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Biomedical subjects

J M Hoffman

Publications and source records attributed to J M Hoffman.

At least 19 recordsLinked to original sources
PubMed1998

Brain blood flow alterations induced by therapeutic vagus nerve stimulation in partial epilepsy: I. Acute effects at high and low levels of stimulation.

PURPOSE: Left cervical vagus nerve stimulation (VNS) decreases complex partial seizures (CPS) by unknown mechanisms of action. We hypothesized that therapeutic VNS alters synaptic activities at vagal afferent terminations and in sites that receive polysynaptic projections from these medullary nuclei. METHODS: Ten patients with partial epilepsy underwent positron emission tomographic (PET) measurements of cerebral blood flow (BF) three times before and three times during VNS. Parameters for VNS were at high levels for 5 patients and at low levels for 5. Resting BF measurements were subtracted from measurements during VNS in each subject. Subtraction data were averaged in each of 2 groups of 5 patients. t Tests were applied to BF changes in brain regions that receive vagal afferents and projections (significant at p < 0.05, corrected for repeated measures). RESULTS: In both the low- and high-stimulation groups during VNS, brain BF was (a) increased in the rostral, dorsal-central medulla; (b) increased in the right postcentral gyrus, (c) increased bilaterally in the hypothalami, thalami, and insular cortices, and in cerebellar hemispheres inferiorly; and (d) decreased bilaterally in hippocampus, amygdala, and posterior cingulate gyri. The high-stimulation group had greater volumes of activation and deactivation sites. CONCLUSIONS: Our findings suggest that left cervical VNS acutely increases synaptic activity in structures directly innervated by central vagal structures and areas that process left-sided somatosensory information, but VNS also acutely alters synaptic activity in multiple limbic system structures bilaterally. These findings may reflect sites of therapeutic actions of VNS.

Adult↗
PubMed1997

Feeling with the mind's eye.

Mental imagery is thought to play a key role in certain aspects of visual perception and to depend on neural activity in visual cortex. We asked whether tactile discrimination of grating orientation, which appears to involve visual mental imagery, recruits visual cortical areas. H215O positron emission tomography was performed in humans during presentation of gratings to the right index fingerpad. Selective attention to grating orientation significantly increased regional cerebral blood flow, relative to a control task involving selective attention to grating dimensions, in a region located in left parieto-occipital cortex. We propose that this activation reflects the use of imagery-related visuo-spatial processes to enable the tactile discrimination of orientation.

Adult↗
PubMed1997

Sex differences in the relationship of body fat distribution with psychosocial variables.

OBJECTIVE: This study tested the hypothesis that the relationship of psychosocial variables to body fat distribution would differ in men and women and would vary according to gender differences in natural patterns of fat distribution. METHOD: Body fat distribution and psychological functioning were examined in 5,930 male and 7,598 female dieters. RESULTS: Upper body size and shape were more strongly related to psychological functioning in men and lower body size and shape were more important in women. DISCUSSION: To better understand the association of weight with psychosocial status, patterns of body fat distribution should be considered.

Adipose Tissue↗
PubMed1997

Pulmonary abnormalities and PET data analysis: a retrospective study.

PURPOSE: To assess methods of standard uptake ratio (SUR) calculation with 2-deoxy-2-[fluorine-18]fluoro-D-glucose (FDG) positron emission tomography (PET) in indeterminate focal pulmonary abnormalities. MATERIALS AND METHODS: One hundred ninety-seven adult patients with indeterminate pulmonary abnormalities had complete FDG PET data, consistent methods of data acquisition, and definitive diagnosis with tissue biopsy or negative 2-year follow-up findings. PET studies were evaluated by using SURs calculated with the average or maximum region-of-interest pixel value in the numerator and with weight, lean body mass, or body surface area in the denominator. RESULTS: One hundred twenty malignant lesions and 77 benign processes were identified. Receiver operating characteristic (ROC) curve areas were statistically significantly larger with the average rather than the maximum pixel value in the calculation of the SUR for any of the three denominators (P < or = .05). SURs calculated with weight versus lean body mass versus body surface area in the denominator showed no statistically significant difference in ROC curve areas. CONCLUSION: SURs determined by using average pixel values provide statistically significant improvement in ROC curve areas over those determined by using maximum pixel values. Weight, lean body mass, and body surface area in the denominator of the SUR calculation provide equivalent ROC curve areas and are therefore equivalent in accuracy in this population.

Adult↗
PubMed1997

Fluorine-18-FPCT: a PET radiotracer for imaging dopamine transporters.

