Volume 51, Issue 1
January 1960, pages 1-55
pp 1-8 January 1960
pp 9-18 January 1960
pp 19-31 January 1960
pp 32-36 January 1960
Different amounts of ammonium sulphate, potassium nitrate, aspartic acid and peptone supplying different amounts of nitrogen to the medium were added to the mannite solution. The materials were inoculated with a strain ofAzotobacter isolated from Delhi soil and incubated at 32° C. for three weeks. Nitrogen contents of the materials were determined.
It was observed that the addition of nitrogen through these substances had an inhibitory effect on nitrogen fixations byAzotobacter. The relation between the amounts of nitrogn supplied and those fixed had been quantitatively worked out.
It could be observed from the quantitative expressions that ammoniacal nitrogen had the least and nitrate nitrogen the highest inhibitory effect on nitrogen fixation byAzotobacter. In small amounts, nitrogen in the form of aspartic acid had a stimulatory effect on nitrogen fixation, but in higher doses it became even more toxic than potassium nitrate.
Peptone seemed to have a very strong inhibitory effect on nitrogen fixation byAzotobacter.
pp 37-51 January 1960
pp 52-55 January 1960
1. The vagus nerves of the frog’s heart were stimulated in 26 experiments. In 11 experiments, there was no detectable release of acetylcholine; in 15 there was release in variable amounts.
2. Direct electrical stimulation caused release of acetylcholine in all the 26 experiments, in amounts greater than that released by nervous stimulation after the fatigue of the vagus nerves, and also in those experiments in which the stimulation of the vagus nerves did not show any detectable release of acetylcholine. It is concluded, therefore, that the acetylcholine liberated on stimulation of the vagus nerves comes from the heart muscle cells and not the nerve endings.