Compartmentation of glutamic acid metabolism in brain slices

— (1) Compartmentation of glutamate metabolism in brain cortex previously observed only in vivo, has now been demonstrated in vitro.This was shown by using [U-¹⁴C]aspartate and [U-¹⁴C]glutamate as tracer substrates. (2) Preparation and maintenance of the slices at 0° resulted in reversible inhibition of glutamine synthesis. Preincubation at 37° for 10 min or preparation of the slices at room temperature partially overcame this inhibition. (3) Transfer to fresh medium after preincubation had an added stimulatory effect on glutamine synthesis. (4) Incubation in high K⁺ medium (27 mm ) altered the relative specific activity of glutamine. (5) The data are in keeping with the postulate of the existence of at least two different pools of citric acid cycle intermediates in the cerebral cortex.     

Observations on lysogeny in glutamic acid bacteria.

Induced lysis occurred in a number of different strains of glutamic acid bacteria. Mixed culture experiments indicated that induced cultures produce phages or bacteriocins. Temperate phages were isolated from two related strains of Brevibacterium divaricatum.     

Immune responses of inbred guinea pigs against random terpolymers containing L glutamic acid and L alanine.

The immune responses of the inbred guinea pig strains 2 and 13 have been determined against random terpolymers of L glutamic acid and L alanine and a third amino acid. Strain 2 guinea pigs responded against GAT10, GAT20(LLD), GAT10(NO2)15, GAT4, and GAL10. However, strain 13 guinea pigs responded only against GAT10. The explanation offered is that strain 2 guinea pigs, which have the Ir-GA gene, recognize the polymers via random GA determinants present in sufficient concentration in all of the above polymers. However, strain 13 guinea pigs recognize the GAT10 via the Ir-GT gene, and reduction in the concentration of tyrosyl residues below 10 mole % by various procedures alters the concentration of available random GT determinants necessary for interaction with the gene product of the Ir-GT gene.     

不同的中和剂对L(+)-乳酸发酵的影响

分别利用CaCO3、6 mol/L氨水和6 mol/L NaOH溶液调控乳酸发酵过程的pH,得到的乳酸浓度为169.1g/L、187.9g/L和170.1g/L(以发酵液的初始体积计算),分别是无pH调控发酵过程的4.9倍、5.4倍和4.9倍;得到的OD620分别为19.3、21.6和16.4,分别是无pH调控(OD620为8.5)的2.3倍、2.5倍和1.9倍.相对于氨水和NaOH来说,CaCO3粉末是一种缓慢型的酸中和剂,pH调节能力有限,只能将pH维持在4.9～5.2.但CaCO3可以将乳酸以生成乳酸钙的形式沉淀下来,给下游乳酸的分离提取带来一定的方便.因此对于传统的分批式发酵,CaCO3仍不失为一种较好的选择.氨水和NaOH溶液都可以很好地将发酵液的pH调控在6.0,其中氨水是一种最理想的酸中和剂,既有利于乳酸的生物合成又能促进乳酸菌的生长.