UNLABELLED: Fluorine-18-labeled 2 beta-carbomethoxy-3 beta-(4-chlorophenyl)-8-[-3-fluoropropyl) nortropane (FPCT) has been synthesized as a new dopamine transporter imaging agent. METHODS: Fluorine-18 was introduced into 2 beta-carbomethoxy-3 beta-(4-chlorophenyl)-8-[-3-fluoropropyl) nortropane by preparation of 1-[18F]fluoro-3-iodopropane followed by alkylation of 2 beta-carbomethoxy-3 beta-(4-chlorophenyl)nortropane. RESULTS: Tissue distribution studies in rats with [18F]FPCT showed high striatal uptake (0.70% dose/g at 60 min; 0.38% dose/g at 120 min) and good striatal-to-cerebellum ratios (5.5 at 60 min; 6.2 at 120 min). Imaging studies in rhesus monkeys (n = 2) with [18F]FPCT showed high uptake and retention in the putamen (P) (P = 0.03%-0.12% dose/g; at 115 min) and good putamen-to-cerebellum ratios of 3.40-3.43 at 115 min. Plasma metabolites were analyzed in rhesus monkeys (n = 2) by ether extraction and HPLC. The radioactivity in the ether-extractable fraction displayed a single peak that corresponded on HPLC to unmetabolized authentic FPCT. CONCLUSION: These results suggest that [18F]FPCT is an excellent candidate for PET imaging of dopamine transporters.

Animals↗
PubMed1996

Role of posterior parietal cortex in the recalibration of visually guided reaching.

Visually guided reaching requires complex neural transformations to link visual and proprioceptive inputs with appropriate motor outputs. Despite the complexity of these transformations, hand-eye coordination in humans is remarkably flexible, as demonstrated by the ease with which reaching can be adapted to distortions in visual feedback. If subjects attempt to reach to visual targets while wearing displacing prisms, they initially misreach in the direction of visual displacement. Given feedback about their reaching errors, however, they quickly adapt to the visual distortion. This is shown by the gradual resumption of accurate reaching while the prisms remain in place, and by the immediate onset of reaching errors in the opposite direction after the prisms have been removed. Despite an abundance of psychophysical data on adaptation to prisms, the functional localization of this form of sensorimotor adaptation is uncertain. Here we use positron emission tomography (PET) to localize changes in regional cerebral blood flow (rCBF) in subjects who performed a prism-adaptation task as well as a task that controlled for the sensory, motor and cognitive conditions of the adaptation experiment. Difference images that reflected the net effects of the adaptation process showed selective activation of posterior parietal cortex contralateral to the reaching limb.

Adaptation, Physiological↗
PubMed1996

Adult age differences in regional cerebral blood flow during visual world identification: evidence from H215O PET.

We used H215O PET to investigate adult age differences in regional cerebral blood flow (rCBF) during the performance of a visual word identification task. The study participants were 20 healthy, right-handed men: 10 young adults between 18 and 27 years of age, and 10 older adults between 63 and 75 years of age. The word identification task comprised six blocks of test trials representing four task conditions; subjects responded manually. The task conditions varied with regard to whether semantic retrieval was required (e.g., word/nonword discrimination vs simple response to each stimulus) and with regard to the difficulty of visual encoding (e.g., words presented normally vs words with asterisks inserted between adjacent letters). Each subject performed all six trial blocks, concurrently with each of six H215O PET scans. Analyses of quantitative CBF data obtained from the arterial time-activity curve demonstrated a significant age-related decline in global CBF rate. Analyses of the changes in rCBF between task conditions indicated that retrieval of semantic information sufficient to distinguish words from nonwords is mediated by a ventral occipitotemporal cortical pathway. Specific areas within this pathway were also associated with visual encoding processes. Several rCBF activations were significantly greater for young adults than for older adults, indicating an age-related decline in processing efficiency within this ventral occipitotemporal pathway. Although the performance data demonstrated a greater age-related slowing for visual encoding than for semantic retrieval, these age-related performance changes were not associated with corresponding changes in rCBF activation.

Adolescent↗
PubMed1996

Positron emission tomography in the pretreatment evaluation and follow-up of non-small cell lung cancer patients treated with radiotherapy: preliminary findings.

