Schlagwort: temperature
Study: How do plants adapt to cold ambient temperatures and frost?
New study warns: global warming and invasive species threaten seagrass meadows in the Mediterranean
Zebrafish Navigate to Find Their Comfortable Temperature
Deciphering nature’s climate shield: Plant diversity stabilises soil temperature
Heat Sensor Protects the Venus Flytrap From Fire
Roots are capable of measuring heat on their own, new study shows
6.1 million data points prove the influence of climate on global fungal occurrence
Cold is beneficial for healthy aging
Global study by the University of Bayreuth shows influences of climate change on terrestrial ecosystems
Temperature perception influences protein degradation and lifespan
The last 12,000 years show a more complex climate history than previously thought
Worldwide assessment of protected areas
An innovative imaging technique for dynamic optical nanothermometry
At what temperature the weather becomes a problem
Heavy water makes biological clocks tick more slowly – How to Retard Time for Cells
Extreme CO2 greenhouse effect heated up the young Earth
Novel hydrogel carriers for anti-cancer drugs offer new hope for cancer treatment
Implications of quantum metabolism and natural selection for the origin of cancer cells and tumor progression
Energy transfer in material solids is driven primarily by differences in intensive thermodynamic quantities such as pressure and temperature. The crucial observation in quantum-theoretical models was the consideration of the heat capacity as associated with the vibrations of atoms in a crystalline solid. However, living organisms are essentially isothermal. Because of very little differences in temperature between different parts of a cell it is assumed that energy flow in living organisms is mediated by differences in the turnover time of various metabolic processes in the cell, which occur in cyclical fashion. It has been shown that the cycle time of these metabolic processes is related to the metabolic rate, that is the rate at which the organism transforms the free energy of whatever source into metabolic work, maintenance of constant temperature and structuraland functional organization of the cells. Quantum Metabolism exploits the methodology of the quantum theory of solids to provide a molecular level which derives new rules relating metabolic rate and body size.
Einstein A (1920), Schallausbreitung in teilweise dissozieirten Gasen
Einstein A (1924) Quantentheorie des einatomigen, idealen Gases
Three-dimensional super-resolution microscopy of the inactive X chromosome territory reveals a collapse of its active nuclear compartment harboring distinct Xist RNA foci
Daniel Smeets, Yolanda Markaki, Volker J Schmid, Felix Kraus, Anna Tattermusch, Andrea Cerase, Michael Sterr, Susanne Fiedler, Justin Demmerle, Jens Popken, Heinrich Leonhardt, Neil Brockdorff, Thomas Cremer1, Lothar Schermelleh and Marion Cremer
Abstract
Background
A Xist RNA decorated Barr body is the structural hallmark of the compacted inactive X territory in female mammals. Using super-resolution three-dimensional structured illumination microscopy (3D-SIM) and quantitative image analysis, we compared its ultrastructure with active chromosome territories (CTs) in human and mouse somatic cells, and explored the spatio-temporal process of Barr body formation at onset of inactivation in early differentiating mouse embryonic stem cells (ESCs).
Results
We demonstrate that all CTs are composed of structurally linked chromatin domain clusters (CDCs). In active CTs the periphery of CDCs harbors low-density chromatin enriched with transcriptionally competent markers, called the perichromatin region (PR). The PR borders on a contiguous channel system, the interchromatin compartment (IC), which starts at nuclear pores and pervades CTs. We propose that the PR and macromolecular complexes in IC channels together form the transcriptionally permissive active nuclear compartment (ANC). The Barr body differs from active CTs by a partially collapsed ANC with CDCs coming significantly closer together, although a rudimentary IC channel system connected to nuclear pores is maintained. Distinct Xist RNA foci, closely adjacent to the nuclear matrix scaffold attachment factor-A (SAF-A) localize throughout Xi along the rudimentary ANC. In early differentiating ESCs initial Xist RNA spreading precedes Barr body formation, which occurs concurrent with the subsequent exclusion of RNA polymerase II (RNAP II). Induction of a transgenic autosomal Xist RNA in a male ESC triggers the formation of an ‘autosomal Barr body’ with less compacted chromatin and incomplete RNAP II exclusion.
Conclusions
3D-SIM provides experimental evidence for profound differences between the functional architecture of transcriptionally active CTs and the Barr body. Basic structural features of CT organization such as CDCs and IC channels are however still recognized, arguing against a uniform compaction of the Barr body at the nucleosome level. The localization of distinct Xist RNA foci at boundaries of the rudimentary ANC may be considered as snap-shots of a dynamic interaction with silenced genes. Enrichment of SAF-A within Xi territories and its close spatial association with Xist RNA suggests their cooperative function for structural organization of Xi.
The carcinogenic effect of various multi-walled carbon nanotubes (MWCNTs) after intraperitoneal injection in rats
Susanne Rittinghausen, Anja Hackbarth, Otto Creutzenberg, Heinrich Ernst, Uwe Heinrich, Albrecht Leonhardt and Dirk Schaudien
Abstract
Background
Biological effects of tailor-made multi-walled carbon nanotubes (MWCNTs) without functionalization were investigated in vivo in a two-year carcinogenicity study. In the past, intraperitoneal carcinogenicity studies in rats using biopersistent granular dusts had always been negative, whereas a number of such studies with different asbestos fibers had shown tumor induction. The aim of this study was to identify possible carcinogenic effects of MWCNTs. We compared induced tumors with asbestos-induced mesotheliomas and evaluated their relevance for humans by immunohistochemical methods.
Methods
A total of 500 male Wistar rats (50 per group) were treated once by intraperitoneal injection with 109 or 5 × 109 WHO carbon nanotubes of one of four different MWCNTs suspended in artificial lung medium, which was also used as negative control. Amosite asbestos (108 WHO fibers) served as positive control. Morbid rats were sacrificed and necropsy comprising all organs was performed. Histopathological classification of tumors and, additionally, immunohistochemistry were conducted for podoplanin, pan-cytokeratin, and vimentin to compare induced tumors with malignant mesotheliomas occurring in humans.
Results
Treatments induced tumors in all dose groups, but incidences and times to tumor differed between groups. Most tumors were histologically and immunohistochemically classified as malignant mesotheliomas, revealing a predominantly superficial spread on the serosal surface of the abdominal cavity. Furthermore, most tumors showed invasion of peritoneal organs, especially the diaphragm. All tested MWCNT types caused mesotheliomas. We observed highest frequencies and earliest appearances after treatment with the rather straight MWCNT types A and B. In the MWCNT C groups, first appearances of morbid mesothelioma-bearing rats were only slightly later. Later during the two-year study, we found mesotheliomas also in rats treated with MWCNT D – the most curved type of nanotubes. Malignant mesotheliomas induced by intraperitoneal injection of different MWCNTs and of asbestos were histopathologically and immunohistochemically similar, also compared with mesotheliomas in man, suggesting similar pathogenesis.
Conclusion
We showed a carcinogenic effect for all tested MWCNTs. Besides aspect ratio, curvature seems to be an important parameter influencing the carcinogenicity of MWCNTs.
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