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J Kessler

Publications and source records attributed to J Kessler.

At least 19 recordsLinked to original sources
PubMed1992

Severity of vascular dementia is related to volume of metabolically impaired tissue.

The relation between dementia severity and regional cerebral metabolic rate of glucose was studied in 28 patients with vascular dementia (VD) in comparison with 20 age-matched patients who were suffering from Alzheimer's disease (AD) and 24 normal subjects by using positron emission tomography with fludeoxyglucose F 18. Similar metabolic impairment was found in the temporoparietal and frontal association cortex in patients with VD and in those with AD. Metabolism of the basal ganglia, thalamus, and cerebellum was reduced significantly in patients with VD only. The total volume of regions with metabolism below the 95% confidence interval of control values was significantly related to the severity of dementia but did not differ between patients with VD and those with AD. A metabolic ratio of regional cerebral glucose metabolism of association areas divided by regional cerebral glucose metabolism of structures that were typically not affected by AD was significantly lower in patients with AD than in those with VD. This ratio was also related to dementia severity in both types of dementia.

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PubMed1992

Subcortical damage and cortical dysfunction in progressive supranuclear palsy demonstrated by positron emission tomography.

Regional cerebral glucose metabolism was studied in nine patients with progressive supranuclear palsy (PSP). (18F)-2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) revealed general cerebral hypometabolism in all PSP patients in comparison with an age-matched reference group. When comparing the degree of regional metabolic deterioration, a consistent pattern of the most affected brain regions became obvious: the strongest significant alteration of cerebral glucose metabolism was observed in subcortical regions, e.g. in caudate nucleus, lentiform nucleus and upper mid-brain, which showed nerve cell loss in previous pathological studies. Less severe, but still significant hypometabolism was observed in frontal cortex. This pattern of hypometabolism was distinctly different from that typically seen in dementias of Alzheimer's type. The present data show that PET findings agree with histopathological studies: PSP is a primarily subcortical disease with secondary inactivation of cortical, especially of frontal brain regions.

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PubMed1992

Quantitative EEG mapping and PET in Alzheimer's disease.

Quantitative analysis of topographical EEG was studied in comparison with measurement of regional glucose metabolism by PET in 42 patients with clinical diagnosis of probable dementia of Alzheimer type (AD) and in 15 age-matched normal controls. Measures analyzed included global and regional data from areas typically affected and not affected by AD pathology. While disturbance of metabolism followed a typical regional pattern, relative alpha, theta and delta power were more globally altered without selectivity for specific regions. Separation between AD and age matched controls by relative theta power was correct in 86% and was close to that by temporo-parietal glucose metabolism (correct classification 87%). Relative theta power as well as temporo-parietal glucose metabolism were significantly correlated (tau B = 0.54 and -0.53, respectively) to severity of AD assessed by the global deterioration scale. These results indicate that EEG measures may be used with an accuracy close to metabolic values from PET for the assessment of severity of AD.

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PubMed1992

PET correlates of normal and impaired memory functions.

To date, positron emission tomography (PET) has been the only technology for the quantitative imaging of the changes of regional cerebral glucose (rCMRGl) or oxygen metabolism and blood flow (rCBF) associated with psychophysical stimulation and with the performance of mental tasks. So far, the majority of studies performed in healthy subjects demonstrated activation patterns involving not only certain limbic structures, most of all hippocampus, amygdala, parahippocampus, and cingulate, but also temporal, parietal, and occipital association cortex, depending on the applied paradigm. Indeed, the closest correlation between regional metabolism and memory test scores was found in mesiotemporal structures during the performance of memory tasks. Metabolic or CBF studies also seem to indicate that memorizing strategies may differ among individuals. PET was repeatedly used to investigate metabolic and/or blood flow abnormalities in patients with various amnestic syndromes. In cases with uni- or bilateral lesions of mesiotemporal structures, caused by surgery, herpes simplex encephalitis, or permanent ischemic, anoxic, or toxic damage, disturbances of metabolism and blood flow typically extended far beyond the morphological defects detected by computed tomography or magnetic resonance. In acute transient global amnesia, CBF and metabolism were decreased bilaterally in the mesiotemporal lobes, where hypometabolism persisted for some time, while higher values were observed in thalamus and some cortical areas. Diencephalic lesions causing Korsakoff's syndrome were associated with decreased rCMRGl in the hippocampal formation, upper brainstem, cingulate, and thalamus. Discrete thalamic infarcts caused amnesia and metabolic depression in the morphologically intact ipsilateral thalamus and in various projection areas of the infarcted nuclei. In ischemic forebrain lesions, amnestic deficits could be related to involvement of the anterior cingulate and of basal cholinergic nuclei. A large number of pathologies are diffusely spread out in the brain and affect partially or predominantly structures in memory processing. This holds true especially in the various dementias where memory disturbances are a consistent and often leading feature. Notably, Alzheimer's disease can be distinguished from other dementias by its characteristic pattern of metabolic dysfunction, with the most prominent changes occurring in parietotemporal and frontal association cortex whose residual metabolism is related to the severity of the disease. Therefore, activation studies using paradigms involving memory functions enhance that typical pattern. Only in the activated state is metabolism of mesiotemporal structures significantly correlated with the performance in memory tests. Other dementias also affect some of the distributed memory networks, with Huntington's disease suggesting a role of the striatum in memory processing.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Cultured astrocytes release proenkephalin.

