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PubMedDate not supplied

Improving the reproducibility of acoustic rhinometry in the assessment of nasal function.

Acoustic rhinometry readings are very position dependent, and it was hypothesized that this accounts for its relative lack of reproducibility on a day-to-day basis. Multiple readings on each visit were taken to investigate their impact, if any, on improving the day-to-day reproducibility of the method. Measurements of the minimal cross-sectional area of the nose as measured by acoustic rhinometry were studied in 10 subjects following nasal decongestion. For each individual, acoustic rhinometry was performed ten times. The ten recordings were repeated again, in an identical manner on a separate day. The subjects were repositioned and the nasal probes reinserted between each measurement. The mean coefficient of variation for minimal cross-sectional area readings in all 10 subjects was calculated as 9.92%. This is comparable to the day-to-day variability of acoustic rhinometry as measured by other workers and thus supports the hypothesis that the high measurement error of the device (rhinometer) is a function of positional variation during data acquisition. We were able to demonstrate a minimal gain in intervisit reproducibility by doing multiple recordings per person, with a plateau effect of reproducibility after 7 repeat readings.

Humans↗
PubMed1999

Word decoding and picture naming in children with a reading disability.

Poor readers and reading age level matched controls performed a primed picture-naming task and a lexical decision task; their vocabulary performance was also assessed. Picture-naming data showed that poor readers were slower in the repeated prime condition only. This effect could not be explained by differences in vocabulary. Semantically related primes were ineffective compared with the repeated prime condition. Lexical decision data replicated the nonword reading deficit hypothesis: Poor readers were slower, particularly on the pseudowords and nonwords. A separately conducted analysis of the real word data showed strong effects of acquisition age. Late-acquired words had longer reaction times. Vocabulary performance as the covariate could explain the between-groups effects on this task. Semantic processing, as it is involved in picture naming, and phonological processing, as it is involved in decoding printed words, appear to be 2 relatively independent sources of reading deficits.

Adolescent↗
PubMed1992

Dyslexia; ophthalmological aspects 1991.

Dyslexia or specific reading disability is an important and frequent handicap afflicting 5-10% of the population. It is basically a disorder of acquisition of written language, probably due to a poorly developed phonological awareness, which in turn may be neurologically related. As anatomical correlates symmetry of the planum temporale and ectopies in the cerebral cortex have been suggested. Functional correlates are discovered with brain electrical mapping and stimulation of brain structures during neuro surgery. From an ophthalmological point of view there are no relations between dyslexia and ocular problems including refractive errors and accommodation, problems of binocular control and stereopsis, eye dominance instability etc. However, contrast sensitivity seems to be reduced in dyslexics for the middle range of spatial frequencies, which may be related to impaired function of the 'transient' visual system. With regard to eye movements, there is no firm experimental proof for any disturbances in dyslexia, be it with the different movement systems or in the best movement direction. 'Backward saccades' or regressions are typical not only for dyslexic reading but in all types of reading when comprehension is poor. Although there is no treatment for dyslexia itself that can be based on ophthalmological findings, the ophthalmologist must after careful examination discover and treat any ocular, orthoptic or neuroophthalmological problem that may make reading difficult for the dyslexic child. The ophthalmologist must explain to the child and the parents that dyslexia usually has no ophthalmological or visual cause but is a disability with a neurobiological background, still unknown, in which the only efficient treatment is within the area of pedagogy.

Dyslexia↗
PubMed1999

Improved device definition in interventional magnetic resonance imaging using a rotated stripes keyhole acquisition.

Keyhole acquisition techniques have been used to reduce image acquisition times primarily in contrast agent studies and via simulation in interventional MRI procedures. More recent simulations have suggested that improved definition of an interventional device [e.g., biopsy needles, radio frequency (RF) electrodes] could be achieved by rotating the keyhole pattern in k-space so that the read out direction lies perpendicular to the device orientation in real space. This study seeks to validate the earlier predictions of improved efficacy of a rotated stripes keyhole acquisition in actual in vitro and in vivo interventional MR imaging procedures. A true-FISP sequence was modified to perform central stripes keyhole (as known as conventional keyhole) acquisitions after a full initial reference data set was acquired. The gradients of this sequence were then modified to rotate the k-space definition and the keyhole stripes by 10 degrees, 20 degrees, 30 degrees, 45 degrees, and 60 degrees from their conventional k-space orientation. Acquisitions were performed during insertion of interventional devices in phantom and in vivo RF ablation procedures, using the modified sequence selected which placed the phase encoding axis at parallel and perpendicular orientations to the devices. Resulting images were compared between the two orientations for needle width and tip accuracy. Apparent needle width was thinner and tip position more accurately determined for placement of phase encoding parallel to the needle in all cases. Rotated keyhole imaging provides the required temporal advantage of conventional keyhole imaging along with a near optimal definition of an interventional device when the phase encoding is oriented parallel to the direction of the needle motion. Magn Reson Med 42:554-560, 1999.

