Lysogenization by bacteriophage lambda: III. - Multiplicity dependent phenomena occuring upon infection by lambda

Lysogenization by bacteriophage λ involves at least two multiplicity dependent processes [2, 3]. For the purpose of comparison, other multiplicity dependent phenomena which occur upon infection by λ have been reviewed. These include the inhibition of host'syntheses as already described by others [9] and two phenomena which are shown to be multiplicity dependent, host killing by phage unable to replicate and inhibition of cell division. It is also demonstrated that, in at least two cases (lysogenization by phage able to replicate and killing by phage unable to replicate) the multiplicity dependent character disappears at slow cellular growth rates. The significance of these results is discussed with regard to three models which are susceptible to account for multiplicity dependent phenomena in general.     

Contact potential difference of cellsin vitro as a measure of hydrophilic properties of the cell membrane

Construction of an apparatus for the determination of the cell contact potential difference and the measuring method are described. The contact potential differences are attributed to the degree of hydrophobic properties of the cell surface and referred to human erythrocytes and chloroplasts.     

The Process-inducing Activity of Transmembrane Agrin Requires Follistatin-like Domains

Clustering or overexpression of the transmembrane form of the extracellular matrix proteoglycan agrin in neurons results in the formation of numerous highly motile filopodia-like processes extending from axons and dendrites. Here we show that similar processes can be induced by overexpression of transmembrane-agrin in several non-neuronal cell lines. Mapping of the process-inducing activity in neurons and non-neuronal cells demonstrates that the cytoplasmic part of transmembrane agrin is dispensable and that the extracellular region is necessary for process formation. Site-directed mutagenesis reveals an essential role for the loop between β-sheets 3 and 4 within the Kazal subdomain of the seventh follistatin-like domain of TM-agrin. An aspartic acid residue within this loop is critical for process formation. The seventh follistatin-like domain could be functionally replaced by the first and sixth but not by the eighth follistatin-like domain, demonstrating a functional redundancy among some follistatin-like domains of agrin. Moreover, a critical distance of the seventh follistatin-like domain to the plasma membrane appears to be required for process formation. These results demonstrate that different regions within the agrin protein are responsible for synapse formation at the neuromuscular junction and for process formation in central nervous system neurons and suggest a role for agrin''s follistatin-like domains in the developing central nervous system.     

Study of the combined effects of PTH treatment and mechanical loading in postmenopausal osteoporosis using a new mechanistic PK-PD model

Biomechanics and Modeling in Mechanobiology - One of only a few approved and available anabolic treatments for severe osteoporosis is daily injections of PTH (1-34). This drug has a specific dual...     

Early vigour in wheat: Could it lead to more severe terminal drought stress under elevated atmospheric [CO2] and semi‐arid conditions?

Early vigour in wheat is a trait that has received attention for its benefits reducing evaporation from the soil surface early in the season. However, with the growth enhancement common to crops grown under elevated atmospheric CO₂ concentrations (e[CO₂]), there is a risk that too much early growth might deplete soil water and lead to more severe terminal drought stress in environments where production relies on stored soil water content. If this is the case, the incorporation of such a trait in wheat breeding programmes might have unintended negative consequences in the future, especially in dry years. We used selected data from cultivars with proven expression of high and low early vigour from the Australian Grains Free Air CO₂ Enrichment (AGFACE) facility, and complemented this analysis with simulation results from two crop growth models which differ in the modelling of leaf area development and crop water use. Grain yield responses to e[CO₂] were lower in the high early vigour group compared to the low early vigour group, and although these differences were not significant, they were corroborated by simulation model results. However, the simulated lower response with high early vigour lines was not caused by an earlier or greater depletion of soil water under e[CO₂] and the mechanisms responsible appear to be related to an earlier saturation of the radiation intercepted. Whether this is the case in the field needs to be further investigated. In addition, there was some evidence that the timing of the drought stress during crop growth influenced the effect of e[CO₂] regardless of the early vigour trait. There is a need for FACE investigations of the value of traits for drought adaptation to be conducted under more severe drought conditions and variable timing of drought stress, a risky but necessary endeavour.