Pesticides for locust control.

The factors influencing the choice of insecticides for locust control are effectiveness, safety in use, relative cost, and the formulations available. The relative importance of these factors varies with the scale of control. In small scale control by farmers safety and simplicity are paramount and a BHC dust is commonly used, but in large scale control operations by specialized organizations more toxic formulations ultra-low-volume (u.l.v.) concentrates and methods of application requiring considerable skills can be used. The remarkable effectiveness of dieldrin as a stomach poison appears to be due to its conversion to photodieldrin after application. Cases of poisoning following large scale control operations are rare, and fatalities in man unknown. Alternatives to organochlorine insecticides include fenitrothion, already recommended and used on a large scale against adults. Against nymphs the correct dosage of fenitrothion would cost nearly 11 times as much as that of dieldren. Recent experimental work with new insecticides has included safety tests with domestic animals and measurements of persistence. 1 microgram deposits of cyanofenphos, decamethrin and mecarphon, as well as of dieldrin and photodieldrin, on wheat seedlings left in the open under tropical conditions for two days, killed 80% or more first instar nymphs of the Desert Locust which fed on them.     

Rabies control and management.

Since the 1950s rabies has become a familiar threat in southern Canada. Periodic outbreaks remind us how slight our control over it is. Although new vaccines such as human diploid-cell rabies vaccine have greatly improved the management of rabies in humans, true control must be sought through knowledge of the disease in or wildlife. A guide to rabies prophylaxis in humans is presented, courtesy of the National Advisory Committee on Immunization.     

Progress towards rabies control.

Although safe and efficacious tissue-culture-derived rabies vaccines are available in developed countries, much of the world still depends on vaccines derived from neural tissue which were introduced half a century ago. Considerable advances have been made in our understanding of the molecular biology of rabies virus, and genetically engineered recombinant viruses (vaccinia-rabies virus glycoprotein) have been developed. These may facilitate the control of rabies in some species by oral vaccination campaigns.     

Metabolic control analysis. Sensitivity of control coefficients to elasticities

This paper illustrates a method to calculate the sensitivities of control coefficients to the elasticities which determine their values and it is shown that these sensitivities are systemic properties. We show, both theoretically and with a practical example, how they can be used to investigate: (a) the relative importance of a particular elasticity in the determination of the value of a control coefficient; (b) the effect of experimental error on the values of the control coefficients and (c) the construction of confidence limits around the values of the control coefficients.     

Cell proliferation and control.

In the past year much of the focus in cell-cycle research has turned from the regulation of mitosis to the control of the initiation of DNA replication. Novel findings include the discovery of vertebrate G1 cyclins, an additional cdc2-related kinase potentially involved in G1 phase, and a positive-feedback loop regulating the start of the cell cycle in yeast.