Is the Effect of Aerobic Exercise on Cognition a Placebo Effect?

A number of studies and meta-analyses conclude that aerobic fitness (walking) interventions improve cognition. Such interventions typically compare improvements from these interventions to an active control group in which participants engage in non-aerobic activities (typically stretching and toning) for an equivalent amount of time. However, in the absence of a double-blind design, the presence of an active control group does not necessarily control for placebo effects; participants might expect different amounts of improvement for the treatment and control interventions [1]. We conducted a large survey to explore whether people expect greater cognitive benefits from an aerobic exercise intervention compared to a control intervention. If participants expect greater improvement following aerobic exercise, then the benefits of such interventions might be due in part to a placebo effect. In general, expectations did not differ between aerobic and non-aerobic interventions. If anything, some of the results suggest the opposite (e.g., respondents expected the control, non-aerobic intervention to yield bigger memory gains). These results provide the first evidence that cognitive improvements following aerobic fitness training are not due to differential expectations.     

Modeling the Effect of Prey Refuge on a Ratio-Dependent Predator–Prey System with the Allee Effect

The extinction of species is a major threat to the biodiversity. The species exhibiting a strong Allee effect are vulnerable to extinction due to predation. The refuge used by species having a strong Allee effect may affect their predation and hence extinction risk. A mathematical study of such behavioral phenomenon may aid in management of many endangered species. However, a little attention has been paid in this direction. In this paper, we have studied the impact of a constant prey refuge on the dynamics of a ratio-dependent predator–prey system with strong Allee effect in prey growth. The stability analysis of the model has been carried out, and a comprehensive bifurcation analysis is presented. It is found that if prey refuge is less than the Allee threshold, the incorporation of prey refuge increases the threshold values of the predation rate and conversion efficiency at which unconditional extinction occurs. Moreover, if the prey refuge is greater than the Allee threshold, situation of unconditional extinction may not occur. It is found that at a critical value of prey refuge, which is greater than the Allee threshold but less than the carrying capacity of prey population, system undergoes cusp bifurcation and the rich spectrum of dynamics exhibited by the system disappears if the prey refuge is increased further.     

Effect of Dephosphorylation on the Self-association and the Precipitation of β-Casein

The pyrolyzate of the nondialyzable melanoidin prepared from glucose-ammonia reaction system (kept in pH 5.3~6.0 during the reaction) was fractionated to volatile fraction and nonvolatile fraction. Among the volatile components, two pyridines and four alkylpyrazines were identified. On the other hand, one imidazole compound and two β-hydroxypyridines isolated from the nonvolatile fraction were identified as 4(5)-methylimidazole, 3-hydroxypyridine and 2-methyl-5-hydroxypyridine, respectively. It is inferred that these compounds are not produced by the fission of the main skeleton in the melanoidin molecule, but formed by pyrolysis of the heterocyclic compounds present as a small moiety in the melanoidin.     

The Rise and Fall of Flue-Cured Tobacco in the Copán Valley and Its Environmental and Social Consequences

From approximately 1952–1995 the Copán Valley in western Honduras was the site of intensive production of flue-cured tobacco. Local growers and laborers produced flue-cured tobacco for the transnational corporation, British-American Tobacco (BAT) under a contract farming arrangement. BAT introduced new tobacco varieties, cultivation techniques, mechanization and agrochemicals, as well as the flue-cured processing technique, and then purchased tobacco leaf for the manufacture of cigarettes in their Honduran subsidiary. Using ethnographic data and the interpretation of time series aerial photographs, this article documents the social and ecological impacts of this production system including extent of production, labor requirements, deforestation, exposure to agrochemicals and reinforcement of a hierarchical social system based on low-wage employment among landlessness agricultural workers. The paper also explores the reasons for, and consequences of, the decline of this system.     

