CT-Kolonographie mit dem 16-Zeilen-Detektor zur Diagnostik kolorektaler Neoplasien und entzündlicher Kolonerkrankungen

PURPOSE

Comparison of the performance of virtual and conventional colonoscopy for the detection of colorectal polyps and inflammatory colon diseases using a 16-slice spiral CT scanner. Furthermore, presentation of the first experiences with a new three-dimensional reconstruction mode ("colon-dissection") that dissects the colonic wall like a pathologic-anatomic preparation to increase the sensitivity.

MATERIALS AND METHODS

Forty patients were studied using a 16-slice spiral CT (Lightspeed 16, General Electric Medical Systems, Milwaukee, Wisconsin 53201, USA). The examination was performed after standard oral preparation for colonoscopy. The colonic distension was achieved with room air and intravenous butylscopolamine. Images were obtained in supine and prone position using a detector configuration of 16 x 0.625 mm, pitch 1.7, rotation time 0.5 s, 160 mAs and 120 kV. Axial reconstruction with a slice thickness of 0.625 mm. The CT data were assessed by two radiologists on an Advantage Workstation (Volume Analysis 2, USA) using a software with the capabilities of axial, multiplanar and volume rendering, virtual endoscopy, and colon dissection. Conventional colonoscopy was used to determine the sensitivity.

RESULTS

A total of 30 polyps were found in 8 patients and a carcinoma was detected in two patients. Colonography identified 4 polyps with a diameter of 10 mm or more, 6 polyps with a diameter of 5 mm to 9.9 mm, 11 polyps with a diameter of 3 to 4.9 mm and 9 polyps with a diameter of 3.0 mm or less. There were two false negative findings (one polyp of 3 mm and one of 4 mm had been overseen) and two false positive findings for polyps (polyps of 4 mm and 6 mm). The sensitivity and specificity for the detection of colonic polyps were 93% and 94% with the "colonic-dissection" mode, 87 % and 94 % with the "virtual-endoscopy" mode and 63 % and 97 % with multi-planar reconstruction, respectively. Depending on the diameter of the colonic polyps, the "colon-dissection" mode ("virtual-coloscopy") had a sensitivity and specificity of 100 % and 100 % for polyps with a diameter over 5.0 mm, 91 % and 82 % for polyps with a diameter from 3.0 to 4.9 mm and 89 % and 78 % for polyps with a diameter under 3.0 mm, respectively. Inflammatory colon diseases presented as thickening of the colon wall over 5 mm.

CONCLUSIONS

Virtual colonoscopy with 16-slice spiral CT allows accurate detection of colonic polyps, including small polyps below a diameter of 3 mm. In comparison with the 2D- and 3D-"virtual-endoscopic" reconstruction, the 3D-reconstruction software "colon-dissection" achieves the highest sensitivity for the detection of colonic masses. Therefore, the combination of a 16-slice spiral CT and the "colon-dissection" reconstruction software provides a high resolution in the z-axis for detecting colonic masses and polyps down to a diameter of less than 2 mm, with a sensitivity of about 90 %. This sensitivity is much higher than the sensitivity achievable with 4-slice spiral CT and without "colon-dissection" mode. A thickened colon wall over 5 mm indicates inflammatory colon disease.

[Accuracy of routine MRI in lesions of the supraspinatus tendon--comparison with surgical findings]

PURPOSE

To determine the correlation of the extent of lesions of the supraspinatus tendon in MRI's of the shoulder with surgical or arthroscopic findings using the classification of Snyders and Batemann, respectively.

MATERIALS AND METHODS

The preoperative MRI's of 80 patients (age: 16 - 76/47.4 +/- 14.0 years) which were performed due to various complaints of the shoulder were analyzed retrospectively by two experienced and blinded radiologists. We evaluated the incidence and the extent of partial or complete ruptures of the supraspinatus tendon. After MRI, an arthroscopic or open surgical intervention was performed (= gold standard). Various MR-scanners were used with a field strength of 1.0 T (17 cases), or 1.5 T (63 cases) and flexible or inflexible arthro coils. Additionally to plain MRI, 38 of 80 patients underwent contrast enhanced MRI. The MR and the surgical or arthroscopic findings were compared and statistically analyzed.

RESULTS

Neglecting the localization and the extent of discontinuity of the supraspinatus tendon, the sensitivity of the 80 MRI's was 0.93, the specificity 0.69, and the accuracy 0.85. The sensitivity increased to 0.96 with constant specificity and an accuracy of 0.83 excluding the lesions with an extent below 1 cm. Compared with non-enhanced examinations, the contrast enhanced MRI revealed higher sensitivity (+ 7 %, 0.89 vs. 0.96), higher specificity (+ 11 %, 0.64 vs. 0.75), and higher accuracy (+ 8 %, 0.81 vs. 0.89) in depicting lesions of the supraspinatus tendon at all. On T 1 -weighted images, the detection of lesions at all and the differentiation between partial and complete ruptures were improved significantly by contrast enhancement, especially in lesions with an extent below 1 cm. Diagnostic failures were seen in examinations without intravenous contrast application, artifacts, extent of the lesion below 1 cm, differentiating between degeneration and partial rupture of the tendon, differentiating between severely degenerated tendons with partial rupture and complete rupture, and covered ruptures.

CONCLUSIONS

The performance and consecutively the analysis of the widely used MRI of the shoulder is often not sufficiently reliable in its present routine form. To be able to compete with other imaging modalities such as sonography, standardized MR protocol, contrast enhancement as needed, avoiding the described source of failure, and an exact analysis should be applied.

