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Purpose: A prospective evaluation before and after the introduction of PACS should evaluate the level of acceptance by the referring physicians and indicate possible weaknesses., Materials and Methods: In a hospital with 816 beds, questionnaires were sent to all referring physicians before and after the introduction of PACS to inquire how the physicians deal with radiological images., Results: Without PACS, 62 % of the referring physicians spent up to one hour per day searching for radiological images. With PACS, 52 % needed less time to find the correct images. 63 % believe that the radiological image demonstration is more informative due to PACS. The possibility to view radiological images was criticized by 29 % of the referring physicians at the ambulatory units and 34 % at the wards. Before PACS, the service of the department of radiology was considered to be very good by 20 % of the physicians. After PACS, this value increased to 31 %. 93 % of the physicians questioned would recommend the introduction of PACS to other hospitals., Conclusion: Digital image distribution that takes into account the demands of referring physicians can achieve high acceptance and improve workflow. The quality of the computer monitors in the operating rooms, wards and ambulatory units should be improved.

To evaluate possible pathophysiologic links between cerebral changes in diabetic patients detected by proton magnetic resonance spectroscopy and clinical as well as laboratory parameters. The brains of 30 patients with diabetes mellitus and 30 healthy volunteers were examined using a STEAM sequence (TR 1500 ms, TE 20 ms). We measured in occipital gray matter and parietal white matter in a 1.5-Tesla magnet. Laboratory parameters were acquired before and after the examination. In diabetic patients a significant elevation of the myo-inositol/creatine ratio in gray and white matter was present (p = 0.006). Choline/creatine ratio in gray matter was elevated compared to normal controls (p = 0.002). No correlation with laboratory parameters was detected. Myo-inositol was even more elevated in patients with polyneuropathy (p = 0.024). No correlation with age or sex was detected. The changes found in diabetes are similar to those found in patients with Alzheimer's disease, dialysis, and after renal transplant, suggesting a similar etiology. Elevated myo-inositol may not only indicate osmolar changes in glial cells but also glial cell alteration due to amyloid or amylin deposition with formation of neurofibrillary tangles, especially as these changes are found in all of these diseases and no correlation to osmolar deterioration exists.

Objectives: The aim of this study was to assess the potential of heavily T2* weighted 2D spoiled gradient echo multiecho sequence MEDIC (multi echo data image combination) with magnetization transfer saturation pulse (MTS) for detecting abnormality of the cervical spinal cord., Methods: 11 patients, 5 women and 6 men aged from 14 to 79 years (mean age 51.18 years), with traumatic, hemolytic-hemorrhagic or neoplastic diseases of the cervical spinal cord were examined with MRI. In cases with suspected myelopathy, the feasibility of the 2D spoiled gradient echo multiecho sequence MEDIC with MTS was evaluated in comparison with the results of spin echo T1W, spin echo T2W, multi echo (TSE in our case) and spin-echo multi-echo technique with magnetization preparation (turbo inversion recovery--TIR--in our case) sequences., Results: Distortion of the "H" sign was found in all but one case. Hemorrhage was best shown by MEDIC, massive edema was very well visible using MEDIC, TIR and TSE T2W, whereas mild edema was visible with MEDIC only., Conclusions: Our preliminary experience in 11 patients shows that MEDIC can be used for the diagnosis of cervical spinal cord pathology.

Purpose: Analysis of costs for vascular radiological interventions on a per patient basis and comparison with reimbursement based on GOA (Gebührenordnung für Arzte) and DKG-NT (Deutsche Krankenhausgesellschaft-Nebenkostentarif)., Material and Methods: The ten procedures most frequently performed within 12 months were evaluated. Personnel costs were derived from precice costs per hour and estimated procedure time for each intervention. Costs for medical devices were included. Reimbursement based on GOA was calculated using the official conversion factor of 0.114 DM for each specific relative value unit and a multiplication factor of 1.0. The corresponding conversion factor for DKG-NT, determined by the DKG, was 0.168 DM., Results: A total of 832 interventional procedures were included. Marked differences between calculated costs and reimbursement rates were found. Regarding the ten most frequently performed procedures, there was a deficit of 1.06 million DM according GOA data (factor 1.0) and 0.787 million DM according DKG-NT. The percentage of reimbursement was only 34.2 (GOA; factor 1.0) and 51.3 (DKG-NT), respectively., Conclusion: Reimbursement of radiological interventional procedures based on GOA and DKG-NT data is of limited value for economic controlling purposes within a hospital.

