Inhibitory Effect Of Sucrose Research Articles

Comparative Assessment of Effectiveness of Calcium Silicate Dispersions Produced Using Sucrose and Lactose as Components of Composite Cement Binder

Silicate micro- and nano-additives are multifunctional in relation to cement systems. Their application can solve a wide range of technological problems while maintaining the economic efficiency of technical solutions. The effect of silicate additives and fillers is determined by their level of dispersion, due to which the technologies for producing nano- and submicro-sized dispersed materials are being developed. The combination of mechanochemical synthesis of modified calcium hydrosilicates with subsequent thermolysis makes it possible to produce calcium silicate dispersions (SCD), which differ in polymodality of the fractional composition including submicro (10–7–10–6 m) and microdimensional (≥10–6 m) modes. The main element of the technology is the use of modifying carbohydrate, which acts as a stabilizer of hydrated phases of silicates. A comparative study of SCD produced using sucrose (sSCD) and lactose (lSCD) revealed the effect of these carbohydrates on the properties of sSCD and lSCD, as well as their effectiveness as a component of cementitious composite binder. It was found that the level of adsorption of modifying carbohydrate determines the physical properties of SCD (granulometry, specific surface area). The relatively high residual content of free sucrose (0.24%) in the composition of sSCD prevents the consolidation of silicates nanoparticles formed during the thermolysis, causes a high content of submicro sized fractions and a high specific surface area with sSCD (26.3 ± 0.7 m2/g). Lactose is absorbed by the silicate phase; the residual content of free lactose does not exceed 0.028% of lSCD. The low content of stabilizing carbohydrate contributes to the development of nanoparticle consolidation, a decrease in the specific surface area of lSCD to 13.0 ± 0.2 m2/g and content of submicrosized fractions. The residual content of free carbohydrates and particle size characteristics of sSCD and lSCD determine the nature of their influence on Cement-SCD-based concrete setting and hardening. The presence of residual sucrose in the composition of sSCD and fine fractions determines the competitive nature of the processes of retardation of hardening and acceleration of hardening of the cement system due to the nucleation effect, as a result of which the curve of the setting time is extreme. In addition, the inhibitory effect of sucrose reduces the strength of concrete on the 7th day. By the 28th day, the inhibitory effect of sucrose has been overcome, and concrete samples demonstrate an 18% increase in compressive strength with a sSCD content of 30%. The low content of residual free lactose in the composition of lSCD causes the nucleation effect. As a result, there is a monotonous reduction in the setting time of concrete mix with an increase in the content of lSCD in the composition of HF, as well as a significant increase in concrete strength (up to 127%) on the 7th day. At the same time, on the 28th day the strength of concrete increases slightly

Sucrose increases the activation energy barrier for actin–myosin strong binding

To determine the mechanism by which sucrose slows in vitro actin sliding velocities, V, we used stopped flow kinetics and a single molecule binding assay, SiMBA. We observed that in the absence of ATP, sucrose (880mM) slowed the rate of actin–myosin (A–M) strong binding by 71±8% with a smaller inhibitory effect observed on spontaneous rigor dissociation (21±3%). Similarly, in the presence of ATP, sucrose slowed strong binding associated with Pi release by 85±9% with a smaller inhibitory effect on ATP-induced A–M dissociation, kT (39±2%). Sucrose had no noticeable effect on any other step in the ATPase reaction. In SiMBA, sucrose had a relatively small effect on the diffusion coefficient for actin fragments (25±2%), and with stopped flow we showed that sucrose increased the activation energy barrier for A–M strong binding by 37±3%, indicating that sucrose inhibits the rate of A–M strong binding by slowing bond formation more than diffusional searching. The inhibitory effects of sucrose on the rate of A–M rigor binding (71%) are comparable in magnitude to sucrose’s effects on both V (79±33% decrease) and maximal actin-activated ATPase, kcat, (81±16% decrease), indicating that the rate of A–M strong bond formation significantly influences both kcat and V.

