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1.
2.
Intracellular crystals of aragonite have been identified by selected area electron diffraction (SAED) in a species of the freshwater filamentous alga Spirogyra from the Thames River, Ontario, Canada. The crystals are 2 to 24 μm in diameter, and characterized by a unique cross-shaped morphology, in which needle-like, or prismatic outgrowths develop from a common axis. Crystals may be dispersed throughout filaments, but tend to cluster as aggregates towards the centre . 相似文献
3.
Identification of major common extracellular proteins secreted by Aeromonas salmonicida strains isolated from diseased fish. 总被引:3,自引:1,他引:2 下载免费PDF全文
Ten different strains of Aeromonas salmonicida that were isolated from diseased fish were grown under identical conditions (24 h at 25 degree C) in 3% (wt/vol) tryptone soya broth medium supplemented with vitamins and inorganic ions. In each case the extracellular proteins that were formed were compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and it was found that there were two significant common components, one with a molecular weight of 70,000 and the other with a weight of 56,000. Application of enzyme purification techniques to the supernatant fraction proteins of a culture of one of the strains resulted in the isolation of a 70-kilodalton (kDa) component, which was found to be a serine protease, and a 56-kDa component, which was hemolytic to trout erythrocytes. Rocket immunoelectrophoresis with rabbit antibodies to the isolated protease and hemolysin showed the same antigenic components in the supernatant fractions of all the cultures. These activities were assayed, and protease activity was found to vary by a factor of three, from 59 to 195 U/ml, while the range of hemolytic activity was over a narrow band, from 28 to 43 U/ml. There was an inconsistency between the immunoelectrophoretic and direct assay data in only one case. This indicated the presence of additional hemolytic activity, in addition to the 56-kDa component. The detection of large amounts of the same protease and hemolysin, two potent degradative activities, in a random series of strains of A. salmonicida suggests that they may be obligatory virulence factors in the development of furunculosis. 相似文献
4.
Enzymatic assay for deoxyribonucleoside triphosphates using synthetic oligonucleotides as template primers 总被引:12,自引:0,他引:12
The enzymatic assay for deoxyribonucleoside triphosphates has been improved by using synthetic oligonucleotides of a carefully defined sequence as template primers for DNA polymerase. High backgrounds, which limit the sensitivity of the assay when calf thymus DNA or alternating copolymers are used as template primers, were eliminated with these oligonucleotide template primers. Sensitivity was further increased by designing the template primer to incorporate multiple labeled deoxyribonucleotides per limiting unlabeled deoxyribonucleotide. Each of several DNA polymerases exhibited unique reaction characteristics with the oligonucleotide template primers, which was attributed to the differing exonuclease activities associated with these various enzymes. Assay optimization therefore included matching the polymerase with the template primer to obtain the lowest background reaction and highest sensitivity. This modified assay is particularly well suited for keeping cell sample size to a minimum in experimental protocols which generate large numbers of data points or require careful timing of sampling. With this technique, we measured the levels of all four deoxyribonucleoside triphosphates in extracts from as few as 2 x 10(4) cultured cells. 相似文献
5.
Inhibition by local anaesthetics of adenine nucleotide translocation in rat liver mitochondria 总被引:3,自引:3,他引:0 下载免费PDF全文
1. The mechanism of adenine nucleotide translocation in mitochondria isolated from rat liver was further examined by using the local anaesthetics procaine, butacaine, nupercaine and tetracaine as perturbators of lipid-protein interactions. Each of these compounds inhibited translocation of ADP and of ATP; butacaine was the most effective with 50% inhibition occurring at 30mum for 200mum-ATP and at 10mum for 200mum-ADP. The degree of inhibition by butacaine of both adenine nucleotides was dependent on the concentration of adenine nucleotide present; with low concentrations of adenine nucleotide, low concentrations of butacaine-stimulated translocation, but at high concentrations (greater than 50mum) low concentrations of butacaine inhibited translocation. Butacaine increased the affinity of the translocase for ATP to a value which approached that of ADP. 2. Higher concentrations of nupercaine and of tetracaine were required to inhibit translocation of both nucleotides; 50% inhibition of ATP translocation occurred at concentrations of 0.5mm and 0.8mm of these compounds respectively. The pattern of inhibition of ADP translocation by nupercaine and tetracaine was more complex than that of ATP; at very low concentrations (less than 250mum) inhibition ensued, followed by a return to almost original rates at 1mm. At higher concentrations inhibition of ADP translocation resulted. 3. That portion of ATP translocation stimulated by Ca(2+) was preferentially inhibited by each of the local anaesthetics tested. In contrast, inhibition by the anaesthetics of ADP translocation was prevented by low concentrations of Ca(2+). 4. The data provide further support for our hypothesis that lipid-protein interactions are important determinants in the activity of the adenine nucleotide translocase in mitochondria. 相似文献
6.
