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31.
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On the occasion of the first international workshop on systems radiation biology we review the role of cell renewal systems
in maintaining the integrity of the mammalian organism after irradiation. First, 11 radiation emergencies characterized by
chronic or protracted exposure of the human beings to ionizing irradiation were “revisited”. The data provide evidence to
suggest that at a daily exposure of about 10–100 mSv, humans are capable of coping with the excess cell loss for weeks or
even many months without hematopoietic organ failure. Below 10 mSv/day, the organisms show some cellular or subcellular indicators
of response. At dose rates above 100 mSv/day, a progressive shortening of the life span of the irradiated organism is observed.
To elucidate the mechanisms relevant to tolerance or failure, the Megakaryocyte–thrombocyte cell renewal system was investigated.
A biomathematical model of this system was developed to simulate the development of thrombocyte concentration as a function
of time after onset of chronic radiation exposure. The hematological data were taken from experimental chronic irradiation
studies with dogs at the Argonne National Laboratory, USA. The results of thrombocyte response patterns are compatible with
the notion of an “excess cell loss” (compared to the steady-state) in all proliferative cell compartments, including the stem
cell pool. The “excess cell loss” is a function of the daily irradiation dose rate. Once the stem cell pool is approaching
an exhaustion level, a “turbulence region” is reached. Then it takes a very little additional stress for the system to fail.
We conclude that in mammalian radiation biology (including radiation medicine), it is important to understand the physiology
and pathophysiology of cell renewal systems in order to allow predicting the development of radiation induced lesions. 相似文献
33.
Deciduous lower premolars (milk teeth) of the Eocene artiodactyl family Cebochoeridae possess accessory denticles and are
remarkably similar to both deciduous and adult teeth of the cetacean family Basilosauridae, suggesting that morphological
characters of juvenile dentitions are important to understanding the phylogenetic origin of whales and morphological transitions
in the cetartiodactyl lineage. Incorporation of these new characters into a larger phylogenetic analysis of morphological
characters of artiodactyls, mesonychids, and basal and recent whales supports a monophyletic Cetartiodactyla, but does not
directly support a whale–hippo relationship. However, the presence of accessory denticles on some artiodactyl dentitions weakens
the morphological support for a monophyletic Artiodactyla, suggesting either that whales and cebochoerids may be more closely
related than had been thought, or that cebochoerids share a developmental pathway with cetaceans. 相似文献
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35.
Th. Boveri 《Development genes and evolution》1915,41(2):264-311
Ohne Zusammenfassung 相似文献
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Theodor Frhr. v. Brand 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1928,8(3-4):613-624
Zusammenfassung Der Ätherextrakt von Fasciola hepatica setzt sich nach meinen Untersuchungen folgendermaßen zusammen (in abgerundeten Prozentzahlen: Lecithin und andere Phosphatide. 30% Gesättigte Fettsäuren als Glyzeride vorliegend. 4,, Ungesättigte Fettsäuren als Glyzeride vorliegend' 12,, Glyzerin 2,, Cholesterin. 19,, Fettsäuren in Seifenform vorliegend 15,, Asche aus der Seife 1,, Nicht näher charakterisierte Lipoide. 17 相似文献