Sugars, hormones, and environment affect the dormancy status in underground adventitious buds of leafy spurge (Euphorbia esula)

Signals from both leaves and apical or axillary meristems of leafy spurge are known to inhibit root bud growth. To test the hypothesis that carbohydrates and growth regulators affect root bud growth, decapitated leafy spurge plants were hydroponically treated with glucose, sucrose, gibberellic acid (GA), abscisic acid (ABA), 1-naphthaleneacetic acid (NAA), 6-benzylaminopurine (BA), and a GA biosynthesis inhibitor, paclobutrazol. Both glucose and sucrose caused suppression of root bud growth at concentrations of 30 mM. The inhibitory effect of sucrose was counteracted by GA at 15 μM. In contrast, BA, ABA, NAA, and paclobutrazol inhibited root bud growth at concentrations as low as 1, 2, 1, and 16 μM, respectively. Sugar and starch levels were also determined in root buds at various times after decapitation. Buds of intact plants contained the highest level of sucrose compared with buds harvested 1, 3, and 5 d after decapitation. To determine how seasonal changes affect root bud dormancy, growth from root buds of field-grown plants was monitored for several years. Root buds of field-grown leafy spurge had the highest level of innate dormancy from October to November, which persisted until a prolonged period of freezing occurred in November or early December. Our data support the hypothesis that carbohydrates may be involved in regulating dormancy status in root buds of leafy spurge.

Inhibitory effects of sucrose on larval development of housefly, Musca domestica L. (Diptera: Muscidae)

Inhibitory effects of sucrose on larval development of housefly, Musca domestica L. (Diptera: Muscidae)

A transfer of carbon atoms from fatty acids to sugars and amino acids in yellow lupine ( Lupinus luteus L.) seedlings

The metabolism of 14C-acetate was investigated during the in vitro germination of yellow lupine seeds. Carbon atoms (14C) from the C-2 position of acetate were incorporated mainly into amino acids: aspartate, glutamate, and glutamine and into sugars: glucose, sucrose, and fructose. In contrast to this, 14C from the C-1 position of acetate was released mainly as 14CO2. Incorporation of 1-14C and 2-14C from acetate into amino acids and sugars in seedling axes was more intense when sucrose was added to the medium. However, in cotyledons where lipids are converted to carbohydrates, this process was inhibited by exogenous sucrose. Since acetate is the product of fatty acid beta-oxidation, our results indicate that, at least in lupine, seed storage lipids can be converted not only to sucrose, but mainly to amino acids. Inhibitory effects of sucrose on the incorporation of 14C from acetate into amino acids and sugars in cotyledons of lupine seedlings may be explained as the effect of regulation of the glyoxylate cycle by sugars.

Thermodynamic non-ideality as an alternative source of the effect of sucrose on the thrombin-catalyzed hydrolysis of peptide p-nitroanilide substrates

The inhibitory effect of sucrose on the kinetics of thrombin-catalyzed hydrolysis of the chromogenic substrate S-2238 ( d-phenylalanyl–pipecolyl–arginoyl– p-nitroanilide) is re-examined as a possible consequence of thermodynamic non-ideality—an inhibition originally attributed to the increased viscosity of reaction mixtures. However, those published results may also be rationalized in terms of the suppression of a substrate-induced isomerization of thrombin to a slightly more expanded (or more asymmetric) transition state prior to the irreversible kinetic steps that lead to substrate hydrolysis. This reinterpretation of the kinetic results solely in terms of molecular crowding does not signify the lack of an effect of viscosity on any reaction step(s) subject to diffusion control. Instead, it highlights the need for development of analytical procedures that can accommodate the concomitant operation of thermodynamic non-ideality and viscosity effects.

Gelatinisation of sago starch in the presence of sucrose and sodium chloride as assessed by differential scanning calorimetry

The inhibitory effect of sucrose and sodium chloride on sago starch gelatinisation was investigated by differential scanning calorimetry (DSC). The temperature of gelatinisation of starch in the presence of low levels of water and high levels of sucrose was found to increase in the presence of sucrose, whereas the gelatinisation enthalpy was unaffected. The gelatinisation temperature range was not as broad in the presence of sucrose as without sucrose. Furthermore, the shape of the gelatinisation endotherm was changed by the addition of sucrose. The double endotherm obtained in limited water:starch systems was changed into a single endotherm, similar to the endotherm obtained in excess water:starch systems at a higher temperature. DSC was also used to examine the effects of water and sodium chloride content on the phase transitions of sago starch. Samples were adjusted to starch:water ratios of 2:3 and 3:2 in sodium chloride concentrations of 0.0, 1.0, 2.0, 3.0, 4.0, 5.0 M. The gelatinisation temperatures of sago starch increased and then decreased as the sodium chloride concentration increased. Sodium chloride created similar effects on the endotherms in excess water content and on the first endotherm with limited water content. In the presence of sucrose and sodium chloride, gelatinisation shifted to higher temperatures, and enthalpy associated with the endothermic process decreased. The extent of temperature shift and enthalpy change was dependent on the water to starch to solutes ratios.

