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Biomedical subjects

D Luck

Publications and source records attributed to D Luck.

8 recordsLinked to original sources
PubMed2004

Trace fear conditioning: a role for context?

Fear conditioning can be rapidly obtained over long trace intervals, but its specificity with respect to both time and stimulus is uncertain. Long-trace fear conditioning often parallels contextual conditioning, and it is sensitive to hippocampal lesions. These properties of trace conditioning are not directly addressed by timing models and multiple-time-scale models of conditioning. It is proposed that during early stages of conditioning, a joint representation of the context and the stimulus trace may underlie conditioned responses, and that discriminative processes allow the emergence of specific responses in a later stage.

Acoustic Stimulation↗
PubMed1995

Single-photon emission computed tomography of the brain in acute mania and schizophrenia.

Single-photon emission computed tomography (SPECT) imaging with n-isopropyliodoamphetamine (IMP) was performed on 11 patients with bipolar mania, 21 acute schizophrenics, and 15 healthy control subjects. Subjects were evaluated with neuropsychological tests and psychiatric rating scales. SPECT brain studies were blindly evaluated to assess the degree of radiopharmaceutical uptake in three neuroanatomical regions of interest in each hemisphere. All the control subjects, 1 manic patient, and 1 schizophrenic patient had normal brain SPECT uptake patterns. The scans of all others were read as abnormal. Hypofrontality was noted in some schizophrenics and maniacs. A significant increase in tracer uptake in temporal lobes was observed in both patient groups, more prominently in the manic patients. Increased and decreased basal ganglia uptake was also observed in patients. Both manic and schizophrenic patients showed cortical tracer heterogeneity of varying degree. The patterns of cerebral SPECT uptake seen in these acute psychoses were not specific for a diagnosis, but may be associated with dimensions of psychopathology. Because the patterns are different from those seen in cerebrovascular disease and the dementias, they may prove to be helpful in differential diagnosis.

Adult↗
PubMed1994

Early single-photon emission computed tomography in mild head trauma. A controlled study.

Although computed tomography (CT) and magnetic resonance imaging scans often appear normal after mild head trauma, many patients experience attentional or other cognitive disturbances that are difficult to quantify by neuropsychological testing in the absence of a premorbid profile. Within 2 days of mild head trauma, 14 patients with normal-appearing brain CTs were studied with single-photon emission computed tomography (SPECT). They were compared to 15 normal control subjects and to 12 patients with mild human immunodeficiency virus (HIV) encephalopathy. Ten of 14 head trauma patients were separated from the normal control subjects by both independent readers, blinded to the clinical diagnosis. None of the SPECT results from normal control subjects were "read" as trauma. Trauma could not be differentiated from HIV encephalopathy. The observed percentage agreement between raters was 0.83 (kappa = 0.72). SPECT is more sensitive than CT in detecting brain injury after mild head trauma.

AIDS Dementia Complex↗
PubMed1991

The role of SPECT brain imaging in assessing psychopathology in the medically ill.

Cerebral single photon emission computed tomography (SPECT), a method of functional brain imaging, measures cerebral blood flow and metabolism. This paper describes the imaging procedure and several cases where cerebral SPECT was of use in the differential diagnosis of medically ill patients who also presented with psychopathology. SPECT patterns in cerebrovascular disease, dementia, focal epilepsy, and AIDS are at present the best described and seem to be the most specific. Often changes in regional cerebral blood flow are seen before structural changes become apparent on CT or MRI. Cerebral SPECT can add valuable diagnostic information in assessing psychopathology in the medically ill and can often lead to changes in treatment.

AIDS Dementia Complex↗
PubMed1991

Single-photon emission computed tomography in human immunodeficiency virus encephalopathy: a preliminary report.

Depression or psychosis in a previously asymptomatic individual infected with the human immunodeficiency virus (HIV) may be psychogenic, related to brain involvement by the HIV or both. Although prognosis and treatment differ depending on etiology, computed tomography (CT) and magnetic resonance imaging (MRI) are usually unrevealing in early HIV encephalopathy and therefore cannot differentiate it from psychogenic conditions. Thirty of 32 patients (94%) with HIV encephalopathy had single-photon emission computed tomography (SPECT) findings that differed from the findings in 15 patients with non-HIV psychoses and 6 controls. SPECT showed multifocal cortical and subcortical areas of hypoperfusion. In 4 cases, cognitive improvement after 6-8 weeks of zidovudine (AZT) therapy was reflected in amelioration of SPECT findings. CT remained unchanged. SPECT may be a useful technique for the evaluation of HIV encephalopathy.

AIDS Dementia Complex↗
PubMed1989

Single photon emission computed tomography (SPECT) with [123I]IMP in the differential diagnosis of psychiatric disorders.

Single photon emission computed tomography (SPECT) with [123I]N-isopropyl iodoamphetamine--[123I]IMP--was used to study regional cerebral blood flow (rCBF) in 94 psychiatric patients and six controls. Patients with dementias had distinct brain-image patterns, consistent with the expected neuropathology. Major depressives had decreased cortical and subcortical rCBF. Increased caudate rCBF was observed in schizophrenics and other psychoses with positive symptoms. SPECT is a practical method of functional brain imaging with potential in the differential diagnosis of neuropsychiatric disorders. Further studies are needed to assess the effect of other variables on brain-image patterns.

AIDS Dementia Complex↗
PubMed1977

Flagellar mutants of Chlamydomonas: studies of radial spoke-defective strains by dikaryon and revertant analysis.

The motility mutant of Chlamydomonas reinhardtii pf14 lacks radial spoke structures in its flagellar axonemes, and 12 proteins present in wild type are missing from a two-dimensional map (isoelectrofocusing/sodium dodecyl sulfate electrophoresis) of its (35)S-labeled flagellar proteins. Six of these same proteins are missing in pf1, which lacks spoke-heads. To determine whether any of the missing proteins represent the mutant gene product two experimental approaches have been applied. The first makes use of the fact that gametes of either mutant strain when fused with wild-type gametes to form quadriflagellate dikaryons undergo recovery of flagellar function. Recovery at the molecular level was monitored by prelabeling the mutant proteins with (35)S and allowing recovery to occur in the absence of protein synthesis. It is to be expected that the mutant gene product would not be restored as a radioactive protein and that recovery would depend on the assembly of the wild-type counterpart that is not labeled. The second technique makes use of revertants induced by UV irradiation. Dikaryon rescue in the case of pf14 leads to restoration of 11 radioactive components; only protein 3 fails to appear as a radioactive spot. For pf1 only two radioactive proteins are restored; proteins 4, 6, 9, and 10 were not radioactive. Analysis of revertants of pf1 gave evidence (altered map positions) that protein 4 is the mutant gene product. In the case of pf14, analysis of 22 revertants has not provided similar positive evidence that protein 3 is the gene product.

Alleles↗