Biomedical subjects

A Uecker

Publications and source records attributed to A Uecker.

12 recordsLinked to original sources

PubMed1999

Preclinical memory decline in cognitively normal apolipoprotein E-epsilon4 homozygotes.

OBJECTIVE: To determine, in a cross-sectional evaluation of nondemented individuals, if age-related memory decline is influenced by apolipoprotein E (apoE) genotype. BACKGROUND: The apoE-4 allele is an important risk factor for AD. PET in cognitively normal apoE-4 carriers (mean age, 56 years) shows reduced cerebral metabolism suggestive of very early AD that precedes clinically evident memory loss or MRI-based hippocampal atrophy. METHODS: Tests of immediate and delayed recall (primary outcome measures) and other neuropsychological measures (secondary outcome measures) were given to three genetically defined groups of cognitively normal individuals (age, 49 to 69 years) including apoE-4 homozygotes (n = 25), apoE-4 heterozygotes (n = 25, all epsilon3/4), and apoE-4 noncarriers (n = 50). Groups were matched for age, gender, and educational background. Cross-sectional comparisons between the genetic subgroups of the relationship between age and test score were performed for each neuropsychological measure. RESULTS: There were no intergroup differences in mean scores on any neuropsychological measure, but tests sensitive to immediate and delayed recall showed a significant negative correlation with age in the apoE-4 homozygote group relative to the noncarrier group. CONCLUSION: Consistent with previous neuropsychological studies of early AD, this cross-sectional study suggests that age-related memory decline occurs earlier in cognitively healthy apoE-4 homozygotes than in apoE-4 heterozygotes and noncarriers, and precedes clinically detectable AD.

Age Factors↗

PubMed1999

A dual inhibitor of platelet-derived growth factor beta-receptor and Src kinase activity potently interferes with motogenic and mitogenic responses to PDGF in vascular smooth muscle cells. A novel candidate for prevention of vascular remodeling.

PP1 has previously been described as an inhibitor of the Src-family kinases p56(Lck) and FynT. We have therefore decided to use PP1 to determine the functional role of Src in platelet-derived growth factor (PDGF)-induced proliferation and migration of human coronary artery smooth muscle cells (HCASMCs). A synthetic protocol for PP1/AGL1872 has been developed, and the inhibitory activity of PP1/AGL1872 against Src was examined. PP1/AGL1872 potently inhibited recombinant p60(c-src) in vitro and Src-dependent tyrosine phosphorylation in p60(c-srcF572)-transformed NIH3T3 cells. PP1/AGL1872 also potently inhibited PDGF-stimulated migration of HCASMCs, as determined in the modified Boyden chamber, as well as PDGF-stimulated proliferation of HCASMCs. Surprisingly, in addition to inhibition of Src kinase, PP1/AGL1872 was found to inhibit PDGF receptor kinase in cell-free assays and in various types of intact cells, including HCASMCs. PP1/AGL1872 did not inhibit phosphorylation of the vascular endothelial growth factor receptor KDR (VEGF receptor-2; kinase-insert domain containing receptor) in cell-free assays as well as in intact human coronary artery endothelial cells. In line with the insensitivity of KDR, PP1/AGL1872 had only a weak effect on vascular endothelial growth factor-stimulated migration of human coronary artery endothelial cells. On treatment of cells expressing different receptor tyrosine kinases, the activities of the epidermal growth factor receptor, fibroblast growth factor receptor-1, and insulin-like growth factor-1 receptor were resistant to PP1/AGL1872, whereas PDGF alpha-receptor was susceptible, albeit to a lesser extent than PDGF beta-receptor. These data suggest that the previously described tyrosine kinase inhibitor PP1/AGL1872 is not selective for the Src family of tyrosine kinases. It is also a potent inhibitor of the PDGF beta-receptor kinase but is not a ubiquitous tyrosine kinase inhibitor. PP1/AGL1872 inhibits migration and proliferation of HCASMCs probably by interference with 2 distinct tyrosine phosphorylation events, creating a novel and potent inhibitory principle with possible relevance for the treatment of pathological HCASMC activity, such as vascular remodeling and restenosis.

3T3 Cells↗

PubMed1999

Neuroanatomical correlates of hunger and satiation in humans using positron emission tomography.