Effect of α-p-chlorophenoxyisobutyrate on the metabolism of isoprenoid compounds in the rat

1. Feeding of alpha-p-chlorophenoxyisobutyrate (CPIB) to rats increased ubiquinone concentration in the liver but not in other tissues. The increase was progressive with the time of feeding and related to the concentration of CPIB in the diet. 2. Incorporation of [1-(14)C]acetate, but not of [2-(14)C]mevalonate, into sterols in the liver in vivo or by liver slices in vitro was decreased on feeding the rats with CPIB. However, incorporation of mevalonate into ubiquinone increased. 3. CPIB, when added in low concentrations to liver slices, had no effect on isoprene synthesis from acetate; higher concentrations, however, were inhibitory. 4. No activation of ubiquinone synthesis from mevalonate was observed when CPIB was added to the liver slices synthesizing ubiquinone. 5. The increase in ubiquinone in CPIB-fed animals appears to be due to increased synthesis in the initial stages and to decreased catabolism in the later stages. 6. An inverse relationship was found between the concentration of ubiquinone in the liver and the serum sterol concentration in CPIB-fed rats.     

Estimation of the Parameters for Tremograms According to the Eskov–Zinchenko Effect

The features of the chaotic dynamics of parameters of the neuromuscular system (tremors) were studied using conventional and novel biological methods based on a multidimensional phase-space representation. The dynamics of involuntary micromovements of limbs (finger tremor) both in the relaxation phase (F = 0) and under static load (F = 3N) was manifested in a change in the number of “coincidences” of randomly selected sample pairs (k) of matrices (15 × 15) in paired comparison of tremograms, which demonstrated the global statistical instability of the samples (statistical distribution functions f(x), spectral densities of signals, and autocorrelation A(t)). The samples that result from one experiment cannot be randomly repeated in the next experiment (with the same homeostasis). This represents a quantitative measure of the Eskov–Zinchenko effect in the analysis of chaotically changing statistical distribution functions of tremogram samples. In this paper, the use of quasi-attractor parameters of tremograms (their areas) is proposed to represent changes in the neuromuscular system when passing from one homeostasis to another (G₁ ≠ G₂).

     

Effect of the three-dimensional organization of liver cells on the biogenesis of the γ-glutamyltransferase fraction pattern

Context Four gamma-glutamyltransferase (GGT) fractions with different molecular weights (big-, medium-, small- and free-GGT) are detectable in human plasma. Objective Verify if liver cells can release all four GGT fractions and if the spatial cell organization influences their release. Methods Hepatoma (HepG2) and melanoma (Me665/2/60) cells were cultured as monolayers or spheroids. GGT released in culture media was analysed by gel-filtration chromatography. Results HepG2 and Me665/2/60 monolayers released the b-GGT fraction, while significative levels of s-GGT and f-GGT were detectable only in media of HepG2-spheroids. Bile acids alone or in combination with papain promoted the conversion of b-GGT in s-GGT or f-GGT, respectively. Conclusions GGT is usually released as b-GGT, while s-GGT and f-GGT are likely to be produced in the liver extracellular environment by the combined action of bile acids and proteases.     

Effect of additives on the thermostability ofBacillus stearothermophilus α-amylase

The effect of additives on the thermostability ofBacillus stearothermophilus -amylase was determined. Polyols, dimethyl formamide, and dimethyl sulfoxide all increased the half life of the enzyme approximately 2-fold when tested at a 10% (w/v) addition. These results suggest that the enzyme's structure is stabilized against thermal denaturation through ionic interactions. Addition of dextran or polyvinyl alcohol (hydrophilic polymers which increase the viscosity of the solution) had a slight positive effect on enzyme stability while addition of polyethylene glycol or polyvinylpyrrolidone (hydrophobic polymers which increase the viscosity of the solution) resulted in a 2-fold decrease in enzyme half life.     

