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991.
Comparison of Growth and Toxin Production in Two Vaccine Strains of Bacillus anthracis 总被引:2,自引:0,他引:2 下载免费PDF全文
Two vaccine strains of Bacillus anthracis were monitored in a 10-liter fermentor to compare growth patterns and toxin production. Under identical conditions, the Sterne strain produced all three components of anthrax toxin, whereas strain V770 produced only the protective antigen. 相似文献
992.
Reduction of Brain Calcium After Consumption of Diets Deficient in Calcium or Vitamin D 总被引:4,自引:2,他引:2
Abstract: Rats fed diets deficient in calcium or vitamin D for 4 weeks displayed hypocalcemia, as indicated by a 50% reduction in serum calcium and a sevenfold elevation of serum parathyroid hormone. These treatments also decreased the calcium content of brain tissue. On a regional basis. this effect was greatest in the brain stem (24% decrease) and least in striatum (10% decrease). Subcellular analysis indicated that the depletion of brain calcium was greatest in the soluble and the microsomal fractions. Infusion of calcium solutions reversed the depletion of brain calcium produced by dietary deficiencies. In control rats. parathyroidectomy or infusion of parathyroid hormone did not alter the calcium content of brain tissue, although these treatments affected the levels of calcium in the serum. In general, these treatments had no effect on the magnesium content of serum or brain tissue. However, vitamin D deficiency did increase the magnesium content of the myelin and synaptosomal fractions. This increase was reversed by parathyroidectomy. These observations demonstrate that long-term hypocalcemia produces distinct changes in the localization of calcium and magnesium in brain tissue. Furthermore. these studies suggest that though brain calcium levels are influenced by serum concentrations, serum changes must be of large magnitude and long duration for brain calcium levels to be affected. 相似文献
993.
994.
T. Leonard Swanson Gordon E. Gibbs 《In vitro cellular & developmental biology. Plant》1980,16(9):761-766
Summary The effect of spermidine and fetal bovine serum on DNA, RNA, and protein synthesis in phytohemagglutinin-stimulated human
lymphocytes was investigated. At 10−4
M spermidine, DNA, RNA, and protein synthesis ceased and 70% of the original cell population died within 62 hr. Lower spermidine
concentrations had no significant effect on DNA and protein synthesis, but caused an early, unexplained increase in the rate
of RNA synthesis. Heating at 56°C for 30 min had no effect on the plasma amine oxidase activity in fetal bovine and horse
sera but abolished the activity in human plasma. It is concluded that low amounts of aminoaldehydes and acrolein produced
by plasma amine oxidase at spermidine concentrations below 10−4
M do not noticeably alter lymphocyte metabolism. However, the aminoaldehydes and acrolein produced become abruptly cytotoxic
at 10−4
M spermidine.
This work was supported in part by the Cystic Fibrosis Foundation. 相似文献
995.
J. L. Leonard 《Helgoland Marine Research》1980,34(1):55-59
The majority of wild-caughtSarsia tubulosa M. Sars medusae are less dense than the surrounding water. The bell ofS. tubulosa is the buoyant structure; the tentacles and manubrium sink if cut off from the bell.S. tubulosa individuals placed in dilute seawater sink initially but recover positive or neutral buoyancy and normal activity within a couple of hours. In all cases observed animals were able to achieve positive buoyancy in seawater of 20.25 S and some individuals were able to adjust to lower salinities. In most cases where positive buoyancy was not attained within two hours the animal did not achieve positive buoyancy within twelve hours and died within that period. While the mechanism of regulation is not known, ionic pumping, possibly involving the extrusion of sulphate ion, has been suggested to be responsible for the buoyancy of mesoglea in other jellyfishes. 相似文献
996.
L.Lee Melhado Cedric J. Pearce Marc dAlarcao Nelson J. Leonard 《Phytochemistry》1980,21(12):2879-2885
Regiospecific syntheses of monodeuterated and monotritiated natural auxin (indole- 3-acetic acid), a synthetic auxin (naphthalene-1-acetic acid) and a photoaffinity labeling auxin (5-azidoindole-3-acetic acid) are described. These syntheses provide benzene-ring tritiated auxins for use in reversible and covalent binding studies. 相似文献
997.
An aneurysm that develops within a normal segment of the ascending aorta in a child with asymptomatic and previously undiagnosed congenital heart disease at the atrial level is most unusual and highly lethal. This report describes a child who had successful corrective surgery for this anomaly. 相似文献
998.
Flowering in Xanthium strumarium: INITIATION AND DEVELOPMENT OF FEMALE INFLORESCENCE AND SEX EXPRESSION 下载免费PDF全文
Vegetative plants of Xanthium strumarium L. grown in long days were induced to flower by exposure to one or several 16-hour dark periods. The distribution of male and female inflorescences on the flowering shoot was described, and a scoring system was designed to assess the development of the female inflorescences. The time of movement of the floral stimulus out of the induced leaf and the timing of action of high temperature were shown to be similar for both the apical male and lateral female inflorescences. 相似文献
999.
1000.