Astrocytes as well as neurons express the mRNA encoding the opioid peptide precursor, proenkephalin. In neurons proenkephalin is cleaved intracellularly to yield smaller, bioactive peptides such as Met-enkephalin and Leu-enkephalin. By contrast, utilizing a combination of radioimmunoassay and chromatographic analysis, we report here that astrocytes cultured from neonatal rat brain contain primarily unprocessed proenkephalin and only small amounts of Met-enkephalin. Further, similar experiments with and without the inclusion of several peptidase inhibitors indicate that cultured astrocytes release proenkephalin itself into the medium where it may be subsequently cleaved to smaller peptide products. The release of intact proenkephalin by astrocytes suggests that the glial propeptide subserves a different function than neuronal proenkephalin and that opioid peptides may play novel roles in the central nervous system.

Animals↗
PubMed1991

Positron emission tomography in the differential diagnosis of organic dementias.

At present, PET is the only technology affording the quantitative, three-dimensional imaging of various aspects of brain function. Since function and metabolism are coupled, and since glucose is the dominant substrate of the brain's energy metabolism, studies of glucose metabolism by PET of 2(18F)-fluoro-2-deoxy-D-glucose (FDG) are widely applied for investigating the participation of various brain systems in simple or complex stimulations and tasks. In focal or diffuse disorders of the brain, functional impairment of affected or inactivated brain regions is a reproducible finding. While glucose metabolism is decreased slightly with age in a regionally different degree, in most types of dementia severe changes of glucose metabolism are observed. Degenerative dementia of the Alzheimer type is characterized by a metabolic disturbance most prominent in the parieto-occipito-temporal association cortex and later in the frontal lobe, while primary cortical areas, basal ganglia, thalamus, and cerebellum are not affected. By this typical pattern Alzheimer disease can be differentiated from other dementia syndromes, as e.g., Pick's disease (with the metabolic depression most prominent in the frontal and temporal lobe), multi infarct dementia (with multiple focal metabolic defects), and Huntington's chorea (with metabolic disturbance in the neostriatum). In demented patients PET studies can also be applied to the quantification of treatment effects on disturbed metabolism.

Alzheimer Disease↗
PubMed1991

Impaired metabolic activation in Alzheimer's disease: a PET study during continuous visual recognition.

Regional cerebral metabolic rate of glucose (rCMRGl) was studied in 21 patients with probable Alzheimer's disease (AD) and nine age-matched normal controls by positron emission tomography (PET) of 2(18F)-fluoro-deoxy-D-glucose (FDG) at rest and during stimulation with a continuous visual recognition task. While global metabolism at rest was comparable in both groups, rCMRGl in the temporo-parietal junction area, the mid-temporal and the frontal cortex was typically decreased in the AD patients. The continuous visual recognition task adapted to the individual performance capacity increased the global metabolic rate in the controls by 21 +/- 18%, while in the AD patients the metabolic change (5.7 +/- 11.1%) during activation was significantly weaker (P = 0.023). Due to the tasks chosen the activation of rCMRGl in both groups was most prominent in the visual cortex and the temporo-parietal association areas, although the recognition task additionally involved widespread brain structures with varying rCMRGl. A significant correlation was found between rCMRGl in areas usually severely affected by AD pathology, e.g. the temporo-parietal cortex, and GDS scores, and became stronger during metabolic activation. Neither at rest nor during stimulation was there a relationship between the rCMRGl of structures usually less involved in AD, e.g. the sensorimotor cortex, and the severity of dementia as assessed by the global deterioration scale (GDS). From these results it can be concluded that metabolic rate at rest reflects the extent of morphologic damage, while PET studies during activation indicate the brain's reserve capacity to respond to functional tasks. Since metabolism in AD patients during activation is more severely impaired than at rest, PET studies during functional tests could help in the selection of patients with a potential to benefit from therapeutic intervention.

