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1.
2.
Seeds of the root parasitesStriga (several spp.) andBuchnera americana were examined by means of SEM. The surface patterns of the seeds in both genera resemble each other closely, especially those ofS. angustifolia andB. americana. SomeStriga spp. can be clearly distinguished by their surface characteristics, while this is quite difficult in others. The taxonomic value of the seed surface features ofStriga andBuchnera is discussed. 相似文献
3.
Janusz Janiszewski Dietmar Otto 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1988,162(6):739-746
1. | Intracellular recordings of suboesophageal neurons were performed in the cricketGryllus bimaculatus during applied changes of head temperature in the range 8 to 32.5 °C. The temperature was controlled by perfusing the head with Ringer solution of appropriate temperature. Subsequent staining with Lucifer Yellow revealed descending, ascending or T-shaped cells with ventrally located somata (Fig. 1). |
2. | In 6 out of 7 neurons recorded (Fig. 1, neurons A, B, C, D, E, G) the firing rate was correlated with abdominal ventilatory pumping (Fig. 2a, b). These neurons also received input from cereal sensory hairs (Fig. 2c). Furthermore, one of them (Fig. 1, neuron A) showed responses to auditory (Fig. 2d) and another (Fig. 1, neuron E) to visual input (Fig. 2e). |
3. | Activity of every tested neuron was correlated with the temperature of the perfusing Ringer solution: the amplitude and duration of spikes and excitatory postsynaptic potentials increased with cooling (Fig. 3). Two types of temperature-dependent changes in firing rate were identified. In type I the spiking rate was higher at higher temperature (Figs. 4a, b; 5). In type II spiking rate was related to the direction of temperature change (Fig. 4c, d). |
4. | The possible involvement of one of the recorded cells (Fig. 1, neuron F) in thermoreception processes is discussed. Activity of this neuron was not related to the rhythm of abdominal ventilatory pumping, nor did the cell receive cereal, visual or auditory input. Its activity was related mainly to the direction of temperature changes i.e. with an increase in firing rate during cooling, independent of the temperature at which the cooling started and with a transient decrease in firing rate during warming from starting point of 10 °C. |
4.
Spyridon Vamvakas Wolfgang Dekant Dietmar Schiffmann Dietrich Henschler 《Cell biology and toxicology》1988,4(4):393-403
S-(chloroethyl)-cysteine (CEC) and S-(1,2-dichlorovinyl)cysteine (DCVO) have been proposed as intermediates in the metabolic transformation of the carcinogens 1,2-dichloroethane and 1,1,2-trichloroethylene. We have tested the ability of CEC and DCVC to induce DNA repair and genotoxic effects at the chromosomal level by comparative assessment of unscheduled DNA synthesis induction and micronucleus formation in Syrian hamster embryo fibroblasts. CEC induced a potent and dose-dependent response in both assays, whereas DCVC treatment resulted in a comparatively weak induction of DNA repair and failed to raise micronucleus formation above control rates. Inhibition of cysteine conjugate \gB-lyase diminished the effect of DCVC, but had no influence on the genotoxicity of CEC either in the unscheduled DNA synthesis or micronucleus assay.Abbreviations AOAA
aminooxyacetic acid
- CEC
S-(chloroethyl)-cysteine; \gB-lyase, cysteine conjugate -lyase
- DCE
1,2-dichloroethane
- DCVC
S(1,2-dichlorovinyl)-cysteine
- GSH
glutathione
- HU
hydroxyurea
- IBR
IBR-modified Dulbecco's Eagle's reinforced medium
- MN2
micronuclei/2,000 cells
- 4-NQO
4-nitroquinoline-1-oxide
- SHE
Syrian hamster embryo fibroblasts; 3H-Thd, 3H-thymidine
- TCE
1,1,2-trichloroethylene
- UDS
unscheduled DNA synthesis 相似文献
5.
