Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Electronic Resource  (14)
  • 1995-1999  (8)
  • 1980-1984  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Methylation of deoxyribonucleic acid in the rat by the mushroom poison gyromitrin (1983)
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 31 (1983), S. 1117-1120 
    Details
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jf00119a048
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Multicopy single-stranded DNA of Escherichia coli enhances mutation and recombination frequencies by titrating MutS protein (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 19 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Multicopy single-stranded DNA (msDNA) molecules consist of single-stranded DNA covalently linked to RNA. In Escherichia coli, such molecules are encoded by genetic elements called retrons. The DNA moieties of msDNAs have characteristic stem-loop structures, and most of these structures contain mismatched base pairs. Previously, we showed that retrons encoding msDNAs with mismatched base pairs are mutagenic when present in multicopy plasmids. In this study we show that such msDNAs, in a similar manner to genetic defects in mismatch repair, increase the frequency of interspecies recombination in matings between Salmonella typhimurium and E. coli. To demonstrate interference with mismatch repair by msDNA, we show that the addition of a plasmid containing the gene for MutS protein suppresses the mutagenic and recombinogenic effects of msDNAs. We also show that in mutS mutants, msDNA does not increase the frequency of either mutations or interspecies recombination. We conclude from these findings that the mutagenic and recombinogenic effects of msDNAs are due to titrating out MutS protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.392921.x
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Influence of long-term conservation tillage on soil and rhizosphere microorganisms (1999)
    Springer
    Biology and fertility of soils 29 (1999), S. 81-86 
    Details
    ISSN: 1432-0789
    Keywords: Key words Soil tillage ; Rhizosphere microorganisms ; Cereals ; Nitrogen fixation ; Gaeumanomyces graminis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  In long-term field experiments on sandy loam and loamy sand soils, the influence of conservation and conventional tillage on soil and rhizosphere microorganisms was studied. Conservation tillage stimulated rhizosphere bacteria on winter wheat, winter barley, winter rye and maize in different soil layers. Particularly the populations of Agrobacterium spp. and Pseudomonas spp. were increased. On the sandy loam, N2 fixation and nodulation of pea plants were significantly increased. No influence of different soil tillage was determined on the colonization of the rhizosphere by mycorrhiza and saprophytic fungi. Stubble residues infected with Gaeumanomyces graminis were infectious for a longer time on the soil surface than after incorporation into the soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050528
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Stimulation of cell division in the rat by NaCl, KCl, MgCl2, and CaCl2, and inhibition of the sodium chloride effect on the glandular stomach by ascorbic acid and β-carotene (1999)
    Springer
    Journal of cancer research and clinical oncology 125 (1999), S. 209-213 
    Details
    ISSN: 1432-1335
    Keywords: Key words Cell division ; Stomach ; Neoplasms ; Sodium chloride ; Ascorbic acid ; β-carotene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Three questions associated with the stimulation of cell division by chloride salts have been investigated: (i) whether cations other than sodium show a similar effect, (ii) whether vitamins can have a preventive activity, and (iii) whether subchronic treatment with sodium chloride in the diet is also effective. Male Fischer 344 rats were given solutions of the chloride salts of sodium, potassium, magnesium, and calcium by oral gavage. Water was used for control. After 4 h, a 24-h osmotic minipump containing 5-bromo-2′-deoxyuridine was implanted subcutaneously. The forestomach and glandular stomach, as well as liver and bladder were analyzed immunohistochemically 24 h later for the proportion of cells in S phase as an indicator of the rate of replicative DNA synthesis. For both the forestomach and the glandular stomach, potassium was as potent as sodium, and the divalent cations Mg and Ca were even more potent on a molar basis. Supplementation of