The purpose of this study was to prospectively evaluate positron emission tomography (PET) for delineating lung cancers preradiotherapy and to assess PET's ability to distinguish residual tumor from scarring following radiotherapy. Between April 1991 and October 1992, 20 patients underwent 18fluoro-2-deoxyglucose (18FDG) PET scanning of the chest prior to radiotherapy for lung cancer. Tumor volumes on chest x-ray (CXR) and computerized tomography (CT) scan were correlated with abnormalities on PET scans. Follow-up PET studies were compared to postradiotherapy chest x-ray and/or CT scans, and correlated with clinical outcome. Six of seven well-demarcated tumors showed increased uptake of 18FDG correlating with the CT/CXR tumor volume. Twelve poorly demarcated tumors demonstrated increased 18FDG uptake. In seven of 12, the CT/CXR abnormality correlated with changes on PET scan. In three of 12, CT/CXR abnormalities were larger than on PET, whereas in two of 12, abnormalities on PET extended outside the region of CT/CXR changes. The 13th patient in the poorly demarcated category had diffuse carcinoma in situ at the surgical margin that demonstrates increased 18FDG uptake, but was not visible by CT/CXR. Of 12 patients with follow-up studies, all had changes on CXR and/or CT that made it difficult to assess response. Four of 12 had a complete response by PET; all remain locally controlled. The remaining eight patients had either a partial response (n = 6) or no response (n = 2) by PET. Four of these eight patients remain alive and well 11-24 months after therapy. 18FDG PET may be useful for delineation of lung cancer volumes that are poorly defined by CXR and/or CT scan. The value of PET in differentiating tumor from fibrosis after radiotherapy for lung cancer remains to be established.

Carcinoma in Situ↗
PubMed1996

Interpretation variability of 18FDG-positron emission tomography studies in dementia.

RATIONALE AND OBJECTIVES: Functional imaging studies such as 18F-fluoro-18-labeled-deoxyglucose-positron emission tomography (18FDG-PET) are being used increasingly in the evaluation of patients with dementia. The authors evaluate inter- and intraobserver interpretation agreement in a diverse group of patients with clinically diagnosed dementia and subjective memory complaints, as well as two healthy control subjects. METHODS: Ninety-six patients with clinical diagnoses of probable Alzheimer's disease (n = 18), possible Alzheimer's disease (n = 33), dementia (n = 26), and mild memory impairment (n = 17), as well as two healthy control subjects were studied using 18FDG-PET. Three observers graded all studies for regional 18FDG uptake in the temporal, parietal, and frontal regions bilaterally. The studies also were interpreted for the presence of bilateral temporoparietal hypometabolism, which typically is present in Alzheimer's disease. The kappa statistic was used to determine intra- and interobserver agreement for regional 18FDG uptake and bilateral temporoparietal hypometabolism. RESULTS: There was excellent intraobserver (kappa = .56, P < 0.0005) and interobserver (kappa = .51, P < 0.0005) interpretation agreement for bilateral temporoparietal hypometabolism. There also was excellent intraobserver (kappa = .61, P < 0.000) and interobserver (kappa = .55, P < 0.000) interpretation agreement of regional 18FDG uptake. Interobserver agreement was extremely high in those patients who were considered clinically to have possible (kappa = .42, P < 0.001) or probable (kappa = .42, P < 0.01) Alzheimer's disease. CONCLUSIONS: Results confirm that bilateral temporoparietal hypometabolism is the metabolic abnormality associated with the diagnosis of probable Alzheimer's disease. Furthermore, intra- and interobserver agreement of visual interpretation of 18FDG-PET images indicates that 18FDG-PET is acceptable as an imaging technique in the clinical evaluation of the dementia patient.

Adult↗
PubMed1996

PGY1.

Explore the source record for details and available documents.

Curriculum↗
PubMed1995

Differential recovery of volitional motor function, lateralized cognitive function, dopamine agonist-induced rotation and dopaminergic parameters in monkeys made hemi-parkinsonian by intracarotid MPTP infusion.

There is still controversy regarding the frequency and extent of spontaneous functional recovery in primate models of parkinsonism, perhaps in part stemming from the variety of ways in which recovery has been assessed. The present study examined functional recovery in monkeys made unilaterally parkinsonian by intracarotid infusion of MPTP. Monkeys were evaluated prior to lesioning and for at least 1 year after lesioning on a battery of tests including a rating of spontaneous behaviors, a learned reaction time/movement time task, tests of lateralized neglect or inattention (i.e. lateralized reward retrieval task, extinction with double simultaneous stimulation, and response to a target moving from one hemispace to the other), and rotational asymmetry in response to a dopamine agonist. Some animals also received 6-[18F]Fluoro-L-Dopa (F-DOPA) position emission tomography (PET) scans before MPTP, when symptomatic, and when showing signs of functional recovery. These animals were sacrificed for post mortem neurochemical assessment following the last PET scan. Results showed that estimates of functional recovery in hemi-parkinsonian monkeys may depend upon the behavioral assay used. Even in behavioral tasks that were sensitive to recovery effects, the degree of functional recovery shown by an animal on one such task did not predict recovery on another. This may in part be due to the inherent difficulty in designing behavioral tests to assess basal ganglia functioning, when there is no consensus concerning which aspects of behavior the normal basal ganglia actually control.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1995

Taste sensitivity and aging: high incidence of decline revealed by repeated threshold measures.

