Genetic dissection of catalytic activities of the Salmonella typhimurium mannitol enzyme II.

Approximately 60 mutants of Salmonella typhimurium were isolated which exhibited altered levels of the activities of the mannitol enzyme II. The mutants were grouped into six distinct categories based on their mannitol fermentation, transport, chemotaxis, and phosphorylation activities.     

Comparison of Growth and Toxin Production in Two Vaccine Strains of Bacillus anthracis

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.     

Reduction of Brain Calcium After Consumption of Diets Deficient in Calcium or Vitamin D

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.     

Inhibition of lymphocyte growth by spermidine in medium containing fetal bovine serum

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.     

Density regulation inSarsia tubulosa (Hydrozoa)

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.     

Specifically deuterated and tritiated auxins

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.     

Mycotic aortic aneurysm complicating isolated partial anomalous pulmonary venous drainage

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.     

Flowering in Xanthium strumarium: INITIATION AND DEVELOPMENT OF FEMALE INFLORESCENCE AND SEX EXPRESSION

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.