This study identifies by microautoradiography activated microglia/macrophages as the main cell ty... more This study identifies by microautoradiography activated microglia/macrophages as the main cell type expressing the peripheral benzodiazepine binding site (PBBS) at sites of active CNS pathology. Quantitative measurements of PBBS expression in vivo obtained by PET and [ 11 C](R)-PK11195 are shown to correspond to animal experimental and human post-mortem data on the distribution pattern of activated microglia in inflammatory brain disease. Film autoradiography with [ 3 H](R)-PK11195, a specific ligand for the PBBS, showed minimal binding in normal control CNS, whereas maximal binding to mononuclear cells was found in multiple sclerosis plaques. However, there was also significantly increased [ 3 H](R)-PK11195 binding on activated microglia outside the histopathologically defined borders of multiple sclerosis plaques and in areas, such as the cerebral central grey matter, that are not normally reported as sites of pathology in multiple sclerosis. A similar pattern of [ 3 H](R)-PK11195 binding in areas containing activated microglia was seen in the CNS
The objective of the study has been to investigate whether cold-adapted microorganisms (CAMs) are... more The objective of the study has been to investigate whether cold-adapted microorganisms (CAMs) are metabolising hydrocarbons in situ at sub-zero temperatures. Since the summer 2001, soil temperatures and soil gas concentrations of oxygen (O 2 ) and carbon dioxide (CO 2 ) at various depths at a petroleum hydrocarbon contaminated permafrost site at Longyearbyen, Spitsbergen, have continuously been measured and compared to data from a nearby non-contaminated site. We have previously reported on unchanged microbial O 2 consumption in the active layer for about 12 days after the soil temperatures decreased below 0 8C in late October 2001 and we are now reporting on the microbial activity in the soil profile from January to September 2002. The empirical data have been compared to theoretical simulations of O 2 concentration as a function of soil depth and time from when the CAMs became active in spring until steady-state conditions were achieved in the summer. At the 0.7 m depth in the oil-plume site, microbial O 2 consumption started in the middle of April, about 45 days before the soil thawed. There was no coincidence between the microbial activation time and the thawing time of the soil. The CAMs became active at temperatures of about À6 8C, but the main degradation activity occurred at temperatures between À1 and À3 8C. When the soil thawed, the hydrocarbon degradation was probably limited by the O 2 supply. In the summer months where we expected the greatest degradation activity to occur because of positive temperatures and access to water, the degradation was limited by O 2 depletion. The overall data from this arctic permafrost site indicate that without other limiting conditions such as O 2 and 0165-232X/$ -see front matter D substrate availability, the active biodegradation period can be extended to about 6 months despite periods with sub-zero soil temperatures. D
If the universe was reionized by O and B stars in an early population of galaxies, the associated... more If the universe was reionized by O and B stars in an early population of galaxies, the associated supernovae should have enriched the universe to a mean metallicity Z¯=10-5(1+nrec), where nrec is the mean number of times that each baryon recombined during the reionization era. This is consistent with recent observations of the metallicity in the Lyα forest at z ~= 3. The mean surface brightness observable at present from the galaxies that produced these heavy elements, in the rest-frame wavelengths 1216 Å < λ <~ 2500 Å, should be ~10-6(Z¯/10-4)(Ωbh2/0.02) photons cm-2 s-1 arcsec-2. Most of this radiation should be emitted at z > 5, before reionization was complete. These high-redshift galaxies may be detectable in near-infrared photometric surveys, identifying them via the Gunn-Peterson trough (analogous to the use of the Lyman limit cutoff to search for galaxies at z ~ 3, where the Lyα forest blanketing is smaller). Their spectrum may also be characterized by a strong Lyα emission line. However, the spectra of galaxies seen behind intervening gas that is still neutral should show the red damping wing of the Gunn-Peterson trough, with a predictable profile that obstructs part of the Lyα emission. The low-mass galaxies formed before reionization might constitute a distinctive population; we discuss the signature that this population could have in the faint number counts. Although most of these galaxies should have merged into larger ones, those that survived to the present could be dwarf spheroidals.
