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Biomedical subjects

R Dann

Publications and source records attributed to R Dann.

18 recordsLinked to original sources
PubMed1994

Molecular cloning of a cDNA from Brassica napus L. for a homologue of acyl-CoA-binding protein.

A cDNA encoding an acyl-CoA-binding protein (ACBP) homologue has been cloned from a lambda gt11 library made from mRNA isolated from developing seeds of oilseed rape (Brassica napus L.). The derived amino acid sequence reveals a protein 92 amino acids in length which is highly conserved when compared with ACBP sequences from yeast, cow, man and fruit fly. Southern blot analysis of Brassica napus genomic DNA revealed the presence of 6 genes, 3 derived from the Brassica rapa parent and 3 from Brassica oleracea. Northern blot analysis showed that ACBP genes are expressed strongly in developing embryo, flowers and cotyledons of seedlings and to a lesser extent in leaves and roots.

Acyl Coenzyme A↗
PubMed1990

The effect of focal cerebral atrophy in positron emission tomographic studies of aging and dementia.

We used x-ray computed tomographic (XCT) scans to measure the degree of cerebral atrophy in brain regions defined by a region of interest (ROI) anatomy atlas. The same atlas was employed for quantitation of local cerebral glucose metabolic rates (LCMRglc) by PET. PET data were obtained from 9 young controls, 7 healthy elderly controls, and 10 patients with dementia. Cerebrospinal fluid (CSF) in atrophic brain regions was assumed to be metabolically inert, and LCMRglc measurements were corrected for the degree of atrophy. Significantly greater atrophy was seen for 7 of 8 regions in comparisons between demented patients and age-matched controls. This atrophy was most pronounced in superior parietal (SP) regions. Decreases in parietal LCMRglc in dementia patients and SP LCMRglc in old controls were no longer significant after correction for atrophy. These results emphasize the need to consider focal atrophy effects in regional quantitative analyses of emission tomographic data.

Aged↗
PubMed1988

Cerebral metabolism and patterned visual stimulation: a positron emission tomographic study of the human visual cortex.

We studied the impact of visual stimulation upon cerebral metabolism in normal young men using FDG-PET. Results obtained from subjects receiving patterned visual stimulation while performing an ocular fixation task were compared with results from ocular fixation alone. Visual stimulation in the macular region of either hemifield produced significant increases in metabolism of the contralateral posterior striate cortex. Visual stimulation induced highly significant asymmetries in metabolism of the prefrontal and inferior parietal cortices. Metabolic activation in extrastriate areas tended to be right-sided. These findings support the classic notion of retinotopic organization within the primary visual sensory cortex. They also indicate that the patterns of cerebral metabolism are not equivalent between the two cerebral hemispheres. This latter finding suggests that in humans the right cerebral hemisphere may be specialized for visual processing.

Adolescent↗
PubMed1988

Resolving metabolic abnormalities in a case of pure alexia.

We report resolving metabolic abnormalities corresponding to clinical improvement in a patient with pure alexia secondary to acute cerebral infarction. Local cerebral glucose metabolism (lCMRgl) was measured with positron emission tomography (PET) using 18F-fluorodeoxyglucose (18F-FDG) close to ictus and 4 1/2 months later. Serial CTs and a subsequent MRI demonstrated small, unchanging left-hemispheric lesions involving the area of the lateral geniculate body and the splenium of the corpus callosum. PET demonstrated the evolution of the metabolic abnormality resulting from intrahemispheric (lateral geniculate) and interhemispheric (splenium) disconnection in the absence of occipital lobe infarction. This case illustrates that cerebral disconnection can result in the syndrome of pure alexia. The factors accounting for focal hypometabolism in the absence of cerebral infarction are discussed.

Brain↗
PubMed1987

Cerebral glucose consumption following verbal auditory stimulation.

