Amino acids in a carbonaceous chondrite from Antarctica

Summary A carbonaceous chondrite from the Antarctic, referred to as the Allan Hills meteorite 77306, appears to be free from terrestrial organic contamination. The presence of both protein and non-protein amino acids and an equal abundance of D- and L-enantiomers of amino acids, is testimony to the extraterrestrial nature of these compounds.     

The Effect of Some Protein and Non-Protein Amino Acids on the Growth of Cladosporium herbarum and Trichothecium roseum

The effect of ten amino acids as the sole nitrogen source for the growth of Cladosporium herbarum (Link.) Fr. and Trichothecium roseum (Bull.) Link. was studied in order to clarify the fungus-host plant relationship. Special attention was paid to some rare non-protein amino acids of legumes. The best nitrogen sources for both fungi were γ-aminobutyric acid, arginine, serine and proline. Cladosporium could use homoarginine and canavanine, but these two amino acids were not used by Trichothecium when each was given as the only nitrogen source. Both fungi utilized ornithine, homoserine and a,γ-diaminobutyric acid to a limited extent. Pipecolic acid was not growth promoting. The growth-retarding effects of rare non-protein amino acids (homoarginine, canavanine, a,γ-diaminobutyric acid and pipecolic acid) were usually reversed by higher concentrations of their normal analogues. It is possible that rare non-protein amino acids may slightly protect the host plant against fungal infections, but there are clear differences between fungi in their reaction to non-protein amino acids.     

Cell suspensions for kinetic studies of inhibitor action

Because of uniformity and small distances for transport, cell suspensions offer a system for rapid measurements of initial reactions of phytotoxic compounds. We had previously shown that a growth regulator, dikegulac (2,3:4,6 di-o-isopropylidine-2-keto-L-gulonate) inhibits amino acid incorporation into proteins. Using Solanum nigrum suspension cultures, it was found that dikegulac rapidly inhibits amino acid uptake into cells, before inhibiting incorporation, with time points starting at a few minutes, and kinetics that can be extrapolated back to time zero. With more rapid kinetics this compound induces leakage of a preloaded dye. The rate of leakage was less with stationary cells in suspension, reiterating that they are more resistant to the effects of this compound. It was thus concluded that at the concentrations used, the first effect of dikegulac (or one very close to the first effect) is on the cell membrane.Abbreviation FDA fluorescein diacetate     

Studies on lysine analogs,aspartate-derived amino acids,and attempted mutant selection on oat seedlings

The lysine analogs S-2-aminoethyl-L-cysteine (AEC) and DL--hydroxylysine (DHL) caused severe growth inhibition in dark-grown oat seedlings (Avena sativa L. and A. nuda L.) at similar concentrations while L-lysine methyl ester (LME) had little effect. Lysine, arginine, and ornithine reversed the inhibition caused by AEC and DHL, the order of effectiveness being lysine>arginine>ornithine. Of aspartate-pathway amino acids, tested individually and in combinations for inhibitory effects on seedling growth, lysine and combinations containing lysine were the most inhibitory, but the inhibition was much less than that produced by AEC. Only slight synergistic effects occurred when oat seedlings were grown in the presence of paired combinations of aspartatepathway endproduct amino acids.Ca. 54,000 seeds obtained from 3,463 plants grown from ethyl-methanesulfonate (EMS) treated seed were screened for resistance to AEC. Three resistant variants were identified but the resistance was not recovered among their self-pollinated progeny.Abbreviations AEC S-2-aminoethyl-L-cysteine - DHL DL--hydroxylysine - EMS ethyl methanesulfonate - LME L-lysine methyl ester Paper No. 10351, Scientific Journal Series, Minnesota Agricultural Experiment Station     

Effect of starvation on the content of free amino acids in plasma of different breeds of hen

Summary Leghorn, Cornish and White Rock hens were subjected to starvation. Free amino acids were determined in blood samples taken after 48, 72 and 96 h of starvation. A progressive decrease in concentration of the majority of amino acids was found. Changes in amino acid concentrations during starvation were dependent on the breed of hen.     

Genotypic effects on the amino acid relationships in maize (Zea mays L.) pollen and style

Summary The free amino acid content of the pollen grains and the style from three single cross hybrids (Wf9 x H55, Ky49 x Ky27, K64 x K55) and two inbred lines (Oh43, H55) was determined. No tyrosine was detected in the pollen grains of any genotype. Significant differences between pollen genotypes were found for aspartic acid, threonine, serine, lysine and histidine with no effect resulting from the vigor of the pollen source. No proline was found in the style of any genotype. Significant differences between style genotypes were obtained for threonine, serine, glutamic acid, leucine, tyrosine, ethanolanine, aminobutyric acid and histidine with a relationship between vigor of the style genotype present for tyrosine, ethanolanine and aminobutyric acid. The relationship between the pollen and style level for each amino acid as influenced by genotype was analyzed. A significant negative correlation was found only for threonine. Apparently, a complementary relationship between the pollen and style exists for some amino acids. Proline and tyrosine are available only from the pollen and style respectively. Threonine levels are balanced with varying contributions from both pollen and style depending on the genotype.     