Objective: The purpose of this study was to evaluate the effectiveness of a large-area, flat-panel X-ray detector for performing routine chest radiography at two different detector doses., Materials and Methods: The chest radiographs of 50 patients (age range, 16-79 years; mean age, 57 years) were obtained at two different detector dose levels. Digital images were taken from the same patients in posteroanterior and lateral views with detector doses of 2.5 microGy and 1.8 microGy, respectively, at 125 kVp tube voltage. The cesium iodide-amorphous silicon active-matrix imager had a panel size of 43 x 43 cm, a matrix of 3000 x 3000, and a pixel pitch of 143 microm. Images were presented in a random order to three independent radiologists who were unaware of the dose level at which the images had been obtained. They subjectively rated image quality on a 4-point scale, according to six criteria (presentation of obscured lung, unobscured lung, airways, mediastinum and hilum, bony thorax, and overall impression). Statistical significance of differences was evaluated with Student's t test for paired samples (confidence level, 95%)., Results: Digital radiographs obtained at 2.5 and 1.8 microGy were equivalent on all quality criteria. No statistically significant differences and no tendency toward a preference for images obtained at one or the other dose level were observed. According to the registered mAs values, the average difference in patient dose was 33%., Conclusion: Use of flat-panel digital imagers based on the cesium iodide-amorphous silicon technique allows a considerable dose reduction during routine chest radiography without loss of image quality.

Objective: The purpose of this study was to evaluate the visibility of the IXth to XIIth cranial nerves using different magnetic resonance sequences. Thirty healthy volunteers underwent magnetic resonance imaging at 1.5 T using 3-dimensional constructive interference in steady state (CISS) sequence (TR = 17 ms, TE = 8.08 ms, alpha = 70 degrees), 3-dimensional magnetization-prepared rapid gradient echo (MP-RAGE) sequence (TR = 11.08 ms, TE = 4.3 ms, alpha = 15 degrees), and T2-weighted (w) 2-dimensional turbo spin echo (TSE) sequence (TR = 4000 ms, TE = 102 ms, alpha = 180 degrees, slice thickness = 2 mm). Visibility of the IXth to XIIth cranial nerves in each sequence was evaluated by consensus of 2 radiologists using an evaluation scale from 1 (excellently visible) to 5 (not visible). A correlation with anatomic specimens was made. The 3-dimensional CISS sequence provides best resolution of the IXth to XIIth cranial nerves and their relation to surrounding structures. Additional information is given by the 3-dimensional MP-RAGE when nerves are surrounded by soft tissues. Using the T2w 2-dimensional TSE sequence, even whole nerves cannot be visualized due to intersection gap and partial volume effects. However, even in 3-dimensional high-resolution sequences, segments of nerves are not always visualized. A combination of 3-dimensional CISS and 3-dimensional MP-RAGE proved to be useful to visualize the IXth to XIIth cranial nerves, whereas the 2-dimensional technique failed. Further investigations using 3-dimensional MP-RAGE with contrast medium should be performed in the case of abnormality.

Aim: Planning a PACS (Picture Archiving and Communication System) with the aim of a filmless hospital. The service for the referring physicians should be optimised., Methods: Statistical analysis of data from the RIS (Radiological Information System), customer survey, workflow analysis and cost effectiveness analysis was the basis for planning the PACS., Results: The calculated data quantity of the institute is 6.2 gigabyte per day or 1.7 terabyte per year. The referring physicians wanted to have the examination in 93% of the cases on the same day. For 53% of the cases remote studies were necessary for reading. Only 2.3% of these pictures were older than two years. The organisation of the department makes it necessary to have access to the examination of all modalities from each diagnosis workstation., Conclusions: Due to specific attributes of the institute, a fast nearline archive, a clustering of the diagnosis workstations and a DiCOM based picture distribution were planned.

