Nachweis von3H-Digitoxin in der Herzmuskelzelle

Summary In autoradiographs of intraventricular muscle bundles of beef heart, tritiated digitoxine is found outside the membrane and inside the muscle cell at the moment of maximal inotropic action.     

Patterns of neuroglial proliferation in spinal cord white matter following exposure to ionizing radiation

Summary X-irradiation temporarily decreases the proliferative activity of neuroglia in immature rat spinal cord. Later, the proliferative activity in these irradiated regions surpasses that noted in control rats. Areas adjacent to the irradiated region have a greater than normal percentage of labelled neuroglia and may also be a source for neuroglia which re-populate the irradiated zone.Acknowledgments. Sincere thanks to Ms Jane Leiting for her assistance in doing the cell counts and to Mr Napoleon Phillips for preparing the autoradiographs. Supported by USPHS grant NS 04761.     

Bestimmung der Zahl aktiver Zentren der Acetylcholinesterase in motorischen Endplatten

Summary ³²P or¹⁴C-labelled diisopropyl-fluoro-phosphate (DFP) was bound to endplates of mouse diaphragms by incubation. The number of molecules was determined by densitometric measurement of autoradiographs. One endplate contains 2.4·10⁷ active centres for acetylcholine, blocked by DFP. The turnover time for acetylcholine is very short: 15µsec.     

Autoradiographische Untersuchungen zur Frage des Eiweißstoffwechsels in den lymphoretikulären Organen

Summary The size of protein-metabolism in lympho-reticular organs (spleen and lymph-nodes) is examined by means of autoradiography. Mice, rats and rabbits were fed with S³⁵-labelled thioamino-acids. The density of the silver grains in the autoradiographs allows a statement about the size of proteinmetabolism in relation to thioaminoacids. From this point of view the problem of the germinal centres and marginal zones of theMalpighian follicles, the «Basophileninseln» in the red pulp and the endothel of the splenic sinuses is discussed.     

Zur klinischen Bedeutung des autoradiographischen Verfahrens bei der Verwendung von kurzlebigen künstlichen radioaktiven Isotopen (Autoorganographie,Autoangiographie)

Summary The author demonstrates the possibility to realize on living human individuals big sizeautoradiographs afterintravenous injections of an artificial radioactive isotope of a relatively short activity. Strong preparations (100 millicuries) of radiozinc (Zn⁶³) in form of soluble oxide have been employed. These injections were performed on two patients suffering from general carcinosis. The humanauto-organographs (autohepatographs, automammographs, autonephrographs, etc.), as well as theautoangiographs of the blood vessels of the skin and the subcutaneous tissues, thus realized for the first time, are quite interesting. The possibilities of a clinical utilization of such autoradiographs are briefly discussed.     

DNA damage repair and transcription

DNA mutations and aberrations are a problem for all forms of life. Eukaryotes specifically have developed ways of identifying and repairing various DNA mutations in a complex and refractory chromatin environment. The chromatin structure is much more than a packaging unit for DNA; it is dynamic. Cells utilize and manipulate chromatin for gene regulation, genome organization and maintenance of genome integrity. Once a DNA aberration has occurred, the various DNA repair machineries interact with chromatin proteins, such as the histone variant H2A.X, and chromatin remodeling machines of the SWI/SNF family to gain access and repair the lesion in a timely manner. Recent studies have thus begun to address the roles of chromatin proteins in DNA repair as well as to dissect the functions of DNA repair machinery in vitro on more physiological, nucleosomal templates.     

Emerging connections between DNA methylation and histone acetylation

Modifications of both DNA and chromatin can affect gene expression and lead to gene silencing. Evidence of links between DNA methylation and histone hypoacetylation is accumulating. Several proteins that specifically bind to methylated DNA are associated with complexes that include histone deacetylases (HDACs). In addition, DNA methyltransferases of mammals appear to interact with HDACs. Experiments with animal cells have shown that HDACs are responsible for part of the repressive effect of DNA methylation. Evidence was found in Neurospora that protein acetylation can in some cases affect DNA methylation. The available data suggest that the roles of DNA methylation and histone hypoacetylation, and their relationship with each other, can vary, even within an organism. Some open questions in this emerging field that should be answered in the near future are discussed.     

DNA damage repair and transcription

Silencing of DNA repair genes plays a critical role in the development of the cancer because these genes, functioning normally, would prevent the accumulation of mutations leading to carcinogenesis. Epigenetic gene silencing is an alternative mechanism to genetic gene aberration, inactivating those genes in cancer. DNA methylation and histone modification are the major factors for epigenetic regulation of gene expression. Here, we describe recent advances in understanding of epigenetic silencing of DNA repair genes and their epigenetic mechanisms involving DNA methylation and histone modification.     

