Reaction of some D-glucobioses with 2,2-dimethoxypropane

Laminarabiose, cellobiose, and gentiobiose were acetonated with 2,2-dimethoxy-propane under various conditions. Two isopropylidene acetals in which the reducing D-glucose residue had the furanoid form were obtained from laminarabiose, and two, in which the reducing D-glucose residue formed the acyclic dimethyl acetal, from cellobiose. Gentiobiose gave both types of isopropylidene compound.     

Absence of pantothenic acid in gramicidin S synthetase 2 obtained from some mutants of Bacillus brevis

The pantothenic acid content of gramicidin S synthetase 2(GS 2) was estimated microbiologically with enzymes obtained from the wild strain and gramicidin S-lacking mutant strains of Bacillus brevis. Four mutant enzymes from BI-4, C-3, E-1, and E-2 lacked pantothenic acid. Other mutant enzymes from BII-3, BI-3, BI-9, and BI-2 contained the same amount of pantothenic acid as the wild-type enzyme. Pantothenic acid-lacking GS 2 belonged to group V of mutant enzymes, which could activate all amino acids related to gramicidin S; their complementary enzyme, gramicidin S synthetase 1(GS 1), lacked racemizing activity. To ascertain whether 4'-phosphopantetheine is involved in the formation of D-phenylalanyl-L-prolyl diketopiperazine (DKP) and gramicidin S, combinations were tested of intact GS 1 from the wild strain with various mutant GS 2 either containing or lacking pantothenic acid. Only the combinations of wild-type GS 1 with mutant GS 2 containing pantothenic acid could synthesize DKP. Combinations with pantothenic acid-lacking GS 2 also failed to elongate peptide chains. Pantothenic acid-lacking GS 2 could bind the four amino acids which constitute gramicidin S as acyladenylates and thioesters, but the binding abilities were lower than those of the wild-type enzyme and other mutant enzymes containing the pantothenic group.     

Pectinase and plant growth-promoting factors in the salivary glands of the larva of the bug,Lygus disponsi

Pectinase was detected in the salivary gland of the larvae of Lygus disponsi. The pectinase activity per bug may increase gradually from the first instar larva to the adult. The salivary gland of the third instar larva contained substances indirectly promoting plant growth, i.e. the factor promoting the activity of 3-indoleacetic acid (IAA) or the factor inhibiting the activity of IAA-oxidase, whereas those of the fourth and 5th instar larvae seemed to contain, in addition, auxins which directly promote plant growth. Larvae of all instars had a significant promoting factor only in fraction III of the salivary gland solution. The larvae are as toxic as the adults to sugar beet plants. The presence of pectinase and plant growth-promoting factors in the salivary gland is compared among mirid bugs, and their significance is discussed.     

The accumulation of manganese from the environmental medium by the egg of Oryzias latipes

The manganese content of the egg and embryo of the Medaka, Oryzias latipes was determined by activation analysis. A remarkable increase in the amount of manganese in the egg was observed within one hour after fertilization. The rate of increase was reduced by the gastrula stage and the concentration of manganese remained unchanged at a later stage. The accumulation of manganese by the Oryzias egg was discussed in relation to the effect of manganese on respiratory enzyme systems.     

Catalysis by human leukocyte elastase: mechanistic insights into specificity requirements

Steady-state kinetic parameters were determined for the human leukocyte elastase catalyzed hydrolysis of a series of peptide-based thiobenzyl esters and p-nitroanilides. The peptide units are MeOSuc-Val, MeOSuc-Alan-Pro-Val (n = 0-2), and MeOSuc-Alan-Pro-Ala (n = 1 or 2). The results of this study suggest five important mechanistic features for HLE. Few important remote subsite contacts are established in the Michaelis complex. Full recognition and tight binding of the substrate occurs in the transition state for acylation. The P3-S3 interaction is critical during acylation. Subsite contacts are unimportant in deacylation. P1 specificity is regulated by peptide length. An important steady-state kinetic consequence of this specificity is that the rate-limiting step of kc for p-nitroanilide hydrolysis changes from acylation to deacylation as the peptide chain is lengthened.     

Life history and population dynamics of the Japanese Yam,Dioscorea japonica Thunb.

The adaptive significance of the emergence mode ofDioscorea japonica was studied with respect to initial plant size (seed, bulbil and tuber) and light intensity, using mathematical simulation based on Yokoi's (1976) model. Under 1.5% full sunlight conditions, plants emerging with only one leaf did not develop a shoot system throughout the growing period (Hori and Oshima, 1986). Simulation indicated that, for this species of plant under poor productive conditions, the optimal time for switch-over from the vegetative to reproductive growth phase to maximize the tuber weight at the end of the growing period, occurred immediately following the start of autotrophic growth. By means of shoot growth patterns, small and large size plants acquired the ability of shade tolerance and shade avoidance, respectively. Further, the life history ofD. japonica could be expressed as a flow chart based on plant size and light intensity data.     

Is Working More Costly than Waiting in Monkeys?

We studied how value for instrumental action is discounted by predicted effort and delay. The monkeys were trained to perform instrumental trials that required a bar release when a visual target changed from red-to-green. There were two trial conditions. In delay trials, after the monkeys performed one instrumental trial correctly a reward was delivered 0–7 seconds later. In work trials, the monkeys had to perform 0, 1, or 2 additional instrumental trials to obtain a reward. The lengths of trials in delay matched the time it took to complete work trials. The length of delay or number of trials was indicated by a visual cue presented throughout the trial. Our hypothesis was that the monkeys would all show temporal discounting of reward in the delay trials, and that in the work trials the monkeys’ performance might reflect an additional cost due to working. The error rate increased linearly as remaining cost increased for all 8 monkeys. For 4 monkeys the error rate was significantly larger in work trials than in delay trials (effort sensitive monkeys). For the other 4 monkeys there was no significant difference in error rate (effort insensitive monkeys). Since the error rate has an inverse relation with value for action, these results suggest that value is discounted hyperbolically by effort as well as by delay. Error rates generally increased as the testing sessions progressed and the total reward accumulated (i.e., effect of reward devaluation). The relative impact of delay and effort on error rates was reasonably stable within subjects. Thus, within the monkey population there seems to be a significant dichotomy in the sensitivity governing whether working is more costly than waiting, possibly arising from a constitutional or genetic trait.