Brain perfusion SPECT in patients with mild cognitive impairment and Alzheimer's disease: comparison of a semiquantitative and a visual evaluation.

Due to the increasing importance of early recognition and differential diagnosis of dementias, cerebral perfusion scans using "single photon emission computed tomography" (SPECT) are increasingly integrated into the examination routine. The goal of this study was to check the diagnostic validity of SPECT scans of MCI- and DAT-patients, two subgroups out of 369 persons with etiologically unclear cognitive dysfunction, which underwent an assessment program for probable dementia including cognitive testing, cranial computed tomography, ultrasound, routine laboratory testing including vascular risk factors. After exclusion of patients with no or other forms of dementia we analyzed SPECT data of patients with mild cognitive impairment (MCI; n = 85) and dementia of the Alzheimer type (DAT; n = 78) in comparison with a healthy control group (n = 34).Visual assessment as well as a manual "regions of interest" (ROI) regionalization of the cortex were performed, whereby a ROI/cerebellum ratio was calculated as a semi-quantitative value. Association cortex areas were assessed regarding frontal, temporal, and parietal lobes of both hemispheres. When comparing the ratios of patients with DAT and controls, we found a statistically significant reduction of the cerebral perfusion in all measured cortex areas (p < 0.001). The comparison of patients with MCI with the selected control group also established a statistically significant difference in the cerebral perfusion for the evaluated cortex areas with the exception of the left hemispheric frontal and parietal cortex.A considerable number of the MCI patients showed an MMSE-score within the normal range, but with regard to the perfusion in the right hemispheric association cortex these patients also could be distinguished unambiguously from controls. Sensitivity levels found by visual assessment were at least as high as those found by the ROI method (pathological assessment: visual 49.4% vs. ROI 47.1% for MCI; visual 75.6% vs. ROI 73.1% for DAT). High experienced visual assessment of cerebral perfusion scans using SPECT provides an useful additional tool in diagnosis of cognitive impairment. The used semiquantitative ROI-method is nearly equivalent and does not depend on the experience of the investigator.

Processing biological images from very low light emissions.

As opposed to strong light signals (> 10(8) photons mm-2 s-1), the construction of images from object sources with low level signals (< 10(2) photons mm-2 s-1) involves a probabilistic transfer- or point-spread function. The resulting images carry considerable uncertainty or spread, restricting resolution and quantification. In this paper we propose various strategies how to reconstruct object characteristics from very low light emissions by unfolding the imaging equation. Further, calibration techniques which help to associate light emissions with the decomposition of luminogenic substrates in a spatially selective way will be discussed.

Recognition and classification of structure by means of stereological methods in neurobiology.

The problem of measuring fine structure of individual particles without losing information on largescale characteristics of particle arrangement is discussed. With the help of stereological and pattern recognition methods a possible solution of this important problem is introduced. The domain specimen for which the brain serves as an example is characterized by two main properties. One of them being the position dependent 'aggregate characteristics' (distribution of neurons within the specimen), the other position invariant 'single cell characteristics' (structural properties of single neurons). It is shown that by simultaneous observation both properties together cannot be detected with sufficient accuracy by conventional methods. This is the decisive problem of 'correlation microscopy'. The method described in this paper is based on selection of the most informative variables and selection of subdomains (e.g. sections and reference planes). This results in a very general probabilistic concept in modern stereology, offering solutions to complex structure classification problems in biology.

Sex steroid-opioid interactions associated with the temporal component of avian calling patterns.

Isolation from conspecifics in young, precocial birds predictably induces distress vocalizations (DV) and androgens change this type of vocalization into male typical "crowing" (CR). In addition, opioid peptides are known to exert potent effects on avian vocal behavior. Here we investigate the organizational and activational correlates of sex-steroid actions on opioid-receptor organization and their relevance to the temporal evolution of DV and CR. From the effects of pre- and postnatal steroid applications and postnatal [3H]etorphin binding studies, we find that early steroidal effects become manifested at the behavioral level by changing the characteristic duration of vocalizations. In the male quail this extension of calling duration is accompanied by a clear decrease in opiate binding, whereas in the female there is a moderate increase in binding sites. The transition from DV to CR (within hours) induced by testosterone is correlated with "upregulation" of opiate receptor sites within unilateral brainstem areas of young male quail. Based on these findings, we suggest that organizational steroid effects change the characteristic duration of isolation-induced vocalizations and these effects appear to be manifested at the level of opioid-receptor distribution.

The effect of chronic administration of a synthetic LH-RH analogue intranasally in cryptorchid boys.

Eighteen boys with either unilateral or bilateral cryptorchidism were treated with a synthetic LH-RH analogue ("D-Leu 6, Des-Gly-10 LH-RH ethylamide") intranasally. The peptide was dissolved in aqueous solution (25 micrograms in 0,2 ml) and administered in the form of nasal drops. The patients were divided in two groups: in group A, 50 micrograms of the synthetic LH-RH analogue were administered intranasally every 48 h for 36 days; in group B same dose was given every 24 h. Additionally, in 4 cases a LH-RH test prior the trial was performed with the same peptide. The nasal administration resulted in a fivefold increase of LH and of FSH plasma concentration in 30 min and in 60 min, respectively. The endocrine profiles for T, LH and FSH were studied in each group over the treatment period and in group B (same dose was given every 24 h) a significant decrease of the LH and FSH plasma levels could be found. The clinical effect of treatment was same in the both groups. In the whole material 44% had either unilateral or bilateral descent of the testis after the therapy.