Animals↗
PubMed2004

Cognitive reserve-mediated modulation of positron emission tomographic activations during memory tasks in Alzheimer disease.

BACKGROUND: Cognitive reserve (CR) is the ability of an individual to cope with advancing brain pathological abnormalities so that he or she remains free of symptoms. Epidemiological data and evidence from positron emission tomography suggest that it may be mediated through education or IQ. OBJECTIVE: To investigate CR-mediated differential brain activation in Alzheimer disease (AD) subjects compared with healthy elderly persons. PARTICIPANTS: Using radioactive water positron emission tomography, we scanned 12 AD patients and 17 healthy elderly persons while performing a serial recognition memory task for nonverbalizable shapes under 2 conditions: low demand, in which one shape was presented in each study trial, and titrated demand, in which the study list length was adjusted so that each subject recognized shapes at approximately 75% accuracy. Positron emission tomographic scan acquisition included the encoding and recognition phases. A CR factor score that summarized years of education, National Adult Reading Test estimated IQ, and Wechsler Adult Intelligence Scale-Revised vocabulary subtest score (explaining 71% of the total variance) was used as an index of CR. Voxel-wise, multiple regression analyses were performed with the "activation" difference (titrated demand-low demand) as the dependent variables and the CR factor score as the independent one. Brain regions where regression slopes differed between the 2 groups were identified. RESULTS: The slopes were significantly more positive for the AD patients in the left precentral gyrus and in the left hippocampus and significantly more negative in the right fusiform, right middle occipital, left superior occipital, and left middle temporal gyri. CONCLUSION: Brain regions where systematic relationships (slopes) between subjects' education-IQ and brain activation differ as a function of disease status may mediate the differential ability to cope with (ie, delay or modify) clinical manifestations of AD.

Aged↗
PubMed1990

Fast and precise T1 imaging using a TOMROP sequence.

Proton spin-lattice (T1) relaxation time images were computed from a data set of 32 gradient-echo images acquired with a fast TOMROP (T One by Multiple Read Out Pulses) sequence using a standard whole-body MR imager operating at 64 MHz. The data acquisition and analysis method which permits accurate pixel-by-pixel estimation of T1 relaxation times is described. As an example, the T1 parameter image of a human brain is shown demonstrating an excellent image quality. For white and gray brain matter, the measured longitudinal relaxation processes are adequately described by a single-component least-squares fit, while more than one proton component has to be considered for fatty tissue. A quantitative analysis yielded T1 values of 547 +/- 36 msec and 944 +/- 73 msec for white and gray matter, respectively.

Brain↗
PubMed2002

Less developed corpus callosum in dyslexic subjects--a structural MRI study.

BACKGROUND: Based on previous studies and due to the characteristics of dyslexia as an auditory phonological decoding disorder, we predicted that the shape of the posterior corpus callosum (CC) would differ between dyslexic and control subjects. METHOD: Twenty right-handed boys with developmental dyslexia were selected from a carefully screened general population sample (mean age 11 years) and compared to a matched control group. The CC contour was manually traced on the aligned midsagittal MR slice and total callosal area and its subregions were compared between the groups. A statistical shape analysis and subsequent CC classification was performed using a recently developed shape model method. RESULTS: The shape analysis revealed shorter CC shape in the dyslexic group, localised in the posterior midbody/isthmus region. This region contains interhemispheric fibers from primary and secondary auditory cortices. A shape length difference larger than a fixed threshold in the posterior midbody region could correctly discriminate between control and dyslexic subject in 78% of the cases, where a dyslexic CC was shorter in this region than a control CC. However, there were no significant group differences with respect to overall CC area or subregions. CONCLUSION: A clear shape difference in the posterior midbody of the CC was found between dyslexic and control subjects. This fits with recent other studies that have reported a strong growth factor in this CC region during the late childhood years, coinciding with literacy acquisition. Our results show that the dyslexic group has not undergone the same growth pattern as the normal reading group.

Agenesis of Corpus Callosum↗
PubMed1999

Developmental surface dysgraphia: what is the underlying cognitive impairment?

The purpose of this study was to investigate the cognitive causes underlying spelling difficulties in a case of developmental surface dysgraphia, AW. Our results do not support a number of possibilities that could be the cause of AW's poor orthographic lexicon, including difficulties in phonological processing, phonological short-term memory, configurational visual memory, and lexical semantic memory. We have found instead that AW performs poorly in tasks that involve detection of the order of adjacent letters in a word or the order of adjacent units in strings of consonants or symbols. Finally, he performs poorly in tasks that involve reconstructing the order of a series of complex visual characters (Japanese and Hindi characters) especially when these are presented sequentially. We advance the hypothesis that AW's poor spelling and good reading skills stem from an underlying pattern of cognitive abilities where a very good visual configurational memory is coupled with a poor ability to encode serial order. This may have resulted in a holistic word-based reading strategy, which, together with the original problem of encoding order, may have had detrimental effects for the acquisition of spelling.