We studied the effect of auditory stimulation upon cerebral glucose metabolism in young normals. The stimulus consisted of a non-English discourse which was presented monaurally to 10 normal blindfolded subjects (5 left ear, 5 right); the opposite ear was plugged. Six subjects studied blindfolded and with ears plugged served as controls. Sixteen discrete homologous cortical and subcortical regions of interest were examined. Regional glucose consumption and side-to-side differences in glucose metabolism were analyzed. Monaural stimulation produced significant increases in temporal metabolism contralateral to the side of stimulation. Significant asymmetries in metabolism were found at the temporoparietal junction, inferior parietal region, insula and corpus collosum. The left frontal speech areas remained unaffected. These findings demonstrate that in man the primary auditory pathways retain a contralateral organization. Further, cerebral activation induced by non-meaningful verbal stimulation is widespread within the left temporal and parietal regions but does not impact upon the frontal speech cortices.

Adult↗
PubMed1987

Regional brain function in schizophrenia. I. A positron emission tomography study.

Local cerebral glucose metabolism was determined with 18-F-fluorodeoxyglucose using positron emission tomography in a sample of 12 unmedicated schizophrenics and 12 matched normal controls. The data were analyzed for absolute metabolic rates and region/whole-brain ratios using the cortical-subcortical, antero-posterior, and laterality dimensions. Lobar areas within cortical regions were also compared. Across groups, subcortical metabolism was higher than cortical metabolism. Patients had lower metabolism, cortically and subcortically, and a steeper subcortical to cortical gradient. Patients with higher scores on the Brief Psychiatric Rating Scale had higher absolute metabolism and higher left relative to right hemispheric metabolism than did patients with lesser severity. The results did not show "hypofrontality" in schizophrenia. These findings provide some support for cerebral dysfunction in schizophrenia and indicate the need for further examination of the cortical-subcortical dimension.

Brain↗
PubMed1987

Recovery of vision after ischemic lesions: positron emission tomography.

We used [18F]fluoro-2-deoxyglucose positron emission tomography (PET) to study serial changes in the local cerebral metabolic rate of glucose in 5 patients with ischemic lesions of the posterior afferent visual system causing homonymous visual field defects. All 5 patients had striking impairment of glucose metabolism in the striate cortex shortly after ictus. In 2 patients, visual field defects abated, and repeat PET scans showed reduced size of the metabolic lesion and improvement of striate metabolism. Three patients did not recover vision, and repeat PET scans did not show improvement. Patients who recovered vision had ischemic lesions outside the occipital lobe, while those who did not experience improvement had primary damage to the occipital lobe itself.

Aged↗
PubMed1987

Regional cerebral glucose metabolism in aphemia: a case report.

Local cerebral metabolism was determined in a patient suffering aphemia following cerebral infarction using the 18FDG-PET technique. The syndrome was characterized by profound ictal nonfluency with sparing of other language functions. Speech subsequently improved so that content and grammar were appropriate but mild dysprosody persisted. Conventional CT showed no lesion of the left hemisphere while PET revealed a discrete focus of hypometabolism on the left which partially resolved on serial studies. The metabolic lesion could be localized to the region of the inferior precentral gyrus and the adjacent subcortical space.

Aged↗
PubMed1987

Sequential computerized tomography and positron emission tomography studies in a patient with malignant glioma.

Computerized tomography (CT) and positron emission tomography (PET) using fluorine-18-deoxyglucose were performed in a patient with malignant glioma over a one-year period. Postoperatively and during radiation therapy, there was slight improvement in metabolic activity in the hemisphere ipsilateral to the tumor. After radiation therapy and during chemotherapy, there was a rapid and then gradual decline in whole brain metabolic rate by 39%. This might have been explained by radiation effect on brain. The tumor area was metabolically similar to the adjacent brain until one year after diagnosis, when an area of abnormal increased activity was noted. Even though CT scans showed minimal evidence of tumour growth, a large glioblastoma multiforme was found at autopsy at the site of the increased activity. Radiation leukoencephalopathy was also observed at autopsy. It is concluded that PET studies may offer new information regarding the metabolic effects of anti-tumor therapy, and may demonstrate regrowth of tumor prior to CT.