PET imaging with yttrium-86: comparison of phantom measurements acquired with different PET scanners before and after applying background subtraction

Quantitative imaging with the positron emitter (86)Y is the method of choice to determine the uptake and dosimetry of (90)Y-labelled radiopharmaceuticals. To examine the quantitative accuracy of positron emission tomography findings with (86)Y, this non-pure positron emitter was evaluated in a cylindrical phantom with rods of Teflon, water and air and measured with three different scanners: ECAT EXACT (2D/3D), ECAT HR+ (2D/3D) and PC4096+ (2D). After standard reconstruction, (86)Y radioactivity measured with the ECAT EXACT and related to the true radioactivity varied between 0.84 and 0.99 in 2D and between 0.93 and 1.20 in 3D from the first to the last acquisition (eight half-life times later). The water and Teflon rods exhibited considerable amounts of reconstructed radioactivity-21% in 2D and 67% in 3D for water and 65% and 147%, respectively, for Teflon-compared with the actual (86)Y radioactivity of the phantom. For the ECAT HR+ similar results were obtained in 3D, but there were even greater overestimations in 2D. Measurements with the PC4096+ showed rather small errors, with 10% for water and 20% for Teflon. To correct for the background of gamma-coincidences, sinograms were analysed and an experimental percentage of the background was subtracted from the sinograms. In order to minimise the errors in reconstructed radioactivity, the subtraction value had to be different for the individual scanners and modes. Our results demonstrate that (90)Y/(86)Y-based dosimetry for bone and red marrow must be regarded with caution if it is derived from regions of interest over the bone, the density of which is similar to that of Teflon. To obtain more reliable estimates, an appropriate background correction must be applied and tailored individually with respect to the scanner and acquisition mode.

[The (11C) acetate positron emission tomography in prostatic carcinoma. New prospects in metabolic imaging]

The exact staging of prostate cancer is mandatory to allow selection of the appropriate primary therapy. In addition, if the PSA level rises again it is extremely important to find the site(s) of local recurrence or metastatic spread as soon as possible. However, with the morphological and metabolic imaging techniques currently available it is often not possible to answer these questions with adequate sensitivity and specificity, since small metastases < or = 1 cm in diameter are likely to remain undetected by them. In the last few years new radioactive labelled tracers have been introduced for use in positron emission tomography (PET), and it is hoped that the shortcomings in the diagnostic procedures used for prostate carcinoma might be compensated by their use. Besides 11C- or 18F-labelled choline, [11C]Acetate is also attracting attention as a promising PET tracer. In this paper we review the various PET tracers available and evaluate the advantages and the drawbacks of [11C]Acetate in three case studies by comparing [11C]Acetate-PET with histology and with other imaging techniques. The use of [11C]Acetate appears to be feasible and helpful in the diagnosis of prostate carcinoma. However, its final value relative to other imaging techniques needs further investigation, with special reference to initial lymph node involvement, early localisation of recurrence and possible noninvasive differentiation between prostate cancer, prostatis and benign hyperplasia of the prostate.

Novel neuropeptide Y1 and Y5 receptor gene variants: associations with serum triglyceride and high-density lipoprotein cholesterol levels

Neuropeptide Y (NPY) appears to play a critical role in the integration of appetite and energy expenditure through NPY Y1 and Y5 receptor subtypes. Moreover, the NPY Y1 receptor is highly expressed on human adipocytes, where it inhibits lipolysis. The genes encoding these receptors are transcribed co-ordinately in opposite directions from a common promoter in a region of chromosome 4 that has been previously linked to triglyceride and small low-density lipoprotein (LDL) particle concentration. Therefore, the purpose of this investigation was to examine the relationship between polymorphisms in the genes encoding NPY Y1 and Y5 and the development of obesity and dyslipidemia. We screened the promoter and coding regions and identified four polymorphic variants. One of these, a cytosine to thymine (C-->T) substitution in the untranslated region between the genes for NPY Y1 and Y5 (allele frequency 0.11), was significantly associated with both lower fasting triglyceride level (152 vs 125 mg/dl), and higher high-density lipoprotein (HDL) concentrations (49 vs 45 mg/dl) (p < 0.01) in 306 obese subjects. Given the stimulatory effect of NPY on adipocyte lipoprotein lipase (LPL) activity, and the lack of association of other polymorphisms with serum lipid levels, we hypothesize that this is a gain-in-function polymorphism.

Expression of the neuropeptide Y Y1 receptor in the CNS of rat and of wild-type and Y1 receptor knock-out mice. Focus on immunohistochemical localization

The distribution of neuropeptide Y (NPY) Y1 receptor-like immunoreactivity (Y1R-LI) has been studied in detail in the CNS of rat using a rabbit polyclonal antibody against the C-terminal 13 amino acids of the rat receptor protein. The indirect immunofluorescence technique with tyramide signal amplification has been employed. For specificity and comparative reasons Y1 knock-out mice and wild-type controls were analyzed. The distribution of Y1R mRNA was also studied using in situ hybridization. A limited comparison between Y1R-LI and NPY-LI was carried out.A widespread and abundant distribution of Y1R-LI, predominantly in processes but also in cell bodies, was observed. In fact, Y1R-LI was found in most regions of the CNS with a similar distribution pattern between rat and wild-type mouse. This staining was specific in the sense that it was absent in adjacent sections following preadsorption of the antibody with 10(-5) M of the antigenic peptide, and that it could not be observed in sections of the Y1 KO mouse. In contrast, the staining obtained with an N-terminally directed Y1R antiserum did not disappear, strongly suggesting unspecificity. In brief, very high levels of Y1R-LI were seen in the islands of Calleja, the anterior olfactory nucleus, the molecular layer of the dentate gyrus, parts of the habenula, the interpeduncular nucleus, the mammillary body, the spinal nucleus of the trigeminal, caudal part, the paratrigeminal nucleus, and superficial layers of the dorsal horn. High levels were found in most cortical areas, many thalamic nuclei, some subnuclei of the amygdaloid complex, the hypothalamus and the nucleus of the stria terminalis, the nucleus of the solitary tract, the parabrachial nucleus, and the inferior olive. Moderate levels of Y1R-LI were detected in the cornu Ammonis and the subicular complex, many septal, some thalamic and many brainstem regions. Y1R staining of processes, often fiber and/or dot-like, and occasional cell bodies was also seen in tracts, such as the lateral lemniscus, the rubrospinal tract and the spinal tract of the trigeminal. There was in general a good overlap between Y1R-LI and NPY-LI, but some exceptions were found. Thus, some areas had NPY innervation but apparently lacked Y1Rs, whereas in other regions Y1R-LI, but no or only few NPY-positive nerve endings could be detected. Our results demonstrate that NPY signalling through the Y1R is common in the rat (and mouse) CNS. Mostly the Y1R is postsynaptic but there are also presynaptic Y1Rs. Mostly there is a good match between NPY-releasing nerve endings and Y1Rs, but 'volume transmission' may be 'needed' in some regions. Finally, the importance of using proper control experiments for immunohistochemical studies on seven-transmembrane receptors is stressed.