The aim of this study was to assess the detectability and distinguishability of the cervical spinal cord, the anterior and posterior spinal roots and of the internal anatomy of the cord (distinction of grey and white matter). For this purpose 20 healthy volunteers were examined using a 1.5 T MR unit with 20 mT/m gradient strength and a dedicated circular polarized neck array coil. Three T2* weighted (w). 2D gradient echo sequences, two T2 w. 2D turbo spin echo (TSE) sequences and one T2 w. 2D turbo gradient spin echo (TGSE) sequence were compared. The multiecho 2D fast low angle shot (FLASH) sequence with magnetization transfer saturation pulse (me FLASH+MTS) yielded the best results for liquor/compact bone, liquor/spinal cord and grey/white matter contrast, as found with regions of interest (ROI) analysis. The single echo 2D FLASH sequence was significantly poorer than the two me FLASH+/-MTS sequences. Two-dimensional TGSE as well as 2D TSE with a 256 matrix and with a 512 matrix yielded the poorest results. In the visual analysis the contrast between liquor and compact bone, liquor and cord as well as liquor and roots was best with me FLASH+MTS, whereas grey/white matter distinction was best using me FLASH-MTS. In conclusion, we would therefore recommend the inclusion of an axial T2* w. multiecho 2D spoiled gradient echo sequence with magnetization transfer saturation pulse and gradient motion rephasing in a MR imaging protocol of the cervical spine.

The aim of this study was to assess the detectability of the trigeminal nerve and its branches using T1 weighted (w.) 3-D magnetization prepared rapid gradient echo (MP-RAGE), T2* w. 3D CISS and T2 w. 2-D turbo spin echo MR sequences. Thirty healthy volunteers were examined for this purpose using a 1.5 Tesla MR unit. The detectability of the trigeminal nerve and Gasser's Ganglion, i.e. structures that are surrounded by liquor was best using 3-D CISS. In the case of the ophthalmic, maxillary and mandibular nerves, the T1 w. 3-D MPRAGE was significantly better than T2* w. CISS and T2 w. 2-D turbo spin echo. The latter yielded the poorest results. We conclude that both high resolution T2* w. and T1 w. 3-D sequences are necessary in order to detect the liquor-surrounded trigeminal nerve and its soft tissue-surrounded branches. We would therefore recommend the inclusion of constructive interference in steady state (CISS) and MP-RAGE in a MR imaging protocol of the trigeminal nerve and its branches.

A total of 30 healthy volunteers underwent magnetic resonance imaging (MRI) with T1 weighted (w.) 3D magnetization prepared rapid gradient echo (MP-RAGE), T2 w. 2D turbo spin echo (TSE) and T2* w. 3D constructive interference in steady state (CISS) sequences to evaluate the detectability of the optic, oculomotor, trochlear and abducens nerves. CISS yielded the best results for the trochlear and abducens nerve, MP-RAGE for the optic chiasm and tract. The optic and oculomotor nerves were very well detectable using both CISS and MP-RAGE without any statistically significant difference between the two.

Thirty healthy volunteers were examined with a T2* w. 3D CISS and a T2 w. 3D turbo spin echo (TSE) sequence in order to compare the facial and vestibulocochlear nerve detectability in the cerebellopontine angle and the internal auditory canal. CISS was significantly better than 3D TSE for nerve detectability in the cerebellopontine angle and equally as good as 3D TSE in the internal auditory canal. We would therefore recommend the inclusion of CISS in an MR imaging protocol of the facial and vestibulocochlear nerves.

Thirty healthy volunteers underwent MRI with 3D MP-RAGE, 3D CISS and 2D turbo spin echo sequences to compare the detectability of olfactory fibers, bulb, tract, and sulcus. The overall detectability was slightly better using MP-RAGE compared with CISS. Both 3D sequences were superior to 2D turbo spin echo. We therefore recommend including the MP-RAGE sequence in an MR imaging protocol of the olfactory nerve.

