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221.
Mark Tony Lieberman Robert M. Zablotowicz Naida P. Davis-Omholt 《Applied microbiology》1986,51(4):715-719
An improved method for antibiotic resistance recovery of Bradyrhizobium japonicum from soybean (Glycine max (L.) Merr.) nodules that is simple, time saving, and economical was developed. This technique involves the use of two 96-well microtiter plates as a multinodule sterilization chamber and a template and a third plate as a 16-point replicator constructed with steel nails affixed to the plate with epoxy cement. With this system a team of four technicians could type 3,000 nodules per day. This method was useful in assessing strain establishment and interstrain competition when one or more uniquely labeled strains of B. japonicum were inoculated onto either growth-room- or field-grown soybeans. Contamination was low and reproducibility across replicates approached the theoretical upper limit. Simplicity in design and use made this recovery method especially adaptable for field studies in which large numbers of nodules were required to provide a representative statistical sample offering good precision. 相似文献
222.
Inhibitory Effect of Autoclaving Whey-Based Medium on Propionic Acid Production by Propionibacterium shermanii 总被引:3,自引:1,他引:2 下载免费PDF全文
Thomas M. Anderson Elizabeth A. Bodie Nelson Goodman Robert D. Schwartz 《Applied microbiology》1986,51(2):427-428
Propionic acid production by Propionibacterium shermanii was compared in pasteurized and autoclaved whey-based media. Propionic acid production decreased with increasing whey concentration in autoclaved media but not in pasteurized media. Increasing the yeast extract concentration from 5 to 10 g/liter greatly reduced the inhibitory effect of autoclaving. 相似文献
223.
Acclimation of a sandy soil to an air-natural gas mixture stimulated the biological oxidation of chloroform to carbon dioxide. Acetylene and methane inhibited chloroform oxidation. Chloroform oxidation continued up to 31 days in the absence of methane. Chloroform oxidation rates increased at chloroform concentrations up to 5 μg g of soil-1. 相似文献
224.
225.
[3H]Indole-3-Acetyl-myo-Inositol Hydrolysis by Extracts of Zea mays L. Vegetative Tissue 总被引:3,自引:3,他引:0
[3H]Indole-3-acetyl-myo-inositol was hydrolyzed by buffered extracts of acetone powders prepared from 4 day shoots of dark grown Zea mays L. seedlings. The hydrolytic activity was proportional to the amount of extract added and was linear for up to 6 hours at 37°C. Boiled or alcohol denatured extracts were inactive. Analysis of reaction mixtures by high performance liquid chromatography demonstrated that not all isomers of indole-3-acetyl-myo-inositol were hydrolyzed at the same rate. Buffered extracts of acetone powders were prepared from coleoptiles and mesocotyls. The rates of hydrolysis observed with coleoptile extracts were greater than those observed with mesocotyl extracts. Active extracts also catalyzed the hydrolysis of esterase substrates such as α-naphthyl acetate and the methyl esters of indoleacetic acid and naphthyleneacetic acid. Attempts to purify the indole-3-acetyl-myo-inositol hydrolyzing activity by chromatographic procedures resulted in only slight purification with large losses of activity. Chromatography over hydroxylapatite allowed separation of two enzymically active fractions, one of which catalyzed the hydrolysis of both indole-3-acetyl-myo-inositol and esterase substrates. With the other fraction enzymic hydrolysis of esterase substrates was readily demonstrated, but no hydrolysis of indole-3-acetyl-myo-inositol was ever detected. 相似文献
226.
Specific cell surface insulin binding to embryonic chick neural retina cells has been demonstrated in vivo. Kinetics of insulin binding as well as hormonal specificity were similar to those reported for other vertebrate cells and tissues, both neural and nonneural. When surface insulin binding to retinal cells was studied as a function of embryonic age, a developmental relationship was observed. Scatchard analysis revealed that the number of cell surface insulin receptors decreased approximately 75% between days 10 and 16 of embryonic development. Receptor affinities remained fairly constant for this period. 相似文献
227.
