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141.
Switzerland is one of the few countries where high fertility rates have been reported in cattle hydatid cysts and where the cattle/dog cycle is the most important for the maintenance of Echinococcus granulosus. The developmental and morphological characteristics of E. granulosus of Swiss cattle origin were studied and compared with that of E. granulosus of domestic animal origin from Great Britain and Australia, countries where bovine hydatid cysts are usually sterile and cattle play little role in the life-cycle of the parasite. Adult E. granulosus of Swiss cattle origin differed markedly in its developmental characteristics compared to other isolates, particularly in its rate of maturation in dogs, producing eggs as early as 35 days post-infection. The morphology of E. granulosus of Swiss cattle origin was characteristic and it could be easily distinguished from other isolates of the parasite. Further, E. granulosus of Swiss cattle origin was found to closely resemble that occurring in cattle in South Africa where high fertility rates have also been reported in bovine hydatid cysts. It is concluded that a strain of E. granulosus exists which is adapted to cattle and that further studies are required to determine whether this strain warrants formal taxonomic status as the species E. ortleppi which was originally described for the parasite of South African cattle origin. 相似文献
142.
Use of chromosomal integration in the establishment and expression of blaZ, a Staphylococcus aureus beta-lactamase gene, in Bacillus subtilis 总被引:19,自引:12,他引:7
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C W Saunders B J Schmidt M S Mirot L D Thompson M S Guyer 《Journal of bacteriology》1984,157(3):718-726
With several different vectors, attempts were made to establish blaZ, a Staphylococcus aureus beta-lactamase gene, in Bacillus subtilis. Stable establishment of blaZ in B. subtilis was achieved by use of a vector that allowed the integration of a single copy of the gene into the chromosome of that host. blaZ was expressed in the heterologous host since B. subtilis strains carrying integrated blaZ produced beta-lactamase and were more resistant to ampicillin than was wild-type B. subtilis. blaZ was stably inherited in such strains, as no loss of the ability to produce beta-lactamase was observed after growth in nonselective liquid medium or on solid medium. In contrast, a blaZ-containing restriction fragment could not be established in B. subtilis with either pUB110- or pC194-based vectors. Similarly, a pC194-based shuttle vector (pGX318) containing the 5' end of blaZ (including the promoter and the coding region for the signal sequence and the first few amino acids of the mature protein) was unable to transform B. subtilis. Two derivatives of pGX318 that could be stably established in B. subtilis were isolated. The structures of these derivatives suggested that inactivation of the blaZ promoter was associated with the acquisition of the ability to be established. 相似文献
143.
Order in supported phospholipid monolayers detected by the dichroism of fluorescence excited with polarized evanescent illumination. 总被引:9,自引:8,他引:1
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A technique is described and demonstrated for measuring the orientation distribution of fluorescent molecules in a two-dimensional system. A laser beam is totally internally reflected at the interface between a glass slide and an aqueous solution, which creates a thin layer of evanescent illumination that excites fluorescent molecules near the interface. Molecules with absorption dipoles at different tilts from the normal to the interface are preferentially excited when the laser polarization is rotated. Approximately one-half of the emitted fluorescence is collected with an inverted microscope using a high-aperture objective. The fluorescence vs. polarization curve yields the value of an order parameter that is related to the orientation distribution of absorption dipoles. This technique is applied to phospholipid monolayers made at an air/water interface and transferred to hydrophobic glass microscope slides. Dipalmitoylphosphatidylcholine monolayers were doped with 2 mol% phosphatidylethanolamine labeled with the fluorescent moiety nitrobenzoxadiazole, either on an acyl chain or on the head group. The measured value of the order parameter for the head-labeled probe decreases as a function of the surface pressure at which the monolayer is transferred to the slide, as the surface pressure increases from 10 to 40 dyne/cm. The measured value of the order parameter for the chain-labeled probe is high for all coating pressures. These results can be interpreted in terms of probe partitioning into coexistent fluid and solid domains. Dimyristoylphosphatidylcholine monolayers were doped with 2 mol% chain-labeled phosphatidylethanolamine, either free or covalently conjugated to a small peptide.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
144.