Purpose: To evaluate the availability and completeness of previous radiological examinations., Material and Methods: Seven different types of examinations were analysed separately: 1) chest examinations, 2) bedside chest examinations, 3) skeletal examinations, 4) angiographic examinations, 5) mammographic examinations, 6) CT examinations, and 7) MR examinations. A retrospective part of the study covered the calendar year 1997, while a prospective part referred to 1998. The sample size in each modality and each part of the study was 100 observations, resulting in a total number of 1,400 examinations., Results: The average availability and completeness of radiographs in the retrospective analysis was 96.9% in 1997. The average availability and completeness of radiographs in the prospective analysis was 85.5% for the year 1998. This applied to necessary previous examinations of the same or different modality irrespective whether the examination was conducted internally or externally., Conclusion: The real loss rate of radiographs derived from the retrospective investigation was 3.1%. The prospective part of the study showed that 14.5% of the required previous internal and external examinations of the same or different modality were not available completely and in time to the examining radiologist.

In order to gain information about lignin molecular characteristics with a direct bearing on the remarkable susceptibility of some Austral hardwoods to biological delignification, milled-wood lignins were isolated and analyzed by spectroscopic techniques in the solid state. Cross polarization and magic-angle spinning 13C nuclear magnetic resonance (13C CPMAS NMR) and Fourier-transform infrared (FTIR) spectra of the lignin preparations were obtained. The most diagnostic peaks were assigned and quantified as percentages of the total spectral area, and the differences observed discussed in terms of lignin composition. The spectral patterns obtained revealed that the woods from Gevuina avellana, Eucryphia cordifolia and Nothofagus dombeyii have lignin with high syringyl/guaiacyl ratio, as evidenced by relative areas of 13C NMR signals at 153 and 148 ppm, and FTIR bands at 1,335 and 1,275 cm-1. The presence of syringyl-rich lignins, characterized by lower redox potential and condensation degree than guaiacyl-rich lignins, could be a structural factor contributing to the ease of extensive delignification of these woods by white-rot fungi.

Purpose: Experimental and clinical evaluation of a digital flat-panel X-ray system based on cesium iodide (CsI) and amorphous silicon (a-Si)., Methods: Performance of a prototype detector was compared with conventional screen-film radiography (SFR) using several phantom studies. Foreign bodies, fractures, osteolyses, and pulmonary lesions were analyzed. Additionally, 120 patients were studied prospectively, resulting in 400 comparative X-ray studies. The flat-panel detector was exposed with standard dose and with a dose reduction of up to 75%. Detector size was 15 x 15 cm, pixel matrix was 1 x 1 k with a pixel size of 143 microns. Modulation-transfer function was determined to be 18% at the maximum spatial resolution of 3.5 lp/mm., Results: The diagnostic results achieved with the digital detector were similar to those of conventional SFR, even at reduced radiation exposure. A potential for dose reduction was observed: 50% with respect to osteoarthrosis and fractures, and 75% for determining bony alignment., Discussion: This new technology can be used in thoracic and skeletal radiography. A significant dose reduction is possible, depending on the suspected disease.

Objective: The purpose of this study was to compare images obtained with a self-scanning, flat-panel X-ray detector based on amorphous silicon technology with conventional screen-film radiographs and to evaluate the possibility of radiation dose reduction in skeletal radiography., Subjects and Methods: One hundred twenty patients were examined prospectively using a conventional screen-film system (speed, 400; detector dose, 2.5 microGy) and a prototype digital amorphous silicon detector (simulated speed, 400 and 800, n = 120; simulated speed, 1600, n = 40). The resulting 400 images were evaluated independently by six radiologists using a subjective five-point preference scale that rated overexposure, underexposure, contrast resolution, spatial resolution, and soft-tissue presentation. Image quality was ranked on a scale from 0 to 10 according to subjective criteria. Statistical significance of differences was determined using Student's t test and confidence intervals (95% confidence level)., Results: Comparison of conventional radiographs with digital images revealed a statistically significant preference for the digital system for soft-tissue presentation (speed 400 and 800) and visualization of osteoarthrotic changes (speed 400). A small but statistically significant preference for conventional images was found with respect to contrast and spatial resolution when digital speed was 800 or 1600; and the visibility of arthrosis at digital speed 1600, osteolysis at digital speed 800 and 1600, and fractures at digital speed 1600., Conclusion: The amorphous silicon-based system with a simulated speed of 400 provided images equivalent to screen-film radiographs. For clinical tasks such as routine follow-up studies, assessment of instability, or orthopedic measurements, a radiation dose reduction of up to 75% may be possible.