PET quantitation and imaging of the non-pure positron-emitting iodine isotope 124I

A series of PET studies using phantoms is presented to characterize the imaging and quantitative performance of the positron-emitting iodine isotope 124I. Measurements were performed on the 2D-PET scanner GE 4096+ as well as on the Siemens PET scanner HRR+ operated in both 2D and 3D modes. No specific correction was applied for the gamma-rays emitted together with the positrons. As compared to 18F, in studies with 124I there is a small loss of image resolution and contrast, and an increase in background. The quantitative results varied between different scanners and various acquisition as well as reconstruction modes, with an average relative difference of -6 +/- 13% (mean+/-SD) in respect of the phantom radioactivity as measured with gamma-ray spectroscopy. We conclude that quantitation of a radiopharmaceutical labelled with 124I is feasible and may be improved by the development of specific corrections.

Brain systems engaged in encoding and retrieval of word-pair associates independent of their imagery content or presentation modalities

In this study, we aimed to characterize commonalities and differences of activation patterns during verbal episodic memory processes across different presentation modalities (visual or auditory) and different imagery content (low or high) of the presented verbal memory items. Twelve right-handed normal male volunteers took part in the study. Each subject underwent six O-15-butanol positron emission tomography scans. In six of the subjects the verbal material was presented visually, and in six subjects auditorily. The subjects had to encode and retrieve two sets of 12 word-pair associates of high (set 1) or low (set 2) imagery content (not semantically related). The presentation of nonsense words served as reference condition. Images were analyzed with statistical parametric mapping. Conjunction analysis was used to identify commonalities, and cognitive subtraction analysis was used to identify differences. The use of conjunction analyses enabled us to identify commonly activated regions involved in episodic encoding and retrieval of verbal material irrespective of the presentation modality or the imagery content. Our results add further evidence to recent findings that bilateral prefrontal activations are important for episodic retrieval and thus the role of the left prefrontal cortex has been underestimated during episodic retrieval. Furthermore, our results support the idea of functionally segregated areas in the prefrontal cortex. Finally, our results provide strong evidence that mesial parietal cortex (precuneus) involvement is not restricted to processes involving imagery.

Conscious and subconscious sensorimotor synchronization--prefrontal cortex and the influence of awareness

One of the most compelling challenges for modern neuroscience is the influence of awareness on behavior. We studied prefrontal correlates of conscious and subconscious motor adjustments to changing auditory rhythms using regional cerebral blood flow measurements. At a subconscious level, movement adjustments were performed employing bilateral ventral mediofrontal cortex. Awareness of change without explicit knowledge of the nature of change led to additional ventral prefrontal and premotor but not dorsolateral prefrontal activations. Only fully conscious motor adaptations to a changing rhythmic pattern showed prominent involvement of anterior cingulate and dorsolateral prefrontal cortex. These results demonstrate that while ventral prefrontal areas may be engaged in motor adaptations performed subconsciously, only fully conscious motor control which includes motor planning will involve dorsolateral prefrontal cortex.

Two-dimensional NMR studies of size fractionated Suwannee River fulvic and humic acid reference

Two-dimensional phase sensitive 13C,1H correlation spectra were applied to the investigation of substructures in size fractions obtained by tangential flow multistage ultrafiltration (MST-UF) of humic substances (HS) Suwannee River Fulvic Acid Reference (HS SR FA) and Suwannee River Humic Acid Reference (HS SR HA), purchased from the International Humic Substances Society (IHSS). After size fractionation with MST-UF the HS samples give well resolved two-dimensional 13C,1H-correlated NMR spectra which offer a great potential for substructure elucidation and even quantification. It is shown that low molecular size lignin moieties undergo demethylation of the methoxy groups, accompanied by removal of the phenylpropane side chains and subsequent reaggregation of the aromatic rings. These findings provide insight into the processes of lignin degradation. Only the fraction >100 kDa contains macromolecules that have spin-spin relaxation times too short for investigations employing NMR multipulse sequences.

