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  • 1
    Electronic Resource
    Electronic Resource
    Laser induced visual pigment conversions in fly photoreceptors measured in vivo (1983)
    Springer
    European biophysics journal 9 (1983), S. 299-307 
    Details
    ISSN: 1432-1017
    Keywords: Fly photoreceptors ; Visual pigment ; Intermediates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The photochemical cycle of fly visual pigment was studied in vivo with laser methods. Two pulsed dye lasers were used, one delivering the visual pigment converting flash and the other testing the pigment state after a variable interval. Transmission through the rhabdomeres was measured in the eye of blowfly Calliphora erythrocephala. It followed that rhodopsin R490 converts into metarhodopsin M580 via two intermediates, with time constants of 700 ns and 80 Μs respectively. In the reverse pathway, i.e. the photoconversion of metarhodopsin into rhodopsin, an intermediate decaying with a time constant of 4 Μs was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00535665
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  • 2
    Electronic Resource
    Electronic Resource
    Positron emission tomographical studies of 1-11C-acetoacetate, 2-18F-fluoro-deoxy-D-glucose, and L-1-11C-tyrosine uptake by cat brain with an experimental lesion (1989)
    Springer
    Acta neurochirurgica 99 (1989), S. 166-172 
    Details
    ISSN: 0942-0940
    Keywords: Positron emission tomography ; 18F-fluorodeoxyglucose ; ketone bodies ; 11C-tyrosine ; brain oedema ; blood-brain barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In cat brain with a freezing injury, the uptake of 1-11C-acetoacetate (11C-ACAC), 2-18F-fluorodeoxy-D-glucose (18FDG), and L-1-11C-tyrosine (11C-TYR) was monitored by positron emission tomography following intravenous administration of the tracers, at 1 day and 1–3 weeks after the injury. The development and further course of the cold-induced oedema was monitored by magnetic resonance imaging. In the fresh (1 day old) lesion there was increased uptake of11C-ACAC, probably due to release of the restrictive influence of the blood-brain barrier upon passage of the substance into brain. The uptake of18FDG, which normally occurs by carrier-mediated transport at the barrier, was decreased in the fresh lesion, probably as a result of damage of the carrier mechanism. In the 3 week old lesion18FDG uptake was still reduced, and11C-ACAC uptake was still increased, although barrier function to Evans blue had recovered. It is suggested, that the increased11C-ACAC uptake in the chronic lesion bears upon the proliferation of macrophages and reactive glial cells in the lesion. This is supported by the increased uptake of11C-TYR in the 2 weeks old lesion, while in the fresh lesion11C-TYR uptake was unchanged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01402328
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  • 3
    Electronic Resource
    Electronic Resource
    On the principles underlying the diagnosis of brain tumours — A survey article (1995)
    Springer
    Acta neurochirurgica 135 (1995), S. 1-11 
    Details
    ISSN: 0942-0940
    Keywords: Brain tumour ; brain oedema ; blood brain barrier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A survey is given of the principles underlying the diagnosis of brain tumours. Traditionally diagnosis and localization of brain tumours have been based upon morphological criteria. Currently unsurpassed levels in imaging of anatomical details and topographical relations by the techniques of computed tomography (CT) and magnetic resonance imaging (MRI) have been achieved. The techniques of positron emission tomography (PET) and of magnetic resonance spectroscopy (MRS), which depict also metabolic and blood flow aspects, provide a refinement of our knowledge on the metabolism, structure and pathophysiological relations of a tumour to the surrounding parenchyma. Recent advances in the recording of function-related changes of the cerebral electro-magnetic field allow a better definition of critical functional areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02307407
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  • 4
    Electronic Resource
    Electronic Resource
    A study on peritumoural brain oedema around meningiomas by CT and MRI scanning (1993)
    Springer
    Acta neurochirurgica 125 (1993), S. 41-46 
    Details
    ISSN: 0942-0940
    Keywords: Brain oedema ; meningioma ; CT ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary There is a great variability in the amount of peritumoural brain oedema accompanying meningiomas. In a previous study it was found that the degree of brain oedema in the white matter around meningiomas correlated with disruption of the layers (especially the cerebral cortex), which separate the tumour from the white matter, as well as with the size and histological subtype of the tumour. In the present study comprising 9 meningiomas, the volume of oedema was calculated by integration of the cross-sectional oedematous areas on serial MRI slices. The volume of oedema was zero in 3 cases and ranged from 11 to 176.4 ml in the other 6 cases. The MRI-scans also showed disruption of the cortex in all cases, ranging from slight to severe. T1 and T2 measurements were made at the level of maximum extension, using a mixed sequence at a field strength of 1.5 T. From the T2 values tissue water content in % was calculated using the equations: WC=39.36/(R2 + 37.2) for cortex, and WC=29.63/(R2 + 27.8) for white matter. These had been obtained by correlating water content with relaxation rates, measured in vitro on human brain autopsy specimens which were subjected to