Rationale and Objectives: The authors compared a solid-state amorphous silicon (a-Si) detector and screen-film radiography (SFR) with regard to the detection of simulated pulmonary lesions. Evaluation of the impact of a dose reduction of 50% with this digital flat-panel detector was of special interest., Methods: A self-scanning flat-panel detector, based on a-Si technology with 143 x 143 microm pixel size, 1 k x 1 k matrix and 12-bit digital output was used. An asymmetric state-of-the-art screen-film system was compared with a-Si images taken at the same dose as SFR-images and at a dose reduced by 50%. An anthropomorphic chest phantom was superimposed by templates containing nodules, linear structures, reticular, and micronodular opacities in a random distribution. Receiver operating characteristic analysis was performed for 23,040 observations made by four independent observers. Student's t test (95% confidence-level) was used for statistical analysis., Results: Receiver operating characteristic analysis showed that a-Si images taken at the same dose as SFR-images were significantly superior to SFR with respect to the detectability of lines (P = 0.01) and micronodular opacities (P < 0.01). For the other objects and the a-Si images taken at a reduced dose, it yielded no statistically significant differences between both imaging modalities., Conclusions: The results of this phantom study indicate that a-Si detector technology holds promise in terms of dose reduction in chest radiography without loss of diagnostic accuracy compared with SFR.

Rationale and Objectives: The purpose of this phantom study was to assess the diagnostic performance of a self-scanning, solid-state amorphous silicon (a-Si) detector in skeletal radiography using different exposure parameters., Methods: A flat-panel detector (15 cm x 15 cm), based on a-Si technology with 143 microm x 143 microm pixel size, 1k x 1k matrix, and 12 bit digital output was used. State-of-the-art screen-film radiography (SFR; speed 400, detector dose 2.5 microGy) was compared with a-Si images taken at doses that were equivalent to a speed of 400, 800, 1,250, and 1,600, respectively. A total of 232 segments of long tubular deer-bones (femur, tibia, humerus, radius) had 110 artificial fractures and 112 cortical defects simulating osteolytic lesions. Receiver operating characteristic analysis was performed for 9,280 observations made by four independent observers. Two-tailed Student's paired t test was used for statistical analysis (95% confidence level)., Results: Receiver operating characteristic analysis yielded equivalent results of the a-Si and SFR system. Even at the lowest dose there were no statistically significant differences between both imaging modalities with respect to the detectability of fractures and cortical defects., Conclusions: The results of this study indicate that a-Si detector technology holds promise in terms of dose reduction in skeletal radiography without loss of diagnostic accuracy.

We show a detailed magnetic resonance (MR) examination of two rare pericallosa lipomas with a fat suppression imaging sequence and proton MR spectroscopy. For comparison, subcutaneous fat and lipids in glioblastomas were examined with H MR spectroscopy in vivo and ex vivo. Fat suppression makes the identification of lipomas simple. It is suggested that H MR spectroscopy shows no differences in the aliphatic chain length of lipoma and subcutaneous fat, whereas lipids in glioblastomas have a much shorter chain length. Chain length of fatty acids in lipoma measured with in vivo MR spectroscopy are in concordance with data from the literature.

Background/aims: Early cognitive disturbances in patients with cirrhosis (Ci) are difficult to assess. Therefore, we evaluated the role of topographic auditory evoked cerebral potentials (P300-EP)., Methodology: Prospective longitudinal study., Setting: Tertiary clinical care institution., Participants: 45 patients with cirrhosis were compared to 22 healthy subjects., Main Outcome Measures: Hepatic Encephalopathy (HE) was assessed using the clinical grading, standardized psychometric tests, and auditory evoked P300-EP by multichannel EEG recordings., Results: In the patients, the mean P300 peak latency was significantly increased (386.7 +/- 26.7 versus 318.6 +/- 22.2 ms in controls, p < 0.00001). Even in patients with cirrhosis but no HE (n = 18) the P300 peak latency was abnormally prolonged (> 384 ms) in 8 cases (44%). In addition, P180 peak latency was significantly longer in patients with liver cirrhosis as compared to controls (p = 0.021). The maximal P300 amplitude was significantly lowered in patients with liver cirrhosis in the frontocentral and central cortical regions (FZ: p < 0.008; Cz: p < 0.04). Liver function and etiology of liver disease were not related to the increased peak latencies of the P300 and P180 peaks., Conclusions: P300-EP is a sensitive measure to detect functional cognitive impairment in cirrhotic patients with subclinical HE and clinically apparent HE. Typical changes include latency prolongation and decreased central peak amplitude. Some 40% of patients with no clinical evidence of HE and normal psychometric tests show abnormal results during P300 testing, which is likely to reflect early impairment of cognitive function. Auditory evoked P300 potentials are more sensitive than psychometric testing alone.