Cerebral glucose transport implies individualized glial cell function

Previous positron emission tomography (PET) measurements of cerebral glucose transport using [11C]-3-O-methylglucose (CMG) suggested an interindividual variation in the values of the rate constant of tracer outflow (k2) larger than that for the clearance rate of inflow (K1). These two parameters were examined in healthy cerebral cortex by dynamic PET in 4 men and 2 women (aged 24 to 73 years) without neurologic disease, and in 1 man (42 years) with a recent left hemispheric cerebral infarction under normoglycemia (average blood plasma d-glucose concentration, 5.44 +/- 1.94 micromol/mL) and again under hyperglycemia (average, 10.24 +/- 1.44 micromol/mL). Time-radioactivity curves were obtained from healthy cortex (grey matter) and plasma and analyzed for the values of K1 and k2 by two graphical approaches and two fitting procedures. Both K1 and k2 significantly declined with increasing plasma glucose levels. A highly significant interindividual but not intraindividual variability for k2 was found at normoglycemia and hyperglycemia. The interindividual variability of K1, although borderline significant, was less than that of k2. Accordingly variable were the distribution volumes K1/k2. These data suggest individualized glial cell function and may be relevant to pathogenesis of neuropsychiatric disease.

Syntactic processing in left prefrontal cortex is independent of lexical meaning

In language comprehension a syntactic representation is built up even when the input is semantically uninterpretable. We report data on brain activation during syntactic processing, from an experiment on the detection of grammatical errors in meaningless sentences. The experimental paradigm was such that the syntactic processing was distinguished from other cognitive and linguistic functions. The data reveal that in syntactic error detection an area of the left dorsolateral prefrontal cortex, adjacent to Broca's area, is specifically involved in the syntactic processing aspects, whereas other prefrontal areas subserve general error detection processes.

The peptide YY-preferring receptor mediating inhibition of small intestinal secretion is a peripheral Y(2) receptor: pharmacological evidence and molecular cloning

A peptide YY (PYY)-preferring receptor [PYY > neuropeptide Y (NPY)] was previously characterized in rat small intestinal crypt cells, where it mediates inhibition of fluid secretion. Here, we investigated the possible status of this receptor as a peripheral Y(2) receptor in rats. Typical Y(2) agonists (PYY(3-36), NPY(3-36), NPY(13-36), C2-NPY) and very short PYY analogs (N-alpha-Ac-PYY(22-36) and N-alpha-Ac-PYY(25-36)) acting at the intestinal PYY receptor were tested for their ability to inhibit the binding of (125)I-PYY to membranes of rat intestinal crypt cells and of CHO cells stably transfected with the rat hippocampal Y(2) receptor cDNA. Similar PYY preference was observed and all analogs exhibited comparable high affinity in both binding assays. The same held true for the specific Y(2) antagonist BIIE0246 with a K(i) value of 6.5 and 9.0 nM, respectively. BIIE0246 completely abolished the inhibition of cAMP production by PYY in crypt cells and transfected CHO cells. Moreover, the antagonist 1) considerably reversed the PYY-induced reduction of short-circuit current in rat jejunum mucosa in Ussing chamber and 2) completely abolished the antisecretory action of PYY on vasoactive intestinal peptide (VIP)-induced fluid secretion in rat jejunum in vivo. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) experiments showed that Y(2) receptor transcripts were present in intestinal crypt cells (3 x 10(2) molecules/100 ng RNA(T)) with no expression in villus cells, in complete agreement with the exclusive binding of PYY in crypt cells. Finally, a full-length Y(2) receptor was cloned by RT-PCR from rat intestinal crypt cells and also from human small intestine. We conclude that the so-called PYY-preferring receptor mediating inhibition of intestinal secretion is a peripheral Y(2) receptor.

Integrating electrophysiology and neuroimaging of spatial selective attention to simple isolated visual stimuli

Visual-spatial attention involves modulations of activity in human visual cortex as indexed by electrophysiological and functional neuroimaging measures. Prior studies investigating the time course and functional anatomy of spatial attention mechanisms in visual cortex have used higher-order discrimination tasks with complex stimuli (e.g. symbol matching in bilateral stimulus arrays, or letter discrimination), or simple detection tasks but in the presence of complex distracting information (e.g. luminance detection with superimposed symbols as distractors). Here we tested the hypothesis that short-latency modulations of incoming sensory signals in extrastriate visual cortex reflect an early spatially specific attentional mechanism. We sought evidence of attentional modulations of sensory input processing for simple, isolated stimuli requiring only an elementary discrimination (i.e. size discrimination). As in prior studies using complex symbols, we observed attention-related changes in regional cerebral blood flow in extrastriate visual cortex that were associated with changes in event-related potentials at a specific latency range. These findings support the idea that early in cortical processing, spatially-specific attentional selection mechanisms can modulate incoming sensory signals based on their spatial location and perhaps independently of higher-order stimulus form.

A new two-dimensional pulse sequence for T(2)* measurements of protons in (13)C isotopomers

A new two-dimensional pulse sequence for T(2)* measurement of protons directly coupled to (13)C spins is proposed. The sequence measures the tranverse relaxation time of heteronuclear proton single-quantum coherence under conditions of free precession and is therefore well suited to evaluate relaxation losses of proton magnetization during preparation delays of heteronuclear pulse experiments in analytical NMR. The relevant part of the pulse sequence can be inserted as a "building block" into any direct or inverse detecting H,C correlation pulse sequence if proton spin-spin relaxation is to be investigated. In this contribution, the building block is inserted into a HETCOR as well as into a HMQC pulse sequence. Experimental results for the HETCOR-based sequence are given.

Interdependence of regional and global cerebral blood flow during visual stimulation: an O-15-butanol positron emission tomography study

The authors investigated the influence of variations in global cerebral blood flow (gCBF) on regional flow changes during visual stimulation. Global flow was varied using different end-expiratory CO2 values (PETCO2) between 20 and 70 mm Hg. Visual stimulation was performed with a red LED-array flashing at 8 Hz. Blood flow was measured with 0-15-butanol, continuous arterial blood sampling, and positron emission tomography (PET). Global flow changes surpassed the published values of O-15-H2O studies, better fitting the results of the inert gas technique (gCBF at 20, 40, and 70 mm Hg PETCO2 +/- SD was 31 +/- 4, 48 +/- 13, and 160 +/- 50 mL 100 g(-1) min(-1), respectively). The relation between PETCO2 and CBF in the current study was best described by an exponential rather than a linear function. At low PETCO2, the activation-induced flow changes are moderately damped, whereas at high PETCO2, they are nearly lost (deltaCBF (+/-SD): 52% +/- 25%, 68% +/- 22%, 16% +/- 25% at PETCO2 = 20, 40, 70 mm Hg, respectively).

