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1.
Differences in the cyclic AMP-dependent plasma membrane phosphorylation system of undifferentiated and differentiated L6 myogenic cells have been detected. Endogenous plasma membrane protein phosphorylation in undifferentiated L6 myoblasts was stimulated more than three fold by 5 × 10−5 M cyclic AMP, whereas no statistically significant cyclic AMP-dependent phosphorylation of endogenous plasma membrane proteins was observed in differentiated L6 cells. In undifferentiated cells cyclic AMP promoted the phosphorylation of several proteins, the most prominent of which had a molecular weight of 110,000. In differentiated cells cyclic AMP did not selectively promote the phosphorylation of specific plasma membrane proteins. Both differentiated and undifferentiated L6 cells, however, contain a cyclic AMP-dependent protein kinase capable of catalyzing the phosphorylation of exogenous substrates, such as histone f2b. Therefore, the data show that differentiation in L6 cells is associated with a selective change in the activity of a plasma membrane cyclic AMP-dependent protein kinase which employs endogenous membrane proteins as substrate.  相似文献   

2.
Abstract— A microscale modification for the preparation of subcellular fractions employing milligram and submilligram amounts of neuronal tissue (brain nuclei and autonomic ganglia) is described.
Electron microscope characterization and enzymic studies were carried out on the six subcellular fractions of sympathetic ganglia of cat thus prepared.
The synaptosomal preparations obtained from individual ganglia were poorer in their nerve ending content than those obtained from brain by previous investigators. The highest RSA for AChE was found in layer L2 which was rich in membranes and vesicle components. ChAc activity was also highly concentrated in layers L2 and L3 (membranes, nerve ending-like particles, mitochondria and 'ghosts'). MAO activity was particularly high in the layers L4 and L5 which contained a large number of mitochondria. Layer L1 (membrane fragments) and particularly layer L6 which contained mainly collagen fibres, were low in activity of all three enzymes.
After preganglionic denervation, both ChAc and AChE activities were significantly reduced in the purest nerve ending fraction, L3 while MAO activity was practically unchanged.  相似文献   

3.
The sap flow (Jv) and the osmotic pressure-dependent hydraulic conductance (L0) of detached exuding root systems from paprika pepper plants (cv. Albar) were measured. Plants stressed with NaCl (30 m M ) and with six times the macronutrients of the Hoagland nutrient solution (6×HNS) were compared with controls grown in complete Hoagland nutrient solution. Jv of +NaCl and +6×HNS plants decreased markedly, but recovered to values similar to those of controls after removal of the treatments. Hydraulic conductance L0 was always less in NaCl plants than in controls and 6×HNS. A total increase in the ion concentration of the xylem (except Na+ and Cl) was observed with both treatments. In control and 6×HNS plants, HgCl2 treatment (50 μ M ) caused a sharp decline in L0 to values similar to those of NaCl-stressed roots, but were restored by treating with 5 m M dithiothreitol (DTT). However, in NaCl roots only a slight effect of Hg2+ and DTT was observed. In each treatment, there was no difference in the flux of K+ into the xylem after HgCl2 and DTT application. The results suggest that NaCl decreased L0 of the roots by reducing either the activity or abundance of Hg-sensitive water channels. The putative reduction in water-channel function of NaCl-treated plants did not seem to be due to the osmotic effect.  相似文献   

4.
Abstract: The relationship between the transport of thyroid hormones and that of amino acids was examined by measuring the uptake of amino acids that are characteristic substrates of systems L, A, and N, and the effect of 3,3',5-triiodo-L-thyronine (T3) on this uptake, in cultured astrocytes. Tryptophan and leucine uptakes were rapid, Na+-independent, and efficiently inhibited by T3 (half-inhibition at ∼ 2 μ M ). Two Na+-independent L-like systems (L1 and L2), common to leucine and aromatic amino acids, were characterized kinetically. System L2 had a low affinity for leucine and tryptophan ( K m= 0.3–0.9 m M ). The high-affinity system L1 ( K m∼ 10 μ M for both amino acids) was competitively inhibited by T3 with a K i of 2–3 μ M (close to the T3 transport K m). Several T3 analogues inhibited system L1 and the T3 transport system similarly. Glutamine uptake and α-(methylamino)isobutyric acid uptake were, respectively, two and 200 times lower than tryptophan and leucine uptakes. T3 had little effect on the uptakes of glutamine and α-(methylamino)isobutyric acid. The results indicate that the T3 transport system and system L1 are related.  相似文献   