The inhibition of mitochondrial calcium transport by lanthanides and Ruthenium Red 总被引:28,自引:16,他引:12 下载免费PDF全文
An EGTA (ethanedioxybis(ethylamine)tetra-acetic acid)-quench technique was developed for measuring initial rates of (45)Ca(2+) transport by rat liver mitochondria. This method was used in conjunction with studies of Ca(2+)-stimulated respiration to examine the mechanisms of inhibition of Ca(2+) transport by the lanthanides and Ruthenium Red. Ruthenium Red inhibits Ca(2+) transport non-competitively with K(i) 3x10(-8)m; there are 0.08nmol of carrier-specific binding sites/mg of protein. The inhibition by La(3+) is competitive (K(i)=2x10(-8)m); the concentration of lanthanide-sensitive sites is less than 0.001nmol/mg of protein. A further difference between their modes of action is that lanthanide inhibition diminishes with time whereas that by Ruthenium Red does not. Binding studies showed that both classes of inhibitor bind to a relatively large number of external sites (probably identical with the ;low-affinity' Ca(2+)-binding sites). La(3+) competes with Ruthenium Red for most of these sites, but a small fraction of the bound Ruthenium Red (less than 2nmol/mg of protein) is not displaced by La(3+). The results are discussed briefly in relation to possible models for a Ca(2+) carrier. 相似文献
7.
Isolation of microfilaments from Amoeba proteus 总被引:2,自引:0,他引:2
8.
The molecular evolution of mammalian Y-linked DNA sequences is of special
interest because of their unique mode of inheritance: most Y- linked
sequences are clonally inherited from father to son. Here we investigate
the use of Y-linked sequences for phylogenetic inference. We describe a
comparative analysis of a 515-bp region from the male sex- determining
locus, Sry, in 22 murine rodents (subfamily Murinae, family Muridae),
including representatives from nine species of Mus, and from two additional
murine genera--Mastomys and Hylomyscus. Percent sequence divergence was
< 0.01% for comparisons between populations within a species and was
0.19%-8.16% for comparisons between species. Our phylogenetic analysis of
12 murine taxa resulted in a single most- parsimonius tree that is highly
concordant with phylogenies based on mitochondrial DNA and allozymes. A
total evidence tree based on the combined data from Sry, mitochondrial DNA,
and allozymes supports (1) the monophyly of the subgenus Mus, (2) its
division into a Palearctic group (M. musculus, M. domesticus, M.
spicilegus, M. Macedonicus, and M. spretus) and an Oriental group (M.
cookii++, M. cervicolor, and M. caroli), and (3) sister-group relationships
between M. spicilegus and M. macedonicus and between M. cookii and M.
cervicolor. We argue that Y- chromosome DNA sequences represent a valuable
new source of characters for phylogenetic inference.
相似文献
9.
10.
Active and passive cation transport and L antigen hertogeneity in low potassium sheep red cells 下载免费PDF全文
Several lines of experimental evidence are presented suggesting that the L antigens in low potassium (LK) sheep red cells are associated with separate Na(+)K(+) pump flux is distinct from the action of anti-L(l) on K(+) leak flux, implying that K(+) leak transport sites may not be converted into active pumps by the L antiserum. Treatment of LK red cells with trypsin completely abolished both the stimulation of K(+) pump flux and the enhancement of the rate of ouabain binding brought about by anti- L. That this effect is due to a total destruction of the L(p) determinant associated with the LK pump was evident from the complete failure of anti-L(p) to bind to trypsinized LK red cells. The L(p) antigen can be effectively protected against the trypsin attack by prior incubation with anti-L, indicating that the sites for antibody binding and trypsin action may be closely adjacent at the structural level. Trypsin treatment, however, did not interfere with anti-L(l) reducing ouabain insensitive K(+) leak influx, nor did it prevent binding of anti-L(ly), the hemolytically active L antibody which is probably identical with anti-L(l). The functional independence of the L(p) and L(l) sites was documented by the observation that anti-L(l) still reduced K(+) leak influx in LK cells with experimentally induced high potassium concentrations, at which K(+) pump flux is fully suppressed, whether or not anti-L(p) was binding to the L(p) antigen associated with the LK pump. 相似文献