Effect of PLCβ4 in the thalamus on the EEG in REM sleep

Sleep and Biological Rhythms -     

Effect of aluminum on the binding properties of α-chymotrypsin

 The effect of aluminum ions on the binding properties of α-chymotrypsin has been studied. The results show that aluminum does not affect the catalytic rate constant k _cat, but it acts as an enzyme activator favoring the binding of the substrate to the catalytic site (i.e. decreasing K _m). Furthermore, aluminum binding to α-chymotrypsin displays about a threefold decrease in its affinity for the macromolecular inhibitor bovine pancreatic trypsin inhibitor (BPTI). Altogether, the different effect of aluminum on the binding of synthetic substrates (e.g. N-α-benzoyl-l-tyrosine ethyl ester, BTEE) and macromolecular inhibitors (e.g. BPTI) to α-chymotrypsin suggests the occurrence of an aluminum-linked conformational change in the enzyme molecule which brings about a marked structural change at the primary and secondary recognition sites for substrates and inhibitors. The modulative effect exerted by aluminum on the enzyme hydrolytic activity has been investigated also as a function of pH. The ion-linked effect appears to be dependent on the pH in a complex fashion, which suggests that aluminum binding is controlled by the protonation of at least two classes of residues on the enzyme molecule. Received: 5 December 1996 / Accepted: 11 March 1997     

Effect of cortisone on the developmental pattern of the neutral and the acid β-galactosidases of the small intestine of the rat

1. The developmental pattern and effect of cortisone on acid beta-galactosidase and neutral beta-galactosidase were studied in postnatal rats by a recently proposed method for their independent determination. 2. After birth the acid beta-galactosidase activity increases in the ileum, whereas it decreases slightly in the jejunum. On day 16 after birth the activity in the ileum decreases and in 20-day-old rats activity in both parts of the intestine decreases to adult values. In suckling animals the activity in the ileum exceeds the jejunal activity severalfold and in adult animals the activity in the jejunum is slightly higher than that in the ileum. 3. Neutral beta-galactosidase activity is high after birth and decreases in both jejunum and ileum after day 20 after birth. In 12-20-day-old rats activity in both parts is essentially the same, but in adult animals jejunal activity exceeds ileal activity four-to five-fold. 4. Cortisone (0.5, 2.0 or 5.0mg/100g body wt. daily for 4 days) does not influence the activity of either enzyme in 60-day-old rats. Acid beta-galactosidase activity is decreased after cortisone treatment in 8-, 12-, 16-and 18-day-old rats, with sensitivity to cortisone increasing with the approach of weaning. No effect of cortisone on acid beta-galactosidase is seen in 8-day-old rats. Neutral beta-galactosidase activity is increased in the ileum of 8-, 12-, 16- and 18-day old rats, but only in the jejunum of 8-and 12-day-old rats.     

Effect of cysteine modifications on the activity of the ‘small’ Clostridium perfringens sialidase

The small (43 kDa) sialidase of Clostridium perfringens is inhibited by low concentrations of mercury ions. For the investigation of possible functional roles of the enzyme's four cysteine residues at the amino acid positions 2, 282, 333 and 349, they were separately altered to serine by site-directed mutagenesis. The four mutant sialidases expressed in E. coli and purified by metal chelate chromatography were markedly reduced in specific activity when compared to the wild-type enzyme but with the exception of C282S exhibited similar KM-values indicating an unchanged mode of substrate binding. The substrate specificity was also conserved for C2S, C282S, and C333S. Only the C349S sialidase exhibited a higher relative activity with colominic acid and the 2,6-linked sialic acid of sialyllactose compared to the 2,3-linked isomer than the other mutants. Chemical modifications with the thiol-blocking reagents N-ethylmaleimide (NEM), p-chloromercuribenzoate (pCMB) and HgCl2 had little effect on the C282S sialidase, e.g., 6% inhibition by 5 m M NEM compared to reductions in activity between 65 and 90% for the wild-type and other mutant enzymes, supporting the idea that among the enzyme's cysteines, Cys-282 has the highest structural or functional significance. The results also explain the higher mercury tolerance of Salmonella typhimurium and Clostridium tertium sialidases, which have the positions equivalent to Cys-282 altered to Val and Thr, respectively, indicating that the thiol group of Cys-282, despite being situated near the active site, is not involved in catalysis.     