A neural correlate of syntactic encoding during speech production

Spoken language is one of the most compact and structured ways to convey information. The linguistic ability to structure individual words into larger sentence units permits speakers to express a nearly unlimited range of meanings. This ability is rooted in speakers' knowledge of syntax and in the corresponding process of syntactic encoding. Syntactic encoding is highly automatized, operates largely outside of conscious awareness, and overlaps closely in time with several other processes of language production. With the use of positron emission tomography we investigated the cortical activations during spoken language production that are related to the syntactic encoding process. In the paradigm of restrictive scene description, utterances varying in complexity of syntactic encoding were elicited. Results provided evidence that the left Rolandic operculum, caudally adjacent to Broca's area, is involved in both sentence-level and local (phrase-level) syntactic encoding during speaking.

Uptake of cis-4-[18F]fluoro-L-proline in urologic tumors

Tumor uptake of the amino acid cis-4-[18F]fluoro-L-proline (cis-FPro) was studied with PET in eight patients with urologic tumors.

METHODS

Three patients had primary renal cell carcinomas (RCCs), one had a local recurrence of RCC, one had squamous RCC, one had an adrenal hemangioma, one had inguinal metastases of penile squamous carcinoma, and one had suspected metastatic disease from prostate cancer. PET scans of the trunk were acquired at 1 and 3-5 h after intravenous injection of 400 MBq cis-FPro and compared with 18F-FDG PET scans and CT.

RESULTS

None of the tumors or metastases showed significant uptake of cis-FPro. FDG uptake was seen in one of the three primary RCCs, in the local recurrence of RCC, in the squamous RCC, and in the metastases of penile cancer.

CONCLUSION

Cis-FPro appears not to be a promising PET tracer in oncology.

Impaired thrombin generation in beta 2-glycoprotein I null mice

Autoimmune antibodies to beta(2)-glycoprotein I (beta2GPI) have been proposed to be clinically relevant because of their strong association with thrombosis, miscarriage, and thrombocytopenia. By using a homologous recombination approach, beta2GPI-null mice were generated to begin to understand the physiologic and pathologic role of this prominent plasma protein in mammals. When beta2GPI heterozygotes on a 129/Sv/C57BL/6 mixed genetic background were intercrossed, only 8.9% of the resulting 336 offspring possessed both disrupted alleles. These data suggest that beta2GPI plays a beneficial role in implantation and/or fetal development in at least some mouse strains. Although those beta2GPI-null mice that were born appeared to be relatively normal anatomically and histologically, subsequent analysis revealed that they possessed an impaired in vitro ability to generate thrombin relative to wild type mice. Thus, beta2GPI also appears to play an important role in thrombin-mediated coagulation.

Dosimetry related to SPECT and PET applications

Nuclear medicine methods permit the in vivo measurement of physiological and metabolic functions. For this purpose metabolically active molecules are labelled with radionuclides. After the injection, these radiopharmaceuticals can be detected from outside the body with appropriate detectors such as conventional gamma cameras, single photon emission computerized tomographs (SPECT), or positron emission tomographs (PET). As with any application of ionizing radiation the benefits of nuclear medicine (the diagnosis and treatment of disease) must be balanced against the risks of the procedures. Risks in nuclear medicine are evaluated through dosimetry, the calculation of the radiation dose estimates, in which the energy deposited by the radiation in human tissues is quantitated. The first step of dosimetry is the determination of the biodistribution, i.e. the spatial and temporal distribution of the radiopharmaceutical within the body. When a new radiopharmaceutical is introduced such data are first derived from ex vivo experiments in animals. Further evaluations of the biokinetics and dosimetry are carried out via quantitative measurements in humans using the nuclear medicine imaging equipment, applying whole-body planar and tomographic methods. Based on the knowledge of the biodistribution and using the framework introduced by the MIRD committee as well as by the ICRP, the radiation dose to single organs and to the total body can be calculated. The purpose of this paper is to review methods for measuring radiopharmaceutical biodistributions in humans and for calculating the appropriate radiation dose quantities.

Whole-body kinetics and dosimetry of cis-4-[(18)F]fluoro-L-proline

The whole-body distribution of 4-cis[(18)F]fluoro-L-proline (cis-FPro) was studied in six patients with urological tumors by PET. Based on the IMEDOSE and MIRDOSE procedures radiation absorbed doses were estimated from whole-body PET scans acquired at 1 and 3-5 h after i.v. injection of 400 MBq cis-FPro. Cis-FPro showed high retention in the renal cortex and a slight uptake in liver and pancreas. Urinary excretion ranged from 12 to 19% at 5 h p.i. Highest absorbed doses were found for the urinary bladder wall and the kidneys (44.1/44.0 microGy/mbq). The effective dose according to ICRP 60 was 15.1 microSv/mbq for adults. This leads to an effective dose of 6.0 mSv in a PET study using 400 MBq cis-FPro.

Neural correlates of religious experience

The commonsense view of religious experience is that it is a preconceptual, immediate affective event. Work in philosophy and psychology, however, suggest that religious experience is an attributional cognitive phenomenon. Here the neural correlates of a religious experience are investigated using functional neuroimaging. During religious recitation, self-identified religious subjects activated a frontal-parietal circuit, composed of the dorsolateral prefrontal, dorsomedial frontal and medial parietal cortex. Prior studies indicate that these areas play a profound role in sustaining reflexive evaluation of thought. Thus, religious experience may be a cognitive process which, nonetheless, feels immediate.