Alzheimer Disease↗
PubMed1991

Abnormalities of energy metabolism in Alzheimer's disease studied with PET.

Positron emission tomography (PET) is currently the only technology affording three-dimensional measurement of the brain's energy metabolism which is closely coupled to brain function. Studies of glucose metabolism by PET of (18F)-2-fluoro-2-deoxy-D-glucose are therefore widely applied to show the contribution of various brain structures in the performance of a variety of tasks or their participation in functional deficits associated with various diseases. Although glucose metabolism decreases slightly with age to a regionally different degree, most types of dementia show severe changes in glucose metabolism. Alzheimer's disease (AD) is characterized by metabolic disturbances most prominent in the parietotemporal association cortex and later in the frontal lobe, whereas primary cortical areas, basal ganglia, thalamus, brainstem, and cerebellum are not affected. It is this typical pattern that distinguishes AD from other dementia syndromes. A ratio calculated from the metabolic rates of glucose of "affected" and "nonaffected" brain regions was able to separate patients with AD from age-matched controls and permitted the discrimination of patients with cognitive impairment of other origin in 85%. The discriminative power can be further improved by activation studies. A continuous visual recognition task increased the metabolic rate in normal subjects by 21% and in patients with AD by 6% on average, with significant regional differences. During activation the significant relation between severity of disease and temporoparietal metabolic rate became even stronger. In the assessment of effects of treatment on disturbed metabolism, PET studies demonstrated an equalization of metabolic heterogeneities in patients responding to a muscarinergic cholinagonist, whereas general increases in glucose utilization were observed with piracetam, pyritinol, and phosphatidyl-serine. The therapeutic relevance of such metabolic effects, however, must be proved in controlled clinical trials.

Adult↗
PubMed1991

Complex sensory cross integration deficits in a case of corpus callosum agenesis with bilateral language representation: positron-emission-tomography and neuropsychological findings.

A 45-year-old right-handed patient with total callosal agenesis and absence of the anterior commissure was examined neuropsychologically and with magnetic resonance and positron emission tomography (PET with 18FDG) of the brain. PET results showed, in the resting state, a bilateral metabolic reduction in the hippocampal formation and a left hemispheric reduction in the amygdala, thalamus and in the occipital and temporoparietal junction areas of the cerebral cortex. Under speech activation hypermetabolic glucose activity was observed bilaterally in the region of the Wernicke area and within the left Broca area. Neuropsychologically, on the whole the patient behaved normally, the exceptions being an inability to associate olfactory stimuli with words, a clear left ear advantage in dichotic listening, and a similar high performance in recognizing verbal stimuli presented tachistoscopically to either hemisphere. From comparing the patient's behavior with that of other acallosals it appears that highly individual variants of cerebral organization and/or reorganization result from the lack of the brain's main commissural system and that the processing of sensory information deviates considerably especially in cases in whom the two main telencephalic commissures--corpus callosum and anterior commissure--are absent.

Brain↗
PubMed1990

Positron emission tomography findings relevant to neurosurgery for epilepsy.

Using the 2-[F-18]fluorodeoxyglucose method, 213 positron emission tomographic (PET) studies of local brain glucose metabolism (CMRglu) were performed in 124 patients with various forms of epilepsy. Interictal PET scans of primary epileptics typically showed some global metabolic depression and decreased functional activity of insular, basal and anterior temporal cortex. Epilepsia partialis continua Kozevnikov was characterized by hypo- or hyper-metabolism of perirolandic cortex. Tuberous sclerosis was distinguished by neocortical foci of significantly decreased glucose consumption. Even in the interictal resting state, with regard to sensitivity (greater than 90%) and accuracy of focus localization. PET was superior to other diagnostic methods in typical temporal lobe epilepsy. Averaging 23% below normal CMRglu, the majority of hypometabolic foci were found in mesial temporal structures. Improved distinction between the epileptogenic area and the surrounding tissue showing comparatively normal functional responsiveness, was achieved by psychophysical activation using emotional speech or continuous visual recognition during PET scanning. In patients who had undergone total cerebral hemispherectomy because of uncontrolled epilepsy, remarkable recruitment of association areas was observed on both motor and speech activation.

Blood Glucose↗
PubMed1990

Antibody-mediated in vitro neutralization of human immunodeficiency virus type 1 abolishes infectivity for chimpanzees.

