Aggregation of rat hepatocytes was effectively inhibited by monovalent antibodies (Fab fragments) directed against hepatocyte plasma membranes, but monovalent antibodies against some distinct, known hepatocyte surface antigens had no effect. Surface antigens, which neutralized the Fab inhibiting effect on cell aggregation, could be solubilized from plasma membranes by limited proteolytic digestion. Thus, hepatocyte intercellular adhesion seems to involve specific cell surface components, which may be proteins or protein derivatives. 相似文献
A bacteriocin was found in the supernatant fluid of Clostridium septicum strain Ovinus. Sensitivity to the bacteriocin was confined to other strains of C. septicum and to strains of C. chauvoei; the other Gram-positive and Gram-negative bacteria tested for sensitivity were unaffected by the bacteriocin. The bacteriocin killed sensitive cells rapidly but cell lysis did not appear to be involved. The bacteriocin inhibited protein and RNA synthesis immediately after its addition to sensitive cells; DNA synthesis was inhibited 10 min later. 相似文献
The reactions of tympanic nerve fibers ofLocusta migratoria were recorded by glass microelectrodes in the metathoracic ganglion.
2.
The units were classified by frequency-, intensity-, and directional characteristics as well as by their response pattern. The response to speciesspecific song is compared with the response to song ofEphippiger ephippiger.
3.
The physiological properties lead to a classification into three types of low-frequency neurons (characteristic frequency 3.5–4 kHz; 4kHz; 5.5–6 kHz) and one type of high-frequency neuron (12–20 kHz). This is similar to other species (Gray, 1960, Michelsen, 1971).
4.
Intensity-coding is done by sharp rising intensity characteristics and by different absolute thresholds of the units.
5.
There is a marked directional sensitivity with some differences between LF and HF units. In the low frequency range the tympanal organ seems to react as a pressure gradient receiver; for high frequencies another mechanism is discussed.
6.
No filtering of species-specific song takes place at the level of the receptor cells.
The Working Party on Safety in Biotechnology of the European Federation of Biotechnology has proposed a classification of microorganisms that cause diseases in plants. In this paper appropriate safety levels are proposed for these classes of microorganisms in order to ensure that research, development and industrial fermentation work with plant pathogens will limit the risk of outbreaks of diseases in crops that could result from work with such microorganisms when they are cultivated in laboratories, glasshouses and biotechnology installations.Co-opted: J. Dähne, J. Drozd, M. Lemattre, I. M. Smith , E. M. A. WaterschootA Report prepared by the Working Party on Safety in Biotechnology of the European Federation of Biotechnology (EFB)相似文献
The dicarboxylate carrier from rat liver mitochondria was purified by the Amberlite/hydroxyapatite procedure and reconstituted in egg yolk phospholipid vesicles by removing the detergent with Amberlite. The efficiency of reconstitution was optimized with respect to the ratio of detergent/phospholipid, the concentration of phospholipid and the number of Amberlite column passages. In the reconstituted system the incorporated dicarboxylate carrier catalyzed a first-order reaction of malate/phosphate exchange. V of the reconstituted malate/phosphate exchange was determined to be 6000 mumol/min per g protein at 25 degrees C. This value was independent of the type of substrate present at the external or internal space of the liposomes (malate, phosphate or malonate). The half-saturation constant was 0.49 mM for malate, 0.54 mM for malonate and 1.41 mM for phosphate. The activation energy of the exchange reaction was determined to be 95.8 kJ/mol. The transport was independent of the external pH in the range between pH 6 and 8. 相似文献
X-Irradiation of rat hippocampus in vitro with low doses accelerated spontaneous impulse passage without concomitant changes in synaptic activity. There was a negative correlation between the original frequency of neuron discharges and the degree of quickening the impulses in response to the effect of radiation. Perfusion of slices by a noncalcium solution blocked the synaptic transmission but did not influence the response to the effect of ionizing radiation. 相似文献
Phosphate limitation induces the turimycin biosynthesis as well as the cAMP phosphodiesterase and phosphatase. The results are discussed in connection with the observation of general high activities of dephosphorylating enzymes and low concentrations of phosphorylated intermediates under conditions of phosphate limitation and secondary product biosynthesis, respectively. 相似文献
Determination of the optimal inoculation method and concentration to use for plant-bacteria interaction studies is important in many cases, such as the phytoremediation of heavy metals and other toxic compounds in contaminated areas. The aim of this study was to compare different concentrations and times of inoculation of Pseudomonas putida with various growth stages of Arabidopsis thaliana in 14-d in vitro cultures. A significant beneficial impact of the bacterium was detected in the shoot length and root weight of seedlings. The highest shoot length and root fresh and dry weights were detected in 14-d and 2 × 103 cfu mL−1 inoculated samples. In addition, the increase in root weight could be visualized with crystal violet staining, as relatively more root hair and lateral root formation occurred in seedlings inoculated with moderate concentrations of bacteria, possibly due to the ability of P. putida to produce indole-acetic acid. Moreover, the highest photosynthetic pigment accumulation was obtained with the highest bacterial inoculum (2 × 106 cfu mL−1), which was tested in 0- or 3-d-old seedlings. Rhizospheric bacterial colonization was also visualized with GFP-labeled bacteria by confocal microscopy. These results showed that biotization of A. thaliana with P. putida KT2440 did not cause severe oxidative stress in seedlings, because H2O2 accumulation levels together with CAT and POX activities were not significantly induced. Therefore, this strain could be used for several applications based on plant-bacteria interactions.