Über die Verwendung von künstlichen radioaktiven Isotopen zur Erzielung von lokalisierten biologischen Strahlenwirkungen

Summary Intratumoral injection of an artificial radioactive isotope (radiozinc), suspended in a solution of pectin: The author has previously reported on a method, which consists in the utilization of an artificial radioactive isotope for the production oflocalized biological radiation effects, by means of intraperitoneal injections of radiozinc (Zn⁶³) suspended in a suitably prepared solution of pectin. This procedure was applied to a small number of cases of cancer of the ovaries, with severe peritoneal extension, and yielded rather interesting therapeutic effects in these particularly bad conditions. Evidently this method can be applied also to malignant fumors of cavitary organs, such as the urinary bladder etc.The author investigated further, whether this procedure would also be suitable for interstitial radiotherapy, as previously presumed. Subcutaneous and intramuscular injections of the same suspension of radiozinc in pectin were thus performed on rabbits and were not followed by any diffusion of radioactivity outside the injected areas, as shown both by autoradiographs and controls of blood specimens with a counter. For the purpose of preliminary clinical investigation two cases of extended cancer of the uterine cervix recieved injections of 15 millicuries of radiozinc suspended in pectin within the tumor and its immediate surroundings (these cases were also submitted to the usual X-ray and radium-therapy). Specimens of blood and urine were checked with a counter and showed practically no radioactivity. Distinct fibrinous spots were observed a tew days later at the points of injection. This special form of interstitial radiotherapy will presumably gain some practical significance, as it offers the advantage that no foreign bodies have to be inserted in tissues as it is the case with radium needles and radon seeds, pectin being very well tolerated and resorbed by living tissues.     

Deoxyribozymes: new activities and new applications

DNA in its single-stranded form has the ability to fold into complex three-dimensional structures that serve as highly specific receptors or catalysts. Only protein enzymes and ribozymes are known to be responsible for biological catalysis, but deoxyribozymes with kinetic parameters that rival ribozymes can be created in the laboratory. Some of these engineered DNA catalysts are showing surprising potential as therapeutic agents, which makes them biologically relevant if not biologically derived. If DNA's natural role is strictly genomic, how significant is its innate catalytic prowess? New examples of engineered deoxyribozymes serve as empirical examples of the potential for catalysis by DNA. These results indicate that the true catalytic power of DNA is limited by discovery and not by chemistry.     

Understanding paternal genome demethylation through live-cell imaging and siRNA

Identification of a DNA demethylase responsible for zygotic paternal DNA demethylation has been one of the most challenging goals in the field of epigenetics. Several candidate molecules have been proposed, but their involvement in the demethylation remains controversial, partly due to the difficulty of preparing a sufficient quantity of materials for biochemical analysis. In this review, we utilize a recently developed method for live-cell imaging of mouse zygotes combined with RNA interference (RNAi) to search for factors that affect zygotic paternal DNA demethylation. The combined use of various fluorescent probes and RNAi is a useful approach for the study of not only DNA demethylation but also the spatiotemporal dynamics of histone depositions in zygotes, although it is not appropriate for large-scale screening or knockdown of genes that are abundantly expressed before fertilization. This new technique enables us to understand the epigenetic hierarchy during cellular response and differentiation in preimplantation embryos.     

Alternariol, a dibenzopyrone mycotoxin of Alternaria spp., is a new photosensitizing and DNA cross-linking agent

The mycotoxin alternariol (3,4',5-trihydroxy-6'-methyldibenzo [a] pyrone) but not alternariol monomethyl ether (3,4'-dihydroxy-5-methoxy-6'-methyldibenzo [a] pyrone) is phototoxic to Escherichia coli in the presence of near UV light (320-400 nm). The phototoxicity bioassays with a DNA repair-deficient mutant of E. coli suggested that DNA may be the molecular target for photo-induced toxicity of alternariol. Interactions between alternariol and double-stranded, supercoiled DNA suggest that alternariol interacts with DNA by intercalation. No DNA breakage was detected in this system; however, alternariol forms a complex and cross-links double-stranded DNA in near UV light. These results suggest that alternariol is a new phototoxic, DNA-intercalating agent and is a DNA cross-linking mycotoxin in near UV light.     

Control of DNA integrity in skeletal muscle under physiological and pathological conditions

Skeletal muscle is a highly oxygen-consuming tissue that ensures body support and movement, as well as nutrient and temperature regulation. DNA damage induced by reactive oxygen species is present in muscles and tends to accumulate with age. Here, we present a summary of data obtained on DNA damage and its implication in muscle homeostasis, myogenic differentiation and neuromuscular disorders. Controlled and transient DNA damage appears to be essential for muscular homeostasis and differentiation while uncontrolled and chronic DNA damage negatively affects muscle health.