The efflux of K+ and Na+ from sea urchin eggs during Ca2+ ionophore A23187-induced parthenogenesis was studied in a K+ and Na+-free artificial seawater using extracellular ion-specific electrodes. We have probed this model system with monovalent cation-specific ionophores to determine if they affect K+ efflux in the unfertilized egg and whether any changes in ionophore sensitivity are observed during egg activation. In 500 mM choline chloride, 10 mM CaCl2, 50 mM MgCl2, 10 mM Tris-Cl pH 8.0, A23187 induced a rapid efflux of K+ and Na+ from the eggs after a short lag time (10–15 seconds). After the burst, the rate of K+ efflux remained higher than the pre-activation rate, but was lower than during the burst phase, while the rate of Na+ efflux became nearly zero. Monovalent cation-specific ionophores (valinomycin, gramicidin and nigericin) had no effect on K+ efflux from the unfertilized eggs in our model system. However, once the egg was activated by A23187, each of the above ionophores caused a prolongation of the burst phase for many minutes. These results show that the unfertilized egg plasma membrane (using our artificial conditions) is not susceptible to the monovalent cation-specific antibiotics and suggest that either the inserted cortical granule membrane or the developing fertilization envelope interacts with these ionophores to cause the change in rate-limiting step for K+ efflux observed egg activation. 相似文献
228.
James Varani Jefferey D. Hasday Robert G. Sitrin Pamela G. Brubaker William A. hillegas 《In vitro cellular & developmental biology. Plant》1986,22(10):575-582
Summary Human diploid fibroblasts were cultured on microcarriers made from DEAE-dextran, denatured collagen, DEAE-dextran linked to
denatured collagen, and glass. Cells grown on these four substrates were examined for the production of proteolytic enzymes
and arachidonic acid metabolites. Culture fluids from cells grown on the DEAE-dextran microcarriers contained the highest
amounts of proteolytic enzyme activity. Both plasminogen-independent and plasminogen-dependent fibrinolytic activities were
present and the plasminogen-dependent activity seemed to result from the presence of both urokinase and tissue plasminogen
activator. Culture fluid from the cells grown on the glass microcarriers contained the least amount of protease activity,
and nearly all of the plasminogen-activator activity seemed to be of the urokinase type. Protease activity in the culture
fluids of cells grown on the other two substrates were intermediate. With regard to arachidonic acid metabolites, cells grown
on the DEAE-dextran microcarriers produced the highest amounts of cyclooxygenase products but very low levels of lipoxygenase
metabolites. Cells grown on the other three substrates produced comparable amounts of various cyclooxygenase products (lower
than that produced by cells on the DEAE-dextrans substrate). Cells grown on the glass microcarriers also produced detectable
amounts of two lipoxygenase metabolites—leukotriene B4 and leukotriene C4. Inasmuch as both proteolytic enzymes and arachidonic acid metabolites regulate basic cell properties, the differential amount
of these metabolites observed in the culture fluids on the various substrates may contribute to the biological differences
that exist on these substrates.
This study was supported in part by grants R44 CA 36656 and IK08HL01332-01 from the Public Health Service, U. S. Department
of Health and Human Services and by grant BC-512 from the American Cancer Society. JDH is a research fellow of the American
Lung Association. 相似文献
229.
Two sessions of relaxation instructions were administered under high and low expectancy conditions. Fifty-four college students scoring high on a self-report measure of anxiety served as subjects. Live and taped abbreviated progressive muscle relaxation instructions and a self-relaxation condition were equally effective in reducing within-session self-report and physiological indices of anxiety. High expectancy instructions led to greater reductions in heart rate than did low expectancy instructions. Factors controlling anxiety reduction during relaxation therapies are discussed.This experiment was submitted by the first author in partial fulfillment for a master of science degree at VPI and SU. The authors would like to thank Jean Sales and Dan Fones for their help in this investigation. The First author is now at Johns Hopkins Hospital, Baltimore. The second author is currently at the Department of Neurology, University of Wisconsin-Madison. 相似文献
230.
Human blood was sheared between rotating polyethylene disks and plasma hemoglobin measured at intervals to produce kinetic
hemolysis curves (KHC), plotted as free hemoglobin concentration vs time. The KHC produced by blood samples incubated in the
presence of penicillin, streptomycin, gentamicin, and amikacin lie always below those for control samples, indicating a reduction
in hemolysis; this reduction was greater as the drug concentration was increased. Explanations in terms of alterations in
red cell structure were sought by several characterization tests of amikacin-loaded blood samples. Drug-localization studies
demonstrated that significant fractions of the total dosage were associated with the red-cell membrane. Resistive pulse spectroscopy
was used to show how amikacin affected cell size, deformability, and osmotic fragility; results were sensitive to storage
age of the blood. In all cases, the effect of shearing was to reduce cell size, deformability, and osmotic fragility. Mechanisms
for hemolytic protection by drugs are proposed. 相似文献