In vivo monitoring of cellular transplants by magnetic resonance imaging and positron emission tomography.

Cellular loss is a common pathological observation in many disease conditions. Recent evidence that these cells can be replaced has generated huge excitement over possible clinical applications. The use of stem or progenitor cells, which can differentiate into site-appropriate phenotypes required to "repair" the damaged tissue, has already demonstrated potential in animal models, but many aspects of this novel treatment strategy require further elucidation.

Clonogenic analysis reveals reserve stem cells in postnatal mammals. II. Pluripotent epiblastic-like stem cells.

Undifferentiated cells have been identified in the prenatal blastocyst, inner cell mass, and gonadal ridges of rodents and primates, including humans. After isolation these cells express molecular and immunological markers for embryonic cells, capabilities for extended self-renewal, and telomerase activity. When allowed to differentiate, embryonic stem cells express phenotypic markers for tissues of ectodermal, mesodermal, and endodermal origin.

Functional magnetic resonance imaging of verbal fluency and confrontation naming using compressed image acquisition to permit overt responses.

Verbal fluency and confrontation naming, two tests of word retrieval, are of great utility in the field of cognitive neuroscience. However, in the context of functional magnetic resonance imaging (fMRI), movement artefact has necessitated the use of covert paradigms, which has limited clinical application. We developed two overt fMRI paradigms that allowed for performance measurement and hence were appropriate for use with patient groups.

Neural correlates of tactile prepulse inhibition: a functional MRI study in normal and schizophrenic subjects.

Prepulse inhibition (PPI) of the startle reflex refers to the ability of a weak prestimulus, the prepulse, to inhibit the response to a closely following strong sensory stimulus, the pulse. PPI is found to be deficient in a number of psychiatric and neurological disorders associated with abnormalities at some level in the limbic and cortico-pallido-striato-thalamic circuitry. We applied whole-brain functional magnetic resonance imaging to elucidate the neural correlates of PPI using airpuff stimuli as both the prepulse and the pulse in groups of (i) healthy subjects and (ii) schizophrenic patients.

Ketamine alters neural processing of facial emotion recognition in healthy men: an fMRI study.

Disruption of facial emotion perception occurs in neuropsychiatric disorders where the expression of emotion is dulled or blunted, for example depersonalization disorder and schizophrenia. It has been suggested that, in the clinical context of emotional blunting, there is a shift in the relative contribution of brain regions subserving cognitive and emotional processing. The non-competitive glutamate receptor antagonist ketamine produces such emotional blunting in healthy subjects.

Ketamine and fMRI BOLD signal: distinguishing between effects mediated by change in blood flow versus change in cognitive state.

No human fMRI studies have examined ketamine effects on the BOLD signal change associated with cognitive task performance. We wished to distinguish between effects on 1) cerebral blood flow, with resultant change in BOLD signal; and 2) cognition and neural mechanisms underlying BOLD signal change associated with task performance. Eight right-handed men (mean age 28.

Practice and difficulty evoke anatomically and pharmacologically dissociable brain activation dynamics.

Brain activation is adaptive to task difficulty and practice. We used functional MRI to map brain systems activated by an object-location learning task in 24 healthy elderly volunteers each scanned following placebo and two of four active drugs studied. We distinguished a fronto-striatal system adaptive to difficulty from a posterior system adaptive to practice.

Acoustic noise and functional magnetic resonance imaging: current strategies and future prospects.

Functional magnetic resonance imaging (fMRI) has become the method of choice for studying the neural correlates of cognitive tasks. Nevertheless, the scanner produces acoustic noise during the image acquisition process, which is a problem in the study of auditory pathway and language generally. The scanner acoustic noise not only produces activation in brain regions involved in auditory processing, but also interferes with the stimulus presentation.

Functional magnetic resonance neuroimaging of drug dependence: naloxone-precipitated morphine withdrawal.

This study investigated the potential utility of fMRI as a neuroimaging technique to examine drug dependence using a robust animal model of drug withdrawal. Two groups of rats chronically pretreated with incremental doses of morphine sulfate (2, 7, 15, 30, 40, 50, 50, and 50 mg/kg--subcutaneous injection) were subjected to opioid precipitated withdrawal (using the opioid antagonist, naloxone) and subsequently behaviorally assessed or gradient-echo imaged under urethane anesthesia. Whole brain, group statistical parametric maps revealed statistically significant changes in signal intensity following administration of 1 mg/kg naloxone (corrected for multiple comparisons: P < 0.