Brain↗
PubMed1987

Positron emission tomography in aging and dementia: effect of cerebral atrophy.

The spatial resolution of current positron emission tomography (PET) scanners does not allow a distinction between cerebrospinal fluid (CSF) containing spaces and contiguous brain tissue. Data analysis strategies which therefore purport to quantify cerebral metabolism per unit mass brain tissue are in fact measuring a value which may be artifactually reduced due to contamination by CSF. We studied cerebral glucose metabolism (CMRglc) in 17 healthy elderly individuals and 24 patients with Alzheimer's dementia using [18F]fluorodeoxyglucose and PET. All subjects underwent x-ray computed tomography (XCT) scanning at the time of their PET study. The XCT scans were analyzed volumetrically, in order to determine relative areas for ventricles, sulci, and brain tissue. Global CMRglc was calculated before and after correction for contamination by CSF (cerebral atrophy). A greater increase in global CMRglc after atrophy correction was seen in demented individuals compared with elderly controls (16.9% versus 9.0%, p less than 0.0005). Additional preliminary data suggest that volumetric analysis of proton-NMR images may prove superior to analysis of XCT data in quantifying the degree of atrophy. Appropriate corrections for atrophy should be employed if current PET scanners are to accurately measure actual brain tissue metabolism in various pathologic states.

Aged↗
PubMed1986

Positron emission tomography imaging of regional cerebral glucose metabolism.

The (F-18) fluorodeoxyglucose (FDG) technique to measure local cerebral metabolic rate for glucose (LCMRglu) is well accepted and widely used by many institutions around the world. A large number of studies has been carried out in normal volunteers and patients with a variety of CNS disorders. Several investigators have noted that no significant age-related changes in cerebral glucose use occur with normal aging. Some important and interesting findings have been revealed following sensory, motor, visual, and auditory stimulations. Functional imaging with FDG in certain neurologic disorders has dramatically improved our understanding of their underlying pathophysiologic phenomena. Some abnormalities detected on the positron emission tomography (PET) images have no corresponding changes on either x-ray computed tomograms (XCT) or magnetic resonance images (MRI). In patients with Alzheimer's disease, primary sensorimotor, visual, and cerebellar metabolic activity appears relatively preserved. In contrast, parietal, temporal, and to some degree, frontal glucose metabolism is significantly diminished even in the early stages of the disease. Patients with Huntington's disease and those at risk of developing this disorder have a typical pattern of diminished CMRglu in the caudate nuclei and putamen. In patients with stroke, PET images with FDG have demonstrated abnormal findings earlier than either XCT or MRI and with a wider topographic distribution. FDG scans have revealed interictal zones of decreased LCMRglu in approximately 70% of patients with partial epilepsy. The location of the area of hypometabolism corresponds to the site of the epileptic focus as determined by electroencephalography and microscopic examination of the resected tissue. Ictal scans during partial seizures demonstrate areas of hypermetabolism corresponding to the sites of seizure onset and spread. Several investigators have reported relative hypofrontal CMRglu in patients with schizophrenia. In our center, FDG scans from patients with schizophrenia were successfully differentiated from those obtained in normal controls. Finally, our preliminary data (using PET, XCT, and MRI) in patients with CNS disorders indicate that MRI provides excellent delineation of the structural abnormalities. It may prove to be superior to XCT in the evaluation of certain diseases such as cerebral ischemia and infarcts, head injury, tumors, and white matter lesions. Metabolic imaging with FDG provides functional information not obtainable with either MRI or NMR spectroscopy. Therefore, PET studies will play a complementary role to the anatomic imaging in the management of patients with CNS disorders.

Aging↗
PubMed1985

Cerebral blood flow with the continuous infusion of oxygen-15-labeled water.