5.
Two pectic lyases, L1 and L2, from culture liquids of Aureobasidium pullulans LV 10 were partially purified by ultrafiltration, CM-Sepharose 6B, DEAE-cellulose and/or Sephadex G 100 column chromatography, and characterized. L1 and L2 showed optimum activity at pH 5 and 7.5 respectively, and at 40°C. The molecular weights of the enzymes determined by gel filtration were estimated to be 89000 1000 and 55000 1000 for L1 and L2 respectively. Both lyases were activated by Ca2+ ions. L1 attacked highly esterified pectins, L2 attacked low methoxy-pectins in preference to polygalacturonic acid.  相似文献   

6.
Fork length was measured in two groups of salmon parr (32–139 mm, frozen in a straight posture and frozen in a curved posture) before (L1) and after (L2) freezing and thawing. All the fish shrank. The decrease in length was significantly greater in the curved fish than the straight fish. The absolute reduction in length (L1–L2) was related directly to L1, whereas the percentage reduction in length [(L1–L2)/L1× 100] was related inversely to L1.  相似文献   

7.
The nucleotide sequence for the Rhodobacter sphaeroides form II ribulose 1,5-bisphosphate carboxylase/oxygenase was determined. The deduced product is highly homologous with the form II-like enzyme of Rhodospirillum rubrum , but appears to be more distantly related to the large subunit of the L8S8 enzyme found in autotrophic bacteria, cyanobacteria and higher plants. Several regions highly conserved among L8S8 and LX enzymes correspond with regions previously implicated in catalytic activity and subunit interactions. An imperfect palindrome and a stem loop structure were identified in the 5' and 3' flanking sequences, respectively, of R. sphaeroides rbpL .  相似文献   

8.
The duration of the immature stages of Cacopsylla pyri L. was studied under field conditions by artificially infesting pear branches on several dates during the year. The duration of the egg stage decreased from winter to summer, as the season progresses and temperature rises, and slightly increased in September. It ranged from 27.4 to 6.7 days. The same trend was observed in the duration of the first three larval stages (L1−3) which ranged from 18.8 to 10.3 days. For eggs deposited during the period February–August the duration of the last two larval stages (L4−5) ranged from 17.5 to 12.1 days. However, the duration of L4−5 developed from eggs deposited in September and which give rise to winter-form adults were the longest observed. The rate of egg development was related to average ambient temperature with a highly significant linear relationship. This relationship indicates that the egg stage requires a constant number of 158.9 (SD = 5.0) of day-degrees above an average temperature of 2.31°C to complete development. The rate of development both of L1−3 and L4−5 were related to average ambient temperature with curvilinear relationships. These relationships indicate a proportional increase in the developmental rate as temperature rises between 10–22°C. At the higher average temperatures that occurred in the summer experiments (24–27°C) the acceleration of development of L1−3 is reduced and the developmental rate of L4−5 decreases. The developmental rates of L4−5 developed from eggs deposited in September did not follow the established relationship with temperature and they were lower than those in the other periods of the year with the same average temperature.  相似文献   

9.
ABSTRACT. According to the different reactions to the juvenoid Altosid®, the last larval instar (L5) of Laspeyresia pomonella (L.) (Tortricidae) reared under 'long day' conditions (constant light) was subdivided into three sensitive phases: an additional larval instar, a larval–pupal intermediate, or a pupa. Under short day conditions, the prothoracotropic effect of juvenile hormone (JH) in L5, which have a continuous high titre of JH during the whole instar, indicated that it is not a particular titre of JH but a rise in the titre that can induce the production of moulting hormone. Neck-ligation experiments showed that JH acts not directly on the prothoracic glands but via the head, probably via the neurosecretory system. The meaning of the JH-peak in mature L5 reared under long days was determined either by injections with the anti-JH, precocene II, in combination with applications of Altosid, or by forcing precocene-treated larvae to a precocious moult by injecting them with ecdysterone. Precocene delayed, and JH accelerated pupation if administered 4.5 days after the L5 -moult. JH was also found to stimulate the growth and differentiation of the imaginal discs. Moulting hormone in long-days reared insects was detected one day after the larvae had spun their cocoon, with a maximum on the second day after spinning. The hormone was also present in freshly moulted pupae. Neck-ligation of mature larvae indicated that the delay between activation of the prothoracic glands and the production of an effective amount of moulting hormone is less than one day.  相似文献   

