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Biomedical subjects

E Plante

Publications and source records attributed to E Plante.

At least 19 recordsLinked to original sources
PubMed2001

Normal fMRI brain activation patterns in children performing a verb generation task.

Although much is known concerning brain-language relations in adults, little is known about how these functions might be represented during the developmental period. We report results from 17 normal children, ages 7-18 years, who have successfully completed a word fluency paradigm during functional magnetic resonance imaging at 3 Tesla. Regions of activation replicate those reported for adult subjects. However, a statistically significant association between hemispheric lateralization of activation and age was found in the children. Specifically, although most subjects at all ages showed left hemisphere dominance for this task, the degree of lateralization increased with age. This study demonstrates that fMRI can reveal developmental shifts in the pattern of brain activation associated with semantic language function.

Adolescent↗
PubMed2000

Unmyelinated nerve fiber degeneration in chronic inflammatory demyelinating polyneuropathy.

To determine whether unmyelinated nerve fibers escape degeneration as one might expect in an immune response exclusively directed at myelin, we performed a morphometric examination of unmyelinated axons and myelinated nerve fibers in sural nerve biopsy specimens of 14 patients with a chronic inflammatory demyelinating polyneuropathy (CIDP) and of 12 age-matched normal controls. The numbers of unmyelinated axons, myelinated nerve fibers, denervated Schwann cell units and collagen pockets were quantified and related to the clinical and electrophysiological data of the patients with CIDP. In 4 patients with a rapid onset of the neuropathy and a highly elevated CSF protein, the numbers of both unmyelinated axons and myelinated nerve fibers were decreased equally. In 8 patients we found that the unmyelinated axons were relatively spared compared with the loss of myelinated nerve fibers. In these patients, however, the presence of denervated Schwann cell units and of collagen pockets was increased. We conclude that unmyelinated nerve fibers are affected in patients with CIDP.

Adult↗
PubMed2000

Electrophysiological dissociation between verbal and nonverbal semantic processing in learning disabled adults.

Event-related potentials (ERPs) were recorded as 16 adults with learning disabilities (LD) and 16 controls were presented with two sets of stimuli. The first set comprised pairs of line drawings and environmental sounds (nonverbal condition); the second consisted of printed and spoken words (verbal condition). In the controls, semantically related items elicited smaller N400s than unrelated items in both conditions, with opposing hemispheric asymmetries for spoken words and environmental sounds. The LD group did not show a significant difference between related and unrelated words, despite a robust context effect for nonspeech sounds. The results suggest anomalous processing limited to the verbal domain in a simple semantic association task in the LD group. Semantic deficits in this group may reflect a relatively specific deficit in forming verbal associations rather than a more general difficulty that spans both verbal and nonverbal domains.

Adolescent↗
PubMed2000

The distinct HERG missense mutation L564P causes long QT syndrome in one French Canadian family.

BACKGROUND: Long QT syndrome is a congenital abnormality of cardiac repolarization causing syncope and sudden death from ventricular tachyarrhythmias known as torsades de pointes. This hereditary cardiac disorder often shows an increase of the value of the QT interval corrected for heart rate over 0.45 s in a 12-lead electrocardiogram. OBJECTIVE: To find and identify pertinent mutations occurring in French Canadians by extracting genomic DNA from blood samples and performing a combination of polymerase chain reaction (PCR), single-strand conformational polymorphism and DNA sequencing. RESULTS: A novel mutation was identified in the S5 region of the HERG potassium channel. In codon 564 CTA, T was replaced by C, resulting in a leucine to proline substitution. Two family members had the mutation in two distinct generations. A new restriction site was created at this position and therefore enabled the development of a rapid diagnostic test using PCR. HERG wild type and mutant potassium channel mRNAs were then expressed in Xenopus laevis oocytes. CONCLUSION: This electrophysiological study suggests that coexpression of HERG wild type and mutant L564P results in a dominant negative effect of the mutation.

Adult↗
PubMed1999

Time course of word identification and semantic integration in spoken language.

The minimum duration signal necessary to identify a set of spoken words was established by the gating technique; most words could be identified before their acoustic offset. Gated words were used as congruous and incongruous sentence completions, and isolation points established in the gating experiment were compared with the time course of semantic integration evident in event-related brain potentials. Differential N400 responses to contextually appropriate and inappropriate words were observed about 200 ms before the isolation point. Semantic processing was evident before the acoustic signal was sufficient to identify the words uniquely. Results indicate that semantic integration can begin to operate with only partial, incomplete information about word identity. Influences of semantic constraint, word frequency, and rate of presentation are described.

Adolescent↗
PubMed1998

Image manipulation and error estimation for MRI analysis.

Manipulation of MRI images prior to volumetric analysis is a common practice that may unwittingly lead to errors in measurement. In this study, we examine the effects of two types of image manipulation: changes in the total number of slices used to obtain volume estimates (slice sampling rate) and image rotation. A phantom containing two regularly-shaped and two irregularly-shaped regions of interest (ROIs) was scanned using an SPGR sequence and 1-mm slices. Changes in slice sampling rate produced marked effects on volume estimation of irregularly-shaped ROls. Comparatively little error was associated with changes in slice sampling rates for regularly-shaped ROIs. In addition, there was an interaction between image rotation in non-orthogonal planes and slice sampling rate. The data suggests that the ability to detect anatomical effects may be influenced by an investigator's choices concerning the number of slices included in a region of interest and image rotation when estimating volumes.

