Sister chromatid exchanges--a sensitive assay of agents damaging human chromosomes

Sister chromatid exchange frequencies in human lymphocyte chromosomes are greatly increased by alkylating agents, but ionizing radiation has little if any such effect. Scoring these exchanges may provide a useful technique for exploring the mechanisms of chromosome breakage and repair.

The use of lorazepam as a soporific and for premedication

An open study, in which 48 patients scheduled for elective surgery received either 1,25 mg or 2,5 mg of lorazepam (orally) as a soporific the night before surgery and as premedication immediately prior to surgery, revealed that lorazepam produced a good night's rest and a desirable calm immediately prior to surgery. Vital signs remained stable throughout the operative procedure, and vomiting and other reactions were virtually absent.

Membrane translocation of mannitol in Escherichia coli without phosphorylation

Galactosyl-mannitol can be transported into cells of Escherichia coli by beta-galactoside permease and can be hydrolyzed rapidly to mannitol and galactose by beta-galactosidase. When a mutant strain lacking enzyme I of the phosphoenolpyruvate phosphotransferase system and constitutive in the lactose system was presented with galactosyl-mannitol in which the mannitol moiety was labeled with (3)H, the liberated mannitol remained inside the cell if the Enzyme II complex of the phosphoenolpyruvate phosphotransferase system for mannitol was uninduced. It is postualted that one of the enzyme II proteins can still catalyze translocation of mannitol across the cell membrane even when phsophorylation is not possible.

Mutations affecting the dissimilation of mannitol by Escherichia coli K-12

Mutants of Escherichia coli K-12 defective in the mannitol-specific enzyme II complex of the phosphoenolpyruvate phosphotransferase system (PTS) or lacking mannitol-1-phosphate dehydrogenase have been isolated. These mutants fail only to grow on mannitol. Growth of the dehydrogenase-negative mutant on casein hydrolysate can be abruptly inhibited by exposure to mannitol. A mutant with constitutive expression of both of these enzymes has also been isolated. All three mutations are clustered in a region represented at min 71 of the Taylor map. In a mutant with less than 5% of the activity of enzyme I of the PTS, both the enzyme II complex and the dehydrogenase remain inducible by mannitol. In the mutant defective in the enzyme II complex, mannitol is able to induce the dehydrogenase. Thus, mannitol, rather than its phosphorylated product, seems to be the inducer.

Metabolism of camphanediols

1. The metabolism of the camphane-2,3-diols and camphane was investigated in rabbits. All the compounds increased the content of glucuronide in the urine. 2. Both trans- and cis-diols gave rise to ketols; the cis-diols gave rise to trans-diols, but not vice versa; camphorquinone gave cis-diol, ketols and trans-diol; camphane did not give rise to diols. 3. The possibility is discussed that an enediol is the intermediate for ketol interconversions in the present series of compounds and in other series such as hydroxyoestrones and hydroxyindanones.