10.
11.
Abstract The structural gene for the haemolysin and two accessory genes from a Vibrio cholerae O1 El Tor strain have previously been cloned in Escherichia coli K-12 to give the plasmid pPM431. This plasmid has been used as a probe with a variety of O1 and non-O1 Vibrio cholerae strains to examine by Southern DNA hybridisations for the presence of homologous DNA. Such experiments show that the DNA homologous to that present in pPM431 is present in all of the 20 strains examined, whether they were haemolytic or non-haemolytic, implying that the genes were present but not expressed in non-haemolytic strains. Using a variety of restriction enzymes to cut the chromosomal DNA of different V. cholerae strains and probing with pPM431, it was possible to distinguish O1 and non-O1 strains, as well as haemolytic or non-haemolytic strains. This variability between hly+ and hly may be indicative of a change in the regulatory region of the haemolysin genes. The results also imply a high degree of homology of the haemolysin of O1 and non-O1 strains.  相似文献   

12.
Abstract A gene library of Chlamydia trachomatis serovar L2 (strain 434) was constructed in Escherichia coli using plasmid pBR322. Amongst 200 recombinants we have identified and characterized a recombinant E. coli that expresses a protein antigen of M r 74 000 similar in size to an outer membrane antigen produced by elementary bodies of C. trachomatis . Immunologically, the molecule synthesised by E. coli has the same specificity as the protein encoded by serovar L2. A 1.8 kb DNA fragment from the recombinant insert, used as a hybridization probe, confirmed the species specificity of this clone at the gene level.  相似文献   

13.
Abstract Ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) was purified from an obligately autotrophic hydrogen-oxidizing bacterium, Hydrogenovibrio marinus MH-110. The protein has a M r value of approximately 110 000, and is composed of two identical subunits of 55 000. To our knowledge, the existence of L2-form RubisCO in a chemolithoautotrophic bacterium is first reported in this paper. The N-terminal amino acid sequence determination of the purified enzyme showed high homology with those of the L2-form RubisCO of Rhodospirillum rubrum and the L x -form RubisCO from Rhodobacter sphaeroides .  相似文献   

14.
Abstract The C-terminal domain of the alpha-toxin (cpa247–370) of Clostridium perfringens has been expressed in Escherichia coli and purified. Antiserum raised against cpa247–370 reacted in an identical manner to anti-alpha-toxin serum when used to map epitopes in the C-terminal domain, suggesting that cpa247–370 was immunologically and structurally identical to this region in the alpha-toxin. The isolated cpa247–370 was devoid of sphingomyelinase activity or haemolytic activity and was not cytotoxic for mouse lymphocytes. Haemolytic activity was detected when cpa247–370 was tested with the N-terminal domain of the alpha-toxin (cpa1–249), confirming that cpa247–370 confers haemolytic properties on the phospholipase C activity of the alpha-toxin. Haemolytic activity was not detected if cpa247–370 was tested with the Bacillus cereus phosphatidylcholine phospholipase C, nor if cpa1–249 and cpa247–370 were incubated sequentially with erythrocytes.  相似文献   

15.
Abstract  The potential of a new, previously unidentified Serangium species (Col., Coccinellidae) to control the high Bemisia tabaci (Gennadius) (Hom., Aleyrodidae) populations on cassava was evaluated. Field and laboratory studies were carried out to determine the abundance and feeding capacity of this Serangium species feeding on B. tabaci on cassava. Serangium nymphs and adults were most abundant in cassava fields late in the season, rising sharply from 5 months after planting (MAP) to a peak at 7–8 MAP. Pre-imaginal development averaged 21.2 days and was longest in eggs and shortest in the L1 instar. Mean total prey consumption of immature Serangium increased with the stage of development with the lowest consumption in the L1 instar and highest in the L4 instar. Mean daily consumption was lowest on the first day after hatching in the L1 instar and rose to a peak on the 13th day after hatching in the L4 instar. Each Serangium larva consumed a mean of over 1000 nymphs during its entire development. These results have demonstrated the potential of this Serangium species to control B. tabaci populations on cassava.  相似文献   

16.
Lytic and bactericidal properties of salmonid sera   总被引:1,自引:0,他引:1  
There are two types of haemolytic activity against heterologous red blood cells in the sera of fishes including salmonids: a specific antibody-dependent complement-mediate activity 'CH50' and a natural, non-specific activity 'SH50'. Sera of coho salmon, Oncorhynchus kisutch , masu salmon, O. masou , rainbow trout and steelhead trout, Salmo gairdneri , were assayed for CH50 and SH50 activities by incubation at 30°C for 60 min with goldfish red blood cells (GFRBC) sensitized with the rainbow trout antiGFRBC serum and unsensitized GFRBC for CH50 and SH50, respectively. SH50 activity was usually half that of CH50 in each serum. In healthy individuals, both CH50 and SH50 activities were confined to a narrow range specific for each species. While EDTA abolished both haemolytic activities, moieties of the activities remained in the presence of EGTA. Incubation with lipopolysaccharide and zymosan reduced both CH50 and SH50 activities. Fish serum possessed a natural, powerful bactericidal action, which for Aeromonas salmonicida was proportional to the level of SH50 activity. Changes in the SH50 activity were related to starvation and infectious diseases. The SH50 activity decreased as the diseases (furunculosis and vibriosis) progressed.  相似文献   