Inhibitory effects of central neuropeptide Y on the somatotropic and gonadotropic axes in male rats are independent of adrenal hormones

Neuropeptide Y (NPY) in the hypothalamus exerts multiple physiological functions including stimulation of adipogenic pathways such as feeding and insulin secretion as well as inhibition of the somatotropic and gonadotropic axes. Since hypothalamic NPY-ergic activity is increased by negative energy balance, NPY enables coordinated regulation of growth and reproduction in parallel with energy availability. Chronic pathological increases in central NPY-ergic activity contribute to obesity. Many of the adipogenic effects of NPY are specifically dependent on adrenal glucocorticoids. However, in the current study we show that central NPY does not require adrenal hormones to inhibit the somatotropic and gonadotropic axes in rats. Male adrenalectomized and sham-operated normal rats were intracerebroventricularly (ICV) infused with NPY (15 microg/day) or saline for 5-7 days, and plasma leptin, insulin-like growth factor (IGF-1) and testosterone were assayed, and epididymal white adipose tissue (WATe) was weighed. In normal intact rats, WATe weight and leptinemia were significantly increased by NPY, and these effects were prevented by adrenalectomy. In normal rats, NPY markedly reduced plasma IGF-1 levels (470 +/- 40 versus 1260 +/- 90 ng/ml) and testosterone (0.53 +/- 0.28 versus 5.4 +/- 0.80 nmol/l in saline-infused controls, p < 0.0001). Adrenalectomy decreased plasma IGF-1 concentrations to 290 +/- 30 (p < 0.0001 versus normal rats), which were significantly reduced further by NPY. However, adrenalectomy had no significant effect on basal nor on NPY-induced plasma testosterone concentrations. In conclusion unlike the stimulatory effects of NPY on fat mass and leptinemia, NPY-induced inhibition of the somatotropic and gonadotropic axes in male rats do not require adrenal hormones.

Quantification of carbohydrate structures in size fractionated aquatic humic substances by two-dimensional nuclear magnetic resonance

Two-dimensional phase sensitive C,H correlation spectra were successfully applied to the quantification of carbohydrate substructures in aquatic humic substance (HS) fractions obtained by tangential flow multistage ultrafiltration (TFMSTUF) of a selected bog water HS (HO13, German Research Program DFG-ROSIG) as well as a river HS (Suwannee River Fulvic Acid Reference of the International Humic Substances Society, IHSS). It turns out that after size fractionation the HS samples give very well resolved C,H-correlation spectra which offer a great potential for substructure quantification. Details of the combined substructure quantification technique, novel in HS characterization, are presented. The results of the combined procedure point out that carbohydrate moieties predominantly occur in higher molecular mass fractions (> 10 kDa) of isolated HS.

Multiple Y receptors mediate pancreatic polypeptide responses in mouse colon mucosa

A functional study has been performed to characterise the Y receptors responsible for NPY, PYY and PP-stimulated responses in mouse colonic mucosal preparations. Electrogenic ion secretion was stimulated with VIP following which NPY, PYY and PP analogues were, to varying degrees, inhibitory. PYY(3-36), hPP, Gln(23)hPP and rPP were effective but less potent than full length PYY, NPY or their Pro(34)-substituted analogues, while the Y(5) agonist Ala(31), Aib(32)hNPY was the least active peptide tested. The Y(1) antagonists, BIBP3226 and BIBO3304 virtually abolished Pro(34)PYY and PYY responses while PYY(3-36) responses were selectively inhibited by the Y(2) antagonist, BIIE0246. A combination of BIBO3304 and BIIE0246 also partially attenuated hPP responses, leaving residual effects that were most probably Y(4)-mediated. Thus we conclude that Y(1), Y(2) and Y(4) receptors attenuate ion secretion in mouse colon.

The motion aftereffect: more than area V5/MT? Evidence from 15O-butanol PET studies

The motion aftereffect is a perceptual phenomenon which has been extensively investigated both psychologically and physiologically. Neuroimaging techniques have recently demonstrated that area V5/MT is activated during the perception of this illusion. The aim of this study was to test the hypothesis if a more broadly distributed network of brain regions subserves the motion aftereffect. To identify the neuronal structures involved in the perception of the motion aftereffect, regional cerebral blood flow (rCBF) measurements with positron emission tomography were performed in six normal volunteers. Data were analysed using SPM96. The motion-sensitive visual areas including area V5/MT were activated in both hemispheres. Additionally, the lateral parietal cortex bilaterally, the right dorsolateral prefrontal cortex, the anterior cingulate cortex and the left cerebellum showed significant increases in rCBF values during the experience of the waterfall illusion. In a further reference condition with identical attentional demand but no perception of a motion aftereffect elevated rCBF were found in these regions as well. In conclusion, our findings support the notion that the perceptual illusion of motion arises exclusively in the motion-sensitive visual area V5/MT. In addition, a more widespread network of brain regions including the prefrontal and parietal cortex is activated during the waterfall illusion which represents a non-motion aftereffect-specific subset of brain areas but is involved in more basic attentional processing and cognition.

[Comparison of PET and fMRI activation patterns durnig declarative memory processes]

AIM

In this study neuronal correlates of encoding and retrieval in paired association learning were compared using two different neuroimaging methods: positron emission tomography (PET) and functional magnetic resonance imaging (fMRI).

METHODS

6 right-handed normal male volunteers took part in the study. Each subject underwent six 0-15-butanol PET scans and on fMRI study comprising four single epochs on a different day. The subjects had to learn and retrieve 12 word pairs which were visually presented (highly imaginable words, not semantically related).