The central role of the hypothalamus in the origination and/or processing of feeding-related stimuli may be modulated by the activity of other functional areas of the brain including the insular cortex (involved in enteroceptive monitoring) and the prefrontal cortex (involved in the inhibition of inappropriate response tendencies). Regional cerebral blood flow (rCBF), a marker of neuronal activity, was measured in 11 healthy, normal-weight men by using positron emission tomography in a state of hunger (after 36-h fast) and a state of satiation (after a liquid meal). Hunger was associated with significantly increased rCBF in the vicinity of the hypothalamus and insular cortex and in additional paralimbic and limbic areas (orbitofrontal cortex, anterior cingulate cortex, and parahippocampal and hippocampal formation), thalamus, caudate, precuneus, putamen, and cerebellum. Satiation was associated with increased rCBF in the vicinity of the ventromedial prefrontal cortex, dorsolateral prefrontal cortex, and inferior parietal lobule. Changes in plasma insulin concentrations in response to the meal were negatively correlated with changes in rCBF in the insular and orbitofrontal cortex. Changes in plasma free fatty acid concentrations in response to the meal were negatively correlated with changes in rCBF in the anterior cingulate and positively correlated with changes in rCBF in the dorsolateral prefrontal cortex. In conclusion, these findings raise the possibility that several regions of the brain participate in the regulation of hunger and satiation and that insulin and free fatty acids may be metabolic modulators of postprandial brain neuronal events. Although exploratory, the present study provides a foundation for investigating the human brain regions and cognitive operations that respond to nutritional stimuli.

Adult↗

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

Hippocampal volumes in cognitively normal persons at genetic risk for Alzheimer's disease.

Brain imaging techniques have the potential to characterize neurobiological changes that precede the onset of cognitive impairment in persons at risk for Alzheimer's disease. As previously described, positron emission tomography (PET) was used to compare 11 cognitively normal persons 50 to 62 years of age who were homozygous for the epsilon4 allele of apolipoprotein E and 22 persons without the epsilon4 allele with a reported family history of Alzheimer's dementia who were matched for sex, age, and level of education. The epsilon4 homozygotes had significantly reduced glucose metabolism in the same brain regions as patients with Alzheimer's dementia; the largest reduction was in the posterior cingulate cortex. As described here, magnetic resonance imaging (MRI) was used to compare hippocampal volumes in the same subject groups. The epsilon4 homozygotes showed nonsignificant trends for smaller left and right hippocampal volumes; overall, smaller hippocampal volumes were associated with reduced performance on a long-term memory test. Whereas PET measurements of cerebral glucose metabolism begin to decrease before the onset of memory decline, MRI measurements of hippocampal volume begin to decrease in conjunction with memory decline in cognitively normal persons at risk for Alzheimer's disease.

Aged↗

PubMed1998

Spatial but not object memory impairments in children with fetal alcohol syndrome.

Behavioral dissociations on tests of cognitive abilities are powerful tools that can help define the neuropsychology of developmentally disabling conditions. Animals gestationally exposed to alcohol demonstrate spatial (place) but not object (cue) memory impairments. Whether children with fetal alcohol syndrome demonstrate a similar dissociation has received little attention. In this experiment, 30 Native American children, 15 previously identified with fetal alcohol syndrome and 15 control children, were asked to recall places and objects in a task previously shown to be sensitive to memory skills in individuals with and without mental retardation. As in animal models, children with fetal alcohol syndrome demonstrated a spatial but not an object memory impairment. A possible role for the hippocampus was discussed.

Arizona↗

PubMed1997

Effects of size and orientation change on hippocampal activation during episodic recognition: a PET study.

To determine whether physical match between studied and tested items influences blood flow increases in the hippocampal formation associated with recognition memory, positron emission tomography (PET) was used to measure changes in regional cerebral blood flow while healthy volunteers made old/new judgements about line drawings of objects. Some objects were tested in the same size and orientation as they had appeared earlier during the study phase of the experiment; other objects were tested in a different size or orientation than when they were studied. Blood flow increases in the vicinity of the hippocampal formation were observed in the same object condition compared with the size change and the orientation change conditions, even though recognition accuracy was affected significantly only by orientation change. Results add to previous findings suggesting that physical similarity between studied items and test cues may contribute to hippocampal activation during episodic retrieval.

Adult↗

PubMed1997

Hippocampal glycogen metabolism, EEG, and behavior.

Glycogen phosphorylase a (GPa) is correlated with metabolic activation, suggesting its potential use as a marker for neuronal activity. In dentate gyrus, GPa patches are induced by glutamate infusion. Hippocampal electroencephalogram (EEG) and neuronal firing rates are modulated by behavioral state, and cell discharge is suppressed by restraint. In rats, under conditions of free exploration, passive movement under loose or secure restraint, quiet wakefulness, and anesthesia, GPa activity and 6-10-Hz theta power were inversely related: The more active the animal, the stronger the theta rhythm and the lower the GPa activity. Thus, GPa was least under conditions in which the hippocampus processes external information, and at intermediate levels during restraint, when neuronal firing is lowest. This dissociation raises doubts about the use of metabolic activity as an indicator of changes in neuronal activity or of information processing per se.