This study identifies by microautoradiography activated microglia/macrophages as the main cell ty... more This study identifies by microautoradiography activated microglia/macrophages as the main cell type expressing the peripheral benzodiazepine binding site (PBBS) at sites of active CNS pathology. Quantitative measurements of PBBS expression in vivo obtained by PET and [ 11 C](R)-PK11195 are shown to correspond to animal experimental and human post-mortem data on the distribution pattern of activated microglia in inflammatory brain disease. Film autoradiography with [ 3 H](R)-PK11195, a specific ligand for the PBBS, showed minimal binding in normal control CNS, whereas maximal binding to mononuclear cells was found in multiple sclerosis plaques. However, there was also significantly increased [ 3 H](R)-PK11195 binding on activated microglia outside the histopathologically defined borders of multiple sclerosis plaques and in areas, such as the cerebral central grey matter, that are not normally reported as sites of pathology in multiple sclerosis. A similar pattern of [ 3 H](R)-PK11195 binding in areas containing activated microglia was seen in the CNS
The objective of the study has been to investigate whether cold-adapted microorganisms (CAMs) are... more The objective of the study has been to investigate whether cold-adapted microorganisms (CAMs) are metabolising hydrocarbons in situ at sub-zero temperatures. Since the summer 2001, soil temperatures and soil gas concentrations of oxygen (O 2 ) and carbon dioxide (CO 2 ) at various depths at a petroleum hydrocarbon contaminated permafrost site at Longyearbyen, Spitsbergen, have continuously been measured and compared to data from a nearby non-contaminated site. We have previously reported on unchanged microbial O 2 consumption in the active layer for about 12 days after the soil temperatures decreased below 0 8C in late October 2001 and we are now reporting on the microbial activity in the soil profile from January to September 2002. The empirical data have been compared to theoretical simulations of O 2 concentration as a function of soil depth and time from when the CAMs became active in spring until steady-state conditions were achieved in the summer. At the 0.7 m depth in the oil-plume site, microbial O 2 consumption started in the middle of April, about 45 days before the soil thawed. There was no coincidence between the microbial activation time and the thawing time of the soil. The CAMs became active at temperatures of about À6 8C, but the main degradation activity occurred at temperatures between À1 and À3 8C. When the soil thawed, the hydrocarbon degradation was probably limited by the O 2 supply. In the summer months where we expected the greatest degradation activity to occur because of positive temperatures and access to water, the degradation was limited by O 2 depletion. The overall data from this arctic permafrost site indicate that without other limiting conditions such as O 2 and 0165-232X/$ -see front matter D substrate availability, the active biodegradation period can be extended to about 6 months despite periods with sub-zero soil temperatures. D
If the universe was reionized by O and B stars in an early population of galaxies, the associated... more If the universe was reionized by O and B stars in an early population of galaxies, the associated supernovae should have enriched the universe to a mean metallicity Z¯=10-5(1+nrec), where nrec is the mean number of times that each baryon recombined during the reionization era. This is consistent with recent observations of the metallicity in the Lyα forest at z ~= 3. The mean surface brightness observable at present from the galaxies that produced these heavy elements, in the rest-frame wavelengths 1216 Å < λ <~ 2500 Å, should be ~10-6(Z¯/10-4)(Ωbh2/0.02) photons cm-2 s-1 arcsec-2. Most of this radiation should be emitted at z > 5, before reionization was complete. These high-redshift galaxies may be detectable in near-infrared photometric surveys, identifying them via the Gunn-Peterson trough (analogous to the use of the Lyman limit cutoff to search for galaxies at z ~ 3, where the Lyα forest blanketing is smaller). Their spectrum may also be characterized by a strong Lyα emission line. However, the spectra of galaxies seen behind intervening gas that is still neutral should show the red damping wing of the Gunn-Peterson trough, with a predictable profile that obstructs part of the Lyα emission. The low-mass galaxies formed before reionization might constitute a distinctive population; we discuss the signature that this population could have in the faint number counts. Although most of these galaxies should have merged into larger ones, those that survived to the present could be dwarf spheroidals.
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