Somatic genetic analysis of cyclic AMP action: selection of unresponsive mutants.

Dibutyryl cyclic AMP and theophylline kill S49.1 mouse lymphoma tissue culture cells. When cells are grown in soft agar with these drugs, the few clones that survive are resistant to cytolysis. The rate of mutation to resistance is 1-3 times 10-7/cell/generation in both diploid and tetraploid cells. The incidence of mutants is increased by treatment with a chemical mutagen, ICR 191. The mutation is consistently associated with greatly reduced or absent cytoplasmic cyclic AMP binding protein. These results suggest that a somatic mutation leads to a defect of the protein kinase regulatory subunit and that activity of this kinase is required for induction of cell death by cyclic AMP.     

The Effect of the Phenolic Antioxidant Ferulic Acid on the Oxidation of Low Density Lipoprotein Depends on the Pro-oxidant Used

The action of ferulic acid during the oxidation of LDL has been investigated using both copper ions and the haem protein metmyoglobin as pro-oxidants. The results demonstrate the ability of ferulic acid to act as a pro-oxidant when LDL oxidation is induced by copper at concentrations of the phenolic acid which are protective when the LDL oxidation is mediated by metmyoglobin. The suggested mechanism involves the reduction of Cu²⁺ to Cu⁺ by ferulic acid resulting in the production of the ferulic phenoxyl radical.     

Plant palatability and disturbance level in aquatic habitats: an experimental approach using the snail Lymnaea stagnalis (L.)

1. The palatability of aquatic macrophytes to the snail Lymnaea stagnalis was investigated in the laboratory. Eight species of macrophyte were selected from habitats that differed in either flood disturbance regime or nutrient status.
2. In a non-choice test, single macrophyte species were offered to individual snails. The average amount of plant dry mass consumed per Lymnaea dry mass ranged from 3.6 ± 1.4 (±SE) to 63.6 ± 13.9 mg g^–1 day^–1 across plant species. In a choice test, all eight plant species were presented simultaneously to sets of five snails. The average total consumption was 66.1 ± 3.8 mg g^–1 day^–1 and the maximum average consumption for a single plant was 26.2 ± 3.6 mg g^–1 day^–1.
3. In both tests, the amount consumed by snails differed significantly between the plant species. The species growing in undisturbed habitats were the least consumed. Habitat nutrient status was unrelated to plant palatability.
4. These results suggest that macrophyte species growing in habitats that are rarely disturbed by floods allocate a greater proportion of their resources to resisting herbivory.     

Further observations on the activation of lysosomal acid α-glucosidase by cortisone derivatives

1. Cortisone acetate activates the acid alpha-glucosidase in rat liver slices and in isolated liver lysosomes. 2. The reaction is steroid specific and moreover does not occur with lysosomal acid phosphatase or beta-galactosidase. 3. After pretreatment of the lysosomes with cortisone, substrate (maltose) binding to the soluble lysosomal acid alpha-glucosidase is not affected, but the steroid does increase the V(max.) value. Membrane-bound enzyme is not activated by cortisone. 4. 4-[(14)C]Cortisone is preferentially bound to the lysosomal membrane and the possible involvement of this structure in the activation phenomenon is discussed.     

HISTOCHEMICAL MAPPING OF MONOAMINE OXIDASE AND LACTIC DEHYDROGENASE IN THE PONS AND MESENCEPHALON OF SQUIRREL MONKEY (SAIMIRI SCIUREUS)

The detailed distribution of lactate dehydrogenase and monoamine oxide has been described at various levels through the pons and mesencephalon of the brain of the squirrel monkey. A comparison of the two enzymes has given an interesting picture of their selective localization in the different nuclei. Particular attention has been paid to select sections at comparative levels. Marked monoamine oxidase activity has been observed in the nucleus interpeduncularis, the nucleus centralis superior, the nucleus annularis, and in the neuropil and in the cytoplasm of neurons of some other nuclei. Particularly strong lactate dehydrogenase activity has, however, been observed in the corpus geniculatum laterale and mediale, the nucleus pulvinaris, the superior and inferior colliculi, the substantia grisea centralis and some of the nuclei of cranial nerves.