Poly(ADP-ribose) metabolism appears normal in EM9, a mutagen-sensitive mutant of CHO cells 总被引:5,自引:1,他引:4
EM9 is a mutagen-sensitive CHO cell whose phenotype resembles that of normal CHO cells exposed to 3-aminobenzamide, an inhibitor of poly(ADP-ribose) synthesis. This phenotype suggested that EM9 might be defective in poly(ADP-ribose) metabolism, but we now cannot find any abnormality in the synthesis or in the degradation of poly(ADP-ribose) in permeabilized EM9 cells. Thus the effects of 3-aminobenzamide on wild-type cells may be due to the inhibition of processes other than poly(ADP-ribose) synthesis. 3-Aminobenzamide enhances the cytotoxicity of EMS toward EM9 and control cells to the same degree. 相似文献
145.
Coupled transcription--translation in extracts of Streptomyces lividans 总被引:10,自引:0,他引:10
146.
Heterogeneity among microtubules of the cytoplasmic microtubule complex detected by a monoclonal antibody to alpha tubulin 总被引:14,自引:9,他引:5
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Three monoclonal antibodies specific for tubulin were tested by indirect immunofluorescence for their ability to stain cytoplasmic microtubules of mouse and human fibroblastic cells. We used double label immunofluorescence to compare the staining patterns of these antibodies with the total microtubule complex in the same cells that were stained with a polyclonal rabbit antitubulin reagent. Two of the monoclonal antitubulin antibodies bound to all of the cytoplasmic microtubules but Ab 1-6. 1 bound only a subset of cytoplasmic microtubules within individual fixed cells. Differential staining patterns were observed under various fixation conditions and staining protocols, in detergent-extracted cytoskeletons as well as in whole fixed cells. At least one physiologically defined subset of cytoplasmic microtubules, those remaining in cells pretreated for 1 h with 5 microM colcemid, appeared to consist entirely of Ab 1-6. 1 positive microtubules. The same was not true of the microtubules that remained in either cold-treated cells or in cells that had been exposed to hypotonic medium. The demonstration of antigenic differences among microtubules within single fixed cells and the apparent correlation of this antigenic difference with at least one "physiologically" defined subset suggests that mechanisms exist for the differential assembly or postassembly modification of individual microtubules in vivo, which may endow them with different physical or functional properties. 相似文献
147.
The levels of adenylate nucleotides were examined in 4th-instar Trichoplusia ni larvae 3 days after parasitization by the insect parasite Hyposoter exiguae. In general, parasitization caused a decrease in the level of ATP and increased ADP and AMP levels. These changes resulted in alteration of the adenylate kinase mass-action ratio. The overall energy status of parasitized larvae, however, as indicated by energy ratios, including the “energy charge,” was affected only slightly. The result demonstrates that the host maintained an active and viable metabolic state despite extensive alterations in physiology which occur at this stage of the parasite-host association. 相似文献
148.
Rapid recovery from K current inactivation on membrane hyperpolarization in molluscan neurons 总被引:3,自引:1,他引:2
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Recovery from K current inactivation was studied in molluscan neurons using two-microelectrode and internal perfusion voltage clamps. Experiments were designed to study the voltage-dependent delayed outward current (IK) without contamination from other K currents. The amount of recovery from inactivation and the rate of recovery increase dramatically when the membrane potential is made more negative. The time course of recovery at the resting potential, -40 mV, is well fit by a single exponential with a time constant of 24.5 s (n = 7). At more negative voltages, the time course is best fit by the sum of two exponentials with time constants at -90 mV of 1.7 and 9.8 s (n = 7). In unclamped cells, a short hyperpolarization can cause rapid recovery from inactivation that results in a shortening of the action potential duration. We conclude that there are two inactivated states of the channel and that the time constants for recovery from both states are voltage dependent. The results are discussed in terms of the multistate model for K channel gating that was developed by R. N. Aldrich (1981, Biophys. J., 36:519-532). 相似文献
149.