Rationale and Objectives: The authors evaluate a new flat-panel x-ray detector (FD) with respect to foreign body detection and reduction of radiation dose compared with screen-film radiography., Methods: Flat-panel x-ray detector is based on amorphous silicon technology and uses a 1 k x 1 k photo-detector matrix with a pixel size of 143 x 143 microns and 12-bit digital output. A thallium-dotted cesium iodide scintillation layer converts x-rays into light. An ex vivo experimental model was used to determine the detectability of foreign bodies. Foreign bodies with varying sizes were examined: glass with and without addition of lead, bone, aluminium, iron, copper, gravel fragments, and graphite. Four hundred observation fields were examined using conventional radiography (speed, 400; system dose: 2.5 microGy) as well as FD with a simulated speed of 400, 800, 1200, and 1600, corresponding to a detector dose of 2.5 microGy, 1.25 microGy, 0.87 microGy, and 0.625 microGy, respectively. Four independent radiologists performed receiver operating characteristic analysis of 8000 observations., Results: Flat-panel x-ray detector with a simulated speed of 400 was significantly superior (P = 0.012) to screen-film radiography (speed, 400). At a simulated speed of 800 and 1200 FD yielded results equivalent to screen-film radiography. Flat-panel x-ray detector was significantly inferior to screen-film radiography at a simulated speed of 1600 (P = 0.012)., Conclusions: Flat-panel x-ray detector technology allows significant reduction in radiation dose compared with screen-film radiography without loss of diagnostic accuracy.

Hepatic encephalopathy is a common problem in cirrhosis. The pathogenesis of this complication of advanced liver disease still remains unclear. Magnetic resonance spectroscopy was used to assess prospectively cerebral metabolism in 51 patients with histologically proven cirrhosis (Child-Pugh classes A, B, and C, 18, 18, and 15, respectively) and 36 healthy volunteers. According to the results of psychometric tests, overt hepatic encephalopathy, subclinical encephalopathy, and no encephalopathy were found in 14, 21, and 16 patients, respectively. Myoinositol/creatine ratios in gray (.36 +/- .17) and white (.35 +/- .22) matter voxel were reduced significantly (P < .0001) in cirrhotic patients compared with healthy volunteers (gray matter, .51 +/- .11; white matter, .64 +/- .16). In addition, patients showed a significant reduction (P = .024) in white matter choline/creatine ratio (.77 +/- .27) compared with controls (.92 +/- .25), and glutamine/glutamate level was elevated in cirrhotic patients compared with controls (gray matter, P < .0001; white matter, P = .036). Changes in cerebral myoinositol and glutamine/glutamate levels correlated significantly with the severity of hepatic encephalopathy (P < .0001). However, these metabolic alterations were also detected in patients without hepatic encephalopathy (normal psychometric test results). N-acetyl aspartate/creatine ratios did not differ between patients and controls. Magnetic resonance imaging detected bright basal ganglia in 37 patients, which correlated significantly with portal-systemic shunting and elevation of glutamine/glutamate, but not with the degree of hepatic encephalopathy. In conclusion, magnetic resonance imaging and spectroscopy showed that alterations of cerebral metabolism are common in patients with cirrhosis, even without evidence of clinical or subclinical hepatic encephalopathy.

