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101.
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
102.
Snow Finches and Mountain-steppe Sparrows differ in habitat selection, feeding, social and vocal behaviour. For these reasons, separation of the genusMontifringilla intoMontifringilla andPyrgilauda is recommended. 相似文献
103.
A cytogenetic map of chromosome 5 from the Mediterranean fruit fly, Ceratitis capitata, was constructed. Six mutations were located by translocation, transposition or deletion mapping. This knowledge allowed alignment and orientation of the existing linkage map with the polytene chromosomes. In addition, mapping of mutations used as selectable markers in genetic sex-separation strains is an essential prerequisite for the improvement of genetic stability during mass-rearing. 相似文献
104.
Cotesia rubecula Marshall (Hymenoptera: Braconidae) is a specialist larval parasitoid of the butterfly Pieris rapae L. which itself feeds almost exclusively upon cruciferous plants. Female wasps are attracted to the odour of host-infested plant (plant-host complex: PHC) and the probability of flights in a wind tunnel depends on females' prior oviposition experience with the PHC and on the concentration of the PHC odour. This study considers the effect of both factors on characteristics of oriented flight upwind towards the PHC. The flight track parameters that we measured and calculated were not significantly affected by these factors. C. rubecula females exhibited high average flight velocity and relatively straight flight tracks. There was a considerable variability between individuals, however, in their odour-modulated upwind flight tracks. Some females generated a zigzagging upwind flight track similar to those commonly observed from male moths responding to female sex pheromone. Other females flew along a straight track directly upwind. The flight tracks of most female wasps were intermediate between these extremes. The full range of these flight performances was observed to all experimental treatments. 相似文献
105.
Lars Iversen †Eileen Mulvihill †Betty Haldeman ‡Nils Henrik Diemer Frank Kaiser Malcolm Sheardown Peter Kristensen 《Journal of neurochemistry》1994,63(2):625-633
Abstract: Metabotropic glutamate receptors mediate their intracellular response by coupling to G proteins and may be divided into three subfamilies: mGluR1 and mGluR5, which stimulate phosphatidylinositol hydrolysis; mGluR2 and mGluR3, which are negatively coupled to cyclic AMP formation; and mGluR4 and mGluR6, which also inhibit forskolin-stimulated cyclic AMP formation. The mGluR4 subtypes may represent l -2-amino-4-phosphonobutyrate-sensitive presynaptic autoreceptors, and two alternatively spliced variants of the mGluR4 coding for two receptors with different C termini have been identified. Using in situ hybridization, we measured the levels of mGluR1–mGluR5 mRNA in regions of the rat brain 24 h after transient global ischemia, a time point when no neuronal damage can yet be observed morphologically. In the hippocampus, the mRNA levels for mGluR1, mGluR2, and mGluR5 were decreased, mGluR3 mRNA levels were unchanged, and the mGluR4 mRNA levels were strongly increased. The strongest increase appeared to be in the mRNA encoding mGluR4b. The mGluR4 mRNA was also increased in the parietal cortex, whereas the ventral posteromedial thalamic nucleus showed a small decrease in its mRNA content. These results suggest that vulnerable neurons react to an increased extracellular glutamate concentration by differential regulation of the mRNA for pre- and postsynaptically located metabotropic glutamate receptors. 相似文献
106.
