480 H. H. TALLAN 
nerve!. The presence of anserine in rat brain has been reported*®*; anserine is absent 
in rabbit and guinea-pig-brain extracts, though methylhistidine appears after 
hydrolysis!**, 
Peptides are present in squid giant nerve axoplasm*’. An unknown material, 
which on hydrolysis yielded threonine, other ninhydrin-positive substances, and 
phosphate, was found in the brains of a large number of species, though in especially 
high concentrations in fish, tortoise, and frog brain!”*. An unknown material yielding 
phosphoserine, phosphoethanolamine, glutamic acid and valine upon hydrolysis has 
been found in hen spinal cord!*,. Peptides occur, too, as part of some complex 
lipids?®; 107, 146, 177° large numbers of lipophilic peptides have been detected in mouse 
brain?”°, 
Glutathione concentrations in brain have been measured recently by MARTIN 
AND McILWAIn"™®; their figures, obtained by use of a yeast apoglyoxalase, are higher 
than those obtained by chemical reaction or by chromatography and undoubtedly 
represent more nearly the true values. The amount of oxidized glutathione present 
was found to be 2-4% of the total when the brain was frozen in situ; with other 
methods of preparation the proportion was much higher, though the total gluta- 
thione (-SH plus S-S) remained constant™4?. The distribution of glutathione in 
various parts of the rat brain has been studied! 27, 42. Glutathione is present in 
bovine retina at a concentration of 2.5 wmoles/g; no oxidized form was detected”. 
Substance P, a peptide that stimulates smooth muscle, is found in intestinal 
muscle as well as in the central nervous system. The peptides from the two sources 
have identical properties with regard to counter-current distribution, paper electro- 
phoresis, paper chromatography, enzymatic inactivation by chymotrypsin®, and 
biological activity®! 182. Possibly there are two different fractions in brain, for after 
brain tissue has been thoroughly extracted with ethanol, boiling at pH 3 releases 
more Substance P activity; the two fractions behave differently upon autolysis and 
dialysis and are affected differently by pretreatment of the animals with various 
drugs!**. The properties and distribution of Substance P are reviewed by PERNow™? 182 
(for detailed studies, see ref. 2, 37, 38, 55, 65, 95, 98, 108, 129, 130, 152, 183, 184). 
Another material from brain, which appears to be a peptide of large molecular 
weight, has the property of enhancing antithrombin activity; the best source of the 
material is reported to be infant human brain!”9, 
Ethanolamine (Table IV). The presence of ethanolamine in brain lipids was esta- 
blished at an early date (cf. ref. 52). More recently, the derivatives glycerophospho- 
ethanolamine (GPE) and phosphoethanolamine (PE) have been shown to occur as 
such in brain tissue, and it is likely that there is also some free ethanolamine, though 
the amount of the latter is not certain!?*, 16°, The exact amount of GPE normally 
present is also in doubt (for example refs. 160, 161), because of the lability of GPE 
and of phosphatidylethanolamine®. Other than in the brains of the species given in 
the table, GPE has been reported present in brains of the rabbit!**®, guinea-pig?*®, 
cow!’3, and sheep*4, and in hen spinal cord!**, GPE seems to be neither a metabolic 
breakdown product of phosphatidylethanolamine, nor to lie on the main synthetic 
pathway to it®?, PE, which was first found in brain by AWAPARA, LANDUA AND 
FuErst", is not a breakdown product of phosphatidylethanolamine?; it is possibly 
on the synthetic pathway to the phosphatide, via cytidine-diphosphate-ethanol- 
References p. 482/485 