J F Bastian J M Ruedi G A MacPherson H E Golembesky R D O'Connor L F Thompson 《Journal of immunology (Baltimore, Md. : 1950)》1984,132(4):1767-1772
Ecto-5'-nucleotidase activity was measured in peripheral blood lymphocytes isolated from serial specimens from nine healthy full-term infants and two premature infants at 0, 2, 4, and 6 mo of age. The postnatal nadir in activity was 7.1 +/- 2.0 nmol/hr/10(6) cells, which is the same as the activity in cord blood lymphocytes (7.0 +/- 2 nmol/hr/10(6) cells). The activity rose twofold to 13.2 +/- 3.8 nmol/hr/10(6) cells at 6 mo of age (p less than 0.001, paired t-test), which is similar to the activity in adult peripheral blood lymphocytes (14.1 +/- 6.3 nmol/hr/10(6) cells). This increased activity in total lymphocytes reflects increased activity in the B cell population. B cell ecto-5'-nucleotidase activity in two infants at 12 to 13 mo of age was 19.3 and 25.2 nmol/hr/10(6) cells, values that are four-to fivefold higher than for cord blood B cells (5.6 +/- 2.8 nmol/hr/10(6) cells) and within the normal range for adult B cells (27.9 +/- 12 nmol/hr/10(6) cells). In spite of a greatly expanded peripheral blood B cell population, studies of immunoglobulin biosynthesis in vitro demonstrated that infant peripheral blood B cells are functionally immature with no synthesis of IgG in response to Epstein Barr virus. Thus, the increase in peripheral blood B lymphocyte ecto-5'-nucleotidase activity in infants precedes their acquisition of a capacity for IgG synthesis in vitro. Data from a hypogammaglobulinemic infant revealed a persistently low ecto-5'-nucleotidase activity over a 10-mo period until at 14 mo of age the activity was 8.8 nmol/hr/10(6) cells in total lymphocytes and 13.0 nmol/hr/10(6) cells in B cells, which correlated with in vivo and in vitro evidence of delayed B cell maturation. Thus, ecto-5'-nucleotidase activity may be a useful cell surface marker in studies of human postnatal B cell maturation. 相似文献
150.
Phenotype and function of engrafted maternal T cells in patients with severe combined immunodeficiency 总被引:6,自引:0,他引:6
L F Thompson R D O'Connor J F Bastian 《Journal of immunology (Baltimore, Md. : 1950)》1984,133(5):2513-2517
Engrafted maternal T cells from two patients with severe combined immunodeficiency (SCID) and graft-vs-host disease (GVHD) were characterized for surface phenotype, function, and ecto-5'-nucleotidase (ecto-5'-NT) activity. The majority of engrafted T cells from both patients were T6-, T3+, and Ia+; the ratio of T4+:T8+ cells varied from 0.89 to 3.1 for Patient 1 and was 0.17 for Patient 2. The sum of T4+ + T8+ cells was greater than the number of T3+ cells, and approximately one-third of the patients' T cells were T3-. Two-color immunofluorescent staining showed that one-third of the T cells from Patient 1 had a novel cell surface phenotype (T6-, T3-, T4+, T8+) that was not previously described. T cells from Patient 1 failed to proliferate in response to allogeneic cells or specific antigen and provided little help for PWM-driven Ig synthesis in vitro. However, they did suppress Ig synthesis in vitro and proliferate in response to PHA and Con A; thus they appeared to be more mature than the T cells of Patient 2 and of most previously reported patients with SCID and maternal T cell grafts. Both patients lacked detectable lymphocyte ecto-5'-NT activity, suggesting that either the ecto-5'-NT activity of maternal T cells is lost after engraftment or that a specific subset(s) of ecto-5'-NT-negative maternal T cells predominates in infants with SCID and GVHD. Thus, in vitro T cell function and the proportions of T cells bearing T4 and T8 may vary in SCID patients with maternal T cell grafts. However, the presence of the Ia antigen and the absence of ecto-5'-NT activity may be consistent features of activated maternal T cells responsible for GVHD. 相似文献