the diet with ascorbic acid (2 g/kg food) or β-carotene (12.5 mg/kg food) for 1 week before gavage of the sodium chloride solution resulted in an inhibition of the stimulation of cell division. A putative tumor-chemopreventive activity of the two vitamins might therefore not only rely on their antioxidative properties but may include effects on the cell cycle. A 4-week treatment with a sodium chloride supplement in the diet (2% and 4% supplement) resulted in a significant stimulation of cell division not only in both parts of the stomach and in the bladder (with the 4% supplement) but also in the liver (even with the 2% supplement). Sodium-chloride-stimulated cell turnover therefore is a sustained effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004320050264
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Study of the analytical solution to the heat transfer problem and surface temperature in a semi-infinite body with a constant heat flux at the surface and an initial temperature distribution (1995)
    Springer
    Heat and mass transfer 30 (1995), S. 183-186 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung In vielen praktischen Fällen erhitzt man einen halbunendlichen Festkörper mit einer konstanten Wärmestromdichte an der Oberfläche. Im Fall einer einheitlichen Anfangstemperatur des Körpers wurde eine analytische Lösung zu diesem instationären Wärmetransportproblem von Carslaw und Jäger gegeben. Die Oberflächentemperatur des unendlichen Festkörper verläuft nach der $$\sqrt t $$ -Regel. Das heißt, die Oberflächentemperatur ändert sich proportional zur Wurzel der Erhitzungszeit. Im Fall der uneinheitlichen Anfangstemperatur des Körpers wurde noch keine analytische Lösung entwickelt. In diesem Aufsatz werden analytische Lösungen zu diesem instationären Problem mit einer exponentiellen oder einer linearen Anfangstemperaturverteilung gegeben. Es zeigt, daß im Fall der linearen Anfangstemperatureverteilung die Oberflächentemperatur der $$\sqrt t $$ -Regel folgt. Für eine beliebige Anfangstemperaturverteilung kann man sie in der Nähe von der Oberfläche mit ihrer Tangente an der Oberfläche linearisieren, deshalb gilt auch hier die $$\sqrt t $$ -Regel. Die Meßdaten unterstützen dieses Argument. Außerdem wurde ein Verhältnis zwischen der Oberflächentemperatur und der Erhitzungszeit ermittelt, aus dem die konstante Wärmestromdichte berechnet werden kann. Dieses Verhältnis wurde in diesem Aufsatz für eine bekannte Anfangstemperaturverteilung oder für eine bekannte erste Ableitung der Anfangstemperaturverteilung an der Oberfläche abgeleitet.
    Notes: Abstract In many practical cases, one heats a semi-infinite solid with a constant heat flux source. For such an unsteady heat transfer problem, if the body has a uniform initial temperature, the analytical solution has been given by Carslaw and Jaeger. The surface temperature of the semi-infinite body follows the $$\sqrt t $$ -rule, that is, the surface temperature changes in proportion to square root of heating time. But if, instead of the uniform initial temperature, the body has a temperature distribution at the beginning of heating, the analytical solution has not yet been developed. Analytical solutions to the same problem with an exponential or a linear initial temperature distribution are obtained in this paper. It is shown, that in the case of a linear initial temperature distribution the surface temperature also changes according to $$\sqrt t $$ -rule Approximating the initial temperature distribution near the surface by its tangent at the surface, it is found that the surface temperature within a short time after the start of heating should also satisfy the $$\sqrt t $$ -rule, in spite of an arbitrary initial temperature distribution. The experimental data support this argument. Furthermore, the constant heat flux can be calculated after relationship between the surface temperature and heating time according to the equation derived in this paper, if the initial temperature distribution or its first-order derivative at the surface is known.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01476528
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Study of the analytical solution to the heat transfer problem and surface temperature in a semi-infinite body with a constant heat flux at the surface and an initial temperature distribution (1995)
    Springer
