the rat following a single oral, dermal, or intravenous dose of 1 nmol/kg. The 1,2,7,8-TBDF was rapidly excreted in the bile (approximately 50% of the dose in 8 h). Likewise, over half of the administered dose was found in the feces and intestine contents 24 h after iv administration and in feces 72 h after oral administration. Thus, the half-life of 1,2,7,8-TBDF is approximately 1 d. Major tissue depots included the liver, adipose tissue, and skin. The decline in hepatic concentrations observed in the iv and bile studies occurred in conjunction with metabolic elimination as well as a slight accumulation in adipose tissue. Dermal absorption of 1,2,7,8-TBDF, quantified as the amount contained in tissues (excluding the skin site) and excreta at 72 h, was estimated to be 29% of the administered dose. Thus, the general disposition profile of 1,2,7,8-TBDF in the rat is similar to that of other polyhalogenated aromatic hydrocarbons. Due to its rapid elimination, which is consistent with its predicted susceptibility to metabolic elimination, acute exposure to 1,2,7,8-TBDF would not be expected to result in the degree of toxicity associated with other more persistent congeners.

Absorption↗
PubMed1994

A study of masked form priming in picture and word naming.

We report a series of picture- and word-naming experiments in which the masked priming paradigm with prime exposures brief enough to prevent prime identification were used. Experiment 1 demonstrates that the prior presentation of the same word prime facilitates both picture and word naming independently of target frequency. In Experiments 2 and 3, primes that were pseudohomophones of picture targets produced facilitatory effects compared with orthographic controls, but these orthographically similar nonword primes did not facilitate picture naming compared with unrelated controls. On the other hand, word targets were primarily facilitated by orthographic prime-target overlap. This marked dissociation in the priming effects obtained with picture and word targets is discussed in relation to different explanations of masked form priming effects in visual word recognition and current models of picture and word naming.

Attention↗
PubMed1993

Masked partial-word priming in visual word recognition: effects of positional letter frequency.

In 4 primed lexical decision experiments, it was found that the positional frequencies of letters shared by the prime and target relative to the overall positional letter frequency of the target determined the magnitude of priming effects. The lower the positional frequency of shared letters, the stronger the facilitatory effect observed. Both an interactive and noninteractive semistochastic version of the interactive activation model captured the principal trends in the data. It is argued that masked partial-word priming arises from a tradeoff between the facilitation generated by prime-target letter overlap and the inhibition generated from all lexical representations activated by letters in the prime that receive further support on target presentation.

Adult↗
PubMed1992

Testing a semistochastic variant of the interactive activation model in different word recognition experiments.

A semistochastic variant of the interactive activation (IA) model of context effects in letter perception (McClelland & Rumelhart, 1981) was used to simulate response time distributions and means in different experiments investigating the effects of word frequency, neighborhood size and frequency, and orthographic priming in visual word recognition. The results provide evidence in favor of the connectivity assumption underlying the model but question the necessity of the interactivity assumption for simulating latencies in word recognition tasks. Together with those of a recent study by McClelland (1991), the present results suggest that 10 years after its appearance, the IA model's potential for testing hypotheses about the structure and dynamics of basic phenomena of human information processing in a variety of perceptual and cognitive tasks is not yet fully exploited.

Arousal↗
PubMed1992

Phonology and orthography in visual word recognition: evidence from masked non-word priming.

Three lexical decision experiments in French investigated the effects of briefly presented forward-masked non-word primes on latencies to phonologically and/or orthographically related targets. At 64-msec prime presentation durations, primes that are pseudohomophones of the target produced facilitatory effects compared to orthographic controls, but these orthographically similar non-word primes did not facilitate target recognition compared to unrelated controls. These results were obtained independently of target word frequency and independently of the presence or absence of pseudohomophone targets in the experimental lists. With a 32-msec prime duration, on the other hand, pseudohomophone and orthographic primes had similar effects on target recognition, both producing facilitation relative to unrelated controls. The results are discussed in terms of the time course of phonological and orthographic code activation in the processing of pronounceable strings of letters.

Adult↗
PubMed1992

Neighborhood frequency effects and letter visibility in visual word recognition.

Two experiments are described that measured lexical decision latencies and errors to five-letter French words with a single higher frequency orthographic neighbor and control words with no higher frequency neighbors. The higher frequency neighbor differed from the stimulus word by either the second letter (e.g., ASTRE-AUTRE) or the fourth letter (CHOPE-CHOSE). Neighborhood frequency effects were found to interact with this factor, and significant interference was observed only to CHOPE-type words. The effects of neighborhood frequency were also found to interact with the position of initial fixation in the stimulus word (either the second letter or the fourth letter). Interference was greatly reduced when the initial fixation was on the critical disambiguating letter (i.e., the letter P in CHOPE). Moreover, word recognition was improved when subjects initially fixated the second letter relative to when they initially fixated the fourth letter of a five-letter word, but this second-letter advantage practically disappeared when the stimulus differed from a more frequent word by its fourth letter. The results are interpreted in terms of the interaction between visual and lexical factors in visual work recognition.

Adult↗
PubMed1991

Prescribed fenoterol and death from asthma in New Zealand, 1981-7: a further case-control study.

The association between inhaled fenoterol and death from asthma has been investigated further by studying 112 asthma deaths (cases) during 1981-7 in patients aged 5-45 years who had been admitted to a major hospital for asthma during the 12 months before death. Two age matched control groups were chosen. Control group A comprised 427 patients who had been admitted to hospital for asthma during the calendar year that the corresponding death occurred and who had also had a previous admission for asthma in the previous 12 months. Control group B comprised 448 patients admitted to hospital for asthma during the calendar year in which the admission of the corresponding case occurred. The inhaled fenoterol odds ratio was 2.11 (95% confidence interval (CI) 1.37-3.23, p less than 0.01) when group A was used as the control (the approach used in previous studies), and 2.66 (95% CI 1.74-4.06, p less than 0.01) with group B as the control (the approach recommended by critics of previous studies). Markers of chronic asthma severity were associated with asthma death when control group B was used, but not when control group A was used (which indicates that these markers were indirectly matched for when control group A was used). Information was also collected on various markers of acute asthma severity and prescription of psychotropic drugs, but it was found that these were not important confounders. These findings address the major criticisms of previous case-control studies of this issue, and add support to the hypothesis that inhaled fenoterol increases the risk of death in patients with severe asthma.

Administration, Inhalation↗