Essential Role of Dynamin in Internalization of M2Muscarinic Acetylcholine and Angiotensin AT1AReceptors

Most G protein-coupled receptors (GPCRs), including the M(1) muscarinic acetylcholine receptor (mAChR), internalize in clathrin-coated vesicles, a process that requires dynamin GTPase. The observation that some GPCRs like the M(2) mAChR and the angiotensin AT(1A) receptor (AT(1A)R) internalize irrespective of expression of dominant-negative K44A dynamin has led to the proposal that internalization of these GPCRs is dynamin-independent. Here, we report that, contrary to what is postulated, internalization of M(2) mAChR and AT(1A)R in HEK-293 cells is dynamin-dependent. Expression of N272 dynamin, which lacks the GTP-binding domain, or K535M dynamin, which is not stimulatable by phosphatidylinositol 4, 5-bisphosphate, strongly inhibits internalization of M(1) and M(2) mAChRs and AT(1A)Rs. Expression of kinase-defective K298M c-Src or Y231F,Y597F dynamin (which cannot be phosphorylated by c-Src) reduces M(1) mAChR internalization. Similarly, c-Src inhibitor PP1 as well as the generic tyrosine kinase inhibitor genistein strongly inhibit M(1) mAChR internalization. In contrast, M(2) mAChR internalization is not (or is only slightly) reduced by expression of these constructs or treatment with PP1 or genistein. Thus, dynamin GTPases are not only essential for M(1) mAChR but also for M(2) mAChR and AT(1A)R internalization in HEK-293 cells. Our findings also indicate that dynamin GTPases are differentially regulated by c-Src-mediated tyrosine phosphorylation.

Inhibitory Effect of Sucrose on the Plasma Membrane H+ Pump Activity and Possible Involvement of the C-terminal Region in the Sucrose Effect

pump activity is unclear. In the plasma membrane vesicles from rye leaves high concentrations of sucrose had significant inhibitory effects on the plasma membrane H+ pump activity. Fusicoccin and trypsin treatment experiments suggest that the C-terminal region of the H+ pump may partially but significantly be involved in the sucrose effect.

Specific solute effects on Staphylococcus aureus cells subjected to reduced water activity

The behaviour of Staphylococcus aureus cells subjected to lowered water activity ( a w) by the addition of various solutes was examined by transmission electron microscopy. Solutes included sodium chloride, sucrose, propylene glycol, butylene glycol and various polyethylene glycols. Changes in other physical properties of the liquid growth medium brought about by the solutes were estimated theoretically. They did not correlated with the bacterial biological response. The inhibitory effects of sucrose and sodium chloride against S. aureus were primarily ascribed to their water activity-lowering abilities, showing no significant specific solute effects. However, the other solutes examined showed specific antibacterial activity against S. aureus which may be compatible with cell wall attack.

Mg2+‐ATPase activity in wheat root plasma membrane vesicles: Time‐dependence and effect of sucrose and detergents