Heiko Traupe Dietmar Müller David Atherton D. Chester Kalter Frans P. M. Cremers Bernard A. van Oost Hans-Hilger Ropers 《Human genetics》1992,89(6):659-665
Summary Homology with the mouse bare patches mutant suggests that the gene for the X-linked dominant chondrodysplasia punctata / ichthyosis / cataract / short stature syndrome (Happle syndrome) is located in the human Xq28 region. To test this hypothesis, we performed a linkage study in three families comprising a total of 12 informative meioses. Multiple recombinations appear to exclude the Xq28 region as the site of the gene. Surprisingly, multiple crossovers were also found with 26 other markers spread along the rest of the X chromosome. Two-point linkage analysis and analysis of recombination chromosomes seem to exclude the gene from the entire X chromosome. Three different mechanisms are discussed that could explain the apparent exclusion of an X-linked gene from the X chromosome by linkage analysis: (a) different mutations on the X chromosome disturbing X inactivation, (b) metabolic interference, i.e. allele incompatibility of an X-linked gene, and (c) an unstable pre-mutation that can become silent in males. We favour the last explanation, as it would account for the unexpected sex ratio (MF) of 1.21 among surviving siblings, and for the striking clinical variability of the phenotype, including stepwise increases in disease expression in successive generations. 相似文献
6.
The affinity of amino acid residues to nucleic acids is probed by measurements of melting temperatures tm for the helix–coil transition at various concentrations of amino acid amides. The increase of tm on addition of ligand is described by the equation tm = t*m + αlog(1+Ktcλ), where t*m is the melting temperature in the absence of ligand, cλ the ligand concentration, and Kt the “tm-onset” constant, which is analogous to an equilibrium constant. It is shown that Kt is closely related to the affinity of the ligands to the double helix, whereas the slope α mainly reflects the preference of the ligand binding to the helix versus the coil form. In the case of the amino acid amides, α is found to be virtually independent of the nature of the side chain with few exceptions, e. g., aromatic amides. The tm-onset constant, however, strongly depends on the nature of the amino acid side chain. For simple aliphatic amino acids, the relative free energy of binding decreases with increasing hydrophobic free energy, e.g., a high affinity is found for Gly-amide and a low affinity for Leu-amide. This relation is modified by functional groups like OH in Ser-amide. The helices poly[d(A-T)], ploy[d(I-C)]. and poly[d(A-C)]·poly[d(G-T)] exhibit similar affinity scales with relatively small variations. Our results demonstrate that the hydrophilic character of double helices at their surface disfavors binding of hydrophobic ligands unless special contacts can be formed. From our results we establish an affinity scale for the binding of amino acids to double helices. 相似文献
7.
Ingo Marenholz Armin Volz Andreas Ziegler Angela Davies Ioannis Ragoussis Bernhard P. Korge Dietmar Mischke 《Genomics》1996,37(3):295
The epidermal differentiation complex (EDC) unites a remarkable number of structurally, functionally, and evolutionarily related genes that play an important role in terminal differentiation of the human epidermis. It is localized within 2.05 Mb of region q21 on human chromosome 1. We have identified and characterized 24 yeast artificial chromosome (YAC) clones by mapping individual EDC genes, sequence-tagged site (STS) markers (D1S305, D1S442, D1S498, D1S1664), and 10 new region-specific probes (D1S3619–D1S3628). Here we present a contig that covers about 6 Mb of 1q21 including the entire EDC. Fluorescencein situhybridization on metaphase chromosomes with two YACs flanking the EDC determined its chromosomal orientation and established, in conjunction with physical mapping results, the following order of genes and STSs: 1cen–D1S442–D1S498–S100A10–THH–FLG–D1S1664–IVL–SPRR3–SPRR1–SPRR2–LOR–S100A9–S100A8–S100A7–S100A6–S100A5–S100A4–S100A3–S100A2–S100A1–D1S305–1qtel. These integrated physical, cytogenetic, and genetic mapping data will be useful for linkage analyses of diseases associated with region 1q21 and for the identification of novel genes and regulatory elements in the EDC. 相似文献
8.