Animals↗

PubMed1996

Spatial locations gone awry: object and spatial memory deficits in children with fetal alcohol syndrome.

Hippocampus vulnerability following gestational alcohol exposure has been demonstrated neuroanatomically and behaviorally in animal models of fetal alcohol syndrome (FAS). There has been no similar demonstrations in humans. The Smith and Milner (1981) Memory for 16 Objects task has been used to explore the effects of right vs left temporal lobectomy with varying degrees of damage to the hippocampus. In the present experiment, this same task was administered to 15 children with FAS (mean age 10.03, S.D. = 2.33) and 15 control children (mean age 10.02, S.D. = 2.31). Similar to patients with right temporal lobectomies and a large excision to the hippocampus, children with FAS were able to perform immediate but not delayed object recall, had a general spatial memory deficit (P < 0.05), and significantly distorted the spatial array (P < 0.05). Although these results are consistent with an interpretation of hippocampal dysfunction, gestational alcohol exposure is known to result in a wide-ranging spectrum of neuropsychological deficits that vary in both extent and severity. Visuospatial deficits on the Beery test of Visuomotor Integration and Clock Drawing are suggestive of the other neural regions that may be involved in producing the behavioral deficits in children with FAS.

Adolescent↗

PubMed1995

Brain regions associated with retrieval of structurally coherent visual information.

An object's global, three-dimensional structure may be represented by a specialized brain system involving regions of inferior temporal cortex. This system's role in object representation can be understood by experiments in which people study drawings of novel objects with possible or impossible three-dimensional structures, and later make either possible/impossible object decisions or old/new recognition decisions about briefly flashed studied and non-studied objects. Although object decisions about possible objects are facilitated by prior study, there is no corresponding facilitation for impossible objects, thereby implicating a system that is specifically involved in the representation of structurally coherent visual objects. Here we show, by positron emission tomography (PET), that increases in blood flow in inferior temporal regions are associated with object decisions about possible but not impossible objects, and that there are increases in the vicinity of the hippocampal formation associated with episodic recognition of possible objects.

Brain Mapping↗

PubMed1993

Hemisphere and gender differences in mental rotation.

Hemisphere and gender differences in mental rotation for tachistoscopically presented stimuli were assessed in 40 right-handed university students. Twenty male and 20 female subjects each were individually administered (via computer) a mental rotation task which included 10 stimulus presentations at each of eight angular disorientations (0 degrees, 45 degrees, 90 degrees, 135 degrees, 180 degrees, 225 degrees, 270 degrees, and 315 degrees) in each visual half-field (VHF) for a total of 160 trials. Analyses of variance performed on reaction time and accuracy data revealed only a main effect for orientation. A typical mental rotation function for both the left VHF and the right VHF for both genders resulted; however, no gender x visual field interaction was found. Lack of hemisphere and gender differences provide further evidence questioning the interpretation of right-hemisphere male superiority for spatial tasks. Investigation into factors such as task complexity, stimulus familiarity, and task demands may lend further insight into hemisphere and gender differences in mental rotation.

Adolescent↗

PubMed1993

The influence of attention on the dichotic REA with normal and learning disabled children.

Recently, Mondor and Bryden (Neuropsychologia, 29, 1179-1190, 1991; Percept. Psychophys. 52, 393-402, 1992) developed a lateralized cueing technique which appears to be a more powerful method than is the forced-attention technique (Bryden, 1978) of controlling the contribution of attentional biases to auditory perceptual asymmetries. This lateralized cueing technique was used to determine the influence of attentional biases on perceptual asymmetries obtained for normal and specific learning disabled (LD) children. Subjects were instructed to attend to, and report from, only the ear in which the cue sounded. The interval between the onset of the cue and the onset of the dichotic trial is varied so as to control the amount of time available to subjects to allocate attention to the cued ear. Results indicated that, for normal children capable of performing the task at a better than chance level, a large REA apparent at 150 msec Stimulus Onset Asynchromy (SOA) was attenuated at longer cueing intervals (450 and 750 msec SOA). For LD children, the magnitude of the initial REA appeared to be attenuated at 450 msec SOA. Thus, these data demonstrate that for normal children as well as for children with specific learning disabilities, attentional factors may contribute to the magnitude of the REA.

Attention↗