17.
Abstract.  The Indian meal moth, Plodia interpunctella Hübner (Lepidoptera: Pyralidae) may enter diapause in the last larval instar in response to the photoperiod during the preceding instars. An hourglass-type photoperiodic clock may measure night length for this purpose. The present study describes the resetting of the hourglass by light pulse(s) in the early scotophase and by scanning the subsequent clock phase by another light pulse (P). When the lights-off time of a first light pulse is fixed at 4 h after dusk under LD 4 : 20 h and LD 6 : 18 h photoperiods and its duration is increased from 1 to 3 h, the critical night length (CNL) from dawn is decreased, but that from dusk to P increases. A 3-h first light pulse efficiently resets the time measuring system. If this 3-h light pulse is split into two 1-h light pulses (L1 and L2) by 1 h of darkness, the dark-time measuring function appears to be impeded and CNL from P to dawn disappears, but that from L2 to P is expressed. This indicates that the receptivity to light pulses varies among individual insects.  相似文献   

18.
Aims:  The present study was aimed to develop a loop-mediated isothermal amplification (LAMP) assay for rapid and specific detection of Vibrio cholerae .
Methods and Results:  A set of five designed primers that recognized specifically the V. cholerae ompW gene was used. The optimized time and temperature conditions for the LAMP assay were 75 min at 65°C, respectively. The LAMP method accurately identified 16 isolates of V. cholerae but did not detect 28 non- cholerae Vibrio isolates and 37 non- Vibrio bacterial isolates. The sensitivity of LAMP for V. cholerae detection in pure cultures was 2·2 × 103 CFU ml−1 or equivalent to 8 CFU per reaction. In the case of spiked shrimp samples without enrichment, the detection limit for V. cholerae was 2·2 × 104 CFU g−1 or equivalent to 20 CFU per reaction, while that of PCR was 100 CFU per reaction.
Conclusion:  The developed LAMP assay targeting ompW gene was rapid, specific and sensitive for V. cholerae detection.
Significant and Impact of the study:  The developed LAMP assay appears to be precise, accurate and a valuable tool for detection of V. cholerae . This assay can replace laborious biochemical tests for the identification of V. cholerae in contaminated food sample.  相似文献   

19.
Under saline conditions, an optimal cell water balance, possibly mediated by aquaporins, is important to maintain the whole-plant water status. Furthermore, excessive accumulation of boric acid in the soil solution can be observed in saline soils. In this work, the interaction between salinity and excess boron with respect to the root hydraulic conductance (L0), abundance of aquaporins (ZmPIP1 and ZmPIP2), ATPase activity and root sap nutrient content, in the highly boron- and salt-tolerant Zea mays L. cv. amylacea, was evaluated. A downregulation of root ZmPIP1 and ZmPIP2 aquaporin contents were observed in NaCl-treated plants in agreement with the L0 measurements. However, in the H3BO3-treated plants differences in the ZmPIP1 and ZmPIP2 abundance were observed. The ATPase activity was related directly to the amount of ATPase protein and Na+ concentration in the roots, for which an increase in NaCl- and H3BO3+ NaCl-treated plants was observed with respect to untreated and H3BO3-treated plants. Although nutrient imbalance may result from the effect of salinity or H3BO3 alone, an ameliorative effect was observed when both treatments were applied together. In conclusion, our results suggest that under salt stress, the activity of specific membrane components can be influenced directly by boric acid, regulating the functions of certain aquaporin isoforms and ATPase as possible components of the salinity tolerance mechanism.  相似文献   

20.
Abstract Three enterotoxic components have been isolated from a strain of Bacillus cereus which was involved in a large food poisoning outbreak in Norway in 1995. The components were purified by chromatography on three different columns. Three proteins of 39, 45 and 105 kDa, respectively, were found to be necessary for maximum cytotoxicity. The amino acid N-terminal sequences of the 39 and 45 kDa proteins were determined. The 45 kDa component was the same protein as the main antigen detected in the Bacillus Diarrhoeal Enterotoxin Visual Immunoassay (Tecra). The 39 kDa protein showed some similarity to the l1 protein of haemolysin BL from B. cereus . Furthermore, the three toxic components were all recognised by a polyclonal antiserum reported to detect enterotoxin from B. cereus . The proteins were different from the B- and L2-components of haemolysin BL, previously suggested to be a primary virulence factor, and had no detectable haemolytic activity.  相似文献   

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