RESULTS

Mean recall accuracy was 93% in the PET as well as in the fMRI experiment. During encoding and retrieval we found anterior cingulate cortex activation, and bilateral prefrontal cortex activation in both imaging modalities. Furthermore, we demonstrate the importance of the precuneus in episodic memory. With PET the results demonstrate frontopolar activations whereas fMRI fails to show activations in this area probably due to susceptibility artifacts. In fMRI we found additionally parahippocampal activation and due to the whole-brain coverage cerebellar activation during encoding. The distance between the center-of-mass activations in both modalities was 7.2 +/- 6.5 mm.

CONCLUSION

There is a preponderance of commonalities in the activation patterns yielded with fMRI and PET. However, there are also important differences. The decision to choose one or the other neuroimaging modality should among other aspects depend on the study design (single subject vs. group study) and the task of interest.

A neural basis for general intelligence

Universal positive correlations between different cognitive tests motivate the concept of "general intelligence" or Spearman's g. Here the neural basis for g is investigated by means of positron emission tomography. Spatial, verbal, and perceptuo-motor tasks with high-g involvement are compared with matched low-g control tasks. In contrast to the common view that g reflects a broad sample of major cognitive functions, high-g tasks do not show diffuse recruitment of multiple brain regions. Instead they are associated with selective recruitment of lateral frontal cortex in one or both hemispheres. Despite very different task content in the three high-g-low-g contrasts, lateral frontal recruitment is markedly similar in each case. Many previous experiments have shown these same frontal regions to be recruited by a broad range of different cognitive demands. The results suggest that "general intelligence" derives from a specific frontal system important in the control of diverse forms of behavior.

Molecular cloning and characterisation of GPR74 a novel G-protein coupled receptor closest related to the Y-receptor family

A novel gene product, GPR74, with homology to the seven transmembrane-domain receptor superfamily, has been cloned. GPR74 has been identified from the expressed sequence tags (EST) database. Subsequent PCR amplification of that sequence and screening of a human heart cDNA library led to the isolation of a 1.7-kb cDNA clone encoding a protein of 408 amino acids. GPR74 shows highest amino acid identity (33%) to the human neuropeptide Y-receptor subtype Y2. The human and mouse genes for GPR74 have been isolated and their exon-intron structures determined. In both species the gene consists of four exons spanning around 20 kb with the exon-intron borders being 100% conserved. Northern analysis of various human tissues reveals highest levels of mRNA expression in brain and heart. In situ hybridisation analysis of rat brain tissue confirms this result and identifies the hippocampus and amygdala nuclei as the brain areas with particular high expression of GPR74 mRNA. Fluorescence in situ hybridisation, PCR analysis on a radiation hybrid panel and interspecific mouse backcross mapping have localised the genes to human chromosome 4q21 and mouse chromosome 5. Expression of the human GPR74 cDNA as a GFP-fusion protein in various cell lines reveals the inability of the recombinant receptor protein to reach the cell surface. This is consistent with the lack of NPY specific binding in these cells and suggests that unknown factors are required for a full functional receptor complex.

Novel polymorphisms in the neuropeptide-Y Y5 receptor associated with obesity in Pima Indians

OBJECTIVE

To investigate whether the neuropeptide Y receptor 5 gene (NPY5R) is associated with obesity in humans.

DESIGN

The NPY5R gene was screened for polymorphisms by direct sequencing in two groups of Pima Indians, selected for extremes of body mass index (BMI). Genotype frequencies were analyzed for association with BMI extreme.

SUBJECTS

Full-heritage Pima Indians, non-diabetic and not first degree relatives. Obese group: 19 M/24 F, BMI = 49+/-7 kg/m2 (mean+/-s.d.) age = 24+/-2 y, lean group: 16 M/16 F, BMI = 23+/-2 kg/m2, age = 27+/-3 y.

MEASUREMENTS

Initially, the entire gene (proximal promoter, exon 1A, coding sequence, 5' and 3' UTRs) was sequenced in a subset of 20 individuals. No variants were found in the coding sequence, however three novel single nucleotide polymorphisms were detected in the non-coding regions: (1) a C-->T transition located within the promoter 28 bp upstream of the exon 1A transcription start site; (2) a T-->C transition 94 bp downstream of the stop codon; and (3) a G-->A transition 432 bp downstream of the stop codon. The polymorphisms were then screened in all 75 subjects.

RESULTS

The polymorphisms had mean heterozygosities of 0.34-0.50 and were in strong linkage disequilibrium (P<0.001). Genotype frequencies differed significantly in lean and obese Pimas for P2 (P=0.04) and for a triple haplotype (P=0.02, Bonferroni corrected).

CONCLUSION

Considering the importance of this gene in regulation of body weight, the association of these polymorphisms with extremes of BMI in Pima Indians indicates that NPY5R, or a locus nearby, may contribute to susceptibility to obesity in this population.

Adrenalectomy reduces neuropeptide Y-induced insulin release and NPY receptor expression in the rat ventromedial hypothalamus

Chronic central administration of neuropeptide Y (NPY) causes hyperphagia, hyperinsulinemia, and obesity, a response that is prevented by prior adrenalectomy (ADX) in rats. The basis of NPY's effect and how the acute responses to this peptide are affected by ADX remain unknown. This study investigates the role of glucocorticoids in acute NPY-stimulated food intake, acute NPY-induced insulin release, and hypothalamic NPY-receptor mRNA expression levels. NPY-induced food intake was similar in ADX and control rats after acute intracerebroventricular injection of NPY. Injection of NPY caused a significant increase in plasma insulin in control rats, but this effect was completely absent in ADX rats in which basal plasma insulin levels were also lower than controls. In addition, ADX significantly reduced the number of neurons expressing NPY receptor Y(1) and Y(5) mRNAs in the ventromedial hypothalamus (VMH), without affecting Y(1)- or Y(5)-mRNA expression in the paraventricular hypothalamus or the arcuate nucleus. These data indicate that glucocorticoids are necessary for acute NPY-mediated insulin release and suggest that the mechanisms involve glucocorticoid regulation of Y(1) and Y(5) receptors specifically within the VMH nucleus.

