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11.
Release of leukotriene C4 from guinea pig trachea 总被引:1,自引:0,他引:1
Immunological (ovalbumin) and non-immunological (calcium ionophore A23187) stimulation of guinea pig trachea induces a prolonged contraction that is enhanced by indomethacin (8.5 microM) and inhibited by nordihydroguaiaretic acid (50 microM) pretreatment of the tissue. The mediator released by the above stimuli was identified as leukotriene C4 by reverse-phase high performance liquid chromatography, and quantitated by bioassay. Indomethacin, and/or arachidonic acid (32.8 microM) did not enhance the release, whereas nordihydroguaiaretic acid reduced the contraction and release of LTC4. The results demonstrate the hitherto unproved capability of the large airways to synthesize leukotrienes and emphasize the importance of examining their role in asthma. 相似文献
12.
Preliminary Observations on the Pathogenesis of a Virulent Strain of Newcastle Disease Virus in Chickens
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Development of Newcastle disease, after experimental and natural infection with the virulent strain VLT of Newcastle disease virus, and its growth and distribution in some selected tissues as assayed by the enumeration of plaques are reported. 相似文献
13.
Dr. María Cristina Maldonado Ana María Strasser de Saad Danley Callieri 《Current microbiology》1989,18(5):303-306
Several recent reports have described large numbers of monoclonal antibodies that cross-react with toxins A and B ofClostridium difficile; this suggests that the toxins share major epitopes. Our results show that monoclonal antibodies (MAb) against other antigens bind nonspecifically to both toxins. Therefore, we believe that the cross-reacting MAb bind by this manner and not by a true immune reaction. 相似文献
14.
Previous studies have shown that the esterase 6 (EST6) enzyme ofD. melanogaster is mainly produced in the sperm ejaculatory duct of the adult male and comparisons of wild-type males with laboratory null mutants have suggested that the enzyme plays a role in reproductive fitness. In this study we have compared 18 field-derived lines each isoallelic forEst6 for differences in five components of male reproductive fitness. No consistent fitness differences were found among lines differing in respect of the two major allozyme classes EST6-F and EST6-S, despite other evidence that these two classes are not selectively equivalent in the field. However, differences in reproductive fitness were found among lines differing in the minor mobility variants that segregate within EST6-F and EST6-S. A failure to distinguish among these minor forms may explain the discrepancies in previous studies on the effects of the major EST6 allozymes on reproductive fitness. The most significant associations we have found between EST6 and reproductive fitness were due to variation in EST6 activity levels. Male EST6 activity levels were found to be positively correlated with their time to first mating, negatively correlated with the numbers of eggs laid and progeny produced by their mates, and negatively correlated with the frequency with which their mates remate. We conclude that some EST6 variants differ in components of male reproductive fitness operative in laboratory cultures. However, the evidence for fitness differences is stronger for variants affecting the amount, rather than the structure of the enzyme, and the direction of the differences varies between some of the fitness components tested. 相似文献
15.
Andrea Evangelina Arcángel Emiliano Alexis Rodríguez Juan Francisco Saad Paula de la Barra Maite Andrea Narvarte Lorena Pía Storero Patricio Javier Pereyra 《Journal of phycology》2023,59(6):1310-1322
Population dynamics can be influenced by physical and biological factors, particularly in stressful environments. Introduced species usually have great physiological plasticity, resulting in populations with different traits. Undaria pinnatifida, a macroalga originally described from northeast Asia, was introduced in Northern Patagonia, Argentina (San Matías Gulf) around 2010. To describe the spatio-temporal variability in population structure and morphometry of U. pinnatifida, we conducted monthly field samplings for 2 years at the intertidal area of two contrasting sites in the San Matías Gulf. Individuals of U. pinnatifida were classified by developmental stage, and their morpho-gravimetric variables were measured. In both intertidal sites juveniles were found in higher proportion during austral autumn and grew and matured during the autumn-winter months (from May onwards), and individuals senesced during early austral summer (December and January). Conversely, density and biomass were largely different between sites, and individuals showed slight morphological variability between sites. Environmental (e.g., nutrient concentration, available substrate) and biological factors (e.g., facilitation, competition) may explain the observed differences. Since there is not a macroalga with U. pinnatifida morphometrical characteristics in the intertidal environments of San Matías Gulf, studying this recent introduction gives us a better understanding of its potential ecological effects. 相似文献
16.