Purpose: To analyze metabolic changes in the brain of patients undergoing dialysis., Materials and Methods: Sixteen patients undergoing hemodialysis, 10 patients undergoing continuous ambulatory peritoneal dialysis (CAPD), and 42 healthy volunteers underwent magnetic resonance (MR) spectroscopy and MR imaging. Spectra were obtained from one occipital gray matter voxel and one parietal white matter voxel. Changes in N-acetylaspartate (NAA), choline (Cho), myo-inositol and glycine (Myo), and creatine (Cr) were analyzed and the results presented as ratios, with Cr as the reference., Results: Three abnormalities were observed in the spectra of the hemodialysis patients: (a) significant elevation of the Cho/Cr ratio in gray matter, (b) significant elevation of the Myo/Cr ratio in gray matter, and (c) significant reduction of the NAA/Cr ratio in gray and white matter. The strongest metabolic alterations were found in cortical gray matter. In CAPD patients, only gray matter Cho/Cr ratio was significantly elevated. An increased frequency of focal white matter lesions was observed on MR images in the dialysis patients., Conclusion: Proton MR spectroscopy is useful for in vivo monitoring of metabolic alterations in the brain due to chronic dialysis.

The role carbohydrate moieties play in determining the structure and energetics of glycolipid model membranes has been investigated by small- and wide-angle X-ray scattering, differential scanning densitometry (DSD), and differential scanning microcalorimetry (DSC). The dependence of a variety of thermodynamic and structural parameters on the stereochemistry of the OH groups in the pyranose ring and on the size of the sugar head group has been studied by using an homologous series of synthetic stereochemically uniform glyceroglycolipids having glucose, galactose, mannose, maltose, or trimaltose head groups and saturated ether-linked alkyl chains with 10, 12, 14, 16, or 18 carbon atoms per chain. The combined structural and thermodynamic data indicate that stereochemical changes of a single OH group in the pyranose ring can cause dramatic alterations in the stability and in the nature of the phase transitions of the membranes. The second equally important determinant of lipid interactions in the membrane is the size of the head group. A comparison of lipids with glucose, maltose, or trimaltose head groups and identical hydrophobic moieties has shown that increasing the size of the neutral carbohydrate head group strongly favors the bilayer-forming tendency of the glycolipids. These experimental results provide a verification of the geometric model advanced by Israelachvili et al. (1980) [Israelachvili, J. N., Marcelja, S., & Horn, R. G. (1980) Q. Rev. Biophys. 13, 121-200] to explain the preferences lipids exhibit for certain structures. Generally galactose head groups confer highest stability on the multilamellar model membranes as judged on the basis of the chain-melting transition. This is an interesting aspect in view of the fact that galactose moieties are frequently observed in membranes of thermophilic organisms. Glucose head groups provide lower stability but increase the number of stable intermediate structures that the corresponding lipids can adopt. Galactolipids do not even assume a stable intermediate L alpha phase for lipids with short chain length but perform only Lc----HII transitions in the first heating. The C2 isomer, mannose, modifies the phase preference in such a manner that only L beta----HII changes can occur. Maltose and trimaltose head groups prevent the adoption of the HII phase and permit only L beta----L alpha phase changes. The DSD studies resulted in a quantitative estimate for the volume change associated with the L alpha----HII transition of 14-Glc. The value of delta v = 0.005 mL/g supports the view that the volume difference between L alpha and HII is minute.(ABSTRACT TRUNCATED AT 400 WORDS)

15N and 13C CPMAS spectra of composted plants are presented. The plants (L. rigidium and Zea mays) were grown in 15N enriched medium and fermented for several months until an approx. 80% of the dry matter was lost. In all 15N spectra the secondary amide/peptide peaks at 87 ppm contributes more than 80% of the total intensity. No new 15N peaks are formed during the fermentation process. Older attempts to assign a significant fraction of humic acid nitrogen to heteroaromatic structures formed in the fermentation process are thus most probably wrong.

The sulphated glycoprotein SSG 185 is the monomeric precursor of a highly aggregated structural element in the extracellular matrix of the multicellular green alga Volvox carteri. A phosphodiester of arabinose was isolated from a saccharide fragment of SSG 185. The structure of this phosphodiester was investigated by methylation analysis, 13C-NMR, photometric methods and enzymatic assays and identified as D-Araiota-5-phospho-5-D-Araiota. The function of this phosphodiester bridge as a crosslink of different carbohydrate chains in SSG 185 is discussed.