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71.
The morphology of Mucor racemosus in cultures continuously sparged with nitrogen gas was investigated. When appropriate precautions were taken to prevent oxygen from entering the cultures, the morphology of the cells was uniformly yeastlike irrespective of the N2 flow rate. When small amounts of oxygen entered the cultures the resulting microaerobic conditions evoked mycelial development. Polypeptides synthesized by aerobic mycelia, microaerobic mycelia, anaerobic yeasts, and yeasts grown in a CO2 atmosphere were compared by two-dimensional gel electrophoresis. The results indicated that a large number of differences in polypeptide expression exist when microaerobic mycelia or anaerobic yeasts are compared with aerobic mycelia and that these alterations correlate with a change from an oxidative to a fermentative metabolic mode. Relatively few differences in polypeptide composition exist when microaerobic cells are compared with anaerobic cells, but these changes correlate with a change from the mycelial to the yeast morphology. We hypothesize that oxygen regulates the expression of polypeptides involved in both the metabolic mode and in morphogenesis. 相似文献
72.
Crystals of type I cAMP-dependent protein kinase regulatory subunit have been grown from solutions of ammonium sulfate. The crystals are square bipyramids, space group P4(1)2(1)2 (P4(3)2(1)2), with a = b = 106.9 +/- 0.6 A and c = 212.4 +/- 1.0 A. There are two dimers of the regulatory subunit/crystallographic asymmetric unit. The crystals are stable for 3-4 days in the x-ray beam and diffract to at least 3.5-A resolution. 相似文献
73.
Organogenesis in pepper tissue cultures 总被引:6,自引:0,他引:6
Knowledge concerning in vitro growth and developmental responses of bell and chile peppers (Capsicum annuum L.) has been limited. Shoot and root organogenesis in cultures of seedling explants was restricted to primary cultures or those less than three months old under 12-and 16-h photoperiod at 25°C. Shoot organogenesis was extended to 5 months under continuous light at 25°C, and to 8 months under continuous light at 28.5°C. Murashige and Skoog basal media containing 0.05mg/l each of IAA and BA promoted shoot elongation and rooting of some explant sources, while 0.05-4 mg/l IAA with 10–50 mg/l BA promoted adventitious shoot bud formation. Glucose was superior to sucrose as the carbon source. Leaf discs collected from greenhouse-grown plants regenerated shoots for at least 2 months. Incubation environment, carbon source, explant source, growth regulator treatment and passage number were not independent variables as demonstrated by statistical analysis. The plant regeneration techniques described here have useful but limited applications, not extending to unorganized callus or cell suspension cultures.Journal article no. 1151 of the New Mexico Agricultural Experiment Station. 相似文献
74.
Using a commercial flow cytometer (Cyto-fluorograf), narrow-forward-angle (NFA) light-scatter signals were detected for spore preparations of Bacillus anthracis Vollum, B. anthracis Sterne, B. cereus NCTC 8035, and B. subtilis var niger. In the flow immunofluorescence (FIF) analysis of spores stained with fluorescein-conjugated hyperimmune antibody to B. anthracis Vollum spores, fluorescence histograms could be acquired by selecting on NFA scatter. Fluorescence data selected on ninety degree scatter were rather noisier. Fluorescence analysis by dual parameter NFA scatter-FIF techniques was shown to have several advantages over the subtraction FIF method reported earlier. The implication from FIF analysis of spore suspensions and corresponding cell-free supernatants that the peak in the fluorescence histogram was caused by signals from fluorescing spores, was confirmed by use of the cell sorter and subsequent microscopy of the sorted samples. Although a proportion of spore aggregates was present in samples sorted from the right-hand tail of the fluorescence histogram, it was demonstrated that the majority of the observed distribution of fluorescence was not due to the formation of aggregates but was rather an expression of variation in the degree of staining of individual spores. 相似文献
75.
Abstract Hydrogen fluoride treatment of [14 C-glycerol]lipoteichoic acid synthesized by growing Streptococcus faecium ATCC9790 in the presence of 1,3[14 C]glycerol produced five radioactive, water-soluble products which were identified by chromatographic and analytical techniques to be tetraglucosyl glycerol, triglucosyl glycerol, diglucosyl glycerol, monoglucosyl glycerol and unsubstituted glycerol. The percent composition of each varied modestly from culture to culture and ranged between 7 and 8% for the tetra-, 20.5 and 31.2% for the tri-, 11.3 to 23.5% for the di-, 20.9 to 26.8% for the mono-, and 23.1 to 34.8% for the unsubstituted glycerol. The same glucosylated glycerol compounds could be obtained in an in vitro reaction in which a 30 000 × g particulate enzyme catalyzed the incorporation of [3 H]glucose from UDP [3 H]glucose into lipoteichoic acid. 相似文献
76.