Early metabolic changes in regenerating microfragments of the liverwort Riella helicophylla (Bory et Mont.) Mont.: Protein and RNA synthesis,free α-amino concentration

Microfragments of constant size were isolated from the thallus of Riella by a rapid punching procedure. Thus it was possible to study various metabolic parameters especially during the first hours after fragment isolation. Protein synthesis increases rapidly after a slight decrease at 30 min. The earliest significant increase in RNA synthesis occurs at 8 h, indicating a different activation pattern. The concentration of -amino compounds drops at 30 min and then increases continuously, thus exhibiting a close relationship with the measured alterations in protein synthesis. Another indication of metabolic conversions during regeneration is provided by the changing level of free radioactive leucine, which shows a marked turning point at 24 h after fragmentation. Analysis of free -amino concentrations in small regions of larger fragments also indicates the establishment of new intercellular correlations only a few hours after isolation of the cells from the meristem. Up to the 8th h after fragmentation, the contents of both the adaxial and peripheral fragment regions increase. Thereafter only the adaxial (regenerating) cells continue accumulating; the peripheral (nonregenerating) ones remain at the same level.     

Evaluation of compositional nonrandomness in proteins

Summary Cornish-Bowden and Marson have recently suggested that the finite sampling component of Q, a measure of nonrandomness in the amino acid composition of proteins, may have been underestimated because it was calculated on the basis of the genetic code table frequencies rather than on the basis of the average natural abundance with which the twenty amino acids actually occur in proteins. This underestimate would lead to an overestimate of Q_c a measure of selective effects above and beyond those imposed by the average natural abundance of the amino acids. In this paper the finite sampling component of Q is quantitatively estimated on the basis of these natural abundances and found to reduce Q_c from its previous average value of 24.3 to the lower value of 9.7, with the standard deviation of the population of Q_c values being 12.5. Individual Q_c values are given for 81 protein families of mean composition per 61 codons of Ala_5.3 Arg_2.4 Asn_3.0 Asp_3.6 Cys_1.5 Gln_2.6 Glu_3.5 Gly_4.7 His_1.3 Ile_3.4 Leu_4.5 Lys_4.2 Met_1.0 Phe_2.3 Pro_2.3 Ser_4.2 Thr_3.6 Trp_0.8 Tyr_2.6 Val_4.2. The mean Q_c value of 9.7 is notably small, and indicates that quantitatively minimal adjustments away from the average protein composition are necessary to maintain many different biological functions. This small value, however, is shown to differ significantly from the value of zero expected were the natural abundances of the amino acids the only selective constraint. These small deviations from the natural abundances are thus effectively selected for in the Darwinian sense.     

ABO、MN血型及其与测量体征关系的初步探讨

本文提供了男、女两性共404人ABO、MN血型各表现型的35个体质特征测量数据,对血型和测量体征的关系进行了初步讨论。统计分析表明,不同血型群体的某些单个体征平均值之间有显著差异。对所调查的35个体征作整体分析,可见男性MN系统和女性ABO、MN系统各血型群体平均值之间差异显著。在MN血型系统,MN型群体的测量体征平均值低于M型和N型与MN基因型的杂合状态有密切关系。本文还分析了4个民族的血型资料,表明MN血型在ABO血型系统是随机分布的。     

Na+-dependent transport of glycine in renal brush border membrane vesicles: Evidence for a single specific transport system

The uptake of glycine in rabbit renal brush border membrane vesicles was shown to consist of glycine transport into an intravesicular space. An Na⁺ electrochemical gradient (extravesicular>intravesicular) stimulated the initial rate of glycine uptake and effected a transient accumulation of intravesicular glycine above the steady-state value. This stimulation could not be induced by the imposition of a K⁺, Li⁺ or choline⁺ gradient and was enhanced as extravesicular Na⁺ was increased from 10 mM to 100 mM. Dissipation of the Na⁺ gradient by the ionophore gramicidin D resulted in diminished Na⁺-stimulated glycine uptake. Na⁺-stimulated uptake of glycine was electrogenic. Substrate-velocity analysis of Na⁺-dependent glycine uptake over the range of amino acid concentrations from 25 μM to 10 mM demonstrated a single saturable transport system with apparent K_m = 996 μM and V_max = 348 pmol glycine/mg protein per min. Inhibition observed when the Na⁺-dependent uptake of 25 μM glycine was inhibited by 5 mM extravesicular test amino acid segregated dibasic amino acids, which did not inhibit glycine uptake, from all other amino acid groups. The amino acids d-alanine, d-glutamic acid, and d-proline inhibited similarly to their l counterparts. Accelerative exchange of extravesicular [³H]glycine was demonstrated when brush border vesicles were preloaded with glycine, but not when they were preloaded with l-alanine, l-glutamic acid, or with l-proline. It is concluded that a single transport system exists at the level of the rabbit renal brush border membrane that functions to reabsorb glycine independently from other groups of amino acids.