Margarete Traiser Bernd Diener Dietmar Utesch Franz Oesch 《In vitro cellular & developmental biology. Animal》1995,31(4):266-273
Summary In primary monocultures of adult rat liver parenchymal cells (PC), the activities of the xenobiotic metabolizing enzymes microsomal
epoxide hydrolase (mEHb), soluble epoxide hydrolase (sEH), glutathione S-transferases (GST), and phenolsulfotransferase (ST) were reduced after 7
d to values below 33% of the initial activities. Furthermore, the gap junctional intercellular communication (GJIC), measured
after microinjection by dye transfer, decreased from 90% on Day 1 to undetectable values after 5 d in monoculture. Co-culture
of PC with nonparenchymal rat liver epithelial cells (NEC) increased (98% on Day 1) and stabilized (82% on Day 7) the homotypic
GJIC of PC. Additionally, most of the measured xenobiotic metabolizing enzyme activities were well stabilized over 1 wk in
co-culture. Because GJIC is one of several mechanisms playing an important role in cell differentiation, the importance of
GJIC for the stabilization of xenobiotic metabolizing enzymes in PC was investigated. PC in monoculture were, therefore, treated
with 2% dimethyl sulfoxide (DMSO), a differentiation promoting factor, and 1,1,1-trichloro-2,2,-bis (p-chlorophenyl) ethane
(DDT) (10 μg/ml), a liver tumor promotor and inhibitor of GJIC, was given to co-cultures of PC with NEC. DMSO significantly
stabilized (68% on Day 7), while DDT significantly inhibited (8% on Day 7) homotypic GJIC of PC in the respective culture
systems. In contrast, the activities of mEHb, sEH, GST, and ST were not affected in the presence of DMSO or DDT. These results lead to the assumption that the differentiation
parameters measured in this study (i.e., homotypic GJIC and the activities of xenobiotic metabolizing enzymes) are independently
regulated in adult rat liver PC. 相似文献
9.
Uwe Scherf Brigitte Söhling Gerhard Gottschalk Dietmar Linder Wolfgang Buckel 《Archives of microbiology》1994,161(3):239-245
Anaerobically prepared cell extracts of Clostridium kluyveri grown on succinate plus ethanol contained high amounts of 4-hydroxybutyryl-CoA dehydratase, which catalyzes the reversible dehydration of 4-hydroxybutyryl-CoA to crotonyl-CoA. The enzyme was purified 12-fold under strictly anaerobic conditions to over 95% homogeneity and had a specific activity of 123 nkat mg-1. The finding of this dehydratase means that all of the enzymes necessary for fermentation of succinate plus ethanol by C. kluyveri have now been demonstrated to exist in this organism and confirms the proposed pathway involving a reduction of succinate via 4-hydroxybutyrate to butyrate. Interestingly, the enzyme is almost identical to the previously isolated 4-hydroxybutyryl-CoA dehydratase from Clostridium aminobutyricum. The dehydratase was revealed as being a homotetramer (m=59 kDa/subunit), containing 2±0.2 mol FAD, 13.6±0.8 mol Fe and 10.8±1.2 mol inorganic sulfur. The enzyme was irreversibly inactivated after exposure to air. Reduction by sodium dithionite also yielded an inactive enzyme which could be reactivated, however, up to 84% by oxidation with potassium hexacyanoferrate(III). The enzyme possesses an intrinsic vinylacetyl-CoA isomerase activity which was also found in 4-hydroxybutyryl-CoA dehydratase from C. aminobutyricum. Moreover, the N-terminal sequences of the dehydratases from both organisms were found to be 63% identical. 相似文献
10.
Lolium perenne growing with high root density on a fine nylon mesh (Kuchenbuch and Jungk, 1982) caused the development of element gradients in the rhizosphere below the mesh. Micro-liter soil solutions from 2-mg soil samples were sprayed onto Formvar-coated grids and analyzed by X-ray microanalysis in a transmission electron microscope. The results were comparable to those obtained by flame photometry and atomic absorption spectrometry (AAS) of conventional soil solutions from 1 g soil. X-ray microanalysis of micro-soil solutions allows the application of different extraction procedures to even small amounts of soil usually available from rhizosphere experiments. Information about soil buffering characteristics in the rhizosphere can thus be obtained. Aluminum accumulation in the rhizosphere of small segments of single Picea abies fine roots grown in undisturbed natural forest soil could be detected with this technique. 相似文献