    Heat and mass transfer 30 (1995), S. 183-186 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung In vielen praktischen Fällen erhitzt man einen halbunendlichen Festkörper mit einer konstanten Wärmestromdichte an der Oberfläche. Im Fall einer einheitlichen Anfangstemperatur des Körpers wurde eine analytische Lösung zu diesem instationären Wärmetransportproblem von Carslaw und Jäger gegeben. Die Oberflächentemperatur des unendlichen Festkörper verläuft nach der √—t-Regel. Das heißt, die Oberflächentemperatur ändert sich proportional zur Wurzel der Erhitzungszeit. Im Fall der uneinheitlichen Anfangstemperatur des Körpers wurde noch keine analytische Lösung entwickelt. *In diesem Aufsatz werden analytische Lösungen zu diesem instationären Problem mit einer exponentiellen oder einer linearen Anfangstemperaturverteilung gegeben. Es zeigt, daß im Fall der linearen Anfangstemperaturverteilung die Oberflächentemperatur der √—t-Regel folgt. *Für eine beliebige Anfangstemperaturverteilung kann man sie in der Nähe von der Oberfläche mit ihrer Tangente an der Oberfläche linearisieren, deshalb gilt auch hier die √—t-Regel. Die Meßdaten unterstützen dieses Argument. *Außerdem wurde ein Verhältnis zwischen der Oberflächentemperatur und der Erhitzungszeit ermittelt, aus dem die konstante Wärmestromdichte berechnet werden kann. Dieses Verhältnis wurde in diesem Aufsatz für eine bekannte Anfangstemperaturverteilung oder für eine bekannte erste Ableitung der Anfangstemperaturverteilung an der Oberfläche abgeleitet.
    Notes: Abstract In many practical cases, one heats a semi-infinite solid with a constant heat flux source. For such an unsteady heat transfer problem, if the body has a uniform initial temperature, the analytical solution has been given by Carslaw and Jaeger. The surface temperature of the semi-infinite body follows the √—t-rule, that is, the surface temperature changes in proportion to square root of heating time. But if, instead of the uniform initial temperature, the body has a temperature distribution at the beginning of heating, the analytical solution has not yet been developed. *Analytical solutions to the same problem with an exponential or a linear initial temperature distribution are obtained in this paper. It is shown, that in the case of a linear initial temperature distribution the surface temperature also changes according to √—t-rule. *Approximating the initial temperature distribution near the surface by its tangent at the surface, it is found that the surface temperature within a short time after the start of heating should also satisfy the √—t-rule, in spite of an arbitrary initial temperature distribution. The experimental data support this argument. *Furthermore, the constant heat flux can be calculated after relationship between the surface temperature and heating time according to the equation derived in this paper, if the initial temperature distribution or its first-order derivative at the surface is known.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01476528
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Endogenous and exogenous factors in carcinogenesis: limits to cancer prevention (1996)
    Springer
    International archives of occupational and environmental health 68 (1996), S. 120-125 
    Details
    ISSN: 1432-1246
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Organ-specific cancer incidence rates can vary dramatically between low- and high-incidence areas. Such differences are due to (1) heritable susceptibility determinants, (2) risk factors associated with the environmental and local living conditions (e.g., viruses, pollution), and (3) personal life-style factors. For organs showing large differences between cancer registries, exogenous factors might be most important, while for organs showing only small differences, endogenous and unavoidable factors are expected to be more important. In this paper, a working hypothesis based on descriptive cancer epidemiology is presented to estimate, in a quantitative manner, the unavoidable contribution to the process of carcinogenesis and to discuss limitations to individual cancer prevention. Cumulative cancer incidence rates for a 75-year period of life (CR74, in percent) were taken from IARC Scientific Publication No. 120 (1992). For each organ, values were ranked in ascending order, and the ratio between high-rate and low-rate registries (90th percentile/10th percentile) was determined. This measure of variability among registries differed strongly between organs. Largest ratios were seen for organs with well-known exogenous risk factors, such as pharynx, lip, tongue, mouth, liver, esophagus, and melanoma in males, and lung, esophagus, gallbladder, liver, and