Nuclear Overhauser Effect and Computational Characterization of the β-Spiral of the Polypentapeptide of Elastin

Abstract

The structure of the elastin polypentapeptide, poly(VPGVG), was studied by nuclear Overhauser effect experiments using perdeuterated Val¹ and Val⁴ samples under the condition where intermolecular interactions are absent. More extensive interaction was found between the Val¹ γCH and Pro² βCH protons than between the Val⁴ γCH and Pro² βCH protons. The Val¹ γCH₃—Pro² βCH interaction does not occur within the same pentamer as previously shown experimentally and as expected from steric considerations. The results are incompatible with the presence of a random chain network in poly(VPGVG) at room temperature but are readily explicable in terms of interturn interactions in a β-spiral structure. More specifically, the results indicate that the β-spiral conformation with 2.9 pentamers/turn is more prevalent than that with 2.7 pentamers/turn. Using conformations developed by molecular mechanics calculations, molecular dynamics simulations were carried out to compare the relative energies of these two variants of this class of β-spiral structures. It was found in vacuo that the structure with 2.9 pentamers/turn is indeed more stable than that of 2.7 pentamers/turn by ~ 1 kcal/mole-pentamer.     

Effect of progesterone pretreatment on the uptake of estradiol-17β by the uterine epithelium of the rat

Summary Progesterone pretreatment of ovariectomised rats resulted in a moderate (44%) lowering of the level of nuclear estradiol receptors found in the uterine epithelium 2 h after a single injection of this estrogen.     

Effect of the charge distribution along the “ferritin-like” pores of the proteins from the Dps family on the iron incorporation process

DNA-binding proteins from starved cells (Dps) differ in the number and position of charged residues along the “ferritin-like” pores that are used by iron to reach the ferroxidase center and the protein cavity. These differences are shown to affect significantly the electrostatic potential at the pores, which determines the extent of cooperativity in the iron uptake kinetics and thereby the mass distribution of the ferric hydroxide micelles inside the protein cavity. These conclusions are of biotechnological value in the preparation of protein-enclosed nanomaterials and are expected to apply also to ferritins. They were reached after characterization of the Dps from Listeria innocua, Helicobacter pylori, Thermosynechococcus elongatus, Escherichia coli, and Mycobacterium smegmatis. The characterization comprised the calculation of the electrostatic potential at the pores, determination of the iron uptake kinetics in the presence of molecular oxygen or hydrogen peroxide, and analysis of the proteins by means of the sedimentation velocity after iron incorporation.     

Effect of codon optimization on the enhancement of the β-carotene contents in rice endosperm

A β-carotene is the most well-known dietary source as provitamin A carotenoids. Among β-carotene-producing Golden Rice varieties, PAC (Psy:2A:CrtI) rice has been previously developed using a bicistronic recombinant gene that linked the Capsicum Psy and Pantoea CrtI genes by a viral 2A sequence. To enhance β-carotene content by improving this PAC gene, its codon was optimized for rice plants (Oryza sativa L.) by minimizing the codon bias between the transgene donor and the host rice and was then artificially synthesized as stPAC (stPsy:2A:stCrtI) gene. The GC content (58.7 from 50.9%) and codon adaptation index (0.85 from 0.77) of the stPAC gene were increased relative to the original PAC gene with 76% DNA identity. Among 67 T₁ seeds of stPAC transformants showing positive correlations between transgene copy numbers (up to three) and carotenoid contents, three stPAC lines with a single intact copy were chosen to minimize unintended insertional effects and compared to the representative line of the PAC transgene with respect to their codon optimization effects. Translation levels were stably increased in all three stPAC lines (3.0-, 2.5-, 2.9-fold). Moreover, a greater intensity of the yellow color of stPAC seeds was correlated with enhanced levels of β-carotene (4-fold, 2.37 μg/g) as well as total carotenoid (2.9-fold, 3.50 μg/g) relative to PAC seeds, suggesting a β-branch preference for the stPAC gene. As a result, the codon optimization of the transgene might be an effective tool in genetic engineering for crop improvement as proven at the enhanced levels of translation and carotenoid production.