Purified plasma membrane vesicles were isolated in the presence of 250 mM sucrose from 7‐day‐old roots of Triticum aestivum L. cv. Drabant by aqueous polymer two‐phase partitioning. When added to a low‐salt medium containing 9‐aminoacridine (9‐AA), the vesicles caused a much larger total decrease in 9‐AA fluorescence when sucrose was absent than when sucrose was present. A slow component of the decrease was also larger in the absence of sucrose. Triton X‐100 reduced the decrease in 9‐AA fluorescence upon vesicle addition and abolished completely the slow component of the decrease. There was no correlation between the time‐dependence of 9‐AA fluorescence and that of the Mg2+‐ATPase described below.The time course of Mg2+‐ATPase activity was followed by sampling at short intervals (down to 10 s) and analyzing for P, released. In the absence of detergent, the rates of P, release were linear from zero minutes, whether 250 mM sucrose was present or not, but the rate was 10−50% higher in the absence of sucrose than in its presence. Sucrose (250 mM) added during a minus‐sucrose assay lowered Mg2+‐ATPase activity within 2 min to the level observed with 250 mM sucrose present from the start. The effect of 25‐1 100 mM sucrose was tested and there was little or no effect below KM) mM. Above 100 mM sucrose the rate of P, release decreased drastically; at 1 100 mM sucrose the rate was ca 20% the rate at 25 mM sucrose. The inhibitory effect of sucrose was not alleviated by increased concentrations of Mg2+ and/or ATP. nor was it affected by the presence or absence of Triton X‐100. We conclude that sucrose somehow inhibits the Mg2+‐ATPase directly or affects the conformation of the plasma membrane in such a way as to inhibit the enzyme.The presence of detergents increased Mg2+‐ATPase activity in the order Triton X‐100 (4–5‐fold) > Zwittergent 3–14 = Na‐cholate = octylglucoside > digitonin (2‐fold). In all cases optimal activity was observed at detergent concentrations at or below the critical micellar concentration. The detergent concentration curves could be simulated by the sum of a stimulatory and an inhibitory reaction. At the optimal concentration, digitonin gave a linear time‐course of P, release, whereas all the other detergents showed a distinct lag of 1–3 min before maximal rates were attained. The problems of using detergents in polarity assays are discussed.

Effects of hypertonic solutions on catecholamine release from cat adrenal glands

The effects of hypertonic solutions on the spontaneous and evoked catecholamine release from isolated, perfused cat adrenal glands were studied. Hypertonic solutions enhanced three times the spontaneous release of the amines, but markedly inhibited the release evoked by nicotine 15μM for 2 min or high K +(17.7 mM for 2 min). Using sucrose as osmoticant, the secretory response to high K + was decreased to 53 and 15% of controls at 344 and 416 mosM, respectively At 512 mosM sucrose inhibited poorly the release of catecholamines evoked by nicotine, but reduced it by 90% at 1000 mosM; sodium chloride behaved similarly to sucrose. A rise in the osmolarity of only 7.5% with choline chloride produed a complete inhibition of the K +-evoked response. These effects were not seen using isotonic choline chloride; on the contrary, isotonic choline chloride enhanced the K + response, probably by stimulating nicotinic receptors. Since atropine did not modify this effect, it seems that secretion of catecholamines evoked by choline is mediated by nicotinic receptors. While the inhibitory effects of sucrose and NaCl were completely reversed when the tonicity of the perfusion medium was restored to its normal value (320 mosM), the effects of choline seemed to be long lasting and were reversed only partially. It is worth noting that the inhibitory effects of hyperosmotic solutions developed very fast. It is concluded that an increase in the tonicity of the medium bathing the chromaffin cell depresses profoundly the exocytotic catecholamine release response to nicotine and high K + these experiments suggest that the existence of an osmotic gradient across the plasma and or vesicular membranes might be a prerequisite for fusion of both membranes and or the subsequent extracellular discharge of chromaffin granule contents to the cell exterior.

In vitro and in vivo inhibition of sucrose synthesis by sucrose

The inhibitory effects of sucrose on rates of sucrose synthesis by sucrose phosphate synthase (SPS) from the maize scutellum and on net rates of sucrose production in maize scutellum slices from added glucose or fructose were studied. Scutellum extracts were prepared by freezing and thawing scutellum slices in buffer. The extracts contained SPS and sucrose phosphate phosphatase, but were free of sucrose synthase. SPS activity was calculated from measurement of UDP formation in the presence of UDPG, fructose-6-P and sucrose. The ranges of metabolite concentrations used were those estimated to be in scutellum slices after incubation in water or fructose for periods up to 5 hr. UDPG and fructose-6-P also were added at concentrations that saturated SPS. At saturating substrate levels, sucrose inhibition of SPS was less than that when tissue levels of substrates were used. With tissue levels of substrates and sucrose concentrations up to ca 166 mM, sucrose inhibitions of sucrose synthesis in vitro by SPS were similar to those observed in vivo. However, as the sucrose concentration rose above 166 mM, SPS activity was not inhibited further, whereas there was a further sharp decline in sucrose production by the slices. It is concluded that sucrose synthesis in vivo is controlled by sucrose inhibition of SPS over a considerable range of internal sucrose concentrations.