bladder in females. Small ratios were seen for rectum, brain, colon, and Hodgkin's disease in males, and breast, rectum, ovary, brain, and colon in females. It is concluded that the process of carcinogenesis in the latter organs has a stronger endogenous/unavoidable component, for some tissues possibly of hormonal type. A fictitious population was composed where, for each organ, the minimum reported cancer rate was taken. When based on all cancer registries world-wide, CR74 sums over all sites of 2.0% and 2.3% resulted in males and females, respectively. When only Central/Western European countries were included in the analysis in order to reduce differences in risk factors nos, 1 and 2, the sum of the minimum values was 10.4% and 8.7%. After correction of the data for smoking, ‘minimum’ cancer incidence rates in males and females were estimated to be 7.6% and 6.8%. Based on a median cancer incidence rate for nonsmoking males in Europe of about 21%, therefore, individual preventive measures taken by a nonsmoker can reduce the cancer risk, on average, ‘only’ by a factor of about 3. A considerable fraction of cases thus appears to be hardly avoidable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00381244
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Interaction of estrone and estradiol with DNA and protein of liver and kidney in rat and hamster in vivo and in vitro (1984)
    Springer
    Archives of toxicology 55 (1984), S. 97-103 
    Details
    ISSN: 1432-0738
    Keywords: Estrogen ; Hormone ; Carcinogenesis ; DNA binding ; Protein binding ; Estrone ; Estradiol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract [6,7-3H] Estrone (E) and [6,7-3H]estradiol-17β (E2) have been synthesized by reduction of 6-dehydroestrone and 6-dehydroestradiol with tritium gas. Tritiated E and E2 were administered by oral gavage to female rats and to male and female hamsters on a dose level of about 300 μg/kg (54 mCi/kg). After 8 h, the liver was excised from the rats; liver and kidneys were taken from the hamsters. DNA was purified either directly from an organ homogenate or via chromatin. The radioactivity in the DNA was expressed in the units of the Covalent Binding Index, CBI = (μmol chemical bound per mol DNA-P)/(mmol chemical administered per kg b.w.). Rat liver DNA isolated via chromatin exhibited the very low values of 0.08 and 0.09 for E and E2, respectively. The respective figures in hamster liver were 0.08 and 0.11 in females and 0.21 and 0.18 in the males. DNA isolated from the kidney revealed a detectable radioactivity only in the female, with values of 0.03 and 0.05 for E and E2, respectively. The values for male hamster kidney were 〈 0.01 for both hormones. The minute radioactivity detectable in the DNA samples does not represent covalent binding to DNA, however, as indicated by two sets of control experiments. (A) Analysis by HPLC of the nucleosides prepared by enzyme digest of liver DNA isolated directly or via chromatin did not reveal any consistent peak which could have been attributed to a nucleoside-steroid adduct. (B) All DNA radioactivity could be due to protein contaminations, because the specific activity of chromatin protein was determined to be more than 3,000 times higher than of DNA. The high affinity of the hormone to protein was also demonstrated by in vitro incubations, where it could be shown that the specific activity of DNA and protein was essentially proportional to the concentration of radiolabelled hormone in the organ homogenate, regardless of whether the animal was treated or whether the hormone was added in vitro to the homogenate. Carcinogens acting by covalent DNA binding can be classified according to potency on the basis of the Covalent Binding Index. Values of 103–104 have been found for potent, 102 for moderate, and 1–10 for weak carcinogens. Since estrone is moderately carcinogenic for the kidney of the male hamster, a CBI of about 100 would be expected. The actually measured limit of detection of 0.01 places covalent DNA binding among the highly unlikely mechanisms of action. Similar considerations can be made for the liver where any true covalent DNA binding must be below a level of 0.01. It is concluded that an observable tumor induction by estrone or estradiol is unlikely to be due to DNA binding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346046
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Tests for mutagenicity in salmonella and covalent binding to DNA and protein in the rat of the riot control agent o-chlorobenzylidene malononitrile (CS) (1981)