Evaluation Studies as Topic↗
PubMed1998

Morphology of the inferior frontal gyrus in developmentally language-disordered adults.

The inferior frontal gyrus has traditionally been considered an important cortical region for language and may be important for understanding developmental language disorders. The morphology of the inferior frontal gyrus, as it appeared on T1-weighted sagittal magnetic resonance imaging (MRI) scans, was evaluated using a classification system that distinguished between seven basic morphological variants of the gyral and sulcal patterns in this region. This classification scheme was applied to the MRI scans of 41 neurologically normal adult subjects. To examine the relation between sulcal morphology and subject status, these subjects were sorted first by family history for developmental language disorders and then resorted by expression of behavioral signs consistent with a diagnosis of this disorder as determined by standardized testing. Morphological types that included an extra sulcus in the inferior frontal gyrus were statistically associated with the behaviorally based classification of subjects, but not with a positive family history for developmental language disorders. Because gyral patterns are prenatally determined, this finding is consistent with the theory that altered prenatal development contributes to the expression of a developmental language disorder.

Adult↗
PubMed1998

Criteria for SLI: the Stark and Tallal legacy and beyond.

Since it first appeared, the Stark and Tallal (1981 ) criteria for the selection of children with specific language impairment (SLI) has had a profound influence on research with this population. A review of the recent literature indicates that these criteria continue to be used, in part or in whole, in current research. However, the recent literature also provides illustrations of the use and interpretations of norm-referenced tests that can serve to update current best practices in subject selection. The original criteria for IQ and language test scores, along with their more recent adaptations, are reconsidered in light of current information on the use of tests with SLI.

Child↗
PubMed1996

Gyral morphology in the posterior Sylvian region in families affected by developmental language disorder.

This study describes the family aggregation of gyral morphology in the posterior perisylvian region in families that contain one or more children with a developmental language disorder. The probands in these families were 8 male and 2 female children referred through therapy programs and schools for children with language and reading problems. Family members included both biological parents (10 m, 10 f) and all available siblings (6 m, 4 f). Gyral morphology in the members of these families was compared with control subjects (10 m, 10 f) who were without a personal or family history of developmental language disorders. Gyral morphology was evaluated using T1-weighted sagittal scans from a GE Signa 1.5T magnet, 5 mm consecutive slices through the full brain volume. A less common type of Sylvian fissure morphology was more frequently found in the hemispheres of language-disordered subjects and their first-degree relatives than in control subjects. In addition, the pattern of Sylvian fissure morphology across generations within the families suggests that this feature might be inherited from either parent. The elevated rate of extra gyri in the posterior perisylvian region in families affected by language disorder links an anomaly within a language-related brain region with familial risk for this disorder.

Adult↗
PubMed1996

Sea anemone toxin (ATX II) modulation of heart and skeletal muscle sodium channel alpha-subunits expressed in tsA201 cells.

We have expressed recombinant alpha-subunits of hH1 (human heart subtype 1), rSkM1 (rat skeletal muscle subtype 1) and hSkM1 (human skeletal muscle) sodium channels in human embryonic kidney cell line, namely the tsA201 cells and compared the effects of ATX II on these sodium channel subtypes. ATX II slows the inactivation phase of hH1 with little or no effect on activation. At intermediate concentrations of ATX II the time course of inactivation is biexponential due to the mixture of free (fast component, taufasth) and toxin-bound (slow component, tauslowh) channels. The relative amplitude of tauslowh allows an estimate of the IC50 values approximately 11 nM. The slowing of inactivation in the presence of ATX II is consistent with destabilization of the inactivated state by toxin binding. Further evidence for this conclusion is: (i) The voltage-dependence of the current decay time constants (tauh) is lost or possibly reversed (time constants plateau or increase at more positive voltages in contrast to these of untreated channels). (ii) The single channel mean open times are increased by a factor of two in the presence of ATX II. (iii) The recovery from inactivation is faster in the presence of ATX II. Similar effects of ATX II on rSkM1 channel behavior occur, but only at higher concentrations of toxin (IC50 = 51 nM). The slowing of inactivation on hSkM1 is comparable to the one seen with rSkM1. A residual or window current appears in the presence of ATX II that is similar to that observed in channels containing mutations associated with some of the familial periodic paralyses.

Cell Line↗
PubMed1996

Classification of adults for family studies of developmental language disorders.

A variety of approaches has been used to classify the status of adult subjects in familial studies of developmental language disorders. In this report, we directly compare the results of four different methods that appear in the research literature. Two of the approaches rely on case history reports, and two are performance-based methods. Subjects included 24 parents (12 mothers, 12 fathers) of children with developmental language disorders and 24 unrelated adult control subjects (12 female, 12 male) who completed case history items and standardized language testing designed for classification purposes. All classification methods identified more parents than control subjects as "affected". However, classification by case history methods resulted in fewer affected adults than classification through standardized testing. This outcome suggests that the variability in classification rates in studies to date may be the result of method rather than subject sample differences.