Maria Rova Lars-Gunnar Franzén Per-Olof Fredriksson Stenbjörn Styring 《Photosynthesis research》1994,39(1):75-83
The psbP gene product, the so called 23 kDa extrinsic protein, is involved in water oxidation carried out by Photosystem II. However, the protein is not absolutely required for water oxidation. Here we have studied Photosystem II mediated electron transfer in a mutant of Chlamydomonas reinhardtii, the FUD 39 mutant, that lacks the psbP protein. When grown in dim light the Photosystem II content in thylakoid membranes of FUD 39 is approximately similar to that in the wild-type. The oxygen evolution is dependent on the presence of chloride as a cofactor, which activates the water oxidation with a dissociation constant of about 4 mM. In the mutant, the oxygen evolution is very sensitive to photoinhibition when assayed at low chloride concentrations while chloride protects against photoinhibition with a dissociation constant of about 5 mM. The photoinhibition is irreversible as oxygen evolution cannot be restored by the addition of chloride to inhibited samples. In addition the inhibition seems to be targeted primarily to the Mn-cluster in Photosystem II as the electron transfer through the remaining part of Photosystem II is photoinhibited with slower kinetics. Thus, this mutant provides an experimental system in which effects of photoinhibition induced by lesions at the donor side of Photosystem II can be studied in vivo.Abbreviations Chl
chlorophyll
- DCIP
2,6-dichlorophenolindophenol
- DPC
2,2-diphenylcarbonic dihydrazide
- HEPES
4-(2-hydroxyethyl)-1-piperazinethanesulfonic acid
- P680
the primary electron donor to PS II
- PpBQ
phenyl-p-benzoquinone
- PS II
Photosystem II
- QA
the first quinone acceptor of PS II
- QB
the second quinone acceptor of PS II
- SDS
sodium dodecyl sulfate
- Tris
tris(hydroxymethyl)aminomethane
- TyrD
accessory electron donor on the D2-protein
- TyrZ
tyrosine residue, acting as electron carrier between P680 and the water oxidizing system 相似文献
107.
Heber Ulrich; Wagner Ute; Kaiser Werner; Neimanis Spidola; Bailey Karen; Walker David 《Plant & cell physiology》1994,35(3):479-488
Induction of photosynthesis in leaves was prolonged, and steadystate photosynthesis was inhibited by very high CO2 concentrationswhich cause cytoplasmic acidification. Prolonged exposure tohigh CO2 relieved initially observed inhibition of photosynthesisat least partially. The sensitivity of carbon assimilation tohigh CO2 was different in different plant species. Acidificationby CO2 (or subsequent alkalization) was detected by measuringrapid CO2-release from the tissue and by monitoring fluorescenceof pH-indicating dyes which had been fed to the leaves throughthe petiole. The results indicate that two different mechanismsoperate in leaves to achieve and maintain pH homeostasis. Rapidand efficient pH-adjustment is provided by proton/cation exchangeacross the tonoplast. Slower and less efficient regulation occursby formation or consumption of base. In the presence of highCO2 concentrations, protons are pumped from the cytosol intoalready acidic vacuoles. In turn, vacuolar cations replace exportedprotons in the cytosol permitting bicarbonate accumulation andincreasing the pH of the acidified cytosol. Similarly effectiveand fast proton/cation exchange relieves acid-stress in thechloroplast stroma and permits photosynthesis to proceed withhigh quantum efficiency or high light-saturated rates in thepresence of CO2 concentrations which would, in the absence offast cytoplasmic pH regulation, inhibit photosynthesis. By inference,proton/cation exchange must also occur across the mitochondrialboundary. After cytoplasmic pH adjustment in the presence ofhigh CO2, removal of CO2 results in transient cytoplasmic alkalizationand, subsequently, in the return of cytoplasmic pH values tolevels observed prior to acid-stress. In addition to fast pHregulation by rapid proton/cation exchange across biomembranes,slow base production (e.g. NH3-formation) also contributes torelieving acid stress. Base produced in the presence of highCO2 is rapidly consumed after removal of CO2. Implications of the findings in regard to forest damage by potentiallyacidic air pollutants such as SO2 are briefly discussed. (Received November 8, 1993; Accepted February 3, 1994) 相似文献
108.
109.
110.
Liang Ru Shi Dirk Eichelbauer Franz Borchard Herbert Jürgens Ulrich Göbel E. Marion Schneider 《Cancer immunology, immunotherapy : CII》1994,38(3):208-213
A selection of 16 monoclonal antibodies has been produced against a fresh Ewing's sarcoma (ES) tumor mixed with a permanent ES cell line. The majority of antibodies identify an 80-kDa molecule, which is not detected on healthy tissues except on certain cultured monocytes. One antibody recognize the CD2 ligand MIC2 and 2 antibodies (numbers 13 and 16) define a higher-molecular-mass antigen. Antibody 16 is also expressed on mesenchymal fibroblasts of bone marrow or fetal origin. Tumorspecific antigen expression is potentially linked to the chromosome 22 abnormality decribed in Ewing's sarcoma. 相似文献