    Springer
    Archives of toxicology 49 (1981), S. 15-27 
    Details
    ISSN: 1432-0738
    Keywords: o-Chlorobenzylidene malononitrile ; Riot control agents ; DNA Binding ; Salmonella/microsome assay ; Carcinogens ; Mutagens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this study was to determine whether o-chlorobenzylidene malononitrile (CS) exhibits any genotoxic activity towards Salmonella or mammalian DNA in vivo. CS was synthesized with a [14C]-label at the benzylic carbon atom. It was administered i.p. at a dose level of 13 mg/kg (1 mCi/kg) to young adult male rats. Liver and kidney DNA was isolated after 8,25, and 75 h. The radioactivity was at (liver, 8 and 75 h) or below (all other samples) the limit of detection of 3 dpm. Therefore, a possible binding of CS to DNA is at least 105 times lower than that of the strong hepatocarcinogen aflatoxin B1, and 4,000 times lower than that of vinyl chloride. In contrast to this lack of DNA binding, but in agreement with the chemical reactivity of CS, a binding to nuclear proteins could be detected with specific activities ranging between 50 and 121 dpm/mg for liver and between 3 and 41 dpm/mg for kidney. Protein binding could well be responsible for its pronounced cytotoxic effects. CS was also tested in the Ames Salmonella/microsome assay. Strains TA 1535, TA 1537, TA 1538, TA 98, and TA 100 were used with or without pre-incubation. Only with strain TA 100 and only without pre-incubation, a doubling of the number of revertants was detectable at the highest dose levels used, 1,000 and 2,000 μg CS per plate. With pre-incubation of TA 100 with CS, a slight increase of the number of revertants was seen at 100 and 500 μg per plate, and a subsequent fall below control values at 1,000 μg. A check for the number of surviving bacteria revealed a strong bacteriotoxicity of the higher doses of CS so that the calculated mutation frequencies, i.e., the number of revertants per number of surviving bacteria, increased with doses up to 500 μg. This toxicity could be counteracted in part by the addition of increasing amounts of rat liver microsomes. In the view of these results, and taking into account the rare and low exposure of man, it is concluded that CS will not create a risk for the induction of point mutations or of carcinogenic processes mediated by DNA binding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00352067
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Frontal brain activation during the Wisconsin Card Sorting Test assessed with two-channel near-infrared spectroscopy (1998)
    Springer
    European archives of psychiatry and clinical neuroscience 248 (1998), S. 245-249 
    Details
    ISSN: 1433-8491
    Keywords: Key words NIRS ; WCST ; Mental activation ; Laterality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Near-infrared spectroscopy (NIRS) is a new non-invasive optical technique suitable to assess the concentration changes of oxygenated (O2HB) and deoxygenated (HHB) hemoglobin in brain tissue. Previous NIRS studies showed distinct patterns of blood oxygenation changes during different cognitive tasks. In particular, bilateral frontal hypo-oxygenation was found during reading, right frontal hyper-oxygenation during the Continuous Performance Test, and left frontal hyper-oxygenation during the Verbal Fluency Test. The Wisconsin Card Sorting Test (WCST) is a neuropsychological test which is presumed to activate prevalently the frontal lobes. This was demonstrated by lesion studies and functional imaging (single photon emission computed tomography and positron emission tomography). In the present study, a two-channel NIRS system was applied to investigate frontal brain areas of ten healthy subjects during performance of the WCST. A significant bilateral increase of O2HB in frontal brain regions without hemispheric differences was found during the WCST compared with a baseline at rest. This result indicates an enhanced perfusion of the frontal lobes consistent with local activation. The findings add further evidence that the NIRS technique is sensitive enough to detect physiological blood oxygenation changes. Furthermore, a comparison with previous studies revealed an activation pattern distinct from those observed during other cognitive tasks. It is concluded that the results reflect local responses to specific task demands of the WCST.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004060050045
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...