Three hundred and twenty five episodes of pneumococcal bacteraemia occurred at St Thomas''s Hospital during 1970-84, accounting for 13.3% of all episodes of bacteraemia. Twice as many cases occurred in male as in female patients, and common predisposing factors included chronic chest disease, alcoholism, haematological malignancies, cirrhosis, and sickle cell anaemia. Mortality was 28.6% overall but only 11.8% among patients who received antibiotic treatment for at least 24 hours. Most patients (261) had pneumonia, 26 had meningitis, and eight were children with occult bacteraemia. The commonest serotype of pneumococcus in adults was type 3 (39 episodes), and these strains were associated with a high mortality. Other factors determining a fatal outcome included underlying disease (such as cirrhosis, malignancy, and chronic chest disease) and extrapulmonary infection. Almost half the survivors were treated for 10 days or less and became afebrile within 48 hours. 相似文献
77.
78.
Kraig Adler John B. Phillips 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1985,156(4):547-552
Summary The diurnal escape response of fringetoed lizards (Uma notata) startled by predators demonstrates clear directional orientation not likely to depend on local landmarks in the shifting sands of their desert environment. Evidence that celestial orientation is involved in this behavior has been sought in the present experiments by testing the effects of (1) phase shifting the animal's internal clock by 6 h and (2) by training the lizards to seek shelter while exposed to natural polarization patterns. In the first case, 90° shifts in escape direction were demonstrated in outdoor tests, as expected if a time-compensated sun or sky polarized light compass is involved. In the second instance, significant bimodale-vector dependent orientation was found under an overhead polarizing light filter but this was only evident when the response data were transposed to match the zenithe-vector rotation dependent on the sun's apparent movement through the sky. This extends to reptiles the capacity to utilize overheade-vector directions as a time-compensated sky compass. The sensory site of this discrimination and the relative roles of sun and sky polarization in nature remain to be discovered. 相似文献
79.
Cross-linking of B lymphocyte Fc gamma receptors and membrane immunoglobulin inhibits anti-immunoglobulin-induced blastogenesis 总被引:22,自引:0,他引:22
The Fc portion of rabbit anti-mouse immunoglobulin (Ig) antibodies interferes with anti-Ig-induced B lymphocyte activation as measured by DNA synthesis on day 3 of culture or maturation to Ig-secreting cells in the presence of soluble helper factors on day 4 or 5. To investigate this Fc-dependent effect at an earlier stage in B cell activation, rabbit IgG anti-mouse mu-chain- or delta-chain-specific antibodies were compared with their F(ab')2 fragments for the ability to induce mouse B cells to undergo blast transformation, as defined by an increase in cell volume during the first 24 hr of culture. Both F(ab')2 anti-Ig reagents induce blast transformation, although F(ab')2 anti-mu antibodies induce a greater size change than F(ab')2 anti-delta antibodies. Whole anti-mu or anti-delta antibodies do not induce blast transformation; however, in the presence of a monoclonal anti-mouse Fc gamma receptor antibody that blocks IgG binding to Fc gamma receptors (Fc gamma R), whole anti-mu or anti-delta antibodies induce blast transformation as well as their F(ab')2 fragments. Because the anti-Fc gamma R antibody alone has no effect on blast transformation, it appears that the simultaneous binding of membrane IgM (or IgD) and Fc gamma R by whole anti-Ig antibodies prevents this early event in membrane Ig-induced B cell activation. 相似文献
80.
B L Doughty E A Ottesen T E Nash S M Phillips 《Journal of immunology (Baltimore, Md. : 1950)》1984,133(2):993-997
An in vitro model of granuloma formation was used to study the cellular immune responses of Schistosoma mansoni-infected patients. The purposes of this study were to determine the relationship of granulomatous hypersensitivity to S. mansoni eggs in recent, well-defined infections and long-term chronic infections, and to determine the role of T cell subsets (OKT3, 4, and 8) defined by monoclonal antibodies in granulomatous hypersensitivity. Peripheral blood mononuclear cells obtained from patients with recent S. mansoni infections demonstrated increased granulomatous hypersensitivity responses in vitro when compared to peripheral blood mononuclear cells obtained from patients infected for 5 yr or more. The selective removal of infected for 5 yr or more. The selective removal of OKT3+ or OKT4+ cells reduced the ability of peripheral blood mononuclear cells to form granulomas in vitro. Positive selection for OKT4+ T cells produced optimal granulomatous hypersensitivity when compared to that produced by the unfractionated peripheral blood mononuclear cell population. OKT8+ cells demonstrated no ability to form granulomas in vitro. Selective removal of OKT8+ T cells produced variable results in the ability of the remaining peripheral blood mononuclear cells to form granulomas in vitro. These studies demonstrate the feasibility of investigating granulomatous hypersensitivity and immunoregulatory mechanisms operative in S. mansoni-infected patients by using in vitro technology. 相似文献