Sanaa Hamdy Omar Siegfried Honecker Hans-Jürgen Rehm 《Applied microbiology and biotechnology》1992,36(4):518-524
Summary The formation of citric acid, oxalic acid, erythritol and glycerol by three strains of Aspergillus niger immobilized in calcium alginate was investigated and compared with that of free cells when cultivated in shake flasks under phosphate limitation. Morphological changes were followed using an electron microscope. The production of acids and polyols, the consumption of glucose and fructose, and also the morphological changes were strain-dependent. The results also reflected the influence of long storage of a strain on productivity, morphological behaviour and phosphate consumption.
Offprint requests to: H.-J. Rehm 相似文献
17.
A.D. Saad B.M. Soh A.A. Moscona 《Biochemical and biophysical research communications》1981,98(3):701-708
Cortisol induces glutamine synthetase (GS) in neural retina tissue of chick embryos. GS induction represents a characteristic feature of embryonic retina differentiation. However, if the tissue is dissociated into single cells, the dispersed cells are not inducible for GS. We report that cell dispersion results in a rapid and marked reduction in the level of cortisol-binding cytoplasmic receptors. This reduction persists if the cells are maintained in a dispersed state. However, if the cells are reaggregated and they reconstruct tissue-like contacts and architecture, the level of cortisol receptors increases, and so does inducibility for GS. The results indicate that, in the embryonic neural retina histotypic cell contacts and interactions are involved in regulating the level of cortisol receptors. We propose that cell contact-dependent signals from the cell surface may modulate levels of cytoplasmic cortisol receptors necessary for GS induction. 相似文献
18.
A series of aroyl- and aryl-hydrazide derivatives was prepared from d-glycero-d-gulo-heptono-1,4-lactone (1). The reactivity of the NH proton in these hydrazides, in terms of their dissociation constants (pKa), was determined from their electronic spectra, and correlated to the Hammett σ values of the substituents. Comparable reactivities of the NH protons for the compounds, and the effect of the substituent, were studied by n.m.r. spectroscopy. Decomposition of the aroylhydrazides with copper(II) sulfate or nitrous acid resulted in the regeneration of 1. 相似文献
19.
A 60Co source was used to determine the effects of thermoradiation on Achromobacter aquamarinus, Staphylococcus aureus, and vegetative and spore cells of Bacillus subtilis var. globigii. The rate of inactivation of these cultures, except vegetative-cell populations of B. subtilis, was exponential and in direct proportion to temperature. The D10 (dose that inactivates 90% of the microbial population) value for A. aquamarinus was 8.0 Krad at 25 degrees C and 4.9 Krad at 35 degrees C. For S. aureus, D10 was 9.8 and 5.3 Krad at 35 and 45 degrees C, respectively. Vegetative cells of B. subtilis demonstrated a rapid initial inactivation followed by a steady but decreased exponential rate. The D10 at 25 degrees C was 10.3 Krad, but at 35 and 45 degrees C this value was 6.2 and 3.8 Krad, respectively. Between 0 and 95 Krad, survival curves for B. subtilis spores at 75 degrees C showed slight inactivation, increasing in rat at and above 85 degrees C. The D10 values for spores at 85 and 90 degrees C were 129 and 92 Krad, respectively. Significant synergism between heat and irradiation was noted at 35 degrees C for A. aquamarinus and 45 degrees C for S. aureus. The presence of 0.1 mM cysteine in suspending media afforded protection to both cultures at these critical temperatures. On the other hand, cysteine sensitized B. subtilis spores at radiation doses greater than 100 Krad. The combined effect of heat and irradiation was more destructive to bacteria than either method alone. 相似文献
20.
Summary The antibacterial effect of negapillin in combination with other antibiotics and sulfa drugs was studied using Gram+ve and Gram-ve bacteria as test organisms. Subsequently, various proportions of negapillin in combination with the antibiotics and the sulfa drugs were examined to determine the optimum proportions which exert maximum inhibitory effects on the bacterial growth. Mixtures of these antibiotics with negapillin were found more superior not only as antimicrobial agents but also for having comparatively low toxicity. 相似文献