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  • 1
    Electronic Resource
    Electronic Resource
    Tumour-like thallium-201 accumulation in brain infarcts, an unexpected finding on single-photon emission tomography (1994)
    Springer
    European journal of nuclear medicine 21 (1994), S. 191-195 
    Details
    ISSN: 1619-7089
    Keywords: Thallium ; Technetium ; Single-photon emission tomography ; Regional cerebral blood flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Thallium-201 brain single-photon emission tomography (201Tl-SPET) is widely used to detect viable tumour tissue with increased metabolic activity. When reperfusion takes place early in cerebrovascular lesions of embolic origin, the presence of tissue areas with increased regional blood flow and preserved metabolic activity can also be assumed. In the present study our purpose was to investigate whether or not foci of 201Tl accumulation occur in reperfused areas with sustained morphological integrity indicated by computed tomography (CT) scans not showing hypodensity in the acute or subacute period.In 16 stroke patients with possible cortical embolic infarction, dual 201Tl and technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) SPET was performed in both the acute and the subacute period. 99mTc-HMPAO SPET was performed to detect reperfusion. Follow-up CT scans from the same period were also available. In five cases 99mTc-HMPAO SPET ruled out reperfusion and 201Tl SPET was also negative. In four cases 99mTc-HMPAO studies indicated reperfusion early in the acute phase (24–72 h), and comparative CT, without showing hypodensity in the acute or subacute period, also favoured the possibility of sustained metabolic activity. In these cases 201Tl SPET was negative in both the acute and the subacute period. In seven cases CT already showed necrosis in 99mTc-HMPAO hypoperfused areas in the acute period, with negative results on corresponding 201Tl SPET. Later reperfusion occurred in the subacute period (8–14 days) as indicated by 99mTc-HMPAO SPET, at which time an unexpected focal accumulation of 201Tl was detected. We cannot give any explanation for the findings, but further studies might clarify the matter and improve our knowledge of the precise mechanism of 201Tl uptake under different conditions. Until then the phenomenon should be borne in mind as a possible pitfall when assessing tissue viability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188664
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  • 2
    Electronic Resource
    Electronic Resource
    Comparative EPR and thermoluminescence study of anoxic photoinhibition in Photosystem II particles (1995)
    Springer
    Photosynthesis research 46 (1995), S. 213-218 
    Details
    ISSN: 1573-5079
    Keywords: Photoinhibition ; Photosystem II ; quinone-iron complex ; electron paramagnetic resonance (EPR) ; thermoluminescence (TL)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosystem II particles were exposed to 800 W m−2 white light at 20 °C under anoxic conditions. The Fo level of fluorescence was considerably enhanced indicating formation of stable-reduced forms of the primary quinone electron acceptor, QA. The Fm level of fluorescence declined only a little. The g=1.9 and g=1.82 EPR forms characteristic of the bicarbonate-bound and bicarbonate-depleted semiquinone-iron complex, QA −Fe2+, respectively, exhibited differential sensitivity against photoinhibition. The large g=1.9 signal was rapidly diminished but the small g=1.82 signal decreased more slowly. The S2-state multiline signal, the oxygen evolution and photooxidation of the high potential form of cytochrome b-559 were inhibited approximately with the same kinetics as the g=1.9 signal. The low potential form of oxidized cytochrome b-559 and Signal IIslow arising from TyrD + decreased considerably slower than the g=1.9 semiquinone-iron signal. The high potential form of oxidized cytochrome b-559 was diminished faster than the low potential form. Photoinhibition of the g=1.9 and g=1.82 forms of QA was accompanied with the appearance and gradual saturation of the spin-polarized triplet signal of P 680. The amplitude of the radical signal from photoreducible pheophytin remained constant during the 3 hour illumination period. In the thermoluminescence glow curves of particles the Q band (S2QA − charge recombination) was almost completely abolished. To the contrary, the C band (TyrD +QA − charge recombination) increased a little upon illumination. The EPR and thermoluminescence observations suggest that the Photosystem II reaction centers can be classified into two groups with different susceptibility against photoinhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020433
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    Paper (German National Licenses)
    Fulltext
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