Multiplicity of spinach root phenolase and its monophenolase activity

Soluble phenolase of spinach roots is present in multiple forms, none of which is electrophoretically identical with those detected in the chloroplasts     

Optimal cell density and multiplicity of infection for the propagation of human rotavirus in monkey kidney cells

The human rotavirus titer was optimal at an infection cell density of about 4–8 × 10⁴ cells cm^–2 in monkey kidney cell cultures. The highest viral titers (3.8 × 10⁷ TCID₅₀ ml^–1 and 3.7 × 10⁷ TCID₅₀ ml^–1) were obtained at an multiplicity of infection of 0.05 in well plate and T-flask, respectively.     

The functions of multiple visual signals in a fiddler crab

In many species, it is common for animals to have multiple signals within one channel of communication. Multiple signals may, however, be inefficient if they are redundant in nature. Identifying the functional significance of these multiple signals is therefore important if we are to understand the evolution of such elaborated behaviours. We proposed to identify the roles of movement-based multiple signals in a model animal system. Male fiddler crabs wave their sexually dimorphic enlarged claw during social interactions. Some species present multiple signals, where the level of complexity of the movement changes. Males of Austruca mjoebergi can perform a double wave consisting of a high- followed by a low-elevation lifting of the claw, or a single wave consisting of the high-elevation movement alone. We first investigated structural differences between the double and single wave types, and found that single waves were lower in elevation than double waves. We then explored the adaptive meaning of the wave types by manipulating the social context in which males wave. We found that double waves were given in all contexts and in higher proportions at long distances, suggesting a function of broadcasting male location. Single waves, on the other hand, were mainly given at close range and in the presence of conspecifics, suggesting intraspecific communication. Female presence elicited the highest number and proportion of single waves, a likely result of a female preference for higher wave rates. Finally, we point out that there is an element of interaction between wave types that deserves future attention. This paper is an important contribution to expand our understanding of the adaptive meaning of multiple visual signals and help reach a unified theory of their evolution.     

Selective retention of recombinant plasmids coding for human insulin

Plasmids may be lost from Escherichia coli K-12 hosts that are cultured without selection for plasmid retention. This is particularly true for chimeric plasmids that incorporate genes for human insulin into vectors derived from pBR322. The cIts857 gene of bacteriophage lambda was inserted into the bla gene of the human-insulin-coding plasmids, pIA7 delta 4 delta 1, pIB7 delta 4 delta 1 and pHI7 delta 4 delta 1, generating the new plasmids pPR17, pPR18 and pPR19, respectively, which produced the thermosensitive lambda repressor. The cI gene was downstream from the pM and pbla promoters, so that it may have been expressed from either or both promoters. Separate E. coli K-12 RV308 host strains containing the new recombinants were lysogenized with the repressor-defective bacteriophage lambda cI90. Loss of the plasmid from the lysogens causes concomitant loss of the lambda repressor and cell death, because the prophage is induced to enter the lytic growth cycle. The system effectively forces retention of the plasmid in all viable cells in the culture.     

SV40 DNA transfection of cells in suspension: analysis of efficiency of transcription and translation of T-antigen

A modification of the Graham and Van der Eb (1974) DNA-calcium phosphate coprecipitation technique is shown to routinely transfect 15% of CV-1 cells with SV40 DNA. The transfection is done in suspension after detachment of cells by trypsin digestion. Transfection efficiency was measured by staining cells for the presence of SV40 T-antigen by indirect immunofluorescence and by assaying for the presence of SV40 early message by the Berk and Sharp (1978) technique.     

Cosmid DNA packaging in vivo

The packaging of cosmid DNA into phage particles during phage lambda growth is described. Evidence is presented supporting the work of others that cosmid transducing phages contain linear multimers of cosmid DNA in which the number of cosmid copies is that required to make a packagable DNA length (greater than 0.77 of the lambda DNA length). The yield of cosmid transducing phages declines sharply as the number of cosmid copies required to make a packagable DNA length increases. The cosmid DNA replication that produces the packaging substrate shares with lambda rolling-circle replication a dependence on the lambda gam gene product.