Effect of noradrenaline on oxygen consumption and tissue blood flow in young pigs

Metabolic rate and tissue blood flow were measured by indirect calorimetry and the radioactive microsphere technique, respectively, in anaesthetized pigs aged 10, 17, and 28 days during infusions of saline or noradrenaline. Noradrenaline produced a rise in oxygen consumption in all pigs but the magnitude of the response declined with age in Large White pigs (percent increase: 10 days old, 29.5 +/- 3.3; 17 days old, 15.3 +/- 3.2; 28 days old, 5.4 +/- 0.17) and was less in 10-day-old Minipigs (9.1 +/- 5.1). Regional blood flow per gram of tissue was similar for pigs of all ages and noradrenaline produced increases in flow to heart and skin, and small reductions in blood flow to skeletal muscle. Noradrenaline increased average blood flow to adipose tissue (four sites) by 21-fold in 10-day-old Large White pigs, but had less effect in 10-day-old Minipigs (9.5-fold) and in older Large White pigs (9-fold), where the effect on metabolic rate was diminished. It is calculated that adipose tissue could be responsible for the increase in metabolic rate during infusion of noradrenaline. Macroscopically there are no gross differences between various adipose tissue depots in the pig but those which showed the greatest response to noradrenaline correspond to areas where brown adipocytes have previously been identified by electron microscopy.     

Comparison of the fecundity of three species of grain store mites on fungal diets

The egg production of isolated pairs ofAcarus siro, Glycyphagus destructor andTyrophagus longior fed on a control diet of wheatgerm and yeast was compared with that on mycelial pellets from shake cultures ofCladosporium cladosporiodes, Aspergillus repens, A. ruber andPenicillium cyclopium as well as spores ofP. cyclopium andA. repens. The mites always produced fewer eggs on the fungal diets than on the ideal diet.Tyrophagus longior usually did best of the three mite species on the fungal diets, andG. destructor worst.Aspergillus ruber proved the most suitable fungus for all mite species, whileC. cladosporiodes was the least suitable. Spores were a less suitable diet than mycelial pellets from shake cultures, which were predominantly mycelium.