hydration with distilled water or dehydration by hyperosmolar solutions. Mean water content amounted to 82.53% for normal cortex, 74.72% for normal white matter, and 84.59% for oedematous white matter around the tumour. On the assumption that the spread of contrast agent marks the advancement of the front of oedema produced by the tumour, CT-studies were made before, and at 1 1/2, 3 and 6h after contrast infusion. The increase in diameter of the contrast-stained area on the CT-scan allows calculation of the excess of oedema production per unit tumour volume. Of 6 tumours with oedema (mean peritumoural water content of 91% and mean volume of oedema of 69.2 ml) the production excess at the steady-state was 0.18–1.08 ml/h/cm3 tumour volume, whereas 3 tumours without associated oedema had a production excess of 0.03–0.12 ml/h/cm3. Moreover, penetration of the cortex seems to constitute a separate factor determinig the spread of oedema.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01401826
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  • 5
    Electronic Resource
    Electronic Resource
    Localised proton spectroscopy and spectroscopic imaging in cerebral gliomas, with comparison to positron emission tomography (1995)
    Springer
    Neuroradiology 37 (1995), S. 198-206 
    Details
    ISSN: 1432-1920
    Keywords: Key words Gliomas ; Proton magnetic resonance spectroscopy ; Proton magnetic resonance spectroscopic imaging ; Brain oedema ; Positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In 32 patients with gliomas, one- and two-dimensional proton magnetic resonance spectroscopy (1H-MRS) has been conducted, the latter allowing reconstruction of spectroscopic data into a spectroscopic image (MRSI), showing the distribution of the various metabolite concentrations over the cross-sectional plane. For lack of absolute concentrations, the measured concentrations of phosphocholine (CHOL), N -acetyl-L-aspartate (NAA), and lactate (LAC) were conventionally expressed in ratios relative to that of creatine (CREAT). Compared to normal brain tissue, an increased CHOL/CREAT ratio was found in all groups of tumours, in glioblastomas, high-, middle- and low-grade astrocytomas both at the margin and the core of the tumours, but in oligodendrogliomas only at the margin. This is consistent with an increased phosphocholine turnover in relation to membrane biosynthesis by the proliferating cells. The NAA/CREAT ratio was decreased in all groups of tumours, both in the centre and at the margin, reflecting replacement of functioning neurons by neoplastic cells. The LAC/CREAT ratio was elevated in the core of malignant gliomas, which may be the result of a prevailing glycolysis, characteristic of tumours, possibly in conjunction with hypoxia/ischaemia. In the perifocal oedema, there was neither elevation of the CHOL/CREAT ratio nor decrease of the NAA/CREAT ratio; an increased LAC/CREAT ratio therefore rather reflected ischaemia/hypoxia probably due to locally elevated pressure and compromised regional perfusion. In the normal brain, the metabolite ratios of grey matter did not differ from those of white matter. The frontal lobe and basal ganglia showed lower NAA/CREAT ratios than the other cerebral areas. In 7 patients positron emission tomography was also performed with [18F]fluoro-2-deoxy-D-glucose (18FDG) or L-[1-11C]-tyrosine (11C-TYR); the latter demonstrated a pattern of 11C-TYR uptake similar to that of CHOL elevation in the MRSI.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01578258
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  • 6
    Electronic Resource
    Electronic Resource
    11C-tyrosine position emission tomography and 1H magnetic resonance spectroscopy of the response of brain gliomas to radiotherapy (1998)
    Springer
    Neuroradiology 40 (1998), S. 103-108 
    Details
    ISSN: 1432-1920
    Keywords: Key words Gliomas ; cerebral ; Radiotherapy ; Magnetic resonance spectroscopy ; Position emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We monitored 10 patients with unresected (9) or partially resected (1) supratentorial gliomas with 11C-tyrosine position emission tomography (TYR-PET) before and after radiotherapy. TYR-PET tumour volumes were measured using a threshold technique. In seven patients the tumour volume decreased after radiotherapy, although all gliomas persisted on TYR-PET images. In eight patients the tumour protein synthesis rate (PSR) was calculated using a dynamic study protocol in combination with a PATLAK analysis. There were no changes in PSR after radiotherapy, but the PSR was calculated on the remaining tumour volume using the same threshold technique as before therapy, i. e. the decrease in tumour volume was not taken into account. In eight patients the PET data were compared with magnetic resonance spectroscopic imaging (1H-MRSI) performed simultaneously. Although there was no statistically significant correlation between TYR-PET volume changes and 1H-MRSI choline level we observed a simultaneous decrease in volume and choline in four patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050548
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  • 7
    Electronic Resource
    Electronic Resource
    Localised proton spectroscopy and spectroscopic imaging in cerebral gliomas, with comparison to positron emission tomography (1995)
    Springer
    Neuroradiology 37 (1995), S. 198-206 
    Details
    ISSN: 1432-1920
