Reinitiation of chromosome replication in a thermosensitive DNA mutant of Escherichia coli. II. Synchronization of chromosome replication after temperature shifts

A short incubation at the non-permissive temperature, 10 to 15 minutes at 40 °C, suffices to induce chromosome reinitiation in CRT 266, a thermosensitive DNA mutant of Escherichia coli. In order to acquire the potentiality to reinitiate chromosome replication, protein synthesis is necessary, both during the 40 °C incubation and also during the first 15 minutes after returning to 30 °C.     

Nonsteady-State Three Compartment Tracer Kinetics: II. Sodium Flux Transients in the Toad Urinary Bladder in Response to Short Circuit

The theoretical approach presented in the previous paper provides an analytical method for determining the unidirectional, nonsteady-state fluxes in a three compartment system. Based on this a study was made of the sodium flux transients in the toad urinary bladder. A transient time-dependent state was generated by suddenly short-circuiting a bladder previously maintained in an open-circuited steady state. The sequence of experiments suggested by the theory provided the data required for the analysis. The results of these tracer experiments were consistent with the complex non-three compartmental structure of this tissue. As a result both of the inadequacy of the three compartment model in representing the tissue and of certain experimental difficulties, attempts at a quantitative solution were not entirely successful. Useful information was nevertheless obtained through a careful use of this model, and a qualitative analysis implied that the sodium influxes into the tissue at both of its surfaces are sensitive to changes in electrical potential while both effluxes are insensitive to this change. This suggests that both of the effluxes result from active processes while both influxes are associated with passive processes. The net transepithelial transport of sodium would then necessarily result from a more complex polarization than that proposed by Koefoed-Johnsen and Ussing.     

Effects of gradual expansign on arterial stenosis

The blood flow through an arterial stenosis can theoretically be increased by gradual expansion of the stenosis. This hypothesis was tested by comparing the flow through abruptly expanding and gradually expanding stenosed plastic conduits. The conduits were tested in non-pulsatile flow with water and bank blood and in pulsatile flow in dog's descending aorta. It was found that:

1. (a)
   The pressure drop in arterial stenoses is larger than that predicted by non-pulsatile theory.