This work describes the determination of CBF in eight normal human subjects with positron emission tomographic (PET) imaging using the continuous intravenous infusion of H2(15)O. A whole-brain CBF model is described that permits the comparison of the CBF values determined using PET with those obtained using other methods. This model includes a correction for whole-brain recovery coefficient, a correction for the underestimation of flow due to the nonlinearity of the CBF model when considering tissue that includes both gray and white matter, the use of in vitro-determined brain-blood partition coefficients for gray and white matter, and a variation of the equilibrium model that permits the arterial concentration to vary. CBF values using this method compare well with values determined previously. Regional determinations using a brain overlay atlas are presented. Radiation dosimetry for the continuous infusion of H2(15)O is also included.

Adult↗
PubMed1985

Ischemic lesions of the occipital cortex and optic radiations: positron emission tomography.

We used 18-F-fluoro-2-deoxyglucose positron emission tomography (PET) and computed tomography (CT) to study eight patients with homonymous hemianopias or quadrantanopias due to ischemic lesions of the visual pathways. Four patients with ischemic damage to all or part of the occipital lobe had decreased glucose metabolism in the affected region. Three patients with ischemic damage limited to the optic radiations had decreased glucose metabolism in the portion of striate cortex appropriate for the visual field defect. Changes in glucose metabolism frequently occurred in the undamaged ipsilateral thalamus and visual association areas.

Adult↗
PubMed1984

Contralateral cerebellar hypometabolism following cerebral insult: a positron emission tomographic study.

Positron emission tomographic studies of 16 patients with cerebral ischemia and brain tumor showed asymmetries in cerebellar metabolism not encountered in 14 normal control subjects. An asymmetry was present in 62.5% of cases. The lower metabolic rate occurred in the cerebellar hemisphere contralateral to the cerebral lesion (p less than 0.001; sign test). In all cases computed tomography showed the supratentorial lesion to be unilateral and the posterior fossa contents to be unaffected. The presence of depressed cerebellar metabolism was highly associated with involvement of the contralateral parietal lobe (p less than 0.02; phi coefficient). The presence of a cerebellar abnormality was not related to the presence of any particular sign. Serial studies showed normalization of cerebellar metabolism over time. It is likely that this effect is a result of interruption of the functional interconnections between the cerebrum and the cerebellum.

Adult↗
PubMed1981

Metabolic mapping of functional activity in human subjects with the [18F]fluorodeoxyglucose technique.

The 2-[18F]fluoro-2-deoxy-D-glucose technique was used to measure regional cerebral glucose utilization by human subjects during functional activation. Normal male volunteers subjected to one or more sensory stimuli (tactile, visual, or auditory) exhibited focal increases in glucose metabolism in response to the stimulus. Unilateral visual hemifield stimulation caused the contralateral striate cortex to become more metabolically active than the striate cortex ipsilateral to the stimulated hemifield. Similarly, stroking the fingers and hand of one arm with brush produced an increase in metabolism in the contralateral postcentral gyrus, compared with the homologous ipsilateral region. The auditory stimulus, which consisted of a monaurally presented factual story caused an increase in glucose metabolism in the auditory cortex in the hemisphere contralateral to the stimulated ear. These results demonstrate that the technique is capable of providing functional maps in vivo related to both body region and submodality of sensory information in the human brain.

Adult↗
PubMedDate not supplied

Evaluation of elastic matching system for anatomic (CT, MR) and functional (PET) cerebral images.

To evaluate the performance of our elastic matching system, we have created a digitized atlas from the brain of a normal young man, using 135 myelin-stained sections at 700 microns spacing. Software was written to enter and edit regional anatomic contours, which were stacked and aligned to create a three-dimensional atlas. We then evaluated the matching system by comparing computer generated contours with expert defined contours for several subcortical structures, based on CT scans from six neurologically normal patients. The error in positioning, as defined by the distance between the centers of gravity, averaged 4.2 mm for the computer and 1.7 mm for the worst expert's reading, with the computer drawn region frequently inscribed within that of the expert. Comparison was also made for each structure by determining the volume of overlap and the volumes not overlapping. On average, the computer's agreement with the experts was approximately 20% less than the agreement among the experts. This was a preliminary test of the system using only subcortical structures. The results are promising, and techniques are being implemented to overcome the current deficiencies.

Brain↗