Contrary to what has often been said about the subject, decline in taste sensitivity with aging characterizes virtually everybody and is not the artificial result of averaging large losses of a minority with negligible losses of a majority. This assertion is supported by six repeated measures of sucrose thresholds in each of 15 older (over 64 years) and 15 younger (under 27 years) adult subjects. Threshold was determined by a procedure similar to past studies and with the same results: much scatter and considerable overlap between the thresholds of younger and older subjects. A quite contrasting picture emerges, however, when each subject's six threshold determinations are averaged. Averaging shrinks the individual differences among subjects, as well as the over-lap between younger and older subjects. Although virtually all elderly subjects now revealed taste weakness, reliable individual differences in degree of weakness abound among them, suggesting various individual rates of physiological aging. In contrast, young persons exhibit greater uniformity of sensitivity. These findings were brought out by inter-test correlations, which were much higher for the older subjects; i.e. an older subject who tended to score high (low) on one test tended to score high (low) on the other tests. The study confirms the tenuous nature of brief threshold tests as indices of personal sensitivity as found earlier also in olfactory thresholds and in concurrent measurement of two-point touch thresholds in the present study. This revealed correlated losses between repeated taste and touch thresholds from the same 15 older subjects, unrelated to their exact chronological age.

Adult↗
PubMed1995

18-Fluorodeoxyglucose positron emission tomography in children and adolescents with traumatic brain injury.

Twenty-two previously normal children and adolescents who suffered a severe, non-penetrating traumatic brain injury had PET during rehabilitation at a median of 1.5 months after the injury. Outcome was assessed at a median of 25 months after brain injury. 16 subjects had CT or MRI within 24 days of PET and 11 subjects had a second PET at the point of outcome (median 28 months after first PET). The PET score (obtained by adding the score of 15 brain regions: normal metabolism = 1; reduced = 0) was significantly associated with the clinical outcome measure. PET earlier than 12 weeks after head trauma correlated with outcome, but later PET did not. PET scores improved significantly between rehabilitation and outcome for the 11 subjects who had two PETs, but improvement was not associated with improvement in clinical condition. PET score did not add to the amount of variance explained in the last regression model for prediction of outcome when the results of contemporaneous CT/MRI and clinical condition were taken into account. The data suggest that routine PET during rehabilitation is no more useful than contemporaneous CT or MRI for prediction of outcome.

Brain Injuries↗
PubMed1995

Optimum scanning protocol for FDG-PET evaluation of pulmonary malignancy.

UNLABELLED: FDG-PET can differentiate benign from malignant focal pulmonary opacities. We performed dynamic FDG-PET studies to determine the optimum time for emission data acquisition. METHODS: Patients with focal pulmonary abnormalities demonstrated by biopsy to be malignant (n = 10) or benign (n = 4) were evaluated with dynamic FDG-PET. Dynamic PET data were acquired as sequential 5-min images for 2.5 hr. Radioactivity concentration measurements of the focal abnormality, a similar area in the opposite lung, and both lungs in the field of view were made throughout the period of acquisition. Standardized uptake ratios (SUR) of the lesions were calculated. SUR data and lesion-to-background ratios were plotted. The time that the SUR provided the maximum separation between benign and malignant masses after FDG administration was determined. RESULTS: The SUR values provided the greatest separation between benign and malignant abnormalities beginning at 50 min and no advantage was identified in imaging later. Achievement of a 4:1 lesion-to-background ratio occurred by 50 min in malignant lesions. CONCLUSION: The acquisition of the emission data used in the evaluation of pulmonary malignancy should begin approximately 50 min after FDG administration.

Deoxyglucose↗
PubMed1994

Neuronal migration disorders: positron emission tomography correlations.

We analyzed the interictal [18F]fluoro-2-deoxy-D-glucose positron emission tomography (PET) findings of 17 epileptic patients with neuronal migration disorders (NMDs). Fifteen patients had abnormal PET findings, i.e., focal hypometabolism in 9 patients and displaced metabolic activity of normal gray matter in 6. All 15 patients had magnetic resonance imaging (MRI) abnormalities; however, PET abnormality assisted in the identification of NMDs on MRI in 3 patients. Two patients with negative MRI also had negative PET studies. PET hypometabolism appeared to correlate with severity of neuronal dysgenesis or temporal lobe involvement, or both. Displaced metabolic activity of gray matter is regarded as a unique interictal [18F]fluoro-2-deoxy-D-glucose-PET finding in NMD. This study demonstrates variable metabolic patterns in NMD and that PET may be a useful complement to MRI in the evaluation of NMD.

Adult↗