Adult↗
PubMed1996

Elevated androgen, brain development and language/learning disabilities in children with congenital adrenal hyperplasia.

Individuals with congenital adrenal hyperplasia (CAH) provide a test population for the theory that elevated testosterone levels alter prenatal brain development and increase the risk of learning disabilities. Eleven subjects with CAH, five of their non-CAH siblings and 16 matched control subjects participated in two studies. The first study documented hand preference, verbal skills and non-verbal skills. A higher prevalence of language/learning disability was found in both the CAH subjects and their families than in the control subjects. The second study examined the prevalence of atypical perisylvian asymmetries on MRI scans. These revealed an atypical pattern of asymmetry (R = L or R > L) in the majority of the subjects with CAH and in all of their siblings. One subject with CAH also showed evidence of a neuromigratory disturbance in the posterior left hemisphere. Of the control subjects, only one showed an atypical pattern of asymmetry and none showed evidence of a neuromigratory disorder. The findings indicate that an elevated familial rate for language-based learning disabilities and altered brain asymmetries co-occur in families with the gene for CAH.

Adolescent↗
PubMed1995

Effect of implicit and explicit "rule" presentation on bound-morpheme generalization in specific language impairment.

This study addressed whether generalization of a trained bound morpheme to untrained vocabulary stems differs between children with specific language impairment (SLI) and children with normal language (NL) under two controlled instructional conditions. Twenty-five children with NL and 25 children with SLI matched for age served as subjects. Contrasts between affixed and unaffixed words highlighted the affixation "rule" in the "implicit-rule" condition. The "rule" was verbalized by the trainer in the "explicit-rule" condition. Bimodal generalization results occurred in both subject groups, indicating that generalization was not incremental. Chi-square analyses suggested that the SLI group generalized the bound morpheme less often than the NL group under the explicit-rule training condition. The findings add to those that indicate children with SLI have a unique language-learning style, and suggest that the explicit presentation of metalinguistic information during training may be detrimental to bound-morpheme generalization by preschool-age children with SLI.

Child↗
PubMed1994

Bound-morpheme skills in the oral language of school-age, language-impaired children.

Bound-morphine skills of school-age, language-impaired (LI) children were explored with three tasks designed to assess multiple dimensions of this component of language. Ten English-speaking, school-age LI children (Mean age: 10:3) and ten children with normal language (Mean age: 9:9) served as subjects. A two-way analysis of variance revealed significant group differences. Fisher a priori testing documented significant group differences for a measure of English bound-morpheme skill levels, a measure of ability to generalize English bound-morphemes to novel words, and a measure of ability to learn novel bound-morphemes attached to novel words. The findings indicate that core features of developmental language impairment in preschool children--poor ability to learn, to use, and to generalize bound-morphemes--are also present in school-age, LI children.

Child↗
PubMed1993

Crystal-induced neutrophil activation. II. Evidence for the activation of a phosphatidylcholine-specific phospholipase D.

OBJECTIVE: To investigate the involvement of phospholipase D in the signaling pathways activated by 2 pathologically relevant inflammatory microcrystals, monosodium urate (MSU) and calcium pyrophosphate dihydrate (CPPD). METHODS: Human peripheral blood neutrophils were used throughout. Phospholipase D activity was monitored by measuring 3 separate indices: 1) the mass of phosphatidic acid, 2) the levels of alkyl-phosphatidic acid, and 3) the levels of formation, in the presence of ethanol, of phosphatidylethanol. The latter 2 parameters were measured in cells labeled with 1-0-3H-alkyl-2-acetyl-sn-glycero-3-phosphocholine. The cells were stimulated with microcrystals of triclinic morphology. RESULTS: Both MSU and CPPD crystals induced a time- and concentration-dependent accumulation of phosphatidic acid mass and elevation in levels of alkyl-phosphatidic acid and phosphatidylethanol in prelabeled cells. The activation of phospholipase D by the microcrystals was partially sensitive to colchicine and largely resistant to pertussis toxin. Inhibition of phosphatidic acid formation by wortmannin or ethanol reduced the microcrystal-stimulated production of superoxide anions. CONCLUSION: These results indicate that microcrystals stimulate phospholipase D in human neutrophils and that at least some of the functional consequences of neutrophil-microcrystal interactions may be dependent on this biochemical pathway.

Androstadienes↗
PubMed1993

Language matches: illuminating or confounding? Research note.

The practice of matching younger, language-matched controls, in addition to age-matched controls, is often used in studies of language-disordered children to examine the role of "language level" on performance. However, the interpretation of the relative performance of subjects in studies using such dual control groups is problematic. Conceptual concerns arise with the use of language matches because language is a multidimensional skill that is not reflected equivalently for the language-disordered children and their language-matched controls. Furthermore, matching by language level inevitably introduces an extraneous age effect that confounds interpretation. In addition, erroneous interpretations of null findings can occur when no differences are found between language-disordered and language-matched groups.

Age Factors↗