Y-receptor-like genes GPR72 and GPR73: molecular cloning, genomic organisation and assignment to human chromosome 11q21.1 and 2p14 and mouse chromosome 9 and 6

Two novel G-protein-coupled receptors, one from human, GPR72, and one from mouse, GPR73 have been isolated, sequenced and their genomic organisation determined. Non-isotopic in situ hybridisation and radiation hybrid mapping have identified GPR72 to be localised on human chromosome 11q21.1, and GPR73 on human chromosome 2p14. Interspecific mouse backcross mapping has localised the genes to mouse chromosomes 9 and 6, respectively. Northern analysis reveals GPR72 mRNA expression only in brain tissue. However, GPR73 mRNA can be found in heart, skeletal muscle and pancreas. Both receptors are closely related with 36 and 33% overall amino acid identity, respectively, to the Y-receptor family. However, although successful cell surface expression in a heterologous expression system can be achieved no specific binding to this ligand family can be detected, indicating that perhaps additional factors are required for binding.

Visual hallucinations in recovery from cortical blindness: imaging correlates

OBJECTIVE

To investigate the cerebral metabolic and functional patterns during recovery from cortical blindness.

DESIGN

Follow-up study with serial clinical, metabolic, and functional imaging and visual evoked potentials.

CASE PRESENTATION

A 24-year-old woman suffered from cortical blindness after cardiac arrest and recovered over a 6-month period. During recovery, she experienced complex visual hallucinations that could be initiated by visual imagery.

RESULTS

Initially, the regional cerebral metabolic rate of glucose was severely reduced in the visual and parieto-occipital cortex bilaterally but recovered almost completely. Visual hallucinations led to significant increases of the regional cerebral blood flow in the initially severely hypometabolic parieto-occipital and temporo-lateral cortex.

CONCLUSIONS

Recovery of vision was related to normalization of the postlesionally dysfunctional cortex. Visual hallucinations appeared as the clinical correlate of the electrophysiological hyperexcitability of the recovering partially damaged visual cortex.

Peptide YY-2 (PYY2) and pancreatic polypeptide-2 (PPY2): species-specific evolution of novel members of the neuropeptide Y gene family

Several gene duplication events have led to the creation of at least five distinct members of the neuropeptide Y gene family. We now reveal that the most recent of these events, involving the PYY-PPY gene cluster on chromosome 17q21.1, has led to the creation of novel PYY- and PP-like genes on chromosome 17q11 in the human genome. Sequence analysis of the novel human PYY2 and PPY2 genes shows an extensive homology to the peptide YY-pancreatic polypeptide genes, at the level of gene structure, nucleotide sequence, and primary amino acid sequence. The extremely high degree of homology between the PYY-PPY and the PYY2-PPY2 gene clusters, in both coding regions and especially noncoding regions, suggests that the PYY2 and PPY2 genes have arisen by a very recent gene duplication. Similar gene duplication events of the PYY-PPY gene cluster have also occurred in other species, including cow and baboon, but have not been confirmed in the rat and mouse genomes. Interestingly, despite the greater than 92% nucleotide sequence identity between these new genes, a few specific mutations have resulted in significantly altered peptide sequences. These altered sequences are accompanied by acquisition of new functions apparently unrelated to the neurotransmitter/endocrine role of PYY and PPY, as demonstrated by the major involvement of bovine PYY2, also known as seminal plasmin, in the fertilization process.

2-36[K4,RYYSA(19-23)]PP a novel Y5-receptor preferring ligand with strong stimulatory effect on food intake

Members of the neuropeptide Y (NPY) family regulate many physiological processes via interaction with at least four functional, pharmacologically distinct Y-receptors. However, selective antagonists developed for several subtypes have not been useful in defining particular Y-receptor functions in vivo. To identify critical residues within members of the NPY family required for Y-receptor subtype-selectivity we have determined the contribution of each residue within NPY to receptor binding by replacing them with L-alanine. In a second study, chimeric peptides where single or stretches of residues were interchanged between members of the NPY family were generated and tested in radioligand binding studies. Overall, substituted alanine analogues exhibited similar orders of affinities at each Y-receptor subtype with no obvious subtype-selectivity. Residues of particular interest are Leu30 which exhibited selectivity for the Y4-receptor, whereas Asp16 does not appear to play any role in ligand binding. Several chimeric peptides, e.g., [K4]pancreatic polypeptide ([K4]PP) and [RYYSA(19-23)]PP clearly showed higher affinity at the Y4 and Y5 subtypes compared to the Y1 and Y2 subtypes. In addition, the transfer of a proline residue from position 14 to 13 in peptide YY decreases its affinity at the Y1-, Y4- and Y5-receptors but is unchanged at the Y2 subtype. Combining these results, and with the help of molecular modelling, second generation chimeras were designed. The most significant improvement was achieved in chimera 2-36[K4,RYYSA(19-23)]PP where the affinity for the Y5 subtype increased by ninefold over that from NPY. Several of these compounds were also tested for their ability to stimulate food intake in a rat model. Interestingly, again 2-36[K4,RYYSA(19-23)]PP showed the most dramatic effect with a major increase on food intake over a range of doses compared to NPY suggesting a possible synergistic effect of several Y-receptors on feeding behaviour.