Adult↗
PubMed2006

Mutualistic mycorrhiza in orchids: evidence from plant-fungus carbon and nitrogen transfers in the green-leaved terrestrial orchid Goodyera repens.

The roles of mycorrhiza in facilitating the acquisition and transfer of carbon (C) and nitrogen (N) to adult orchids are poorly understood. Here, we employed isotopically labelled sources of C and N to investigate these processes in the green forest orchid, Goodyera repens. Fungus-to-orchid transfers of C and N were measured using mass spectrometry after supplying extraradical mycelial systems with double-labelled [13C-15N]glycine. Orchid-to-fungus C transfer was revealed and quantified by radioisotope imaging and liquid scintillation counting of extraradical mycelium following 14CO2 fixation by shoots. Both 13C and 15N were assimilated by the fungus and transferred to the roots and shoots of the orchid. Contrary to previous reports, considerable quantities (2.6% over 72 h) of fixed C were shown to be allocated to the extraradical mycelium of the fungus. This study demonstrates, for the first time, mutualism in orchid mycorrhiza, bidirectional transfer of C between a green orchid and its fungal symbiont, and a fungus-dependent pathway for organic N acquisition by an orchid.

Carbon↗
PubMed1997

[Combined conventional magnetic resonance, magnetic resonance angiography, and magnetic resonance cholangiopancreatography in the diagnosis and staging of pancreatic carcinoma].

PURPOSE: This study was aimed to integrating MR CholangioPancreatography (MRCP) and MR Angiography (MRA) to conventional MR images in the diagnosis and resectability assessment of pancreatic adenocarcinoma. MATERIAL AND METHODS: Twenty-three consecutive patients with pancreatic adenocarcinoma (16 in the head and 7 in the body-tail region) were examined with MR. Conventional MR, 3D MRCP and venous and arterial MRA images were acquired to assess biliary and vascular involvement. Acquisition time never exceeded 40-45 minutes. The images were independently studied by two radiologists and the final reading was decided upon consensus among readers. Sixteen patients underwent surgery. RESULTS: The diagnosis was confirmed at surgery in 16 patients and at percutaneous biopsy in 7. Interreader agreement was considered high, with .83 interobserver variability. Pancreatic adenocarcinoma was found in all patients examined. Unresectability because of vascular involvement was correctly assessed in all patients but 1. Biliary obstruction was demonstrated in 13 patients, involving the biliary and pancreatic ducts in 9 and the biliary ducts only in 4. CONCLUSION: Technical advances now permit the extensive application of MRI to the study of abdominal conditions. The combination of MRI, MRCP and MRA can provide most of the information needed for the diagnosis and resectability assessment of pancreatic adenocarcinoma, which can otherwise be obtained only performing three different exams.

Adenocarcinoma↗
PubMed1998

Pancreatic adenocarcinoma: combination of MR imaging, MR angiography and MR cholangiopancreatography for the diagnosis and assessment of resectability.

The purpose of this study was to determine the possibility of integrating MR cholangiopancreatography (MRCP) and MR angiography (MRA) to conventional MR images in the diagnosis and assessment of resectability of pancreatic adenocarcinoma. Twenty-three patients with pancreatic adenocarcinoma were prospectively examined with MR. Conventional MR images were acquired in all patients. Three-dimensional MRCP and MRA images were acquired in all patients with suspected biliary and vascular involvement. Acquisition time was less than 45 min in all cases. Images were independently evaluated by two radiologists, with final reading decided by consensus among readers. Diagnosis was confirmed with surgery in 16 patients and with percutaneous biopsy in 7. Concordance among readers was high with a kappa value of 0.83. Pancreatic adenocarcinoma was observed in all patients. Correct assessment of unresectability due to vascular involvement was found in 22 of 23 patients. Biliary obstruction was evident in 13 patients, involving the biliary and pancreatic ducts in 9 and the biliary ducts only in 4. Technical advances permit extensive use of MRI in the evaluation of abdominal pathologies. The combination of MR imaging, MRCP, and MRA can provide sufficient information for the diagnosis and assessment of resectability of pancreatic adenocarcinoma, which otherwise would require three different exams.

Adenocarcinoma↗
PubMed1983

Gene rearrangements leading to the expression of an insertion-inactivated tetracycline resistance gene in pBR322.