An in vitro kinetic study of the mixed inhibition of honeybee hemolymph PNP-α-D-glucosidase by sucrose

Sucrose acts in vitro as a mixed inhibitor of (V+K+n) type towards honeybee hemolymph PNP-α-D-glucosidase activity. Between the stages of emergence and foraging, there is little change in the effect of the inhibitor on VM (fi=from 1.31 to 1.35 respectively) or n (fi=from 1.09 to 1.07) but K is more markedly affected (fi−1=from 1.17 to 1.87)M. These observations reflect the decrease of Ki from 277 to 98 mM and of I50 from 154 to 111 mM, but K′i scarcely alters during development (from 477 to 425 mM). These inhibitory effects of sucrose are intermediate between those previously reported for trehalose and glucose.

Effect of Hypertonic Sucrose Upon the Immune Bactericidal Reaction

This study was performed to determine the mechanism whereby hypertonic sucrose inhibits the immune bactericidal reaction. Other investigators had postulated that the initial attack of complement (C) on the cell wall was followed with lysozyme-containing whole serum by an enzymatic reaction upon the peptidoglycan substrate resulting in cell death. In the absence of serum lysozyme, secondary lethal changes might occur from damage to the cell's inner membrane as a result of osmotic forces in the presence of a defective cell wall. Hypertonic sucrose giving rise to plasmolysis and protection of the inner membrane was presumed to differentially inhibit the immune response mediated by lysozyme-free serum. The experimental results observed in this investigation have indicated, however, that the inhibitory effect of sucrose upon the bactericidal reaction may be explained simply by its anticomplementary effect and not by any effect on the bacterial cell. This view was supported by the following observations: (i) the comparability of the inhibitory effect of sucrose upon the immune hemolytic and bactericidal reactions, (ii) the comparable percentage loss in bactericidal activity of whole serum and lysozyme-free serum resulting from hypertonic sucrose, (iii) bactericidal antibody titrations were relatively unaffected and C titrations markedly inhibited by sucrose, (iv) the inhibitory effect of sucrose on the bactericidal reaction was unaffected by prior growth of the organism in the presence of sucrose, (v) the kinetics of the bactericidal reactivity of lysozyme-free serum in hypertonic sucrose, compared with whole serum, did not reveal a prolonged lag phase with lysozyme-free serum, but simply diminished reactivity at all times. These observations are compatible with the view that the C attack upon the outer surface of gram-negative bacteria, which plays a part in the cell's permeability control, may account for cell death. In this regard, the immune bactericidal reaction is quite comparable to the lysis of red cells or nucleated cells by C despite the lack of overt lysis in bacteria, probably because of their underlying supporting structures.

Mitochondrial swelling at acid pH.

The effect of variations of pH on swelling of rat liver mitochondria was studied.It was found that mitochondria swell at acid pH (5.0–6.0) when they are incubated in isotonic solution of potassium chloride. The extent of swelling increased with decreasing tonicity of the medium. However, mitochondria did not swell at acid pH when they were incubated in isotonic sucrose. The inhibitory effect of sucrose was partially released by the addition of electrolytes to the medium.When unbuffered suspensions of mitochondria with different pH values were prepared by the addition of hydrochloric acid or sodium hydroxide to the incubation medium, it was observed that the extent of swelling increased both with acidity (6.0 to 5.0) and with alkalinity (7.0 to 8.0).Titration of the unbuffered mitochondrial suspensions showed a maximum buffering capacity in the ranges of pH values where maximum rate of swelling occurred.These results suggest that the mitochondrion behaves as a combination of osmometer and protein gel.

CARBOHYDRATE INHIBITORS OF SUCROSE UPTAKE BY RESTING CELLS OF AGROBACTERIUM TUMEFACIENS.

The rapid uptake of sucrose-C14from the surrounding medium by resting cells of Agrobacterium tumefaciens is strongly inhibited in a competitive manner by D-glucose, D-galactose, D-xylose, D-fucose, and L-arabinose while their enantiomorphs do not inhibit. It has been possible to formulate specific structural requirements for the monosaccharides which are necessary to produce such powerful inhibitory effects of sucrose uptake.Strong inhibition has also been obtained with 3-ketoglucose, 3-ketosucrose, 3-ketomaltose, 3-ketolactose, and 3-ketotrehalose, as well as with the disaccharides maltose and cellobiose. In these cases, however, specific structural requirements for inhibition have not been determined as yet.