Cclxii. the Effect of Vitamin B, upon the Respiratory Quotient of Brain Tissue

GAVRLEScu AND PETERS have shown [1931, 1] that minced polyneuritic pigeon's brain tissue, suspended in glucose-phosphate solution, gives a lowered oxygen uptake as compared with the normal. Later they found [1931, 2] that this deficiency was partially restored in vitro by adding vitamin B, concentrates in very small amount. The effect was catalytic. Peters and his colleagues [Gavrilescu et al., 1932] showed that the effect was enhanced in lactate solution; but since the avitaminous tissue oxidised succinate normally, the cytochrome system was not impaired. They concluded that vitamin B, was specifically concerned with carbohydrate metabolism. The simplest explanation was that vitamin B, was a catalyst essential for the oxidative removal of lactic acid. It is not, however, the lactic oxidase coenzyme described by Banga et al. [1932], neither can preparations of the latter give the in vitro effect of vitamin B, [Boyland, 1933, using the Thunberg technique; Peters and Sinclair, unpublished, using measurement of oxygen uptake]. Also, Meiklejohn [1933] could find no extra disappearance of lactic acid corresponding to the. extra respiration produced by the addition of the concentrates to the polyneuritic tissue. It was therefore important to study the R.Q. of the tissue under these conditions. A preliminary account of these experiments has already appeared [Sinclair, 1933]. The respiratory quotient of brain tissue from various animals has usually been found to be nearly unity. Loebel [1925] found that the R.Q. of excised rat brain was 099 in fructose, 0-92 in glucose and 086 in Ringer solution. Dickens and Greville [1933] reported that the R.Q. of brain cortex of rats and rabbits, buffered either with phosphate or bicarbonate, was unity whether glucose, fructose or no substrate was present. Ashford and Holmes [1931] found that the R.Q. of chopped rabbit brain, in Ringer-phosphate (apparently unbuffered), was 0O88 and rose to unity when lactate was added. Himwich and Nahum [1929] analysed the gases in the blood entering and leaving the brains of dogs and obtained values of unity under a variety of conditions. Himwich and Fazikas [1932] stated that minced tissue of rats, in glucose-phosphate solution, gave the following values: cortex 0 99, stem 093, cerebellum 0-89, medulla 0-89. All this work has emphasised that the metabolism of mammalian brain under a variety of conditions is essentially that of carbohydrate. Very recently Himwich et at. [1933] have reported observations on the R.Q. of the cerebral cortex of three pigeons and one dog suffering from polyneuritis. The values obtained with the avian tissue, using the Warburg apparatus, were 076, 086 and 0-66, but it is not stated in what medium the determinations were made. Himwich assumes, apparently on no evidence, that the R.Q. of