Cloning into the HindIII site of plasmid pBR322 inactivates the tetR promoter and usually prevents the expression of the tetR gene. The corresponding clones revert to tetracycline resistance at a low frequency. Such reversion is caused by gene rearrangement within the plasmids. DNA sequence analysis reveals three classes of revertants. The first class contains plasmids with partial duplications, which result in the fusion of the promoter of the RNA I species to the tetR gene. The event itself destroys the region encoding the RNA primer for replication and thus the plasmids would be replication defective if the duplication did not also include this region of the molecule. The plasmids from the second class are simple deletions which again fuse the tetR region to the RNA I promoter. In one case, the junction takes place at the end of the RNA I transcript, leaving RNA I and the RNA primer virtually intact. However, it removes the promoter of the RNA primer, the latter now being read from the cloned material. The second member of this class has fused the tetR gene well upstream of the RNA I region so that the RNA primer is still read from its own promoter. The low-level tetracycline resistance is probably due to partial read-through of the RNA I terminator. The third class of revertants differs from the previous two by the acquisition of foreign DNA in the form of an IS2-type insertion element which is known to promote transcription.

Base Sequence↗
PubMed2004

Identification of a novel splice variant of the human anti-apoptopsis gene survivin.

Survivin, a new member of the inhibitor of apoptosis protein (IAP) family, has been reported to be expressed in many cancers but not in differentiated normal tissues. In the present study, we describe the identification of a novel alternatively spliced survivin transcript, designated as survivin-3B. It comprises 5 exons including novel exon 3B derived from a 165-bp long portion of intron 3. Acquisition of a new in-frame TGA stop codon within the novel exon 3B results in an open reading frame (ORF) of 363 nucleotides, predicting a truncated 120 amino acid protein. Expression of survivin-3B was detected in human colon and gastric adenocarcinoma cell lines as well as mononuclear cells prepared from patients with myelodysplastic syndrome (MDS) and acute myelogenous leukemia (AML). Survivin-3B contains a single baculovirus IAP repeat (BIR), which is critical for apoptosis inhibition. However, it lacks a carboxyl-terminal coiled-coil domain, suggesting that survivin-3B may not be associated with G2/M phase. These data indicate that the function of survivin-3B may be different from that of regular survivin.

Alternative Splicing↗
PubMed2002

Correction of probe pressure artifacts in freehand 3D ultrasound.

We present an algorithm which combines non-rigid image-based registration and conventional position sensing to correct probe-pressure-induced registration errors in freehand three-dimensional (3D) ultrasound volumes. The local accuracy of image-based registration enables the accurate freehand acquisition of high resolution (>15 MHz) 3D ultrasound data, opening the way for 3D musculoskeletal examinations. External position sensor readings guarantee the large-scale positional accuracy of the data. Pressure correction is shown to dramatically increase the perceived quality of extended-field-of-view data sets and reslices through volumetric data sets, while quantitative comparisons of multiple in vivo volumes demonstrate the superior precision of the corrected data.

Algorithms↗
PubMed2001

Word reading and picture naming in Italian.

Results from two separate norming studies of lexical access in Italian were merged, permitting a comparison of word-reading and picture-naming latencies and the factors that predict each one for an overlapping subsample of 128 common nouns. Factor analysis of shared lexical predictors yielded four latent variables: a frequency factor, a semantic factor, a length factor, and a final factor dominated by frication on the initial phoneme. Age of acquisition (AoA) loaded highly on the first two factors, suggesting that it can be split into separate sources of variance. Regression analyses using factor scores as predictors showed that word reading and picture naming are both influenced by the frequency/AoA factor. The semantics/AoA factor influenced only picture naming, whereas the length and frication factors influenced only word reading. Generalizability of these results to other languages is discussed, including potential effects of cross-language differences in orthographic transparency.

Adult↗
PubMed2004

Using our current understanding of dyslexia to support early identification and intervention.

One of the major risk factors for reading disability is difficulty learning to read words in text in an accurate and fluent manner. This is apparent when a child at risk of dyslexia first starts to attempt to read. Dyslexic children struggle to grasp and automate the alphabetic principle (ie, they cannot "sound out" words or use phonemic decoding strategies) and therefore have difficulty deciphering unfamiliar words that they have not encountered before. Even though many of these words are part of the child's oral vocabulary, the child cannot recognize them in printed form. As a result, reading can be extremely laborious and time-consuming, fraught with errors, and altogether an unrewarding, aversive experience. To be an efficient reader, one must be able to rapidly and effortlessly recognize many words by sight, and for a child to acquire this facility requires multiple exposures to these words. The difficulty that dyslexic children have in developing reliable and efficient phonemic decoding ability makes the acquisition of a lexicon of sight words a much slower process than it is for the average reader. Several other factors can affect a child's ability to read, which are reviewed herein. However, early recognition and treatment of deficient phonologic awareness are an extremely important step in the prevention of a reading problem in the child who is at risk of dyslexia.

Child↗