A functional magnetic resonance imaging study of overt letter verbal fluency using a clustered acquisition sequence: greater anterior cingulate activation with increased task demand.

Regional cerebral activation during a cognitive task can vary with task demand and task performance. In a functional magnetic resonance imaging study, we examined the effect of manipulating task demand on activation during verbal fluency by using "easy" and "hard" letters. A "clustered" image acquisition sequence allowed overt verbal responses to be made in the absence of scanner noise which facilitated "on-line" measurement of task performance.

Spatial normalization and averaging of diffusion tensor MRI data sets.

Diffusion tensor magnetic resonance imaging (DT-MRI) is unique in providing information about both the structural integrity and the orientation of white matter fibers in vivo and, through "tractography", revealing the trajectories of white matter tracts. DT-MRI is therefore a promising technique for detecting differences in white matter architecture between different subject populations. However, while studies involving analyses of group averages of scalar quantities derived from DT-MRI data have been performed, as yet there have been no similar studies involving the whole tensor.

Interim analysis of a prospective, randomized trial of vacuum-assisted closure versus the healthpoint system in the management of pressure ulcers.

Twenty-eight patients with 41 full-thickness decubitus ulcers were randomized to compare the Vacuum-Assisted Closure device (VAC) with the Healthpoint System (HP) of wound gel products in promoting ulcer healing. A total of 22 patients with 35 full-thickness ulcers completed the 6-week trial of treatment, during which time 2 patients (10%) in the VAC group (N =20) and 2 patients (13%) in the HP group (N = 15) healed completely. The mean percent reduction in ulcer volume was 42.

Novelty-related activation within the medial temporal lobes.

Functional magnetic resonance imaging (fMRI) was used to examine whether (1) verbal associative encoding activates the medial temporal lobes (MTL) and related regions more than non-associative encoding, (2) verbal associative novelty is related to enhanced MTL activation, and (3) verbal item novelty is related to enhanced MTL activation and, if so, whether these activations are in different or overlapping sites. No increase in MTL activation was found during verbal associative encoding relative to non-associative encoding, although associative encoding was related to a relative increase in activation in the posterior cingulate cortex. In contrast, verbal associative novelty was found to activate the MTL and posterior cingulate cortex.

Justice and organizational citizenship behavior intentions: fair rewards versus fair treatment.

In a sample of 114 employees from various industries, organizations, and positions, the likelihood of organizational citizenship behaviors (OCB) increased when employee perceptions of fair treatment by supervisors became more positive. Perceptions of fair rewards and fair formal procedures were not predictors of OCB intentions. After the authors controlled for established patterns of OCB and demographic characteristics, interactional justice perceptions were significantly related to the intention of performing specific organizationally beneficial activities.

Isotropic resolution diffusion tensor imaging with whole brain acquisition in a clinically acceptable time.

Our objective was to develop a diffusion tensor MR imaging pulse sequence that allows whole brain coverage with isotropic resolution within a clinically acceptable time. A single-shot, cardiac-gated MR pulse sequence, optimized for measuring the diffusion tensor in human brain, was developed to provide whole-brain coverage with isotropic (2.5 x 2.

Sex differences in functional brain activation during a lexical visual field task.

Functional MRI was used to investigate sex differences in brain activation during a paradigm similar to a lexical-decision task. Six males and 6 females performed two runs of the lexical visual field task (i.e.

Combined helical computed tomographic pulmonary angiography and lung perfusion scintigraphy for investigating acute pulmonary embolism.

Aim: To evaluate a diagnostic protocol incorporating helical computed tomographic pulmonary angiography (CTPA) and lung perfusion scintigraphy in the detection or exclusion of pulmonary embolism (PE) in routine clinical practice.

Materials And Methods: A prospective observational study of 808 consecutive patients with suspected acute PE was undertaken over a 23-month period. Twenty-nine cases who failed to follow the protocol were excluded, leaving 779 cases to be reviewed.

Storage of verbal associations is sufficient to activate the left medial temporal lobe.

Neuroimaging studies have shown that memory encoding activates the medial temporal lobe (MTL). Many believe that these activations are related to novelty but it remains unproven which is critical - novelty detection or the rich associative encoding it triggers. We examined MTL activation during verbal associative encoding using functional magnetic resonance imaging.