This study was undertaken to establish whether antibody directed against the human immunodeficiency virus type 1 (HIV-1) principal gp120 type-specific neutralization determinant can abolish the infectivity of HIV-1 in chimpanzees. Challenge inocula of the IIIb virus isolate were mixed in vitro with either immunoglobulin G (IgG) from an uninfected chimpanzee, nonneutralizing IgG from an HIV-seropositive human, a virus-neutralizing murine monoclonal antibody directed against the HIV-1 IIIb isolate, or virus-neutralizing IgG from a chimpanzee infected with the IIIb isolate. Both neutralizing antibodies were directed against the principal neutralization determinant of the challenge isolate. Establishment of infection following inoculation of each virus-antibody mixture into chimpanzees was assessed by virus-specific antibody development and by virus isolation. No protective effect was noted either with the control IgG or with the nonneutralizing anti-HIV IgG. By contrast, the polyclonal chimpanzee virus-neutralizing IgG prevented HIV-1 in vivo infection, while the neutralizing monoclonal antibody notably decreased the infectivity of the challenge virus. Hence, antibody to the gp120 principal neutralization determinant is able both to prevent HIV-1 infection in vitro and to inhibit infection in vivo.

Animals↗
PubMed1989

The biology of human immunodeficiency virus-1 IIIB infection in the chimpanzee: in vivo and in vitro correlations.

Human immunodeficiency virus (HIV)-1 IIIB infection of chimpanzees leads to a compartmentalized, nonpathogenic in vivo and in vitro relationship with the virus. The absence of an acquired immunodeficiency syndrome (AIDS)-like disease in over 100 chimpanzees persistently infected may be related to some or all of the findings reported here. Further characterizing these possible host adapative mechanisms may be critical in both understanding pathogenesis, as well as elucidating novel mechanisms for therapeutic and/or the preventive strategies for AIDS in humans.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Cognitive functioning of juveniles with Down syndrome and other forms of mental retardation.

The performance of juvenile Down syndrome individuals and two groups of oligophrenes was compared in several cognitive tests. All three groups of subjects were of the same CA, the Down's and one group of mentally retarded non-Down's had an average MA of 62, the other group an MA of 86 months. Though the group with the highest mental age usually outperformed the other two, significant differences were rare. It is concluded that at this age Down's and mentally retarded with different etiologies generally have rather similar cognitive abilities and that the intellectual deterioration of Down's, which at a later age inevitably leads to Alzheimer's disease, indeed starts only at a later CA.

Adolescent↗
PubMed1987

Primate learning tasks reveal strong impairments in patients with presenile or senile dementia of the Alzheimer type.

Eight subjects with the likely diagnosis of presenile or senile dementia of the Alzheimer type were tested on two frequently used primate learning tasks: a concurrent object discrimination task and a delayed non-match-to-sample task. In addition, various tests for cognitive, mnemonic, perceptual, and language functions were applied. The results suggest a severe decline of the Alzheimer subjects in all measures when compared with 10 control subjects matched for age, gender, and education. The two animal learning tasks revealed strong impairments, thus demonstrating a high sensitivity for the detection and assessment of human amnesic disorders. Implications of these findings for human neuropsychological, and especially comparative neuropsychological, research are discussed.

Aged↗
PubMed1986

Korsakoff and alcoholic subjects are severely impaired in animal tasks of associative memory.

Korsakoff subjects, members of the Alcoholics Anonymous, and alcoholics with 1 week or 5-6 months of abstinence were tested in a concurrent object discrimination task with 10 and 20 pairs of objects and compared to control subjects matched for age and education. The anonymous alcoholics were moderately Korsakoff subjects strongly impaired, whereas alcoholics with 1 week or 5-6 months abstinence performed similar to control subjects. The results are discussed with respect to current research on human amnesia and comparative neuropsychological topics.

Adult↗
PubMed1986

[Possibilities and weaknesses of psychopathometric diagnosis of dementia].

As cognitive deficiencies in aged people constitute a growing factor in our societies, the possibilities for diagnosing dementia are described and analyzed critically. Based on a discussion of those changes in intellectual performance which are typical for normal aging (e.g., reduction in so-called fluid intelligence combined with preservation of so-called crystallized intelligence), the pathological forms of aging, especially Alzheimer's disease, are outlined. The present, internationally favored psychometrical measures for recording dementia in the aged and for evaluating and diagnosing it differentially are listed. Finally, certain requirements which have to be imposed on a diagnostic test for dementia are discussed.

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