    Keywords: Gliomas ; Proton magnetic resonance spectroscopy ; Proton magnetic resonance spectroscopic imaging ; Brain oedema ; Positron emission tomography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In 32 patients with gliomas, one- and two-dimensional proton magnetic resonance spectroscopy (1H-MRS) has been conducted, the latter allowing reconstruction of spectroscopic data into a spectroscopic image (MRSI), showing the distribution of the various metabolite concentrations over the cross-sectional plane. For lack of absolute concentrations, the measured concentrations of phosphocholine (CHOL),N-acetyl-L-aspartate (NAA), and lactate (LAC) were conventionally expressed in ratios relative to that of creatine (CREAT). Compared to normal brain tissue, an increased CHOL/CREAT ratio was found in all groups of tumours, in glioblastomas, high-, middle- and low-grade astrocytomas both at the margin and the core of the tumours, but in oligodendrogliomas only at the margin. This is consistent with an increased phosphocholine turnover in relation to membrane biosynthesis by the proliferating cells. The NAA/CREAT ratio was decreased in all groups of tumours, both in the centre and at the margin, reflecting replacement of functioning neurons by neoplastic cells. The LAC/ CREAT ratio was elevated in the core of malignant gliomas, which may be the result of a prevailing glycolysis, characteristic of tumours, possibly in conjunction with hypoxia/ischaemia. In the perifocal oedema, there was neither elevation of the CHOL/CREAT ratio nor decrease of the NAA/CREAT ratio; an increased LAC/CREAT ratio therefore rather reflected ischaemia/hypoxia probably due to locally elevated pressure and compromised regional perfusion. In the normal brain, the metabolite ratios of grey matter did not differ from those of white matter. The frontal lobe and basal ganglia showed lower NAA/CREAT ratios than the other cerebral areas. In 7 patients positron emission tomography was also performed with [18F]fluoro-2-deoxy-D-glucose (18FDG) or L-[1-11C]-tyrosine (11C-TYR); the latter demonstrated a pattern of11C-TYR uptake similar to that of CHOL elevation in the MRSI.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01578258
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Ex vivo magnetic resonance imaging of pretransplant human donor liver (1994)
    Springer
    Transplant international 7 (1994), S. 272-277 
    Details
    ISSN: 1432-2277
    Keywords: Liver transplantation, MRI ; MRI, pretransplant, liver Pretransplant, liver, MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Magnetic resonance imaging (MRI) was performed on 66 cold-stored human donor livers. spin echo images were obtained with a clinical whole body MRI system. Various parenchymal and vascular abnormalities were found. An unexpected finding was the abundant presence of intrahepatic air. Although the majority of parenchymal abnormalities that were found would not have precluded transplantation, the rationale of pretransplant MRI was to prevent the introduction of unidentified pathology into the recipient. Guided by the MR images, lesions in the isolated organ can be easily located for biopsy and resection. Unnecessary or inadequate therapeutic interventions after transplantation can thus be avoided. In addition, the visualization of the hepatic veins with their confluence appears to be useful in split-liver procedures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327155
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  • 9
    Electronic Resource
    Electronic Resource
    In vivo 31P magnetic resonance spectroscopy (MRS) of tender points in patients with primary fibromyalgia syndrome (1991)
    Springer
    Rheumatology international 11 (1991), S. 51-54 
    Details
    ISSN: 1437-160X
    Keywords: Primary fibromyalgia syndrome ; Tender points ; Magnetic Resonance ; Spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 31P Magnetic Resonance-Spectroscopy was performed at the site of tender points in the trapezius muscle of patients with primary fibromyalgia syndrome. Earlier, in vitro studies have reported changes in the high energy phosphate-metabolism in biopsies taken from tender points of fibromyalgia patients. The observed alterations could not be confirmed with in vivo Magnetic Resonance-Spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00291145
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  • 10
    Electronic Resource
    Electronic Resource
    Localized proton spectroscopy of inoperable brain gliomas. Response to radiation therapy (1993)
    Springer
    Journal of neuro-oncology 17 (1993), S. 27-35 
    Details
    ISSN: 1573-7373
    Keywords: human brain gliomas ; proton NMR spectroscopy ; radiation therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Within vivo 1H-MRS resonances of several metabolites were simultaneously measured in cerebral gliomas and adjacent normal brain. 15 patients with inoperable brain gliomas all histologically verified were monitored with 1H-MRS and MRI before and after radiotherapy. 11 patients were evaluable. 1H-MRS technique evolved from single volume measurements to one dimensional and two dimensional 1H spectroscopic imaging. In all patients N-acetyl-aspartate signals were decreased in tumour areas compared to the normal brain hemisphere. No recovery was seen after radiotherapy. Choline signals were increased in tumour margins of high grade gliomas and more diffusely in low grade gliomas. In 5 patients the choline resonance decreased after radiotherapy, accompanied by a shrinkage of tumour diameter on MRI. Lactate signals were present in high grade and unspecified astrocytomas and absent in most low grade gliomas. In 3 patients the lactate signal disappeared after radiotherapy. These observations indicate the feasibility of 1H-MRS in monitoring metabolic responses on radiotherapy of brain gliomas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01054271
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