Nucleosome Phasing in Tetrahymena Macronuclei1

Core-protected DNA can drive only 60% of the Tetrahymena thermophila macronuclear genome into duplexes in hybridization experiments. This core-protected DNA therefore contains only a subset of the genome complexity. We interpret this to mean that a large fraction, if not all, of the genome is phased with respect to nucleosome placement. Among the sequences present in total DNA and absent from core-protected DNA are most of the sequences containing N⁶-methyladenine (MeAde) residues, consistent with our previous demonstration that most of these residues lie in linker DNA. We show that these results are not due to artifacts resulting from the small size of the DNA driver, nor are they due to any sequence preferences exhibited by staphylococcal (staph) nuclease. This is the first evidence that nucleosome phasing may be a bulk genome characteristic.     

Cyclomorphosis in Daphnia galeata mendotae Birge and D. retrocurva Forbes as a predator-induced response

SUMMARY. 1. Populations of Daphnia galeata mendotae and D. retrocurva were exposed for one generation to predators enclosed in mesh bags. The exposed Daphnia showed adaptive morphological changes that mimic cyclomorphosis in nature. The invertebrate predators Chaoborus and Notonecta induced longer helmets, while the fish Lepomis induced shorter bodies but had no effect on helmet length. Longer tail spines (relative to body length) were induced by Notonecta and Lepomis.
2. The responses of D. retrocurva were influenced by algae concentration, with the more extreme responses occurring at a higher food concentration and higher lipid index.     

A trial to control the tsetse fly,Glossina morsitans centralis,with low densities of odour-baited targets in west Zambia

Abstract. A large-scale trial investigated the possibility of eradicating G.m.centralis from a traditional cattle rearing area using odour-baited targets at a reduced overall target density from 4 to 0.5-2.3 per km², thus cutting down initial material costs by about 50%. Only the periphery of what was thought to be prime tsetse habitat (dense woodland) was treated with targets. These were all black or blue/black cloth (1.8 × 1m), sprayed with deltamethrin suspension concentrate and baited with butanone and/or acetone (40-130mg/h) and l-octen-3-ol (0.5mg/h). Although fly catches from traps and flyrounds initially dropped by approximately 3% per day and trypanosomiasis cases declined by 99% within a year, eradication was not achieved, so that more targets were deployed at a later stage. Although initially cheaper, the option of using reduced target densities proved financially unattractive because of prolonged periods of target maintenance prior to eradication. Revised strategies for tsetse control with odour-baited, insecticide-impregnated targets in west Zambia are presented.     

Utilization of Messenger in Adenovirus-2-infected Cells at Normal and Elevated Temperatures

THE regulation of protein synthesis in eukaryotic cells appears to be distinctly different from that in prokaryotes. The long-lived messenger RNA in eukaryotes suggests that control of protein synthesis occurs partially at the level of translation and regulation at the level of initiation of translation of messenger RNA has been found under several different conditions in mammalian cells^1–6.